JP6295540B2 - Lighting device and lighting apparatus - Google Patents

Description

The present invention relates to a lighting device and a lighting fixture .

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1, a technique for lighting control of an LED in a flyback type switching lighting device has been found. Specifically, in Patent Document 1, when performing LED lighting control with a single converter circuit, a technique for performing constant current control of LEDs by suppressing harmonic currents generally required for LED lighting fixtures is seen. Has been issued. Further, as disclosed in, for example, Patent Document 2 and Patent Document 3, a technique for dimming lighting control of an LED is known.

JP 2009-134945 A JP 2012-104367 A

  In recent years, demands for energy saving and power saving have increased, and it is an important issue to reduce useless lighting in lighting fixtures. While light-emitting diodes (hereinafter also referred to as LEDs) with excellent energy saving performance are being promoted, various technical developments are also underway for lighting devices that control lighting of these LEDs.

  In a switching power supply using a single converter circuit such as a flyback power supply, a secondary zero current is generally detected to improve efficiency as in the ringing choke converter system for higher efficiency. . However, there is a limit to the operating frequency of the switching power supply, and there is a problem that it is difficult to perform sufficient dimming control on an input power supply over a wide range (for example, a range of AC100V to AC254V or the like). For this reason, there is a limit to the brightness that can be selected by the user, and there has been a demand for the realization of a lighting fixture with a higher degree of freedom in brightness.

SUMMARY An advantage of some aspects of the invention is that it provides a lighting device and a lighting fixture with an increased degree of freedom in brightness that can be selected by a user.

The lighting device according to the present invention is
A converter comprising an inductor element and a switching element, wherein the converter stores the energy stored in the inductor element when the switching element is on;
A detection resistor for detecting a current flowing in a light emitting diode connected to the output side of the converter;
A comparator that switches an output according to a comparison result between a target value determined according to a specified dimming rate and a detection value of the detection resistor;
When the release of the energy stored in the inductor element is detected, the switching element is turned on after a delay time determined according to the target value elapses, and the switching element is turned off after an on time elapses according to the output of the comparator. A control circuit and
Equipped with a,
Over the lower limit from the upper limit value of the target value, the delay time is characterized that you continuously changes with a change in the target value.

The lighting apparatus according to the present invention is
A lighting device according to the present invention;
A light emitting element that is turned on by the lighting device;
It is characterized by providing.

  According to the present invention, the degree of freedom in brightness that the user can select increases.

It is a circuit diagram which shows the lighting device concerning embodiment of this invention, and the integrated circuit used for this. It is a wave form diagram which shows the operation | movement implement | achieved in the lighting device concerning embodiment of this invention, and the integrated circuit used for this. It is a wave form diagram which shows the operation | movement implement | achieved in the lighting device concerning embodiment of this invention, and the integrated circuit used for this. It is a circuit diagram of the light control signal conversion circuit used for the lighting device concerning embodiment of this invention. It is a graph which shows the relationship between the target value memorize | stored in the lighting device concerning embodiment of this invention, and the integrated circuit used for this, and delay time.

  FIG. 1 is a circuit diagram showing a lighting device according to an embodiment of the present invention and an integrated circuit used therefor. The lighting device according to the embodiment includes a rectifier circuit DB1 connected to an AC power supply AC and a DC power supply circuit 1 connected to the rectifier circuit DB1. The rectifier circuit DB1 is a diode bridge, and receives an AC power supply AC and converts the AC voltage into a pulsating DC voltage (hereinafter also referred to as a rectified voltage). The DC power supply circuit 1 supplies a constant current to the connected light emitting diode LA. The lighting device according to the present embodiment further includes a starting resistor R1 for starting and operating the DC power supply circuit 1, and this starting resistor R1 generates a control power supply.

  The DC power supply circuit 1 is a so-called flyback converter type constant current circuit. The DC power supply circuit 1 includes an electrolytic capacitor C10 (hereinafter also referred to as a smoothing capacitor C10), a transformer TR, a MOSFET Q1, a lighting control circuit IC1 that controls on / off of the MOSFET Q1, and a detection resistor R10 that detects an LED current. . The lighting control circuit IC1 includes a control power supply terminal S1, a zero cross detection terminal S2, a drive terminal S3, an on time detection terminal S4, and a delay time detection terminal S5.

  The transformer TR includes a primary winding T1, a secondary winding T2, and an auxiliary winding T3. The secondary winding T2 is a main secondary winding that generates a voltage according to the winding ratio with the primary winding T1. The auxiliary winding T3 is a secondary winding that generates a voltage proportional to the secondary winding T2. The secondary winding T2 is connected to the diode D10, and the high frequency voltage generated in the secondary winding T2 is smoothed by C10 and supplied to the light emitting diode LA.

  The starting resistor R1 has one end connected between the output side of the rectifier circuit DB1 and the primary winding T1 of the transformer TR, and the other end connected to the control power supply terminal S1 of the lighting control circuit IC1. When the AC power supply AC is input, the control power is supplied to the lighting control circuit IC1 through the starting resistor R1.

  The zero cross detection terminal S2 of the lighting control circuit IC1 is connected to the auxiliary winding T3 via the diode D1 and the resistor R2. Specifically, one end of the resistor R2 is connected to the auxiliary winding T3 of the transformer TR, the anode of the diode D1 is connected to the other end of the resistor R2, and the cathode of the diode D1 is connected to the zero cross detection terminal S2. ing. The resistor R2 suppresses the current from the auxiliary winding T3. The voltage generated in the auxiliary winding T3 can be detected by the zero cross detection terminal S2, and the timing at which the MOSFET Q1 should be turned on can be detected.

  A voltage proportional to the LED current and the resistance value of the detection resistor R10 is generated in the detection resistor R10 that detects the LED current. The voltage generated in the detection resistor R10 is input to the comparator OP1 in which the LED current is constant-current controlled via the control resistor R20. A target value V1 for setting the LED current flowing through the light emitting diode LA is input to the other end of the input side of the comparator OP1.

  The output of the comparator OP1 is connected to the lighting control circuit IC1 through the control resistor R23. The lighting control circuit IC1 determines the ON time of the MOSFET Q1 based on the output voltage of the comparator OP1, and turns on the MOSFET Q1 for the ON time.

  The lighting control circuit IC1 controls the DC power supply circuit 1 so that the target value V1 and the voltage generated at the detection resistor R10 match. Between the LED current detection terminal and the output terminal of the comparator OP1, a resistor R21 and a capacitor C21 that cause a delay in the response of the comparator OP1 are connected.

  The off time of the MOSFET Q1 is determined by detecting the voltage generated in the auxiliary winding T3, and the on time of the MOSFET Q1 is determined by the output voltage of the comparator OP1. By changing the target value V1 input to the comparator OP1, the LED current can be changed and the dimming control can be performed.

  By reducing the capacitance of the capacitor C1, the following effects can be obtained. A full-wave rectified pulsating voltage is applied across the capacitor C1. The power factor of the AC power supply can be increased by switching the pulsating voltage with the primary winding T1 of the transformer TR and the MOSFET Q1.

  However, the voltage and phase output from the secondary winding T2 of the transformer TR are different. Therefore, the feedback speed on the so-called constant current feedback detection loop (path from R10 → R20 → R21 → C21 → R23 → lighting control circuit IC1) from the detection resistor R10 to the lighting control circuit IC1 (on-time detection) It is necessary to be slower than the full-wave rectification period.

  For example, when the feedback speed through the detection loop is faster than the full-wave rectification period, when the input voltage is in a high phase and the LED current detection is in a low phase, the comparator OP1 outputs a signal so as to increase the LED current. There is a risk of output. When such a situation occurs, the light-emitting diode LA flickers. Therefore, it is preferable to perform steady lighting of the light emitting diode LA such that the feedback speed on the detection loop is slower than the full wave rectification cycle.

  The target value V1 described above is generated by the dimming signal conversion circuit 4. The dimming signal conversion circuit 4 is a circuit that converts a PWM signal input from the outside into a predetermined voltage. The target value V1 generated by the dimming signal conversion circuit 4 is also input to the delay time detection terminal S5 of the lighting control circuit IC1.

  FIG. 4 is a circuit diagram of the dimming signal conversion circuit 4. The dimming signal conversion circuit 4 includes a rectifier circuit DB2 to which a PWM signal is input, and a photodiode of a photocoupler PC that receives the output of the rectifier circuit DB2. One end of the resistor R42 is connected to the control power source Vcc, and the other end of the resistor R42 is connected to the phototransistor of the photocoupler PC and one end of the resistor R41.

  The other end of the resistor R41 is connected to one end of the capacitor C40, and the other end of the capacitor C40 is connected to the ground. The target value V1 is taken out from the other end of the capacitor C40. The target value V1 is generated by charging the capacitor C40 with a DC voltage.

  The PWM signal input from the outside is first input to the rectifier circuit DB2 so that the polarity does not matter. When the PWM signal is high, the photodiode of the photocoupler PC emits light and the transistor of the photocoupler PC is turned on. On the other hand, when the PWM signal is low, the transistor of the photocoupler PC is turned off.

  The photocoupler PC repeats such an on / off operation according to the ON duty of the input PWM signal. For this reason, a signal obtained by inverting the ON duty of the PWM signal is obtained at the collector of the transistor of the photocoupler PC. As a result, by setting the resistors R41 and R42 and the capacitor C40 to appropriate values, the DC voltage charged to the capacitor C40 is a value obtained by substantially averaging the ON duty obtained by inverting the PWM signal with respect to the voltage value of the control power supply Vcc. Is the value multiplied by the coefficient.

  Thus, the target value V1 can be changed according to the PWM signal input from the outside. Thereby, dimming control of the light emitting diode LA can be performed according to the PWM signal.

  2 and 3 are time charts showing output waveforms at specific locations in the lighting device according to the embodiment shown in FIG.

  FIG. 2 shows the drain current and drain source voltage waveforms of the MOSFET Q1, the current waveform flowing through the diode D10, and the output voltage waveform of the diode D1 when all the lights are on. When the PWM signal input from the outside is low or no PWM signal is input from the outside, the target value V1 is maximized and all the lights are turned on.

  The period from time t1 to time t2 is a period during which the MOSFET Q1 is on. The period from time t2 to time t3 is a period during which the MOSFET Q1 is off. Until the current flowing from the secondary winding T2 becomes zero, the output voltage of the diode D1 via the auxiliary winding T3 is a voltage proportional to the turn ratio with respect to the voltage applied to the secondary winding. Is applied.

  At time t3, the current in the secondary winding T2 becomes 0, and the voltage applied to the auxiliary winding T3 starts to drop. At time t4, the zero cross detection terminal S2 of the lighting control circuit IC1 detects that the output voltage of the diode D1 has decreased, and turns on the MOSFET Q1 again.

  At this time, the length of time that the MOSFET Q1 is on from time t1 to time t2 is determined by the output voltage of the comparator OP1 as described above. Here, it is assumed that the ON time is set shorter as the voltage of the ON time detection terminal S4 of the lighting control circuit IC1 is lower. Although not shown, the output voltage of the secondary winding T2 is substantially equal to Vf of the connected light emitting diode LA. Further, the LED current is obtained by averaging the output current of the secondary winding with the capacitor C10.

  Thus, by detecting that the current of the secondary winding T2 becomes 0 and turning on the MOSFET Q1, loss in the transformer TR, the MOSFET Q1, and the diode D10 can be reduced, and a high-efficiency power supply circuit can be obtained. it can. In addition, noise due to the switching operation can be reduced.

  When the target value V1 is high, that is, when the LED current is large to some extent, dimming can be performed by the above-described control. This is because the on-time of the MOSFET Q1 is short or the operating frequency is high, so that the LED current can be reduced because it is a flyback power supply circuit.

  On the other hand, in order to further reduce the LED current, it is necessary to shorten the ON time of the MOSFET Q1 and increase the operating frequency. However, the actual operation is limited because the switching of the MOSFET Q1 is too short. Therefore, if the LED current becomes a small value exceeding a certain level, desired dimming control cannot be performed only by switching the MOSFET Q1.

  Therefore, in the present embodiment, the target value V1 is input to the delay time detection terminal S5 of the lighting control circuit IC1. The lighting control circuit IC1 delays the timing at which the MOSFET Q1 is turned on according to the voltage (target value V1) input to the delay time detection terminal S5.

  FIG. 5 is a graph showing the relationship between the target value V1 and the delay time td. When the target value V1 is high, the delay time td is set to 0, and the delay time td increases linearly as the target value V1 decreases. That is, the delay time is set to zero when all the lights are turned on, and the delay time td is set to be larger as the dimming rate is lower and the LED current is smaller. The lighting control circuit IC1 stores the function shown in FIG. 5 in the internal memory, and delays the turning on of the MOSFET Q1 by a delay time td corresponding to the current target value V1.

  FIG. 3 shows the drain current and drain source voltage waveforms of the MOSFET Q1, the current waveform flowing through the diode D10, and the output voltage waveform of the diode D1 at the time of dimming lighting where all light is not lit. FIG. 3 shows an operation when the delay time td is not zero. The waveform up to time t4 is the same as that in FIG.

  The time from time t4 to time t5 is the delay time td. Compared to the all-light lighting shown in FIG. 2, the MOSFET Q1 has a longer off time. Thus, as described above, the average value of the output current of the secondary winding T2 is reduced, so that the LED current can be lowered.

  In this way, the delay time td is set based on the target value V1, and the lighting control circuit IC1 delays the turn-on of the MOSFET Q1 by this delay time td, whereby the LED current can be further reduced.

The relationship between the delay time td, the DC power supply circuit 1, and the LED output is roughly the following relational expression.

However,

  The L value of the primary winding T1 is Lp, the number of turns of the primary winding T1 is Np, the number of turns of the secondary winding T2 is Ns, the LED voltage is Vo, the LED current is Io, and the forward voltage of the diode D10 is Vf. did. The applied voltage of the capacitor C1 is Vin, and the on-time of the MOSFET Q1 is ton. From this relational expression, it can be seen that the ON time ton of the MOSFET Q1 can be increased by increasing the delay time td.

  Further, the relationship between the delay time td and the target value V1 may be a linear function as shown in FIG. 5, but is not limited thereto, and may be another graph such as a quadratic function. These are appropriately changed depending on circuit constants, input conditions, and output conditions.

  Further, the delay time td when all the lights are lit is determined from the L value of the primary winding T1 and the capacitor component C value between the drain and source of the MOSFET Q1 after the energy of the transformer TR has been released after the MOSFET Q1 is turned off. The MOSFET Q1 may be set to be turned on at half the resonance frequency. Such setting of the delay time td is most preferable from the viewpoint of reducing the switching loss of the MOSFET Q1. Also, by providing a capacitor between the drain and source of MOSFET Q1, it is not necessary to rely on a parasitic capacitor component.

  In the present embodiment, the flyback circuit is shown as an example. However, the same idea can be applied to circuit systems such as a buck converter and a buck boost converter as long as the system uses one converter.

  As described above, according to the present embodiment, it is possible to contribute to the energy saving performance of the luminaire to be finally mounted by increasing the efficiency of the lighting device in a high dimming degree, that is, in a bright state. In addition, since a delay time can be provided at the timing when the MOSFET Q1 is turned on, it is possible to realize a dimming control with a dark dimming degree, so that the degree of freedom of brightness that can be selected by the user is increased and the lighting apparatus is easy to use. Can be provided. In addition, since such a function is realized by a single converter, it is possible to reduce the size of the lighting device and reduce the number of parts.

1 DC power supply circuit, 4 dimming signal conversion circuit, AC AC power supply, C1 capacitor, C10 capacitor, C21 capacitor, C40 capacitor, D1 diode, D10 diode, DB1 rectifier circuit, DB2 rectifier circuit, IC1 lighting control circuit, LA light emitting diode , OP1 comparator, PC photocoupler, Q1 MOSFET, R1 start resistance, R10 detection resistance, R2, R21, R41, R42 resistance, R20, R23 control resistance, S1 control power supply terminal, S2 zero cross detection terminal, S3 drive terminal, S4 ON time detection terminal, S5 delay time detection terminal, T1 primary winding, T2 secondary winding, T3 auxiliary winding, td delay time, TR transformer

Claims (7)

A converter comprising an inductor element and a switching element, wherein the converter stores the energy stored in the inductor element when the switching element is on;
A detection resistor for detecting a current flowing in a light emitting diode connected to the output side of the converter;
A comparator that switches an output according to a comparison result between a target value determined according to a specified dimming rate and a detection value of the detection resistor;
When the release of the energy stored in the inductor element is detected, the switching element is turned on after a delay time determined according to the target value elapses, and the switching element is turned off after an on time elapses according to the output of the comparator. A control circuit and
Equipped with a,
The lighting device characterized in that the delay time continuously changes as the target value changes from an upper limit value to a lower limit value of the target value . The lighting device according to claim 1, wherein the delay time increases or decreases in a linear function with respect to the change in the target value. The lighting device according to claim 1, wherein the delay time increases or decreases according to a higher-order function than a linear function with respect to the change in the target value. A converter comprising an inductor element and a switching element, wherein the converter stores the energy stored in the inductor element when the switching element is on;
  A detection resistor for detecting a current flowing in a light emitting diode connected to the output side of the converter;
  A comparator that switches an output according to a comparison result between a target value determined according to a specified dimming rate and a detection value of the detection resistor;
  When the release of the energy stored in the inductor element is detected, the switching element is turned on after a delay time determined according to the target value elapses, and the switching element is turned off after an on time elapses according to the output of the comparator. A control circuit and
  With
  In the first range including the upper limit value of the target value, the delay time is set to a first time longer than zero, and the delay time is set in the second range closer to the lower limit value of the target value than the first range. Set to a second time longer than the first time,
The delay time at least when all the lights are lit is generated by the inductance of the inductor element and the capacitance component in parallel to the switching element after the release of the energy from the inductor element in response to the switching element being turned off. The lighting device according to claim 1, wherein the switching device is set to a time for turning on the switching element at a timing at which a switching loss is smaller than when the delay time is zero during resonance.   The lighting device according to claim 4, wherein increasing the delay time increases an on-time of the switching element. The lighting device according to any one of claims 1 to 5, wherein the delay time is reduced as the target value is higher, and the delay time is increased as the target value is lower .   The lighting device according to any one of claims 1 to 6,
  A light emitting element that is turned on by the lighting device;
  A lighting apparatus comprising:

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