Modeling, analysis and comparison of four charging interface circuits for piezoelectric energy harvesting

Abstract

Four interface circuits have been widely studied in piezoelectric energy harvesting over the last two decades, namely, the standard energy harvesting (SEH) circuit, synchronized charge extraction (SCE) circuit, parallel synchronized switch harvesting on inductor (P-SSHI) circuit and series synchronized switch harvesting on inductor (S-SSHI) circuit. However, the abilities of these four circuits to charge storage capacitors are yet to be understood. This work focuses on the modeling and comparison of the charging process of these four circuits. First, the solutions of the voltage variations on the storage capacitors during charging process in each half-cycle are derived. Subsequently, the equivalent circuit model of the harvester interfaced with SEH and self-powered SCE, P-SSHI and S-SSHI circuits are implemented and simulated to validate the theoretical results. In the evaluation of the four circuits, different electromechanical coupling conditions of the PEH have been considered. The influence of the storage capacitance on charging performance are investigated. It is shown that for the SEH, P-SSHI or S-SSHI circuit, an optimal storage capacitor exists to maximize the accumulated energy and it varies with coupling condition. For a PEH with weak coupling, the P-SSHI circuits is suitable for energy charging. For the medium and strong coupling conditions, the SEH and S-SSHI circuits are more efficient as compared to the P-SSHI and SCE circuits.