Research on Two-Stage DC-DC Converter Suitable for High Voltage Input and Low Voltage Output

In this paper, a two-stage DC-DC converter topology is proposed to tackle the challenges of wide input range and high voltage levels in vehicle-mounted DC buses. A three-level Buck (TL Buck) converter is utilized as the front stage, thereby reducing the voltage stress on the MOSFETs to half of the input voltage. This makes it suitable for applications with high voltage levels and wide input ranges. Additionally, a star-connected three-phase LLC is employed as the rear stage to minimize output current ripple and achieve zero voltage switching (ZVS) and zero current switching (ZCS). A cascaded loop control with fixed frequency modulation strategy is adopted, demonstrating strong adaptability to wide input voltages. Finally, a simulation model is constructed to verify the correctness and feasibility of the proposed topology and control strategy.