JP5606899B2 - Drive control device for brushless motor - Google Patents

Description

  The present invention relates to a drive control device that controls a brushless motor.

  One of the causes of vibration noise of brushless motors is torque fluctuation. In particular, when driving with a 120-degree energization method, vibration and noise occur due to a drop in torque during commutation.

  In order to reduce such torque drop during commutation, a technique has been proposed in which a predetermined overlap period is provided at the time of phase switching before and after commutation (see Patent Document 1).

  In Patent Document 1, when the switching element of the inverter device is turned on / off, both the upper arm signal and the lower arm signal are converted into PWM signals within the overlap period, so that the slope of the current change that occurs when the phases are switched. To reduce vibration and noise.

JP2008-118830A

  However, Patent Document 1 has the following problems.

  In other words, since the PWM signal within the overlap period is generated based on the carrier frequency, it is difficult to arbitrarily adjust the pulse width of the PWM signal, and it can be said that the slope of the current change can be made gentle. Since only minor adjustments can be made, the effect of suppressing vibration and noise is limited.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a brushless motor drive control device that can efficiently suppress vibration and noise during phase switching with a relatively simple circuit configuration. Is to provide.

In order to solve the above-described problem, according to one aspect of the present invention, a brushless motor that rotates a rotor having a plurality of magnetic poles by applying overlapping current to a plurality of armature coils provided in a stator. In the drive control device,
An inverter circuit for energizing the plurality of armature coils;
A motor drive circuit for generating a drive signal for driving the inverter circuit;
A motor control unit that sets an overlap period for performing the overlap energization and controls the motor drive circuit based on the overlap period, and
The inverter circuit is
A plurality of upper arm side switching elements provided for each phase of the armature coils of the plurality of phases;
A plurality of lower arm side switching elements provided for each phase of the multiple phase armature coils and connected in series to the corresponding upper arm side switching elements;
In the steady driving, the motor drive circuit is configured to switch one of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements for each phase of the plurality of armature coils. On / off control by PWM signal, and on / off control of the other by constant voltage signal,
The motor control unit, with respect to the upper arm side or lower arm side switching element that has supplied the first PWM signal immediately before the overlap period within the overlap period, The second PWM signal having a frequency higher than that of the PWM signal is supplied, and the first arm is supplied to the lower arm side or upper arm side switching element that has supplied the constant voltage signal immediately before the overlap period. A drive control device is provided that controls the motor drive circuit to supply a third PWM signal having a frequency higher than that of the PWM signal.

  It is possible to provide a drive control device for a brushless motor that can efficiently suppress vibration and noise during phase switching with a relatively simple circuit configuration.

The block diagram which shows schematic structure of the drive control apparatus of the brushless motor 2 which concerns on the 1st Embodiment of this invention. The signal waveform diagram which shows an example of each switching signal of upper arm side switching element Q1, Q3, Q5 and lower arm side switching element Q2, Q4, Q6. FIG. 3 is a detailed signal waveform diagram in a period from T2 to T3 in FIG. The figure which compared and showed the measurement result of the noise peak value at the time of the drive of the brushless motor 2 using the drive control apparatus 1 which concerns on this embodiment, and the conventional drive control apparatus 1. FIG. The block diagram which shows schematic structure of the drive control apparatus 1a of the brushless motor 2 which concerns on the 2nd Embodiment of this invention. The figure which shows an example of the table which shows the correspondence of target rotation speed and the ON duty of 2nd PWM signal SG3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a drive control device for a brushless motor 2 according to the first embodiment of the present invention. The drive control device 1 in FIG. 1 is used for drive control of a three-phase brushless motor 2 (hereinafter simply referred to as a motor 2), for example. Lap energization is performed to rotate the rotor 4 of the motor 2. Various types of motors 2 are applicable to drive control, and the number of phases is not particularly limited as long as it is two or more. Hereinafter, an example of driving the three-phase motor 2 will be described for the sake of simplification. Hereinafter, the three phases are referred to as a U phase, a V phase, and a W phase.

  Here, the overlap energization provides an overlap period for supplying current to the two types of armature coils 3 before and after switching when switching the type of the armature coil 3 that supplies current, that is, at the time of phase switching. Refers to the energization method. The overlap energization itself is known as described in Patent Document 1 described above, but this embodiment is characterized in that a unique energization method related to overlap energization is adopted as described later. .

  The overlap period can be arbitrarily set according to the rotational speed. However, in the drive control device 1 according to the present embodiment, the rotor 4 is driven at a constant rotational speed (rotational speed), and The overlap period at the time of switching is set to a predetermined value in advance.

  The drive control device 1 in FIG. 1 includes an inverter circuit 5, a motor drive circuit 6, a motor control unit 7, and a rotational position detection unit 8. The inverter circuit 5 includes three upper arm side switching elements Q1, Q3, and Q5 provided for each phase and three lower arm side switching elements Q2, Q4, and Q6, and the corresponding upper arm side switching elements and The lower arm side switching element is connected in series.

  The motor control unit 7 includes an overlap control unit 11 that sets a switching signal (described later) output from the motor drive circuit 6 to the switching element of each phase within the overlap period and the overlap period, and switching control of each phase. And an energization switching timing control unit 12 to perform.

  One end of the U-phase armature coil 3 is connected to the connection node between the upper arm side switching element Q1 and the lower arm side switching element Q2, and the connection node between the upper arm side switching element Q3 and the lower arm side switching element Q4 is connected to the connection node between the upper arm side switching element Q3 and the lower arm side switching element Q4. Is connected to one end of the V-phase armature coil 3, and one end of the W-phase armature coil 3 is connected to a connection node between the upper arm side switching element Q5 and the lower arm side switching element Q6.

  The motor drive circuit 6 includes a first PWM signal SG1 for on / off control of the upper arm side switching elements Q1, Q3, and Q5 and a lower arm during steady driving (which indicates an energization period other than the overlap period). A constant voltage signal SG2 for on / off control of the side switching elements Q2, Q4, Q6 is output. Here, the first PWM signal SG1 is a PWM (pulse width modulation) signal that can adjust the pulse width output from the motor drive circuit 6. The constant voltage signal SG2 is a signal that is output from the motor drive circuit 6 and that is at a high level only for a specific phase (that is, an energized phase), and that is at a low level in other phases. Hereinafter, the first PWM signal SG1 and the constant voltage signal SG2 are collectively referred to as a switching signal. In the present embodiment, the frequency and on-duty (ratio of the on period with respect to the switching period) of the first PWM signal SG1 are fixed values determined in advance by the rotational speed of the rotor 2.

  FIG. 2 is a signal waveform diagram showing an example of each switching signal of the upper arm side switching elements Q1, Q3, Q5 and the lower arm side switching elements Q2, Q4, Q6. Incidentally, when the first PWM signal SG1 or the constant voltage signal SG2 is at a high level, the corresponding switching element is turned on.

  FIG. 2A is a signal waveform diagram of the first to third PWM signals SG1, SG3, SG4 and the constant voltage signal SG2 in the period from T1 to T10. In FIG. 2A, the overlap period is indicated by a broken line.

  As shown in FIG. 2A, in the present embodiment, the timing at which the phase of the first PWM signal SG1 is switched by the overlap control unit 11 included in the motor control unit 7 and the timing at which the phase of the constant voltage signal SG2 is switched. And the overlap period is always set. For example, in the period T3, the overlap period A is set for the upper arm side U phase and the V phase, and in the period T2, the overlap period B is set for the lower arm side V phase and the W phase.

  FIG. 2B is an enlarged view of the overlap period A of the period T3, and FIG. 2C is an enlarged view of the overlap period B of the period T2.

  As can be seen from FIG. 2B, the overlap control unit 11 sets the second PWM signal SG3 having a frequency higher than that of the first PWM signal SG1 within the overlap period of the period T3. The first PWM signal SG1 is replaced with the second PWM signal SG3. More specifically, in the upper arm side U phase, in the overlap period A within the period T3, the first phase of the V phase, which is the next phase to be switched, at the timing when the upper arm side V phase first PWM signal SG1 rises. During the two high level periods of one PWM signal SG1, a second PWM signal SG3 consisting of three pulses is set by the overlap controller 11 and output from the motor drive circuit 6 to the upper arm U phase. The

  The second PWM signal SG3 is set by the overlap controller 11 for each high level period of the first PWM signal SG1 within the overlap period. Therefore, the second PWM signal SG3 is a PWM signal output from the motor drive circuit 6 only during each high level period of the first PWM signal SG1 within the overlap period.

  On the other hand, in the overlap period B in the period T2, as shown in FIG. 2C, the third PWM signal SG4 is continuously output during the high level period of the constant voltage signal SG2 of the lower arm side W phase. It is set by the overlap controller 11. In the example of FIG. 2C, the third PWM signal SG4 composed of 12 pulses is set by the overlap control unit 11 in the high level period of the constant voltage signal SG2 in the overlap period B, and the motor drive circuit 6 to the lower arm side V phase. Unlike the second PWM signal SG3 in FIG. 2B, the third PWM signal SG4 is continuously output in the same cycle.

  The frequency and on-duty of the second and third PWM signals SG3 and SG4 are controlled by the motor control unit 7 and are not necessarily fixed values. In the present embodiment, they are fixed values. As an example, the first PWM signal SG1 is set to 16 kHz, and the second and third PWM signals SG3 and SG4 are set to 270 kHz. The second PWM signal SG3 and the third PWM signal SG4 do not necessarily have the same frequency. However, when the same frequency is set, the motor controller 7 that controls these signals and the motor controller 7 The internal configuration of the motor drive circuit 6 that outputs these signals under control can be simplified.

  As described above, the frequency and on-duty of the second and third PWM signals SG3 and SG4 may be arbitrarily set. In general, the frequency of the second and third PWM signals SG3 and SG4 is set as high as possible. However, the inclination of the phase current flowing through the armature coil 3 at the time of phase switching becomes more gentle, and the vibration and noise of the motor 2 can be more efficiently suppressed. On the other hand, if the frequency is set high, the switching loss of the switching elements Q1 to Q6 increases, so it is desirable to set an optimal frequency in a trade-off between the two. Conditions for setting the frequencies of the second and third PWM signals SG3 and SG4 include the types and electrical characteristics (for example, rise / fall response) of the circuit elements used in the switching elements Q1 to Q6 and their peripheral circuits, The length of the overlap period can be considered. It is desirable to determine the frequency by comprehensively considering these.

  In the example of FIG. 2A, the overlap period is defined as an electrical angle of 30 degrees. This is merely an example, and the overlap period may be defined by time instead of the electrical angle, and the specific overlap period is determined in advance in consideration of the design specifications of the motor 2 to be driven. It may be set to a predetermined value, or may be adjusted by the number of rotations of the motor 2 as will be described later.

  FIG. 2A shows an example in which the first PWM signal SG1 is supplied to the upper arm side switching elements Q1, Q3, Q5 and the constant voltage signal SG2 is supplied to the lower arm side switching elements Q2, Q4, Q6. However, conversely, the constant voltage signal SG2 may be supplied to the upper arm side switching elements Q1, Q3, Q5 and the first PWM signal SG1 may be supplied to the lower arm side switching elements Q2, Q4, Q6. .

  As can be seen from FIG. 2A, in the present embodiment, the upper arm side switching elements Q1, Q3, and Q5 are PWM-controlled, whereas the lower arm side switching elements Q2, Q4, and Q6 have a constant voltage for each phase. It is assumed that it will be supplied. Since the lower arm side switching elements Q2, Q4, and Q6 are supplied with one of two types of constant voltages (high level and low level) for each phase during steady driving, the lower arm side switching elements are described below. Control of Q2, Q4, and Q6 is called constant voltage control.

  By performing constant voltage control on the lower arm side switching elements Q2, Q4 and Q6, the internal configuration of the motor control unit 7 can be simplified as compared with the case where both the upper and lower arms are PWM controlled.

  The first to third PWM signals SG <b> 1, SG <b> 3, SG <b> 4 and the constant voltage signal SG <b> 2 described in FIG. 2 are output from the motor drive circuit 6 under the control of the motor control unit 7.

  As described above, the overlap control unit 11 may set the overlap period to a predetermined value, or may adjust the overlap period based on the number of rotations of the motor 2. The energization switching timing control unit 12 determines whether or not the phase switching timing has been reached based on the rotational position of the motor 2 detected by the rotational position detection unit 8, and the first to third PWM signals SG1, SG3, The motor drive circuit 6 is notified of the switching timing between SG4 and constant voltage signal SG2. The rotational position detector 8 detects the rotational position without a sensor (without a sensor) by an induced voltage induced at one end P of each armature coil 3 of the motor 2.

  FIG. 3 is a detailed signal waveform diagram in the period from T2 to T3 in FIG. In the period T2, the first PWM signal SG1 is supplied to the upper arm side U-phase switching element Q1, and in the period T3, the first PWM signal SG1 is supplied to the upper arm side V-phase switching element Q3. During the period T2, the U-phase current of the armature coil 3 is substantially constant.

  The overlap period is set within a predetermined period immediately after switching to the period T3, and the first PWM signal SG1 of the upper arm side U phase is switched to the second PWM signal SG3 having a higher frequency. As a result, the voltage between the U terminal and the W terminal of the armature coil 3 also changes at a fast cycle in synchronization with the second PWM signal SG3 as shown in FIG. Thereby, the U-phase current decreases almost linearly in proportion to the UW voltage. The slope of this U-phase current is gentler than the slope when no overlap period is provided (broken line in FIG. 3).

  Similarly, when switching from the period T1 to T2, an overlap period is set within a predetermined period immediately after the period T2. In the period T1, as shown in FIG. 2, the constant voltage signal SG2 is supplied to the lower arm side V-phase second switching element Q2, and in the period T2, the lower arm side W phase third switching element Q3 A constant voltage signal SG2 is supplied. In the overlap period immediately after the period T2, the third PWM signal SG4 is supplied to the second arm side V-phase second switching element Q2. As a result, the UV voltage within the overlap period changes with a short period as shown in FIG. 3, and the slope of the V-phase current becomes gentle. The slope of this V-phase current is gentler than the slope when no overlap period is provided (broken line in FIG. 3).

  FIG. 4 shows a comparison between the measurement results of the noise peak value when the brushless motor 2 is driven using the drive control device 1 according to the present embodiment and the noise peak value when the conventional drive control device 1 is used. FIG. In FIG. 4, when the rotation frequency f of the motor 2 is 490 Hz in the measurement of the present embodiment and when the rotation frequency f of the motor 2 is 472 Hz in the conventional measurement, the noise peak values 37 [dB] and 42 [dB] are obtained, respectively. ]showed that. This numerical value is a measured value at a distance of about 1 m from the motor.

  As described above, according to the drive control device 1 according to the present embodiment, as an example, a noise reduction effect of about 5 dB is obtained as compared with the related art.

  As described above, in the present embodiment, the first PWM signal within the overlap period is supplied to the upper arm side switching element that has supplied the first PWM signal SG1 during the steady drive immediately before the overlap period. The second PWM signal SG3 having a frequency higher than that of SG1 is supplied to simultaneously turn on the upper arm side switching elements for two phases. Alternatively, the third PWM having a frequency higher than that of the first PWM signal SG1 within the overlap period with respect to the lower arm side switching element that has supplied the constant voltage signal SG2 at the time of steady driving immediately before the overlap period. The signal SG4 is supplied to simultaneously turn on the lower arm side switching elements for two phases. As a result, the slope of the phase current flowing during the overlap period becomes gentle, torque fluctuation can be reduced, and vibration and noise of the brushless motor 2 can be greatly suppressed.

(Second Embodiment)
In the second embodiment, the overlap period and the on-duty of the second and third PWM signals SG3 and SG4 can be adjusted according to the rotational speed.

  FIG. 5 is a block diagram showing a schematic configuration of the drive control device 1a of the brushless motor 2 according to the second embodiment of the present invention. In FIG. 5, the same reference numerals are given to the components common to FIG. 1, and the differences will be mainly described below.

  The drive control device 1a in FIG. 5 includes a reference rotation speed calculation unit 21, a target rotation speed calculation unit 22, and a speed control unit 13 in addition to the configuration in FIG. Based on the rotational position of the rotor 4 detected by the rotational position detector 8, the reference rotational speed calculator 21 calculates the rotational speed of the rotor 4 at a predetermined reference time (hereinafter referred to as a reference rotational speed). The target rotational speed calculation unit 22 calculates a target value (hereinafter referred to as a target rotational speed) of the rotational speed of the rotor 4 based on a rotational speed command supplied from the outside of the drive control device 1a.

  The speed control unit 13 provided in the motor control unit 7 is based on the reference rotational speed calculated by the reference rotational speed calculation unit 21 and the target rotational speed calculated by the target rotational speed calculation unit 22. A speed control signal for controlling the rotation speed is generated, and the generated speed control signal is supplied to the motor drive circuit 6. Similarly, the overlap control unit 11 in the motor control unit 7 includes an overlap period based on the reference rotation number calculated by the reference rotation number calculation unit 21 and the target rotation number calculated by the target rotation number calculation unit 22. In addition, the switching signal output to the switching element of each phase from the motor drive circuit 6 within the overlap period and the two phases to be overlapped are determined, and the determination information is notified to the energization switching timing control unit 12. .

  The speed control unit 13 in the motor control unit 7 adjusts the on-duty of the second PWM signal SG3 output from the motor drive circuit 6 based on the target rotation number calculated by the target rotation number calculation unit 22. Here, the on-duty refers to a ratio of a period during which the switching element is on (ton / tp in FIG. 2B).

  FIG. 6 is a diagram illustrating an example of a table indicating a correspondence relationship between the target rotation speed and the on-duty of the second PWM signal SG3.

  As shown in FIG. 6, the motor control unit 7 switches the on-duty of the second PWM signal SG <b> 3 so as to decrease the on-duty as the target rotational speed increases, according to the target rotational speed.

  Hereinafter, the reason why the table of FIG. 6 is effective will be described. Regardless of the target rotational speed, the second PWM signal SG3 that is supplied within the overlap period to the phase that was supplying the first PWM signal SG1 immediately before the overlap period is the one whose on-duty is increased. However, in reality, if the on-duty is too large, it will be difficult to switch to a new phase after phase switching. The amount of current flowing through the switching element increases, resulting in problems such as increased noise. Therefore, there is a limit to increasing the on-duty.

  For example, when the rotational speed of the motor 2 is increased so as to approach the target rotational speed, the first PWM signal SG1 that controls on / off of the switching element of the new phase according to the increase in the rotational speed at the time of phase switching. It is necessary to increase the on-duty. If the on-duty of the second PWM signal SG3 described above at the time of phase switching is the same when the on-duty of the first PWM signal SG1 is large and small, the on-duty of the first PWM signal SG1 is large. However, the period during which current flows through the switching element in the immediately preceding phase becomes longer, and as a result, noise increases.

  In order to reduce this kind of noise during phase switching, it is necessary to optimize the slope of the current decrease in the phase immediately before the phase switching and the slope of the current increase in the phase immediately after the phase switching. However, the on-duty of the first PWM signal SG1 changes according to the target rotational speed, and the optimum value of the on-duty of the second PWM signal SG3 at the time of phase switching also depends on the on-duty of the first PWM signal SG1. Change.

  In view of such circumstances, as a result of trial and error by the inventor, for example, a correspondence relationship as shown in FIG. 6 was obtained. As shown in FIG. 6, the higher the target rotational speed, the smaller the on-duty can optimize the slope of the current decrease in the phase immediately before phase switching and the slope of the current increase in the phase immediately after phase switching. It was also found that noise can be suppressed.

  As described above, in the second embodiment, the slope of the phase current is optimized according to the target rotational speed of the motor 2 by adjusting the on duty of the second PWM signal SG3 according to the target rotational speed. Therefore, the vibration and noise of the motor 2 can be suppressed more efficiently. It should be noted that the same effect can be obtained even if the on-duty of the second PWM signal SG3 is adjusted not in accordance with the target rotational speed but in accordance with the reference rotational speed.

  Further, in the second embodiment, since the overlap period is set based on the target rotation speed and the reference rotation speed, the overlap energization can be performed in consideration of the actual rotation state of the motor 2, and more stably. While driving the motor 2, the effect of suppressing vibration and noise can be enhanced.

  FIG. 6 shows the correspondence relationship between the target rotational speed and the on-duty of the second PWM signal SG3. If the frequency of the third PWM signal SG4 is the same as the frequency of the second PWM signal SG3, the third The on-duty of the PWM signal SG4 can be set based on FIG. If the frequency of the third PWM signal SG4 is different from the frequency of the second PWM signal SG3, the correspondence relationship between the target rotational speed and the on-duty of the third PWM signal SG4 is shown separately from FIG. A table is provided, and the on-duty of the third PWM signal SG4 may be determined using this table.

(Other variations)
In the embodiment described above, the upper arm side and the lower arm are kept in mind that the switching speeds of the switching elements Q1, Q3, Q5 on the upper arm side and the switching elements Q2, Q4, Q6 on the lower arm side are substantially the same. The on-duty of the second PWM signal SG3 was set without distinguishing the sides. However, the switching speed may be different between the upper arm side and the lower arm side. In this case, it is desirable to change the on-duty of the second PWM signal SG3 between the upper arm side and the lower arm side. More specifically, it is desirable to increase the on-duty of the second PWM signal SG3 of the switching element having the slower switching speed on the upper arm side and the lower arm side. In order to realize this, a table as shown in FIG. 6 may be provided separately on the upper arm side and the lower arm side.

  The rotational position detection unit 8 described above has shown an example in which an induced voltage induced in each armature coil 3 is detected without a sensor. However, a position sensor that detects the rotational position of the rotor 4 is provided, and The rotational position may be detected by a signal.

  Further, the second PWM signal SG3 is not limited to a PWM signal output only during each high level period of the first PWM signal SG1 within the overlap period shown in FIG. Depending on the operating conditions of the motor, the second PWM signal SG3 may be used as a PWM signal that is also output during all or part of the low level periods of the first PWM signal SG1 within the overlap period. You may make it finely adjust the inclination of.

  Further, the third PWM signal SG4 is not limited to the PWM signal that is continuously output within the overlap period shown in FIG. 2C, and the third PWM signal SG4 depends on the operating condition of the motor. The signal SG4 may be finely adjusted for the slope of the phase current as an intermittently output PWM signal that is not output during a part of the overlap period.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1,1a Drive control apparatus 2 Brushless motor 3 Armature coil 4 Rotor 5 Inverter circuit 6 Motor drive circuit 7 Motor control part 8 Rotation position detection part 11 Overlap control part 12 Energization switching timing control part 13 Speed control part 21 Reference | standard rotation speed Calculation unit 22 Target rotational speed calculation unit

Claims (5)

In a drive control device for a brushless motor that rotates a rotor having a plurality of magnetic poles by performing overlap energization on a plurality of armature coils provided in a stator,
An inverter circuit for energizing the plurality of armature coils;
A motor drive circuit for generating a drive signal for driving the inverter circuit;
A motor control unit that sets an overlap period for performing the overlap energization and controls the motor drive circuit based on the overlap period, and
The inverter circuit is
A plurality of upper arm side switching elements provided for each phase of the armature coils of the plurality of phases;
A plurality of lower arm side switching elements provided for each phase of the multiple phase armature coils and connected in series to the corresponding upper arm side switching elements;
In the steady driving, the motor drive circuit is configured to switch one of the plurality of upper arm side switching elements and the plurality of lower arm side switching elements for each phase of the plurality of armature coils. On / off control by PWM signal, and on / off control of the other by constant voltage signal,
The motor control unit, with respect to the upper arm side or lower arm side switching element that has supplied the first PWM signal immediately before the overlap period within the overlap period, The second PWM signal having a frequency higher than that of the PWM signal is supplied, and the first arm is supplied to the lower arm side or upper arm side switching element that has supplied the constant voltage signal immediately before the overlap period. A drive control device that controls the motor drive circuit so as to supply a third PWM signal having a frequency higher than that of the PWM signal. The second PWM signal is a PWM signal generated in a period in which at least the first PWM signal is at a high level within the overlap period,
The third PWM signal is a PWM signal generated continuously in at least a part of a period in which the constant voltage signal takes a high level in the overlap period. The drive control apparatus described in 1. The overlap period is set for each phase at the time of phase switching,
The motor driving circuit supplies the first PWM signal to the switching element of the phase to be switched next on the upper arm side or the lower arm side to which the first PWM signal is supplied in the overlap period, The second PWM signal is supplied to the upper arm side or lower arm side switching element that supplied the first PWM signal immediately before the overlap period within the ON period of the switching element of the next switching phase. On the upper arm side or lower arm side to which the constant voltage signal is supplied, the third PWM is supplied to the upper arm side or lower arm side switching element that has supplied the constant voltage signal immediately before the overlap period. The drive control apparatus according to claim 2, wherein a signal is supplied. A rotational position detector for detecting the rotational position of the rotor;
A reference rotation number calculation unit that calculates a reference rotation number representing the rotation number of the rotor at a predetermined reference time based on the rotation position detected by the rotation position detection unit;
A target rotational speed calculation unit that calculates a target rotational speed that is a target value of the rotational speed of the rotor based on a predetermined rotational speed command,
The motor control unit sets the overlap period based on the target rotation speed and the reference rotation speed, and the second and the second rotation period within the overlap period based on the target rotation speed or the reference rotation speed. The drive control apparatus according to claim 3, wherein the on-duty of the third PWM signal is variably controlled.   5. The motor control unit according to claim 4, wherein the motor control unit variably controls the on-duty of the second and third PWM signals separately for each of the upper arm side and lower arm side switching elements. Drive control device.

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