Optimization of an SSHC-based full active rectifier for piezoelectric energy harvesting

This paper presents a compact and efficient integrated interface circuit for piezoelectric energy harvesting. While state-of-the-art interface circuits require either an external inductor or a significant number of additional capacitors to achieve high voltage flip and thus improve power efficiency, the proposed Full Active Rectifier on Flipping Capacitor (FAR-FC) is based on a reduced set of flipping capacitors and an active rectifier to efficiently flip the voltage across the piezoelectric transducer. In addition, this optimized SSHC circuit reaches better power efficiency when the piezoelectric transducer operates under low mechanical excitation, i.e. when the open-circuit voltage of the piezoelectric transducer is Voc=1 V , while usually Voc≥ 2 V in literature. Furthermore, the FAR-FC supports piezoelectric transducers with higher inherent capacitance values compared to those usually reported in literature, which makes the circuit potentially suitable for a larger variety of applications. The interface circuit was designed and fabricated in a 0.35 μm CMOS process. Measurement results show that the voltage flip efficiency goes up to 90% . It also reveals that the proposed FAR-FC circuit achieves power performance up to 5.64× higher than a conventional full-bridge rectifier.