JPS5929403Y2 - switch circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a switch circuit for performing one-touch play and auto-stop in a magnetic sheet type recording/reproducing machine using an electronic circuit.

A small magnetic card recording/playback machine presses the start switch to keep the motor, recording/playback amplifier, pilot lamp, etc. in an on state, and the motor rotates the turntable to record on or play back the magnetic card. When the rotation speed reaches a predetermined number of revolutions, a stop switch is automatically activated and the load is turned off.

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 to 3.5 square meters, 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 are shown in FIGS. 1 and 2.

The electrical holding switch in FIG. 1 consists of flip-flops F and F.
and switching transistor TR, and utilizes the holding function of flip-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.

Furthermore, if the holding function element is formed of a flip-flop, an initial reset is required, which causes the problem that the entire circuit becomes complicated.

Figure 2 shows an example of a conventional switch circuit with a simpler configuration than the circuit shown in Figure 1 (Utility Model Application No. 51-34363).
Transistors TR1 and TR5, a start switch S1 and a stop switch 82, which are composed of normally open contacts, are connected as shown in the figure.

When power is supplied to the load RL, the transistor TR1 is made conductive by pressing the start switch S1, and this conduction also makes the transistor TR5 conductive, and these conductive states are self-maintained.

In addition, when stopping the power supply to the load RL, pressing the stop switch S2 causes the transistor TR5 to become non-conductive, and accordingly, the transistor TR1 becomes non-conductive, and the connection between the load RL and the power source E is severed. becomes.

In the switch circuit shown in Fig. 2, the base of the transistor TR5 is connected to one end of the load via the resistor R2, so if a load that includes a power generating element, such as a motor, is connected, the load will be removed when the switch circuit is turned off. When an applied voltage is generated from the power generating element of the transistor TR5, the base-emitter of the transistor TR5 is forward biased, and the transistor TR5 is forward biased.
There is a problem in that R5 becomes conductive, and therefore transistor TR1 also becomes conductive, resulting in malfunction.

The purpose of this invention is to solve these problems of the prior art and to provide a switch circuit that consumes less power when not in operation and that does not malfunction even when a load with a power generating element is connected.

FIG. 3 is an electrical circuit diagram for explaining one embodiment of the switch circuit according to this invention. As shown in the figure, the collector and emitter of the switching transistor TR2 which controls the on/off of the load in series with the load is shown in FIG. the circuit is connected,
A voltage dividing resistor R4 is connected to the base of the transistor TR2.
A collector-emitter circuit of transistor TR3 is connected through R3.

A current limiting resistor R6 is connected to the base of the transistor TR3.
A collector-base circuit of a transistor TR4 is connected through the transistor TR4, and the base of the transistor TR4 is connected to an intermediate point between the voltage dividing resistors R4 and R5.

Therefore, we now have a start switch S consisting of a normally open contact.
When transistor TR3 is turned on, transistor TR gauze becomes conductive, and therefore, switching transistor TR2 becomes conductive and power is supplied to the load.

After that, even if the start switch S3 is released and turned off, the transistor TR4 becomes conductive, and therefore the conduction of the transistor TR3 is maintained, so the transistor TR2
holds the on condition.

In this way, when power is supplied to the load and, for example, the turntable rotates a predetermined number of times and the stop switch S4 consisting of a normally open contact is turned on, a short circuit occurs between the base and emitter of the transistor TR4. As a result, the transistor TR4 becomes non-conductive, which causes the transistor TR3 to become non-conductive, and then the switching transistor TR2 becomes non-conductive, cutting off the supply of power to the load.

In the switch circuit of this embodiment, when the switching transistor TR2 is in a non-conducting state, no power is consumed except for the dark current of the switching transistor TR2, and the voltage of the operating power supply is
Since it is sufficient that the voltage is at least the sum of the base-emitter voltages of transistors TR2 and TR3 and the saturation voltage of transistor TR4, 2V is sufficient.

In addition, both the start switch and the stop switch are configured with normally open contact switches, that is, instantaneous closing switches, which improves reliability during operation of the equipment.
Since a normally open contact switch can be used, a switch with a small switching capacity can be used, and therefore the size of the device can be reduced.

Furthermore, even if the load has a power generating element, such as a motor, it will not be operated by the power supplied from the load side.

As is clear from the above explanation, this invention has the advantages of low power consumption, low operating voltage, and small size, and it does not malfunction even if a load including a power generating element is connected. It is possible to realize a switch circuit without any

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional example of a switch circuit for operation control, and FIG. 3 is a diagram for explaining an embodiment of the switch circuit according to this invention. E...Power supply, L...Load, TR2...
...Switching transistor for load control, TR
3, TR4... Self-holding transistor, S3
...Start switch, S4...Stop switch, R4, R5...Voltage dividing resistor, R
6... Current limiting resistor.

Claims (1)

[Scope of utility model registration request] A switching transistor TR2, whose collector-emitter circuit is connected in series with a load having a power generation element, and a transistor TR2-, whose collector-emitter circuit is connected to its base, have the same polarity and their on/off state. Transistor TR3 for controlling off
and a transistor TR having a collector-emitter circuit connected to the base of the transistor TR3 and having a polarity different from that of the transistor TR3 and controlling its on/off state.
4, a normally open contact switch S3 for starting connected in parallel to the collector-emitter circuit of the transistor TR4, and a normally open contact switch S3 connected in series to the collector-emitter circuit of the transistor TR3 to supply a bias voltage to the base of the transistor TR4. means for and the transistor TR
and a stop normally open contact switch S4 connected in parallel between the base and emitter of the transistor TR2. conducts, and the stop normally open contact switch s
4 by instantaneously closing said transistor TR4.
A switch circuit characterized in that the transistor TR3 is made non-conductive by making the transistor TR3 non-conductive, thereby making the switching transistor TR2 non-conductive.