SU978265A1 - Device for protecting transistorized switch from current overloads - Google Patents

Description

one

The invention relates to a converter technique and can be used in devices for protecting key & controllers, converters and amplifiers operating in key mode.

The protection devices of transiotor switches are known, which contain a driver control driver, connected between the collector and the base of the protective resistor, and diodes, one of which is between the emitter of the protecting transistor and the collector of the key transistor, and the second, their bases l.

A disadvantage of the known ss 5 devices is the low efficiency due to losses on the diode included in the base circuit of the switch & t transistor.

The closest technical to the invention in terms of means and results achieved is a device for protecting a power source from current overloads, containing a mold, an optocoupler, a diode and a transistor switch 2.

A disadvantage of the known device is the low coefficient of operation of the device to protect the transistor switch.

The purpose of the invention is to increase the efficiency of the device for protection.

This goal is achieved by the fact that in a known device the collector of the transistor is connected to a terminal for connecting a load with a series-connected current source and to the cathode of the diode, the anode of which is connected to one output side of the driver, the second output of which is connected to the terminal of the power supply and the emitter of the transistor the base of which is connected to the anode of the diode through a light-emitting diode of the optocoupler, whose photo-thyristor is connected to the control input of the driver.

The device is equipped with a threshold element, two resistors and a transformer, the input winding of which is connected to the outputs of the driver, the output windings of the transformer are connected by one output to the emitter of the transistor switch, and the second output of the first input winding of the transformer is connected to the first output of the first resistor, the second output of which is connected through About the threshold element to the anode of the diode and at the same time through the capacitor to the emitter of the transistor key, and the second output of the second winding of the transformer connects & d inen through the second resistor to the transistor tS base of the resistor switch.

FIG. 1 is a circuit diagram of a device for protecting a transistor switch; in fig. 2 -. device diagram with a driver having a transformer output.

Device to protect the transistor switch 1 (Fig. 1} with a collector load

2 contains shaper 3 control

impulses, diode 4 and optrn 5. ..

I

A device for protection with a transformer contains (Fig. 2) terminals for connecting a key transistor 1 with a collector load 2, the driver

3 impulses, diode 4, optocoupler 5, threshold element 6, capacitor 7, resistor

8 and a transformer 9.

A device for protecting a transistor switch against current overloads (Fig. 1) works as follows.

When a pulse appears at the output of the driver control driver 3, the key transistor 1 opens. In this case, a signal appears at the output of the rptron 5, under the influence of which a

The rover 3 of the controllers guards delays the protection action by unlocking the transistor 1 until it enters saturation saturation. At the point in time when the voltage at the collector-emitter junction of transistor 1 becomes less than the voltage across its base-to-junction transition, the signal from the output of the optocoupler 5 disappears, and in the control pulse shaper 3, the signal from the protection element is removed, and the control & its triggering. When a current overload occurs, the transistor 1 goes from saturation to unsaturated states, the voltage at its transition; the collector-emitter increases 55 s and when its voltage is exceeded at the junction, the base-collector triggers the optro 5. The output of the optocoupler 5 acts

on the driver 3 of the control pulses in such a way that it interrupts j current flow in the base circuit of transistor 1. The transistor closes, thereby stopping the flow of emergency current through its collector-emitter junction.

The protection device of the transistor I key against current overloads, which includes a control driver driver with a transformer output (Fig. 2), works as follows.

When a positive potential appears on the final leads of the secondary windings of the transformer 9, the transistor 1 closes and the capacitor 7 acquires the polarity shown in FIG. 2 in brackets. When a positive potential appears on. The beginning of the secondary windings of the current flows through the limiting resistor 8, the recharge of the capacitor 7 in reverse polarity to the trigger voltage of the threshold element 6. The recharge time is chosen equal to the opening time of the transistor 1. Therefore, the same time the operation of the optocoupler 5 will be blocked . Further, the operation of the device is similar to the device shown in FIG. one.

The use of the invention provides an increase in the efficiency of the device for protecting the transiotor key, since it allows refusing the use of diodes, in the control circuits of the key transistors, as well as from an additional galvanically developed power source in the driver of the control pulses.

Claims (2)

1. A device for protecting a transistor switch against current overloads, comprising a driver, an optocoupler, a diode and a transistor switch, characterized in that, in order to increase the efficiency, in it the collector of the transistor is connected to a terminal for connecting a load with a series-connected current source and to the cathode of the diode, the anode of which is connected to one output terminal of the former, the second diode of which is connected to a terminal to receive a power source and the emitter of the transistor, the base of which is connected to svetoizGlUchayushy node through the diode of the optocoupler diode, fototiristory ko4 torogo connected to the control input of the. 2. The device according to claim 1, so that it is equipped with a threshold element, two resistors and: a transformer, the input winding of which is connected to the terminals forming the body, the output windings of the transformer are connected by one leads to the emitter "transistor key, with the second output. . I the first output winding of the transformer is connected to the first output of the first I resistor, the second output of which is a plug; the target is through the threshold element to the diode anode and alternately through the capacitor to the emitter of the key transistor, and the second second of the second secondary winding of the transformer is connected to the key of the transistor. Sources of information taken in view by Iran Ensp 1. USSR author's certificate No. 625286, kp. HO2H 7/20, 1979. 2. The author's certificate of the USSR; No. 688953, cl. H02H 7/10, 1979.