A 48V-0.8V/300A xPU Voltage Regulator with Improved Sigma Converter

A 48V-0.8V/300A xPU voltage regulator is investigated in this paper. The converter is an improved version of the sigma converter, which is composed of a LLC and switched-capacitor hybrid DC transformer and a buck converter. The hybrid DC transformer is derived by integrating a 2:1 resonant switch-capacitor converter and the LLC resonant converter by merging the switching bridge and the resonant tank. The output of the LLC transformer is directly connected to the load, while the output of the integrated switched capacitor converter is used as the intermediate-bus and employed as the input of the buck converter. All the switches of the hybrid DCX can achieve soft-switching, while the voltage stress of the buck converter is reduced with the help of the integrated switched capacitor converter. The operation principles and characteristics of the improved sigma converter are analyzed in detail. An experimental prototype is built and tested. Peak efficiency of 93.34% and full load efficiency of more than 87% is achieved with the presented converter.