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 $C_P$

A Nail-Size Piezoelectric Energy Harvesting System Integrating a MEMS Transducer and a CMOS SSHI Circuit

Piezoelectric vibration energy harvesting has drawn much interest to power distributed wireless sensor nodes for Internet of Things (IoT) applications where ambient kinetic energy is available. For certain applications, the harvesting system should be small and able to generate sufficient output power. Standard rectification topologies such as the full-bridge rectifier are typically inefficient when adapted to power conditioning from miniaturized harvesters. Therefore, active rectification circuits have been researched to improve overall power conversion efficiency, and meet both the output power and miniaturization requirements while employing a MEMS harvester. In this paper, a MEMS piezoelectric energy harvester is designed and cointegrated with an active synchronized switch harvesting on inductor (SSHI) rectification circuit designed in a CMOS process to achieve high output power for system miniaturization. The system is fully integrated on a nail-size board, which is ready to provide a stable DC power for low-power mini sensors. A MEMS energy harvester of 0.005 cm3 size, co-integrated with the CMOS conditioning circuit, outputs a peak rectified DC power of 40.6 µW and achieves a record DC power density of 8.12 mW/cm3 when compared to state-of-the-art harvesters

Un nuevo rectificador reconfigurable CMOS para recolectores de energía piezoeléctrica en dispositivos portables

Los recolectores de energía para dispositivos portables tienen una aplicación potencial en la conversión de la energía del movimiento humano en energía eléctrica para alimentar dispositivos inteligentes de monitoreo de la salud, de la industria textil, así como de relojes y lentes inteligentes. Estos recolectores de energía requieren circuitos rectificadores óptimos que maximicen sus eficiencias de carga. En este estudio se presenta el diseño de un novedoso rectificador reconfigurable metal óxido semiconductor complementario (CMOS) para recolectores de energía piezoeléctrica portables que puede aumentar sus eficiencias de carga. El rectificador diseñado se basa en la tecnología de proceso CMOS estándar de 0,18 µm considerando un patrón geométrico con un área total de silicio de . El circuito rectificador propuesto tiene dos puertas de transmisión (TG) que están compuestas por cuatro transistores rectificadores con una carga de 45 kΩ, un voltaje mínimo de entrada de 500 mV y un voltaje máximo de 3,3 V. Los resultados de las simulaciones numéricas del funcionamiento del rectificador indican una eficiencia de conversión de voltaje del 99,4 % y una eficiencia de conversión de potencia de hasta el 63,3 %. El rectificador propuesto puede utilizarse para aumentar la eficiencia de carga de los recolectores de energía piezoeléctrica portables.Wearable energy harvesters have potential application in the conversion of human-motion energy into electrical energy to power smart health-monitoring devices, the textile industry, smartwatches, and glasses. These energy harvesters require optimal rectifier circuits that maximize their charging efficiencies. In this study, we present the design of a novel complementary metal-oxide semiconductor (CMOS) reconfigurable rectifier for wearable piezoelectric energy harvesters that can increase their charging efficiencies. The designed rectifier is based on standard 0.18 µm CMOS process technology considering a geometrical pattern with a total silicon area of 54.765 µm x 86.355 µm. The proposed rectifier circuit has two transmission gates (TG) that are composed of four rectifier transistors with a charge of 45 kΩ, a minimum input voltage of 500 mV and a maximum voltage of 3.3 V. Results of numerical simulations of the rectifier performance indicate a voltage conversion efficiency of 99.4% and a power conversion efficiency up to 63.3%. The proposed rectifier can be used to increase the charging efficiency of wearable piezoelectric energy harvesters

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

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

DESIGN AND IMPLEMENTATION OF ENERGY HARVESTING CIRCUITS FOR MEDICAL DEVICES

Technological enhancements in a low-power CMOS process have promoted enhancement of advanced circuit design techniques for sensor related electronic circuits such as wearable and implantable sensor systems as well as wireless sensor nodes (WSNs). In these systems, the powering up the electronic circuits has remained as a major problem because battery technologies are not closely following the technological improvements in semiconductor devices and processes thus limiting the number of sensor electronics modules that can be incorporated in the design of the system. In addition, the traditional batteries can leak which can cause serious health hazards to the patients especially when using implantable sensors. As an alternative solution to prolonging the life of battery or to mitigate serious health problems that can be caused by battery, energy harvesting technique has appeared to be one of the possible solutions to supply power to the sensor electronics. As a result, this technique has been widely studied and researched in recent years. In a conventional sensor system, the accessible space for batteries is limited, which restricts the battery capacity. Therefore, energy harvesting has become an attractive solution for powering the sensor electronics. Power can be scavenged from ambient energy sources such as electromagnetic signal, wind, solar, mechanical vibration, radio frequency (RF), and thermal energy etc. Among these common ambient sources, RF and piezoelectric vibration-based energy scavenging systems have received a great deal of attention because of their ability to be integrated with sensor electronics modules and their moderate available power density. In this research, both RF and piezoelectric vibration-based energy harvesting systems have been studied and implemented in 130 nm standard CMOS process

Energy Harvesting on Footsteps Using Piezoelectric based on Circuit LCT3588 and Boost up Converter

Piezoelectric utilization as a generator is an effort to obtain electrical energy that refers to the concept of energy harvesting referring the development of piezoelectric as a generator that converts the pressure or vibration generated from steps into electrical energy that can be used on low-power electronic devices. Because the use of piezoelectric as a generator allows the use in charging low voltage, a larger resource is required in different series. Based on the problem, an energy harvesting device and a voltage amplifier are created to increase the voltage of the pizoelectric output. An arduino microcontroller is used to control the energy harvesting device and voltage booster. It is required approximately 10 steps to charge four AA 1.2 Volt batteries and 80 steps to charge two 12 volt batteries respectively

An Efficient SSHI Interface With Increased Input Range for Piezoelectric Energy Harvesting Under Variable Conditions

Piezoelectric vibration energy harvesters have been widely researched and are increasingly employed for powering wireless sensor nodes. The synchronized switch harvesting on inductor (SSHI) circuit is one of the most efficient interfaces for piezoelectric vibration energy harvesters. However, the traditional incarnation of this circuit suffers from a significant start-up issue that limits operation in low and variable amplitude vibration environments. This paper addresses this start-up issue for the SSHI rectifier by proposing a new architecture with SSHI startup circuitry. The startup circuitry monitors if the SSHI circuit is operating correctly and re-starts the SSHI interface if required. The proposed circuit is comprehensively analyzed and experimentally validated through tests conducted by integrating a commercial piezoelectric vibration energy harvester with the new interface circuit designed in a 0.35-μm HV CMOS process. Compared to conventional SSHI rectifiers, the proposed circuit significantly decreases the required minimum input excitation amplitude before energy can be harvested, making it possible to extract energy over an increased excitation range.Engineering and Physical Sciences Research Counci

Ultrasonically powered compact implantable dust for optogenetics

This paper presents an ultrasonically powered microsystem for deep tissue optogenetic stimulation. All the phases in developing the prototype starting from modelling the piezoelectric crystal used for energy harvesting, design, simulation and measurement of the chip, and finally testing the whole system in a mimicking setup are explained. The developed system is composed of a piezoelectric harvesting cube, a rectifier chip, and a micro-scale custom-designed light-emitting-diode (LED), and envisioned to be used for freely moving animal studies. The proposed rectifier chip with a silicon area of 300 μm × 300 μm is implemented in standard TSMC 0.18 μm CMOS technology, for interfacing the piezoelectric cube and the microLED. Experimental results show that the proposed microsystem produces an available electrical power of 2.2 mW while loaded by a microLED, out of an acoustic intensity of 7.2 mW/mm 2 using a (1 mm) 3 crystal as the receiver. The whole system including the tested rectifier chip, a piezoelectric cube with the dimensions of (500 μm) 3 , and a μLED of 300 μm × 130 μm have been integrated on a 3 mm × 1.5 mm glass substrate, encapsulated inside a bio-compatible PDMS layer and tested successfully for final prototyping. The total volume of the fully-packaged device is estimated around 2.85 mm 3