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Wireless energy transmission using a planar coil array with minimized mutual coupling

IP.com Disclosure Number: IPCOM000209825D
Publication Date: 2011-Aug-17
Document File: 8 page(s) / 143K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method is presented for a coil setup allowing for efficient inductive energy transmission on a planar surface. Several primary coils which are located in an array act as single switchable and controllable transmission coils of an inductive power transfer system. Integrated receiving coils which are positioned in the proximity of the transmission coils can be provided with energy. The relative position and the shape of the transmission coils are designed via optimization routines in such a way that the mutual electromagnetic interaction of all trans-mission coils among each other is reduced to a minimum. Due to this each transmission coil can be activated separately. In addition to that, a parallel and simultaneous operation of multiple coils without a mutual interference is enabled. The optimized geometry of all coils allows for an arbitrary scalability, a high density of coils as well as a location independent transmission of energy to a multitude of receivers.

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Wireless energy transmission using a planar coil array with minimized mutual coupling

ABSTRACT

A method is presented for a coil setup allowing for efficient inductive energy transmission on a planar surface. Several primary coils which are located in an array act as single switchable and controllable transmission coils of an inductive power transfer system. Integrated receiving coils which are positioned in the proximity of the transmission coils can be provided with energy. The relative position and the shape of the transmission coils are designed via optimization routines in such a way that the mutual electromagnetic interaction of all transmission coils among each other is reduced to a minimum. Due to this each transmission coil can be activated separately. In addition to that, a parallel and simultaneous operation of multiple coils without a mutual interference is enabled. The optimized geometry of all coils allows for an arbitrary scalability, a high density of coils as well as a location independent transmission of energy to a multitude of receivers.

INTRODUCTION

Wireless energy transmission systems based on the concept of induction are well known. The concept is based on the phenomenon that a time varying current in one or more sending coils or primary coils causes an induced voltage in one or more receiving coil or secondary coil located in the proximity according to the law of induction. As an example, the time varying voltage induced in the receiving coil could be rectified and utilized in order to provide power to an electronic circuit and/or charging a battery. Many applications of this setup can be found in the area of consumer electronics where mobile devices like notebooks or smart phones can be equipped with at least one receiving coil. Such a device may be placed on a surface containing one or more sending coils like a desk pad in order to provide energy inductively to the mobile device. Besides the application on providing power and charging the batteries of mobile devices further applications utilizing the induction principle are for instance radio frequency identification (RFID) systems.

In some areas of application it is advantageous if the sending coil or many sending coils are integrated into a planar unit. For this purpose thin winded, printed or etched coils on a single-layer or multi-layer carrier like a printed circuit board (PCB) can be used. Such a planar unit can be integrated in numerous ways into the daily life environment like walls, floors, drawers, tables, cabinets etc.

The spatial adjacent coils of the single or many sending coils and the receiving coils set up a mutual coupling according to the transformer principle. The coupling between two coils each characterized by the self-inductances L1 and L2 can be expressed by the coupling factor k which defines the relation between the mutual inductance M and the square root of the product of the two self-inductances. This is formulated by

In addition to this def...