A 48-to-12 V Cascaded Multi-Resonant Switched Capacitor Converter with 4700 W/in3 Power Density and 98.9% Efficiency

The cascaded resonant switched capacitor converter topology has been demonstrated to have significant advantages on system efficiency and power density in 48-to-12 V data center applications. This work presents a cascaded multi-resonant variant of this topology that enables further improvements on the power density. The first stage needs only two switches and one flying capacitor to perform a 2-to-1 conversion. The second stage has two interleaved 2-to-1 converters, and shares the resonant inductors with the first stage to realize soft switching and soft charging. With the reduction of active and passive components, this converter achieves a power density of 4700 W/in ³ with a 48 V input and 60 A output, at a fixed 4-to-1 voltage stepdown. Peak efficiency reaches 98.94%, and full-load efficiency reaches 97.97%, including gate drive loss. Both power density and efficiency are superior to the state-of-the-art.