JPS5936039Y2 - switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching circuit that can turn on and off a controlled circuit by using the switching action of a transistor when a power supply is turned on and off.

Conventional switching circuits that can take out three outputs when the power is on, when the power is off, and when the power is off, configure the circuits for the power on and power off independently, and furthermore, the common signal for the power on and off is Since it uses an AND circuit, the switching circuit has a complicated configuration, lowers reliability, and has the disadvantage of being expensive.

The present invention has been made in consideration of the above, and aims to provide a switching circuit that solves the above problems and can output three outputs when the power is on, when it is off, and when it is on and off with a simple circuit configuration. This is the purpose.

The present invention will be explained below with reference to examples.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

A is a DC power supply, B is a switching circuit according to an embodiment of the present invention, D is a controlled circuit, and C is a drive circuit that drives the controlled circuit with the output of the switching circuit B.

Switching circuit B has a time constant consisting of a series circuit of transistors 1 and 2 commonly connected through diodes 5 and 6 whose collectors are respectively connected in the forward direction, and a resistor 7 and capacitor 9 connected to the base of transistor 1. a diode 4 connected between the output terminal of the DC power supply A and the emitter of the transistor 1 in order to guide the voltage Va of the DC power supply A to the emitter of the transistor 1;
Connected between the common connection point of the resistor 7 and the capacitor 9 and the emitter of the transistor 1 in order to guide the output voltage of the time constant circuit, that is, the voltage vb at the common connection point of the resistor 7 and the capacitor 9 to the emitter of the transistor 2. and a diode 3 whose one end is connected to one end of the diode 4, and a transistor 2 to form a base current path of the transistor 2.
Resistor 8 connected between the base of and the output terminal of DC power supply A
and transistors 10 and 11 forming an emitter follower driven by the collector outputs of transistors 1 and 2.
and an emitter-follower connected transistor 12 driven by the collector output of either transistor 1 or 2.

Now assume that the output terminals of transistors 10, 11, and 12 are 2a, 2b, and 2C, respectively.

In the above switching circuit B, the diode 3 prevents the application of the output voltage Va of the DC power supply A to the base of the transistor 1, and the diode 4 prevents the application of the output voltage Vb of the time constant circuit to the base of the transistor 2. prevent.

First, a description will be given of when the DC power supply A is turned on.

The voltage supplied to the switching circuit B when the DC power supply A is turned on reaches the voltage Va with a predetermined time constant as shown by curve 1 in FIG.

When the DC power supply A is turned on, the capacitor 9 is charged through a path including the diode 4, the emitter of the transistor 1, the base of the transistor 1, and the resistor 7.

At this time, transistor 1 is in an on state, an output is generated at collector 1a of transistor 1, and transistor 1
0 is driven and an output is generated at the output terminal 2a.

At the same time, the output of transistor 1 is output through diode 5, transistor 12 is driven, and output terminal 2C
output is generated.

In this case, the base-emitter junction of the transistor 2 is reverse biased by the forward voltage of the diode 4 and is in an off state.

Therefore, no output is generated at the collector of transistor 2,
The transistor 11 remains in the off state and the output terminal 2b
No output is generated at the output terminals 2a and 2C, except for the time constant of the DC power supply A, which increases due to the time constant of the time constant circuit of the resistor 7 and the capacitor 9, and the output voltage Va of the DC power supply 4 and the time constant. This continues until the output voltages vb of the circuits become equal.

When the voltage Va=Vb, the transistor 1 is turned off, the transistors 10 and 11 are also turned off, and there is no output from the output terminals 2a and 2c.

Therefore, in a steady state, the outputs of the output terminals 2a, 2b, and 2C are zero.

Next, a description will be given of when the DC power supply A is turned off.

When the DC power supply A is turned off, the voltage Va of the DC power supply A decreases with a predetermined time constant, as shown by curve 2 in FIG.

Therefore, when the DC power supply A is off, the voltage Va < Vb, and the charging voltage vb of the capacitor 9 is discharged through the path of the diode 3, the emitter of the transistor 2, the base of the transistor 2C, and the power supply circuit A, and the transistor 2 is in the on state. becomes.

Therefore, an output is generated at the collector 1b of the transistor 2, and the transistor 11 is driven to generate an output at the output terminal 2b.

At the same time, the output of transistor 2 is output through diode 6, transistor 12 is driven, and output terminal 2C
output is generated.

In this case, the base-emitter junction of the transistor 1 is reverse biased by the forward voltage of the diode 3, and becomes off-state.

Therefore, no output is generated at the collector of transistor 1,
The transistor 10 is in the off state, and the output terminal 2
No output is generated at a.

As described above, when the power is turned on, outputs are generated at the output terminals 2a and 2C, and when the power is turned off, outputs are generated at the output terminals 2b and 2C.

Therefore, three outputs can be obtained from the output terminals 2a, 2b, and 2C when the power is turned on, when the power is turned off, and when the power is turned on and off, respectively.These outputs are sent to the drive circuit C as necessary to control the controlled circuit. can be controlled.

The controlled circuit may be an analog circuit or a digital circuit.

As explained above, according to the present invention, outputs can be obtained when the power is turned on, when the power is turned off, and when the power is turned on and off.

Therefore, it is possible to drive the controlled circuit when the power is turned on, drive the controlled circuit when the power is turned off, and drive the controlled circuit when the power is turned on or off. etc. can be operated.

Moreover, the configuration of the switching circuit is simple, and reliability is improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a characteristic diagram when the DC power supply voltage is turned on and off. A: DC power supply, B: switching circuit, C: drive circuit, D: controlled circuit, 1. 2.10°11 and 12...transistor, 3.4.5 and 6...diode, 9...capacitor.

Claims (1)

[Scope of utility model registration request] a first transistor whose base is connected to the output end of the power supply circuit through a first resistor; a second transistor whose base is connected to a time constant circuit consisting of a series circuit of a second resistor and a capacitor; and the power supply circuit. a first diode connected between the output terminal of the first transistor and the emitter of the first transistor; a first diode connected between the common connection point of the second resistor and the capacitor and the emitter of the second transistor; a second diode having one end connected to one end of the first diode, and a third diode having one electrode commonly connected and the other electrode connected to the collectors of the first and second transistors, respectively. and a fourth diode, from the collectors of the first and second transistors and the common connection point of the third and fourth diodes, respectively, when the power supply circuit is off, on, and on.
A switching circuit characterized by obtaining an output when it is off.