Analysis and optimization of self-powered parallel synchronized switch harvesting on inductor circuit for piezoelectric energy harvesting

Due to its strong environmental robustness and high energy density, piezoelectric energy harvesting is considered one of the most promising methods to power wireless sensor nodes under extreme conditions. The interface circuit is essential to a piezoelectric energy harvester to reduce internal energy dissipation, achieve impedance matching, and improve energy conversion efficiency. Existing researches show that a parallel synchronized switch harvesting on inductor (P-SSHI) interface circuit compared with a standard energy harvesting (SEH) circuit can significantly improve the output power. Therefore, this paper proposes a self-powered optimized PSSHI (SP-OPSSHI) circuit, which adopts a new peak detection switching circuit to replace the switches in the P-SSHI circuit. It can realize switch control without an external starting power supply, i.e. cold start. Compared with an existing self-powered PSSHI (SP-PSSHI) circuit, it can effectively eliminate the 'second inversion' phenomenon caused by the parasitic capacitors of transistors after the voltage inversion process. The cause and effect of 'second inversion' on energy harvesting are analyzed in this study. Then, the working principle and process of the optimized circuit are discussed, and energy harvesting under the ideal state is conducted. Finally, the SP-OPSSHI circuit is developed and tested. The experimental waveforms show that the SP-OPSSHI circuit compared with the SP-PSSHI circuit can significantly reduce the impact of parasitic capacitors in the energy harvesting process. The output performance of the SP-OPSSH circuit is tested with the variation of resistance. The experimental results indicate that the SP-OPSSHI circuit has an optimal load resistance of 350 k omega, achieving a maximum harvested power being 2.91 times that of the SEH circuit.