A Variable-Frequency Asymmetric Control Strategy for Resonant Switched Capacitor Converter with Inverted Output Voltage

Resonant Switched-Capacitor Converter (RSCC) is a promising DC/DC topology due to its high efficiency, high power density and wide output voltage range. This paper proposes a variable frequency asymmetric control strategy for a four switches RSCC, which simultaneously adjusts switching frequency and duty cycle of each switching-leg independently. By leveraging the asymmetric waveform of the resonant current, the proposed control strategy enables all MOSFETs turn on with zero-voltage-switching (ZVS) and three MOSFETs turn off at minimal current. To achieve better performance, a variable turn-off current strategy is further proposed, enabling wider output power range, lower peak current value and reduced switching frequency variation range. A 400W high power density prototype was built and tested, which has recorded 99% peak efficiency at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(-48\mathrm{V}_{\mathrm{d}\mathrm{c}}\ \text{to}\ 48\mathrm{V}_{\mathrm{d}\mathrm{c}})$</tex> case.