Hybrid Resonant and Non-Resonant Coupled-Inductor-Based Current-Fed DC–DC Converter

This article presents a hybrid resonant and non-resonant coupled-inductor-based current-fed DC-DC converter, designed for solar-tile microinverter (MI) applications requiring high voltage gain. In the proposed circuit, a boost half-bridge (BHB) is connected to the PV side, providing higher voltage for the half-bridge stage and reducing the primary conduction losses. Additionally, an active voltage-doubler rectifier is utilized on the secondary-side to achieve a two-fold voltage gain, thereby reducing the required transformer turns ratio and size. The proposed circuit is derived by integrating the input dc inductor of the BHB into a coupled-inductor, introducing an additional resonant path that enhances power transfer capacity without requiring extra active switches. The introduction of the resonant path contributes to narrow the switching-frequency range, reduce the turn-off current and switching losses, and improve the efficiency while increasing the power transfer capability compared to the non-resonant configurations. The design procedure is presented to minimize current stress, extend ZVS range, and reduce reverse input current. The ZVS regions for primary and secondary switches are determined under different load conditions and voltage gains. Two control parameters, phase-shift and switching frequency, emerges due to the active rectifier and the resonant coupled-inductor, providing more flexibility in regulating output power, minimizing back-flow power, and maintaining ZVS across all switches. Experimental results provided from a 100 W prototype, to validate the performance of the proposed converter.