Patent ID: 7656116

Claim:
A power supply system comprising: a pair or a plurality of pairs of an upper switching element and a lower switching element connected in series between power sources for sequentially energizing a motor drive winding of a single phase or a plurality of phases; a control circuit that starts outputting a control signal for controlling energization of the motor drive winding based on an energization instruction; a pre-drive circuit for controlling ON/OFF of the upper switching element and the lower switching element based on the control signal from the control circuit; and a short circuit detection circuit for detecting a short circuit in a node between the upper switching element and the lower switching element to a higher-potential power source or a lower-potential power source based on the control signal from the control circuit and a voltage of the node, wherein the short circuit detection circuit is controlled to perform at least one operation of: detecting a short circuit in the node to the lower-potential power source with all the upper switching element turned ON and all the lower switching element turned OFF; and detecting a short circuit in the node to the higher-potential power source with all the upper switching element turned OFF and all the lower switching element turned ON, in a state where the motor drive winding is not energized.