Using a Strong Coupling Effect to Reduce the Size of the Receiving Coil without Reducing the Stability of the Inductive Energy Transfer System to Implants

The study of methods for reducing the size of the implanted part, including the receiving coil of the inductive energy transfer system, is a topical area of development of implantable medical devices. At the same time, miniaturization of the receiving inductance coil reduces the system’s resistance to displacements; i.e., it leads to an increase in the power drop when the relative position of the receiving and transmitting inductance coils changes. Therefore, it is necessary to develop methods for reducing the size of the receiving inductance coil that allow maintaining the required resistance to displacements. In this study, a method for reducing the size of the receiving inductance coil is proposed, based on the simultaneous reduction in the size of the receiving and an increase in the size of the transmitting coil. The developed method is based on an algorithm for designing inductance coils, which ensures the achievement of the specified stability for the given range of displacements. The result of the algorithm is used to minimize the size of the receiving coil, which consists of a coordinated change in the size of the receiving and transmitting inductance coils to a certain limiting point, upon reaching which further change in size while maintaining the specified output characteristics becomes impossible. The developed method is verified by numerical modeling. According to the calculation results, it is established that the size (outer radius) of the receiving coil can be reduced by 30%. It is demonstrated that the limiting point is reached when the critical coupling between the coils occurs at the given (nominal) axial distance in the absence of lateral displacements. If the coupling between the coils is higher than critical at the nominal axial distance, it is possible to reduce the size of the receiving inductance coil.