JP2011045209A - Motor drive device and method - Google Patents

Abstract

A current supply efficiency to a motor coil is improved during a start-up period.
A motor driving device detects a rotation speed of a motor in a start-up period from the start of the motor until the rotation speed of the motor reaches a target rotation speed, and a control signal (in accordance with the detected rotation speed ( 72), and a PWM frequency changing means (53) for increasing the PWM frequency in response to the control signal (72).
[Selection] Figure 1

Description

  The present invention relates to a motor drive device, and more particularly to a technique for PWM driving a motor.

  2. Description of the Related Art Conventionally, in a motor drive device that drives a motor by PWM (Pulse Width Modulation), drive control is performed to quickly start the motor and suppress rotation unevenness after the start. In order to quickly start the motor, a large current is supplied to the motor coil during the starting period until the rotational speed of the motor reaches the target rotational speed. Further, in order to suppress the rotation unevenness, the motor is driven with high resolution in the steady rotation period after the motor is started. In order to drive the motor with high resolution, it is desirable to increase the PWM frequency. However, if the PWM frequency is increased during the start-up period, a switching loss due to frequent switching on and off of the switching element occurs and heat is generated.

  As a solution to such a problem, a motor driving device is disclosed that drives a motor at a low PWM frequency during the startup period and drives the motor at a high PWM frequency during the steady rotation period (see, for example, Patent Document 1). .

JP 2004-7894 A

  FIG. 15 shows operation waveforms of a conventional motor driving device. The motor rotation speed gradually increases during the start-up period, increases and decreases in the vicinity of the target rotation speed during the pull-in period after the motor rotation speed reaches the target rotation speed, and becomes constant at the target rotation speed during the steady rotation period. The torque voltage is at the maximum level during the startup period, rises and falls near the low level during the pull-in period, and is constant at a low level during the steady rotation period. The PWM frequency is set low during the start-up period, and is set high during the pull-in period and the steady rotation period.

  The problem here is that, despite the torque voltage being at the maximum level during the start-up period, the rotational acceleration decreases as the motor rotational speed increases, and the motor rotational speed is sluggish at high rotational speeds. Considering the cause, the current ripple generated due to the back electromotive force generated in the motor coil increases as the motor speed increases, and the effect of canceling the current supplied to the motor coil increases. It has been found that the average electrical energy supplied to is reduced. Therefore, it is expected that the startup period of the motor can be shortened if current can be efficiently supplied to the motor coil even if the motor rotation speed increases.

  Accordingly, an object of the present invention is to improve the efficiency of supplying current to the motor coil during the startup period.

  In order to solve the above-mentioned problems, the present invention has taken the following solutions. That is, as a motor driving device that drives the motor by PWM, the number of rotations of the motor is detected during the start-up period from when the motor is started until the number of rotations of the motor reaches the target number of rotations. It is assumed that a rotation speed detecting means for outputting a control signal and a PWM frequency changing means for increasing the PWM frequency according to the control signal are provided.

  According to this, in the start-up period that requires a large current to start the motor, the current ripple caused by the counter electromotive force generated in the motor coil is reduced by increasing the PWM frequency as the motor speed increases. Even if the rotational speed of the motor increases, the average electrical energy supplied to the motor coil can be increased.

  Specifically, the rotation speed detection means switches the control signal every time the rotation speed of the motor exceeds a set value. Preferably, the rotation speed detection means performs hysteresis control on the control signal.

  Preferably, the rotation speed detection means includes a rotation speed calculation means for calculating the rotation speed of the motor, and a rotation speed ratio calculation means for calculating a ratio between the rotation speed calculated by the rotation speed calculation means and the target rotation speed. The rotation speed ratio calculation means switches the control signal every time the calculated ratio exceeds a set value. According to this, uniform control can be performed for any motor regardless of the target rotational speed for each motor.

  Specifically, the PWM frequency changing means sets the PWM frequency to a predetermined value when the rotational speed of the motor reaches the target rotational speed. More specifically, the rotational speed detection means outputs a detected rotational speed signal that is a pulse train having a period corresponding to the detected rotational speed, and the motor driving device uses a pulse train having a period corresponding to the target rotational speed. Synchronization detection means for detecting phase synchronization between a certain target rotation speed signal and a detected rotation speed signal is provided, and the PWM frequency changing means sets the PWM frequency to a predetermined value when the synchronization detection means detects phase synchronization. May be. Alternatively, the motor drive device includes torque command means for outputting a torque voltage for controlling the torque of the motor, and torque voltage comparison means for comparing the torque voltage with a predetermined voltage. The PWM frequency may be set to a predetermined value when the output of the comparison means indicates that the torque voltage has fallen below the predetermined voltage. Alternatively, the rotational speed detection means outputs a detected rotational speed signal, and the motor driving device compares the phases of the target rotational speed signal and the detected rotational speed signal, and the phase of the detected rotational speed signal is the target rotational speed. A phase comparison unit that outputs a deceleration signal when the phase is more than the phase of the number signal, and a latch circuit that latches the deceleration signal, and the PWM frequency changing unit performs PWM when the output of the latch circuit becomes active The frequency may be set to a predetermined value.

  According to these, after the rotation speed of the motor reaches the target rotation speed, the motor can be driven with high resolution.

  According to the present invention, since the current supply efficiency to the motor coil can be improved during the startup period, the startup period of the motor can be shortened.

It is a circuit diagram which shows the structure of the motor drive device which concerns on 1st Embodiment. It is a figure which shows the example of the relationship between the control value of the motor drive device which concerns on 1st Embodiment, and the rotation speed of a motor. It is an operation | movement waveform diagram of the motor drive device which concerns on 1st Embodiment. It is a figure which shows another example of the relationship between the control value of the motor drive device which concerns on 1st Embodiment, and the rotation speed of a motor. It is a figure which shows another example of the relationship between the control value of the motor drive device which concerns on 1st Embodiment, and the rotation speed of a motor. It is a circuit diagram which shows the structure of the motor drive device which concerns on 2nd Embodiment. It is a figure which shows the example of the relationship between the control value of the motor drive device which concerns on 2nd Embodiment, and ratio of rotation speed. It is an operation | movement waveform diagram of the motor drive device which concerns on 2nd Embodiment. It is a circuit diagram which shows the structure of the motor drive device which concerns on 3rd Embodiment. It is an operation | movement waveform diagram of the motor drive device which concerns on 3rd Embodiment. It is a circuit diagram which shows the structure of the motor drive device which concerns on 4th Embodiment. It is an operation | movement waveform diagram of the motor drive device which concerns on 4th Embodiment. It is a circuit diagram which shows the structure of the motor drive device which concerns on 5th Embodiment. It is an operation | movement waveform diagram of the motor drive device which concerns on 5th Embodiment. It is an operation | movement waveform diagram of the conventional motor drive device.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a circuit diagram showing the configuration of the motor drive device according to the first embodiment. The motor drive device performs PWM control on the current supplied to the motor coils 21 to 23 of the three-phase motor, for example. The position detection means 31 detects the relative position between the rotor and the stator (not shown), for example, by a position detection element such as a Hall element or a back electromotive force induced in the motor coils 21 to 23. The energization switching unit 32 outputs a timing signal for switching the phases of the motor coils 21 to 23 based on the detection result of the position detection unit 31. The PWM control means 33 receives the output of the energization switching means 32 and the pulse signal 74 which is the output of the pulse width control means 54, and receives the upper switching elements 41 to 41 connected in series between the power supply VM and the power supply GND, respectively. 43 and the lower switching elements 44 to 46 are on / off controlled. Flywheel diodes 24 to 29 are connected in parallel to the upper switching elements 41 to 43 and the lower switching elements 44 to 46, respectively. The torque command means 51 receives a torque control signal for controlling the torque of the motor from the outside, for example, and outputs a torque voltage 71.

  The rotational speed detection means 52 receives a motor rotational speed detection signal such as an FG signal, for example, detects the rotational speed of the motor, and outputs a control signal 72 corresponding to the detected rotational speed. For example, as shown in FIG. 2, n1-n3 are set in advance as the number of revolutions in the revolution number detection means 52. The rotational speed detection means 52 outputs a control signal 72 having a control value c1 when the rotational speed is n1 or less, and outputs a control signal 72 having a control value c2 when the rotational speed exceeds n1. Similarly, when the rotational speed exceeds n2 and n3, rotational speed detection means 52 outputs control signals 72 of control values c3 and c4, respectively.

  The PWM frequency changing means 53 receives the control signal 72 and increases the PWM frequency according to the control value. For example, when receiving the control signal 72 of the control value c1, the PWM frequency changing means 53 sets the PWM frequency to the lowest f1, and when receiving the control signal 72 of the control value c2, the PWM frequency is changed to f2 higher than f1. Set to. Similarly, when control signals 72 of control values c3 and c4 are received, the PWM frequency is set to f3 and f4 higher than f2, respectively. The PWM frequency changing unit 53 outputs a PWM signal 73 corresponding to the frequencies f1 to f4.

  The pulse width control unit 54 receives the torque voltage 71 and the PWM signal 73 and generates and outputs a pulse signal 74. In addition, you may provide the electric current detection means which detects the electric current which flows into the resistance which is not shown between the connection point of the lower side switching elements 44-46, and power supply GND. In this case, the pulse width control means 54 outputs a pulse signal 74 for receiving on / off control of the upper switching elements 41 to 43 and the lower switching elements 44 to 46 in response to the detection signal of the current detection means.

  Next, the operation of the motor drive device according to this embodiment will be described. FIG. 3 is an operation waveform diagram of the motor drive device according to the present embodiment. First, during the start-up period, the maximum level torque voltage 71 is output, and the PWM frequency is set to f1. When the rotational speed of the motor exceeds n1, the PWM frequency is set to f2. When the rotational speed exceeds n2, the PWM frequency is set to f3, and when the rotational speed exceeds n3, the PWM frequency is set to f4.

  When the rotational speed of the motor reaches the target rotational speed, a transition is made to the pull-in period. In the pull-in period, an overshoot or undershoot of the motor rotation speed occurs, so that the torque voltage 71 is in an unstable state in which it rises and falls. In the pull-in period, the PWM frequency is fixed at f4. When the pull-in period ends and a transition is made to a steady rotation period in which the rotation speed of the motor is constant, the torque voltage 71 becomes a low level.

  As described above, according to the present embodiment, it is possible to reduce the current ripple generated by the counter electromotive force generated in the motor coils 21 to 23 in the high rotation range during the motor startup period. Thereby, even if the rotation speed of the motor rises, current can be efficiently supplied to the motor coils 21 to 23, so that the motor start-up period can be shortened.

  In addition, as shown in FIG. 4, the rotation speed detection means 52 may change the control value of the control signal 72 linearly. Further, as shown in FIG. 5, the rotational speed detection means 52 may perform hysteresis control on the control value of the control signal 72. According to this, it is possible to suppress fluttering of the control signal 72 due to slight fluctuations in the rotational speed of the motor at the switching point of the control signal 72.

  Further, the rotational speed detection means 52 may receive the output of the position detection means 31 and detect the rotational speed of the motor. Further, the rotational speed detection means 52 may receive the torque voltage 71 and output a control signal corresponding to the torque voltage 71. Alternatively, the rotation speed detection means 52 may output a control signal corresponding to the elapsed time after the motor is started.

  Further, when the motor is driven and controlled with the off-time of the upper switching elements 41 to 43 and the lower switching elements 44 to 46 being constant, the on-time may be gradually shortened. Thereby, the PWM frequency can be substantially increased gradually. On the contrary, the on-time may be made constant.

<Second Embodiment>
FIG. 6 is a circuit diagram showing a configuration of a motor drive device according to the second embodiment. Only the differences from the first embodiment will be described below.

  The rotation speed detection means 52 has a rotation speed calculation means 52a and a rotation speed ratio calculation means 52b. The rotational speed calculation means 52a receives the motor rotational speed detection signal and calculates the rotational speed of the motor. The rotation speed ratio calculation means 52b calculates the ratio of the rotation speed of the motor to the target rotation speed from the rotation speed calculated by the rotation speed calculation means 52a and the target rotation speed recorded in, for example, a register. For example, as shown in FIG. 7, m1 to m3 are set in advance as the rotation speed ratio in the rotation speed ratio calculation means 52b. The rotation speed ratio calculation means 52b outputs a control signal 72 having a control value c1 when the rotation speed ratio is less than or equal to m1, and each time the rotation speed ratio exceeds m1 to m3, the rotation speed ratio calculation means 52b responds to each. A control signal 72 having control values c2 to c4 is output. When receiving the control signal 72 during the startup period, the PWM frequency changing unit 53 sets the PWM frequency to f1 to f4 accordingly.

  Next, the operation of the motor drive device according to this embodiment will be described. FIG. 8 is an operation waveform diagram of the motor drive device according to the present embodiment. In the start-up period, the PWM frequency is first set to f1. When the rotational speed of the motor increases and the rotational speed ratio exceeds m1, the PWM frequency is set to f2. Similarly, when the rotation speed ratio exceeds m2 and m3, the PWM frequency is set to f3 and f4, respectively.

  As described above, according to the present embodiment, even when motors with different target rotation speeds are controlled, each motor can be controlled uniformly by setting a predetermined rotation speed ratio in the rotation speed ratio calculation means 52b. .

  In place of the rotation speed ratio calculation means 52b, a means for calculating the difference in rotation speed between the target rotation speed and the rotation speed of the motor may be provided. In this case, the difference between the target rotational speed and the rotational speed of the motor is set in advance, and the control value is switched every time the rotational speed difference exceeds the set value.

  Further, the rotation speed ratio may be calculated as an analog value. In this case, the rotation speed ratio calculation means 52b compares the voltage according to the target rotation speed with the voltage according to the motor rotation speed, and outputs a control signal 72 based on the ratio.

<Third Embodiment>
FIG. 9 is a circuit diagram showing a configuration of a motor drive device according to the third embodiment. Only the differences from the first embodiment will be described below.

  The rotational speed detection means 52 outputs a control signal 72 and a detected rotational speed signal 75. The detected rotational speed signal 75 is a pulse train having a period corresponding to the rotational speed detected by the rotational speed detecting means 52. The synchronization detection means 56 receives the detected rotation speed signal 75 and the target rotation speed signal 76, detects that these phases are synchronized, and outputs a synchronization detection signal 77. The target rotational speed signal 76 is a pulse train having a period corresponding to the target rotational speed. When detecting the phase synchronization, the synchronization detecting means 56 sets the synchronization detection signal 77 to L level, for example. When receiving the control signal 72, the PWM frequency changing unit 53 sets the PWM frequency to f1 to f4 according to the control value. The PWM frequency changing means 53 sets the PWM frequency to f5 higher than f4 when the synchronization detection signal 77 becomes L level.

  Next, the operation of the motor drive device according to this embodiment will be described. FIG. 10 is an operation waveform diagram of the motor drive device according to the present embodiment. In the start-up period, the PWM frequency is first set to f1. Each time the number of rotations of the motor increases and the number of rotations exceeds n1 to n3, the PWM frequency is set to f2 to f4, respectively.

  When the rotational speed of the motor reaches the target rotational speed, phase synchronization is detected and the synchronization detection signal 77 becomes L level. When the synchronization detection signal 77 becomes L level, the PWM frequency is set to f5.

  As described above, according to the present embodiment, the motor can be driven with high resolution by setting the PWM frequency to a high frequency when the rotational speed of the motor becomes equal to the target rotational speed. When the PWM frequency is set to f5 when the synchronization detection signal 77 becomes L level, the motor may be driven with the PWM frequency maintained at f5.

<Fourth Embodiment>
FIG. 11 is a circuit diagram illustrating a configuration of a motor drive device according to the fourth embodiment. Only the differences from the first embodiment will be described below.

  The torque voltage comparison means 57 compares the torque voltage 71 with a predetermined voltage VA set in advance. The torque voltage comparison unit 57 outputs, for example, an H level torque voltage comparison signal 78 when the torque voltage 71 exceeds the voltage VA. When receiving the control signal 72 during the start-up period, the PWM frequency changing unit 53 sets the PWM frequency to f1 to f4 accordingly, and when the torque voltage comparison signal 78 becomes L level, sets it to f5 higher than f4.

  Next, the operation of the motor drive device according to this embodiment will be described. FIG. 12 is an operation waveform diagram of the motor drive device according to the present embodiment. In the start-up period, the PWM frequency is first set to f1. Each time the number of rotations of the motor increases and the number of rotations exceeds n1 to n3, the PWM frequency is set to f2 to f4, respectively.

  When the rotation speed of the motor continues to increase and exceeds the target rotation speed, the torque voltage 71 starts to decrease. When torque voltage 71 falls below voltage VA, torque voltage comparison signal 78 becomes L level. When the torque voltage comparison signal 78 becomes L level, the PWM frequency is set to f5.

  As described above, according to the present embodiment, it is possible to detect that the rotational speed of the motor exceeds the target rotational speed by comparing the torque voltage 71 and the voltage VA. As a result, even when a signal corresponding to the target rotational speed cannot be obtained, the motor can be driven with high resolution in the steady rotational period. If the PWM frequency is set to f5 when the torque voltage 71 falls below the voltage VA, the motor may be driven while maintaining the PWM frequency at f5.

<Fifth Embodiment>
FIG. 13 is a circuit diagram showing a configuration of a motor drive device according to the fifth embodiment. Only the differences from the first embodiment will be described below.

  The rotational speed detection means 52 outputs a control signal 72 and a detected rotational speed signal 75. The detected rotational speed signal 75 is a pulse train having a period corresponding to the rotational speed detected by the rotational speed detecting means 52. The phase comparison means 61 compares the phase of the detected rotational speed signal 75 with the phase of the target rotational speed signal 76. The target rotational speed signal 76 is a pulse train having a period corresponding to the target rotational speed. The phase comparison means 61 outputs an acceleration signal 81 when the phase of the target rotational speed signal 76 is ahead of the phase of the detected rotational speed signal 75, that is, when the rotational speed of the motor is slower than the target rotational speed. When the phase of the target rotational speed signal 76 is delayed from the phase of the detected rotational speed signal 75, that is, when the rotational speed of the motor is earlier than the target rotational speed, the deceleration signal 82 is output.

  The latch circuit 62 latches the deceleration signal 82. When receiving the control signal 72 during the startup period, the PWM frequency changing means 53 sets the PWM frequency to f1 to f4 accordingly, and sets the PWM frequency to f5 higher than f4 when the deceleration detection signal 83 becomes active. .

  Next, the operation of the motor drive device according to this embodiment will be described. FIG. 14 is an operation waveform diagram of the motor drive device according to the present embodiment. In the start-up period, the PWM frequency is first set to f1. Each time the number of rotations of the motor increases and the number of rotations exceeds n1 to n3, the PWM frequency is set to f2 to f4, respectively.

  When the rotational speed of the motor exceeds the target rotational speed, a deceleration signal 82 is output. When the deceleration signal 82 is latched, the deceleration detection signal 83 becomes active, and the PWM frequency is set to f5.

  As described above, according to the present embodiment, the PWM frequency changing means 53 can drive the motor with high resolution by setting a high PWM frequency when the deceleration detection signal 83 becomes active. When the PWM frequency is set to f5 when the deceleration detection signal 83 becomes active, the motor may be driven while maintaining the PWM frequency at f5. Further, the torque command means 51 may output a torque voltage 71 based on the acceleration signal 81 and the deceleration signal 82.

  The motor drive device according to the present invention can be driven with high resolution in the steady rotation period while shortening the motor start-up period, and thus is useful for information equipment and the like that require quick and stable drive.

51 Torque command means 52 Rotational speed detection means 52a Rotational speed calculation means 52b Rotational speed ratio calculation means 53 PWM frequency change means 54 Pulse width control means 56 Synchronization detection means 57 Torque voltage comparison means 61 Phase comparison means 62 Latch circuit 71 Torque voltage 72 Control signal 75 Detected rotation speed signal 76 Target rotation speed signal 77 Synchronization detection signal 78 Torque voltage comparison signal 82 Deceleration signal

Claims (9)

A motor driving device that drives a motor by PWM (Pulse Width Modulation),
Rotational speed detection means for detecting the rotational speed of the motor and outputting a control signal corresponding to the detected rotational speed during the startup period from when the motor is started until the rotational speed of the motor reaches the target rotational speed When,
A motor drive device comprising: PWM frequency changing means for increasing the PWM frequency according to the control signal. The motor driving device according to claim 1,
The motor drive device according to claim 1, wherein the rotation number detection means switches the control signal every time the rotation number of the motor exceeds a set value. In the motor drive device of Claim 2,
The rotational speed detection means performs hysteresis control on the control signal. The motor driving device according to claim 1,
The rotation speed detecting means is
A rotational speed calculating means for calculating the rotational speed of the motor;
A rotational speed ratio calculating means for calculating a ratio between the rotational speed calculated by the rotational speed calculating means and the target rotational speed;
The motor drive apparatus characterized in that the rotation speed ratio calculation means switches the control signal every time the calculated ratio exceeds a set value. The motor driving device according to claim 1,
The PWM frequency changing means sets the PWM frequency to a predetermined value when the rotational speed of the motor reaches the target rotational speed. In the motor drive device of Claim 5,
The rotational speed detection means outputs a detected rotational speed signal that is a pulse train having a period according to the detected rotational speed,
The motor drive device is
Synchronization detecting means for detecting phase synchronization between the target rotational speed signal and the detected rotational speed signal, which is a pulse train having a period according to the target rotational speed,
The PWM frequency changing means sets the PWM frequency to the predetermined value when the synchronization detecting means detects the phase synchronization. In the motor drive device of Claim 5,
Torque command means for outputting a torque voltage for controlling the torque of the motor;
A torque voltage comparison means for comparing the torque voltage with a predetermined voltage;
The PWM frequency changing means sets the PWM frequency to the predetermined value when the output of the torque voltage comparing means indicates that the torque voltage is lower than the predetermined voltage. . In the motor drive device of Claim 5,
The rotational speed detection means outputs a detected rotational speed signal that is a pulse train having a period according to the detected rotational speed,
The motor drive device is
When the phase of the target rotational speed signal, which is a pulse train having a period corresponding to the target rotational speed, is compared with the detected rotational speed signal, and the phase of the detected rotational speed signal is ahead of the phase of the target rotational speed signal Phase comparison means for outputting a deceleration signal to
A latch circuit for latching the deceleration signal,
The PWM frequency changing means sets the PWM frequency to the predetermined value when the output of the latch circuit becomes active. A motor driving method for PWM driving a motor,
Detecting the rotational speed of the motor in a startup period from when the motor is started until the rotational speed of the motor reaches a target rotational speed;
Outputting a control signal according to the detected number of revolutions;
And a step of increasing the PWM frequency according to the control signal.

Images