Wireless Power Transfer to a Visual Prosthesis: 100 mW at 6.78 MHz

An inductive wireless power transfer system for a neural implant is presented. The prototype can transfer 100
$\mathbf{mW}$
at 6.
$\mathbf{78}$
MHz transcutaneously for
$0.08\leq k\leq 0.31$
, which corresponds to a distance of 8 to 15 mm, and a lateral misalignment of 0 to 15 mm. The achieved efficiency ranges from 55 to 77 %, depending on the relative distance between the coils. The transmitter coil outer diameter is 55 mm, the receiver coil outside diameter is 35 mm. The inverter is class-E, using a GaN MOSFET, and the receiver is class-DE.