JPH08266078A - Control circuit of motor and disk device - Google Patents

Abstract

PURPOSE: To shorten the rotational settling times of a control circuit of a motor which controls the motor at a plurality of rotational speeds and to improve the disturbance torque suppressing characteristic of a disk device. CONSTITUTION: In a control circuit of a motor, in response to the command signal of a speed-command device 13, a gain switch 15 selects one charge pump from a plurality of charge pumps 15B by a switch 15A. Since the charge pumps 15B have respectively different output resistances from each other, with respect to the gain variation of a controlled system, the gain of a compensation element is varied by the switching of the charge pumps 15B. Thereby, the stable control of the control circuit of the motor is always obtained, keeping its gain crossover frequency constant. As a result, the rotational settling times of the control circuit of the motor are shortened adaptively to a plurality of rotational speeds, and when the control circuit is used for a disk device, the disturbance torque suppressing characteristic of the disk device is improved adaptively to the plurality of rotational speeds.

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 for controlling a plurality of rotation speeds and a disk device using the same.

[0002]

2. Description of the Related Art In recent years, a disk device having a large capacity and a high access speed is desired, and several rotation control methods have been proposed so far. Hereinafter, a disk device of the CLV system, which is one of the conventional rotation control systems, will be described. The advantage of the CLV method is that the recording density can be optimized by controlling the rotational speed so that the linear velocity is constant even if the radial position for recording / reproducing changes, and that the recording / reproducing frequency is constant. In addition, the circuit configuration of the recording / reproducing system can be simplified. However, in the CLV method, it is necessary to wait until the rotational speed of the disk medium stabilizes at a specified value each time the radial position for recording / reproducing changes.
The long waiting time (rotation settling time) is a drawback. In order to realize a disk device with a high access speed, it is desirable that the rotation settling time be short. Further, when a disturbance torque is generated during recording / reproduction, the rotational speed of the disk medium is temporarily changed, which causes a recording / reproduction jitter and causes an error. The ability to maintain a stable rotation speed (disturbance suppressing characteristic) with respect to disturbance torque is an essential element not only in the CLV system but also in general disk devices.

A conventionally known motor control circuit for controlling a motor at a plurality of rotation speeds will be described below. FIG. 2 is a circuit diagram showing a conventional motor control circuit.
In FIG. 2, 21 is a motor, 22 is an encoder, 23 is a speed commander, 24 is a speed discriminator, 25 is a charge pump, 26 is an integrator, and 27 is a motor driver. The charge pump 25 includes two transistors TR
The emitters of 1 and TR2 are connected in series between the power supply voltages Vdd and Vss. The deceleration pulse signal output from the speed discriminator 24 is connected to the base of the transistor TR1 on the Vdd side, and the acceleration pulse signal is connected to the base of the transistor TR2 on the Vss side. The collectors of the transistors TR1 and TR2 are connected to the integrator 26 at the next stage via the resistor Rs. The integrator 26 has an operational amplifier OP1, and its inverting input terminal-is connected to the resistor Rs of the charge pump 25 at the preceding stage. The capacitor C1 and the resistor Rf are connected in series, and are connected in parallel to the output terminal and the inverting input terminal-of the operational amplifier OP1. Similarly for the capacitor C2, the operational amplifier OP1
In parallel. Non-inverting input terminal of operational amplifier OP1 +
Is connected to a reference voltage Vref that holds the rotation speed of the motor. The output terminal of the operational amplifier OP1 is connected to the motor driver 27 at the next stage, and the output of the motor driver 27 is connected to the motor 21.

The operation of the conventional motor control circuit configured as described above will be described below. The encoder 22 detects the rotation speed of the motor 21 as an FG signal. The speed command device 23 outputs the target rotation speed as a command signal. The speed discriminator 24 discriminates between the FG signal and the command signal, and outputs a deceleration pulse when the rotation speed of the motor is faster than the rotation speed indicated by the speed command device, and outputs an acceleration pulse when the rotation speed is slower. The pulse signal output by the speed discriminator 24 is input to the charge pump 25. FIG. 3 shows an operation waveform diagram of a conventional example. 3a shows a deceleration pulse waveform of the speed discriminator 24, 3b shows an acceleration pulse waveform, and 3c shows a waveform at the output terminal P point of the charge pump 25. When a deceleration pulse is input to the charge pump 25, the transistor T
R1 is turned on, and the potential at point P transitions to near Vdd. When the deceleration pulse is input, the transistor TR2 is turned on, and the potential at the point P transits to near Vss. When no pulse signal is input, the potential at point P is the reference potential Vre.
f. The integrator 26 integrates the acceleration pulse and the deceleration pulse output from the charge pump 25 into a continuous control signal, which is amplified by the motor driver 27 so that the rotation speed of the motor 21 reaches a target rotation speed. Change.

[0005]

However, the above-mentioned conventional structure has the following problems with respect to the rotation settling time of the motor control circuit and the disturbance suppressing characteristic of the disk device.

First, regarding the rotation settling time of the motor control circuit, in the conventional configuration, the rotation settling time is shortest only for a specific rotation speed, and the rotation settling time is long for other rotation speeds. Had a point. Less than,
The cause will be described with reference to the drawings. FIG. 4 is a frequency characteristic diagram showing the gain of the conventional motor control circuit. In FIG. 4, 4a represents the gain characteristics of the controlled object and the compensation element, and 4b represents the open-loop gain characteristics obtained by combining them. Reference numeral 41 represents a gain characteristic of an integrator which is a compensation element, and reference numerals 42, 43 and 44 respectively represent a gain characteristic of a motor at rotational speeds A, B and C which are control targets. Reference numerals 45, 46 and 47 represent open loop gain characteristics of the motor control circuit at the rotational speeds A, B and C, respectively. In the motor control circuit of the conventional example, since the gain of the compensation element can be set only once,
It is designed so that an optimum gain characteristic can be obtained for a specific rotation speed. In FIG. 4, the gain characteristic 4 of the compensation element
1 is the gain crossover frequency f so that the sum of the gains of both is 0 dB when the control target is the gain characteristic 43 of the rotation speed B.
c is provided. Since the control system can obtain the most stable control at the gain intersection frequency fc, the conventional motor control circuit has the shortest rotation settling time when the rotation speed is switched to B.

However, when the number of revolutions is switched to A or C, the stability of the control is deteriorated and the settling time of the revolution is increased because it deviates from the gain intersection frequency fc like the open loop gain characteristics 45 and 47. FIG. 6 is a velocity waveform diagram showing the number of revolutions of a conventional motor, which expresses the above problem. In FIG. 6, reference numeral 61 indicates the number of revolutions A,
Reference numeral 62 indicates a state when switching to the rotation speed B, and 63 indicates a state when switching to the rotation speed C. When the gain of the motor control circuit is the optimum value for the rotation speed B, the rotation settling time is shortest when switching to the rotation speed B of 62, but as shown by 61 and 63, other rotation speeds A and It can be seen that the rotation settling time becomes longer when switching to C.

When the conventional motor control circuit is used to form the disk device, the suppression characteristic against the disturbance torque is excellent only at a specific rotation speed,
For other rotation speeds, there was a problem that the suppression characteristics deteriorate. FIG. 8 shows the above-mentioned problem, and is a waveform diagram of the rotation speed of the conventional motor with respect to the disturbance torque. In FIG. 8, reference numerals 81, 82, and 83 represent the speed fluctuations when the disturbance torque occurs at the rotation speeds A, B, and C, respectively. When the gain of the motor control circuit is the optimum value for the rotation speed B, the speed fluctuation at the rotation speed B is minimum, but the speed fluctuations at the other rotation speeds A and C are large. .

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a motor control circuit in which the rotation settling time is optimum for a plurality of rotation speeds, and a disk device having excellent disturbance suppression characteristics. And

[0010]

In order to achieve this object, a motor control circuit of the present invention uses a speed command means for outputting a plurality of rotation speed command signals, and an error between the motor speed and the command signal. Speed identification means for digitally outputting the error signal obtained, a plurality of charge pump circuits for D / A converting the error signal, and a plurality of charge pump circuits for transmitting the error signal according to the command signal. Selecting means for selecting from among the plurality of charge pump circuits, and each of the plurality of charge pump circuits has a different output resistance.

Further, the disk device of the present invention has a structure using the above-mentioned motor control circuit.

[0012]

With this configuration, stable control can be obtained by switching the gain of the motor control circuit according to the target rotation speed, and the rotation settling time can be shortened for a plurality of rotation speeds. Further, when used in a disk device, the disturbance suppression characteristic can be improved for a plurality of rotation speeds.

[0013]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 11 is a motor, 12 is an encoder, 13 is a speed commander, 14 is a speed discriminator, 15 is a gain switcher, 16 is an integrator, and 17 is a motor driver. The gain switcher 15 includes a switch 15A and a plurality of charge pumps 15B. Since the pulse signal output from the speed discriminator 14 is a digital signal, the switch 15A can be realized by using a digital multiplexer of a standard logic circuit. The charge pump 15B is composed of a plurality of charge pump circuits having different output resistances Rn, and each charge pump circuit connects the emitters of two transistors TRna and TRnb in series between the power supply voltages Vdd and Vss, and
The deceleration pulse signal is connected to the base of the transistor ddna on the dd side, and the acceleration pulse signal is connected to the base of the transistor TRnb on the Vss side. Transistor TRn
The collectors of a and TRnb are connected to the integrator 16 of the next stage via the resistor Rn. The integrator 16 is an operational amplifier OP1
And an inverting input terminal-of the charge pump 1 of the preceding stage
Resistance R of one charge pump circuit selected from 5B
connect to n.

The capacitor C1 and the resistor Rf are connected in series, and are connected in parallel to the output terminal and the inverting input terminal-of the operational amplifier OP1. Similarly, the capacitor C2 is an operational amplifier OP.
Connect to 1 in parallel. The non-inverting input terminal + of the operational amplifier OP1 is connected to the reference voltage Vref that holds the rotation speed of the motor. The output terminal of the operational amplifier OP1 is connected to the next-stage motor driver 17, and the output of the motor driver 17 is connected to the motor 11.

The operation of the motor control circuit of this embodiment constructed as described above will be described below. The encoder 12 detects the rotation speed of the motor 11 as an FG signal. The speed command device 13 outputs a target rotation speed as a command signal. The speed discriminator 14 discriminates between the FG signal and the command signal, and outputs a deceleration pulse when the rotation speed of the motor is faster than the rotation speed indicated by the speed command device, and outputs an acceleration pulse when the rotation speed is slow. The pulse signal output by the speed discriminator 14 is
It is input to the gain switcher 15. The gain switcher 15 is
A switch 15A selects a charge pump having a gain corresponding to the command signal.

The selection method can be realized by using a digital multiplexer and previously determining the combination of the command signal and the charge pump. The integrator 16 is a gain switch 1
The acceleration pulse and the deceleration pulse output from 5 are integrated into a continuous control signal, and this control signal is used by the motor driver 1
It is amplified by 7, and the rotation speed of the motor 11 changes to the target rotation speed.

The gain of the motor control circuit depends on the resistance Rn of the charge pump 15B and the integrator 1 in the circuit diagram of FIG.
It is determined by the ratio of the resistance Rf of 6. Therefore, by switching the charge pump with the switch 15A of the gain switching device, the value of the resistor Rn changes, so that the gain of the motor control circuit changes.

FIG. 5 is a frequency characteristic diagram showing the gain of the motor control circuit of the first embodiment. In FIG. 5, 5a represents the gain characteristics of the controlled object and the compensation element, and 5b
Represents the open-loop gain characteristic that combines them. Reference numerals 51, 52 and 53 represent the gain characteristics of the compensation elements when the charge pumps having the gains A, B and C are selected, and 54, 55 and 56 are the rotation speeds A, B and C.
3 shows the gain characteristic of the controlled object in. Reference numeral 57 represents the open loop gain characteristic of the first embodiment.

In FIG. 5, for example, when the rotation speed B of the motor is switched to C, the gain characteristic of the motor to be controlled changes from 55 to 56. At this time, by switching the gain characteristic of the compensation element from 52 to 53, the open loop gain characteristic obtained by combining the gains of both can be maintained at 57. As described above, in this embodiment, when the number of revolutions is switched, the gain of the compensating element is also changed by the gain switching device, so that the gain intersection frequency of both the controlled object and the compensating element does not change. Therefore, since the motor control circuit can always obtain stable control at the gain intersection frequency, the rotation settling time can be shortened without depending on the rotation speed.

FIG. 7 is a velocity waveform diagram showing the number of rotations of the motor of the first embodiment. In FIG. 7, reference numerals 71, 72 and 73 represent the states when switching to the rotation speeds A, B and C, respectively. When compared with FIG. 6 of the speed waveform diagram of the conventional example, it is understood that the present embodiment has a stable rotation speed in a short time regardless of the rotation speed. Therefore, in this embodiment, the rotation settling time is shortened for a plurality of rotation speeds, and the superiority of this embodiment can be seen.

(Embodiment 2) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 10 is a schematic diagram of a disk device showing a second embodiment of the present invention. FIG.
In No. 0, 101 is the motor control circuit shown in the first embodiment of the present invention, and the motor is also included in 101. 102 is a disk medium, and 103 is a hub that supports the disk medium. Reference numeral 104 is a head, and 105 is an arm that supports the head.

The operation of the disk device configured as described above will be described below. First, the torque generated by the motor control circuit 101 rotates the disk medium 102 through the hub 103. On the other hand, the head 104 is in contact with the disk medium 102 during recording or reproduction.
Even after the motor control circuit 101 switches the rotation speed and the rotation speed of the disk medium 102 is settled, the contact state between the head 104 and the disk medium 102 (for example, the disk medium 102).
Since the friction coefficient changes due to surface wobbling, scratches, dirt, etc., disturbance torque is generated. The generated disturbance torque temporarily changes the rotation speed of the disk medium 102, but the motor control circuit 101 controls the rotation speed to the original rotation speed again.

FIG. 9 is a velocity waveform diagram showing the velocity fluctuation with respect to the disturbance torque in the second embodiment. When compared with FIG. 8 of the speed waveform diagram of the conventional example, the speed variation is small at the rotational speed B because the gain of the motor control circuit is constant in the conventional example, but at the other rotational speeds A and C, the speed variation is small. Grows larger. On the other hand, in the second embodiment, the speed variation is suppressed at any of the rotation speeds A, B, and C. This is a new effect of the motor control circuit 101 that switches the gain according to the number of revolutions, and shows the effectiveness when the motor control circuit of the present invention is applied to a disk device.

In the first embodiment, a plurality of charge pumps having different output resistances are used for the gain switching device, and switching is performed for each charge pump.
The gain switcher may be configured as shown in FIG. 11 by using one charge pump and using only a plurality of output resistors thereof.
FIG. 11 is a circuit diagram showing another configuration of the gain switching device in the first embodiment. In this case, since the output of the charge pump, that is, the analog signal is switched, the switch 111 in FIG. 11 can be realized by using an analog multiplexer of a standard logic circuit.

In the first embodiment, the speed waveform diagram of FIG. 7 shows an example in which the rotation speed is switched from low speed to high speed. However, in the first embodiment, when the rotation speed is switched from high speed to low speed, a motor is used. It is also effective when used at startup.

Further, in the second embodiment, the description has been given by taking the example of the disk device in which the head is in contact with the disk medium, but the present embodiment is effective if the disk device has a disturbance torque factor. . For example, even in a disk device in which the head and the disk medium are not in contact with each other, vibration of the disk device, uneven rotation balance of the disk medium and components rotating with the disk medium, eccentricity of the disk medium, poor clamping accuracy of the disk medium, and chucking accuracy. Disturbance torque is also generated due to the badness of. Therefore, in the second embodiment, the head may be in non-contact with the disk medium. An optical pick may be used instead of the head.

Further, since the motor control circuit of the present invention is effective for a device for controlling a motor at a plurality of rotation speeds, it is not limited to the disk device shown in the second embodiment, and a plurality of rotation speeds can be controlled. It goes without saying that it is also effective for controlling tape devices.

[0029]

As described above, according to the present invention, by switching the gain according to the speed command value, a motor control circuit having a short rotation settling time for a plurality of rotation speeds, and a disk having excellent disturbance suppressing characteristics. The device can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a motor control circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional motor control circuit.

FIG. 3 is an operation waveform diagram of a conventional motor control circuit.

FIG. 4 is a frequency characteristic diagram of a conventional motor control circuit.

FIG. 5 is a frequency characteristic diagram of the motor control circuit according to the first embodiment of the present invention.

FIG. 6 is a speed waveform diagram of a conventional motor control circuit.

FIG. 7 is a velocity waveform chart of the motor control circuit according to the first embodiment of the present invention.

FIG. 8 is a velocity waveform diagram of a conventional disk device.

FIG. 9 is a velocity waveform chart of a disk device according to a second embodiment of the present invention.

FIG. 10 is a schematic diagram of a disk device according to a second embodiment of the present invention.

FIG. 11 is a circuit diagram of another configuration of the gain switching device according to the first embodiment of the present invention.

[Explanation of symbols]

 11 Motor 12 Encoder 13 Speed Commander 14 Speed Discriminator 15 Gain Switcher 15A Switch 15B Charge Pump 16 Integrator 17 Motor Driver

Claims (4)

[Claims] 1. A motor control circuit for controlling a motor at a plurality of rotation speeds, wherein a speed command means for outputting a plurality of rotation speed command signals and an error between a motor rotation speed and the command signal are obtained. A speed identifying means for digitally outputting a signal, a plurality of charge pump circuits for D / A converting the error signal, and a destination of the error signal is selected from the plurality of charge pump circuits according to the command signal. A motor control circuit comprising: selection means, wherein each of the plurality of charge pump circuits has a different output resistance. 2. A motor control circuit for controlling a motor at a plurality of rotation speeds, wherein a speed command means for outputting a plurality of rotation speed command signals and an error between the rotation speed of the motor and the command signal are obtained. A speed identification means for digitally outputting a signal, one charge pump circuit for D / A converting the error signal, and a plurality of output resistors for transmitting the D / A converted error signal according to the command signal. A motor control circuit comprising: 3. An apparatus for performing recording or reproduction on a disk medium, comprising the motor control circuit according to claim 1 or 2. 4. The disk device according to claim 3, wherein the disk medium is a read-only optical disk provided with a magnetic recording portion.