A closed loop transcutaneous power transfer system for implantable devices with enhanced stability

This paper describes a closed-loop wireless inductive power transfer system for an implantable retinal prosthetic device. The proposed system is designed to ensure optimal power transfer to the implanted unit despite coil displacements and changes in load current while minimizing the sensitivity to component and process variation. Based on the system modeling, stability constraints are identified and applied to the feedback control system. The model is crucial in determining component values, circuit topology and number of transmitted bits per sampling period required to ensure system stability. In addition, the model significantly reduces design iterations compounded by lengthy circuit simulation. The model is verified by Matlab and SPICE level simulations. The critical analog circuits of the control system have been designed and fabricated through AMI 1.6 μm process.