Modeling, analyzing and designing a phase-locked battery charger

In this paper, a linear model for describing the Li-ion battery charging response is developed. Then a Phase-Locked Battery Charger (PLBC) mathematical model is built, and its s-domain transfer function is also derived. The stable, safe and fast charging conditions of the PLBC are discussed and many criteria are proposed. After that, a complete design procedure is presented for designing a fast and safe PLBC. Finally, a test example of the PLBC is designed and implemented for a 700 mAh Li-ion battery in order to assess the performance of the presented Li-ion battery model, PLBC mathematical model and design criteria. Experiments show that the computer simulation is close to the actual measurement. This means that the presented models of the Li-ion battery and the PLBS are correct and can capture major electrical characteristics. Experiments also show that a stable, fast and non-overcharging PLBC is successfully implemented as we wanted. This indicates that the presented PLBC design procedure is valid and can really help engineers design a fast and safe battery charging system.