Automatic Current Sharing Mechanism in the Series Capacitor Buck Converter

This study examines the mechanism and effectiveness of current sharing in a multiphase, series capacitor buck converter. The automatic current sharing mechanism is inherent to the series capacitor buck topology and uniquely utilizes its series capacitor. Unlike conventional multiphase buck converters, current sharing is achieved without any current sensing circuits or added external control loops. Analysis of the automatic current sharing mechanism explains its robustness to variations in inductance, dc resistance (DCR), and temperature. Unequal control switch on-times are found to have measurable impact on sharing accuracy. Results from a two-phase, 12 V input, 10 A output hardware prototype demonstrate the simple, highly accurate current sharing capabilities of the series capacitor buck converter. Experimental results for unequal on times exhibit unmatched average currents but stable operation with a dc offset.