Voltage stabilizer with protection against KZ

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to Many radoilyubitel is familiar to font face the circuit of this simple voltage stabilizer with protection against overloads and short circuits of a chain of an exit. It possesses a number of merits and consequently received wide popularity of radio fans.

However the lack of the stabilizer is that the threshold of restriction of a current of loading of its device of protection depends on static factor of transfer of the regulating transistor. As at a transistor warming up its static factor of transfer of a current increases, the current of restriction of the stabilizer increases also. The capacity allocated on the regulating transistor that can lead to its overheat and failure as a result increases. The V4 diode which has been switched on between base of the managing director and a collector regulating (it is shown in drawing), practically eliminates this shortcoming. In a normal operating mode of the stabilizer the V5 diode is open, and the V4 diode is closed and does not influence operation of the device.

If a current of loading to increase, target tension of the stabilizer will start to decrease, the V5 diode will be closed, and the V2 transistor together with resistors R1, R3 and a stabilitron of V3 will work as the current stabilizer. In this regard the base current of the regulating V1 transistor, so and its collector current appear limited. At the same time with closing of the V5 diode the V4 diode opens, shunts V3 stabilitron, and it leaves a stabilization mode. It leads to tension reduction on the basis of the V2 transistor and respectively to reduction of a current of restriction. If as the V4 diode to apply a light-emitting diode, for example АЛ102А, it will serve as the indicator of an overload of the stabilizer, but in this case the current of short circuit will increase owing to bigger power failure on light-emitting diode transition a little.