Research On Implantable Wireless Power Transfer System Based On Transmitting Side Detection

Due to the advantage of higher transfer sufficiency and longer transfer distance,the magnetic coupled resonant wireless power transfer technology is suitable for long-term power supply of the implantable medical devices.However,when the transfer distance and the load change,the output voltage of implantable wireless power transfer system will be unstable,which is not good for the operation of the devices.Therefore,it is necessary to study the output voltage stabilization measures of implantable wireless power transfer system.Because of the limited implantable space,the receiving side circuit should be simplified as much as possible.To solve this problem,this paper studies the method of estimating and controlling the output voltage on the transmitting side in implantable wireless power transfer system.The main work of this paper includes:Firstly,based on the equivalent circuit model of the magnetic coupled resonant wireless power transfer system,the expressions of transfer efficiency and voltage gain in four traditional resonant compensation topologies are derived.For the change of mutual inductance and load in the implanted wireless power transfer system.Compare the transmission performance of four traditional resonant topologies.In contrast,the SP resonant compensation topology has higher transfer efficiency and voltage gain,Therefore,it is determined that the SP compensation resonant topology is suitable for application in implantable medical device.For the case where the mutual inductance and load are easily changed,Class D power amplifier is selected as the high-frequency inverter for the implantable wireless power transfer system.Secondly,an output voltage estimation and control method based on the transmitting side detection is proposed for implantable wireless power transfer system with the SP compensation topology.The method identifies the mutual inductance and load according to the reflected impedance on the transmitting side and then estimates the output voltage.On the basis of the estimated output voltage,by adjusting the input voltage of the wireless power transfer system,the output voltage is constant when the mutual inductance and load change.The system output voltage can be controlled by detecting the voltage and current only on the transmitting side.Then,for the above method,the output voltage estimation process is complicated,and the errors in the estimation process is easy to cause the estimation result deviating from the actual output voltage,the LCL resonant compensation topology is used on the receiving side to improve the implanted wireless power transfer system.The transmission characteristics of the S/LCL type radio energy transmission system and the parameters of the resonant inductance are determined,so that the system can maintain high transmission efficiency within the variation range of load and mutual inductance.The output voltage estimation method of implantable wireless power transfer system with the S/LCL resonant compensation topology is proposed.Compared with the method of the SP topology,the process of output voltage estimation is simplified,and the accuracy of estimation is improved.Finally,a prototype of 6.78 MHz implantable wireless power transfer system was built,and the output voltage estimation method of implantable wireless power transfer with S/LCL resonant compensation topology was experimentally verified.The experimental results show that the estimated output voltage is more accurate by using this method.