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

This paper introduces a fully integrated switched-capacitor (SC) DC-DC boost converter suitable for energy harvesting in miniature sensor systems with varying harvesting source and battery voltages. Unlike the conventional SC DC-DC boost converters, where efficiency is optimized only for a few topology-dependent voltage conversion ratios (VCRs), the proposed soft-charging-based SC converter achieved VCR-insensitive evenly high efficiency for a wide range of input and output voltages. A test chip was fabricated in 180nm process, and the measured peak efficiency and average efficiency are 85.3% and 83.6%, respectively, for 1.8V regulated output voltage and a wide range of input voltages (0.95-1.8 V). Also, a peak efficiency of 88.9% and average efficiency of 87.6% are achieved for a wide range of battery output voltages (3.0-4.2 V) and a 1.2V harvesting source input voltage.