Taguchi-Based Design of Planar Circular Coils Used in Wireless Charging of Mobile Phones

In this study, a Taguchi-based optimization method is proposed to search the coil parameters used for low-power wireless charging that will maximize the transmission efficiency. The coils were then implemented to charge a battery with a nominal voltage of 3.7 V and a rated capacity of 760 mAh, and it was found that the coil transmission efficiency increased by 3.7% compared to adopting the coil parameters obtained by using a genetic algorithm. Moreover, a 5-watt wireless charging system integrated with the Taguchi-based coils was built to charge a battery with a nominal voltage of 3.7 V and a rated capacity of 2200 mAh. The results showed that the coil transmission efficiency was higher than that of a commercial charger, but the dimension of the coil was larger than that of the commercial charger. Nevertheless, the air gap between transmitter and receiver coils was larger than that in the charger, and the charge time required for a 2200 mAh battery to reach a full charge was shorter than that required for the commercial charger. Although outcomes are still far from being satisfactory in the transmission efficiency, the proposed approach can greatly reduce computation cost in designing coils used for wireless charging.