An Improved Rectifier less Switching Circuit for Piezoelectric Energy Harvesting Systems

This paper describes an improved rectifier-less switching circuit (IRLSC) for active rectification of voltage and reduction of ripples in its waveform for piezoelectric energy harvesting (PEH) system. The proposed converter controls the alternating current (AC) generated by the piezoelectric device (PD) under mechanical vibration. The proposed circuit combines the boost and buck-boost processes through a switching process, which functions in both positive and negative cycles. In addition, it controls the voltage and frequency of the load capacitor. In this process, the passive components in the circuit are energised by being short with the AC voltage using switching signals, which facilitates the active rectification of ultra-low AC voltage. Design considerations, theoretical analysis, simulations and experimental results are presented. It is shown that the circuit is able to control the switching signal and to convert low AC voltage (0.44 Vi) to high direct current (DC) voltage (6.5 Vdc) while achieving an output power of 469 µW, which outperforms existing synchronous rectifier circuit. Index Terms— AC-DC conversion, boost, buck-boost, switching circuit, piezoelectric devices, rectifier-less circuit, synchronous rectifier circuit.