Study Of Optimizing The Efficiency Of Wireless Power Transfer For Implanted Devices

Implantable devices play an important role in the medical and health field,which has brought good news to many patients.However,the traditional lithium batteries supplying power for the implanted devices need to be replaced regularly,posing the surgical risk,economic and time burden to patients.Wireless power transfer is an effective way to resolve these problems.Based on the wireless power supply for implantable devices,this dissertation aims to improve the wireless power transfer efficiency.Firstly,the circuit models of the wireless power transfer system of two coils,three coils,and four coils are established,especially the efficiency expressions are obtained.Secondly,three methods,including optimizing geometries of coils,optimizing operating frequency,and using ferrite core,to improve the power transfer efficiency are studied.An optimal value of the radius of the transmitting coil is obtained when the radius of the receiving coil and the powr transfer distance are fixed based on single-turn circular PCB coil situation,which is verified by simulation and experiments.By taking the example of using circular wound wire coil,the optimal operating frequency selection method is introduced based on the analytical models of self-and mutual-inductances,parasitic resistance,and parasitic capacitance.Finally,starting from the demagnetizing factor of magnetic medium,the way of adding ferrite core to the helical coil at the receiving end is studied to improve the efficiency.The formula to calculate the effective relative permeability of the tubular ferrite core is obtained.An analytical model for solenoidal receiving coils with a tubular ferrite core is obtained,which is verified by simulation and experiment.