Power Optimization of Vibration Energy Harvesters Utilizing Passive and Active Circuits

This article presents the maximum power operating conditions for piezoelectric energy harvesters when connected to several different circuit topologies. Four circuits are studied herein for comparison: a simple resistive load, the standard rectifier circuit, and parallel and series synchronized switch harvesting on inductor. A single-mode model of a vibration-based energy harvester under base excitation is developed to capture the important dynamics near its fundamental resonance while providing a simple basis for performing design optimization. Relevant dimensionless parameters are given to provide a scale-free context for discussing the optimal operating points. For a prescribed vibration energy harvester, the base excitation frequency and load impedance for maximum power generation are provided by the results of this study. Furthermore, the effects of mechanical damping, electromechanical coupling, circuit quality factor, and rectifier forward voltage are presented. These effects are discussed in order to cite the salient parameters in the design of these energy harvesting systems.