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 (
$I_{L,\mathrm{DC}})$
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
$I_{L,\mathrm{DC}}$
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
$^{2}$
chip area, the converter prototype attains a peak conversion efficiency of 91% when converting a 2.7
$\sim$
4.2 V input to a 1
$\sim$
1.8 V output. It delivers a maximum load current of 4.2 A using two 4.7-
$\mu $
H inductors with 175 m
$\Omega $
DCR in 16.7 mm
$^{3}$
each and achieves an average efficiency of 90% with only 1.5% variation.