JPS5830299Y2 - Low voltage power on/off device for small electronic equipment - Google Patents

Description

[Detailed description of the invention] This invention is a small electronic device that turns on and off the power supply from the power source to the load by mechanically operating the normally open contact in small electronic devices such as magnetic sheet type recorders and playback machines. The present invention relates to an equipment low frequency voltage power on/off device.

A small magnetic card recording/playback machine presses the start switch to keep the motor, recording/playback amplifier, pylon lamp, etc. loads on, and the motor rotates the turntable to record or play back the magnetic card, and then turns. When the table completes a predetermined number of revolutions, a stop switch is automatically activated to turn off the load.

Since the main purpose of small magnetic sheet type recording and playback devices is generally as small personal learning devices, it is convenient to use batteries as the main power source for convenience of use. The actual situation is that the power supply voltage is 2.5.3.5 V, and the power capacity is also limited.

Therefore, it is very important to minimize the power consumption during non-operation and to lower the operating voltage.

In order to solve this problem, attempts have been made to replace the conventional operation control switch mechanism using relays and the like with electronic circuits using transistors, SCRs, and the like.

Examples thereof are shown in FIGS. 1 and 2.

The electric holding switch shown in FIG. 1 is a combination of a flip-flop FF and a switching transistor TR, and utilizes the holding function of the control flops F and F.

However, in order to keep the switching transistor TR in the on state, it is necessary to supply current to the flip-flops F and F, which are holding function elements, resulting in power loss.

In addition, when the holding function element is configured with a flip-flop, there is a problem that the entire circuit becomes complicated because an initial reset is required. The electric holding switch shown in FIG. 2 was devised in 1995.

That is, instead of configuring the holding function element with a clip-flop, the self-holding function of the SCR is used.

This electrical holding switch circuit includes a stop switch 81 consisting of a normally closed contact switch, and a start switch S2 consisting of a normally open contact switch. SCR as a self-holding functional element.

Switching transistor TR1 and protection resistor R1
, R2, and R3.

Briefly explaining the operation of this circuit, when the start switch S2 is pressed, a pulsed current flows through the gate of the SCR, turning on the SCR.

Therefore, the switching transistor TR1 becomes conductive, and power is supplied to the load.

Next, when the stop switch S1 is pressed, the current between the emitter and the base of the switching transistor TR1 is cut off, so the SCR is turned off, and therefore the switching transistor TR1 becomes non-conductive.

However, since the stop switch S1 is configured with a normally closed contact switch, it has low reliability.
The purpose of this invention is to solve the problem that when transistor TR1 becomes open, the SCR is turned off and the switching transistor TR1 is held in a non-conductive state, causing the device to stop mid-operation. By configuring both the start switch and stop switch in a low-voltage power supply on/off device for equipment, such as a switch circuit for controlling the operation of a magnetic sheet type recording/playback machine, with normally open contact switches,
It is an object of the present invention to provide a power on/off device that solves the above-mentioned problems.

FIG. 3 is an electrical circuit diagram for explaining one embodiment of this invention. As shown in the figure, the construction of the PNP transistor TR2 which controls the on/off of the load in series with the load is shown in FIG. A collector-emitter circuit of an NPN transistor TR4 functioning as a self-holding function element is connected to the base of the transistor TR2 through a base current limiting resistor R4.

In addition, a series circuit consisting of a resistor R5, a collector-collector circuit of a PNP transistor TR3, and a resistor R6 is connected to the load side terminal of the collector side of the transistor TR2, and the base of the transistor TR3 is connected in parallel to the load side terminal. is connected to the connection point a between the resistor R4 and the collector of the transistor TR4, and the base of the transistor TR4 is connected to the connection point a between the collector of the transistor TR3 and the resistor R6.

In the circuit of FIG. 3, when the normally open starting contact switch S3 is instantaneously closed, the transistor TR2.

TR3 becomes conductive and power is supplied to the load.

After that, even if switch S3 is opened, transistor TR
Since a positive potential is generated at point b due to conduction of transistor TR3, transistor TR4 is conductive, and therefore transistor TR2
, TR3 continue to conduct, and power continues to be supplied to the load.

In this way, when power is supplied to the load and, for example, the tar/table rotates a predetermined number of times and the stop switch S4, which is constituted by a normally open contact, is turned on, the base of the transistor T R,1 is turned on. The emitter is short-circuited and the transistor TR4 becomes non-conductive, so that the transistor gr
TR2 and TR3 become non-conductive, cutting off the current to the load.

As is clear from the above description, according to the present invention, when the switching transistor TR2 is in a non-conducting state, no power is consumed other than the dark current of the switching transistor TR2, and the operating power supply The voltage need only be higher than the sum of the base-emitter voltage of the switching transistor TR2 and the saturation voltages of the self-holding transistors TR3 and TR4, so 2<2> is sufficient.

Furthermore, since both the start switch and stop switch are configured with normally open contact switches, that is, instantaneous close switches, reliability during equipment operation is improved, and since normally open contact switches can be used, switching capacity is small. can be used, which has the advantage of reducing the size of the device.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are diagrams showing a conventional example of an operation control switch circuit, and FIG. 3 is an electrical circuit diagram for explaining an embodiment of this invention. E...power supply, L...load, TR2...switching transistor for load control, TR3, TR4...transistor for self-holding, S3...normally open contact switch for start, S4...for stop Normally open contact switch.

Claims (1)

[Scope of claim for utility model registration] The load that generates the functions of electronic equipment is the emitter. A switching transistor TR2 connected in series to the collector circuit, a power source E for supplying power to the series circuit of the load and the switching transistor TRz, and a resistor R4 having one end connected to the base of the transistor TR2. and a series circuit consisting of a collector and emitter circuit of a transistor TR4 whose emitter side is connected to the connection point between one pole of the power source E and the load, and a series circuit consisting of a resistor R5 and a transistor TR3 connected in parallel with the load. a series circuit consisting of an emitter-collector circuit and a resistor R6 whose one end is connected to one pole of the power supply E; a connection point a between the base of the transistor TR3 and the collector of the transistor TR4 and one pole of the power supply E; a normally open contact switch S3 for starting for driving the load connected between the connection point of the collector of the transistor TR3 and the base of the transistor TR4 and one pole of the power source E; A low-voltage power supply on/off device for a small electronic device, comprising: a normally open contact switch S4 for stopping, which is connected to a stop switch S4 for canceling driving of the load.