Resonant Push-Pull Converter With Flyback Regulator for MHz High Step-Up Power Conversion

With the trend toward achieving high efficiency, high power density and high operating frequency in power converters, a galvanic isolated circuit architecture is proposed in this article for high step-up applications with wide input-voltage range. This converter consists of a current-fed resonant push-pull (PP) converter as a dc transformer (dcX) dealing with most of the power with high efficiency and an active clamp flyback converter (ACF) as a regulator within a large conversion range. As a single-stage converter, the ACF regulator is paralleled with PP converter to share the total power and regulates the high output voltage. An experimental prototype with an input-voltage range of 24-32 V and output 400 V/400 W is built under 1 MHz switching frequency. A peak efficiency of 97.1% and a power density of 210 W/in(3) (or 13 W/cm(3)) are achieved. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter for MHz high step-up dc-dc conversion.