Dual-Path Three-Level Buck Converter With Loop-Free Autocalibration for Flying Capacitor Self-Balancing

Abstract

This letter proposes a loop-free autocalibration technique for self-balancing of flying capacitors in a three-level dc-dc buck converter. The proposed converter utilizes a dual-path power stage with balancing switches that adaptively short flying capacitors at de-energizing phases. Thus, the dual-path three-level converter ensures that flying capacitor voltages are self-balanced at half the input voltage without using additional feedback calibration loops, leading to robust operation and competitive efficiencies. The prototype was fabricated in the 0.13-mu m CMOS BCD process and adopted two flying capacitors of 4.7 mu F each and an inductor of 10 mu H with a dc resistance of 128 m omega. When an 8-V input was converted to a 3-V output voltage with a load current of 400 mA, the measured efficiency was 88.6% at 800 kHz switching while flying capacitors are automatically balanced.