High-voltage generation using a CMOS image sensor with dual photo-sensing and energy harvesting capabilities

A CMOS image sensor with dual photo-sensing and energy harvesting capabilities is presented. The image sensor is comprised of an array of configurable pixels. Configurable pixels can be programmed to work as tiny solar cells or as photosensors. To work as photo-sensors, the in-pixel photodiode is reverse biased. To work as a solar cell, the reverse bias network is disconnected allowing the photodiode to work in the photovoltaic region. As a proof of concept, an image sensor consisting of a 32 × 32 pixel array has been designed and fabricated in a standard 0.5 m CMOS process. A DC-DC boost converter is proposed to step-up the low voltage of the photodiodes working as solar cells. The DC-DC converter uses a flying inductor to avoid connecting the photodiodes N-well to ground improving the energy conversion efficiency. Measurements show that voltages up to 3.9 V can be generated using the hybrid pixels enough to charge a small battery.