To stop only a power supply circuit that fails in a device having a plurality of the power supply circuits.

If an output a1 of the power supply circuit 1 is short-circuited, a signal of an output voltage divided by resistors 9, 10 is inputted into a voltage comparator 3'. An output a3 of an fault detection signal of the voltage comparator 3' becomes "H". Then, a timer circuit 6 is started, and an output a5 is outputted in a fixed period of time and inputted into one of AND circuits 7, 8. With regard to the other input of the AND circuit 7, the output a3 of the fault detection signal is "H" so that the AND circuit 7 transmits an output a6 of an operation-stop signal to the power supply circuit 1 to stop the operation of the power supply circuit 1. Because a fault detection signal a4 of the other input of the AND circuit 8 is "L", no output signal is generated. Thus, the power supply circuit 2 maintains the present state so that the remaining power supply circuit can operate, being individually protected from a short circuit.