| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a power supply device and in addition to reduce the cost of its manufacture. SOLUTION: When a switching element 22 is turned off, as a result of a level of a current In1 flowing in a primary side winding N1 of a transformer 21 reduced almost to zero; when the level of voltage Vn2 of a secondary side winding N2 is decreased to a level smaller than around the level of a prescribed reference voltage Vref2, or when a timer 111 counts a time corresponding to the lowest switching frequency of a preset switching element 21, an AND circuit 112 outputs a set signal relating to a flip-flop circuit 39. Then the flip-flop circuit 39 generates an output voltage (control signal) Sc at a high level, to turn on the switching element 22. This invention is applicable for a step-up chopper type power factor which improves capacitor. COPYRIGHT: (C)2005,JPO&NCIPI
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