SWITCHING POWER SUPPLY UNIT AND DRIVING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To solve the problem that the switching power supply unit where an AC/DC conversion circuit having a power factor improvement function is combined with a DC/DC conversion circuit may not be smoothly activated. SOLUTION: An AC/DC conversion circuit 3 having a power factor improvement function is connected to a DC/DC conversion circuit 4. When the detection value of an output voltage Eoin the AC/DC conversion circuit 3 becomes higher than a specified value, the supply of power is started to the control circuit of the DC/DC conversion circuit 4. A retention means retains the fact that a voltage detector has become higher than the specified value. COPYRIGHT: (C)2003,JPO