Self-Powered Electronics for Piezoelectric Energy Harvesting Devices

International audienc

Synchronous charge extraction and voltage inversion (SCEVI): a new efficient vibration-based energy harvesting scheme

This paper presents a new interface technique called synchronous charge extraction and voltage inversion (SCEVI), which consists of a synchronous inductor and a buck-boost converter for vibration-based energy harvesting using piezoelectric elements. The theoretical calculation of the harvested power obtained by using such a technique are proposed and compared with the so-called Standard, SECE (Synchronous Electric Charge Extraction), Parallel-SSHI (Parallel Synchronized Switch Harvesting on Inductor) and Series-SSHI (Series Synchronized Switch Harvesting on Inductor) methods commonly used in piezoelectric vibration-powered generator considering both constant displacement amplitude and force amplitude. From the harvested power point of view, SCEVI and Parallel – SSHI techniques are the better ones and each has its own merits. But the harvested power of SCEVI is independent of the load connected to the generator and Parallel – SSHI depend on the load resistance. The harvested power of SECE is also independent of the load, but the further experimental results show that the proposed SCEVI interface technique dramatically increases the harvested power by almost up to 150 % compared with the SECE method under the same amplitude of displacement excitation

A Passive Design Scheme to Increase the Rectified Power of Piezoelectric Energy Harvesters

Piezoelectric vibration energy harvesting is becoming a promising solution to power wireless sensors and portable electronics. While miniaturizing energy harvesting systems, rectified power efficiencies from miniaturized piezoelectric transducers (PT) are usually decreased due to insufficient voltage levels generated by the PTs. In this paper, a monolithic PT is split into several regions connected in series. The raw electrical output power is kept constant for different connection configurations as theoretically predicted. However, the rectified power following a full-bridge rectifier (FBR), or a synchronized switch harvesting on inductor (SSHI) rectifier, is significantly increased due to the higher voltage/current ratio of series connections. This is an entirely passive design scheme without introducing any additional quiescent power consumption and it is compatible with most of state-of-the-art interface circuits. Detailed theoretical derivations are provided to support the theory and the results are experimentally evaluated using a custom MEMS PT and a CMOS rectification circuit. The results show that, while a PT is split into 8 regions connected in series, the performance while using a FBR and a SSHI circuit is increased by 2.3X and 5.8X, respectively, providing an entirely passive approach to improving energy conversion efficiency.UK Engineering and Physical Sciences Research Council (EPSRC) (Grant number: EP/L010917/1 and EP/N021614/1

A Cold-Startup SSHI Rectifier for Piezoelectric Energy Harvesters with Increased Open-Circuit Voltage

Piezoelectric vibration energy harvesting has drawn much research interest over the last decade towards the goal of enabling self-sustained wireless sensor nodes. In order to make use of the harvested energy, interface circuits are needed to rectify and manage the energy. Among all active interface circuits, SSHI (synchronized switch harvesting on inductor) and SECE (synchronous electric charge extraction) are widely employed due to their high energy efficiencies. However, the cold-startup issue still remains since an interface circuit needs a stable DC supply and the whole system is completely out of charge at the beginning of implementations or after a certain period of time without input vibration excitation. In this paper, a new cold-startup SSHI interface circuit is presented, which dynamically increases the open-circuit voltage generated from the piezoelectric transducer (PT) in cold-state to start the system under much lower excitation levels. The proposed circuit is designed and fabricated in a 0.18 um CMOS process and experimentally validated together with a custom MEMS (microelectromechanical systems) harvester, which is designed with split electrodes to work with the proposed power extraction circuit. The experiments were performed to start the system from the cold state under variable excitation levels. The results show that the proposed system lowers the required excitation level by at least 50% in order to perform a cold-startup. This aids restarting of the energy harvesting system under low excitation levels each time it enters the cold state

System-level coupled modeling of piezoelectric vibration energy harvesting systems by joint finite element and circuit analysis

A practical piezoelectric vibration energy harvesting (PVEH) system is usually composed of two coupled parts: a harvesting structure and an interface circuit. Thus, it is much necessary to build system-level coupled models for analyzing PVEH systems, so that the whole PVEH system can be optimized to obtain a high overall efficiency. In this paper, two classes of coupled models are proposed by joint finite element and circuit analysis. The first one is to integrate the equivalent circuit model of the harvesting structure with the interface circuit and the second one is to integrate the equivalent electrical impedance of the interface circuit into the finite element model of the harvesting structure. Then equivalent circuit model parameters of the harvesting structure are estimated by finite element analysis and the equivalent electrical impedance of the interface circuit is derived by circuit analysis. In the end, simulations are done to validate and compare the proposed two classes of system-level coupled models. The results demonstrate that harvested powers from the two classes of coupled models approximate to theoretic values. Thus, the proposed coupled models can be used for system-level optimizations in engineering applications

Analysis on One-Stage SSHC Rectifier for Piezoelectric Vibration Energy Harvesting

Conventional SSHI (synchronized switch harvesting on inductor) has been believed to be one of the most efficient interface circuits for piezoelectric vibration energy harvesting systems. It employs an inductor and the resulting RLC loop to synchronously invert the charge across the piezoelectric material to avoid charge and energy loss due to charging its internal capacitor ($C_P$). The performance of the SSHI circuit greatly depends on the inductor and a large inductor is often needed; hence significantly increases the volume of the system. An efficient interface circuit using a synchronous charge inversion technique, named as SSHC, was proposed recently. The SSHC rectifier utilizes capacitors, instead of inductors, to flip the voltage across the harvester. For a one-stage SSHC rectifier, one single intermediate capacitor ($C_T$) is employed to temporarily store charge flowed from $C_P$ and inversely charge $C_P$ to perform the charge inversion. In previous studies, the voltage flip efficiency achieves 1/3 when $C_T = C_P$. This paper presents that the voltage flip efficiency can be further increased to approach 1/2 if $C_T$ is chosen to be much larger than $C_P$

Simulation and performance analysis of self-powered piezoelectric energy harvesting system for low power applications

Energy harvesting is a process of extracting energy from surrounding environments. The extracted energy is stored in the supply power for various applications like wearable, wireless sensor, and internet of thing (IoT) applications. The electricity generation using conventional approaches is very costly and causes more pollution in the environmental surroundings. In this manuscript, an energy-efficient, self-powered battery-less piezoelectric-based energy harvester (PE-EH) system is modeled using maximum power point tracking (MPPT) module. The MPPT is used to track the optimal voltage generated by the piezoelectric (PE) sensor and stored across the capacitor. The proposed PE system is self-operated without additional microarchitecture to harvest the Power. The experimental simulation results for the overall PE-EH systems are analyzed for different frequency ranges with variable input source vibrations. The optimal voltage storage across the storing capacitor varies from 1.12 to 1.6 V. The PE-EH system can harvest power up to 86 µW without using any voltage source and is suitable for low-power applications. The proposed PE-EH module is compared with the existing similar EH system with better improvement in harvested power