TSV Based Orthogonal Coils With High Misalignment Tolerance for Inductive Power Transfer in Biomedical Implants

To improve the misalignment tolerance for inductive power transfer (IPT) systems in implantable medical devices, like retinal prosthesis, a 3-D through silicon via (TSV) based orthogonal receiving coil is proposed in this brief. The mutual inductance between the receiving coil and the transmitting coil is calculated, analyzed, and compared. Results obtained from the analytical model and finite element method show the proposed coil structure significantly enhances the inductive coupling between coils under misalignment. Furthermore, we present receiving circuits with current summing techniques to enhance the energy transfer between the receiving coil to the load. The prototype of the inductive power transfer system is developed and the experimental results demonstrate that the proposed coil structure can provide a good misalignment tolerance. A maximum variation of the power transfer efficiency (PTE) is only 18.0% under angular misalignment of 90° and 23.4% under lateral misalignment of 37.5% of the transmitting coil's diameter, which indicates the proposed coil structure can meet the demand of IPT systems in retinal prosthesis applications.