Design of programmable switched-capacitor DC-DC converters with arbitrary conversion ratio

Switched-capacitor (SC) DC-DC converters have been widely used for their compatibility to a fully on-chip implementation of DC-DC converters. The conversion ratio of a SC DC-DC converter is determined by its topology. This means, in order to obtain various conversion ratios, different circuit topologies are required. It has been a drawback of SC DC-DC converters. This paper proposes an SC DC-DC converter with programmable conversion ratio. The proposed programmable SC DC-DC converter is based on a systematical topology derivation using continued fraction. A design strategy to reduce the complexity of control circuit is presented. The validity of the proposed system is demonstrated using Hspice simulation of a buck converter with various conversion ratios. Although there is a small error in the output voltage due to charge injection of the switches, the output voltage of the proposed SC DC-DC converter approaches the ideal value.