KR19980013994A - Dithering method of hard disk drive for adsorption and scratch prevention - Google Patents

Abstract

end. TECHNICAL FIELD OF THE INVENTION

How to dither the hard disk drive

I. Technical Problems to be Solved by the Invention

Thereby realizing a dithering method of a hard disk drive for preventing adhesion and scratching.

All. The point of the solution of the invention

In the present invention, the asymmetric dithering signal is applied to the voice coil motor during the dithering interval for the dithering, and then the dithering signal of a predetermined size in the feedforward direction is applied to the voice coil motor do.

la. Important Uses of the Invention

Hard disk adsorption and scratch prevention

Description

Dithering method of hard disk drive for adsorption and scratch prevention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard disk drive (HDD), and more particularly, to a dithering method for preventing sticking and scratching of a disk.

In the HDD, the adsorption phenomenon refers to a phenomenon in which the head does not fall off the disk as a recording medium due to a specific cause. If such a suction phenomenon occurs, the spindle motor, which is the initial operation of the power-on operation, is not rotated properly and a no spindle error occurs. That is, a spindle motor drive fail. A conventional technique for overcoming the attraction phenomenon is to perform VCM dithering in which an actuator connected to a voice coil motor (VCM) is shaken for a predetermined time immediately after driving a spindle motor. The operation for VCM dithering will be described in detail as follows. Immediately after driving the spindle motor, the controller of the HDD applies a specific frequency (referred to as a dithering signal) having a symmetrical magnitude value in the normal forward direction and the backward direction to the VCM DAC (VCM Digital to Analog Converter). FIG. 3 shows the dithering signal output from the control unit during the dithering period t1t2. Referring to FIG. 3, it can be seen that the dithering signal has a symmetric magnitude value in the forward direction bwd and the backward direction fwd. Accordingly, the VCM DAC converts the specific frequency to analog and applies it to the VCM driving unit, and the VCM driving unit applies the driving current for VCM dithering to the VCM in response thereto. The VCM then alternately shakes the actuator in the forward and backward directions in response to the driving current. As a result, the adsorption phenomenon occurring on the disk surface is prevented.

However, such a conventional dithering method is very likely to cause the following problems. The dithering performed during the dithering period is added to the rotational force of the rotating spindle motor to cause the actuator to be subjected to greater force in the disk circumferential direction. So that the latch can be released and the head can then deviate from the parking zone and invade the data area. During this dithering period, the head is in a state in which the spindle motor does not rotate up to the required speed yet, and thus it is not lifted up to the prescribed flying height. In this state, when the head invades the data area, the disk is scratched by the head. These scratches erase the data recorded in the data area or damage the servo information, thereby damaging the performance of the HDD.

It is therefore an object of the present invention to provide a dithering method for adsorption and scratch prevention.

According to another aspect of the present invention, there is provided a method of dithering a hard disk drive for preventing adherence and scratching, the method comprising: a first step of applying an asymmetric dithering signal to the voice coil motor during a dithering interval for dithering; And a second step of applying a dithering signal of a predetermined size in the feedforward direction to the voice coil motor until immediately before unlatching to push the disc toward the disc.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram

2 is a diagram showing a dithering signal according to an embodiment of the present invention;

3 is a diagram showing a dithering signal according to the prior art;

4 is a diagram showing a block configuration of a conventional hard disk drive

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of a conventional hard disk drive. Referring to FIG. 4, the disks 10 are rotated by a spindle motor 34. Each of the heads 12 is located on a corresponding one of the disks 10 and is moved from the E-block assembly 14 coupled with the rotary voice coil actuator 30 to the disks 10 Respectively, of the support arms. The preamplifier 16 pre-amplifies the signal picked up by one of the heads 12 at the time of reading and applies the analog read signal to the read / write channel circuit 18, Write channel data supplied from the read / write channel circuit 18 to be written on the disk via a corresponding head of the heads 12. [ The read / write channel circuit 18 detects and decodes the data pulse from the read signal applied from the preamplifier 16, applies it to the DDC (Disk Data Controller) 20, and outputs the write data supplied from the DDC 20 Decode it and apply it to the preamplifier 16. The DDC 20 writes the data received from the host computer on the disk via the read / write channel circuit 18 and the preamplifier 16 or reads data from the disk and transmits it to the host computer. In addition, the DDC 20 interfaces communication between the host computer and the microcontroller 24. The buffer RAM 22 temporarily stores data to be transferred between the host computer and the microcontroller 24 and the read / write channel circuit 18. The microcontroller 24 controls track seeking and track following in response to a read or write command received from the host computer. The memory 26 stores programs to be executed by the microcontroller 24 and various setting values. The servo drive unit 28 generates a drive current for driving the actuator 30 in response to a signal for controlling the position of the heads 12 provided by the microcontroller 24 and supplies the drive current to the voice coil of the actuator 30 do. The actuator 30 moves the heads 12 on the disks 10 in accordance with the direction and the level of the drive current applied from the servo driver 28. The spindle motor driving unit 32 drives the spindle motor 34 to rotate the discs 10 according to a control value for controlling the rotation of the discs 10 generated from the microcontroller 24.

FIG. 1 is a block diagram of an embodiment of the present invention, which includes a controller 50, a digital to analog converter 52, a VCM driver 54, a VCM 56, an actuator 58, a head 60 ), And a disc 62. As shown in Fig. 1 corresponding to the embodiment of the present invention corresponds to FIG. 4 as follows. 1, the DAC 52 and the VCM driver 54 of FIG. 4 correspond to the servo driver 28 of FIG. 4, the VCM 56 of FIG. 1, the actuator 58 correspond to the annular voice coil actuator 30, respectively.

The dithering method according to an embodiment of the present invention includes the steps of applying an asymmetric square wave for a dithering period to prevent adsorption and scratching and then continuously applying a force in a feedforward direction of a certain size for pushing the disk to the inside thereof until just before unlatching .

Hereinafter, an operation according to an embodiment of the present invention will be described in detail with reference to FIG. The controller 50 of the HDD sends a specific frequency (dithering signal) having an asymmetrical magnitude value in the normal forward direction fwd and the backward direction bwd to the Digital to Analog Converter (DAC) during the dithering period t1t2 immediately after the spindle motor is driven. The dither signal is applied to the DAC 52 applied by the control unit 50 during the dithering period t1t2 in FIG. Referring to FIG. 2, it can be seen that the dithering signal has an asymmetric magnitude value (amplitude) between the backward direction bwd and the forward direction fwd. The amplitude of the backward direction bwd is smaller than the amplitude of the backward direction bwd (fwd) is larger. In the dithering signal, the amplitude of the feed back direction (bwd) means a magnitude value for pushing to the outside of the disk, and the amplitude of the feedforward direction (fwd) means a magnitude value for pushing the inside of the disk. The width of the dithering signal is 2 ms, for example.

The DAC 52 converts the asymmetrical dither signal output from the control unit 50 into an analog signal and applies the analog signal to the VCM driver 54. The VCM driver 54 responds to the VCM driver 56). The VCM 56 alternately shakes the actuator 58 in the forward direction fwd and the backward direction bwd in response to the driving current. At this time, the actuator 58 shakes greatly in the backward direction bwd and in the forward direction fwd. In the embodiment of the present invention, the larger the amplitude of the backward direction (fwd) than the amplitude of the forward direction (bwd), the better the adsorption can be overcome.

When dithering performed in the dithering period t1t2 is completed, the control unit 50 supplies the dither signal of the magnitude value of the forward direction bwd to the DAC 52 from the time t2 to the unlatching time t3 of the latch device do. The size value of the forward direction bwd applied during the time period t2t3 serves to push the head 60 toward the inside of the disk. Thereby, the head 60 remains in the parking zone until unlatched in the latch device, so that the data area is not scratched.

As described above, the present invention applies the asymmetric dithering signal during the dithering period and then applies the dithering signal of the magnitude value of the forward direction (fwd) until unlatching, thereby preventing the disk from being attracted and scratching in the hard disk drive.

Claims (2)

A dithering method of a hard disk drive for preventing adhesion and scratching, A first step of applying an asymmetric dithering signal to the voice coil motor during the dithering period for the dithering; And a second step of applying a dithering signal of a predetermined size in a feed-forward direction to the voice coil motor until immediately before unlatching to push the disc inward after the first process. The dithering method according to claim 1, wherein the square wave has at least a larger amplitude in a feedforward direction for pushing the disc inner side than an amplitude in a feed back direction for pushing the disc outward.