Robert Boschgmbh

Bernhard Rasch

Harald Eisenhardt

Rolf Falliano

A protective circuit for a series circuit of a power semiconductor and an inductive load, to which a freewheeling circuit of a freewheeling diode and a reverse polarity protection semiconductor switch connected in series is connected in parallel. The power semiconductor output stage may be switched on and off depending on a predetermined setpoint value with a pulse-width modulated control signal and the reverse polarity protection semiconductor switch may be made non-conducting via a charging pump when the polarity of the supply voltage is reversed. The destruction of components in the case of non-functioning of the freewheeling circuit may be avoided by monitoring a point in the freewheeling circuit of a freewheeling diode and a reverse polarity protection semiconductor switch or in the series circuit of load and power semiconductor output stage for a voltage or a current which appears if the freewheeling circuit is non-functioning, and by initiating the shut-off of the control of the power semiconductor output stage with this fault indicating voltage or current.

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Fellbach, Germany

Bernhard Rasch