An Efficient Inductive Coil Link Design for Wireless Power Transfer to Visual Prostheses

Powering therapeutic devices plays a crucial role in the design phase of implantable electronic units. Batteries could not provide sufficient charge storage, used for the lifetime of the device, considering the space available for them. As sophisticated surgical procedures are required with the possible trauma to the patient such as material discrepancy and tissue damage, replacement is quite risky and not an option. Thus, therapeutic devices, especially visual prostheses, receive power wirelessly through inductive coil links which are connected to a battery outside the body. An inductive link is based on the main principle that there are two components such as primary and secondary units. Although primary unit includes the battery outside the body, power transmitter, and control unit, secondary unit under the skin contains amplifier, rectifier regulators, and power control unit. In this study, an inductive coil link is modelled to evaluate fundamental design specifications for visual prostheses. Inductive coil link parameters are quantitatively investigated so that maximum power transfer efficiency and miniaturization, which are critically important for electronics placed in intraocular region, are provided. Considering 20 mm distance, it is concluded that the separation and the size of the coil pair, loop diameter, frequency have a major role to determine the system performance.