A Single-Stage AC/DC LLC Resonant Converter

Abstract

A single-stage ac/dc LLC resonant converter is proposed to draw a sinusoidal line current, for achieving power factor correction (PFC). The proposed ac/dc converter composes of a boost-PFC semi-stage and a LLC-SRC semi-stage. The boost-PFC semi-stage, working in discontinuous conduction mode (DCM) functions as a power factor corrector, and the LLC-SRC semi-stage operates above the resonance to achieve zero-voltage switching (ZVS) operation. The proposed converter has the feature of variable-frequency control, which provides a constant output voltage, high power factor, high efficiency, and low component count. Finally, the experimental results are provided to verify the performance as expected.