Patent ID: 6986067

Claim:
An AC adaptor connectable to a main body of an apparatus through a power line, comprising: a rectifying and smoothing circuit to rectify and smooth an alternating current voltage; a switching section to switch the rectified and smoothed alternating current voltage at a prescribed operating frequency, wherein a level of the prescribed operating frequency is proportional to a value of an output voltage of the AC adaptor in a voltage line associated with the power line; an operating frequency control unit to control the prescribed operating frequency of the switching section based on a control line associated with the power line, wherein the operating frequency control unit controls the switching section to switch according to a first operating frequency when the main body of the apparatus operates in a normal state, and controls the switching section to switch according to a second operating frequency when the power line is separated from the main body of the apparatus or when the main body of the apparatus is in a prescribed standby state, the second operating frequency being lower than the first operating frequency; and a plug to connect the power line to the main body of the apparatus, wherein the plug comprises an operating section that provides a control signal through the control line to the operating frequency control unit to switch the prescribed operating frequency from the second operating frequency to the first operating frequency when the plug is connected to the main body of the apparatus.