A Comparative Study on the Mechatronic and Electronic Self-Powered Synchronized Switch Interfaces for Piezoelectric Energy Harvesting Systems

By scavenging the vibration energy from the ambience, the piezoelectric energy harvesting (PEH) technology provides one of the most promising solutions towards the everlasting power supplies for distributed wireless sensors. Given the capacitive characteristics of the piezoelectric devices, synchronized switch interface circuits, such as the synchronized switch harvesting on inductor (SSHI), have been developed towards the harvested power enhancement. The self-powered sensing, synchronization, and switching issues are essential for implementing these circuit innovations towards practical applications. This paper provides a comparative study on the recently proposed mechatronic self-powered SSHI (MSP-SSHI) and the existing electronic self-powered SSHI (ESP-SSHI) interfaces. The MSP-SSHI uses a single-pole-double-throw switch to simultaneously perform the sensing and switching functions. It reduces the switching threshold and energy losses caused by the semiconductors in the electronic solution, and also eliminates the high-voltage breakdown problem in MOS based ESP-SSHI. On the other hand, the distance between the pole and throws will introduce some switching phase difference under large vibrations. A piecewise linear model is built for analyzing the switching phase difference in MSP-SSHI. It was found that the damping ratio and stiffness of the mechanical switch can significantly influence the switching phase difference. Experimental result shows that the MSP-SSHI can effectively increase the harvested power under small and medium vibration levels, compared to the standard bridge rectifier; whereas, the ESP-SSHI performs better under medium and strong vibration.