Interleaved ZVS DC-DC converter with ultrahigh step-down and flexible gain

This paper proposes a novel non-isolated ultrahigh step-down interleaved DC-DC converter with an extremely extended duty cycle based on the series capacitor and coupled-inductor techniques. The proposed converter utilizes a three-winding coupled inductor (TWCI) to enhance the step-down conversion ratio. In contrast to conventional coupled inductor-based step-down converters, its voltage gain improves as the turn ratio approaches unity. Consequently, coupled inductors have significantly lower winding losses. Furthermore, there is no extra constraint on the turn ratio of the TWCI. It results in a highly flexible voltage gain and more design freedom. Other advantages of the employed series capacitor and coupled inductor techniques can be listed as, zero voltage switching (ZVS) condition for all switches, significant reduction of the total switching device power (SDP) and recovery of the energy of leakage inductors. They all reduce power losses and costs. Steady-state analysis, derivation of voltage gain and design considerations are discussed in detail. Finally, a 200 W, 400-to-12 V experimental prototype is implemented to verify the effectiveness and feasibility of the proposed converter.