An integrated voltage-current compensator of LLC resonant converter for Li-ion battery charger applications

The typical conventional battery charger requires the two separated voltage and current compensators to achieve both the constant current and the constant current (CC-CV) charging profile. This paper proposes a single integrated voltage-current compensator of the LLC resonant converter for lithium-ion battery charger applications. The proposed compensator is designed to provide a smooth and reliable performance during entire charging process, while providing the reduced design efforts and seamless mode transient response due to its inherent integration. The theoretical analysis and the design consideration of the proposed compensator is illustrated based on a frequency response domain, especially with the considerations of the nonlinearly varied equivalent resistor and/or effective capacitance based on the proposed battery model, and as a result, the integrated compensator guarantees a stable and robust operation. Finally several experimental results verify the effectiveness of the proposed posed compensator and its theoretical analysis.