JPH0520808A - Magnetic-head positioning device of magnetic-disk apparatus - Google Patents

Abstract

PURPOSE:To restrain the heat of the title device from being generated by a method wherein a power amplifier is made to perform a switching operation. CONSTITUTION:In the acceleration region of a magnetic head, a switch 9 is made to select a signal 8; in an in-seek operation, a switch 7 is made to select a positive reference voltage +Vref. A gate signal 10 is set to a high level. When an electric current detection signal 23 is smaller than a speed error signal 4, the output of a comparator 12 is set the high level, and a counter 15 performs the counting operation of a clock signal 11 and outputs a signal 16 at a low level until it reaches a prescribed value. Consequently, a signal 18 is at the low level, and an amplifier 20 makes a saturation current flow to a voice-coil motor 21 on the basis of the reference voltage +Vref. When the electric current is increased, the signal 23 is raised and the output of the comparator 12 is set to the low level, the counter 15 is reset and the signal 18 is set to the high level. Consequently, the amplifier 20 stops the driving operation of the voice-coil motor 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head positioning device for a magnetic disk device.

[0002]

2. Description of the Related Art Generally, in a magnetic disk device, in order to position a magnetic head, control for moving the magnetic head from a current track to a target track and control for holding the magnetic head on the target track are performed. In these controls, the magnetic head attached to the movable part is driven by the voice coil motor, and when the current is supplied from the power amplifier, the voice coil motor drives the magnetic head by generating a force proportional to its magnitude. To do. Then, the power amplifier supplies a current proportional to the input voltage to the voice coil motor.

When the magnetic head is moved to the target track, the moving speed of the magnetic head is controlled as shown in FIG. In the figure, the speed signal 24 is a signal whose value changes in proportion to the speed of the magnetic head. However, in the figure, the polarity is reversed. This velocity signal is usually generated based on a signal obtained by differentiating a position signal that changes in a triangular wave shape with the movement of the magnetic head, and is specifically generated by a circuit called an electronic tachometer circuit. Speed reference signal 25
Is generated using a table stored in memory. That is, the track difference from the current track to the target track is set, and the output of a counter called a difference counter, which is subtracted by 1 each time the magnetic head moves one track, corresponds to the number of remaining tracks up to the target track. The data of the speed reference signal is given as an address to the read-only memory in which the data is written, and the data read from the memory is DA-converted.

In FIG. 4, at the time when the magnetic head starts moving, the speed signal 24 is zero and the speed reference signal 2
5 has a large voltage value from the beginning. The difference between the speed reference signal 25 and the speed signal 24 is input to the power amplifier. Since the difference between the speed reference signal 25 and the speed signal 24 is large in the acceleration region of the magnetic head, the power amplifier can output the power amplifier. A voltage larger than the maximum input voltage corresponding to the maximum current value will be applied. Therefore, in this region, the power amplifier is saturated, and a maximum current determined by the power supply voltage of the power amplifier and the resistance value of the voice coil motor flows in the voice coil motor as shown in the figure as the voice coil motor current 26.

As the magnetic head continues to move, the speed reference signal 25 begins to decrease, so that the voice coil motor current 26 has the opposite polarity as shown in the latter half of the figure, and the magnetic head decelerates. At this time, the speed signal 24 follows the speed reference signal 25 and decreases, and the magnetic head reaches the target track.

As described above, in the case of the control method in which a large value is given as the speed reference signal 25 from the beginning, a rapidly rising current flows through the voice coil motor in the acceleration region of the magnetic head, so that the acceleration of the movable part is Becomes larger and induces mechanical resonance of the movable part. The damped vibration remains even after reaching the target cylinder, resulting in deterioration of the positioning accuracy of the magnetic head or an increase in noise during seek.

As a method of solving this problem, as shown in FIG. 5, there is a method of using a speed reference signal 28 in which the voltage value gradually increases from zero in the acceleration region of the magnetic head. In this case, the change of the voice coil motor current 29 becomes smooth as shown in the figure even in the acceleration region, and the problems of deterioration of positioning accuracy and noise can be solved. It should be noted that such a speed reference signal 28 is obtained by reading the value of the difference counter using a microprocessor and DA converting the speed reference signal data written in the read-only memory. Further, in the figure, 27 indicates a speed signal.

[0008]

However, when the voltage value of the speed reference signal is gradually increased from zero,
Although it is possible to smooth the changes in the voice coil motor current, the power amplifier operation becomes linear rather than saturated in the magnetic head acceleration region, increasing the heat loss of the power transistors that make up the power amplifier. However, there is a problem that the heat generation of the device increases.

An object of the present invention is to solve the above problems and to provide a magnetic head positioning device for a magnetic disk device which can smooth the change of the voice coil motor current and saturate the operation of the power amplifier. To provide.

[0010]

The present invention provides a voice coil motor for moving a magnetic head of a magnetic disk device,
In a magnetic head positioning device including this voice coil motor drive circuit, the voice coil motor is driven only when a predetermined control signal is given, and a current corresponding to an input voltage is supplied to the voice coil motor. A power amplifier, a power supply that supplies the input voltage that is constant to the power amplifier, a current detection unit that detects the magnitude of the current flowing through the voice coil motor, and a magnitude of the current detected by the current detection unit. When it is smaller than the specified value,
Switching control means for applying the control signal to the power amplifier is provided in the drive circuit.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an example of a magnetic head positioning device of a magnetic disk device according to the present invention. Reference numeral 21 is a voice coil motor, and 20 is a power amplifier for supplying a current to the voice coil motor 21. The resistor 22 connected in series with the voice coil motor 21 is for detecting a current flowing through the voice coil motor 21.

The summing amplifier 3 receives the speed reference signal 1 and the speed signal 2 and outputs a speed error signal 4. The speed error signal 4 is input to the analog switch 9, the non-inverting input terminal of the comparator 12, and the inverting input terminal of the comparator 13. The analog switch 7 selects and outputs either the positive reference voltage + Vref or the negative reference voltage -Vref, and the analog switch 9 selects either the output voltage or the speed error signal 4 from the summing amplifier 3. , And outputs to the amplifier 20 as a power amplifier input signal 19. Positive and negative reference voltages + Vref, -Vr
The absolute value of ef is sufficiently large, and the power amplifier 20 operates in a saturated state when these voltages are input.

The current detection signal 23 from the connection point between the resistor 22 and the voice coil motor 21 is fed back to the amplifier 20 and also input to the inverting input terminal of the comparator 12 and the non-inverting input terminal of the comparator 13. The output terminals of the comparators 12 and 13 are wired-OR connected,
It is given to the counter 15 as the reset signal 14. The counter 15 counts the clock signal 11 having a constant frequency, and outputs a counter output signal 16 whose level changes every time the predetermined number of clock signals 11 are counted. The gate signal 10 and the counter output signal 16 are input to the AND circuit 17, and when both are at the high level, the inhibit signal 18 at the high level is output. When the high-level inhibit signal 18 is input, the power amplifier 20 stops driving the voice coil motor 21.

Next, the operation at the time of in seek for moving the magnetic head toward the center of the disk will be described. FIG. 2 shows changes in each signal in that case. The voltage value of the speed reference signal 1 gradually increases from zero to the maximum value at the start of the seek operation, and then gradually decreases in the deceleration region. The speed signal 2 changes following the change in the speed reference signal 1. However, in the drawing, in order to make the correspondence with the speed reference signal 1 easy to understand, the polarities are reversed. The adding amplifier 3 adds the speed reference signal 1 and the speed signal 2 and outputs the result as a speed error signal 4. The velocity error signal 4 has a positive polarity in the acceleration area of the magnetic head and a negative polarity in the deceleration area.

As the gate signal 10, a signal having a high level in the section of the acceleration region of the magnetic head is given. The gate signal 10 is referred to a table of time values corresponding to the length of each seek written in the read-only memory by the microprocessor, and becomes high level for the time corresponding to the acceleration region after the start of seek. To generate. While the gate signal 10 is at the high level, the AND circuit 17
The counter output signal 16 is supplied to the amplifier 20 through.

In the acceleration region of the magnetic head, the analog switch 9 is made to select the reference voltage signal 8 and the analog switch 7 is made to select the positive reference voltage + Vref because of the in-seek operation.

FIG. 3 is an enlarged view of a part of the acceleration region of FIG. In the in-seek acceleration region, the comparator 12 operates. First, when the current detection signal 23 is smaller than the speed error signal 4, the output signal of the comparator 12, that is, the reset signal 14 is at the high level, and therefore the counter 15 performs the counting operation. The low-level output signal 16 is output until the predetermined number of clock signals 11 are counted, and this signal 16 is given to the power amplifier 20 as the inhibit signal 18 through the AND circuit 17. Since the inhibit signal 18 is at a low level, the amplifier 20 has a sufficiently large voltage value (+ V) of the input signal 19.
The current is supplied to the voice coil motor 21 according to ref). As a result, the current flowing through the voice coil motor 21 increases according to the time constant determined by the inductance of the voice coil motor 21, and the voltage value of the current detection signal 23 also increases. When the current detection signal 23 becomes larger than the speed error signal 4, the reset signal 14 output from the comparator 12 becomes low level and the counter 15 is reset. As a result, the output signal 16 of the counter 15 changes to high level, and the high-level inhibit signal 18 is supplied to the amplifier 20, so that the amplifier 20 stops driving the voice coil motor 21. Therefore, the current flowing through the voice coil motor 21 decreases, and the current detection signal 2
3 is also smaller.

On the other hand, after the counter 15 is reset,
When the counting operation is restarted and then the count value reaches the predetermined value,
The level of the output signal 16 is inverted and returned to the low level.
Therefore, at this time, the inhibit signal 18 also becomes low level, and the power amplifier 20 restarts the driving of the voice coil motor 21. As a result, the current detection signal 23 starts rising again, and when the speed error signal 4 is exceeded, the counter 15 is reset again and the amplifier 20 causes the voice coil motor 2 to operate.
Stop the driving of 1.

That is, in this magnetic head positioning apparatus, the voice coil motor 21 is switching-driven by the power amplifier 20 in the acceleration region, and the current flowing through the voice coil motor 21 repeats rising and falling within a narrow range to the speed reference signal 1. Controlled to follow.

When the acceleration region of the magnetic head ends, the gate signal 10 becomes low level, and the high level inhibit signal 18 is not input to the amplifier 20.
The amplifier 20 is always driven. In this case, the analog switch 9 is caused to select the speed error signal 4. As a result, the amplifier 20 performs a linear operation, and supplies a current corresponding to the voltage value of the speed error signal 4 to the voice coil motor 2
Supply to 1.

When seeking the magnetic head in the outer peripheral direction of the disk, the analog switch 7 is made to select a negative reference voltage -Vref, and the voltage is supplied to the power amplifier 20 through the analog switch 9 in the acceleration region. The operation in this case is basically the same as the above case except that the comparator 13 operates.

[0022]

As described above, in the magnetic head positioning device of the magnetic disk device according to the present invention, the power amplifier for driving the voice coil motor is switched in the acceleration region of the magnetic head to cause the current flowing through the voice coil motor. Is controlled, it is possible to reduce the heat loss of the power transistor constituting the power amplifier, and it is possible to realize an excellent device with less heat generation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a magnetic head positioning device of a magnetic disk device according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the magnetic head positioning device of FIG.

3 is another waveform diagram for explaining the operation of the magnetic head positioning apparatus of FIG.

FIG. 4 is a waveform diagram for explaining the operation of the conventional magnetic head positioning device.

FIG. 5 is another waveform diagram for explaining the operation of the conventional magnetic head positioning device.

[Explanation of symbols]

 3 Addition amplifier 7,9 Analog switch 12,13 Comparator 15 Counter 20 Power amplifier 21 Voice coil motor 22 Resistance

Claims (1)

Claim: What is claimed is: 1. A magnetic head positioning device comprising a voice coil motor for moving a magnetic head of a magnetic disk device and a drive circuit for the voice coil motor, wherein a predetermined control signal is applied. Only when the voice coil motor is driven, a power amplifier for supplying a current corresponding to the input voltage to the voice coil motor, a power supply for supplying the input voltage to the power amplifier at a constant level, and a power amplifier for the voice coil motor. The drive circuit is provided with current detection means for detecting the magnitude of the current, and switching control means for giving the control signal to the power amplifier when the magnitude of the current detected by the current detection means is smaller than a predetermined value. A magnetic head positioning device for a magnetic disk device characterized by the above.