POWER SUPPLY CONTROL CIRCUIT

A power supply control circuit that allows the power to be supplied from a power supply such as a sub-battery to a load for a longer period of time, in the event of a failure of a main power supply. The power supply control circuit () includes: a first circuit () connecting a main battery () and a sub-battery () via a DC/DC converter (); a second circuit () connecting a main battery () and a load (); and a third circuit () connecting the sub-battery () and a load () via a semiconductor switch (). When the main battery () fails, the semiconductor switch () is turned ON to supply the power from the sub-battery () to the load (), and the forward direction of a parasitic diode () of the semiconductor switch () is a direction from the load () to the sub-battery (). Furthermore, the DC/DC converter () boosts the voltage from the main battery () and supplies the boosted voltage to the sub-battery ().