Power Management Circuit Research Articles

An Efficient Inductorless Dynamically Configured Interface Circuit for Piezoelectric Vibration Energy Harvesting

Vibration energy harvesting based on piezoelectric materials is of interest in several applications such as in powering remote distributed wireless sensor nodes for structural health monitoring. Synchronized switch harvesting on inductor and synchronous electric charge extraction circuits show good power efficiency among reported power management circuits; however, limitations exist due to inductors employed, adaption of response to varying excitation levels, and the synchronized switch damping (SSD) effect. In this paper, an inductorless dynamically configured interface circuit is proposed, which is able to configure the connection of two piezoelectric materials in parallel or in series by periodically evaluating the ambient excitation level. The proposed circuit is designed and fabricated in a 0.35 μHV CMOS process.The fabricated circuit is cointegrated with a piezoelectric bimorph energy harvester and the performance is experimentally validated. With a low power consumption (0.5 μW), the measured results show that the proposed rectifier can provide a 4.5 × boost in harvested energy compared to the conventional full-bridge rectifier without employing an inductor. It also shows a high power efficiency over a wide range of excitation levels and is less susceptible to SSD.

A Novel Solar and Electromagnetic Energy Harvesting System With a 3-D Printed Package for Energy Efficient Internet-of-Things Wireless Sensors

This paper discusses the design of a novel dual (solar + electromagnetic) energy harvesting powered communication system, which operates at 2.4 GHz ISM band, enabling the autonomous operation of a low power consumption power management circuit for a wireless sensor, while featuring a very good “cold start” capability. The proposed harvester consists of a dual port rectangular slot antenna, a 3-D printed package, a solar cell, an RF-dc converter, a power management unit (PMU), a microcontroller unit, and an RF transceiver. Each designed component was characterized through simulation and measurements. As a result, the antenna exhibited a performance satisfying the design goals in the frequency range of 2.4–2.5 GHz. Similarly, the designed miniaturized RF-dc conversion circuit generated a sufficient voltage and power to support the autonomous operation of the bq25504 PMU for RF input power levels as low as −12.6 and −15.6 dBm at the “cold start” and “hot start” condition, respectively. The experimental testing of the PMU utilizing the proposed hybrid energy harvester confirmed the reduction of the capacitor charging time by 40% and the reduction of the minimum required RF input power level by 50% compared with the one required for the individual RF and solar harvester under the room light irradiation condition of 334 lx.

Thermally Chargeable All-Solid-State Flexible Supercapacitor for Waste Heat Harvesting and Storage

Low-grade thermal energy is an abundantly available, sustainable and clean energy source. Its source includes waste heat from power plants, ocean thermal energy, geo-thermal energy, distributed solar energy among others. Conventional solid-state thermoelectric devices are limited in application due to their high cost, intrinsically low Seebeck coefficient (10-100 μV/K) and inflexible nature. Thermogalvanic systems, also known as thermocells have recently been found to be a promising alternative. These devices using the temperature dependence of electrochemical potential of redox electrolytes such as aqueous ferri/ferrocyanide possess the advantages of simple design, direct thermal-to-electric energy conversion, continuous operation, low mainte­nance, zero carbon emissions and low cost. However, these devices need to be connected to energy storage devices (battery or capacitor) by a power management circuit in order to store energy. This leads to complexity in system design and operation. Here, we demonstrate an integrated thermal energy harvesting supercapacitor device that can convert a temperature gradient applied over a short period of time, into stored charge. The stored electrical energy can be used to power an external load long after the temperature gradient is disengaged. Furthermore, it is flexible, thin, lightweight and all-solid-state which makes it ideal for powering portable and wearable devices. Electrodes consisting of graphene petals (GP) grown on conductive carbon cloth by microwave plasma chemical vapor deposition (MPCVD) are sandwiched onto a polyvinyl alcohol (PVA)/potassium ferrocyanide/ferricyanide gel electrolyte film to build a supercapacitor device. The device exhibits a Seebeck coefficient of -1.21 mV/K, a high areal capacitance near 9 F cm-2 at a current density of 0.1 mA cm-2 and excellent charge retention capability.

Rectifying the output of vibrational piezoelectric energy harvester using quantum dots

Piezoelectric energy harvester scavenges mechanical vibrations and generates electricity. Researchers have strived to optimize the electromechanical structures and to design necessary external power management circuits, aiming to deliver high power and rectified outputs ready for serving as batteries. Complex deformation of the mechanical structure results in charges with opposite polarities appearing on same surface, leading to current loss in the attached metal electrode. External power management circuits such as rectifiers comprise diodes that consume power and have undesirable forward bias. To address the above issues, we devise a novel integrated piezoelectric energy harvesting device that is structured by stacking a layer of quantum dots (QDs) and a layer of piezoelectric material. We find that the QD can rectify electrical charges generated from the piezoelectric material because of its adaptable conductance to the electrochemical potentials of both sides of the QDs layer, so that electrical current causing energy loss on the same surface of the piezoelectric material can be minimized. The QDs layer has the potential to replace external rectification circuits providing a much more compact and less power-consumption solution.

A Review on Piezoelectric Energy Harvesting: Materials, Methods, and Circuits

Abstract Piezoelectric microelectromechanical systems (PiezoMEMS) are attractive for developing next generation self-powered microsystems. PiezoMEMS promises to eliminate the costly assembly for microsensors/microsystems and provide various mechanisms for recharging the batteries, thereby, moving us closer towards batteryless wireless sensors systems and networks. In order to achieve practical implementation of this technology, a fully assembled energy harvester on the order of a quarter size dollar coin (diameter=24.26 mm, thickness=1.75 mm) should be able to generate about 100 μW continuous power from low frequency ambient vibrations (below 100 Hz). This paper reviews the state-of-the-art in microscale piezoelectric energy harvesting, summarizing key metrics such as power density and bandwidth of reported structures at low frequency input. This paper also describes the recent advancements in piezoelectric materials and resonator structures. Epitaxial growth and grain texturing of piezoelectric materials is being developed to achieve much higher energy conversion efficiency. For embedded medical systems, lead-free piezoelectric thin films are being developed and MEMS processes for these new classes of materials are being investigated. Non-linear resonating beams for wide bandwidth resonance are also reviewed as they would enable wide bandwidth and low frequency operation of energy harvesters. Particle/granule spray deposition techniques such as aerosol-deposition (AD) and granule spray in vacuum (GSV) are being matured to realize the meso-scale structures in a rapid manner. Another important element of an energy harvester is a power management circuit, which should maximize the net energy harvested. Towards this objective, it is essential for the power management circuit of a small-scale energy harvester to dissipate minimal power, and thus it requires special circuit design techniques and a simple maximum power point tracking scheme. Overall, the progress made by the research and industrial community has brought the energy harvesting technology closer to the practical applications in near future.

Harvesting Ambient Vibration Energy over a Wide Frequency Range for Self-Powered Electronics.

Vibration is one of the most common energy sources in ambient environment. Harvesting vibration energy is a promising route to sustainably drive small electronics. This work introduces an approach to scavenge vibrational energy over a wide frequency range as an exclusive power source for continuous operation of electronics. An elastic multiunit triboelectric nanogenerator (TENG) is rationally designed to efficiently harvest low-frequency vibration energy, which can provide a maximum instantaneous output power density of 102 W·m-3 at as low as 7 Hz and maintain its stable current outputs from 5 to 25 Hz. A self-charging power unit (SCPU) combining the TENG and a 10 mF supercapacitor gives a continuous direct current (DC) power delivery of 1.14 mW at a power management efficiency of 45.6% at 20 Hz. The performance of the SCPU can be further enhanced by a specially designed power management circuit, with a continuous DC power of 2 mW and power management efficiency of 60% at 7 Hz. Electronics such as a thermometer, hygrometer, and speedometer can be sustainably powered solely by the harvested vibration energy from a machine or riding bicycle. This approach has potential applications in self-powered systems for environment monitoring, machine safety, and transportation.

Magnetically levitated-triboelectric nanogenerator as a self-powered vibration monitoring sensor

This paper presents a magnetically levitated-triboelectric nanogenerator to harvest mechanical energy and detect acceleration of the vibratrion in the surroundings. Based on the effective conjunction of triboelectrification and electromagnetic induction, maximum power density of 3.23Wm−3 is obtained at 100MΩ and 10ms−2 for the triboelectric part, while the electromagnetic part can provide power density of 2.25Wm−2 at 1KΩ and 10ms−2. The hybridized nanogenerator also exhibits a good stability for the output performance and a good charging performance. This hybridized nanogenerator can light up 40 commercial light-emitting diode bulbs and charge a 470 μF capacitor by using a power management circuit. Furthermore, due to the magnetically-levitated structure, the hybridized nanogenerator has been utilized as a vibrometer. It can clearly detect the vibration with the acceleration less than 30ms−2 and amplitude less than 7.5mm. This work not only presents a novel approach in the field of mechanical energy harvesting, but also a solid step towards self-powered monitoring technology.

TFET-Based Power Management Circuit for RF Energy Harvesting

This paper proposes a Tunnel FET (TFET)-based power management circuit (PMC) for ultra-low power RF energy harvesting applications. In contrast with conventional thermionic devices, the band-to-band tunneling mechanism of TFETs allows a better switching performance at sub-0.2 V operation. As a result, improved efficiencies in RF-powered circuits are achieved, thanks to increased rectification performance at low power levels and to the reduced energy required for a proper PMC operation. It is shown by simulations that heterojunction TFET devices designed with III–V materials can improve the rectification process at received power levels below −20 dBm (915 MHz) when compared to the application of homojunction III–V TFETs and Si FinFETs. For an available power of −25 dBm, the proposed converter is able to deliver 1.1 ${\mu }\text{W}$ of average power (with 0.5 V) to the output load with a boost efficiency of 86%.

A piezoelectric impact-induced vibration cantilever energy harvester from speed bump with a low-power power management circuit

An energy harvesting system for road speed bumps was proposed, which consists of a piezoelectric impact-induced vibration cantilever energy harvester and a low-power power management circuit. The piezoelectric impact-induced vibration cantilever was used to harvest the energy from speed bump as it is suitable for converting the low-frequency mechanical impact to high-frequency vibrations. Furthermore, considering the characteristics of piezoelectric energy harvester for speed bumps, a high-efficiency and low-power power management circuit was designed to collect the electric energy from the harvester. A buck-boost DC–DC switching converter is used to match the impedance of PZT and so as to obtain the maximum energy from the harvester, and a wake-up circuit is designed to reduce the power dissipation of the power management circuit itself. A prototype of the piezoelectric impact-induced vibration cantilever energy harvesting system was constructed and the experiment results showed that, the controller in the power management circuit consumed only 3% of the ideal energy generated by one tire in the awake mode and less than 1% of it in the sleep mode. The efficiency of the circuit was around 74% at various vehicle speeds. In addition, the total ideal energy generated by one piezoelectric cantilever from one car passing the speed bump was 1.26mJ. This energy was exhausted by the power management circuit without sleep mode within 25s, whereas with sleep mode, the energy of 0.82μJ was delivered to the battery. Therefore, the sleep mode function in the circuit is essential to reduce the energy loss and improve the efficiency of the speed bump energy harvester.

Effective energy storage from a hybridized electromagnetic-triboelectric nanogenerator

We report a hybridized electromagnetic-triboelectric nanogenerator including an electromagnetic generator (EMG) and a triboelectric nanogenerator (TENG) for simultaneously scavenging wind energy. The TENG can deliver a largest output power of about 1.7mW under a loading resistance of 10MΩ, while the EMG can deliver a largest output power of about 2.5mW under a loading resistance of 1kΩ. A power management circuit has been designed to store the produced energy from the TENG into a capacitor, resulting in the enhanced energy-storage efficiency of up to 112% as compared with that of using a traditional rectifier. The charging rate of the capacitor by using the TENG has been optimized by changing the inductance and the switching on/off time. As compared with the individual TENG or EMG, the hybridized nanogenerator has a much better ability for sustainably powering a temperature sensor, exhibiting the potential applications of hybridized nanogenerators in self-powered sensor systems.

An inductor-free auto-power-management design built-in triboelectric nanogenerators

Triboelectric nanogenerator (TENG) has the output characteristics of high voltage but low current/charge-transfer, making its low efficiency in powering most of electronics. To address this problem, power management circuits consisting of coupled inductors or transformers are usually employed. Here we report an inductor-free, auto-power-management design based on automatic switches between serial-connected and parallel-connected capacitors in a rationally designed manner, so that the output voltage can be lowered and the output charge is enhanced in proportion. In conjunction to theoretical analysis, a TENG along with proof-of-concept power-management units as automatically driven by the triggering motion for TENG is fabricated, which improves the rate for charging a supercapacitor by 5 times. Compared to previous work, this power-management design shows advantages of capability for harvesting low power/frequency scale energy, high scalability, and light weight, which paves a new approach for achieving high-efficient portable TENG-based self-powered system.

Power density improvement of the power conditioning circuit for combined piezoelectric and electrodynamic generators

In this study, we report a power management circuit for a combined piezoelectric- electrodynamic generator. A piezoelectric element is bonded to a spring steel cantilever beam and a magnet, used as tip mass, oscillates through a coil. This principle creates the combined generator. A test setup has been created to automate the characterization of the piezoelectric generator and its power management circuit. Three different power management circuits for the piezoelectric part of the combined generator have been analysed: a bridge rectifier, an SSHI circuit with an external inductance and an SSHI circuit which utilizes the coil of the electrodynamic generator as circuit element. The three circuits are compared in terms of their output power, efficiency and power density. The SSHI circuit with an external inductance has the highest output power and efficiency, followed by the SSHI circuit with the electrodynamic generator coil. The power density of the bridge rectifier is the highest but for higher efficiency the power density of the SSHI circuit with the coil of the electromagnetic generator reaches the best results.

Triple Hybrid Energy Harvesting Interface Electronics

This study presents a novel triple hybrid system that combines simultaneously generated power from thermoelectric (TE), vibration-based electromagnetic (EM) and piezoelectric (PZT) harvesters for a relatively high power supply capability. In the proposed solution each harvesting source utilizes a distinct power management circuit that generates a DC voltage suitable for combining the three parallel supplies. The circuits are designed and implemented in 180 nm standard CMOS technology, and are terminated with a schottky diode to avoid reverse current flow. The harvested AC signal from the EM harvester is rectified with a self-powered AC-DC doubler, which utilizes active diode structures to minimize the forward- bias voltage drop. The PZT interface electronics utilizes a negative voltage converter as the first stage, followed by synchronous power extraction and DC-to-DC conversion through internal switches, and an external inductor. The ultra-low voltage DC power harvested by the TE generator is stepped up through a charge-pump driven by an LC oscillator with fully- integrated center-tapped differential inductors. Test results indicate that hybrid energy harvesting circuit provides more than 1 V output for load resistances higher than 100 kΩ (10 μW) where the stand-alone harvesting circuits are not able to reach 1 V output. This is the first hybrid harvester circuit that simultaneously extracts energy from three independent sources, and delivers a single DC output.

A triboelectric wind turbine for small-scale energy harvesting

This paper deals with a rotational energy harvester including a Horizontal Axis Wind Turbine (HAWT), a cylindrical stator covered by several electrodes, and thin Teflon dielectric membranes hung on the rotor. The sliding contact of the Teflon membranes on the stator provides simultaneously large capacitance variations and a polarization source for the electrostatic converter by exploiting triboelectric phenomena. 1μW has been harvested at 4m/s; 130μW at 10m/s and 550μW at 20m/s with a 40mmØ device. In order to validate the energy harvesting chain, the airflow energy harvester has been connected to a power management circuit implementing Synchronous Electric Charge Extraction (SECE) to supply a wireless sensor node with temperature and acceleration measurements, transmitted to a computer at 868MHz.

Water flow energy harvesters for autonomous flowmeters

This paper reports on a water flow energy harvester exploiting a horizontal axis turbine with distributed magnets of alternate polarities at the rotor periphery and air coils outside the pipe. The energy harvester operates down to 1.2L/min with an inlet section of 20mm of diameter and up to 25.2mW are provided at 20L/min in a 2.4V NiMH battery through a BQ25504 power management circuit. The pressure loss induced by the insertion of the energy harvester in the hydraulic circuit and by the extraction of energy has been limited to 0.05bars at 30L/min, corresponding to a minor loss coefficient of KEH=3.94.

Retraction: Jafer et al. Design of New Power Management Circuit for Light Energy Harvesting System. Sensors 2016, 16, 270.

We have recently discovered that the majority of the text and figures in the title paper [1] is copied from a previously published thesis [2].[...].

A Fully Integrated SoC for Smart Capsule Providing In-Body Continuous pH and Temperature Monitoring

This paper presents a SoC (System-on-a-Chip) dedicated for a single-chip smart capsule which can be used to continuously monitor human alimentary canal pH and temperature values. The SoC is composed of the pH and temperature sensor interface circuit, a wireless transceiver, the power management circuit and the flow control logic. Fabricated in 0.18 μm standard CMOS technology, the SoC occupies a die area of ~9 mm². The SoC consumes 6.15 mW from a 3 V power supply, guaranteeing the smart capsule battery life is no less than 24 hours when using 50 mAh coin batteries. The experimental results show that measurement accuracy of the smart capsule is ±0.1 pH and ±0.2°C for pH and temperature sensing, respectively, which meets the requirement of in-body pH and temperature monitoring in clinical practice.

A rationally designed output current measurement procedure and comprehensive understanding of the output characteristics for piezoelectric nanogenerators

Scavenging energy by piezoelectric nanogenerators (PENG) has been spotlighted as a promising approach to convert tiny mechanical energy into electricity. Many works have been done to improve the measurement techniques as well as reveal the output characteristics of PENGs. However, for the precise measurement of the output current, there still remains uncertainty stems from the effect of strain rate when applying mechanical impact onto PENGs. Herein, a theoretical derivation is performed to prove the existence of the maximum peak current (MPC) for PENGs, which is not influenced by strain rate but only determined by the magnitude of the applied force and inherent parameters of PENGs. A rationally designed procedure is proposed to measure the MPC with high accuracy and stability, from which an analytical model describing the MPC is established. The influence of device capacitance and the applied force on the output characteristics of PENGs are revealed, from which essential rules pertaining to the characterization and optimization for PENGs are proposed. Through this study, we can get comprehensive insight into the output characteristics of PENGs and acquire new guidelines for purpose design of PENGs and corresponding power management circuits.

A Thermoelectric Energy Harvesting System for Powering Wireless Sensors in Nuclear Power Plants

Safety is the most important issue in the development of nuclear energy. This paper reports experimental studies of a thermoelectric energy harvesting system designed for integration in a nuclear power plant capable of performing in radiation rich environments and producing enough power to run wireless sensors meant to increase plant safety. Furthermore, the system, which utilizes wasted heat present in coolant system piping, has the unique ability to provide power in both normal and accidental situations, to run the sensors without the need for external power. Two energy harvesting prototypes were designed utilizing a heat pipe for heat transfer. The first can supply a maximum power of 2.25 W using two Bi2Te3 thermoelectric modules of 2.79cm $(1.1{''}) \times 2.79$ cm (1.1”), in a source temperature near 250 °C. A second design was put forward to extend the application in higher-temperature primary loops, in which one PbTe-Bi2Te3 hybrid TEG module of 5.6cm $(2.2{''}) \times 5.6$ cm (2.2”) can provide a power of 3.0 W when the hot side temperature reaches 340 °C. In addition to the energy harvester, wireless communication circuits were developed along with an integrated power management circuit for wireless data transmission. A high intensity gamma radiation experiment was conducted during which each component was irradiated. A total dose of 200 kGy±10% (20M rads) was applied to the first prototype in order to approximate the expected lifetime accumulation for one implemented thermoelectric generator. Results showed that thermoelectric modules used in the prototype had no reduction in voltage output throughout irradiation. Throughout the experiment the harvester system witnessed a small voltage drop in open circuit voltage attributed to a reduction in heat pipe performance from radiation exposure. We also acquired a baseline radiation survivability level for non-hardened, non-shielded electronics of $10^{2}$ Gy.

Highly Stretchable Microsupercapacitor Arrays with Honeycomb Structures for Integrated Wearable Electronic Systems

The rapid development of portable and wearable electronics has greatly increased the demand for energy storage devices with similar physical properties and integration capability. This paper introduces a honeycomb polydimethylsiloxane substrate for stretchable microsupercapacitor (MSC) arrays, which enables facile integration with other electronics. The honeycomb structure can accommodate a large deformation without producing excessive strain in the MSCs and interconnects. The results of this study show that such stretchable MSC arrays with single-walled carbon nanotube electrodes demonstrate excellent rate capability and power performance as well as electrochemical stability up to 150% (zero prestrain) or 275% (-50% prestrain) stretching and under excessive bending or twisting. The present stretchable MSC arrays with honeycomb structures show high potential for integration with other electronics, such as energy harvesters, power management circuits, wireless charging circuits, and various sensors, encompassing a wide range of wearable, bioimplantable electronic systems.