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

• Published in: IEEE journal of solid-state circuits pp. 1 - 12
• Main Authors: Ma, Qiaobo, Li, Huihua, Zhang, Xiongjie, Zhao, Anyang, Jiang, Yang, Law, Man-Kay, Martins, Rui P., Mak, Pui-In
• Format: Journal Article
• Language: English
• Published: IEEE 05.07.2024
• Subjects: Cross-coupled; DC resistance (DCR); hybrid switched-capacitor (SC); inductor current reduction; Inductors; level shifter; Lithium-ion batteries; Steady-state; Switches; Topology; Voltage
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2024.3416408

This article presents a hybrid switched-capacitor (SC) buck converter designed to optimize the reduction in inductor average current (<inline-formula> <tex-math notation="LaTeX">I_{L,\mathrm{DC}})</tex-math> </inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">I_{L,\mathrm{DC}}</tex-math> </inline-formula> 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 mm<inline-formula> <tex-math notation="LaTeX">^{2}</tex-math> </inline-formula> chip area, the converter prototype attains a peak conversion efficiency of 91% when converting a 2.7 <inline-formula> <tex-math notation="LaTeX">\sim</tex-math> </inline-formula> 4.2 V input to a 1 <inline-formula> <tex-math notation="LaTeX">\sim</tex-math> </inline-formula> 1.8 V output. It delivers a maximum load current of 4.2 A using two 4.7-<inline-formula> <tex-math notation="LaTeX">\mu </tex-math> </inline-formula>H inductors with 175 m<inline-formula> <tex-math notation="LaTeX">\Omega </tex-math> </inline-formula> DCR in 16.7 mm<inline-formula> <tex-math notation="LaTeX">^{3}</tex-math> </inline-formula> each and achieves an average efficiency of 90% with only 1.5% variation.