JP2008172880A - Method and device for driving brushless dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly attain high efficiency and safe driving in case of voltage fluctuation in a brushless DC motor. <P>SOLUTION: A voltage state recognition part 7 capable of recognizing the state of voltage supplied to an inverter 3 enables the driving device for a brushless DC motor provided with the recognition part to maintain motor current constant, even when there is a voltage fluctuation occurring during synchronous drive operation, with the stability of the system improved and step-out shutdown suppressed. Furthermore, a change in the supply voltage can be recognized to allow the supply voltage during synchronous operation to be adjusted, thereby an effect such as enhancement during synchronous operation can be exhibited. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  More particularly, the present invention relates to a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding. More particularly, the present invention relates to a method and apparatus for driving a brushless DC motor that is optimal for driving a compressor such as a refrigerator or an air conditioner.

  In recent years, large-scale models of 400L or more have become mainstay refrigerators, and most of these refrigerators are inverter-controlled refrigerators that variably drive the rotational speed of a highly efficient compressor. These refrigerator compressors generally employ a brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding for high efficiency. In addition, since the brushless DC motor is installed in an environment of high temperature, high pressure, refrigerant atmosphere, and oil atmosphere in the compressor, a position detection sensor such as a hall element normally used in a brushless DC motor cannot be used. Therefore, generally, a method of detecting the rotational position of the rotor from the counter electromotive voltage or direct current of the motor is often used.

  A conventional technique is disclosed in Patent Document 1, for example. The prior art will be described with reference to the drawings. FIG. 10 is a block diagram of a conventional driving device for driving a brushless DC motor.

  In FIG. 10, a commercial power source 101 is an AC power source having a frequency of 50 Hz or 60 Hz and a voltage of 100 V in Japan.

  The rectifier circuit 102 converts the AC voltage of the commercial power supply 101 into a DC voltage. The rectifier circuit 102 includes bridge-connected rectifier diodes 102a to 102d and smoothing electrolytic capacitors 102e and 102f. In the circuit shown in FIG. 10, the voltage rectifier circuit is a double voltage rectifier circuit. Can be obtained.

  The inverter circuit 103 has a three-phase bridge configuration including six switch elements 103a, 103b, 103c, 103d, 103e, and 103f. Each switch element includes a diode for return current in the reverse direction of each switch element, but this is omitted in the figure.

  The brushless DC motor 104 includes a rotor 104a having a permanent magnet and a stator 104b having a three-phase winding. When the three-phase alternating current generated by the inverter 103 flows through the three-phase winding of the stator 104b, the rotor 104a can be rotated. The rotational movement of the rotor 104a is changed to a reciprocating movement by a crankshaft (not shown), and a piston (not shown) reciprocates in a cylinder (not shown) to compress the refrigerant. Drive.

  The counter electromotive voltage detection circuit 105 detects the rotational relative position of the rotor 104a from the counter electromotive voltage generated by the rotation of the rotor 104a having the permanent magnet of the brushless DC motor 104.

  The commutation circuit 106 performs logical signal conversion based on the output signal of the back electromotive voltage detection circuit 105, and generates a signal to be driven by sequentially switching the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103.

  The synchronous drive circuit 107 forcibly outputs an output of a predetermined frequency from the inverter 103 and drives the brushless DC motor 104, and forcibly outputs a signal having the same shape as the logical signal generated by the commutation circuit 106. It is generated at a predetermined frequency.

  The load state determination circuit 108 determines a load state in which the compressor 104 is operated.

  The switching circuit 109 switches whether the brushless DC motor of the compressor 104 is driven by the commutation circuit 106 or the synchronous driving circuit 107 according to the output of the load state determination circuit 108.

  The drive circuit 110 drives the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103 by the output signal from the switching circuit 109.

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

  When the load detected by the load state determination circuit 108 is a normal load, driving by the commutation circuit 106 is performed.

  The back electromotive voltage detection circuit 105 detects the relative position of the rotor 104 a of the brushless DC motor 104. Next, the commutation circuit 106 creates a commutation pattern that drives the inverter 103 in accordance with the relative position of the rotor 104a.

  This commutation pattern is supplied to the drive circuit 110 through the switching circuit 109, and drives the switch elements 103a, 103b, 103c, 103d, 103e, and 103f of the inverter 103.

  By this operation, the brushless DC motor 104 is driven in accordance with its rotational position.

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

  When the load of the brushless DC motor increases, the rotational speed decreases due to the characteristics of the brushless DC motor. This state is determined by the load state determination circuit 108 to be a high load state, and the output of the switching circuit 109 is switched to the signal from the synchronous drive circuit 107.

By driving in this way, it is possible to suppress a decrease in the rotational speed at the time of high load.
JP-A-9-88837

  However, the conventional configuration has the following problems.

  If the voltage supplied to the inverter 103 by the rectifier circuit 102 is stable, the control stability depends only on the strength of the magnetic force of the permanent magnet and the strength of the rotating magnetic field generated by the stator 104b. Even when the synchronous drive circuit 107 that is open loop control is in operation, stable operation can be maintained. However, the voltage output from the commercial power supply 101 fluctuates, the amount of charge to the electrolytic capacitors 102e and 102f fluctuates due to the inductance characteristics of the previous stage of the commercial power supply 101 and the rectifier circuit 102, and the capacitance of the electrolytic capacitors 102e and 102f. When the voltage supplied to the inverter 103 fluctuates when the voltage is low, the relative position of the rotor 104a is not detected, which may cause an unstable operation state. That is, when the output limit torque of the brushless DC motor 104 is extremely low compared to the initial state due to secular change or the like (although there is no problem in a situation where there is a sufficient margin with respect to the load torque) When operating in a system that requires a very large load torque that could not be predicted at the time of design, the system was in an unstable operating state.

  Further, when an instantaneous voltage drop occurs in the output voltage of the commercial power supply 101, the characteristics of the electrolytic capacitors 102e and 102f (the characteristic that the voltage changes gently when the voltage drops and the voltage changes sharply when the voltage rises) are as follows. It will fall into the driving state like. 1) Due to the voltage drop, the load state determination circuit 108 detects a torque shortage state, and the switching circuit 109 selects the synchronous drive circuit 107. 2) The switching circuit 109 remains in the state of selecting the synchronous drive circuit 107 until the excessive torque is detected even after the power supply voltage is restored, and the stator 104b and the six switch elements 103a to 103f are excessive. Current continues to flow. 3) In some cases, an excessive torque state cannot be detected, and an excessive current continues to flow for a long time.

  In addition, when the magnitude and time of the current that can be passed from the six switch elements 103a to 103f are relatively small, passing an excessive current for a long time as described above can cause deterioration in the performance of the element. There is sex.

  Further, when the brushless DC motor 104 has an IPM structure, a reluctance torque can be generated larger than that of an SPM structure. Therefore, the output torque can be increased by increasing the commutation timing relative to the rotor 104a. Therefore, it can be said that it is suitable for operation with the synchronous drive circuit 107. However, when the operation is performed by the synchronous drive circuit 107, a current larger than the current that can be output by the commutation circuit 106 can be realized, so that the magnitude of the excessive current is relatively large. In addition, even when the motor has a relatively small amount of iron loss reduction type stator 104b, high-speed and high-output torque operation can be realized by operating with the synchronous drive circuit 107. As in the case, the magnitude of the excessive current is relatively large.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to provide a brushless DC motor driving method and driving apparatus capable of controlling the current flowing through the motor in accordance with the supply voltage state to the inverter. It is another object of the present invention to provide a brushless DC motor driving method and apparatus capable of further improving reliability by enabling selection of a waveform generating means in accordance with a supply voltage state to an inverter.

  In order to solve the above-described conventional problems, the brushless DC motor of the present invention includes a method in which a synchronous drive waveform generator that generates a waveform synchronized with the frequency while changing a predetermined frequency drives the motor, The current flowing through the motor can be controlled in accordance with the state of the supply voltage to the inverter.

  An apparatus comprising: a synchronous drive waveform generator that generates a waveform synchronized with the frequency while changing a predetermined frequency; and a position detection drive waveform generator that generates a waveform according to the rotational position of the rotor. By making it possible to select the waveform generating means according to the state of the supply voltage to the device, it is possible to prevent the generation of excessive motor current in advance.

  In addition, while the synchronous drive waveform generator is driving the motor, the current flowing through the motor can be controlled according to the state of the supply voltage to the inverter, so that the synchronous drive waveform generator is driving the motor. Among them, it is a device that makes it possible to adjust the voltage.

  The brushless DC motor of the present invention can control the amount of current flowing to the motor according to the state of the supply voltage to the inverter, and the applied voltage to the motor varies even during driving by the synchronous drive waveform generator. There is no direct influence on the motor current, and the effect of improving the stability can be exhibited.

  In addition, by switching the waveform generating means according to the voltage state, it is possible to prevent the generation of excessive motor current in advance, suppress the peak current, and further, the magnet in the semiconductor element and the rotor The effect of improving the reliability of parts can be demonstrated.

  In addition, since the motor current can be controlled according to the state of the supply voltage to the inverter, it is possible to adjust the voltage even while the synchronous drive waveform generator is driving the motor. When the current level reaches the lower limit level of the conduction angle, lowering the supply voltage can achieve an effect of realizing a more efficient operation.

  The invention according to claim 1 is a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying electric power to the three-phase winding, and the inverter being supplied to the inverter A voltage detection circuit that detects a voltage, and a synchronous drive waveform generator that outputs a waveform with a conduction angle of less than 180 degrees in synchronization with the frequency while changing a predetermined frequency, and according to a voltage state supplied to the inverter Thus, the current flowing through the brushless DC motor can be controlled, and the effect of improving the stability in driving during voltage fluctuation can be exhibited.

  The invention according to claim 2 is based on a brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying power to the three-phase winding, and motor operating state information. A load detection circuit that detects a load state of the motor, a voltage detection circuit that detects a voltage supplied to the inverter, and a synchronization that outputs a waveform with a conduction angle of less than 180 degrees in synchronization with the frequency while changing a predetermined frequency. A drive waveform generator, a position detection drive waveform generator that outputs a waveform with a conduction angle of 150 degrees or less in accordance with the rotational position of the rotor, the synchronous drive waveform generator, and the position detection drive waveform generator; A drive means switching determination section that switches according to the operating state of the drive means, and the drive means switching determination section has two drive waveform generation means according to the state of the voltage supplied to the inverter. Is intended to operate in-option, long it enables avoidance of state passing excessive current can exhibit the effect of component reliability improvement.

  According to a third aspect of the present invention, there is provided a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying power to the three-phase winding, and motor operating state information. A load detection circuit that detects a load state of the motor, a voltage detection circuit that detects a voltage supplied to the inverter, and a synchronization that outputs a waveform with a conduction angle of less than 180 degrees in synchronization with the frequency while changing a predetermined frequency. A drive waveform generator, and a voltage controller that adjusts the voltage supplied to the inverter, and the supply voltage to the inverter is adjusted during operation by the synchronous drive waveform generator according to the supply voltage state. The current flowing through the brushless DC motor is controlled, and the performance improvement effect of improving the efficiency during operation by the synchronous drive waveform generator can be exhibited.

  According to a fourth aspect of the present invention, there is provided an inverter from the semiconductor element according to any one of the first to third aspects, wherein the amount of current that can flow for an arbitrary time is defined by a relatively small value. It is possible to suppress the generation of excessive current during driving with an inverter composed of a semiconductor element having a relatively small amount of current that can be passed, and the effect of improving the reliability of the element can be exhibited.

  The invention according to claim 5 is the invention according to any one of claims 1 to 3, wherein the brushless DC motor has a stator having a relatively large winding amount (number of turns). Even when driving a motor that requires a synchronous drive waveform generator, such as a brushless DC motor having an iron loss reduction type stator having a relatively large winding amount, the current depends on the voltage. It becomes possible to control the amount, and the effects of improving the stability of operation and improving the reliability of parts can be exhibited.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to third aspects, the brushless DC motor is a rotor in which a permanent magnet is embedded in the iron core of the rotor. Even when driving a motor that requires a synchronous drive waveform generator, such as a brushless DC motor having a rotor having polarity and having an IPM structure type rotor in which a permanent magnet is embedded in an iron core, a voltage is required. Accordingly, the amount of current can be controlled according to the above, and effects such as improved operational stability and improved component reliability can be achieved.

  A seventh aspect of the present invention is the invention according to any one of the first to sixth aspects, wherein the brushless DC motor drives the compressor, and a highly efficient and low speed operation such as a refrigerator or an air conditioner. For compressors in systems that require a wide operating range from high torque to high speed operation, the efficiency is improved in the low speed range where normal operation is performed, and rapid cooling, quick freezing, and (system-in) initial operation are performed. It is extremely important to exhibit the effect that the torque can be stably increased in a high speed region such as. In addition, by detecting the voltage fluctuation state and controlling the current during operation in the synchronous drive waveform generator, or by prohibiting the operation by the synchronous drive waveform generator weak against the voltage fluctuation, The effect of reducing noise, vibration, and peak current is also very important for compressors installed in refrigerators and air conditioners where the need for quietness and long-term reliability is extremely high.

  The invention according to claim 8 is the invention according to claim 7, in which the compressor operates the refrigerator, and the step-out stop caused by the compressor can be prevented by avoiding the unstable state of the compressor. This makes it possible to prevent the occurrence of uncooling and slow cooling in the refrigerator. In addition, it has improved cooling performance by enabling stable high-speed operation, and also has the effect of suppressing rotational speed fluctuations and noise / vibration. These effects can be achieved in refrigerators with diverse needs such as energy saving, high power, and quietness. Very important.

  Hereinafter, embodiments of a refrigerator according to 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 a brushless DC motor driving apparatus related to driving by a synchronous driving waveform generator in Embodiment 1 of the present invention.

  In FIG. 1, a commercial power source 1 is an AC power source having a frequency of 50 Hz or 60 Hz and a voltage of 100 V in Japan.

  The rectifier circuit 2 converts the AC voltage of the commercial power source 1 into a DC voltage. The rectifier circuit 2 comprises bridge-connected rectifier diodes 2a to 2d, smoothing electrolytic capacitors 2e and 2f, and a voltage regulator circuit 2g. In the case of a voltage doubler rectifier circuit as shown in FIG. Therefore, a DC voltage of about 280V can be obtained. Although voltage doubler rectification is used here, the voltage adjustment circuit 2g corresponds to a DC voltage variable chopper circuit or voltage doubler rectification / full wave rectification switching type circuit. In addition, although the voltage adjustment circuit 2g is arranged between the connection point connecting the diodes 2b-2d and the connection point connecting the electrolytic capacitors 2e-2f, the voltage supplied to the inverter 3 can be adjusted. If so, it is not limited to the location. The voltage adjustment circuit 2g includes a case where the voltage adjustment circuit 2g does not have an adjustment function. That is, the configuration of the rectifier circuit 2 is a circuit in which the voltage adjustment circuit 2g is always open at both ends (full wave rectification circuit), or a circuit in which the voltage adjustment circuit 2g is always short-circuited at both ends (double voltage rectification circuit). Including.

  The inverter 3 has a three-phase bridge structure including six switch elements 3a, 3b, 3c, 3d, 3e, and 3f. Each switch element includes a diode for return current in the reverse direction of each switch element, but this is omitted in the figure.

  The brushless DC motor 4 includes a rotor 4a having a permanent magnet and a stator 4b having a three-phase winding. When the three-phase alternating current generated by the inverter 3 flows in the three-phase winding of the stator 4b, the rotor 4a can be rotated. The rotary motion of the rotor 4a is changed to a reciprocating motion by a crankshaft (not shown), and a piston (not shown) reciprocates in a cylinder (not shown) to compress the refrigerant. Drive. The three-phase winding portion connected to the switch element 3a (3b) is a U-phase winding, the three-phase winding portion connected to the switch element 3c (3d) is a V-phase winding, and the switch element 3e (3f). The three-phase winding portion connected to is called a W-phase winding.

  The synchronous drive waveform generator 5 generates a signal for driving the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3 while changing the output frequency and the conduction angle while keeping the duty constant. This driving signal creates a rectangular wave with a conduction angle of less than 180 degrees. In addition to the rectangular wave, a waveform conforming thereto such as a sine wave or a distorted wave may be used. The synchronous drive is a waveform generating means adapted to a high rotation operation region where high torque is required by utilizing the self-advance characteristic of the motor itself. Furthermore, in accordance with the signal output by the voltage state recognition unit 7, the waveform is adjusted to control the amount of current, and in some cases, the output from the synchronous drive waveform generation unit 5 is stopped to stabilize the system. It also has a function to plan.

  In the present embodiment, the waveform output from the synchronous drive waveform generator 5 does not mention duty control, but duty control is also required when finer current control is required. Synchronous driving refers to a driving method that outputs a waveform in accordance with a predetermined frequency regardless of the relative position of the rotor 4a, and is not limited to a property that keeps elements such as a conduction angle and a duty constant.

  The drive unit 6 drives the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3 by the output signal from the synchronous drive waveform generation unit 5. By this drive, an optimal AC output is applied from the inverter 3 to the brushless DC motor 4 to realize the rotation of the rotor 4a.

  Based on the signal output from the voltage detection circuit 8, the voltage state recognition unit 7 outputs information on the voltage supplied to the inverter 3 to the synchronous drive waveform generation unit 5. The “voltage information” described here does not limit the static state of the voltage, but also includes dynamic state information such as a change amount per unit time and a fluctuation cycle.

  The voltage detection circuit 8 detects the voltage supplied to the inverter 3 or the voltage state. Further, the voltage detection circuit 8 in the present embodiment detects the DC voltage rectified and smoothed by the rectification circuit 2, but the present invention can be applied to any part where the change in the state of the voltage supplied to the inverter 3 can be estimated. This is not the case because it becomes effective. For example, a method of detecting an AC voltage immediately after the commercial power supply 1 may be used. When the AC voltage is detected, not only the magnitude change of the voltage supplied to the inverter 3 can be estimated, but also the frequency of charging the electrolytic capacitors 2e and 2f can be known by detecting the frequency of the AC voltage. This is one of the advantages compared to the detection of.

  The microcomputer 9 realizes the aforementioned functions. These functions can be realized by a microcomputer program.

  The reference potential G is a potential reference point in this block diagram and corresponds to a potential at the connection point between the rectifier diode 2d and the electrolytic capacitor 2f. When the voltage supplied from the commercial power source 1 is AC100V, a DC voltage of about 280V can be obtained between the reference potential G and the connection point between the electrolytic capacitor 2e and the rectifier diode 2c and supplied to the inverter 3. Become.

  Next, the operation in FIG. 1 will be described with reference to FIGS.

  FIG. 2 is a flowchart showing an outline of the current control operation of the microcomputer according to the first embodiment.

  First, in STEP 21, voltage detection processing is executed. Specifically, an instantaneous voltage value is derived based on a signal output from the voltage detection circuit 8.

  Next, in STEP 22, a voltage state recognition process is executed. Specifically, the instantaneous value of the voltage derived by the voltage detection process is accumulated, the amount of change in unit time is derived, the maximum value and minimum value of an arbitrary period are derived, and the time inflection point of the voltage The voltage change state is derived, for example, by deriving the period when the voltage reaches.

  In STEP 23, waveform synthesis processing is executed. Specifically, the waveform is synthesized so that an appropriate current is applied to the motor 4 in accordance with the voltage change state derived by the voltage state recognition process.

  Finally, in STEP 24, the waveform output process is executed, and the process returns to the start. Specifically, the waveform synthesized by the waveform synthesis process is output to the drive unit 6.

  The voltage state recognition unit 7 or the synchronous drive waveform generation unit 5 constituting the microcomputer 9 is responsible for the entire processing, but the components responsible for each STEP (particularly STEP 22 and STEP 23) are limited. Any component, not a thing, may be responsible.

  FIG. 3 is a flowchart showing an example of an algorithm for outputting a waveform in the first embodiment. In other words, in order to explain the detailed processing of STEP22 and STEP23 in FIG.

  First, in STEP 31, a voltage change amount at an arbitrary time is calculated from the accumulated voltage information. Here, as an extremely simple example, the case of calculating from two pieces of accumulated information is shown.

  Next, in STEP 32, the energization angle adjustment determination is executed. Specifically, the necessity / adjustment of the energization angle and the adjustment amount are determined according to the voltage change amount calculated in STEP 31. If the voltage change amount is zero as a result of the determination, the process proceeds to STEP33. When the voltage change amount is negative, the process proceeds to STEP34. When the voltage change amount is positive, the process proceeds to STEP35.

  In STEP 33, the waveform is synthesized so that the energization angle remains the same.

  In STEP 34, the waveform is synthesized so that the energization angle is expanded. At this time, an energization angle adjustment amount for keeping the current amount constant is derived from the amount of change in voltage and the electrical characteristics of the motor 4, and a waveform is synthesized based on that.

  Finally, in STEP 35, the waveform is synthesized so that the energization angle is reduced. At this time, an energization angle adjustment amount for keeping the current amount constant is derived from the amount of change in voltage and the electrical characteristics of the motor 4, and a waveform is synthesized based on that.

  Although an example in which the energization angle is adjusted has been described here, the present embodiment can be realized by adjusting any element as long as it is an element that acts to keep the current constant, such as duty. In the processing of STEP 34 and STEP 35 described above, when the duty is adjusted, maintaining the relationship of “supply voltage to the inverter 3” × (duty) = constant ”is an example of an adjustment method for keeping the current constant. Become.

  In other words, the current can be kept constant by adjusting the duty in STEP 34 to increase the duty and in STEP 35 to decrease the duty.

  FIG. 4 is a flowchart showing an example of an algorithm for stopping waveform output in the first embodiment. That is, it is a flowchart showing a very simple example in order to explain the detailed processing of STEP 22 and STEP 23 in FIG.

  First, in STEP 41, normality determination processing is executed. Specifically, it is determined whether or not the voltage change amount and the voltage instantaneous value satisfy preset conditions. Here, the condition is “the instantaneous voltage value is not less than an arbitrary voltage”. If the result of determination is normal, that is, the condition is satisfied, the routine proceeds to STEP42. If abnormal, that is, the condition is not satisfied, the process proceeds to STEP43. The “arbitrary voltage” of the normal determination condition may be, for example, the minimum required voltage obtained from the electrical characteristics of the motor 4 or the maximum output torque required for the motor 4.

  Next, in STEP 42, normal waveform synthesis processing is executed. An example of this process is the process shown in FIG.

  In STEP 43, stop waveform synthesis processing is executed. This process is executed in order to avoid the worst situation in which it is determined that it is difficult for the synchronous drive waveform generator 5 to operate and the reliability is deteriorated.

  As described above, in the present embodiment, the voltage detection unit detects the supply voltage to the inverter, so that an unstable state of the motor current that may occur particularly in a low voltage environment or a voltage fluctuation environment is detected. It is possible to prevent this, and by keeping the current constant by adjusting the energization angle or changing the duty, it is possible to suppress step-out stop, prevent system stop by reducing peak current, and the motor itself And ensuring the reliability of the system. In addition, when the supply voltage to the inverter drops or fluctuates to a level where stable operation is not possible under the desired load conditions, the output of the synchronous drive waveform generator is stopped to ensure reliability. It is possible to avoid the worst situation that worsens the motor, and this can also exert effects such as ensuring the reliability of the motor itself and the system.

  The conventional driving apparatus as shown in FIG. 10 has only the counter electromotive voltage detection circuit 105 and cannot detect the state of the voltage supplied to the inverter 103. Thus, by having the voltage detection circuit 8, it is possible to avoid an unstable state during driving by the synchronous drive waveform generator 5, and bring about effects such as stabilization of the driving state and improvement of reliability.

  In addition, there is a method of increasing the winding amount (number of turns) of the stator as one of the means for improving the motor efficiency, but this method can reduce the iron loss of the motor, but has the disadvantage that the output torque decreases. there were. In such a motor, synchronous drive control is useful for realizing high-speed and high-torque drive, but the control device of the present embodiment is also very effective in improving the resistance to voltage fluctuations of this control. Demonstrate. As a means for increasing the torque, there is a method in which the structure of the rotor is an IPM type structure, but in this case as well, synchronous drive control that can make use of reverse saliency is useful. In this embodiment, the same effect as that of the low iron loss type motor is exhibited.

  Furthermore, suppression of power supply harmonic distortion is indispensable in products such as refrigerators and air conditioners that have been remarkably advanced in inverters in recent years. As this suppression method, there are various means such as an active filter method and a transformation method. In particular, in a refrigerator, a “reactor method” that is inexpensive and easy to system-in is a common means. The reactor system has a disadvantage of reducing power supplied to the inverter while suppressing power supply harmonic distortion. The control device of the present embodiment is also very useful for stabilizing synchronous drive operation under such a situation where the power supplied to the inverter is reduced.

(Embodiment 2)
FIG. 5 is a block diagram of a brushless DC motor driving apparatus including a driving means switching determination unit according to the second embodiment of the present invention. Note that the same components in FIG. 5 as those in FIG. 1 have already been described and are omitted.

  In FIG. 5, the position detection drive waveform generator 50 performs logical signal conversion based on the output signal of the load detection circuit 52 to drive the switch elements 3 a, 3 b, 3 c, 3 d, 3 e, 3 f of the inverter 3. Create a signal. This driving signal is based on rectangular wave energization, and creates a rectangular wave with an energization angle of 150 degrees or less. In addition to the rectangular wave, a trapezoidal wave having a slight inclination in rising / falling may be used as a waveform conforming thereto. Further, in order to keep the rotation speed constant, duty control of PWM control and control of energization angle are also performed. According to the rotational position, the actual rotational speed of the brushless DC motor 4 can be detected and compared with the target rotational speed, and can be operated with an optimum duty, so that the most efficient operation is possible. The detection of the actual rotational speed can be realized by counting the output signal of the load detection circuit 52 for a certain time or measuring the period. It is a waveform generating means suitable for a low-rotation operation region where high efficiency and low vibration are required.

  The drive means switching determination unit 51 includes the rotation number calculated by the position detection drive waveform generation unit 50, the duty and conduction angle controlled based on the rotation number, the frequency controlled by the synchronous drive waveform generation unit 5, and the like. Based on the energization angle, the operation state information from the load detection circuit 52, etc., the operation state of the brushless DC motor 4 is judged, and the drive means for outputting the waveform for operating the inverter 3 is detected by the synchronous drive waveform generator 5 or the position detection. The drive waveform generator 50 is selected and switched. For example, when the rotational speed is low, the signal from the position detection drive waveform generator 50 is selected, and when the rotational speed is high, the signal from the synchronous drive waveform generator 5 is selected to operate the inverter 3.

  The load detection circuit 52 can detect the rotational relative position of the rotor 4a from the counter electromotive voltage generated when the rotor 4a having the permanent magnet of the brushless DC motor 4 rotates. In addition to detecting the rotation relative position, it is also possible to detect disturbances in the motor current and changes in the load state by detecting an increase or decrease in the time during which the current flows through the return current diode. From these detections, the advance degree of the motor current phase can be known. The load detection circuit 52 outputs not only the relative position signal but also the result of comparing the voltage with respect to the reference potential G of the three-phase winding (U, V, W) with a predetermined arbitrary reference voltage. It is a circuit which has.

  Here, the voltage with respect to the reference potential G of the three-phase winding (U, V, W) is compared with an arbitrary reference voltage set in advance. However, the position detection of the rotor 4a and the motor current A configuration using other means such as current detection may be used as long as it can detect the state.

  Next, the operation in FIG. 5 will be described with reference to FIGS. 2, 3, 5, and 6.

  2 and 3 are flowcharts showing the current control operation of the microcomputer according to the first embodiment. However, since this figure also shows a meaning as a flowchart according to the second embodiment, it is also here. The description will be made with reference to FIG.

  In STEP 23 in FIG. 2, waveform synthesis processing is executed. Depending on the signal output from the load detection circuit 52, whether it is executed by the position detection drive waveform generation unit 50 or by the synchronization drive waveform generation unit 5. The drive means switching determination unit 51 selects the drive unit.

  Other STEPs are the same as those in the first embodiment, and also in the second embodiment, the voltage state recognition unit 7, the synchronous drive waveform generation unit 5, and the position detection drive waveform generation that constitute the microcomputer 9. The whole processing of FIG. 2 is performed by any element of the unit 50 and the drive means switching determination unit 51, but the component responsible for each STEP (especially STEP22 and STEP23) is not limited, and which component bears. May be.

  FIG. 6 is a flowchart showing an example of an algorithm for prohibiting waveform synthesis by the synchronous drive waveform generator in the second embodiment. In other words, in order to explain the detailed processing of STEP22 and STEP23 in FIG.

  First, in STEP 61, normality determination processing is executed. Specifically, it is determined whether or not the voltage change amount and the voltage instantaneous value satisfy preset conditions. Here, the condition is “the instantaneous voltage value is not less than an arbitrary voltage”. If the result of determination is normal, that is, if the condition is satisfied, the routine proceeds to STEP62. If abnormal, that is, the condition is not satisfied, the process proceeds to STEP63. The “arbitrary voltage” of the normal determination condition is, for example, the minimum required voltage that can be driven by the synchronous drive waveform generator, which is obtained from the electrical characteristics of the motor 4 or the maximum output torque required for the motor 4. Good.

  Next, in STEP 62, normal waveform synthesis processing is executed. An example of this process is the process shown in FIG. In the second embodiment, the processing of FIG. 3 may be performed by either the drive by the synchronous drive waveform generator 5 or the drive by the position detection drive waveform generator 50. Switching between the two waveform generation units is executed by the drive means switching determination unit 51 according to the output of the load detection circuit 52.

  In STEP 63, synchronous drive waveform synthesis prohibition processing is executed. This process is executed in order to avoid the worst situation in which it is determined that it is difficult for the synchronous drive waveform generator 5 to operate and the reliability is deteriorated. For example, when this STEP is executed during operation by the position detection drive waveform generation unit 50, switching to the synchronous drive waveform generation unit 5 is prohibited, and execution is performed during operation by the synchronous drive waveform generation unit 5. In this case, the position detection drive waveform generation unit 50 is switched quickly or the output to the drive unit 6 is stopped quickly.

  As described above, in the present embodiment, the voltage detection unit detects the supply voltage to the inverter, so that an unstable state of the motor current that may occur particularly in a low voltage environment or a voltage fluctuation environment is detected. It is possible to prevent in advance, and by prohibiting driving by the synchronous drive waveform generator that drives without detecting the relative position of the rotor, suppression of step-out stop, prevention of system stop by reducing peak current, The effect of ensuring the reliability of the motor itself and the system can be exhibited.

  The conventional driving apparatus as shown in FIG. 10 has only the counter electromotive voltage detection circuit 105 and cannot detect the state of the voltage supplied to the inverter 103. Thus, by having the voltage detection circuit 8, it is possible to avoid an unstable state during driving by the synchronous drive waveform generator 5, and bring about effects such as stabilization of the driving state and improvement of reliability.

  In addition, there is a method of increasing the winding amount (number of turns) of the stator as one of the means for improving the motor efficiency, but this method can reduce the iron loss of the motor, but has the disadvantage that the output torque decreases. there were. In such motors, synchronous drive control is useful to achieve high-speed and high-torque drive, but it covers the weakness of this control, “characteristics that can easily fall into an unstable state during voltage fluctuations”. In contrast, the control device of the present embodiment is very effective. As a means for increasing the torque, there is a method in which the structure of the rotor is an IPM type structure, but in this case as well, synchronous drive control that can make use of reverse saliency is useful. In this embodiment, the same effect as that of the low iron loss type motor is exhibited.

  Furthermore, suppression of power supply harmonic distortion is indispensable in products such as refrigerators and air conditioners that have been remarkably advanced in inverters in recent years. As this suppression method, there are various means such as an active filter method and a transformation method. In particular, in a refrigerator, a “reactor method” that is inexpensive and easy to system-in is a common means. The reactor system has a disadvantage of reducing power supplied to the inverter while suppressing power supply harmonic distortion. The control device of the present embodiment that can realize the prohibition of the synchronous drive operation under such a situation where the power supplied to the inverter is reduced and can avoid the situation that deteriorates the reliability is very useful.

(Embodiment 3)
FIG. 7 is a block diagram of a brushless DC motor driving apparatus including a voltage control unit according to Embodiment 3 of the present invention. 7 that are the same as those in FIG. 1 have already been described, and will not be described.

  In FIG. 7, the voltage control unit 70 operates the voltage adjustment circuit 2 g in the rectifier circuit 2 to control the voltage supplied to the inverter 3. By controlling the voltage, it is possible to improve the operation efficiency during driving by the synchronous drive waveform generator 5. The details are as follows. In the operation by the synchronous drive waveform generator 5, since the operation is performed without detecting the position of the rotor 4a, when the supply voltage to the inverter 3 is excessive, an appropriate advance angle with respect to the brushless DC motor 4 is obtained. You may not be able to drive. That is, the operation is performed inefficiently (by delay control). Therefore, the voltage state recognition unit 7 recognizes that the supply voltage to the inverter 3 is excessive compared to an appropriate voltage value derived from the electrical characteristics of the motor, the output torque necessary for the system, and the like. If the voltage control unit 70 can appropriately adjust the supply voltage based on the voltage information, an efficient operation at an appropriate advance angle is possible.

  Next, the operation in FIG. 7 will be described with reference to FIG. 3, FIG. 7, FIG. 8, and FIG.

  Note that FIG. 3 is a flowchart showing the current control operation of the microcomputer in the first embodiment, but this figure also makes sense as the flowchart in the third embodiment. The description will be omitted, and the overlapping description will be omitted. Since FIG. 8 is similar to FIG. 2 in the first embodiment, the description of the common processing is omitted with the same reference numerals.

  FIG. 8 is a flowchart showing an outline of the current control operation of the microcomputer according to the third embodiment.

  First, in STEP80 in FIG. 8, a voltage control process is executed. Specifically, the voltage supplied to the inverter 3 is changed by the voltage control unit 70. Conditions for the voltage control unit 70 to execute the process are when the target operation rotational speed changes or when the load state (torque to be output by the motor, etc.) changes. In the case of a change in the above, a general control method is to change the voltage supplied to the inverter 3 to be low, and in the case of a change in the direction of high speed and high torque, to change the voltage supplied to the inverter 3 to be high. Become.

  Other steps are the same as those in the first embodiment, and also in the third embodiment, the voltage state recognition unit 7, the synchronous drive waveform generation unit 5, and the voltage control unit 70 that constitute the microcomputer 9. Although any element is responsible for the entire processing of FIG. 8, the constituent elements responsible for each STEP (particularly STEP 22 and STEP 23) are not limited, and any constituent element may be responsible.

  Next, FIG. 9 is a graph showing temporal changes in the inverter supply voltage when the voltage control process is executed. Here, as one of the simplest examples, by changing the voltage adjustment circuit 2g to the connected / disconnected state, the rectifier circuit 2 changes to the double voltage rectified state / full wave rectified state, and is supplied to the inverter 3 The graph shows the case where the voltage is changed. Further, as a means for changing the rectification state, a case where a mechanical contact type relay which is a relatively simple means is used is taken as an example. That is, it changes to the full-wave rectification state when the relay is turned off, and changes to the voltage doubler rectification state when the relay is turned on.

  FIG. 9 is a characteristic diagram showing an example of a temporal change when the voltage controller in the third embodiment adjusts the voltage supplied to the inverter. 9A on the upper side changes the state of the rectifier circuit 2 from the double voltage rectification state to the full-wave rectification state, the lower FIG. 9B changes from the full-wave rectification state to the double-voltage rectification state. FIG. 6 is a characteristic diagram when the state of the rectifier circuit 2 is changed.

  As can be seen from FIG. 9A, when the relay is turned off in the vicinity of 100 msec, the supply voltage to the inverter 3 drops to about half after several hundred msec. This is because the supply voltage gradually changes because discharge is performed with a time constant delay due to the action of the electrolytic capacitors 2e and 2f. In the case of such a change, it is possible to perform processing at a relatively low voltage detection speed, and control to keep the current constant even in a detection cycle of the order of several msec is possible. The specific current control method is as shown in FIG. 3 as a very simple example, and the details thereof are omitted since they have already been described in the first embodiment.

  As can be seen from FIG. 9B, when the relay is turned on in the vicinity of 300 msec, the supply voltage to the inverter 3 rises to about twice over 10 msec to several tens msec. The reason why the rise does not start immediately after turning on is that the electrolytic capacitors 2e and 2f are charged after the relay is turned on until the relationship [charging voltage of electrolytic capacitor] <[output voltage of diode bridge] is established. It is because it is not implemented.

  Therefore, charging of one electrolytic capacitor is started with a slight delay after the relay is turned on. Charging is performed according to the voltage waveform of the AC power supply 1 while the above relationship is established from the start of charging, and charging is performed while the above relationship is also established after the completion of charging. Therefore, even when there is no load (the discharge amount of the electrolytic capacitors 2e and 2f is minimum), the time from 2/3 cycle to 5/6 cycle (when the power supply frequency is 50 Hz: from 13 to 17 msec / 60 Hz: 11 to 14 msec), and the higher the load, the larger the amount of discharge of the electrolytic capacitor during charging of the electrolytic capacitors 2e and 2f. Therefore, more time is spent, and the supply voltage is doubled. The time as described above is required until the above. In the case of such a change, a relatively high speed processing is required as the voltage detection speed, and control that keeps the current constant is impossible unless the detection cycle is on the order of tens to hundreds of μsec. The specific current control method is as shown in FIG. 3 as a very simple example, and the details thereof are omitted since they have already been described in the first embodiment.

  As described above, in the present embodiment, the voltage detection unit detects the supply voltage to the inverter, so that even when driving by the synchronous drive waveform generation unit that tends to be relatively weak against voltage fluctuation, The supply voltage can be controlled, and the effect of improving the operation efficiency by the synchronous drive waveform generator can be exhibited. Also, by adjusting the energization angle or changing the duty, the current is kept constant, thereby suppressing the step-out stop, preventing the system stop by reducing the peak current, ensuring the reliability of the motor itself and the system, etc. The effect of can be demonstrated.

  The conventional driving apparatus as shown in FIG. 10 includes only the counter electromotive voltage detection circuit 105 and cannot detect the state of the supply voltage to the inverter 103. Therefore, by having the voltage detection circuit 8, it is possible to avoid an unstable state during driving by the synchronous drive waveform generator 5, and the effect of high efficiency by voltage adjustment during synchronous drive is brought about.

  In addition, there is a method of increasing the winding amount (number of turns) of the stator as one of the means for improving the motor efficiency, but this method can reduce the iron loss of the motor, but has the disadvantage that the output torque decreases. there were. In such motors, synchronous drive control is useful to achieve high-speed and high-torque drive, but it covers the weak point of this control, “characteristics that can easily lead to inefficient driving conditions when the voltage is excessive”. In contrast, the control device of the present embodiment is very effective. As a means for increasing the torque, there is a method in which the structure of the rotor is an IPM type structure, but in this case as well, synchronous drive control that can make use of reverse saliency is useful. In this embodiment, the same effect as that of the low iron loss type motor is exhibited.

  Furthermore, suppression of power supply harmonic distortion is indispensable in products such as refrigerators and air conditioners that have been remarkably advanced in inverters in recent years. As this suppression method, there are various means such as an active filter method and a transformation method. In particular, in a refrigerator, a “reactor method” that is inexpensive and easy to system-in is a common means. The reactor system has a disadvantage of reducing power supplied to the inverter while suppressing power supply harmonic distortion. The synchronous drive operation under such a situation where the power supplied to the inverter is reduced is effective, and the control device of the present embodiment that can realize high efficiency of the synchronous drive operation is very useful.

  As described above, the brushless DC motor driving method and apparatus according to the present invention have effects such as noise and vibration reduction, prevention of step-out stop, suppression of peak current generation, improvement of driving efficiency, and improvement of output torque. Since it can be used, it can be applied to various applications equipped with a brushless DC motor regardless of whether it is for home use or industrial use.

1 is a block diagram of a brushless DC motor driving device related to driving by a synchronous driving waveform generator in Embodiment 1 of the present invention. The flowchart which showed the outline of the current control operation | movement of the microcomputer in Embodiment 1 of this invention. The flowchart which showed an example of the algorithm which outputs the waveform in Embodiment 1 of this invention The flowchart which showed one example of the algorithm which stops the waveform output in Embodiment 1 of this invention Block diagram of a brushless DC motor drive device provided with a drive means switching determination unit in Embodiment 2 of the present invention The flowchart which showed one example of the algorithm which prohibits the waveform synthesis by the synchronous drive waveform generation part in Embodiment 2 of this invention The block diagram of the drive device of the brushless DC motor provided with the voltage control part in Embodiment 3 of this invention The flowchart which showed the outline of the current control operation | movement of the microcomputer provided with the voltage control part in Embodiment 3 of this invention. (A) The characteristic diagram which showed an example of the time change when the voltage control part in Embodiment 3 of this invention adjusted the voltage supplied to an inverter (b) The voltage control part in the same embodiment supplied to an inverter Characteristic diagram showing an example of the change over time when the voltage to be adjusted is adjusted A block diagram of a driving device related to driving a conventional brushless DC motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Inverter 4 Brushless DC motor 4a Rotor 4b Stator 5 Synchronous drive waveform generation part 8 Voltage detection circuit 50 Position detection drive waveform generation part 51 Drive means switching determination part 52 Load detection circuit 70 Voltage control part

Claims (8)

  A brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding; an inverter that supplies power to the three-phase winding; and a voltage detection circuit that detects a voltage supplied to the inverter; A synchronous drive waveform generator that outputs a waveform with a conduction angle of less than 180 degrees in synchronization with the frequency while changing a predetermined frequency, and a current flowing through the brushless DC motor according to a voltage state supplied to the inverter A brushless DC motor driving method enabling control.   A brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying electric power to the three-phase winding, and load detection for detecting a load state of the motor from motor operating state information A circuit, a voltage detection circuit that detects a voltage supplied to the inverter, a synchronous drive waveform generator that outputs a waveform having a conduction angle of less than 180 degrees in synchronization with the frequency while changing a predetermined frequency, and the rotor Driving means switching determination that switches between a position detection drive waveform generation section that outputs a waveform with an energization angle of 150 degrees or less according to the rotation position of the motor, and the synchronous drive waveform generation section and the position detection drive waveform generation section, depending on the motor operating state And the driving means switching determination section selects two driving waveform generating means according to the state of the voltage supplied to the inverter. DC motor of the drive unit.   A brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying electric power to the three-phase winding, and load detection for detecting a load state of the motor from motor operating state information A circuit, a voltage detection circuit for detecting a voltage supplied to the inverter, a synchronous drive waveform generator for outputting a waveform with a conduction angle of less than 180 degrees in synchronism with the frequency while changing a predetermined frequency, and the inverter A voltage control unit that adjusts the voltage to be supplied, and controls the current flowing to the brushless DC motor according to the supply voltage state when the supply voltage to the inverter is adjusted during operation by the synchronous drive waveform generation unit Drive device for brushless DC motor.   The drive of the brushless DC motor according to any one of claims 1 to 3, wherein the inverter is composed of a semiconductor element in which an amount of current that can flow for an arbitrary time is defined by a relatively small value. apparatus.   The brushless DC motor drive device according to any one of claims 1 to 3, wherein the brushless DC motor includes a stator having a relatively large winding amount (number of turns).   The brushless DC motor according to any one of claims 1 to 3, wherein the brushless DC motor is a rotor in which a permanent magnet is embedded in an iron core of the rotor and has a rotor having saliency. DC motor drive device.   The brushless DC motor driving device according to any one of claims 1 to 6, wherein the brushless DC motor drives the compressor.   8. The brushless DC motor driving apparatus according to claim 7, wherein the compressor operates the refrigerator.

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