A High-Efficiency MHz-Integrated Three-Phase Interleaved Boost–LLC Converter With Voltage Regulation

Three-phase interleaved LLC can achieve high-efficiency and low-ripple conversion, but it is difficult to reach a wide voltage regulation range due to the difficulty of synchronous rectification. Based on the principle of bridge arm multiplexing, this article proposes a three-phase interleaved boost and three-phase interleaved LLC integrated topology. The integrated topology adopts a modulation strategy in which the duty and frequency change cooperatively, which can achieve decoupling of boost and LLC and smooth gain. Among them, the boost works in the forced continuous conduction mode, using the inductor current to realize zero-voltage turn-on of all switching devices, which can realize an air-gap-free transformer design and help reduce winding losses. Based on the modal analysis, this article gives the switching function of the proposed topology to achieve synchronous rectification in the voltage regulation range. Furthermore, this article analyzes the effect of the transformer ratio on device stress and provides an optimization strategy for integrated transformers. Finally, a prototype with a switching frequency of 1 MHz, 40–60-V input, and 400-V at 1.5-kW output was designed to verify the proposed topology and the modulation strategy, achieving a full-load efficiency of 97.7% and a power density of 159 W/in³.