A Family of Step-Up Resonant Switched-Capacitor Converter with a Continuously Adjustable Conversion Ratio

In this paper, a family of step-up resonant switched-capacitor converters (RSCs) with a continuously adjustable conversion ratio is proposed based on the Cuk dual-resonance core (DRC) featuring two resonant paths. By adopting the on-time fixed frequency modulation, the two resonant paths can conduct simultaneously and satisfy the charge balance of the flying capacitor during the overlapping period. As a result, the conversion ratio-upper bounded by two determined by the circuit configuration-can vary continuously and efficiently even at the light load condition (1/10 of the rated power). A comprehensive analysis-the operation principle, voltage-gain curve, and voltage/current stresses- A bout the DRC is given. In addition, the Cuk DRC was extended to the series-parallel switched-capacitor converter (SCC), Fibonacci SCC, and voltage doubler to form a family of step-up RSCs, whose voltage-gain curves of different topologies are derived. Moreover, a characteristic comparison between the Cuk DRC and the traditional 'direct' and 'indirect' resonant core is given. Then, a 48 to 62-94.6 V resonant core with peak efficiency 97.8% and maximum power 120 W under the open loop condition was built. The analyses were verified by both experimental and simulation results.