Multi-load constant current charging technology for wireless charging system

ABSTRACT

In wireless charging system, limited by the coupling effect between the loads and the change of the equivalent impedance of the battery, it becomes difficult to provide efficient and stable energy supply for multiple load devices. In this paper, a multi-load constant current charging technology for wireless charging system is proposed, which combines the primary side control and the secondary side control to achieve quick charge for multiple load batteries at the same time. The system reduces the influence of interference factors by designing the primary side control module and the transmission structure, to ensure sufficient and stable transmission of energy. And utilising the secondary side control module to charge the battery with constant current, which increases the charging speed, and reduces the impact of battery impedance changes on the system’s transmission state. It is verified by experiments that when charging four 1.2 V Ni-MH batteries, the receiver at different positions within the coverage of the transmitting coil can achieve 100mA constant current charging for the battery and the output voltage fluctuation range of each receiver is within 0.2 V, and the working efficiency of the system can reach 70%.