Design of a High-Efficient IPT System for Battery Charging Under CP-CV Charging Scenarios

Maintaining high efficiency and controlling output voltage with variable load is challenging for inductive power transfer (IPT) based battery charging systems. In addition, choosing the proper charging scenarios simultaneously with the battery's equivalent load variation significantly improves the charging rate. This paper proposes a semi-active rectifier (SAR) battery charging system on the basis of a series-series resonant IPT system using constant-power (CP) and constant-voltage (CV) charging modes. A novel control approach based on the adaptive selection of the operating frequency of IPT and the conduction angle of the SAR is used to achieve high efficiency in CP-CV modes. The inverter and the SAR are both capable of soft switching. Furthermore, considering the same maximum power in CP and constant-current (CC) modes, the CP mode offers more charging rate with less destructive effects. The proposed control strategy has been simulated, and a prototype system is implemented to show the high-efficiency performance of the system during CP-CV modes.