Patent ID: 7839659

Claim:
An alternating current power supply device comprising: a direct current power supply; a switch element for converting direct current power from the direct current power supply into alternating current power; a transformer for converting voltage of the alternating current power converted by the switch element into other voltage; a load connected to an output terminal of the transformer; a first detecting circuit for detecting a first electric signal indicating power to be supplied to the load; a second detecting circuit for detecting a second electric signal indicating the voltage of the direct current power supply; a feedback circuit for generating a feedback signal based on the first electric signal detected by the first detecting circuit and the second electric signal detected by the second detecting circuit; and a control circuit for generating a control signal based on the feedback signal from the feedback circuit and controlling on/off of the switch element by the control signal so that power to be supplied to the load is at a prescribed value, wherein the second detecting circuit is configured to detect, as the second electric signal, a control signal outputted from the control circuit to control on/off the switch element.