Power supply system using electromagnetic induction for three-dimensionally stacked retinal prosthesis chip

We have proposed a new retinal prosthesis system consisting of a three-dimensionally (3-D) stacked retinal prosthesis chip, a flexible cable with an electrode array stimulus, and a power supply system for the retinal prosthesis chip. Electromagnetic induction with a primary coil and a secondary coil was employed as the power supply system. The power was transmitted to the retinal prosthesis chip through an RF/DC voltage conversion chip that converted AC voltage into DC voltage. The 3-D stacked retinal prosthesis chip operates with a DC supply voltage of 3.3 V, and the secondary coil requires a transmitted voltage that is 1 V higher than the DC supply voltage. In order to receive a sufficient supply voltage, several parameters such as external supply voltage and transmission frequency were optimized. A peak RF voltage of 4.5 V was obtained when we employed a primary coil with 50 turns, a secondary coil with 20 turns, an external supply voltage of 4.1 V, and a frequency of 3 MHz. We also successfully fabricated Schottky barrier diodes to rectify the RF voltage received by the secondary coil. The fabricated Schottky barrier diodes have a high breakdown voltage of 4.6V, which is sufficient for our 3-D stacked retinal prosthesis chip.