High-voltage high-frequency non-isolated DC–DC converters with passive-saving two-phase QSW-ZVS technique

This paper presents a new technique to improve the power efficiency for high-voltage non-isolated DC–DC converters running at high switching frequencies. A passive-saving two-phase quasi-square-wave zero-voltage-switching (PS-TPZVS) cell that consists of an auxiliary inductor and a capacitor sharing between two phases of sub-converters is proposed to realize ZVS operation for all power FETs under different conditions. Compared to the traditional two-phase ZVS topology, the proposed design saves 1 auxiliary inductor and 1 auxiliary capacitor for establishing ZVS of power FETs, and thus reduces both the volume and power losses of the auxiliary circuitry. To verify the performances of the proposed PS-TPZVS cell, a 140-W 4-MHz two-phase QSW-ZVS converter is designed and verified by simulations to achieve peak efficiencies of 97 % with enhancement-mode GaN FETs and 95 % with power MOSFETs. The proposed PS-TPZVS cell can also be applied to various topologies of non-isolated DC–DC converters and extended into a 2 N-phase topology with only N additional branches of the proposed cell.

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