Modified charge inversion and extraction switching strategies for a strongly coupled piezoelectric vibration energy harvester

Abstract

The objective of this study is to enhance the output power of a high-electromechanical-coupling piezoelectric vibration energy harvester, incorporating a synchronous inversion and charge extraction (SICE) circuit. The SICE circuit employs charge inversion and charge extraction switches to boost the voltage of the piezoelectric transducer and to extract electrical energy. In cases of weak electromechanical coupling, the SICE circuit is preferred over the synchronized electric charge extraction circuit. However, when a strongly coupled transducer is used within the SICE circuit, harvesting efficiency can decrease. In this study, two novel methods for controlling the SICE circuit were introduced: short-duration switching and phase-shifted switching. An analytical model was developed to examine the relationship between the phase shift required for switching and the output power. The voltage generator model of the piezoelectric transducer was used to illustrate the temporal variation in the piezoelectric charge. The analysis revealed that the piezoelectric charge in the voltage generator model remains constant during the intervals between switching operations. This characteristic is beneficial for the theoretical computation of solutions to the equations of motion. The numerical simulations and experimental results confirmed the effectiveness of the proposed methods, which achieved a 48% improvement in the output power of the SICE circuit, particularly for strongly coupled energy harvesters.