Receiver electrodes of a capacitive wireless powering system

Various receiver electrodes for supplying power to a load connected in a capacitive power transfer system are disclosed. In one embodiment, the receiver electrodes include a first conductive plate (212) connected to a first sphere-shaped hinge (211), wherein the first sphere-shaped hinge is coupled to a first receiver electrode (210); and a second conductive plate (222) connected to a second sphere-shaped hinge (221), wherein the second sphere-shaped hinge is coupled to a second receiver electrode (220), the second receiver electrode being connected to an inductor of the capacitive power transfer system and the first receiver electrode being connected to the load, the inductor being connected to the load to resonate the capacitive power transfer system.

The invention generally relates to capacitive powering systems for wireless power transfers, and more particularly to receiver electrodes structures to transfer power over a large area.

A wireless power transfer refers to the supply of electrical power without any wires or contacts, whereby the powering of electronic devices is performed through a wireless medium. One popular application for contactless powering is for the charging of portable electronic devices, e.g., mobiles phones, laptop computers, and the like.

One implementation for the wireless power transfer is by an inductive powering system. In such a system, the electromagnetic inductance between a power source (transmitter) and the device (receiver) allows for contactless power transfers. Both the transmitter and receiver are fitted with electrical coils, and when brought into physical proximity, an electrical signal flows from the transmitter to the receiver.

In inductive powering systems, the generated magnetic field is concentrated within the coils. As a result, the power transfer to the receiver pick-up field is very concentrated in space. This phenomenon creates hot-spots in the system which limits the efficiency of the system. To improve the efficiency of the power transfer, a high quality factor for each coil is needed. To this end, the coil should be characterized with an optimal ratio of an inductance to resistance, be composed of materials with low resistance, and fabricated using a Litze-wire process to reduce skin-effect. Moreover, the coils should be designed to meet complicated geometries to avoid Eddy-currents. Therefore, expensive coils are required for efficient inductive powering systems. A design for a contactless power transfer system for large areas would necessitate many expensive coils, whereby for such applications an inductive powering system may not be feasible.

Capacitive coupling is another technique for transferring power wirelessly. This technique is predominantly utilized in data transfers and sensing applications. A car-radio antenna glued on the window with a pick-up element inside the car is an example of a capacitive coupling. The capacitive coupling technique is also utilized for contactless charging of electronic devices. For such applications, the charging unit implementing the capacitive coupling operates at frequencies outside the inherent resonance frequency of the device.

A capacitive power transfer system can also be utilized to transfer power over large areas, e.g., windows, walls having a flat structure and so on. An example for such a captive power transfer system100is depicted inFIG. 1. As illustrated inFIG. 1, a typical arrangement of such a system includes a pair of receiver electrodes111,112connected to a load120and an inductor130. The system100also includes a pair of transmitter electrodes141,142connected to a power driver150, and an insulating layer160.

The transmitter electrodes141,142are coupled to one side of the insulating layer160and the receiver electrodes111,112are coupled from the other side of the insulating layer160. This arrangement forms capacitive impedance between the pair of transmitter electrodes141,142and the receiver electrodes111,112. Therefore, a power signal generated by the power driver can be wirelessly transferred from the transmitter electrodes141,142to the receiver electrodes111,112to power the load120. Efficiency of the system is increased when a frequency of the power signal matches a series-resonance frequency of the system. The series-resonance frequency of the system100is a function of the inductive value of the inductor130and/or inductor131as well as of the capacitive impedance between the pair of transmitter electrodes141,142and the receiver electrodes111,112(C1and C2inFIG. 1). The load may be, for example, a LED, a LED string, a lamp, and the like. As an example, the system100can be utilized to power lighting fixtures installed on a wall.

The capacitance impedance (C1and C2) is a function of the distance between the receiver electrodes and the transmitter electrodes. The capacitance value should be computed as followed:

where, A is the area of the receiver electrodes (shown as S1and S2inFIG. 1), d is the thickness of the insulating layer160, and, ∈ is the dielectric value of the dielectric.

The distance between the receiver and transmitter electrodes, and thus capacitance impedance can vary or can be varied, for example, when the surface of the insulation layer and/or the transmitter electrodes is not uniform (e.g., variable thickness across the insulation layer, curved, sloppy, or variable-shaped electrodes). In the capacitive wireless system100, power is efficiently wirelessly transferred from the driver150to the load120when the frequency of the power signal substantially matches a series-resonance frequency of the system100. Thus, fluctuations in the capacitance impedance would fluctuate the current flows through the load120.

Therefore, it would be advantageous to structure receiver electrodes that would be aligned with the transmitter electrodes to ensure efficient power transfer in the capacitive power system.

Certain embodiments disclosed herein include an article of manufacture for supplying a power to a load connected in a capacitive power transfer system. The article of manufacture comprises a first conductive plate (212) connected to a first sphere-shaped hinge (211), wherein the first sphere-shaped hinge is coupled to a first receiver electrode (210); and a second conductive plate (222) connected to a second sphere-shaped hinge (221), wherein the first sphere-shaped hinge is coupled to a second receiver electrode (220), the second receiver electrode is connected to an inductor of the capacitive power transfer system and the first receiver electrode is connected to the load, the inductor is coupled to the load to resonate the capacitive power transfer system.

Certain embodiments disclosed herein also include an article of manufacture for supplying a power to a load connected in a capacitive power transfer system. The article of manufacture comprises a flexible pocket (330); a first receiver electrode (310) connected to the flexible pocket and connected to the load; and a second receiver electrode (320) connected to the flexible pocket and connected to an inductor of the capacitive power transfer system, the inductor is connected to the load to resonate the capacitive power transfer system.

Certain embodiments disclosed herein also include a magnetic fixture900for mechanically fixing a receiver to a transmitter of a capacitive power transfer system. The magnetic fixture includes a first group of a plurality of transmitter electrodes (910-1,910-r) including a plurality of permanent magnets having a first magnetic pole orientation, each of the transmitter electrodes of the first group of the plurality of transmitter electrodes having a first electric potential; a second group of a plurality of transmitter electrodes (920-1,920-r) including a permanent magnet having a second magnetic pole orientation opposite to the first magnetic pole orientation, wherein each of the transmitter electrodes of the second group of the plurality of transmitter electrodes having electric potential opposite to the electric potential of each of the plurality of the plurality of transmitter electrodes; a first receiver electrode having the first electric potential and including a permanent magnet having the first magnetic pole orientation; and a second receiver electrode having the second electric potential and including a permanent magnet having the second magnetic pole orientation; wherein the first receiver electrode is orientated with one of the transmitter electrodes of the first group of the plurality of transmitter electrodes and the second receiver electrode is orientated with one of the transmitter electrodes of the second group of the plurality of transmitter electrodes, the receiver is mechanically fixed to the transmitter to allow a power signal to be wirelessly transferred from the transmitter to a load connected to the receiver.

FIG. 2shows a schematic diagram of a pair of receiver electrodes210and220structured according to an embodiment of the invention. The receiver electrodes210and220are part of a capacitive powering system200operative as described in detail herein. The system200includes a power driver201connected to a pair of transmitter electrodes202and203covered by an insulation layer204. The connection may be a galvanic or a capacitive coupling connection. On the receiver side, the receiver electrodes210and220are connected to a load205and an inductor206, respectively.

As depicted inFIG. 2, the insulating layer204is a thin layer having a curved shape. The insulating layer204can be of any insulating material, including, for example, paper, wood, textile, glass, DI-water, and so on. In an embodiment, a material with dielectric permittivity is selected. The thickness of the insulating layer204is typically between 10 microns (e.g., a paint layer) and a few millimeters (e.g., a glass layer). The transmitter electrodes202,203also have a curved shape to fit the structure of the insulating layer204. The transmitter electrodes202,203may be of any conductive material, such as carbon, aluminum, indium tin oxide (ITO), organic material, such as Poly(3,4-ethylenedioxythiophene) (PEDOT), copper, silver, conducting paint, or any conductive material.

To allow efficient power transfer the surface area of the transmitter electrodes substantially overlaps the surface area of the receiver electrodes to allow constant distance between the electrodes, whereby any fluctuations in the capacitive impedance and in the current flows through the load205are eliminated.

According to this embodiment, the receiver electrodes210,220are shaped in such way as to overlap the surface area of the transmitter electrodes202,203. To this end, each of the receiver electrodes210,220includes a conductive plate212,222connected to a sphere-shaped hinge211,221, also made of a conductive material.

The conductive plates212,222and sphere-shaped hinges211,221can be of the same conductive material as the transmitter electrodes or made of different conductive material. Such material may include, for example, carbon, aluminum, indium tin oxide (ITO), organic material, conductive polymer, PEDOT, copper, silver, conducting paint, or any conductive material.

The structure of the receiver electrodes allows freedom in the movement of the conductive plates212,222along the horizontal axis. Therefore, on any place along the insulation layer204the conductive plates substantially overlap the surface area of the transmitter electrodes202,203. Further, this structure advantageously provides for a substantially uniform gap between the transmitter and receiver electrodes, reducing the possibility of a large gap between the transmitter and receiver electrodes, thereby substantially ensuring that the capacitance is formed between them.

In one embodiment, the sphere-shaped hinges211,221are realized as mechanical springs to allow movement of the conductive plates212,222in the horizontal and vertical direction.

In yet another embodiment, the receiver electrodes are connected to a fixing means230to firmly fix the receiver device (including the electrodes210,220, load205, and inductor206) to an infrastructure (e.g., a wall, a window, etc.). The fixing means230may include, for example, a permanent magnet, a suction cap, a glue layer, and hook-and-loop tape, and the like. Various embodiments of a magnetic fixture are discussed below. When using glue as the fixing means, the glue layer serves as the insulating layer204.

Another embodiment for structuring the receiver electrodes to easily and seamlessly adapt to a shape of the surface of the infrastructure (insulating layer and transmitter electrodes) is illustrated inFIGS. 3A and 3B. According to this embodiment, the receiver electrodes310,320are fixed on the outside surface of a flexible pocket330. The flexible pocket330may be any flexible container to enclose gas or liquid volume, for example, an inflated plastic bag or a balloon. The material of the flexible pocket330is a non-conductive material.

The material of the receiver electrodes310,320may include any conductive material, such as those mentioned above. The electrodes310,320are connected to the receiver device340that includes a load and an inductor (not shown inFIGS. 3A, 3B) as described in detail above.

To power the load in the receiver device340, the flexible pocket is pressed against the insulation layer350, as shown inFIG. 3B. As a result, transmitter electrodes360,361connected to the insulation layer350are aligned with the receiver electrodes310,320. Consequently, the load in the receiver device340is wirelessly powered as discussed in detail above. The power signal is generated by a driver370connected to the transmitter electrodes360,361.

As depicted inFIGS. 3A and 3Bmultiple transmitter electrodes are placed along the curved-shape insulation layer350. The design of the receiver electrodes310,320provides that on every pair of transmitter electrodes360,361the respective surface areas are substantially overlapped when the flexible pocket330is pressed against the insulation layer350.

FIGS. 4A and 4Bshow another embodiment of the receiver electrodes410,420connected inside a flexible pocket430. Such a design can be used when the receiver electrodes410,420are to be isolated from the environment, for instance, for hygienic reasons. In a certain configuration, a receiver device which includes a load and an inductor (not shown inFIGS. 4A and 4B) may also be placed inside the flexible pocket430. The flexible pocket430is made of a non-conductive material. The receiver electrodes410,420can be made using any of the conductive material mentioned above.

The capacitive impedance is created between the receiver electrodes410,420and transmitter electrodes450,451, when the receiver and transmitter electrodes are in alignment. With this aim, as shown in4B, when the flexible pocket430is pressed against an insulation layer460, the receiver electrodes are deformed to be in alignment with the transmitter electrodes450,451. At this position, the load in the receiver device is wirelessly powered as discussed in detail above. The power signal is generated by a driver470connected to the transmitter electrodes450,451.

FIG. 5shows a practical application of a flexible pocket500according to one embodiment. The flexible pocket500is an inflated plastic bag having a pair of receiver electrodes501and502realized as two copper strips adhered on the plastic bag. The flexible pocket500is a complete receiver device including a LED lamp (load)503and an inductor504. The flexible pocket500may be any shape (e.g., shaped as an action figure toy) or any color. Thus, the embodiments of the flexible pocket can be utilized as a night lamp, an outdoor light fixture, and so on.

In one embodiment, the flexible pockets disclosed herein include a fixing means to secure the receiver device to the surface of the insulating layer. The fixing means may include, for example, a permanent magnet, a suction cap, a glue layer, and the like. In the embodiment of permanent magnets, the surface of the insulating layer may include a soft-magnetic material, such as iron orferrite paint. The flexible pocket is attracted to the surface by one or more magnets. The magnets may be adhered to the outside or the inside layer of the flexible pocket, but are not in direct contact with the receiver electrodes. In a preferred embodiment, the magnets are arranged behind the electrodes of the pocket inside the device. The magnets of the flexible pocket may include solid blocks or a powdered magnetic material mixed in flexible polymer.

In another embodiment, one or more suction caps are utilized as the fixing means to attach the flexible pocket to the surface of the insulation layer. To this end, the surface should be very smooth to allow the suction cap to maintain vacuum with the surface. The suction cap may be arranged beside the receiver electrodes of the pocket device.

It should be noted that with respect to the embodiments described with reference toFIGS. 3, 4, and 5, the system is a capacitive power system in which the load (e.g., a lamp) is wirelessly powered when the frequency of the power signal substantially matches the series-resonance frequency related to the capacitance impedance formed between the electrodes and the inductor connected to the load. Thus, for example, the embodiments disclosed herein can be utilized to power a lamp fixed to a wall without wires or power outlets.

For aesthetical reasons it may be desired to connect the receiver device to a large surface, such as a wall or a window without any mechanical means, such as screws and nails. Accordingly, various embodiments disclosed herein include a magnetic fixture utilized in a capacitive wireless power system.

In one embodiment, shown inFIG. 6, transmitter electrodes601,602are stripes made from paramagnetic and conductive material and are connected to an infrastructure, e.g., a wall. For example, each of the electrodes601,602may be an iron metal sheet with a thickness of about 0.5 mm to 1 mm. A receiver device610includes one permanent magnet611which is attracted to the transmitter electrodes601and602, thus magnetically fixing the receiver device610to the infrastructure.

The receiver device610further comprises electrodes612,613that when the magnet611and transmitter electrodes601,602are in contact, the receiver electrodes612,613are at a close distance to the transmitter electrodes601,602(but do not touch each other as there is an insulation layer between them). At this position, a load614connected to an inductor615is wirelessly powered as discussed in detail above. The power signal is generated by a driver (not shown) connected to the transmitter electrodes601and602. Thus, the air or the finishing layer of a wall (e.g. wallpaper, foil or paint) can serve as the insulation layer. When air is the insulation layer, spacers are used between the transmitter and receiver electrodes to prevent them from making galvanic contact. In this embodiment, the receiver electrodes612,613are made of conductive and non-magnetic material, such as copper or of any of the organic material mentioned above.

In another embodiment, the receiver device includes at least two magnets. The magnets are covered with a thin electric conducting layer to form the receiver electrodes. The conductive layer can be made from a tin metal sheet and adhered to the magnets. Alternatively, the magnets can be covered with metal material by a deposition process, e.g., galvanic deposition.

In this embodiment, the receiver electrodes are magnetically attracted to the transmitter electrodes, thereby magnetically fixing the receiver device to the infrastructure (e.g., wall). The transmitter electrodes may be of any shape installed behind a decorative cover.

FIG. 7is a cross-section diagram of a magnetic fixture according to another embodiment. A transmitter device includes permanent magnets703,704installed in the back of the transmitter electrodes701,702. The magnet703is oriented in a first magnetic pole, while the magnet702is oriented in the opposite magnetic pole of the first transmitter electrode702.

In the receiver device, a first receiver electrode713includes a permanent magnet711in a direction such that it is attracted by the magnet703associated with the first transmitter electrode701. That is, the magnetic orientation of the magnet711is opposite to that of the magnet703. The second receiver electrode712comprises a magnet714such that is attracted to the magnet704of the second transmitter electrode702. As a result, the receiver device can be fixed to the infrastructure only when the device is in the correct orientation, thereby ensuring proper electrical connections. It should be noted that when the receiver device is mechanically fixed to the transmitter device by magnetic force, there is no direct electrical contact between them, as the receiver electrodes712,713and the transmitter electrodes701,702are separated by an insulating layer720. The insulating layer720may be air, a paint layer, a wall paper, and the like. The ‘+’ and ‘−’ labels inFIG. 7indicate the magnetic orientation.

In yet another embodiment, a transmitter device includes permanent magnets associated with the transmitter electrodes. For example, a transmitter electrode can be placed in front of a permanent magnet. The transmitter electrodes associated with the permanent magnets may be of different potential or phase shift. As shown inFIG. 8, a reference electrode801associated with a permanent magnet (not shown) oriented in a first magnetic pole is arranged in the center of a circle. Around the reference electrode, a number of adjacent transmitter electrodes802,803,804, and805are arranged, where each of them is being associated with a permanent magnet (not shown) oriented in a second magnetic pole being opposite to the first magnetic pole. Each of the adjacent transmitter electrodes802to805has a different electrical potential compared to the reference electrode801. According to this embodiment, a receiver device810can then be placed with one receiver electrode811on the reference transmitter electrode801and with the other receiver electrode812on one of the adjacent electrodes802to805. Each of the receiver electrodes811,812may be placed in front of a permanent magnet (not shown inFIG. 8).

It should be noted that as each pair of transmitter electrodes has a different potential, the placement of the receiver electrodes respective of the transmitter electrodes determines the amount of power to be transmitted. This allows tuning the power level by selecting a different potential. For example, this can be utilized to dim the light illuminated by a lamp in the receiver device810. It should be further noted that when the receiver device810is mechanically fixed to the transmitter device800by magnetic force, there is a no direct electric contact between them, as they are separated by an insulating layer. The ‘+’ and ‘−’ labels inFIG. 8indicate the magnetic orientation.

In another arrangement, depicted inFIG. 9, a number of first transmitter electrodes910-1through910-rare arranged in a half circle, and a number of second transmitter electrodes920-1through920-rare also arranged in a half circle, such that both half circles combine to form a circle. Each of the electrodes910-1through910-rand920-1through920-rhas a different electric potential, such that by turning a receiver device930, a different power level can be selected. In addition, the first group of transmitter electrodes910-1through910-rand second group of transmitter electrodes920-1through920-rare associated with a different magnetic pole. The ‘+’ and ‘−’ labels inFIG. 9indicate the magnetic orientation.

According to this embodiment, one receiver electrode931of the receiver device930can then be aligned with one of the first transmitter electrodes910-1through910-r, while the second receiver electrode932is aligned with the second transmitter electrodes920-1through920-r. In a different exemplary arrangement, the receiver and transmitter electrodes with different potential are arranged in two parallel rows.