POWER OPTIMIZATION USING RESONANCE AND ANTIRESONANCE OF MEMS PIEZOELECTRIC VIBRATION ENERGY HARVESTERS

Piezoelectric vibration energy harvesters (PVEH) are a relevant alternative to electrochemical batteries for the electrical powering of the nodes in wireless sensor networks. Usually, PVEH based on a resonant principle are designed in such a way that their resonance frequency matches the dominant harmonic of the input vibration. In some conditions it is possible to adopt a different optimization rule making profit of the frequencydependant electrical impedance of the PVEH and its resonant/anti-resonant behavior. For a similar generated power, this allows tuning the voltage or current delivered by the device, which is of importance for the design of rectifying electronics. The theoretical description of this optimization method and its experimental validation are presented. In the case of microfabricated PVEH based on AlN, it is shown that optimum and almost constant power can be obtained for load impedances ranging from 100 kΩ to 1 MΩ.