A Study on Wide Input Range Switched Inductor-Based Full-Bridge LLC Converter Topology

To broaden the input range and stabilize the output of the full-bridge LLC resonant converter, a topology combining the switched inductor buck converter (SLD) with the full-bridge LLC converter is proposed. This topology not only provides the wide voltage regulation range of the source-level converter (SLD buck unit) but also keeps the advantages of the load-level converter (LLC resonant converter) such as zero-voltage switching (ZVS) and zero-current switching (ZCS). Firstly, the characteristics and advantages of the two stages of the cascade converter are analyzed based on the working principle of the cascade converter. Subsequently, a fixed-frequency control strategy based on the overall output voltage feedback is adopted. Specifically, when the LLC resonant converter consistently operates at its dual-resonant frequency, the converter achieves maximum efficiency, effectively compensating for the potential efficiency drop in the first stage SLD unit, thereby improving the overall system efficiency. Finally, theoretical analysis is validated on the Matlab/Simulink platform.