Multi-Ratio DC-DC Converter Based on Resonant Switched-Capacitor and Sigma Architecture

In data centers, the 48 V two-stage vertical power distribution architecture operates within the 36 V–60 V voltage range of backup batteries under emergency conditions, leading to significant intermediate bus voltage fluctuations. To address this challenge, this paper proposes a switched-capacitor based multi-ratio DC-DC converter as an intermediate bus converter (IBC), which suppresses voltage fluctuations by dynamically adjusting its step-down ratio. Derived from the Sigma architecture, the proposed IBC employs modulation schemes that enable zero-current switching (ZCS) in each submodule, ensuring high conversion efficiency. To further enhance gain flexibility, an optimized topology is introduced, incorporating an auxiliary switch to optimize current distribution among submodules. Experimental results demonstrate that the proposed IBC can seamlessly reconfigured during bus voltage fluctuations, effectively stabilizing the output voltage within the range of 5.14 V to 6 V. Additionally, both power density and conversion efficiency are superior in comparison to conventional solutions.