A Cross-Coupled Hybrid Switched-Capacitor Buck Converter With Extended Conversion Range and Enhanced DCR Loss Reduction

This article presents a hybrid switched-capacitor (SC) buck converter designed to optimize the reduction in inductor average current ( <tex-math notation="LaTeX">IL,DC </tex-math> ) across a wide voltage conversion ratio (VCR) range for Li-ion battery-powered systems. The proposed topology is bases on a modified dual-path (DP) hybrid power stage structure and elevates the inductor de-energizing voltage to enhance <tex-math notation="LaTeX">IL,DC </tex-math> reduction. With a dual-branch interleaved cross-coupled structure, it reduces the required number of SC cells, thereby lowering costs. Moreover, the converter attains a seamless switching-phase transition around VCR of 0.5, ensuring smooth operations and simplifying control complexity. A stable efficiency is maintained across the entire VCR range by balancing inductor DC resistance (DCR) loss and switch/path conduction loss. In the circuit design aspect, a two-quadrant level shifter (2QLS) is proposed to meet power switch driving requirements in a positive-negative wide-range floating domain. Fabricated in a 180-nm BCD process with a 4.42 mm2 chip area, the converter prototype attains a peak conversion efficiency of 91% when converting a <tex-math notation="LaTeX">2.7~~ ~4.2 </tex-math> V input to a <tex-math notation="LaTeX">1~~ ~1.8 </tex-math> V output. It delivers a maximum load current of 4.2 A using two 4.7- <tex-math notation="LaTeX">μ </tex-math> H inductors with 175 m <tex-math notation="LaTeX">Ω </tex-math> DCR in 16.7 mm3 each and achieves an average efficiency of 90% with only 1.5% variation.