A Reconfigurable Multi-Resonant Switched-Capacitor Converter for 48 V Data Center Application

In the emerging two-stage architecture of 48 V data center power systems, the wide voltage range of backup batteries (36 V-60 V) leads to significant fluctuations in intermediate bus voltages when transmitted through fixed-gain intermediate bus converters (IBCs), creating a challenge in optimizing the height of point-of-load (PoL) converters. To address this, a reconfigurable IBC based on multi-resonant switched capacitors (SCs) is proposed in this paper, achieving both 8:1 and 6:1 conversion ratios to suppress intermediate bus voltage fluctuations. The proposed topology combines a 2:1 SC with two 4:1 Fibonacci SCs, eliminating decoupling capacitors while reducing two switches. Two modulation modes with zero-current switching (ZCS) are described, and their corresponding component stresses are analyzed. Utilizing a two-phase output structure, the converter demonstrates low output impedance, which is estimated, decomposed, and discussed. Phase expansion can further reduce output impedance or enable dual-port outputs for dual intermediate buses. An experimental prototype with a 36-60 V input and 5.625-7.5 V output was implemented, achieving a nominal power density of 2,266 W/in³ and a peak efficiency of 98.8% in 8:1 mode (3,021 W/in³ and 99.1% in 6:1 mode). The reconfiguration capabilities of the proposed converter are also demonstrated.