Self-powered gas sensor IC based on photovoltaic energy harvesting

Abstract

A self-powered gas sensor integrated circuit (IC) suitable for wireless sensor nodes is designed in $0.18\mum$ CMOS process. The novel idea of using the output of the photovoltaic (PV) cell covered by the gas-sensing film allows the proposed sensor system to have low power consumption and compact size. A dual-input shared-inductor boost converter is used to harvest energy efficiently from two PV cells instead of connecting these cells in parallel when the system is exposed to gases. This shows 17% improvement of conversion efficiency at 200ppm nitrogen dioxide gas concentration. Maximum end-to-end efficiency of 87% is achieved at a maximum available power of $446.6\muW$ from two PV cells, and the quiescent current is only 270nA. An input-offset-storage autozeroing technique is used for opamp offset cancellation in order to achieve the high-accuracy gas detection. A modified split-capacitor digital-to-analog converter (DAC) architecture is used for achieving small area in the signal-processing block.