A Two-Stage Isolated High Step-Up Quasi-Resonant DC-DC Converter with Pre-Voltage Regulator

A two-stage isolated high step-up quasi-resonant DC-DC converter with pre-voltage regulator is proposed in this article. A quasi-resonant network and a voltage doubler are added on the secondary side of the transformer to achieve voltage lift-up in the latter stage, which can realize the ZVS turn-on of primary switches and there is also no reverse recovery loss in the secondary side diodes. In order to ensure the efficient operation of the system, the latter stage is designed to operate at the rated state to achieve a constant output. While the front-stage synchronous Buck-Boost converter acts as a voltage regulator to realize constant voltage regulation in a wide input voltage range. An experimental prototype with an input voltage range of 20-28 V and output 400 V/ 0.5 A is built under 1 MHz switching frequency. A peak efficiency of 93.6% is achieved. The experimental results verify the correctness of the theoretical analysis.