RU1800610C - Transistor switch - Google Patents

Abstract

The invention relates to a pulse technique and can be used in automation devices for switching current and protecting against short circuit in a load. SUMMARY OF THE INVENTION: the device comprises transistors 1, 2, 13, strabilitrons 3, resistors 4, 14, resistor voltage dividers 5, 9, an RC circuit 6, a control element 12. 1 ill.

Description

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The invention relates to pulsed technology and can be used in various automation devices for switching current and protecting against short circuit in a load.

The purpose of the invention is to increase the reliability of the transistor switch compared to the prototype under the same operating conditions. To increase the reliability of the device, an additional coupling resistor has been inserted into it.

The drawing shows a circuit diagram of the claimed device.

The transistor switch contains transistors 1, 2, a zener diode 3, a resistor 4, a first resistor voltage divider 5, an RC circuit 6 consisting of a resistor 7 and a capacitor 8, a second resistor voltage divider 9 on the resistors 10 and 11, controls - a flashing element 12, a transistor 13, an additional resistor 14.

Transistors 1, 2 of different types of conductivity are connected by emitters to different poles of the voltage source, the first resistor voltage divider 5 is connected between the collector of transistor 1 and the emitter of transistor 2, the base of transistor 2 is connected to the midpoint of the voltage divider, connected in series to zener diode 3 and resistor 4 is connected between the base of transistor 1, collector 2 and the output terminal. The emitter of the transistor 1 is connected to a common bus, to which the common wire of the control element 12, the emitter of the transistor 13 and the first output of the resistor 11 of the second resistive voltage divider 9, the middle point of which is connected to the base of the transistor 13, are also connected. The collector of the latter is connected with the input of the control element 12 and the first output of the additional resistor 14, the second output of which is connected to the positive pole of the power source, and the output of the control element 12 is connected to the base of the transistor 1 and the first output of the resistor 7 RC- enu b, the second terminal of which is connected via a capacitor 8 to the bus control device and to the second terminal of resistor 10, second resistor 9.

The key works as follows.

When voltage is applied to the device, transistors 1 and 2 are closed, transistor 13 is closed, control element 12 is open by positive potential coming from the power source through resistor 14 to its input. An open control element 12 shunts the base - the emitter junction of the transistor 1. When a positive control appears at the input of the device

the signal, then the transistor 13 is opened, thereby shunting the input of the control element 12, the latter is closed, the capacitor 8 starts charging in the circuit; the control input of the device, a resistor 7, the base-emitter junction of the transistor 1, which is saturated during the charging of the capacitor 8. In this case, the voltage at the base of transistor 2 is sufficient to open it to saturation. In the absence of a short circuit, the voltage at the collector of transistor 2 becomes maximum, and its collector current flows to the load and through resistor 4 and a punched zener diode 3 to the base of transistor 1. The current from the collector of transistor 2 continues to open transistor 1. If there is an overload in the load circuit or short circuit, the voltage at the collector of transistor 2 is less than the breakdown voltage of zener diode 3 and transistors 1 and 2 are closed. The charged capacitor 8 does not affect the transistor 1. The short circuit current is equal to the leakage current of the transistor 2. After eliminating the overload or short circuit, it is necessary for a short time determined by the parameters of the RC circuit 6 and the resistor divider 9 to remove the positive control signal As a result, the transistor 13 is closed and the control element 12 is opened. The capacitor 8 is discharged in a circuit: the left side of the capacitor 8, the second resistor voltage divider 9, the common bus, the open control element 12, the resistor 7, rights laying the capacitor 8. After re-feeding the control signal on control bus unit resumes its operation.

Claims (1)

SUMMARY OF THE INVENTION A transistor switch containing three transistors, a control element, two resistor voltage dividers, an RC circuit, a first and a second transistor have different types of conductivity, the emitters of which are connected to different power supply buses, the first resistor voltage divider is connected between the collector of the first and the emitter of the second transistor, and the base of the second transistor is connected to the midpoint of the first voltage divider, the zener diode and the first resistor connected in series are connected between the base of the first of the second transistor, the collector of the second transistor and the output bus, the output of the control element is connected to the base of the first transistor, which means that, in order to increase reliability, a second resistor is introduced, which is connected between the positive bus of the power supply and the collector of the third transistor, the conductivity of which corresponds to the conductivity of the first transistor, the input of the control element is connected to the collector of the third transistor, and the output through the RC circuit is connected to the control bus of the device to which the second resistor divider is connected, the middle the point of which is connected to the base of the third transistor, the emitter of which is connected to a common bus.