JP2003173640A - Vcm control system and magnetic disk storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize the seeking operation and following operation of a magnetic disk by VCM (voice coil motor). <P>SOLUTION: A digital control value generated based on the difference between the position of the magnetic head and a desired recording track position is converted to analog controlled voltage by a D/A converter 28 to control the driving current of the VCM 16 for move-driving the magnetic head by this controlled voltage. In the case of seeking for moving the magnetic head between tracks, the converting gain of the D/A converter 28 is set to be high to expand the oscillation range of the driving current. In the case of following for making the magnetic head follow the desired recording track, the converting gain is set to be low to improve the controlling resolution of the driving current. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VCM control system for controlling a voice coil motor, and more particularly to a VC
A magnetic head driven by an M (voice coil motor) is driven at high speed by a platter (magnetic recording disk).
The present invention relates to a technique suitable for optimizing a seek operation and a following operation of a magnetic head by the VCM in an HDD (hard disk driver) that reads / writes information by tracing a recording track on the surface.

[0002]

2. Description of the Related Art A hard disk driver reads / writes information by causing a magnetic head to trace a recording track on the surface of a platter that is driven to rotate at high speed. The magnetic head is provided at the tip of a movable head arm that swings along the platter surface. Movable head arm is VC
Driven by M. The VCM is connected to the VCM control unit incorporated in the hard disk driver with a flexible cable. Drive control of the VCM and transmission of read / write signals are performed via the flexible cable. The VCM control unit moves the magnetic head to a target recording track position and controls the current supplied to the VCM so that the magnetic head follows the target recording track position. This VCM
The drive control is performed based on digital position information analyzed from the read signal of the magnetic head.

That is, the difference (error) between the position of the magnetic head and the position of the target recording track is digitally detected, and the control value of the VCM drive current is generated based on this detection. Since this control value is generated as a digital value, it is converted into an analog control voltage by a D / A converter (D / A converter).
I when the analog conversion output of the D / A converter is current
It is converted into voltage by the / V (current / voltage) converter. This control voltage is used to feedback control the VCM drive current. The VCM drive current is detected by a sense resistor inserted in series with the drive current supply line. The VCM drive current is feedback-controlled so that the difference between the current detection voltage (divided voltage) of the sense resistor and the analog control voltage becomes zero. In the VCM drive control described above, the seek operation of moving the magnetic head to the target recording track position can be performed at the highest speed, while the following operation of causing the magnetic head to follow the target recording track position can be performed with the highest accuracy. desired. For this purpose, as shown in FIG. 4A, the D / A conversion gain is switched between high gain (Hi) and low gain (Lo) at the seek time and the following time.

In order to perform the seek operation at high speed, the above D
Increase the analog output amplitude for the digital input value of the / A converter. That is, the D / A conversion gain may be increased. As a result, the amplitude range of the VCM drive current value becomes large, and a large current for moving the magnetic head at high speed can be supplied to the VCM. On the other hand, in order to perform the following operation with high accuracy, the D / A conversion gain is lowered. In this case, the amplitude range of the VCM drive current value becomes smaller, but the control resolution of the drive current becomes higher accordingly, and high current control accuracy for finely controlling the movement of the magnetic head can be obtained.

Therefore, if the D / A conversion gain is switched between the seek operation and the following operation, the seek operation can be speeded up and the following operation can be highly accurate. The seek operation and the following operation can be determined based on digital position information obtained by analyzing the read signal of the magnetic head. The gain is switched based on this determination. When the magnetic head is away from the target track position, the D / A conversion gain is set to a high value to perform a rough control of moving the magnetic head to the vicinity of the target track position in the shortest time, while When it reaches the vicinity of the recording track, the movement of the magnetic head is finely and precisely controlled by setting the D / A conversion gain low.

The D / A conversion gain can be variably set by switching the gain of an amplifier transmitting the analog conversion output of the D / A converter. The gain of the amplifier can be changed by switching the resistance value of the negative feedback circuit. When the converted output of the D / A converter is current, the gain setting resistance value of the I / V converter that converts the current into voltage may be switched. Most of the functions of the VCM control unit described above can be integrated into a semiconductor integrated circuit (LSI).

[0007]

The present inventors have clarified that the above-mentioned technique has the following problems. That is, in the above-described system, the drive current of the VCM greatly differs between seek and following, and a very large drive current (for example, 1 A or more) is supplied to the VCM during seek, but the VC during follow is large.
Only a very small current (for example, several μ to several tens mA) is supplied to M. With the head accurately following the target track position, the VCM current becomes almost zero. The VCM current is a current that flows to correct the positional deviation between the head and the track when the positional deviation occurs between the head and the track. Therefore, in a completely following state in which the head stands still at the target recording track position, (a) in FIG. As shown in
Theoretically it should be zero.

However, in reality, even in the completely following state, as shown in FIG. 4B, the VCM current does not become zero, and a small but significant offset current flows. This offset current flows to feedback-correct the stress of the flexible cable connected to the head. Although flexible cables are used that are sufficiently flexible, it is not possible to completely eliminate the stress acting on the head. Therefore, even in the completely following state, it is necessary to keep the offset current flowing in order to correct the positional deviation of the head due to the stress. Therefore, in the following state, a control value corresponding to the offset current is digitally generated. This control value is converted into an analog voltage by the D / A converter and finally becomes the VCM drive current value (offset current value). At this time, however, the present inventor clearly causes the following problem. Was done.

(1) When shifting from the following operation to the seek operation, the conversion gain of the D / A converter is switched from low gain to high gain. At this time, the offset current value set at the time of low gain is scale-enlarged at the moment of switching to high gain, and this is supplied to the VCM as a drive current. That is, the control immediately after switching to the high gain is started not at the center (zero point) of the conversion range (dynamic range) of the D / A converter, but at a position outside the center. Therefore, there is a problem that the VCM drive current changes discontinuously during the transition from the following operation to the seek operation, and the operation immediately after the change becomes unstable. Although this unstable operation is converged by the subsequent control, it is an extra control operation and causes a delay in the seek operation. The delay of the seek operation causes a decrease in the access speed of the hard disk driver. (2) It is necessary to improve the positioning accuracy of the magnetic head in order to perform high-density recording by the hard disk driver. The positioning accuracy of the magnetic head depends on the control resolution of the VCM drive current by the D / A converter. A high resolution D / A converter is required to perform the following with high accuracy, but the resolution of the D / A converter is limited.

In order to maximize the limited resolution (bit range) to obtain high control accuracy, as described above, the D / A conversion gain is switched between the seek time and the following time, and the seek time is followed. It is desirable that the center of the conversion range (dynamic range) of the D / A converter be the center of head positioning during both following and following. This makes it possible to perform the positioning control under the symmetrical control condition optimized in the same dynamic range in both directions, regardless of the direction in which the head is displaced. However, if there is the above-described offset current, the center of positioning the head deviates from the center of the dynamic range, and an optimized symmetrical control condition cannot be obtained. When trying to obtain symmetrical control conditions,
As shown in FIG. 4C, the control range (Lo) becomes narrow.

As a means for avoiding the influence of the above-mentioned offset, the present inventor has considered canceling the offset current by using a correction D / A converter. That is, a correction D / A converter is prepared separately from the control D / A converter described above, and a predetermined correction value is input to this. The center of the dynamic range of the control D / A converter is aligned with the head positioning center by adding (or subtracting) the analog conversion output of the correction D / A converter to the analog conversion output of the control D / A converter. You can That is, the offset current can be made to flow at the center point of the dynamic range of the control D / A converter. This technique is effective when the offset current is previously set to a constant value. However, the offset current generated by the stress of the flexible cable is not constant and varies from device to device. It also changes over time. Therefore, the above means cannot reliably avoid the influence of the offset.

(3) The seek operation is desired to be as fast as possible in order to increase the access speed of the hard disk driver. VCM to speed up seek operation
It suffices to increase the drive current value.
It is better to reduce the value of the current measuring sense resistor that is interposed in series in the current supply path. However, when the sense resistance value is reduced, the offset current also easily flows, and the problems (1) and (2) above become more prominent. The present invention has been made in view of the above problems, and an object thereof is to provide a technique effective for improving the recording density, access speed, and reliability of a hard disk driver. Further, in order to achieve this, a technique suitable for optimizing the seek operation and the following operation of the magnetic head by the VCM is provided.

More specifically, it is possible to surely cancel the offset generated when the magnetic head follows the target recording track position, and to maximize the control resolution of the VCM drive current by the D / A converter. The purpose is to provide technology that has made it possible. The above and other objects and characteristics of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0014]

The typical ones of the inventions disclosed in the present application will be outlined below. That is, the digital control value generated based on the difference between the head position and the target recording track position is D
A / A converter converts into an analog control voltage, and the control voltage controls the drive current of the voice coil motor for moving the head, and the D / A converter during seek for moving the head between tracks. The conversion gain of is set to a high gain to expand the amplitude range of the above drive current,
A VCM control system in which the conversion gain is set to a low gain to increase the control resolution of the drive current at the time of following in which the head follows a target recording track, and the D / A converter at the time of following. The means for detecting the offset value and the means for correcting the offset of the D / A converter are provided so as to be controllable from the outside.

According to the above means, it is possible to surely cancel the offset generated when the magnetic head follows the target recording track position under the control operation from the outside. This makes it possible to maximize the control resolution of the VCM drive current by the D / A converter. Further, it becomes possible to optimize the seek operation and the following operation of the magnetic head by the VCM, and it is possible to improve the recording density of the hard disk driver, the access speed, and the reliability.

Further, a main D / A converter for converting the digital control value into an analog control voltage and a sub D / A conversion having an analog conversion output to be added to or subtracted from the output value of the main D / A converter. And a counter for stepping up or down the digital input value of the sub D / A converter, and a comparator for detecting whether or not the converted output value of the main D / A converter has reached a predetermined center value. Is provided so as to be controllable from the outside. As a result, the offset value detecting means and the offset correcting means can be configured to be controllable from the outside with a small-scale circuit element such as a counter or a register.

Further, preferably, a register for holding a correction value input to the sub D / A converter at the time of following and a register for holding a correction value input to the sub D / A converter at the seek time are provided. In addition, the contents held in each register can be controlled externally. Accordingly, it is possible to relatively easily configure a unit that can appropriately correct the offset during the following and during the seek.

Further, the main D / A converter and the sub D / A converter
In addition to converting the analog conversion output format of the A converter to a current, an I / V converter for converting the current output to a voltage output is provided, and the gain of this I / V converter is switched and set by an external control operation. To As a result, each D /
The operation of adding or subtracting the output of the A converter can be performed relatively easily and highly accurately by adding or subtracting the current. In general, addition or subtraction of analog outputs is easier and more accurate than voltage.

Further, the I / V converter is constructed by using a differential amplifier capable of performing negative feedback operation, and the connection of the negative feedback resistor of the differential amplifier is switched and set by external control, so that The operation modes of the gain I / V conversion, the low gain I / V conversion, and the open gain comparator can be switched and set. This allows
Since the above three types of operation modes can be realized by a single circuit, the configuration can be greatly simplified. further,
Since the operation reference voltage and the like can be shared between the operation modes, the operation accuracy can be improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a VCM control system to which the technique of the present invention is applied. The system shown in the figure has a VCM control unit 20 which is an LSI. The control unit 20 includes a digital control circuit 22, a control register 24, a DAC current generator 26,
It has an I / V conversion section 32, a VCM drive circuit 34, a current sense amplifier 36, an offset correction setting section 38, and the like.

The digital control circuit 22 centrally controls each function in the VCM control unit 20. The digital control circuit 22 includes an external control unit (controller) 50.
It is operated by a clock (CLK) and an enable signal (ENABLE) input from the device, and bidirectional serial communication of data (DATA) is performed with the external control unit 50. The external control unit 50 generates the control value of the VCM drive current based on the digital position information analyzed from the read signal of the magnetic head. This control value is digital data, is transferred to the control register 24 via the digital control circuit 22 in the VCM control unit 20, and is further input from the control register 24 to the DAC current generator 26.

The DAC current generator 26 includes a main D / A converter 28 for VCM control and a sub D / A for offset correction.
It is composed of the converter 30. The main D / A converter 26 converts the digital control value input from the control register 24 into an analog current value. The sub D / A converter 30 is for offset measurement and correction, and its converted output value is added (or subtracted) to the converted output value of the main D / A converter 26.

The D / A converters 28 and 30 are both of the current output type. This is because the addition or subtraction of the analog output is performed by the current rather than the voltage, because the circuit is simpler and higher accuracy can be easily obtained. Further, the operation of adding or subtracting the D / A conversion outputs of both D / A converters 28 and 30 can be performed more simply and more accurately by adding or subtracting the currents.

The I / V converter 32 includes a differential amplifier 33, negative setting resistors R1 and R2 for gain setting, and a switch circuit s.
1, s2, etc., the DAC current generator 26
The analog current value output from is converted into voltage. In this case, the differential amplifier 33 is supplied with a constant reference voltage so that it operates based on the center level of the amplifier input range. One of the negative resistances R1 and R2 has a relatively high resistance value (4R), and the other has a relatively low resistance value (R). The on / off states of the switch circuits s1 and s2 are controlled by the digital control circuit 22. The digital control circuit 22 operates under the control of the external control unit 50.

The I / V converter 32 has the following (1) to (1).
It has the operation mode of (3). (1) High gain mode: When the switch circuit s1 is turned on and the switch circuit s2 is turned off, the negative resistance R1 (= 4R) having a high resistance value operates as a high gain I / V converter. (2) Low gain mode: When the switch circuit s1 is turned off and s2 is turned on, the negative resistance R2 having a low resistance value
By (= R), it operates as a low gain I / V converter. (3) Comparator mode: switch circuit s
When both 1 and s2 are set to OFF, the differential amplifier 33 enters an open gain state and operates as a comparator using the center level of the input range of the differential amplifier 33 as a comparison reference.

The control voltage output from the I / V converter 32 is applied to the control input of the VCM drive circuit 34 via the resistor R3 in series. The VCM drive circuit 34 supplies a drive current to the VCM 16. The drive current is supplied through the current detection sense resistor Rs in series. Sense resistor R
A current detection voltage corresponding to the VCM drive current is divided across both ends of s. This current detection voltage is amplified by the sense amplifier 36, and then the VCM drive circuit 34 is connected through the resistor R4 in series.
It is fed back to the control input side of. The control voltage is input to the control input of the VCM drive circuit 34, and the V is set so that the difference between the control voltage and the current detection voltage becomes zero.
The output current of the CM drive control circuit 34 is feedback-controlled. As a result, the VCM drive circuit 34 supplies the VCM 16 with a drive current having a magnitude corresponding to the control voltage.

In the seek operation, the I / V converter 32 is used.
Is operated in the high gain mode, the amplitude range of the VCM drive current value is expanded. As a result, it is possible to perform rough control of moving the magnetic head to the vicinity of the target track position in the shortest time. Further, during the following operation, the amplitude range of the VCM drive current value is reduced by operating the I / V converter 32 in the low gain mode. This improves the control resolution of the drive current,
The movement of the magnetic head can be finely and precisely controlled.

The offset correction setting section 38 is composed of an offset measuring counter 40 and a register 42, a low gain correction register 44, a high gain correction register 46 and the like. The offset correction setting unit 38 is
The offset value of the A / A converter 28 is measured, and the offset correction value calculated based on the result of the measurement is used to correct the center of the conversion range of the main D / A converter 28 to the center of the head positioning. I do. The offset value measurement and the correction based on this measurement result are shown in FIG.
The procedure can be performed as shown in.

FIG. 2 is a flow chart showing the procedure for using the system according to the present invention. In this case, the functions in the VCM control unit 20 described above are opened so that the external (user) can perform control operation via the digital control circuit 22. The external control unit 50 can execute the following procedure by operating the opened function.

First, in steps S1 to S4, the offset value (OF11) of the main D / A converter 28 is detected. S1: The VCM drive circuit 34 is set to the non-operation state. In this state, the output of the VCM drive circuit 34 is in a high impedance state, and head drive is not performed. The head is in an unloading state. S2: The central value of the digital input range is input to the main D / A converter 28. S3: The operation of the I / V converter 32 is set to the comparator mode, and the offset calibration of the main D / A converter 28 by the sub D / A converter 30 and the counter 40 is performed. The calibration is performed by inputting the count value of the counter 40 to the sub D / A converter 30 and counting up (or down) the count value by one. The count up (down) is performed until the comparator output of the I / V converter 32 is inverted. When the comparator output is inverted, the count value at that time is registered in the register 42.
Write in. The comparator output is inverted at the center of operation of the I / V converter 32. As a result, the offset value (OF11) of the main D / A converter 28 is written in the register 42. S4: The external control unit 50 reads the offset value (OF11) of the register 42.

Next, in steps S5 to S8, the offset value (OF12) at the time of following is detected. S5: Input the center value of the digital input range to the sub D / A converter 30. S6: Head loading is performed with the VCM drive circuit 34 in an operating state. S7: Put the head in the following state. In this following state, the I / V converter 32 is set to the low gain mode. S8: Main D / A when the head is in the following state
The digital input value of the converter 28 is set in the low gain correction register 44. The input value set in the register 44 is read by the external control unit 50 as an offset value (OF12) at the time of following. At this time, the offset value (OF12) set in the register 44 is
It is used as an offset correction value at the time of following, that is, when the I / V converter 32 is in the low gain mode. This correction value (OF12) is added (subtracted) to the center value of the digital input range of the sub D / A converter 30. By this addition (subtraction), the output of the sub D / A converter 30 is the output value of the main D / A converter 28 at the time of following.
It is corrected so that it becomes the center value of the / A conversion range (dynamic range). This makes it possible to perform positioning control under symmetrical control conditions optimized in the same dynamic range in both directions, regardless of which direction the head is displaced.

The correction value is set in the high gain correction register 46 in the subsequent steps S9 to S11. S9: High gain is set in the high gain correction register 46. S10: Calculate a correction value (OF13). This correction value (OF1
The value 3) may be a value that can cancel the offset current generated by the two offset values (OF11 and OF12). Such a correction value (OF13) is OF13 = (1/4) × OF12 if the gain difference between the high gain mode and the low gain mode of the I / V converter 32 is four times (4R / R).
It can be obtained by the calculation formula of + (3/4) × OF11. S11: The correction value (OF13) thus obtained is set in the high gain correction register 46. I / V converter 3
When 2 is in high gain mode, set the correction value (OF13) to sub-D
By adding (subtracting) to the center value of the digital input range of the / A converter 30, it is possible to suppress the change in the VCM drive current when the state changes from the following state to the seek state. As a result, the operational stability immediately after the seek transition can be ensured, and the seek operation can be speeded up and highly stabilized.

FIG. 3 shows a schematic configuration example of a hard disk driver to which the VCM control system according to the present invention is applied. The hard disk driver 10 shown in the same figure reads / writes information by causing the magnetic head 14 to trace the recording track on the surface of the platter 12 which is rotationally driven at high speed. The magnetic head 14 is provided at the tip of a movable head arm 15 that swings along the surface of the platter 12. The movable head arm 15 is driven by the VCM 16. The VCM 16 is connected to the VCM control unit 20 incorporated in the hard disk driver 10 with a flexible cable 18. Drive control of the VCM 16 and transmission of read / write signals are performed via the flexible cable 18.

The flexible cable 18 causes an offset, but in the system of the present invention using the VCM control unit 20 described above, the offset generated when the magnetic head is made to follow the target recording track position is externally controlled. It can be surely canceled under the operation, which allows the VCM by the D / A converter.
The control resolution of the drive current can be maximized.
Therefore, the seek operation and the following operation of the magnetic head by the VCM can be optimized to improve the recording density, access speed and reliability of the hard disk driver.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say. For example, the offset value of the main D / A converter 28 (OF1
The comparator used to detect 1) is I / V
It may be an independent comparator separate from the converter 32. In addition, the offset value of the main D / A converter 28 (OF
11) means for detecting VCM control unit (LS
It may be outside of I).

In the above description, the case where the invention made by the present inventor is mainly applied to a magnetic disk storage device having a hard disk as a storage medium, which is the field of application in the background, has been described, but the present invention is not limited thereto. However, it can also be used for a magnetic disk storage device using a flexible disk as a storage medium.

[0037]

The effects obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows. That is, it is possible to reliably cancel the offset that occurs when the magnetic head follows the target recording track position, and it is possible to maximize the control resolution of the VCM drive current by the D / A converter. Thereby, the seek operation and the following operation of the magnetic head by the VCM can be optimized, and the recording density, access speed, and reliability of the magnetic disk storage device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a system according to the present invention.

FIG. 2 is a flow chart showing an example of use of the system according to the invention.

FIG. 3 is a plan view showing a schematic configuration of a hard disk driver to which the system according to the present invention is applied.

FIG. 4 is a characteristic diagram showing D / A conversion gain and D / A conversion characteristics at the time of following and seeking.

[Explanation of symbols]

10 HDD (hard disk driver) 12 platter (magnetic recording disk) 14 magnetic head 15 head arm 16 VCM (voice coil motor) 18 flexible cable 20 VCM control unit 22 Digital control circuit 24 control registers 26 DAC current generator 28 Main D / A converter for VCM control 30 Sub D / A converter for offset correction 32 I / V converter 33 differential amplifier 34 VCM drive circuit 36 current sense amplifier 38 Offset correction setting section 40 Offset measurement counter 42 registers 44 Low gain correction register 46 High gain correction register 50 External control unit (controller) R1 to R4 resistance s1, s2 switch circuit

Continued front page    (72) Inventor Hiroshi Sato             5-22-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stock             Ceremony Company Hitachi Cho-LS System             Within (72) Inventor Yasuhiko Kogami             5-22-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stock             Ceremony Company Hitachi Cho-LS System             Within (72) Inventor Kenji Nishimura             5-22-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stock             Ceremony Company Hitachi Cho-LS System             Within F term (reference) 5D096 RR01 RR18 TT03 UU03

Claims (7)

[Claims] 1. A voice for moving a head by driving a digital control value generated on the basis of a difference between a head position and a target recording track position into an analog control voltage by a D / A converter. When controlling the drive current of the coil motor to move the head between tracks,
When the conversion gain of the D / A converter is set to the first gain, the amplitude range of the drive current is expanded, and during the following in which the head follows the target recording track, the conversion gain is set to the second gain. A VCM control system which is set so as to increase the control resolution of the drive current, wherein a means for detecting an offset value of the D / A converter at the time of following, and an offset of the D / A converter are corrected. VCM control system, characterized in that the means are provided in a state in which they can be controlled and operated from the outside. 2. A main D / A converter for converting the digital control value into an analog control voltage, and an analog conversion output that is added to or subtracted from the output value of the main D / A converter. A sub D / A converter having a counter, a counter for stepping up or down a digital input value of the sub D / A converter, and whether a conversion output value of the main D / A converter has reached a predetermined value. A VCM control system characterized in that a comparator for detecting whether or not it is provided in a state in which control can be performed from the outside. 3. The invention according to claim 2, wherein a register holding a correction value input to the sub D / A converter at the time of following and a correction value input to the sub D / A converter at the time of seeking are held. The VCM control system is characterized in that the contents held in each register can be externally controlled and operated. 4. The invention according to claim 2 or 3, wherein the analog conversion output format of the main D / A converter and the sub D / A converter is current, and the current output is converted to a voltage output. A VCM control system characterized in that a / V converter is provided and the gain of the I / V converter is switched and set by an external control operation. 5. The invention according to claim 4, wherein the I / V converter is configured by using a differential amplifier capable of negative feedback operation, and the connection of the negative feedback resistor of the differential amplifier is controlled by an external control. By switching setting, high 1st
VCM control system characterized in that it is configured such that each operation mode of the gain I / V conversion, the low second gain I / V conversion, and the open gain comparator can be switched. 6. A voice for driving a head to move by driving a digital control value generated based on a difference between a head position and a target recording track position into an analog control voltage by a D / A converter. While controlling the drive current of the coil motor and at the time of seeking to move the head between tracks, the conversion gain of the D / A converter is set to a high first gain to expand the amplitude range of the drive current. A VCM control system for increasing the control resolution of the drive current by setting the conversion gain to a low second gain at the time of following in which the head follows a target recording track. Main D to convert to analog control voltage
/ A converter, a sub D / A converter having an analog conversion output to be added to or subtracted from the output value of the main D / A converter, and a correction value input to the sub D / A converter at the time of following. A first register for holding the
And a second register that holds a correction value that is input to the / A converter. 7. A VCM control system according to any one of claims 1 to 6, and a head for reading information from a storage track on a magnetic storage disk controlled and rotated by the VCM control system. A magnetic disk storage device characterized by the above.