The device for wireless transfer of electrical power

The gist of the invention is the device for wireless transfer of power making use of the phenomenon of electromagnetic induction. The prime application of the solution is to supply power to laptops in conference or lecturing halls, etc. without any of the limitations affecting the time and volume of the energy consumed, which are experienced when power supply is provided from power cells. The solution can also be used to supply power to various kinds of other portable equipment which require to be fed power, and to charge cells and/or batteries.

Together with the development and ever increasing number and variety of portable devices which require the supply of electrical energy finding a solution to the problem of providing the supply in the possibly most effective and most user- convenient way is growing in significance. Long known has been the method of feeding power from cells and batteries of various designs and capacities. However, because of their limited life, cells require frequent replacement or recharging. Meanwhile, in the case of such devices as portable computers and other equipment based on computer technology, the ever new applications developed, particularly of the multimedia type, carry the need for increasing power consumption, which frequently requires feeding from the mains, hence turns them into stationary devices. Another acute inconvenience of supplying power by direct electrical contact between the receiver and the source of power consists in the sensitivity of electrical contacts to the ambient conditions, e.g. humidity. The above inconveniences are eliminated by the methods and devices for cordless transfer of electrical energy via a magnetic stream, i.e. inductive coupling of the elements of the transmitter and receiver.

The patent description US5519262 makes known the device for cordless transfer of electrical energy via a magnetic field, equipped with a transmitter in the form of a planar surface with a row of elements generating a magnetic field, each supplied from a separate source of power with signals of growing phase shift, and a receiver with at least one element receiving the field. In one of the variants of the solution the elements generating the field take the form of rectangular capacity plates arranged one after another, and the function of the receiving elements is played by capacity plates in the shape of a rectangle or wedges creating the segment-divided disk. In another variant the transmitter contains a row of mutually unconnected, parallel-arranged windings with rectangular coils, which form the inductive elements, and the receiver is equipped with an inductive element coupled with at least two inductive elements in the transmitter. The inductive element of the receiver has one or more ring-shaped windings.

The British patent application GB2398176 presents a device composed of a transmitter and receiver of the electrical energy with at least one inductive element. The magnetic field is generated and shaped by the coils of the transmitter

in different shapes, sizes, positioning of one to another, and different sizes and shapes of the active surfaces. One of the variants entails inductive elements which are ordinary conductive loop. The coils of the transmitter can enclose mutually different dimensional areas or the same dimensional area, they can be arranged concentrically, or neighbouring contained one within another. This variety of shapes and sizes of the transmitter's inductive elements is intended to ensure effective energy supply to the receivers of various sizes, differing requirements in terms of the power to be supplied and various positioning on the transmitter.

In the device for cordless energy transfer known from the description in the patent application US2003/0210106 the gist also consists of shaping the magnetic field with shapes of the inductive elements. The transmitter has basically laminar surface and at least one conductor shaped so that the lines of the field it generates are parallel to the surface of the active area. The perimeter of the transmitter's active area is large enough to surround the inductive element of at least one receiver in at least one or all of its orientations to the transmitter.

The inconvenience of the heretofore solutions consists in low efficiency of electrical power transmission, and its severe dependence on the positions and sizes of the receiver's inductive elements in relation to the inducing element of the transmitter, as well as the problem of leakage of the magnetic field beyond the active surfaces of the inductive elements.

The device for wireless transfer of the electrical power, which in accordance with the invention has a transmitter formed substantially into a planar surface with an in-built set of inductive elements, on which at least one receiver with an inductive element is placed, where the inductive elements can be stimulated independently of one another or together, is characterised by the fact that the single inductive element of the receiver has the core shaped so as to form two active surfaces coupled with the active surface of the cores of the inductive elements in the transmitter. The dimensions, geometry, and arrangement of the inductive elements are selected so that irrespective of the positioning of the receiver on the surface of the transmitter, in each of the two active surfaces of the same inductive element of the receiver at least one complete active surface of the inducing element in the transmitter is contained.

The inductive elements of the transmitter, placed under different active surfaces of the same inductive element in the receiver are stimulated with signals in antiphase.

It is advantageous when all inductive elements of the transmitter are placed on a plate of low magnetic resistance.

AU inductive elements of the transmitter are arranged in a regular configuration, adjacent on one another, and their active surfaces take the shape of a circle.

In one of the variants the inductive elements of the transmitter are arranged into rows and columns.

All inductive elements of the transmitter are identical, and their cores are shaped into cylinders.

Both active surfaces of the core of the inductive element in the receiver are identical.

The active surfaces of the core of the inductive element in the receiver are given the shape of a circle.

Especially advantageous effects are achieved when the core of the inductive element in the receiver is shaped into a U letter placed up-side-down, and the tips of its open arms are the active surfaces.

The core of the inductive element in the receiver is made of a material of- low magnetic resistance.

This solution, as claimed, enables the receiver to move freely over the planar surface of the transmitter while at the same time ensures maximum effectiveness of the transfer of the electrical power and minimises the effect of the magnetic field's "leakage" beyond the active surfaces of the inductive elements. At the same time, in order to optimize the efficiency of the electrical energy transfer it is not necessary for the active surfaces of the coils in the transmitter and receiver to be identical.

An exemplary realisation of the solution is illustrated with a drawing where Fig. 1 presents, in a schematic way, the structure of the device, Fig. 2 presents the mutual positioning of the active fields in the transmitter and receiver, and Fig. 3 — presents the flows of the current in the stimulated inductive elements of the transmitter.

The device for wireless transfer of power is composed of an electrical energy transmitter N and the inductively coupled electric energy receiver O. The transmitter N is a desk with in-built coils which constitute the inductive elements 1 of the transmitter N. All coils are identical, have cylindrical air cores whose active surfaces have the shape of a circle. They are arranged regularly, one after another in columns and rows, covering the whole surface of the desk. On the bottom, the desk is equipped with a ferromagnetic plate 2 combined with the coil cores. AU inductive elements 1 of the transmitter N are connected with the power supply and control block ZS enabling excitation of selected inductive elements 1 in any desired way. Each coil can be connected independently to a separate feeder and control, or all coils can be connected with one another and a common feeder via a control so as to enable independent activation of the coils in the transmitter N. The receiver O is equipped with one inductive element in the form of a coil with a ferromagnetic core 3 given the shape of the letter U turned up side down, its circular cross-section identical along all its length. Having placed the receiver O on the desk of the transmitter N, the circular tip surfaces of both open arms of this core 3 constitute the active surfaces in contact with the active surfaces of the coil cores in transmitter N. Each of the two active surfaces of the receiver O is larger than a single active surface of the transmitter N. The dimensions of the core active surfaces 3 of the inductive element in the receiver O and the cores of the inductive elements 1 in the transmitter N, and the distances between them are

selected so that in every position of the receiver O on the desk of the transmitter N each of the two active surfaces of the inductive element in the receiver O cover the entire active surface of at least one inductive element in the transmitter N. For example, when the surface of the transmitter N is covered to the maximum with circular active surfaces of the inductive elements, and an infinitely thin coil winding, as shown on Fig.2, is assumed, the ratio of the radius R of each of the two adjacent active circular surfaces in the receiver O to the radius r of a single active surface in the transmitter N should be ca. 2.15, which is the result of geometric calculations. Having detected the position of the receiver O, in the transmitter N there are selected and simultaneously stimulated two of such inductive elements 1, the active surface of each being wholly contained within the perimeter of one of the two active surfaces of the core 3 of the inductive element in the receiver O, where the currents Il and 12 flowing in the inducing coils must always be counterdirectional, Le. the coils must be stimulated with a signal shifted in phase by 180°. Such stimulation, given the described design, causes electromagnetic coupling of the "transformer" type to occur between the receiver O and transmitter N. The coupling consists in forcing the closure of the magnetic field in those elements of the transmitter N and receiver O which conduct the magnetic stream SM. With such a coupling in place the efficiency of energy transfer increases substantially, since a closed magnetic circuit is characterised with lower magnetic resistance. The closure of the almost entire magnetic stream in each position of the receiver on the surface of the transmitter causes that high efficiency is retained irrespective of whether the coils in the transmitter and receiver are coaxial, hence with the receiver moving freely.