A piezoelectric energy-harvesting interface circuit with fully autonomous conjugate impedance matching, 156% extended bandwidth, and 0.38μW power consumption

Abstract

Harvesting energy from ambient vibrations with piezoelectric transducers is an alternative solution for the surging needs of self-powered devices, such as IoT devices, condition and structural monitoring devices, or biomedical implants. A limiting factor for piezoelectric transducer is the narrow bandwidth due to the high mechanical quality factor. Therefore, the output power drops significantly when the excitation frequency deviates from the resonant frequency in a real environment. One solution is to introduce time delays into active harvesting-interface concepts such as Synchronous Electric-Charge Extraction (SECE) or Synchronized Switch Harvesting on Inductor (SSHI). This emulates conjugate impedance, which matches that of the transducer, resulting in higher power from vibrations at non-resonant frequencies.