A Power-Efficient Single-Mode Buck-Boost DC–DC Converter With Bilaterally Symmetrical Hybrid Topology

This article presents a bilaterally symmetrical hybrid buck-boost (BS-HBB) dc-dc converter designed for battery-to-3.4-V power conversion. Traditional buck-boost converters suffer from high inductor currents ( $I_{\text {L}}$ ) compared to load currents, resulting in considerable conduction losses. While many hybrid designs incorporating flying capacitors have attempted to reduce $I_{\text {L}}$ , these topologies often struggle with non-smooth transitions between modes, the inability to reduce $I_{\text {L}}$ in either the buck or boost region, and inefficient high-voltage switches with poor ON-resistances. In contrast, the BS-HBB topology proposed in this work enables seamless single-mode operation throughout its entire voltage conversion range. This converter not only achieves lower $I_{\text {L}}$ in both buck and boost regions but also utilizes low-voltage CMOS switches that exhibit low ON-resistance, thereby enhancing power efficiency. The BS-HBB chip was fabricated using a 180-nm CMOS process. Designed to supply up to 1 A, this chip outputs a voltage of 3.4 V from an input voltage ranging from 2.7 to 4.2 V. A peak efficiency of 96.9% (95.5%) was achieved using an inductor having a dc resistance of 9 m $\Omega $ (250 m $\Omega $ ). This work also successfully validated the single-mode operation by demonstrating a flawless output voltage under continuously fluctuating input voltage.