JPH081578B2 - Power supply switching control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply switching control device, and more particularly to a power supply switching control device for word processors and personal computers.

[0002]

2. Description of the Related Art Conventionally, in a personal computer or word processor, if the power is turned off while data is being written to a recording medium such as a floppy disk, a write error may occur and the already recorded data may be destroyed. Therefore, a handling instruction to prohibit the input operation of the power switch is given during the reading and writing of data.

[0003]

Despite the above-mentioned handling instructions, if the power switch is erroneously operated to turn off the power during reading and writing of data, a data destruction accident will occur. Therefore, there arises a technical problem to be solved in order to prevent an accident of this kind, and an object of the present invention is to solve the problem.

[0004]

The present invention is proposed in order to achieve the above-mentioned object, and is a monostable circuit connected to a switch circuit 6 inserted in a power supply line 4 and a control terminal 18 of the switch circuit 6. A circuit 8 and a manual switch 7 for turning on / off the power supply to the monostable circuit 8. The open / close signal of the manual switch 7 is connected to the open / close signal input port 22 of the central processing unit 2, and A power supply switching device 1 in which an output port 24 of a power supply switching control signal of the processing device 2 is connected in parallel to a control terminal 18 of the switch circuit 6, and the switch circuit 6 is turned on by a signal from the monostable circuit 8, A power supply on / off control device for turning off the switch circuit 6 in response to a power supply cutoff signal of the central processing unit 2.

[0005]

When the manual switch is closed, the monostable circuit is turned on for a fixed time, the switch circuit of the power supply line is turned on, and the central processing unit is activated. An ON signal is output from the output port of the activated central processing unit to the control terminal of the switch circuit. The switch circuit continues to be turned on by the ON signal from the output port even after the monostable circuit returns to OFF,
Power is supplied to the equipment.

The opening and closing of the manual switch is read from the input port to the central processing unit, and when the manual switch is turned off, the central processing unit outputs an off signal from the output port after finishing the processing currently being executed according to the power-off processing program. Then
Turn off the switch circuit to cut off the power supply.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example in which a power supply switching control device 1 is provided in the DC power supply part of a word processor using a magnetic recording medium such as a floppy disk, and power is supplied to the entire equipment including a central processing unit (hereinafter referred to as CPU) 2. A first switch circuit 6 including a PNP transistor 5 is inserted in the input power supply line of the three-terminal constant voltage regulator 3.
The input power source branched in the preceding stage of the switch circuit 6 is connected to the monostable circuit 8 and the second switch circuit 9 via the manual switch 7.
Is connected to the control terminal 10. The monostable circuit 8 includes a differentiator 14 including a capacitor 11, a resistor 12, and a diode 13, and a third switch circuit 15,
The time constant of the differentiator 14 is set to about several seconds as a time sufficient for starting the CPU 2 described later. Collector 1 of NPN transistor 16 of third switch circuit 15
7 is connected to the control terminal 18 of the first switch circuit 6.

The NPN transistor 19 of the second switch circuit 9 has a collector 20 connected to a power source 21 and an input / output signal input port 22 of the CPU 2, and an emitter 23 grounded. Output port 24 for power supply switching signal of CPU2
Is connected to the control terminal 26 of the fourth switch circuit 25,
The collector 28 of the NPN transistor 27 is connected to the control terminal 18 of the first switch circuit 6 by the third switch circuit 15
And are connected in parallel. After the power is turned on, the CPU 2 outputs a Hi signal from the output port 24, which is a power switching control terminal, and when the input signal level of the input port 22 becomes Lo, the data currently being executed by the power on / off processing program. After the processing is completed, the system is controlled so that the output level of the output port 24 becomes Lo.

Next, the operation of the power supply switching control device 1 will be described with reference to FIGS. First, when the manual switch 7 is off, the control terminal 18 of the first switch circuit 6 is not energized, and the voltages at A, B, C and D in FIG. 1 are Lo. Also, since A is Lo, the second switch circuit 9 is off, and the voltage from the power supply 21 to the input port 22 is shown at E.
Hi is entered.

Next, when the manual switch 7 is closed at time t ₁ shown in FIG. 2, the second switch circuit 9 is turned on and a current flows from the power source 21 to the ground 29, and the input level E of the input port 22 is changed. Becomes Lo. At the same time, the third switch circuit 15 is turned on by the differentiated output of the differentiator 14 of the monostable circuit 8, and the first switch circuit 6 connected to the collector 17 is turned on. As a result, the constant voltage regulator 3 operates to supply power to the entire system including the CPU 2, and the CPU 2 is activated. The voltage Hi shown at D is output from the output port of the activated CPU 2 to turn on the fourth switch circuit 25. The monostable circuit 8 causes the output B to fall to Lo after a fixed time due to the time constant, but at this time, the fourth switch circuit 25 is already on, so the first switch circuit 6 continues to be on.

Next, when the power supply being supplied is shut off, the manual switch 7 is turned off, the potential of A is turned off as indicated by t ₂ in FIG. 2, and the second switch circuit 9 is turned off. , E rises to Hi. CPU2 is input port 22
Read this from, according to the power off processing program,
After the reading / writing operation of the recording medium such as the floppy disk is completed (t ₃ ), the output of the output port 24 is lowered to Lo. Therefore, the first switch circuit 6 is turned off, the power supply C to the constant voltage regulator 3 is cut off, and the power supply to the device is stopped. In this way, the power is not cut off during the writing operation to the recording medium, and the contents being written and the recorded contents are prevented from being destroyed.

On the other hand, as shown by the chain line in FIG. 2, even when the manual switch 7 is on, A is Hi, and the read signal E of the input port 22 is in the Lo state, the input operation to the keyboard or the like is performed. When the undisturbed state continues for a certain period of time, the CPU 2 sets the output D of the output port 24 to Lo by the system control to turn off the first switch circuit 6 and turn off the power. Therefore, when the battery is used as a power source, it is possible to prevent an accident that the battery is consumed by leaving the manual switch on.

Further, the CPU 2 constantly monitors the power supply voltage, and when the voltage drops below the normal operation level of the device due to consumption of the power supply battery or the like, as in the case where the above-mentioned input operation is not performed, The output D of the output port 24 is set to Lo and the power supply is cut off. This prevents runaway of the CPU 2 and malfunction of the device. The present invention is not limited to the above-described embodiment, but the first to fourth switch circuits 6, 9, 1
The switches 5 and 25 may be replaced with an electric switch such as a switch circuit using an FET or a relay. And it goes without saying that the present invention extends to those modifications.

[0014]

Since the present invention is configured as described in detail in the above one embodiment, the power supply is turned off even if the manual switch is accidentally turned off during reading / writing on a recording medium such as a floppy disk or a RAM card. Is not blocked, and is blocked after the reading / writing process is completed. Therefore, destruction of the data being read and the recorded contents can be prevented, and safety can be ensured.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply switching control device.

FIG. 2 is a timing chart of each part of the power supply switching control device.

[Explanation of symbols]

 1 Power Supply Switching Control Device 2 Central Processing Unit 4 Input Power Line 6 Switch Circuit 7 Manual Switch 8 Monostable Circuit 18 Control Terminal 22 Input Port 24 Output Port

Claims (1)

[Claims] 1. A switch circuit 6 inserted in a power supply line 4.
A monostable circuit 8 connected to the control terminal 18 of the switch circuit 6 and a manual switch 7 for turning on / off the power source to the monostable circuit 8. 2 is connected to the input / output signal input / output port 22 of the switching circuit 6 and the output port 24 of the power supply open / close control signal of the central processing unit 2 is connected to the control terminal 18 of the switch circuit
A power switchgear 1 connected in parallel to the switchgear 1 for turning on the switch circuit 6 in response to a signal from the monostable circuit 8 and turning off the switch circuit 6 in response to a power-off signal from the central processing unit 2.