Optimization of a Wide‐Range Regulated Four‐Switch Multiplexed Cascade Converter for Fuzzy Control Loss Reduction

ABSTRACT DC‐DC converters play a critical role in DC power delivery systems. To accommodate wide input voltage ranges and minimize converter losses, a bridge‐arm multiplexed Four‐Switch Buck‐Boost (FSBB) cascaded capacitor‐inductor‐inductor‐inductor‐capacitor (CLLLC) converter topology is implemented. In this configuration, the FSBB converter is utilized for wide‐range voltage regulation, while the CLLLC converter provides electrical isolation. Component count reduction is achieved through bridge‐arm multiplexing, resulting in significant cost savings. Resonant operation of the CLLLC converter is maintained via a Tri‐State Phase‐Frequency Detector‐based frequency tracking technique, ensuring high‐efficiency power transfer in the isolation stage. Soft‐switching conditions and conduction losses of all FSBB switches are analytically investigated. An efficiency‐optimized fuzzy control strategy is proposed for phase‐shift angle adjustment of FSBB control signals. This strategy, when integrated with duty cycle control of the FSBB converter, enables soft‐switching across all power devices, reduces conduction currents, and consequently enhances system efficiency. The effectiveness of the proposed control methodology is validated through comprehensive simulations, demonstrating a minimum efficiency improvement of 1.1 percentage points under full‐load conditions, with peak efficiency reaching 98.2%. System efficiency is maintained above 94% during light‐load operation. Practicality and efficacy of this control strategy are further confirmed through hardware‐in‐the‐loop simulation.