A Highly Adaptive and Flipping-Time Optimized Piezoelectric Energy Harvesting Interface IC With Synchronized Triple Bias-Flip

This article presents a piezoelectric energy harvesting interface circuit with high adaptability to external inductors, transducer types, and vibration frequencies. High output power can be obtained with the help of triple bias-flip and optimal flipping time control. The triple bias-flip enables both higher efficiency and the use of an inductor with lower volume compared to conventional bias-flip topologies. Besides, owing to the highly adaptive circuit design and reverse current reduction in the LC resonant loop, the proposed interface circuit not only automatically adjusts flipping time according to external inductance and piezoelectric transducer, but also reduces the reverse current of the inductor effectively. Also, an active rectifier that can reduce conduction loss of the diode-based rectifier has been implemented. The prototype integrated circuit has been fabricated in 180-nm CMOS technology and the chip area is 0.646 mm2. The measurement results show that the proposed circuit achieves cold start-up without any external power supply, and can work with high efficiency when the external inductor is varying from 0 to 10 mH, transducer capacitance is changing from 20 to 90 nF, and vibration frequency is ranging from 35 to 200 Hz. The measured maximum output power of the proposed design can achieve as high as 473% enhancement to the full-bridge rectifier.