Efficiency Analysis and Optimization of Wireless Power Transfer System for Freely Moving Biomedical Implants

In the wireless power transfer system for freely moving biomedical implants, the receiving unit was generally inefficient for the reason that its design parameters including the receiving coil’s dimension and receiving circuits’ topology were always determined by experiments. In order to build the relationship between these parameters and the total transfer efficiency, this paper developed a novel efficiency model based on the impedance model of the coil and the circuit model of the receiving circuits. According to the design constraints, the optimal design parameters in the worst case were derived. The results indicate that the combination of the two-layered receiving coil and half-bridge rectifier has more advantages in size, efficiency and safety, which is preferred in the receiving unit. Additionally, when the load resistance increases, the optimal turn number of the receiving coil basically keeps constant and the corresponding transmitting current and total efficiency decrease. For 100 Ω load, the transmitting current and total efficiency in the worst case were measured to be 5.30 A and 1.45% respectively, which are much better than the published results. In general, our work provides an efficient method to determine the design parameters of the wireless power transfer system for freely moving biomedical implants