Performance improvement of flexible piezoelectric energy harvester for irregular human motion with energy extraction enhancement circuit

A Piezoelectric Harvesting Interface with Capacitive Partial Electric Charge Extraction for Energy Harvesting from Irregular High-Voltage Input

“…A simplified circuit diagram of the proposed piezoelectric harvesting interface is shown in Figure 2a. To maximize the energy extraction from the PZT, no external load capacitor is added [14,19]. As the PZT is deformed, C P is charged until V P reaches its peak (V PK ).…”

“…In the case of strong input excitation, where V P can exceed the V MAX , PECE is activated to extract a partial amount of charges from C P , and V P decreases by PECE step voltage (∆V). Here, ∆V is kept to a minimum to keep the electric damping force of the PZT high and to generate maximum energy after a PECE cycle [14,19]. Multi-ratio switched capacitors are utilized to harvest energy from Energies 2020, 13,1939 4 of 12 the PZT and transfer it to the battery.…”

“…For example, when VRECT is near VMAX, a configuration ratio of 1/8 is selected for down- During PZT deformation, a PZT-generated current (I P ) charges the internal capacitance (C P ). To maximize the energy extraction with maximized output voltage (V P ) [19], the load capacitance seen by the PZT is minimized by keeping S 1 and S X turned off. A clocked voltage-level tracker (VLT) is also activated to track the voltage level of V P , and to initiate partial charge extraction in case V P approaches V MAX .…”

“…In the case of strong input excitations (which can generate high V OC ) applied to SSHI or FCR-based harvesters [13,[15][16][17][18], V P does not change much, due to fixed energy storage voltage (V RECT ), which acts as protection against strong input excitations. However, keeping storage voltage limited significantly reduces the energy extraction from the PZT [19], since it decreases PZT damping force, and hence lower energy extraction.…”

Modulation of surface physics and chemistry in triboelectric energy harvesting technologies

“…When a piezoelectric device is deformed by an external mechanical stress, a dipole moment is changed inside the piezoelectric material, and thereby an electric charge is generated [31][32][33][34][35][36][37]. Although inorganic ceramics such as a lead zirconate titanate (PZT) or organic polymers such as polyvinylidene fluoride (PVDF) were widely used as active materials of energy harvesters, but the brittle nature and the thick thickness or the low piezoelectric coefficient caused limitations in the various applications [38][39][40][41][42][43][44]. In recent years, high-performance flexible energy harvesters based on composites or inorganic thin films were successfully developed with the advanced fabrication processes, which are suitable for diverse self-powered biomonitoring and biomedical sensors [45][46][47][48][49][50][51][52].…”