Voltage Flip Efficiency Enhancement for Piezo Energy Harvesting

Vincent Frick,Ehsan Jamshidpour,Liana Wassouf

doi:10.3390/electronics10192400

Abstract

In this paper, we analyze the effect of an enhanced voltage flip technique on the power performance of a piezoelectric energy harvester. The enhanced voltage flip principle is based on a synchronized-switch-based architecture, and is referred to as FAR (Full Active Rectifier). It uses a tiny amount of the stored charge to boost the voltage flip. This work aims to demonstrate that, beside the enhanced flip efficiency, the FAR also contributes to improve the power efficiency of the harvester, especially under changing load constraint. Therefore, the paper proposes a thorough comparison between the FAR and its conventional counterpart, the Switch-only technique. The FAR is easy to implement and does not require any external inductor or capacitor. It only needs a reduced set of switches, an active diode and a simple control sequence, and can thus be implemented on a fully integrated circuit. The FAR can be used as a standalone voltage flip solution or in addition to further boost the flip efficiency in a state-of-the-art architecture such as SSHC for example. Tests were performed on a 0.35-µm process CMOS prototype IC. Experimental results revealed that the FAR extracts 19.1μW from an off-the-shelf piezoelectric transducer when the output voltage is regulated at 1 V with 1 V open-circuit voltage and delivers up to 20% more power than the conventional Switch-only technique under load constraint. It also shows over 11× power efficiency improvement compared to a conventional diode-based full bridge rectifier.

Highlights

With the advent of IoT, the need for portable, and self-powered devices has been dramatically increasing
We demonstrate the benefit of a synchronized-switch-based architecture, referred to as full active rectifier (FAR) and first proposed in Wassouf et al [24], to alleviate the load influence of the piezoelectric energy harvester
After the voltage flip operation, the voltage across Cpeh was Vbuilt = 0.864 V. This corresponded to 86.4% voltage flip efficiency, which was lower than the Cadence simulated value

Summary

Introduction

With the advent of IoT, the need for portable, and self-powered devices has been dramatically increasing. Batteries are still the most common way of powering embedded applications. Due to their size, weight, impractical replacement, limited lifetime, and above all environmental impact, batteries tend to become unwelcomed in ultra-compact ultra-low power applications. The goal is to do without batteries by implementing highly efficient dynamic power generators. The literature reports many implementations of kinetic harvesters involving piezoelectric devices Çiftci et al [1], Chen et al [2], Du and Seshia [3], Sanchez et al [4], inductive devices Rahimi et al [5], and electrostatic (capacitive) devices Tao et al [6], Stanzione et al [7]

Objectives

Results

Conclusion