JPH0636207A - Magnetic disk unit - Google Patents

Abstract

(57) [Summary] [Object] To obtain a magnetic disk device in which the compensation amount of magnetization reversal recorded on a medium can be adjusted to an optimum value for the magnetic head, and the manufacturing yield of the magnetic head can be improved. [Structure] The first and second delay circuits 12 and 18 delay the output signals of the flip-flop 11 so as to have different output times, and the exclusive OR circuit 17 obtains a logical sum of them to correct them. Recording driver circuit 3 as recording data
By alternately outputting recording data pulses of different widths to the recording / reproducing head 1 via the recording / reproducing head 1, the magnetization reversal recorded on the medium is compensated, and the asymmetry during reproduction is reduced.
However, since the asymmetry differs depending on the magnetic head,
If the compensation amount is fixed, a magnetic head not suitable for this compensation value can be obtained. Therefore, the resistor 1 of the first delay circuit 11
5 is a variable resistance, and the compensation amount of the magnetization reversal recorded on the medium is set to the optimum compensation amount for each magnetic head to reduce the asymmetry during reproduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to an asymmetry correction circuit.

[0002]

2. Description of the Related Art FIG. 3 illustrates the magnetic recording characteristics of a conventional magnetic disk device. In a magnetic disk device having an erasing head 2 dedicated to erasing in front of a recording / reproducing head 1, as shown in FIG. In addition, a peak shift in which a direct current component, which is generally called asymmetry, is superimposed, that is, even when a single cycle is recorded, a difference occurs in a reproduced data peak interval depending on whether or not the recording magnetization of data is the same as that of direct current erasure.

Usually, when the magnetization generated in the erasing head 2 and the magnetization generated in the recording / reproducing head 1 are in the same direction, the peak interval tends to be long, and in the opposite direction, the peak interval tends to be short. is there. As a result, the reliability of the device may decrease. Therefore, the following method is used to reduce this asymmetry.

FIG. 4 is an asymmetry correction circuit diagram of a conventional magnetic disk device. In FIG. 4, 1 is a recording / reproducing head having a center tap CT, 2 is an erasing head,
A recording driver circuit 3 is composed of an internal flip-flop 4, transistors 5 and 6, an erasing circuit 7, and a transistor current source 8. Reference numeral 9 is a recording data pulse input terminal, 10 is a write gate signal input terminal, and 11 is an external flip-flop for inputting a recording data pulse from the recording data pulse input terminal 9.

Reference numeral 12 is a first delay circuit connected to the positive output terminal Q of the external flip-flop 11, and is composed of a diode 14, a resistor R15, and a capacitor C16 connected between the connection point and the ground. ing. Reference numeral 18 is a second delay circuit connected to the negative output terminal bar Q of the flip-flop 11, and 17 is an exclusive OR circuit, which inputs the outputs of the delay circuits 12 and 18 and outputs the exclusive OR output to the inside. It is sent to the flip-flop 4.

Next, the operation of the above configuration will be described. The flip-flop 11 outputs an inverted signal for each pulse of the recording data to each output terminal so that the first and second delay circuits 12 and 18 output the output signal of the output terminal of the flip-flop 11 at different output times. Delayed to
The exclusive OR circuit 17 obtains a logical sum of the delayed outputs and outputs the corrected recording data as recording data to the recording / reproducing head 1 via the recording driver circuit 3 by alternately outputting recording data pulses of different widths.

As a result, the magnetization reversal recorded on the medium is compensated, and the asymmetry during reproduction is reduced. However, since the asymmetry differs depending on the magnetic head, if the compensation amount is fixed, a magnetic head that is not suitable for this compensation value can be produced, and as a result, the reliability of the device may decrease.

[0008]

As described above, since the asymmetry correction circuit of the magnetic disk device in which the erasing head 2 dedicated to erasing is provided in front of the recording / reproducing head 1 is constructed as described above, the medium is The magnetization reversal compensation amount recorded above is uniquely determined by the fixed resistor R and the capacitor C of the first delay circuit 12. However, the optimum compensation amount of the magnetization reversal recorded on the medium is slightly different for each magnetic head.

Therefore, the resistance R of the first delay circuit 12 is
On the other hand, if is fixed, on the contrary, the optimum compensation amount of the magnetization reversal recorded on the medium cannot be obtained for each magnetic head, and the asymmetry cannot be sufficiently reduced. The characteristics deteriorate.

Further, when the magnetic head is manufactured, if the resistance R of the first delay circuit 12 is determined, a magnetic head having a characteristic matching the resistance R must be manufactured, and the yield is deteriorated accordingly. . Further, the magnetic head is a high-priced component of the magnetic disk device, but its yield is low, so that the magnetic disk device becomes more expensive.

The present invention has been made to solve the above problems, and the amount of compensation for the magnetization reversal recorded on the medium can be adjusted to an optimum value for the magnetic head, resulting in good magnetic recording characteristics. An object of the present invention is to obtain an inexpensive magnetic disk device which can improve the manufacturing yield of magnetic heads.

[0012]

DISCLOSURE OF THE INVENTION A magnetic disk device according to the present invention is a recording / reproducing head for recording and reproducing, and an erasing head for erasing direct current in a predetermined direction with respect to a recording track prior to recording. A recording driver circuit for supplying a recording current to the recording / reproducing head at the time of recording by recording data and a direct current to the erasing head at the time of erasing; and a flip-flop for sending an output which is sequentially inverted by a recording data pulse. A first delay circuit that delays only the rise of one output of the flip-flop for a predetermined time, and a second delay circuit that delays the fall of the other output of the flip-flop at a time different from the delay time of the first delay circuit. Of the output of the first delay circuit and the output of the second delay circuit In a magnetic disk device comprising an exclusive OR circuit for inputting to the recording driver circuit as recording data, the first delay circuit is constituted by a variable means capable of adjusting a rising time of a delayed signal. is there.

[0013]

In the magnetic disk apparatus according to the present invention, the resistance value of the first delay circuit can be adjusted by the variable resistance, so that the magnetization recorded on the medium one by one based on the asymmetry of each magnetic head. Optimize the amount of inversion compensation.

[0014]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a first embodiment of the present invention.
1 is a recording / reproducing head having a center tap CT, 2
Is an erasing head, 3 is a recording driver circuit, an internal flip-flop 4, transistors 5 and 6, an erasing circuit 7,
And a current source 8 of a transistor. Reference numeral 9 is a recording data pulse input terminal, 10 is a write gate signal input terminal, and 11 is a flop for inputting the recording data pulse from the recording data pulse input terminal 9.

Reference numeral 12 is a first delay circuit connected to the positive output terminal Q of the external flip-flop 11 and is composed of a variable resistor VR15 and a capacitor C16 connected between this connection point and ground. 18 is a second delay circuit connected to the negative output terminal bar Q of the flip-flop 11,
An exclusive OR circuit 17 inputs the outputs of the delay circuits 12 and 18, and outputs the exclusive OR output to the internal flip-flop 4.

Next, the operation of the above configuration will be described with reference to the waveform chart of each part shown in FIG. The external flip-flop 11 outputs outputs which are sequentially inverted by the input of the recording data pulse based on the input of the write gate signal (FIGS. 2A, 2B and 2C). The output of the first delay circuit 12 rises based on the Q output of the external flip-flop 11 and outputs an output that exceeds the threshold value V _th after a predetermined time t _{r has} elapsed due to the time constant of the variable resistor 15 and the capacitor 16. (FIG. 2 (d)).

On the other hand, the negative output bar Q of the external flip-flop 11 is delayed by the second delay circuit 18 for a predetermined time t _d (FIG. 2 (e)). Therefore, the output of the exclusive OR circuit 17 becomes L level when the time t _{r has} elapsed from the rise of the positive output Q of the external flip-flop 11, and the change point of the output of the second delay circuit 18, that is, the external flip-flop. After a lapse of time t _d from the rise of the positive output Q of 11, the signal becomes H level (FIG. 2 (f)).

Next, the recording data pulse (see FIG.
When (b)) is input, the positive output Q of the external flip-flop 11 becomes L level (FIG. 2 (c)). At this time, the delay time of the first delay circuit 12 becomes almost zero by turning on the diode 14. The output of the exclusive OR circuit 17 becomes L level when the positive output Q of the external flip-flop 11 falls, and becomes H level when the output of the second delay circuit 18 becomes H level.

As described above, the output signals of the exclusive OR circuit 17 have different pulse widths. Therefore, if the internal flip-flop 4 is inverted by the output signal of the exclusive OR circuit 17, the time difference between the H level and the L level occurs by 2 × t _r (FIG. 2 (g)) and is recorded on the medium. The magnetization reversal is also compensated for this time difference. Therefore, asymmetry during reproduction can be reduced.

Therefore, according to the above embodiment, the resistor 15 of the first delay circuit 12 is a variable resistor,
This resistance is adjusted so that the magnetic head can obtain an optimum compensation amount of the magnetization reversal recorded on the medium, and asymmetry at the time of reproduction can be reduced.

Example 2. In the above embodiment, the resistance R15 of the first delay circuit 12 is made variable so that the compensation amount of the magnetization reversal recorded on the medium is adjusted to the optimum value for each head. Even if the capacitor C16 of the one delay circuit 12 is a variable capacitor, the compensation amount of the magnetization reversal can be adjusted to an optimum value, and the asymmetry during reproduction can be reduced.

Example 3. Further, in the above embodiment, only the resistor R15 of the first delay circuit is made a variable resistor to adjust the compensation amount of the magnetization reversal recorded on the medium to an optimum value for each head. Even if both the resistor 15 and the capacitor 16 of the first delay circuit 12 are variable,
The compensation amount of the magnetization reversal can be adjusted to an optimum value, and the asymmetry during reproduction can be reduced.

[0023]

As described above, according to the present invention, the delay circuit is the variable means so that the compensation amount of the magnetization reversal recorded on the medium is optimized for each magnetic head.
Asymmetry at the time of reproduction can be reduced, a magnetic disk device having good magnetic recording characteristics can be obtained, the yield of magnetic head manufacturing can be improved, and an inexpensive magnetic disk device can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an asymmetry correcting circuit of a magnetic disk device according to a first embodiment of the present invention.

FIG. 2 is an output waveform diagram of each part of FIG.

FIG. 3 is an explanatory diagram of magnetic recording characteristics of a conventional magnetic disk device.

FIG. 4 is a circuit diagram of an asymmetry correction circuit of a conventional magnetic disk device.

[Explanation of symbols]

 1 recording / reproducing head 2 erasing head 3 recording driver circuit 4 internal flip-flop 7 erasing circuit 8 current source 9 recording data pulse input terminal 10 write gate signal input terminal 11 external flip-flop 12 first delay circuit 17 exclusive OR circuit 18 Second delay circuit

Claims (1)

[Claims] 1. A recording / reproducing head for recording and reproducing, an erasing head for erasing direct current in a predetermined direction with respect to a recording track prior to recording, and a recording / reproducing head for recording data according to recorded data during recording. A recording driver circuit for supplying a recording current and a direct current to the erasing head at the time of erasing, a flip-flop for outputting an output which is sequentially inverted by a recording data pulse, and a delay of only one output of the flip-flop for a predetermined time. An output of the first delay circuit, and a second delay circuit for delaying the fall of the other output of the flip-flop at a time different from the delay time of the first delay circuit And an exclusive OR of the output of the second delay circuit and corrected recording data, which is input to the recording driver circuit as corrected recording data. A magnetic disk device comprising an alternative logical sum circuit, wherein the first delay circuit is constituted by a variable means capable of adjusting a rising time of a delayed signal.