JPH0821162B2 - Writing circuit of flexible disk device - Google Patents

Description

The present invention relates to a write circuit for a flexible disk device, and more particularly to a flexible disk device that operates at a low voltage.

(Prior Art) Conventionally, a write circuit of this type is configured as shown in FIG. 3, and a power supply voltage is applied to the write / read head during writing.

In FIG. 3, 31 is a toggle flip-flop, 32 is a constant current source, 33 and 34 are MOS-FETs respectively, 35 and 36 are diodes respectively, and 37 and 38 are head inductors. The write data is input to the write circuit via the signal line 301 and added to the drive MOS-FETs 33 and 34 via the toggle flip-flop 31.

(Problems to be Solved by the Invention) In the above-described conventional write circuit, the power supply voltage is applied only when writing. Therefore, the flexible disk device operating at a low voltage has a drawback that the write current rises slowly due to the inductance of the write / read head and the overwrite characteristic is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a write circuit for a flexible disk device which is configured to eliminate the above-mentioned drawbacks by applying a voltage double to the write / read head for a certain period and improve the rising characteristic of the write current. .

(Means for Solving the Problem) A writing circuit of a flexible disk device according to the present invention comprises a toggle flip-flop, a monostable multivibrator, first and second ADN gates, a NOT gate, first and A second diode, first to sixth n-channel MOS-FETs, first and second resistors,
It comprises a constant current source and a capacitor.

The toggle flip flop is for receiving a write data signal sent from the host and detecting a state change.

The monostable multivibrator is for receiving the write data signal sent from the host and generating a pulse.

The first ADN gate is for obtaining the logical product of the Q output of the toggle flipflop and the output of the monostable multivibrator.

The second AND gate is for obtaining a logical product of the output of the toggle flipflop and the output of the monostable multivibrator.

The NOT gate is for obtaining negation of the output of the monostable multivibrator.

The first diode has an anode connected to one end of the write / read head.

The second diode has the anode connected to the other end of the write / read head.

The first n-channel MOS-FET has its drain terminal connected to the cathode of the first diode and its gate terminal connected to the output of the first AND gate.

The second n-channel MOS-FET has its drain terminal connected to the cathode of the second diode and its gate terminal connected to the output of the second AND gate.

The third n-channel MOS-FET has its drain terminal connected to the cathode of the first diode and its gate terminal connected to the Q output of the toggle flip-flop.

The fourth n-channel MOS-FET has its drain terminal connected to the cathode of the second diode and its gate terminal connected to the output of the toggle flip-flop.

The first resistor is for connecting between the cathodes of the first and third diodes.

The constant current sources are the third and fourth n-channel MOS-FETs.
Is commonly connected to the source of.

The fifth n-channel MOS-FET has its gate terminal connected to the output of the monostable multivibrator.

The sixth n-channel MOS-FET has its gate terminal NO.
The drain terminal is connected to the output of the T gate, and the drain terminal is connected to the source terminals of the first and second n-channel MOS-FETs.

The second resistor has one end connected to the power supply and the other end connected to the fifth n
It is connected to the drain terminal of a channel MOS-FET.

The capacitor has one end connected to the second resistor and the other end connected to the drain terminal of the sixth n-channel MOS-FET.

(Example) Next, this invention is demonstrated with reference to drawings.

FIG. 1 is a circuit diagram showing an embodiment of a writing circuit of a flexible disk device according to the present invention.

In FIG. 1, 1 is a toggle flip-flop, 2 is a monostable multivibrator, and 3 and 4 are AND respectively.
Gate, 5 is a NOT gate, 6 is a constant current source, 7 to 12 are n-channel type MOS-FETs, 13 and 14 are diodes, and 15 and 16 are
Is a head inductor, 17 and 19 are resistors, and 18 is a capacitor. The toggle flip-flop 1 inverts the output level for each write data sent from the host via the signal line 101. The monostable multivibrator 2 is for a certain time after the write data is added,
Hold a high level. The AND gates 3 and 4 output the logical product of the inputs, and the NOT gate 5 outputs the negative level of the inputs. n
Each of the channel type MOS-FETs 7 to 12 is turned on when the gate terminal voltage is high level.

FIG. 2 is a timing chart showing the operation of the write circuit shown in FIG.

The above operation will be described below with reference to the timing chart of FIG.

First, the operation starts from the state where the write data is not sent. In this state, the Q output of the toggle flip-flop 1 is at low level and its output is at high level. Also, n-channel MOS-FET7 is off, n-channel MOS-
FET8 is on. The output of the monostable multivibrator 2 is low, the output of the NOT gate 5 is high, the n-channel MOS-FET 12 is on, and the n-channel MOS-FET 11 is off. Therefore, Kyapashita
18 is charged to the power supply voltage Vcc through the resistor 19 and has a potential substantially equal to the power supply voltage Vcc at both ends.

Here, when write data is sent from the host through the signal line 101, the toggle flip-flop 1 is inverted, the n-channel MOS-FET 7 is turned on, and the n-channel MOS-
FET8 turns off. At this time, the output of the monostable multivibrator 2 also becomes high level, the output of the AND gate 4 becomes high level, and the n-channel MOS-FET 9 is also turned on.

Therefore, the n-channel type MOS-FET 11 is turned on and the n-channel type MOS-FET 12 is turned off, so that the n-channel type MO-FET is turned on.
The drain terminal of S-FET11 becomes almost equal to the GND level. Since the capacitor 18 is charged to the potential Vcc at this point, the voltage of the source terminal of the n-channel type MOS-FET 9 becomes -Vcc. Therefore, a voltage of approximately 2 Vcc is applied to the write / read head and the current rises rapidly.

After that, the output of the monostable multivibrator 2 becomes low level, the output of the AND gate 3 becomes low level, n
The channel type MOS-FET 9 is turned off, and the circuit operation becomes equivalent to that of the prior art. Also, the n-channel type MOS-FET11 is turned off and the n-channel type MOS-FET12 is turned on.
18 is charged by resistor 19.

When the next write data is input, the toggle flip-flop 1 is inverted, the n-channel MOS-FET 10 is turned on and the same operation is performed, and the current of the write / read head rises rapidly.

(Effect of the Invention) As described above, the present invention has an effect that the rising characteristic of the current can be improved and the overwrite characteristic can be improved by applying the doubled voltage to the write / read head only for a certain period. .

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of a writing circuit of a flexible disk device according to the present invention. FIG. 2 is a timing chart showing the operation of the write circuit of FIG. FIG. 3 is a circuit block diagram showing an example of a writing circuit of a flexible disk device according to the prior art. 1,31 ...... Toggle flip flop 2 …… Monostable multivibrator 3,4 …… AND gate 5 …… NOT gate 7 to 12,33,34 …… n Channel type MOS-FET 15,16,37, 38 …… Write / read head inductor 13,14,35,36 …… Diode 17,19,39 …… Resistor 18 …… Capacitor 6,32 …… Constant current source 101,301 …… Signal line

Claims (1)

[Claims] 1. A toggle flip-flop for receiving a write data signal sent from a host to detect a state change, and a monoslip for receiving a write data signal sent from the host to generate a pulse. A table multi-vibrator, a first AND gate for obtaining a logical product of the Q output of the toggle flip-flop and the output of the monostable multi-vibrator, the output of the toggle flip-flop and the monostable multi-vibrator. A second AND gate for obtaining the logical product of the output of the vibrator, a NOT gate for obtaining the negation of the output of the monostable multivibrator, and a first anode connected to one end of the write / read head with the anode connected. A diode,
A second diode having an anode connected to the other end of the write / read head, a drain terminal connected to the cathode of the first diode, and a gate terminal connected to the first diode.
N-channel MOS- connected to the output of the AND gate of
An FET, a second n-channel MOS-FET having a drain terminal connected to the cathode of the second diode and a gate terminal connected to the output of the second AND gate, and a drain terminal of the first diode. A third n-channel MOS-FET having a gate terminal connected to the Q output of the toggle flipflop, a drain terminal connected to the cathode of the second diode, and a gate terminal connected to the A fourth n-channel MOS-FET connected to the output of a toggle flipflop, a first resistor for connecting between the cathodes of the first and second diodes, and the third
And a constant current source commonly connected to the sources of the fourth n-channel MOS-FET, a fifth n-channel MOS-FET having a gate terminal connected to the output of the monostable multivibrator, and a gate terminal. Connect to the output of the NOT gate and connect the drain terminal to the first and second channel types.
6th n-channel type MO connected to the source terminal of MOS-FET
An S-FET, a second resistor having one end connected to a power supply and the other end connected to the drain terminal of the fifth n-channel MOS-FET, and one end connected to the second resistor, and the other. The end is the sixth
And a capacitor connected to the drain terminal of the n-channel type MOS-FET of the present invention, the writing circuit of the flexible disk device.