Abstract
Purpose :
The conventional circuits for artificial retina system has diode-based power transmission and recovery circuit, showing low power transmission efficiency and high stimulation power consumption. In this work, CMOS-based circuit and channel sharing-based stimulation circuit is investigated to maximize output power delivery.
Methods :
A transformer using near field wireless power transmission was designed to deliver maximum power with a limited size receiver coil. Clocks generated by non-overlapping clock generator are passed through amplifying part to series - parallel tuned transformer. In consideration of low coupling by body tissue between transceiver, a robust power recovery circuit is designed for k factor that can deliver target power and voltage. A channel-sharing stimulation circuit is designed so that one current generator can stimulate several electrodes continuously. Suggested circuit connects one channel to four electrodes at the same time, allowing each electrode to be stimulated in chronological order to reduce instantaneous maximum power consumption while using a 60Hz fixed frame rate, ensuring stimulation frequency. In addition, the cathodic and anodic currents can be designed to flow on nearby electrodes at the same time, aiming spatial resolution.
Results :
By tuning the transformer, we designed a power recovery circuit delivering 5V output voltage and nominal 40mW was delivered to the output with 3V of input voltage without additional matching network at coupling condition of k = 0.037. With channel sharing technique, one current generator designed to sequentially stimulate four electrodes, resulting in reduction of instantaneous maximum power consumption of the stimulator stage by a quarter. Moreover, the time allocation using 60Hz fixed frame rate greatly reduces circuit complexity of the digital controller stage. The whole stimulator system designed to have little effect on actual stimulation frequency.
Conclusions :
A circuit focused on delivering power efficiently in harsh coupling condition was designed, and target output power could be achieved regardless of weak coupling condition compared to existing artificial retina stimulation circuit. In the future. In vivo performance will be evaluated as a whole package soon.
This is a 2020 ARVO Annual Meeting abstract.