JP2011010476A - Motor drive device and electric apparatus employing the same - Google Patents

Abstract

[PROBLEMS] To increase the stability of a brushless DC motor at high loads and high speeds and to expand the driving range, to suppress unstable states due to external factors, and to stabilize even under excessive load conditions. Provided is a highly reliable brushless DC motor driving apparatus.
A current and voltage state grasped by a current-voltage state grasping means 16 and a target current and voltage state are made to coincide with an output of a second waveform generator 15 that outputs at a predetermined frequency at a high load. By driving the high speed with the output of the waveform correction unit 18 that corrects the output and further corrects the output with the voltage detected by the voltage means 17, the phase is maintained in an appropriate phase relationship depending on the driving speed, load state, input voltage state, etc. Therefore, it can be driven stably even when a disturbance occurs.
[Selection] Figure 1

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 apparatus that is optimal for an electric device that drives a compressor such as an air conditioner.

  A conventional motor drive device is provided with a step of switching between speed feedback operation and speed open loop operation according to a current state and a speed state to drive the motor (for example, Patent Document 1). FIG. 14 shows a conventional motor driving device described in Patent Document 1. In FIG.

  In FIG. 14, a DC power supply 201 is input to an inverter circuit having six switching elements having a three-phase bridge configuration, and an inverter 202 converts the input DC voltage into an AC voltage having an arbitrary frequency, and supplies it to the brushless DC motor 203. input.

  The position detector 204 detects the relative position of the rotor 203 a of the brushless DC motor 203 based on the induced voltage information generated by the rotation of the brushless DC motor 203 from the output terminal voltage of the inverter 202. The control circuit 205 receives the position signal output from the position detection unit 204 and generates a control signal for the switching element of the inverter 202.

  The position calculation means 206 calculates magnetic pole position information of the rotor 203a of the brushless DC motor 203 from the signal of the position detection unit 204. Based on the magnetic pole position of the rotor 203a obtained from the position calculating means 206 and the speed command value, the self-regulating operation means 207 switches the current flowing through the three-phase winding of the brushless DC motor 203 by feedback control of the brushless DC motor. The other driving operation means 210 performs open-loop driving by switching the current flowing through the three-phase winding of the brushless DC motor based on the speed command, and the selection means 211 performs the self-limiting operation of the brushless DC motor. It is selected whether to drive by means or other driving means.

  The drive control means 212 generates a control signal for the switching element of the inverter 202 based on the operation means selected by the selection means 211.

  As described above, the conventional motor drive device can change the operation range of the brushless DC motor by switching from the self-regulated operation by the feedback control to the other control operation that performs the open loop drive when the brushless DC motor is driven at a high speed or a high load. It has been expanded.

JP 2003-219681 A

  However, the above-described conventional configuration drives the brushless DC motor in an open loop during high-speed or high-load operation, so that stable driving performance can be obtained with a relatively small load. If it becomes larger, it may fall into an unstable driving state.

  FIG. 9 shows the phase relationship between the phase current and the terminal voltage when the brushless DC motor is driven in an open loop synchronous manner. In FIG. 9, the horizontal axis represents time, the vertical axis represents the phase based on the induced voltage phase (that is, the phase difference from the induced voltage), (A) represents the phase current, (B) represents the terminal voltage, and (C). Is the phase difference between the phase current and the terminal voltage. FIG. 5 (a) shows a relatively low load state, and FIG. 5 (b) shows a high load state. In both cases (a) and (b), the current phase advances from the terminal voltage phase due to the difference from the induced voltage phase. From this, it can be seen that it is driven at a very high speed by synchronous driving.

  As shown in FIG. 9 (a), in synchronous driving in which the load is relatively small with respect to the driving speed, the rotor is delayed by an angle corresponding to the load state with respect to commutation, that is, the rotor (induced voltage). ), The commutation (that is, the voltage and current phase) becomes the leading phase and the predetermined relationship is maintained, so that the same state as the flux-weakening control is achieved, and high-speed driving is possible. On the other hand, as shown in (b), in a state where the load is large with respect to the driving speed, as in (a), “the rotor is delayed with respect to the commutation so that the magnetic flux is weakened and the commutation cycle is synchronized. Thus, the acceleration of the rotor and the acceleration of the rotor repeatedly reduce the current phase lead angle and the rotor decelerates ", and the drive state (drive speed) is not stabilized after all. That is, as shown in (b), since the rotation of the brushless DC motor fluctuates with respect to the commutation repeated at a constant period, the terminal voltage phase fluctuates when the induced voltage phase is used as a reference. In such a driving state, occurrence of problems such as the occurrence of “swelling noise” accompanying fluctuations in the rotational speed of the brushless DC motor and the possibility of overcurrent stop due to current pulsation is expected.

  Therefore, in order to avoid the possibility of the above-mentioned problems, it can be dealt with by reducing the load or reducing the speed until the rotational state of the brushless DC motor becomes unstable. This limits the high speed and high load driving of the DC motor, and has a problem that it is difficult to sufficiently expand the drive region.

  Furthermore, in the above conventional configuration, since the motor current phase and voltage phase are determined by speed and load, the motor current and voltage phase states are ideal in an ideal environment where the load and input voltage of the brushless DC motor are very stable. However, the rotation fluctuation phenomenon described above is affected by the driving speed and the load size, and the load fluctuation (the motor during one rotation of the motor such as a compressor) is affected. (Including load fluctuations) and input voltage fluctuations (including ripple voltage associated with AC voltage rectification and smoothing) are also greatly affected by external factors. Had problems.

  The present invention solves the above-described conventional problems, and enhances the stability of a brushless DC motor at a high load and high speed driving to expand the driving range, and also suppresses an unstable state due to an external factor and has high reliability. A brushless DC motor driving apparatus is provided.

  In addition, by expanding the drive range due to the stability of high-speed and high-load drive, high-efficiency low-torque motors that increase the number of stator winding turns and sacrifice high-speed drive performance can be driven at high speed and high load. An object is to realize a motor drive device with high efficiency and high torque.

In order to solve the conventional problem, the motor driving method of the present invention is configured such that the energization angle of the brushless DC motor is 120 degrees or more and 150 degrees or less at low speed or low load, and 120 degrees or more and less than 180 degrees at high speed or high load. At high speed, the relationship between the current and the terminal voltage state corresponding to the speed and load state of the brushless DC motor is maintained at a predetermined frequency with a constant duty, and further the energization timing is achieved by the terminal voltage value. As a result, the phase current and terminal voltage phase of the brushless DC motor are maintained in an appropriate phase relationship with respect to the induced voltage phase depending on the driving speed, load state, input voltage state, etc., and also stable when a disturbance occurs. Can be driven.

  According to the motor driving method of the present invention, it is possible to stably drive to the vicinity of the limit torque of the motor by a simple waveform generation method, and it is possible to provide a highly reliable motor driving device with an extended operation range.

  In addition, by expanding the operating range, high-efficiency motors that increase the number of motor turns and sacrifice high-speed drive performance can be driven at high loads and high speeds, while maintaining the same load drive range as before. Efficiency can be improved.

  Further, since the commutation speed is changed in accordance with the change in voltage, it is possible to drive stably with respect to the change in voltage.

  Further, when the motor driving device of the present invention is used for driving a compressor of a refrigeration cycle, it is possible to increase the efficiency of the device, particularly in the driving at a low speed, and to save the energy of the electric device.

1 is a block diagram of a brushless DC motor driving apparatus according to Embodiment 1 of the present invention. Timing chart of inverter driving at low speed in Embodiment 1 of the present invention Energization angle at low speed = Efficiency characteristic diagram in Embodiment 1 of the present invention Timing chart of inverter drive at high speed in Embodiment 1 of the present invention The graph which shows the phase state with respect to the load at the time of the synchronous drive of a brushless DC motor Vector diagram showing phase relationship between phase current and terminal voltage depending on load condition The graph which shows the phase state with respect to DC bus voltage at the time of the synchronous drive of a brushless DC motor Vector diagram showing phase relationship between phase current and terminal voltage due to fluctuation of DC bus voltage at specified load A graph showing the phase relationship when a brushless DC motor is driven in an open loop synchronous manner The flowchart which shows operation | movement of the current voltage state grasping | ascertainment means 16 and the waveform correction part 18 in Embodiment 1 of this invention. The flowchart which shows operation | movement of the voltage detection part 17 and the waveform correction | amendment part 18 in Embodiment 1 of this invention. Rotation speed = duty characteristic diagram in Embodiment 1 of the present invention Structure diagram of rotor of brushless DC motor according to embodiment 1 of the present invention Block diagram of a conventional motor drive device

A first invention is 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 a voltage for detecting an input voltage to the inverter The energization angle is 120 degrees or more and less than 150 degrees by the output of the detection section, the current phase detection section for detecting the current phase of the brushless DC motor, the position detection section for detecting the rotational position of the rotor, and the previous position detection section. A first waveform generator for driving the inverter by outputting a rectangular wave or a waveform equivalent thereto at a predetermined frequency, a frequency setting unit for changing only the predetermined frequency with a constant duty, and a conduction angle of 120 degrees or more and less than 180 degrees A second waveform generating unit that outputs a rectangular wave or a waveform conforming thereto at a predetermined frequency determined by the frequency setting unit, and a current detected by the current phase detecting unit Current voltage state grasping means for detecting the phase and the state of the drive signal of the second waveform generating section, the state detected by the current voltage state grasping means, and the second waveform generating section Correcting the output, further correcting the waveform by the voltage value detected by the voltage detection unit, and outputting the waveform correction unit to the inverter and the first waveform generation unit to the inverter at low speed or low load, Operation switching means for switching the waveform correction section to output to the inverter at high speed or high load, thereby driving the phase current and terminal voltage phase of the brushless DC motor with respect to the induced voltage phase. It is held in an appropriate phase relationship depending on the speed, load state, input voltage state, etc., and can be driven stably even when a disturbance occurs.

  In addition, by expanding the operating range, high-efficiency motors that increase the number of motor turns and sacrifice high-speed drive performance can be driven at high loads and high speeds, while maintaining the same load drive range as before. Efficiency can be improved.

  In the second aspect of the invention, in particular, the waveform correction unit of the first aspect of the invention accelerates commutation as the voltage value output from the voltage detection unit is higher, and the voltage value detected by the voltage detection unit is lower. By correcting to delay commutation, it is possible to prevent excessive current and step-out due to excessive advancement of the voltage phase, and it is possible to prevent excessive current due to a delayed phase in which the terminal voltage phase is delayed from the induced voltage, The reliability can be improved by preventing damage to the inverter elements due to voltage fluctuation and demagnetizing the motor by a simple method.

  In the third invention, in particular, the voltage detection unit according to the first or second invention periodically detects the voltage value at a period earlier than the driving period of the brushless DC motor, and integrates the detection results. As an output, the integrated value is cleared each time correction is performed by the waveform correction unit, so that the voltage of the entire correction cycle can be measured, and more stable driving is possible in accordance with the actual voltage state. Become.

  In the fourth aspect of the invention, in particular, the voltage detector according to any one of the first to third aspects of the invention performs average of the detected voltages, and outputs a difference between the average and the detected value, thereby driving stably until just before. Therefore, it is possible to avoid the excessive correction of the voltage change due to the fluctuation of the load, and to perform more stable driving utilizing the characteristic of convergence to the stable state of the synchronous driving.

  According to a fifth aspect of the invention, in particular, the waveform correction unit according to any one of the first to fourth aspects of the present invention is based on a correction amount for causing the output of the current / voltage state grasping means to coincide with the target state, and the output of the voltage detection unit. By providing an upper limit to the correction amount, the amount of change is limited against disturbance, and strong driving is possible due to noise and disturbance.

  In a sixth aspect of the invention, in particular, the position detector of any one of the first to fifth aspects of the present invention detects a position from a voltage induced by the brushless DC motor, and the current phase detector detects the brushless DC motor and the The timing at which the voltage appearing at the terminal of the brushless DC motor generated when the return current flows in the inverter is turned off is detected as a current phase 0, and the current phase detection unit performs the position detection unit to newly generate a current phase. Since it is not necessary to provide a detection unit, a simple configuration can be taken at low cost.

  In the seventh aspect of the invention, in particular, the operation switching means of any one of the first to sixth aspects uses the output of the first waveform generator when the switching is less than a predetermined speed, and the output of the waveform corrector when the speed is higher than the predetermined speed. By doing so, an appropriate driving method is selected with a simple configuration, and the system configuration can be simplified in a case where the system load range is clear and nominal.

In the eighth invention, in particular, when the operation switching means of any one of the first to sixth inventions switches from the first waveform generator to the output of the waveform corrector, the duty output of the first waveform generator is a predetermined reference. When the value is exceeded, and when the output is switched from the waveform correction unit to the first waveform generation unit, the position detection unit can detect the position of the rotor. Since driving by one waveform generator is performed, more stable driving can be performed.

  According to a ninth aspect of the invention, in particular, the brushless DC motor according to any one of the first to eighth aspects is a rotor in which a permanent magnet is embedded in an iron core, and the rotor has saliency. This makes it possible to use reluctance torque due to saliency in addition to the magnet torque of the permanent magnet, which naturally increases the efficiency at low speed and further increases the high-speed driving performance.

  In the tenth aspect of the invention, in particular, the load driven by the brushless DC motor according to any one of the first to ninth aspects is a compressor, so that a motor with an increased winding amount is used. Since the torque-reduced brushless DC motor can be driven at a predetermined high speed, the duty at a low rotation speed can be made larger than that of the conventional driving method, so that motor noise, particularly carrier noise, can be reduced.

  In the eleventh aspect of the invention, in particular, since the compressor of the tenth aspect of the invention constitutes a refrigeration cycle of the refrigerator, the load fluctuation of the refrigerator is not steep, and the change in the phase difference target between the current phase and the terminal voltage phase is reduced. Therefore, more stable driving is possible.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing a brushless DC motor driving apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, an AC power source 1 is a commercial power source having 50 or 60 Hz and an effective value of 100 V in Japan. The rectifying / smoothing circuit 2 receives the AC power supply 1 as an input and rectifies and smoothes the DC power supply. The rectifying / smoothing circuit 2 includes four bridge-connected rectifier diodes (2a to 2d) and smoothing capacitors (2e and 2f). Although the voltage doubler rectifier circuit is used in this embodiment, a full wave rectifier circuit may be used. Furthermore, in this embodiment, the AC power source is a single phase, but when a three-phase AC power source is used, a three-phase rectifying / smoothing circuit may be used as the rectifying / smoothing circuit.

  The inverter 3 receives the DC voltage output from the rectifying and smoothing circuit 2 and converts DC power into AC power, and is configured by connecting six switching elements (3a to 3f) in a three-phase bridge. . In addition, a diode for return current (3g to 3l) is connected in the reverse direction of each switching element.

  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 through the winding of the stator 4b. The stator 4a can be rotated. The rotary motion of the rotor 4a is converted into reciprocating motion by a crankshaft (not shown), and the compressor 5 that compresses the refrigerant by reciprocating the piston (not shown) in a cylinder (not shown) is driven. I do.

  The compression method (mechanism form) of the compressor 5 may be anything such as a rotary or a scroll, but this time, it is a reciprocating type. Since the reciprocating type has particularly large inertia, synchronous driving can perform more stable driving.

The refrigerant gas may be anything such as R134a, but R600a is adopted in the first embodiment. The R600a has a lower refrigeration capacity than the R134a, and the cylinder capacity of the compression element 6 is increased to compensate for a decrease in the refrigeration capacity. As a result, the compressor 5 has a large inertia. As a result, even when the voltage drops, the brushless DC motor 4 rotates due to the inertia, so that the speed is unlikely to fluctuate and more stable synchronous driving is possible.

  The discharge gas compressed by the compressor 5 constitutes the refrigerator 10 that returns to the suction of the compressor 5 through the condenser 7, the decompressor 8, and the evaporator 9. At this time, since the condenser 7 radiates heat and the evaporator 9 absorbs heat, cooling and heating can be performed. If necessary, a blower or the like can be used for the condenser 7 or the evaporator 9 to further promote heat exchange.

  The position detection unit 11 detects the relative magnetic pole position of the rotor 4a of the brushless DC motor 4. In this embodiment, the relative position of the rotor 4a is determined from the induced voltage generated in the three-phase winding of the stator 4b. Rotating position is detected. As a method for detecting the stator position, the magnetic pole position may be estimated through the vector calculation from the detection of the motor current (phase current or bus current).

  The first waveform generator 12 generates a signal for driving the switching element of the inverter 3 based on the position information of the rotor 4 a obtained by the position detector 11. This driving signal is based on rectangular wave energization, and the energization angle is 120 degrees or more and 150 degrees or less. However, there is no problem even if the waveform other than the rectangular wave is a trapezoidal wave having a slight slope in the rising / falling as a waveform conforming thereto.

  The first waveform generator 12 further performs PWM duty control in order to keep the rotation speed constant. As a result, it is possible to operate with an optimum duty according to the rotational position, and the brushless DC motor can be most efficiently operated.

  The speed detector 13 detects the speed of the brushless DC motor 4 from the output signal of the position detector 11. As a specific method, it can be easily detected by measuring a signal from the position detection unit 11 generated at a constant period.

  The frequency setting unit 14 outputs only the frequency with a constant output duty.

  The second waveform generation unit 15 outputs a rectangular wave drive signal of 120 degrees or more and less than 180 degrees based on the output signal of the frequency setting unit 14. However, there is no problem even if it is a sine wave or a waveform similar to that such as a distorted wave. Here, driving is performed with the maximum duty, which is a constant duty of 90 to 100%.

  The current voltage state grasping means 16 grasps the relationship between the current flowing through the brushless DC motor 4 and the terminal voltage based on the output signal of the position detector 11 and the waveform output from the second waveform generator 15.

  The relationship between the current flowing through the brushless DC motor 4 and the terminal voltage may be a phase difference between the current and the terminal voltage, or may be a time difference under a specific condition such as zero crossing. Further, in order to perform more simply, the terminal voltage itself may not be acquired, but may be performed based on a drive signal that substantially matches the terminal voltage state.

  In the present embodiment, the time difference between the current zero cross and the rise of the drive signal is grasped as the current voltage state, and the current voltage state grasping means 16 functions as the current phase detecting means.

Moreover, what is adopted as the output signal of the position detection unit 11 is a detection result of the presence or absence of current flowing in the diode for the return current of the inverter 3 that appears in the terminal voltage. In other words, the current flow coincides with the point at which the current flow switches from positive to negative or from negative to positive, and the zero cross of the current is an input to the current voltage state grasping means 16.

  Since the position detection unit 11 outputs a signal indicating whether the terminal voltage state is high or low with reference to the threshold value, the zero-crossing point of the induced voltage of the brushless DC motor 4 used as the reference in the first waveform generation unit is output. There is no need to change detection and configuration.

  The voltage detector 17 detects and integrates the voltage between the DC buses output from the rectifier circuit 2 and input to the inverter 3. Further, the average of the integration is calculated and the integration is cleared. The calculation and clear of the average are performed every time the waveform correction is performed by the waveform correction unit 18 that corrects the waveform.

  The waveform correction unit 18 corrects the waveform output from the second waveform generation unit 15 based on the outputs of the current voltage state grasping means 16 and the voltage detection unit 17 and outputs a signal for driving the inverter 3.

  The operation switching means 20 determines whether the inverter 3 is operating at the low speed / high speed, and switches the waveform for operating the inverter 3 between the first waveform generator 12 and the waveform corrector 18. Specifically, when the rotation speed is low, the signal from the first waveform generation unit 12 is selected, and when the rotation speed is high, the signal from the waveform correction unit 18 is selected to operate the inverter 3.

  Here, the determination of whether the rotation speed is low or high may be determined from the actual speed detected by the speed detection unit 13 or may be determined from the set rotation speed or the duty. If the judgment is based on the speed, the configuration becomes very simple and the development becomes easy. Since the determination by duty is the maximum duty (generally 100%) and the maximum speed in driving by position detection, the waveform generator is switched from the first waveform generator 12 to the waveform corrector 18 under this condition. As a result, it is possible to drive with the necessary voltage optimally applied. Further, switching from the drive waveform of the waveform correction unit 18 to the first waveform generation unit may be performed when the position detection signal can be acquired by the position detection unit 11, and a reliable shift to sensorless drive is possible.

  In the present embodiment, when the maximum duty is reached, the first waveform generator 12 is switched to the waveform corrector 18, and when the position detector 11 can reliably detect the position, the waveform corrector 18 performs the first operation. Suppose you want to switch to the waveform generator.

  The drive unit 19 drives the switch elements (3 a to 3 f) of the inverter 3 by the output signal from the operation switching means 20. By this driving, an optimal AC output can be applied from the inverter 3 to the brushless DC motor 4, so that the rotor 4a can be rotated.

  Next, the operation in Embodiment 1 of the present invention will be described.

  First, the operation at low speed will be described. FIG. 2 is a timing diagram of inverter driving at low speed in Embodiment 1 of the present invention. When the rotational speed of the brushless DC motor 4 is low, the brushless DC motor 4 is driven by a signal from the first waveform generator 12 that operates according to the output of the position detector 11, and the operation is as shown in FIG.

In FIG. 2, U is a drive signal for the switch element 3a, V is a drive signal for the switch element 3c, W is a drive signal for the switch element 3e, X is a drive signal for the switch element 3b, Y is a drive signal for the switch element 3d, and Z Is a drive signal for the switch element 3f, and Iu, Iv, and Iw indicate currents of U phase, V phase, and W phase of each winding of the stator 4b. In driving at low speed, commutation is performed sequentially in intervals of 120 degrees in accordance with a signal from the position detection unit 11. The upper arm drive signals U, V, and W are duty controlled by PWM control. At this time, the current waveform is a sawtooth waveform as shown in FIG. At this time, since the commutation is performed at an optimum timing based on the output of the position detector 11, the brushless DC motor can be driven most efficiently.

  Next, the optimum energization angle will be described with reference to FIG. FIG. 3 is a conduction angle = efficiency characteristic diagram at low speed in Embodiment 1 of the present invention. In FIG. 3, the solid line indicates the motor efficiency, the broken line indicates the circuit efficiency, and the alternate long and short dash line indicates the total efficiency (motor efficiency × circuit efficiency). As shown in FIG. 3, when the energization angle is larger than 120 degrees, the motor efficiency is improved. This is because the effective angle of the motor current decreases (that is, the power factor increases) and the motor efficiency increases as the copper loss of the motor decreases as the conduction angle increases. However, in the circuit, the number of times of switching increases and the switching loss increases, so that the circuit efficiency decreases. Therefore, the point with the highest overall efficiency appears. In the present embodiment, 130 degrees can be said to be the most efficient point.

  Next, the operation at high speed will be described. FIG. 4 is a timing diagram of inverter driving at high speed in the first embodiment of the present invention. When the rotation speed of the brushless DC motor 4 is high, the second waveform generation unit 15 outputs a signal from the output of the frequency setting unit 14, the waveform correction unit corrects the signal output from the second waveform generation unit 15, Driven by outputting a signal, the operation is as shown in FIG.

  The symbols in FIG. 4 are the same as those in FIG. Each drive signal is commutated so as to output a predetermined frequency in accordance with the output of the frequency setting unit 14. At this time, the conduction angle is set to 120 degrees or more and less than 180 degrees. This is shown in FIG. 4 where the conduction angle is 150 degrees. By increasing the conduction angle, the current waveform of each phase approximates a sine wave.

  By increasing the frequency while keeping the duty constant, the number of revolutions can be significantly increased compared to the prior art. In this state where the rotational speed is increased, the brushless DC motor 4 is operated as a synchronous motor, and the current increases as the drive frequency increases. At this time, by increasing the conduction angle to less than 180 degrees at the maximum, the peak current value can be suppressed, and a higher current can be operated without overcurrent protection.

  Here, the timing when the switching element is turned on by the waveform correction unit 18 that receives the signals from the second waveform generation unit 15, the current / voltage state grasping unit 16, and the voltage detection unit 17 to correct and output the drive waveform will be described.

  FIG. 5 is a graph showing a phase state with respect to a load when the brushless DC motor is synchronously driven. In FIG. 5, the horizontal axis represents the motor torque, and the vertical axis represents the phase difference based on the induced voltage phase. When the phase is positive, the phase is positive with respect to the induced voltage phase. Further, (a) in FIG. 5 is the motor current, and (b) is the phase of the motor phase voltage, which shows a stable state in the synchronous operation. Since the current phase is ahead of the terminal voltage phase even in a low load state, it can be said that the brushless DC motor is driven at high speed by synchronous driving. As is clear from the relationship between the phase current phase and the phase voltage phase shown in FIG. 5, the change in the current phase is small with respect to the load torque, and the terminal voltage phase changes linearly. It can be seen that the phase difference between and increases substantially linearly.

  As described above, in the synchronous drive, it is stable at an appropriate current and voltage phase relationship according to the drive speed and load of the brushless DC motor. FIG. 6 shows the relationship between the terminal voltage and the current phase at this time. FIG. 6 is a vector diagram showing the phase relationship between the current and the terminal voltage depending on the load state in a dq plane.

As shown in FIG. 6, in the synchronous drive, the phase of the terminal voltage vector changes in the advance direction while keeping the magnitude almost constant when the load increases. On the other hand, the current vector changes its magnitude as the load increases while maintaining a substantially constant phase (current increases as the load increases).

  Next, the voltage between the DC buses of the inverter 3 and the phase state of the brushless DC motor will be described with reference to FIG. FIG. 7 is a graph showing a phase state with respect to the DC bus voltage when the brushless DC motor 4 is synchronously driven. In FIG. 8, the horizontal axis indicates the voltage value between the DC buses, and the vertical axis indicates the phase difference based on the induced voltage phase. When the phase is positive, it indicates that the phase is positive with respect to the induced voltage phase. Moreover, (b) in FIG. 7 is the motor current, and (b) is the phase of the motor phase voltage, which shows a stable state in the synchronous operation at a specific load.

  Even at a high voltage, since the current phase is ahead of the terminal voltage phase, it can be said that the brushless DC motor 4 is driven at high speed by synchronous driving. As is clear from the relationship between the phase current phase and the phase voltage phase shown in FIG. 7, both the current phase and the voltage phase monotonously decrease with respect to the DC bus voltage, and the change in the voltage phase is larger than the current phase. It can be seen that the phase difference between the current and the voltage monotonously increases according to the DC bus voltage.

  FIG. 8 shows the relationship between the terminal voltage and the current phase at this time. FIG. 8 is a vector diagram showing the phase relationship between the current and the terminal voltage due to fluctuations in the DC bus voltage at a specific load in the dq plane.

  As shown in FIG. 8, in the synchronous drive, the terminal voltage vector increases as the DC bus voltage increases, and the phase shifts in the direction in which the advance angle decreases. On the other hand, the phase of the current vector changes more greatly than the terminal voltage while the magnitude of the vector decreases with the voltage between the DC lead wires, and the advance angle decreases.

  In this way, the phase relationship between the vectors is determined in an appropriate state in which the voltage and current vectors are in accordance with the driving environment (input voltage, load torque, driving speed, etc.).

  Here, the temporal change of the phase state in a certain load state / speed state will be described with reference to FIG. As described in the problem of the prior art, when the driving state is stable by synchronous driving, the phase difference between the phase current phase and the terminal voltage phase is constant as shown by the waveform (c) in FIG. Kept stable.

  On the other hand, when the load is extremely large, or when the driving state is unstable due to disturbance or the like (when fluctuations in rotational speed occur), current and terminal voltage based on the induced voltage phase due to fluctuations in the rotor speed The phase relationship between the current and the terminal voltage also varies because the variation in the terminal voltage phase is larger than the variation in the current phase.

  In other words, when an unstable phenomenon occurs in synchronous drive, the phase relationship between the induced voltage, motor terminal voltage, and motor current is in an unstable (fluctuating) state, and is unstable once in an open loop drive. When falling into a phase state, it is difficult to converge to a phase relationship commensurate with load and speed. Therefore, by maintaining the phase difference between the current phase and the terminal voltage in an appropriate phase relationship corresponding to the load and the voltage between the DC buses as shown in FIGS. 5 and 7, the unstable phenomenon due to the synchronous drive can be suppressed. It becomes possible.

  As a method of maintaining the phase relationship between the terminal voltage and the phase current, in this embodiment, the reference phase of the terminal voltage (that is, the commutation reference position of the drive signal) and the reference point of the current phase are detected, and the open loop synchronization is performed. The commutation timing in driving (commutation with a fixed period) is corrected. Furthermore, commutation timing in open-loop synchronous driving is corrected according to fluctuations in the DC bus voltage.

  First, a method for determining the control timing of the switching element of the inverter 3 that detects and corrects the reference point of the terminal voltage and the reference point of the current phase is shown in FIG. And a flowchart showing the operation of the waveform correction unit 18 will be described.

  First, at step 101, the current / voltage state grasping means 16 waits for the OFF timing of the first specific switch element of the inverter 3 from the drive signal output from the waveform correction unit 18. In the present embodiment, it is assumed that the U-phase lower switch element, that is, the switch element 3b of the inverter 3 is waiting for the off timing. If it is the OFF timing of the switch element 3b, the process proceeds to step 102.

  In step 102, the current / voltage state grasping means 16 starts a timer for time measurement, and the process proceeds to step 103.

  In step 103, the position detector 11 determines whether or not the spike voltage of the specific phase has dropped from “terminal voltage—the voltage drop of the switch element 3a” to near 0V. In the present embodiment, it is determined whether or not the terminal voltage of the U phase has decreased to around 0V. In other words, it is the timing at which the current flowing through the return current diode 3g does not flow after the switching element 3b of the inverter 3 that is the switching element under the U phase is turned off. The cross is judged.

  Here, assuming that the spike voltage has dropped to around 0 V, the routine proceeds to step 104.

  In step 104, the current voltage state grasping means 16 stops the timer started in step 102 and stores the timer count value. That is, the time from when the switch element 3d is turned on to when the spike voltage generated while the current flows through the return current diode 3g of the inverter is measured. Next, it progresses to step105.

  In step 105, the time measured by the current / voltage state grasping means 16 is input to the waveform correction unit 18, and the waveform correction unit 18 calculates the difference from the average time so far, and proceeds to step 106.

  In step 106, the correction amount of the commutation timing is calculated based on the difference, and the process proceeds to step 107.

  Here, the commutation timing correction amount is to correct the commutation timing with respect to the basic commutation period output from the second waveform generation unit based on the command speed set by the frequency setting unit 14. Therefore, when a large correction amount is added, it causes overcurrent and step-out stop. Therefore, in determining the correction amount, by adding a low-pass filter, setting the upper limit of the correction amount, multiplying the difference by a value less than 1, etc. ing. As a result, even when the current zero cross detection fails (false detection) due to the influence of noise or the like, the influence on the correction amount can be reduced, and the driving stability can be further improved. Furthermore, suppressing a sudden change in the correction amount calculation also slows down the change in commutation timing during acceleration / deceleration of the brushless DC motor, so the command speed is greatly changed and the commutation cycle by the frequency setting unit is greatly increased. Even when changed to, the change in commutation timing becomes gradual, and smooth acceleration / deceleration performance with suppressed current disturbance can be obtained.

  Specifically, the commutation timing is corrected so that the phase difference always approaches the average time (the phase difference can be maintained at the average time).

For example, when the load becomes large, the current phase is delayed due to a decrease in the rotor speed, and the measurement time is longer than the average time from the terminal voltage reference phase to the phase current reference phase, the commutation timing is the timing of the commutation cycle based on the rotation speed. The commutation timing is corrected so that it is delayed (the measurement time is longer because the current phase is delayed, so the terminal voltage phase is delayed by delaying the commutation timing, and the phase difference from the current phase is brought closer to the average time).

  Conversely, when the load decreases, the rotor speed increases, the current phase advances, and the measurement time becomes shorter than the average time from the terminal voltage reference phase to the phase current phase, the commutation timing is temporarily changed based on the rotation speed. Correction is made so that it is earlier than the current cycle timing (since the current phase is faster and the measurement time is shorter, the commutation timing is advanced to advance the terminal voltage phase and the phase difference of the current phase is closer to the average time) To do.

  Further, the commutation timing is corrected as an arbitrary timing of a specific phase (for example, only switching on the U phase) (such as once per rotation of the rotor), and the commutation of other phases is based on the target rotational speed. Perform in time by cycle. As a result, the phase relationship between the phase current and the terminal voltage phase can be optimally maintained according to the load, and the driving speed of the brushless DC motor can be maintained.

  Next, in step 107, the calculation is performed and updated as an average time including the time from the commutation obtained in step 104 to the specific phase of the current, and then the process proceeds to step 108.

  As a result, when the load becomes heavy, the phase difference, which is the difference between the specific current phase and the commutation timing, is narrowed. The motor 4 is driven with reference to a state where the phase difference is narrower. That is, the motor 4 is driven with a larger advance angle, and the output torque is increased and the required output torque is secured by improving the flux-weakening effect.

  Conversely, if the load becomes lighter and the phase difference, which is the difference between the specific current phase and the commutation timing, increases, the average of the correction reference becomes larger and the phase difference becomes wider than before the load becomes lighter. The motor 4 is driven with reference to this state. That is, the brushless DC motor 4 is driven with a smaller advance angle, the output torque is reduced by reducing the weakening magnetic flux effect, and no more torque than necessary is output.

  In other words, it is possible to ensure the necessary output and drive without extra output.

  In step 108, the commutation timing is determined by adding a correction amount to the commutation cycle of the switch element based on the driving speed set by the frequency setting unit.

  On the other hand, when the specific phase spike is not turned off in step 103, the process proceeds to step 109, and it is determined whether or not the second specific SW element is commutated in step 109. Here, the second specific SW element is a switch that changes at the timing when a section in which a spike can occur is completed, and here is the switch element 3a on the U phase. Here, when the second specific SW element does not commutate, the process returns to step 103 again and waits for spike OFF. Further, when the second specific SW element commutates, it means that no spike has occurred. Therefore, the process proceeds to step 110, and the process proceeds to step 108 with the commutation timing correction amount set to zero. In step 108, since the correction amount is 0, the timing of the commutation cycle based on the rotational speed is determined as the next commutation timing.

  Here, the state in which no spike occurs is a state in which the current phase is sufficiently advanced with respect to the terminal voltage, the load is light, and the necessary torque is sufficiently secured. It is in a state where it can be driven.

  On the other hand, if it is not the commutation timing of the first specific switch element (switch element 3b in the present embodiment) in step 101, the process proceeds to step 111.

  In step 111, the commutation timing correction amount is set to 0, and the flow proceeds to step 108.

  Since the correction amount is 0 at step 108, the timing of the commutation cycle based on the rotational speed is determined as the next commutation timing.

  In this embodiment, since the commutation cycle is corrected only by the ON timing of the U-phase upper switch element 3a, the correction is performed once during the electrical angle cycle. However, the application of the motor drive device, the inertia of the motor, etc. In consideration of the above, the correction may be performed once per rotation, twice in one electrical angle cycle, or at each timing when each switch element is turned on.

  Next, a method for determining the control timing of the switching element of the inverter 3 that corrects the commutation timing in the open-loop synchronous drive in accordance with the fluctuation of the DC bus voltage will be described with reference to FIG. The operation of the unit 17 and the waveform correction unit 18 will be described with reference to flowcharts.

  First, in step 201, the process waits for the OFF timing of the first specific switch element of the inverter 3. In the present embodiment, similarly to step 101 in the flow of FIG. 10, the process waits for the U-phase lower switch element 3b to be turned off. The switches need not be the same, and may wait for a switch different from step 101 to be turned off. If the switch is not turned off, the process proceeds to step 202.

  In step 202, it is determined whether or not a predetermined time has elapsed. This predetermined time is required twice or more in one correction. For example, assuming that the carrier cycle is driven at a low speed, there is no need to change the carrier between the synchronous driving and the driving by the first waveform generation unit. Can do. Also in the present embodiment, the carrier period is set to a predetermined time.

  If the predetermined time has not passed, the process returns to step 201 again. If the predetermined time has elapsed, the process proceeds to step 203.

  In step 203, the voltage detector 17 detects and stores the voltage between the DC buses. After the processing is completed, the process proceeds to step 204.

  In step 204, the voltage detection unit 17 adds the voltage value stored in step 203 as an integrated value to the integrating variable and stores it. After storing, the process proceeds to step 205. By accumulating the voltage values, it is possible to grasp a voltage in accordance with the actual condition of the waveform correction period, so that appropriate correction can be performed.

  In step 205, the voltage detection unit 17 subtracts the integrated value of the voltage value stored in step 204 from the average of the integrated voltage and stores it as a difference in a variable. After storing, the process transits again to step 201. Since it is driven by the first waveform generator at low speed, it will be driven by the first waveform generator immediately after startup, so the average of the integration is calculated even while processing is performed in the first waveform generator, When driven by the waveform correction unit, it does not become zero.

  In addition, by calculating the average, the difference in the current state can be seen, so that it is possible to take advantage of the characteristic of convergence to the stable state of synchronous driving, and more stable driving is possible.

  Further, when the first specific switch element is turned OFF in step 201, the process proceeds to step 206.

  In step 206, the voltage detection unit 17 calculates the average value of the integrated voltage values calculated in step 204, and the process proceeds to step 207. The average calculation method is to prepare multiple buffers and store them in the buffer in order. After the buffer is full, it is overwritten in order from the first buffer, and the total of those buffers is divided by the number of buffers. Can be easily obtained. If it is difficult to secure a plurality of buffers, the integrated voltage value may be obtained by applying a low-pass filter. In the present embodiment, it is assumed that a plurality of buffers are prepared and obtained.

  In step 207, the waveform correction unit 18 calculates the correction amount based on the difference from the average of the integrated voltage, and the process proceeds to step 208. The correction amount is calculated by multiplying a coefficient for converting the differential voltage into time.

  In step 208, the waveform correction unit 18 adds the correction amount to the current commutation timing to perform correction, and the process proceeds to step 209. Here, when the correction amount is negative and the voltage is insufficient with respect to the average, that is, when the voltage is lowered, the commutation timing is delayed from the original cycle, and the terminal voltage phase is compared with the induced voltage phase. Will lead to a decrease in the advance angle.

  On the other hand, when the correction amount is positive and the voltage exceeds the average, that is, when the voltage is rising, the commutation timing is set earlier than the timing at which the current commutation is about to be performed, Increase the advance angle of the voltage phase.

  This suppresses an increase in current due to a large advance angle when the voltage is insufficient. On the other hand, even when the voltage rises and the terminal voltage phase becomes a lag phase with respect to the induced voltage phase, an excessive current does not flow because the advance angle is increased and the lag phase is improved.

  Finally, at step 209, the integrated voltage value is cleared so that the voltage detector 17 can calculate the integrated voltage per cycle.

  By repeating these operations, stable driving can be performed even with a high speed and high load against voltage fluctuations.

  Further, by combining the correction by the current / voltage state grasping means 16 described with reference to FIG. 10 and the correction by the voltage detection unit 17 described with reference to FIG. 11, more stable driving is possible. Although each correction means alone is effective, it becomes stronger when combined with the current voltage state grasping means 16 with respect to a steep change in voltage such as a momentary power interruption, and the voltage detection unit 17 against a sudden load fluctuation. Although it is difficult only by correction, driving is possible by combining them.

  Moreover, even if phase detection noise or voltage detection noise is input, the amount corrected by the current / voltage state grasping unit 16 and the amount corrected by the voltage detection unit 17 are limited. Since the correction amount is within a range that does not lead to overcurrent, stable driving is possible.

  Next, the switching operation of the waveform generator by the operation switching means 20 will be described.

  FIG. 12 is a graph showing the rotation speed = duty characteristic in the first embodiment of the present invention.

  In FIG. 12, when the rotation speed is 50 r / s or less, the first waveform generator 12 drives the motor. The duty is automatically adjusted to the most efficient point from the rotational speed by feedback control.

  At 50 r / s, the duty becomes 100%, and the drive by the first waveform generator 12 reaches a limit that cannot be rotated any further.

  In the present embodiment, when the duty reaches 100%, the driving is switched to the driving by the waveform correcting unit 18, and the output of the waveform correcting unit 18 that has been corrected based on the signal of the second waveform generating unit 15 is here. Will be selected.

  If the rotational speed command is 80 r / s, the frequency is increased by the acceleration set in advance by the frequency setting unit 14 up to 80 r / s with a fixed duty, and a drive signal is generated by the second waveform generation unit, Acceleration is performed while outputting the waveform corrected by the waveform correction unit, and when the frequency reaches 80 r / s, the frequency set by the frequency setting means is fixed.

  Next, when the command rotational speed decreases while driving with the output waveform of the waveform correction unit 18, the duty is fixed and the frequency is decreased by the acceleration set in advance by the frequency setting unit to detect the position. When the position detection signal can be acquired by the unit 11, the driving is switched to the driving by the first waveform generation unit that generates the drive signal based on the signal of the position detection unit 11. It converges and stabilizes by feedback control to the command speed.

  Next, the structure of the brushless DC motor 4 will be described.

FIG. 13 is a structural diagram of the rotor of the brushless DC motor according to the first embodiment of the present invention.
The rotor core 21 is formed by stacking punched thin steel sheets of about 0.35 mm to 0.5 mm. The four magnets 22a to 22d are embedded in the rotor core 21 in a reverse arc shape. This magnet is usually a ferrite type, but if a rare earth magnet such as neodymium is used, a plate structure may be used.

  In a rotor having such a structure, assuming that the axis from the rotor center to the magnet center is the d axis and the axis between the rotor center and the magnet is the q axis, the inductances Ld and Lq in the respective axial directions are reversed. It has saliency and will be different. That is, this means that the motor can effectively use torque (reluctance torque) using reverse saliency in addition to torque (magnet torque) due to magnetic flux of the magnet. Therefore, the torque can be used more effectively as a motor. As a result, the motor is a highly efficient motor.

  Further, when the control according to the present embodiment is used, when driving is performed by the waveform correction unit 18, the current is operated in a leading phase, and this reluctance torque is used greatly, so there is no reverse saliency. It can be operated up to a higher rotational speed than a motor.

As described above, the brushless DC motor driving method according to the present embodiment is a three-phase winding of the brushless DC motor 4 including the rotor 4a having a permanent magnet and the stator 4b having a three-phase winding, and the stator 4b. An inverter 3 that supplies power to the wire, a position detector 11 that also functions as a current phase detector that detects the current phase of the brushless DC motor 4, a position detector 11 that detects the rotational position of the rotor 4a, and a position detector The first waveform generator 12 that drives the inverter 3 by outputting a rectangular wave having an energization angle of 120 degrees to less than 150 degrees or a waveform corresponding thereto at a predetermined frequency by the output of the section 11, and changing only the predetermined frequency with a constant duty And a rectangular wave having a conduction angle of 120 degrees or more and less than 180 degrees or a waveform corresponding thereto is output at a predetermined frequency determined by the frequency setting section 14. The second waveform generator 15, the current voltage state grasping means 16 for detecting the current phase detected by the position detector 11 and the state of the drive signal of the second waveform generator 15 and grasping the current voltage state; The output of the second waveform generator 15 is corrected so that the voltage detection unit for detecting the voltage between the DC buses, which is the input voltage, and the state grasped by the current voltage state grasping means 16 and the target state are matched, and further the voltage The waveform is corrected by the voltage value detected by the detection unit 17 and output to the inverter 3, and the first waveform generation unit 12 is output to the inverter 3 at low speed or low load, and at high speed or high load And the operation switching means 20 for switching the waveform correction unit 18 to be output to the inverter 3, it is possible to secure the torque necessary for driving the motor at a predetermined speed. As a result, the phase current and terminal voltage phase of the brushless DC motor are maintained in an appropriate phase relationship with respect to the induced voltage phase depending on the driving speed, load state, input voltage state, etc., and stable when a disturbance occurs. Can be driven.

  In addition, since the relationship between the phase current phase and the terminal voltage phase is fixed according to the load and speed, it can be driven stably against disturbances such as load fluctuations and voltage fluctuations, so that the reliability of the motor drive device is improved Can do.

  In addition, since the current peak can be kept low by wide-angle energization with high-speed driving at high load, the current rating of the inverter can be lowered, and the cost of the motor drive device can be reduced.

  Also, at low speed, it has a position detection unit that detects the rotational position of the rotor, and speed feedback control is performed while the relative position of the brushless DC motor rotor is detected by the position detection unit, so that the motor drive device is driven with high efficiency. I can do it.

  Furthermore, in the low-speed drive region, by outputting a rectangular wave with an energization angle of 120 degrees or more and 150 degrees or less, or a waveform corresponding thereto (for example, a trapezoidal wave), the copper loss is reduced by reducing the effective current, the circuit loss is reduced, and the circuit Operation in the lowest loss state that balances with an increase in switching loss is possible, and operation at the highest efficiency is possible. In general, sinusoidal drive is said to have good motor efficiency, but since the conduction angle is 180 degrees, the switching loss of the circuit increases. The driving method is superior.

  In addition, the waveform correction unit 18 corrects the commutation to advance as the voltage value output from the voltage detection unit 17 increases, and to delay the commutation as the voltage value detected by the voltage detection unit 17 decreases. Thus, it is possible to prevent excessive current and step-out due to excessive advancement of the voltage phase, prevent excessive current due to a delayed phase in which the terminal voltage phase lags behind the induced voltage, prevent destruction of elements of the inverter 3 and the motor 4. This can prevent demagnetization and improve the reliability.

  Further, the voltage detection unit 17 periodically detects the voltage value at a period earlier than the driving cycle of the brushless DC motor 4 and outputs the sum of the detection results, and the integrated value is corrected by the waveform correction unit 18. Since it is cleared every time it is performed, the entire voltage of the correction cycle can be measured, and more stable driving according to the actual voltage state becomes possible.

  In addition, the voltage detector 17 averages the detected voltages and sees the difference in the current state, so that excessive correction due to a change in voltage due to a load change is avoided, and convergence to a stable state of synchronous driving is achieved. More stable driving is possible utilizing the characteristics to be achieved.

In addition, since the waveform correction unit 18 sets an upper limit on the correction amount for matching the output of the current / voltage state grasping unit 16 and the target state and the correction amount by the output of the voltage detection unit 17, the waveform correction unit 18 becomes resistant to noise. Strong driving is possible due to disturbance.

  Further, the position detection unit 11 detects the position from the voltage induced by the brushless DC motor 4, and the current phase detection means is connected to the terminal of the brushless DC motor 4 generated when the return current flows between the brushless DC motor 4 and the inverter 3. The timing at which the voltage appears OFF is detected as the current phase 0, and the current phase detection unit is performed by the position detection unit 11, so that it is not necessary to provide a new current phase detection unit, so a low-cost and simple configuration is taken. Can do.

  Further, when the operation switching means 20 switches from the first waveform generation unit 12 to the output of the waveform correction unit 18, the duty output of the first waveform generation unit 12 exceeds a predetermined reference value. When the output is switched to the one waveform generator 12, the position detector 11 can detect the position of the rotor 4a, so that the first waveform generator can be driven in a state where the position signal can be reliably acquired. Therefore, more stable driving can be performed.

  The operation switching means 20 uses the output of the first waveform generator 12 when the switching is less than a predetermined speed, and the output of the waveform correction unit 18 when the speed is higher than the predetermined speed. The system configuration can be simplified.

  The brushless DC motor 4 is a rotor 4a in which permanent magnets 21a to 21d are embedded in the iron core of the rotor 4a, and has a rotor 4a having saliency. In addition to the magnet torque of the permanent magnet, By using reluctance torque due to saliency, the efficiency at low speeds is naturally increased, and the high-speed driving performance is further improved. In addition, by adopting a rare earth magnet such as neodymium as the permanent magnet to increase the ratio of magnet torque, or to increase the ratio of reluctance torque by increasing the difference between inductances Ld and Lq, the optimum conduction angle is changed. Efficiency can be increased.

  In addition, the use of the motor driving device of the present embodiment for driving the compressor increases the winding amount of the winding and reduces the torque (that is, lowers the maximum number of rotations than the brushless DC motor used in the conventional motor driving device). Since the DC motor can be driven at a predetermined high speed, the duty at a low rotation speed can be made larger than that of the conventional driving method, so that motor noise, particularly carrier noise (equivalent to the frequency of PWM control, for example, 3 kHz) can be reduced. This is a very important application.

  In this embodiment, the brushless DC motor drives the compressor of the refrigerator. However, even when driving the compressor of the air conditioner, the high-efficiency driving at low speed and the high-load high-speed driving are similarly performed. It is possible to cover a wide driving range from the lowest load during cooling to the maximum load during heating, and in particular, it is possible to reduce power at a relatively low load below the rating.

  The motor driving device according to the present invention and the electric equipment using the motor driving device are efficient in a wide range from low speed to high speed, and can be driven stably. Therefore, the motor driving device is useful for driving a fan such as a compressor, a refrigerator, and a fan. It is.

DESCRIPTION OF SYMBOLS 3 Inverter 4 Brushless DC motor 5 Compressor 10 Refrigerator 11 Position detection part 12 1st waveform generation part 14 Frequency setting part 15 2nd waveform generation part 16 Current voltage state grasping means 17 Voltage detection part (current phase detection part)
18 Waveform Correction Unit 20 Operation Switching Means 21 Rotor Core 22a-22d Magnet

Claims (11)

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; a voltage detection unit that detects an input voltage to the inverter; A rectangular wave with a conduction angle of 120 degrees or more and less than 150 degrees depending on the output of the current phase detection section for detecting the current phase of the brushless DC motor, the position detection section for detecting the rotational position of the rotor, and the previous position detection section, or A first waveform generator for driving the inverter by outputting a conforming waveform at a predetermined frequency, a frequency setting unit for changing only the predetermined frequency with a constant duty, and a rectangular wave having a conduction angle of 120 degrees to less than 180 degrees, or A second waveform generator for outputting a conforming waveform at a predetermined frequency determined by the frequency setting unit, a current phase detected by the current phase detector, and the first A current voltage state grasping means for detecting a state of a drive signal of the waveform generation section, a state detected by the current voltage state grasping means, and an output of the second waveform generation section are corrected so as to match a target state; Further, the waveform is corrected by the voltage value detected by the voltage detection unit, and the waveform correction unit that outputs to the inverter, and the first waveform generation unit at the low speed or low load is output to the inverter, and the high speed or high load is output. A brushless DC motor drive device having operation switching means for switching the waveform correction unit to output to the inverter. The waveform correction unit corrects the commutation so that the commutation is advanced as the voltage value output from the voltage detection unit is higher, and the commutation is delayed as the voltage value detected by the voltage detection unit is lower. The brushless DC motor drive device described. The voltage detection unit periodically detects the voltage value at a period earlier than the driving cycle of the brushless DC motor, and outputs the result of integrating the detection results. The integrated value is corrected by the waveform correction unit. 3. The brushless DC motor drive device according to claim 1, wherein the brushless DC motor drive device is cleared. The brushless DC motor drive device according to any one of claims 1 to 3, wherein the voltage detection unit averages the detected voltages and outputs a difference between the average and a detection value. 5. An upper limit is set for a correction amount for causing the waveform correction unit to match the output of the current / voltage state grasping means with a target state, and a correction amount based on the output of the voltage detection unit. The drive apparatus of the brushless DC motor as described in any one of these. The position detection unit detects a position from a voltage induced by the brushless DC motor, and the current phase detection unit appears at a terminal of the brushless DC motor generated when a return current flows between the brushless DC motor and the inverter. The brushless DC motor driving device according to any one of claims 1 to 5, wherein a timing when the voltage is turned off is detected as a current phase 0, and the current phase detection unit is performed by the position detection unit. The brushless DC motor according to any one of claims 1 to 6, wherein the operation switching means sets the switching to be the output of the first waveform generator when the speed is less than a predetermined speed, and outputs the waveform correction section when the speed is higher than the predetermined speed. Drive device. When the operation switching means switches from the first waveform generation unit to the output of the waveform correction unit, the duty output of the first waveform generation unit exceeds a predetermined reference value and is output from the waveform correction unit to the first waveform generation unit. The brushless DC motor drive device according to any one of claims 1 to 6, wherein the position of the rotor can be detected by the position detection unit when switching the motor. The brushless DC motor according to any one of claims 1 to 8, wherein the brushless DC motor is a rotor in which a permanent magnet is embedded in an iron core, and the rotor has saliency. Motor drive device. The drive device for a brushless DC motor according to any one of claims 1 to 9, wherein a load driven by the brushless DC motor is a compressor. The drive device of the brushless DC motor according to claim 10, wherein the compressor constitutes a refrigeration cycle of a refrigerator.

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