Design of an Interleaved Half-Bridge CLLC Resonant AC-AC Converter

This paper proposes an interleaved half-bridge CLLC resonant ac-ac converter composed of multiple half-bridge CLLC resonant converters and bidirectional dc-ac unfolders. In general, there are three power stages for the ac-dc, dc-dc, and dc-ac functions in one ac-ac converter. Therefore, the power efficiency is a significant issue for the three-stages configuration. In this paper, there is only one stage of high-frequency pulse frequency modulation (PFM) to control the half-bridge CLLC resonant converter to generate the desired output voltage with galvanic isolation. The bidirectional ac-dc unfolder and dc-ac unfolder switch with the ac-mains frequency with lower switching loss. Advantages of the proposed converter include one-stage of high-frequency conversion, simple control circuit, and flexible capacity. In addition, the zero voltage switching (ZVS) can be achieved in the half-bridge CLLC resonant converter. The proposed converter has been verified experimentally by using simulations and a 1-kW prototype for 380 V/110 V and 260 V/110V applications. The total harmonic distortions of the output voltage are 2.51 % and 2.19% under full load condition. The maximum conversion efficiency is about 93.3%.