A 1-MHz Series Resonant DC-DC Converter With a Dual-Mode Rectifier for PV Microinverters

The photovoltaic (PV) output voltage varies over a wide range depending on operating conditions. Thus, the PV-connected converters should be capable of handling a wide input voltage range while maintaining high efficiencies. This paper proposes a new series resonant dc-dc converter for PV microinverter applications. Compared with the conventional series resonant converter (SRC), a dual-mode rectifier (DMR) is configured on the secondary side, which enables a twofold voltage gain range for the proposed converter with a fixed-frequency phase-shift modulation scheme. The zero-voltage switching (ZVS) turn-on and zero-current switching (ZCS) turn-off can be achieved for active switches and diodes, thereby minimizing the switching losses. Moreover, a variable dc-link voltage control scheme is introduced to the proposed converter, leading to a further efficiency improvement and input-voltage-range extension. The operation principle and essential characteristics (e.g., voltage gain, soft-switching, and root-mean-square current) of the proposed converter are detailed in this paper, and the power loss modeling and design optimization of components are also presented. A 1-MHz 250-W converter prototype with an input voltage range of 17 V – 43 V is built and tested to verify the feasibility of the proposed converter.