Circuit Solutions towards Broadband Piezoelectric Energy Harvesting: An Impedance Analysis

TL;DR

This paper presents an impedance-based analysis of various circuit solutions for broadband piezoelectric energy harvesting, introducing an ideal model and comparing practical circuit ranges to guide future high-capability PEH system design.

Contribution

It introduces a comprehensive ideal model for PEH systems, analyzes the attainable dynamic ranges of different circuits, and provides a quantitative impedance analysis to improve broadband energy harvesting.

Findings

Resonance tunability depends on reactive impedance range.

Practical circuits operate within subsets of the ideal dynamic range.

Simulation and experiments confirm theoretical impedance analysis.

Abstract

In the studies of piezoelectric energy harvesting (PEH) systems, literature has shown that circuit advancement has a significant effect on the enhancement of energy harvesting capability in resonance. On the other hand, some recent studies using the phase-variable (PV) synchronized switch technologies have found that the advanced circuit solutions can also broaden the harvesting bandwidth. However, the available span of the electrically induced dynamics by the existing energy harvesting circuits was not properly defined and demonstrated. Performance comparison among different circuits cannot be fairly achieved without using a common theoretical language. Given these, this paper provides an impedance-based analysis and comparison on the electromechanical joint dynamics of the PEH systems using different interface circuits. Given that the resonance tunability by circuit solutions has received no attention in the conventional ideal model of kinetic energy harvester, we firstly propose a more inclusive ideal model for better generalization. In practice, it was proven that the attainable dynamic ranges of the practical energy harvesting circuits are only some subsets of the ideal realm. A detailed quantitative study on the attainable ranges of the PV circuit solutions is provided after the introduction of the ideal target. Simulation and experimental results of different interface circuits show good agreement with the theoretical analysis. It can be concluded that the resonance tunability strongly depends on the achievable extent in the reactive direction of the equivalent impedance plane. In practice, the electromechanical coupling conditions and dielectric loss might also influence the resonance tunability. The general ideal model and quantitative impedance analysis provided in this paper help guide the future design effort towards high-capability and broadband PEH systems.