A Single-Mode Dual-Path Buck-Boost Converter with Reduced Inductor Current Across All Duty Cases Achieving 95.58% Efficiency at 1A in Boost Operation

Abstract

In mobile devices, there are various functional blocks requiring different voltage levels, which should be generated from a single lithium-ion battery (Fig. 1), and 3.3V is one of the most demanded voltage levels. Since the battery output voltage discharges gradually from 4.2 to 2.9V, it requires a buck-boost converter that addresses the following challenges. 1) Due to ever-increasing load-current $(\mathsf{I}_{\mathsf{LOAD}})$ demands in the mobile device, the conduction loss by the DC resistance (DCR) of the inductor overwhelms other losses, especially when a small-size inductor is used. 2) At large $\mathsf{I}_{\mathsf{LOAD}}$, the battery output voltage decreases due to its internal resistance, making the boost operation more dominant. 3) Due to the controllability of display brightness and processing speed, burst currents are generated, resulting in unpredictable input voltage fluctuations.