Design and implementation of a DSP-based fast charger for Li-ion battery

This paper provides a fully-digital controlled fast charger for Li-ion battery. The dc/dc buck converter is used as the charger circuit and a DSP TMS320F2812 by Texas Instruments is adopted to control the designed current and voltage loops. By digital controller design, the fast charging method is achieved, including the charging pattern comprised of CC mode and CV mode. The specifications are the input voltage is 9V, the output constant current is 1A, and the output voltage is from 3V to 5V. The Li-ion battery is used as the secondary battery because of the advantages including high energy density, high operation voltage and no memory effect. The Motorola charging method is utilized to implement the fast charging functionality in which a charging period includes a charging time, a rest time and a discharging time. The rest time and the discharging time can speed up the chemical reaction to increase the endurable charging current and shorten the charging time. The charging time is within 40mins in experiments, the change in charging temperature increase is within 1.1°C, and the charging efficiency is up to 87.51%. Experimental results confirm the accuracy of the design and the implementation.