JPS5961225A - Electronic circuit - Google Patents

Abstract

PURPOSE:To restore a silicon controlled rectifier (SCR) automatically by interrupting the connection of the SCR by the disconnection of a transistor (TR) in an electronic circuit provided with the SCR and a switch restoring the SCR. CONSTITUTION:The SCR and the TR are connected in series and bias voltage is previously applied to the base of the TR to make the TR active status. When a gate pulse is applied to the SCR, the SCR is also turned on and current flows into a load L. When the SCR is to be turned off, the TR is turned off at first by reducing the base bias voltage of the TR and then current flowing into the SCR is interrupted to turn off the SCR.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in an electronic circuit having a silisk and its return switch.

Prior Art and Problems Hitherto, the type of electronic circuit shown in FIG. 1 is known.

In the figure, L represents a load, SCR represents a chilisk, and SW represents a switch.

Generally, once the thyristor SCR is turned on, it cannot be turned off unless the current supply is cut off. Therefore, in the circuit shown in Figure 1, the thyristor SCR is turned off for one summer by pressing the switch SW to open it. ing.

By the way, this circuit cannot be incorporated into a fully automatic control system because it depends on the human hand to press the switch SW.

In order to achieve this purpose, all electronic circuits may be made into semiconductors, but in that case, it is desirable to have a configuration as simple as possible.

OBJECTS OF THE INVENTION The present invention uses transistors to realize an electronic circuit that satisfies the above-mentioned needs, that is, an electronic circuit that automatically resets a diristor in an on state.

Embodiment of the Invention FIG. 2 is a circuit diagram of a main part of the embodiment of the present invention, and the same parts as those explained in connection with FIG. 1 are indicated by the same symbols.

In the figure, R represents a transistor, and R represents a resistor.

Honjitsu Jt+ (In III, a bias voltage is applied to the base of the transistor TR in advance to make it active,
When a gate pulse is applied to thyristor SCR, thyristor SCR is also turned on and current flows through load I4.

To turn off the thyristor SCR, the transistor T R
By lowering the base bias voltage of thyristor SCR, transistor 1R is first turned off, thereby cutting off the current flowing through thyristor SCR and turning it off.

FIG. 3 is a main circuit diagram for explaining a specific embodiment.

In the figure, Vin is an input terminal, Vout is an output terminal,
GND is the ground terminal, SCR is the thyristor, TRI~'
FR3 is a transistor, Dl to D3 are Zener diodes, R1 to R6 are resistors, I<Vl and RV2 are variable resistors, "I' II is a thermistor, and sps is a constant voltage circuit portion.

This embodiment is a power supply circuit used as a power supply for a microwave amplifier. A thermistor T II is pasted on the case of the microwave amplifier, and when the temperature of the case rises above a predetermined value, the power supply circuit is activated. The output from the output terminal Vout can be turned off, and when the temperature of the case falls below a predetermined value, the output can be turned on again.

First, the operation of the constant voltage circuit section sps when the thyristor SCR is off will be described.

In this constant voltage circuit part sps, when a positive voltage is applied between the input terminal Vin and the ground terminal GND, the positive voltage is applied to the transistor i' R1 for output control via its base resistor R2. Therefore, it is turned on, and an output voltage appears at the output terminal Vout.

Resistors R4 and R5 connected in series are inserted between the output terminal Vout and the ground terminal GND, and at the connection point between the resistors R, 4 and R5, the emitter is connected to a Zener diode D3 for generating a reference voltage. and the collector is connected to the base of the transistor 1'R1, so that the transistor i' 1? Since the base of the transistor ``I'' R2 that controls the on/off of 1 is connected, the voltage at that connection point, that is, the base voltage of the transistor ``I'' R2, is compared with the emitter voltage, which is the reference voltage. When the value exceeds a predetermined value, the activity of the transistor 'l''R2 tends to increase.

When the activity of the transistor TR2 increases and its conductivity increases, the base voltage of the transistor i'R1 decreases, so its conductivity decreases, and it operates to suppress the increase in the output voltage of the output terminal Vout. It turns out.

Further, when the base voltage of the transistor i'R2 becomes lower than a predetermined value compared to the emitter voltage, the activity of the transistor TR2 tends to decrease, contrary to the above. If the conductivity of transistor TR2 becomes small, transistor TR
As the base voltage of I increases, its conductivity increases,
An operation is performed to suppress a drop in the output voltage of the output terminal V OIJ L.

The above-described operation is the same as that of a constant voltage circuit having a trial circuit configuration.

Now, in this embodiment, the output control transistor 1'R1
A thyristor SCR and a transistor 'I'R3 connected in series are inserted between the base of the transistor 1'R3 and the ground terminal GNI.
Connected to the connection point between Mr. TH and variable resistor RVI,
And thyristor S CF? The gate of the thermistor TII and the variable resistor RV
It is connected to the connection point with 2. Variable resistance RVI and R
V2 is I-ranjisku'1'3 and thyristor SC-
' This is to adjust the operating point of R.

Next, the operation will be explained, but it will be easier to understand by referring to the timing chart in FIG.

In FIG. 4, TtIl is the temperature of the thermistor TH, TI is the temperature at which the transistor 'rR3 is turned on,
'T'2 is the temperature at which the thyristor SCR is turned on, and T I <'r2.

Now, if the microwave amplifier is operated and its temperature gradually rises, the resistance of the thermistor 1H attached to its case will decrease. When the temperature reaches TI, the voltage at the connection point between the thermistor 1'II and the variable resistor RVI turns on the transistor TR3. If the temperature further rises to '2', the voltage at the connection point of the thermistor 1 and variable resistor RV2 turns on the SiRISC SCR.Then, the transistor TRI turns on.
The base voltage of the power supply circuit drops and turns off, so that the output of the power supply circuit becomes zero and no current is supplied to the microwave amplifier.

If the microwave amplifier does not operate, the temperature of the case will drop, and when the temperature falls below T1, the transistor "I" I
Since ≧3 is turned off, the thyristor SCR is also restored, and a high voltage is applied to the base of the transistor 'I' R1, turning it on and restarting the supply of current to the microphone and single-wave amplifier.

In this embodiment, a thermistor is used to detect the temperature of the case of the microwave amplifier, but a posistor may be used instead. However, in that case, the POSISTOR must be placed where the variable resistor is located, and the variable resistor must be placed where the THERMISTOR is located.

Effects of the Invention According to the electronic circuit of the present invention, the thyrisk and the transistor are connected in series, and the transistor becomes conductive before the thyrisk and becomes non-conductive, thereby interrupting the conduction of the thyrisk. Can this electronic circuit be intransitive? 1 (It is easy to incorporate into the 1st system.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the main part of the conventional example, FIG. 2 is a circuit diagram of the main part of the embodiment of the present invention, FIG. 3 is a circuit diagram of the main part of the specific embodiment of the invention, and FIG. This is a timing chart for explaining the operation of the circuit shown in FIG. In the figure, L is a load, SCR is a silicon risk '1'', R is a transistor, and R is a resistor. Patent applicant: Fujitsu Ltd. Representative patent attorney Kugobe Tamamushi (3 others) Figure 1 Figure 2

Claims (1)

[Claims] 1. An electronic circuit comprising a transistor connected in series to a cyrisk, which becomes conductive before the cyrisk, and cuts off conduction of the cyrisk by becoming non-conductive.