Harvesting Interface Circuit Research Articles

A single‐inductor self‐powered SECE interface circuit for dynamic load multi‐PZTs energy harvesting

AbstractThere is always considerable inconsistency between the input energy and the amount of the energy required for the load in piezoelectric transducers (PZTs) energy harvesting interface circuits that often degrades the harvesting performance of most of them. Multiple piezoelectric transducers (multi‐PZTs) vibration scavenging may address this issue by enhancing input power and, consequently, environmental adaptability and reliability. The proposed interface circuit may extract energy from a PZT array regardless of each PZT amplitude, frequency, or phase, even under dynamic or heavy load circumstances. The circuit is thoroughly simulated by LTSpice software and evaluated by post‐simulation calculations and discussions. The simulation findings demonstrate that the proposed self‐powered (SP) SECE‐based multi‐PZT EH interface circuit, named MI‐SP‐SECE, can extract a peak power of 12.8 µW from three PZTs in the provided actual scenario at a dynamic load regime with a simulated excitation of 1.5 g and 50 Hz. The proposed circuit's energy integration and harvesting efficiencies are 75% and 85%, respectively. It can achieve a power enhancement of 2.8× relative to a multi‐input full‐bridge rectifier. In addition, the proposed circuit is scalable effectively because it requires just one inductor component.

A Self-Bias-Flip With Charge Recycle Interface Circuit With No External Energy Reservoir for Piezoelectric Energy Harvesting Array

This paper presents a piezoelectric energy harvesting (PEH) interface circuit using a new self-bias-flip with charge recycle (SBFR) technique without employing any additional energy reservoir. Traditional designs, including synchronous-switch harvesting on inductor (SSHI), synchronous-switch harvesting on capacitor (SSHC), synchronous electric charge extraction (SECE), etc., require additional capacitors or inductors to reverse the voltage on the PEH at the zero-crossing point. This design innovatively uses the inherent capacitors of the piezoelectric harvesters as the flipping capacitors. In order to improve the extract efficiency of the interface, the zero-crossing state is split into charge recycle stage and voltage-flip stage. For a piezoelectric array with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{n}$</tex-math></inline-formula> PEHs, a configuration with (n-1) phases in the charge recycle stage is adopted to reduce the loss caused by direct charge neutralization. The charge redistribution loss is reduced by employing (2n+1) phases in the voltage-flip stage. The proposed principle has been implemented with discrete components and is verified by 3 different prototypes. The measurement results show that a flipping efficiency of 67% is achieved by utilizing SBFR with 4 PEHs. And the proposed interface can provide up to 5.2x improvement when compared with the full-bridge rectifier (FBR).

Analysis and Optimization of Switched-Capacitor Piezoelectric Energy Harvesting Interface Circuits

Analysis and Optimization of Switched-Capacitor Piezoelectric Energy Harvesting Interface Circuits

Bias-Voltage-SSHI Interface Circuit for Strong Coupling Piezoelectric Energy Systems

Compared with the standard extraction interface circuit (SEH), the harvested energy and harvested power of synchronized switching harvesting interface circuits (SSHI) and synchronous charge extraction interface circuit (SECE) cannot improve more effectively. This paper proposes a Bias-Voltage-SSHI Interface Circuit (BV-SSHI), consisting of a single peak voltage detection switch and a rectifier, to solve this problem. The proposed BV-SSHI improves the output voltage by biasing the voltage of the piezoelectric energy harvester and obtains similar harvested power as SSHI. Simulation results show that the BV-SSHI can obtain more harvested energy and harvested power than SEH under weak, medium, and strong coupling systems. Results show that the higher harvester's voltage and the larger phase difference cause the electrical restoring force (χV) to significantly weaken the vibration displacement, especially under strong coupling systems. Thus, the gain effect of the SSHI and SECE is weakened. The experimental results of the medium coupling systems show that the BV-SSHI can obtain 247.2% harvested energy and 121.2% maximum harvested power compared with SEH. The BV-SSHI can achieve at least 142.4% harvested energy and 100.3% maximum harvested power compared with what SSHI and SECE can achieve.

A Fully Autonomous SSHIC Interface Circuit With Configurable Multi-Step Bias-Flip for Piezoelectric Energy Harvesting

This brief presents a piezoelectric energy harvesting interface circuit with a multi-step bias-flip strategy to boost the energy extraction capability. The optimized parallel synchronized switch on inductor and capacitor (SSHIC) technique is adopted. Except for the external inductor and capacitors, the proposed interface circuit is designed for fully integrated control without any external adjustment during the bias-flip process. Moreover, the steps for bias-flip can be configured flexibly, and the circuit can work even without an inductor. The interface circuit has been designed and implemented with 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> CMOS technology. With the 5-step bias-flip SSHIC topology and a 1-mH inductor, the simulated whole current dissipation is 106 nA, the measured maximum flipping efficiency is 90.3%, and the measured maximum power efficiency improvement is 642% compared to the ideal full bridge rectifier (FBR).

A Highly Adaptive and Flipping-Time Optimized Piezoelectric Energy Harvesting Interface IC With Synchronized Triple Bias-Flip

This article presents a piezoelectric energy harvesting interface circuit with high adaptability to external inductors, transducer types, and vibration frequencies. High output power can be obtained with the help of triple bias-flip and optimal flipping time control. The triple bias-flip enables both higher efficiency and the use of an inductor with lower volume compared to conventional bias-flip topologies. Besides, owing to the highly adaptive circuit design and reverse current reduction in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonant loop, the proposed interface circuit not only automatically adjusts flipping time according to external inductance and piezoelectric transducer, but also reduces the reverse current of the inductor effectively. Also, an active rectifier that can reduce conduction loss of the diode-based rectifier has been implemented. The prototype integrated circuit has been fabricated in 180-nm CMOS technology and the chip area is 0.646 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measurement results show that the proposed circuit achieves cold start-up without any external power supply, and can work with high efficiency when the external inductor is varying from 0 to 10 mH, transducer capacitance is changing from 20 to 90 nF, and vibration frequency is ranging from 35 to 200 Hz. The measured maximum output power of the proposed design can achieve as high as 473% enhancement to the full-bridge rectifier.

A review of nonlinear piezoelectric energy harvesting interface circuits in discrete components

Piezoelectric energy harvesting is considered as an ideal power resource for low-power consumption gadgets in vibrational environments. The energy extraction efficiency depends highly on the interface circuit, and should be highly improved to meet the power requirements. The nonlinear interface circuits in discrete components have been extensively explored and developed with the advantages of easy implementation, stable operation, high efficiency, and low cost. This paper reviews the state-of-the-art progress of nonlinear piezoelectric energy harvesting interface circuits in discrete components. First, the working principles and the advantages/disadvantages of four classical interface circuits are described. Then, the improved circuits based on the four typical circuits and other types of circuits are introduced in detail, and the advantages/disadvantages, output power, efficiency, energy consumption, and practicability of these circuits are analyzed. Finally, the future development trends of nonlinear piezoelectric energy harvesting circuits, e.g., self-powered extraction, low-power consumption, and broadband characteristic, are predicted.

Efficient self-powered piezoelectric energy harvesting interface circuit with wide rectified voltage

Synchronized Switching Harvesting on Inductor (SSHI) and Synchronous Electric Charge Extraction (SECE) are two classic interface circuit techniques for Piezoelectric energy harvesting. But the former has high peak output power with narrow rectified voltage range, while the latter has wide rectified voltage range with lower peak output power. This paper presents a self-powered interface circuit for piezoelectric energy harvesting to achieve a good balance between the two. The proposed interface circuit is based on the Series-SSHI (S–SSHI) and SECE. The circuit proposed can harvest energy through S–SSHI and SECE in positive and negative half cycles, respectively. Moreover, the figure of merit (FOM), optimal rectified voltage range (ORVR) and region of interest (SRoI) of simulation and experiment results are discussed. The maximum FOM of the proposed circuit is as high as 2.15, which is 1.68 times that of the SECE, and it can reach 6 times the ORVR of the S–SSHI. SRoI factor of the proposed circuit show that the proposed method has better performance. In addition, the circuit shows a simpler implementation compared with state-of-the-art designs.

Energy Harvesting for Tire Pressure Monitoring Systems From a Mechanical Energy Point of View

Intelligent tires are one key element for autonomous self-driving cars and the Internet of Vehicles (IoV), especially if the battery-driven sensor systems attain the transition to be self-powered. Harvesting vibrational energy of these tire pressure monitoring systems (TPMSs) is the promising technique to make tire sensors self-sufficient and to provide additional energy for sophisticated algorithms, which constitute the intelligence of vehicle tires. Despite of two decades of intense research, no commercial product has been established. This work analyzes the technological reasons and presents both challenges and opportunities of TPMS energy transducers. First, this article specifies significant system requirements and characterizes common energy sources. The authors determine the necessary amount of energy on two different paths. A throughout comparison between different TPMS transducers overviews the state of the art, comprehensively. Typical TPMS energy harvesters are summarized, distinctive TPMS transducers are shortly presented and common problems are outlined, focusing on the harvesting mechanism, restoring force, interface circuit, and energy generation. The pros and cons of different energy transducer principles for their operation inside the tire are balanced. Focusing on reliability and on normalized energy generation, this publication highlights potent energy harvesters for system enhancement and gives recommendations for future developments. Two significant outcomes among others are to switch the focus from linear systems to systems with a nonlinear restoring force as well as to more efficient interface circuits than low-efficient full-wave rectifiers.

A non-time division multiplexing single inductor solar and piezoelectric energy multi-input harvesting interface circuit

Due to time-varying and instability, single environmental energy cannot provide reliable energy for wireless sensor network nodes. Therefore, researchers propose to use multi-source synergy to provide power. Still, these circuits take time-division multiplexing or setting priority, which can only harvest one kind of environment energy at a particular moment, resulting in low energy harvesting efficiency and complex circuit structure. Also, a single vibration source is configured with multiple piezoelectric (PZT) harvesters to obtain more power. For the above questions, this paper proposes a non-time-division multiplexing single-inductor synchronous electric charge extraction circuit (NTD-SECE), which is mainly composed of rectifier bridge, peak detection circuit, control circuit, input comparison circuit, and buck-boost circuit. Theoretical analysis and experiments verify the effectiveness of the interface circuit. The results show that NTD-SECE can extract energy from photovoltaic (PV) and multi-PZTs by non-time division multiplexing, the maximum power is 450 mW. It has broad application prospects in the energy supply of low-power equipment.

Design of an Energy Harvesting Interface Circuit Consecutively Powering Two Loads

ABSTRACT This paper presents an energy harvesting interface circuit for a single ambient energy source that consecutively delivers power supply to two loads including one light load and one heavy load. The proposed circuit consists of a step-up converter, a temporary storage element (e.g. supercapacitor), two charge control circuits for the loads, and two power transistors. The converter receives low-voltage from the output of the energy source to charge the supercapacitor at the output of the converter to high voltage levels. The supercapacitor delivers energy to the light load through corresponding control circuit. Due to the light load, the generated energy by the energy source is greater than the required power by the load. This results in accumulating the surplus energy into the supercapacitor. Once the supercapacitor stores sufficient energy, the energy direction from the supercapacitor is shifted from the light load to the heavy load. Once the supercapacitor discharges to a voltage level where the heavy load stops to receive power supply, the energy direction will be toward to the light load again. The same powering pattern will be repeated over the time. As a result, these loads operate in burst mode. The proposed circuit, constructed with off-the-shelf components, regulates outputs to nearly 3.9 V, starts the operation from an input voltage as low as 0.1 V and achieves a peak efficiency of 73.29%. The proposed circuit provides the highest output power of 124.14 mW which is greater than prior IC work supports. Apart from the highest output power, the proposed circuit meets the goal of self-sustainability since there is no need of extra power source (e.g., battery) other than the ambient energy source.

Lumped Parameter Evaluation Model Analysis and Load Coupling Modeling of Piezoelectric Composite Cantilever Beam

In order to study the working mechanism of piezoelectric composite cantilever beam and improve the ability of predicting the power generation performance of piezoelectric composite cantilever vibration energy harvester (CVEH), the simple and high-precision analysis models of equivalent mass and equivalent stiffness of CVEH are proposed. The natural frequency method is used to compare the calculation results of the evaluation model, Rayleigh Ritz method and finite element simulation, and the results show that the consistency (Ω) between the evaluation model and the finite element simulation is more than 95%. The influence of the mass ratio (α) between the end mass of the beam and the weight of the beam itself on Ω is analyzed by using the proposed evaluation model, which shows that Ω increases with the increase of α, and the increase is more significant in the range of 0<α<4. The analysis of the influence of α on the natural frequency of the beam () shows that decreases with the increase of α, and the decrease is more obvious in the range of 0<α<2. According to the evaluation model, the electromechanical conversion analysis models of CVEH and its control equation with coupling of standard energy harvesting (SEH) interface circuit and Double synchronous switch harvesting (DSSH) interface circuit are established respectively, and the mathematical models of its output voltage are derived. The power generation experiment of CVEH is carried out, and the results show that the proposed models are in good agreement with the experimental results.

A unified equivalent circuit and impedance analysis method for galloping piezoelectric energy harvesters

In the past decade, galloping-based energy harvesters (GPEH) connected with various interface circuits have been developed and analytical models have been built. However, the power performances of these advanced structures and circuits are always treated separately, and a general model is missing to gain insights at a system level. To tackle this issue, this paper proposes a unified analysis framework for GPEHs. Its results are consistent with validated (but disconnected) results in the literature. The method provides an integrated view of the physics of linear GPEHs in multiple domains at the system level, and elucidates the similarities and differences among power behaviors of GPEHs connected with various interface circuits. The framework is based on two major elements: an equivalent circuit that represents the entire system, and an equivalent impedance that represents the interface circuit. Firstly, the electromechanical system is linearized and modeled in the electrical domain by an equivalent self-excited circuit with a negative resistive element representing the external aerodynamic excitation, and a general load impedance representing the interface circuit. Then, a closed-form, analytical expression of the harvested power is obtained based on the Kirchhoff’s Voltage Law, from which the optimal load, maximum power, power limit, and critical electromechanical coupling (minimum coupling to reach the power limit) are determined. In this unified analysis, the exact type of energy harvesting interface circuit is not assumed. After that, the power characteristics of a GPEH connected with five representative interface circuits are analytically derived and discussed, by using the particular equivalent impedance of the interface circuit of interest. It is shown that they are subjected to the same power limit. However, the critical electromechanical coupling depends on the type of circuit. Throughout the discussions, impedance plots are used to illustrate the relationship between the internal system characteristics and external load impedance, facilitating the understanding of system power behavior.

A Self-Adapting Synchronized-Switch Interface Circuit for Piezoelectric Energy Harvesters

This paper presents a self-adapting synchronized-switch harvesting (SA-SSH) interface circuit to extract energy from vibration-based piezoelectric energy harvesters (PEHs). The implemented circuit utilizes a novel switching technique to recycle optimum amount of harvested charge on piezoelectric capacitance to strengthen the damping force, and simultaneously achieve load-independent energy extraction with a single inductor. Charge recycling is realized by adjusting extraction time, and optimized through a maximum power point tracker based on charge-flipping dissipation. The circuit has been implemented using 180 nm HV CMOS technology with 0.9 × 0.6 mm2 active area. Self-adapting SSH circuit has been validated with both macro-scaled and MEMS PEHs with different inductor values. The interface circuit provides maximum energy extraction for the full storage voltage range of 1.8–3.7 V. The implementation harnesses have 500% more power compared to an ideal full-bridge rectifier, and output 3.4 μW for 2.24 V peak-to-peak open-circuit piezoelectric voltage from MEMS PEH excited at its resonant frequency.

Thermoelectric Energy Harvesting Interface Circuit With Capacitive Bootstrapping Technique for Energy-Efficient IoT Devices

This paper presents a low-input-voltage (100 mV), low-output-voltage (500–600 mV) thermoelectric energy harvesting interface circuit for near-threshold energy-efficient Internet-of-Things (IoT) devices. The capacitive bootstrapping technique is used to generate a positive and negative bias pair for alleviating the significant conduction losses of power MOSFETs in a near-threshold operation. Internal bias voltages are automatically boosted to different levels as per the loading conditions to extend the output power range. The deployment of constant on-time digital pulse skip modulation with digital zero current detection (ZCD) achieves an ultralight load operation, and precluding a reverse current. The digital ZCD is capable of dynamically adjusting the off-time ( ${T}_{\mathrm {OFF}}$ ) of the power transistors, which vary according to the input and output voltage levels. The proposed step-up dc-dc power converter implemented using a 180 nm CMOS technology demonstrates a maximum conversion efficiency of 76.4% over a $1~{\mu }\text{W}$ – $500~{\mu }\text{W}$ load range, significantly evaluating the feasibility of the near-threshold interface circuit architecture for energy-efficient IoT devices.

A self-powered piezoelectric energy harvesting interface circuit with efficiency-enhanced P-SSHI rectifier * * Project supported by the National Natural Science Foundation of China (Nos. 61574103, U1709218) and the Key Research and Development Program of Shaanxi Province (No. 2017ZDXM-GY-006).

The key to self-powered technique is initiative to harvest energy from the surrounding environment. Harvesting energy from an ambient vibration source utilizing piezoelectrics emerged as a popular method. Efficient interface circuits become the main limitations of existing energy harvesting techniques. In this paper, an interface circuit for piezoelectric energy harvesting is presented. An active full bridge rectifier is adopted to improve the power efficiency by reducing the conduction loss on the rectifying path. A parallel synchronized switch harvesting on inductor (P-SSHI) technique is used to improve the power extraction capability from piezoelectric harvester, thereby trying to reach the theoretical maximum output power. An intermittent power management unit (IPMU) and an output capacitor-less low drop regulator (LDO) are also introduced. Active diodes (AD) instead of traditional passive ones are used to reduce the voltage loss over the rectifier, which results in a good power efficiency. The IPMU with hysteresis comparator ensures the interface circuit has a large transient output power by limiting the output voltage ranges from 2.2 to 2 V. The design is fabricated in a SMIC 0.18 μm CMOS technology. Simulation results show that the flipping efficiency of the P-SSHI circuit is over 80% with an off-chip inductor value of 820 μH. The output power the proposed rectifier can obtain is 44.4 μW, which is 6.7× improvement compared to the maximum output power of a traditional rectifier. Both the active diodes and the P-SSHI help to improve the output power of the proposed rectifier. LDO outputs a voltage of 1.8 V with the maximum 90% power efficiency. The proposed P-SSHI rectifier interface circuit can be self-powered without the need for additional power supply.

Vibration Based Energy Harvesting Interface Circuit using Diode-Capacitor Topologies for Low Power Applications

&lt;span&gt;A battery-less energy harvesting interface circuit to extract electrical energy from vibration has been proposed in this paper for low power applications. The voltage doubler integrated with DC – DC boost converter circuits were designed and simulated using MultiSIM software. The circuit was then fabricated onto a printed circuit board (PCB), using standard fabrication process. The Cockcroft Walton doubler was chosen to be implemented in this study by utilizing diode-capacitor topologies with additional RC low pass filter. The DC – DC boost converter has been designed using a CMOS step -up DC – DC switching regulators, which are suitable for low input voltage system. The achievement of this interface circuit was able to boost up the maximum voltage of 5 V for input voltage of 800 mV.&lt;/span&gt;

A Self-Powered Piezoelectric Energy Harvesting Interface with Wide Input Range in 65 nm CMOS Process

ABSTRACTA self-powered piezoelectric energy harvesting interface circuit (PEHIC) with wide input range and good performance is presented in this paper. The proposed PEHIC consists of a two-stage active charge pump rectifier and an ultra-low power intermittent power management unit (IPMU). Active diodes based on unbalanced-biased comparators improve the reverse leakage current problem that conventional active diodes faced. By limiting the output voltage between 1.2 and 0.8 V, the IPMU working in intermittent mode can provide an expanded input range and ensure that the interface circuit has a large transient output power. Implemented in a 65 nm standard complementary metal oxide semiconductor (CMOS) technology, the PEHIC has been simulated and verified. Simulation results show that an AC signal with amplitude ranging from 0.32 to 1.5 V and frequencies of 20 Hz–3 kHz can be rectified. The maximum output current is as large as 5 mA. The peak power conversion efficiency is up to 81% when the input voltage is 0.8 V at 200 Hz. The PEHIC can be self-powered without the need for additional power supply.

Synergy of Wind Energy Harvesting and Synchronized Switch Harvesting Interface Circuit

Due to the complex aero-electro-mechanical coupling involved in wind energy harvesting systems, power enhancing efforts in the literature are mostly devoted to structural modifications while the interface circuit is simplified to a resistive ac load. Yet the ac outputs are not applicable for practical usage. In this paper, we study the dynamics and dc power generation of galloping energy harvester. In particular, the enhancement of wind power extraction using the synchronized switching harvesting on inductor (SSHI) power conditioning circuit is emphasized. Analytical solution of the steady-state mechanical and electrical responses with the SSHI interface is derived explicitly and validated with wind tunnel experiment and circuit simulation. The performance of SSHI interface is compared to that of a standard bridge rectifier interface circuit. It shows that the SSHI interface achieves tremendous power enhancement in a weak-coupling system, and higher wind speeds render more significant power enhancement. Moreover, given the same wind condition and output power requirement, a system connected to the SSHI uses much less piezoelectric material compared to that connected to the standard circuit. With a weak-coupling harvester operating at a wind speed of 7 m/s, the SSHI can harvest up to 143% more wind power than the standard circuit.

Simulation Analysis of Interface Circuits for Piezoelectric Energy Harvesting with Damped Sinusoidal Signals and Random Signals

Various interface circuits for collecting the energy of piezoelectric cantilever beams have been widely investigated. Such circuits include the standard interface, series synchronized switch harvesting interface circuit, parallel synchronized switch harvesting interface, synchronized charge extraction interface, and others. Most studies focus on the performance of different interface circuits with standard sinusoidal excitations. However, in real situations where constant harmonic vibrations are not present, the equivalent voltage from piezoelectric cantilever beams with excitations is not necessarily sinusoidal. In the present study, a simulation analysis of four different interface circuits with signal sources that are both damped sinusoidal and random was performed using Matlab and PSpice. The results show that the interface circuits have improved performance under low load resistance values with damped sinusoidal signal. In addition, the parallel and series synchronized switch harvesting interface circuits may perform well in collecting piezoelectric energy with random excitations.