ISBN 9783843927642

978-3-8439-2764-2, Reihe Elektrotechnik

Christian Brendler
Leistungsregelung bei drahtloser Energie- und Datenübertragung für biomedizinische Implantate

175 Seiten, Dissertation Universität Ulm (2016), Hardcover, B5

Zusammenfassung / Abstract

Vision is undoubtedly considered to be our most important sense. Loosing the sense of sight is often caused by degenerative eye diseases as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). In our group a biomedical microelectronic implant was developed, that mimics the functionality of photoreceptors, which become dysfunctional for RP and AMD patients. Supplying biomedical implants with energy is a major challenge and is in our application realised using an inductive link. Due to large and fast coupling variations in this inductively powered retinal implant, caused by the eye movement, excessive power has to be controlled. In this work a power control circuit by magnetic field diminishment was developed and combines an open and closed loop power control by attenuating the magnetic field in the secondary coil to reduce received power and using that as an inherent back channel as closed loop power control. By shorting the receiving coil to ground using varying switching pulse repetition rates with a constant short duration to enable a parallel downlink ASK data transmission, the magnetic field is diminished and the load is nearly canceled. This reduces the energy absorbed by the implant and consequently the transmitted power decreases with a slight increase of the voltage amplitude in the primary transmitting coil. These amplitude peaks on the transmitter coil are measured in order to determine the on-chip power control state. Finally, the transmitting power is adjusted in a way to transmit only sufficient power for chip operation. This reduces the transmitting power. Therefore the power control unit within the implant has to control less excessive power. The system was fabricated and measured using a 350nm BiCMOS High Voltage technology. Measurement results show a reduction of the thermal power generated by the implant and compared to a shunt power control the power in the implant can be reduced by a factor of 3.6.