JP2017220970A - Motor drive device, and electrical equipment that has compressor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of equipment by enhancing efficiency of a motor drive device.SOLUTION: A motor drive device comprises: a brushless DC motor; an inverter that supplies a power to the brushless DC motor; and position detection means that detects a rotor position of the brushless DC motor. The inverter is configured by six switching elements that are turned on and off depending on a position signal obtained by the position detection means. By making a timing of turning off the switching elements of the inverter in response to the position signal of the position detection means progress ahead of a timing of turning on the switching elements, a power supply period to the brushless DC motor can be adjusted. Thereby, an ON time ratio by PWM control becomes large, and a high-frequency current component of the brushless DC motor is suppressed. Thus, an iron loss of the brushless DC motor can be reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor driving device that drives a brushless DC motor by inverter control, and an electric device having a compressor using the motor driving device.

  Conventionally, this type of brushless DC motor drive device drives a brushless DC motor based on PWM (Pulse-Width-Modulation) controlled rectangular wave 120 degree energization, and is energized when the on-duty of PWM control reaches 100%. By extending the section to 120 degrees or more, the high-speed / high-load drive region is expanded (see, for example, Patent Document 1).

  FIG. 8 shows a motor driving device described in Patent Document 1. In FIG. As shown in FIG. 8, when each switching element 3a to 3f constituting the inverter 3 shifts from OFF to ON, the advance timing control is performed by the ON timing control means 103, and when switching from ON to OFF, By not performing advance angle control by the off timing control means 104, overlap energization is performed.

  Further, the conduction angle and the lead angle and the inverter input DC voltage are controlled so that the motor drive power becomes the target power value, thereby enabling a high output and a high rotation speed (see Patent Document 2, for example). FIG. 9 shows a motor driving device described in Patent Document 2. In FIG. As shown in FIG. 9, the drive control unit 201 of the brushless DC motor has a power detection unit 202 that detects drive power, and an energization pulse signal generation unit 203 that generates an inverter drive signal pattern and sets an inverter input voltage. The inverter input voltage value, the energization angle, and the advance angle are controlled so that the drive power matches the target set power value.

JP 2006-50804 A JP 2008-167525 A

  However, in the configuration of the above-mentioned Patent Document 1, it is possible to expand the high load / high speed drive region by speeding up the turn-on of the switching element and expanding the power supply section to the brushless DC motor to 120 degrees or more. There was no improvement in the low-speed drive region, and there was a problem that the efficiency of the motor drive device was lower than the circuit and motor loss.

  In the configuration described in Patent Document 2, it is necessary to select three independent parameters of input voltage, conduction angle, and advance angle according to each driving state such as a load state and a driving speed state of the brushless DC motor. Increased development man-hours, calculation / selection of 3 parameters according to driving conditions, etc., and use of calculation elements capable of high-speed calculation due to complicated control, or table of optimum values for each parameter according to driving conditions There was a problem that the cost of the motor drive device was increased, such as the use of a memory element.

  The present invention solves the above-mentioned conventional problems, and provides a motor drive device with high efficiency and low power consumption at a low cost by reducing the loss of the device when the brushless DC motor is driven at low load and low speed. With the goal.

  In order to solve the conventional problems, a motor driving device of the present invention includes a brushless DC motor, an inverter that supplies power to the brushless DC motor, and a position detection unit that detects a rotor position of the brushless DC motor. The inverter includes six switching elements that are turned on or off in accordance with the position signal obtained by the position detection means, and the inverter switching element is turned off with respect to the position signal of the position detection means. The timing of turning on is advanced from the timing of turning on.

  As a result, when the brushless DC motor is driven at a low load and at a low speed, the section for supplying power to the brushless DC motor stator winding is narrowed, so the on-time ratio of PWM control is increased and flows to the brushless DC motor. Motor iron loss can be reduced by suppressing the high-frequency current component of the current.

  The motor driving device of the present invention can achieve high efficiency and low power consumption of the device when the brushless DC motor is driven at low load and low speed.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Waveform and timing chart of each part in Embodiment 1 of the present invention Switching element off-tamming adjustment control start determination flowchart Flow chart from PWM control to off-timing adjustment control Flow chart showing operation of off-timing adjustment control The figure which shows the terminal voltage waveform of a brushless DC motor The figure which shows the phase current waveform of a brushless DC motor Block diagram of a conventional motor drive device Control block diagram of a conventional motor drive device

  A first invention includes a brushless DC motor, an inverter that supplies electric power to the brushless DC motor, and position detection means that detects a rotor position of the brushless DC motor, wherein the inverter is obtained by the position detection means. It is composed of six switching elements that are turned on or off in accordance with the received position signal, and is advanced from the timing of turning on the timing for turning off the switching element of the inverter with respect to the position signal of the position detecting means. Since the power supply section to the brushless DC motor can be shortened in the low load / low speed driving of the DC motor, the switching loss due to the reduction in the number of PWM switchings can be suppressed, so that the efficiency of the motor driving device can be improved.

  According to a second invention, in the first invention, the PWM control means for adjusting the voltage supplied to the brushless DC motor at a high ratio of the ON period by switching at a high frequency of the switching element of the inverter; A commutation control unit for controlling the timing of turning off, and adjusting the off-timing of the switching element so that the duty ratio of the on-period by the PWM control means is 100%, thereby turning on / off the switching element at a high frequency. Since the turn-off is not performed, the switching loss is greatly suppressed, and the efficiency of the circuit can be increased. In addition, since no high-frequency current is generated in the motor current when the PWM control is turned on / off, the motor efficiency can be improved by reducing the motor iron loss, and the motor drive device can be greatly improved in efficiency. Furthermore, since the generation of high-frequency sound associated with high-frequency switching by PWM control is eliminated, the motor drive device can be quieted.

According to a third invention, in the first or second invention, the switching element is switched from the on-state to the off-state within an electrical angle range of 0 to 30 degrees with respect to the switching from the off-state to the on-state. By performing it at an early timing, an advance angle of 1/2 of the electrical angle that speeds up the turn-off of the switching element is automatically added. However, it is possible to secure a stable driving performance in which step-out or the like hardly occurs.

  According to a fourth invention, in any one of the first to third inventions, when the on-time ratio of the switching element by the PWM control means becomes a predetermined value or more, the commutation control means turns off the switching element. By moving the motor from the on-timing, it is possible to ensure stable start-up by using PWM control at ultra-low speed immediately after starting the brushless DC motor, or at low load / low-speed drive, and at ultra-low load, ultra-low speed. The driving stability of is improved.

  According to a fifth aspect of the present invention, a brushless DC motor driven by the motor driving device according to any one of the first to fourth aspects drives a compressor of a refrigeration cycle. The COP of the compressor can be improved, and a highly efficient refrigeration cycle can be provided.

  The sixth invention is an electric device having a compressor driven by the motor drive device of any one of the first to fifth inventions, and thereby, an electric device with low power consumption can be provided by a highly efficient refrigeration cycle. At the same time, noise in the high frequency band associated with high-frequency switching is suppressed, and the electric equipment can be quieted.

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

(Embodiment 1)
FIG. 1 shows a block diagram of a motor drive apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, an AC power source 1 is a general commercial power source, and has an effective value of 100 V 50 Hz or 60 Hz in Japan. The converter circuit 2 converts the AC power source 1 into a DC voltage. The converter circuit 2 in FIG. 1 includes a rectifier circuit 2a in which four diodes are bridge-connected, a smoothing circuit 2b using a capacitor, and a switch unit 2c for switching the output voltage, thereby allowing the output voltage to be double voltage rectification and full wave rectification. Although it is configured to switch to a stage, a single output configuration of a double voltage rectified output or a full wave rectified output may be used without any problem, and a configuration using a step-up chopper or a step-down chopper or a configuration capable of adjusting the output to an arbitrary voltage may be used.

  The inverter 3 is composed of six switching elements 3a to 3f, and MOSFETs are used in the present embodiment. Then, each switching element is connected in a three-phase bridge, and an arbitrary direct current voltage is converted into a three-phase alternating current voltage by switching on / off an arbitrary switching element.

  The brushless DC motor 4 includes a stator having a three-phase winding and a rotor having a permanent magnet, and is driven by the three-phase AC power from the inverter 3.

  The position detecting means 5 detects the magnetic pole position of the brushless DC motor. In the first embodiment of the present invention, the phase of the induced voltage (zero cross point) generated in the stator winding by the rotation of the rotor from the motor terminal voltage. However, a method using a position sensor such as a Hall IC or a current detection method using a current sensor may be used.

The speed detection means 6 detects the driving speed of the brushless DC motor from the output signal of the position detection means 5, and in this embodiment, the induced voltage zero-cross period generated in the stator winding by the rotation of the brushless DC motor rotor is detected. Calculate based on

  The error detection means 7 detects the difference between the drive speed of the brushless DC motor 4 obtained by the speed detection means 6 and the target speed.

  The commutation control unit 8 sets a phase for supplying power to the brushless DC motor stator winding in the range of electrical angle of 90 degrees or more and 150 degrees or less based on the signal from the position detection means 5. Further, the commutation control unit 8 includes an on timing control unit 9 that sets a timing for turning on and off the switching elements 3 a to 3 f and an off timing control unit 10, so that the switching element of the inverter 3 is turned on and off. Each timing can be set individually.

  The PWM control unit 11 controls the three-phase AC output of the inverter by adjusting the output voltage by PWM control so that the brushless DC motor 4 is driven at the target speed. Here, when driving at a PWM on-time time ratio larger than the value obtained by dividing “the minimum electric angle of the power supply section to the brushless DC motor winding” by “electric angle 120 degrees”, the PWM control means has a time ratio of 100. %, The off-timing controller 10 advances the turn-off timing of the switching element earlier.

  It is desirable to change the turn-off timing gradually in order to prevent an abrupt change to the operating state of the brushless DC motor, but there is no particular problem even if it is performed in one control cycle. The speed control of the brushless DC motor 4 by adjusting the on-time ratio by the PWM control means 11 is performed when the driving speed is very low such as when the brushless DC motor 4 is started or when the driving load is small. In other states, the PWM control means 11 controls the speed of the brushless DC motor 4 by adjusting the OFF timing of the switching element by the commutation control unit 8 so that the on-time ratio is 100%.

  The waveform synthesizing unit 12 synthesizes the PWM signal generated by the PWM control unit 11 and the signal generated by the commutation control unit 8, and based on the synthesized signal, the drive unit 13 turns on the switching elements 3a to 3f of the inverter 3. In an off state, an arbitrary three-phase AC voltage is generated, supplied to the brushless DC motor 4 and driven.

  The compression element 14 is connected to the rotor shaft of the brushless DC motor 4 and sucks, compresses and discharges the refrigerant gas. The brushless DC motor 4 and the compression element 14 are accommodated in the same hermetic container to constitute the compressor 15. The discharge gas compressed by the compressor 15 constitutes a refrigerating and air-conditioning system that returns to the suction of the compressor 15 through the condenser 16, the decompressor 17, and the evaporator 18. Then, since heat is absorbed, heating and heat absorption can be performed. If necessary, a heat blower may be further promoted by using a blower or the like for the condenser 16 or the evaporator 18. In the first embodiment, the refrigeration and air conditioning system is used as a refrigeration cycle of the refrigerator 19, and the evaporator 18 is used to cool the food storage chamber 21 surrounded by the heat insulating wall 20.

  The operation and action of the motor driving apparatus configured as described above will be described below.

FIG. 2 is a timing chart of the motor drive apparatus according to Embodiment 1 of the present invention. FIG. 2 (1) is a driving waveform and timing diagram in a general 120-degree energization, and (2) is a waveform when the brushless DC motor is driven by adjusting the off timing of the switching element by the off timing control unit 10. FIG. And shows the timing. The induced voltage generated by the rotation of the brushless DC motor 4 is shown as E, the terminal voltage is shown as Vu, and both waveforms show only the U phase, but the V phase and W phase waveforms have the same shape with their phases shifted by 120 degrees. It has a waveform. The drive signals of the switching elements 3a, 3b, 3c connected to the high voltage side are indicated as U +, V +, W +, and the drive signals of the switching elements 3d, 3e, 3f connected to the low voltage side are 180 degrees from the drive signals of the respective high voltage side SW elements. The waveform is out of phase.

  In order to detect the timing (not shown) of switching the energized phase of the stator winding, the zero cross point of the induced voltage is detected as a position signal in the rotor magnetic pole relative position detection. The detection of the zero cross point appears in a section (C1, C2, C3, C4) in which no voltage is applied to the phase winding (in the U phase shown in FIG. 2, both switching elements 3a and 3d are turned off). A point (P1, P2) at which the 1/2 magnitude relationship between the induced voltage and the inverter input voltage Vdc is inverted is detected. Therefore, a position signal is generated every electrical angle of 30 degrees twice per phase of electrical angle, 6 times in total for 3 phases.

  When the energization pattern (U +, V +, W +) of the switching elements (high voltage side connection 3a, 3b, 3c) in 120 degree energization shown in FIG. 2 (1) is seen, W + after position detection (P1) 30 degrees electrical angle By turning on U + (switching element 3a) at the same time as turning off, one of the three-phase windings is always energized in the entire electrical angle range of 360 degrees. On the other hand, in FIG. 2 (2), after position detection (P1), W + (switching element 3c) is turned off before 30 electrical degrees elapses, and then U + is turned on 30 electrical degrees later.

  The induced voltage appears in the C1 to C4 interval only when the switching element of the other phase is on, that is, the PWM on period. Therefore, the switching element is turned off earlier than the turn-on, and the power supply section to the brushless DC motor is shortened. As a result, the power supply section of the fixed winding is shortened, and the loss of the inverter circuit can be suppressed by reducing the number of on / off operations by PWM control. Furthermore, by shortening the power supply section, the on-time of the PWM control becomes longer, and the period in which the position detection signal can be acquired becomes longer. Therefore, the position detection accuracy is improved.

  Furthermore, the timing for turning off the switching element is from immediately after position detection until after 30 degrees of electrical angle has elapsed after position detection (range A1 with respect to position detection P1). Consideration is made so that a torque drop is not caused by a lag phase so that the phase can be made to be a leading phase with respect to the induced voltage.

  In this way, by setting the off timing of the switching elements (3a to 3f) within 30 degrees immediately after position detection, the power supply section to the three-phase winding is adjusted to 90 degrees or more and 120 degrees or less, and power supply is suspended. The shorter the section (A1, A2, A3), the larger advance angle B (1/2 of the electrical angle of the no power supply section) is automatically added, the motor torque increases and there is no power supply section. Nevertheless, stable driving without step-out is possible.

  Next, the operation of adjusting the OFF timing of the SW element will be described using a flowchart.

  FIG. 3 is a flowchart for determining the start of the OFF timing control of the switching element. In FIG. 3, first, in S11, it is confirmed whether the on-time ratio of the switching element generated by the PWM control means 11 is larger than a predetermined value. If it is larger than the predetermined value, the process proceeds to S12 to start off timing adjustment control. If the value is smaller than the predetermined value, PWM control is performed. The predetermined value of the on-time ratio is set to 75% from the ratio of 120 degrees energization because the minimum power supply interval to the winding is 90 degrees in this embodiment, but it is appropriate for the application. Select any value.

In this way, the start of the switching element off-timing adjustment control is used in combination with the PWM control when the ratio is greater than the predetermined PWM on-time ratio, which is extremely low when the drive speed is extremely low such as at the time of start-up or at the time of low-speed drive. Stable drive can be realized under all load conditions by preventing start-up failure, unstable operation state, extreme torque drop, etc. due to extremely short power supply section to windings when load is low etc. I am doing so.

  FIG. 4 is a flowchart showing a transition from PWM control to off timing adjustment. When the start of the off-timing adjustment control is determined according to the flow shown in FIG. 3, the switching element is turned off by an arbitrary time in S21, and the speed is controlled by PWM control in S22. Since the power supply section to the brushless DC motor is shortened by shortening the off timing, the time ratio of the on time by PWM control increases. When the on-time ratio by PWM control is less than 100 in S23, the process returns to S21 and continues its operation. When the on-time ratio reaches 100% in S23, the process proceeds to S24, the state where the on-time ratio is 100% is maintained, and the adjustment control of the switching element off-timing is started in S25.

  Next, the operation of the speed control of the brushless DC motor after shifting to the off timing adjustment control of the switching element will be described with reference to FIGS.

  FIG. 5 is an operation flowchart of the off-timing adjustment control of the switching element according to the first embodiment. In FIG. 5, first, in S31, the deviation between the driving speed of the brushless DC motor 4 detected by the speed detecting means 6 and the target speed is detected by the error detecting means 7, and if it is faster than the target speed, the process proceeds to S32. In S32, the on-time ratio in the PWM control means 11 is maintained at 100%, and it is determined whether or not the off-timing control unit 10 can advance the off-timing. If possible, the off-time of the switching element is determined. The speed control is performed so that the speed of the brushless DC motor is reduced by reducing the power supply section to the winding by speeding up (S33). If impossible, the PWM control by the PWM control means 11 is performed (S34). In the first embodiment, it is possible to determine whether or not the off timing can be advanced earlier if the switching element is off immediately after the position detection of the switching element. Judge that there is no. In the first embodiment, since the advance angle is 0 degree, the minimum power supply section to the stator winding is an electrical angle of 90 degrees.

  When it is determined that the driving speed of the brushless DC motor is slower than the target speed (S35), the process proceeds to S36, and if the switching element is off-timed until the electrical angle of 30 degrees elapses from the position detection, the process proceeds to S37. By delaying the off timing, speed control is performed so that the drive speed is increased by increasing the power supply period to the brushless DC motor winding. If the off timing of the off switching element is the position where the electrical angle of 30 degrees has elapsed in S36, the process proceeds to S38. In S38, if the OFF timing of the switching element is further delayed, the applied voltage phase becomes a lagging phase with respect to the induced voltage, and there is a possibility of motor torque reduction and step-out associated therewith. The speed control is performed so that the drive speed of the brushless DC motor is increased by increasing the power supply section to the winding. Note that the upper limit to advance the on-timing is until immediately after position detection, and the maximum power supply section to the winding at this time is an electrical angle of 150 degrees.

In the first embodiment, since the advance angle is set to 0 degree, the energization at the electrical angle of 120 degrees is performed by matching the off-timing and the on-timing of the switching element. In an IPM motor in which a permanent magnet is embedded in the stator, it is necessary to provide an arbitrary advance angle in order to achieve optimal driving. Therefore, the OFF timing adjustment range of the switching element is the position where “(electrical angle 30 degrees) − (advance angle)” has elapsed from the position detection timing immediately after position detection so that any motor such as an IPM motor can be optimally driven. . The on-timing of the switching element is the timing when “(electric angle 30 degrees) − (advance angle)” has elapsed from the position detection timing (for example, when the advance angle is 10 degrees, the turn-off is from the position detection until the electric angle has elapsed 20 degrees. The turn-on is performed at an electrical angle of 20 degrees after the position detection), and the sum of the electrical angle from the position detection to the turn-off and the electrical angle from the position detection to the turn-on is set to 60 degrees or less. Adjustable in an arbitrary range from 0 degrees to 30 degrees electrical angle from the turn-on, the advance angle and on / off timing can be freely set between position detection and electrical angle 30 degrees.

  In addition, the electric power supply section to the winding when the advance angle is added is adjusted in the range of “90 degrees + advance angle” to 120 degrees in terms of electrical angle.

  Further, when the brushless DC motor 4 is driven at a high speed and with a high load, the turn-off timing is set as the timing at which “(electrical angle 30 degrees) − (advance angle)” has elapsed from the position detection, and the position detection is performed immediately after the position detection. By adjusting within the range of timing when “electrical angle 30 degrees−advance” has elapsed, the power supply section to the winding can be adjusted within the range of electric angle 120 degrees to “electrical angle 150—advanced”.

  Therefore, by adjusting the turn-on and turn-off timing of the switching element, it is possible to adjust the power supply section to the brushless DC motor in the range of electrical angle from 90 degrees to 150 degrees (when the advance angle is 0 degrees). It can handle a wide range of loads and speeds from driving to high-speed and high-load driving.

  Next, the terminal voltage of the brushless DC motor in the present embodiment will be described with reference to FIG. 6 (1) and (2) show the sections C1 and F1 in FIG. 2 (1), and FIGS. 6 (3) and (4) show the sections C3 and F2 in FIG. 2 (2).

  As shown in FIGS. 6 (1) and 6 (2), FIG. 2 (1) showing a waveform in 120 degree energization PWM control has a high frequency PWM carrier frequency component (period f) superimposed thereon. As shown in FIG. 6 (1), in the section C1, the ringing noise component due to the influence of the motor winding, the stray capacitance, etc. is also superimposed at the moment when the PWM is turned on. In the C1 section, the terminal voltage Vu of the brushless DC motor is compared with 1/2 of the inverter input voltage, and the point where the magnitude relationship is inverted is detected as the zero crossing point (P point) of the induced voltage of the brushless DC motor. The Px point is erroneously detected due to the noise component. This position detection misalignment causes pulsation and vibration of the driving speed of the brushless DC motor, an increase in noise, and a decrease in driving efficiency.

  On the other hand, as shown in FIG. 6 (3), when the on-time ratio of PWM control is 100%, an induced voltage waveform appears in the terminal voltage Vu, and position detection at an accurate zero cross point (point P) is possible. It is possible to realize a stable drive with low noise, low vibration and low loss.

  Further, in the section F1, a switching loss due to switching on / off of the switching element at a high frequency by PWM control occurs as shown in FIG. 6 (2), but the on-time ratio 100 is shown in FIG. 6 (4). Switching operation is not performed in% driving, so switching loss does not occur, and high efficiency can be realized by reducing circuit loss.

  Furthermore, the electric current which flows into a brushless DC motor is shown in FIG. FIG. 7 (1) shows a waveform in PWM control by 120-degree energization, and it can be seen that a high-frequency current component accompanying the on / off of the switching element in PWM control is superimposed. While this high-frequency current component causes motor iron loss, since the high-frequency current component is not generated in the operation at the PWM on-time ratio of 100% shown in FIG. High efficiency can be achieved.

A refrigerator having a cooling system for driving a compressor with the motor driving apparatus configured as described above will be described.

  In recent refrigerators, heat penetration from the outside is very little due to improvement of heat insulation technology such as adoption of vacuum heat insulating material. Therefore, except for housework hours in the morning and evening when doors are frequently opened and closed, the refrigerator is in a stable cooling state for most of the day, and the compressor is driven at low speed and low load with reduced refrigeration capacity. Has been done. Therefore, in order to reduce the power consumption of the refrigerator, it is very effective to increase the driving efficiency at the time of low speed and low output of the compressor, that is, the brushless DC motor.

  In Embodiment 1 of the present invention, in a state where the brushless DC motor is driven at a low speed and a low load, high frequency on / off control by PWM control is not performed, and the PWM on-time ratio is set to 100%. The drive speed is controlled while adjusting the power supply interval to the windings of. Thereby, since the inverter 3 does not generate a switching loss due to PWM control, the inverter circuit efficiency can be greatly improved.

  In the present embodiment, a MOSFET is used as the switching element of the inverter 3. Due to its structural characteristics, the MOSFET does not have a PN junction in the path of the output current at the time of on, so the loss at the time of on especially at the time of low current output is very low compared to other power devices such as IGBTs. .

  As described above, since the refrigerator is driven at a low speed and a low load for most of the day, the current flowing through the brushless DC motor is low. Therefore, when the present invention is used for driving the compressor of the refrigerator, using the MOSFET as the switching element of the inverter 3 is very effective for reducing the power consumption of the refrigerator.

  Further, by not performing on / off control by PWM control, the winding current of the brushless DC motor has no high-frequency current component, and motor iron loss can be significantly suppressed, and motor efficiency can be improved.

  Further, in the PWM control, a switching operation is generally performed at a PWM frequency of about 1 kHz to 20 kHz, and this frequency component is generated as noise. Since the refrigerator is operated all day regardless of day and night, the quiet design is very important. The motor driving device of the first embodiment has a duty ratio of 100%, which is caused by PWM control. Therefore, it is very effective for quiet design of refrigerators.

  As described above, the first embodiment includes the brushless DC motor 4, the inverter 3 that supplies power to the brushless DC motor 4, and the position detection unit 5 that detects the rotor position of the brushless DC motor 4. Is composed of six switching elements that are turned on or off according to the position signal obtained by the position detection means 5, and turns on the timing for turning off the switching element of the inverter 3 with respect to the position signal of the position detection means 5. By moving ahead of the timing, it is possible to shorten the section of the brushless DC motor that is fixed and supplying power to the winding, so the on-time ratio by PWM control increases, and the high-frequency current component of the brushless DC motor is suppressed. The iron loss of the brushless DC motor can be reduced. Further, the number of on / off times of the switching element associated with the PWM control is reduced, and the motor drive device can be made highly efficient by reducing the inverter loss.

In the present embodiment, the switching element of the inverter 3 is switched at a high frequency to thereby adjust the voltage supplied to the brushless DC motor 4 and the commutation for controlling the timing for turning on and off the switching element. Since it has the control unit 8 and the off-timing of the switching element is adjusted so that the time ratio of the on-time by the PWM control means 11 becomes 100%, it becomes possible to greatly suppress the switching loss accompanying the on / off of the switching element. The efficiency of the inverter 3 can be improved. Further, since no high frequency component is generated in the current flowing through the brushless DC motor due to the high frequency on / off of the switching element, motor iron loss can be significantly suppressed. As a result, it is possible to provide a highly efficient motor drive device with low loss of the brushless DC motor and circuit. Further, since the on-time ratio of PWM control is set to 100%, no noise in a high frequency band due to high frequency switching is generated, and the apparatus can be quieted. Furthermore, driving with an on-time duty ratio of 100% can eliminate position detection deviation due to the influence of ringing noise and realize accurate position detection, so that driving stability can be further improved, thereby further increasing the motor driving device. Increase efficiency, reduce noise, and reduce vibration.

  The switching element is switched from the on-state to the off-state by switching the switch from the off-state to the on-state with an early timing in an electrical angle range of 0 degrees to 30 degrees. An advance angle of ½ of the angle is automatically added, and even when driving with a driving waveform having a power supply pause period, stable driving is possible without occurrence of step-out.

  Also, the switching timing of the energized phase of the brushless DC motor stator winding is the sum of the electrical angle that advances the OFF timing of the switching element and the electrical angle that advances the ON timing with respect to the position signal of the position detection means. The electrical angle for advancing the off timing is set to be greater than the electrical angle for advancing the on timing. As a result, since the advance angle and the power supply suspension period to the brushless DC motor can be set in the range of electrical angle 0 degree to 30 degrees, the optimum power supply period can be set according to the load and driving speed state of the brushless DC motor. Since it becomes possible to optimally drive an embedded magnet (IPM) motor that needs to give an optimal advance angle depending on the load state and speed, various types of permanent magnet motors can be driven with high efficiency.

  Also, the power supply section to the three-phase winding of the brushless DC motor is set to an electrical angle of 90 degrees or more and 150 degrees or less, and when the power supply section is an electrical angle of 90 degrees or more and less than 120 degrees, the switching element is turned off. It is possible to realize an optimum driving state over a wide range of loads and driving speed ranges of the brushless DC motor as it is further advanced.

  In addition, when the on-time ratio of the switching element by the PWM control unit 11 is equal to or greater than a predetermined value, the commutation controller 8 advances the OFF of the switching element from the on-timing, so that the PWM on-time ratio is lower than the predetermined value. Even when the load is very low during low speed driving or when starting up, the power supply section to the winding becomes extremely short, causing startup failure, unstable operation during driving, or extreme torque drop. It prevents it and realizes stable driving under all load conditions.

  In addition, the brushless DC motor can provide a compressor having a high COP and a highly efficient refrigeration cycle by improving the motor efficiency by reducing iron loss by driving the compressor of the refrigeration cycle.

  Further, if the refrigeration cycle that drives the compressor with the motor driving device of the present invention is adopted in the refrigerator, the circuit efficiency of the motor driving device is improved and the use of the high-efficiency refrigeration cycle using the high COP compressor reduces the power consumption. In addition to providing a low refrigerator, there is no generation of noise in the high frequency band associated with the switching operation of PWM control, and the refrigerator can be quiet.

As described above, the motor driving device according to the present invention can reduce the circuit loss of the motor driving device, improve the motor efficiency, and reduce the driving noise and vibration. Therefore, the refrigerator, the air conditioner, the washing machine, the pump, the electric fan, It can be applied to any device using a brushless DC motor such as a fan or a vacuum cleaner.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter circuit 3 Inverter 4 Brushless DC motor 5 Position detection means 6 Speed detection means 7 Error detection means 8 Commutation control part 9 On timing control part 10 Off timing control part 11 PWM control part 12 Waveform synthesis part 13 Drive means DESCRIPTION OF SYMBOLS 14 Compression element 15 Compressor 16 Condenser 17 Depressurizer 18 Evaporator 19 Refrigerator 20 Insulation wall 21 Food storage room

Claims (6)

A brushless DC motor; an inverter that supplies power to the brushless DC motor; and a position detection unit that detects a rotor position of the brushless DC motor. The inverter corresponds to a position signal obtained by the position detection unit. A motor driving device comprising: six switching elements that are turned on or off in advance, and a timing for turning off the switching element of the inverter is advanced with respect to a position signal of the position detecting means from a timing of turning on. PWM control means for adjusting the voltage to be supplied to the brushless DC motor at a high ratio of the ON period by switching at a high frequency of the switching element of the inverter, and a commutation control unit for controlling the timing for turning on and off the switching element. The motor drive device according to claim 1, wherein the off-timing of the switching element is adjusted so that the duty ratio of the ON period by the PWM control means is 100%. 3. The motor according to claim 1, wherein the switching element is switched from the on state to the off state at an earlier timing in the range of electrical angle of 0 to 30 degrees with respect to the switching from the off state to the on state. Drive device. The commutation control means causes the switching element to be turned off from the on timing when the ratio of the on-period of the switching element by the PWM control means exceeds a predetermined value. The motor drive device described. The motor driving apparatus according to any one of claims 1 to 4, wherein the brushless DC motor drives a compressor of a refrigeration cycle. An electric apparatus having a compressor driven by the motor drive device according to any one of claims 1 to 5.

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