SU851617A1 - Device for overload protection of transistor - Google Patents

Description

(54) DEVICE FOR PROTECTION AGAINST TRANSISTOR OVERLOAD

one

This invention relates to protection and can be used to protect transistors of pulsed devices. with limited collector current in case of short circuit of the collector load.

A device for protecting a transistor is known, which contains a resistor and a capacitor included in the base circuit, in parallel with which the collector-emitter junction of the additional transistor 1 is turned on. A disadvantage of this device is the lack of indication of the emergency mode.

The closest to the proposed technical means and the achieved result is a device for protection against overload of a transistor operating in a pulsed mode on a load p, inserted into a collector circuit through an output transformer containing transistors and a capacitor included in the emitter circuit included collector-emitter junction of an additional transistor, a diode and an additional resistor

A disadvantage of this device is low reliability due to the presence of

additional relay and no indication.

The purpose of the invention is to increase reliability.

. This goal is achieved by the fact that the device is equipped with a display unit, and the output transformer is made with an additional winding, the first output of which is connected to the base

10 additional transistor, the baso-emitter junction of which is diode-shunted, and the second through an additional resistor is connected to the input of the display unit.

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The drawing is a schematic diagram of the proposed protection device.

The device contains a protected transistor 1, the base of which is connected to the input of the device, the emitter is connected to the first terminals of resistor 2 and capacitor 3. The second terminals of resistor 2. and capacitor 3 are connected to ground. Transistor collector

25 1 is connected to the first terminal of the primary winding 4 of the transformer 5, the second terminal of the primary winding 4 is connected to the positive terminal of the power source. Additional switching transistor 6 protection, the collector of which is connected to the emitter of transistor 1 and to the first terminals of resistor 2 and capacitor 3, the emitter of transistor b is connected to ground. Diode 7, the anode of which is connected to ground, and the cathode to the base of the switching transistor b and to the first output of the secondary winding 8 of the transformer 5 Additional resistor 9, the first output of which is connected to the second output of the secondary winding 8 of the transformer 5 Diode 10, the cathode of which is connected to the second output resistor 9 and the anode is connected to ground. The display unit 11 performed in the form of a transistor switch, the input of which is connected to the second terminal of the resistor 9 and to the cathode of the diode 10. A two-wire communication line 12, the conductors of which are connected to the terminals of the third winding of the 13-transformer 5,

In normal mode, the device operates as follows.

For the transit time of the positive-polarity impulse signal entering the device, transistor 1 opens and capacitor 3 charges. After the input signal passes, transistor 1 closes and the switching protection transistor 6 opens from the ground-positive current surge generated in transformer winding 8 5, while the discharge of the capacitor 3 occurs through the collector of the transistor b. The main signal arriving at the base of the transistor b is negative with respect to ground and about The diode 7 is limited. The control current output entering the device 11 is negative and limited by the diode 10. Resistor 9 is the load of the winding 8 of the transformer 5, the protection of the transistor against preload when the wires of the communication line 12 are interconnected or short-circuited the ground is accomplished by limiting the collector current of transistor 1,

In emergency mode, when a single signal arrives at the device input, it works as follows,

Due to a short circuit in the winding 13 (in the wires of the communication line), the magnetizing current in the pulse transformer 5 decreases and the ejection current of the pulse signal arriving at the base of the switching transistor b of the protection becomes insufficient to open it, V

In this case, the discharge of the capacitor 3 through the collector of the switching transistor 6 of protection does not take place after the passage of the main signal, since this transistor is closed. The discharge of the capacitor 3 through the limiting resistor 2, which has a high resistance, flows very slowly. Increase voltage potential relative to device ground

- at the emitter junction of the transistor 1 of a pulse shaper, due to the charge of the capacitor 3 and holding this charge after the passage of the main signal leads to a decrease in the collector current of transistor 1,

5 in the emergency mode, if a signal sequence arrives at the device input, capacitor 3 will charge to a certain value greater than when a single signal is input, which will further limit the collector current of transistor 1.

The proposed protection device has an increased speed, and the transistor is protected even when a single pulse signal arrives at the device input.

Claims (1)

Invention Formula Device for protection against overload of a transistor operating in a pulsed mode on the load connected to the collector circuit through output transformer containing included in the emitter circuit of the transistor; a resistor and a capacitor, in parallel with which a collector-emitter junction of an additional transistor is connected, a diode and an additional resistor, characterized in that with. In order to increase reliability, it is equipped with a display unit, and the output transformer is made with an additional winding, the first output of which is connected to an additional transistor, the basic-emitter junction of which is diode bridged, and to the output terminal through an additional resistor is connected to the input of the display unit. Sources of information passed into consideration during the examination  1, USSR Copyright Certificate No. 2077442 / 24-07, Cl, H 02 H 7/10, 1974, 2, Patent of England No. 925027, class, 40 (6), 1963, five QfOd