JPH0380404A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To decrease the strains remaining in a magnetic head at the end of writing and to eliminate the reading out errors of data by inputting the oscillation signal gradually increasing oscillation frequencies to the winding of the magnetic head in place of a data signal at the end of the writing action. CONSTITUTION:As oscillation circuit 1 is so constituted that the oscillation frequency of its output 12 increases gradually. A writing control signal 10 is inputted to the input terminal for frequency control of the oscillation circuit 1 and the input terminals of a delay circuit 2 and a selector circuit 3. The selector circuit 3 selects the writing data 11 and the writing action of the data is executed by a magnetic head 5 when the control signal 10 is a low level. The selector circuit 3 selects the output 12 of the oscillation circuit and the selected output 13 shifts gradually to the higher frequencies from this point of time when the writing control signal 10 attains a high level upon ending of the writing action. The writing current 15 attenuates gradually in this way and the magnetic head 5 is put into the state in which AC degaussing is executed. The magnetic strains do not remain any more.

Description

TECHNICAL FIELD The present invention relates to a magnetic disk drive, and more particularly to a write circuit that is a constituent circuit of a magnetic disk drive used as an auxiliary storage device in a computer system or the like.

BACKGROUND ART Conventionally, a write circuit of this type of disk device terminates its operation by writing an external write data signal as it is as a magnetization pattern in accordance with an external write control signal.

However, in the write operation by the conventional write circuit described above, the end point of the external write signal is not synchronized with the external write data signal, and the magnetic head section There is a high probability that the current flowing is at its maximum.

Therefore, if the write operation ends when the current reaches its maximum, the magnetic distortion generated by the strong magnetic field generated during the write operation will remain in the head portion even after the write operation is completed. This distortion is dissipated by external magnetic or mechanical stress, but there is a drawback that noise at that time may cause errors in read data.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a highly reliable magnetic disk device that reduces magnetic distortion at the end of writing. .

Composition of the Invention A magnetic disk device according to the present invention is a magnetic disk device that writes data on a magnetic medium by applying a data signal corresponding to write data to a magnetic head winding, and the magnetic disk device writes an oscillation signal whose oscillation frequency gradually increases. The present invention is characterized in that it has an oscillation means for sending out the oscillation signal, and the oscillation signal is input to the magnetic head winding instead of the data signal at the end of the write operation.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing the configuration of a write circuit of an embodiment of a magnetic disk device according to the present invention.

In the figure, a write circuit in a magnetic disk drive according to an embodiment of the present invention includes an oscillation circuit 1, a delay circuit 2, a selector circuit 3, a write driver circuit 4, and a magnetic head 5. Note that 10 is a write control signal and 11 is a write data signal.

The oscillation circuit 1 is configured such that the oscillation frequency of its output 12 gradually increases. Note that its internal configuration will be described later.

The delay circuit 2 has a function of delaying the trailing edge of the input write control signal, and includes a time constant circuit.

The selector circuit 3 selectively sends out the write data signal 11 and the output 12 of the oscillation circuit 1 depending on the logic level of the write control signal 10.

The write control signal 10 is input to the frequency control input terminal of the oscillation circuit 1, the input terminal of the delay circuit 2, and the selection control input terminal of the selector circuit 3. Further, both the write data signal 11 and the output 12 of the oscillation circuit 1 are input to the selected input OU 'E' of the selector circuit 3.

A selection output 13 from the selector circuit 3 is input to an input terminal for write current inversion of the write driver circuit 4.

Further, the output 14 of the delay circuit 2 is input to the write/non-write switching input terminal of the write driver circuit 4.

The magnetic head 5 is connected to the write driver circuit 4,
A write current 15 will flow through the winding.

Next, the operation of this circuit will be explained using FIG.

FIG. 2 is a time chart showing signals of each part in FIG. 1. In the figure, a write control signal 10, a write data signal 11, an output 12 of the oscillation circuit 1, an output 14 of the delay circuit 2, a selection output 13, and a write current 15 are shown. Note that signals 10 to 14 represent the logic level of each signal, and signal 15 represents the current value of the write current 15 flowing through the magnetic head 5.

Now, the write control signal 10 is in the enabled state (-“0”
), the output 14 of the delay circuit 2 also becomes low level (
Time Tl). At this time, the selector circuit 3 selects the write data signal 11. Then, the write driver circuit 4 inverts the write current 1 according to the selection output 13.
5 and performs a data write operation.

Next, the write control signal 10 is in the disabled state a(-7
1''), the selector circuit 3 outputs the output 12 of the oscillation circuit.
is selected (time T2). On the other hand, the output 12 of the oscillation circuit 1
starts to oscillate from a predetermined frequency to a gradually higher frequency from the time the write control signal 10 becomes disabled.

Therefore, the write current 15 gradually attenuates due to a delay in rising due to inductance caused by the winding of the magnetic head 5, and finally stops flowing.

Due to this attenuation, the magnetic head 5 undergoes bulk erase (r3
(ulk erase), that is, AC demagnetization has been performed, and the above-mentioned magnetic distortion does not remain.

Next, using FIGS. 3 and 4, the oscillation circuit 1 in FIG.
The internal configuration of is explained below. Both FIGS. 3 and 4 are block diagrams showing examples of the internal configuration of the oscillation circuit 1, and parts equivalent to those in FIGS. 1 and 2 are indicated by the same reference numerals. Further, FIG. 3 shows an example of a configuration using an analog method, and FIG. 4 shows an example of a configuration using a digital method.

In FIG. 3(a), the oscillation circuit 1 includes an inverter 30, a transistor Tr, resistors R1 and R2, a capacitor C, and a voltage controlled oscillation circuit (hereinafter abbreviated as VCO) 31.
and a monostable multivibrator (hereinafter abbreviated as MM) 32 for adjusting the pulse width.

Note that the resistor R1 is pulled up to the power supply voltage Vcc.

The operation of the oscillation circuit 1 having such a configuration is shown in FIG.
This will be explained using the time chart shown in b).

First, when the write control signal 10 is in a disabled state, that is, at a high level, the transistor Tr is turned off. Then, it is sent from VCO31~IM32
The output 12, whose pulse width has been adjusted by, has a constant frequency depending on the value of the voltage Vcc.

Now, when the write control signal 10 is enabled, that is, becomes low level at time TI, the transistor T
r is turned on. Then, the input signal 20 to the VCO 31 becomes low level.

Note that, in reality, the level changes to low level with a certain time constant.

Therefore, the frequency of the output 12 sent from the VCO 31 and whose pulse width has been adjusted by the MM 32 becomes lower than before time Tl. Here, a write operation is performed.

When the write operation is completed and the write control signal 10 is disabled at time T2, that is, becomes high level, the transistor T' is turned off again. Then,
The capacitor C is gradually charged, and the input signal 20 to the VCO 31 changes to a high level while drawing a curve according to the time constant of the resistor R1 and the capacitor C.

Then, while this input signal 20 changes slowly from low level to high level, it is sent out from VCO 31 and M
The frequency of the output 12, whose pulse width has been adjusted by M32, gradually increases and returns to the original frequency. Therefore, if this output 12 is input to the write driver circuit 4 via the selector circuit 3, the magnetic head 5 is demagnetized by AC demagnetization as described above.

In addition, in FIG. 4(a), the oscillation circuit 1 is an oscillator 40
, AND circuit 41, counter 42, and decoder 43
, a NAND circuit 44 , and an inverter 45 . Note that the write control signal 10 is transmitted to the counter 42.
Master reset terminal Ml? has been entered.

The operation of the oscillation circuit 1 having such a configuration is shown in FIG.
This will be explained using the time chart shown in b).

In the figure, the output 21 of the oscillator 40, the write control signal 10, the output 22 of the AND circuit 41, and the counter 42
output 23 of counter 42, output 24 of counter 42, and oscillation circuit l
The output 12 of is shown. Note that the output 23 is a signal corresponding to the carry of the counter 42.

First, when the write control signal 10 is enabled, that is, becomes low level at time Tl, the counter 42
is in a reset state and its output 24 is no longer delivered. A write operation is now performed. When the write operation is completed and the write control signal 10 becomes disabled, that is, becomes high level at time T2, the reset state of the counter 42 is released.

Then, the counter 42 converts the value of the output 24 into D 1 . D2. ...and the count goes up. This output 24 is decoded by a decoder 43. Here, since the decoded output of the decoder 43 is input to the NAND circuit 44 together with the output 21 of the oscillator 40 inverted by the inverter 45, the oscillation circuit 1
If the decoding conditions are set in advance so that the pulse width of the output 12 becomes gradually shorter, the required signal can be obtained.

Therefore, if this output 12 is input to the write driver circuit 4 via the selector circuit 3, the magnetic head 5 is demagnetized by AC demagnetization as described above.

Note that when the output 23, which is a carry signal, is sent from the counter 42, the output 21 of the oscillator 40 is suppressed by the AND circuit 41, and the counting operation of the counter 42 is stopped.

Effects of the Invention As explained above, the present invention provides a means for performing AC demagnetization in the write circuit of a magnetic disk drive, and performs demagnetization at the end of the write operation, thereby reducing the distortion remaining in the magnetic head at the end of the write operation. This has the effect of eliminating data read errors due to noise when distortion diverges and improving the reliability of the magnetic disk drive.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a write circuit of a magnetic disk device according to an embodiment of the present invention, FIG. 2 is a time chart showing signals of each part in FIG. 1, and FIGS.
2 is a circuit diagram showing an example of the internal configuration of the oscillation circuit shown in the figure, and a time chart showing its operation. Explanation of symbols of main parts

Claims (1)

[Claims] (1) A magnetic disk device that writes data onto a magnetic medium by applying a data signal corresponding to write data to a magnetic head winding, and has an oscillation means that sends out an oscillation signal whose oscillation frequency gradually increases. . A magnetic disk device, wherein the oscillation signal is input to the magnetic head winding instead of the data signal at the end of a write operation.