A Switching-Inductor Hybrid Step-Down DC-DC Converter for Battery Charger Applications Implemented in CMOS Process

This letter presents a switching-inductor hybrid dc-dc converter designed for battery charger applications, operating with a 5 V input and an output range of one-cell battery (3–4.3 V). The hybrid converter effectively reduces the rms inductor current compared to conventional buck and three-level buck converters, enabling the use of a compact inductor while maintaining high efficiency. The design has been fabricated in a 180 nm CMOS process and is implemented using only CMOS devices. To enable high-voltage operation up to 8.6 V without requiring high-voltage laterally diffused MOS (LDMOS) transistors, a level-shifted gate driver is proposed. The measurement results demonstrate a peak efficiency of 96.3% using a 2.2 μH compact discrete inductor with a dc resistance (DCR) of 46 mΩ. In addition, efficiency and DCR loss analysis with different inductors verify that DCR loss is not the dominant factor in the overall power loss of the converter, validating its effectiveness for compact and efficient power management applications.