| 摘要 |
AC-DC converter is provided which comprises an auxiliary winding 8c in a transformer 8, a voltage detector 21 for detecting a voltage VN appearing on auxiliary winding 8c of transformer 8 by on-off operation of a main switching element 9 in a DC-DC converter 10 to produce an output signal VCP1 when voltage VN on auxiliary winding 8c has a negative polarity, a waveform shaper 23 for generating chopping signals VRC from output signal VCP1 of voltage detector 21, and a PWM circuit 27 for comparing output voltage VRC from waveform shaper 23 and output voltage VCH from a boosting chopper 3 to supply drive signals VG1 to step-up switching element 5 in boosting chopper 3 when output voltage VRC from waveform shaper 23 exceeds output voltage VCH from boosting chopper 3. While controlling fluctuation in output voltage from boosting chopper with respect to fluctuation in AC input voltage, the converter can improve input power factor relative to AC voltage and also reduce consumption power during light load period.
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