A High-Efficiency Multimode Li–Ion Battery Charger With Variable Current Source and Controlling Previous-Stage Supply Voltage

A high-efficiency multimode Li-ion battery charger with variable current source and controlling previous-stage supply voltage is presented in this paper. Using variable current source can achieve the goal of constant-current mode to charge the battery and control previous-stage supply voltage which could increase the efficiency of the multimode battery charger. Moreover, the charging mode adopted in this charger is applied by two types of dual-mode strategy decided by the value of the equivalent series resistance of the Li-ion battery. This technique will reduce the damage of Li-ion battery. The Li-ion battery charger is designed with 0.35-mum CMOS double-poly four-metal processes. The experimental results show that the charger works well and the theoretical analysis can be confirmed. The average power efficiency of the multimode Li-Ion battery charger can be up to 91.2% under the average power of 1.24 W, and the accuracy of the adaptive reference voltage is up to 97.3%. The chip area is only 1.32 times 0.95 mm².