JP2012070605A - Motor drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start a motor quickly.SOLUTION: A motor drive circuit includes: a drive circuit 1 for outputting a drive signal to rotate a motor in a normal direction or reverse direction in accordance with a rotation direction indication signal indicating a normal or reverse rotation of the motor; a rotational frequency comparison circuit 4 for determining whether or not the rotational frequency of the motor is higher than a reference rotational frequency; a short brake control circuit 2 for controlling braking in accordance with the comparison result of the rotational frequency comparison circuit 4 when the rotation direction indication signal changes; an energized phase order changeover control circuit 3 for changing the direction of rotation; and a determination circuit 110 for controlling the drive circuit 1 such that the direction of rotation of the motor is changed without the action of braking the motor irrespective of the comparison result of the rotational frequency comparison circuit 4 if the rotation direction indication signal changes while the motor is stopped.

Description

  The present invention relates to a motor drive circuit.

  In general, there is known a motor control circuit capable of preventing destruction of a control semiconductor element without increasing a power supply voltage when switching the rotation direction of the motor (Patent Document 1).

  When the motor control circuit switches the rotation direction of the motor, in order to prevent an overcurrent caused by a counter electromotive voltage due to the rotation of the motor from being supplied to the control semiconductor element and destroying the control semiconductor element, The rotation direction of the motor is switched based on the comparison result comparing the rotation speed of the motor and the reference rotation speed. That is, when the motor speed is higher than the reference speed, the motor control circuit switches the motor rotation direction after braking the motor until the motor speed is lower than the reference speed, while the motor speed is When the rotation speed is lower than the reference rotation speed, the motor control circuit switches the rotation direction of the motor without braking the motor.

JP-A-2005-130538

  For example, a system having a function of starting a motor when a rotation direction instruction signal for switching the rotation direction by instructing rotation in the forward direction or the reverse direction of the motor when the motor is stopped is known. . For example, the motor control circuit of Patent Document 1 has this function. In this motor control circuit, when the rotation direction indication signal changes after the power is turned on and after the motor is restrained, the overcurrent caused by the counter electromotive voltage due to the rotation of the motor is not supplied to the control semiconductor element, and the semiconductor element is destroyed. The motor control circuit performs a comparison operation for comparing the rotational speed of the motor with the reference rotational speed despite the fact that there is no fear of being performed. Therefore, there is a possibility that the motor cannot be started quickly.

  The main present invention that solves the above-described problem is a drive that outputs a drive signal for rotating the motor in the forward direction or the reverse direction in accordance with a rotation direction instruction signal that instructs rotation in the forward direction or the reverse direction of the motor. A circuit, a comparison circuit for comparing whether the rotational speed of the motor is higher than a reference rotational speed, and when the rotational direction indication signal changes when the rotational speed of the motor is higher than the reference rotational speed, The drive circuit is controlled so that the motor is braked, and the drive circuit is controlled so that the motor is not braked when the rotation direction instruction signal changes when the rotation speed of the motor is lower than the reference rotation speed. When the rotation direction instruction signal changes when the rotation speed of the motor is higher than the reference rotation speed, the motor rotates in a state where the motor is braked. The drive circuit is controlled so that the direction is changed, and when the rotation direction instruction signal changes when the rotation speed of the motor is lower than the reference rotation speed, the motor is not braked. A second control circuit that controls the drive circuit so that the rotation direction is changed, and the motor when the rotation direction instruction signal changes when the motor is stopped, regardless of a comparison result of the comparison circuit. And a third control circuit for controlling the drive circuit so that the rotation direction of the motor is changed without performing the braking operation.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, the motor can be started quickly.

It is a figure which shows the motor drive circuit which concerns on embodiment of this invention. It is a wave form diagram showing a signal at the time of initial starting of a motor by a motor drive circuit concerning an embodiment of the present invention. It is a wave form diagram which shows the signal at the time of starting a motor, after the motor drive circuit which concerns on embodiment of this invention performs restraint protection.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Overall Configuration of Motor Drive Circuit ===
FIG. 1 is a diagram illustrating a motor drive circuit according to the present embodiment.
The motor drive circuit 100 is a circuit for supplying a drive current to, for example, a drive coil of a three-phase sensorless motor (hereinafter referred to as a motor), and includes a drive circuit 1, a short brake control circuit 2 (first control circuit), and an energized phase. Order switching control circuit 3 (second control circuit), rotation speed detection circuit 9, rotation speed comparison circuit 4 (comparison circuit), determination circuit 110 (first determination circuit, second determination circuit), control circuit 120 and five Terminals Tb, Tc, Tu, Tv, Tw are provided.

  The terminals Tu, Tv, and Tw of the motor drive circuit 100 are three-phase (U-phase, V-phase, and W-phase) that are star-connected and wound around the stator of the motor with a phase difference of 120 degrees in electrical angle. The drive coils Lu, Lv, and Lw are connected to one end opposite to the neutral point P100. A rotation direction instruction signal Sc3 for instructing rotation in the forward direction or the reverse direction of the motor, and a threshold signal Sc6 for setting a reference rotation speed to be compared with the rotation speed of the motor are each input from, for example, a microcomputer (not shown). Input to Tc and Tb. Details of the reference rotation speed will be described later.

  The drive circuit 1 is a circuit that supplies a drive current for rotating the motor to the drive coils Lu, Lv, and Lw. The drive circuit 1 has three-phase source transistors and sink transistors for supplying drive currents to the three-phase drive coils Lu, Lv, and Lw, respectively. Each connection point between the source transistor and sink transistor of each phase is connected to terminals Tu, Tv, and Tw.

  The energization phase sequence switching control circuit 3 is a circuit that switches the supply sequence and supply direction of the drive current supplied from the drive circuit 1 to the drive coils Lu, Lv, and Lw in order to change the rotation direction of the motor.

  The short brake control circuit 2 is a circuit that controls the drive circuit 1 so that the motor is braked by, for example, a short brake. The short brake control circuit 2 brakes the motor by turning on all source transistors, for example, for three phases of the drive circuit 1 or turning on all sink transistors, for example, for three phases.

  The rotation speed detection circuit 9 is a circuit that outputs an FG signal having a frequency corresponding to the rotation speed of the motor.

  The rotation speed comparison circuit 4 is a circuit that compares whether the rotation speed of the motor is higher than the reference rotation speed based on the FG signal and outputs a comparison signal Sc2 indicating the comparison result.

  The determination circuit 110 is a circuit that determines whether or not the motor is stopped based on the FG signal and outputs a determination signal Sc1 indicating the determination result. Details of the determination circuit 110 will be described later.

  The control circuit 120 is a circuit that controls the short brake control circuit 2 and the energized phase sequence switching control circuit 3 based on the determination signal Sc1 and the comparison signal Sc2 when the rotation direction instruction signal Sc3 changes. For example, when the rotation direction instruction signal Sc3 is changed while the determination signal Sc1 indicating that the motor is not stopped is output, the control circuit 120 determines that the rotation speed of the motor is not higher than the reference rotation speed. The short brake control circuit 2 is controlled so that the motor is braked until a comparison signal Sc2 is output. Thereafter, the control circuit 120 controls the energized phase sequence switching control circuit 3 so that the rotation direction of the motor is changed. On the other hand, for example, when the rotation direction instruction signal Sc3 changes when the determination signal Sc1 indicating that the motor is stopped is output, the control circuit 120 does not depend on the comparison result indicated by the comparison signal Sc2. The energized phase sequence switching circuit 3 is controlled so that the rotation direction of the motor is changed. Details of the control circuit 120 will be described later.

=== Determination circuit ===
The determination circuit 110 is a circuit that determines whether or not the motor is stopped based on the FG signal and outputs a determination signal Sc1 indicating the determination result.
The determination circuit 110 includes a rotation speed comparison / selection circuit 5, a constraint protection circuit 6, and an FG counter 7 (counter).

  The constraint protection circuit 6 receives the FG signal and the rotation direction instruction signal Sc3, and outputs a SET signal and a control signal Sc9. When the first predetermined number (for example, one) of FG signals is not input within the predetermined period Ta, the constraint protection circuit 6 controls the control signal Sc9 and the SET signal to stop the supply of the drive current to the drive coils Lu, Lv, and Lw. Is output. The SET signal has a rising edge of the FG signal to the constraint protection circuit 6 when the rising edge of the FG signal is not input again within a predetermined period Ta after the rising edge of the FG signal is input to the constraint protection circuit 6. This is a one-shot pulse signal output from the constraint protection circuit 6 when a predetermined period Ta has elapsed after being input. When, for example, the rotation direction instruction signal Sc3 is changed after the control signal Sc9 for stopping the supply of the drive current to the drive coils Lu, Lv, Lw is output, the restraint protection circuit 6 is connected to the drive coils Lu, Lv, Lw. A control signal Sc9 for starting the supply of the drive current is output. The constraint protection circuit 6 also outputs a SET signal when the power supply voltage is applied to the constraint protection circuit 6 after the motor drive circuit 100 is powered on.

  The FG counter 7 receives the FG signal and the rotation direction instruction signal Sc3, and outputs a RESET signal. The FG counter 7 counts the number of rising edges of the FG signal, and resets the count value when the rotation direction instruction signal Sc3 changes. The FG counter 7 outputs a RESET signal when the count value reaches a second predetermined number (for example, 10). The RESET signal is a one-shot pulse signal output from the FG counter 7 when the count value of the FG counter 7 reaches the second predetermined number.

  The rotation speed comparison / selection circuit 5 receives the SET signal and the RESET signal and outputs a determination signal Sc1. The rotation speed comparison / selection circuit 5 is a circuit that holds the SET signal and the RESET signal input to the rotation speed comparison / selection circuit 5 and outputs a determination signal Sc1 indicating the held signal. For example, when the SET signal is input to the rotation speed comparison / selection circuit 5, the rotation speed comparison / selection circuit 5 outputs a high-level determination signal Sc 1. For example, the RESET signal is input to the rotation speed comparison / selection circuit 5. In this case, a low level determination signal Sc1 is output.

=== Rotation speed comparison circuit ===
The rotation speed comparison circuit 4 is a circuit that compares whether the rotation speed of the motor is higher than the reference rotation speed based on the FG signal and outputs a comparison signal Sc2 indicating the comparison result. The rotation speed comparison circuit 4 receives the threshold signal Sc6, the rotation direction instruction signal Sc3, and the FG signal, and outputs a comparison signal Sc2. When the rotation direction instruction signal Sc3 changes, the rotation speed comparison circuit 4 compares, based on the FG signal, whether or not the rotation speed of the motor is higher than the reference rotation speed set by the threshold signal Sc6. To start. Here, when the drive current for changing the rotation direction of the motor is supplied from the drive circuit 1 to the drive coils Lu, Lv, and Lw from the drive circuit 1, the overcurrent caused by the counter electromotive voltage due to the rotation of the motor is caused by the drive circuit 1. The rotation speed is lower than the rotation speed at which there is no possibility that the drive circuit 1 is destroyed and is set to 100 Hz, for example. For example, the rotation speed comparison circuit 4 within a time (for example, 10 milliseconds) corresponding to one cycle of the reference rotation speed (for example, 100 Hz) from when the rising edge of the FG signal is input to the rotation speed comparison circuit 4. It is determined whether or not the rotational speed of the motor is higher than the reference rotational speed based on whether or not the rising edge of the FG signal is input. The FG signal is a pulse signal having the same frequency as the rotational speed of the motor. For example, when the rising edge of the FG signal is input within a time (for example, 10 milliseconds) corresponding to one cycle of the reference rotation speed (for example, 100 Hz), the rotation speed comparison circuit 4 determines that the rotation speed of the motor is the reference rotation. Judged higher than the number. On the other hand, for example, when the rising edge of the FG signal is not input within a time (for example, 10 milliseconds) corresponding to, for example, one period of the reference rotation speed (for example, 100 Hz), the rotation speed comparison circuit 4 It is determined that it is not higher than the reference rotational speed.

  When the rotational speed comparison circuit 4 determines that the rotational speed of the motor is higher than the reference rotational speed, the rotational speed comparison circuit 4 outputs, for example, a low-level comparison signal Sc2, and determines that the rotational speed of the motor is not higher than the reference rotational speed. The rotation speed comparison circuit 4 outputs a high level comparison signal Sc2, for example. The rotation speed comparison circuit 4 outputs a low-level comparison signal Sc2 when a power supply voltage is applied to the rotation speed comparison circuit 4 after power is supplied to the motor drive circuit 100.

=== Control circuit ===
The control circuit 120 is a circuit that controls the short brake control circuit 2 and the energized phase sequence switching control circuit 3 based on the determination signal Sc1 and the comparison signal Sc2 when the rotation direction instruction signal Sc3 changes. The control circuit 120 includes a forward / reverse rotation direction control circuit 8 and an OR circuit 300.
The OR circuit 300 receives the determination signal Sc1 and the comparison signal Sc2, and outputs an output control signal Sc7.
The forward / reverse rotation direction control circuit 8 receives the rotation direction instruction signal Sc3 and the output control signal Sc7, and outputs the rotation direction signal Sc8. For example, when the high-level output control signal Sc7 is input to the forward / reverse rotation direction control circuit 8, the forward / reverse rotation direction control circuit 8 outputs the rotation direction signal Sc8 having the same logic level as the rotation direction instruction signal Sc3. Shall. On the other hand, for example, when the low-level output control signal Sc7 is input to the forward / reverse rotation direction control circuit 8, the forward / reverse rotation direction control circuit 8 outputs the logical level rotation direction signal Sc8 that was output immediately before. Shall.

=== Short brake control circuit ===
The short brake control circuit 2 is a circuit that controls the drive circuit 1 so that the motor is braked by, for example, a short brake. The short brake control circuit 2 receives the rotation direction instruction signal Sc3 and the output control signal Sc7, and outputs a brake signal Sc4.
For example, when the rotation direction instruction signal Sc3 is changed in a state where the low level output control signal Sc7 is input to the short brake control circuit 2, the short brake control circuit 2 includes, for example, all the source transistors for the three phases of the drive circuit 1. It is assumed that a brake signal Sc4 for turning on is output. On the other hand, for example, when the high-level output control signal Sc7 is input to the short brake control circuit 2, the short brake control circuit 2 does not output the brake signal Sc4.

=== Energized phase sequence switching control circuit ===
The energization phase sequence switching control circuit 3 is a circuit that switches the supply sequence and supply direction of the drive current supplied from the drive circuit 1 to the drive coils Lu, Lv, and Lw in order to change the rotation direction of the motor. The energized phase sequence switching control circuit 3 receives the rotation direction signal Sc8 and outputs an energized phase sequence signal Sc5.
For example, when a high-level rotation direction signal Sc8 is input to the energized phase sequence switching control circuit 3, the energized phase sequence switching control circuit 3 controls the drive circuit 1 so that the motor rotates, for example, forward. Assume that Sc5 is output. For example, when a low-level rotation direction signal Sc8 is input to the energized phase sequence switching control circuit 3, the energized phase sequence switching control circuit 3 controls the drive circuit 1 so that the motor rotates in reverse, for example. Assume that Sc5 is output.

=== Drive circuit ===
The drive circuit 1 is a circuit that supplies a drive current for rotating the motor to the drive coils Lu, Lv, and Lw. The drive circuit 1 receives the brake signal Sc4, the energized phase sequence signal Sc5, and the control signal Sc9, and supplies a drive current to the drive coils Lu, Lv, and Lw.

  For example, when a brake signal Sc4 for turning on all the source transistors, for example, for all three phases of the drive circuit 1 is input to the drive circuit 1, the drive circuit 1 causes the source for the three phases so that the motor is braked by a short brake. All the transistors are turned on. For example, when the energization phase sequence signal Sc5 for controlling the drive circuit 1 so that the motor rotates in the forward direction is input to the drive circuit 1, the drive circuit 1 receives the drive currents for driving the motor in the forward direction as drive coils Lu and Lv. , The source transistor and the sink transistor for three phases are appropriately turned on and off so as to be supplied to Lw. For example, when an energized phase sequence signal Sc5 for controlling the drive circuit 1 so that the motor rotates in the reverse direction is input to the drive circuit 1, the drive circuit 1 receives a drive current for rotating the motor in the reverse direction as the drive coils Lu, Lv. , The source transistor and the sink transistor for three phases are appropriately turned on and off so as to be supplied to Lw. For example, when the control signal Sc9 for stopping the supply of the drive current is input to the drive circuit 1, the drive circuit 1 uses, for example, a three-phase source so that the drive current is not supplied to the drive coils Lu, Lv, and Lw. All transistors are turned off. For example, when the control signal Sc9 for starting the supply of the drive current is input to the drive circuit 1, the drive circuit 1 receives a drive current that causes the motor to rotate forward or backward based on the energized phase sequence signal Sc5. It is assumed that source transistors and sink transistors for three phases are appropriately turned on and off so as to be supplied to Lu, Lv, and Lw.

=== Operation of Motor Drive Circuit ===
The operation of the motor drive circuit 100 will be described with reference to FIGS.
FIG. 2 is a waveform diagram showing signals when the motor driving circuit according to the present embodiment initially starts the motor. FIG. 3 is a waveform diagram showing signals when the motor is started after the motor driving circuit according to the present embodiment performs constraint protection. 2 and 3 are assumed to be continuous on the coaxial time axis.
For example, it is assumed that the motor drive circuit 100 is powered on at time T1, an initial startup period (from time T1 to time T3), a steady rotation period (from time T3 to time T6), and a restraint period (from time T12 to time T13). The operation of the motor drive circuit 100 will be described by dividing it into a constraint protection period (from time T13 to time T14) and an activation period (from time T14 to T15).

<Initial startup period (from time T1 to time T3)>
For example, at time T1, the constraint protection circuit 6 is applied with a power supply voltage and outputs a pulsed SET signal. The rotation speed comparison / selection circuit 5 receives the SET signal and outputs a high-level determination signal Sc1. The OR circuit 300 receives the high level determination signal Sc1 and outputs a high level output control signal Sc7 regardless of the logic level of the comparison signal Sc2. The short brake control circuit 2 receives the high level output control signal Sc7 and does not output the brake signal Sc4. The forward / reverse rotation direction control circuit 8 receives the high level output control signal Sc7 and outputs a rotation direction signal Sc8 having the same logical level as the rotation direction instruction signal Sc3. The energized phase sequence switching control circuit 3 receives the high-level rotation direction signal Sc8 and outputs an energized phase sequence signal Sc5 that controls the drive circuit 1 so that the motor rotates forward. The drive circuit 1 receives an energized phase sequence signal Sc5 for controlling the drive circuit 1 so that the motor rotates forward, and a drive current for rotating the motor forward is supplied to the drive coils Lu, Lv, Lw. Then, the source transistor and sink transistor for three phases are turned on and off as appropriate. The motor rotates forward by the drive current supplied to the drive coils Lu, Lv, Lw.

  For example, when the rotation direction instruction signal Sc3 changes from the high level to the low level at time T2, the FG counter 7 resets a count value that is the number of rising edges of the FG signal counted between time T1 and time T2. . The rotation speed comparison / selection circuit 5, the OR circuit 300, the short brake control circuit 2, and the forward / reverse rotation direction control circuit 8 perform the same operations as those at the time T1, and thus the description thereof is omitted. The energized phase sequence switching control circuit 3 receives the low-level rotation direction signal Sc8 and outputs an energized phase sequence signal Sc5 for controlling the drive circuit 1 so that the motor rotates in the reverse direction. The drive circuit 1 receives an energized phase sequence signal Sc5 that controls the drive circuit 1 so that the motor rotates in reverse, and a drive current for rotating the motor in reverse is supplied to the drive coils Lu, Lv, and Lw. Then, the source transistor and sink transistor for three phases are turned on and off as appropriate. The motor rotates in reverse by the drive current supplied to the drive coils Lu, Lv, Lw.

  Therefore, when the rotation direction instruction signal Sc3 changes during the initial activation period, the motor drive circuit 100 switches the rotation direction of the motor without braking the motor regardless of the comparison signal Sc2 of the rotation speed comparison circuit 4.

<Normal rotation period (from time T3 to time T6)>
For example, at time T3, the FG counter 7 reaches the second predetermined number (for example, 10) and outputs a RESET signal. The rotation speed comparison / selection circuit 5 receives the RESET signal and outputs a low-level determination signal Sc1.

  For example, when the rotation direction instruction signal Sc3 changes from the low level to the high level at time T4, the rotation speed comparison / selection circuit 5 outputs the low level determination signal Sc1 output at time T3. Based on the FG signal, the rotation speed comparison circuit 4 compares whether or not the rotation speed of the motor is higher than the reference rotation speed, and shows a low level indicating that the rotation speed of the motor is higher than the reference rotation speed, for example. The comparison signal Sc2 is output. The OR circuit 300 receives a low level determination signal Sc1 and a low level comparison signal Sc2, and outputs a low level output control signal Sc7. The short brake control circuit 2 outputs a brake signal Sc4 that turns on, for example, all the source transistors for the three phases of the drive circuit 1 when the low-level output control signal Sc7 is input and the rotation direction instruction signal Sc3 changes. To do. The drive circuit 1 receives the brake signal Sc4 and turns on all the three-phase source transistors so that the motor is braked by the short brake. The motor is braked by a short brake of the drive circuit 1.

  For example, at time T5, the rotation speed comparison circuit 4 compares whether or not the rotation speed of the motor is higher than the reference rotation speed based on the FG signal, and the rotation speed of the motor is higher than the reference rotation speed, for example. It is assumed that a high level comparison signal Sc2 indicating that it is not high is output. The OR circuit 300 receives a low level determination signal Sc1 and a high level comparison signal Sc2, and outputs a high level output control signal Sc7. The short brake control circuit 2 and the forward / reverse rotation direction control circuit 8 perform the same operation as at the time T1, and therefore the description thereof is omitted. The energized phase sequence switching control circuit 3 receives the high-level rotation direction signal Sc8 and outputs an energized phase sequence signal Sc5 that controls the drive circuit 1 so that the motor rotates forward. The drive circuit 1 receives an energized phase sequence signal Sc5 for controlling the drive circuit 1 so that the motor rotates forward, and a drive current for rotating the motor forward is supplied to the drive coils Lu, Lv, Lw. Then, the source transistor and sink transistor for three phases are turned on and off as appropriate. The motor rotates forward by the drive current supplied to the drive coils Lu, Lv, Lw.

  Therefore, when the rotation direction instruction signal Sc3 changes during the steady rotation period, the motor drive circuit 100 brakes the motor so that the rotation speed of the motor is not higher than the reference rotation speed, and then changes the rotation direction of the motor. Switch. Therefore, when the rotation direction instruction signal Sc3 changes during the steady rotation period, the motor drive circuit 100 switches the rotation direction of the motor according to the comparison signal Sc1 of the rotation speed comparison circuit 4.

<Restriction period (from time T12 to time T13), Restriction protection period (from time T13 to time T14), Activation period (from time T14 to T15)>
For example, at the time T13, the constraint protection circuit 6 supplies the SET signal and the drive current without the first predetermined number (for example, one) of the rising edge of the FG signal being input during the predetermined period Ta from the time T12 to the time T13. And a control signal Sc9 for stopping. The drive circuit 1 receives the control signal Sc9 for stopping the supply of the drive current, and turns off all the source transistors and the sink transistors, for example, for three phases so that the drive current is not supplied to the drive coils Lu, Lv, Lw. To do. The rotation speed comparison / selection circuit 5 receives the SET signal and outputs a high-level determination signal Sc1. The OR circuit 300 receives the high level determination signal Sc1 and outputs a high level output control signal Sc7 regardless of the logic level of the comparison signal Sc2.

  For example, when the rotation direction instruction signal Sc3 changes from the high level to the low level at time T14, the rotation speed comparison / selection circuit 5 and the OR circuit 300 respectively output the high level determination signal Sc1 and the high level output at time T13. Output control signal Sc7. The short brake control circuit 2, the forward / reverse rotation direction control circuit 8, and the energized phase sequence switching control circuit 3 operate in the same manner as at time T1, and therefore the description thereof is omitted. The constraint protection circuit 6 outputs a control signal Sc9 for starting the supply of drive current. The drive circuit 1 receives the control signal Sc9 for starting the supply of the drive current, and the source for three phases so that the drive current for rotating the motor forward is supplied to the drive coils Lu, Lv, Lw The transistor and the sink transistor are turned on and off as appropriate. The motor rotates forward by the drive current supplied to the drive coils Lu, Lv, Lw.

  Therefore, when the rotation direction instruction signal Sc3 changes during the constraint protection period, the motor drive circuit 100 switches the rotation direction of the motor without braking the motor regardless of the comparison signal Sc2 of the rotation speed comparison circuit 4.

  For example, at time T15, the count value reaches the second predetermined number (for example, 10), and the RESET signal is output. The rotation speed comparison / selection circuit 5 receives the RESET signal and outputs a low-level determination signal Sc1. When the rotation direction instruction signal Sc3 changes after time T15, the motor drive circuit 100 performs the same operation as in the above-described steady rotation period, and thus the description thereof is omitted.

  As described above, the drive circuit 1 supplies a drive current for rotating the motor to the drive coils Lu, Lv, and Lw. The rotation speed comparison circuit 4 compares whether the rotation speed of the motor is higher than the reference rotation speed based on the FG signal. The short brake control circuit 2 controls the drive circuit 1 based on the comparison result of the rotation speed comparison circuit 4 so that the motor is braked so that the rotation speed of the motor becomes lower than the reference rotation speed. When the rotation direction instruction signal Sc3 changes, the energized phase sequence switching control circuit 3 determines that the drive circuit 1 is driven when the rotation speed of the motor becomes lower than the reference rotation speed based on the comparison result of the rotation speed comparison circuit 4. The supply order and supply direction of the drive current supplied to the drive coils Lu, Lv, and Lw are switched. The determination circuit 110 determines whether the motor is stopped based on the FG signal. When the rotation direction instruction signal Sc3 changes when the determination circuit 110 determines that the motor is stopped, the control circuit 120 performs the braking operation of the motor regardless of the comparison result of the rotation speed comparison circuit 4. Instead, the energized phase sequence switching control circuit 3 is controlled so that the rotation direction of the motor is changed. Therefore, when the motor drive circuit 100 has a function of starting the motor by a change in the rotation direction instruction signal Sc3, the motor is turned on regardless of the comparison result of the rotation speed comparison circuit 4 when the rotation direction instruction signal Sc3 changes. It can be started quickly.

  Further, the determination circuit 110 includes a constraint protection circuit 6. The determination circuit 110 determines that the motor is stopped when the first predetermined number (for example, one) of FG signals is not input to the constraint protection circuit 6 within the predetermined period Ta. Therefore, the motor drive circuit 100 can quickly start the motor when the rotation direction instruction signal Sc3 changes while the constraint protection circuit 6 is performing the constraint operation.

  Further, the determination circuit 110 has an FG counter 7. The determination circuit 110 determines that the motor is not stopped when the FG counter 7 counts the second predetermined number (for example, 10) of rising edges of the FG signal after determining that the motor is stopped. Therefore, when the rotation direction instruction signal Sc3 changes after the FG counter 7 has counted the second predetermined number (for example, 10) of the rising edge of the FG signal, the motor drive circuit 100 determines that the motor rotation speed is higher than the reference rotation speed. After the motor is braked so as to be lowered, the rotation direction of the motor is switched. Therefore, the motor drive circuit 100 can prevent the motor drive circuit 100 from being destroyed due to the overcurrent caused by the counter electromotive voltage caused by the rotation of the motor being supplied to the motor drive circuit 100.

  The FG counter resets the count value when the rotation direction instruction signal Sc3 changes. Therefore, the determination circuit 110 determines that the motor has stopped when the rising edge of the FG signal when rotating only in either the forward direction or the reverse direction is counted by the second predetermined number (for example, 10) FG counter 7. Judge that there is no. Therefore, when the rotation direction instruction signal Sc3 is changed, the motor drive circuit 100 is not supplied with the overcurrent due to the counter electromotive voltage due to the rotation of the motor, and the motor drive circuit 100 may be destroyed. In spite of the absence, it is possible to prevent the switching of the rotation direction based on the comparison result of the rotation speed comparison circuit 4 and to start the motor quickly.

  The short brake control circuit 2 controls the drive circuit 1 so that the motor is braked by the short brake. Therefore, when the rotation direction instruction signal Sc3 changes, the motor drive circuit 100 can quickly brake the motor so that the rotation speed of the motor becomes lower than the reference rotation speed, and can quickly switch the rotation direction of the motor.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Drive circuit 2 Short brake control circuit 3 Energization phase sequence switching control circuit 4 Rotation speed comparison circuit 5 Rotation speed comparison selection circuit 6 Restriction protection circuit 7 FG counter 8 Forward / reverse rotation direction control circuit 9 Rotation speed detection circuit 100 Motor drive circuit 110 Determination circuit 120 Control circuit Lu, Lv, Lw Driving coil Tb, Tc, Tu, Tv, Tw terminal

Claims (5)

A drive circuit for outputting a drive signal for rotating the motor in the forward direction or the reverse direction in response to a rotation direction instruction signal for instructing rotation in the forward direction or the reverse direction of the motor;
A comparison circuit for comparing whether the rotational speed of the motor is higher than a reference rotational speed;
When the rotation direction instruction signal changes when the rotation speed of the motor is higher than the reference rotation speed, the drive circuit is controlled so that the motor is braked, and the rotation speed of the motor is higher than the reference rotation speed. A first control circuit that controls the drive circuit so that the motor is not braked when the rotation direction instruction signal changes when
When the rotation direction instruction signal changes when the rotation speed of the motor is higher than the reference rotation speed, the drive circuit is controlled so that the rotation direction of the motor is changed in a state where the motor is braked, If the rotation direction instruction signal changes when the rotation speed of the motor is lower than the reference rotation speed, the drive circuit is controlled so that the rotation direction of the motor is changed in a state where the motor is not braked. A second control circuit;
If the rotation direction instruction signal changes while the motor is stopped, the drive is performed so that the rotation direction of the motor is changed without performing the braking operation of the motor regardless of the comparison result of the comparison circuit. A third control circuit for controlling the circuit;
A motor drive circuit comprising: The third control circuit includes:
A first determination circuit configured to determine that the motor is stopped when the number of pulse signals having a frequency corresponding to the number of rotations of the motor generated in the first predetermined period is equal to or less than the first predetermined number; The motor drive circuit according to claim 1. The third control circuit includes:
After the first determination circuit determines that the motor is stopped, the motor is rotating when the number of the pulse signals generated in the second predetermined period is equal to or greater than the second predetermined number. The motor drive circuit according to claim 2, further comprising: a second determination circuit that determines that the state is in effect. The second determination circuit includes:
A counter that counts the number of the pulse signals and resets the count value when the rotation direction instruction signal changes; and when the counter counts the second predetermined number of the number of the pulse signals, the motor The motor drive circuit according to claim 3, wherein the motor drive circuit is determined to be in a rotating state. The first control circuit includes:
The drive circuit is controlled so that the motor is braked by a short brake when the rotation direction instruction signal changes when the rotation speed of the motor is higher than the reference rotation speed. The motor drive circuit according to any one of 4.

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