| 摘要 |
PURPOSE:To provide a protector circuit which can prevent the breakage of a power transistor by detecting surely occurrence of a ground fault even right after the protector circuit is started. CONSTITUTION:A protector circuit contains an output circuit 1 which includes output power transistor TR 6a and a boot strap capacitor 16, a starting circuit 2 which keeps the voltage of an output terminal at a high potential only for a prescribed time after application of a power supply and then starts the protector circuit when the voltage of the output terminal is stabilized at an intermediate potential, an overcurrent detecting circuit 3 which detects the faulty current of the TR 6a caused by a ground fault, an off-driver circuit 4 which cuts off the TR 6a based on the detection signal of the circuit 3, and a sensitivity setting circuit 5 which sets the ground fault protecting sensitivity to actuate the circuit 4 based on the detection signal of the circuit 3. Furthermore a sensitivity switching circuit 35 switches the ground fault protecting sensitivity set by the circuit 5 after the protector is started.
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