Research And Design Of Lithium-ion Battery Charger With High Efficiency And Equalization Circuit

Li-ion and Li-polymer battery are being widely used in portable devices. Due to its particularity extremely strict charging requirements, and accordingly it needs a charger of good performance, whether the charger is good or bad plays a very important role for the performance and cycle life of Li-ion and Li-polymer battery. On the basis of the operation principle and charging strategies of Li-ion and Li-polymer battery, a switch mode charger of small and medium-power size that can be used to double, three sections and four lithium battery pack is designed, which the charging current and charging voltage are adjustable, and additional equalization charging protection circuit is added, such that the safety of lithium batteries in the charging process can be improved, and can extend the cycle life of lithium batteries.The design of the whole system is divided into two modules. The first module is the design of the main charging circuit, the use of highly integrated and fully functional charging management and control chip MAX1772, using three-stage constant current and constant voltage charging strategy, based on the structure of a non-isolated step-down synchronous rectification DC-DC converter, achieving constant current and constant voltage charging lithium-ion battery pack with high efficiency; The second module is the design of the balanced charging protection circuit, when the multi-cell lithium-ion batteries charging in series, after the analysis of the necessity of balanced charging, for security charge, plus a balance control circuit of the system, using diverter equilibrium strategy, the equalization protection circuit is designed based on chip S-8209A, improving the prevailing imbalanced charging phenomenon in the market, achieving a supplement to the MAX1772 main charging circuit’s functions.Finally, the results of system experiments and simulation are described. Experimental results show that the charging circuit can high efficiently charge lithium battery with constant current and constant voltage. Built S-8209A simulation model and use OrCAD simulation software to simulate the balanced charging circuit, the simulation results demonstrate the feasibility of the balanced charging and protection program.