Single-phase bidirectional AC-AC converter with H-bridge energy buffer for wireless power transfer applications

For designing a wireless power transfer (WPT) converter with high power transfer efficiency, the design methodology of adequate input voltage and magnetizing inductance to regulate reactive power is suggested. In addition, as increasing the magnetizing inductance, the turn number of the WPT coil increases, and it induces high parasitic resistance in the coil. Since the higher resistance makes the higher conduction loss, the analysis of the conduction loss is used in the design of the WPT coil and the operating point of the WPT converter. To verify the proposed design methodology, the mathematical analysis of the conduction loss is presented with experimental results.

A wide-dynamic range high-efficiency differential RF-to-DC power converter for wireless power transfer (WPT) applications is presented. The architecture offers high power conversion efficiency (PCE) over a wide range of input powers by employing cross-coupled high-threshold rectifying devices with stacking diodes. The proposed rectifier uses the adaptive biasing technique to control the rectifying devices’ conduction and minimizes the leakage current of the feedback diodes by utilizing the dynamic body biasing. Compared to the conventional cross-coupled rectifier, the proposed rectifier has a [Formula: see text] dynamic range. A prototype of the proposed rectifier is implemented in 65-nm CMOS technology and occupies an area of 0.0148[Formula: see text]mm2. The rectifier achieves [Formula: see text][Formula: see text]dBm sensitivity for 1[Formula: see text]V output and a 79.4% peak PCE. A dynamic range of 17.3[Formula: see text]dB is achieved at the 433[Formula: see text]MHz in the Industrial Scientific Medical band (ISM band) with a 100-K[Formula: see text] load. Furthermore, the proposed design offers a peak PCE of 62.6% and a wide dynamic range of 16.1[Formula: see text]dB at the UHF 900[Formula: see text]MHz band with a load resistance of 100-K[Formula: see text].

This book is the first systematic exposition on the emerging domain of wireless power transfer in ad hoc communication networks. It selectively spans a coherent, large spectrum of fundamental aspects of wireless power transfer, such as mobility management in the network, combined wireless power and information transfer, energy flow among network devices, joint activities with wireless power transfer (routing, data gathering and solar energy harvesting), and safety provisioning through electromagnetic radiation control, as well as fundamental and novel circuits and technologies enabling the wide application of wireless powering. Comprising a total of 27 chapters, contributed by leading experts, the content is organized into six thematic sections: technologies, communication, mobility, energy flow, joint operations, and electromagnetic radiation awareness. It will be valuable for researchers, engineers, educators, and students, and it may also be used as a supplement to academic courses on algorithmic applications, wireless protocols, distributed computing, and networking.

RF complex permeability spectra of Ni-Cu-Zn ferrites prepared under different applied hydraulic pressures and durations for wireless power transfer (WPT) applications

ABSTRACTFlux pipe couplers are compact coils used in wireless power transfer (WPT) applications. The first part of this paper investigates the effect number of sub-coils on the magnetic characteristics. Flux pipe couplers with more than two sub-coils exhibit higher coupling coefficient as compared to traditional flux pipe couplers with two sub-coils. Furthermore, multi sub-coil flux pipe couplers better distribute the magnetic flux inside the core, making them attractive in high power applications. The second part presents an experimental WPT system employing multi sub-coil flux pipe couplers with three sub-coils. More than 82% power transfer efficiency is observed when couplers are separated with 100 mm vertical gap. Lateral misalignments up to 200 mm are then applied, and meantime, the separation between sub-coils is varied for achieving maximum efficiency. A near-constant efficiency is obtained up to 150 mm misalignment. Therefore, this paper announces another potential use of flux pipe couplers realizing an adaptive WPT system.

Nowadays, near-field wireless power transfer is realized by inductive or capacitive coupling. Power transmission is respectively accomplished by a time-varying magnetic or electric field as medium. Recently, mixed or hybrid near-field wireless power transfer is being developed as a possible mean to increase the power density of the system by utilizing both the magnetic and the electric near-field. The fundamental basics of mixed coupling are well understood. However, the implications of the mixed coupling theory on wireless power transfer applications is not rigorously described. Moreover, no general description is available that allows for a detailed comparison between current hybrid systems, especially for a series topology of inductive and capacitive coupling. In this work, we analytically solve a general mixed wireless power transfer configuration with series topology. We determine the optimal load to maximize the amount of power transfer and calculate the maximum achievable output power. The analytical derivation is validated by numerical simulation in SPICE. Our solution provides insight in the mixed wireless link and can serve as a reference point to evaluate the performance of mixed systems with regard to power transfer.

This paper presents a complete design methodology of a Class-E inverter for capacitive wireless power transfer (CWPT) applications, focusing on the capacitance coupling influence. The CWPT has been investigated in this paper, because most of the literature refers to inductive power transfer (IWPT). However, CWPT in perspective can result in lower cost and higher reliability than IWPT, because it does not need coils and related shields. The Class-E inverter has been selected, because it is a single switch inverter with a grounded MOSFET source terminal, and this leads to low costs and a simple control strategy. The presented design procedure ensures both zero voltage switching (ZVS) and zero derivative switching (ZDS) conditions at an optimum coupling coefficient, thus enabling a high transmission and conversion efficiency. The novelties of the proposed method are that the output power is boosted higher than in previous papers available in the literature, the inverter is operated at a high conversion efficiency, and the equivalent impedance of the capacitive wireless power transfer circuit to operate in resonance is exploited. The power and the efficiency have been increased by operating the inverter at 100 kHz so that turn-off losses, as well as losses in inductor and capacitors, are reduced. The closed-form expressions for all the Class-E inverter voltage and currents waveforms are derived, and this allows for the understanding of the effects of the coupling coefficient variations on ZVS and ZDS conditions. The analytical estimations are validated through several LTSpice simulations and experimental results. The converter circuit, used for the proposed analysis, has been designed and simulated, and a laboratory prototype has been experimentally tested. The experimental prototype can transfer 83.5 W at optimal capacitive coupling with operating at 100 kHz featuring 92.5% of the efficiency, confirming that theoretical and simulation results are in good agreement with the experimental tests.

This paper presents a new approach to simplify the design of class-E power amplifier (PA) using hybrid artificial neural-optimization network modeling. The class-E PA is designed for wireless power transfer (WPT) applications to be used in biomedical or internet of things (IoT) devices. Artificial neural network (ANN) models are combined with optimization algorithms to support the design of the class-E PA. In several amplifier circuits, the closed form equations cannot be extracted. Hence, the complicated numerical calculations are needed to find the circuit elements values and then to design the amplifier. Therefore, for the first time, ANN modeling is proposed in this paper to predict the values of the circuit elements without using the complex equations. In comparison with the other similar models, high accuracy has been obtained for the proposed model with mean absolute errors (MAEs) of 0.0110 and 0.0099, for train and test results. Moreover, root mean square errors (RMSEs) of 0.0163 and 0.0124 have been achieved for train and test results for the proposed model. Moreover, the best and the worst-case related errors of 0.001 and 0.168 have been obtained, respectively, for the both design examples at different frequencies, which shows high accuracy of the proposed ANN design method. Finally, a design of class-E PA is presented using the circuit elements values that, first, extracted by the analyses, and second, predicted by ANN. The calculated drain efficiencies for the designed class-E amplifiers have been obtained equal to 95.5% and 91.2% by using analyses data and predicted data by proposed ANN, respectively. The comparison between the real and predicted values shows a good agreement.

In this article, we propose a new antenna geometry for near-field magnetoelectric wireless power transfer (ME-WPT) application, where the antenna geometry is found to be resilient to misalignment between the receiving and the transmitting antennas. The proposed geometry is simple to fabricate and is planar, and therefore it can be easily integrated with various platforms suitable for wearable applications. The proposed structure is demonstrated to show improved WPT efficiency under different forms of misalignment between the transmitting and receiving antennas by the virtue of miniaturization and the fringing fields. Specifically, a central bar structure is added in the traditional loop antenna to provide dipole-like and miniaturized performance. Concurrently, a discontinuity in the loop is introduced to enable fringing fields beyond the aperture of the antenna. Investigations are conducted to conclude that a superiority in the performance is associated with these fringing fields. Design-optimization, simulation, and measurement investigations are conducted to estimate the WPT performance under various forms of misalignment. Notably, the proposed structure shows an increase as high as 65% in power transfer efficiency within the range of misalignment considered in this work.

© 2019 Progress In Electromagnetics Research B. We present an optimization procedure for wireless power transfer (WPT) applications and test it numerically for a WPT system design with four resonant circuits that are magnetically coupled by coaxial coils in air, where the magnetic field problem is represented by a fully populated inductance matrix that includes all magnetic interactions that occur between the coils. The magnetically coupled resonators are fed by a square-wave voltage generator and loaded by a rectifier followed by a smoothing filter and a battery. We compute Pareto fronts associated with a multi-objective optimization problem that contrasts: 1) the system efficiency; and 2) the power delivered to the battery. The optimization problem is constrained in terms of: 1) the physical construction of the system and its components; 2) the root-mean-square values of the currents and voltages in the circuit; and 3) bounds on the overtones of the currents in the coils in order assure that the WPT system mainly generates magnetic fields at the operating frequency. We present optimized results for transfer distances from 0.8 to 1.6 times the largest coil radius with a maximum power transfer from 4 kW to 9 kW at 85 kHz, which is achieved at an efficiency larger than 90%.

This paper presents a comprehensive evaluation of fabrication techniques for the integration of coils into textiles, for the purpose of enabling low-power wireless power transfer; for example, the powering of on-body monitoring devices, such as heart-rate monitors. Key electrical parameters of the coils required to maximize power transfer efficiency are identified from theory. Flexible coils have been fabricated using standard processes widely used in the textile industry, such as screen printing and embroidery. The screen printed coils were fabricated with a silver-polymer ink on a printed interface layer; the embroidered coils were fabricated using a variety of conductive threads formed by coating textile fibers and through the use of copper fibers. These coils have been experimentally characterized and evaluated for use in wireless power transfer applications. The effects of coil geometry and separation on the dc–dc power transfer efficiency using Qi standard compliant driver and receiver circuits are reported.

Resonant dc-dc converter regularly use Schottky diodes for high frequency rectification. Si Schottky diodes have relatively low voltage ratings and present reverse-recovery type losses when driven hard enough. SiC Schottky diodes can operate at high frequencies, but incur higher conduction losses. This paper presents a bidirectional dc-dc resonant converter having two ground referenced switches. The prototype converter delivers 400 W between a source of 170 V and a load of 50 V while delivering 250 W in the opposite direction. The converter presented herein can potentially be used in applications such as wireless power transfer, fuel cell and battery applications, bus converters, etc.

Wireless power transfer (WPT) systems can potentially provide simultaneous power and data transfer for Internet-of-Things devices, such as smart speakers, glasses, and watches. However, due to the high quality factor of coils, the intrinsically narrow WPT channel bandwidth severely limits the data transmission capability of the system, especially for data downloading links requiring higher data rates. In addition, the channel bandwidth varies with power transfer distances, which is also undesirable for wireless communication. In this study, the channel features of a two-coil series-series matching magnetic resonance wireless power and data transfer (MWPDT) system, including the bandwidth and the roll-off slope are characterized analytically. Based on the characterization results, a receiver front-end circuit with a three-stage cascaded equalizer (EQ) is proposed and implemented to extend the bandwidth of a MWPDT system at different distances. The proposed EQ can provide a frequency response with a variable roll-up slope from 10 to 45 dB/dec to compensate for the distance-dependent channel response of an MWPDT system. A complete MWPDT system is built and tested to verify the performance of the proposed method. Experimental results demonstrate that the data rates can be extended from 650, 500, and 350 kbps to 850, 700, and 650 kbps at 0.4, 0.5, and 0.6-m distances, respectively. The highest data rate extension ratio is 85% at a transmission distance of 0.6 m, which is 2.4 times the radii of the coil employed in the system.

Design and application of wireless power transfer using Class-E inverter based on Adaptive Impedance-Matching Network

The rectifier is one of parts from receiver circuit used for wireless power transfer (WPT) and energy harvesting (EH) application, so improving the efficiency of rectifier is a critical point for WPT and EH application. The previous research of cross-coupled inverter (CCI) rectifier used 0.35 μm CMOS process technology. It showed the highest power conversion efficiency (PCE) achieved 60% when 100 kOhm load, 0.7 V voltage input and 13.56 MHz RFID frequency input. This paper uses CCI rectifier circuit design with 0.18 μm CMOS process technology for improving voltage output. The result shows PCE 0.18 μm higher than 0.35 μm CCI rectifier with 0.4 mW of maximum power output and 93.30%, when it uses load 2 kOhm, 300 kHz frequency input and ideal voltage source. It occurred because 0.18 μm CCI rectifier has lower leakage current drain to source (Ids) of MOSFET. In addition, the internal resistance voltage source from 1 to 100 Ohm can decrease efficiency of CCI rectifier from 86% to 79%. The result of voltage co version efficiency is slightly raised from 95% to 99%, with maximum voltage output of 3.28 V on load over than 1 kOhm.