JPS61210575A - Positioning circuit for magnetic head - Google Patents

Abstract

PURPOSE:To reduce the cost by providing a sample-and-hold circuitinputting an output of a DA converter to eliminate the need for a DA converter for generating an AGC reference signal. CONSTITUTION:When a magnetic head is in track follow operation, a binary value corresponding to an AGC reference signal 6 is added as a DA converter input signal 1. In this case, a sample-and-hold control signal 5 is at a low level and an analog switch 13 is set, then the AGC reference signal 6 is generated in the output of an operational amplifier 14. When a magnetic head is in seek operation, the signal 5 goes to a high level and the switch 13 is reset, then a voltage before the switch 13 is turned off is kept by a hold capacitor 12 and the same AGC reference voltage is kept even during the seek operation. In this case, as the signal 1, a binary value is added corresponding to the signal 3 and the DA converter 2 outputs the signal 3. Thus, a DA converter for generat ing the AGC reference signal is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head positioning circuit, and more particularly to a magnetic head positioning circuit for a magnetic disk device.

[Conventional technology]

In a magnetic disk drive, the moving speed of the magnetic head is controlled by a servo circuit, and in the acceleration section, the maximum current is applied to the voice coil motor that drives the moving section to accelerate it.
In the deceleration portion, the speed of the magnetic head is controlled by a speed reference signal having a voltage value predetermined from the current position of the magnetic head to the number of tracks of the target track salt. It also has a magnetic disk surface (usually called a servo surface) on which position information for positioning the magnetic head is written in advance, and the position information from this servo surface is read by a read-only magnetic head called a servo head. The signal is read out, amplified, and demodulated to generate a position signal that changes in a triangular waveform as the magnetic head moves. At this time,
The position information signal is controlled by an AGC (automatic gain control) circuit so that the amplitude of the position signal is constant. here,
When the reference voltage of the AGC circuit is increased or decreased, the position signal amplitude is also increased or decreased. The magnetic head speed signal is generated in a circuit called an electronic tachometer by differentiating a position signal that changes in the form of a triangular wave and alternately selecting its polarity. Therefore, increasing the AGC reference voltage will increase the position signal amplitude. As a result, the gain of the electronic tachometer circuit increases, and as a result, the moving speed of the magnetic head becomes slower. Using this relationship, in recent magnetic disk drives, the speed of the magnetic head during seek is measured by a microprocessor, etc., and if the speed is fast, the AGC reference voltage is decreased, and if the speed is slow, the AGC reference voltage is increased. AG than doing
A method of automatically adjusting the C reference voltage is adopted.

FIG. 3 shows a block diagram of a conventional circuit, in which a DA converter 2 receives an input signal 7 for generating a speed reference signal, which is a binary value corresponding to the speed reference signal, and generates a speed reference signal 3. The DA converter 9 receives an input signal 8 for generating an AGC reference signal, which is a binary value corresponding to the AGC reference signal, and generates an AGC reference signal 6.

[Problem that the invention seeks to solve]

The above-described conventional circuit requires a DA converter 9 for generating an AGC reference signal in addition to the ODA converter 2 for generating a speed reference signal, which has the disadvantage of increasing costs.

The present invention solves the above problems and provides a circuit that does not require an ODA converter for generating an AGC reference signal.

[Failure to solve the problem]

The magnetic head positioning circuit of the present invention includes a DA converter that receives a DA converter input signal from an upper circuit and outputs a speed reference signal, and inputs the speed reference signal and a sample hold control signal from the upper circuit. Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

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

In the figure, a DA converter 2 receives a DA converter input signal 1 and generates a speed reference signal 3. A sample and hold circuit 4 receives a speed reference signal 3 and a sample and hold control signal 5 and generates an AGC reference signal 6. Details of the sample and hold circuit 4 are shown in FIG. A hold capacitor 12 is connected between the inverting input terminal and the output terminal of the operational amplifier 14, and the inverting input terminal is also connected to the input resistor 10 and the feedback resistor 11.
is connected via an analog switch 13 to a connection point. The analog switch 13 is turned off when the sample hold control signal, which is a logic signal, is at a high level and turned on when it is at a low level. Here, the DA converter input signal 1 serves as the speed reference signal generation input signal 7 and the AGC reference signal generation input signal 8 in the conventional circuit shown in FIG.

When the magnetic head is held on the track and is performing track following operation, the speed reference signal 3 for controlling the speed of the magnetic head is not required, so in this case, the DA converter input signal 1 is A binary value corresponding to the 〇〇 reference signal 6 is added.

At this time, the sample hold control signal is at a low level and the analog switch 13 is on, so the operational amplifier 1
An AGC reference signal 6 is generated at the output of 4.

When the magnetic head performs a seek operation to move to the next target track, the sample hold control signal 5 becomes high level and the analog switch 13 is turned off. is maintained, so the same AGC reference voltage is maintained even during the seek operation. At this time, a binary value corresponding to the speed reference signal 3 is added to the DA converter input signal 1, and the DA converter 2 outputs the speed reference signal 3. Since the seek operation is normally switched to the track follow operation, the capacitance value of the hold capacitor 12 should be selected so that the AGO reference signal 6 can be held during the maximum seek time. In the circuit shown in FIG. 2, the polarity of the AGC reference voltage 6 is inverted by the operational amplifier 14, but the polarity can be restored by further adding an inverting amplifier.

〔Effect of the invention〕

As explained above, the present invention uses a sample and hold circuit that receives the output of a DA converter as an input.
This has the advantage that an ODA converter is not required for generating the C reference signal, and a magnetic disk device with reduced cost can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of FIG. 1, and FIG. 3 is a block diagram of a conventional garden path. ■...DA converter input signal, 3...Speed reference signal,
5... Sample hold control signal, 6... AGC reference signal, 7... Input signal for speed reference signal generation, 8...
- Input signal for AGC reference signal generation, 10... Input resistor, 11... Feedback resistor, 12... Hold capacitor, 13... Analog switch, 14... Operational amplifier patent applicant NEC Corporation Fig. 1 I: DA change g 9 5 sample hold signal 3: Speed base 4! signal θ-, A (3C reference signal Fig. 2

Claims (1)

[Claims] (1) Input the DA converter input signal from the upper circuit,
A magnetic head positioning circuit comprising: a DA converter that outputs a speed reference signal; and a sample hold circuit that receives the speed reference signal and a sample hold control signal from an upper circuit as input and outputs an AGC reference signal. .