Multiple conversion ratio resonant switched-capacitor converter with active zero current detection

This paper introduces an active method for zero current switching for resonant switched capacitor converters (SCC) with wide dynamic range. The method is demonstrated on a binary SCC that features wide range of conversion ratios. Due to the resultant high efficiency of the converter operating under soft-switching conditions, it is applicable for higher power levels up to the medium power range (100 W). The resonant operation is achieved with a single air core inductor and precise commutation at zero current. The sensing signals of the resonant currents are obtained from the flying capacitors rather than form element in which the current includes a dc component. The zero detection method developed is capable of compensating for both the processing delays (from detection to switching action) and for the large variations of the resonant characteristics (due to transition between subcircuits), and for any other component variations. A 100 W prototype with maximum input voltage of 100 V and up to 19 conversion ratios has been built and tested experimentally. The current sensing has been implemented with a simple, cost-efficient, passive sensor. For proper construction of a higher power experimental prototype with desired target efficiency, a set of design considerations for the selection of the power stage components, based on an expanded equivalent resistance concept for multiple subcircuits converter, has been delineated. In addition, a simple and efficient isolated gate driver circuitry is presented.