Characterization of capacitor charging by vibration-based piezoelectric power generator

Mechanical vibration energy can be converted into electrical energy using piezoelectric power generator. The electrical energy is usually collected by a storage capacitor instead of being directly consumed by the load. In this way, to characterize the charging of the storage capacitor is important and necessary. This paper focuses on the characterization of the piezoelectric power generator with capacitive load. Analytical expression of the voltage across the storage capacitor is derived and analyzed. Analysis results show that the storage capacitor is exponentially charged and the maximum instant power occurs when one-half the maximum voltage of the storage capacitor. These analytical results are well conformed by experiments. They are useful for both macro and MEMS-based energy-harvesting devices.