Low-Cost Fully Autonomous Piezoelectric Energy Harvesting Interface Circuit with up to 6.14x Power Capacity Gain

Abstract

This paper presents a novel self-powered and fully autonomous interface circuit to extract piezoelectric energy from vibrations available in the environment for supplying DC voltage to electronic loads. A new energy extraction technique called Synchronized Switch Harvesting on Capacitor-Inductor (SSHCI) is utilized, which reduces system cost through a downsized inductor in the range of tens of μH's, while achieving as high voltage flipping efficiency as conventional SSHI circuits. Fabricated in 180 nm standard CMOS technology, the interface circuit has been tested on a MEMS piezoelectric energy harvester with 2 nF intrinsic capacitance in presence of vibrations at 415 Hz resonant frequency. SSHCI circuit provides 6.14× relative improvement over maximum output power of an ideal full-bridge rectifier (FBR) by utilizing a 68 μH inductor to charge a 453 nF storage capacitance. A maximum power conversion efficiency of 90.1% has been measured for SSHCI operation due to low power design techniques and optimized switching time for charge flipping.