An Energy Harvester Using Image Sensor Pixels With Cold Start and Over 96% MPPT Efficiency

Abstract

This letter presents an energy harvester using conventional 4-T CMOS image sensor pixels in 0.13-µm CMOS. Its 320 240 pixel array can be time multiplexed to capture images or harvest energy. Among reported pixels with energy harvesting capability, we achieve the highest fill factor of 60.4% at a pitch of 5 µm. Auxiliary photodiodes that are placed outside the imager array generate a supply rail that enables cold start at incident light levels as low as 25 lux. A switched-capacitor (SC) boost converter steps up the harvested energy from 0.25–0.4 V to 1.8-V analog and 0.6-V digital supplies. The design achieves a peak power efficiency of 52.4% at an output power of 266 nW, while its analog maximum input power point tracking control circuit maintains over 96% tracking efficiency across all lighting conditions.