Abstract
In piezoelectric energy harvesting, the harvesting efficiency can be greatly improved with the switching interface called synchronized switch harvesting on inductor. However, we found from experiments that, the voltage across the piezoelectric element reverses a little bit after every inversion. This reversion, although small compared to the inversion, weakens the inversion effect produced by the switching inductive shortcut, and therefore decreases the voltage magnitude as well as the harvesting efficiency a lot. This phenomenon can also be found from the experimental waveforms in the previous studies; but it has never been pointed out. In these studies, the analytical results, which used the measured effective inversion factor in calculation, agreed with experiments; yet, the origin of the reversion after every switching action, as well as the quantitative relation between the ideal and effective inversion factors are of interest. In this article, the phenomenon on voltage reversion after every inversion is first described. Based on the experimental results, it is analyzed that this reversion is caused by the transducer internal loss. A revised model considering the influence of the internal energy loss is introduced. With this model, not only the reason, which causes the reversion after every inversion, can be explained; but also the quantitative relation between the ideal and effective inversion factors can be obtained. Experiments are also conducted to validate the revised model.
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