PURPOSE: A switch mode power supply device and method are provided to reduce stand-by power by supplying energy to load at ordinary times through momentary energy charge and repetition of a combless power range of long time. CONSTITUTION: An AC power input unit(310) receives AC voltage. A rectifier circuit(320) full wave rectifies and levels the AC voltage. A PFC(Power Factor Capacitor) circuit(330) comprises a PFC bulk capacitor(331) and a PFC controller. The PFC controller charges voltage to the PFC bulk capacitor. A first resistance(361) and a second resistance(363) divide the voltage of the PFC bulk capacitor and output a reference voltage. A controller(370) controls charge and discharge of the PFC bulk capacitor according to the reference voltage. The controller comprises a Zener diode(371) and a transistor(373).
