| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply control circuit in which power efficiency is improved when a switching frequency is lowered at light loading. SOLUTION: Between a single-shot circuit 13 generating the on-trigger of a switch element and a comparator 15 which stops switching operation when an FB terminal voltage drops below 0.5V, a pulse counter circuit 23 is provided additionally in order to count a switching pulses outputted from a flip-flop circuit 19. An upper limit frequency when the switch element is turned on by a switching command signal is specified by a timer circuit 24 of a fixed period. Consequently, intermittent operation where the switch element turns on N times continuously (N is an appropriate positive integer) and then stops is performed in the case of light loading. COPYRIGHT: (C)2007,JPO&INPIT
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