On lossless switched-capacitor power converters

This paper addresses the design of efficient switched-capacitor power converters. The discussion starts with a review of the fundamental limitation of switched-capacitor circuits which shows that the topology of such circuits and the "forced" step changes of capacitor voltages are the inherent attributes of power loss. Although the argument follows from a rather trivial result from basic circuit theory, it addresses an important issue on the maximum efficiency achievable in a switched-capacitor power converter circuit. Based on the observed topological constraint of switched-capacitor power converter circuits, the simplest lossless topology for AC/DC power conversion is deduced. Also discussed is a simple version of lossless topology that achieves isolation between the source and the load. Finally, an experimental AC/DC switched-capacitor power converter, based on the proposed idea, is presented which demonstrates an improved efficiency over other existing switched-capacitor power converters. The proposed AC/DC power converter contains no inductors and thus is suitable for custom IC implementation for very low power applications. >