A High-Efficiency Single-Mode Dual-Path Buck-Boost Converter With Reduced Inductor Current

Abstract

This article presents a single-mode dual-path buck-boost converter (SDBBC) for mobile devices powered by lithium-ion batteries. Unlike the conventional buck-boost converter (CBBC), this SDBBC conducts buck and boost operations using a hybrid structure with two flying capacitors (C-F1, C-F2) and one inductor. This hybrid structure eliminates any mode transition between circuit configurations, covering both the buck and boost operations continuously within a single-mode operation. By con-sistently connecting the inductor to the load with a secondary path formed by C-F1 and C-F2, the average of the inductor current (I-L) is always smaller than the load current (I-LOAD) across all the output voltage conversion ratios, thus incurring low conduction loss and switch transition loss. Also, the current delivered to the load increases as the duty ratio increases, so the right half-plane (RHP) zero is removed. Therefore, the proposed SDBBC achieves high power efficiency seamlessly across the whole conversion range, 94.8% peak efficiency is achieved even with an inductor of 175 m omega dc resistance (DCR), and 95.58% efficiency is achieved in the boost operation at a heavy load current of 1 A using a large size inductor with 19 m omega DCR.