Exponential Flying Capacitor Converter

Abstract

A novel flying capacitor (FC)-based dc-dc converter topology is introduced. This aptly named Exponential Flying Capacitor (EFC) topology achieves an exponential, rather than linear, decline in flying capacitor voltages when compared against the conventional multi-level flying capacitor (MLFC) topology. Such an abrupt drop in FC voltages not only significantly reduces the total operational flying capacitive energy storage/volume, but additionally permits the use of a smaller output filter inductance relative to the conventional MLFC when both topologies are paired equally with more than 3 FCs. This paper describes the structure and operation of the EFC topology, as well as further elaborates on the comparisons between the conventional MLFC. Finally, the potential advantages of the EFC are experimentally verified using a 3-FC, 48 V to 5 V / 3.3 V / 1.0 V (1.0 A) discrete converter prototype running at a 12.5 kHz switching frequency. At these stated operating levels, the 3-FC EFC requires an in-ductor that is up to 3 times smaller compared to the conventional 5-level (3-FC) MLFC.