Proceedings Article•
Limitation of inductive power transfer for consumer applications
06 Oct 2009-pp 1-10
TL;DR: In this article, the authors derived the matching conditions for optimal power efficiency for inductive power transmission structures with varying distance and size ratios and investigated the achievable power efficiency of a given structure with respect to resonant matching and load impedance.
Abstract: Inductive power transmission is proposed more and more also for consumer applications. In this work, limitations with respect to efficiency of the whole magnetic system are investigated. The power efficiency of a given structure is dependent on resonant matching and on the load impedance. First, the matching conditions for optimal power efficiency are derived. Then the achievable efficiency for inductive transmission structures with varying distance and size ratios are investigated. Recent publications on inductive power transmission are evaluated and discussed based on these results. As a conclusion, inductive power transmission in a larger space (e.g. a whole room) is very inefficient. On the other hand, inductive power transmission at a surface can be efficient as conventional power supplies. Based on this insight, an inductive power transmission pad has been designed and built, with the purpose to charge mobile devices like mobile phones. It can charge an arbitrary number of devices and allows free positioning of the devices on the pad. It consists of an array of planar transmitter coils and has a size of 20 cm x 26 cm. It can detect the position of a receiver and activates only the coils underneath a receiver.
Citations
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Patent•
08 May 2008
TL;DR: In this paper, the authors present a system and method for variable power transfer in an inductive charging or power system. In accordance with an embodiment, the system comprises a pad or similar base unit that contains a primary, which creates an alternating magnetic field, and a receiver comprises a means for receiving the energy from the magnetic field from the pad and transferring it to a mobile device, battery, or other device.
Abstract: A system and method for variable power transfer in an inductive charging or power system. In accordance with an embodiment the system comprises a pad or similar base unit that contains a primary, which creates an alternating magnetic field. A receiver comprises a means for receiving the energy from the alternating magnetic field from the pad and transferring it to a mobile device, battery, or other device. In accordance with various embodiments, additional features can be incorporated into the system to provide greater power transfer efficiency, and to allow the system to be easily modified for applications that have different power requirements. These include variations in the material used to manufacture the primary and/or the receiver coils; modified circuit designs to be used on the primary and/or receiver side; and additional circuits and components that perform specialized tasks, such as mobile device or battery identification, and automatic voltage or power-setting for different devices or batteries.
1,317Â citations
TL;DR: In this paper, a critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension, and summarizes the operating principles of a range of wireless power research into the maximum power transfer and the maximum energy efficiency principles.
Abstract: Starting from Tesla's principles of wireless power transfer a century ago, this critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<;50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load.
1,209Â citations
TL;DR: This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer and discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas.
Abstract: Wireless power transfer (WPT) is an emerging technology that can realize electric power transmission over certain distances without physical contact, offering significant benefits to modern automation systems, medical applications, consumer electronics, etc. This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer. Compensation topologies are reviewed and evaluated based on their basic and advanced functions. Individual passive resonant networks used to achieve constant (load-independent) voltage or current output are analyzed and summarized. Popular WPT compensation topologies are given as application examples, which can be regarded as the combination of multiple blocks of resonant networks. Analyses of the input zero phase angle and soft switching are conducted as well. This paper also discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas.
659Â citations
Patent•
19 Dec 2013
TL;DR: In this paper, a power source, charging system, and inductive receiver for mobile devices are described, where the primary unit creates a magnetic field by applying an alternating current to a winding, coil, or any type of current carrying wire.
Abstract: A power source, charging system, and inductive receiver for mobile devices. A pad or similar base unit comprises a primary, which creates a magnetic field by applying an alternating current to a winding, coil, or any type of current carrying wire. A receiver comprises a means for receiving the energy from the alternating magnetic field and transferring it to a mobile or other device. The receiver can also comprise electronic components or logic to set the voltage and current to the appropriate levels required by the mobile device, or to communicate information or data to and from the pad. The system may also incorporate efficiency measures that improve the efficiency of power transfer between the charger and receiver.
640Â citations
Patent•
14 Mar 2013
TL;DR: In this paper, the authors present a system and methods for enabling efficient wireless power transfer, and charging of devices and batteries, in a manner that allows freedom of placement of the devices or batteries in one or multiple (e.g., one, two or three) dimensions.
Abstract: Systems and methods for enabling efficient wireless power transfer, and charging of devices and batteries, in a manner that allows freedom of placement of the devices or batteries in one or multiple (e.g., one, two or three) dimensions. In accordance with various embodiments, applications include inductive or magnetic charging and power, and wireless powering or charging of, e.g., mobile, electronic, electric, lighting, batteries, power tools, kitchen, military, medical or dental, industrial applications, vehicles, trains, or other devices or products. In accordance with various embodiments, the systems and methods can also be generally applied, e.g., to power supplies or other power sources or charging systems, such as systems for transfer of wireless power to a mobile, electronic or electric device, vehicle, or other product.
555Â citations
References
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TL;DR: In this article, the physical phenomenon of long-lifetime resonant electromagnetic states with localized slowly-evanescent field patterns was investigated to transfer energy efficiently over non-negligible distances even in the presence of extraneous environmental objects.
1,628Â citations
Patent•
05 Jul 2006TL;DR: In this paper, the authors proposed an electromagnetic energy transfer device that includes a first resonator structure receiving energy from an external power supply, and a second resonance structure is positioned distal from the first, and supplies useful working power to an external load.
Abstract: The electromagnetic energy transfer device includes a first resonator structure receiving energy from an external power supply. The first resonator structure has a first Q-factor. A second resonator structure is positioned distal from the first resonator structure, and supplies useful working power to an external load. The second resonator structure has a second Q-factor. The distance between the two resonators can be larger than the characteristic size of each resonator. Non-radiative energy transfer between the first resonator structure and the second resonator structure is mediated through coupling of their resonant-field evanescent tails.
730Â citations
20 Jun 2004
TL;DR: In this paper, a planar inductive battery charger for portable electronic equipment such as mobile phones, palm pilots and CD players is proposed, which can generate magnetic flux of almost even magnitude over the surface of the winding arrays.
Abstract: This invention is related to a new planar inductive battery charger for portable electronic equipment such as mobile phones, palm pilots and CD players. New multilayer printed-circuit-board (PCB) winding matrices of hexagonal structures that can generate magnetic flux of almost even magnitude over the surface of the winding arrays have been developed. The new concept forms the basis for a new generation of universal charging platform for a wide range of portable electronic equipment. Different types of portable electronic equipment can be placed and charged simultaneously on the charging platform, regardless of their positions and orientation. The principle and structure of the charging platform are explained and the feasibility has been confirmed with practical measurements. The proposed universal charging platform has been successfully used for mobile phones, MP3 players and electronic dictionaries.
536Â citations
"Limitation of inductive power trans..." refers background in this paper
...[9], the coils of the different layers overlap such that the black spot in the centre between three neighbouring coils is covered by a coil in a different layer....
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...To address this issue, the Wireless Power Consortium [9] has recently started to create such a standard....
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16 May 2008
TL;DR: In this paper, a mathematical analysis based on simplified circuit model is presented to determine the optimal operating range for SS and SP mode, respectively, from the efficiency point of view, and calculated and measured results have been given to verify the theory.
Abstract: Contactless transformer is an essential element in inductive power transfer systems. To improve its efficiency performance, a resonant tank is normally formed at the secondary side by adding an external capacitor in series (SS) or in parallel (SP) with the secondary winding. In this paper, a mathematical analysis based on simplified circuit model is presented. It leads to the theory of the boundary frequency which can be used to determine the optimal operating range for SS and SP mode, respectively, from the efficiency point of view. Calculated and measured results have been given to verify the theory in a case study.
82Â citations
01 Jan 1992
9Â citations
"Limitation of inductive power trans..." refers background in this paper
...The coupling inductance of two concentric loop inductors with radius r1 and r2, number of turns N1 and N2 located at and an axial distance b can be calculated as follows [7]: (9)...
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