Adaptive piezoelectric energy harvesting circuit for wireless, remote power supply

Efficiency of energy conversion for a piezoelectric power harvesting system

“…Note that (5) is identical with that derived by [39,43,44]. We next need to find out u 0 to determine V c .…”

“…Note that the regulation circuit and battery are replaced with an equivalent resistor R and V c is the rectified voltage across it. The common approach to having the stable output dc voltage is to assume that the filter capacitor C e is large enough so that the rectified voltage V c is essentially constant [39]. Specifically, V c (t) = V c (t) + V ripple , where V c (t) and V ripple are the average and ripple of V c (t), respectively.…”

“…If the modal density of such a device is widely separated and the structure is vibrating at around its resonance frequency, we may model the power generator as a mass+spring+damper+piezo structure, as schematically shown in figure 1 [33,39,44]. It consists of a piezoelectric element coupled to a mechanical structure.…”

“…It is shown that direct charging will result in a low efficiency of energy conversion, since the equivalent impedance of the battery may not match that of the optimal load in most situations. Ottman et al [39,40] have developed an adaptive electric circuit to optimize the energy transfer from the piezoelectric element to the stored device. It is based on the principle of load impedance adaptation by tuning the load impedance to obtain a higher power flow.…”

Introduction to Smart Structures

“…In some cases the 'harvesting' of electrical energy by means of piezoelectric devices could apply to many devices that are not reached by the wires of an electrical connection but have some vibrating parts, as proposed by Lesieutre [26]. A review of the research findings in the field can be found in [27].…”