A Resonant Switched-Capacitor LLC DCX in Data Center Applications

In this paper, a novel resonant switched-capacitor LLC topology is proposed to serve as the dc transformer (DCX) in data center applications. The proposed DCX is formed by a 2:1 resonant switched-capacitor cell and an LLC converter. To achieve a
$\boldsymbol{4n}:\boldsymbol{1}$
voltage step-down ratio, only an
$\boldsymbol{n}:\boldsymbol{1}$
turns ratio transformer is required. It presents good soft-charging and soft-switching performances to effectively mitigate charge distribution loss and switching loss. Furthermore, the voltage stresses of primary switches are only half of the input voltage, and the current stresses are also lower than that of conventional LLC converter. The operational principle of steady-state circuit and theoretical analysis are provided to highlight its advantages. To verify the proposed concept, a 300W-rated hardware prototype that converts 48 V to 12 V is designed and tested with 1MHz switching frequency.