A High-Efficiency Full Active Rectifier for Piezo Energy Harvesting

This paper presents a concept of fully integrated interface circuit dedicated to harvest piezoelectric energy. The concept draws on the use of a fraction of the stored charge to flip the voltage across the piezoelectric transducer. Under specific conditions, this voltage flip allows to dramatically improve the efficiency of the energy harvesting system. While state of the art systems proposed so far require either an external inductor, i.e. not suitable for integration, or additional capacitors and/or complex voltage flipping control, the proposed Full Active Rectifier is based on a reduced set of switches, an active diode and a simple control sequence. The interface circuit has been designed in a 0.35-mu m CMOS process. Simulation results reveal the proposed Full Active Rectifier can achieve 50% efficiency when the output voltage is regulated at 1.2 V with a 1.2 V open-circuit piezo device. It also shows 8x performance improvement compared to the conventional diode-based full bridge rectifier method.