JP5903551B2 - Inverter control device, electric compressor and electrical equipment - Google Patents

Description

  The present invention relates to an energization control method in an inverter control device of a brushless DC motor, an electric compressor using the inverter control device, and a household refrigerator equipped with a brushless DC motor driven by the inverter control device. The present invention relates to a control method in electrical equipment.

  Conventionally, this type of inverter control device generates a rotating magnetic field by switching the energized phase of the three-phase winding of the stator, that is, a commutation operation, according to the rotor magnetic pole position of the brushless DC motor, and the rotor outputs Controlled to obtain torque. Therefore, in the operation of the brushless DC motor, it is necessary to obtain the relative relationship of the rotor magnetic flux with respect to the magnetic flux generated by the stator winding current.

  In a motor using a sensor such as a hall element, the rotor magnetic pole position can be accurately recognized by the sensor, so there is no need to detect the rotor magnetic pole position by an indirect induced voltage, and the rotor magnetic pole position can be directly detected from the sensor. Since it can be determined, motor control can be easily performed.

  However, in a hermetic compressor, embedding a sensor such as a Hall element itself is not easy to adopt from the viewpoint of sensor failure due to the use environment, reliability such as refrigerant leakage, and maintenance of the motor in the event of failure due to the sensor integrated type. In general, a sensorless inverter control device that detects the rotor magnetic pole position by an induced voltage generated in the stator winding without using a sensor such as a Hall element is used.

  In general, as a waveform control of a sensorless inverter control device, a 120-degree conduction waveform is often used. In a system that drives a brushless DC motor, each phase switch of the inverter is electrically connected for a period of 120 degrees. The remaining electrical angle of 60 degrees is not controlled. In this case, the rotor magnetic pole position is obtained by using the electrical angle of 60 degrees during the non-control period and observing the induced voltage appearing at the motor terminal during the off-period of the upper and lower arm switches (for example, see Patent Document 1). ).

  In addition, the motor terminal voltage is changed according to the rotational speed of the rotor observed by the induced voltage, and the rotational speed of the motor is controlled so that the relative position between the rotor magnetic pole position and the rotating magnetic field is kept constant. In general, the terminal voltage is changed by PWM control.

  Furthermore, when the output duty by PWM control reaches a maximum of 100%, the brushless DC motor decreases in speed as the load increases. In order to suppress a decrease in the rotational speed at high load (see, for example, Patent Document 2).

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

  FIG. 4 is a diagram illustrating a configuration of a conventional inverter control device described in Patent Document 1. In FIG.

  FIG. 5 is a time chart showing signal waveforms and processing contents of each part of the conventional inverter control device described in Patent Document 1.

  In FIG. 4, an inverter circuit unit 140 is configured by connecting three pairs of switching transistors Tru, Trx, Trv, Try, Trw, and Trz in series between terminals of a DC power supply 001. The brushless DC motor 105 includes a stator 105b having a four-pole distributed winding structure and a rotor 105a. The rotor 105a has a magnet embedded structure in which permanent magnets 105α and 105β are embedded.

  The connection point between each pair of switching transistors is connected to the terminals of the Y-connected stator windings 105u, 105v, and 105w of the brushless DC motor 105, respectively.

  Note that protective reflux diodes Du, Dx, Dv, Dy, Dw, and Dz are connected between collector-emitter terminals of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz, respectively.

  The resistors 101 and 102 are connected in series between the buses 103 and 104, and the detection terminal ON, which is a common connection point, is set to the neutral point voltage of the stator windings 105u, 105v, and 105w of the brushless DC motor 105. A voltage VN at a virtual neutral point that is ½ of the voltage of the corresponding DC power supply 001 is output.

  In the comparators 106a, 106b, 106c, these non-inverting input terminals (+) are connected to the output terminals OU, OV, OW through resistors 107, 108, 109, respectively, and the inverting input terminals (−) are Connected to the detection terminal ON.

  The output terminals of these comparators 106a, 106b, and 106c are connected to input terminals I1, I2, and I3 of the microprocessor 110, which is a logic means, respectively. The output terminals O1 to O6 drive the switching transistors Tru, Trx, Trv, Try, Trw, Trz via the drive circuit 120.

  The brushless DC motor 105 has a four-pole distributed winding structure, and the rotor 105a has a surface magnet structure in which permanent magnets 105α and 105β are arranged on the rotor surface.

  Next, the control operation will be described with reference to FIG.

  (A), (B), and (C) show the terminal voltages Vu, Vv, and Vw of the stator windings 105u, 105v, and 105w during steady operation.

  These terminal voltages are supplied voltages Vua, Vva, Vwa by the inverter circuit unit 140, induced voltages Vub, Vvb, Vwb generated in the stator windings 105u, 105v, 105w, and the return of the inverter circuit unit 140 when switching commutation. 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. These terminal voltages Vu, Vv, Vw and the virtual neutral point voltage VN, which is a half voltage of the DC power supply 001, and the output signals PSu, PSv, PSw compared by the comparators 106a, 106b, 106c are represented by (D), ( E) and (F).

  In this case, the output signals PSu, PSv, PSw of the comparator are the signals PSua, PSva, PSwa representing the positive and negative and the phases of the induced voltages Vub, Vvb, Vwb and the pulse voltages Vuc, Vvc, Vwc. Signal PSsub, PSvb, PSwb.

  Further, since the pulse voltages Vuc, Vvc, and Vwc are ignored by the wait timer, the comparator output signals PSu, PSv, and PSw show the positive and negative and the phase of the induced voltages Vub, Vvb, and Vwb as a result. It will be a thing.

  The microprocessor 110 recognizes the six modes A to F shown in (G) on the basis of the states of the output signals PSu, PSv, and PSw of the respective comparators, and performs the electrical operation from the time when the level of the output signals PSu, PSv, and PSw changes. DSz (O) is output from the drive signal DSu (J) with a delay of 30 degrees in angle.

  Each time T (H) in modes A to F indicates an electrical angle of 60 degrees, and a time (I) that is 1/2 of A to F, that is, T / 2 is a delay corresponding to 30 degrees in electrical angle. Indicates time.

  Thus, the position state of the rotor 105a is detected from the induced voltage generated in the stator windings 105u, 105v, and 105w according to the rotation of the rotor 105a of the brushless DC motor 105, and the change time (T) of the induced voltage is determined. The drive signal for energizing each phase stator winding 105u, 105v, 105w is determined and executed according to the detection mode and timing to the stator windings 105u, 105v, 105w.

  FIG. 6 is a block diagram of a conventional inverter control device described in Patent Document 2. In FIG.

  In FIG. 6, a commercial power supply 151 is an AC power supply having a frequency of 50 Hz or 60 Hz and a voltage of 100 V in Japan.

  The rectifier circuit 152 converts the AC voltage of the commercial power supply 151 into a DC voltage. The rectifier circuit 152 includes bridge-connected rectifier diodes 152a to 152d and smoothing electrolytic capacitors 152e and 152f. In the circuit shown in FIG. 6, the voltage rectifier circuit is a voltage doubler rectifier circuit. Can be obtained.

  The inverter circuit 153 has six switch elements 153a, 153b, 153c, 153d, 153e, and 153f in a three-phase bridge configuration. Each switch element includes a diode for return current in the reverse direction of each switch element, but this is omitted in this figure.

  The brushless DC motor 154 includes a rotor 154a having a permanent magnet and a stator 154b having a three-phase winding. When the three-phase alternating current generated by the inverter 153 flows through the three-phase winding of the stator 154b, the rotor 154a can be rotated.

  The counter electromotive voltage detection circuit 155 detects the rotational relative position of the rotor 154a from the counter electromotive voltage generated when the rotor 154a having the permanent magnet of the brushless DC motor 154 rotates.

  The commutation circuit 156 performs logical signal conversion based on the output signal of the back electromotive voltage detection circuit 155, and generates a signal to be driven by sequentially switching the switch elements 153a, 153b, 153c, 153d, 153e, and 153f of the inverter 153.

  The synchronous drive circuit 157 forcibly outputs a predetermined frequency from the inverter 153 and drives the brushless DC motor 154. The synchronous drive circuit 157 forcibly outputs a signal having the same shape as the logical signal generated by the commutation circuit 156. It is generated at a frequency.

  The load state determination circuit 158 determines a load state in which the brushless DC motor 154 is operated.

  The switching circuit 159 switches whether the brushless DC motor 154 is driven by the commutation circuit 156 or the synchronous drive circuit 157 according to the output of the load state determination circuit 158.

  The drive circuit 160 drives the switch elements 153a, 153b, 153c, 153d, 153e, and 153f of the inverter 153 by the output signal from the switching circuit 159.

  Next, the operation of the above configuration will be described.

  When the load detected by the load state determination circuit 158 is a normal load, driving by the commutation circuit 156 is performed.

  A back electromotive voltage detection circuit 155 detects the relative position of the rotor 154a of the brushless DC motor 154. Next, the commutation circuit 156 creates a commutation pattern for driving the inverter 153 according to the relative position of the rotor 154a.

  This commutation pattern is supplied to the drive circuit 160 through the switching circuit 159, and drives the switch elements 153a, 153b, 153c, 153d, 153e, and 153f of the inverter 153.

  By this operation, the brushless DC motor 154 performs driving that matches the rotational position.

  Next, the operation when the load increases will be described.

  When the load of the brushless DC motor 154 increases, the rotation speed decreases due to the characteristics of the brushless DC motor 154. This state is determined by the load state determination circuit 158 to be a high load state, and the output of the switching circuit 159 is switched to the signal from the synchronous drive circuit 157. By driving in this way, it is possible to suppress a decrease in the rotational speed at the time of high load.

Japanese Patent Laid-Open No. 1-8890 JP-A-9-88837

  However, in the above conventional configuration, when PWM control is performed to vary the rotation speed of the brushless DC motor 105, the input terminals of the comparators 106a, 106b, 106c connected to the output terminals OU, OV, OW are In order to detect the voltage on which the PWM signal is superimposed, the PWM signal is also superimposed on the detected voltage waveforms of the induced voltages Vub, Vvb, and Vwb of the rotor 105a, and the microprocessor 110 outputs each comparator output while the PWM signal is on. Need to be determined as a position detection signal.

Therefore, when the duty value of the PWM signal is small and the time for which the PWM signal is on is short, the point in time when the comparison results of the induced voltages Vub, Vvb, Vwb and the virtual neutral point voltage VN match is the off period of the PWM signal The delay time until the determination result of the position detection signal output generated when the PWM signal is turned on thereafter is obtained increases.

  For this reason, commutation is delayed with respect to the position of the rotor 105a, and there is a problem that the brushless DC motor 105 stops stepping out when the load torque increases.

  The present invention solves the above-described conventional problems. When the ON time of the PWM signal is equal to or less than a predetermined time, the present invention is compulsory by a drive waveform having a predetermined frequency based on the target rotation speed and the operation rotation speed at that time The motor operation state is maintained by forced synchronous commutation that continues the commutation at the same time, and the inverter output voltage is changed according to the state of the induced voltage phase with respect to the inverter output voltage, thereby stabilizing the motor during forced synchronous commutation. The present invention provides a highly reliable inverter control device that realizes operation.

  In order to solve the above-described conventional problems, an inverter control device of the present invention includes a brushless DC motor including a rotor provided with a permanent magnet and a stator provided with a three-phase winding, and an inverter circuit unit that drives the brushless DC motor; Output voltage control means for changing the three-phase output voltage of the inverter circuit unit by PWM control in order to vary the operating rotational speed of the brushless DC motor, and the induced voltage of the brushless DC motor and the output voltage of the inverter circuit unit. A position detection circuit section for comparing and detecting the generated reference voltage, a position detection determination means for outputting a rotor position detection signal from an induced voltage zero cross point based on a signal of the position detection circuit section, and an output signal from the position detection determination means Position detection commutation control means for outputting the commutation waveform of the inverter circuit unit based on The phase difference of the induced voltage phase with respect to the output voltage phase of the inverter circuit unit is detected based on the signal of the output circuit unit, and the three-phase output voltage by the output voltage control means is changed according to the phase state to Phase difference determining means for maintaining the rotor induced voltage phase with respect to the output voltage at a predetermined phase, and forced synchronous commutation control means for outputting a commutation waveform preset at a predetermined frequency in accordance with a target rotational speed of the brushless DC motor. In the position detection commutation of the brushless DC motor, when it is estimated that the detection of the position detection signal is generated more than a certain amount during the off period of the PWM control of the output voltage control means, the brushless DC motor operates by forced synchronous commutation. At the same time, the output voltage is changed in accordance with the change state of the rotor phase so as to follow the operation state of the motor.

  As a result, when the rotor position detection signal of the brushless DC motor is unstable, the forced synchronization that forcibly continues commutation with a drive waveform of a predetermined frequency based on the target rotational speed and the operating rotational speed at that time. The motor operating state is maintained by commutation, and the inverter output voltage is changed according to the state of the induced voltage phase with respect to the inverter output voltage, thereby realizing stable motor operation during forced synchronous commutation operation and target rotation Even when the operating state of the brushless DC motor changes due to a change in the number, the inverter output voltage is changed according to the state of the induced voltage phase with respect to the inverter output voltage, and the motor output torque becomes excessive torque or insufficient torque. Therefore, stable motor operation can be realized by preventing step-out stop. .

  In the sensorless drive of the brushless DC motor, the inverter control device according to the present invention forcibly continues the operation state by the synchronous drive even when the duty value is small and the magnetic pole position of the rotor is difficult to detect during the low speed operation. By doing so, it is possible to expand the operation range, and to prevent the brushless DC motor from stepping out when the load torque increases during the operation by the synchronous drive, and to enable stable operation to be continued.

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

  The invention according to claim 1 is a brushless DC motor comprising a rotor provided with a permanent magnet and a stator provided with a three-phase winding, an inverter circuit section for driving the brushless DC motor, and an operation rotation of the brushless DC motor. The output voltage control means for changing the three-phase output voltage of the inverter circuit unit by PWM control in order to vary the number, and the reference voltage generated by the induced voltage of the brushless DC motor and the output voltage of the inverter circuit unit are compared and detected A position detection circuit unit that outputs a rotor position detection signal from an induced voltage zero-cross point based on a signal of the position detection circuit unit, and an output signal of the inverter circuit unit based on an output signal from the position detection determination unit A position detection commutation control means for outputting a commutation waveform; and the inverter based on a signal from the position detection circuit section. The phase difference of the induced voltage phase with respect to the output voltage phase of the inverter circuit unit is detected, the three-phase output voltage by the output voltage control means is changed according to the phase state, and the rotor induced voltage phase with respect to the output voltage of the inverter circuit unit is changed. A phase difference determining means for maintaining a predetermined phase; a forced synchronous commutation control means for outputting a commutation waveform preset at a predetermined frequency in accordance with a target rotational speed of the brushless DC motor; and a position of the brushless DC motor. In the detection commutation, when it is estimated that the detection of the position detection signal is generated at a certain level or more during the OFF period of the PWM control of the output voltage control means, the operation is performed by forced synchronous commutation, and the rotor phase is changed. Accordingly, the output voltage is changed to follow the operation state of the motor.

  As a result, when the rotor position detection signal of the brushless DC motor is unstable, the frequency of the inverter circuit unit output voltage is forcibly output at the synchronous frequency, and the commutation operation is stabilized and the inverter output voltage By changing the inverter output voltage according to the state of the induced voltage phase with respect to, stable motor operation during synchronous operation by forced commutation can be realized.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the set value of the PWM control of the output voltage control means becomes smaller than a predetermined value, the operation is performed by forced synchronous commutation. It is.

  As a result, the frequency of the inverter circuit unit output voltage is forcibly output at the synchronous frequency during low-speed operation of the brushless DC motor, and the on-time due to PWM control of the output voltage, in which the detection of the induced voltage is difficult, that is, Even when the rotor position detection signal becomes unstable, the commutation operation is stabilized and the inverter output voltage is changed according to the state of the induced voltage phase with respect to the inverter output voltage to synchronize by forced commutation. Stable motor operation during operation can be realized.

  A third aspect of the present invention is an electric compressor that includes the brushless DC motor and is driven by the inverter control device according to the first or second aspect.

  As a result, it is possible to operate the brushless DC motor with high efficiency in the low rotation speed region and high torque in the high rotation speed region, and to provide a highly reliable electric compressor that follows the load fluctuation of the refrigeration cycle. it can.

  Invention of Claim 4 is an electric equipment which comprises the said electric compressor and is driven by the inverter control apparatus of Claim 1 or Claim 2.

  As a result, it is possible to provide an electric device such as a household refrigerator that performs drive control with high efficiency, a wide operation range, and high reliability.

  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 device according to Embodiment 1 of the present invention. FIG. 2 is a time chart showing signal waveforms and processing contents of each part of the inverter control device according to the first embodiment. FIG. 3 is a flowchart showing a control operation in the first embodiment.

  In FIG. 1, the inverter control device 200 is connected to a commercial AC power source 201, an electric compressor 220 having a compression mechanism (not shown) having a well-known configuration and a brushless DC motor 203. Is converted to a DC power source, and an inverter circuit unit 204 that drives the brushless DC motor 203 of the electric compressor 220 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 position detection determination means 208 that detects the magnetic pole position of the brushless DC motor 203 with respect to the output signal from the position detection circuit unit 206, and position detection commutation that generates a commutation signal based on the position detection signal. And a control means 209.

  In addition, the microprocessor 207 includes a phase difference determination unit 210 that detects a phase difference of an induced voltage phase of the brushless DC motor 203 with respect to an output voltage phase of the inverter circuit unit 204 based on an output signal from the position detection circuit unit 206, and a phase difference Forced synchronous commutation control means 211 that generates a commutation signal based on the detection signal is provided.

  Further, a rotation speed detection unit 212 that calculates a rotation speed based on an output from the position detection determination unit 208, and an output voltage control for performing PWM modulation on the output voltage according to the rotation speed and the rotation speed command, or the phase difference. And a drive control means 216 for driving the drive circuit 205 by the output of the position detection commutation control means 209 or the forced synchronous commutation control means 211.

  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, and the rotor 203b is a magnet-embedded structure in which permanent magnets 203α, 203β, 203γ, 203δ, 203ε, and 203ζ are arranged to generate reluctance torque. is there.

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 each of them. It is configured.

The position detection circuit unit 206 includes a comparator (not shown) and the like, and a terminal voltage signal based on the induced voltage of the brushless DC motor 203 and a reference voltage generated by the output voltage of the inverter circuit unit 204 are output by the comparator. A position detection signal is obtained by comparison.

  The position detection determination unit 208 obtains a position signal of the rotor 203b from the output signal of the position detection circuit unit 206 and generates a position detection signal. The position detection commutation control unit 209 is a position detection signal of the position detection determination unit 208. To calculate the commutation timing and generate commutation signals for the switching transistors Tru, Trx, Trv, Try, Trw, and Trz.

  The phase difference determination unit 210 generates a phase difference signal between the output voltage phase of the inverter circuit unit 204 and the induced voltage phase generated in the stator windings 203u, 203v, and 203w from the output signal of the position detection circuit unit 206, and performs forced synchronization. The commutation control means 211 calculates the commutation timing based on the rotational speed command, and generates commutation signals for the switching transistors Tru, Trx, Trv, Try, Trw, and Trz.

  The rotation speed detection means 212 calculates the rotation speed of the brushless DC motor 203 based on the position signal from the position detection determination means 208, and outputs the deviation between the rotation speed obtained from the rotation speed detection means 212 and the command rotation speed.

  The output voltage control means 213 outputs a PWM modulation signal for changing the inverter output voltage in accordance with the state of the deviation signal of the rotation speed detection means 212 or the phase difference signal of the phase difference determination means 210.

  By the way, in the conventional inverter control device (FIG. 4), each of the input terminals of the comparators 106a, 106b, 106c connected to the output terminals OU, OV, OW detects the inverter output voltage on which the PWM signal is superimposed. The PWM signal is also superimposed on the detected voltage waveforms of the induced voltages Vub, Vvb, Vwb (FIG. 2) of the rotor 105a. Therefore, the position detection determination unit 208 of the present embodiment needs to determine each comparator output while the PWM signal is on as a position detection signal.

  At this time, when the duty value of the output voltage by the PWM control from the output voltage control means 213 is small and the time for which the PWM signal is on is short, the output signal of the position detection circuit unit 206 input to the position detection determination means 208 When the time point when the comparison results of the induced voltages Vub, Vvb, Vwb (FIG. 2) described later and the virtual neutral point voltage VN coincide with each other occurs during the OFF period of the PWM signal, the PWM signal is turned on thereafter. Since the delay time until the determination result of the generated position detection signal output is obtained, commutation is delayed with respect to the position of the rotor 105a.

  In addition, when the ON time of the PWM signal is short, the determination time of the detection level of the induced voltage is limited, so that it is difficult to detect the position detection signal from the induced voltage waveform.

  As an example, when voltage control is performed with a PWM period of 100 μs, when the on-time duty value is 50% or less, that is, the PWM on-time is 50 μs or less, the time during which position detection is possible decreases to less than half. In addition, the margin of the position detection signal becomes unstable because the margin is insufficient to secure the position detection failure such as the induced voltage fluctuation and the waveform distortion caused by the detection circuit.

For this reason, when the ON time by the PWM modulation of the output voltage control means 213 continues in a state of a predetermined value or less, the position detection commutation is switched to the forced synchronous commutation.

  That is, the drive control unit 216 determines which one of the position detection commutation control unit 209 and the forced synchronous commutation control unit 211 according to the PWM modulation duty value of the output voltage control unit 213 and the rotation speed deviation signal of the rotation speed detection unit 212. The drive circuit 205 is driven by the commutation signal.

  Then, the drive control means 216 combines the commutation signal of the position detection commutation control means 209 or the forced synchronous commutation control means 211 and the PWM modulation signal of the output voltage control means 213, and the switching transistors Tru, Trx, Trv, A drive signal for turning ON / OFF Try, Trw, and Trz is generated and output to the drive circuit 205.

  Based on the drive signal, the drive circuit 205 performs ON / OFF switching of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz, and drives the brushless DC motor 203.

  Next, various waveforms of the inverter control device 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 each phase changes in a state 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.

  In addition, each phase terminal voltage (value) Vu, Vv, Vw is compared with a virtual neutral point voltage (value) VN that is a half of the DC power supply voltage converted into the DC power supply by the rectifier 202, Output signals output from each comparator (not shown) are PSu, PSv, and PSw.

  The output signals PSu, PSv, PSw are output signals PSua, PSva, PSwa corresponding to the supply voltages Vua, Vva, Vwa, output signals PSuc, PSvc, PSwc corresponding to the spike voltages Vuc, Vvc, Vwc, and induced voltage. This is a composite signal of the output signals PSub, PSvb, PSwb corresponding to the period during comparison of Vub, Vvb, Vwb and the virtual neutral point voltage VN.

  Here, PSu, PSv, and PSw when the induced voltage phase is an intermediate phase are (D), (E), and (F), and the state of the output signal of the phase difference determination means at that time is (G). .

  Further, PSu, PSv, and PSw when the induced voltage phase is a delayed phase are (H), (I), and (J), and the state of the output signal of the phase difference determining means at that time is (K).

  Similarly, PSu, PSv, and PSw when the induced voltage phase is the leading phase are (L), (M), and (N), and the state of the output signal of the phase difference determination means at that time is (O).

  The microprocessor 207 counts the reference timer count value (P) according to the target rotation speed, and generates a forced synchronization reference signal (Q).

Further, the commutation signal (R) and the sampling start signal (S) are generated at regular intervals with the forced synchronization reference signal as a reference, and the drive signals DSu (T) to DSz (Y) are generated according to the state of the commutation signal. ) Is output.

  Next, a detailed operation for determining the induced voltage phase during the synchronous operation of the brushless DC motor 203 by the inverter control device 200 will be described with reference to the flowchart of FIG. 3.

  In FIG. 3, each step shows operations of the phase difference determination unit 210, the forced synchronous commutation control unit 211, and the output voltage control unit 213.

  First, in step 101, a timer count of a reference time corresponding to an electrical angle of 120 degrees with respect to a target frequency is started by a reference timer.

  Here, step 101 is the time when the forced synchronization reference signal (Q) is generated, and corresponds to a phase advance determination period described later.

  Thereafter, in step 102, the states of the output signals PSu, PSv, PSw from the position detection circuit unit 206 are detected, and the output states of the switching transistors Tru, Trx, Trv, Try, Trw, Trz, that is, the operation mode in FIG. The phase detection determination is performed according to the states of the output signals PSu, PSv, and PSw corresponding to the state.

  Here, in the rising period of the induced voltage of any one of the U phase, V phase, and W phase, the corresponding energized phase is in a non-energized state for a period corresponding to an electrical angle of 60 degrees, and before and after the start of each non-energized period. , The lower drive signals DSx, DSy, DSz are switched to the upper drive signals DSu, DSv, DSw, respectively.

  When the output voltage of the inverter circuit unit 204 has a rising waveform and the induced voltage is in the lead phase, the terminal voltage does not fall below the virtual neutral point voltage value VN during the phase lead detection period. Does not become an 'L' signal. That is, when the 'L' signal output from the position detection circuit unit is detected, it is determined in step 103 that the induced voltage phase is not advanced and not in the phase state, and the advance phase state is set.

  Then, in step 104, the process returns to step 102 until the reference timer count value (P) passes a commutation time, for example, a time corresponding to an electrical angle of 30 degrees, and the advance phase detection determination is continued. If the commutation time has elapsed, the process proceeds to step 105.

  In step 105, a commutation signal (R) is generated, and the upper drive signal DSu, DSv, or DSw is turned ON, respectively, according to the state of the U phase, the V phase, or the W phase to perform the commutation operation.

  Thereafter, in step 106, the process waits until the reference timer count value (P) reaches the delay phase detection start time.

  In step 106, when the reference timer count value (P) has passed the delayed phase detection start time, for example, 100 μs before the time corresponding to the electrical angle of 90 degrees, the output signals PSu, PSv from the position detection circuit unit 206. , PSw state is detected, and phase detection determination is made according to the output state of the switching transistors Tru, Trx, Trv, Try, Trw, Trz, that is, the state of the output signals PSu, PSv, PSw corresponding to the state of the operation mode in FIG. To do.

  When the output voltage of the inverter circuit unit 204 has a falling waveform and the induced voltage is in the delayed phase, the terminal voltage exceeds the virtual neutral point voltage value VN during the phase delay detection period, so that the position detection circuit unit output Becomes the 'H' signal. That is, when the 'H' signal output from the position detection circuit unit is detected, it is determined in step 108 that the induced voltage phase is in the delayed phase state, and the delayed phase state is set.

  Then, in step 109, the process returns to step 107 until the reference timer count value (P) has passed the commutation time, the delayed phase detection is continued, and if the commutation time has elapsed, the process proceeds to step 110.

  Step 110 generates a commutation signal (R), and performs a commutation operation with the lower drive signal DSx, DSy, or DSz turned on, depending on the state of the U-phase, V-phase, or W-phase, respectively.

  Thereafter, in step 111, the process waits until the reference timer count value (P) advances and the phase detection start time elapses.

  Subsequently, in step 112, when the reference timer count value (P) advances and a time of 100 μs immediately after a phase detection start time, for example, a time corresponding to an electrical angle of 90 degrees has elapsed, an output signal PSu from the position detection circuit unit 206 is obtained. , PSv, PSw are detected, and the phase is determined depending on the output state of the switching transistors Tru, Trx, Trv, Try, Trw, Trz, that is, the state of the output signals PSu, PSv, PSw corresponding to the state of the operation mode in FIG. Perform detection judgment.

  Thereafter, Step 112 and Step 113 are advance phase determination periods, and the advance phase of the induced voltage is detected as in Steps 102 and 103 described above.

  In step 114, the process returns to step 112 and continues phase detection until the reference timer count value (P) has passed a reference time, for example, a time corresponding to an electrical angle of 120 degrees.

  If the reference timer count value (P) has passed the reference time in step 114, the process proceeds to step 115.

  Step 115 determines the delayed phase state, and the comparator output of the corresponding phase remains in the “H” state until immediately before the lower drive signal is output, and the phase of the induced voltage is in the extremely delayed phase state. In step 116, the output voltage control means 213 increases the output duty of the voltage PWM control signal by a constant value. After step 116, the process returns to step 101, and the same operation is repeated thereafter.

  On the other hand, if the induced voltage is not in the delayed phase state in step 115, the process proceeds to step 117.

  In step 117, the lead phase state is determined, and the comparator output of the corresponding phase does not detect the 'L' state until immediately before the upper drive signal is output, and the phase of the induced voltage is in the extreme lead phase state. In step 118, the output voltage control means 213 decreases the output duty of the voltage PWM control signal by a constant value. After step 118, the process returns to step 101, and the same operation is repeated thereafter.

On the other hand, when the state of the induced voltage is not advanced and not in the phase state in step 117, the process returns to step 101 and the same operation is repeated thereafter.

  In this way, the phase neutral terminal voltages (values) that are ½ of the DC power supply voltage converted into the DC power supply by the rectifying unit 202 and the phase terminal voltages (values) Vu, Vv, Vw of the brushless DC motor. ) By comparing with VN, the phase difference between each phase output voltage phase due to the commutation operation of the inverter circuit unit and the induced voltage generated in the stator winding due to the rotor magnetic flux change is determined, and the induced voltage is compared with the inverter output voltage phase. When the phase is delayed, the inverter circuit output voltage is increased. Conversely, when the induced voltage phase is advanced with respect to the inverter output voltage phase, the inverter circuit output voltage is decreased.

  Therefore, during low-speed operation of the brushless DC motor, the on-time by the PWM control of the output voltage, which makes it difficult to detect the rotor position based on the induced voltage waveform, is short by forcibly outputting the frequency of the output voltage of the inverter circuit unit at the synchronous frequency. Even in a state (for example, 50 μs or less), that is, when the rotor position detection signal becomes unstable, it is forcibly switched by a drive waveform of a predetermined frequency based on the target rotational speed and the operating rotational speed at that time. The operation state of the brushless DC motor can be stably maintained by the synchronous operation that continues the flow.

  In addition, even when the operating state of the brushless DC motor changes due to load torque fluctuations or changes in the target rotational speed during synchronous operation due to forced commutation in a state where the rotor position cannot be detected by the induced voltage waveform. Because the inverter output voltage changes according to the state of the induced voltage phase with respect to the inverter output voltage, the motor output torque is prevented from being stepped out due to excessive torque or insufficient torque, and synchronized operation by forced commutation Stable motor operation at the time can be realized.

  As described above, since the reliability of the rotation control of the brushless DC motor 203 can be obtained, even when the inverter control device 200 according to the first embodiment is used for the electric compressor 220 provided with the brushless DC motor 203, a satisfactory operation is achieved. Is possible.

  Further, in the article storage device such as a refrigerator, which is an electric device including an electric compressor 220, a condenser, a decompression device, and a refrigeration cycle (all not shown) in which an evaporator is connected in a ring shape, the electric compressor 220 By controlling the drive using the inverter control device 200 of the first embodiment, it is possible to obtain a good system operation, stabilize the article storage temperature of the article storage device, and increase the reliability of article storage. Can do.

  As described above, the inverter control device according to the present invention compulsorily synchronizes even when the duty value is small and the magnetic pole position of the rotor is difficult to detect during low speed operation in the sensorless drive of the brushless DC motor. The driving range can be expanded by continuing the driving state by driving, and the brushless DC motor can be prevented from stepping out when the load torque increases during driving by synchronous driving, and stable driving operation can be continued. Therefore, it is useful for home electric appliances such as air conditioners, refrigerators, washing machines, etc., electric vehicles, etc. in which the operating speed of the brushless DC motor is changed to cause load fluctuations and voltage fluctuations.

200 Inverter Control Device 203 Brushless DC Motor 203a Stator 203b Rotor 203α Permanent Magnet 203β Permanent Magnet 203γ Permanent Magnet 203δ Permanent Magnet 203ε Permanent Magnet 203ζ Permanent Magnet 203u Stator Winding 203v Stator Winding 203w Stator Winding 204 Inverter Circuit Unit 206 Position Detection Circuit Numeral 208 Position detection determination means 209 Position detection commutation control means 210 Phase difference determination means 211 Forced synchronous commutation control means 213 Output voltage control means 220 Electric compressor

Claims (4)

A brushless DC motor comprising a rotor provided with a permanent magnet and a stator provided with a three-phase winding, an inverter circuit section for driving the brushless DC motor, and the inverter circuit for varying the operating rotational speed of the brushless DC motor Output voltage control means for changing the three-phase output voltage of the unit by PWM control, a position detection circuit unit for comparing and detecting an induced voltage of the brushless DC motor and a reference voltage generated by the output voltage of the inverter circuit unit, and the position Position detection determination means for outputting a rotor position detection signal from an induced voltage zero cross point based on a signal of the detection circuit section, and position detection conversion for outputting a commutation waveform of the inverter circuit section based on an output signal from the position detection determination means. Current control means and the output voltage phase of the inverter circuit unit based on the signal of the position detection circuit unit A phase difference that detects a phase difference of the induced voltage phase relative to the output voltage control unit and changes the three-phase output voltage by the output voltage control means according to the phase state to maintain the rotor induced voltage phase with respect to the output voltage of the inverter circuit unit at a predetermined phase. Determining position, and forced synchronous commutation control means for outputting a preset commutation waveform at a predetermined frequency in accordance with a target rotational speed of the brushless DC motor, and position detection in the position detection commutation of the brushless DC motor. When it is estimated that signal detection occurs above a certain level during the PWM control off period of the output voltage control means, it operates by forced synchronous commutation and changes the output voltage according to the change state of the rotor phase. An inverter control device that follows the operating state of the motor. The inverter control device according to claim 1, wherein when the set value of PWM control of the output voltage control means becomes smaller than a predetermined value, the inverter control device operates by forced synchronous commutation. The electric compressor which comprises the said brushless DC motor and is driven by the inverter control apparatus of Claim 1 or 2. An electric apparatus comprising the electric compressor and driven by the inverter control device according to claim 1.