A Single-Mode Hybrid Buck-Boost Converter with Always-Half Inductor-Current, Use of all CMOS switches, and RHP zero free for Li-Ion Battery Management

Abstract

Mobile devices increasingly require high-efficiency PMICs(Power Management Integrated Circuits) due to rising usage time and the adoption of power-intensive functions such as on-device AI, and high-performance gaming. However, the output voltage of Li-ion batteries varies widely from 2.7V to 4.2V, necessitating DC–DC converters capable of regulating a stable output voltage under significant input variation of Li-ion battery. Conventional buck–boost converters can be feasible option, but it suffer from two inherent limitations: the inductor current always exceeds the output current, leading to high conduction loss, and the presence of a right- half-plane(RHP) zero that degrades transient response. Although numerous hybrid buck-boost topologies have been introduced to mitigate these limitations, they still face several drawbacks: large output fluctuations caused by discontinuous mode transitions; the requirement for high-voltage LDMOS devices that increase cost and area; incomplete inductor current reduction, resulting in high conduction loss; and the presence of RHP zero. To overcome these limitations, this paper proposes a single-mode hybrid buck-boost converter for Li-ion battery management. It uniquely features: 1) seamless single-mode control across buck and boost regions using a single-duty cycle; 2) always-half inductor current enabling significant conduction loss reduction; 3) use of all CMOS switches reducing area and cost; and 4) elimination of RHP zero, ensuring fast transient response. The overall circuit is implemented in TSMC 180nm BCD technology. It operates over an input range of 2.7–4.2V, generates a 3.3V output, and supports load currents up to 1A. A peak efficiency of 97.6% is achieved, and the load transient recovery time, simulated across the full input voltage range(2.7–4.2 V), varies from 9.6µs to 25µs, outperforming those of prior works.