|Title||Power Converters for Piezoelectric Energy Extraction|
|Publication Type||Conference Paper|
|Year of Publication||2006|
|Authors||Ngo, K., A. Phipps, T. Nishida, J. Lin, and S. Xu|
|Conference Name||Proceedings of ASME International Mechanical Engineering Congress and Exposition, Paper IMECE2006-14343|
Passive circuits and active circuits (i.e., switched-mode power converters) for vibration-energy harvesting are reviewed, focusing on power-extraction efficiency (PEE). Optimal battery voltage and resistance are given for maximal power extraction by passive circuits. Switched-mode converters are reviewed as means to match the actual battery voltage or load resistance to the optimal ones. To emulate the optimal battery voltage or load resistor, these converters could be controlled by pulse-width modulation (PWM) or by resonance, could operate in continuous or discontinuous conduction modes (CCM or DCM), and could leverage the piezoelectric (PZT) impedances in the energy extraction process. The large filter capacitor usually found after the bridge rectifier actually degrades the PEE. Resonance between the output capacitor of the PZT and the converter inductor improves the PEE at the expense of higher voltage and current stresses.