JPH07118045B2 - Voltage booster circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage boosting circuit used in, for example, a writing circuit of a battery-driven compact digital magnetic recording device.

2. Description of the Related Art In magnetic recording, magnetization reversal is written on a magnetic surface (track) to be recorded by a magnetic head. At this time, in order to accelerate the magnetization reversal, a write voltage higher than the flyback voltage determined by the head inductance and the stray capacitance is required. That is, the write circuit is configured by a constant current circuit and drives the head terminal with a constant current, but the constant current circuit does not function as a constant current unless the voltage of the power supply is equal to or higher than the flyback voltage.

Therefore, conventionally, a 12V power supply is separately used, or in the case of a device having only a 5V power supply, a new power supply circuit by a booster circuit is independently used to obtain a required voltage.

Problems to be Solved by the Invention When a 12V power supply is used for the writing circuit, other circuits are 5V
Since a power source is used, it becomes a dual power source and the cost is high. Also, in the case of a single 5V power supply, a new power supply circuit with a booster circuit is required independently, which increases the cost.

An object of the present invention is to provide a voltage boosting circuit that generates a high voltage only in a pulse period in synchronization with an input pulse signal.

Means for Solving the Problems A voltage booster circuit of the present invention includes a switching circuit connected between an output terminal and a ground terminal, a coil connected between the output terminal and a power supply terminal, an input terminal and the And a timer which is connected between the switching circuits and outputs a constant pulse width in synchronization with the input pulse signal.

Effect According to the voltage booster circuit of the present invention, the boosted voltage is obtained only in the required time in synchronization with the input signal, whereby the high voltage is obtained only in the required time without supplying the high voltage from the outside. be able to.

Embodiment An embodiment of the voltage boosting circuit of the present invention will be described with reference to the digital magnetic recording / writing circuit using the present invention shown in FIG.

In the voltage booster circuit 1 shown in the dotted frame of the present invention, the input terminal 2 is a timer (monostable multivibrator).
3, the output terminal 4 of the timer is connected to the base of the NPN transistor 6 via the inverter 5, the emitter of the transistor 6 is connected to the ground terminal 8 via the resistor 7, and the collector of the transistor 6 is connected to the output terminal 9 The coil 11 and the diode 12 are connected in parallel between the output terminal 9 and the 5V power supply terminal 10, and the capacitor 13 is connected between the output terminal 9 and the ground terminal 8.

Furthermore, the digital magnetic recording / writing circuit has a constant voltage terminal.
14, a constant current source circuit composed of NPN transistor 15 and resistor 16, a current mirror circuit composed of PNP transistors 17 and 18, a toggle flip-flop circuit 19, a gate circuit composed of MOS transistors 20 and 21, and a coil 22. It consists of

Next, the operation of the voltage booster circuit of the present invention and the digital magnetic recording / writing circuit using the same will be described with reference to the timing chart shown in FIG.

FIG. 2A shows a signal pulse input to the input terminal 2,
(B) is an output waveform from the output terminal 4 of the timer 3, (c)
Is the output waveform of the inverter 5, (d) is the output waveform from the output terminal 9 of the voltage booster circuit 1, and (e) is the current waveform flowing through the coil 22.

First, the input pulse shown in FIG. 2 (a) is led to the timer (monostable multivibrator) 3, and then the input pulse shown in FIG.
As shown in, a pulse having a constant time width (T) is obtained in synchronization with the rising edge of the input pulse.

Further, the pulse-shaped pulse signal is fed to the inverter 5
, The phase is inverted, and the result is input to the base of the transistor 6. When the output voltage of the inverter 5 is low level, the transistor 6 is cut off. At this time, the current flowing from the coil 11 to the transistor 6 stops, and a flyback voltage higher than the power supply voltage is generated at the output terminal 9 as shown in FIG. 2 (d). This is used as the power source of the constant current circuit for writing.

The high voltage is required for a moment, and the booster circuit synchronizes with the input pulse to boost the voltage only for that moment.

The capacitor 13 has a function of extending the holding time of the boosted voltage, and is used when the stray capacitance is insufficient. This is because the diode 12 prevents the voltage from decreasing after the boosting is completed.

Next, the operation of the digital magnetic recording / writing circuit using the voltage boosting circuit of the present invention will be described.

At the time of writing, the current determined by the constant current source circuit by the NPN transistor 15 is taken out as a constant current (I) by the current mirror circuit composed of the PNP transistors 17 and 18. At this time, the voltage is raised by the voltage booster circuit. There is.
On the other hand, the signal output from the timer 3 forms two types of signals whose phases are inverted by the toggle flip-flop circuit 19,
The signal is input to the respective gate circuits to alternately turn on the MOS transistors 20 and 21. As a result, the constant current (I) taken out from the current mirror circuit alternately flows through the anti-coil in the opposite direction as shown in FIG. 2 (e), and escapes from the center tap of the coil 22 to the ground terminal 8. In this way, the magnetization of the head is reversed and recording is performed on the magnetic surface (track).

EFFECTS OF THE INVENTION According to the voltage boosting circuit of the present invention, a boosted voltage can be obtained only in a necessary time in synchronization with an input signal, and when used in a battery-driven magnetic recording device, inexpensive and high-speed magnetization reversal writing It will be possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a digital magnetic recording / writing circuit using the voltage booster circuit of the present invention, and FIG. 2 is a timing chart for explaining the operation of FIG. 1 ... voltage booster circuit, 2 ... input terminal, 3 ... timer,
4 …… Timer output terminal, 5 …… Inverter, 6 …… NPN
Transistor, 7 ... Resistor, 8 ... Ground terminal, 9 ... Output terminal, 10 ... 5V power supply terminal, 11 ... Coil, 12 ... Diode, 13 ... Capacitor.

Claims (3)

[Claims] 1. A switching circuit connected between an output terminal and a ground terminal, a coil connected between the output terminal and a power supply terminal, an input pulse signal connected between an input terminal and the switching circuit. And a timer that outputs a constant pulse width in synchronization with the voltage boosting circuit. 2. The voltage boosting circuit according to claim 1, further comprising a diode connected in parallel with the coil. 3. The voltage boosting circuit according to claim 1, further comprising a capacitor connected between the output terminal and the ground terminal.