Abstract
Among the various methods of extracting energy harvested by a piezoelectric vibration energy harvester, full-bridge rectifiers (FBR) are widely employed due to its simplicity and stability. However, its efficiency and operational range are limited due to a threshold voltage that the open-circuit voltage generated from the piezoelectric transducer (PT) must attain prior to any energy extraction. This voltage linearly depends on the output voltage of the FBR and the forward voltage drop of diodes and the nature of the interface can significantly limit the amount of extracted energy under low excitation levels. In this paper, a passive scheme is proposed to split the electrode of a micromachined PT into multiple (n) equal regions, which are electrically connected in series. The power output from such a series connected MEMS PT allows for the generated voltage to readily overcome the threshold set by the FBR. Theoretical calculations have been performed in this paper to assess the performance for different series stages (n values) and the theory has been experimentally validated. The results show that a PT with more series stages (high n values) improves the efficiency of energy extraction relative to the case with fewer series-connected stages under weak excitation levels.
Highlights
Along with increasing research interests on piezoelectric vibration energy harvesting (PVEH), efficient interface rectification circuits have drawn much attention and interests with respect to extracting as much energy as possible from miniaturized piezoelectric transducers (PT) [1, 2]
This paper addresses the issue of the high threshold voltage that exists in a full-bridge rectifier (FBR), which should be overcome prior to any energy extraction from the piezoelectric transducer (PT)
In order to flip the voltage generated by the PT between the positive and negative threshold voltages, a significant amount of energy is wasted
Summary
Along with increasing research interests on piezoelectric vibration energy harvesting (PVEH), efficient interface rectification circuits have drawn much attention and interests with respect to extracting as much energy as possible from miniaturized piezoelectric transducers (PT) [1, 2]. Full-bridge rectifiers (FBR) are widely employed in commercial energy harvesting systems due to its stability and simplicity; they set high threshold voltages for the generated energy in the PTs to be extracted by the rectifiers [4]. This limitation prevents the system from operating if the environmental excitation is not high enough to attain the required operational threshold voltage, considering miniaturized formats. Assuming Vpp(open) as the peak-to-peak open-circuit voltage generated from the PT, the condition Vpp(open) > 2(VS + 2VD) should be satisfied to transfer energy from the PT to CS. The power performance for different number of series stages is theoretically studied and experimentally validated
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