Power supply circuit

The invention provides a circuit for supplying electric power to a load using a high voltage battery, the circuit supplying a dark current when the load is not being operated. A high voltage load and a low voltage load are attached to a battery and electric power is supplied to the low voltage load through a main DC-DC converter and a sub DC-DC converter. When an ignition switch is OFF, only the sub converter supplies the dark current to the low voltage load and the main DC-DC converter is turned OFF. When the ignition switch is ON, the main DC-DC converter supplies required electric power. Since a low-capacity sub DC-DC converter supplies the dark current, the battery discharge can be prevented.