High-efficiency multi-mode linear battery charger with adaptive current sensor for multiple energy harvesting systems

Abstract With the increasing integration of energy-harvesting systems into low-power applications, the need for efficient and accurate battery-charging circuits has become critical. In such systems, fluctuating energy sources affect the stability and precision of conventional linear chargers, especially in terms of current sensing and charging efficiency across a wide range of charging currents. To address these challenges, this paper proposes a multi-mode linear battery charger that incorporates an adaptive current sensor based on a current-reuse structure. This sensor dynamically adjusts its sensing ratio to maintain high accuracy under variable input conditions. The proposed charger supports Li-ion batteries and operates in three charging modes trickle charge, constant current, and constant voltage to accommodate charging voltages from 3.8 to 4.8 V. Across a charging current range of 10–500 mA, the design achieves a minimum current-sensing error of 0.05% and a maximum charging efficiency of 95.62% at 4.8 V and 500 mA. A compact and high-performance solution for energy-harvesting battery is fabricated in a 130 nm BCD process, where the entire layout area is 750 µm × 650 µm.