A Single-Inductor Dual-Path Three-Switch Converter With Energy-Recycling Technique for Light Energy Harvesting

This work proposes an energy-recycling (ER) technique for power management among a photovoltaic (PV) module, battery, and load in light energy harvesting systems. The ER technique delivers all harvested PV energy directly to the load with surplus energy recycled from the load to the battery, and can eliminate inductor-sharing power switches in single-inductor dual-input dual-output (SIDIDO) converters. Accordingly, the proposed dual-path 3-switch (2P3S) converter, which operates in discontinuous-conduction mode and regulates load voltage by constant-on-time pulse-skipping modulation, was developed. Under dynamic PV power PPand load power PLprofiles, the 2P3S converter's advantageous applications are identified by comparing efficiencies of state-of-the-art SIDIDO converters. The overall efficiency under static PPand PLprofiles and indirect-path efficiency under dynamic PPand PLprofiles are maximized by optimizing switch sizes and on-time. The chip has three power switches and a controller employing low-power circuits, and is fabricated in 0.5 μm CMOS process with 0.5 mm2active area. The measured controller current is 0.85 μA. Under static PPand PLprofiles, for PPof 40 μW, efficiency is 80.7% to 95.0% for 0 μW to 20 mW load power. Compared with other state-of-the-arts, the 2P3S converter has the highest efficiency under static PPand PLprofiles and higher efficiency with more PV energy directly consumed by the load under dynamic PPand PLprofiles.