Analysis of the wireless charging's multiple coils structure and efficiency based on magnetic field

The wireless charging system based on inductive coupled power transfer (ICPT) is widely used in mobile phone charging and electric vehicle (EV) charging because of its high efficiency. The main structure includes rectifier/inverter circuit, loosely coupled transformer and so on. In order to find out the mutual inductance characteristics, the different kinds of coil structures were analyzed. Aim at the inductive wireless charging system, the structure of the primary coil is changed to improve the coupling performance of the system and the number of the primary coils is increased into two or three. Through the comparison of different structures, the better structure is selected. Also the modular processing of the system can reduce the use of high power devices, so the cost can be reduced and the stability can be improved. The derivation of the coupling coefficient of multi coils is provided. The result provides a theoretical basis for the application of engineering.