JP2015223042A - Non-contact power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power supply device which suppresses a harmonic wave applied to a power reception coil.SOLUTION: The non-contact power supply device includes: a power reception coil which receives power supplied from a power transmission coil connected to a power supply; a resonance circuit which includes a resonance capacitor connected in series with the power reception coil; a rectifier for rectifying AC power input from the resonance circuit; a smoothing capacitor which is connected between the output terminals of the rectifier and charged by a current output from the rectifier; a discharge switching element connected between the smoothing capacitor and a load; and control means which controls the discharge switching element. The control means discharges the charge of the smoothing capacitor through the discharge switching element, before timing in which the polarity of the rectifier is switched.

Description

  The present invention relates to a non-contact power feeding device.

  Formed by a feed transformer that transmits power by magnetically coupling a primary feed line and a secondary winding, and an inductance of the feed transformer and a capacitor connected in series to the secondary winding of the feed transformer In a non-contact power supply apparatus including a series resonance circuit, a full-wave rectifier that rectifies a voltage output from the series resonance circuit, and a constant-voltage control unit that outputs the full-wave rectifier with a constant voltage. Consists of an E-shaped core and a secondary winding wound around the center leg of this core. The on-duty ratio of the switching element of the step-up chopper, which is a constant voltage control means, is greater than that under heavy load. In addition, there is disclosed one that controls the light load to be smaller (Patent Document 1).

JP 2008-259419 A

  In the conventional non-contact power feeding device, a smoothing capacitor is connected to the input side of the boost chopper in order to smooth the voltage output from the rectifier. When the rectifier is conducting, the voltage of the smoothing capacitor is applied to the capacitor of the series resonant circuit and the secondary winding, and when the conduction direction of the rectifier current is switched, the polarity of the voltage applied to the secondary winding is It changes rapidly. For this reason, there has been a problem that a harmonic having a large amplitude is generated in the secondary winding.

  The problem to be solved by the present invention is to provide a non-contact power feeding device that suppresses harmonics applied to the power receiving coil.

  The present invention relates to a resonance circuit including a resonance capacitor connected in series to a power receiving coil, a rectifier that rectifies AC power input from the resonance circuit, a smoothing capacitor that is charged by a current output from the rectifier, and a smoothing capacitor. A discharge switching element connected between the load and the load and a control means for controlling the discharge switching element, and discharging the charge of the smoothing capacitor through the discharge switching element by the timing when the polarity of the rectifier is switched. To solve the above problem.

  In the present invention, since the voltage of the smoothing capacitor is low when the polarity of the rectifier is switched, even if the polarity of the rectifier is switched, the voltage fluctuation of the receiving coil is suppressed and the harmonics of the receiving coil are suppressed. Can do.

It is a circuit diagram of the non-contact electric supply system concerning the embodiment of the present invention. It is a circuit diagram of the non-contact electric supply system concerning a comparative example. In the non-contact power feeding system according to the comparative example, the coil current characteristic (a) of the secondary coil 6, the input voltage characteristic (b) of the bridge diode 9, the input current characteristic (c) of the converter 20, and the DC bus capacitor voltage It is the graph which showed the characteristic (d) of (DC bus voltage), and the characteristic (e) of the voltage of the secondary coil 6, respectively. In the non-contact electric power feeding system which concerns on this invention, it is a graph for demonstrating the voltage characteristic of the secondary side circuit, the current characteristic, and the characteristic of a switching signal. In the non-contact electric power feeding system which concerns on this invention, it is a graph for demonstrating the voltage characteristic of the secondary side circuit, the current characteristic, and the characteristic of a switching signal. It is a circuit diagram of the non-contact electric power feeding system concerning other embodiments of the present invention. It is a graph for demonstrating the voltage characteristic of the secondary side circuit, the current characteristic, and the characteristic of a switching signal in the non-contact electric supply system concerning other embodiments of the present invention. It is a graph for demonstrating the voltage characteristic of the secondary side circuit, the current characteristic, and the characteristic of a switching signal in the non-contact electric supply system concerning other embodiments of the present invention. In the non-contact electric power feeding system which concerns on other embodiment of this invention, it is the graph which showed the ratio of the 3rd harmonic of the secondary coil 6 with respect to voltage ratio ( _Vmin / _Vavg ). It is a graph for demonstrating the voltage characteristic and electric current characteristic of a secondary side circuit in the non-contact electric power feeding system which concerns on other embodiment of this invention. It is a graph for demonstrating the voltage characteristic of the secondary side circuit, the current characteristic, and the characteristic of a switching signal in the non-contact electric supply system concerning other embodiments of the present invention. It is a circuit diagram of the non-contact electric power feeding system concerning other embodiments of the present invention. It is a circuit diagram which shows the example of the circuit of the reverse blocking type switching element of FIG. It is a graph for demonstrating the voltage characteristic and electric current characteristic of a secondary side circuit in the non-contact electric power feeding system which concerns on other embodiment of this invention. It is a graph for demonstrating the electric current characteristic of a secondary side circuit, and the characteristic of a switching signal in the non-contact electric power feeding system which concerns on other embodiment of this invention. It is a circuit diagram of the non-contact electric power feeding system concerning other embodiments of the present invention. It is a circuit diagram of the non-contact electric power feeding system concerning other embodiments of the present invention. It is a graph for demonstrating the voltage characteristic and electric current characteristic of a secondary side circuit in the non-contact electric power feeding system which concerns on other embodiment of this invention. It is a graph for demonstrating the electric current characteristic of a secondary side circuit, and the characteristic of a switching signal in the non-contact electric power feeding system which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
The contactless power supply system according to the present embodiment is a system for supplying contactless power from the ground side to the vehicle battery when charging a battery of a vehicle such as an electric vehicle, for example. As another example, the non-contact power feeding system can also be applied to a system that supplies power to a running vehicle.

  Hereinafter, the configuration of the non-contact power feeding system of this example will be described with reference to FIG. FIG. 1 is a circuit diagram of a contactless power feeding system according to the present invention. The non-contact power feeding system includes a primary non-contact power feeding device provided on the ground side and a secondary non-contact power feeding device provided on the vehicle side. The primary-side non-contact power supply apparatus includes a DC power source 1, a smoothing capacitor 2, an inverter 3, a resonance capacitor 4, and a primary coil 5. The non-contact power feeding device on the secondary side includes a secondary coil 6, a resonant capacitor 7, voltage sensors 8, 11, 16, a bridge diode 9, a DC bus capacitor 10, a switching element 12, a diode 13, a resistor 14, a current sensor 15, A load 17, a converter 20, a controller 100, and a phase synchronization circuit (PLL circuit) 110 are provided.

  The DC power source 1 is configured by connecting a plurality of batteries. The smoothing capacitor 2 is connected between the DC power source 1 and the inverter 3. The inverter 3 converts the power supplied from the DC power source 1 into AC power and outputs the AC power to the resonance capacitor 4 and the primary coil 5. The inverter 3 has a plurality of switching elements 3a to 3d connected in series to each phase. The inverter 3 performs a switching operation at several tens of k to several hundreds of kHz and outputs high-frequency AC power. Note that semiconductor elements such as MOSFETs are used for the switching elements 3a to 3d.

  The resonant capacitor 4 and the primary coil 5 are connected in series and connected to the output side of the inverter 3. A resonant circuit is formed by the resonant capacitor 4 and the primary coil 5. The primary coil 5 is a coil for supplying electric power to the secondary coil 6 in a non-contact manner. The primary coil 5 is configured by, for example, a parking space in which a vehicle is parked or a loop-shaped coil having a coil surface along the ground surface such as a traveling surface of the vehicle.

  Next, the configuration on the secondary side will be described. The secondary coil 6 is a coil that secondaryally supplies power supplied from the primary coil 5 in a non-contact manner. The secondary coil 6 is configured by, for example, a loop-like coil similar to the primary coil 5, and is attached so that the coil surface follows the chassis of the vehicle. The resonant capacitor 7 is connected in series with the secondary coil 6 and forms a resonant circuit with the secondary coil 6. When a magnetic flux is generated in the primary coil 5, an electromotive force is generated in the secondary coil 6 as the magnetic flux passes through the coil surface of the secondary coil 6. After the phase of the power secondary by the secondary coil 6 is compensated by the resonance capacitor 7, the received power of the secondary coil 6 is output to the bridge diode 9.

  The bridge diode 9 is a rectifier in which the diodes 9 a to 9 d are connected in a bridge shape, and rectifies AC power input from the resonance circuit of the secondary coil 6 and the resonance capacitor 7. The bridge diode 9 switches the current direction of the diodes 9a to 9d (changes the conducting diode) by switching the polarity of the input alternating current.

  A voltage sensor 8 is connected to the AC input terminal of the bridge diode 9. The voltage sensor 8 measures the input AC voltage input to the bridge diode 9 and outputs it to the phase synchronization circuit 110.

  The DC bus capacitor 10 is connected between the DC output terminals of the bridge diode 9. The DC power output by the bridge diode 9 is a full-wave rectified sine wave (input power to the bridge diode 9), and therefore includes a large ripple current. Therefore, the DC bus capacitor 10 smoothes the output of the bridge diode 9 and suppresses fluctuations in the voltage input to the converter 20.

  The voltage of the DC bus capacitor 10 is boosted by the converter 20 and supplied to the load 17. As will be described later, converter 20 boosts the electric power charged in DC bus capacitor C11. Therefore, the state where the DC bus capacitor 10 is charged must be maintained during the operation of the converter 20. The secondary side of the non-contact power feeding system of this example has a configuration using the resonance capacitor 7, and the input current to the DC bus capacitor 10 is supplied from the secondary coil 6. The power supplied cannot be increased rapidly.

  On the other hand, when the input current to converter 20 increases rapidly and the charging voltage of DC bus capacitor 10 becomes zero, the input current of converter 20 becomes zero and the output power of converter 20 decreases. In order to prevent such a decrease in the output voltage, the DC bus capacitor 10 needs to store charges so that a current can be supplied to the converter 20, and the DC bus capacitor 10 needs a certain amount of capacity. And In this example, a capacitor having a capacitance of several hundred μF to several thousand μF is used for the DC bus capacitor 10 in order to stabilize the DC bus voltage.

  The voltage sensor 11 is a sensor for measuring the voltage of the DC bus capacitor 10 and is connected to the DC bus capacitor 10 in parallel. The voltage measured by the voltage sensor 11 is output to the controller 100.

  The switching element 12 is a switch for discharging the electric charge charged in the DC bus capacitor 10. The switching element 12 is a semiconductor element such as a MOSFET. The drain terminal (high potential side terminal) of the switching element 12 is connected to the positive input terminal 20a of the converter 20 via a wiring.

  The resistor 14 is a resistor for consuming electric charges discharged from the DC bus capacitor 10 and input through the switching element 12, and is connected to the switching element 12 in series. One terminal of the resistor 14 is connected to the source terminal (low potential side terminal) of the switching element 12, and the other terminal of the resistor 14 is connected to the negative input terminal 20b of the converter 20 via a wiring. Yes. The series circuit of the switching element 12 and the resistor 14 is a discharge circuit that is connected between the DC bus capacitor 10 and the converter 20 and discharges the DC bus capacitor 10.

  The converter 20 is a circuit that converts the voltage output from the bridge diode 9 and smoothed by the DC bus capacitor 10, and is a boost converter. The converter 20 has positive and negative input terminals 20a and 20b on the input side, and positive and negative output terminals 20c and 20d on the output side. The input terminal 20a and the output terminal 20c are connected to the positive power line, and the input terminal 20b and the output terminal 20d are connected to the negative power line.

The converter 20 is connected between the DC bus capacitor 10 and the load 17. The converter 20 includes an inductor 21, a switching element 22, a diode 23, and a capacitor 24. One terminal of the inductor 21 is connected to the input terminal 20 a, and the other terminal of the inductor 21 is connected to the drain terminal of the switching element 22 and the anode terminal of the diode 23. The drain terminal of the switching element 22 is connected to the connection point between the other terminal of the inductor 21 and the anode terminal of the diode 23. The source terminal of the switching element 22 is connected to the input terminal 20b and the output terminal 20d.

  The anode terminal of the diode 23 is connected to the connection point between the other terminal of the inductor 21 and the drain terminal of the switching element 22, and the cathode terminal of the diode 23 is connected to the output terminal 20 c and one terminal of the capacitor 24. . One terminal of the capacitor 24 is connected to the output terminal 20c, and the other terminal of the capacitor 24 is connected to the output terminal 20d.

  The switching element 22 is controlled by the controller 100. When the switching signal transmitted from the controller 100 is input to the gate terminal of the switching element 22, the switching element 22 is turned on and off, and the input voltage is boosted and output to the load 17.

  The current sensor 15 is a sensor that is connected to the output terminal 20 d of the converter 20 and measures an output current from the converter 20 to the load 17. The voltage sensor 16 is connected between the input terminal 20 c and the output terminal 20 d of the converter 20 and measures the output voltage from the converter 20 to the load 17. Measurement values of the current sensor 15 and the voltage sensor 16 are output to the controller 100.

  For example, when the non-contact power supply system is applied to a vehicle battery non-contact charging device, the load 17 is a battery. For example, when the non-contact power supply system is applied to a power supply device for a traveling vehicle, the load 17 is a motor.

  When the load 17 is a battery, the output voltage required for the load 17 is determined by the state of charge (SOC) of the battery. Therefore, the converter 20 is provided as a mechanism for adjusting the output voltage to the load 17. In addition, when the non-contact power feeding system is applied to a power supply device for a traveling vehicle, it is possible to control the power output to the load 17 on the ground side. The necessary power information is vehicle-side information. For this reason, the necessary power information must be transmitted from the vehicle to the apparatus on the ground side by radio or the like. However, wireless communication may be hindered by noise or the like. In addition, when a plurality of coils are arranged on the vehicle side with respect to one ground side coil, if the output voltage to the load 17 is controlled on the ground side, there arises a problem that it cannot be individually controlled. Therefore, converter 20 is provided so that the output voltage can be controlled on the vehicle side.

  The phase synchronization circuit 110 generates the clock signal according to the frequency of the acquired AC voltage while acquiring the AC voltage on the input side of the bridge diode 9 from the voltage sensor 8. At this time, the frequency of the clock signal is set to twice the frequency of the AC voltage. The phase synchronization circuit 110 performs feedback control based on the input signal input from the voltage sensor 8, generates a clock signal so as to be synchronized with the input signal, and outputs the clock signal to the controller 100.

  The controller 100 is a control circuit that drives the switching element 12 and the switching element 22. The controller 100 generates a switching signal for driving the switching element 12 based on the clock signal input from the phase synchronization circuit 110 and outputs the switching signal to the gate terminal of the switching element 12. In addition, the controller 100 acquires the output power to the load 17 from the current sensor 15 and the voltage sensor 16 and performs feedback control so that the output power matches the required power to the load 17 to drive the switching element 22. .

  Here, unlike the present invention, FIGS. 2 and 3 are used for the circuit operation of the non-contact power feeding system according to the comparative example in which the switching element 12 and the resistor 14 are not provided and the harmonics generated in the secondary coil 6. I will explain. FIG. 2 is a circuit diagram of a non-contact power feeding system according to a comparative example. FIG. 3 shows the characteristics (a) of the coil current of the secondary coil 6, the characteristics (b) of the input voltage of the bridge diode 9, the characteristics (c) of the input current of the converter 20, and the DC bus capacitor voltage (DC bus voltage). It is the graph which showed the characteristic (d) and the characteristic (e) of the voltage of the secondary coil 6, respectively.

  As shown in FIG. 2, the contactless power feeding system according to the comparative example does not include the switching element 12 and the resistor 14 and does not include the phase synchronization circuit 110 as compared with the present invention. Other configurations are the same as those of the non-contact power feeding system according to the present invention. In FIG. 2, the configuration on the primary side is omitted and illustrated.

  For example, it is assumed that the contactless power feeding system is operating in a state where the voltage of the DC bus capacitor 10 is + 340V. At this time, the DC bus voltage is maintained at a constant voltage value of 340V. The waveform of the alternating current of the secondary coil 6 is a sine wave as shown in FIG. When the polarity of the current of the secondary coil 6 changes (when the alternating current changes from plus to minus or from minus to plus), the polarity of the bridge diode 9 is switched, and the waveform of the input voltage to the bridge diode 9 is As shown in FIG. 3B, the rectangular wave is obtained by alternately switching between positive and negative.

At time _{t 1,} the diode 9a of the bridge diode 9, 9d becomes conductive, diode 9b, When 9c was shut off, the input voltage of the bridge diode 9 becomes + 340 V. Then, at time t _2, the the polarity of the current in the secondary coil 6 is switched, changes the conduction direction of the current in the bridge diode 9, a diode 9a, 9d are cut off, diode 9b, 9c becomes conductive. Therefore, at time _{t 2, the} input voltage of the bridge diode 9 becomes -340V. That is, at time t ₂ , a voltage change of 680 V, which is twice the DC bus voltage, is applied to the resonance circuit of the secondary coil 6 and the resonance capacitor 7.

  Since such a rapid voltage change occurs at a high frequency component, the capacitor 7 connected in series with the secondary coil 6 has no voltage drop due to the voltage change of the high frequency component, and the voltage change of the high frequency component does not occur. 6 is applied. An alternating current flows through the secondary coil 6 due to magnetic coupling with the primary coil 5. Therefore, in a state where an alternating current due to magnetic coupling between the coils flows through the secondary coil 6, an alternating current due to a voltage change of the high frequency component also flows through the secondary coil 6. A voltage proportional to the slope of the alternating current is generated in the secondary coil 6. When the AC voltage of the secondary coil 6 is maximum or minimum, the direction in which the AC current flows is switched from positive to negative, or from negative to positive.

  As shown in FIG. 3 (e), the voltage waveform of the secondary coil 6 has a step-like voltage change twice the DC bus voltage at the apex of the AC voltage waveform of the secondary coil 6. The waveform is superimposed on the AC voltage. Since the step-like voltage change superimposed on the AC voltage includes harmonics, noise (harmonic noise) is generated in the secondary coil 6 due to this large voltage change.

Furthermore, the voltage change that causes the generation of harmonic noise depends on the magnitude of the voltage charged in the DC bus capacitor 10 when the polarity of the bridge diode 9 is reversed. In the comparative example, as shown in FIGS. 3B and 3D, the DC bus capacitor 10 accumulates a large amount of charge at the timing (time t ₁ , t ₂ , t ₃ ) at which the polarity of the bridge diode 9 is inverted. The charging voltage of the DC bus capacitor 10 is high. Then, the voltage change of the bridge diode 9 at times t ₁ , t ₂ , and t ₃ is twice the charging voltage of the DC bus capacitor 10 and is superimposed on the AC current of the secondary coil 6. Therefore, in the comparative example, large noise (harmonic noise) is generated in the secondary coil 6.

  In the non-contact power feeding system according to the present invention, in order to suppress the above harmonics, the circuit is operated as described below while providing the switching element 12 and the resistor 14.

  4A and 4B are graphs for explaining voltage characteristics, current characteristics, and switching signal characteristics of the secondary circuit of the contactless power feeding system according to the present invention. 4A and 4B, (a) shows the characteristics of the coil current of the secondary coil 6, (b) shows the characteristics of the input voltage of the bridge diode 9, and (c) shows the characteristics of the switching signal of the switching element 22. (D) shows the characteristic of the input current of the converter 20, (e) shows the characteristic of the switching signal of the switching element 12, (f) shows the characteristic of the current flowing through the switching element 12, and (g) The characteristic of a DC bus capacitor voltage (DC bus voltage) is shown, (h) The characteristic of the voltage of the secondary coil 6 is shown.

The input current of the secondary coil 6 has an AC waveform as shown in FIG. 4A (a), and the direction of current flow is reversed at times t ₁ , t ₂ , and t ₃ . An input current of the secondary coil 6 is input to the bridge diode 9, and a voltage waveform measured by the voltage sensor 8 is as shown in FIG. 4A (b). The waveform of the input voltage of the bridge diode 9 is inverted between positive and negative at times t ₁ , t ₂ , and t ₃ , similarly to the input current of the secondary coil 6.

The phase synchronization circuit 110 generates a clock signal from the waveform of the measurement voltage of the voltage sensor 8. The clock signal has a period from time t ₁ to time t ₂ (time from time t ₂ to time t ₃ ) as one cycle. This period (frequency of the clock signal) is set to be twice the frequency of the current of the secondary coil 6.

  The output voltage of the bridge diode 9 is applied to the DC bus capacitor 10, and the DC bus capacitor 10 is charged. The voltage of the DC bus capacitor 10 is measured by the voltage sensor 11, and the measured voltage is input to the controller 100.

  The controller 100 generates a switching signal for driving the switching element 12 and a switching signal for driving the switching element 22. The switching signal of the switching element 22 is a rectangular wave as shown in FIG. 4A (c). The switching element 22 is turned on at a high level of the waveform shown in FIG. 4A (c), and is turned off at a low level. The high level period is the on period of the switching element 22, and the low level period is the off period (hereinafter, the same applies to other switching signals).

  Since the inductor 21 is connected to the input side of the converter 20, the input current of the converter 20 takes a relatively smooth constant value as shown in FIG. 4A (d). Therefore, even if the switching element 22 is switched on and off, the current on the input side of the converter 20 does not change, so the amount of electric charge discharged from the DC bus capacitor 10 cannot be adjusted.

  The duty ratio that determines the ON period of the switching element 22 is determined by the voltage required for the load 17. That is, since the frequency and duty ratio of the switching signal of the switching element 22 are determined by the request from the load 17 side, it is difficult to use as a switch for discharging the charge of the DC bus capacitor 10.

The switching signal of the switching element 12 is a rectangular wave as shown in FIG. 4B (e). The switching signal of the switching element 12 has a waveform that rises after the elapse of time t ₂ (time t _a ) and immediately before time t ₃ (time t _b ) until the switching element 12 is turned on. In other words, the switching signal of the switching element 12 rises from the time t ₂ after the elapse of a half period (half period of the clock signal), the falling thing until after the time t _3, the half period elapses in the time since, and has been up to time t _b and on period. The ON period of the switching signal is generated not only from time t ₂ to time t ₃ but also from time t ₁ to time t _{2 in} the same cycle.

Then, during the on period from time t _a to time t _b, the switching element 12 is turned on like body, since the DC bus capacitor 10 is electrically connected to the resistor 14 via the switching element 12, the charge of the DC bus capacitor 10 Is discharged through the switching element 12 and consumed by the resistor 14. Then, by the time _{t 3,} the switching element 12 is switched off, the discharge of the DC bus capacitor 10 is completed. As a result, the electric charge of the DC bus capacitor 10 is discharged through the switching element 12 by the timing of inversion of the polarity of the bridge diode 9.

Voltage of the DC bus capacitor 10, as shown in FIG. 4B (g), by increasing the voltage drop between t _b from time t _a which is the ON period of the switching element 12, in the polarity of the switching timing of the bridge diode 9 It has become 30V is at a certain time _{t 3.} Since the voltage fluctuation generated in the secondary coil 6 is suppressed to 60V, which is twice 30V (FIG. 4B (f)), the generation of harmonic noise can be suppressed.

  As described above, in the present invention, the switching element 12 is connected to the DC bus capacitor 10 as a discharging switching element, and the charge of the DC bus capacitor 10 is discharged through the switching element 12 by the timing when the polarity of the bridge diode 9 is switched. I am letting. Thereby, the amount of discharge from the DC bus capacitor 10 can be controlled by the conduction time of the switching element 12. Further, according to the present invention, the DC bus capacitor 10 is discharged before the polarity of the bridge diode 9 is switched (just before the polarity is switched), so that the voltage of the DC bus capacitor 10 is changed at the timing of switching the polarity of the bridge diode 9. Can be reduced. Therefore, the voltage fluctuation of the secondary coil when the polarity of the bridge diode 9 is switched can be reduced, and the harmonic noise of the secondary coil can be suppressed.

  In the present invention, the clock signal is generated by setting the frequency of the clock signal to twice the frequency of the AC voltage measured by the voltage sensor 8, and the switching signal of the switching element 12 is generated so as to be synchronized with the clock signal. Thereby, it is possible to grasp the timing at which the polarity of the bridge diode 9 is inverted from the measured value of the voltage sensor 8. Further, since the clock signal and the switching signal are synchronized, the controller 100 can be easily designed.

In the present invention, the ON period of the switching element 12 is set so that the DC bus capacitor 10 is discharged until immediately before the end of the clock of the clock signal (corresponding to the times t ₁ , t ₂ , and t ₃ ). Thereby, the DC bus capacitor 10 can be in the most discharged state at the timing when the polarity of the bridge diode 9 is switched. Therefore, the harmonics of the secondary coil 6 can be reduced.

  The switching elements 12 and 22 are not limited to MOSFETs but may be semiconductor elements such as IGBTs. When IGBTs are used for the switching elements 12 and 22, the collector terminal is a high potential side terminal and the emitter terminal is a low potential side terminal.

  The secondary side resonance circuit is not limited to a series resonance circuit, but may be a parallel series resonance circuit (a circuit in which a capacitor is connected in parallel to the secondary coil 6 and a capacitor is connected in series to the secondary coil 6). Good. By making the secondary side resonance circuit a parallel series resonance circuit, it is possible to prevent a decrease in output power when the relative positions of the primary coil 5 and the secondary coil 6 are shifted.

  The bridge diode 9 corresponds to the “rectifier” of the present invention, the controller 100 corresponds to the “control means” of the present invention, the secondary coil 6 corresponds to the “power receiving coil” of the present invention, and the DC bus capacitor 10. Corresponds to the “smoothing capacitor” of the present invention, the voltage sensor 8 corresponds to the “first voltage measuring means” of the present invention, and the voltage sensor 11 corresponds to the “second voltage measuring means” of the present invention.

<< Second Embodiment >>
FIG. 5 is a circuit diagram of a non-contact power feeding system according to another embodiment of the invention. This example is different from the above-described first embodiment in that the DC bus capacitor 10 is discharged by a switching element in the converter 20 instead of the switching element 12 and the resistor 14. Other configurations are the same as those in the first embodiment described above, and the description thereof is incorporated.

  Hereinafter, the structure different from 1st Embodiment among the structures of the non-contact electric power feeding system which concerns on other embodiment of this invention is demonstrated. The converter 20 includes a switching element 25, an inductor 26, a diode 27, and a capacitor 28. Converter 20 is a buck-boost converter. The drain terminal of the switching element 25 is connected to the positive input terminal 20 a of the converter 20, and the source terminal of the switching element 25 is connected to the connection point between one terminal of the inductor 26 and the cathode terminal of the diode 27. One terminal of the inductor 26 is connected to a connection point between the source terminal of the switching element 25 and the cathode terminal of the diode 27, and the other terminal of the inductor 26 is the negative input terminal 20 b of the converter 20 and the other terminal of the capacitor 28. Connected to the terminal.

  The anode terminal of the diode 27 is connected to one terminal of the capacitor 28 and the positive output terminal 20 c of the converter 200, and the cathode terminal of the diode 27 is connected to the connection point between the source terminal of the switching element 25 and one terminal of the inductor 26. It is connected. One terminal of the capacitor 28 is connected to the anode terminal of the diode 27 and the positive output terminal 20 c of the converter 20, and the other terminal of the capacitor 28 is connected to the negative output terminal 20 d of the converter 20.

  Next, the operation of the circuit of the non-contact power feeding system will be described with reference to FIGS. 6A and 6B. 6A and 6B are graphs for explaining voltage characteristics, current characteristics, and switching signal characteristics of the secondary circuit of the non-contact power feeding system according to the present invention. 6A and 6B, (a) shows the characteristics of the coil current of the secondary coil 6, (b) shows the characteristics of the input voltage of the bridge diode 9, (c) shows the clock signal, and (d) shows the clock signal. The characteristics of the switching signal of the switching element 25 are shown, (e) shows the characteristics of the input current of the converter 20, (f) shows the characteristics of the DC bus capacitor voltage (DC bus voltage), and (e) the secondary coil 6 The voltage characteristics are shown.

The input current of the secondary coil 6 has an AC waveform as shown in FIG. 6A (a), and the direction of current flow is reversed at times t ₁ , t ₂ , and t ₃ . Further, the polarity of the bridge diode 9 is also inverted at times t ₁ , t ₂ , and t ₃ (see FIG. 6A (b)). As shown in FIG. 6A (c), the phase synchronization circuit 110 generates a clock signal having a period determined by times t ₁ , t ₂ , and t ₃ .

The controller 100 generates a switching signal having the falling edges at times t ₁ , t ₂ , and t ₃ while synchronizing with the clock signal of the phase synchronization circuit 110. The switching signal is a signal for driving the switching element 25. The switching signal is a signal that, after the elapse of time t ₁ , sets a certain period as an off period and sets an on period from the middle of one cycle to time t ₂ .

  The input current of the converter 20 has an intermittent current waveform as shown in FIG. 6B (e). Since the switching element 25 is provided on the input side of the converter 20, the input current of the converter 20 becomes zero during the off period of the switching element 25, and the input current flows during the on period of the switching element 25.

The voltage waveform of the DC bus capacitor 10 is as shown in FIG. 6B (f). The DC bus capacitor 10 is charged during a period when the current of the converter 20 is not flowing, and the DC bus capacitor 10 is discharged during a period when the current of the converter 20 is flowing. That is, since the DC bus capacitor 10 is electrically connected to the converter 20 during the ON period of the switching element 25, the charge of the DC bus capacitor 10 is discharged and the input current of the converter 20 flows. The voltage of the DC bus capacitor 10 becomes a minimum value of 35 V at times t ₁ , t ₂ , and t ₃ .

Since the times t ₁ , t ₂ , and t ₃ are timings at which the polarity of the bridge diode 9 is inverted, a voltage fluctuation of 70V, which is twice the 35V of the DC bus voltage, occurs. And the voltage fluctuation accompanying the inversion of the polarity of the bridge diode 9 is superimposed on the AC voltage of the secondary coil 6. Therefore, as shown in FIG. 6B (g), the voltage waveform of the secondary coil 6 has a shape in which a step voltage of 70 V is superimposed on the AC waveform at the timings of times t ₁ , t ₂ , and t ₃ . The voltage waveform of the secondary coil 6 of the present invention is greatly reduced in voltage fluctuations at times t ₁ , t ₂ , and t ₃ compared to the secondary coil voltage waveform of Comparative Example 1 shown in the first embodiment. ing. Thereby, harmonic noise can be significantly reduced.

  The level at which harmonic noise can be reduced depends on the voltage of the DC bus capacitor 10 when the polarity of the bridge diode 9 is inverted. Therefore, how much the voltage of the DC bus capacitor 10 should be reduced will be described below.

The average voltage of the DC bus capacitor 10 is V _avg, and the lowest voltage of the DC bus capacitor 10 (the voltage when the polarity of the bridge diode 9 is inverted) is V _min . Then, when the voltage ratio of the minimum voltage to the average voltage of the DC bus capacitor 10 (V _min / V _avg ) and the ratio of the third harmonic of the secondary coil 6 are plotted, a graph as shown in FIG. 7 is obtained. FIG. 7 is a graph showing the ratio of the third harmonic of the secondary coil 6 to the voltage ratio (V _min / V _avg ).

As shown in FIG. 7, the harmonics are reduced as the minimum voltage of the DC bus capacitor 10 is lowered. For example, when the voltage ratio (V _min / V _avg ) is 0.6, the ratio of the third harmonic becomes about 10%, and a large noise reduction effect can be obtained. On the other hand, when the voltage ratio (V _min / V _avg ) is 0.3 or less, the ratio of the third harmonic becomes a substantially constant value, and the harmonic noise reduction effect does not increase. Then, when the voltage of DC bus capacitor 10 becomes zero, the output voltage of converter 20 decreases. Therefore, the voltage ratio (V _min / V _avg ) is preferably designed so as to be between 0.1 and 0.6 (or between 0.1 and 0.3).

  Next, the capacitance of the DC bus capacitor 10 will be described. As described above, when the input current of the converter 20 flows, the voltage of the DC bus capacitor 10 decreases. In order to optimize the magnitude of the voltage to be reduced, it is required to set the capacitance of the DC bus capacitor 10 to an appropriate value at the design stage, as will be described below.

  FIG. 8 is a graph for explaining voltage characteristics and current characteristics of the secondary side circuit of the non-contact power feeding system according to the present invention. 8A shows the input current characteristic of the DC bus capacitor 10, FIG. 8B shows the input current characteristic of the converter 20, and FIG. 8C shows the input / output current characteristic of the DC bus capacitor 10. , (D) shows the characteristics of the DC bus capacitor voltage (DC bus voltage). In the graph of (c), plus indicates the input current to the DC bus capacitor 10 and minus indicates the output current from the DC bus capacitor 10.

An input current having a waveform shown in FIG. 8A is input to the DC bus capacitor 10. The waveform of the input current of the converter 20 is shown in FIG. 8 (b), the period of time t ₅ from the time t _4, the flowing the input current of the converter 20. Note that the period from time t ₄ to time t ₅ corresponds to the ON period of the switching element 25. During the period from time t ₄ to time t ₅ , the DC bus capacitor 10 is discharged by outputting current to the converter 20, so that an output current as shown in FIG. 8C is output from the DC bus capacitor 10. Is done. Then, as shown in FIG. 8 (d), from time _{t 4} to time _{t 5,} the discharge of the DC bus capacitor 10, the voltage of the DC bus capacitor 10 is reduced. The voltage of the DC bus capacitor 10 becomes the minimum value (V _min ) at the timing of inversion of the polarity of the bridge diode 9 (time t ₅ ).

A voltage half the voltage ripple of the DC bus capacitor 10 is represented by a voltage difference (V _avg −V _min ) between the average voltage (V _avg ) and the minimum voltage (V _min ) of the DC bus capacitor 10. Then, the voltage of the DC bus capacitor 10 drops in a period from time _{t 4} to time _{t 5,} since the whole of the voltage ripple _is represented by _{2 · (V avg -V min)} .

When the capacitance of the DC bus capacitor 10 is C _dc , the magnitude of the charge (Q ₃ ) output from the DC bus capacitor 10 from time t ₄ to time t ₅ is the relationship between the voltage of the capacitor and the charge. From the formula, it is expressed by formula (1).

As shown in FIG. 8 (a) ~ (c) , the period until time _{t 5} from the time _{t 4,} the DC bus capacitor 10, while the inflow Figure 8 (a) charge due to the input current _{Q 1,} converter 20 charge Q ₂ is flowing through the input current (DC become viewed as the output from the bus capacitor 10). That is, the charge (Q ₃ ) actually output from the DC bus capacitor 10 is the difference between the charge (Q ₁ ) and the charge (Q ₃ ).

The charge Q ₁ has a value obtained by integrating the current waveform shown in FIG. 8A from time t ₄ to time t ₅ . DC input current of bus capacitor 10 is a waveform obtained by full-wave rectifying a sine wave by a bridge diode 9, the integrated value of the time t ₄ to time t _5, the area of a portion of the full-wave rectified waveform (FIG. 8 ( The operating frequency (driving frequency) F _{wcs of} the non-contact power feeding system which is the hatched portion of a), the output power of the converter 20 is P _out , the switching cycle of the converter 20 is T _s , and the duty ratio of the converter 20 is D. The switching period T _s is expressed by equation (2).

The average value (I _avg1 ) of the input current of the DC bus capacitor 10 is expressed by equation (3).

The input current of the DC bus capacitor 10 has a sine wave shape, and the maximum value (I _max ) of the input current of the DC bus capacitor 10 is expressed by Expression (4).

Integrated value of the sine wave from the time t ₄ to time t ₅ are represented by the formula (5).

Then, when the equations (4) and (5) are multiplied and further multiplied by (T _s / π) for conversion into one period, the charge Q ₁ is calculated as in the equation (6).

The charge Q ₂ corresponds to an area obtained by multiplying the time from time t ₄ to time t ₅ by the value of the input current of the converter 20. When the current flowing through the inductor 26 of the converter 20 is approximated as being constant, the average value (I _avg2 ) of the input current of the converter 20 is expressed by Expression (7).

The time from time t ₄ to time t ₅ is represented by D · T _s . Then, by multiplying the equation (7) by the time (D · T _s ), the charge Q ₂ is calculated as in the equation (8).

Then, the charge Q ₃ is a value obtained by subtracting the charge Q ₁ from the charge Q ₂ , and further using the equation (1), the capacitance (C _dc ) of the DC bus capacitor 10 is calculated as in the equation (9). Is done.

As shown in FIG. 7, the harmonic noise reduction effect is preferably such that the voltage ratio (V _min / V _avg ) is higher than zero (V _min = 0) and is 0.6 or less. Then, by substituting the range of the voltage ratio with high harmonic noise reduction into the equation (9), the range of the capacitance (C _dc ) is determined as the equation (10).

In the value set by the capacitance C _dc , the output power P _out of the converter 20 is set to the rated power (maximum power) in the non-contact power feeding system of the present invention. When the value of the capacitance C _dc is set with the output power P _out as the rated power, V _min becomes an appropriate value at the rated power at which the noise is greatest. Then, when the output power P _out decreases from the rated power and the input current of the converter 20 decreases, V _min increases. Therefore, since the voltage of DC bus capacitor 10 does not become zero in any operating range, it is possible to prevent the input current of converter 20 from becoming zero.

  As described above, according to the present invention, the converter 20 is configured as a boosting converter circuit, and the switching element 25 included in the converter 20 is driven as a switching element for discharging the DC bus capacitor 10. The charge of the DC bus capacitor 10 is discharged through the switching element 25 by the timing when the polarity is switched. Thereby, the amount of discharge from the DC bus capacitor 10 can be controlled by the conduction time of the switching element 25. Moreover, the present invention can reduce the voltage fluctuation of the secondary coil when the polarity of the bridge diode 9 is switched, and can suppress the harmonic noise of the secondary coil.

As a modification of the present invention, the controller 100 measures the average voltage (V _avg ) of the DC bus capacitor 10 from the measured voltage of the voltage sensor 11, and the DC bus capacitor 10 at the time when the polarity of the bridge diode 9 is inverted. The on-time of the switching element 25 may be set so that the voltage (V _min ) is 0.6 times the average voltage (V _avg ). For example, when adjusting the ON period of the switching element 25 up to time t ₃ , the controller 100 calculates an average voltage (V _avg ) from the voltage of the DC bus capacitor 10 that rises during the OFF period of the switching element 25. Alternatively, the controller 100 calculates the average voltage (V _avg ) from the voltage waveform of the DC bus capacitor 10 before time t ₃ . The amount of voltage change that drops from the peak value of the voltage of the DC bus capacitor 10 to time t ₃ corresponds to the ON time of the switching element 25. Therefore, the controller 100 generates the switching signal so that the on-time of the switching element 25 becomes longer as the amount of voltage change to be lowered with respect to the average voltage (V _avg ) is larger. Further, the controller 100 may perform feedback control on the input current of the converter 20 so that the voltage (V _min ) is 0.6 times the average voltage (V _avg ). Thereby, the non-contact electric power feeding system which concerns on a modification can reduce the harmonic noise of the secondary coil 6. FIG. The target value of the voltage _{(V min)} is multiplied need not necessarily be 0.6 times the average voltage _{(V avg),} a predetermined coefficient to the average voltage _{(V avg)} and (1 positive value less than) The value should be

  In the present embodiment, the case where the converter 20 is a boost converter has been described as an example, but the converter 20 may be a step-down converter. By configuring the converter 20 with a step-down converter, the input current of the converter 20 can be periodically changed as in the case of the step-up converter, and harmonic noise of the secondary coil 6 can be reduced. Further, when the output voltage to the load 17 is lower than the voltage of the DC bus capacitor 10, the efficiency of the converter 20 can be increased.

  Further, since the converter 20 is a step-up / down converter, the switching element 25 is connected in series to the input of the converter 20, and the input current can be made intermittent. Since the input current is intermittent, the charge can be selectively extracted from the DC bus capacitor 10 just before the switching time of the input current of the bridge diode 9. The voltage of the DC bus capacitor 10 can be reduced. Thereby, the voltage step which generate | occur | produces in the secondary coil 6 can be reduced, and the harmonic of the secondary coil 6 can be reduced as a result. Furthermore, when the power reception voltage of the secondary coil 6 and the voltage of the load 17 are different, the voltage output in accordance with the load 17 can be adjusted.

The operation waveforms shown in FIGS. 6A, 6B, and 8 are such that the output power P _out is 24 kW, the average voltage V _avg of the DC bus capacitor 10 is 320 V, and the duty ratio D of the switching signal of the switching element 25 is 0.45. And the simulation result when the value of V _min / V _avg is approximately zero and the capacitance C _dc of the DC bus capacitor 10 is 0.4 μF under the condition that the operating frequency F _wcs of the non-contact power feeding system is 85 kHz. is there.

<< Third Embodiment >>
A non-contact power feeding system according to another embodiment of the present invention will be described. In this example, the switching signal of the switching element 25 is different from the first embodiment described above. Other configurations are the same as those of the second embodiment described above, and the description thereof is incorporated.

In the non-contact power feeding system according to the second embodiment, when the output voltage of the converter 20 is converted, the input current of the converter 20 also changes, so the voltage (V _min ) of the DC bus capacitor 10 changes. And the magnitude | size of the harmonic noise of the secondary coil 6 changes with the change of voltage ( _Vmin ). In the present embodiment, the following control is performed so that the amount of change in the harmonic noise of the secondary coil 6 can be suppressed even if the output voltage of the converter 20 changes.

  The operation of the circuit of the contactless power feeding system of the present invention will be described with reference to FIG. FIG. 9 is a graph for explaining voltage characteristics, current characteristics, and switching signal characteristics of the secondary circuit of the non-contact power feeding system according to the present invention. 9, (a) shows the characteristic of the coil current of the secondary coil 6, (b) shows the characteristic of the input voltage of the bridge diode 9, (c) shows the characteristic of the switching signal of the switching element 25, (D) shows the characteristics of the input current of the converter 20, (e) shows the characteristics of the DC bus capacitor voltage (DC bus voltage), and (f) shows the characteristics of the voltage of the secondary coil 6.

The switching signal of the switching element 25 has a waveform as shown in FIG. The switching signal includes a plurality of ON times with respect to one cycle of the clock signal. In the example of FIG. 9C, the switching signal includes two on times per cycle. An off time is included between the two on times. In the period from time t ₂ to t _3, the on time before the two on-time is the time from the time t _a (time after time t ₂₎ to time t _a, after the on-time Time This is the time from t _c to time t ₃ . And, the time from the time t _b until the time t _c is turned off time. Also, the length of the previous on-time is shorter than the length of the subsequent on-time. That is, the switching signal, the on-time pulse having a falling edge time _{t 1, t 2, t 3} , during each pulse of the time _{t 1, t 2, t 3} , the additional on-time pulse Contains. Converter 20 is driven by the switching signal of FIG.

  The input current of the converter 20 has a waveform as shown in FIG. 9D and flows in synchronization with the ON state of the switching signal. At this time, the output current of the converter 20 increases as the input current of the converter 20 increases. The voltage drop of the DC bus capacitor 10 is determined according to the length of the ON time of the switching signal. Therefore, the voltage drop of DC bus capacitor 10 increases by increasing the input current of converter 20 and increasing the output current of converter 20.

The voltage of the DC bus capacitor 10 has a waveform as shown in FIG. Is in the ON state of the switching element 25, the time up to time _{t b} from time _{t a,} DC voltage of the bus capacitor 10 is 100V drop in time until _{t c} is the time _{t b,} the voltage of the DC bus capacitor 10 Has dropped 600V. The total drop voltage of the DC bus capacitor 10 is 700V. Assuming that the voltage allowed for the DC bus capacitor 10 is 650 V, the voltage drop of the DC bus capacitor 10 exceeds the allowable voltage (650 V) of the DC bus capacitor 10.

Unlike the present embodiment, the switching signal is a signal including one on-time pulse per cycle indicated by times t ₁ , t ₂ , and t ₃ , and is further turned on to obtain a drop voltage of 700V. When the time is set, the voltage of the DC bus capacitor 10 at time t ₁ , t ₂ , t ₃ becomes zero. When the voltage of the DC bus capacitor 10 becomes zero, the converter 20 cannot take an input current, and the output power of the converter 20 decreases.

  On the other hand, in the present embodiment, since the switching signal is generated so that there are a plurality of ON-time pulses per cycle, the voltage drop of the DC bus capacitor 10 per cycle is distributed according to the plurality of pulses. Thus, the width of the voltage ripple of the DC bus capacitor 10 is reduced, and the magnitude of the voltage ripple is suppressed to 650 V or less. Therefore, the voltage of DC bus capacitor 10 does not become zero, and the output reduction of converter 20 is suppressed.

Further, in the present embodiment, the width of the pulse signal from the time t _a to time t _b (of the present invention corresponds to the length of the "first on-period") is a pulse signal from the time t _b until the time t _c The width is set to be equal to or less than the width (corresponding to the length of the “second ON period” in the present invention). Therefore, the voltage of the DC bus capacitor 10, at the fall time of the pulse signal from the time t _b until the time t _c, it is possible to the lowest, it is possible to suppress the harmonic noise.

  Regarding the waveform of the switching signal, the number of pulses in the on period is not limited to two per cycle, and may be three or more. As a result, the width of the voltage ripple of the DC bus capacitor 10 can be further reduced, and higher power can be handled.

In the present invention, when determining the magnitude of the electrostatic capacity (C _dc ) of the DC bus capacitor 10, an optimum electrostatic capacity that does not cause a problem of harmonic noise by the method shown in the second embodiment. Set the capacity (C _dc ). At this time, the optimum value of the capacitance (C _dc ) is calculated on the assumption that the switching signal includes one ON period pulse per cycle. Thereby, in the predetermined output range of the converter 20, even if the converter 20 is driven by a switching signal including one pulse per cycle, the harmonic noise is suppressed to an allowable value or less. When the output power of the converter 20 exceeds a predetermined output range, the controller 100 drives the converter 20 with a switching signal including a plurality of pulses per cycle under the method shown in this embodiment. Thus, the output power can be increased while keeping the harmonic noise low while preventing the voltage of the DC bus capacitor from becoming zero.

<< 4th Embodiment >>
FIG. 10 is a circuit diagram of a non-contact power feeding system according to another embodiment of the invention. In this example, the configuration of the converter and a part of the control of the converter are different from the second embodiment described above. Other configurations and controls are the same as those of the second embodiment described above, and the descriptions of the first to third embodiments are incorporated as appropriate.

  Hereinafter, the structure different from 2nd Embodiment among the structures of the non-contact electric power feeding system which concerns on embodiment of this invention is demonstrated. The converter 30 includes switching elements 31 and 33, a diode 32, an inductor 34, reverse blocking switching elements 35 and 36, and a capacitor 37.

  The configuration of the reverse blocking switching elements 35 and 36 will be described with reference to FIG. FIG. 11 shows an example of a circuit of the reverse blocking switching elements 35 and 36. The reverse blocking switching elements 35 and 36 are configured by a semiconductor element such as an IGBT. The reverse blocking switching elements 35 and 36 are elements that conduct current only in one direction and do not conduct current in the reverse direction. For example, as shown in FIG. 11A, the reverse blocking switching element 35 includes diodes 35a and 35d and switching elements 35b and 35c. The diode 35a and the switching element 35b are connected in series with the current conduction direction being the same direction. The diode 35d and the switching element 35c are connected in series with the same direction of current conduction. A series circuit of the diode 35a and the switching element 35b and a series circuit of the diode 35d and the switching element 35c are connected in parallel with the current conduction directions being opposite to each other. In such a circuit, the controller 100 switches on / off of the switching element 35b while maintaining the switching element 35c in the off state, thereby switching the conduction and interruption of the current in only one direction and the current in the other direction. Shut off. Note that the circuit of the reverse blocking switching element 35 is not limited to the circuit shown in FIG. 11A, and may be the circuit shown in FIGS. 11B and 11C, or another circuit. Further, the reverse blocking switching elements 35 and 36 do not need to be constituted by a plurality of circuit elements as shown in FIGS. 11A to 11C, and may be a single element. Further, by using a high-speed element such as a MOSFET for the reverse blocking switching elements 35 and 36, switching loss can be reduced as compared with the reverse blocking IGBT.

  In FIG. 10, as shown in FIG. 11, the circuit of the reverse blocking switching elements 35 and 36 is represented by a circuit symbol of one transistor (IGBT). The collector terminals of the reverse blocking switching elements 35 and 36 shown in FIG. 10 are positive terminals in the current conduction direction, and the emitter terminals of the reverse blocking switching elements 35 and 36 are negative in the current conduction direction. It becomes a terminal.

  The drain terminal of the switching element 31 is connected to the positive input terminal 30 a of the converter 30, and the source terminal of the switching element 31 is connected to the connection point between one terminal of the inductor 34 and the cathode terminal of the diode 32. The anode terminal of the diode 32 is connected to the negative input terminal 30 b of the converter 30.

  One terminal of the inductor 34 is connected to a connection point between the source terminal of the switching element 31 and the cathode terminal of the diode 27, and the other terminal of the inductor 26 is connected to the drain terminal of the switching element 33. The drain terminal of the switching element 33 is connected to the connection point between the collector terminal of the reverse blocking switching element 35 and the emitter terminal of the reverse blocking switching element 36, and the source terminal of the switching element 33 is the other terminal of the capacitor 37. And the negative output terminal 30 d of the converter 30.

  The emitter terminal of the reverse blocking switching element 35 is connected to the drain terminal of the switching element 31 and the positive input terminal 30 a of the converter 30. The collector terminal of the reverse blocking switching element 35 is connected to the reverse blocking switching element 36. The collector terminal, the other terminal of the inductor 34, and the drain terminal of the switching element 33 are connected.

  The emitter terminal of the reverse blocking switching element 36 is connected to the positive output terminal 30 c of the converter 30 and one terminal of the capacitor 37. The collector terminal of the reverse blocking switching element 36 is connected to the reverse blocking switching element 35. The collector terminal, the other terminal of the inductor 34, and the drain terminal of the switching element 33 are connected. One terminal of the capacitor 37 is connected to the positive output terminal 30 c of the converter 30, and the other terminal of the capacitor 38 is connected to the negative output terminal 30 d of the converter 30.

  Next, the operation of the circuit of the non-contact power feeding system will be described with reference to FIGS. 12A and 12B. 12A and 12B are graphs for explaining voltage characteristics, current characteristics, and switching signal characteristics of the secondary circuit of the non-contact power feeding system according to the present invention. 12A and 12B, (a) shows the characteristics of the coil current of the secondary coil 6, (b) shows the characteristics of the input voltage of the bridge diode 9, and (c) shows the DC bus capacitor voltage (DC bus voltage). (D) shows the characteristic of the voltage of the inductor 34, (e) shows the characteristic of the switching signal of the switching elements 31 and 33, and (f) shows the characteristic of the switching signal of the reverse blocking type switching element 35. (G) shows the characteristic of the switching signal of the reverse blocking type switching element 36, and (h) shows the characteristic of the input current of the converter 30.

The input current of the secondary coil 6 has an AC waveform as shown in FIG. 12A (a), and the direction of current flow is reversed at times t ₁ , t ₂ , and t ₃ . Further, the polarity of the bridge diode 9 is also inverted at times t ₁ , t ₂ , and t ₃ (see FIG. 12A (b)). The phase synchronization circuit 110 generates a clock signal having a period determined by times t ₁ , t ₂ , and t ₃ and outputs the clock signal to the controller 100.

The controller 100 generates switching signals of the switching elements 31 and 33 having the falling edges at the times t ₁ , t ₂ , and t ₃ while synchronizing with the clock signal of the phase synchronization circuit 110, and the reverse blocking switching element 35 and A switching signal for each of the reverse blocking switching elements 36 is generated. The switching signals of the switching elements 31 and 33 have waveforms as shown in FIG. The switching signal of the switching element 31 and the switching signal of the switching element 33 have the same waveform. Therefore, the ON period of the switching element 31 corresponds to the ON period of the switching element 31, and the OFF period of the switching element 31 and the OFF period of the switching element 31 correspond to each other. The switching elements 31 and 33 are driven so that the periods and the off periods are synchronized.

  When the switching elements 31 and 33 are driven by the switching signal shown in FIG. 12B (e), the DC bus capacitor 10 and the inductor 34 are conducted during the ON period of the switching signal, and energy is stored in the inductor 34. Then, the energy accumulated in the inductor 34 is adjusted by adjusting the length of the ON period indicated by the switching signals of the switching elements 31 and 33.

  The diode 32 is a diode for circulating the current of the inductor 34 during the off period of the switching elements 31 and 33. When the switching elements 31 and 33 are turned off, the energy stored in the inductor 34 is released from the other terminal of the inductor 34. The switching element 33 is connected to the other terminal of the inductor 34. Since the switching element 33 is in the off state, the energy of the inductor 34 goes to the connection point of the reverse blocking switching elements 35 and 36. When the reverse blocking type switching element 35 is in the ON state, the energy of the inductor 34 is released to the input terminal side of the converter 30, and the amount of energy of the released inductor 34 is equal to that of the reverse blocking type switching element 35. It is adjusted in the on period. Further, when the reverse blocking type switching element 36 is in an ON state, the energy of the inductor 34 is released to the output terminal side of the converter 30, and the energy amount of the released inductor 34 is equal to that of the reverse blocking type switching element 36. It is adjusted in the on period.

The switching signals of the reverse blocking switching elements 35 and 36 are as shown in FIGS. 12B (f) and 12 (g). The switching signal of the reverse blocking type switching element 35 includes the switching elements 31 and 33 while the on period (between the time t _c and the time t ₃ ) of the switching elements 31 and 33 is the off period of the reverse blocking type switching element 35. off period (time t between ₂ to time t _c) in the contains the oN period of the reverse blocking switching element 35 (during the time t _a to time t _b).

In the switching signal of the reverse blocking switching element 36, the ON period (between time t _c and time t ₃ ) of the switching elements 31 and 33 is the OFF period of the reverse blocking switching element 36. In addition, the switching signal of reverse blocking switching element 36 is in the OFF period of the switching element 31, 33 (during the time _{t 2} to time _{t c),} reverse blocking ON period of the switching element 36 (time _{t 2} between to time t _a, and, by including between) from the time t _b until the time t _c, and, in the oFF period of the switching element 31 and 33, opposite the off period of the reverse blocking switching element 35 (during the time _{t 2} to time _{t a,} and, during the time _{t b} until the time _{t c)} elimination oN period of the switching element 36 to.

  That is, the ON period of the switching elements 31 and 33 is the OFF period of the reverse blocking switching elements 35 and 36. In addition, during the OFF period of the switching elements 31 and 33, one of the reverse blocking switching element 35 and the reverse blocking switching element 36 is in the ON period, and the other reverse blocking switching is performed. The elements 35 and 36 are in the off period.

When reverse blocking switching element 35 is turned on (during the time t _a to time t _b), the switching elements 31, 33 and reverse blocking switching element 36 is in the OFF state. When the energy stored in the inductor 34 is released to the input side of the converter 30, the switching elements 31 and 33 are turned off, so that one terminal of the inductor 34 (terminal on the diode 32 side) The potential of the negative input terminal is taken, and the other terminal of the inductor 34 (terminal on the switching element 33 side) takes the potential of the input terminal of the converter. Thereby, the energy of inductor 34 is released to the input side of converter 30.

(During the time _{t 2} to time _{t a,} and, during the time _{t b} until the time _{t c)} reverse blocking switching element 36 is in the on state, the switching elements 31, 33 and reverse blocking switching element 35 It is off. When the energy stored in the inductor 34 is released to the output side of the converter 30, the switching elements 31 and 33 are turned off, so that one terminal of the inductor 34 (terminal on the diode 32 side) The potential of the negative input terminal is taken, and the other terminal of the inductor 34 (terminal on the switching element 33 side) takes the potential of the positive input terminal. Thereby, the energy of inductor 34 is released to the output side of converter 30.

  Further, since the reverse blocking switching elements 35 and 36 are configured by elements that do not flow current in the reverse direction, when any one of the reverse blocking switching elements 35 and 36 is turned on, the input terminal 30a of the converter 30 is turned on. And the output terminal 30c can be prevented from being short-circuited.

  The controller 100 monitors the output power of the current sensor 15 and the voltage sensor 16 converter 30 and adjusts the ON period of the reverse blocking switching element 35 according to the output power. When the output power is reduced, the controller 100 increases the ON period of the reverse blocking switching element 35 as the output power decreases. Thereby, since the energy of the inductor 34 is not output from the converter 30, the output power is reduced.

The input current of the converter 30 has a waveform as shown in FIG. A period from time t _c to time t ₃ is a period in which the switching elements 31 and 33 are turned on and energy is accumulated in the inductor 34, and an input current flows so as to flow into the converter 30. On the other hand, the period of t _b from time t _a, reverse blocking switching element 35 is turned on, the energy stored in the inductor 34 is a period for emitting the input side of the converter 30, to flow back from the converter 30 Input current flows.

The voltage waveform of the DC bus capacitor 10 is as shown in FIG. 12A (c). Since a current flows from the DC bus capacitor 10 to the input side of the converter 30 from time t _c to t ₃ , a voltage drop of about 600 V occurs in the DC bus capacitor 10. Then, at time t ₃ is a timing of the reversal of polarity of the bridge diodes 9, the voltage of the DC bus capacitor 10 is reduced to 35V. Therefore, at time _{t 3,} as shown in FIG. 12A (b), the voltage fluctuation of the input bridge diode 9 can be suppressed to 70V is twice the 35V. Further, as shown in FIG. 12A (d), the voltage fluctuation of the secondary coil 6 can be suppressed to 70V. Thereby, harmonic noise can be reduced.

  By the way, when the output power of the converter 30 decreases during the operation of the converter 30, the current flowing from the DC bus capacitor 10 to the converter 30 decreases, and the voltage drop of the DC bus capacitor 10 decreases. If the voltage of the DC bus capacitor 10 is kept high at the polarity inversion timing of the bridge diode 9, harmonic noise of the secondary coil 6 becomes large.

In the present invention, as shown in FIG. 12B (h), current flows backward from the input terminal of the converter 30 toward the DC bus capacitor 10 between time t _a and time t _b , As shown, the voltage of the DC bus capacitor 10 is greatly increased. Therefore, even when the output power of converter 30 decreases, the voltage ripple of DC bus capacitor 10 can be increased, and the width of the voltage drop of DC bus capacitor 10 can be increased. Then, at time t ₃ is a timing of the polarity reversal of the bridge diode 9, the voltage of the DC bus capacitor 10 is low, harmonic noise of the secondary coil 6 is prevented. Thereby, even when the output power of converter 30 decreases, the effect of reducing harmonic noise can be obtained.

  As described above, according to the present invention, the switching elements 31 and 33 included in the converter 30 are driven as the switching elements for discharging the DC bus capacitor 10 and the switching element 31, The electric charge of the DC bus capacitor 10 is discharged through 33. Thereby, the amount of discharge from the DC bus capacitor 10 can be controlled by the conduction time of the switching elements 31 and 33. Further, the present invention can reduce the voltage fluctuation of the secondary coil 6 when the polarity of the bridge diode 9 is switched, and can suppress the harmonic noise of the secondary coil 6.

  In the present invention, the inductor 34 is connected to the switching elements 31 and 33. Thereby, the amount of energy stored in the inductor 34 from the DC bus capacitor 10 can be adjusted by the switching elements 31 and 33. Moreover, since the stored energy can be used for the output power of the converter 30, the efficiency of the circuit can be increased.

  In the present invention, the switching elements 31 and 33 are connected in series from the positive input terminal 30a of the converter 30 to the negative output terminal 30d. The amount of energy to be stored can be adjusted. In the present invention, the diode 32, the inductor 34, and the reverse blocking switching element 35 are connected in series from the negative input terminal 30b of the converter 30 to the positive input terminal 30a. Of the energy stored in the inductor 34, the amount of backflow to the input side of the converter 30 can be adjusted.

  In the present invention, the diode 32, the inductor 34, and the reverse blocking switching element 36 are connected in series from the negative input terminal 30b of the converter 30 to the positive output terminal 30c. Of the energy stored in 34, the amount to be released to the output side of the converter 30 can be adjusted.

In the present invention, when the magnitude of the capacitance (C _dc ) of the DC bus capacitor 10 is determined, harmonic noise is a problem in the predetermined output range of the converter 30 by the method shown in the second embodiment. An optimum capacitance (C _dc ) is set so as not to become. When the output power of the converter 30 is lower than the predetermined output range, the harmonic noise is kept low by returning the current from the input terminal of the converter 30 to the DC bus capacitor 10 by the method of this embodiment. The output power can be reduced while remaining.

  In the present invention, as in the third embodiment, the controller 100 adds pulses per cycle to generate switching signals of the switching elements 31 and 33 including a plurality of pulses per cycle, 30 may be driven. In a plurality of pulse periods (a period from the rising timing of the first pulse to the falling edge of the last pulse), the reverse blocking switching element 35 is always in an off state, and the reverse blocking switching element 36 is switched to the switching element 31. , 33 in the off period. As a result, the pulse width of the input current of converter 30 is shortened, so that the voltage ripple generated in DC bus capacitor 10 is reduced. And it can control so that the output electric power of converter 30 becomes high, preventing the voltage of DC bus capacitor 10 becoming zero.

In the present invention, when the control is performed using the additional pulse as in the third embodiment as described above, the capacitance C _dc of the DC bus capacitor 10 is calculated using the intermediate value of the required output power range. To do. In addition, when it is desired to reduce the actual output power rather than the output power used for the calculation of the capacitance C _dc, the pulse width included in the switching signal of the reverse blocking switching element 35 is increased to increase the actual output power. If desired, the reverse blocking switching element 35 is turned off, and the pulse width of the on period of the switching elements 31 and 33 is divided as described above (additional pulses are added). As a result, converter 30 can cope with a wider range of received power.

  The switching element 31 corresponds to the “first switching element” of the present invention, the switching element 33 corresponds to the “second switching element” of the present invention, and the reverse blocking type switching element 35 corresponds to the “first reverse element” of the present invention. The reverse blocking type switching element 36 corresponds to the “second blocking type switching element” of the present invention.

<< 5th Embodiment >>
FIG. 13 is a circuit diagram of a non-contact power feeding system according to another embodiment of the invention. In this example, the configuration of the converter and a part of the control of the converter are different from the above-described fourth embodiment. Other configurations and controls are the same as those of the fourth embodiment described above, and the descriptions of the first to fourth embodiments are incorporated as appropriate.

  Hereinafter, the structure different from 4th Embodiment among the structures of the non-contact electric power feeding system which concerns on embodiment of this invention is demonstrated. The converter 40 includes a coupled inductor (transformer) 41, a switching element 42, a diode 43, reverse blocking switching elements 44 and 45, and a capacitor 46. The coupled inductor 41 includes a coil 41a and a coil 41b that can be magnetically coupled. The winding directions of the coil 41a and the coil 41b are opposite to each other.

  One terminal of the coil 41 a is connected to the positive input terminal 40 a of the converter 40, and the other terminal of the coil 41 b is connected to the drain terminal of the switching element 42. One terminal of the coil 41 b is connected to a connection point between the collector terminal of the reverse blocking switching element 44 and the emitter terminal of the reverse blocking switching element 45, and the other terminal of the coil 41 b is connected to the cathode terminal of the diode 43. It is connected.

  The source terminal of the switching element 42 is connected to the positive input terminal 40 a of the converter 40. The cathode terminal of the diode 43 is connected to the source terminal of the switching element 42, the other terminal of the capacitor 46, and the output terminal 40 d of the converter 40.

  The emitter terminal of the reverse blocking switching element 44 is connected to one terminal of the coil 41 a and the positive input terminal 40 a of the converter 40, and the collector terminal of the reverse blocking switching element 44 is connected to the reverse blocking switching element 45. The collector terminal and one terminal of the coil 41b are connected.

  The emitter terminal of the reverse blocking switching element 45 is connected to the positive output terminal 40 c of the converter 30 and one terminal of the capacitor 46, and the collector terminal of the reverse blocking switching element 45 is connected to the reverse blocking switching element 44. The collector terminal and the other terminal of the coil 41b are connected. One terminal of the capacitor 46 is connected to the positive output terminal 40 c of the converter 30, and the other terminal of the capacitor 46 is connected to the negative output terminal 40 d of the converter 40.

  The operation of the circuit of the non-contact power feeding system of the present invention is the same as the operation of the circuit of the non-contact power feeding system according to the fourth embodiment. The switching signal of the switching element 42 is the same as the switching signal of the switching elements 31 and 33 according to the fourth embodiment. Further, the switching signal of the reverse blocking switching element 44 is the same as the switching signal of the reverse blocking switching element 35, and the switching signal of the reverse blocking switching element 45 is the same as the switching signal of the reverse blocking switching element 36. is there.

  As described above, according to the present invention, the switching element 42 included in the converter 40 is driven as a switching element for discharging the DC bus capacitor 10, and the DC bus is switched through the switching element 42 before the polarity of the bridge diode 9 is switched. The electric charge of the capacitor 10 is discharged. Thereby, the amount of discharge from the DC bus capacitor 10 can be controlled by the conduction time of the switching element 42. Further, the present invention can reduce the voltage fluctuation of the secondary coil 6 when the polarity of the bridge diode 9 is switched, and can suppress the harmonic noise of the secondary coil 6. In addition, the present invention can reduce the cost because only one switching element for discharging is required.

  In the present invention, the coil 41a and the switching element 42 are connected in series from the positive input terminal 40a of the converter 40 to the negative input terminal 40b. Thereby, the amount of energy stored in the coupled inductor 41 can be adjusted by turning the switching element 42 on and off. Further, in the present invention, the diode 43, the coil 41b, and the reverse blocking switching element 44 are connected in series from the negative input terminal 40b of the converter 40 to the positive input terminal 40a. Thus, the amount of energy flowing back to the input side of the converter 40 out of the energy stored in the coupling inductor 41 by turning on and off the reverse blocking switching element 44 can be adjusted.

  In the present invention, the diode 43 and the coil 41b are connected in series from the negative output terminal 40d of the converter 40 to the positive output terminal 40c. Thereby, the energy accumulated in the coupled inductor 41 can be released to the output side.

  The above switching element 42 corresponds to the “discharging switching element” of the present invention, the reverse blocking type switching element 44 corresponds to the “first reverse blocking type switching element” of the present invention, and the reverse blocking type switching element 45 corresponds to the present invention. This corresponds to the “second reverse blocking switching element” of the invention.

<< 6th Embodiment >>
FIG. 14 is a circuit diagram of a non-contact power feeding system according to another embodiment of the invention. In this example, the configuration of the converter and a part of the control of the converter are different from the second embodiment described above. Other configurations and controls are the same as those of the second embodiment described above, and the descriptions of the first to fifth embodiments are incorporated as appropriate.

  Hereinafter, the structure different from 2nd Embodiment among the structures of the non-contact electric power feeding system which concerns on embodiment of this invention is demonstrated. The converter 50 includes switching elements 51 and 54, a diode 52, an inductor 53, a reverse blocking switching element 55, and a capacitor 56. Converter 50 is a step-down converter.

  The drain terminal of the switching element 51 is connected to the positive input terminal 50 a of the converter 50, and the source terminal of the switching element 51 is connected to the cathode terminal of the diode 52 and one terminal of the inductor 53. The cathode terminal of the diode 52 is connected to the connection point between the source terminal of the switching element 51 and one terminal of the inductor 53.

  The other terminal of the inductor 53 is connected to the drain terminal of the switching element 54 and the collector terminal of the reverse blocking type switching element 55. The drain terminal of the switching element 54 is connected to the other terminal of the inductor 53 and the collector terminal of the reverse blocking switching element 55, and the source terminal of the switching element 54 is one terminal of the capacitor 56 and the positive terminal of the converter 50. It is connected to the output terminal 50c.

  The emitter terminal of the reverse blocking switching element 55 is connected to the connection point between the positive input terminal 50 a of the converter 50 and the drain terminal of the switching element 51. The collector terminal of the reverse blocking switching element 55 is connected to the inductor 53. It is connected to the connection point between the other terminal and the drain terminal of the switching element 54. One terminal of the capacitor 56 is connected to the positive output terminal 50 c of the converter 50, and the other terminal of the capacitor 56 is connected to the negative output terminal 50 d of the converter 50.

  Next, the operation of the circuit of the non-contact power feeding system will be described with reference to FIGS. 15A and 15B. 15A and 15B are graphs for explaining voltage characteristics, current characteristics, and switching signal characteristics of the secondary circuit of the non-contact power feeding system according to the present invention. 15A and 15B, (a) shows the characteristics of the coil current of the secondary coil 6, (b) shows the characteristics of the input voltage of the bridge diode 9, and (c) shows the DC bus capacitor voltage (DC bus voltage). (D) shows the voltage characteristic of the inductor 53, (e) shows the switching signal characteristic of the switching element 51, and (f) shows the switching signal characteristic of the reverse blocking switching element 55. , (G) shows the characteristics of the switching signal of the switching element 54, and (h) shows the characteristics of the input current of the converter 50.

The input current of the secondary coil 6 has an AC waveform as shown in FIG. 15A (a), and the direction of current flow is reversed at times t ₁ , t ₂ , and t ₃ . Further, the polarity of the bridge diode 9 is also inverted at times t ₁ , t ₂ , and t ₃ (see FIG. 15A (b)). The phase synchronization circuit 110 generates a clock signal having a period determined by times t ₁ , t ₂ , and t ₃ and outputs the clock signal to the controller 100.

The controller 100 generates a switching signal of the switching element 51 having the falling edges at times t ₁ , t ₂ , and t ₃ while synchronizing with the clock signal of the phase synchronization circuit 110, and the reverse blocking switching element 55 and the switching element 51 switching signals are generated.

The switching signal of the switching element 51 and the switching signal of the switching element 54 have waveforms as shown in FIGS. 15B (e) and 15 (g), respectively.
When the switching elements 51 and 54 are driven by the switching signals shown in FIGS. 15B (e) and 15 (f), the DC bus capacitor 10 and the inductor 53 are electrically connected during the ON period of the switching signals of the switching elements 51 and 54. Then, energy is stored in the inductor 53. Then, the energy accumulated in the inductor 53 is adjusted by adjusting the length of the ON period indicated by the switching signal of the switching element 51.

The diode 52 is a diode for circulating the current of the inductor 34 during the OFF period of the switching element 51. When the switching element 51 is turned off, the energy stored in the inductor 34 is released from the other terminal of the inductor 53. The other terminal of the inductor 34, although the reverse blocking type switching element 55 and switching element 54 is connected, at time t _2, the reverse blocking switching element 55 is turned off, the switching element 54 is turned on It is in a state. Therefore, the energy of inductor 53 is released to positive output terminal 50 c of converter 50. The amount of energy of the inductor 34 that is released is adjusted by the ON period of the switching element 54.

After a time t _2, the switching element 54 is turned off at time t _a, reverse blocking switching element 55 is turned on. Therefore, the current output from the other terminal of the inductor 53 flows from the switching element 54 to the reverse blocking switching element 55 while changing the conduction direction. Therefore, the energy of the inductor 53 is released to the positive input terminal 50 a of the converter 50, and the amount of energy of the released inductor 53 is adjusted in the ON period of the reverse blocking switching element 55.

The switching signal of the switching element 54 is an off period of the switching element 51 (from time t ₂ to time t ₂ ) while an on period of the switching element 51 is set to an on period of the switching element 51 (between time t _c and time t ₃ ). during) of up to _c, and includes an off period of the reverse blocking switching element 55 (during the time t _a to time t _b).

Switching signals reverse blocking switching element 55, the OFF period of the switching element 54 (during the time t _a to time t _b), the ON period of the reverse blocking switching element 55, the ON period (time of the switching element 54 between t ₂ to time _{t a,} and, between) from the time _{t b} until the time _{t c,} the off period of the reverse blocking switching element 55.

  That is, the ON period of the switching element 51 is the ON period of the switching element 54 and the OFF period of the reverse blocking switching element 55. Further, during the OFF period of the switching element 51, one of the switching element 54 and the reverse blocking switching element 55 is in the ON period, and the other switching element is in the OFF period. Further, the switching element 51 and the reverse blocking type switching element 55 are not simultaneously turned on.

When reverse blocking switching element 55 is turned on (during the time t _a to time t _b), the switching element 51 and switching element 54 is in the OFF state. When the energy stored in the inductor 53 is released to the input side of the converter 50, the switching elements 51 and 54 are in an off state, so that one terminal of the inductor 34 (terminal on the diode 52 side) The potential of the negative input terminal is taken, and the other terminal (terminal on the switching element 54 side) of the inductor 53 takes the potential of the positive input terminal of the converter 50. Thereby, the energy of inductor 53 is released to the input side of converter 30.

(During the time t ₂ to time t _a, and, during the time t _b until the time t _d) when the switching element 54 is on, reverse blocking switching element 55 is in the OFF state. When the energy stored in the inductor 53 is released to the output side of the converter 50, the reverse blocking type switching element 55 is in the OFF state, so that the other terminal of the inductor 53 (the terminal on the switching element 54 side) is positive. Take the output terminal potential. Thereby, the energy of inductor 53 is released to the output side of converter 50.

  Since the reverse blocking type switching element 55 is composed of an element that does not flow current in the reverse direction, when the switching element 54 is turned on, the input terminal 50a and the output terminal 50c of the converter 50 are short-circuited. Can be prevented.

The input current of the converter 50 has a waveform as shown in FIG. A period from time t _c to time t ₃ is a period in which the switching elements 51 and 54 are turned on and the DC bus capacitor 10 is discharged, and an input current flows into the converter 50 so as to flow. On the other hand, the period of t _b from time t _a, reverse blocking switching element 55 is turned on, the energy stored in the inductor 53 is a period for emitting the input side of the converter 50, to flow back from the converter 50 Input current flows.

The voltage waveform of the DC bus capacitor 10 is as shown in FIG. 15A (c). Since a current flows from the DC bus capacitor 10 to the input side of the converter 50 from time t _c to t ₃ , a voltage drop of about 560 V occurs in the DC bus capacitor 10. Then, at time t ₃ is a timing of the reversal of polarity of the bridge diodes 9, the voltage of the DC bus capacitor 10 is reduced to 30 V. Therefore, at time _{t 3,} as shown in FIG. 15A (b), the voltage fluctuation of the input bridge diode 9 can be suppressed to 60V is twice the 30 V. Further, as shown in FIG. 15A (d), the voltage fluctuation of the secondary coil 6 can be suppressed to 60V. Thereby, harmonic noise can be reduced.

  By the way, when the output power of the converter 50 decreases during the operation of the converter 50, the current flowing from the DC bus capacitor 10 to the converter 50 decreases, and the voltage drop of the DC bus capacitor 10 decreases. If the voltage of the DC bus capacitor 10 is kept high at the polarity inversion timing of the bridge diode 9, harmonic noise of the secondary coil 6 becomes large.

In the present invention, as shown in FIG. 15B (h), between the time _{t a} at time _{t b,} since the current flowing back toward the input terminal of the converter 50 to the DC bus capacitor 10, FIG. 15A (c) As shown, the voltage of the DC bus capacitor 10 is greatly increased. Therefore, even when the output power of converter 50 decreases, the voltage ripple of DC bus capacitor 10 can be increased, and the width of the voltage drop of DC bus capacitor 10 can be increased. Then, at time t ₃ is a timing of the polarity reversal of the bridge diode 9, the voltage of the DC bus capacitor 10 is low, harmonic noise of the secondary coil 6 is prevented. Thereby, even when the output power of converter 50 decreases, the effect of reducing harmonic noise can be obtained.

  As described above, according to the present invention, the switching elements 51 and 54 included in the converter 50 are driven as the switching elements for discharging the DC bus capacitor 10 and the switching element 51, The electric charge of the DC bus capacitor 10 is discharged through 54. Thereby, the amount of discharge from the DC bus capacitor 10 can be controlled by the conduction time of the switching elements 51 and 54. Further, the present invention can reduce the voltage fluctuation of the secondary coil 6 when the polarity of the bridge diode 9 is switched, and can suppress the harmonic noise of the secondary coil 6.

  In the present invention, the switching element 51, the inductor 53, and the switching element 54 are connected in series from the positive input terminal 30a of the converter 30 to the negative output terminal 30d. The amount of energy stored in the inductor 53 can be adjusted. In the present invention, the diode 52, the inductor 53, and the reverse blocking switching element 55 are connected in series from the negative input terminal 50b of the converter 50 to the positive input terminal 50a. Thus, the amount of the energy stored in the inductor 53 that flows back to the input side of the converter 50 can be adjusted.

  In the present invention, since the diode 52, the inductor 53, and the switching element 54 are connected in series from the negative input terminal 50b of the converter 50 to the positive output terminal 50c, they are accumulated in the inductor 53 by the switching element 54. The amount of energy released to the output side of the converter 50 can be adjusted.

  Further, since the present invention uses the step-down converter, the efficiency of the converter 50 can be increased when the voltage of the load 17 is lower than the voltage of the DC bus capacitor 10.

In the present invention, when determining the magnitude of the electrostatic capacitance (C _dc ) of the DC bus capacitor 10, harmonic noise is a problem in the predetermined output range of the converter 50 by the method shown in the second embodiment. An optimum capacitance (C _dc ) is set so as not to become. When the output power of the converter 50 is lower than the predetermined output range, the harmonic noise is kept low by returning the current from the input terminal of the converter 50 to the DC bus capacitor 10 by the method of the present embodiment. The output power can be reduced while remaining.

  In the present invention, as in the third embodiment, the controller 100 adds a pulse per cycle to generate a switching signal of the switching element 51 including a plurality of pulses per cycle, and It may be driven. In a plurality of pulse periods (a period from the rising timing of the first pulse to the falling edge of the last pulse), the reverse blocking switching element 55 is always in the OFF state, and the switching element 54 is in the OFF period of the switching element 51. Then, it is turned on. As a result, the pulse width of the input current of converter 50 is shortened, so that the voltage ripple generated in DC bus capacitor 10 is reduced. And it can control so that the output electric power of converter 50 becomes high, preventing the voltage of DC bus capacitor 10 becoming zero.

In the present invention, when the control is performed using the additional pulse as in the third embodiment as described above, the capacitance C _dc of the DC bus capacitor 10 is calculated using the intermediate value of the required output power range. To do. Further, when it is desired to reduce the actual output power rather than the output power used for the calculation of the capacitance C _dc, the pulse width included in the switching signal of the reverse blocking switching element 55 is increased to increase the actual output power. In order to achieve this, the reverse blocking switching element 55 is turned off, and the pulse width of the on period of the switching element 51 is divided as described above (additional pulses are added). Thus, converter 50 can cope with a wider received power range.

DESCRIPTION OF SYMBOLS 12 ... Switching element 13 ... Resistance 20, 30, 40, 50 ... Converter 21, 26, 53 ... Inductor 22, 25, 31, 33, 42 ... Switching element 23, 27, 32, 43 ... Diode 35, 36, 44, 45, 51, 54, 55 ... reverse blocking type switching element 41 ... coupled inductor 41a, 41b ... coil 100 ... controller 110 ... phase synchronization circuit

Claims (17)

A power receiving coil that receives power supplied in a non-contact manner from a power transmitting coil connected to a power source;
A resonant circuit including a resonant capacitor connected in series to the power receiving coil;
A rectifier that rectifies AC power input from the resonant circuit;
A smoothing capacitor connected between output terminals of the rectifier and charged by a current output from the rectifier;
A discharge switching element connected between the smoothing capacitor and a load;
Control means for controlling the switching element for discharge,
The non-contact power feeding apparatus according to claim 1, wherein the control unit discharges the electric charge of the smoothing capacitor through the discharge switching element by a timing at which the polarity of the rectifier is switched. In the non-contact electric power feeder of Claim 1,
The discharge switching element and the inductor, connected between the smoothing capacitor and the load, comprising a converter that converts the voltage of the smoothing capacitor by a switching operation and outputs the converted voltage to the load,
The non-contact power feeding apparatus, wherein the inductor is connected to the discharge switching element. In the non-contact electric power feeder of Claim 1 or 2,
A converter that is connected between the smoothing capacitor and the load, converts a voltage of the smoothing capacitor by a switching operation, and outputs the converted voltage to the load;
A non-contact power feeding apparatus, wherein the smoothing capacitor satisfies the following formula A.

(Where C _ds indicates the capacity of the smoothing capacitor, P _out indicates the rated output power of the converter, T _s indicates the switching period of the converter, and D indicates the duty ratio of the switching operation of the converter. , V _avg represents the average voltage of the smoothing capacitor.) In the non-contact electric power feeder of any one of Claims 1-3,
First voltage measuring means for measuring an AC voltage on the input side of the rectifier;
A phase synchronization circuit that generates a clock signal having a frequency obtained by doubling the frequency of the AC voltage;
The non-contact power feeding apparatus according to claim 1, wherein the control means generates a switching signal of the discharge switching element synchronized with the clock signal. In the non-contact electric power feeder of any one of Claims 1-4,
Second voltage measuring means for measuring the voltage of the smoothing capacitor;
The control means includes
Calculating an average voltage of the measured voltage of the smoothing capacitor measured by the second voltage measuring means;
The on-period of the discharge switching element is set so that the voltage of the smoothing capacitor at the timing of switching the polarity of the rectifier becomes a value obtained by multiplying the average voltage by a predetermined coefficient,
The non-contact power feeding apparatus according to claim 1, wherein the predetermined coefficient is a positive value smaller than 1. In the non-contact electric power feeder of any one of Claims 1-5,
A converter that is connected between the smoothing capacitor and the load, converts the voltage of the smoothing capacitor by a switching operation, and outputs the converted voltage to the load;
A resistor connected in series with the discharge switching element,
The contactless power supply device, wherein the discharge switching element and the resistor are connected between the smoothing capacitor and the converter. In the non-contact electric power feeder of any one of Claims 1-5,
The discharge switching element, a diode, and an inductor, connected between the smoothing capacitor and the load, and includes a converter that converts the voltage of the smoothing capacitor by a switching operation and outputs the converted voltage to the load.
The discharge switching element has a high potential side terminal connected to the positive input terminal of the converter,
The diode has an anode terminal connected to a positive output terminal of the converter, a cathode terminal connected to a low potential side terminal of the discharge switching element,
The inductor has one terminal connected to a connection point between the discharging switching element and the diode, and the other terminal connected to a negative input terminal of the converter. In the non-contact electric power feeder of any one of Claims 1-5,
A converter that is connected between the smoothing capacitor and the load, converts a voltage of the smoothing capacitor by a switching operation, and outputs the converted voltage to the load;
The converter is
A first switching element and a second switching element included in the switching element for discharge; a first reverse blocking switching element and a second reverse blocking switching element that do not conduct current in the reverse direction; a diode; and an inductor. And
The first switching element has a high potential side terminal connected to a positive input terminal of the converter, a low potential side terminal connected to a cathode terminal of the diode,
The diode connects the anode terminal to the negative input terminal of the converter;
The inductor has one terminal connected to a connection point between the low potential side terminal of the first switching element and the cathode terminal of the diode, and the other terminal connected to the high potential side terminal of the second switching element. And
The second switching element has a low potential side terminal connected to the negative output terminal of the converter,
The first reverse blocking switching element has a negative terminal connected to a positive input terminal of the converter in a current conduction direction, and a positive terminal connected to the other terminal of the inductor in the current conduction direction. Connect to the connection point with the terminal on the high potential side of the second switching element,
The second reverse blocking type switching element connects a positive terminal in a current conduction direction to a connection point between the other terminal of the inductor and a high potential side terminal of the second switching element to conduct current. A non-contact power feeding apparatus, wherein a negative terminal in a direction is connected to a positive output terminal of the converter. In the non-contact electric power feeder of Claim 8,
The control means includes
A first switching signal for driving the first switching element and the second switching element in correspondence with an ON period of the first switching element and an ON period of the second switching element;
A second switching signal for driving the first reverse blocking switching element;
Generating a third switching signal for driving the second reverse blocking switching element,
The second switching signal is:
The ON period of the first switching signal is an OFF period of the first reverse blocking switching element, and the ON period of the first reverse blocking switching element is included in the OFF period of the first switching signal;
The third switching signal is:
The ON period of the first switching signal is the OFF period of the second reverse blocking switching element, and the ON period of the first reverse blocking switching element is the second reverse blocking within the OFF period of the first switching signal. And the off period of the first reverse blocking switching element is the on period of the second reverse blocking switching element within the off period of the first switching signal. Non-contact power feeding device. In the non-contact electric power feeder of any one of Claims 1-5,
A converter that is connected between the smoothing capacitor and the load, converts a voltage of the smoothing capacitor by a switching operation, and outputs the converted voltage to the load;
The converter is
The discharge switching element includes a first reverse blocking switching element and a second reverse blocking switching element that do not conduct current in the reverse direction, a first winding and a second winding forming a transformer, and a diode. And
The discharging switching element has a low potential side terminal connected to the negative input terminal of the converter,
The first winding has one terminal connected to the positive input terminal of the converter, and the other terminal connected to a high potential side terminal of the discharge switching element,
The second winding connects the other terminal to the cathode terminal of the diode;
The diode connects the anode terminal to the negative output terminal of the converter;
The first reverse blocking switching element has a negative terminal connected to a positive input terminal of the converter in a current conduction direction, and a positive terminal connected to one terminal of the second winding in a current conduction direction. Connected to
The second reverse blocking switching element connects a positive terminal in the current conduction direction to the one terminal of the second winding, and a negative terminal in the current conduction direction as a positive output of the converter. A non-contact power feeding device connected to a terminal. In the non-contact electric power feeder of Claim 10,
The control means includes
A first switching signal for driving the discharge switching element;
A second switching signal for driving the first reverse blocking switching element;
Generating a third switching signal for driving the second reverse blocking switching element,
The second switching signal is:
The ON period in which the discharge switching element is turned on is the OFF period in which the first reverse blocking switching element is turned off, and the first reverse blocking switching is performed within the OFF period of the first switching signal. Including the on-time of the device,
The third switching signal is:
The ON period of the first switching signal is the OFF period of the second reverse blocking switching element, and the ON period of the first reverse blocking switching element is the second reverse blocking within the OFF period of the first switching signal. And the off period of the first reverse blocking switching element is the on period of the second reverse blocking switching element within the off period of the first switching signal. Non-contact power feeding device. The contactless power supply device according to claim 9 or 11,
The control means includes
A non-contact power feeding apparatus, wherein an ON period of the first reverse blocking switching element is adjusted according to output power of the converter. In the non-contact electric power feeder of any one of Claims 1-5,
A converter that is connected between the smoothing capacitor and the load, converts a voltage of the smoothing capacitor by a switching operation, and outputs the converted voltage to the load;
The converter is
A first switching element and a second switching element included in the discharge switching element; a reverse blocking switching element that does not conduct current in the reverse direction; a diode; and an inductor;
The first switching element has a low-side terminal connected to a positive input terminal of the converter and a high-potential side terminal connected to a cathode terminal of the diode;
The diode connects the anode terminal to the negative input terminal of the converter;
The inductor has one terminal connected to a connection point between a high-potential side terminal of the first switching element and a cathode terminal of the diode;
The second switching element has a high potential side terminal connected to the other terminal of the inductor, a low potential side terminal connected to a positive output terminal of the converter,
The reverse blocking switching element connects a positive terminal in a current conduction direction to a connection point between the other terminal of the inductor and a low potential terminal of the second switching element, and in a current conduction direction. A non-contact power feeding apparatus, wherein a negative terminal is connected to a low potential terminal of the first switching element. The contactless power supply device according to claim 13,
The control means includes
A first switching signal for driving the first switching element;
A second switching signal for driving the second switching element;
Generating a third switching signal for driving the reverse blocking switching element,
The first switching signal is:
An on period for turning on the first switching element; and an off period for turning off the first switching element;
The second switching signal is:
The ON period of the first switching signal is an ON period in which the second switching element is turned ON, and the OFF period in which the second switching element is turned OFF within the OFF period of the first switching signal is included. ,
The third switching signal is:
The non-contact power feeding apparatus, wherein an off period of the second switching signal is an on period of the reverse blocking switching element, and an on period of the second switching signal is an off period of the reverse blocking switching element. In the non-contact electric power feeder of Claim 14,
The control means includes
A non-contact power feeding apparatus that adjusts an ON period of the reverse blocking switching element according to output power of the converter. The contactless power supply device according to any one of claims 7, 8, 10, and 13,
The switching signal for driving the discharging switching element includes a first on period of the discharging switching element and a second on period of the discharging switching element after the first on period with respect to one cycle,
The control means includes
The non-contact power feeding apparatus, wherein the first on-period is adjusted according to output power of the converter. The contactless power supply device according to claim 16, wherein
The length of the first on period is equal to or shorter than the length of the second on period.

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