Design and analysis of multi-stage switched-capacitor-based step-down DC/DC converters

Abstract

A generalized multi-stage switched-capacitor (SC)-based step-down DC/DC converter is presented. It has the prominent features of continuous supply input current and better regulation capability than the classical SC converters. The problem of conducted electromagnetic interference (EMI) with the supply source is minimized. The concept of energy transfer is achieved by using two multi-stage step-down conversion cells operating in anti-phase. The d.c. voltage conversion ratio is controlled by adjusting the charging trajectories of the capacitors in each cell. As the circuit does not consist of any magnetic element, the converter has the advantages of compact size, lightweight, high power density and is possible to be fabricated in IC technology. By using the state-space averaging technique, a simplified fifth-order state-space model is developed for the analysis of the multi-stage converter. The static and the small-signal dynamic behaviors are presented. The experimental results of a prototype with rated power of 66 W, 48 V/12 V is presented.