PURPOSE: An adapter power device is provided to reduce standby power at a standby mode by operating a switching unit with a quasi-resonant method and detecting the information of a load connected to a rectifier. CONSTITUTION: A switching unit(Qs) switches a DC voltage. A transformer includes a primary winding connected to the switching unit and a secondary winding electromagnetically combined with the primary winding. A rectifier(11) rectifies the voltage outputted from the transformer and includes a rectification diode(Do) and a smoothing capacitor(Co). A controller(12) detects the information about the load connected to the rectifier.
