A Generalized Current Self-Sharing Strategy in Whole Operating Range for Series Capacitor Buck Converter

In high voltage step-down and high output current applications, such as voltage regulator modules, electric vehicles, and battery chargers, a series capacitor buck converter (SCBC) is a good choice but only in a limited duty cycle range. In this article, a generalized current self-sharing strategy for the multiphase SCBC is proposed, which has the ability to self-sharing current and uniform ultrahigh step-down ratio in the whole operating range. Through unified analysis of switching modes, the principles of charge-balance and volt-second balance are applied to achieve the self-sharing current and unified linear voltage step-down ratio. The master-slave phase shift (Ms-Ps) modulation strategy for four-phase SCBC is proposed to verify the proposed scheme, showing that the converter will have ultrahigh 1/ ${M}$ -times voltage step-down and sensor-less current self-sharing over the full duty ratio range. Experiment results on 1.8 V/20 A hardware prototype is built to confirm the performance of the proposed strategy.