KR100432505B1 - Method for optimizing write current applied to plural zones of magnetic disk in consideration of characteristics of each head and disk - Google Patents

Abstract

PURPOSE: A method for optimizing the write current applied to plural zones of a magnetic disk is provided to set up the optimum write current control value by preventing an error of measuring an error rate. CONSTITUTION: Head and zone numbers are set for all heads of a magnetic disk and each zone corresponding to the head to set up test and optimum write current control value in order(90-94). Data are recorded and read at the same frequency while the write current control value of each zone is gradually increased within a predetermined range so that generation of an error is confirmed(96-102). The error frequency of each write current control value is examined to register the error frequency at a comparison table(104). The write current control value having the fewest error is set up as the optimum write current control value of the corresponding zone(106-118).

Description

Method for optimizing the write current of a magnetic disk recording apparatus

The present invention relates to a magnetic disk recording apparatus, and more particularly, to a method for optimizing a write current applied to each zone on a magnetic disk partitioned by a plurality of zones.

Background Art [0002] A magnetic disk recording apparatus such as a hard disk drive (HDD) and a floppy disk drive (FDD) is widely used as an auxiliary storage device of a computer system ought. In particular, HDDs are advantageous in that they can not only store a large amount of data stably but also can access at a high speed.

In the current HDD, the recording density on the disk is gradually increasing in order to increase the storage capacity of the disk, and accordingly, the head is also highly sensitive to the recording current by making the head highly precise. As the recording density increases and the head becomes high-definition, the recording current value applied to the head at the time of data recording on the disk becomes more important and sensitive variable in the performance of the HDD. It may be considered that the larger the write current value is, the larger the amplitude of the signal picked up by the head in reading data from the disk becomes. However, in actuality, The recording current value should be changed according to the characteristic of each disk. The reason is as described below.

First, in the same HDD, since the assembly error of the head, the pole width of the head, and the flying height of the head are different from each other, the saturation of the head with respect to the write current (Iw) ) Characteristics are also different. Therefore, if one of the recording current values is fixed to each head in the same HDD, a data error occurs in the head in which the recording current value is not appropriate at the time of reading / recording.

On the other hand, as for the disk, since the diameter and the recording frequency are not the same for each disk used in the HDD, the recording current value should be different according to the different magnetization intensity. For example, in the case of a disc employing the constant-density recording method, the recording density of all the areas on the disc is not exactly equal to that of the disc on which the constant-density recording method is adopted. Since the radii and angular velocities are different from each other, the recording density varies depending on the zones. That is, the recording density of the zone in the inner circumferential region becomes higher than the recording density of the zone in the outer circumferential region. Therefore, in a zone with a high recording density on one disk, interference will be greater than with a zone with a relatively low recording density. Accordingly, if the write current value is excessively large, a data error due to inter-bit interference occurs in a zone having a high recording density. In order to prevent this, if the recording current value is made small, the amplitude of the signal picked up by the read-out head is insufficient even in the zone where the recording density is relatively low, so that a data error due to noise occurs.

As one of the techniques for optimizing the recording current value in consideration of the characteristics of the heads and disk surfaces in the same HDD for the reasons described above, it is disclosed in Patent Document No. 95-53518 filed by the same applicant as the present applicant in 1995 Quot; write current control circuit of a magnetic disk recording apparatus and its optimization method ". The above-mentioned Patent Application No. 95-53518 regulates a write current by a PWM signal having a duty corresponding to a preset write current control value, and gradually increases the write current control value in a predetermined range by a PWM signal, Discloses a technology for setting a recording current control value optimum based on the number of times of occurrence of errors by performing a reading test a predetermined number of times for each step. Hereinafter, the conventional write current optimization process will be described in detail with reference to FIGS. 1 and 2. FIG.

FIG. 1 shows a block diagram of a hard disk drive provided with a write current adjustment circuit 38 for a write current optimization process. FIG. 1 shows an example in which two disks and four heads corresponding to one side of each disk are provided. . Referring to FIG. 1, first, the disk 10 is installed as a stack on one spindle and is rotated by a spindle motor 34. Each of the heads 12 is located on a corresponding one of the disks 10 and includes an E-block assembly 14 coupled with a rotary voice coil actuator 30, To a support arm extending from the disk 10 toward the disk 10, respectively. The read / write circuit 16 connected to the head 12 pre-amplifies the signal picked up by the data read-out head 12 and outputs an analogue read signal to the read / write channel circuit 18 And at the time of data recording, a write current according to the encoded write data applied from the read / write channel circuit 18 is applied to the head 12 so that the write data is recorded on the disk 10. [ At this time, the read / write circuit 16 has a head switching circuit for selecting one of the heads 12, and the head switching circuit performs one head switching by the selection signal applied from the disk signal control section 36. [ The read / write circuit 16 also has a write current control terminal WC provided for controlling the write current from the outside. The write current value is determined by the resistance value of the external resistor connected to the write current control terminal WC.

The read / write channel circuit 18 detects and decodes the data pulse from the read signal applied from the read / write circuit 16, applies it to the DDC (Disk Data Controller) 20, And applies the encoded data to the read / write circuit 16. The DDC 20 is connected to a read / write channel circuit 18 and a read / write circuit 16, which are controlled by the microcontroller 24 and are received from a host computer such as a PC (Personal Computer) Or reads data from the disk 10 and transmits the read data to the host computer. In addition, the DDC 20 interfaces communication between the host computer and the microcontroller 24. A random access memory (RAM) 22 temporarily stores data transferred between the host computer, the microcontroller 24, and the read / write channel circuit 18. The microcontroller 24 controls the DDC 20 in response to a read or write command received from the host computer, and controls track seeking and track following. The microcontroller 24 generates a PWM signal WC_PWM having a duty corresponding to a preset recording current control value to determine the recording current amount, and outputs the generated PWM signal WC_PWM to the recording current adjustment circuit 38. The write current control value is set by testing the optimum write current control value according to the characteristic of each head 12 and the corresponding region on the disk 10. [ The optimum write current control value thus set is recorded in the maintenance area CYL_M on the disk 10. [ The microcontroller 24 reads out the optimum recording current control value recorded in the maintenance area CYL_M on the disk 10 and writes the data on the disk 10 on which the head 12 for recording data is located, And generates a PWM signal WC_PWM with a duty according to the optimum recording current control value corresponding to the zone of the (10) plane. Therefore, the duty of the PWM signal WC_PWM generated from the microcontroller 24 will vary not only according to the head 12 but also according to the zone on the disk 10.

The write current adjustment circuit 38 is connected between the write current control terminal WC of the read / write circuit 16 and the PWM output terminal of the microcontroller 24 and is connected to the read / write circuit 16 corresponding to the duty of the PWM signal WC_PWM. The amount of current of the write current control terminal WC is adjusted. The ROM 26 stores programs to be executed by the microcontroller 24 and various setting values. The servo driver 28 generates a drive current for driving the actuator 30 by a signal for controlling the position of the head 12 generated from the microcontroller 24 and applies the drive current to the actuator 30. [ The actuator 30 moves the head 12 on the disk 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 disk 10 in accordance with a control value for controlling the rotation of the disk 10 generated from the microcontroller 24. [ The disk signal control unit 36 decodes the servo information from the read data outputted from the read / write channel circuit 18 and applies the decoded servo information to the microcontroller 24 and outputs various control signals required for reading / writing from the DDC 20 Write circuit 18, the DDC 20, and the like by the control of the microcontroller 24 and the signal that is output from the microcontroller 24. The disk signal controller 36 generally uses an ASIC (Application Specific Integrated Circuit) designed for each HDD.

FIG. 2 shows an optimization flowchart for explaining a conventional write current optimization process. First, the microcontroller 24 sets the head number HNO to 0 in step 50 and also sets the zone number ZNO in step 52. FIG. This is for testing and setting the optimum recording current value one by one, one by one, for the zones of the disk 10 surface corresponding to each of the heads 12. By this process, the first zone of the disk surface corresponding to the first head is selected do. At this time, the read / write circuit 16 selects a head corresponding to the head number HNO by a signal applied from the disk signal control unit 36 controlled by the microcontroller 24. [ In this state, the microcontroller 24 selects the cylinder to be tested among the cylinders of the zone in step 54. [ Then, the microcontroller 24 sets the minimum recording current control value MIN_Iwc to the recording current control value Iwc in step 56, and records the test data in the on-track state in the test cylinder in step 58. [ Thereafter, the microcontroller 24 reads out data from the test cylinder in step 60, and performs a readout test for confirming whether or not an error has occurred by a set number of times. At this time, the microcontroller 24 performs a readout test in the off-track state. The microcontroller 24 registers the number of times of occurrence of the error in the comparison table in step 62. If it is not checked in step 64 that the recording current control value Iwc has reached the maximum recording current control value MAX_Iwc in step 64, The control value Iwc is increased to the next step, and then the procedure is executed again from the step 58. [ This completes the test for one zone. In step 68, the microcontroller 24 sets the optimum recording current control value for the zone based on the number of times of error occurrence for each recording current control value of each step obtained as described above.

In the conventional write current optimization process as described above, the test data is recorded with the write current control value Iwc set on the test cylinder, and the readout test is repeated for a given number of times, and the error is recorded and compared. However, if the head is off-tracked during test data recording or a read error occurs due to the wiggle noise, it is difficult to expect an accurate error rate calculation by the set write current control value Iwc even if the readout test is repeated a given number of times. That is, in the conventional write current optimization process, the optimum write current value considering each head and disk characteristics can not be set due to the difference in parameters of test data recording and readout (for example, wiggle noise and off-track recording) .

Therefore, an object of the present invention is to provide a write current optimization method capable of setting an optimum write current value considering the characteristics of each head and disk at the time of reading / writing.

It is another object of the present invention to provide a write current optimization method capable of optimizing a write current by preventing an error of an error rate measurement caused by instability of a head during data writing.

FIG. 1 is a block diagram of a hard disk drive having a write current adjustment circuit for a write current optimization process according to the related art. FIG.

FIG. 2 is an optimization flowchart illustrating a conventional write current optimization process. FIG.

3 is a flow chart of a write current optimization according to an embodiment of the present invention.

FIG. 4 is a flow chart for setting a write current control value optimized by FIG. 3; FIG.

According to an aspect of the present invention, there is provided a magnetic disk drive comprising: a read / write element for applying a write current corresponding to an amount of current of a write current control terminal upon data recording on a magnetic disk to a head in accordance with write data; And a write current adjusting means for adjusting the amount of current of the write current control terminal by a pulse width modulation signal having a duty ratio, the write current control method comprising the steps of: A test step of performing a write and read test at the same number of times for each step while increasing the number of times of error occurrence and checking the number of occurrences of error for each write current control value at each step; And a current control value.

Hereinafter, a write current optimization process according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 shows a flowchart of a write current optimization according to an embodiment of the present invention. First, the microcontroller 24 sets the head number HNO to 0 in step 90 and also sets the zone number ZNO in step 92. FIG. This is for testing and setting the optimum recording current value one by one, one by one, for the zones of the disk 10 surface corresponding to each of the heads 12. By this process, the first zone of the disk surface corresponding to the first head is selected do. At this time, the read / write circuit 16 selects a head corresponding to the head number HNO by a signal applied from the disk signal control unit 36 controlled by the microcontroller 24. [

In this state, the microcontroller 24 selects the cylinder to be tested among the cylinders of the zone in step 94. [ At this time, it is preferable to select and set the test cylinder as the cylinder having the worst condition in the zone, that is, the cylinder having the highest recording density. These cylinders will be cylinders in the most inner zone in the zone. The test cylinder, of course, should be selected as a non-defective cylinder. Next, in step 96 to step 106, the microcontroller 24 sets the recording current value Iwc from the minimum recording current control value MIN_Iwc to the maximum recording current control value MAX_Iwc among the recording current control values stepwisely set within a predetermined range And the number of times of occurrence of errors is registered in the comparison table for each recording current control value of each step. The microcontroller 24 sets the number of times of performing the write and read operations to the same number of times in order to prevent errors in the error rate calculation caused by the instability (e.g., wiggle noise, off-track recording, etc.) . The microcontroller 24 generates the PWM signal WC_PWM whose duty increases to correspond to the stepwise increase from the minimum recording current control value MIN_Iwc to the maximum recording current control value MAX_Iwc, The write current in the memory cell array is changed. Hereinafter, steps 96 to 106 will be described as follows.

The microcontroller 24 sets the minimum recording current control value MIN_Iwc to the recording current control value Iwc in step 96, In step 98, the microcontroller 24 records test data on the test cylinder in an on-track state, and then proceeds to step 100. [ In step 100, the microcontroller 24 reads the data on the test cylinder and performs a read test to check whether or not an error has occurred. At this time, the read test is performed in the off-track state. This off-track is intended to facilitate the reading test by increasing the stress on the test conditions and to increase the sensitivity to data errors. The microcontroller 24 then checks in step 102 whether the test data write and read times are repeated a predetermined number of times. If the number of test data recording and reading is not repeated by the predetermined number of times, the above steps 98 and 100 are repeated for the predetermined number of times, By setting the number of times of recording / reading to be equal to the number of times of reading / writing, the accuracy of calculating the error rate of recording / reading can be increased.

On the other hand, if the test data recording / reading process is repeated a predetermined number of times, the microcontroller 24 proceeds to step 104 and registers the number of times of occurrence of the error in the comparison table. The comparison table is composed of the number of times of error occurrence for each recording current control value of each step and is configured by using a register or a RAM in the microcontroller 24. If it is not inspected whether the recording current control value Iwc reaches the maximum recording current control value MAX_Iwc in step 106, the recording current control value Iwc is increased to the next step in step 108, and then the procedure is executed again from step 98. This completes the test for one zone.

Then, the microcontroller 24 sets the optimal recording current control value for the zone based on the number of times of occurrence of errors for each recording current control value in each step obtained as described above. Hereinafter, a method of setting the optimum write current control value will be described with reference to FIG.

FIG. 4 is a flowchart illustrating an optimum write current control value setting process. Referring to FIG. 4, the microcontroller 24 sets the recording current control value Iwc at the step of the smallest error occurrence number registered in the comparison table as the optimum recording current control value at step 120. [ Then, in step 122, the set optimum recording current control value is recorded as a default value in the maintenance area CYL_M on the disk 10, so that the optimum recording current control value is used for data recording thereafter. The test for the first zone of the disk surface corresponding to the first head and the setting of the optimum write current control value are completed by the above-described procedure.

In step 112, if the zone number ZNO is not checked whether the zone number ZNO is the maximum zone number MAX_ZNO, the microcomputer 24 increases the zone number ZNO in step 114 and selects the next zone. Thus, the test for the disk on one side corresponding to one head and the setting of the optimum write current control value are completed.

In step 112, the microcontroller 24 checks whether the head number HNO is the maximum head number MAX_HNO. If it is not the maximum head number MAX_HNO, the microcomputer 24 proceeds to step 118 and increases the head number HNO to select the next head. do. This completes setting of the test and optimum write current control values for all the heads of the HDD and the areas on the disk corresponding to the respective heads.

On the other hand, the test data is set in advance as data having a pattern for easily checking the response characteristic to the write current, which can be determined in advance by the sample HDD. The off-track value can also be determined by a predetermined stress value or by a specimen HDD. The range of the write current control value Iwc is set sufficiently wide by the sample HDD within the range of the preset write current value of the read / write circuit 16. [

The microcontroller 24 outputs the PWM signal WC_PWM with a duty according to the optimum write current control value corresponding to the zone of the surface of the disk 10 on which the head 12 for recording data is located The recording current value can be adaptively adjusted.

As described above, according to the present invention, in order to optimize the write current in consideration of the characteristics of the head and the disk for each magnetic disk recording apparatus, the number of write / read operations is set to the same number of times, There is an advantage in that an error of the error rate measurement can be prevented and an optimum recording current control value can be set.

Claims (1)

A read / write element for applying a write current corresponding to the amount of current of the write current control terminal to the head in accordance with write data when recording data on the magnetic disk, and a read / And a write current adjusting means for adjusting a current amount of the write current control terminal by a pulse width modulation signal having a duty corresponding to a predetermined write current control value, Setting a head number and a zone number in order to sequentially set test and optimum write current control values for all the heads of the magnetic disk and zones on the disk corresponding to the respective heads; Performing a readout test to record and read out data in each of the preset zones in each of the preset zones in a stepwise manner while increasing the write current control value within a predetermined range to check whether an error has occurred; Checking the number of times of occurrence of an error with respect to the recording current control value of each step, and registering the number of times of occurrence of an error with respect to the current control value for each step in a comparison table; Setting a recording current control value at a stage in which the number of times of error occurrence registered in the comparison table is the smallest as an optimum recording current control value of the zone; And incrementing each head number zone number and proceeding to the reading out step.