JP2010200438A - Inverter controller, electric compressor, and home electrical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable inverter controller wherein step-out stop at start is prevented to ensure favorable startability and production of noise is suppressed by changing a carrier frequency according to each stage of the sequence at startup of a motor. <P>SOLUTION: The inverter controller includes a carrier frequency setting means 213 for setting the carrier frequency of a PWM signal and a drive controlling means 216. The drive controlling means synthesizes a PWM signal from a PWM controlling means 211 with any of the following commutation signals: a commutation signal from a positioning controlling means 214; a commutation signal from a forced commutation controlling means 215; and a commutation signal from a commutation controlling means 209. The drive controlling means thereby operates a semiconductor switch of an inverter circuit 204. It is possible to suppress the production of noise and reduce failure in position detection by changing the carrier frequency of the PWM signal when a brushless DC motor 203 is started. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to start control in an inverter control device of a brushless DC motor, and also relates to start control in household electric equipment such as an electric compressor and a refrigerator using the inverter control device.

  Conventionally, in an inverter control device that detects a rotor magnetic pole position of a brushless DC motor whose rotation speed is controlled by an inverter by a sensorless method using an induced voltage of a stator winding, when the brushless DC motor is started, it is induced in a stopped state. Since no voltage is generated, position detection cannot be performed using the sensorless method. For this reason, up to a certain number of rotations at which position detection is possible, there is a type in which the motor is started by performing forced commutation according to a predetermined start sequence pattern and then switched to a sensorless system (for example, Patent Document 1). reference).

  The conventional inverter control apparatus will be described below with reference to the drawings.

  FIG. 3 is a diagram illustrating a configuration of a conventional inverter control device described in Patent Document 1. In FIG.

  In FIG. 3, the AC voltage of the AC power source 1 is converted into a DC voltage by the voltage doubler rectifier circuit 2. The voltage doubler rectifier circuit 2 has a configuration in which diodes 2a to 2d and capacitors 2e to 2f are connected.

  In the inverter circuit 3, semiconductor switches (transistors) 3a to 3f are connected in a three-phase bridge, and diodes 3g to 3l are connected to the transistors 3a to 3f in parallel and in opposite directions.

  The brushless DC motor 4 that is a DC motor is driven by the output of the inverter circuit 3. The reciprocating compressor 5 is driven by a brushless DC motor 4. The position detection circuit 6 detects the rotational position of a rotor (not shown) of the brushless DC motor 4 and generates a position detection signal for detecting the position from the back electromotive voltage of the brushless DC motor 4.

  The commutation circuit 7 generates a commutation pulse that commutates the semiconductor switches 3 a to 3 f of the inverter circuit 3 from the output of the position detection circuit 6. The rotation speed command means 8 outputs a rotation speed command signal for the brushless DC motor 4. The rotation speed detection means 9 counts the position detection signal of the position detection circuit 6 for a certain period (for example, 0.5 seconds).

  The duty setting means 10 outputs a duty value so that both coincide with each other based on the difference between the rotational speed command signal of the rotational speed command means 8 and the actual rotational speed detected by the rotational speed detection means 9. The chopping signal generation circuit 11 generates waveforms with different on / off ratios at a constant frequency according to the duty value in order to make the rotation speed of the brushless DC motor 4 variable.

  The sensorless operation unit 12 includes a position detection circuit 6, a commutation circuit 7, a rotation speed command means 8, a rotation speed detection means 9, a duty setting means 10, and a chopping signal generation means 11.

  The forced commutation control means 13 stores an output pattern at the time of activation, and outputs the commutation pulse and the chopping signal because the output of the position detection circuit 6 cannot be obtained when the brushless DC motor 4 is activated.

  The activation sequence pattern storage means 14 stores a commutation pulse and a chopping signal for causing the reciprocating compressor 5 to normally rotate at the time of activation.

  The startup sequence operation unit 15 includes forced commutation control means 13 and startup sequence pattern storage means 14.

  The operation mode switching means 16 connects the forced commutation control means 13 and a synthesis circuit 17 to be described later at the time of activation, and connects the commutation circuit 7 and the chopping signal generation circuit 11 to the synthesis circuit 21 after the activation.

  The synthesis circuit 17 synthesizes the commutation pulse and the chopping signal. The drive circuit 18 turns on / off the semiconductor switches 3 a to 3 f of the inverter circuit 3 based on the output of the synthesis circuit 17.

  The rotor position confirmation means 19 confirms the rotor position at the end of forced commutation by the activation sequence.

By configuring as described above, when the brushless DC motor 4 is started, first, the start sequence operation unit 15 forcibly performs commutation. Thereafter, when the number of rotations at which the position of the rotor can be detected is reached, the rotor position is confirmed by the rotor position confirmation means 19, the output pattern of the drive circuit is determined, and forced commutation is terminated. And it switches to the position detection commutation operation by the sensorless operation part 12.
JP-A-8-289585

  However, in the conventional configuration described in Patent Document 1, the PWM signal generation circuit 11 that is a chopping signal generation circuit generates waveforms with different on / off ratios at a constant frequency according to the duty value from the duty setting means 10. In addition, since the on-time is shortened in the low duty region when the brushless DC motor 4 is started, the influence of the ringing waveform or the like cannot be ignored when detecting the induced voltage in the position detection circuit 6, and it is difficult to accurately detect the position when the load is high. It had the problem of being out of step and failing to start up easily.

  Therefore, at the time of starting, it can be considered that the position can be reliably detected by decreasing the carrier frequency of the PWM signal and increasing the ON time of the PWM signal.

  However, in general, the carrier frequency is set to avoid frequencies that cause noise generation in the audible frequency range in order to suppress noise generation during operation of the brushless DC motor 4. Therefore, lowering the carrier frequency may increase noise, and causes the startup sound of the brushless DC motor 4 to increase, especially at startup.

  The present invention solves the above-mentioned conventional problems, and prevents the step-out stop at the start of the motor at the start of the motor by changing the carrier frequency according to each stage of the sequence of the forced commutation operation and the sensorless operation. The present invention provides a highly reliable inverter control device that ensures good startability and suppresses the generation of noise.

  In order to solve the above conventional problems, the inverter control device of the present invention includes a commutation signal by the positioning control means, a commutation signal by the forced commutation control means, or a commutation signal by the commutation control means. Drive control means that synthesizes the PWM signal by the PWM control means to operate the semiconductor switch of the inverter circuit, and suppresses the generation of noise by changing the carrier frequency of the PWM signal at the start of the brushless DC motor, and the position detection It has the effect of reducing failure.

  The inverter control device according to the present invention changes the carrier frequency of the PWM signal in accordance with each stage of the sequence of the positioning operation, forced commutation operation, and sensorless operation when the brushless DC motor is started up. It is possible to prevent the motor from being stopped due to adjustment, and to suppress the generation of noise when starting the motor.

  According to the first aspect of the present invention, there is provided an inverter circuit section in which a plurality of semiconductor switches and diodes for driving a brushless DC motor having a permanent magnet provided on a rotor are bridge-connected, and position detection for detecting an induced voltage of the brushless DC motor. A circuit unit, position detection determination means for outputting a position detection signal of the rotor based on the induced voltage detected by the position detection circuit unit, and a PWM signal for performing PWM control for varying the rotation speed of the brushless DC motor. Generated PWM control means, carrier frequency setting means for setting the carrier frequency of the PWM signal, positioning control means for outputting a commutation signal for tentatively determining the position of the rotor immediately before starting the brushless DC motor, When no output is obtained from the position detection / determination means immediately after the brushless DC motor is started A forced commutation control means for outputting a predetermined commutation signal set in advance and a position detection signal output by the position detection judgment means during operation of the brushless DC motor are received and a commutation signal is output. A flow control means, a commutation signal from the positioning control means, a commutation signal from the forced commutation control means, or a commutation signal from the commutation control means, and a PWM signal from the PWM control means. Drive control means for synthesizing and operating the semiconductor switch of the inverter circuit unit is used to change the carrier frequency of the PWM signal when the brushless DC motor is started. The carrier frequency of the PWM signal is changed according to each stage of the flow operation and sensorless operation sequences. Can.

  The invention according to claim 2 is the invention according to claim 1, wherein the carrier frequency of the PWM signal when the commutation signal is output by the forced commutation control means is output by the commutation control means. In addition to the effect of the invention according to claim 1, in addition to the effect of the invention according to claim 1, commutation failure or It is possible to prevent the motor from stopping due to step-out.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the carrier frequency when the commutation signal is output by the positioning control means at the start is the forced commutation operation to output the commutation signal. In addition to the effect of the first or second aspect of the invention, the generation of noise during the rotor positioning operation at the start of the motor can be suppressed.

  Invention of Claim 4 is an electric compressor using the inverter control apparatus as described in any one of Claim 1 to 3, and suppresses generation | occurrence | production of the noise at the time of motor starting, and commutation failure or step-out. Therefore, it is possible to provide a highly reliable electric compressor.

  Invention of Claim 5 is household electric appliances, such as a refrigerator, using the inverter control apparatus as described in any one of Claim 1 to 4, and suppresses generation | occurrence | production of the noise at the time of motor starting, and commutation A motor stop due to failure or step-out can be prevented, and a highly reliable household electric appliance such as a refrigerator can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of an inverter control apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a diagram showing signal waveforms and processing contents of respective units in the same embodiment.

  In FIG. 1, an inverter control device 200 is connected to a commercial AC power source 201 and an electric compressor (not shown), a rectifying unit 202 that converts the commercial AC power source 201 into a DC power source, and a brushless DC motor of the electric compressor. An inverter circuit unit 204 for driving 203 is provided.

  Furthermore, a drive circuit 205 that drives the inverter circuit unit 204, a position detection circuit unit 206 that detects a terminal voltage of the brushless DC motor 203, and a microprocessor 207 that controls the inverter circuit unit 204 are provided.

  The microprocessor 207 includes a position detection determination unit 208 that detects the magnetic pole position of the brushless DC motor 203 in response to an output signal from the position detection circuit unit 206, and a commutation control unit 209 that generates a commutation signal.

  Further, a rotation speed detection unit 210 that calculates a rotation speed with respect to an output from the position detection determination unit 208, a PWM control unit 211 that outputs a PWM signal for performing PWM modulation on the commutation signal according to the rotation speed, and a rotation Duty setting means 212 for setting the output duty value of the PWM signal in accordance with the deviation between the rotation speed obtained by the speed detection means 210 and the rotation speed command, carrier frequency setting means 213 for setting the carrier frequency of the PWM signal, and The commutation control means 209, the positioning control means 214, the forced commutation control means 215, and the drive control means 216 for driving the drive circuit 205 by the output of the PWM control means 211 are provided.

  The brushless DC motor 203 includes a three-phase winding stator 203a and a rotor 203b.

  The stator 203a is composed of stator windings 203u, 203v, and 203w. The rotor 203b has permanent magnets 203α, 203β, 203γ, 203δ, 203ε, 203ζ arranged therein. The inverter circuit unit 204 includes six switching transistors Tru, Trx, Trv, Try, Trw, Trz connected in a three-phase bridge, and free-wheeling diodes Du, Dx, Dv, Dy, Dw, Dz connected in parallel to the switching transistors Tru, Trx, Trv, Try, Trw, Trz, respectively. It is configured.

  The position detection circuit unit 206 includes a comparator (not shown) and the like, and obtains a position detection signal by comparing a terminal voltage signal based on the induced voltage of the brushless DC motor 203 with a reference voltage using a comparator.

  The position detection determination unit 208 obtains the position signal of the rotor 203b from the output signal of the position detection circuit unit 206 and generates a position detection signal.

  The commutation control unit 209 calculates a commutation timing from the position signal of the position detection determination unit 208 and generates a commutation signal of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz.

  The rotation speed detection unit 210 calculates the rotation speed of the brushless DC motor 203 by a method such as counting a position signal from the position detection determination unit 208 for a certain period or measuring a pulse interval.

  The duty setting means 212 performs an addition / subtraction operation of the duty value from the deviation between the rotation speed obtained from the rotation speed detection means 210 and the rotation speed command, and outputs the duty value to the PWM control means 211. When the actual rotational speed is low with respect to the rotational speed command, the duty value is increased. Conversely, when the actual rotational speed is high, the duty value is decreased.

  The carrier frequency setting means 213 sets the carrier frequency for switching the switching transistors Tru, Trx, Trv, Try, Trw, Trz.

  The PWM control unit 211 outputs a PWM modulation signal from the duty value set by the duty setting unit 212 and the carrier frequency set by the carrier frequency setting unit 213.

  The drive control unit 216 combines the commutation signal and the PWM modulation signal, generates a drive signal for turning on / off the switching transistors Tru, Trx, Trv, Try, Trw, and Trz, and outputs the drive signal to the drive circuit 205. The drive circuit 205 performs ON / OFF switching of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz based on the drive signal to drive the brushless DC motor 203.

  Next, various waveforms of the inverter control device 200 shown in FIG. 2 will be described.

  (A), (B), and (C) are the terminal voltages Vu, Vv, and Vw of the U-phase, V-phase, and W-phase of the brushless DC motor 203, and change in a state where the respective phases are shifted by 120 degrees. .

  These terminal voltages are the supply voltages Vua, Vva, Vwa by the inverter circuit unit 204, the induced voltages Vub, Vvb, Vwb generated in the stator windings 203u, 203v, 203w, and the return of the inverter circuit unit 204 at the time of commutation switching. It becomes a composite waveform with pulse-like spike voltages Vuc, Vvc, Vwc generated when any one of the diodes Du, Dx, Dv, Dy, Dw, Dz becomes conductive.

  Then, these terminal voltages Vu, Vv, Vw are compared with a virtual neutral point voltage VN which is a half voltage of the DC power supply voltage, and output signals PSu, PSv, PSw output from the comparator are (D), ( E) and (F).

  This output signal includes PSua, PSva, PSwa corresponding to supply voltages Vua, Vva, Vwa, PSuc, PSvc, PSwc corresponding to spike voltages Vuc, Vvc, Vwc, and induced voltages Vub, Vvb, Vwb and virtual neutrality. It becomes a composite signal with PSub, PSvb, PSwb corresponding to the period during the point voltage VN comparison.

  Here, since the pulse-like spike voltages Vuc, Vvc, Vwc are ignored by the wait time (G) set in advance by the position detection determination means 208, the output signals PSu, PSv, PSw of the comparator result in the induced voltage Vub. , Vvb, Vwb, and phase.

  The microprocessor 207 recognizes the six modes A to F as shown in (H) based on the states of the output signals PSu, PSv, and PSw of each comparator, and drives according to the states of the output signals PSu, PSv, and PSw. DSz (N) is output from the signal DSu (I).

  About the inverter control apparatus 200 comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  When the brushless DC motor 203 is stopped, the microprocessor 207 activates the brushless DC motor 203 upon recognizing the rotation speed command.

  When the brushless DC motor 203 is started, the drive control unit 216 is operated by the commutation signals from the positioning control unit 214 and the forced commutation control unit 215 to drive the drive circuit 205 and to commutate the inverter circuit unit 204. Perform the action.

  First, the drive control means 216 is operated by the positioning control means 214.

  Since the position of the rotor 203b is indefinite when the brushless DC motor 203 is stopped, the relative position of the rotor 203b with respect to the stator 203a is determined in advance for smooth start-up. For this reason, the drive control means 216 operates the switching transistors Tru, Trx, Trv, Try, Trw, Trz of the inverter circuit unit 204 with a predetermined output pattern in accordance with a signal from the positioning control means 214. For example, by outputting the drive signals DSu and DSy in FIG. 2 to the drive circuit 205, the position of the rotor is temporarily determined in the mode B state.

  Next, the commutation operation is performed by the forced commutation control means 215.

  When the rotational speed of the brushless DC motor 203 is extremely low at the time of startup, the induced voltage generated in the stator windings 203u, 203v, 203w is also small, so that the position detection signal from the position detection determination unit 208 is output by the output from the position detection circuit unit 206. Cannot be obtained. Therefore, the brushless DC motor is forcibly operated at a preset rotation speed, for example, 3 rps, by a commutation signal from the forced commutation control means 215 until position detection by the induced voltage becomes possible. 203 is driven.

  For example, the drive signals DSu, DSv, DSw, DSx, DSy, DSz to the drive circuit 205 are sent to the mode C at every predetermined time with respect to the position of the mode B rotor 203b fixed by the positioning control means 214 described above. D and E are forcibly output to perform the commutation operation.

  Then, the activation is completed when the position detection by the position detection determination unit 208 becomes possible, and the drive control unit 216 is used by the commutation signal from the commutation control unit 209 based on the position detection signal of the position detection determination unit 208. Outputs drive signals DSu, DSv, DSw, DSx, DSy, DSz to the drive circuit 205 to perform a commutation operation, and operates the brushless DC motor 203.

  Since the output voltage of the inverter circuit unit 204 is obtained by PWM-modulating the commutation signal input to the drive control unit 216 by the PWM signal generated by the PWM control unit 211, the switching transistors Tru, Trx, Trv, Try , Trw, Trz perform a switching operation by PWM. The induced voltage waveform of the stator windings 203u, 203v, and 203w input to the position detection circuit unit 206 is a waveform in which a ringing waveform due to switching is superimposed immediately after the transistor element performing the switching operation is turned on.

  Since the duration of the ringing waveform is substantially determined by the configuration of the position detection circuit unit 206, a low-pass filter is provided in the position detection circuit unit 206, or a delay time is provided in the position detection determination unit 208. Removed by means.

  However, when the on-time of the PWM waveform is short, the duration of the ringing waveform cannot be ignored, and the position detection based on the induced voltage fails due to the ringing waveform, resulting in erroneous detection.

  Therefore, in the present embodiment, the carrier frequency setting means depends on which one of the commutation signals of the positioning control means 214, forced commutation control means 215, or commutation control means 209 is operating the drive control means 216. The carrier frequency from 213 to the PWM control means 211 is changed.

  Therefore, during low duty operation by the forced commutation control means 215, the PWM on time is increased by lowering the carrier frequency, thereby preventing position detection failure at start-up and motor stop due to step-out from false detection. be able to.

  Further, at the time of rotor positioning by the positioning control means 214, it is possible to minimize the generation of noise at the time of starting by avoiding the frequency that causes noise generation by increasing the carrier frequency.

  Moreover, even if the inverter control device 200 is used for the electric compressor 220, good operation is possible, and even when the inverter control device 200 is used for household electric appliances such as a refrigerator, good system operation is possible. .

  As described above, the inverter control device according to the present invention can reduce misdetection and failure of position detection and prevent step-out in the transition to sensorless operation at the time of startup of the brushless DC motor, and suppress startup noise. Therefore, it is useful for household electric appliances such as air conditioners and refrigerators.

Block diagram of the inverter control apparatus in Embodiment 1 of the present invention The figure which shows the signal waveform and processing content of each part in the embodiment The figure which shows the structure of the conventional inverter control device

200 Inverter control unit 203 Brushless DC motor 203b Rotor 203α, 203β, 203γ, 203δ, 203ε, 203ζ Permanent magnet 204 Inverter circuit unit 206 Position detection circuit unit 208 Position detection determination unit 209 Commutation control unit 211 PWM control unit 213 Carrier frequency setting Means 214 Positioning control means 215 Forced commutation control means 216 Drive control means

Claims (5)

  A plurality of semiconductor switches for driving a brushless DC motor having a permanent magnet provided on a rotor and an inverter circuit section in which diodes are bridge-connected, a position detection circuit section for detecting an induced voltage of the brushless DC motor, and the position detection circuit section Position detection determination means for outputting a position detection signal of the rotor based on the induced voltage detected in step 1, PWM control means for generating a PWM signal for performing PWM control for varying the rotation speed of the brushless DC motor, and PWM signal Carrier frequency setting means for setting the carrier frequency, positioning control means for outputting a commutation signal for tentatively determining the position of the rotor immediately before starting the brushless DC motor, and immediately after starting the brushless DC motor If no output is obtained from the position detection judgment means A forced commutation control means for outputting a commutation signal of the turn; a commutation control means for outputting a commutation signal in response to a position detection signal output by the position detection determination means during operation of the brushless DC motor; and the positioning One of the commutation signal by the control means, the commutation signal by the forced commutation control means, or the commutation signal by the commutation control means and the PWM signal by the PWM control means are combined to generate the inverter circuit unit. An inverter control device comprising drive control means for operating the semiconductor switch, wherein the carrier frequency of the PWM signal is changed when the brushless DC motor is started.   The carrier frequency of the PWM signal when the commutation signal is output by the forced commutation control means is set smaller than the carrier frequency of the PWM signal when the commutation control means outputs the commutation signal. The inverter control device according to 1.   3. The inverter control according to claim 1, wherein the carrier frequency when the commutation signal is output by the positioning control means is set to be larger than the carrier frequency when the forced commutation operation outputs the commutation signal. apparatus.   The electric compressor using the inverter control apparatus as described in any one of Claim 1 to 3.   Home electric appliances, such as a refrigerator, using the inverter control device according to any one of claims 1 to 4.