JPH05210810A - Write circuit - Google Patents

Abstract

PURPOSE:To normally record magnetic data even under a low power voltage by providing a booster circuit for operating with write data as a clock and impressing about double the power voltage upon a center tap of a magnetic head the moment a current is started to flow. CONSTITUTION:An output of an output buffer 8 is at a low level during a period of a high level of the write data. Then, a diode 10 is under the conductive state because its cathode side is at a low potential. Consequently, a voltage lower than the power voltage by a forward voltage of the diode 10 is charged on both ends of a capacitor 9. Secondly, when the write data becomes a low level, the output of the output buffer 8 becomes a high level. Since the capacitor 9 has been charged during the period of the high level of the write data, the capacitor 9 is at a potential of about double the power voltage at one end connected to the diode 10. Therefore, the diode 10 is at a high potential on the cathode side to be under the nonconductive state, and hence a voltage waveform is impressed upon the center tap of the magnetic head 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writing circuit, and more particularly to a writing circuit for a magnetic recording device such as a floppy disk drive or a hard disk drive.

[0002]

2. Description of the Related Art In a conventional write circuit, as shown in FIG. 4, a magnetic head 1 whose center tap is connected to a power source, and both ends of the magnetic head 1 and the other end thereof are connected to a common constant current source 6. First switch 4 and second switch 5
And the clock is connected to the write data input terminal 2,
The toggle type flip-flop 3 has a non-inverting output connected to the control terminal of the first switch 4 and an inverting output connected to the control terminal of the second switch 5.

Next, the operation of the write circuit of the conventional magnetic recording device will be described with reference to the time chart of FIG. In addition,
The broken line in the figure represents the GND level.

Write data 1 to write data input terminal 2
2 is applied. The toggle-type flip-flop 3 divides this signal by 2 to generate a non-inverted output 13 and an inverted output 14, and controls the first switch 4 and the second switch 5. The first switch 4 and the second switch 5 are controlled by the non-inversion and the inversion output of the same flip-flop, so they are not turned on at the same time.

Here, the toggle type flip-flop 3
The output changes at the falling edge of input data,
It is also assumed that the switches 4 and 5 are turned on when the control input is HIGH level.

If the control signal 13 becomes HIGH level and the first switch 4 is turned on, current flows from the power source to the magnetic head 1 via the starter tap of the magnetic head, passes through the switch 4 and becomes a constant current source. Pour in. At this moment, the counter electromotive voltage is induced by the inductance of the magnetic head at the moment when the first switch 4 is turned on and the current starts to flow. Next, when the control signal 13 becomes LOW level and the first switch 4 is turned off, the back electromotive force having the opposite polarity to the back electromotive force described above is induced by the inductance of the magnetic head. Therefore, the potential 15 at the connection point between the magnetic head 1 and the first switch 4 is equal to the power supply voltage while the current is flowing in the steady state or the current is not flowing.
A pulse is generated by the counter electromotive voltage at the moment when the switch 4 is turned on / off. Control signal 14, magnetic head 1 and second
The same applies to the potential 16 at the connection point with the switch 5.

Further, since the magnitude of the counter electromotive voltage is the potential of the center tap of the magnetic head 1 even at the maximum, the magnitude of the counter electromotive voltage is limited by the power supply voltage.

[0008]

In the write operation of the conventional magnetic recording device, the magnitude of the back electromotive force is limited by the voltage of the center tap of the magnetic head 1, that is, the power supply voltage.

When changing the current flowing through an inductance such as a magnetic head, a counter electromotive voltage of V = -L.di / dt is generated at both ends of the inductance. Conversely, when the counter electromotive voltage is limited, the current changing speed is also limited, and the smaller the counter electromotive voltage, the slower the current changing speed. Therefore, in the time chart shown in FIG. 5, the current 17 flowing at the connection point between the magnetic head 1 and the first switch 4, the magnetic head 1 and the second switch 5
The current 18 flowing at the connection point with and has a waveform with a dull rise because the back electromotive voltage is limited by the power supply voltage.

Therefore, when trying to operate the device with a lower power supply voltage, a sufficiently large counter electromotive voltage cannot be generated, and the time during which the counter electromotive voltage is generated becomes longer, and The flowing current becomes dull. Therefore, there is a drawback that magnetic data cannot be normally recorded at a low power supply voltage.

[0011]

The writing circuit of the present invention is
A write data input terminal, a booster circuit that operates using write data as a clock, a magnetic head whose center tap is connected to the booster circuit, and a constant current source in which one end is connected to each end of the magnetic head and the other end is common. A first switch and a second switch connected to the second switch, a clock connected to the write data input terminal, a non-inverted output connected to the control terminal of the first switch and an inverted output connected to the control terminal of the second switch. It has a toggle type flip-flop.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a write circuit of a magnetic recording apparatus of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the write circuit of the magnetic recording apparatus of the present invention.

The write circuit of the magnetic recording apparatus of this embodiment is
The magnetic head 1 whose center tap is connected to the cathode side of the diode 10 and one end of the capacitor 9, and the diode 10 whose anode side is connected to the power supply and the other end to the write data input terminal 2 via the output buffer 8 and the inverter 7. A booster circuit including a connected capacitor 9, a first switch 4 and a second switch 5 connected to both ends of the magnetic head 1 and the other common current source 6 at the other end, and a clock for writing data. The toggle type flip-flop 3 is connected to the input terminal 2 and has a non-inverted output connected to the control terminal of the first switch 4 and an inverted output connected to the control terminal of the second switch 5.

Next, the operation of the write circuit of the magnetic recording apparatus of the present invention will be described with reference to the time chart of FIG.

While the write data is at the HIGH level, the output of the output buffer 8 is at the LOW level. Further, the diode 10 becomes conductive because the cathode side has a lower potential. Therefore, a voltage lower than the power supply voltage by the forward voltage of the diode 10 is charged across the capacitor 9. Next, when the write data becomes LOW level, the output of the output buffer 8 becomes HIGH level. Since the capacitor 9 is charged while the write data is at the HIGH level, the end of the capacitor 9 connected to the diode 10 has a potential about twice the power supply voltage. Therefore, the diode 10 has a higher potential on the cathode side and is in a non-conductive state. As described above, the voltage waveform 10 is applied to the center tap of the magnetic head 1.

On the other hand, the toggle type flip-flop 3,
The first switch 4 and the second switch 5 operate in the same manner as in the conventional example, and generate the same counter electromotive voltage.

As a result, the magnetic head and the first switch 4
The potential 15 at the connection point with and the potential 16 at the connection point between the magnetic head 1 and the second switch 5 are a combination of the voltage waveform 20 at the center tap of the magnetic head 1 and the pulse due to the back electromotive force. As described above, a voltage about twice the power supply voltage is applied to the center tap of the magnetic head 1 at the moment when the current starts to flow, and a sufficiently large counter electromotive voltage can be generated even with a low power supply voltage. . Therefore, the current flowing through the magnetic head does not become dull, and magnetic data can be normally recorded even with a low power supply voltage.

Next, another embodiment of the present invention will be described.

FIG. 2 is a circuit diagram of another embodiment of the present invention.

The write circuit of the magnetic recording apparatus of this embodiment is
A magnetic head 1 whose center tap is connected to the drain of the MOS transistor 11 and one end of the capacitor 9;
A booster circuit comprising a MOS transistor 11 having a source connected to the power supply and a gate connected to the output of the inverter 7, and a capacitor 9 having the other end connected to the write data input terminal 2 via the output buffer 8 and the inverter 7;
The first switch 4 and the second switch 5 are connected to both ends of the magnetic head 1 and the other end is connected to the common constant current source 6, and the clock is connected to the write data input terminal 2 and the non-inverted output is The first switch 4 is composed of a toggle type flip-flop 3 whose control terminal and inverted output are connected to the control terminal of the second switch 5.

The output of the output buffer 8 is at the LOW level while the write data is at the HIGH level. Also, MO
Since the gate potential of S-transistor 11 becomes LOW, it becomes conductive. Therefore, both ends of the capacitor 9 are charged with a voltage substantially equal to the power supply voltage. Next, when the write data becomes LOW level, the output of the output buffer 8 becomes HIG.
It becomes H level. At this time, the MOS transistor 11 becomes non-conductive because the gate potential becomes HIGH. Since the capacitor 9 is charged while the write data is at the HIGH level, the end of the capacitor 9 connected to the center tap of the magnetic head 1 has a potential twice the power supply voltage.

As described above, the present embodiment has the advantage that the potential of the center tap of the magnetic head 1 can be made twice the power supply voltage.

[0024]

As described above, the present invention is provided with the booster circuit which operates by using the write data as a clock, and at the moment when the current starts to flow, a voltage about twice the power supply voltage is applied to the center tap of the magnetic head. As a result, a sufficiently large counter electromotive voltage can be generated, so that magnetic data can be normally recorded even with a low power supply voltage.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of another embodiment of the present invention.

FIG. 3 is a time chart for explaining the operation of the present invention.

FIG. 4 is a circuit diagram of a conventional writing circuit.

FIG. 5 is a time chart for explaining the operation of the conventional example.

[Explanation of symbols]

1 Magnetic Head 2 Write Data Input Terminal 3 Toggle Type Flip Flop 4 First Switch 5 Second Switch 6 Constant Current Source 7 Inverter 8 Output Buffer 9 Capacitor 10 Diode 11 MOS Transistor 12 Write Data Waveform 13 Toggle Type Flip Flop 3 Non-inverted output waveform of 14 Toggle type flip-flop 3 inverted output waveform 15 Voltage waveform at connection point between magnetic head 1 and first switch 4 16 Voltage waveform at connection point between magnetic head 1 and second switch 5 17 Magnetic head 1 Current waveform at the connection point of the first switch 4 and 18 Current waveform at the connection point of the magnetic head 1 and the first switch 19 Output waveform of the output buffer 8 20 Waveform applied to the center tap of the magnetic head 1

Claims (1)

[Claims] 1. A write data input terminal, a booster circuit that operates using write data as a clock, a magnetic head whose center tap is connected to the booster circuit, and one end of each of the magnetic heads and one end of which is connected to the other end. A first switch and a second switch connected to a common constant current source, a clock connected to the write data input terminal, a non-inverting output of the first switch control terminal and an inverting output of the second switch. A write circuit comprising a toggle type flip-flop connected to a control terminal.