| 摘要 |
The present invention provides an AC-DC converter in which an application range of an AC input voltage can be extended, keeping a voltage in a circuit from rising at a light load. In an AC-DC converter having a rectifier 3, a boost chopper 4 and a DC-DC converter 5, a PWM circuit 6, an one-shot multivibrator 7, a pulse synthesizer 8 and a comparator 9 are further arranged. The pulse synthesizer 8 generates a second pulse signal having a pulse width being narrower by a pulse width of the delay pulse VpD than that of the first pulse signal Vpa by means of the first pulse signal Vpa which the PWM circuit 6 output s and a delay pulse VpD generating in said one-shot multivibrator 7. The comparator 9 compares a voltage VC boosted up by the boost chopper 4 with a reference voltage VREF to stop generating the delay pulse when voltage VC drops below the reference voltage VREF .
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