JPH02177103A - Writing circuit - Google Patents

Abstract

PURPOSE:To give an appropriate damping characteristic irrespective of a variation of a write signal period by providing a variable resistance element which is connected in parallel to a fixed resistance element connected in series between both ends of a head coil and varies its resistance value in accordance with an output of a control circuit. CONSTITUTION:A head coil 1 is provided with a center tap, and provided on a magnetic head for executing write and read-out to and from a magnetic medium, and between both its ends, a damping resistance consisting of fixed resistances 2a, 2b connected in series is connected. To both ends of one fixed resistance 2b, a drain 3a and a source 3b of a field effect element (FET) 3 are connected in parallel, and also, a gate 3c of the FET 3 is connected to a control circuit 9. In this state, by using a variable resistance element consisting of this FET, etc., its resistance value is controlled in accordance with a period of a write signal. In such a way, by varying a damping resistance value of the head coil in accordance with a period of a write signal, an appropriate damping characteristic can be given.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a write circuit in a floppy disk device or the like, and particularly to a write circuit whose damping characteristics can be controlled.

[Conventional technology]

Conventionally, in write circuits for magnetic media in floppy disk drives, etc., as a means of controlling the damping characteristics, a fixed resistor is installed in parallel with the coil of the write magnetic head, and this is used to apply damping to the write circuit. I have to.

[Problem to be solved by the invention]

The damping characteristic in this type of write circuit changes depending on the write signal period, and therefore a damping characteristic control circuit is provided to provide an optimal damping characteristic depending on the write signal period.

However, the damping characteristics in the conventional write circuit described above are fixed and determined by the inductance of the coil of the magnetic head and a fixed resistor connected in parallel thereto. Therefore, even if the write signal cycle changes, the damping characteristics cannot be changed.

In other words, depending on the period of the write signal in the write circuit, the rise time of the write current to the magnetic head coil may be too long, or the damping oscillation time may be too long, making it impossible to write correctly to the magnetic medium. There was an inconvenience.

(Object of the Invention) The present invention improves the disadvantages of the conventional example, and in particular, changes the resistance value connected in parallel to the magnetic head coil according to the write signal period, thereby responding to changes in the write signal period. The object is to provide a write circuit that can provide appropriate damping characteristics regardless of the situation.

[Means for Solving the Problems] In the write circuit of the present invention, a fixed resistor connected in series between both ends of the head coil is provided in the write circuit that writes on a magnetic medium via a magnetic head having a head coil. a control circuit that generates an output by identifying a signal obtained by integrating the write signal through a time constant circuit using a fixed threshold value; and a control circuit that is connected in parallel to one of the fixed resistance elements and whose resistance depends on the output of the control circuit. This is intended to achieve the above-mentioned object by adopting a configuration including a variable resistance element whose value changes.

(Embodiment of the Invention) Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, a head coil 1 is equipped with a center tap, is provided on a magnetic head that performs writing and reading on and from a magnetic medium, and is composed of fixed resistors 2a and 2b connected in series between both ends of the head coil 1. A damping resistor is connected thereto, and a drain 3a and source 3b of a field effect element (hereinafter referred to as FET) 3 are connected in parallel to both ends of one fixed resistor 2b. Also FET3
The gate 3c of is connected to the control circuit 9.

Further, both ends of the head coil l are connected to the collector of a transistor 4.5, and the emitter of the transistor 4.5 is grounded via a constant current circuit 6. Both ends of the head coil 1 are connected to a lead circuit 7. The bases of the transistors 4 and 5 are connected to a flip-flop circuit 8, and the input of the flip-flop circuit 8 is connected to the write signal A. The input of the control circuit 9 is also connected to the write signal A.

FIG. 2 is a time chart showing signals of various parts in the circuit of FIG. 1, including a write signal A in the circuit of FIG. 1, a gate drive signal B for FET 3, drive signals C and D for head coil 1, and a control circuit. 9 shows the control signal waveform E at 9.

The operation of the write circuit of the present invention will be explained below based on each figure.

During reading, the read voltage across the head coil l is amplified via the read circuit 7 to generate a read signal output.

During writing, when the write signal A shown in FIG. 2 is input, the flip-flop circuit 8 divides the frequency of this signal to generate drive signals C and D having opposite phases to each other, and the drive transistors 4 and 5 output the drive signal. Head coil l according to C8D
On the other hand, writing is performed on the magnetic medium by flowing constant currents in opposite directions from the center tap.

The write signal A is also input to the control circuit 9, and the control circuit 9 has an internal time constant circuit, integrates the write signal A to generate a control signal having a waveform E, and converts this signal to a constant reference voltage. Gate drive signal B is generated by slicing by E0.

The FET 3 operates as a variable resistance element by being turned on or off according to the gate drive signal B.

Since FET3 is connected in parallel to fixed resistor 2b,
The resistance value at both ends of the head coil 1 varies depending on whether the drive signal B is turned on or off, from a minimum value of the fixed resistance 2a to a maximum value of the sum of the fixed resistances 2a and 2b.

The PE 73 is turned on only when the cycle of the write signal A is short due to the action of the time constant circuit in the control circuit 9. When the cycle of write signal A is long, FE
T3 is turned off.

Therefore, the damping resistance value for head coil 1 is
It becomes large or small depending on the length of the cycle of the write signal A, and changes to an appropriate value depending on the cycle of the write signal A.

〔Effect of the invention〕

As explained above, according to the present invention, the damping resistance value of the head coil is adjusted according to the cycle of the write signal by using a variable resistance element such as a FET and controlling the resistance value according to the cycle of the write signal. As a result, the damping characteristics of the head coil can be controlled to an approximately appropriate value over the entire practical writing cycle, and writing can always be performed correctly, providing an unprecedented and excellent writing circuit. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a time chart showing signals of various parts in the circuit of FIG. l...Head coil, 2a, 2b...
Fixed resistance element, 3... Field effect element (FET)
, 4.5...Transistor, 6... Constant current circuit, 7... Lead circuit, 8...
Flip-flop circuit, 9... Control circuit. Patent applicant Gunma NEC Co., Ltd.

Claims (1)

[Claims] (1) In a write circuit that writes to a magnetic medium through a magnetic head having a head coil, a fixed resistance element is connected in series between both ends of the head coil, and a write signal is integrated through a time constant circuit. a control circuit that identifies a signal using a certain threshold value and generates an output;
A write circuit comprising: a variable resistance element that is connected in parallel to the one fixed resistance element and changes its resistance value in accordance with the output of the control circuit.