LLC resonant converters are widely used in new energy fields such as electric vehicles

photovoltaic power generation

and energy storage systems due to their advantages of high conversion efficiency

excellent soft-switching characteristics

and low electromagnetic interference (EMI). To address the issues of narrow gain range and large switching losses in traditional LLC resonant converters under wide input voltage ranges

this paper proposes a multi-mode wide input voltage LLC resonant converter based on a reconfigurable bridge and variable turns ratio. Three operating modes are obtained by combining the half-bridge to full-bridge switching of the inverter unit with combinations of transformer turns ratios. Different operating modes are matched to distinct voltage ranges

thereby markedly expanding the voltage gain of the converter. Over the entire input range of the converter

both the switches and diodes can achieve soft switching

improved converter efficiency. This paper introduces a state trajectory model to analyze the operating principle of the proposed LLC resonant converter

and the equations for voltage gain and soft-switching characteristics are derived. Finally

an experimental prototype with 80~400V input

24V output

and 200W power is designed and built

verifying the correctness and feasibility of the proposed topology and principle analysis.