JP3592413B2 - Magnetic recording / reproducing apparatus and its recording / reproducing circuit - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing a signal using a magnetic recording medium such as a magnetic disk, and particularly to a signal read / reproduce / write control technique.
[0002]
[Prior art]
FIG. 2 shows an outline of a signal read / write control circuit of a conventional magnetic recording / reproducing apparatus. At the time of reproducing a signal from a magnetic recording medium such as a magnetic disk (not shown), a signal detected by the magnetic head 50 is amplified by a preamplifier 51, noise is removed by a filter circuit 52, and a reproduced signal processing circuit (not shown) ). On the other hand, when writing signals to the magnetic recording medium, write data is supplied to the magnetic head 50 through the write circuit 53.
[0003]
By the way, generally available magnetic disks are classified into high density and normal density, and it is necessary to perform recording and reproduction in consideration of the characteristic that the recording density has a difference between the inner circumference and the outer circumference. Therefore, the write circuit 53 is provided with a write current switching circuit 54 for switching the write current according to the above characteristics. The filter circuit 52 is also provided with a filter time constant switching circuit 55 for switching the cutoff frequency according to the above characteristics. The write current switching circuit 54 and the filter time constant switching circuit 55 are constituted by constant current circuits (not shown).
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional magnetic recording / reproducing apparatus, the write current switching circuit 54 and the filter time constant switching circuit 55 are configured by the same constant current circuit, so that the circuit configuration is complicated, and the similar constant current There has been a problem in terms of cost performance of using circuits redundantly. When the recording / reproducing circuit is manufactured by a semiconductor integrated circuit (IC) 56, a resistor (not shown) used to set a reference value of a switching current in each of the write current switching circuit 54 and the filter time constant switching circuit 55. Incorporation of (f) in the IC greatly affects the variation in resistance, so that it is necessary to provide an external resistor for each of the switching circuits 54 and 55, which hinders a reduction in the number of components.
[0005]
An object of the present invention is to provide a magnetic recording / reproducing apparatus in which the configuration of a recording / reproducing circuit is simple and inexpensive in view of the above conventional problems.
[0006]
[Means for Solving the Problems]
The applicant of the present invention has focused on the fact that the constant current circuit used for the write current switching circuit and the filter circuit can be shared, and has simplified the recording / reproducing circuit. Therefore, in order to solve the above problem, the invention according to claim 1 includes a magnetic head for recording and reproduction, a filter circuit for correcting a signal waveform read from a magnetic recording medium via the magnetic head at the time of reproduction, and a recording circuit. A write circuit for supplying a write current to the magnetic head, a reproduction mode constant current generation circuit for setting a filter time constant of the filter circuit, and a recording mode constant current generation circuit for setting the write current value. Wherein at least a part of the reproduction mode constant current generation circuit and a part of the recording mode constant current generation circuit that specify a constant current to be generated are shared, and the reproduction mode constant current generation circuit The constant current generated by the constant current generating circuit for the reproduction mode or the recording mode for supplying the constant current generated by the A magnetic recording and reproducing apparatus characterized by comprising a changeover switch for selecting either the recording mode supplied to the write circuit.
[0007]
The invention according to claim 2, wherein the reproduction mode constant current generation circuit and the recording mode constant current generation circuit include a current mirror circuit, the current mirror circuit includes a plurality of input-side transistors, and the plurality of input-side transistors. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein a transistor is shared by the reproducing mode constant current generating circuit and the recording mode constant current generating circuit, and is constituted by a single integrated circuit. .
[0008]
【The invention's effect】
According to the first or second aspect of the present invention, the constant current generating circuit is shared with the writing and reproducing systems in the magnetic recording and reproducing apparatus, and is used by being appropriately switched according to the specifications of the magnetic recording medium. The scale of the integrated circuit can be significantly reduced, and the configuration can be made inexpensively. In addition, when the integrated circuit for the magnetic recording / reproducing device is formed into an IC, only one resistor for adjusting the generated current is required, and the number of components of the entire device can be reduced.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a magnetic recording / reproducing apparatus according to one embodiment of the present invention.
The magnetic recording / reproducing apparatus of this embodiment includes a magnetic head 1, a processing unit 11, and a control unit 5 for controlling signal reading (reproduction) / writing by the processing unit 11. The processing unit 11 is configured by a microcomputer and performs processing of read data and write data. The control unit 5 includes an integrated circuit including a filter circuit 4 used for correcting a waveform of a read signal when reproducing a signal from a magnetic disk (not shown) and a writing circuit 3 used for writing a signal to the magnetic disk. The operation is controlled in accordance with the control signal from the controller 11.
[0010]
At the time of signal reproduction, the signal detected by the magnetic head 1 is amplified by the preamplifier 2, noise-removed by the filter circuit 4, and input as a reproduction output to a reproduction signal processing circuit (not shown). On the other hand, when writing signals to the magnetic disk, write data from the processing unit 11 is supplied to the magnetic head 1 through the writing circuit 3.
[0011]
Next, a write current switching circuit for switching the write current by the write circuit 3 is provided for the specification of the high density or the normal density of the magnetic disk, and for the characteristics according to the difference between the inner and outer circumferences of the recording density. . This write current switching circuit includes a switch group 8 and a constant current generating circuit that generates a constant current corresponding to the content specified by the switch group 8 according to the inner and outer peripheral densities. The constant current generating circuit includes a plurality of input side transistor groups 9 and an output side transistor Q6. A current mirror circuit including a transistor pair Q3 and Q4 is provided between the output side transistor Q6 and the write circuit 3. The base and the collector of the transistor Q3 are connected in common, and an output current flowing to the collector of the output transistor Q6 is supplied to the collector thereof, and the output current is inverted by the current mirror circuit and written through the transistor Q4. It is supplied to the writing circuit 3 as I1.
[0012]
The filter circuit 4 is also provided with a filter time constant switching circuit for switching the cutoff frequency according to the above characteristics. The filter time constant switching circuit includes a switch group 8 and a constant current generating circuit that generates a constant current corresponding to the content specified by the switch group 8 according to the selected filter time constant. The constant current generating circuit includes a plurality of input transistor groups 9 and an output transistor Q5. A current mirror circuit including a transistor pair Q1 and Q2 is provided between the output side transistor Q5 and the filter circuit 4. The base and collector of the transistor Q1 are connected in common, and the collector side is supplied with the output current flowing to the collector side of the output side transistor Q5. The output current is inverted by the current mirror circuit and is filtered through the transistor Q2. The constant switching current I2 is supplied to the filter circuit 4.
[0013]
The switching of the supply constant current by the switch group 8 may additionally include a function of supplying a current corresponding to the front and back of the magnetic disk in accordance with the double-sided specification of the magnetic disk. The switching between the write current switching circuit and the filter time constant switching circuit is performed by a switching switch 10 for switching the operation of the current mirror circuit including the respective transistor pairs Q3, Q4 or Q1, Q2. When the contact of the changeover switch 10 is at A, the common base of the transistor pair Q1 and Q2 is connected to the ground side to enter the write mode. When the contact is at B, the common base of the transistor pair Q3 and Q4 is connected to the ground side to enter the reproduction mode.
[0014]
A constant current source 6 is connected to one common input line of the plurality of input transistor groups 9 via a transistor Q11. The constant current source 6 includes a differential pair including transistors Q7 and Q8, and a current mirror circuit including transistors Q9 and Q10. A constant voltage source VREF is applied to the base of the transistor Q7, and a constant current output from the constant current source 6 is supplied to one common input side line of the transistor group 9 via the transistor Q11. The base of the transistor Q8 is connected to the emitter of the transistor Q11, and the current adjusting resistor R is externally connected to the integrated circuit of the control unit 5.
[0015]
The switch control circuit 7 appropriately switches the respective contacts of the switch group 8 and the changeover switch 10 according to the selection signal from the processing unit 11.
As shown in the above configuration, the constant current circuit used for the writing and reproducing systems in the magnetic recording / reproducing apparatus switches the output current generated by the common input-side transistor group 9 to the writing circuit 3 or the filter circuit 4 by the changeover switch 10. It is configured to switch and supply. Therefore, the scale of the integrated circuit of the control unit 5 can be greatly reduced, and the configuration can be made inexpensively. In addition, only one resistor R for current adjustment needs to be provided on the common input-side transistor group 9 side, which contributes to a reduction in the number of components of the device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.
FIG. 2 is a block circuit diagram showing a schematic configuration of a conventional magnetic recording / reproducing apparatus.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 magnetic head 2 preamplifier 3 writing circuit 4 filter circuit 5 control unit 6 constant current source 7 switch control circuit 8 switch group 9 common input-side transistor group 10 changeover switch R (for current adjustment) resistance

Claims (2)

A magnetic head for recording and reproduction, a filter circuit for correcting a signal waveform read from the magnetic recording medium via the magnetic head during reproduction, a write circuit for supplying a write current to the magnetic head during recording, and a filter circuit for the filter circuit. A reproducing mode constant current generating circuit for setting a filter time constant; and a recording mode constant current generating circuit for setting the write current value. At least a part of the reproducing mode constant current generating circuit and the recording A reproduction mode or a recording mode in which a part of a constant current generating circuit for mode that specifies a constant current to be generated is shared, and a constant current generated by the constant current generating circuit for reproduction mode is supplied to the filter circuit. switching scan for selecting either a recording mode and supplies a constant current generated by the use constant current generating circuit to the write circuit Magnetic recording and reproducing apparatus having a pitch. The reproducing mode constant current generating circuit and the recording mode constant current generating circuit include a current mirror circuit, the current mirror circuit includes a plurality of input transistors, and the plurality of input transistors are configured to control the reproducing mode constant current. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the generating circuit and the recording mode constant current generating circuit are shared by a single integrated circuit.

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