Power Receiver Coil Research Articles

Modeling and Control of Dynamic Wireless Power Transfer System for Electric Vehicle charger application

This paper proposes a nonlinear state-space model for a dynamic wireless power transfer system (DWPT). The DWPT system comprises emitter coils supplied by DC/AC converters, with a phase angle control to achieve maximum power transfer. The power receiver coil is connected to a full bridge diode rectifier followed by an equivalent load resistance. To emulate the dynamic movement property of WPT, the coupling factors between the emitter and receiver coils are set to be variable and depend on the movement of the power receiver alongside the power emitter coils. The control has been successfully demonstrated under variable coupling coefficients to achieve maximum power transfer. Such improvement maintains the power and voltage across the load during transient states.

Accurate Rectifier Characterization and Improved Modeling of Constant Power Load Wireless Power Transfer Systems

Wireless power transfer (WPT) is an emerging technology deployed for a wide range of applications. Various design challenges need to be addressed at both circuit and system levels. However, the conventional modeling methods either require impractical assumptions or only focus on the coil-to-coil part. This article presents a system-level model for WPT applications, including all the critical interior blocks, such as power amplifier, transmitter coil, receiver coil, matching networks, and rectifier. An accurate characterization method is proposed to obtain the rectifier impedance as a realistic load condition. Then, through frequency harmonic analysis, the power capabilities along the power flow path are analytically derived for both the fundamental and higher order harmonic components. The system efficiency and the power loss at each block can be accurately estimated. As a result, this model can not only optimize the system performance, but also help improve the thermal design for WPT products. With the assistance of this improved model, a practical design methodology is introduced to optimize the system parameters. An experimental prototype is built to validate the proposed model and the design methodology. Good correlations are observed between the calculations and experiments in both the time-domain and frequency-domain results.

Quantitative Comparison of Wireless Power Transfer Using HTS and Copper Coils

Wireless power transfer (WPT) technology, especially using the magnetic resonance coupling to transfer the electric power has gained more attention recently. Due to ultra-low electrical resistivity below the critical current, the current density and quality factor of the superconducting wires are much higher than that of the traditional copper wires. Therefore, the transferring performance can be improved greatly. The superconducting wires have been adopted as the power coil, transmitter coil, repeater coil, and receiver coil, respectively. In this paper, performances of WPT systems partially and fully equipped with superconducting wires are quantitatively compared. Firstly, the classical WPT system with four coils has been presented. Then, superconducting coils and cooling facility for WPT systems are discussed. Lastly, by using the finite element method, transferring performance of the WPT system under different scenarios are intensively evaluated and compared.

A power conversion chain with an internally-set voltage reference and reusing the power receiver coil for wireless bio-implants

In this paper, a power conversion chain (PCC) with an internally-set voltage reference is presented. It is comprised of a power receiver coil, an active rectifier and a novel buck-boost converter. The output voltage of the PCC is set by using the parameters of a new buck-boost converter control unit in order to avoid utilizing an extra voltage reference circuit. Furthermore, the proposed PCC reuses the power receiver coil to facilitate the realization of the buck-boost converter. This way, the efficiency of the proposed PCC gets almost independent of the receiving coil voltage amplitude. In addition, the proposed buck-boost converter significantly reduces the size of the PCC and makes it suitable for wireless power transfer via inductive links in bio-implant applications. It should be noted that employing an active rectifier followed by the proposed buck-boost converter enhances the PCC end-to-end efficiency. The proposed PCC is simulated for the input received signal with a frequency of 10 MHz and an amplitude variation within 3–7 V. The simulation results show that the efficiency variation is less than 2.6% and the achieved maximum efficiency is 80.4% and 63.4% for the proposed converter and PCC, respectively. For further verification of the proposed idea, a proof-of-concept prototype is implemented and experimental results are provided.

Closed-Loop Neurostimulators: A Survey and A Seizure-Predicting Design Example for Intractable Epilepsy Treatment.

First, existing commercially available open-loop and closed-loop implantable neurostimulators are reviewed and compared in terms of their targeted application, physical size, system-level features, and performance as a medical device. Next, signal processing algorithms as the primary strength point of the closed-loop neurostimulators are reviewed, and various design and implementation requirements and trade-offs are discussed in details along with quantitative examples. The review results in a set of guidelines for algorithm selection and evaluation. Second, the implementation of an inductively-powered seizure-predicting microsystem for monitoring and treatment of intractable epilepsy is presented. The miniaturized system is comprised of two miniboards and a power receiver coil. The first board hosts a 24-channel neurostimulator system on chip fabricated in a [Formula: see text] CMOS technology and performs neural recording, on-chip digital signal processing, and electrical stimulation. The second board communicates recorded brain signals as well as signal processing results wirelessly. The multilayer flexible coil receives inductively-transmitted power. The system is sized at 2 × 2 × 0.7 [Formula: see text] and weighs 6 g. The approach is validated in the control of chronic seizures in vivo in freely moving rats.

A power efficient buck‐boost converter by reusing the coil inductor for wireless bio‐implants

SummaryIn this paper, a buck‐boost converter circuit for wireless power transfer via inductive links in bio‐implantable systems is presented. The idea is based on reusing the power receiver coil to design a regulator. This method employs five switches to utilize the coil inductor in a frequency other than the power‐receiving signal frequency. Reusing the coil inductor decreases the on‐chip regulator area and makes it suitable for bio‐implants. Furthermore, in the proposed technique, the regulator efficiency becomes almost independent of the coil receiving voltage amplitude. The proposed concept is employed in a buck‐boost regulator, and simulation results are provided. For a 10 MHz received signal with the amplitude variation within 3 ~ 6 V and with the converter switching rate of 200 kHz, the achieved maximum efficiency is 78%. The proposed regulator can also deliver 10 μA to 4 mA to its load while its output voltage varies from 0.6 to 2.3 V. Simulations of the proposed converter are performed in Cadence‐Spectre using TSMC 0.18 μm CMOS technology. Copyright © 2017 John Wiley & Sons, Ltd.

Autonomous Coil Alignment System Using Fuzzy Steering Control for Electric Vehicles with Dynamic Wireless Charging

An autonomous coil alignment system (ACAS) using fuzzy steering control is proposed for vehicles with dynamic wireless charging. The misalignment between the power receiver coil and power transmitter coil is determined based on the voltage difference between two coils installed on the front-left/front-right of the power receiver coil and is corrected through autonomous steering using fuzzy control. The fuzzy control is chosen over other control methods for implementation in ACAS due to the nonlinear characteristic between voltage difference and lateral misalignment distance, as well as the imprecise and constantly varying voltage readings from sensors. The operational validity and feasibility of the ACAS are verified through simulation, where the vehicle equipped with ACAS is able to align with the power transmitter in the road majority of the time during operation, which also implies achieving better wireless power delivery.

A Novel Mat-Based System for Position-Varying Wireless Power Transfer to Biomedical Implants

Wireless power transfer via magnetically resonant coupling is a new technology to deliver power over a relatively long distance. Here, we present a mat-based design to wirelessly power moving targets based on this technology. Our design is specifically applied to transcutaneously power medical implants within free-moving laboratory animals. Our system comprises a driver coil array, a hexagonally packed transmitter mat, a receiver coil, and a load coil, and generates a nearly flat magnetic distribution over a defined area to produce an approximately constant power output independent of the location of the receiver coil. This paper also describes a novel power receiver coil design of the same shape as the exterior of the implant, allowing for maximum magnetic coupling, eliminating the space restrictions due to the coil within the implant, and matching the resonant frequencies of the implant and the transmitter coil. Our new transmitter and receiver designs significantly reduce the size of a biomedical implant and may provide a lifetime power supply to implanted circuits without the need for an internal battery. Our designs are also useful in various other applications involving moving targets, such as part of a robot or a vehicle.