A Conversion-Ratio-Insensitive High Efficiency Soft-Charging-Based SC DC-DC Boost Converter for Energy Harvesting in Miniature Sensor Systems

A switched-capacitor (SC) DC-DC boost converter suitable for energy harvesting in IoT sensor systems with varying harvesting source and battery voltages is presented in this paper. Unlike the conventional multi-staged SC DC-DC converters, where efficiency is optimized only for a few topology-dependent conversion ratios, soft-charging-based SC conversion is adopted to achieve conversion-ratio-insensitive high efficiency. With soft-charging flying capacitors with small voltage steps, charge redistribution loss is minimized and evenly high conversion efficiency can be achieved for a wide range of input and output voltages. The proposed converter exhibited evenly high efficiency by achieving a peak efficiency of 85.3% and an average efficiency of 83.6% for generating regulated 1.8V output from a wide range of input voltages (0.9-1.8V). It also achieved a peak efficiency of 88.9% and an average efficiency of 87.6% for harvesting energy from a 1.2V source with a wide battery voltage range (3.0-4.2V).