and Ya Wang
b
a
School of Information Science and Technology, ShanghaiTech University, Shanghai, China
b
Mechanical Engineering, Stony Brook University, NY, USA
ABSTRACT
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.
Keywords: piezoelectric energy harvesting, synchronized switch interface circuits, self-powered SSHI, vibration sensor
switch
1. INTRODUCTION
Piezoelectric energy harvesting (PEH) technology provides one of the most promising solutions for powering the
distributed wireless sensor networks (WSNs) by scavenging the ambient vibration energy [1-4]. Piezoelectric structure and
power conditioning circuits are two key parts for building an efficient energy harvesting system. In the studies of interface
circuit, synchronized switch harvesting on inductor (SSHI) [5], and other synchronized switch interface circuits [6] can
increase the energy harvesting capability by several hundred percent. In SSHI, we need to sense the maximum deforming
instants of the piezoelectric transducer, and simultaneously turn on an inductive circuit branch for the charge stored in the
piezoelectric element, such that the voltage across the piezoelectric element can be inverted after half of an RLC cycle.
The voltage inversion at its extreme points can stop the energy return from electrical to mechanical parts [3] and thus
enabling higher energy harvesting capability. The building blocks of series SSHI is shown in Figure 1. For the standalone
application of SSHI, the sensing, synchronization, and switching functions should be self-contained without using any
external sensor, power supply, and controller. Given this requirements, some electronic self-powered SSHI (EPS-SSHI)
have been invented [7-9], which consists of three electronic functional blocks, i.e., voltage peak detector, comparator, and
electronic switch. The functional blocks are usually realized by bipolar junction transistors (BJT) [7, 8] or metal oxide
semiconductors (MOS) [9, 10], either of which introduce some side-effects [8, 11]. For example, in the BJT solutions, the
open circuit voltage is decreased, and meanwhile a switching delay as well as a large threshold voltage are introduced [8];
in the MOS solutions, the workable peak voltage is confined by the rating voltage of the MOS processing, usually lower
than 10 volt in existing studies [9, 10]. These side-effects discount the original improvement and confine the application
of EPS-SSHI.
Active and Passive Smart Structures and Integrated Systems 2016, edited by Gyuhae Park, Proc. of SPIE
Proc. of SPIE Vol. 9799 97991Q-1