To improve reliability by omission of a charge pump, by supplying power from a power source to a first load, and by controlling power supply to a second load by control signals from an auxiliary power supply of a different power supply voltage by turning on or off a semiconductor switch based on the difference between its terminal voltage characteristics and a reference voltage having the equal value.

This device comprises a circuit which supplies a power source voltage VB to a first load 510 and a supply circuit to a drive circuit 111 which drops a voltage by a Zener diode 530 and controls a FET QA with a built-in temperature sensor and to a DC-DC converter 540 of a low-tension auxiliary power supply. Also, power is supplied to a second load 520 via a switching circuit 500 with a current oscillation breaking function. A current-limiting resistor 531 prevents the occurrence of an overcurrent, if the equivalent resistance value of the drive circuit 111 side is nearly opened. The operation of the drive circuit 111 is controlled by switching an SW1, which also controls power supply to the second load 520. A source transistor Q5 and a sink transistor Q6 are controlled by on-off changeover signals of the switch, and signals are outputted which drive and control the FET QA with the built-in temperature sensor.