On-Chip Photovoltaic Power Harvesting System With Low-Overhead Adaptive MPPT for IoT Nodes

Abstract

Extracting maximum power from a photovoltaic (PV) harvester with minimum power transfer loss is one of the primary design goals of an energy processing circuit. This paper presents a fully integrated PV power harvesting system with a low-overhead adaptive maximum power point tracking (MPPT) scheme for Internet-of-Things (IoT) nodes. The proposed scheme tracks the MPPs within 12 $\mu \text{s}$ by utilizing an inherent negative feedback loop, within a tracking error of 0.6%. The tracking range has been improved by ~57% using a current-starved voltage-controlled oscillator (CS-VCO) instead of a polynomial VCO. The overhead area and power consumed by this tracking scheme are approximately 0.013% and 0.1%, respectively. Using commercially available solar cell of area 11.3 cm2, the proposed system can provide 833 $\mu \text{W}$ of power with a light intensity of 600 lx. The proposed energy processing circuit has been designed using 0.18- $\mu \text{m}$ CMOS technology node and the circuit simulations demonstrate that the proposed scheme can track maximum power point (MPP) under rapidly changing atmospheric conditions with a peak tracking efficiency of 99%.