POWER SUPPLY APPARATUS HAVING SELF-PROTECTIVE FUNCTION AND SELF-PROTECTING METHOD THEREOF

摘要

PURPOSE: A power supply apparatus having a self-protective function and a self-protecting method thereof are provided to protect a power oscillation integrated circuit when a level of an alternating current input voltage becomes lower than needs. CONSTITUTION: A first rectifier(10) rectifies an input alternating current signal and outputs a first direct current voltage. A transformer(12) includes a main winding and an auxiliary winding connected between the main winding and a reference voltage. A first switch(16) connects a first node of the main winding to the reference voltage in response to an oscillating power supply. A level dropping device(14) drops a voltage level of a second node of the auxiliary winding and outputs a second direct current voltage having a dropped level. A second switch(18) selectively outputs one of the first direct current voltage and a voltage of the second node in response to a selection signal. A third switch(20) switches the voltage of the second node to the second switch(18) in response to the second direct current voltage.