JP2009261107A - Motor control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control circuit which sufficiently diagnoses an abnormality of a motor control circuit, and prevents the undesired stop of a motor. <P>SOLUTION: In the motor control circuit 1 which detects a back electromotive force by using a non-driven coil in a three-phase coil of the three-phase sensorless brushless motor 5 having the three-phase coil as a coil to be detected, and performs control by using the zero-cross timing of the detected back electromotive force (BEMF), the motor control circuit includes a zero-cross timing prediction part 23 which predicts the succeeding zero-cross timing of each phase, and an abnormality determination part 25 which determines the abnormality at the control circuit side by using the predicted zero-cross timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention belongs to the technical field of motor control circuits for sensorless motors.

Conventionally, in a three-phase brushless motor, the counter electromotive voltage and the midpoint voltage of each phase are respectively compared to detect the rotational position of the rotor and perform motor control (see, for example, Patent Document 1). ).
Japanese Patent Laid-Open No. 11-299283 (page 2-7, full view)

  However, conventionally, the abnormality diagnosis of the motor control circuit has not been sufficient.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide a motor control capable of sufficiently performing an abnormality diagnosis of a motor control circuit and preventing an undesired motor stop or the like from occurring. It is to provide a circuit.

  In order to achieve the above object, in the present invention, a motor that detects a counter electromotive force from a connection position between the coils of a motor having a multi-phase coil and performs motor rotation control using a voltage zero cross timing of the detected counter electromotive force. The control circuit includes a zero-cross timing prediction unit that predicts the next zero-cross timing of each phase coil, and an abnormality determination unit that determines an abnormality on the control circuit side using the predicted zero-cross timing. To do.

  Therefore, according to the present invention, the abnormality diagnosis of the motor control circuit can be sufficiently performed, and an undesired motor stop or the like can be prevented.

  Embodiments for realizing a motor control circuit according to the present invention will be described below as a first embodiment corresponding to the first, second, and third embodiments and a second embodiment corresponding to the first, second, and fourth embodiments. A third embodiment corresponding to the invention according to claims 1, 2, 5, 6; a fourth embodiment corresponding to the invention according to claims 1, 2, 3, 7; 8 and the fifth embodiment corresponding to the invention according to FIG.

First, the configuration will be described.
FIG. 1 is a diagram illustrating a circuit configuration of a motor control circuit in the star connection motor according to the first embodiment.
As shown in FIG. 1, the motor control circuit 1 according to the first embodiment includes a control circuit 2, a drive TR circuit 3, and a BEMF detection circuit 4, and controls driving of the three-phase sensorless brushless motor 5. In the first embodiment, an A / D interface circuit 6 is provided. BEMF stands for Back Electromotive Force, which is abbreviated as BEMF hereinafter.
Specifically, the control circuit 2 is, for example, a microcomputer, and receives a rotation input 7 that is a motor rotation speed instruction input from an external unit and sensor (not shown) for the three-phase sensorless brushless motor 5, and the BEMF detection circuit 4. The BEMF voltage zero cross (hereinafter referred to as zero cross) signal is input. Then, a control calculation is performed and a PWM control signal is output to the drive TR circuit 3.
The control circuit 2 also includes an A / D conversion circuit 21 that receives the midpoint voltage signal from the A / D interface circuit 6 and performs digital conversion.

The driving TR circuit 3 is a circuit that functions as an inverter by forming a half-bridge circuit by the upper side switching elements (Qu1, Qv1, Qw1) and the lower side switching elements (Qu2, Qv2, Qw2) for each phase. .
Note that the control signals (base input and gate input) of all the switch elements are PWM control signals from the control circuit 2.
More specifically, for example, the U phase 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 of the three-phase sensorless brushless motor 5. The V phase and the W phase are configured similarly.

The BEMF detection circuit 4 includes a midpoint potential circuit 41. The midpoint potential circuit 41 arranges resistors R1 and R2 in series between the power supply voltage Vbat and the ground, and outputs an intermediate voltage thereof. That is, the resistors R1 and R2 are voltage dividing resistors and a reference value voltage (threshold voltage) is output.
The BEMF detection circuit 4 is input to the plus input terminals of the voltage comparators OP1 to OP3 provided for each phase through resistors R3 to R5 so as to detect the middle of the coil of each phase and the drive TR circuit 3. To do. Further, the reference value voltage from the midpoint potential circuit 41 is input to the negative input terminals of the voltage comparators OP1 to OP3.
The voltage comparators OP1 to OP3 compare the reference voltage and the input from each phase coil, and output the comparison result as a zero cross signal.

The three-phase sensorless brushless motor 5 is a three-phase motor based on the U phase, the V phase, and the W phase, and is a motor that does not use a brush. Further, since the coil itself is used as a sensor, the motor does not have a sensor for detecting the rotational position.
The A / D interface circuit 6 converts the input voltage to the BEMF zero-cross detection circuit and the midpoint (1/2) of the power supply voltage, and controls the difference between the BEMF voltage and the midpoint potential at the zero-cross prediction timing. The circuit 2 can be operated.

Next, a more detailed structure of the control circuit 2 will be described.
FIG. 2 is a diagram illustrating a control block configuration of the control circuit of the motor control circuit according to the first embodiment.
The control circuit 2 includes a PWM control unit 22, a zero cross timing prediction unit 23, a timing adjustment unit 24, an abnormality determination unit 25, and a zero cross timing creation unit 26 in addition to the A / D conversion circuit 21 described above.
The PWM control unit 22 calculates the TR drive timing (commutation timing) for each phase and the PWM value (actual motor rotation number) for each phase output at the TR drive timing from the zero cross signal input of each phase. Then, a PWM control signal composed of a PWM control value for each phase so that the calculated rotational speed becomes a target rotational speed to be controlled that is determined by the motor rotational speed (instruction) input 7 is generated and output to the drive TR circuit 3 To do.

The zero cross timing prediction unit 23 includes abnormality determination data from the abnormality determination unit 25, a control rotation number calculated by the PWM control unit 22 (a rotation number controlled in a calculation step for moving toward the target rotation number), and a zero cross timing generation unit. 26, the zero cross timing in each phase is predicted from the BEMF zero cross detection data from No. 26.
The timing adjustment unit 24 adjusts the difference between the actually detected detection timing and the predicted timing.
The abnormality determination unit 25 determines an abnormality by comparing the midpoint voltage and the bridge voltage at the predicted zero cross timing, and outputs a determination result to the zero cross timing generation unit 26.

  The zero cross timing creation unit 26 creates an abnormal phase zero cross signal and outputs it to the PWM control unit 22.

Next, the operation will be described.
[Motor control by zero cross signal]
Here, the motor control by the zero cross signal executed by the PWM control unit 22 of the control circuit 2 of the motor control circuit 1 of the first embodiment will be described.
In the first embodiment, 120 ° drive control is performed, and the BEMF detection circuit 4 detects the BEMF of each phase and detects the zero cross point of the phase of the BEMF for each phase, thereby driving the stator coil of each phase. Timing, that is, commutation timing is controlled.

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

  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. Specifically, the BEMF zero crossing detection point in the three-phase sensorless brushless motor 5 of three-phase 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 the 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 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, it will be described in other words.
For example, when the three-phase 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, current flows from the power supply voltage Vbat through the switch element Qu1 through the coil 5u and the coil 5v of the three-phase 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 coil 5w can be said to be a state in which 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 coil 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 to drive and control the three-phase sensorless brushless motor 5 by obtaining commutation timing.

[BEMF zero cross signal voltage abnormality detection and commutation compensation]
In the first embodiment, the BEMF zero-crossing occurrence timing is predicted from the control rotation speed, and an abnormality is judged by the deviation between the BEMF zero-crossing voltage actually generated at the zero-crossing prediction timing and the expected midpoint potential. Compensates the commutation timing of the abnormal phase with better accuracy than the BEMF zero cross detection (occurrence) timing. (The standard commutation timing is 30 degrees after the zero cross detection in electrical angle)

First, the BEMF zero-cross timing prediction in the zero-cross timing prediction unit 23 will be described.
FIG. 3 is a time chart in the case where an abnormality occurs in the zero cross timing of one of the three phases in the first embodiment.
The electrical angle expressed by the zero-crossing timing standard in the three-phase sensorless brushless motor 5 (different from the electrical angle in the actual motor) is 0 (360) degrees on the basis of the control electrical angle of each phase determined by the control speed. The time intervals at 120 degrees and 240 degrees are used, and the next phase zero cross occurrence prediction timing based on the BEMF zero cross occurrence point of the previous phase is (Tzul, Tzvl, Tzwl).

  The timing is predicted based on values (Tul, Tv1, Twl) that allow for acceleration / deceleration control in the period estimated from the rotation speed, but the timing adjustment unit 24 predicted the detection timing to actually occur. Fine adjustment of the prediction timing is performed with respect to the next prediction timing based on a deviation from the timing (acceleration / deceleration amount, etc.).

  Based on the predicted zero-cross timing (Tzul, Tzvl, Tzwl, etc.) of each phase predicted above, BEMF zero-cross timing anomaly detection and compensation of the zero-cross prediction timing and commutation timing to the anomaly detection phase are performed as follows. To implement.

Next, abnormality detection using the zero-cross occurrence prediction timing in the abnormality determination unit 25 will be described.
FIG. 4 is an explanatory waveform diagram showing the state of the motor drive waveform when the BEMF voltage deviation occurs.
The deviation (ΔV) of the BEMF voltage at the actual BEMF detection point is as shown in FIG. If the BEMF becomes higher than the original voltage (solid line) due to an abnormality such as a malfunction, the zero-point detection timing is accelerated because detection is performed at the midpoint potential, and the interval after detection (Tz-c: standard is 30 electrical angle) °) The later phase current commutation timing is advanced (see FIG. 4 (b)).
On the other hand, if the BEMF is lower than the original voltage (solid line) due to an abnormality such as a malfunction, the phase current commutation timing is delayed (see FIG. 4C). If this timing is extremely shifted (for example, several tens of degrees or more), abnormal noise is generated or if the timing is further advanced, in the extreme case, GND or power supply voltage is fixed and zero-cross detection is not generated, and the motor is stopped.

  The BEMF voltage varies depending on the motor (configuration and performance of the magnetic circuit), rotation speed, etc., but can be determined individually once the motor specifications are determined. In the first embodiment, the accuracy of the components constituting the detection circuit is about 5 to 10% with respect to the midpoint potential voltage (the BEMF voltage is generated at the same level as the power supply voltage, and the control electrical angle is about 3 to 6 degrees). It is assumed that an abnormality determination is performed for a deviation larger than that, and the width is indicated by Tn in FIG. In the first embodiment, the width Tn is captured by a voltage as shown in FIG. 4 (2ΔV = Tn).

In the first embodiment, if detected at the zero-cross prediction timing, if normal, the BEMF potential detects the midpoint (1/2) potential of the power supply voltage because of the zero-cross point (see FIG. 4A). For example, if the power supply voltage is 12V, the midpoint potential is 6V, and after A / D conversion, the constant of the A / D interface circuit 6 is set to measure about 512LSB if the conversion resolution is 10bit. To do.
If the electrical angle error is 3 degrees and the BEMF power generation potential is 12VP-P, the error tolerance Tn is 0.3V, and the A / D conversion value is about 25LSB, and 512 ± 25LSB is the judgment value. It becomes.

As described above, abnormality judgment is measured when the BEMF potential exceeds 1/2 power supply voltage + allowable voltage (512 ± 25LSB in the example) by comparing the power supply voltage with the BEMF voltage at the zero-cross prediction timing. It is determined that the BEMF zero-crossing timing is abnormal for the current phase.
The signal determined by the abnormality determination unit 25 is transmitted to the zero cross timing generation unit 26. If the signal from the abnormality determination unit 25 is normal, the zero cross timing creation unit 26 generates the zero cross timing data detected by the zero cross signal input. If the signal is abnormal, the zero cross timing generation unit 26 generates the abnormality generated by the zero cross timing prediction unit 23 and the timing adjustment unit 24. Phase zero-cross timing prediction data is generated as zero-cross timing data for each phase and output (transmitted) to the PWM control unit 22.

  Therefore, the data transmitted to the PWM control unit 22 of the zero cross timing creation unit 26 immediately after the abnormality determination in the abnormality determination unit 25 is specifically (Tzul, Tzvl, Tzwl) in the timing diagram 3.

Next, the setting of the prediction timing of the abnormality determination phase after the next time by the zero cross timing prediction unit 23 will be described.
For the prediction timing setting of the abnormality determination phase after the next time, take the time Tzuw = Tzv2 + Tzw2 between the phases before and after the phase determined to be abnormal by the abnormality determination unit 25, and the zero crossing of the abnormal phase Predicted timing (Tzv3). In addition, when the zero-cross abnormal phase of a phase continues, it is set as the base point of the zero-cross prediction timing of each abnormal phase by equal division according to the number of phases.

FIG. 5 is a time chart when an abnormality occurs in which zero loss timing of one of the three phases is lost in the first embodiment.
FIG. 5 shows a case where the V-phase BEMF zero-cross detection signal is not output from the BEMF detection circuit 4, and immediately after the V-phase abnormality is detected, the V-phase BEMF zero-cross detection signal is commutated based on the zero-cross at the Tzvl prediction timing. The next V-phase zero-cross predicted timing is set to half of the U-phase and W-phase zero-cross detection time interval Tzuw = Tzw2 as the U-phase zero-cross reference point and the V-phase zero-cross predicted timing Tzv3.

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

  (1) In the three-phase coil of the three-phase sensorless brushless motor 5 having a three-phase coil, the counter electromotive force is detected from the connection position between the coils, and the motor rotation control is performed using the voltage zero cross timing of the detected counter electromotive force. The motor control circuit 1 includes a zero cross timing prediction unit 23 that predicts the next zero cross timing of each phase coil, and an abnormality determination unit 25 that determines an abnormality on the control circuit side using the predicted zero cross timing. Abnormal diagnosis of the control circuit can be sufficiently performed, and an undesired motor stop or the like can be prevented.

  (2) In the above (1), when the abnormality determination unit 25 determines that there is an abnormality, the zero cross timing generation unit that does not use the zero cross timing detected in the abnormal phase and generates and outputs the zero cross timing of the abnormal phase 26, the control is not performed using the abnormal zero-cross timing, and the control is favorably continued by the generated zero-cross timing instead. When the motor control circuit is abnormal, the motor is not desired. Stops can be prevented from occurring.

  (3) In the above (1) or (2), it is composed of two switch elements (Qu1 and Qu2, Qv1 and Qv2, Qw1 and Qw2) so as to be connected to the coil of the three-phase sensorless brushless motor 5 at a bridge point. The drive TR circuit 3 provided with the half-bridge circuit for each phase and a midpoint potential circuit 41 that outputs a reference voltage set from the midpoint potential of the star connection, and the abnormality determination unit 25 includes a midpoint potential circuit. In order to determine the abnormality by comparing the reference voltage from 41 and the voltage at the bridge point in each phase at the predicted zero cross timing, the BEMF zero cross timing abnormality is accurately detected by voltage comparison, and the motor control circuit Can be sufficiently diagnosed.

The second embodiment is an example in which an abnormal period of the zero cross signal is detected.
The configuration will be described.
FIG. 6 is a diagram illustrating a circuit configuration of a motor control circuit according to the second embodiment.
The motor control circuit 1 according to the second embodiment performs abnormality determination from the zero cross signal. The motor control circuit 1 includes a control circuit 2, a driving TR circuit 3, a BEMF detection circuit 4, a three-phase sensorless brushless motor 5, and does not include an A / D interface circuit 6.

FIG. 7 is a diagram illustrating a control block configuration of a control circuit of the motor control circuit according to the second embodiment.
The control circuit 2 according to the second embodiment includes a PWM control unit 22, a zero cross timing prediction unit 23, a timing adjustment unit 24, a zero cross timing creation unit 26, and an abnormality determination unit 27, and does not include the A / D conversion circuit 21.

The abnormality determination unit 27 performs abnormality determination by comparing the period calculated from the previous detected zero cross timing and the predicted zero cross timing with the period calculated from the previous detected zero cross timing and the currently detected zero cross timing. .
Since other configurations are the same as those of the first embodiment, description thereof is omitted.

The operation will be described.
[Behavior judgment and commutation compensation by BEMF zero-cross signal period]
In the abnormality determination unit 27 according to the second embodiment, a deviation amount with respect to the predicted value, that is, a timing tolerance is set as a time Tn in FIG. 3, and abnormality is determined with respect to a deviation greater than Tn. In the actual circuit configuration and control electrical angle, the time Tn has an accuracy of about ± 3 degrees to 6 degrees.
Referring to FIG. 3, when a deviation occurs in the V-phase zero-cross signal, a Tzul normal signal is generated in the U-phase, and a BEMF zero-cross signal is generated in the V-phase at a short timing of Tzv2. Since the shift is greater than Tn, the V phase is determined to be abnormal.
A signal having a long Tzw2 is detected in the W phase, but it is determined after being corrected with the predicted value Tzvl (error ∠jTV2) of the abnormal V phase, and is determined to be normal.

Further, the case where the V-phase zero-cross signal disappears will be described with reference to FIG. In this case, the U phase is a Tzul normal signal, the V phase has no detection signal, and a failure determination is made when the V phase zero cross prediction timing + time Tn has elapsed.
A signal having a long Tzw2 is detected in the W phase, but it is determined after correction with the predicted value Tzvl of the failure V phase, and is determined to be normal.
Since the compensation processing after the abnormality determination is the same as that of the first embodiment, description thereof is omitted.

Explain the effect. The motor control circuit according to the second embodiment has the following effects in addition to (1) and (2).
(4) In the above (1) or (2), the abnormality determination unit 27 performs prediction in order to determine abnormality by comparing the period calculated from the predicted zero cross timing with the period calculated from the detected zero cross timing. It is not desirable because it is possible to accurately determine the abnormality by whether or not the period calculated from the detected zero-crossing timing is within the range of the time width Tn set for the zero-crossing timing, and sufficiently diagnose the abnormality of the motor control circuit. It is possible to prevent the motor from stopping.
Since other functions and effects are the same as those of the first embodiment, description thereof is omitted.

The third embodiment is an example in which the length of the zero-cross signal cycle is detected.
The abnormality determination unit 27 according to the third embodiment determines an abnormality based on a period difference in zero cross timing detected in the order of the U phase, the V phase, and the W phase.
Since other configurations are the same as those of the second embodiment, the description thereof is omitted.

The operation will be described.
[Abnormality judgment and commutation compensation by BEMF zero-cross signal period length]
In the abnormality determination unit 27 of the third embodiment, when a deviation occurs in the actual BEMF zero-cross detection signal, the zero-cross detection timing of each phase deviates from the timing within the allowable deviation range with respect to the prediction timing. Long timing and short timing are detected. Then, the BEMF zero cross phase sandwiched between the long timing signal and the short timing signal is determined as the failure phase.

  With reference to FIG. 3, the case where a deviation occurs in the V-phase zero-cross signal will be described. In this case, the U phase is a Tzul normal signal, the V phase is a short Tzv2 timing signal, and the W phase is a long Tzw2 signal. Therefore, the abnormal phase is determined to be the V phase.

  A case where the V-phase zero-cross signal further disappears will be described with reference to FIG. In this case, since the U phase has a Tzul normal signal, the V phase has no detection signal, and the W phase has a long Tzw2 signal, the abnormal phase is determined to be the V phase.

  Next, processing when a phase in which the zero-crossing timing is determined to be a failure is detected in the above determination will be described.

The zero cross timing failure phase commutation control is performed by assuming the zero cross timing of the phase determined to be abnormal by using the period between zero crosses of the phase determined to be normal and the zero cross timing.
First, when there is a correction amount performed in the phase before the failure detection phase, commutation control is performed at the prediction timing of the failure detection phase corrected by the correction amount.
Secondly, the time Tz between the zero crosses of the phases before and after the phase determined to be faulty and the zero cross timing are used for the prediction timing setting of the next failure determination phase.

  Furthermore, when there are a plurality of normal phases, the intermediate timing ((Tzv2 + Tzw2) / 2) between the normal two-phase zero crosses before and after the abnormal phase is set as the base point of the next abnormal prediction timing. When the zero-cross fault phases of the phases are continuous, the zero-cross prediction timing of each abnormal phase is set as a base point by equal division according to the number of phases.

  In addition, when the normal phase is 1 phase, the position is advanced by 1 / number of phases (1/3 in the case of 3 phases) from the zero cross position of the phase immediately before the continuous abnormal phase. Is used as the next zero-cross prediction timing of the fault phase, and the interphase commutation control is performed thereafter.

Explain the effect. The motor control circuit according to the third embodiment has the following effects in addition to the above (1) and (2).
(5) In the above (1) or (2), the abnormality determination unit 27 compares the period difference with the other phase calculated from the predicted zero cross timing and the period difference calculated from the detected zero cross timing of a plurality of phases. In order to determine the abnormality, the abnormality of the motor control circuit should be sufficiently diagnosed by accurately detecting the abnormality of the length of the cycle from the period difference with the other phases before and after the electrical angle which is almost equal difference in electrical angle. It is possible to prevent an undesired motor stop or the like from occurring.

(6) In the motor control circuit described in (2) above, the zero cross timing creation unit 26 outputs the zero cross timing of the phase determined to be abnormal from the zero cross timing other than the phase determined to be abnormal to the PWM control unit 22, In consideration of the relationship with other phases, the zero cross timing used in the event of an abnormality can be determined so that an undesired motor stop or the like does not occur.
Since other functions and effects are the same as those of the first embodiment, description thereof is omitted.

Example 4 is an example in which the abnormality determination unit detects an abnormality of the switch element from the comparison voltage.
The configuration will be described.
FIG. 8 is a diagram illustrating a control block configuration of the motor control circuit according to the fourth embodiment.
In the fourth embodiment, the abnormality determination unit 25 includes a switch element abnormality determination unit 251.
Since other configurations are the same as those of the first embodiment, description thereof is omitted.

The operation will be described.
[Switch element abnormality detection action]
The switch element abnormality determination unit 251 detects an abnormality of the switch element based on each zero cross timing (Tzu1, Tzv1, Tzw1) predicted by the zero cross timing prediction unit 23. When the switch element of the drive TR circuit 3 that functions as an inverter for the BEMF detection phase has a low resistance component when the power is turned off due to an abnormality, the bridge voltage detected by the BEMF detection circuit 4, that is, the midpoint connection potential of the phase coil connection Is shifted by ΔV.

FIG. 9 is an explanatory diagram illustrating one circuit state of driving according to the fourth embodiment.
In FIG. 9, the switch elements Qw1, Qv2 are turned on so that the coil portions 5w, 5v are energized, and the other switch elements Qu1, Qu2, Qw2, Qv1 are turned off. Thereby, BEMF is detected by the output from the coil unit 5U to the comparator.

FIG. 10 is an explanatory diagram showing an equivalent circuit in a state where the switch element is normal.
In the equivalent circuit, the coil portion is a resistor representing coil impedance and an AC power source representing BEMF, and the switch element is represented as a switch.
FIG. 11 is an explanatory diagram showing an equivalent circuit when the switching element Qu2 is in an abnormal state having a low resistance. FIG. 12 is an explanatory diagram showing an equivalent circuit when the switching element Qu1 is in an abnormal state having a low resistance.

In the following, the bias of the resistance components Rqu1, Rqu2 and BEMF caused by the abnormality of the switch elements Qu1, Qu2 using this equivalent circuit and the BEMF zero cross point will be described.
The coil resistance component of each phase can be regarded as the same, and assuming that the switch element has N times the resistance value, the voltage ratio at the BEMF measurement point is the voltage Vs, and the following relationship is obtained from the equivalent circuit. The degree of influence can be estimated.

  First, when the high side Qu1 is abnormal as shown in FIG.

  (Formula 1) Vs = (N + 3) / (2N + 3) × Vbat

  Next, when the low side Qu2 is abnormal as shown in FIG.

  (Expression 2) Vs = N / (2N + 3) × Vbat

  From the above formulas 1 and 2, more specifically, for example, when judging from a deviation of 5% or more, the comparison voltage is 1/2 Vbat, and 0.5 is a reference. You can see how many times the resistance can be detected.

Using the high-side equation of Equation 1, (N + 3) / (2N + 3) = 0.525, N = 28.5 (times), and if the motor (stator) coil resistance is 500 mΩ, it is detected from the degraded state of 14.5Ω. It becomes possible. This indicates that the switch element abnormality determination unit 251 of the fourth embodiment can detect the deterioration state of the switch element at an early stage.
Further, in the example where the generated voltage of BEMF is equivalent to the power supply voltage (for example, 12V), the change is about 0.1V per one degree near the zero cross. Detectable.

Explain the effect.
The motor control circuit according to the fourth embodiment has the following effects in addition to the above (1), (2), and (3).
(7) In the above (3), the abnormality determining unit 25 is a switch for determining an abnormality of the switch element from the voltage difference between the reference voltage from the midpoint potential circuit 41 and the voltage at the bridge point in each phase at the predicted zero cross timing. Since the element abnormality determination unit 251 is provided, deterioration of the switch element can be detected at an early stage to sufficiently perform abnormality diagnosis of the motor control circuit, so that an undesired motor abnormality mode does not occur.
Since other functions and effects are the same as those of the first embodiment, description thereof is omitted.

The fifth embodiment is an example in which the abnormality determination unit detects an abnormality of the switch element from the comparison period.
The configuration will be described.
FIG. 13 is a diagram illustrating a control block configuration of a control circuit of the motor control circuit according to the fifth embodiment.
In the fifth embodiment, the abnormality determination unit 27 includes a switch element abnormality determination unit 271.
Since other configurations are the same as those of the second embodiment, description thereof is omitted.

The operation will be described.
[Switch element abnormality detection action]
In the switch element abnormality determination unit 271 according to the fifth embodiment, first, a previous measurement value (for example, Tv1) and a current measurement value (for example, Tv2) are compared at a time T between zero cross timings between phases.
Then, by determining the difference, for example, when it is shorter than the previous measured value, the upper arm side switch element is determined to be deteriorated (short mode), and when it is longer than the previous measured value, the lower arm side switch element is determined. Is determined to be deteriorated (short mode).

Explain the effect.
The motor control circuit according to the fifth embodiment has the following effects in addition to the above (1), (2), and (4).
(8) In the above (4), the abnormality determining unit 27 determines the abnormality of the switch element from the time difference between the cycle calculated from the predicted zero cross timing and the cycle calculated from the detected zero cross timing. Therefore, it is possible to detect deterioration of the switch element at an early stage to sufficiently perform abnormality diagnosis of the motor control circuit, and to prevent an undesired motor stop or the like from occurring.

As mentioned above, although the motor control circuit of the present invention has been described based on the first to fifth embodiments, the specific configuration is not limited to these embodiments, and each claim of the claims Design changes and additions are allowed without departing from the gist of the invention.
For example, the motor connection includes a star connection and a delta connection, and may be another connection.
For example, the switch element includes a transistor, an FET, and the like, and may be used as necessary.

For example, in the first embodiment, the PWM control unit 22 inputs the target rotational speed as an rotational speed instruction input from an external unit or the like and controls the target rotational speed to be the target rotational speed. You may control so that it may become.
For example, in the fourth and fifth embodiments, the abnormality determination unit includes the switch element abnormality determination unit. However, alternatively, only the switch element abnormality determination unit may be provided.

FIG. 3 is a diagram illustrating a circuit configuration of a motor control circuit according to the first embodiment. It is a figure which shows the control block structure of the control circuit of the motor control circuit of Example 1. FIG. 6 is a time chart when the zero-cross timing of one of the three phases is abnormal in the first embodiment. FIG. 6 is an explanatory waveform diagram illustrating a state of a motor drive waveform when a BEMF voltage shift occurs. 6 is a time chart in a case where an abnormality occurs in which zero-cross timing of one of three phases is lost in the first embodiment. FIG. 6 is a diagram illustrating a circuit configuration of a motor control circuit according to a second embodiment. FIG. 6 is a diagram illustrating a control block configuration of a control circuit of a motor control circuit according to a second embodiment. FIG. 10 is a diagram illustrating a control block configuration of a control circuit of a motor control circuit according to a fourth embodiment. FIG. 10 is an explanatory diagram illustrating one circuit state of driving according to a fourth embodiment. It is explanatory drawing which shows the equivalent circuit of a state with a normal switch element. It is explanatory drawing which shows the equivalent circuit in case the switch element Qu2 is in the abnormal state which has low resistance. It is explanatory drawing which shows the equivalent circuit in case the switch element Qu1 is in the abnormal state which has low resistance. FIG. 10 is a diagram illustrating a control block configuration of a control circuit of a motor control circuit according to a fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor control circuit 2 Control circuit 21 A / D conversion circuit 22 PWM control part 23 Zero cross timing prediction part 24 Timing adjustment part 25 Abnormality determination part 251 Switch element abnormality determination part 26 Zero cross timing preparation part 27 Abnormality determination part 271 Switch element abnormality determination Part 3 Drive TR circuit Qu1, Qu2 Switch element Qv1, Qv2 Switch element Qw1, Qw2 Switch element OP1-OP3 Comparator 4 BEMF detection circuit 41 Midpoint potential circuit R1-R5 Resistance 5 Three-phase sensorless brushless motor 5u Coil 5v Coil 5w Coil 6 A / D interface circuit R6 to R13 Resistance 7 Detection speed

Claims (8)

In the motor control circuit that detects the counter electromotive force from the inter-coil connection position of the motor having a plurality of phase coils and performs the motor rotation control using the voltage zero cross timing of the detected counter electromotive force.
Zero cross timing prediction means for predicting the next zero cross timing of each phase coil;
Using the predicted zero-cross timing, an abnormality determination means for determining an abnormality on the control circuit side,
A motor control circuit comprising: The motor control circuit according to claim 1,
When it is determined as abnormal by the abnormality determining means, the zero cross timing detected in the abnormal phase is not used, and the zero cross timing compensating means for creating and outputting the zero cross timing of the abnormal phase is provided.
A motor control circuit characterized by that. In the motor control circuit according to claim 1 or 2,
Drive switch means provided with a half bridge circuit composed of two switch elements in each phase so as to be connected to the coil of the motor at a bridge point;
A midpoint potential output means for outputting a reference voltage set from the potential at the midpoint of the coil driven by the half-bridge circuit;
With
The abnormality determination means compares the reference voltage from the midpoint potential output means with the voltage at the bridge point in each phase at the predicted zero cross timing to determine an abnormality.
A motor control circuit characterized by that. In the motor control circuit according to claim 1 or 2,
The abnormality determination means determines an abnormality by comparing a cycle calculated from the predicted zero cross timing with a cycle calculated from the detected zero cross timing.
A motor control circuit characterized by that. In the motor control circuit according to claim 1 or 2,
The abnormality determination means determines an abnormality by comparing a period difference with the other phase calculated from the predicted zero-cross timing and a period difference calculated from the detected zero-cross timing of the plurality of phases.
A motor control circuit characterized by that. The motor control circuit according to claim 2,
The zero timing compensation means generates the zero cross timing of the phase determined to be abnormal from the zero cross timing other than the phase determined to be abnormal.
A motor control circuit characterized by that. In the motor control circuit according to claim 3,
The abnormality determination unit includes a switching element abnormality determination unit that determines abnormality of the switching element from a voltage difference between a reference voltage from the midpoint potential output unit and a voltage at the bridge point in each phase at a predicted zero-cross timing. The
A motor control circuit characterized by that. The motor control circuit according to claim 4,
The abnormality determining means includes a switching element abnormality determining means for determining an abnormality of the switching element from a time difference between a period calculated from the predicted zero cross timing and a period calculated from the detected zero cross timing.
A motor control circuit characterized by that.

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