Highly accurate and power-efficient battery charger with charging current compensator for wearable devices

Abstract

Highly accurate and power-efficient hybrid battery charger is proposed which includes the switching and linear chargers as well as a charging current compensator. The proposed current compensator operates the switching charger in the constant current (CC) mode to achieve high power efficiency and to improve the charging current accuracy with a small-sized inductor. It also operates the linear charger to minimise the charging current variation in the trickle current (TC) mode and to reduce the battery charging voltage error in the constant voltage (CV) mode. The proposed battery charger was fabricated using a 0.18 m CMOS process and occupies a chip area of 1.63 mm(2). The measurement results show that the proposed battery charger achieves a charging current accuracy of 96.2% in the CC mode, which is improved by 15.8% at a target current of 500 mA, as well as a power dissipation of 0.26 W. In addition, the charging current variation and charging voltage error are measured to be <2 mA(P-P) in the TC mode and 0.48% in the CV mode.