A first power supply of a constant-voltage output supplies a power to a load by using an external power. A signal generating unit generates a control signal for compensating a shortfall of a load current when exceeding an upper limit of an output current of the first power supply. A second power supply of a constant-current output supplies a power to the load based on the control signal by using a power from a capacitor. An output voltage of the first power supply is controlled so that a voltage of a power supply line that is closer to the load than a current detection position of a converting unit that converts the load current into a current signal is made constant.