Multilevel Buck Converter Topologies and Their Applications

Abstract

Multilevel buck topologies eliminate the limitations of conventional buck converters in some specific areas. In this thesis, novel multilevel buck topologies are proposed to meet the specific requirements of two particular applications respectively. In case I, a two-stage power conversion structure for high-voltage, relatively low-current application, such as E-VTOL aircraft is proposed. Flying capacitor multilevel buck topology with soft-switching operation is utilized to achieve high efficiency, light weight, and lower EMI. In case II, a modular series capacitor buck topology for high-current, low duty ratio application, such as point of load applications. Modularized design, where each module only shares a small fraction of the input voltage and load current reduce switching and conduction losses at the same time. A solution to free duty cycle limitation associated with series capacitor Buck converter to enable fast transient response is proposed. Experimental prototypes have been built and tested to validate the proposed methods.