JP3317362B2 - Motor control circuit and motor driven device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control circuit, and more particularly, to a hard disk drive, an optical disk drive, various drive devices having a motor, and a fan motor for detecting the rotation speed of a motor and controlling the rotation. TECHNICAL FIELD The present invention relates to a motor control circuit capable of promptly stopping the rotation of a motor in a device having a motor that rotates at a constant speed, such as various OA devices having a motor, and a driving device using the motor.

[0002]

2. Description of the Related Art FIG. 3 shows a control circuit of a three-phase motor used in various conventional OA equipment. This motor control circuit includes a motor 9 having three coils 8a, 8b, 8c, a sense circuit mainly including a Hall element 1, an input amplification circuit 2 mainly including a differential amplifier 2a, and a rotation of the motor 9. a reference signal generating circuit 3 for generating a signal for determining the reference speed, a torque control signal generating circuit 4, a motor drive times
Path 5 (hereinafter referred to as a drive circuit 5 ) . The torque control signal generation circuit 4 has a speed comparison circuit 4a and an error amplification circuit 4b. The drive circuit 5 outputs a drive current to the motor 9 and switches the direction of the drive current to change the rotation direction. And a stop direction detecting circuit 5b for detecting the number of rotations of the motor for stopping the drive current and generating a signal for stopping the drive current. .

The operation of this motor control circuit will be described focusing on the signal system of one of the three phases. First, the output signal of the Hall element 1 for detecting the rotation state of the motor 9 is input to the input amplifying circuit 2.
And amplify it by the differential amplifier 2a. Thereafter, the waveform is shaped by a logic circuit or the like, and the detection pulse P
And sends it to the torque control signal generation circuit 4 and the drive circuit 5. The reference signal generation circuit 3 generates and outputs a reference pulse K having a pulse width and a phase for determining the rotation speed of the motor 9. The speed comparison circuit 4a
The detection pulse P is compared with the reference pulse K. Then, the period shift amount or phase shift amount of the comparison result is obtained,
It is integrated, and the integrated value (usually a voltage value) is added to the error amplifier circuit 4b as an error. The error amplifying circuit 4b is an amplifier configured by a differential amplifier or the like, amplifies an error with respect to a reference level of torque control, and sets a level of a torque control signal corresponding to the reference rotational speed as a reference level, A necessary torque control signal is generated at that time by adding the amplified error. Thereby, a torque control signal T (usually a voltage value) corresponding to the phase shift amount of these pulses P and K.
Is generated. This signal T is sent to the torque control terminal 5c of the drive circuit 5.

The drive circuit 5 receives the detection pulse P,
A drive waveform is generated from the pulse P. At this time,
In response to the torque control signal T, a drive current that determines the magnitude of the drive waveform (current amount), that is, the magnitude of the torque, is generated and output according to the magnitude of the signal T (its voltage level). As a result, the drive current rotates the motor 9 in a direction in which the error in the error amplifier circuit 4a is eliminated. As a result, automatic control is performed so that the rotation speed becomes the reference rotation speed. More specifically, when the rotation speed of the motor 9 is lower than the period of the reference pulse K for setting the reference rotation speed and the period of the detection pulse P is slower, the reference torque value (reference rotation speed) is determined according to the torque control signal T. In this state, an output current for generating a torque larger than the torque balanced with the load) is output from the drive circuit 5 to the motor 9. Conversely, when the speed is high, the drive circuit 5 supplies a drive current for reducing the torque from the reference torque value to the motor 9 according to the torque control signal T.
Or stop the drive current. When the motor is rotating at the set number of revolutions (in the state of the reference rotational speed), the torque control signal T is at a constant level set as a reference.

[0005]

In the normal control, the torque control signal T is determined based on the one-phase detection pulse P in this manner, and the three-phase coils 8a, 8b, The drive current of 8c is determined, and the drive current is supplied to the motor 9 to control the rotation of the motor to be constant.

When a stop signal S is received from the outside, the drive circuit 5 outputs a drive current for generating a reverse maximum torque so that the rotation direction switching circuit 5a stops the rotation of the motor 9 quickly. To the coils 8a, 8b,
8c, thereby braking. The speed is reduced by the reverse torque, and the speed of rotation of the motor 9 is reduced. When the speed is reduced to a predetermined speed, in other words, when the rotation speed becomes equal to or lower than the predetermined rotation speed, the stop rotation speed detection circuit 5b detects this, and the drive circuit 5 drives the coils 8a, 8b, 8c. Stop. Thereafter, the rotation of the motor 9 is stopped by the frictional force. In the conventional motor control circuit, the rotation of the motor 9 is stopped in this way.

Here, the timing at which the output of the reverse drive current is stopped is further delayed from the point in time at which the output is reduced to the predetermined speed, in other words, the stop rotation speed detecting circuit 5
If the detected rotation speed c is set to a lower rotation speed, the motor can be stopped in a shorter time. However, in this case, in the conventional stop method, there is a danger that the motor will reverse because the braking control is performed by applying the maximum reverse torque. In order to avoid this danger, the predetermined speed cannot be sufficiently reduced, and the motor is stopped by increasing the time depending on the frictional force. As a result, it can not be a short stop time Oa Mari of the motor. SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the prior art. In a motor control circuit for driving a motor in a reverse direction to enter a stop control, a reverse rotation phenomenon does not easily occur in the motor, and the motor rotates quickly. It is an object of the present invention to provide a motor control circuit and a motor drive device capable of stopping the motor.

[0008]

A feature of the motor control circuit according to the present invention is that the motor is driven to rotate by a drive current according to a torque control signal, and a reverse torque is generated in the motor when a stop signal for stopping the motor is received. A motor control circuit for stopping the rotation of the motor by providing a level inversion circuit for inverting the level of the torque control signal with respect to a predetermined reference level between the torque control signal generation circuit and the drive circuit; When receiving the torque control signal, the level control circuit outputs a torque control signal whose level is inverted by the level inversion circuit to the drive circuit, and the reference signal generation circuit receives the stop signal separately from a reference signal corresponding to a rotation speed serving as a reference of the motor. Sometimes, a reference signal corresponding to a rotation speed lower than the reference rotation speed is generated.

[0009]

The motor control circuit having the above-described configuration can stop the motor quickly without risk of reverse rotation of the motor during the motor stop control. First, the operation of maintaining the rotating state of the motor in the forward rotation state is as follows.
As described above, since the operation is completely the same as that of the conventional art, the explanation is omitted, and the reason is described by explaining the operation when the motor is stopped. In the above configuration, when in the normal forward rotation operation state,
When the drive circuit receives a stop signal from the outside to stop the rotation of the motor, the conventional drive circuit first generates a large reverse torque and waits until the number of revolutions becomes equal to or less than a predetermined value. The control at this time has no relation to the torque control signal. On the other hand, in the present invention, the torque control signal inverted by the output level inversion circuit is used at the time of the motor stop control, and the stop control is performed according to the inverted torque control signal. In this case, the reverse rotation torque decreases as the rotational speed of the motor decreases.
As a result, a large reverse rotation torque is not generated near the motor stop point, and the reverse rotation phenomenon of the motor can be suppressed.
If the drive current is cut off when the rotation of the motor is reduced to such an extent that it can be stopped, the motor is immediately stopped by the rotational friction force of the motor. As a result, the period of stopping by friction is reduced as compared with the conventional one in which the stopping time due to the frictional force is mostly reduced, and the rotation of the motor can be stopped in a short time as a whole.

In the above case, a frequency dividing circuit is built in the reference pulse generating circuit, a pulse generating circuit for generating a frequency higher than the reference pulse, and a frequency dividing circuit for generating a reference pulse by dividing the pulse of the pulse generating circuit. The reference pulse generating circuit is constituted by the peripheral circuit. This circuit also receives a stop signal and generates a reference pulse corresponding to a low rotation speed or a low rotation speed close to the stop rotation speed by changing the frequency division ratio of the reference pulse when receiving the stop signal. To do it. A comparison between the reference pulse corresponding to the low rotation speed and the detection pulse P generates a torque control signal having a large error signal, so that a large reverse rotation torque can be generated when the stop signal is received. Moreover, the addition of such a reference pulse generating circuit and a level inverting circuit is a very slight change from the viewpoint of a conventional motor control circuit, and thus, a more effective stop control can be achieved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the motor control circuit shown in FIG. 1, a reference pulse generation circuit 13 is provided in place of the reference pulse generation circuit 3 in the motor control circuit shown in FIG. Drive circuit 1 not provided
3 and an output level inversion switching circuit 16 is provided between the torque control signal generating circuit 4 and the drive circuit 15.

As in the prior art, the output of the Hall element 1 for detecting the rotation state of the motor 9 (see FIG. 2A) is received by the input amplifier circuit 2 and amplified by the differential amplifier 2a. , As a detection pulse P and output. This detection pulse P (see FIG. 2B) is sent to the torque control signal generation circuit 4 and the drive circuit 15. The reference pulse generating circuit 13 includes a clock generating circuit 13a, a counter 13b as a frequency dividing circuit, and the like. By setting the count value of the counter 13b, the clock generation circuit 13a
A reference pulse K having a predetermined pulse width and phase, which determines the rotation speed of the motor 9 by dividing the frequency of the clock according to the set value, is output. The reference pulse K (see (c) of FIG. 2) is a pulse having a cycle corresponding to the target rotation speed, and when the target rotation speed is changed, the counter 1 of the circuit 13 is correspondingly changed.
What is necessary is just to change the target value set to 3b. As a result, the frequency division ratio with respect to the clock changes, which changes the period of the reference pulse K. However, in normal operation, this circuit 13 outputs a pulse K having the same cycle as that of the reference pulse generating circuit 3 of the conventional example.

The torque control signal generation circuit 4 compares the detection pulse P with the reference pulse K by the speed comparison circuit 4a as in the prior art. Then, a period shift amount or a phase shift amount of these pulses as a result of the comparison, in other words, a speed shift amount in a speed state indicated by these pulses is generated, integrated, and added to the error amplifier circuit 4a. As a result, a torque control signal T corresponding to the speed deviation of these pulses P and K is generated. The period between the detection pulse P and the reference pulse K may be measured, for example, by counting the width of each pulse width by the reference lock. When the speed deviation is detected by comparing the phases, the difference between the two pulse widths is determined. Here, a period shift amount is generated as a speed difference signal. However, depending on the form of the waveform of the detection pulse P and the reference pulse K, these phase shift amounts can be used as the speed difference signal.

The output level inversion switching circuit 16 is composed of a changeover switch, an operational amplifier and the like. This circuit sends the torque control signal T to the torque control terminal 15b of the drive circuit 15 as it is in a conventional operation during normal operation in which the rotation of the motor 9 is normal. Therefore, in normal operation, this circuit 16 has no influence on the control operation of the motor. On the other hand, at the time of motor stop control, that is, at the time of motor braking, a voltage signal having a voltage level obtained by inverting the voltage level of the torque control signal T with reference to the voltage level of the torque control signal T in the reference rotation state is generated.

Here, the voltage of the torque control signal T when rotating at the reference rotational speed applied to the torque control terminal 15b is Vr (this is the reference level for signal inversion). In a motor control circuit of this kind, this is usually Vr
= + Vcc / 2 (where + Vcc is the power supply voltage). For example, if + Vcc is 5V, Vr is 2.5
V. Further, the error voltage generated by the error amplifier circuit 4b corresponding to the speed deviation amount between the pulse P and the pulse K is V, the voltage of the torque control signal T is VT, and the motor control operation will be described in detail. , When the period of the pulse P and the period of the pulse K coincide with each other, that is, when the motor 9
Is rotating, the error is zero, and the value of the error voltage V is "0". As a result, the torque control voltage VT becomes Vr + 0, and the voltage Vr is applied to the torque control terminal 15b.

On the other hand, when the rotation of the motor becomes slower than the reference rotation speed, the period of the detection signal on the side of the Hall element 1 decreases, and when the phase is delayed, the phase of the detection pulse P becomes later than that of the reference pulse K. As a result, an error occurs between them, and an error voltage + V is generated. Torque control voltage V
T becomes Vr + V, and Vr is applied to the torque control terminal 15b.
A + V voltage value is applied. On the contrary, when the speed is high, the torque control voltage VT becomes Vr-V, and the torque control terminal 15b
Has a voltage value of Vr-V. Therefore, as shown in FIG. 2C, the output level inversion switching circuit 16
In the normal state, the torque control signal T corresponding to the voltage value of Vr ± V corresponding to the detection pulse P is directly applied to the torque control terminal 15b.

The drive circuit 5 receives the detection pulse P,
A drive waveform for generating torque is generated from the pulse P. As described above, at this time, the torque control terminal 15b receives the signal from the output level inversion switching circuit 16, and according to the magnitude of the voltage Vr ± V, the magnitude of the drive waveform, that is, the magnitude of the torque, is increased. I can decide. For example, in the state of the reference rotational speed, the value of V is “0”, so the voltage value of Vr is received at the torque control terminal 15b, and the amount of current that generates the reference torque balanced with the resistance of the load accordingly. A drive signal having a predetermined voltage waveform (see the solid line in FIG. 2E) corresponding to the pulse P is applied to the motor 9.

When the rotation speed of the motor 9 is lower than the period of the reference pulse K for setting the reference rotation speed and the period of the detection pulse P is longer, the higher voltage (FIG. 2 (e)) in accordance with the signal voltage Vr + V. The driving power of a larger current is transmitted to the motor 9 at the dotted line in FIG. As a result, a torque larger than the reference torque value (a torque larger than the resistance of the load) is generated, and the motor 9 is accelerated. Conversely, when it is fast, the motor 9 sends out a smaller amount of drive power to the motor 9 at the lower voltage (see the dashed line in FIG. 2E) in accordance with the signal voltage Vr-V. This lowers the torque from the reference torque value,
Decelerate by the resistance of the load. In normal control, the coils 8a, 8b, 8c are driven in this way, and the rotation of the motor 9 is maintained. In the above case,
Reducing the torque includes stopping the drive current itself to reduce the torque to zero.

Next, when the vehicle is in such a normal rotation state and further receives a stop signal S from outside,
The stop control of the motor control circuit of this embodiment will be described in detail. Unlike the conventional example, the stop signal S is received by the output level inversion switching circuit 16 and the reference pulse generation circuit 13 in addition to the drive circuit 15, and affects the operation of these circuits. Further, the current direction is switched by the rotation direction switching circuit 15a and is reversed. Upon receiving the stop signal S, the reference pulse generation circuit 13 changes the target rotation speed, and generates and outputs a reference pulse K having a pulse width instructing low-speed rotation as a second reference signal. At this time, since the current direction has already been switched by the rotation direction switching circuit 15a, the following operation is an operation for reverse rotation.

First, when the stop signal S is received,
The detection pulse P is compared with the reference pulse K delayed in phase. This is when the phase of the detection pulse P is ahead of the phase of the reference pulse K, and the rotation state is faster than the setting. At this time, a large phase difference occurs. The output voltage value of the speed comparison circuit 4a becomes large. As a result, the output voltage value of the error amplifier circuit 4b also becomes large. The voltage VT of the torque control signal T at the time of exceeding the speed becomes Vr-V, and the control is performed so as to generate a torque as small as possible by the large error voltage V. This is a low voltage value on the ground level side when viewed from Vr = + Vcc / 2. Here, the reason why the target rotation speed is changed to the low-speed rotation side in response to the stop signal S is to generate a large error voltage V.

The output level inversion switching circuit 16 having received the stop signal S receives this voltage VT = Vr-V and inverts this level with reference to Vr. As a result, the voltage input to the torque control terminal 15b inverts the large error voltage −V and outputs a torque control signal * T (* T is an inverted signal of the torque control signal T) of the output level inversion switching circuit 16. Is Vr + V. In response, the drive circuit 15 attempts to supply a current that generates a large torque. In addition, the drive circuit 15 which has received the stop signal S turns the rotation direction switching circuit 15a.
Has already switched the current direction, this results in a large torque to rotate in the opposite direction. As a result, the motor 9 is driven with a large reverse torque to apply a brake.
Due to this large reverse torque, the motor 9 is rapidly decelerated, and its rotation speed is reduced.

When the rotation speed decreases, the reference signal generation circuit 13
Instructs becomes below the rotational speed of the low speed setting, opposite bets
The level of the control signal of Luk tends to further decrease.
This is because the cycle between the reference pulse K and the detection pulse P is reversed . At this time, the output voltage of the speed comparison circuit 4a and the output voltage of the error amplifier circuit 4b are inverted with reference to the voltage Vr, and the error voltage becomes + V. The output voltage VT of the torque control signal T becomes Vr + V. As a result, the torque control signal * T of the output level inversion switching circuit 16 becomes Vr
From Vr-V. There is inertia in the rotation of the motor
And the frequency of the detection signal gradually decreases,
Thus, the value of the voltage V of -V gradually increases. Thereby, the torque (Vr-V) for reversely rotating the motor gradually decreases. When the rotation speed further decreases, the phase difference increases, the fluctuation voltage + V increases, and the value of the output voltage Vr-V of the torque control signal * T further decreases. When the value of the output voltage Vr-V of the torque control signal * T becomes smaller than a certain value, the output voltage exceeds the lower torque generation control limit point, and no torque is generated, in other words, the drive circuit 15 is driven. No current is output, and the output operation of the driving current is inevitably stopped. Thus, the rotation of the motor is stopped by the frictional force of the motor itself.

As described above, the motor 9 gradually becomes in the state of the small reverse rotation torque, and the rotation is reduced in a short time.
No reversal phenomenon occurs. In this manner, the rotation speed is sufficiently reduced to a speed close to the stop, and the drive current of the coils 8a, 8b, 8c is stopped there. As a result, thereafter, the rotation of the motor 9 is immediately stopped by the frictional force. Therefore, a stop rotation speed detection circuit which is conventionally required can be omitted.

As understood from the above description, in the present invention, the reverse rotation torque at the time of braking acts so as to decrease as the rotation speed of the motor in the forward rotation direction decreases. In addition, the rotation of the motor 9 can be stopped quickly by adding a simple circuit such as adding an output level inversion switching circuit. In the above description, the control is performed such that the torque control signal T of Vr ± V is generated in accordance with the error signal V based on Vr, but when the torque control signal T becomes equal to or lower than Vr, the drive is performed. The output of the circuit 15 may be stopped so that the motor is not driven at all. In this case, when the torque control signal T falls below Vr, the output current of the drive circuit 5 is cut off, and the motor is not driven.

In the above embodiment, the speed comparison circuit generates a signal corresponding to the speed difference by comparing the period or the phase between the reference pulse and the detection pulse. What is necessary is just to generate the signal of the quantity according to the fluctuation | variation with respect to a reference rotation speed. Therefore,
Neither the reference pulse nor the detection pulse need be a pulse signal. The reference pulse may be a constant frequency signal, and the detection pulse may be a signal whose frequency changes according to the rotation of the motor. This is because a signal of a speed difference can be obtained by comparing these frequencies.

[0026]

As can be understood from the above description, according to the present invention, the torque control signal inverted by the output level inversion circuit is used at the time of motor stop control, and the stop control is performed in accordance with the inverted torque control signal. Is performed, the reverse rotation torque decreases as the rotational speed of the motor decreases. As a result, a large reverse rotation torque is not generated near the motor stop point, and the reverse rotation phenomenon of the motor can be suppressed.

If the drive current is cut off when the rotation of the motor is reduced to such an extent that it can be stopped, the motor is immediately stopped by the rotational friction force of the motor. As a result, the period of stopping by friction is reduced as compared with the conventional one in which the stopping time due to the frictional force is mostly reduced, and the rotation of the motor can be stopped in a short time as a whole.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram of a three-phase motor according to an embodiment of a motor control circuit of the present invention.

FIG. 2 is a signal waveform diagram for explaining an operation of the motor control circuit of FIG. 1;

FIG. 3 is a control circuit of a three-phase motor as a conventional motor control circuit.

[Explanation of symbols]

 Reference Signs List 1 Hall element 2 Input amplification circuit 3 Reference signal generation circuit 4 Motor torque control signal generation circuit 5 Motor drive circuit 8 Coil 9 Motor 13 Reference signal generation circuit 15 Motor drive circuit 16 Output level inversion switching circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-250692 (JP, A) JP-A-4-75486 (JP, A) JP-A-60-162491 (JP, A) 113006 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/24

Claims (2)

(57) [Claims] A reference signal generating circuit for outputting a reference signal for setting a rotation speed serving as a reference of the motor; and a detection signal regarding the rotation speed of the motor and a speed state indicated by the reference signal. A torque control signal generating circuit that outputs a torque control signal that returns to the torque corresponding to the reference signal, and sends a drive current that generates a torque according to the torque control signal to the motor to rotationally drive the motor; A motor control circuit having a drive circuit that controls the motor to generate torque in a reverse direction when receiving a stop signal for stopping the motor and stop the rotation of the motor, wherein the torque control signal generation circuit; A level inversion circuit for inverting the level of the torque control signal with respect to a predetermined reference level is provided between the drive circuit and the drive circuit. When the stop signal is received, the level control circuit outputs the torque control signal whose level is inverted by the level inversion circuit to the drive circuit. The reference signal generation circuit uses the reference signal as a first reference signal and outputs the stop signal. And a motor control circuit that outputs a second reference signal based on a rotation speed lower than the reference rotation speed to the torque control signal generation circuit. 2. A motor, a reference signal generation circuit for generating a reference signal indicating a rotation speed serving as a reference of the motor, a speed signal generation circuit for generating a rotation speed signal corresponding to the rotation speed of the motor, A speed comparison circuit that compares a reference signal with the rotation speed signal to generate a speed difference signal corresponding to the speed difference indicated by the reference signal and a torque corresponding to the reference signal in response to the speed difference signal according to the difference; A control signal generating circuit for outputting a torque control signal for generating a torque corresponding to the reference signal when the speed difference signal no longer indicates a difference, and a torque according to the torque control signal. Is transmitted to the motor to rotate the motor, and when a stop signal for stopping the motor is received, the motor is reversely triggered. A drive circuit that controls the motor to stop the rotation of the motor by generating a torque, and is provided between the torque control signal generation circuit and the drive circuit, and a level of the torque control signal with respect to a predetermined reference level. A level inverting circuit for inverting the torque control signal, the level inverting circuit receiving the stop signal, outputting the level-inverted torque control signal to the drive circuit, and the reference signal generating circuit receiving the stop signal. A motor drive device that receives the stop signal and outputs a second reference signal based on a rotation speed lower than the reference rotation speed to the speed comparison circuit as the first reference signal.