Piezoelectric micro generator design and characterization for self-supplying industrial wireless sensor node

Abstract

This paper discusses the design considerations of Piezoelectric MicroGenerators (PMG) dedicated to powering Industrial Wireless Sensors (IWS). State of the art is initially proposed, and it emerges that it is necessary to consider: the characteristics (acceleration@frequency) of the surrounding vibrations, the energy requirement of the IWS (voltage@power), the geometry and the volume of the Piezoelectric Transducer (PT), the choice of piezoelectric materials, and finally, power coupling and conditioning between PT and the rectifier circuit. Note that some of these requirements are ignored in most designs. Several configurations are compared to obtain the best compromise between the output voltage and the harvested power of the PMG. For an acceleration of 0.11 g at 22 Hz, the dimensions obtained for the required PT are 53.5mm×27.6mm×10.232μm, respectively, for the piezoelectric’s length, width, and thickness layers based on the properties of the PMN-PT mono-crystal. The necessary seismic mass is only 20mg to achieve a power of 60.81μW. The characterization of the PT allows to obtain an open-circuit voltage of 6.32V. The harvested energy conditioning circuit is then designed, and to achieve better performance, three commonly considered rectifier circuits are compared. These are the Full-Bridge (FB), the Schenkel type voltage doubler (SVD), and the Latour type voltage doubler (LVD). The LVD topology associated with non-linear processing has made it possible to obtain the best voltage/power compromise. More specifically, it was possible to reach a voltage of 25.32V with a power of 120.7μW when the load resistance is around 25kΩ which would be sufficient to power most currently marketed IWSs.