FIELD OF THE INVENTION

This invention relates to capacitive powering systems for wireless power transfer. In particular the invention relates to a power receiving module for use in such a system.

BACKGROUND OF THE INVENTION

Wireless power transfer systems are known and are gaining increasing attention for powering and charging portable devices including smart phones, cameras, and laptop computers.

The predominant solution today uses an inductive interface between a charging station, acting as the transmitter, and a receiver, typically a portable device. Both the transmitter and receiver are fitted with electrical coils. When brought into physical proximity, power flows from the transmitter to the receiver.

This invention relates to an alternative approach which has been developed, that uses a capacitive, rather than inductive, interface to deliver power.

Figure 1 shows the basic configuration in schematic form.

An ac voltage is generated by a transmitter 2. The ground and high voltage terminals are coupled to the two terminals of a load 4 through capacitive plates. In the capacitive interface, the field is confined between conductive plates, alleviating the need for magnetic flux guiding and shielding components that add bulk and cost to inductive solutions. The capacitive coupling mechanism is also referred to as electrostatic induction, and the process involves the passage of electrical energy through a dielectric from one terminal plate to the other. The electric field is created by charging the terminal plates with a high potential, high frequency alternating current power supply.

A significant amount of work has been carried out to enable the amount of power transferred to be maximized for a given available capacitor plate area, so that wireless capacitive power transfer is gaining attention.

As shown in Figure 1, the coupling between the transmitting module and the receiving module essentially requires at least one contact area but preferably two contact areas, between which a dielectric medium is present. There are essentially two configurations which are used, shown in Figures 2 and 3.

Figure 2 shows a so-called "top-bottom" configuration, in which the power receiving module 8 is sandwiched between top and bottom electrodes 10,12 of the power transmitting module. The receiving module 8 is in the form of a three dimensional body, with two parallel opposing faces, on which receive electrodes 14,16 are provided. No lateral alignment of the module is needed.

Figure 3 shows a so-called "lateral" configuration in which the transmission module has a planar surface on which two adjacent parallel electrodes 10,12 are provided. The receiving module 8 has two side by side receiving electrodes 14,16.

It will be appreciated that the electrode arrangement of the power receiving module of Figure 2 could not be used effectively to receive power from the power transmission module of Figure 3. Similarly, the electrode arrangement of the power receiving module of Figure 3 could not be used effectively to receive power from the power transmission module of Figure 2. This means that for a certain electrode configuration on the transmission module only receiving modules with same or comparable electrodes will fit, and hence will be powered in the configuration.

As a result, there is limited compatibility between different power transmission units and power receiving units.

SUMMARY OF THE INVENTION

The invention is defined by the accompanying claims.

According to the invention, there is provided a power receiving module for use in a capacitive powering system, the module for receiving wireless power for transfer to a load of the module, wherein the module comprises:

a body with a plurality of faces,

a plurality of power receiving electrodes; and

a circuit for receiving power from the power receiving electrodes and delivering energy to a load within the module,

wherein first and second opposite parallel faces of the body each comprise a respective power receiving electrode, such that the first and second opposite parallel faces can be used to receive power when the power receiving module is sandwiched between top and bottom power transmitting electrodes of a power transmitting module, and wherein at least one face of the body comprises a pair of power receiving electrodes, such that the at least one face can can be used to receive power when the at least one face is provided against a face of a power transmitting module which has adjacent power transmitting electrodes.

By providing opposing electrodes as well as at least two electrodes on one face, the power receiving module is able to receive power by wireless power transmission from different configurations of power transmission module, having different electrode

configurations. In particular, the module of the invention can be used to power an associated electronic device in the home or office or a public place equipped with a power transmission module having either of a lateral or a top-down electrode configuration. This provides considerable flexibility for the device owner, removing the need for interchangeable modules or adapters to accommodate different configuration transmission modules, for example when the device owner and device travel.

The module can be incorporated into electrically powered devices at the point of manufacture or can be provided in a retro-fit form and possibly as a form of universal power adapter for electrically powered devices.

The power receiving electrode of the first face can be electrically connected to a first power receiving electrode on a third face, and the power receiving electrode of the second face can be electrically connected to a second power receiving electrode on the third face. In this way, the third face has two electrodes (for lateral powering), but there can be only two electrodes in total. This implementation requires the module to be positioned in dependence on the power transmission module being used.

The first and second power receiving electrodes of the third face are preferably separated by an gap, and this can be offset from a centerline of the third face. This offset can be used as part of an unbalanced Wheatstone Bridge configuration.

The power receiving electrode of the first face can be electrically connected to a first power receiving electrode on a fourth face, and the power receiving electrode of the second face can be electrically connected to a second power receiving electrode on the fourth face, with the third and fourth faces opposite each other. This arrangement can again have only two electrodes in total, with two opposite faces carrying only one of the two electrodes, and another two opposite faces each carrying both electrodes. The first and second power receiving electrodes of the fourth face can again be separated by an gap offset from a centerline of the fourth face. In another set of examples, each face which is provided with electrodes (i.e. they do not all need to have electrodes) comprises at least two electrodes. This means that each electrode face can be coupled to a lateral or top-bottom electrode. When used with a top-bottom architecture, the multiple electrodes need to have the same polarity, whereas when used with a lateral architecture, the multiple electrodes need to have opposite polarity. Internal circuitry can enable the electrodes to be reconfigurable in this way.

In one example, each face of the body can be provided with at least two electrodes. This means the module can be positioned in a variety of orientations with respect to the power transmission module.

The circuit can comprise, for each power receiving electrode:

a first single direction current transfer device in a forward current direction from the electrode to a first common node; and

a second single direction current transfer device in a reverse current direction from the electrode to a second common node.

This circuit means that each electrode will self-configure as a high side electrode or a low side electrode in dependence on the power received by the electrode. The circuit ensures suitable connection to the load, and thus provides a form of self-configuration. Each single direction current transfer device can comprise a diode.

The first common node can comprise a high terminal for connection to a load and the second common node can comprise a low terminal for connection to the load. The load is the device to be powered by the wireless power transfer.

However, in another example, the first and second common nodes are connected together (so that there is effectively only one common node), and each single direction current transfer device comprises a light emitting diode. The light emitting diodes then together function as the load of the power receiving module.

The invention also provides an electrically powered device incorporating the power receiving module of the invention, and also a system comprising one or more electrically powered devices of the invention and a wireless power transmission module, the wireless power transmission module comprising opposing power transmission electrodes between which the module can be positioned for receiving power from the power

transmission electrodes, or else side-by-side power transmission electrodes on a planar surface, onto which the module can be positioned for receiving power from the power transmission electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic drawing of a known wireless power transmission arrangement which uses the principle of capacitive coupling;

Fig. 2 shows a schematic drawing of a power transmission module having a "top-bottom" electrode configuration as known from the prior art;

Fig. 3 shows a schematic drawing of a power transmission module having a "lateral" electrode configuration as known from the prior art;

Fig. 4 shows a schematic diagram of a first embodiment of a power transmission module in accordance with the invention;

Fig. 5 shows a schematic of a second embodiment of a power transmission module in accordance with the invention; and

Fig. 6 shows an internal circuit arrangement suitable for use in a power transmission module in accordance with the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention provides a power receiving module for use in a capacitive powering system for receiving wireless power transfer to a load of the module. The module comprises first and second opposite parallel faces each having a respective power receiving electrode, and at least one face which comprises a pair of power receiving electrodes. In this way, electrodes are present which can be used for receiving power from a top-bottom wireless power transmission module, and electrodes are also present which can be used for receiving power from a lateral wireless power transmission module.

Figures 1 to 3 represent the prior art and are already described above.

Figure 4 shows a schematic of a first embodiment of a power transmission module in accordance with the invention.

The power receiving module 5 is for use in a capacitive powering system for receiving wireless power transfer to a load of the module. The module comprises a three dimensional body with a plurality of faces, with the load and drive circuitry for the load contained within the body. The body is shown as a cube, but it may be a cuboid or indeed other shapes. At the limit, it requires only two opposing planar faces, as will become apparent from the discussion below. The module has a plurality of power receiving electrodes. In the example of Figure 4, there are only two power receiving electrodes 14,16 on opposite parallel faces. The spacing of these faces is designed to be compatible with the spacing between transmission electrodes of a top-bottom power transmission module. The body may be a small unit, for example credit card sized, or it may be much larger.

As shown in Figure 4, the power receiving electrode 14 of the first face overlaps two opposite faces 17,18. In this way, the power receiving electrode 14 is electrically connected to a first power receiving electrode 19 on the third face 17 and also a first power receiving electrode 20 on the fourth face 18. Similarly, the power receiving electrode 16 of the second face overlaps the third and fourth faces 17,18 and is thereby electrically connected to a second power receiving electrode 21 on the third face 17 and a second power receiving electrode 22 on the fourth face 18.

There are thus only two electrode areas, and these define single electrodes on two opposing faces, and also define double electrodes on two other opposing faces.

Within the module 8, there is a circuit for receiving power from the power receiving electrodes and delivering energy to a load within the module,

As a minimum, the invention requires first and second opposite parallel faces of the body which each comprise a respective power receiving electrode (i.e. 14 and 16), and at least one face (i.e. 17 or 18) with a pair of power receiving electrodes. These may be the same faces, so that at the limit only two faces need to be provided with electrodes.

On the third and fourth faces of the example of Figure 4, the first and second power receiving electrodes 19,21 and 20,22 are separated by a gap 23,24. The gap can be offset from a centerline of the third face.

By making the contacts asymmetrical in this way, they can be used to form an unbalanced capacitive Wheatstone Bridge when connected in a top-bottom construction. As each side has one larger capacitance and one smaller capacitance, power is delivered as the bridge is out of balance. The resulting transfer capacitance is the difference value of the larger and the smaller capacitance. In the simple construction shown, this is obtained by having the slit off-center. The length of the electrode areas can be chosen according to the power / frequency used by the AC power supply.

When the load is based on LEDs, the light must come out. This can be achieved using transparent electrodes, or when metallic electrodes they should not cover the full package. Figure 5 shows a second example. In this case, each face which is provided with electrodes comprises at least two electrodes 30-37. This means that any face with electrodes can be used either with a lateral transmission module (in which case the two electrodes function with opposite polarity) or with a top-bottom transmission module (in which case the two electrodes function with the same polarity). It is explained below how the electrodes do not need to have fixed polarity.

Again, at least two opposing faces need electrodes.

In a preferred configuration, each face of the body is provided with at least two electrodes. This means that, for a cube, it can be positioned over lateral electrodes of the power transmission module, or between the electrodes of the power transmission module, in any orientation.

Figure 6 shows an internal circuit arrangement. Each power receiving electrode 30-37 connects through a forward direction diode 40a to the high terminal of the load and through a reverse direction diode 40b to the low terminal of the load.

This provides a rectification circuit which means that each electrode can be floating (i.e. not capacitively coupled), coupled to the high voltage terminal of the

transmission module or coupled to the low voltage terminal of the transmission module. The electrodes in this way are self-configuring. The diodes can be other single direction current transfer devices, such as diode-connected transistors. Indeed, other rectifier circuits can also be used.

With this self-configuration, the most simple design can be one with one electrode on one face and two electrodes on an opposite face. The two electrodes on the same face are for use with a lateral transmission module and the opposite faces are for use with a top-bottom transmission module. This means the body only needs two planar surfaces, and these two planar surfaces can be joined by any body shape, so enabling freedom in the aesthetic design of the power receiving module.

Providing multiple pairs of parallel planar faces, as in the example of Figure 5, enables increased flexibility in the orientations in which the unit can be powered.

In the circuit of Figure 6, the load 42 can be a battery to be charged. However, the load may instead comprise the diodes. In this case, the load is replaced with a short circuit. This short circuit means that all diodes connect to a common point. The diodes then comprise light emitting diodes, and the light emitting diodes together function as the load of the power receiving module. The electrodes need not each be of the same shape or size. Positioning of electrodes on the module may be in a symmetrical or uniform repeating pattern but need not be. Suitable electrode materials are known and may include (without limitation); carbon, aluminum, indium tin oxide (ITO), organic material, such as PEDOT, copper, silver, conducting paint. Some of these electrode materials are transparent and therefore of particular interest for lighting use, and others are light blocking and thus more suitable for e.g. a battery charging devices or any other electrical device requiring a wireless powering method.

The electrode areas can be chosen in dependence on the type of device. For a battery charging application, large electrodes are desired, both to provide large capacitance and also to give freedom in positioning. For lighting applications, where the body 8 functions as a light source, it may be desired to reduce the area of the electrodes to allow the passage of light (particularly if opaque electrodes are used).

The number of faces on which electrodes are provided can also be selected in dependence on the intended use of the device. It might be two, or it might involve using all faces of the receiving module.

When used as an LED device, different LEDs can be of different color. This means that different orientations of the module can correspond to different color output. In this way, the placement position of a cube will determine the (pre-set) light color. Different electrodes can also be associated with different numbers of LEDs to implement different brightness levels, for example.

If many small electrodes are used instead of a small number of large electrodes, the alignment can become less critical.

The other circuitry used in the module does not form part of this invention, and known power receiving circuits can be used. Essentially, the power transmission module applies an ac signal between the power transmission terminals, as shown schematically in Figure 1. The power receiving module typically comprises a rectifier, to deliver a dc current to the device to be powered. The circuit of Figure 6 functions as the rectifier. The dc current can be a battery charging current for portable device recharging. For the example of a lighting device, the current is for example a dc LED drive current.

Inductors are typically used in series with the capacitors formed between the electrodes to reduce the impedance between the transmitter and receiver. In particular, the whole system can be operated in electrical resonance for high power transfer. In addition to wireless powering, some electrodes can be made available for wireless data transfer or control applications using known data transfer and control methods

Various known insulators can be used to separate the electrodes of the transmission module and the receiving module of the invention. The insulator is usefully incorporated into the receiving module of the invention. A dielectric material is for example provided as a layer over exposed surfaces of the electrodes of a receiving module in accordance with the invention. The thickness of such an insulating layer is typically between 1 and 10 microns (e.g., a deposited, evaporated, sprayed or painted layer) and a few millimeters (e.g., a glass envelope at the outer edge of the receiving module layer).

With special techniques even thinner layers may be fabricated, for example 100 nm.

It will be appreciated that, in an alternative, the insulator can be incorporated into the power transmission module.

A manual or automatic short circuit can be incorporated into the module and selectively used to remove unused electrodes from the circuit when the power receiving module and power transmission module are engaged.

As mentioned above, modules of the invention have practical use in the charging of batteries for portable electronic devices such as communications devices. It is envisaged that a power transmission module could be embodied in a large planar surface such as a table, counter or desk top with supplied power, or a portable plug in pad. The portable electronic devices can receive power simply by placing on the table, counter, desk top or pad.

Other practical applications can be found in lighting and display applications. For example, the load may be an illumination device such as a LED, a LED string or a lamp of other form.

The power transmission module could be embodied in a large planar surface such as a wall, ceiling or floor and one or more loads positioned at the preferred site on the wall, ceiling or floor for illuminating.

The module can consist of a substrate on which LEDs and electrodes are mounted. In another embodiment the module is fabricated so small that the LEDs and electrodes are incorporated within one die, thus avoiding the need for an additional substrate carrier. In another construction the electrodes can be placed at the bottom of a lamp-foot and actually can have an area of many cm ² .

In bill-boards the spacing between the individual pixels is a few cm, thus allowing modules of similar size. When used as illumination module within glass bricks for example for decorative purposes in the bathroom, the size might even be larger. Another alternative is to fabricate a large cube-like light device, that is used for general illumination or atmospheric lighting purposes.

As mentioned above, capacitive wireless transfer circuits are known. By way of example, WO 2013/024419 discloses the use of capacitive wireless powering for a lamp, and shows a lateral wireless power transfer approach.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.