JPH05258215A - Writing current switching circuit for magnetic disk device - Google Patents

Abstract

PURPOSE:To obtain the magnetic disk device having high reliability by changing writing current values in correspondence to a fluctuation in overwriting characteristics according to a change in temp. CONSTITUTION:An overwriting judgment circuit 1 judges what are the overwriting characteristics of respective magnetic heads in this environment by using, for example, temp. sensors. The judgment circuit 1 is constituted of the temp. sensors (not shown in Fig.) and a read-on memory (not shown in Fig.) which previously stores the values of overwriting under respective temp. conditions. The temp. of the magnetic disk device is measured by the temp. sensors and the value of the overwriting corresponding to this temp. is selected from a local area network and is outputted as an overwriting signal 2. A writing current judgment circuit 3 selects the optimum writing current value to the overwriting value by the signal 2 and outputs a writing current switching signal 4.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a write current switching circuit of a magnetic disk device pays attention only to a change in overwrite characteristic due to a cylinder, and switches the write current based on the cylinder information. In the conventional write current switching circuit, as shown in FIG. 2, in the write current switching circuit 3, the write current determination circuit 8 inputs the cylinder signal 7 and the write current value set in the cylinder becomes a preset write current value. The write current switching signal 9 is output to. The write current switch 10 is configured to switch the write current by the write current switching signal 9.

[0003]

The above-mentioned write current switching circuit of the magnetic disk device does not consider the change of the overwrite characteristic due to the change of the ambient temperature. If data is written when the write characteristics are good and then rewritten when the temperature drops and the overwriting characteristics are bad, the crosstalk of the previously written data will affect the new data, such as a large peak shift. There is a drawback that a high-quality magnetic disk device cannot be provided.

[0004]

SUMMARY OF THE INVENTION The present invention is a current switching circuit for switching a write current of a magnetic head mounted on a magnetic disk device, which determines an overwriting characteristic in a certain state of the device and corresponds to the overwriting characteristic.
Overwrite determination means for outputting a write signal, a write current setting circuit for setting a predetermined write current based on the overwrite signal and outputting a write current switching signal, and a write current switching signal for switching the write current And a write current switch.

Further, the overwriting judging means is
It may have a temperature sensor for measuring the temperature change of the magnetic disk device, and may output the overwrite signal based on the temperature measured by the temperature sensor, or a timer for measuring the elapsed startup time of the magnetic disk device. Based on the temperature change of the magnetic disk device with respect to the elapsed time to start measured by this timer.
A write signal may be output.

Further, the overwriting / judging means is
It is also possible to measure the overwrite in that state in advance in the overwrite check area provided in each track on the magnetic disk medium, and output the overwrite signal based on this measured value.

[0007]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a write current switching circuit of a magnetic disk device according to an embodiment of the present invention. In the figure, the overwrite judgment circuit 1
Will determine what the overwrite characteristics of each magnetic head are in that environment. In this embodiment, a method of making a determination using a temperature sensor will be described.

The overwrite characteristics of the magnetic disk device are determined by various factors such as the magnetic head, the magnetic disk medium, the flying height of the magnetic head and the write current value, but they are all constant under a certain environment. The optimum write current value under that condition can be set in advance. However, those elements have temperature characteristics,
If the temperature of the magnetic disk device changes, the preset write current value will not be the optimum value. That is,
Even if attention is paid only to the magnetic disk medium, since the Hc (coercive force) of the magnetic layer becomes small at high temperature, the overwrite characteristic, which is the rewriting performance, becomes good, but conversely, at low temperature, Hc becomes large. Overwrite characteristics deteriorate. Therefore, it is necessary to set the write current value in consideration of constantly changing temperature conditions.

The overwrite judgment circuit 1 is composed of a temperature sensor (not shown) and a read only memory (not shown) in which the value of the overwrite under each temperature condition is stored in advance. The temperature sensor measures the temperature of the magnetic disk device, selects the overwrite value corresponding to the temperature from the local area network, and outputs it as the overwrite signal 2.

The write current determination circuit 3 decreases the write current value for the overwriting value by the overwriting signal 2 when the overwriting is good, and when the overwriting signal is good, the writing current value is small. Outputs a write current switching signal 4 by increasing the write current value so that peak shift due to crosstalk of a previously written data pattern does not occur. Then, the write current switch 5 is
Receiving this signal, the write current is switched.

It should be noted that the overwrite judgment circuit 1 has a timer for measuring the elapsed startup time of the magnetic disk device, and the overwrite signal is generated based on the temperature change of the magnetic disk device with respect to the elapsed startup time measured by this timer. 2 may be output, and the overwriting determination circuit 1 measures the overwriting in that state in the overwriting check area provided in each track on the magnetic disk medium in advance, 2 may be output as the overwrite signal.

[0013]

As described above, according to the present invention, since the write current value can be changed in response to the change of the overwrite characteristic due to the temperature change, the peak shift due to the crosstalk of the pattern before rewriting can be minimized. It is possible to obtain a highly reliable magnetic disk device that can be suppressed.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a write current switching circuit of a conventional magnetic disk device.

[Explanation of symbols]

 1 Overwrite determination circuit 2 Overwrite signal 3,8 Write current determination circuit 4,9 Write current switching signal 5,10 Write current switcher 6,11 Write current switching circuit 7 Cylinder signal

Claims (4)

[Claims] 1. A current switching circuit for switching a write current of a magnetic head mounted on a magnetic disk device, the overwriting device determining an overwriting characteristic in a certain state of the device and outputting an overwriting signal corresponding to the overwriting characteristic. A write current setting circuit that sets a predetermined write current based on the overwrite signal and outputs a write current switching signal; and a write current switch that switches the write current according to the write current switching signal. A write current switching circuit for a magnetic disk. 2. The overwriting determination means has a temperature sensor for measuring the temperature change of the magnetic disk device, and outputs the overwriting signal based on the temperature measured by the temperature sensor. The magnetic disk write current switching circuit according to claim 1. 3. The overwriting determination means has a timer for measuring a startup elapsed time of the magnetic disk device, and the overwriting is performed based on a temperature change of the magnetic disk device with respect to the startup elapsed time measured by the timer.
2. The write current switching circuit for a magnetic disk drive according to claim 1, wherein a write signal is output. 4. The overwriting determination means measures the overwriting in that state in advance in an overwriting check area provided in each track on the magnetic disk medium, and based on this measured value, the overwriting 2. A write signal is output.
A write current switching circuit of the magnetic disk device described.