A 500nW-50μ W Indoor Photovoltaic Energy Harvester with Multi-mode MPPT

Abstract

A 500nW$- 50 \mu \mathrm{W}$ indoor photovoltaic energy harvester is presented with a multi-mode maximum power point tracking (MPPT) circuit. Three switched-capacitor DC-DC converters (SCDCs) with different switch sizes and flying capacitors are realized. A multi-mode MPPT circuit is presented to tune the voltage conversion ratios and the switching frequency of the SCDCs. In addition, this multi-mode MPPT circuit also utilizes three reconfigurable SCDCs to cover the input power range of 500nW $\sim 50 \mu \mathrm{W}$. This indoor photovoltaic energy harvester is realized in a 0.18m CMOS process and its active area is 1.15mm2. The measured peak power conversion efficiency is 64.4%.