Patent ID: 7259948

Claim:
A power supply device for driving a motor which comprises a switching control circuit on a primary side of a transformer, which switches a switching element for a power source, an output voltage generation portion on a secondary side of the transformer, which generates a predetermined output voltage in accordance with the switching of the switching element for the power source, and a fail detection circuit, wherein the output voltage generation portion includes an overvoltage detection circuit that detects an overvoltage; the overvoltage detection circuit is connected to the fail detection circuit; the fail detection circuit generates a voltage when the overvoltage detection circuit detects the overvoltage; the fail detection circuit is connected to an output terminal that outputs a normal operation signal to a drive motor control device and to an overvoltage signal terminal that outputs an overvoltage signal to the switching control circuit; and the switching control circuit includes an output voltage suppression processing unit that suppresses an increase in the output voltage when the overvoltage is detected.