Synchronized Triple Bias-Flip Interface Circuit for Piezoelectric Energy Harvesting Enhancement

The power conditioning interface circuit plays a crucial role in the energy harvesting (EH) capability enhancement in piezoelectric EH (PEH) systems. The principle of most existing synchronized switch circuits for PEH enhancement was summarized under the recently introduced synchronized multiple bias-flip (SMBF) model. The optimal bias-flip strategy derived from SMBF provides valuable insights for future circuit development. Based on such theoretical foundation, this paper implements a new interface circuit called the parallel synchronized triple bias-flip (P-S3BF) for further boosting the harvesting capability beyond the state-of-the-art solutions. By sophisticatedly allocating more bias-flip actions, it makes the best compromise between higher extracted power and lower dissipated power for power conditioning, toward maximum net harvested power. Moreover, the bias voltage reference in P-S3BF is self-contained and self-adaptive. Compared to the other existing solutions involving active voltage manipulations, these two conveniences brought in by P-S3BF are the most significant and necessary features, which facilitate the practical stand-alone implementation of P-S3BF under different periodic vibrations. Experimental result shows that, with the piezoelectric cantilever in use, which vibrates at a constant deflection magnitude, the P-S3BF circuit harvests 24.5% more power than its single bias-flip counterpart, the extensively studied parallel synchronized switch harvesting on inductor; and 287.6% more power than its null bias-flip counterpart, the standard EH bridge rectifier.