This article presents a maximum efficiency point tracking (MEPT) scheme for a multiple receivers and loosely coupled wireless power charging (WPC) system with a mutual inductance tracking method. In general, the WPC system should satisfy the requirements of constant output voltage and the highest possible efficiency according to sensitive variation of charging environments. To this end, a state-of-the-art MEPT scheme has been studied in this work. Additionally, one of the advantages of the loosely coupled WPC system is the ability to charge multiple devices simultaneously. However, most studies have focused on a single-input and single-output (SISO) system. In this article, we propose a MEPT scheme for a multiple receiver WPC system and a mutual inductance tracking method. The proposed control scheme determines the current of the transmitter based on the mutual inductance between the transmitter and receivers. For validation, the proposed single-input multiple-output (SIMO) WPC system was implemented at 1 MHz using loosely coupled series-series resonant coils and the proposed mutual inductance tracking method. The results verified the performance of the proposed MEPT scheme in a SIMO system regardless of changing charging environments.
Published in: IEEE Transactions on Microwave Theory and Techniques