Short circuit-protected electronic switch

摘要

Electronic switches are known which, in the case of a short circuit in the output circuit, switch off the current and then periodically apply test pulses to the output until the short circuit is eliminated. In this connection, the problem occurs in the case of an incandescent lamp or a capacitive load that the test pulses must supply sufficient power for heating up the incandescent filament or for charging up the capacitance but, on the other hand, the switch must not heat up excessively when there is a short circuit. This problem is solved by the present invention in that the current/time area of the pulses (P1) is dimensioned in such a manner that the incandescent filament is heated up or the capacitance is charged up with one pulse to such an extent that the output current has dropped below a predetermined value. The mark/space ratio is so small that the switch is not thermally overloaded even with a persistent short circuit. The main field of application of the invention is short circuit-protected digital outputs. <IMAGE>