A Novel Non-Mirrored Buck-Boost Flying Capacitor Multilevel DC-DC Converter Topology

Enabling future electrification of air and ground transportation requires flexible, compact, and highly efficient power converters. Four-switch non-inverting bidirectional buck-boost dc-dc converters allow for wide and overlapping input and output voltage ranges, enabling integration of fuel cells and batteries whose voltages vary with state of charge and operating conditions. In this work, we propose a novel non-mirrored buck-boost (N-MBB) Flying Capacitor Multilevel (FCML) dc-dc converter. The proposed topology integrates the conventionally separated buck and boost bridge-legs, which is enabled by novel monolithic bidirectional GaN transistors featuring bipolar voltage blocking capability. Compared to the conventional mirrored buck-boost FCML converter, the proposed topology shows a higher inductor volume but advantageously a lower component count, better utilization of the installed chip area and flying capacitors, and lower conduction losses. Finally we introduce a topology variant with reduced inductor volume, the return-path-inductor (RPI) N-MBB FCML, and a direct non-isolated single-phase dc-ac N-MBB FCML inverter.