Optimized piezoelectric energy harvesting circuit using DC/DC converter

Abstract

Some electrical devices, such as those harvesting energy from vibrations, deliver an AC output voltage that needs to be rectified. A DC / DC conversion stage is, in most situations, necessary for correct management of the recovered energy. This type of circuit makes it possible to raise or lower the voltage delivered by the generator. To some extent to match the impedance. The impedance match plays an essential role in the performance of the transducer, given that its optimum operating point can vary over time, and deviating from this optimum point can rapidly drop the harvested power.Many approaches proposed in the literature are based on switching converters. The operation of these converters is based on the switching of the current between storage elements, inductors and capacitors. The converters step-down or step-up, these have the advantage of allowing the adjustment of the ratio between output voltage and input voltage, which results in a controllable input impedance.In this study, we propose an architecture associating a rectifier and a Buck converter, allowing charging a battery from a piezoelectric transducer. The measurement of the battery charging current is used to define the duty cycle that maximizes the energy harvested. In this case, the DC/DC down converter is appropriate because the transducer provides a voltage higher than 45 V in open circuit, while the considered power range is from 1 to 120 mW. The authors show a 415% improvement in the recovered power, compared to the case of a direct load.