Piezoelectric Energy Harvesting Interface Using Self-Bias-Flip Rectifier and Switched-PEH DC–DC for MPPT

This article proposes a novel eight-phase self-bias-flip piezoelectric energy harvesting interface with charge recycling and reusing (SBFRR) and a switched-piezoelectric energy harvester (PEH) dc–dc (SPDC) converter. The proposed scheme innovatively utilizes the inherent capacitors ($C_P$) of four PEHs as energy sources, flying capacitors, and flipping capacitors for time-sharing reuse to achieve both a high-voltage flipping and dc–dc conversion efficiency, while avoiding the use of extra energy reservoirs. The design is fully integrated and fabricated in standard 0.18-$\mu$m CMOS. Measurement result demonstrates that the voltage flipping efficiency of up to 80% is achieved. Compared with the ideal full-bridge rectifier (FBR), the measured maximum output power improving rate (MOPIR) can be increased to 4.88$\times$. In addition, with the four$C_P$serving as flying capacitors to achieve SPDC conversion for maximum power point track (MPPT), an MOPIR of$>$3.5$\times$can be maintained with a PEH input voltage from 0.78 to 4.9 V.