A Fully Integrated Multilevel Synchronized-Switch-Harvesting-on-Capacitors Interface for Generic PEHs

This article presents a novel architecture for realizing the synchronized-switch-harvesting-on-capacitors (SSHC) technique used for enhanced energy extraction from piezoelectric transducers. The proposed architecture allows full integration by utilizing the storage capacitor already present in most energy-harvesting systems. A promising circuit implementation of the technique, named multilevel SSHC (ML-SSHC), is proposed as well, and its performance is analyzed theoretically. Based on that, a fully integrated and power-efficient transistor-level design in 0.18-mu m CMOS is presented and fabricated in a prototype chip. When operating at a mechanical excitation frequency of 22 Hz and delivering between 1.51 mu m and 4.82 mu W, the measured increase in extracted power is 7.01x and 6.71x, respectively, relative to an ideal full-bridge rectifier. While the performance is comparable to the state of the art, this is the first implementation allowing full integration at such low frequencies without posing special requirements on the piezoelectric harvester.