To surely detect faults in the short-circuit mode caused in a semiconductor switching element that turns on/off power supply regardless of a simple configuration.
One terminal of a resistor R9 connects to a power supply Vcc and the other terminal connects to ground via a series circuit consisting of a transistor(TR) Q5 that is conductive when no voltage is applied to a gate of a FET 1 and a TR Q3 that is conductive when a source level of the FET 1 rises. Furthermore, a normally closed contact RS connects between a positive terminal of a battery B and a drain of the FET 1, one terminal of an exciting coil RC connects to the positive terminal of the battery B and the other terminal connects to ground via a TR Q6. On the occurrence of a short-circuit fault in the FET 1, the level of a signal at the other terminal of the resistor R9 goes to low level, the normally closed contact RS is open to stop continuous power supply to a lamp L.
HOSHINO TAKASHI
SUMITOMO WIRING SYSTEMS
SUMITOMO ELECTRIC INDUSTRIES
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