This paper presents the novel soft-switching buckboost type ac-dc converter with high power efficiency and high power factor. In this ac-dc converter, the power factor and harmonic distortions are improved by using the third winding of theenergy-storage reactor, and the high power efficiency is achieved by the soft-switching operations of the main power switch and output rectifier diode. The equivalent circuit model with dc voltage sources is derived and the performance characteristics are analysed by this model. The analytical results are confirmed by the experimental ones. As a result, it is clarified that the proposed ac-dc converter satisfies the maximum limits of the input current harmonics distortion in IEC 1000-3-2 Class D and thatits power efficiency is 95% at the rated load current.
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