JPS6017956Y2 - switching circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention is concerned with switching circuits, and its purpose is to control the conduction and non-conduction of one switching transistor using two different control signals.

An embodiment of the present invention will be described below with reference to the drawings.

This embodiment is a switching circuit that rotates and stops a tape drive motor in a tape recorder. 1 is a 10B power supply terminal, 2 is a ground terminal, and the tape drive motor is connected between these terminals 1 and 2. 3 and an npn type switching transistor for rotation and stop are connected in series and interposed.

A control circuit 5 composed of a bistable multivibrator is connected to the base of the switching transistor 4.

This control circuit 5 includes two transistors 6.7 and resistors 8 to 11.7 which are alternately turned on and off in response to a start signal. It is composed of a capacitor 12 that sets the one transistor 7 to non-conduction at the beginning of operation, and the collector of the one transistor 7 is connected to the base of the switching transistor 4 via a resistor 13.

The power supply line 5a of the control circuit 5 is connected to the collector of a pnp transistor 15 for power supply control, together with the recording/reproducing amplification circuit 14, etc., and the emitter of this transistor 15 is connected to the power supply terminal 1. .

Furthermore, the base of this transistor 15 is connected to the ground terminal 2 via a resistor 16 and the collector and emitter of an npn transistor 17.

18 is an input terminal for a first control signal having a waveform as shown in FIG. 2, which is connected to the base of the transistor 17;
Reference numeral 9 denotes an input terminal for a second control signal having a waveform as shown in FIG. 3, and is connected to the base of the transistor 7 constituting the control circuit 5.

The operation of the above embodiment will now be explained.

First, when no control signal is input to any of the input terminals 18 and 19, the transistor 17 is non-conducting.
Transistor 15 is therefore non-conducting and no power is applied to control circuit 5.

Therefore, the base potential of the switching transistor 4 becomes a low (L) level, so that the transistor 4 is non-conductive and the motor 3 is not energized.

Next, when the first control signal is input to the input terminal 18, the transistors 17 and 15 are made conductive, and the control circuit 5 is energized.

Since a capacitor 12 is connected between the base and emitter of one of the transistors 7 constituting the control circuit 5, when the control circuit 5 starts to be energized, the capacitor 1
Charging current flows through transistor 2, transistor 7 becomes non-conductive,
As a result, the base potential of the switching transistor 4 is high (
H) level, conduction occurs, and the motor 3 is energized.

Next, when a second control signal is input to the other input terminal 19 in this state, the transistor 7 becomes conductive, the switching transistor 4 becomes non-conductive, and the power supply to the motor 3 is cut off.

The first control signal includes a signal for turning on and off the power of the entire device, such as a timer output output from a clock circuit at a preset time in the case of a tape recorder with a clock.

The second control signal includes a memory rewind, that is, an automatic stop signal that automatically stops tape feeding when the tape counter specifies a specific value preset, such as 1000 J, while the tape is being rewound. .

Note that in the above embodiment, the switching transistor 4
It goes without saying that by changing the polarity of the motor 3, the motor 3 can be rotated and stopped in the opposite manner to that described above.

As explained above, according to the switching circuit of the present invention, the same switching transistor can be made conductive or non-conductive using two different control signals, the first and second.

Furthermore, there is an advantage that the initial setting of the control circuit for controlling the switching transistors can be carried out with a simple circuit configuration in which a capacitor is provided at the base emitter of one of the transistors constituting the bistable multivibrator.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figures 2 and 3 are
The figure is a waveform diagram showing the control signal. 3... Tape running drive motor, 4...
- Switching transistor, 5... Control circuit, 18, 19... Control signal input terminal.

Claims (1)

[Scope of utility model registration request] The collector of a first transistor having a capacitor between the base and emitter is connected to the base of a second transistor through a resistor, and the collector of the second transistor is connected to the base of the first transistor through a resistor. a control circuit in which the collectors of the first and second transistors are connected via resistors to the collectors of energization control transistors whose emitters are connected to a power supply terminal; The collector of the transistor was connected to the base of the switching transistor via a resistor, and power was supplied to the control circuit by a first control signal applied to the base of the transistor connected between the base of the energization control transistor and the ground. Sometimes the switching transistor is made conductive or non-conductive, and when the control circuit is activated by a second control signal applied to the base of the first transistor constituting the control circuit in this state, the switching transistor is turned on or off. A transistor circuit characterized in that it is configured to be non-conductive or conductive.