A Wide-Dynamic-Range Photovoltaic Energy Harvester With Adaptive Power-Scalable MPPT Control and Direct Power-to-Digital Converter

Abstract

This article presents a photovoltaic energy harvester (PVEH) that achieves high maximum power point tracking (MPPT) efficiency and power conversion efficiency across a 100 000× input power dynamic range (DR) (from 10 µW to 1 W). Wide-dynamic-range operation is challenging due to the inherent tradeoff between MPPT accuracy and controller power consumption. To address this, an adaptive power-scalable MPPT scheme is proposed, employing a direct power-to-digital converter (PDC) that eliminates the need for current sensing, analog multipliers, or lookup tables (LUTs). The PDC utilizes an equivalent power comparison technique, minimizing its power consumption. The MPPT controller autonomously scales its power, consuming minimal energy in low-irradiation conditions while maintaining high tracking accuracy and speed in high-irradiation conditions. Furthermore, a multiple-counting technique mitigates comparator noise and settling errors. Implemented in a 180-nm CMOS process, the harvester achieves a peak MPPT efficiency of 99.9% and maintains >98% across the entire range, representing a 10× improvement in DR over prior art. It also achieves a competitive power conversion efficiency of >82% (peak of 92%) over the same DR.