JP2010252406A - Motor drive and refrigerator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable motor drive capable of attaining efficient drive at a low speed of brushless DC motors, and a high-speed drive at a high load. <P>SOLUTION: A position signal of a brushless DC motor is acquired by a position detection section 5, at a low speed and efficiency is improved by sensorless drive at a first waveform generating section 7; frequency-fixed synchronous drive is performed by a waveform from a second waveform generation section 9 at a high speed; and communication timing is determined for driving, from the rotor position information obtained periodically from the induced voltage zero-cross detection of a brushless DC motor 4 at the position detection section 5, thus obtaining stable drive performance in high-load/high-speed drive by synchronous driving. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a device for driving a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding by means of an inverter that supplies power to the three-phase winding. The present invention relates to a brushless DC motor driving device that is optimal for driving a compressor such as an air conditioner, and a refrigerator using the same.

  Conventionally, this type of motor drive device and a refrigerator using the motor drive have realized optimum driving according to the load by switching the waveform generation method depending on the state of the drive load (see, for example, Patent Document 1).

  FIG. 7 shows a conventional motor driving device described in Patent Document 1. In FIG. As shown in FIG. 7, the conventional motor driving apparatus receives an AC power supply 1 as an input, converts an AC voltage into a DC voltage by a rectifying and smoothing circuit 2, and inputs the DC voltage to an inverter 3. The brushless DC motor 4 includes a rotor 4a having a permanent magnet and a stator 4b having a three-phase winding, and a three-phase alternating current generated by the inverter 3 flows to the three-phase winding of the stator 4b. Thus, the rotor 4a is rotated.

  The counter electromotive voltage detection circuit 105 detects the rotational relative position of the rotor 4 a from the counter electromotive voltage generated when the rotor 4 a having the permanent magnet of the brushless DC motor 4 rotates.

  The commutation circuit 106 performs logical signal conversion based on the output signal of the back electromotive voltage detection circuit 105, and generates signals for driving the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3.

  The synchronous drive circuit 107 forcibly outputs an output of a predetermined frequency from the inverter 3 and drives the brushless DC motor 4. The synchronous drive circuit 107 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 4 is operated.

  The switching circuit 109 switches whether the brushless DC motor of the compressor 4 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 3 a, 3 b, 3 c, 3 d, 3 e, 3 f of the inverter 3 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. At this time, the counter electromotive voltage detection circuit 105 detects the relative position of the rotor 4 a of the brushless DC motor 4. Next, the commutation circuit 106 creates a commutation pattern for driving the inverter 3 from the relative position of the rotor 4a. This commutation pattern is supplied to the drive circuit 110 through the switching circuit 109, and drives the switch elements 3a, 3b, 3c, 3d, 3e, and 3f of the inverter 3. By this operation, the brushless DC motor 4 performs driving that matches the rotational position.

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

The load of the brushless DC motor 4 increases, and the rotational speed decreases due to the characteristics of the brushless DC motor 4. The load state determination circuit 108 determines that this state is a high load state, and switches the output of the switching circuit 109 to the signal from the synchronous drive circuit 107.
By driving as described above, a decrease in the rotational speed at the time of high load is suppressed, and driving at a predetermined rotational speed is possible even at the time of high load.
JP-A-9-88837

  However, in the conventional configuration described above, since the relative position of the brushless DC motor rotor is driven at a high load without detecting the relative position, the inverter commutation occurs when a sudden load fluctuation occurs or the load is very large. On the other hand, in a state where the load cannot follow, there is a possibility of falling into an unstable state such as a fluctuation in the rotational speed.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and ensures stable driving performance in various driving states such as the load and driving speed of a brushless DC motor. A conventional motor driving device and a refrigerator using the same The purpose is to further improve the reliability.

  In order to solve the above-described conventional problems, the motor driving device of the present invention and a refrigerator using the motor driving device apply a duty voltage applied to the brushless DC motor when the brushless DC motor is driven at a high speed of a predetermined number of revolutions or more. The brushless DC motor is driven at a constant value, and an applied voltage pattern for detecting an induced voltage generated by the rotation of the brushless DC motor is output at a predetermined timing.

  As a result, in the driving by the second waveform generator, the rotor relative position of the brushless DC motor can be detected periodically, and commutation based on the detected position signal becomes possible.

  The motor driving device of the present invention and a refrigerator using the motor driving stability with respect to disturbance factors such as load fluctuations and input voltage fluctuations by reliably detecting the rotor relative position of the brushless DC motor during high-load high-speed driving. By improving the reliability, the reliability of the apparatus can be improved.

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 a drive for driving the inverter A position detection unit that detects a relative rotational position of the rotor based on an induced voltage generated in a three-phase winding of the stator of the brushless DC motor and outputs a position signal; and the position detection unit A first waveform generator that outputs a rectangular wave or a sine wave or a waveform conforming thereto while performing duty control based on an output signal from the output signal, and a rectangular wave or a sine wave or a waveform conforming thereto to the brushless DC motor And when the brushless DC motor is rotating at a low speed equal to or lower than a predetermined number of revolutions, the output of the first waveform generating unit A switching determination unit that drives the inverter via the drive unit at the output of the second waveform generation unit when the inverter is driven and the brushless DC motor rotates at a high speed exceeding a predetermined rotation number; When driving by the second waveform generator, a pattern for detecting the induced voltage of the brushless DC motor is output at a predetermined timing, so that the relative movement of the brushless DC motor rotor can be increased even when driven by the second waveform generator. The position can be detected and the applied voltage pattern to the brushless DC motor can be switched at an appropriate timing even if the rotation fluctuates due to fluctuations in disturbance factors such as load fluctuations and voltage fluctuations, improving the driving stability of the motor can do.

  The invention according to claim 2 is the invention according to claim 1, wherein the voltage pattern applied to the brushless DC motor at the timing of detecting the induced voltage is intermittently part or all of the normal waveform that is not the induced voltage detection timing. By using this waveform, it is possible to prevent the induced voltage from being covered by the applied voltage of the brushless DC motor at the induced voltage detection timing, and the relative position of the brushless motor rotor can be accurately detected by reliably detecting the induced voltage. It becomes like.

  The invention according to claim 3 is the invention according to claim 1 and claim 2, wherein the voltage waveform applied to the brushless DC motor generated by the second waveform generator at the timing of detecting the induced voltage of the brushless DC motor is: By setting the conduction angle of at least one phase to 150 degrees or less, the range in which the zero cross point of the induced voltage can be detected can be expanded, and position detection can be performed reliably even when the speed and load conditions fluctuate. The reliability of the apparatus can be improved.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the commutation after detecting the rotor relative position of the brushless DC motor is determined based on the position information to determine the next commutation timing. It is possible to stabilize the driving stability in the second waveform generator.

  According to a fifth aspect of the present invention, in accordance with the first to fourth aspects of the present invention, the phase relationship between the position detection timing and the next rotational flow is maintained according to the load in the drive by the second waveform generation unit. Driving at a current advance angle enables stable high-load and high-speed driving, so that the operating load range and speed range of the apparatus can be expanded and the reliability of the apparatus can be improved by stable driving.

  According to a sixth aspect of the present invention, the motor driving device according to the first to fifth aspects drives the compressor, and the compressor is a load having a relatively large inertia, so that the induced voltage is reduced. The motor driving device of the present invention that inputs a pattern in which a part or all of the motor applied voltage is intermittently detected for detection has little influence on the driving speed variation, and also the driving by the second waveform generator is based on position detection. Since the drive is performed, the drive performance can be further stabilized and the reliability can be improved.

  According to a seventh aspect of the present invention, the compressor of the sixth aspect has a reciprocating configuration. The reciprocating compressor has a configuration in which the brushless motor is suspended by a spring or the like inside the compressor, so that vibration and noise due to the motor are difficult to leak to the outside. In the motor driving device of the present invention, even if a slight speed fluctuation occurs in the motor driving speed by intermittently applying a part or all of the motor applied voltage, the vibration caused by the speed fluctuation can be absorbed inside the compressor, so that the vibration equivalent to the conventional one is used. And can be noise.

  According to an eighth aspect of the invention, the motor driving device according to the sixth or seventh aspect is used for a compressor of a refrigerator. This makes it possible to reduce power consumption by high-efficiency driving in the driving state where the load of the refrigerator that occupies most of the day is in a stable cooling state and a relatively small load, and the door is frequently opened and closed during housework time etc. When it is performed, when the temperature inside the chamber rises due to high temperature food being put in the chamber, or when the outdoor temperature in summer is high, etc., when the load is relatively heavy and driving at high speed is required Drive stability and reliability can be improved.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals are given to the same configurations as those of the conventional examples or the embodiments described above, and detailed descriptions thereof will be omitted. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a motor drive device and a refrigerator using the same according to Embodiment 1 of the present invention.

  In FIG. 1, an AC power source 1 is rectified and smoothed to a DC voltage by a smoothing circuit 2 and input to an inverter 3. The inverter 3 converts DC to AC power and supplies three-phase power to a brushless DC motor (hereinafter referred to as motor) 4. Drive.

  The position detection unit 5 is a position detection unit that detects the relative position of the rotor of the motor 4 by detecting the zero cross point of the induced voltage generated by the rotation of the motor, and is a midpoint of the stator winding of the motor. A method is generally known in which the potential or 1/2 of the inverter input voltage and the output terminal voltage of the inverter 3 are compared, and the timing at which the magnitude relationship is inverted is detected as the zero cross point of the induced voltage.

  In this embodiment, 1/2 of the inverter input voltage and the terminal voltage are compared, and the timing at which the magnitude relationship is inverted becomes the zero cross point of the induced voltage, so that it is detected as the relative rotational position of the motor.

  The rotation speed detection unit 6 receives the position detection signal from the position detection unit 5 and detects the driving speed of the motor. For example, the motor zero-cross signal interval or the total zero-cross signal interval for one rotation of the motor (for example, the motor In the case where the number of pole pairs is two, the position detection interval is 12 times in total).

The first waveform generator 7 generates a signal for driving the switch element of the inverter 3 based on the position detection signal of the position detector 5. This drive signal is based on rectangular wave energization, and produces a rectangular wave with an energization angle of 120 degrees to 150 degrees. Further, here, a rectangular wave having an energization angle exceeding 150 degrees, a non-rectangular wave, a trapezoidal wave with a slight inclination in rising / falling as a waveform corresponding thereto, or a sine wave may be used. Good. Further, the first waveform generator also performs PWM duty control in order to keep the rotation speed constant. As a result, the most efficient operation is possible because the operation can be performed with the optimum duty according to the rotational position of the motor.
The frequency setting unit 8 changes only the output frequency while keeping the output duty constant. The second waveform generation unit 9 generates a signal for driving the switch element of the inverter 3 based on the output signal of the frequency setting unit 8. This driving signal normally generates a rectangular wave with a conduction angle of 130 degrees or more and less than 180 degrees. However, a rectangular wave with a conduction angle of less than 130 degrees or a non-rectangular wave, such as a sine wave or a distorted wave, can be used. A conforming waveform may be used. Further, here, the operation is performed with the maximum duty, which is constant from 90 to 100%.

  Furthermore, the waveform output in the second waveform generation unit does not always output a waveform having a constant energization width, but a part or all of the waveform to be output is intermittently intermittently. Then, the basic energization angle is set to 150 degrees, and the turning on of the switching element on the electrical phase of 30 degrees U phase is delayed from the timing when the U phase on the 150 degrees energization changes from the off state to the on state (that is, the electrical angle is forced off by 30 degrees) The U-phase upper switch is energized 120 degrees.

The switching determination unit 10 determines the low speed / high speed based on the rotational speed detected by the rotational speed detection unit 6 and generates a waveform for operating the inverter 3 by the first waveform generation unit 7 or by the second waveform generation unit 9. The waveform generator is switched by selecting whether to generate. Specifically, when the rotational speed is low, the signal from the first waveform generator 7 is selected and normal sensorless driving is performed. When the rotational speed is high, the signal from the second waveform generator 9 is selected. The inverter 3 is operated. Here, the determination of whether the rotational speed is low or high is made based on the actual rotational speed from the rotational speed detection unit 6, but it may be determined based on the set rotational speed, the duty width, or the like. Since the duty is the maximum duty (generally 100%) and the number of rotations that can be driven by position detection is maximized, the signal can be switched under this condition.

  The drive unit 11 drives the switch element of the inverter 3 based on the output signal from the switching determination unit 10. By this driving, an optimal AC output can be applied from the inverter 3 to the motor 4, so that the rotor can be rotated.

  The position signal determination means 12 determines whether or not the signal input from the position detection unit 5 is credible when driven by the second waveform generation unit 9, and extracts only the signal including the position information of the motor. Then, a signal including the position information of the motor is input to the second waveform generator as a position detection signal.

  The compression element 13 is connected to the rotor shaft of the motor 4 and sucks, compresses and discharges the refrigerant gas. The motor 4 and the compression element 13 are accommodated in the same hermetic container to constitute the compressor 14. The discharge gas compressed by the compressor 14 constitutes a refrigerating and air-conditioning system that returns to the suction of the compressor 14 through the condenser 15, the decompressor 16, and the evaporator 17. Then, since endotherm is performed, cooling and heating can be performed. In addition, a heat exchanger may be further accelerated | stimulated using a fan etc. for the condenser 15 and the evaporator 17 as needed. In the present embodiment, the refrigeration system is configured to cool the interior 18 of the refrigerator 30 by the evaporator 17.

  FIG. 2 shows a cross-sectional view of the compressor according to the first embodiment. In FIG. 2, oil 20 is stored in a sealed container 19 of the compressor, and a refrigerant 21 of R600a is sealed, and a motor 104 including a stator 4b and a rotor 4a, and a compression element 13 driven by the motor 104 are supported by a spring or the like. It is supported elastically and has a configuration in which vibration due to rotation of the motor is difficult to leak out of the compressor. The compression element 13 supports the main shaft portion 22 of the crankshaft 24 composed of the main shaft portion 22 to which the rotor 4 a is fixed and the eccentric shaft portion 23, and has a compression chamber 25 and a cylinder 26. A reciprocating compression mechanism is provided with a reciprocating piston 27 and a connecting means 28 for connecting the eccentric shaft portion 23 and the piston 27. Therefore, in the present embodiment, when driving by the second waveform generator, even when a part or all of the waveform for a certain period is intermittently input to the motor, the characteristics and sealing structure of the reciprocating compressor having a large inertia Therefore, the configuration is such that the occurrence of speed fluctuation is small, vibration and noise due to speed fluctuation are less likely to occur, and noise is less likely to leak outside the compressor.

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

  FIG. 3 is a timing chart showing a driving state at a low speed in the first embodiment, and shows a signal of the drive unit 11 and an output terminal voltage state of the inverter 3. This timing chart is a rectangular wave with an energization angle of 150 degrees and is driven with an advance angle of 15 degrees.

As shown in FIG. 3, in this state, when both the upper and lower switches of each UVW phase are in the OFF state, a dielectric voltage appears in the output terminal voltage. For example, as shown in the figure, for the U phase, when the output pattern is 11 and 5, the U phase upper and lower switches are turned off and an induced voltage appears in the terminal voltage. In order to detect the zero cross point of the induced voltage from the terminal voltage as a position signal, the position detecting unit 5 determines a point where the magnitude relationship between the terminal voltage and 1/2 of the inverter input voltage is inverted (that is, the zero cross point of the induced voltage). Monitor. The detected zero cross point is set as a relative rotational position of the rotor, and the next commutation timing is determined based on the reference position. In the first embodiment, the current commutation advance angle is 15 degrees, and the next commutation is zero seconds after the position detection (that is, at the same time). Therefore, the commutation (output pattern is changed from 11 to 0 or 5 to 6). In addition, in this figure, although the position detection timing by the U-phase terminal voltage and the U-phase is shown, position detection is performed twice for each phase per electrical angle cycle, so that the position of 6 times in one electrical angle cycle is eventually obtained. A detection signal is generated, and the motor is driven by applying an AC voltage of an arbitrary frequency by sequentially switching the output pattern each time this position signal is detected.

  Also, the speed of the brushless DC motor is detected based on the position detection signal. If the detected speed is slower than the target speed, the first waveform generator increases the applied voltage to the brushless DC motor and is faster than the target speed. Controls the PWM duty width so as to reduce the voltage applied to the brushless DC motor to ensure speed stability at the target speed.

  Here, when the motor load is large and the drive speed does not reach the target speed even when the PWM duty is 100%, no further voltage can be applied, so it is impossible to drive at higher speed. Is possible. Therefore, at this time, the switching determination unit 10 performs switching so that the motor is driven by the second waveform generation unit.

  The driving by the second waveform generation unit 9 performs synchronous driving at a frequency set by the frequency setting unit 8 with a waveform having a maximum duty (ie, 100%) and a conduction angle of 130 degrees or more and less than 180 degrees.

  FIG. 4 is a timing chart showing the state of synchronous driving in the conventional motor driving device, and shows the state of the signal of the drive unit 11 and the U-phase terminal voltage. During synchronous operation, the rotor follows the magnetic field generated by the current flowing in the stator winding, that is, the terminal voltage phase advances with respect to the induced voltage, so the motor current phase advances, so-called weakening. Driven by magnetic flux. The lead phase angle of the terminal voltage and current at this time is balanced and stabilized in an appropriate state depending on the load and speed with respect to the applied voltage, thereby enabling high speed and high load driving.

  The conduction angle in FIG. 4 is 150 degrees. In the case of 150 ° energization, the lead angle when the zero cross detection of the induced voltage coincides with the commutation timing (that is, the commutation is performed immediately after the zero cross detection) is 15 °, but in this figure, the lead angle is ahead of the zero cross point of the induced voltage. From this, it can be seen that the actuator is driven at an advance angle of 15 degrees or more by synchronous driving. Although the motor induced voltage appears in the terminal voltage waveform in the figure, it commutates before the induced voltage zero cross point, so it sticks to the potential of the inverter input voltage near the induced voltage zero cross point timing (upper switching It can be seen that sensorless driving by detecting the induced voltage zero cross is impossible.

  In this way, the conventional drive method cannot detect the "zero cross point of the induced voltage", that is, the rotor position, so that sudden load fluctuations or input voltage fluctuations occur, or the load and input voltage conditions are not stable. Then, the phase relationship such as the terminal voltage phase, the current phase, and the induced voltage phase is lost, and there is a possibility that the driving state becomes unstable such as phase relationship fluctuation, speed fluctuation, and current undulation. Therefore, in order to reduce the influence of disturbances such as load fluctuations and input voltage fluctuations, Embodiment 1 of the present invention enables detection of the rotor relative position during synchronous driving, and periodically detects the rotor relative position. And driving stability is achieved by performing commutation based on rotor position information.

FIG. 5 is a timing chart showing a driving state at high speed in the first embodiment, and shows a signal of the drive unit 11 and an output terminal voltage state of the inverter 3. The energization angle in the present embodiment is 150 degrees, and there are 12 energization patterns per electrical angle cycle, which are sequentially switched every 30 degrees. In FIG. 5, since the synchronous driving is performed at 150 degrees, since the commutation is performed before the zero cross point of the induced voltage when looking at the terminal voltage states of the V phase and the W phase, the advance angle is 15 degrees or more. The induced voltage zero cross point is buried in the inverter input potential or the GND level by energization of the switch element and cannot be detected. However, in the first embodiment, the switch element is forcibly turned off during a certain period in which the zero cross point of the induced voltage is expected to occur in the energization section on the upper side of the U phase (the first embodiment). In the output pattern 0, the switching element on the upper side of the U phase is turned on, but the off state is forcibly held). As a result, the induced voltage zero cross can be reliably detected before the upper side of the U phase commutates (that is, before switching to the output pattern 1) as in the U phase terminal voltage waveform of FIG. Therefore, by using the detected zero cross point as a position signal as a reference and determining the next commutation timing from the reference point, it is less affected by disturbances such as load fluctuations and voltage fluctuations, and drive stability can be improved.

  Here, the operation of the position signal determination means 12 will be described. In the first embodiment, the relative position of the motor is detected as position information at the timing when the magnitude relationship is inverted by comparing the magnitude of the inverter input voltage 1/2 and the inverter output terminal voltage. In the phase terminal voltage, it can be seen that the inversion point of the magnitude relationship between the inverter terminal voltage and 1/2 of the inverter input voltage is clearly deviated from the induced voltage zero cross point (in the U phase terminal voltage, the inverter terminal voltage is The same applies to points where the voltage is smaller than 1/2). Therefore, in order to reliably detect the rotor relative position of the motor, it is necessary to take out only the signal including the rotor position information from the output signal of the position detector. Therefore, in the first embodiment, the position signal determination unit 12 selects the output signal of the position detection unit 5 and extracts only the signal including the position information of the motor. Specifically, only a signal obtained during a period in which the switching element is forcibly stopped to acquire the induced voltage (in this embodiment, when the output pattern is 0) is recognized as a position signal.

  As described above, by extracting only the signal including the accurate position information of the motor rotor from the signal from the position detection unit 5, even in the driving by the second waveform generation unit, it is further influenced by disturbance by the reliable position detection. This makes it possible to ensure difficult and stable driving performance. In the present embodiment, the position detection is performed every electrical angle cycle. However, the frequency may be once per mechanical angle cycle.

  Next, a commutation operation in driving by the second waveform generator will be described.

FIG. 6 shows a position detection signal and commutation timing in Embodiment 1 of the present invention. Regardless of the position of the brushless DC motor rotor, the basis of driving by the second waveform generator is commutation at a constant time T corresponding to the driving speed as synchronous driving. However, for the commutation of the output pattern 1, the timing is determined according to (Equation 1) using the position detection signal as a reference.
T = An + (T−Amax) (Equation 1)
Here, T0 is the output time of pattern 0, An is the time from pattern 0 commutation to position detection, and Amax is the maximum value of An when the speed is stable. By determining the commutation timing according to Equation 1, when the load and the input voltage are very stable and there is almost no fluctuation in the motor speed, An and Amax are almost the same value, and the output time T0 of pattern 0 is It is almost the same as T and performs stable commutation.

When the load increases, the rotor starts to be delayed with respect to the commutation timing according to the load state. At this time, since An becomes larger than Amax so far, Amax is updated to An. According to Equation 1, the output time of pattern 0 is equal to T, and the commutation is continued in the commutation period T. At this time, the induced voltage phase becomes a delayed phase state corresponding to the load state with respect to the inverter terminal voltage phase, and the commutation timing is fixed. In other words, as the load increases, the phase relationship is fixed with the terminal voltage and the current advance angle increasing with respect to the induced voltage phase, and as a result, the flux-weakening control becomes effective and the drive load range and speed range are expanded. The reliability of the apparatus can be improved by improving the driving stability at the time of high load high speed driving.

  In the conventional motor drive device, commutation is performed regardless of the relative position of the rotor during synchronous driving, so the speed decreases with respect to commutation (the rotor is delayed with respect to commutation) as the load increases. The flux is in a weak flux control state in which the current advances with respect to the induced voltage phase, and the stator starts to be synchronized with the commutation cycle, and as the rotor speed approaches the commutation cycle, the current advance angle with respect to the induced voltage decreases, Speed unstable phenomena such as a decrease in rotor speed are likely to occur. However, according to Equation 1 in Embodiment 1 of the present invention, when the load increases, the commutation timing after position detection is fixed and the phase relationship is maintained while the advance angle is increased according to the load. In some cases, flux-weakening control is performed at a current advance angle corresponding to the load, enabling high-speed driving at a high load and at the same time realizing stable driving with suppressed occurrence of speed unevenness and the like.

  As described above, in this embodiment, the waveform generator is switched between when the motor is driven at a high speed and when the motor is driven at a low speed. In the low speed drive, the position information of the motor acquired from the position detector 5 is used. In addition, sensorless driving is performed by the first waveform generation unit 7, and at high speed driving, the PWM duty is fixed by the second waveform generation unit 9 and only the frequency is changed by the frequency setting unit 8 to drive the motor 4 by synchronous driving. Further, in the drive by the second waveform generator 9, a drive signal pattern for detecting the induced voltage zero cross point is periodically output in order to detect the induced voltage, thereby enabling position detection by synchronous drive. The commutation control based on the information is possible, and the reliability of the motor drive device can be improved.

  In addition, as an output pattern for detecting the zero cross point of the induced voltage, a section for forcibly stopping an arbitrary switching element from the normal output pattern is provided to prevent the induced voltage zero cross signal from being buried when the switch element is turned on. In addition, since the induced voltage zero-cross signal can be acquired, reliable position detection is possible.

  In addition, by setting the conduction angle of the phase for detecting the induced voltage zero cross point to 150 degrees or less, it is possible to secure a wide expected range of occurrence of the induced voltage zero cross point, so position detection is ensured even when the speed and load conditions vary. Thus, the reliability of the motor drive device can be improved.

  Further, even during synchronous driving by the second waveform generator 9, since commutation is performed based on the relative position of the motor 4, it is possible to prevent an unstable driving state due to disturbance such as load fluctuation or input voltage fluctuation, The reliability of the motor drive device can be improved.

  Also, by fixing the next commutation timing from the position detection signal in the synchronous drive state by the second waveform generator, the weak flux control is performed by the current advance angle according to the load when the load is increased, and the high load high speed drive is stabilized. Can be realized.

  Driving the compressor 14 with this motor drive apparatus is a load with a very large inertia, so there is almost no speed fluctuation due to intermittent part of the output pattern, and a very stable high The load can be driven at a high speed, which is a very useful application for the motor driving apparatus.

Further, if the compressor 14 has a reciprocating structure, vibration and noise are difficult to leak to the outside because of its structure, so even if some speed fluctuation occurs by intermittently outputting a part of the output pattern, the compressor 14 This is a very suitable load because it can suppress the outflow of noise and vibration.

  The brushless DC motor drive device of the present invention achieves high efficiency and low noise operation at low speeds, can ensure stable high speed at high speeds, and further has a current advance angle according to the load when the load is large. High-speed and high-speed driving is also possible with the flux-weakening control by means of, so it is particularly suitable for applications such as driving compressors such as refrigerators and air conditioners, and fans and vacuum cleaners such as fans with a wide speed range and load range.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Sectional drawing of the compressor of this Embodiment 1. Timing chart showing drive state at low speed in the first embodiment Timing chart showing the state of synchronous drive in a conventional motor drive device Timing chart showing driving state at high speed in the first embodiment Position detection signal and commutation timing chart in Embodiment 1 of the present invention Block diagram of a conventional motor drive device

DESCRIPTION OF SYMBOLS 3 Inverter 4 Brushless DC motor 5 Position detection part 7 1st waveform generation part 9 2nd waveform generation part 10 Switching determination part 11 Drive part 14 Compressor 30 Refrigerator

Claims (8)

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, a drive unit for driving the inverter, and the brushless DC motor A position detector that detects the relative rotational position of the rotor based on the induced voltage generated in the three-phase winding of the stator and outputs a position signal, and a duty control based on the output signal from the position detector A first waveform generator that outputs a rectangular wave, a sine wave, or a waveform conforming thereto, and a second waveform generator that outputs a rectangular wave, a sine wave, or a waveform conforming thereto to the brushless DC motor When the brushless DC motor is rotating at a low speed equal to or less than a predetermined number of revolutions, the inverter is driven via the drive unit with the output of the first waveform generating unit, When the brushless DC motor is rotating at a high speed exceeding a predetermined number of revolutions, a switching determination unit that drives the inverter through the drive unit with the output of the second waveform generation unit has a second waveform generation A motor driving device that outputs a pattern for detecting an induced voltage of the brushless DC motor at a predetermined timing when driven by the unit. The waveform at the timing of detecting the induced voltage of the brushless DC motor generated by the second waveform generating unit is one waveform compared to the waveform at the normal timing when the induced voltage of the second waveform generating unit is not detected. The motor driving device according to claim 1, wherein the motor driving device has a waveform in which some or all of them are intermittent. 3. The motor drive device according to claim 1, wherein the waveform of the second waveform generator that is output at a timing of detecting the induced voltage of the brushless DC motor has a conduction angle of at least one phase of 150 degrees or less. 4. The drive by the second waveform generation unit according to claim 1, wherein commutation after detection of a rotor relative position of the brushless DC motor determines a next timing based on position information. 5. Motor drive device. The motor driving device according to any one of claims 1 to 4, wherein a phase relationship between a position signal acquisition timing and a next rotational flow is maintained in the driving by the second waveform generation unit. The motor driving device according to any one of claims 1 to 5, wherein the brushless motor drives a compressor. The motor driving device according to any one of claims 1 to 6, wherein the compressor has a reciprocating configuration. The refrigerator which used the motor drive device of Claim 6 or Claim 7 for the compressor.