Overvoltage protection circuit for inductor, e.g. DC motor - has two transistors connected back=to=back across inductor terminals and with bases connected together

摘要

The circuit prevents the appearance of a damaging overvoltage at the terminals of an inductor, e.g. a d.c. motor when the inductor is switched out of circuit. The inductor, etc. is supplied with control pulses of alternating polarities. In order to limit the positive and negative disconnection voltages two transistors are connected to the inductor's terminals. The bases of the transistors are joined together, and the emitter of each is connected to the collector of the other transistor. The collector-emitter junctions are connected to the inductor's terminals. The two transistors may be of the npn type and formed as an integrated circuit.