A PZT-based Energy Harvester with Working Point Optimization

Energy harvesters are today gaining ever more interest, enabling the recovery of otherwise wasted energy in a large variety of systems. Among them, piezoelectric devices are particularly suitable to generate electrical energy from vibrations and surplus mechanical energy. A two-stage power conditioning circuit, consisting of a AC-DC converter followed by a DC-DC stage, is usually placed at the output of piezoelectric devices in order to optimize the power yield. The efficiency of the piezoelectric device is, in fact, a very critical parameter, due to the poor power density of energy harvesters based on piezoelectric devices. This paper describes a new single-stage, low-power, converter able to automatically follow the variations of the resistive component of the output impedance of a cantilevered PZT (Lead Zirconate Titanate) based piezoelectric energy harvester in order to maximize the energy yield.