Maximum power point of piezoelectric energy harvesters: a review of optimality condition for electrical tuning

This paper is a review and synthetic presentation of existing energy harvesting circuits and techniques for piezoelectric energy scavengers. We provide a hierarchical presentation based on functional analysis to distinguish between existing solutions which may look superficially similar but prove to perform very differently in practice. Based on this hierarchical presentation, definitions of topologies, architectures and techniques are given in order to avoid redundancy among existing and future solutions. Then, after a thorough and unified mathematical analysis of the general problem to address, we present a comparison of the conditions for each technique to maximize the power flow from an external vibration source to an electrical load. This analysis is meant to help researchers and engineers make optimal choices for effective implementation of maximum power point tracking. (topical review)