A Merged H-Bridge Based Switched Tank Converter for Front-End Voltage Regulator Modules

In this paper, a merged H-bridge based switched tank converter is proposed to serve as the front end non-regulated stage of voltage regulator modules. To achieve an n:1 voltage step down ratio, only n+4 switches are required. The proposed converter maintains good soft-charging and soft-switching performances, which effectively mitigate the switching loss. No bulky transformer is required. The design considerations of the tolerance of resonant components is also presented. A small deadband and symmetrical printed-circuit-board design are dedicated to compensating the deviation of resonant frequency caused by tolerance in resonant components. Zero current switching is achieved among all MOSFETs. The low switch count and zero current switching performance facilitate both high power density and high efficiency of the designed prototype. Steady-state circuit analysis is briefed and the simulation model is established to verify the analysis. To verify the proposed concept, a hardware prototype that converts 48 V to 8 V is designed and tested. The maximum output current can reach 28 A, and the peak efficiency is 97.11% at 6.2 A output.