A Direct 24- to 1-V Multilevel Multiphase Hybrid Buck Converter With Automatic V CF Balancing and Current Sharing Mechanism

This article presents a multilevel multiphase (MLMP) dual-path hybrid buck converter for direct 24- to 1-V step-down conversion. Unlike the conventional multilevel buck converter, which requires extra calibration loop(s) to tune the flying capacitor voltage(s) ( $V_{\mathrm {CF}}$ ), automatic $V_{\mathrm {CF}}$ balancing is achieved in the proposed MLMP hybrid buck converter. The intrinsic current balancing among output phases is also attained without the need for dedicated development of current sensors. To reduce the high conduction loss from a high dc resistance (DCR) of the inductor, a dual-path hybrid output stage is adopted, where an assisted capacitive path is added to reduce the current stress on the main inductive path. Thus, DCR's conductive loss is greatly reduced. Detailed analyses on the natures of automatic $V_{\mathrm {CF}}$ and current balancing, the loop performances, and power losses are provided. To verify the effectiveness of the proposed structure, a prototype converter is built. Compared with the MLMP converter using a conventional buck converter (CBU) as the output stage, the conversion efficiency of the proposed MLMP converter with the dual-path hybrid output stage is increased by up to 6.3% at a load of 10 A. The peak efficiency is up to 89% with an adopted inductor with DCR of 2 $\text{m}\Omega $ .