JP5419663B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device that detects a rotor rotation state based on an induced voltage of each phase coil of a motor and performs motor control by phase energization control (hereinafter referred to as “commutation”) to each phase coil of the motor.

  Conventionally, in a sensorless brushless motor, the rotor rotation position is detected by comparing the induced voltage (counterelectromotive force voltage) of each phase coil and the neutral voltage, and the current of each phase coil is switched by an inverter circuit. What performs rotation drive control is known (for example, refer patent document 1).

JP 11-299283 A

  However, in the conventional motor control device, it is difficult to control in synchronization with the rotor rotation phase at the time of start-up and low rotation at which the back electromotive force voltage is not sufficiently generated. There was a problem that sound, rotational step-out, stop, etc. would occur.

  In other words, in the control that compares the counter electromotive force voltage generated in each phase coil with the neutral voltage that is the reference voltage (hereinafter referred to as the midpoint voltage or midpoint potential), the back electromotive force voltage and the midpoint voltage match. Is used as the zero cross timing of the back electromotive force voltage, and this is used as the base point of the commutation timing, so that the rotational drive control is performed. However, at the time of start-up and low rotation when the back electromotive force is not sufficiently generated and the voltage level is low, the zero cross timing cannot be detected due to variations in the back electromotive force voltage and the midpoint voltage, or the phase is Therefore, it is difficult to control in synchronization with the rotational phase of the rotor, and phase asynchronous control (for example, forced driving) must be continuously performed until the zero cross timing can be detected.

  The present invention has been made paying attention to the above-mentioned problem. When the motor is started, the motor rotation drive control can be started with good response, and the asynchronous noise continues, abnormal noise, rotational step-out, stop, overload. It is an object of the present invention to provide a motor control device that can avoid or reduce current and the like.

In order to achieve the above object, the motor control device of the present invention comprises a sensorless brushless motor, a control circuit, a drive transistor circuit, and a counter electromotive force detection circuit, and is generated in each phase coil of the sensorless brushless motor. Motor rotation position information is acquired based on the detection of the voltage zero cross of the back electromotive force, and rotation drive control is performed by commutation control to each phase coil using the motor rotation position information.
In this motor control device, a comparison reference potential circuit that generates a comparison reference potential of the back electromotive force detection circuit and a motor phase coil bias circuit that supplies the comparison reference potential to each phase coil of the sensorless brushless motor are provided. ,
The control circuit performs closed-loop control that repeats all-phase open and set duty drive to open all the phase coils when the motor is started, and the counter-electromotive force and the comparison reference potential voltage zero-cross during all-phase open Based on the detection, the sensorless brushless motor performs a rotation state detection as to whether the sensorless brushless motor is in a normal rotation, stop, or reverse rotation, and the sensorless brushless motor becomes a normal rotation according to a determination result by the rotation state detection. Motor start control means for shifting to commutation control by phase is provided.

For example, when starting a motor with a conventional motor control device, voltage zero cross cannot be detected from an extremely low rotational speed, so positioning driving is first performed to determine a stop phase (several seconds until the motor stops) After that, control (forced drive) that is asynchronous with the rotation phase is continued from that phase until a high rotation state where voltage zero-crossing detection is possible. Transition to flow control.
On the other hand, the present invention has a comparison reference potential circuit and a motor phase coil bias circuit, and has a circuit configuration capable of detecting a voltage zero cross from an extremely low rotational speed when all phases are open. Closed loop control that repeats open and set duty drive is performed, and while all phases are open, by detecting the motor rotation state based on voltage zero cross detection from extremely low rotation speed, even if it does not assume normal rotation, Control capable of shifting to commutation control by a phase that becomes forward rotation is provided. In other words, closed loop control is possible from the time of motor startup, and motor startup control is employed in which positioning drive and forced drive are omitted.
For this reason, unlike the conventional example, it is not necessary to continue the asynchronous control from the start of the motor to the high rotation state where the voltage zero cross detection can be performed, and the asynchronous control by the positioning drive or the forced drive is continued. Abnormal noise, rotational step-out, stop, overcurrent, etc. can be avoided or reduced.
Furthermore, the time required for positioning drive and the time required for forced drive that are spent from the start of motor startup are omitted, and if the commutation phase and commutation timing are determined during closed-loop control, the motor rotation by phase synchronization is responsive. Drive control can be started.
As a result, motor rotation drive control can be started with good response when the motor is started, and abnormal noise, rotational step-out, stop, overcurrent, and the like due to continuing asynchronous control can be avoided or reduced.

1 is an overall circuit configuration diagram showing a motor control device A1 of Example 1. FIG. 3 is a flowchart showing a flow of a motor start control process from a non-energization stop executed by a control circuit 2 of the first embodiment. It is a figure which shows an example of the circuit structure in the motor control apparatus of the comparative example which performs motor control by the BEMF zero cross detection of a comparative example. It is a figure which shows the drive waveform by the BEMF detection at the time of starting and low rotation in the circuit structure of the motor control apparatus of a comparative example. It is a figure which shows the voltage waveform which appears in the connection point (BEMF voltage input to a BEMF detection circuit) of drive TR circuit and a phase coil at the time of closed-loop control in the motor control apparatus of Example 1. FIG. It is a figure which shows the drive waveform by the BEMF detection at the time of starting and low rotation in the circuit structure of the motor control apparatus of Example 1. It is a figure which shows the BEMF voltage waveform with respect to the electrical angle which appears in each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 rotated at the time of the rotation state detection in the motor control apparatus of Example 1. FIG. 4 is a timing chart illustrating a measurement example for every electrical angle of 60 ° to 360 ° as time measurement between BEMF zero crosses according to the first embodiment. 6 is a timing chart showing the state of a driving TR circuit and the characteristics of a BEMF detection signal when the motor control device of Example 1 is rotated forward by a start output when the motor is started from a non-energized stop. 5 is a timing chart showing the state of the drive TR circuit and the characteristics of the BEMF detection signal when the motor control device of Example 1 has the same stop phase and start phase when the motor is started from the non-energized stop and is stopped by rotation start control. The motor control device of the first embodiment shows the state of the drive TR circuit and the characteristics of the BEMF detection signal when the stop phase and the start phase are in a reverse rotation relationship when the motor is started from the non-energized stop and reverse rotation is performed by the rotation start control. It is a timing chart. 6 is a flowchart illustrating a flow of a motor start control process from a non-energized stop executed by a control circuit 2 according to the second embodiment. The motor control device of the second embodiment shows the state of the drive TR circuit and the characteristics of the BEMF detection signal when the stop phase and the start phase are in a reverse rotation relationship when the motor is started from the non-energized stop and reverse rotation is performed by the rotation start control. It is a timing chart. 12 is a flowchart illustrating a flow of a motor start control process from a non-energized rotation state that is executed by the control circuit 2 of the third embodiment. 10 is a flowchart illustrating a flow of a motor rotation return control process that is started when a rotation control interruption condition is executed in a control circuit 2 according to a fourth embodiment. In Example 4, when rotation control is stopped to protect the motor and the circuit due to overvoltage, overcurrent, etc. during rotation of the motor capable of detecting BEMF zero crossing, rotation return is resumed (continuation) while the motor is still rotating. It is a timing chart which shows an example of control. FIG. 10 is a timing chart showing an example of rotation return control for returning (continuing) rotation control in the motor rotation state when stepping out in an unexpected state during rotation of the motor capable of detecting BEMF zero cross in the fourth embodiment. FIG. 10 is an overall circuit configuration diagram illustrating a motor control device A2 according to a fifth embodiment. 10 is a flowchart illustrating a flow of a motor rotation return control process that is started when a rotation control interruption condition is executed, which is executed by a control circuit 2 according to a fifth embodiment. FIG. 10 is a timing chart when failure diagnosis is performed in a period in which all phases are opened due to the establishment of a rotation control interruption condition in the fifth embodiment. Example of diagnosis waveform (a) at normal time, diagnosis waveform (b) at the time of drive TR leak failure, and diagnosis waveform (c) at the time of coil short-circuit failure in the failure diagnosis performed for two cycles at each phase electrical angle of Example 5 It is a timing chart which shows. It is a whole circuit block diagram which shows the motor control apparatus by circuit examples other than motor control apparatus A1 of Examples 1-4. FIG. 10 is a circuit configuration diagram illustrating an example of a diagnostic reference voltage offset circuit other than the motor control device A2 according to the fifth embodiment.

  Hereinafter, the best mode for realizing a motor control device of the present invention will be described based on Examples 1 to 5 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall circuit configuration diagram illustrating a motor control device A1 according to the first embodiment. The apparatus configuration will be described below with reference to FIG.

  As shown in FIG. 1, the motor control device A1 according to the first embodiment includes a control circuit 2, a drive TR circuit 3 (drive transistor circuit), a BEMF detection circuit 4 (back electromotive force detection circuit), a sensorless brushless motor 5, , A motor phase coil bias circuit 6, a comparison reference potential circuit 7, and a rotation speed instruction input 8. Note that “BEMF (abbreviation of Back Electromotive Force)” means back electromotive force, and “BEMF” used in the following description represents a voltage (= generated voltage) due to the back electromotive force generated in the coil.

  The control circuit 2 is a motor control circuit that performs start control, rotation drive control, stop control, rotation return control, and the like of the sensorless brushless motor 5, and includes, for example, a dedicated control IC (ASIC), a microcomputer, and the like. The control circuit 2 inputs a rotational speed instruction input 8 to the sensorless brushless motor 5 from an external unit, a sensor, etc. (not shown), and also receives a BEMF voltage zero cross signal (hereinafter referred to as a zero cross signal) from the BEMF detection circuit 4. Then, based on the input information, control calculation is performed, and a PWM duty control signal (hereinafter referred to as PWM signal) is output to the drive TR circuit 3. The power supply for the control circuit and the signal I / F (interface) are not shown.

  The driving TR circuit 3 includes an upper side switching element (Qu1, Qv1, Qw1) and a lower side switching element (Qu2, Qv2, Qw2) corresponding to each of three phases (U phase, V phase, and W phase). This is an inverter circuit that constitutes a bridge circuit and functions as an inverter. The switch element control signals (base input and gate input) are PWM signals from the control circuit 2. Here, the circuit for driving the base or gate of the switch element is not shown. For example, the U-phase circuit will be described. The switch elements Qu1 and Qu2 are arranged between the power supply voltage Vbat and the ground, and the middle thereof is connected to the U-phase coil 5u of the sensorless brushless motor 5. The V-phase circuit and the W-phase circuit are configured similarly.

  The BEMF detection circuit 4 is a circuit for detecting a zero crossing of BEMF generated in each phase coil 5u, 5v, 5w, and voltage comparators OP1-OP3 provided corresponding to each phase coil 5u, 5v, 5w, and Resistors R1 to R3 are provided. In other words, the positive input terminals of the voltage comparators OP1 to OP3 are connected to the resistors R1 to R0 so as to detect the back electromotive force voltages at the connection points 50u, 50v and 50w between the phase coils 5u, 5v and 5w and the driving TR circuit 3. Input via R3. Further, the reference voltage from the comparison reference potential circuit 7 is input to the negative input terminals of the voltage comparators OP1 to OP3. Then, in the voltage comparators OP1 to OP3, the reference voltage is compared with the BEMF from each phase coil 5u, 5v, 5w, and the comparison result is output to the control circuit 2 as a zero cross signal.

  The sensorless brushless motor 5 is a three-phase motor that is applied as a fan motor of an air conditioner unit for a vehicle and in which a U-phase coil 5u, a V-phase coil 5v, and a W-phase coil 5w are star-connected. The sensorless brushless motor 5 is a brushless motor that does not use a brush in which a permanent magnet is embedded in a rotor and a coil is wound around a stator, and does not have a Hall element for detecting a rotational position. The coil itself is used as a rotational position detection sensor, and the BEMF zero cross generated in each phase coil 5u, 5v, 5w is detected to obtain rotational position information (rotor position information).

  The motor phase coil bias circuit 6 previously adds the comparison reference potential of the BEMF detection circuit 4 to the input, turns off all the switch elements of the drive TR circuit 3, and opens all the phase coils 5u, 5v, 5w. This is a circuit for biasing the BEMF zero-cross potential (midpoint potential) generated in each phase coil 5u, 5v, 5w to the comparison reference potential when it is set to (floating), and includes resistors R4 to R6. One of the resistors R4 to R6 is connected to each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 and connection points 50u, 50v, 50w of the drive TR circuit 3, respectively. The other is connected to the output of the voltage booster OP4 (op-amp) of the comparison reference potential circuit 7 together.

  In the comparison reference potential circuit 7, the drive voltage waveform including noise at the time of driving the motor phase coil wraps around through the resistances R 4 to R 6 of the motor phase coil bias circuit 6 to change the reference potential of the BEMF detection circuit 4 to detect BEMF. This is a voltage follower circuit that outputs a reference voltage so that the circuit 4 does not detect errors, and includes a voltage amplifier OP4 and resistors R7 and R8. The voltage amplifier OP4 has a positive input terminal connected between the resistors R7 and R8 so that the divided voltage values of the resistors R7 and R8 are input. The negative terminal of the voltage amplifier OP4 inputs an output and serves as a negative feedback path. Further, the output of the voltage amplifier OP4 is connected to the negative input terminals of the voltage comparators OP1 to OP3 of the motor phase coil bias circuit 6 and the BEMF detection circuit 4. The resistors R7 and R8 are provided in series between the power supply voltage Vbat and the ground. In this example, the resistors R7 and R8 have the same value, and the divided values (connection points) of the resistors R7 and R8 are set to the midpoint potential (1/2 Vbat).

  FIG. 2 is a flowchart showing the flow of the motor start control process from the deenergization stop executed by the control circuit 2 of the first embodiment (motor start control means). Hereinafter, each step of FIG. 2 will be described.

  In step S101, when starting the motor from the non-energized stop, the motor phase coil at an arbitrary phase regardless of the motor stop position phase due to the minimum required time and low duty according to the motor inertia mass and load of the sensorless brushless motor 5. , And performs (loop) start-up open loop control, and proceeds to step S102.

  In step S102, following the rotation start in step S101, the motor rotation state of the sensorless brushless motor 5 is detected. That is, all-phase open control is performed to open all the phase coils 5u, 5v, 5w of the sensorless brushless motor 5, and based on the back electromotive force voltage and the comparison reference potential zero-cross signal during all-phase open, The commutation phase and commutation timing are monitored, and when all of the rotation phase, commutation phase, and commutation timing are determined (step S102a), the motor rotation direction of the next sensorless brushless motor 5 is determined (step S102b). . If the determination result is the normal rotation state based on the determination of the motor rotation direction, the process proceeds to step S103. If the determination result is the reverse rotation state, the process proceeds to step S106. If the determination result is the stop state, the process proceeds to step S107.

  In step S103, following the determination of the normal rotation state in step S102 or the determination of the presence of zero cross detection in step S105, commutation control to each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 is performed. Then, rotational drive control for normal rotation of the sensorless brushless motor 5 is performed, and the process proceeds to step S104.

  In step S104, following the forward rotational commutation in step S103, the commutation phase and commutation timing are determined based on the BEMF zero cross detection, and the process proceeds to step S105.

  In step S105, following the BEMF zero-cross detection in step S104, the presence / absence of BEMF zero-cross detection is determined. If it is determined that the BEMF zero-cross detection is present, the process returns to step S103. .

  In step S106, following the determination of the reverse rotation state in step S102, for each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 in the reverse rotation state, the rotation direction correction by the phase that becomes the normal rotation is performed. The flow control is performed, the rotation is restarted for a predetermined time without going through the motor stop, and the process returns to step S102.

  In step S107, following the determination that the vehicle is in the stopped state in step S102, it is determined whether or not the number of stop determinations (the number of times the phase has been advanced) is equal to or greater than a preset number of times N. When it is determined that the number of times of phase advance) <N, the process proceeds to step S108, and when it is determined that the number of stop determinations (number of times of phase advance) ≧ N, the process proceeds to step S109.

  In step S108, following the determination in step S107 that the number of stop determinations is smaller than N, commutation control that advances the phase in the forward rotation direction for each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 in the stopped state. , The rotation is restarted for a predetermined time, and the process returns to step S102.

  In step S109, following the determination that the number of stop determinations in step S107 is greater than or equal to N, it is determined that a motor lock failure has occurred, and the process proceeds to a fail-safe operation due to motor energization stop.

Next, the operation will be described.
First, the “problem of motor start control in the comparative example” will be described, and subsequently, the operation in the motor control device of the first embodiment will be described as “motor control operation by zero cross signal”, “time measurement operation between BEMF zero crosses”, “Characteristics of motor start control of embodiment 1”, “motor start control action when rotating forward by start output”, “motor start control action when stopped by rotation start control”, “motor lock determination control action”, The description will be divided into “motor activation control action when the motor rotates in reverse by the activation output”.

[Problems of motor start control in comparative example]
In motor rotation drive control by 120 ° etc. energization control by BEMF zero cross detection, which is generally known for sensorless brushless motors, BEMF zero cross detection compares BEMF voltage with reference to neutral point voltage, and zero cross point The zero crossing point is used as a reference for the electrical angle (rotor position) to perform accurate commutation. However, since the BEMF voltage is small at low speeds including rotation start-up, the zero-cross detection requires that the BEMF waveform center voltage (= zero-cross voltage) matches the BEMF detection circuit voltage (comparison reference voltage). It becomes important.

In a star connection motor, if the potential (neutral point voltage) generated at the star connection point (neutral point) is used as a comparison reference voltage, it has good consistency and can be detected from a low rotational speed. When the neutral point voltage cannot be used on the motor connection for simplification of the output line, etc., and in the delta connection motor, the voltage corresponding to the neutral point voltage (pseudo neutral point voltage) is mainly obtained by the following method. Generated and used as a reference voltage for comparison.
1) A method for generating a circuit configuration using a signal from a line connecting each phase coil and a driving TR circuit,
2) A method using half the motor drive voltage,
There is. The pseudo-neutral point voltage (hereinafter referred to as the midpoint voltage) by these methods does not have good agreement between the center voltage of the BEMF waveform and the comparison reference voltage, and has a large error. There is a problem that BEMF zero cross cannot be detected.

For this reason, for example, the control at the time of start-up of the sensorless brushless motor is performed at a predetermined phase at the beginning of start-up in order to determine the position of the motor phase coil first as disclosed in JP-A-1-308192. It is energized for a predetermined time until the position of becomes stable.
After that, open-loop control (phase asynchronous: forced drive) is performed to repeat the commutation with a predetermined phase and frequency change and reach a predetermined rotation speed regardless of the motor rotation phase at a fixed drive duty, and then BEMF zero cross Closed loop control synchronized with the detected motor rotation position is implemented.

As described above, since the open loop control by the phase asynchronous forced driving is performed at the time of starting the motor, the synchronized closed loop control is performed.
(a) It takes time to start the motor.
(b) Since the motor lock at the start of the motor cannot be detected at an early stage, an overcurrent occurs when the motor is locked, and the circuit element may be damaged in some cases.
(c) Since open loop control is performed when the motor is started, the drive phase does not match the rotation phase, abnormal noise, large start-up overcurrent, and step out in some cases.

  FIG. 3 is a diagram illustrating an example of a circuit configuration in a motor control device of a comparative example that performs motor control based on BEMF zero cross detection. FIG. 4 is a diagram showing drive waveforms based on BEMF detection at the time of start-up and low rotation in the circuit configuration of the motor control device of the comparative example shown in FIG. Hereinafter, the reason why the BEMF zero cross cannot be detected at a low rotational speed including motor rotation start will be described with reference to FIGS. 3 and 4.

Since the generated BEMF voltage is low when the sensorless brushless motor is started up or at a low rotation speed, it is difficult to detect the BEMF zero-cross timing by the BEMF detection circuit due to the following factors.
First, there is an error in the connection potential between the phase coils due to variations in the resistance (impedance) of each phase coil. Second, there is an error in the reference voltage due to the component accuracy of the reference voltage generation circuit that creates the reference voltage for BEMF zero cross timing detection of the BEMF detection circuit. The first and second factors are on the order of V (volts) and are particularly dominant.

The error due to the first and second factors is indicated by ΔV in FIG. During high rotation control, a BEMF voltage exceeding the error ΔV is obtained, and the BEMF zero cross timing can be detected by the BEMF detection circuit (see FIG. 5). However, as shown in FIG. 4, the BEMF voltage does not exceed the error ΔV during start-up / low speed control, and therefore the zero cross timing cannot be detected reliably.
As the third error, there are detection errors due to the BEMF detection circuit component accuracy, the offset of the comparator, the leak, etc., but it is on the order of mV (millivolt) and is not dominant.

  For this reason, the open-loop control by the phase asynchronous forced driving is performed as described above until the rotational speed at which the BEMF voltage becomes a detectable voltage. When the motor is started with this open loop control, the phase of the control electrical angle does not match the actual motor rotation phase. As a result, the sound during driving increases, the acceleration time is also determined by the relationship of the inertial mass of the rotating body (rotor), and there is a problem that acceleration in a short time is limited.

  Also, in order to ensure the start of rotation at the start of rotation and the required number of rotations, the phase before driving (positional relationship between the stopped magnet and the rotor) is confirmed, and the driving phase at the start of rotation is correct. It is necessary to make the torque optimal (large) in the rolling direction. As a method for this, a method of driving at a predetermined phase before starting rotation, or a method of applying a driving pulse that does not rotate the rotor and detecting the phase before driving from the response waveform (Japanese Patent Laid-Open No. 2007-28869). Publication) is known. However, the former method has a problem that it takes time to stop the rotor and takes a long time to start, and the latter method requires a circuit and a control for this processing, and there is a problem that the cost is high. .

  Furthermore, when there is a possibility that the motor has already been rotated at the time of starting rotation, it is necessary to detect the rotation state of the motor in a non-energized state before starting rotation. As a method for this, Japanese Patent Application Laid-Open No. 2007-166695 discloses detection of BEMF in a non-energized state and control according to the state of motor rotation, and rotation continues in a closed loop during normal rotation. When the motor is reversed, stop control of the brake or the like is performed. After positioning to the predetermined phase, rotation is started. However, there is a problem that the brake is stopped during reversal, and a brake sound is generated during high-speed rotation.

[Motor control action by zero cross signal]
On the other hand, in the first embodiment, when the rotation of the sensorless brushless motor 5 is controlled, all the phases of the phase coils 5u, 5v, 5w of the sensorless brushless motor 5 are opened (driving element OFF), and the phase coils 5u, 5v, 5w drive timing is repeated in a predetermined relationship, and a circuit (motor phase coil bias circuit 6) that can bias each phase coil 5u, 5v, 5w with the comparison reference potential of the BEMF detection circuit 4 is inserted, By making each phase coil 5u, 5v, 5w biased to the comparison reference potential when the phase coil is open, BEMF is superimposed on the comparison reference potential, and even if the BEMF voltage waveform is a minute voltage The BEMF detection circuit 4 has a circuit configuration and control capable of detecting a BEMF voltage zero cross.

  Here, in the rotation state detection operation, the upper side and lower side TRs constituting the bridge TR circuit of each phase of the drive TR circuit 3 are turned OFF, and the phase coils 5u, 5v, 5w are driven by the drive TR circuit 3. In this state, each phase coil 5u, 5v, 5w can be biased by the potential applied through the motor phase coil bias circuit 6, that is, the comparison reference potential of the BEMF detection circuit 4. As a result, the BEMF voltage generated in each phase coil 5u, 5v, 5w is generated with the comparison reference potential of the BEMF detection circuit 4 as the midpoint (center) potential. Can be detected.

  The control according to the first embodiment is performed when BEMF voltage generation is small at the time of motor start-up or low rotation, and BEMF cannot be detected. For example, at the time of motor start from deenergized stop, BEMF voltage zero cross can be detected after applying a short rotation start pulse, and based on the detected phase change, the rotation state of forward rotation, reverse rotation, stop is judged, By performing commutation control so as to rotate forward from the determined phase, closed loop control can be performed from the start of startup, and steps out, stop, overcurrent, abnormal noise, Improved the rise time length. Hereinafter, the motor control action by the zero cross signal will be described with reference to FIGS.

  FIG. 5 is a diagram illustrating a voltage waveform appearing at a connection point (BEMF voltage input to the BEMF detection circuit) between the drive TR circuit and the phase coil during closed-loop control in the motor control device of the first embodiment. In FIG. 5, one cycle of control is in the order of time TbF → time TdH → time TbB → time TdL. For example, the electrical angles at 120 ° energization control timing are 60 °, 120 °, 60 °, and 120 °, respectively. One period is composed of a total of 360 ° electrical angles.

Time TbF and time TbB are periods in which BEMF is detected, and are driving off periods of the driving TR circuit 3 corresponding to the detection phase coils. Time TbF is the detection period on the rising side of BEMF, and time TbB is the detection period on the falling side.
During the period of time TbF and time TbB, there is an intersection between the BEMF voltage waveform shown by a bold line in FIG. 5 and the midpoint potential, that is, detection of BEMF zero cross timing (position Z in FIG. 5). Take (for example, 30 degrees in electrical angle) and commutate. When rising is detected, drive control on the high side (upper side) of the drive TR circuit 3 is performed, and when falling is detected, drive control on the low side (lower side) of the drive TR circuit 3 is performed. Times TdH and TdL represent high side and low side TR drive control periods due to commutation, respectively.

  In the BEMF detection at this time, the driving TR circuit 3 of the phase coil of the detection phase is not in the driving state but is opened. However, since the other-phase coil is in the drive state, the BEMF potential is generated by dividing the voltage of the other-phase drive voltage by the phase coil resistance component as the midpoint voltage. For example, if the coil resistance is the same, 1/2 drive voltage = 1/2 Vbat. The midpoint potential corresponds to the voltage comparison reference voltage (reference voltage) generated by the comparison reference potential circuit 7 in the BEMF detection circuit 4.

  In other words, explain. For example, when 120 ° drive control is performed, the BEMF detection circuit 4 detects the BEMF of each phase and detects the zero cross point of the BEMF phase for each phase, thereby driving the stator coil of each phase, that is, commutation. Control timing.

  The drive of each phase coil at the commutation timing is driven by the half bridge circuit of the drive TR circuit 3 functioning as an inverter, and the voltage applied to the coil by PWM control at the time of driving is controlled, so that the sensorless brushless motor 5 is driven. To control the rotation speed.

  Zero cross detection by BEMF is performed by a voltage change appearing at a bridge point of a bridge circuit in an OFF state by a half bridge. In the first embodiment, the BEMF zero-crossing detection point in the three-phase sensorless brushless motor 5 by star connection, that is, the bridge point of the bridge circuit at the off timing of the half bridge, is approximately 1 / of the power supply voltage applied to the coil. Since BEMF is superimposed on the basis of the potential of 2, the potential of about 1/2 of the power supply voltage is set to zero, and detecting the timing at which the BEMF voltage on which the reference potential is superimposed crosses is defined as zero crossing. That is, the threshold for detecting zero crossing with BEMF is a half potential of the power supply voltage.

  Furthermore, in other words, for example, when the sensorless brushless motor 5 is PWM-driven, it is assumed that the switch elements Qu1 and Qv2 are on and the others are off. Then, a current flows from the power supply voltage Vbat through the switch element Qu1, through the U-phase coil 1u and the V-phase coil 1v of the sensorless brushless motor 5, and through the current path from the switch element Qv2 to the ground.

  At this time, the bridge point of the switch elements Qw1 and Qw2 for driving the W-phase coil 1W can be said to be a state where the coil 5w detects the midpoint connection voltage of the coils 5u and 5v. As described above, a voltage waveform in which the BEMF voltage generated in each phase coil 5u, 5v, 5w is superimposed is observed as the voltage at the bridge point in the off state, as described above. If the voltage at this bridge point is compared with the reference voltage, a zero cross signal is obtained. In the first embodiment, a zero-cross signal is input to the control circuit 2, and the sensorless brushless motor 5 is driven and controlled by obtaining commutation timing.

In the first embodiment, a motor phase coil bias circuit 6 that supplies a reference voltage for BEMF zero cross timing detection of the BEMF detection circuit 4 to the phase coil is provided.
In terms of control, all phase coils are driven off and all phases are open (the BEMF midpoint potential generated in each phase coil 5u, 5v, 5w is floating) and the drive of each phase coil 5u, 5v, 5w Closed loop control is performed in which the rotation state is detected alternately at the timing of all-phase open.

  In the rotation state detection control, each phase coil 5u, 5v, 5w is turned off to make the connection point potential between the phase coils floating, and the motor phase coil bias circuit 6 sets the phase coil potential of the BEMF detection circuit 4 to the floating state detection control. Bias to reference voltage for BEMF zero cross detection. Thereby, the midpoint potential of the BEMF generated in the detection phase coil can be used as the reference voltage for the BEMF zero cross detection of the BEMF detection circuit 4, and the error of the zero cross deviation when the BEMF is low is relatively canceled. Therefore, highly accurate BEMF voltage zero cross detection is possible.

  More specifically, when the sensorless brushless motor 5 is in an all-phase open state at a low rotation speed, the BEMF voltage waveform output from the phase coil is the comparison reference voltage biased by the motor phase coil bias circuit 6 as shown in FIG. The waveform is centered. That is, the BEMF voltage waveform has a small amplitude and a small error ΔV ′. However, the BEMF voltage waveform has a waveform centered on the reference potential biased by the motor phase coil bias circuit 6, that is, the midpoint potential of the BEMF. The detection circuit 4 can detect a BEMF voltage zero cross (hereinafter, BEMF zero cross).

  Here, the BEMF voltage waveform by the motor phase coil bias circuit 6 of the motor control device A1 of the first embodiment will be described. FIG. 7 is a diagram illustrating a BEMF voltage waveform with respect to an electrical angle that appears in the phase coils 5u, 5v, and 5w of the sensorless brushless motor 5 that rotates when the rotational state is detected in the motor control device of the first embodiment.

  In the first embodiment, the sensorless brushless motor 5 is star-connected, whereas the motor phase coil bias circuit 6 is connected to each phase coil 5u, 5v, 5w at connection positions 50u, 50v, 50w. And it is biased from three points through the resistors R4 to R6. At this time, it is assumed that the drive signal is off and the rotor of the sensorless brushless motor 5 rotates at an extremely low rotational speed. As shown in the waveform characteristic lines 100u, 100v, and 100w in FIG. 7, the BEMF voltage waveform obtained in this state obtains a voltage waveform equivalent to the BEMF voltage waveform detected by a coil that is not used for driving at high speeds. Can do.

[Time measurement action between BEMF zero crossings]
The motor rotation (startup) control is based on the phase detected immediately after starting the rotation start phase and the rotation state detection control, or the phase relationship sandwiching one BEMF zero cross detection and at least two consecutive BEMF zero cross detections. In this control, the rotational direction, the electrical angle, the commutation control phase, and the commutation timing are determined based on the time measurement value between them and the final zero cross position (timing).

As the time measurement between the BEMF zero crosses, for example, as shown in FIG.
1) One cycle of in-phase (Between rising and falling BEMF = electrical angle every 360 °)
2) Half cycle (Between rising and falling BEMF or vice versa = every 180 ° electrical angle)
3) Between the rise and fall of BEMF between phases (= Electrical angle every 120 °)
4) Between the rise and fall of BEMF across the phase or vice versa (= Electrical angle every 60 °)
There are measurement methods.
In the first embodiment, the measurement is performed between the falling edge and the rising edge of the BEMF over the phase 4) because the time required for the measurement is short. In addition, regarding the time measurement between BEMF zero crosses, the measurement for each electrical angle of 60 ° is similarly adopted in Examples 2 to 5.

Hereinafter, the time measurement operation between the BEMF zero crosses according to the first embodiment will be described with reference to the timing chart of FIG.
A time T1 between a BEMF zero cross (falling) detected from the U-phase coil 5u at phase D and a BEMF zero cross (rising) detected from the W-phase coil 5w at phase E is measured. In this measurement, since the motor rotation state data at the time T1 per 60 ° electrical angle is obtained, the control performs motor phase coil drive (commutation), which is the next control of the rotation state detection control.
Since the motor phase coil drive of the first embodiment is a known 120 ° energization control, the commutation control is performed to the phase F after an electrical angle of 30 °, that is, T1 / 2 = t1 from the zero cross detection timing of the W phase coil 5w. Next, commutation control is performed in phase A.

  The control phase F is the phase where the U phase is the low side TR / ON and the W phase is the high side TR / ON. The control phase A is the phase where the V phase is the low side TR / ON and the W phase is the high side TR / ON. Therefore, the phase coil energization PWM / Duty at the time of commutation control is set higher (longer energization time) than the energization PWM / Duty at the time of startup to drive the phase coil. The control phases F and A are energized for T1 time (electrical angle 60 °), respectively. However, when the PWM / Duty is set high and the acceleration rate is predetermined (known), T1 is applied at a predetermined ratio. It is also possible to set the time short.

[Characteristics of motor start control of embodiment 1]
In view of the problems of the comparative example, the present invention is a sensorless brushless motor that performs rotation control with BEMF zero-cross detection, and even when at least a neutral point voltage cannot be used as a comparison reference voltage, it is extremely low including rotation start-up with a simple circuit configuration. BEM phase and zero-crossing detection from rotation speed is possible. In other words, regardless of the phase (rotor position) state including the stop when the motor is not energized, the rotation start control (closed loop control) synchronized with the rotation phase based on the BEMF zero cross detection from the extremely low rotation speed (for example, 30 rpm or less) The motor rotation start response is quick and quiet, and it is possible to use a cheap circuit and control method.

  In Example 1, when the sensorless brushless motor 5 is rotated and started from a non-energized stopped state, initial energization is performed for a short time (time when the motor starts to rotate) at an arbitrary phase, and immediately after that, a rotation state detection is provided. The motor phase (rotor position) is detected from the low speed. Then, based on the rotation start phase, the state of forward rotation (FIG. 9), stop (FIG. 10), and reverse rotation (FIG. 11) is determined from the phase relationship detected by the rotation state detection, and processing according to the determination The commutation is controlled to the phase after control (the corresponding phase coil is energized and switched), and during the commutation control, when phase commutation by the zero cross detection of the BEMF cannot be performed, the rotation state detection and the commutation control are repeated.

  In this way, the motor drive synchronized with the motor rotation phase (electrical angle position) is enabled by the closed-loop control from the start-up regardless of the motor de-energization phase. The sensorless brushless motor 5 can be activated without any problems.

  Further, there is no need to perform position determination control of the motor de-energization stop phase at the time of starting, and control is started from phase coil driving for rotation starting, and closed loop control is performed. For this reason, since the drive phase is synchronized with the rotational phase of the motor, it is possible to increase the motor drive current (increase the drive duty) from the time of startup, and to realize motor startup with a quick response time. .

  In addition, when the rotation state detection control at the time of rotation start is continuously detected any number of times, the motor lock is reliably detected and the energization release control is performed to prevent overcurrent at the time of motor lock and fail. Safe operation can be realized (FIG. 2).

  In the specific examples shown in FIGS. 9 to 11, energization of the motor phase coil in the rotation start phase is driven by the minimum necessary PWM / Duty and time according to the motor inertia mass and the load, In FIG. 11, when the rotation direction is detected in the rotation state immediately after the start of rotation and the rotation direction is the reverse rotation state, the drive for making the rotation direction forward is performed in the next control. Easy to do.

FIGS. 9 to 11 are timing charts showing specific examples of control in the first embodiment.
The top of FIGS. 9 to 11 shows the “motor phase position”. The electrical angle position obtained by dividing the electrical angle 360 ° with the zero-cross position where the U-phase BEMF rises as 0 ° is divided every 60 ° ( °) is represented by a numerical value, and the drive control position (phase) of each phase coil is represented by AF.

  Below that, the “state of the driving TR circuit” corresponding to each phase coil control phase is shown, and the OFF line of the driving TR is set to the zero cross potential (at the time of rotation state detection control, the comparison reference of the BEMF detection circuit), overlapping that timing. In other cases, the BEMF voltage waveform generated in each phase coil corresponding to each phase timing is indicated by a broken line as neutral point potential by the motor phase coil = BEMF midpoint potential). Note that the zero cross point of the BEMF voltage waveform is indicated by ◯, the control detection points are indicated by ◯ and Z symbols, and the period between zero crosses is indicated by T1 to T8.

  Below that, the “control phase” is shown together with the control contents. Each phase and control contents will be described. "Phase I" is a phase indicating a motor stop state, and is a state where no current is supplied to each phase coil. “Phase II” is a phase in which a predetermined phase coil that is arbitrarily determined is energized to start rotation. The ON / OFF state of the drive TR circuit 3 in accordance with the phase of the energized phase coil is shown. “Phase III” is a phase for performing closed loop control by BEMF detection that alternately repeats all-phase open (rotation state detection) and set duty drive (motor phase coil drive). “Phase IV” is a phase in which 120 ° energization control is performed in which the set duty is driven in the phase matching state.

  Below that, “BEMF detection signals” for U phase, V phase, and W phase are shown, and the BEMF zero cross detection state of each phase after filtering processing in the control circuit 2 to which the zero cross signal from the BEMF detection circuit 4 is input. Is shown by a solid line, and a broken line shows an undefined state. The filtering process includes removal of a noise pulse caused by a PWM signal or the like and a waveform generated by a regenerative current after commutation by a digital filter. In the period of the detection indefinite state after the phase inversion by the zero cross detection, the state is maintained in the control circuit until the inversion by the next zero cross detection is detected.

  Hereinafter, a forward rotation start example (FIG. 9), a stop start example (FIG. 10), and a reverse rotation start example (FIG. 11) will be described based on FIG. 2 and FIGS.

[Motor start control action when rotating forward by start output]
At the time of starting the motor from the non-energized stop, in the flowchart of FIG. 2, the process proceeds from step S101 to step S102, and the process proceeds from step S102a to step S102b, which are detailed steps. In step S101, open loop control is performed in which initial rotation is started by a minimum required time corresponding to the motor inertia mass and load of the sensorless brushless motor 5 and low duty driving. In the next step S102a, all-phase open control is performed to open all of the phase coils 5u, 5v, 5w of the sensorless brushless motor 5, and based on the back electromotive force and the reference reference potential zero-cross signal during all-phase open, The rotation phase, the commutation phase, and the commutation timing are monitored, and all of the rotation phase, the commutation phase, and the commutation timing are determined. In the next step S102b, the motor rotation state of the sensorless brushless motor 5 is determined.

  If the result of the motor rotation state is determined to be the normal rotation state, the process proceeds from step S102b to step S103 → step S104 → step S105, and step S103 → step is performed as long as it is determined that BEMF zero cross detection is detected in step S105. The flow from S104 to step S105 is repeated. In step S103, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to each phase coil 5u, 5v, 5w. In step S104, the commutation phase and the commutation timing are determined based on the BEMF zero cross detection.

  FIG. 9 is a timing chart showing the state of the drive TR circuit and the characteristics of the BEMF detection signal when the motor control device A1 according to the first embodiment is rotated forward by the start output when the motor is started from the non-energized stop. Hereinafter, based on FIG. 9, the motor start control operation when the motor rotates forward by the start output will be described.

  The control example of FIG. 9 is a case of normal rotation from the motor stop position phase to the start control phase. The sensorless brushless motor 5 is not energized in each phase coil, and is rotated from “Phase I” which is stopped in phase B. When the phase shifts to “Phase II” of the start-up, the energization phase to the motor phase coil is started in the energization state of the phase C where the U phase is the high side TR / ON and the W phase is the low side TR / ON. The phase drive (energization) time is driven for a predetermined time required for rotation start (start) of, for example, several tens to several hundreds msec according to the drive PWM / Duty.

With the above control, the sensorless brushless motor 5 starts to rotate forward, and BEMF is generated in each phase coil. Therefore, the control shifts to the next “Phase III”.
After “Phase III”, the motor rotation state (motor electrical angle and rotation speed) is determined by the BEMF voltage zero cross detection, and the control phase is determined to perform closed loop control for commutation control.
For this reason, in the first control of “Phase III”, the rotation state detection control for detecting the rotation state of the motor, that is, detecting the BEMF zero cross is performed.

BEMF detection uses BEMF, which has a proportional correlation with the angular velocity of the motor rotor, using a voltage comparator. When the BEMF voltage waveform crosses the midpoint (center) potential of the BEMF voltage waveform, the zero crossing is obtained. Therefore, the minimum BEMF voltage, that is, the minimum number of revolutions that can be detected by the zero crossing is determined by the matching accuracy between the midpoint potential of the BEMF voltage waveform and the comparison reference potential of the voltage comparator.
For this reason, except for the case where the neutral point potential connected to all motor phase coils in the star connection, which is close to the midpoint potential of the BEMF voltage waveform, is used, the comparison reference for the BEMF detection circuit using the pseudo midpoint voltage Voltage. In the control by the BEMF zero-cross detection circuit configuration of the first embodiment, the voltage error is small, and BEMF zero-cross detection can be performed at low revolutions including at the time of startup.

  Thereafter, the rotation state detection control and the motor phase coil drive control described above are repeated to increase the rotation speed of the sensorless brushless motor 5, and as the rotation speed increases, the BEMF voltage generation value increases, and the known BEMF zero crossing is possible. Reach the correct voltage value.

  In the timing chart of FIG. 9, the TMF measurement and the commutation control to the control phase F by t4 are continued, the BEMF voltage value is increased, and the known BEMF zero-cross detection immediately after the commutation to the control phase F is V It is generated by detecting BEMF zero cross from the phase coil, and the rotation state detection control by “Phase III” ends. Therefore, thereafter, the process proceeds to “Phase IV”, which is 120 ° energization control by the known BEMF zero cross detection.

[Motor start control action when stopped by rotation start control]
When the motor is started after deenergization is stopped, the process proceeds from step S101 to step S102a to step S102b in the flowchart of FIG. In step S101, open loop control is performed in which initial rotation is started by a minimum required time corresponding to the motor inertia mass and load of the sensorless brushless motor 5 and low duty driving. In the next step S102a, all-phase open control is performed to open all of the phase coils 5u, 5v, 5w of the sensorless brushless motor 5, and based on the back electromotive force and the reference reference potential zero-cross signal during all-phase open, The rotation phase, the commutation phase, and the commutation timing are monitored, and all of the rotation phase, the commutation phase, and the commutation timing are determined. In the next step S102b, the motor rotation state of the sensorless brushless motor 5 is determined.

  If the result of the determination is that the motor is in a stopped state, the process proceeds from step S102b to step S107. In step S107, the process proceeds to step S108 based on the determination that the number of stop determinations <N. In step S108, the phaseless coils 5u, 5v, 5w of the sensorless brushless motor 5 in the stopped state are shifted to commutation control for advancing the phase in the positive rotation direction, rotation is restarted for a predetermined time, and the process returns to step S102a. . Then, the process proceeds from step S102a to step S102b, and when it is determined in step S102b that it is in the normal rotation state, the process proceeds from step S102b to step S103 → step S104 → step S105, as long as it is determined that there is BEMF zero cross detection in step S105 The flow from step S103 to step S104 to step S105 is repeated. In step S103, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to each phase coil 5u, 5v, 5w.

  FIG. 10 shows the state of the drive TR circuit and the characteristics of the BEMF detection signal when the motor control device A1 of the first embodiment has the same stop phase and start phase when the motor is started from the non-energized stop and is stopped by the rotation start control. It is a timing chart. Hereinafter, based on FIG. 10, the motor activation control action when stopped by the rotation activation control will be described.

  The control example of FIG. 10 is a case where the motor stop position phase is the same as the start control phase, the rotation of the sensorless brushless motor 5 is stopped without rotation, and each phase coil is de-energized. This is a case where the phase shifts from “Phase I” to “Phase II” of rotational activation, and the energization phase to the motor phase coil starts in the energization state of phase C as in the control example of FIG. Therefore, the motor does not start rotating as shown in FIG. 9, and no BEMF voltage is generated.

  When the motor is stopped, the BEMF zero cross cannot be detected even in the rotation state detection control after the rotation is started. Therefore, the motor rotates after a predetermined time (for example, about several tens of milliseconds to several hundreds of milliseconds corresponding to an electrical angle of 60 ° to 120 °). The state detection control is terminated by the in-phase stop determination, and the next control is in-phase start (re-rotation start) control. The predetermined time is, for example, 333 msec {= (30/60) in the case of starting at 30 rpm with 4 poles and 6 excitations (slow speed of 1 rotation 2 seconds) and requiring an electrical angle of 120 ° to detect the rotation state. ) × 2 × (120/360)}.

  In the next in-phase activation (re-rotation activation), the energization control phase for rotation activation is advanced by one phase with respect to the control phase C of the first rotation activation, and commutation control to forward rotation is performed as the control phase D. Migrate to Thereafter, the phase is different, but the control is the same as in FIG. The next drive phase advanced at the same phase can be arbitrarily determined as long as the electrical angle is less than 180 ° from the same phase.

[Motor lock determination control action]
When the motor is started from the non-energized stop, the process proceeds from step S101 to step S102a to step S102b in the flowchart of FIG. 2, and if it is determined that the motor rotation state in step S102b is the stop state, step S102b to step S107 are performed. In step S107, the process proceeds to step S108 based on the determination that the number of stop determinations (number of times the phase has been advanced) <N. In step S108, the phaseless coils 5u, 5v, 5w of the sensorless brushless motor 5 in the stopped state are shifted to commutation control for advancing the phase in the positive rotation direction, rotation is restarted for a predetermined time, and the process returns to step S102a. .

  And even if it progresses to step S102b from step S102a next, if it determines with a stop state in step S102b, it will progress to step S107 from step S102b, and in step S107, the number of times of stop determination (number of times the phase has been advanced) <N Based on the determination that there is, the process returns to step S102a. In this way, the flow of going from step S102a → step S102b → step S107 → step S108 is repeated, and when the number of repetitions is equal to or greater than a predetermined number N, the process proceeds from step S107 to step S109. It is determined that a lock failure has occurred, and a transition is made to a fail-safe operation due to the motor energization stop.

  This motor lock determination control will be described as a continuation of the above stop / start example. Even if restart is performed at the control phase D, stop determination is also performed. In this case, the phase is further advanced by one and restarted at the control phase E. In this way, it is determined that the motor is locked after the control for restarting by advancing the phase based on the stop determination is repeated for a set number of times (N).

  Further, in this control, for example, the cause of motor lock is assumed to be due to an increase in static friction of the bearing, and the drive duty is increased at the same time in order to increase the drive torque in the advance phase after the stop determination. It is also possible. With this control, the drive duty that has begun to rotate is stored in storage means (EEPROM, etc.), and the start-up time is shortened by the control with a learning function that is used at the next start-up (corrected as necessary). be able to.

[Motor start control action when rotating reversely by start output]
When the motor is started from the non-energized stop, the process proceeds from step S101 to step S102a to step S102b in the flowchart of FIG. 2, and if it is determined that the motor rotation state in step S102b is the reverse rotation state, the process proceeds from step S102b to step S102b. Proceeding to S106, in Step S106, the control is shifted to the commutation control for correcting the rotational direction by the phase of the normal rotation for each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 in the reverse rotation state, and the motor is stopped. Instead, the rotation is restarted for a predetermined time, and the process returns to step S102a.

  Then, the process proceeds from step S102a to step S102b, and when it is determined in step S102b that it is in the normal rotation state, the process proceeds from step S102b to step S103 → step S104 → step S105, as long as it is determined that there is BEMF zero cross detection in step S105 The flow from step S103 to step S104 to step S105 is repeated. In step S103, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to each phase coil 5u, 5v, 5w.

  FIG. 11 shows the state of the driving TR circuit and the BEMF detection when the stop phase and the start phase are in a reverse rotation relationship when the motor is started from the non-energized stop in the motor control device A1 of the first embodiment and the reverse rotation is performed by the rotation start control. It is a timing chart which shows the characteristic of a signal. Hereinafter, based on FIG. 11, the motor activation control operation in the case of reverse rotation by the rotation activation control will be described.

  The reverse rotation start control example of FIG. 11 is a case where the motor stop position phase and the start control phase are in a reverse rotation relationship, and the sensorless brushless motor 5 rotates reversely upon rotation start. The phase shifts from “Phase I” in the stopped state to “Phase II” in the rotation start, and the energization phase to the motor phase coil starts in the energization state of the phase C as in the control example of FIG. However, since the energization phase is reversed in the forward rotation direction, the sensorless brushless motor 5 is rotated in the reverse direction, and the BEMF voltage is also generated in the reverse rotation phase.

  For this reason, in the rotational state detection control after the rotation is started, BEMF zero cross detection is performed by detecting BEMF zero cross (rising) detected from the W phase coil at phase B and U phase coil at phase A as shown in the timing chart of FIG. In order to measure the time T1 between the BEMF zero cross detection (falling) detected from 1), it is determined that the reverse rotation state of C.fwdarw.B.fwdarw.A with respect to C.fwdarw.D.fwdarw.E of the forward rotation phase change.

In the rotation state detection control after rotation start, when reverse rotation is detected, rotation restart control is performed to correct the motor rotation direction to forward rotation.
In the rotation restart control, in the first embodiment, the phase A detected last is commutated to a control phase B that becomes a positive rotation phase with respect to the phase A after t1 corresponding to an electrical angle of 30 °.

  In addition, when the rotational speed is high in the detection of the rotational state at the time of start-up (for example, when the motor inertia mass is large) and the time for reversing the rotation is necessary, the commutation to the control phase B is performed. The control circuit 2 may be commutated to the control phase A. The conditions of the commutation phase and the driving duty for smoothly reversing the rotation are set by the load corresponding to the performance of the sensorless brushless motor 5, and the control circuit 2 It may be stored in storage means such as ROM. The subsequent control is the same as the control in FIG. 9 although the phase is different.

  The control in the case of reverse rotation at the time of start-up is for the control to correct the motor rotation direction to the normal rotation based on the rotation direction and the rotation speed by the BEMF zero cross detection in the rotation state detection control as in the case of the normal rotation. The energization phase and timing can be accurately controlled.

Next, the effect will be described.
In the motor control device A1 according to the first embodiment, the effects listed below can be obtained.

(1) A sensorless brushless motor 5, a control circuit 2, a drive transistor circuit (drive TR circuit 3), and a back electromotive force detection circuit (BEMF detection circuit 4), each phase coil of the sensorless brushless motor 5 The motor rotation position information is acquired based on the voltage zero cross detection of the counter electromotive force generated in 5u, 5v, 5w, and the rotation is performed by commutation control to each phase coil 5u, 5v, 5w using the motor rotation position information. In the motor control device A1 that performs drive control, a comparison reference potential circuit 7 that generates a comparison reference potential of the back electromotive force detection circuit (BEMF detection circuit 4), and each phase coil of the sensorless brushless motor 5 A motor phase coil bias circuit 6 for supplying to 5u, 5v, 5w, and the control circuit 2 is configured to open all phases and set all the phase coils 5u, 5v, 5w to open when the motor is started. The sensorless brushless motor 5 is in any of the normal rotation, stop, and reverse rotation based on the back electromotive force and the reference zero voltage detection of the comparison reference potential while all phases are open. There is a motor activation control means (FIG. 2) that executes such rotation state detection and shifts to commutation control based on a phase in which the sensorless brushless motor 5 is rotated forward according to a determination result by rotation state detection.
For this reason, motor rotation drive control can be started with good response when the motor is started, and abnormal noise, rotational step-out, stop, overcurrent, and the like due to continuing asynchronous control can be avoided or reduced.

(2) The motor activation control means (FIG. 2) determines that the sensorless brushless motor 5 does not go through motor stop control when the determination result by the rotation state detection is reverse rotation determination (when reverse rotation is determined in step S102b). Shifts to commutation control for correcting the rotational direction based on the phase in which the rotation becomes normal (step S106).
For this reason, in addition to the effect of (1) above, it is possible to realize motor activation with good responsiveness even in the reverse rotation state in the motor activation start range.

(3) The motor activation control means (FIG. 2) performs a phase advance so as to promote the rotation of the sensorless brushless motor 5 when the determination result by the rotation state detection is a stop determination (when the stop determination is made in Step S102b). Transition to flow control (step S108), and even if the commutation control for urging the motor to restart is executed, if the experience that the determination result is the stop determination is continued, it is determined that the motor is locked (step S107 is stopped) The number of determinations (the number of times the phase has been advanced)> N), and the process proceeds to a fail-safe operation (step S109).
For this reason, in addition to the effects of (1) and (2) above, the stop determination at the rotation state detection executed during the motor start control is used to reliably determine the motor start lock, and promptly go to fail safe operation. Can be migrated.

(4) When the rotational state, commutation phase, and commutation timing are determined (step S102a), the motor start control unit (FIG. 2) detects that the sensorless brushless motor 5 is rotating forward, stopped, It is determined whether the motor is rotating in the reverse rotation state (step S102b).
For this reason, in addition to the effects (1) to (3), it is possible to accurately determine whether the sensorless brushless motor 5 is in the forward rotation, stop, or reverse rotation state.

(5) The motor start control means (FIG. 2) is open for initial rotation start by the minimum necessary time and drive according to the motor inertia mass and load of the sensorless brushless motor 5 at the time of motor start from the deenergized stop. Perform loop control (step S101), start closed loop control that repeats all-phase open and set duty drive following the initial rotation start, and execute rotation state detection during all-phase open in closed loop control (step S101) S102).
For this reason, in addition to the effects (1) to (3) above, the motor start control is completed with good response by starting the motor with the minimum necessary time and initial rotation when the motor is started after de-energization is stopped. The motor rotation drive control by the forward rotation commutation can be started.

  The second embodiment is an example in which the motor rotation state is determined by determining the rotation phase, the commutation phase, and the commutation timing in the first embodiment. On the other hand, the timing for detecting the reverse rotation state is accelerated and the response to the forward rotation This is an example of improving the delay.

First, the configuration will be described.
FIG. 12 is a flowchart showing the flow of the motor start control process from the deenergization stop executed by the control circuit 2 of the second embodiment (motor start control means). Hereinafter, each step of FIG. 12 will be described. Steps S201 and S203 to S209 are steps that perform the same processing as steps S101 and S103 to S109 in FIG.

In step S202, following the rotation start in step S201, the motor rotation state of the sensorless brushless motor 5 is detected. That is, all-phase open control is performed to open all the phase coils 5u, 5v, 5w of the sensorless brushless motor 5, and the rotation phase and rotation are changed based on the back electromotive force and the zero-cross signal of the comparison reference potential during all-phase open. When the flow phase is monitored and the rotational phase / commutation phase is determined (step S202a), the next motorless state of the sensorless brushless motor 5 is determined (step S202b). If the motor rotation state is determined and the determination result is a normal rotation state, the process proceeds to step S202c, the commutation timing is monitored in step S202c, and if the commutation timing is determined, the process proceeds to step S203. If the determination result is the reverse rotation state, the process proceeds from step S202b to step S206, and if the determination result is the stop state, the process proceeds from step S202b to step S207.
Since the entire circuit configuration is the same as that of FIG.

Next, a description will be given of the motor start control operation in the case of reverse rotation by the start output.
When the motor is started from the non-energized stop, the process proceeds from step S201 to step S202a in the flowchart of FIG. 12, and when the rotation phase and the commutation phase are determined in step S202a, the process proceeds to the motor rotation state determination step in step S202b. If it is determined in step S202b that the motor rotation state is the reverse rotation state, the process proceeds from step S202b to step S206. In step S206, each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 in the reverse rotation state is transferred. On the other hand, the process shifts to commutation control for correcting the rotational direction based on the phase of normal rotation, restarts rotation for a predetermined time without going through motor stop control, and returns to step S202a.

  Then, the process proceeds from step S202a to step S202b. When it is determined in step S202b that the rotation is normal, the process proceeds from step S202b to step S202c. When the commutation timing is determined in step S202c, step S203 → step S204 → step S205. As long as it is determined in step S205 that BEMF zero cross detection is present, the flow of steps S203, S204, and S205 is repeated. That is, in step S203, the rotational drive control for rotating the sensorless brushless motor 5 forward is performed by the commutation control to the phase coils 5u, 5v, 5w of the sensorless brushless motor 5.

  For example, depending on the number of magnetic poles, when the rotational speed is very low at the start of rotation, it may take several hundreds of milliseconds until BEMF zero cross detection, and the response may be delayed.

There are the following methods for improving this.
1) Since the phase signal before BEMF zero crossing is fixed, this phase is determined immediately after the start of rotation and immediately after the shift to the rotation state detection, and forward rotation and reverse rotation are determined with respect to the rotation start phase.
2) After starting rotation, shift to rotation state detection, detect the first BEMF zero cross, and judge forward / reverse based on the phase change before and after that.
In the method 1), only the motor phase state immediately after the rotation start can be detected. Therefore, the stop determination is not reliable, but commutation to a phase that makes a positive rotation is possible with respect to the detected phase.
In the method 2), if the time until the BEMF zero cross detection is set as a predetermined time, the stop can be determined when the time is exceeded.
In the case of forward rotation, commutation is performed to the phase that becomes forward rotation, and in the case of reverse rotation, rotation restart is performed to commutate to the phase that becomes forward rotation with respect to the phase detected by the rotation state detection control described above. To do.

  For example, FIG. 13 shows a timing chart when the 2) method is adopted based on the example of FIG. 11 of the first embodiment.

  When the sensorless brushless motor 5 is not energized in each phase coil and is stopped at phase D, the phase shifts from “Phase I” to “Phase II” of rotation start, and the energization phase to the motor phase coil is the same as the control example of FIG. Similarly, when starting in the energized state of phase C, the phase change before and after the first BEMF zero cross detection is changed from phase C to B after shifting to the rotation state detection. Judged as reverse rotation.

  When it is determined that the rotation is reverse, rotation restart is performed on the detected phase B, and the energization phase at that time is any one of B, C, and D advanced by less than 180 ° in the forward rotation direction. Is selected, and the rotation direction of the sensorless brushless motor 5 can be corrected to a normal rotation at a stroke by commutating to the selected phase, so that a quick start-up of responsiveness can be realized. In the example of FIG. 13, the phase B is selected as the commutation phase for the rotation restart. Since other operations are the same as those of the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the motor control device according to the second embodiment, the following effects can be obtained.

(6) The motor activation control means (FIG. 12) determines whether the sensorless brushless motor 5 is rotated forward, stopped, or reversely rotated after the rotational phase / commutation phase is determined when the rotational state is detected (step S202a). In step S202b, after determining the normal rotation, the commutation timing is determined, and then the control shifts to commutation control based on the phase at which the sensorless brushless motor is rotated in the normal direction.
For this reason, in addition to the effects (1) to (5) above, when the motor is started in the reverse rotation state of the motor, an early detection of the reverse rotation state detection timing can be achieved and the response delay until the forward rotation can be improved. it can.

  The third embodiment is an example of motor start control from a non-energized rotation state, while the first and second embodiments are examples of motor start from a non-energized stop state.

First, the configuration will be described.
FIG. 14 is a flowchart illustrating the flow of the motor start control process from the non-energized rotation state executed by the control circuit 2 of the third embodiment (motor start control means). Hereinafter, each step of FIG. 14 will be described. Steps S303 to S309 are steps for performing the same processing as steps S103 to S109 in FIG.

  In step S302, after the motor power supply Vbat is turned on, the control circuit 2 is reset or the initial circuit operation setting (circuit initialization) is performed, and then the control of the sensorless brushless motor 5 is started after the start of control from the non-energized rotation state. Perform state detection. In other words, closed-loop control that repeats all-phase open and set duty drive to open all the phase coils 5u, 5v, 5w of the sensorless brushless motor 5 is performed, and the back electromotive force and the comparison reference potential are zero-crossed during all-phase open. Based on the signal, the rotational phase, the commutation phase, and the commutation timing are monitored. When all of the rotational phase, the commutation phase, and the commutation timing are determined (step S302a), determination of the motor rotation state of the next sensorless brushless motor 5 is performed. Is performed (step S302b). If the determination result is a normal rotation state based on the determination of the motor rotation state, the process proceeds to step S303. If the determination result is the reverse rotation state, the process proceeds from step S302b to step S302c. In step S302c, the reverse rotation speed is determined, and if the rotation speed is very low, the process proceeds to step S306, and the rotation speed is high to low. Proceed to step S310. If the determination result in step S302b is a stop state, the process proceeds from step S302b to step S307.

  In step S310, following the determination that the rotation speed is high to low in step S302c, or the determination that there is zero cross detection in step S313, deceleration processing is executed by PWM / duty reduction and rotation speed cycle reduction. Proceed to step S311.

  In step S311, following the deceleration process in step S310, rotational drive control is performed to reversely rotate the sensorless brushless motor 5 by commutation control of the sensorless brushless motor 5 to the respective phase coils 5u, 5v, 5w, and the process proceeds to step S312. move on.

  In step S312, following the reverse rotational commutation in step S311, the commutation phase and commutation timing are determined based on the BEMF zero cross detection, and the process proceeds to step S313.

In step S313, following the BEMF zero cross detection in step S312, the presence or absence of BEMF zero cross detection is determined. If it is determined that BEMF zero cross detection is present, the process returns to step S310. If it is determined that BEMF zero cross detection is not present, the process returns to step S302. .
Since the entire circuit configuration is the same as that of FIG.

Next, the pre-startup control action will be described.
In the third embodiment, the motor state before the rotation start is basically deenergized and the motor rotation is stopped. However, the control circuit 2 is reset due to a momentary power interruption, the start control starts immediately after the drive control is stopped, the introduced outside air acts as an external force on the fan, etc., causing the motor to rotate unintentionally, and the sensorless brushless motor 5 rotates before starting the rotation. It may be in a state.

  Regardless of the rotation state of the sensorless brushless motor 5, the rotation activation control that starts from the rotation activation described above functions, but depending on the rotation direction and the rotation speed of the sensorless brushless motor 5, the drive phase at the time of rotation activation is the rotation phase. Since they do not match, overcurrent, abnormal noise, vibration, etc. may occur.

  As a countermeasure to this problem, as shown in the flowchart of FIG. 14, before starting energization of the motor phase coil by the initial rotation start in the motor rotation start control, the control is performed from the rotation state detection, and the control according to the rotation state is performed. In the third embodiment, the operation is switched to the above.

(When forward rotation is detected)
When the motor is started from the non-energized rotation state and the forward rotation is detected, the process proceeds to step S302a → step S302b → step S303 → step S304 → step S305 in the flowchart of FIG. 14, and it is determined in step S305 that BEMF zero cross is detected. As long as the flow proceeds, the flow from step S303 to step S304 to step S305 is repeated. In step S303, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to the phase coils 5u, 5v, 5w.
That is, at the time of detecting the normal rotation, the control is performed from the positive rotation phase commutation after the first rotation state detection in the timing chart shown in FIG.

(When stop is detected)
When the motor is started from the non-energized rotation state and the stop is detected, in the flowchart of FIG. 14, the process proceeds from step S302a to step S302b to step S307. In step S307, the number of stop determinations (number of times the phase has been advanced) <N Then, the process proceeds to step S308. In step S308, since the stop determination is the first time, rotation start (predetermined time) at a predetermined phase is performed, and the process returns from step S308 to step S302a. Then, in step S302b, the rotation direction is determined again, and in the case of stop determination, the process proceeds to step S307, and rotation restart is performed in step S308. If it is determined in step S302b that it is in the forward rotation state, the process proceeds from step S302b to step S303 → step S304 → step S305, and step S303 → step S304 → step S305, as long as it is determined that BEMF zero cross detection is detected in step S305. The forward flow is repeated. In step S303, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to the phase coils 5u, 5v, 5w.
That is, when stop is detected, control is performed from the start of rotation of a predetermined phase in the timing chart shown in FIG.

(When reverse rotation is detected)
At the time of starting the motor from the non-energized rotation state and detecting reverse rotation at a very low speed, the process proceeds to step S302a → step S302b → step S302c → step S306 in the flowchart of FIG. The rotation is restarted (predetermined time), and the process returns from step S306 to step S302a. If it is determined in step S302b that the engine is in the forward rotation state, the process proceeds from step S302b to step S303 → step S304 → step S305, and step S303 → step S304 → step S305 as long as it is determined in step S305 that BEMF zero cross detection is present. The flow to go to is repeated. In step S303, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to the phase coils 5u, 5v, 5w.
That is, at the time of detecting extremely low speed reverse rotation, control is performed from the restart of rotation commutated to the phase for correcting the rotation direction to the normal rotation in the timing chart shown in FIG.

  At the time of starting the motor from the non-energized rotation state and detecting reverse rotation at high speed to low speed, the process proceeds to step S302a → step S302b → step S302c → step S310 → step S311 → step S312 → step S313 in the flowchart of FIG. As long as it is determined in step S313 that BEMF zero cross detection is present, the flow of steps S310, S311, S312, and S313 is repeated as deceleration control. If it is determined in step S313 that there is no BEMF zero cross detection, the process proceeds to step S302, and the deceleration control is executed in the flow of step S310 → step S311 → step S312 → step S313 → step S302 while detecting the rotation state. Then, when the reverse rotation speed is reduced to an extremely low rotation speed, the process proceeds to step S302a → step S302b → step S302c → step S306 as in the case of the extremely low speed reverse rotation detection. Commutation rotation restart (predetermined time) is performed, and the process returns from step S306 to step S302a. If it is determined in step S302b that the engine is in the forward rotation state, the process proceeds from step S302b to step S303 → step S304 → step S305. The flow to go to is repeated. In step S303, rotational drive control for rotating the sensorless brushless motor 5 forward is performed by commutation control of the sensorless brushless motor 5 to the phase coils 5u, 5v, 5w.

  That is, at the time of detecting reverse rotation at an extremely low speed, control is performed from the restart of rotation direction correction with the timing charts shown in FIGS. 11 and 12, and at the time of detecting reverse rotation at a low speed to a high speed, the motor rotation is once performed. The speed is reduced to a rotational speed that can be corrected in the rotational direction to the normal rotation (very low rotational speed), and the rotational phase is corrected to the normal rotation and restarted without passing through the motor rotation stop control time due to braking or the like.

  As a speed reduction method, commutation is succeeded by phase synchronization in reverse rotation, and rotation deceleration control up to extremely low rotation speed or stop condition rotation speed (in contrast to acceleration, the drive duty is decreased and the commutation cycle is lengthened. Implement). Note that at high speeds, BEMF cannot be detected in a normal state during rotational deceleration, so control is performed until the starting rotational speed of the reverse rotation is determined to be extremely low while detecting the rotational state. Since other operations are the same as those of the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the motor control apparatus according to the third embodiment, the following effects can be obtained.

(7) The motor start control means (FIG. 14) starts closed loop control that repeats all-phase open and set duty drive immediately without starting the initial rotation when the motor is started from the non-energized rotation state. Rotation state detection is executed while all phases are open in control (step S302).
For this reason, in addition to the effects (1) to (4) above, when the sensorless brushless motor 5 has already been rotated before the motor rotation activation control, the initial rotation activation as in the first and second embodiments is not required. Thus, the start-up response of the sensorless brushless motor 5 can be further accelerated.

(8) The motor activation control means (FIG. 14), when the determination result by the rotation state detection is reverse rotation determination (reverse rotation determination in step S302b), determines the reverse rotation speed level, and determines the stop state. If it is determined that the rotation speed is within the extremely low speed range that allows the transition from reverse rotation to forward rotation without intervention (determination of the extremely low rotation speed in step S302c), the rotation by the phase at which the sensorless brushless motor 5 becomes normal rotation The process shifts to commutation control for direction correction (step S306), and if it is determined to be in the low speed to high speed rotation range (high to low rotation speed is determined in step S302c), the speed is reduced until it is determined to be in the extremely low speed rotation speed range. (Step S310) After decelerating, the sensorless brushless motor 5 shifts to commutation control for correcting the rotational direction based on the phase in which the sensorless brushless motor 5 is rotated forward.
For this reason, in addition to the effect of the above (7), when the sensorless brushless motor 5 is already reversely rotated before the motor rotation start control, it is immediately in the extremely low speed range, and also in the low to high speed range. Even at a certain time, by reducing the rotational speed to the extremely low speed rotational speed range by the deceleration process, it is possible to shift to the commutation control to the forward rotation with good response without stopping the motor.

  The fourth embodiment uses the fact that BEMF can be accurately detected even at an extremely low rotational speed, as in the first to third embodiments. When the operation is interrupted as necessary during the motor rotation control, the rotation starts from the operation interruption. It is an example of the rotation return control which restarts and continues motor rotation control, without stopping.

First, the configuration will be described.
FIG. 15 is a flowchart showing the flow of the motor rotation return control process started by the establishment of the rotation control interruption condition executed by the control circuit 2 of the fourth embodiment (motor rotation return control means). Hereinafter, each step of FIG. 15 will be described.

In step S401, when the rotation control interruption condition is satisfied, all-phase open processing is performed to stop energization (open) for all of the phase coils 5u, 5v, 5w of the sensorless brushless motor 5, and the process proceeds to step S402. .
Here, the “rotation control interruption condition” includes conditions such as a case where it is necessary to protect the sensorless brushless motor 5 and the motor control circuit such as overvoltage and overcurrent, in addition to the case of momentary power interruption and step-out. .

  In step S402, following the all-phase open process in step S401, motor rotation state detection control of the sensorless brushless motor 5 is performed. That is, based on the back electromotive force and the comparison reference potential zero-cross signal when all phases are open, the rotational phase, commutation phase, and commutation timing are monitored, and all of the rotational phase, commutation phase, and commutation timing are determined. (Step S402a), the process proceeds to the next Step S402b, and it is determined whether the rotation control interruption condition is satisfied or whether the rotation control interruption condition is released. If it is determined that the condition is satisfied, the process returns to step S402a. If it is determined that the condition is canceled, the process proceeds to step S402c. In step S402c, the motor rotation state of the sensorless brushless motor 5 is determined. If the determination result is the normal rotation state, the process proceeds to step S403, and if the determination result is the stop state, the process proceeds to step S405.

  In step S403, following the determination of the normal rotation state in step S402c, forward rotation commutation is performed by phase energization control for rotating each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 in the forward direction. Proceed to S404.

  In step S404, following the forward rotation commutation in step S403, the control returns to motor rotation control (control before the rotation control interruption condition is established) for rotating the sensorless brushless motor 5 forward based on the BEMF zero cross detection.

In step S405, following the determination that the motor is stopped in step S402c, motor rotation start control (FIG. 2 or FIG. 12) is started.
Since the entire circuit configuration is the same as that of FIG.

Next, the operation will be described.
First, “the problem of rotation return control in the comparative example” will be described, and then the operation of the motor control device of the fourth embodiment will be described as “features of rotation return control of the fourth embodiment”, “motor stop when the interruption condition is released” The description will be divided into “rotational return control action when the circuit protection condition is released”, “rotational return control action when the motor is forward when the circuit protection condition is released”, and “rotational return control action when the motor is forward when the step-out condition is released”.

[Problems of rotation return control in comparative example]
The rotation control return technology from the interruption of motor operation is disclosed in Japanese Patent Laid-Open Nos. 5-344787 and 11-103590. Japanese Laid-Open Patent Publication No. 5-344787, which describes a rotation control recovery technique from an interruption of operation due to an instantaneous power failure, describes a state of free running (idling, idling) when the motor rotation control is stopped by an inverter at the momentary power interruption. A technique for detecting the phase of BEMF and resuming rotation control when the drive frequency and phase of the inverter are matched is disclosed. Japanese Patent Application Laid-Open No. 11-103590, which describes a technique for returning to rotational control from a step-out state in which BEMF zero-cross detection cannot be performed, describes a step-out in which BEMF zero-cross cannot be detected by masking a back electromotive voltage waveform due to commutation at a high rotational speed. At this time, a technique is disclosed in which driving is resumed in accordance with the phase when the rotational speed decreases and BEMF zero-cross detection becomes possible from the free-run state in which the rotation control of the motor by the inverter is stopped.

  As described above, when the rotation control interruption condition is satisfied and the motor operation is interrupted during the rotation control of the motor at the motor rotation speed at which BEMF zero cross detection is possible, the motor rotation speed is the predetermined rotation at which BEMF detection is not possible. If it is less than the predetermined number of revolutions, even if BEMF is detected, it is necessary to carry out from the re-rotation start control after stopping the rotation once, in order to apply reliability, The predetermined number of revolutions should be as low as possible.

  On the other hand, BEMF zero-cross detection circuit at both ends of the motor phase coil, such as a BEMF zero-cross detection circuit disclosed in JP-A-11-103590, and a circuit using the neutral point voltage of the star connection as a comparison reference potential of the BEMF zero-cross detection circuit. Can be detected up to a relatively low rotation. However, if the above configuration cannot be performed due to cost or the like, the BEMF zero cross detection is performed using the pseudo neutral point voltage that has generated the equivalent of the neutral point potential in the circuit configuration as the comparison reference voltage. There is a limit to accuracy.

  Therefore, if the rotational speed drops to a rotational speed at which BEMF cannot be detected due to drive stoppage during rotational control due to step-out, etc., the rotational (commutation) phase cannot be determined. There is a problem that the continuity of control is lost.

  In addition, when the above-mentioned rotation control is restored, damage to the motor or circuit is not judged. If the drive TR is damaged under the rotation control interruption condition, an overcurrent will occur. There was a possibility of damage to circuit components.

[Characteristics of rotation return control of embodiment 4]
In the case of the fourth embodiment, even when the drive is stopped due to step-out or the like, the BEMF voltage zero-crossing detection is detected up to an extremely low rotational speed, and the rotation state can be detected. Control.

  That is, as described in the first embodiment, as the motor control circuit configuration, the motor phase coil bias circuit 6 is inserted so that each phase coil 5u, 5v, 5w is biased to the comparison reference potential at the timing of all-phase open. As a result, BEMF is superimposed on the reference voltage reference, and even if the BEMF voltage waveform is very small, the BEMF voltage zero cross can be detected by the BEMF detection circuit, and the BEMF voltage zero cross can be detected even at extremely low speeds. Enabled rotation state detection. For this reason, it is possible to drive by closed loop control in which the phases are matched from the extremely low rotation immediately before the rotation stop due to the decrease in the rotation speed due to the drive stop during the rotation control. That is, the BEMF voltage zero-cross position can be detected even when the rotation speed is low due to the temporary stop of the rotation drive or when the rotation phase is lost due to step-out.

  As described above, even when the sensorless brushless motor 5 reaches an extremely low rotational speed (for example, 30 rpm or less), the BEMF can be accurately detected and the rotational state can be judged. Even if the sensorless brushless motor 5 satisfies the rotation control interruption condition due to short-term protection and step-out, the rotation control is continued without stopping the sensorless brushless motor 5 by the motor rotation recovery based on the rotation state detection. be able to.

  As a specific example, Fig. 16 shows that when rotation control is stopped to protect the motor and the circuit due to overvoltage, overcurrent, etc. during rotation of the motor capable of detecting BEMF zero crossing, rotation control is resumed while the motor is still rotating. It is a timing chart which shows an example of the rotation return control to (continue). FIG. 17 is a timing chart showing an example of rotation return control for returning (continuing) the rotation control while the motor is rotating when an unexpected step-out occurs during the rotation of the motor capable of detecting BEMF zero crossing.

  In the timing charts of FIGS. 16 and 17, “Phase IV” is a phase in which 120 ° energization control is performed to drive the set duty in the phase matching state. “Phase V” is a phase in which all phases are opened to detect the rotation state when rotation control is stopped for circuit protection. “Phase VI” is a phase in which all phases are opened to detect the rotation state when rotation control is interrupted due to step-out. Other descriptions are the same as those in the timing charts of the first to fourth embodiments.

  Hereinafter, based on FIGS. 15 to 17, the rotation return control action when the motor is stopped when the interruption condition is released (FIG. 15), and the rotation return control action when the motor is rotated forward when the circuit protection condition is released (FIGS. 15 and 16). Next, a description will be given of the rotation return control operation (FIGS. 15 and 17) when the motor is rotating forward when the step-out condition is cancelled.

[Rotation return control action when the motor is stopped when the interrupt condition is canceled]
If the rotation control interruption condition is satisfied for a long time, the flow proceeds from step S401 to step S402a to step S402b and from step S402a to step S402b in the flowchart of FIG.
If it is determined in step S402b that the rotation control interruption condition has been canceled and the motor rotation state is in the stopped state, the process proceeds from step S402b to step S402c to step S405 in the flowchart of FIG. The motor rotation start control from the non-energized stop state as shown in FIG. 12 is started.
That is, when the motor is stopped when the interruption condition is released, the motor rotation start control is started again to aim for an early rotation return, but the discontinuous rotation return control is performed after the stop period of the sensorless brushless motor 5 has elapsed.

[Rotation return control action during normal motor rotation when circuit protection conditions are released]
When rotation control is stopped for motor and circuit protection during motor rotation due to overvoltage, overcurrent, etc., the process proceeds from step S401 to step S402a to step S402b and from step S402a to step S402b in the flowchart of FIG. The flow is repeated.
Then, when it is determined in step S402b that the time condition necessary for protection has been released, if the motor rotation state is the normal rotation state, from step S402b to step S402c → step S403 → step S404 in the flowchart of FIG. The rotation return control is performed to return (continue) the rotation control based on the phase synchronization while continuing the motor rotation state.

FIG. 16 is an example of the rotation return control when the energization is stopped for a short period during the 120 ° energization control.
During high-speed rotation of the motor of “Phase IV (120 ° energization control)”, the rotation control interruption condition is satisfied at the timing A at the end of the phase E. For example, in the phase F where the commutation is performed next, the rotation control is performed by the protection function. Stop (turn off all-phase drive TR), turn off all-phase drive TR continuously for a short period of time until the end of phase B when the rotation control interruption condition is released, and turn off the sensorless brushless motor 5 and the circuit. Protect.

  While the all-phase drive TR is OFF, the rotation state is detected, and after the BEMF voltage zero cross position of the phase B including the end timing B of the rotation control interruption condition and the time measurement result T1, the BEMF voltage zero cross of the phase B is , T1 to commutate to phase C, return to “phase IV (120 ° energization control)”, and continue motor rotation.

[Rotation return control action during normal motor rotation when step-out condition is canceled]
When rotation control is stopped due to an unexpected step-out during motor rotation, the flow proceeds from step S401 to step S402a to step S402b and the flow from step S402a to step S402b is repeated in the flowchart of FIG.
If it is determined in step S402b that the step-out condition has been released and the motor rotation state is the normal rotation state, the process proceeds from step S402b to step S402c → step S403 → step S404 in the flowchart of FIG. Rotation return control is performed to return (continue) rotation control based on phase synchronization while continuing the rotation state.

FIG. 17 is an example of rotation return control from step-out detection during 120 ° energization control.
In this control, during the all-phase TR off period after timing A when it is determined that the rotation control interruption condition has occurred, the rotation state detection control capable of detecting BEMF is performed even when the sensorless brushless motor 5 rotates at an extremely low speed. The flow timing and phase are determined, commutation is performed, and rotation of the sensorless brushless motor 5 can be continued.

  As shown in FIG. 17, when it is determined that the BEMF voltage zero cross could not be detected at a predetermined position at the timing A at the end of the phase F during the high-speed rotation of the motor of “Phase IV”, The rotation control is stopped, and the all-phase drive TR is turned off (step-out determination example in time).

  While the all-phase drive TR is OFF, the rotation state is detected, and the BEMF voltage zero cross of the phase B is determined based on the time measurement result T1 between the BEMF voltage zero cross of the phase A and the BEMF voltage zero cross of the phase B and the BEMF voltage zero cross position of the phase B. After voltage zero-crossing, after t1, it commutates to phase C, returns to “Phase IV (120 ° energization control)”, and continues motor rotation.

  A step-out determination example based on the level after commutation will be described. When the BEMF detection signal rises after commutation, it is determined that step-out occurs when a high level is detected although it is originally at a low level. When the BEMF detection signal falls after commutation, it is determined that the step-out occurs when a low level is detected although it is originally a high level.

Next, the effect will be described.
In the motor control device according to the fourth embodiment, the following effects can be obtained.

(9) When the rotation control interruption condition is satisfied during the motor rotation control, the control circuit 2 sets all the phase coils 5u, 5v, 5w to all open (step S401) and compares it with the back electromotive force. Based on the detection of the voltage zero cross of the reference potential, the rotation state of the sensorless brushless motor 5 is detected (step S402). If the rotation control interruption condition is released, the rotation state is determined to be positive (step S402c is determined to be normal rotation). ), Motor rotation return control means (FIG. 15) for returning to the motor rotation control before the rotation control interruption condition is satisfied by the forward rotation commutation control.
For this reason, in addition to the effects (1) to (8) above, when the rotation drive is temporarily stopped due to the establishment of the rotation control interruption condition, the motor rotation is performed even when the rotation control interruption condition is canceled, even if the rotation speed is extremely low. As long as it is in the state, it is possible to return to the rotation control by phase synchronization while maintaining the continuity while the motor rotation state is continued.

  The fifth embodiment is an example in which the circuit failure diagnosis function of the motor control device is added to the rotation return control of the fourth embodiment.

First, the configuration will be described.
FIG. 18 is an overall circuit configuration diagram illustrating the motor control device A2 according to the fifth embodiment. The apparatus configuration will be described below with reference to FIG.

  The motor control device A2 of the fifth embodiment is an example of an arbitrary offset bias setting circuit. As shown in FIG. 18, the control circuit 2, the drive TR circuit 3 (drive transistor circuit), and the BEMF detection circuit 4 (back electromotive force detection). Circuit), a sensorless brushless motor 5, a motor phase coil bias circuit 6, a comparison reference potential circuit 7 ', a rotation speed instruction input 8, a D / A converter 9, and a comparison reference potential selection circuit 10. Yes.

  In the comparison reference potential circuit 7 ′, a drive voltage waveform including noise at the time of driving the motor phase coil wraps around the resistors R 4 to R 6 of the motor phase coil bias circuit 6 to change the reference potential of the BEMF detection circuit 4 and to change the BEMF. This is a voltage follower circuit that outputs a reference voltage so that the detection circuit 4 does not erroneously detect, and includes voltage amplifiers OP4 and OP5 and resistors R7 and R8. The voltage amplifier OP4 has a positive input terminal connected between the resistors R7 and R8 so that the divided voltage values of the resistors R7 and R8 are input. The negative terminal of the voltage amplifier OP4 inputs an output and serves as a negative feedback path. Further, the output of the voltage amplifier OP4 is connected to the negative input terminals of the voltage comparators OP1 to OP3 of the motor phase coil bias circuit 6 and the BEMF detection circuit 4. The resistors R7 and R8 are provided in series between the power supply voltage Vbat and the ground. In this example, the resistors R7 and R8 have the same value, and the divided values (connection points) of the resistors R7 and R8 are set to the midpoint potential (1/2 Vbat). The voltage amplifier OP5 has a positive input terminal connected to the output voltage of the D / A converter 9 and the output voltage of the voltage amplifier OP4 via a resistor, and adds the respective output voltages. The D / A converter 9 is added to the comparison reference potential which is the output voltage of the voltage amplifier OP4. The negative terminal of the voltage amplifier OP5 inputs an output through a resistor to serve as a negative feedback path and is grounded through a resistor to serve as an adder circuit. Further, the output of the voltage amplifier OP5 is connected to the negative input terminals of the voltage comparators OP1 to OP3 of the motor phase coil bias circuit 6 and the BEMF detection circuit 4.

  The D / A converter 9 converts the digital signal from the control circuit 2 into a comparison reference potential offset signal which is an analog signal, the input side is connected to the control circuit 2, and the output side is a plus input terminal of the voltage amplifier OP5. Connected to.

The comparison reference potential selection circuit 10 selects the output of the voltage amplifier OP5 when performing failure diagnosis based on the offset potential based on the comparison reference potential selection signal from the control circuit 2, and the voltage amplifier OP4 when other than failure diagnosis. The output is selected and is inserted between the comparison reference potential circuit 7 ′ and the BEMF detection circuit 4, and is selectively operated by a comparison reference potential selection signal from the control circuit 2.
Since other configurations are the same as those in FIG. 1 of the first embodiment, the corresponding components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 19 is a flowchart showing the flow of the motor rotation return control process started by the establishment of the rotation control interruption condition executed by the control circuit 2 of the fifth embodiment (motor rotation return control means). Hereinafter, each step of FIG. 19 will be described. Note that steps S501 to S505 correspond to steps S401 to S405 in the flowchart of FIG.

  In step S506, failure diagnosis of the sensorless brushless motor 5 and the drive TR circuit 3 is executed following the all-phase open processing in step S501. In other words, following the all-phase open process, the first cycle of detecting a state in which the inductance (number of windings) decreases and the BEMF generation voltage level decreases due to an intermediate short of the motor phase coils 5u, 5v, 5w, etc. Is diagnosed (step S506a). Next, a diagnosis of the second cycle for detecting the state before the element failure in which the drive TR of the drive TR circuit 3 is leak-degraded is performed (step S506b). When the diagnosis ends, it is determined whether the diagnosis result is normal or failure (step S506c). If it is determined that the diagnosis result is normal, the process proceeds to step S502a. If the diagnosis result is determined to be a failure, the process proceeds to step S507.

  In step S507, following the diagnosis result of failure in step S506c, motor energization is stopped upon failure detection.

  Note that the data used in step S502a is the last 60 ° of the final measurement phase of the second period of failure diagnosis (T1 of W phase Td2Wb in FIG. 21) when the failure diagnosis has flowed normally for the first time. Calculate using. The second and subsequent times due to the establishment of the rotation control interruption condition are calculated using T2 to be measured for each zero cross after T1.

Next, the operation will be described.
The operation of the motor control apparatus according to the fifth embodiment will be described by dividing it into “features of failure diagnosis of the fifth embodiment” and “failure diagnosis operation”.

[Features of Failure Diagnosis of Example 5]
In the fifth embodiment, even when the drive is stopped due to step-out, etc., detection of the BEMF voltage zero crossing is detected up to the extremely low rotation speed, and the rotation state can be detected. If it is before the stop, the rotation is continuously resumed and the drive is stopped during the rotation control. The circuit configuration (FIG. 18) and control can be used for fault diagnosis.
In particular, for failure diagnosis, the threshold of the motor phase coil bias circuit 6 is varied while driving is stopped, and duty diagnosis of the BEMF detection waveform is performed, thereby diagnosing the sensorless brushless motor 5 and modes such as overcurrent due to circuit damage. Made possible.

According to the above configuration, the cause of the stop by the sensorless brushless motor 5 and the drive circuit (TR) can be diagnosed, so that overcurrent, motor, and circuit damage due to restart can be avoided.
In addition, drive control can be resumed by phase synchronization even when stepping out or rotating at extremely low speeds, and failure diagnosis can be performed when driving stops due to stepping out. The mode can be avoided.
In addition, since the failure diagnosis is performed in the rotation state detection, the damage due to the rotation control interruption condition (overvoltage, overcurrent, step out, etc.) or the cause can be diagnosed, and the rotation can be resumed after the rotation state is detected. If necessary, the motor can be de-energized to prevent unexpected damage, and if equipped with a communication function, the diagnostic results are reported through a vehicle diagnostic device, etc., enabling quick parts replacement. it can.

[Fault diagnosis]
When the rotation control interruption condition is satisfied, the process proceeds from step S501 to step S506a to step S506b to step S506c in the flowchart of FIG. That is, the diagnosis of the first cycle is performed in step S506a, the diagnosis of the second cycle is performed in step S506b, and whether normal or failure is determined in step S506c. If the failure diagnosis determines that a failure has occurred, the process proceeds to step S507, and the motor energization stoppage is taken.If it is determined that the failure diagnosis is normal, the process proceeds to step S502a and thereafter, and the rotation control interruption condition is As long as the forward rotation is maintained at the time of release, the motor rotation state is maintained and the way to return to the motor rotation control before the rotation control interruption condition is established is opened.

  In other words, failure diagnosis performed using a period in which all phases are open due to the establishment of the rotation control interruption condition is performed for two cycles at each phase electrical angle, and the duty between each phase is compared for each cycle to drive. Carry out TR diagnosis and motor phase coil diagnosis.

  FIG. 20 shows a timing chart when failure diagnosis is performed during a period in which all phases are open due to the establishment of the rotation control interruption condition. FIG. 21 shows timing charts of a normal diagnostic waveform (a), a diagnostic waveform (b) at the time of drive TR leak failure, and a diagnostic waveform (c) at the time of coil short failure.

  Of the two cycles, the first cycle is evident from the comparison of the normal waveform (a), the diagnostic waveform (b) at the time of drive TR leak failure, and the diagnostic waveform (c) at the time of coil short failure, Compared to the normal diagnostic waveform (a), the failure waveforms (b) and (c) differ from other coils in how the duty is output.

In the second period, observation is performed with the bias voltage applied to the motor phase coils 5u, 5v, 5w and the reference voltage of the BEMF detection circuit 4 set to the same potential. Further, in the second period, commutation period measurement is also performed in order to continue the rotation.
If the driving TR of the TR driving circuit 3 is in a state before the element failure where the leakage has deteriorated, a deviation from the comparison reference potential biased by the motor phase coil bias circuit 6 occurs due to the leakage current, and the second cycle Thus, as shown in FIG. 21 (b), the duty phase does not return to 50%, and if the leakage current increases, the deviation from 50% increases, and the failure phase in which the leakage occurs in the drive TR. Diagnose that there is.
On the other hand, if the inductance (the number of windings) is reduced due to an intermediate short of the motor phase coils 5u, 5v, 5w and the generated voltage level of BEMF is lowered, the second cycle, FIG. ), The fact that the duty is returned to 50% is used to diagnose a failure phase in which a coil short-circuit has occurred.
In addition, since another effect | action is the same as that of Example 1- Example 4, description is abbreviate | omitted.

Next, the effect will be described.
In the motor control device according to the fifth embodiment, the following effects can be obtained.

(10) a comparison reference potential circuit 7 ′ that generates an offset potential having a predetermined potential difference with respect to the comparison reference potential; and a comparison reference potential selection circuit 10 that can select the comparison reference potential and the offset potential. The motor rotation return control means (FIG. 19) sets all the phase coils 5u, 5v, 5w to all open when the rotation control interruption condition is satisfied during the motor rotation control (step S501), Cause of failure of the motor drive circuit configuration including each phase coil 5u, 5v, 5w of the sensorless brushless motor 5 by changing the comparison reference potential which is the threshold value of the motor phase coil bias circuit 6 and observing the duty of the detection waveform of the back electromotive force A failure diagnosis unit (step S506).
For this reason, in addition to the effect of (9) above, the transition to the all-phase open state based on the establishment of the rotation control interruption condition in the motor rotation return control is utilized, and the failure of the drive TR or the failure of the motor phase coil Thus, it is possible to carry out a failure diagnosis that causes the rotation control interruption condition to be satisfied.

  As mentioned above, although the motor control apparatus of this invention has been demonstrated based on Example 1-Example 5, it is not restricted to these Examples about a concrete structure, Each claim of a claim is a claim. Design changes and additions are allowed without departing from the gist of the invention.

  In Examples 1-5, the circuit structural example by the three-phase brushless sensorless motor by the star connection was shown. However, as shown in FIG. 22, a circuit configuration example using a three-phase brushless sensorless motor 5 ′ in which motor phase coils 5 ′ u, 5 ′ v, 5 ′ w are delta-connected may be used. In this case, since all three connection points 50u, 50v, and 50w are biased as in the first to fifth embodiments, the connection point J of the resistors R4, R5, and R6 of the motor phase coil bias circuit 6 is used as a base point. Since loop currents are generated by the resistors R4, R5, R6 and the respective phase coils 5'u, 5'v, 5'w and cancel each other, the synthesized voltage waveform is the same as the waveform shown in FIG. Become. Therefore, also in the delta connection, the closed loop control can be performed at the low rotation speed from the start as in the first to fifth embodiments.

  In the fifth embodiment, FIG. 18 shows an example of an arbitrary offset bias setting circuit having a comparison reference potential circuit 7 ′, a D / A converter 9, and a comparison reference potential selection circuit 10 and capable of arbitrarily setting a comparison reference potential to be offset. It was. However, as shown in FIG. 23, the failure diagnosis is performed using the fixed offset bias setting circuit example having the comparison reference potential circuit 7 ″ and the comparison reference potential selection circuit 10 and having the comparison reference potential to be offset fixed. May be.

  In the first to fifth embodiments, the comparison reference potential circuit 7 outputs the output of the voltage amplifier OP4 to the motor phase coil bias circuit 6 and the BEMF detection circuit 4, but outputs the output of the voltage amplifier OP4 to the motor phase coil bias circuit 6. In addition, the outputs of the resistors R7 and R8 may be output to the BEMF detection circuit 4, and if the erroneous detection due to the reference voltage fluctuation of the BEMF detection circuit 4 can be avoided by filtering, the voltage amplifier A voltage follower circuit using OP4 may be omitted. Further, as the switch element, there are a transistor, an FET, and the like, which may be used as necessary.

  In Examples 1-5, the application example to the motor control apparatus of the sensorless brushless motor 5 used as a fan motor of the air-conditioner unit for vehicles was shown. However, a sensorless brushless motor controller that acquires motor rotation position information based on detection of the voltage zero cross of the back electromotive force generated in each phase coil can be used for sensorless brushless motors used in various industrial fields. The present invention can be applied.

A1, A2 Motor control device 2 Control circuit 3 Drive TR circuit (drive transistor circuit)
4 BEMF detection circuit (back electromotive force detection circuit)
5 Sensorless brushless motor
5u, 5v, 5w Phase coil 6 Motor phase coil bias circuit 7 Comparison reference potential circuit 8 Speed indication input 9 D / A converter 10 Comparison reference potential selection circuit
Qu1, Qu2 switch element
Qv1, Qv2 switch element
Qw1, Qw2 switch element
R1 ~ R14 resistance
OP1 to OP5 Voltage comparator
Vbat supply voltage

Claims (10)

A sensorless brushless motor, a control circuit, a drive transistor circuit, and a counter electromotive force detection circuit, and motor rotational position information based on voltage zero cross detection of counter electromotive force generated in each phase coil of the sensorless brushless motor. In the motor control device that performs rotational drive control by commutation control to each phase coil using the motor rotational position information,
A comparison reference potential circuit for generating a comparison reference potential of the back electromotive force detection circuit;
A motor phase coil bias circuit for supplying the comparison reference potential to each phase coil of the sensorless brushless motor;
The control circuit performs closed-loop control that repeats all-phase open and set duty drive to open all the phase coils when the motor is started, and the counter-electromotive force and the comparison reference potential voltage zero-cross during all-phase open Based on the detection, the sensorless brushless motor performs a rotation state detection as to whether the sensorless brushless motor is in a normal rotation, stop, or reverse rotation, and the sensorless brushless motor becomes a normal rotation according to a determination result by the rotation state detection. A motor control device comprising motor activation control means for shifting to commutation control by phase. The motor control device according to claim 1,
When the determination result based on the rotation state detection is a reverse rotation determination, the motor start control means shifts to a commutation control for correcting the rotation direction based on the phase at which the sensorless brushless motor is rotated forward without going through the motor stop control. The motor control apparatus characterized by the above-mentioned. In the motor control device according to claim 1 or 2,
When the determination result by the rotation state detection is a stop determination, the motor activation control unit shifts to the commutation control that advances the phase so as to promote the rotation of the sensorless brushless motor, and executes the commutation control that promotes the motor restart. However, the motor control device is characterized by determining that it is a motor lock failure when continuing the experience in which the determination result is a stop determination, and shifting to a fail-safe operation. In the motor control device according to any one of claims 1 to 3,
The motor activation control means determines whether the sensorless brushless motor is in a normal rotation, stop, or reverse rotation state after the rotation phase, the commutation phase, and the commutation timing are determined when the rotation state is detected. A motor control device for determining a state. In the motor control device according to any one of claims 1 to 4,
The motor start control means performs an open loop control to start an initial rotation by a minimum time and drive according to a motor inertia mass and a load of the sensorless brushless motor when the motor is started from a non-energized stop, and the initial rotation A motor control device characterized by starting closed-loop control that repeats all-phase open and set duty drive following startup and performing rotation state detection during all-phase open in closed-loop control. In the motor control device according to any one of claims 1 to 5,
The motor activation control means determines the motor rotation state as to whether the sensorless brushless motor is in the normal rotation, stop, or reverse rotation after the rotation phase / commutation phase is determined when the rotation state is detected. After the determination of the normal rotation, after the commutation timing is determined, the motor control device shifts to the commutation control based on the phase where the sensorless brushless motor becomes the normal rotation. In the motor control device according to any one of claims 1 to 4,
The motor start control means starts closed-loop control that repeats all-phase open and set duty drive immediately without starting initial rotation when the motor is started from a non-energized rotation state, and all phases are open in closed-loop control. A motor control device that performs rotation state detection. The motor control device according to claim 7,
When the determination result by the rotation state detection is a reverse rotation determination, the motor activation control unit determines whether the reverse rotation speed is high or low and can make a transition from the reverse rotation to the normal rotation without going through the stop state. When it is determined that the rotational speed range is low, the sensorless brushless motor shifts to commutation control for correcting the rotational direction based on the phase in which the motor rotates in the normal direction. The motor control device according to claim 1, wherein the motor control device is decelerated until it is determined to be in a range of several, and after decelerating, shifts to commutation control for rotational direction correction by a phase in which the sensorless brushless motor is rotated forward. In the motor control device according to any one of claims 1 to 8,
When the rotation control interruption condition is established during the motor rotation control, the control circuit sets all the phase coils to open, opens all phases, and detects the sensorless brushless motor based on detection of the back electromotive force and the voltage zero cross of the comparison reference potential. Motor rotation return control that returns to the motor rotation control before the rotation control interruption condition is satisfied by forward rotation commutation control if the rotation control interruption condition is canceled and the rotation control interruption condition is canceled A motor control device comprising means. In the motor control device according to claim 9,
A comparison reference potential circuit that generates an offset potential having a predetermined potential difference with respect to the comparison reference potential; and a comparison reference potential selection circuit capable of selecting the comparison reference potential and the offset potential.
When the rotation control interruption condition is satisfied during the motor rotation control, the motor rotation return control means sets all the phase coils to all phases open, and changes the comparison reference potential that is a threshold value of the motor phase coil bias circuit. A motor control device comprising a failure diagnosis unit that diagnoses a failure factor of a motor drive circuit configuration including each phase coil of the sensorless brushless motor by observing a duty cycle of a detection waveform of a back electromotive force.

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