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

Abstract

This paper presents a compact and efficient integrated interface circuit for piezoelectric energy harvesting. While the state-of-the-art interface circuits require the use of either an external inductor or a significant number of additional capacitors to achieve high voltage flip and 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 is operating under low mechanical excitation, i.e. when the open-circuit voltage of the piezoelectric transducer is V oc = 1V , while this value is usually V oc ≥ 2V 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 MEMS 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.