JP2001078484A - Control circuit of brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect various circuit conditions at rotation failure and to enable restart in the control circuit of a brushless motor which does not use a position sensor element. SOLUTION: The position of a rotor is detected by the induced voltage from a stator coil, and also based on the detection signal, a rotating magnetic field is generated by a motor commutation control circuit 12 so as to control the rotation of a motor, and also a sensor signal changeover logic circuit 8 is switched to output the sensor signal from a start commutation sensor signal generating circuit 8 to the motor commutation control circuit. In the case that the motor stops due to start failure, step out during operation, etc., the fixation of the Hi/Lo of the motor rotation pulse signal is performed, or when the circuit oscillation is detected, a standby-saving power circuit 17 for supply of circuit voltage is reset to stop the rotation control, and restart treatment is performed after a prescribed interval time. Hereby, its restart can be made after an interval time, determining various circuit conditions occurring at rotation troubles, such as motor stoppage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control circuit for a brushless motor that does not use a position sensor element.

[0002]

2. Description of the Related Art Conventionally, a brushless motor is rotated without using a position sensor element (such as a Hall element) by detecting a rotor position using an induced voltage generated in a stator coil due to rotation of a rotor (rotor). A control circuit for a brushless motor that has been made available is known. However, in control of the brushless motor by such a control circuit, there is a problem that a failure such as a failure in starting or a step-out during operation causes a stop of rotation or the like. If the above problem occurs, the motor will be left stopped without detecting the presence or absence of rotation of the motor. Therefore, the stop state is detected by the output of the rotation pulse, and the PWM command is re-input or the power is turned on again. Retrigger the starting circuit.

[0003]

In addition, the driver circuit may be in an oscillating state when the motor is stopped due to a start failure or an overload. Even during such oscillation, the driver repeats the same circuit operation as normal rotation, so it is not known that the driver is in a stopped state, and if the oscillation frequency is high, the impedance increases due to the L component of the winding, so that the conduction current is small. In other words, if the current detecting means cannot detect the restrained state, and if the oscillation state continues after being left as it is, the energization control switching element will be destroyed. Therefore, for example, Japanese Patent Publication No. 6-50957 discloses that when the above oscillation state is detected, it is determined that the rotation is defective, and a motor stop signal is generated.

[0004] However, in the above publication, the rotation failure state is detected only by the oscillation state of the circuit, and the detection when the detection signal is fixed to Hi or Lo is not mentioned. In addition, the processing after the detection of the rotation failure state only stops the rotation of the motor. In addition, CPU
However, there is a problem that the cost of the circuit is increased.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a control circuit for a brushless motor that does not use a position sensor element can detect various circuit states that occur due to motor rotation failure and restart. In the present invention, a rotor position signal generating circuit for detecting a position of a rotor by an induced voltage generated in a stator coil by rotation of the rotor to generate a rotor position signal, and A rotating magnetic field generating circuit for generating a rotating magnetic field in the stator coil for rotating the rotor based on the position signal, and determining whether or not the generation cycle of the rotor position signal is in a normal rotation region; A restart circuit for resetting the rotating magnetic field generating circuit to a restart state when it is determined that the rotating magnetic field is outside the rotation range. And the.

According to this, the lower limit value longer than the cycle of the sensor signal at the start of starting and the upper limit value higher than the maximum motor speed are set, and the sensor signal becomes lower than the lower limit value or higher than the upper limit value. In any case, since the restart process is performed, in any case of the circuit state at the time of stop due to start failure, overload step-out, etc., it will be below the above lower limit or above the upper limit, so ensure each case As a result, the brushless motor without the sensor element can automatically recover when a stop or the like occurs due to a start failure, a step-out of overload, or the like.

Further, the restart circuit resets the rotating magnetic field generating circuit after the determination and performs the restart after an elapse of an interval time for cooling the power element. Thus, heat generated by the power element of the control circuit can be prevented from being accumulated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a circuit block diagram showing a control circuit of a brushless motor to which the present invention is applied. The brushless motor 1 to be controlled in the present embodiment has a three-phase stator coil. Hereinafter, only one of the three phases will be described unless otherwise specified. However, since the difference is only a shift, a detailed description thereof will be omitted. Further, the brushless motor 1 detects the position of the rotor using a voltage induced in the coil without providing a position sensor element, and generates a rotating magnetic field based on the sensor signal (rotor position signal). To rotate the rotor.

As shown in FIG. 1, a PWM signal for controlling the output of the motor 1 is input to an input / output I / F circuit 3 of a driver circuit 2 as a rotating magnetic field generating circuit. The PWM signal may have a rectangular pulse waveform whose pulse width is changed according to a duty ratio set from an operation circuit (not shown).

The output signal of the input / output I / F circuit 3 is PWM
The signal is superimposed on the signal of the motor commutation control circuit 12 based on the sensor signal and is input to the power driver 6 via the pre-driver 5. Each coil U ・ V ・ W
The drive signal is output to the controller. The connection lines to the coils U, V, and W are connected to a sensor signal generation circuit 7 whose drive signal is a rotor position signal generation circuit.

The sensor signal generation circuit 7 detects an induced voltage generated in each of the coils U, V, and W when the rotor of the motor 1 rotates, and uses the detected signal instead of a position sensor signal of a Hall element or the like. And outputs it to the sensor signal switching logic circuit 8.

The sensor signal switching logic circuit 8 receives the starting commutation sensor signal from the starting commutation sensor signal generation circuit 9 and receives the duration signal from the starting commutation duration setting circuit 10. Has become. Note that a clock signal corresponding to the starting frequency is input from the clock signal generating circuit 11 to the starting commutation sensor signal generating circuit 9,
A signal from the starting commutation duration setting circuit 10 is input to the clock signal generation circuit 11.

The sensor signal switching logic circuit 8 outputs a sensor signal to the motor commutation control circuit 12. The sensor signal is a starting commutation sensor signal from the starting commutation sensor signal generation circuit 9 at the time of starting, and is a sensor signal from the sensor signal generation circuit 7 after the elapse of the starting commutation continuation time.

The signal of the protection circuit 13 for detecting the overcurrent detection state of the power driver 6 is input to the motor commutation control circuit 12 via the inhibit circuit 14.

A power supply circuit 16 connected to an external power supply 15 supplies a circuit main voltage Vcc.
The branched signal output from the input / output I / F circuit 3 to the PWM circuit 4 is input as a PWM command signal to the standby power supply circuit 17 to which the circuit main voltage Vcc is supplied. In response to the PWM command signal input, the circuit main voltage Vcc
Is turned on / off, and is supplied to the motor commutation control circuit 12, the restart circuit 18, and other circuits.

A rotation pulse signal is output from the input / output I / F circuit 3 to an external circuit (not shown), and the rotation pulse signal is input to a restart circuit 18. One of the restart signals output from the restart circuit 18 is input to the standby power saving circuit 17, and another restart signal is also output to the start commutation duration setting circuit 10.

The control procedure of the brushless motor 1 in the control circuit constructed as described above will be described below with reference to the time chart of FIG.

As shown in the first stage of FIG. 2, a PWM input from an external circuit is supplied to the PWM input via an input / output I / F circuit 3.
It becomes a command signal and is input to the standby power saving circuit 17. The PWM command signal is a pulse wave of a predetermined frequency that changes the pulse width according to the duty.

In response to the PWM command signal, the circuit saving voltage Vcs rises in the saving standby power supply circuit 17 and when the circuit saving voltage Vcs exceeds the threshold value V1 as shown in the second stage of FIG. After the elapse of the time Tpr), the start control is started.

The start control start signal is generated in the restart circuit 18 as a one-shot trigger signal as shown in the fifth stage of FIG.
Is output to Upon receiving the trigger signal, the starting commutation duration setting circuit 10 outputs a starting signal to the sensor signal switching logic circuit 8 and the clock signal generation circuit 11. In the sensor signal switching logic circuit 8, when the starting signal is input, the starting commutation sensor signal from the starting commutation sensor signal generation circuit 9 is output as a sensor signal to the motor commutation control circuit 12.

In the brushless motor (without the position sensor element) to which the present invention is applied, since the rotor position signal from the stator coil is not input at the start of the start, the start commutation sensor signal generation circuit as described above. The motor commutation control circuit 12 controls the motor rotation based on the sensor commutation sensor signal output from the motor 9 at a predetermined generation cycle. Thereby, a rotating magnetic field is generated regardless of the position of the rotor, and the rotor of the motor 1 can rotate.

When the rotor starts to rotate, a rotor position signal from the stator coil is input to the sensor signal generation circuit 7,
When the level of the rotor position signal is sufficiently increased according to the rotation increase, the sensor signal is output from the sensor signal generation circuit 7 to the sensor signal switching logic circuit 8 in a generation cycle corresponding to the rotation. After the sensor signal from the stator coil is detected, it is not necessary to use the starting commutation sensor signal.
To switch the sensor signal generation circuit 7 to output the sensor signal to the motor commutation control circuit 12, and thereafter,
The brushless motor is controlled using the sensor signal from the stator coil.

As shown in FIG. 3, the restart circuit 18
Is a cycle determination circuit 1 for determining a cycle of a rotation pulse.
8a, a voltage-saving Vcs level detection circuit 18b, a start trigger circuit 18c, and a retrigger interval circuit 18d. The cycle determination circuit 18a has an input / output I
/ F rotation pulse signal FG from circuit 3 (third stage in FIG. 2)
, The circuit saving voltage Vcs from the saving standby power supply circuit 17 is input to the voltage saving Vcs level detection circuit 18b, and the cycle determination circuit 18 is input to the start trigger circuit 18c.
The cycle determination signal from FIG. 2A (the fourth stage in FIG. 2) is input. The start trigger circuit 18c outputs a trigger signal (fifth stage in FIG. 2) to the start commutation duration setting circuit 10. Further, the cycle determination signal from the cycle determination circuit 18a is also input to the retrigger interval circuit 18d. The re-trigger interval circuit 18d outputs an interval signal (the sixth stage in FIG. 2) as a reset signal to the standby power saving circuit 17.

Next, a specific circuit of the restart circuit 18 will be described below with reference to FIG. The input stage of the rotation pulse period determination circuit 18a provides a transistor Q1 in accordance with the on / off state of the open collector output type rotation pulse signal FG.
Turns on / off. Note that the base pull-up resistor R1
And a circuit saving voltage Vcs is supplied as a power supply voltage of the resistor R2 connected to the collector. On the other hand, transistor Q
Since the collector C1 is connected to the ground (GND), the collector voltage of the transistor Q1 has an integral waveform having the rising time constant of the resistor R2 and the capacitor C2. This is watchdog timer 2
1 clock terminal CK.

The cycle judging circuit 18a comprises a band pass circuit using a watchdog timer 21. The capacitor C1 is connected to the capacitor timer terminal Ct of the watchdog timer 21, and the reset output terminal RES is connected to the capacitor C1 via the diode D1. As a result, a reset signal (-RES) is output to the FG input below the low frequency set by the capacitor C1 and the FG input above the high frequency set by the resistor R2 and the capacitor C2. The power supply voltage of the watchdog timer 21 is also the circuit saving voltage Vcs.

The function of a power supply monitoring IC (reset IC) of the watchdog timer 21 is adopted, and a power saving level Vcs level detection circuit 18b for generating a trigger signal of a starting circuit by power supply level monitoring and a power-on reset operation signal is configured. Have been.

The start trigger circuit 18c is constituted by using a monostable multivibrator 22. As shown in the fourth and fifth stages of FIG. 2, the start trigger circuit 18c responds to the rise of the reset signal from the watchdog timer 21. In response, a trigger signal is output to the starting commutation duration setting circuit 10 of the starting circuit. The start control is started by the input of the trigger signal.

The retrigger interval circuit 18d is also formed by using the monostable multivibrator 23, and as shown in the fourth and sixth stages in FIG. 2, the reset signal from the watchdog timer 21 rises. An interval signal is output to the standby power saving circuit 17 via the transistor Q2 in response to the fall. This interval signal is output for a time determined by a time constant set in the monostable multivibrator 23.

Then, the standby power supply circuit 17 saves P
The circuit main voltage Vcc supplied from the power supply circuit 16 in response to the input of the WM command signal is switched by the transistor Q3 to supply the circuit saving voltage Vcs. The transistor Q3
Are turned on / off via a transistor Q4 which is turned on while the PWM command is maintained. Therefore, since the collector of the transistor Q2 which is turned on is connected to the base of the transistor Q4 by the interval signal, the transistors Q4 and Q3 can be turned off even during the PWM command, and the voltage saving Vcs is turned off. Circuit reset can be performed.

The control procedure in the control circuit of the brushless motor constructed as described above will be described below.

In the normal start control, as shown by time T1 in the time chart of FIG.
When the increase in the circuit saving voltage Vcs that rises due to the input of the M command signal becomes equal to or greater than the threshold value V1, after the elapse of the set reset hold time Tpr from the cycle determination circuit 18a, FIG.
The cycle determination signal is output as shown in the fourth row of FIG.
At the same time, a trigger signal is output from the start trigger circuit 18c, and the start control is performed accordingly. In the start control, the pseudo sensor signal is generated as described above, and the commutation is controlled in accordance with the signal to force the motor 1 to rotate.

After that, if the motor 1 stops for some reason and the rotation pulse signal FG output according to the rotation does not occur for a long time as shown in the third row of FIG.
Since the next rotation pulse signal FG is not generated during the monitoring time Twd of the watchdog timer 21, the lower limit value (low frequency or lower) is detected by the band pass function of the cycle determination circuit 18a. The lower limit is the monitoring time Twd
And it is set to be somewhat longer than the cycle of the starting frequency of the motor 1.

As described above, if the motor stops in a state where the next rotation pulse signal FG is not generated during the monitoring time Twd, the period determination signal is reset (falling of the signal) after the monitoring time Twd has elapsed (time T1). Since the interval signal is output at the same time, the output of the circuit power saving voltage Vcs from the standby power supply circuit 17 disappears. Therefore, in the watchdog timer 21 operating at the circuit saving voltage Vcs, the cycle determination signal, which is the reset signal, remains extinguished regardless of the setting of the reset pulse width Twr.

Next, after the lapse of the interval time Ti set by the retrigger interval circuit 18d (time T2)
Then, due to the disappearance of the interval signal (fall of the signal), the standby power supply circuit 17 restarts its operation, the circuit saving voltage Vcs rises, and the restart control for restarting the start control of the motor 1 is performed in the same manner as described above. Will be Thus, in the case of a start failure, an overload step-out, or a stop due to some cause, the restart control can be automatically performed without performing a manual restart operation.

When the driver oscillates (circuit oscillation state) which occurs when the overload is stopped, the rotation pulse signal FG
Are in an oscillating state as shown from the third time T3 in FIG. At this time, the oscillation frequency becomes equal to or higher than the maximum rotation speed of the motor 1. By setting the high frequency setting value (upper limit value) in the band pass function of the cycle determination circuit 18a to be somewhat higher than the motor maximum rotation speed, The oscillation phenomenon can be suitably detected.

When the oscillation phenomenon is detected, the cycle determination signal is reset after the monitoring time Twd has elapsed (time T4). Subsequent processing is the same as that at the time of the stop, and the restart control is performed after the elapse of the interval time Ti.

The range between the lower limit and the upper limit is the normal rotation region, and when the period of the sensor signal is within that region, normal motor rotation control is performed.

Also, since the interval time Ti is provided and the restart processing is performed after the lapse of the interval time Ti,
For example, if the cause of the rotation failure is an overcurrent, the overcurrent detection may be repeated again after the restart, but even in such a case, the control circuit constituting the rotating magnetic field generation circuit By setting the interval time Ti long enough that heat generation of the power element is not accumulated, it is possible to prevent the power element from being adversely affected by heat generation.

Further, when a rotation failure is detected by the upper and lower limits, an abnormality detection signal is output to an external circuit.
By controlling the PWM signal to an OFF state in accordance with the output, control can be performed so as to prohibit automatic return.

[0041]

As described above, according to the present invention, the lower limit value longer than the cycle of the sensor signal at the start of starting and the upper limit value higher than the maximum motor speed are set, and the sensor signal is equal to or less than the lower limit value. Restart processing is performed when the value exceeds the upper limit value, so in any case of the circuit state at the time of stop due to start failure, overload step-out, etc., it becomes less than the above lower limit value or more than the upper limit value Therefore, since each case can be reliably detected and restart processing is performed, automatic recovery can be performed in the case of a failure due to start failure, overload step-out, etc., in a brushless motor without a sensor element. Was. By setting the interval time to be long enough not to accumulate heat of the power element of the control circuit constituting the rotating magnetic field generating circuit, it is possible to prevent the power element from being adversely affected by heat.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a control circuit of a brushless motor to which the present invention is applied.

FIG. 2 is a time chart showing a control procedure of a brushless motor in the present control circuit.

FIG. 3 is a block diagram of a restart circuit 18;

FIG. 4 is a diagram showing a specific circuit of a restart circuit 18;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 brushless motor 2 driver circuit 3 input / output I / F circuit 4 PWM circuit 5 predriver 6 power driver 7 sensor signal generation circuit 8 sensor signal switching logic circuit 9 start commutation sensor signal generation circuit 10 start commutation duration setting circuit 11 Clock signal generation circuit 12 Motor commutation control circuit 13 Protection circuit 14 Inhibit circuit 15 External power supply 16 Power supply circuit 17 Saving standby power supply circuit 18 Restart circuit 18a Period determination circuit 18b Voltage saving Vcs level detection circuit 18c Start trigger circuit 18d Retrigger interval Circuit 21 Watchdog timer 22 ・ 23 Monostable multivibrator

Claims (2)

[Claims] 1. A rotor position signal generating circuit for detecting a position of a rotor by an induced voltage generated in a stator coil by rotation of the rotor to generate a rotor position signal, and rotating the rotor based on the rotor position signal. A rotating magnetic field generating circuit for generating a rotating magnetic field in the stator coil, and determining whether or not the generation cycle of the rotor position signal is in a normal rotation area and determining that the generation cycle is outside the normal rotation area. And a restart circuit for resetting the rotating magnetic field generation circuit to a restart state. 2. The restart circuit according to claim 1, wherein the restart circuit resets the rotating magnetic field generation circuit after the determination, and performs the restart after an elapse of an interval time for cooling a power element. Control circuit for brushless motor.