Publications
191 results found
Arteaga Saenz JM, Aldhaher S, Yates DC, et al., 2019, A multi-MHz wireless power transfer system with mains power factor correction circuitry on the receiver, 34th Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 683-688, ISSN: 1048-2334
This paper proposes the implementation of a new system topology for multi-MHz inductive power transfer (IPT) systems, which achieves unity power factor when fed from a mains power supply without traditional active circuitry in the front-end as a mains interface. Experiments were performed using an IPT-link which consists of two 20 cm two-turn air-core printed-circuit-board (pcb) coils separated by an air-gap of 13 cm. At the transmit side, a push-pull load-independent Class EF inverter fed from a rectified 60 Hz power supply with no bulk capacitor was designed to drive the transmit coil at 13.56 MHz. This inverter, which has two choke inductors between the voltage source and the two switches, similar to that of an interleaved boost converter, is suitable to be fed directly from a rectified mains source because it tolerates large changes on the input voltage. The IPT rectifier in the experiments was built using a dual current-driven Class D-based topology which allows for higher output voltage when the induced electromotive force (emf) on the receive coil is low. The final power conversion stage on the receive side is a power factor correction (PFC) boost converter that regulates the output voltage and shapes the current waveform at the input of the system. This stage is the only part of the system with closed-loop control. The end-to-end efficiency was measured at 73.3% with 99.2% power factor, when powering a load of 150 W.
Lawson J, Yates DC, Mitcheson PD, 2019, High <i>Q</i> Coil Measurement for Inductive Power Transfer, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol: 67, Pages: 1962-1973, ISSN: 0018-9480
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- Citations: 13
Arteaga Saenz J, Lan L, Aldhaher S, et al., 2019, A multi-MHz IPT-link developed for load characterisation at highly variable coupling factor, Wireless Power Transfer Conference, Pages: 1-4
This paper presents the development and characterisation of an inductive link to assess and compare inductive power transfer (IPT) systems that operate at 6.78 or 13.56 MHz. First, the properties of two equal air-core coils were obtained from simulations and corroborated experimentally. Then, the coupling factor between the coils was calculated in function of separation and misalignment. A receiving-end circuit, comprised of a capacitance and a resistive load, was also characterised in order to reflect different loads to the transmitter at different tunings and couplings, and therefore represent the effects produced by changes in coupling and variations in the rectifier's input impedance. The link was tested, firstly using a Class E inverter and then a load-independent Class EF inverter, both at power levels lower than 200 W. The reflected load was changed by altering coupling, and the tuning capacitance. A comparison between these inverter topologies handling highly reactive loads is shown here for the first time.
Pucci N, Kwan CH, Yates DC, et al., 2019, Effect of Fields Generated Through Wireless Power Transfer on Implantable Biomedical Devices, IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW) / Wireless Power Week Conference, Publisher: IEEE, Pages: 160-164
Kwan CH, Arteaga JM, Yates DC, et al., 2019, Design and Construction of a 100W Wireless Charger for an E-Scooter at 6.78MHz, IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW) / Wireless Power Week Conference, Publisher: IEEE, Pages: 186-190
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- Citations: 6
Kwan CH, Yates DC, Mitcheson PD, 2019, Reducing human body heating and temperature rises due to inductively-powered implantable medical devices, 18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Aldhaher S, Mitcheson PD, 2019, 500W 13.56MHz Class EF Push-pull Inverter for Advanced Dynamic Wireless Power Applications, IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW) / Wireless Power Week Conference, Publisher: IEEE, Pages: 263-267
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- Citations: 8
Kim J, Clerckx B, Mitcheson PD, 2019, Experimental Analysis of Harvested Energy and Throughput Trade-off in a Realistic SWIPT System, 2019 IEEE MTT-S WIRELESS POWER TRANSFER CONFERENCE (WPTC) / IEEE PELS WORKSHOP ON EMERGING TECHNOLOGIES: WIRELESS POWER (WOW) / WIRELESS POWER WEEK (WPW 2019), Pages: 1-5, ISSN: 2474-0225
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- Citations: 22
Aldhaher S, Yates D, Mitcheson P, 2018, Load-independent class E/EF inverters and rectifiers for MHz-switching applications, IEEE Transactions on Power Electronics, Vol: 33, Pages: 8270-8287, ISSN: 0885-8993
This paper presents a unified framework for the modeling, analysis, and design of load-independent Class E and Class EF inverters and rectifiers. These circuits are able to maintain zero-voltage switching and, hence, high efficiency for a wide load range without requiring tuning or use of a feedback loop, and to simultaneously achieve a constant amplitude ac voltage or current in inversion and a constant dc output voltage or current in rectification. As switching frequencies are gradually stepping into the megahertz (MHz) region with the use of wide-bandgap (WBG) devices such as GaN and SiC, switching loss, implementing fast control loops, and current sensing become a challenge, which load-independent operation is able to address, thus allowing exploitation of the high-frequency capability of WBG devices. The traditional Class E and EF topologies are first presented, and the conditions for load-independent operation are derived mathematically; then, a thorough analytical characterization of the circuit performance is carried out in terms of voltage and current stresses and the power-output capability. From this, design contours and tables are presented to enable the rapid implementation of these converters given particular power and load requirements. Three different design examples are used to showcase the capability of these converters in typical MHz power conversion applications using the design equations and methods presented in this paper. The design examples are chosen toward enabling efficient and high-power-density MHz converters for wireless power transfer (WPT) applications and dc/dc conversion. Specifically, a 150-W 13.56-MHz Class EF inverter for WPT, a 150-W 10-MHz miniature Class E boost converter, and a lightweight wirelessly powered drone using a 20-W 13.56-MHz Class E synchronous rectifier have been designed and are presented here.
Lan L, Ting NM, Aldhaher S, et al., 2018, Foreign Object Detection for Wireless Power Transfer, 2nd URSI Atlantic Radio Science Meeting (AT-RASC), Publisher: IEEE
This paper presents foreign object detection (FOD) methods for MHz wireless power transfer (WPT) systems. Unlike current FOD implementations, the presented methods can operate without requiring a feedback loop from the wireless power receiver to the transmitter. This allows complete decoupling of the transmitter and receiver and therefore reduces the design complexity and cost of the system. The developed FOD methods were implemented on a 13.56 MHz WPT and experimental results are presented showing successful detection of a wide range of objects regardless of the loading condition of the system.
Arteaga Saenz JMA, Aldhaher SA, Kkelis GK, et al., 2018, Multi-MHz IPT systems for variable coupling, IEEE Transactions on Power Electronics, Vol: 33, Pages: 7744-7758, ISSN: 0885-8993
This paper proposes solutions for an IPT system to operate efficiently when large changes in coupling take place. To achieve high power-efficiency independent of coupling, we utilise inherent regulation properties of resonant converters to avoid losing soft switching for any coupling value, and present the optimal load to the IPT-link at the maximum energy-throughput coupling. A probability-based model is introduced to assess and optimise the IPT system by analysing coupling as a distribution in time, which depends on the dynamic behaviour of the wireless charging system. The proposed circuits are a Class D rectifier with a resistance compression network (RCN) in the receiving-end and a load-independent Class EF inverter in the transmitting-end. Experiments were performed at 6.78 and 13.56 MHz verifying high efficiency for dynamic coupling and variable load resistance. End-to-end efficiencies of up to 88% are achieved at a coil separation larger than one coil-radius for a system capable of supplying 150 W to the load, and the energy-efficiency was measured at 80% when performing a uniformly-distributed linear-misalignment of 0-12.5 cm, corresponding to a receiver moving at constant velocity over a transmitter without power throughput control.
Arteaga Saenz JM, Kkelis G, Aldhaher S, et al., 2018, Probability-based optimisation for a multi-MHz IPT system with variable coupling, IEEE PELS Workshop on Emerging Technologies - Wireless Power Transfer (Wow), Publisher: IEEE
This paper presents the analysis and design of a dynamic inductive power transfer (IPT) system, in which coupling is treated as a stochastic variable and is therefore modelled as a probability distribution. The purpose of this formulation is to optimise the tuning of the inverter and the rectifier to the coupling value that achieves the highest charging energy-efficiency when operating at a broad range of coupling. The analysis is supported by a case study in which two rectifier designs, using the hybrid Class E topology, are tuned at different coupling values in order to verify which version achieves the highest charging efficiency. The load in the experiments is a wirelessly powered drone without a battery hovering randomly over the charging pad, and the range of motion is set by a nylon string tether. The experiments show lower energy consumption when the rectifier is tuned to present the optimal load of the link at the coupling value with the highest probability, as opposed to the first, which was designed to present the optimal load of the link at minimum coupling.
Mitcheson PD, Kkelis G, Aldhaher S, et al., 2018, Power Electronics for Wireless Power Delivery in Synthetic Sensor Networks, 17th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Gadoue S, Chen K-W, Mitcheson P, et al., 2018, Electrochemical Impedance Spectroscopy State of Charge Measurement for Batteries using Power Converter Modulation, 9th International Renewable Energy Congress (IREC), Publisher: IEEE, ISSN: 2378-3435
Aldhaher S, Mitcheson PD, 2018, Sate-Space Modelling and Design of a 10MHz 180W Class E DC/DC Converter using WBG Devices, 33nd Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 2918-2921, ISSN: 1048-2334
Ouda MHI, Mitcheson P, Clerckx B, 2018, Optimal Operation of Multi-Tone Waveforms inLow RF-Power Receivers, IEEE MTT-S Wireless Power Transfer Conference
Aldhaher S, Yates DC, Mitcheson PD, 2018, 13.56MHz 50W Load-Independent Synchronous Class E Rectifier using GaN devices for Space-Constrained Applications, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Mitcheson PD, Boyle D, Kkelis G, et al., 2017, Energy-Autonomous Sensing Systems Using Drones, 16th IEEE SENSORS CONFERENCE, Publisher: IEEE, Pages: 648-650, ISSN: 1930-0395
Pacini A, Costanzo A, Aldhaher S, et al., 2017, Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources, IEEE Transactions on Microwave Theory and Techniques, Vol: 65, Pages: 5367-5376, ISSN: 0018-9480
This paper describes the modeling, analysis, and design of a complete (dc-to-dc) inductive wireless power transfer (WPT) system for industrial moving applications. The system operates at 6.78 MHz and delivers up to 150 W to a load moving along a linear path, providing a quasi-constant dc output voltage and maintaining a zero voltage switching operation, regardless of position and load, without any retuning or feedback. The inductive link consists of an array of stationary transmitting coils and a moving receiving coil whose length is optimized to achieve a constant coupling coefficient along the path. Each Tx coil is individually driven by a constant amplitude and phase sinusoidal current that is generated from a GaN-based coupled load-independent Class EF inverter. Two adjacent transmitters are activated at a given time depending on the receiver’s position; this effectively creates a virtual series connection between the two transmitting coils. The Rx coil is connected to a passive Class E rectifier that is designed to maintain a constant dc output voltage independent of its load and position. Extensive experimental results are presented to show the performance over different loading conditions and positions. A peak dc-to-dc efficiency of 80% is achieved at 100 W of dc output power and a dc output voltage variation of less than 5% is measured over a load range from 30 to 500 Ω . The work in this paper is foreseen as a design solution for a high-efficient, maintenance-free, and reliable WPT system for powering sliders and mass movers in industrial automation plants.
Douthwaite M, Koutsos E, Yates DC, et al., 2017, A thermally powered ISFET array for on-body pH measurement, IEEE Transactions on Biomedical Circuits and Systems, Vol: 11, Pages: 1324-1334, ISSN: 1932-4545
Recent advances in electronics and electrochemical sensors have led to an emerging class of next generation wearables, detecting analytes in biofluids such as perspiration. Most of these devices utilize ion-selective electrodes (ISEs) as a detection method; however, ion-sensitive field-effect transistors (ISFETs) offer a solution with improved integration and a low power consumption. This work presents a wearable, thermoelectrically powered system composed of an application-specific integrated circuit (ASIC), two commercial power management integrated circuits and a network of commercial thermoelectric generators (TEGs). The ASIC is fabricated in 0.35 μm CMOS and contains an ISFET array designed to read pH as a current, a processing module which averages the signal to reduce noise and encodes it into a frequency, and a transmitter. The output frequency has a measured sensitivity of 6 to 8 kHz/pH for a pH range of 7-5. It is shown that the sensing array and processing module has a power consumption 6 μW and, therefore, can be entirely powered by body heat using a TEG. Array averaging is shown to reduce noise at these low power levels to 104 μV (input referred integrated noise), reducing the minimum detectable limit of the ASIC to 0.008 pH units. The work forms the foundation and proves the feasibility of battery-less, on-body electrochemical for perspiration analysis in sports science and healthcare applications.
Douthwaite M, Koutsos E, Yates DC, et al., 2017, A Thermally Powered ISFET Array for On-Body pH Measurement., IEEE Trans. Biomed. Circuits and Systems, Vol: 11, Pages: 1324-1334
Kkelis G, Yates DC, Mitcheson PD, 2017, Class-E half-wave zero dv/dt rectifiers for inductive power transfer, IEEE Transactions on Power Electronics, Vol: 32, Pages: 8322-8337, ISSN: 0885-8993
This paper analyses and compares candidate zero dv/dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv/dt rectifiers is analysed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom which enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: 1) For a constant dc load resistance, a receiving end efficiency of 95% was achieved when utilising the hybrid rectifier, with a tolerance in required input resistance of 2.4% over the tested output power range (50W to 200W). 2) For a variable dc load in the range of 100% to 10%, the hybrid and current driven rectifiers presented an input reactance deviation less than 2% of the impedance of the magnetising inductance of the inductive link respectively and receiving end efficiencies greater than 90%. 3) For a constant current in the receiving coil, both the hybrid and the current driven rectifier achieve inherent output voltage regulation in the order of 3% and 8% of the nominal value respectively, for a variable dc load range from 100% to 10%.
Lawson J, 2017, High frequency electromagnetic links for wireless power transfer
This thesis investigates inductive links used in wireless power transfer systems. Inductive power transfer can be used as a power delivery method for a variety of portable devices, from medical implants to electric vehicles and is gaining increased interest. The focus is on high quality factor coils and MHz operation, where accurate measurements are difficult to achieve. Fast models of all pertinent aspects of inductive power transfer systems for constant cross section coils are developed. These models are used to optimise a new coil winding pattern that aims to increase efficiency in volume constrained scenarios. Measurement systems are developed to measure coil Q factors in excess of 1,000. The prototype measurement systems are verified against models of that system, as well as finite element simulations of the coil under test. Shielding of inductive power transfer systems is then investigated. A structure typically used at GHz frequencies, the artificial magnetic conductor, is miniaturised as an alternative to conventional ferrite backed ground plane shielding. Finite element simulation shows this structure significantly improves link efficiency. The artificial magnetic conductor prototype does not result in a gain in efficiency expected, however it does display the properties expected of an artificial magnetic conductor, including increased coupling factor. Finally, an unconventional inductive power transfer system is presented where transmitter and receiver are up to 6m away from each other and of radically different size. This system provides mW level power to remote devices in a room, for example thermostats or e-ink displays. Conventional approaches to design do not consider the distortion of the magnetic field caused by metallic objects in the room. It was found that treating the system as a decoupled receiver and transmitter provides a better prediction of received power in real world environments.
Pacini A, Costanzo A, Aldhaher S, et al., 2017, Design of a Position-Independent End-to-End Inductive WPT link for Industrial Dynamic Systems, IEEE-Microwave-Theory-and-Techniques-Society International Microwave Symposium (IMS) / Session on Women in Microwaves (WIM), Publisher: IEEE, Pages: 1049-1052, ISSN: 0149-645X
Mitcheson PD, Boyle D, Kkelis G, et al., 2017, Energy-autonomous sensing systems using drones, 2017 IEEE SENSORS, Publisher: IEEE
Allmen L, Bailleul G, Becker T, et al., 2017, Aircraft strain WSN powered by heat storage harvesting, IEEE Transactions on Industrial Electronics, Vol: 64, Pages: 7284-7292, ISSN: 0278-0046
The combination of ultra-low-power wireless communications and energy harvesting enables the realization of autonomous wireless sensor networks. Such networks can be usefully applied in commercial aircraft where wireless sensing solutions contribute to weight reduction and increased ease of installation and maintenance. This paper presents, for the first time, a complete energy-autonomous wireless strain monitoring system for aircraft. The system is based on a multimode wireless time-division multiple access (TDMA) medium access control (MAC) protocol that supports automatic configuration and a time-stamping accuracy better than 1 ms. The energy supply depends solely on an innovative thermoelectric energy harvester, which takes advantage of the changes in environmental temperature during takeoff and landing. The system was successfully integrated and passed the functional and flight-clearance tests that qualify it for use in a flight-test installation.
Kim J, Clerckx B, Mitcheson PD, 2017, Prototyping and Experimentation of a Closed-Loop Wireless Power Transmission with Channel Acquisition and Waveform Optimization, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Kkelis G, Aldhaher S, Arteaga JM, et al., 2017, Hybrid Class-E Synchronous Rectifier for Wireless Powering of Quadcopters, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Aldhaher S, Mitcheson PD, Arteaga JM, et al., 2017, Light-Weight Wireless Power Transfer for Mid-Air Charging of Drones, 11th European Conference on Antennas and Propagation (EUCAP), Publisher: IEEE, Pages: 336-340, ISSN: 2164-3342
Arteaga JM, Aldhaher S, Kkelis G, et al., 2017, Design of a 13.56 MHz IPT system optimised for dynamic wireless charging environments, 2nd IEEE Annual Southern Power Electronics Conference (SPEC), Publisher: IEEE, Pages: 1-6
Inductive power transfer (IPT) systems are often designed to achieve their highest efficiency at a fixed load value and at a fixed coil separation distance and misalignment. A variation in the position of the coils or the load value tends to drastically affect the efficiency, and therefore makes the designed IPT system not practical for applications that are mobile with variable loading conditions such as dynamic wireless charging for electric vehicles. This paper presents a novel design approach for loosely-coupled IPT systems that can inherently maintain efficient operation against changes in the system's characteristics, coil geometries and loading conditions. The transmitting-end of the proposed IPT system consists of a Load-Independent Class EF inverter that provides a constant amplitude current in the transmitting-end coil and achieves zero-voltage switching (ZVS) independent of the coupling factor and the load resistance. A Class D rectifier with a resistance compression network (RCN) was implemented for the receiving-end of the IPT system to ensure that the reflected resistance to the transmitting-end is at its optimum value with minimal dependence on the output load resistance. The combination of the features of the inverter and rectifier allow the IPT system to operate efficiently across a wide range of air gaps, without retuning. Experimental results show a maximum DC-DC efficiency of 83% with a coil separation of one coil diameter and 85 W output power. A weighted average DC-DC energy transfer efficiency (where the coils move through zero alignment, to full alignment, and back to zero alignment at constant velocity), was measured at 73%.
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