Research On Relay Wireless Power Transmission Technology For Implantable Medical Devices

Implantable medical devices,as electronic devices implanted into living organisms or human bodies,play a vital role in the field of biomedical healthcare.Traditional implantable devices usually rely on wires or batteries for power.Wire power can pose risks and may lead to skin infections,while battery power requires frequent battery replacements and also limits the size of implantable devices.The emergence of wireless power transmission technology provides a new solution for powering implantable medical devices.This thesis focuses on the three-coil relay-type wireless power transmission system used for implantable medical devices,with the goal of improving transmission efficiency.The main contents are as follows:First,starting from the traditional two-coil wireless power transmission system,this thesis establishes a circuit model,derives the typical circuit’s transmission efficiency,and analyzes the impact of load and coupling coefficient on transmission efficiency.At the same time,similar derivations are carried out for the three-coil system to lay the theoretical foundation for the subsequent research.Second,in order to study the optimal position of the relay coil in the three-coil system from an efficiency perspective,this thesis starts from the transmission efficiency formula of the three-coil system and obtains the numerical solution for the relay coil’s position when the transmission efficiency is maximum.Simultaneously,this thesis deduces that the optimal position of the relay coil depends on the size of the load;the larger the load,the closer the relay coil should be to the receiving coil,which is verified through simulation.Next,inspired by the optimal position of the relay coil,this thesis directly connects the relay coil to the receiving coil and introduces two different structures based on the compensation capacitor’s connection method.One structure is a two-coil system with a double-layered receiving coil,for which the number of coil layers is the research object,and its impact on transmission efficiency is analyzed.The other is a three-coil structure with a shared compensation capacitor,which can reduce one component to decrease the size of the implantable device and is suitable for larger loads compared to traditional three-coil structures.Finally,this thesis combines the above research contents to optimize the three structures of traditional three-coil,double-layered receiving coil of two-coil,and shared compensation capacitor of three-coil in different load application scenarios.The study shows that the double-layered receiving coil of the two-coil structure has the maximum load capacity,while the traditional three-coil structure has the minimum.Eventually,in an implantable environment,when the transmission distance is 20 mm,the receiving coil size is 9 mm,and the load is 156 kΩ,the transmission efficiency is 5.8%,which is higher than the current application with the same load but larger size and closer distance(transmission efficiency of 5.5%).This study provides guidance for the design of relaytype wireless power transmission systems in different implantable application scenarios and has certain reference significance.