RU2623095C2 - Wireless charging system and its application for charging mobile and portable devices - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: wireless charging system includes a wireless power transmission unit and a wireless power reception unit. The wireless power transmission unit comprises the power source, the transmitting inductance coil, the shielding element and the first impedance matching circuit. The transmitting inductance coil is connected to the power source via the first impedance matching circuit. In the case of power supply by means of the power source, the transmitting inductance coil is capable of emitting electromagnetic radiation. The first impedance matching circuit is made with the possibility to provide impedance matching between the transmitting inductance coil and the power source. The shielding element is located under the transmitting inductance coil and is configured in such a way that the electromagnetic radiation emitted by the transmitting inductance coil is suppressed outside the active charging region. The wireless reception unit includes the receiving inductance coil, the load and the second impedance matching circuit. The receiving inductance coil is made with the possibility to inductively communicate with the transmitting inductance coil, so that the electromagnetic radiation emitted by the transmitting inductance coil induces the charging currents in the receiving inductance coil. The load is connected to the receiving inductance coil through the second impedance matching circuit. The load is made with the possibility to be charged by means of charging currents. The second impedance matching circuit is made with the possibility to ensure matching the optimum impedances between the receiving inductance coil and the load. The first and the second matching circuits are also made with the possibility to ensure the resonance between the transmitting inductance coil and the receiving inductance coil in order to maximize the power transmission efficiency.

EFFECT: increasing the efficiency of energy transmission from the wireless power transmission unit to wireless power reception units embedded in electronic devices by means of suppressing electromagnetic interference via impedance matching circuits and a shielding element.

28 cl, 33 dwg, 1 tbl

Description

FIELD OF THE INVENTION

The present invention, in General, relates to technology for the transfer of electromagnetic energy (WPT) and, in particular, to a wireless charging system configured to simultaneously charge multiple mobile devices.

State of the art

The technology for transferring electromagnetic energy has been developed for mobile and portable electronic devices in order to provide a convenient way to charge the device’s internal batteries or to supply energy to devices connected to them. Wireless power transmission units typically operate in the frequency range from 100 kHz to 100 MHz.

A traditional mobile device with a wireless charging function has a battery pack and a receiving inductor mounted inside it. Its charging is carried out while in the immediate vicinity of the transmitting inductance coil of the wireless energy transfer. An induced electromotive force is generated in the receiving inductor by means of an electromagnetic field generated by the transmitting inductor, while the electric energy induced from this electromotive force charges the battery pack of the mobile device.

The most common architecture for a charging device using electromagnetic energy is a network with a star topology. The wireless power transmission unit interacts with one or more mobile devices to perform simultaneous charging. Wireless communication is achieved through an energy transfer resonator (TX) and power reception resonators (RX): inductors, which are magnetically coupled to impedance matching circuits. An energy source is connected to a power transmission resonator (TX), and a power reception resonator (RX) is connected to a rectifier to convert energy from alternating current to direct current on the receiver side.

The main problem of wireless power transmission units, insensitive to the relative position of the receiver and transmitter and / or long-range, is the high level of electromagnetic interference (EMI). Weakly inductively coupled large-sized units for wireless energy transfer use high switching voltages and high currents in large-sized primary inductors, as a result of which electromagnetic interference (EMI) has a spurious effect on other electronic devices. The use of large-sized unshielded transmitting (TX) inductors for transmitting energy over long distances additionally exposes the surroundings to the effects of electromagnetic interference (EMI).

US 2012/0228959 A1 discloses a method and system for transmitting energy to electronic devices wirelessly by using magnetic coupling between two inductors in close proximity to transfer sufficient energy to charge an electronic device. Flat inducers having characteristics that provide the ability to create a uniform magnetic field are described. The differential control amplifier includes a switching device coupled to the first output node and the second output node. The first output node and the second output node drive a load circuit including transmitting inductors. The first and second output signals can be almost equal in magnitude, while reversing in polarity, relative to the reference voltage. The electromagnetic energy receiver may include a reception circuit configured to communicate with a receiver inductance coil and a load. The receiver is configured to match the load to obtain an impedance that remains almost constant after the receiver is placed within the active charging region of the transmitter. However, US 2012/0228959 A1 does not address the problems of electromagnetic interference filtering (EMI), common mode rejection and isolation of the inductor from surrounding objects, which leads to reduced energy transfer efficiency and violations of compliance with EMI standards.

WO 2013142720 A discloses systems and methods for efficiently transferring electromagnetic energy and charging devices and batteries in a manner that provides freedom with respect to the placement of devices or batteries. In accordance with various embodiments, applications include inductive or magnetic charging, as well as supplying energy to various devices or appliances. In accordance with various embodiments, systems and methods can also generally be applied, for example, to power supplies or other energy sources or charging systems, such as, for example, systems for transmitting electromagnetic energy to a mobile, electronic or electrical device, vehicle or other device. However, WO 2013142720 A does not address the issue of electromagnetic interference filtering (EMI) and common mode rejection, which leads to reduced power transmission efficiency and violations of compliance with EMI standards.

Accordingly, known wireless charging systems suffer from various electromagnetic interference (EMI) and therefore cannot achieve maximum energy transfer efficiency.

Disclosure of invention

An object of the present invention is to overcome the aforementioned disadvantages characteristic of solutions known in the prior art.

The technical result provided by the present invention is to increase the efficiency of energy transfer from the wireless power transmission unit to the wireless power reception units integrated in electronic devices, as well as to suppress electromagnetic interference (EMI) using impedance matching circuits and a shielding element.

The present invention discloses a wireless charging system. The system comprises a wireless power transmission unit and a wireless power reception unit.

The wireless power transmission unit comprises an energy source transmitting an inductor, a first shielding element and a first impedance matching circuit. The transmitting inductor is connected to the energy source through the first impedance matching circuit. In the case of power supply by means of an energy source, the transmitting inductor is capable of emitting electromagnetic radiation. The first impedance matching circuit is configured to match the optimal impedances for the transmitter inductance and the energy source. The first shielding element is located under the transmitting inductor and is configured so that the electromagnetic radiation emitted by the transmitting inductor is suppressed outside the active charging region determined by the structure of the transmitting inductor.

The wireless power receiving unit comprises a receiving inductor, a load, and a second impedance matching circuit. The receiving inductor is inductively coupled to the transmitting inductor, so that the electromagnetic radiation emitted by the transmitting inductor induces charging currents in the receiving inductor. The load is connected to the receiving inductor through a second impedance matching circuit. The load is configured to be charged by charging currents. The second impedance matching circuit is configured to match the optimal impedances for the receiving inductor and load.

The first and second matching circuits are also configured to provide resonance between the transmitting inductor and the receiving inductor, which also maximizes the efficiency of energy transfer.

The transmitting inductor has many conductive turns, separated from each other by gaps. The gaps decrease in the direction of removal from the Central region of the transmitting inductor.

The first shielding element may be made of conductive and / or ferrite materials.

The first impedance matching circuit is also configured to bypass common-mode currents to the first shielding element, which suppresses spurious radiation emitted by a transmitting inductor.

The first impedance matching circuit of the wireless power transmission unit comprises at least two shunt capacitors connected in parallel with the transmitting inductor and at least two series capacitors connecting the contacts of the transmitting inductor with the corresponding terminals of the power source. Shunt capacitors connect the transmitting inductor to the first shielding element and ground the power source, whereby the aforementioned common mode current shunting is provided.

The capacitors of the first impedance matching circuit are also selected in such a way as to convert the impedance of the transmitting inductor to the optimal impedance for the energy source, whereby said matching of the optimal impedances for the transmitting inductor and the energy source is ensured.

The active charging region, determined by the structure of the transmitting inductor, provides an almost constant impedance, regardless of the position and orientation of the load in it.

The transmitting inductor may be a flat inductor made on a single or multi-layer PCB. A flat inductor can be made of groups of layers. Each layer of one group has the same structure of turns. All layers of the same group are connected to each other through multiple interlayer connections and are implemented as a continuous conductive inductor having a thickness equal to the thickness of the said one group.

The first impedance matching circuit is balanced with respect to the output of the energy source, while the center point of the first impedance matching circuit is connected to the ground of the energy source.

The wireless power transmission unit may also contain absorbing resonant elements that are located under the transmitting inductor and are used to attenuate the electromagnetic radiation emitted by the transmitting inductor. The resonant frequencies of the absorbing resonant elements are set equal to the frequencies of the peaks of electromagnetic radiation emitted by the transmitting inductor, as a result of which the absorbing resonant elements are capable of absorbing the peaks of electromagnetic radiation at these resonant frequencies. Absorbing resonant elements can be made as resonators in the form of split rings, resonators in the form of complementary split rings, resonant spirals, complementary resonant spirals or other types of metamaterial structures.

The turns of the transmitting inductor can have maximum radii of curvature at the outer edges of the transmitting inductor and minimum radii of curvature in the central region of the transmitting inductor.

The transmitter inductance may have a central tap connected to the first shield element. A central tap is used to bypass common-mode currents to the first shielding element. The central tap can be connected to the first shielding element through galvanic or capacitive connections. Said capacitive connection is formed as lumped capacitive elements or mutual capacitance between the central outlet and the first shielding element.

In addition, between the transmitting inductor and the first shielding element can be formed many connecting taps through capacitive connections.

The structure of the transmitting inductor is determined as follows:

where lxN, lyN and lx1, lyN are the external and internal dimensions of the transmitting inductor, respectively, N is the number of turns, ri is the radius of curvature of the ith coil, and α is a parameter of the ratio of the turns.

The wireless power reception unit is integrated into the electronic device, and in this case, the load is the battery or battery pack of the electronic device. An electronic device may be a mobile and portable device selected from the group consisting of smartphones, smart watches, smart glasses, tablet computers and laptops. The structure of the transmitting inductor can support the charging of one or more electronic devices within the active charging region.

The second impedance matching circuit of the wireless power receiving unit comprises at least two shunt capacitors connected in parallel with the receiving inductor, and at least two series capacitors connecting the receiving inductor to the load terminals. The capacitors of the second impedance matching circuit are configured to provide, together with the capacitors of the first impedance matching circuit, resonance between the transmitting inductor and the receiving inductor, which also maximizes the efficiency of energy transfer. The capacitors of the second impedance matching circuit are also selected so as to convert the impedance of the receiving inductor to the optimal impedance for the load.

The receiving inductor of the wireless power receiving unit has a plurality of conductive turns. The density and geometry of the said turns depend on the geometry and power consumption of the wireless power receiving unit.

In one embodiment, the wireless power reception unit may also comprise a second shielding element mounted beneath the receiving inductor. In this case, the second shielding element isolates the internal components of the electronic device, inside which the unit for wireless energy reception is built-in, from electromagnetic radiation emitted by the transmitting inductor and the receiving inductor.

In another embodiment, a battery or battery pack of an electronic device insulates the internal components of the electronic device.

The electromagnetic radiation emitted by the transmitting inductor is almost uniform within the active charging region.

The transmitting inductor is also configured to provide an almost constant mutual inductance and intrinsic inductance of the transmitting inductor and the receiving inductor whenever the wireless power receiving unit is randomly located within the active charging area.

The first impedance matching circuit is also configured to change the impedance of the transmitting inductor, depending on the load of the wireless power receiving unit.

The wireless power receiving unit may also include a rectifier that is located in front of the load and is configured to convert AC to DC, relative to the induced charging currents.

The system that was proposed above can operate in the frequency range from 100 kHz to 100 MHz.

The present invention provides the following major improvements:

- the wireless power transmission unit is equipped with a shielding element and an impedance matching circuit. Thus, the electromagnetic radiation emitted by the transmitting inductor is suppressed outside the active charging area of the wireless power transmission unit, while spurious radiation emitted by the transmitting inductor is minimized and does not affect electronic devices.

- Provides maximum power transmission efficiency for a variety of mobile devices that are located in any position and orientation, in the immediate vicinity of the wireless power transmission unit.

Other features and advantages of the present invention will become apparent upon reading the following detailed description and viewing the accompanying drawings.

Brief Description of the Drawings

The essence of the present invention is explained below with reference to the accompanying drawings, which depict the following:

FIG. 1 shows equivalent circuits and components of wireless power reception and transmission units;

FIG. 2 depicts a parametric model and dimensions of a transmitting inductor of a wireless power transmission unit;

FIG. 3 is a plan view of a receiving inductor mounted in a mobile phone;

FIG. 4 is a side view showing an arrangement of a transmitting inductor and a receiving inductor relative to each other;

FIG. 5A-B are various views showing a method of arranging various elements of wireless power reception and transmission units relative to each other, in particular FIG. 5A is a plan view, and FIG. 5B is a cross-sectional view taken along line A-A;

FIG. 6A-B show a current distribution over a housing of a wireless power reception unit located at various positions on a wireless power transmission unit;

FIG. 7A-B depict a method for reducing the total thickness of a wireless power transmission unit using a shielding element as disclosed in the present invention: a copper shielding element (FIG. 7A) and a copper-ferrite shielding element (FIG. 7B);

FIG. 8 shows an arrangement of capacitors of an impedance matching circuit in a wireless power transmission unit;

FIG. 9A-B depict the common-mode voltage spectrum of the transmitter inductor for the following test examples: capacitors are not connected to the ground of the power source and the shield element (Fig. 9A), capacitors are connected to the ground of the power source and the shield element (Fig. 9B);

FIG. 10A-D depict equivalent circuits of a transmitter inductance coupled through a central tap to ground an energy source using a galvanic connection (FIG. 10A) and via a capacitive connection (FIG. 10B); geometry of the transmitting inductor: asymmetric (Fig. 10C) and symmetric (Fig. 10D);

FIG. 11 shows a reduction in the level of electromagnetic (EM) radiation using a transmitting inductor connected through a central tap;

FIG. 12 is an equivalent circuit for connecting 2C2P capacitors to a load ground in a wireless power receiving unit;

FIG. 13A-B depict the voltage and current spectra of the receiving inductor for the following test examples: capacitors 2C2P are not connected to the load ground (Fig. 13A), capacitors 2C2P, C3P and the ferrite ring L2S are connected to the load ground (Fig. 13B);

FIG. 14A-C depict a perspective view, a top view, and a sectional view of respectively absorbing resonant elements disposed between a transmitting inductor and a copper shielding element to reduce the level of electromagnetic interference emission (EMI);

FIG. 15 is a comparison of electromagnetic interference emission (EMI) for a wireless power transmission unit with and without the use of absorbing resonant elements;

FIG. 16A-B depict the impedance dependence of the wireless power transmission unit for correct (Fig. 16A) and incorrect (Fig. 16B) embodiments of a hybrid impedance matching circuit;

FIG. 17A-F depict experimental results for prototypes of wireless power reception and transmission units.

The implementation of the invention

Next, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in many other forms, and should not be construed as limiting any specific structure or function presented in the following description. On the contrary, these embodiments are provided in order to make the description of the present invention detailed and complete. In accordance with the present description, specialists in the art will understand that the scope of the present invention covers any embodiment of the present invention that is disclosed herein, regardless of whether this embodiment is implemented in independent form or in conjunction with any other embodiment of the present inventions. For example, the system disclosed herein may be practiced by using any of the number of embodiments provided herein. In addition, it should be understood that any embodiment of the present invention can be implemented using one or more of the elements presented in the attached claims.

The term "illustrative" is used herein in the context of "used as an example or illustration." Any embodiment described herein as “illustrative” should not be necessarily interpreted as being preferred or taking precedence over other embodiments.

For simplicity, the term “wireless power transmitting unit” is also referred to as a “transmitting (TX) unit”, and the term “wireless power receiving unit” is also referred to as a “receiving (RX) unit." A transmitting (TX) unit can transmit energy to a receiving (RX) unit via inductive coupling. A receiving (RX) unit can be integrated into an electronic device. An electronic device may be a mobile and / or portable device selected from the group consisting of smartphones, smart watches, smart glasses, tablet computers and laptops. The disclosed designs of transmitting (TX) and receiving (RX) units provide an ergonomic solution for charging all portable devices at home or at work, electromagnetic power transmission stations for public places, such as restaurants, cafes, libraries, etc.

As used herein, the term “charging” refers to a battery or battery pack of an electronic device. To charge the battery of an electronic device, the user must manually place the electronic device on the surface of the transmitting (TX) unit. Therefore, the sizes of the transmitting (TX) block are of particular importance. Large transmit (TX) units support the transfer of more energy and more electronic devices that need to be charged simultaneously. Next will be described in more detail the design of the transmitting (TX) and receiving (RX) blocks.

Equivalent circuits and components of transmitting (TX) and receiving (RX) blocks

In FIG. 1 shows equivalent circuits of transmitting (TX) and receiving (RX) blocks.

In a preferred embodiment of the present invention, the transmitting (TX) unit 110 comprises the following elements: an energy source 111, a transmitting (TX) inductor 112, and an impedance matching circuit 113. An energy source 111 is coupled to a transmit (TX) inductor 112 via an impedance matching circuit 113. The ITX current generated by the power source 111 is converted to the ITX_COIL current via the impedance matching circuit 113. The impedance matching circuit 113 comprises two series capacitors 2C1S and two capacitors 2C1P connected in parallel with the transmitting (TX) inductor 112. Capacitors 2C1P connect the transmitting (TX) inductor 112 to the ground of the power source 111 and the shield element 210 shown in FIG. 2, 4, 5A-B. The shielding element 210 may be made of conductive and / or ferrite materials. Although FIG. 1 depicts only two capacitors 2C1S and two capacitors 2C1P, those skilled in the art will understand that any other number of said capacitors may be used depending on the particular application.

In a preferred embodiment of the present invention, the receiving (RX) block 120 comprises the following elements: a receiving (RX) inductor 121, an impedance matching circuit 122 and a load 123. A receiving (RX) inductance 121 is connected to a load 123 via an impedance matching circuit 122. The impedance matching circuit 122 comprises two series capacitors 2C2S and two capacitors 2C2P connected in parallel with a receiving (RX) inductor 121. Capacitors 2C2P connect a receiving (RX) inductor 121 to a ground of the load 123. Although FIG. 1 shows only two capacitors 2C2S and two capacitors 2C2P, those skilled in the art will appreciate that any other number of said capacitors may be used depending on the particular application.

When the receiving (RX) unit 110 is located on the transmitting (TX) unit 120, the receiving (RX) inductance coil 121 and the transmitting (TX) inductance 112 are interconnected by magnetic flux. As a result, the magnetic flux generated by the transmitting (TX) inductor 112 induces currents (see IRX_COIL in FIG. 1) in the receiving (RX) inductor 121, and energy is transmitted to the load 123.

Using capacitors 2C1P connecting the transmitting (TX) inductor 112 to the shield element 210, common-mode currents can be shunted to attenuate spurious electromagnetic interference (EMI) radiation. In addition, due to the presence of the shielding element 210, electromagnetic fields induced by currents in the transmitting (TX) inductor 112 are suppressed at all intermediate points, except for the location of the receiving (RX) block 120. The resulting electromagnetic field is concentrated near the receiving (RX) block 120 and induces currents in the receiving (RX) inductance coil 121 of the receiving (RX) block 120, which can be located in any position and orientation, within the active charging region of the transmitting (TX) block 110. The active region Charging is defined by the structure of the transmitting (TX) inductor 112 and provides an almost constant impedance, regardless of the position and orientation of the load 123 in it.

The transmitting (TX) inductor 112 has a plurality of conductive turns separated by gaps. The gaps decrease in the direction of removal from the Central region of the transmitting inductor. For example, the transmitting (TX) inductor 112 may have, inter alia, a spiral shape in which the gaps between the turns of the transmitting (TX) inductor 112 decrease radially from the center region of the inductor. In addition, the turns of the transmitting (TX) inductor 112 have maximum radii of curvature at the outer edges of the transmitting (TX) inductor 112 and the minimum radii of curvature in the central region of the transmitting (TX) inductor 112.

In addition, the transmitting (TX) inductor 112 may be a flat inductor made on a single-layer or multi-layer PCB. A flat inductor can be made of groups of layers. Each layer of one group has the same structure of turns. All layers of the same group are connected to each other through multiple interlayer connections and are implemented as a continuous conductive inductor having a thickness equal to the thickness of the said one group.

The transmitting (TX) unit 110 may also contain absorbing resonant elements that are located under the transmitting (TX) inductor 112 and are used to attenuate electromagnetic radiation emitted by the transmitting (TX) inductor 112. The resonant frequencies of the absorbing resonant elements are set equal to the frequencies of the peaks of electromagnetic radiation emitted by the transmitting inductor, as a result of which the absorbing resonant elements are capable of absorbing the peaks of electromagnetic radiation at these resonant frequencies. These peaks of electromagnetic radiation must be absorbed or otherwise eliminated, since they can adversely affect the internal components of the charged electronic device. Absorbing resonant elements can be made as resonators in the form of split rings, resonators in the form of complementary split rings, resonant spirals, complementary resonant spirals or other types of metamaterial structures.

The receiving (RX) unit 110 may also include a rectifier connected to the terminal of the receiving (RX) inductor 121 and the impedance matching circuit 122 before the load 123. The rectifier is configured to convert AC to DC relative to the currents induced in the receiving (RX) coil 121 inductance.

A receiving (RX) inductor 121 has a plurality of conductive turns. The external dimensions of the receiving (RX) inductance coil 121 increase as much as possible within the available surface of the receiving (RX) block 120. The density and geometry of the said coils depend on the geometry and power consumption of the receiving (RX) block 120.

In some embodiments of the receiving (RX) unit 120 (FIG. 3), an additional shielding element 125 can also be installed under the receiving (RX) inductor 121 to isolate the internal components 126, 127 (for example, one or more circuits) of the electronic device, within which a receiving (RX) unit 120 is integrated, from electromagnetic radiation emitted by the transmitting (TX) inductor 112 and the receiving (RX) inductor 121. Said additional shielding element 125 may be made of conductive and / or ferrite materials. In alternative embodiments, the internal components of the electronic device may be insulated by existing conductive structures, for example, by a battery or a battery pack.

The geometry of the transmitting (TX) inductor 112 for the transmitting (TX) block 110 supporting the free placement of the receiving (RX) block 120

In accordance with documents US 2011/0198937 A1 and US 2012/0228959 A1, a constant efficiency (energy output) and a constant input impedance ZTX_IN_COIL under various conditions of coupling of the transmitting (TX) and receiving (RX) inductors can be achieved if if the coupling coefficient of the inductors k and the Q factors are invariant to the relative position of the receiving (RX) block 120 on the transmitting (TX) block 110. Next, the geometry of the transmitting (TX) inductance coil 112 will be described in detail.

The center of the conductive core of the transmitting (TX) inductor 112 (see FIG. 2) should be described by the following parametric model:

In this case, lxN, lyN and lxl, lyl are the external and internal dimensions of the transmitting (TX) inductor 112, respectively, N is the number of turns, ri is the radius of curvature of the ith core of the inductor, and α is a parameter of the ratio of turns. It should be noted that in FIG. 2 shx and shy are the length and width of the shielding element 210, respectively.

As mentioned above, the dimensions of the receiving (RX) inductor 121 are set taking into account the geometric constraints of the receiving (RX) unit 120. The sizes N, lxi, lyi and ri of the transmitting (TX) inductor 112 are optimized with maximum efficiency and uniformity criteria for all possible positions of the receiving (RX) block 120.

The presence of a conductive shielding element 210 (see Fig. 2, 4, 5A-B) at a distance of "a" from the transmitting (TX) inductor 112 and receiving (RX) unit 120 at a distance of "h" reduces the inductance of the transmitting (TX) coil 112 inductance. The conductive shielding element 210 has a negligible effect on the losses, while eddy currents induced on the resistive materials of the receiving (RX) unit 120 dissipate energy. As a result, the actual environment of the transmitting (TX) unit 210 introduces significant limitations regarding the energy transfer efficiency (PTE).

Suppression of the magnetic fields of the transmitting (TX) inductor at all intermediate points, except for the positions of the receiving (RX) block

The conditions for isolating the transmitting (TX) block 110 from surrounding objects are achieved by using various shielding elements, as shown in FIG. 7A-B. In particular, to reduce the total thickness of the transmitting (TX) unit 110, a thin film ferrite shield element can be used instead of a conductive shielding element. For example, a ferrite layer with a thickness of 0.5 millimeters is sufficient for a shielding efficiency of 20 dB. FIG. 7A shows a case where a copper shielding element 210 is used, and FIG. 7B shows a case where a copper-ferrite shield element 210 is used. The copper-ferrite shield element 210 consists of a copper layer 211 and a ferrite layer 212. It can be seen that the copper-ferrite shield element provides a better reduction in the total thickness of the transmitting (TX) block 110 ( see distance A, which is shorter when a copper-ferrite shielding element is used).

According to the present invention, the connection of the transmitting (TX) inductor 112 to ground 501 of the power source 111 and the shield element 120 is realized by using the impedance matching circuit 113 (see FIG. 1). The capacitors 2C1S, 2C1P of the impedance matching circuit 113 are located in the region indicated in FIG. 8 by reference numeral 502.

Illustrative parameters for transmitting (TX) inductors 112 inductors obtained by using the described approaches are presented in table 1. In accordance with these results, the use of a copper-ferrite shielding element and a thin transmitting (TX) inductor 112 (d = 0.1 mm) provides the ability to reduce the total thickness of the transmitting (TX) block to 5.7 mm. The use of only a copper shielding element at a small distance from the transmitting (TX) inductance coil 112, for example, a = 5 mm, will reduce the intrinsic inductance L1 by 57%, as well as reduce the coupling coefficient by 40% compared with the case of no shielding. The use of only a ferrite shielding element at a small distance from the transmitting (TX) inductor 112, for example, a = 5 mm, will lead to a decrease in the quality factor by 24% compared with the case of no shielding. Reducing the thickness "d" of the transmitting (TX) inductor from 2 mm to 0.1 mm does not affect the parameters. The use of only a ferrite shielding element makes it possible to achieve high efficiency of the wireless charging system, while the inductance of the transmitting (TX) inductance coil 112 still affects external metal objects (for example, a metal table).

Table 1
The dependence of the parameters of the transmitting (TX) and receiving (RX) blocks on the options for the execution of the shielding element Name
parameter No shielding for transmitting (TX) inductor 0.1 mm copper shielding
a = 10 mm
d = 2 mm 0.1 mm copper shielding
a = 5 mm
d = 2 mm Ferrite shielding 1 mm
a = 5 mm
d = 2 mm Ferrite shielding 0.5 mm
a = 5 mm
d = 2 mm Ferrite shielding 0.5 mm
a = 5 mm
d = 0.1 mm Copper-ferrite shielding 0.1 mm and 0.5 mm
a = 5 mm
d = 0.1 mm L1, uH 2.03 1.26 0.87 2.7 2.6 2.6 2,4 Q1 144 164 138 110 109 108 103 k 0.25 0.18 0.15 0.27 0.26 0.26 0.26 U 32,7 25.5 17.9 29.7 28.8 28.7 27,2

Ways to attenuate electromagnetic interference (EMI)

According to the present invention, the transmitting (TX) inductor 112 must be connected to the ground of the power source 111 and the shield element 210 by using capacitors 2C1P (see FIG. 1). The effect of such a common mode rejection coupling is shown in FIG. 9A-B. The common-mode voltage spectrum for the transmitting (TX) inductor 112 is presented for the following test examples:

- FIG. 9A: 2C1P capacitors are not connected to the ground of the power source 111 and the shield element 210;

- FIG. 9B: 2C1P capacitors are connected to the ground of the power source 111 and the shield element 210.

In accordance with the results presented in FIG. 9A-B, electromagnetic interference (EMI) is attenuated by at least 10 dB in the frequency range above 90 MHz.

The connection of the central branch 701 of the transmitting (TX) inductor 112 to the ground of the power source 111 provides the possibility of attenuation of electromagnetic interference (EMI) radiation (see Fig. 10A-D). The equivalent connection diagrams of the transmitting (TX) inductor 112 and the impedance matching circuit 113 to the output of the energy source 111 are shown in FIG. 10A-B.

In a preferred embodiment, the center tap 701 of the transmitter (TX) inductor 112 is connected to the conductive shield element 210. The conductive shield element 210 is connected to the ground point of the power source 111. Various methods for such a connection are available, including galvanic (FIG. 10A) or capacitive (FIG. 10B) connections. In the case of using these methods, common-mode currents are shunted before entering the transmitting (TX) inductor 112, while the emission of spurious radiation is suppressed. These structures do not affect the supply of differential output energy from the energy source 111 to the transmitting (TX) inductor 112. Therefore, the effectiveness of PTE is not reduced.

A preferred embodiment of the present invention may be based on various types of structures of a transmit (TX) inductor 112: an asymmetric spiral inductor 801 (FIG. 10C) or a symmetrical spiral inductor 802 (FIG. 10D). In each case, the positions of one or more central taps 701 are optimized to balance the amplitude and phase of the voltages at the contacts of the transmitting (TX) inductor 112.

An example of reducing electromagnetic interference emission (EMI) by using a transmit (TX) inductor 112 connected through a central tap is shown in FIG. 11. The transmitting (TX) inductor 112 without a central tap has 2 peaks of radiated electromagnetic interference (EMI): 100-120 MHz and 180-200 MHz (see curve 901 in the insert image shown in Fig. 11). The connected center tap has only 1 peak at 180-200 MHz (see curve 902). As a result, the central branch 701 of the transmitting (TX) inductor 112 suppresses the level of electromagnetic interference (EMI) at 100-120 MHz by at least 40 dB.

A preferred method for mitigating electromagnetic interference (EMI) for the receiving (RX) unit 120 uses a capacitor 2C2P to be connected to the ground of the receiving (RX) unit 120 shown in FIG. 1 way. In addition, EMI can be achieved by using shunt capacitors C3P and a ferrite ring L2S connected as shown in FIG. 12 way. The effect of such a common mode rejection coupling is shown in FIG. 13A-B. The voltage and current spectra of the receiver (RX) inductor 121 are shown in FIG. 13A-B for the following test examples:

- FIG. 13A: 2C2P capacitors are not connected to the ground of the receiving (RX) unit 120;

- FIG. 13B: Capacitors 2C2P, C3P and a ferrite ring L2S are connected to the ground of the receiving (RX) unit 120.

In accordance with the results presented in FIG. 13A-B, the electromagnetic interference spectrum (EMI) is attenuated by at least 20 dB at frequencies above 150 MHz and at least 30 dB at 350-500 MHz.

In some embodiments of the transmitting (TX) unit 110, electromagnetic interference emission (EMI) can be attenuated by using the absorbing resonant elements 1001 of FIG. 14A-C (which depict their perspective view, top view, and sectional view, respectively; the section shown in FIG. 14C is taken along line A-A shown in FIG. 14B). Absorbing resonant elements 1001 damp the spurious resonances of the transmitting (TX) inductor and absorb all or some of the peaks of electromagnetic interference (EMI).

An example of the effect of absorbing resonant elements 1001 with an electromagnetic interference emission (EMI) level is shown in FIG. 15. The quality factor of absorbing elements affects the efficiency of attenuation of electromagnetic radiation (EMI). The following cases demonstrate: transmitting (TX) block 110 without absorbing resonance elements 1001 (see curve 1101), lower resonance absorption structure (see curve 1103), upper resonance absorption structure (see curve 1102), and optimal resonance absorption structure (see curve 1104).

As shown in FIG. 15, the absorbing resonance elements 1001 tuned to a frequency of 412 MHz quench the spurious resonance by 20 dB (see double arrow 1105).

Tuning of transmitting (TX) and receiving (RX) units magnetically connected for maximum energy transfer efficiency

The maximum PTE efficiency for a transmitting (TX) inductor 112 and a receiving (RX) inductor 121 connected inductively can only be achieved by using optimal load impedance. To analyze these parameters, two interconnected inductors with inductance L1, L2, intrinsic losses R1, R2 and mutual inductance M must be taken into account. Suppose that the receiving (RX) inductor 121 is connected to the load with the impedance Z2 shown in FIG. 1 way.

The coordination of the optimal impedances of Z2 must satisfy the resonance conditions in the receiving (RX) inductor 121, while the maximum energy transfer efficiency is achieved in the form of Z2opt:

The following notation will also be used:

- коэффициент индуктивной связи катушек индуктивности, ω - частота, на которой работают передающий (TX) и приемный (RX) блоки. Коэффициент U добротности используется в нижеприведенных уравнениях для простоты.

is the inductive coupling coefficient of the inductors, ω is the frequency at which the transmitting (TX) and receiving (RX) blocks work. The quality factor U is used in the equations below for simplicity.

Maximum energy transfer efficiency for optimal impedance Z2 (1):

The input impedance of the transmitting (TX) inductor 112 in case of optimal load:

Since the input impedance ZTX_IN_COIL and the load impedance Z2 are determined by equation (4), impedance matching circuits 113 and 122 are necessary to match these impedances for the required power source 111 and load 123 shown in FIG. 1 way. The elements of the impedance matching circuit for the receiving (RX) unit 120 must be calculated by using the input impedance ZRECT of the rectifier as follows:

where X = -1 / ωС2Р is the impedance of the capacitor C2Р connected in parallel to the receiving (RX) inductor 121, Y = -1 / ωС2S is the impedance of the capacitor C2S connected in series with the load 123. The serial element with the value from equation (6) can be capacitor or inductor. The presence of a negative root in equation (5) makes it possible to use a capacitor as a shunt element of the impedance matching circuit: C2P = -1 / ωXNEG, where XNEG is the negative root of equation (5). In the case where the obtained Y value is negative, the value of the series capacitor is C2S = -1 / ωY.

Applicability criteria for hybrid parallel-serial elements of the impedance matching circuit 122 in the receive (RX) block are defined as follows:

соответствуют согласованию последовательных импедансов, т.е. C2P=0. В противном случае должны быть использованы гибридные параллельно-последовательные элементы цепи 122 согласования импедансов.Conditions Re (ZRECT) min =

correspond to the coordination of successive impedances, i.e. C2P = 0. Otherwise, hybrid parallel-serial elements of the impedance matching circuit 122 should be used.

Communication of a power source with a transmitting (TX) block, determination for various variations of the impedance of a transmitting (TX) block

The operation of the power source 111 is set by the input impedance ZTX of the transmitting (TX) block (see Fig. 1). The impedance matching circuit 113 for the transmitter (TX) inductor 112 should be calculated using the following equations:

In this case, X is a reactive component connected in parallel to the transmitting (TX) inductor 112, and Y is a reactive component connected in series with the power source 111. The sign of the root in equation (8) determines the parallel type of element, namely, a capacitor or inductor. The serial element with the value from equation (9) can also be a capacitor or inductor. The presence of a negative root makes it possible to use a capacitor as a parallel element of the impedance matching circuit 113:

where XNEG is the negative root of equation (8). In the case when the obtained Y value is negative, the value of the series capacitor should be according to the formula:

Condition (10) provides the maximum Re (ZTX_IN '), which can be matched with a specific transmitting (TX) inductor 112.

In a preferred embodiment of the present invention, the active component ZTX_IN is inversely proportional to the impedance ZRECT of the load 123 (see FIG. 1). Increasing ZRECT will cause decreasing ZTX_IN. A decrease in ZRECT will cause an increase in ZTX_IN. The necessary Z-change is achieved when the impedance matching circuit 113 operates close to series resonance

In this case, the impedance component ZTX_IN decreases with increasing

An example of the dependence of the impedance ZTX_IN on the ZRECT of the transmitting (TX) block is shown in FIG. 16A-B for the following two cases: correct (FIG. 16A) and incorrect (FIG. 16B) implementation of the hybrid impedance matching circuit 113.

With the correct implementation of the impedance matching circuit 113, it is preferable that the horizontal curve ZTX_IN changes in the circular impedance diagram (see curve 201 in FIG. 16A); while the active component of the impedance ZTX_IN gradually decreases with increasing RRECT (see curve 202 in Fig. 16A).

Alternatively, if the impedance matching circuit 113 is not implemented correctly, it is preferable that the vertical curve ZTX_IN change in the pie chart of the impedances (see curve 203 in FIG. 16B); however, the active component of the impedance ZTX_IN has a non-uniform dependence on the increase in RRECT (see curve 204 in Fig. 16B).

Variation of the parameters of the transmitting (TX) block due to a change in the position of the receiving (RX) block

The parameters of the transmitting (TX) inductance coil 112 of the transmitting (TX) block 110 may vary due to a change in the position of the receiving (RX) block 120 relative to the transmitting (TX) inductor 112. The dependence of the coupling coefficient k on the position of the receiving (RX) block 120 is determined by the design parameters lxi, lyi, ri of the transmitting (TX) inductor 112. In general, the inductance and the quality factor of the transmitting (TX) inductance coil 112 are increased for the receiving (RX) unit 120 moving from a central position to an edge position. This is illustrated by Lenz’s law: eddy currents on the surfaces of the receiving (RX) block 120 compensate for the magnetic flux induced by the transmitting (TX) inductor 112. These eddy currents flow along the conductive surfaces of the following elements of the receiving (RX) unit 120: battery, main board, housing frame, etc. The surface current distributions over the receiving (RX) block 120 are shown in FIG. 6A-B for the following typical positions: the receiving (RX) unit 120 (which is integrated in the electronic device) is located in the center of the transmitting (TX) inductor 112 (Fig. 6A) and the receiving (RX) unit 120 is offset from the center (Fig. 6B ) In FIG. 6A-B, dark areas indicate a high surface current density over a receiving (RX) unit housing, and light areas indicate a low surface current density over a receiving (RX) unit body. The variation of the induced currents for different positions of the receiving (RX) block 120 is the cause of the variation in the inductance of the transmitting (TX) inductor 112. When the receiving (RX) unit 120 is placed in a central position, the magnetic field generated by the transmitting (TX) inductor 112 in this area is mostly perpendicular to the surfaces of the receiving (RX) unit 120. In this case, the current distribution over the edges of the receiving (RX) block 120 occurs symmetrically.

In the edge region of the transmitting (TX) inductor 112, the magnetic field has a significant tangent component and a non-uniform normal component. When the receiving (RX) block 120 is located near the edge of the transmitting (TX) inductor 112, the bulk of the magnetic flux is concentrated closer to the center of the transmitting (TX) inductor 112, the eddy current intensity decreases and becomes asymmetric. This current distribution creates a weaker magnetic flux due to the fact that the normal field component relative to the plane of the receiving (RX) block 120 is concentrated in a smaller area, thereby increasing the inductance of the transmitting (TX) inductor 112.

Analytical solutions for matching the optimal impedance matching circuits in equations (5), (6), (8) and (9) provide perfect matching and maximum energy transfer efficiency. However, changes in the parameters of the inductor vary the impedance matching and efficiency for different positions of the electronic device.

The alignment and performance levels at all possible positions of the receiver (RX) block 120 can be estimated by using the reflection coefficient G as a measure of the deviation ZTX_IN from the optimum value. For calculation, the standard formula should be used:

A quantitative assessment of the permissible level of variation of the parameters of the transmitting (TX) inductor is performed by using the sensitivity analysis of the input impedance of the circuit to change the parameters of the inductor. The variation of the reflection coefficient is determined as follows:

where ZIND is the impedance induced by the receive (RX) inductor 121:

Now consider variation as a small deviation from optimal matching and maximum PTE efficiency:

Variation of the active component of the impedance of the transmitting (TX) inductor R1 + ReZIND is directly included in equation (13), while the variation of the reactive component ωL1 + ImZIND is included with the coefficient Q1 / k2Q2, depending on the parameters of the transmitting (TX) and receiving (RX) coils inductance.

When the receiving (RX) inductor 121 is matched by the method defined in equations (5) and (6) and the load is constant (ZRECT = const), the parameters of the receiving (RX) inductor have a fairly small variation, while the transmitting resistance (TX) varies Inductors are negligible:

for all positions of the receiving (RX) inductor.

In this case, the variation of the reflection coefficient determined by equation (13) can be simplified to the following extent:

As a result, a small coupling coefficient (k <0.1) is the reason for the high sensitivity to varying the inductance of the transmitting (TX) inductor 112.

Transmitter (TX) block design

To increase the efficiency of PTE, methods based on increasing inductive coupling and Q factors should be applied. In this direction, the design of the transmitting (TX) inductor 112 is a compromise between the uniformity of the inductive coupling and the variation of the inductance during the position change of the receiving (RX) block 120 relative to the transmitting (TX) inductor 112. Therefore, the criteria for evaluating the design of the transmitting (TX) inductor are based on the efficiency of the PTE (see equation (3)), varying the input impedance of the transmitting (TX) inductor 112 (see equation (4)), depending on the position of the receiving ( RX) block 120 and impedance ZLOAD load.

где β=0,8-0,9 является параметром, определяющим ухудшение взаимной индуктивности между передающей (TX) и приемной (RX) катушками индуктивности вследствие наличия проводящего экранирующего элемента 210 и приемного (RX) блока 120.At the first stage, the average inductive coupling coefficient should be estimated based on the ratio of the surface SRX of the receiving (RX) inductor to the surface STX of the transmitting (TX) inductor in the form

where β = 0.8-0.9 is a parameter determining the deterioration of the mutual inductance between the transmitting (TX) and receiving (RX) inductors due to the presence of a conductive shielding element 210 and a receiving (RX) unit 120.

In a second step, the internal turns of the transmitting (TX) inductor 112 should be designed to minimize the variation of the inductance L1 of the transmitting (TX) inductor when the receiving (RX) block 120 is located in the center of the active charging region and rotates around the center of the receiving (RX) block 120. The unequal length and width of the active charging region and the asymmetry of the receiving (RX) inductance coil 121 provide an inevitable variation in the coupling coefficient. This variation is minimized by adjusting the dimensions of the inner turns lx1, ly1.

The next step is to achieve uniform coupling and constant input impedance of the transmitting (TX) inductor 112 for the necessary offsets of the receiving (RX) block 120 from the center of the active charging region. The external turns of the transmitting (TX) inductance coil 112 should be placed as close as possible to each other in order to minimize the variation of inductance at the edges of the possible positions for the receiving (RX) block 120. In the above-described parametric model of the transmitting (TX) inductor, uniformity is determined by the ratio turns. For the one shown in FIG. 2 examples, the optimal value α = 0.55 was found as a result of the selection of optimal parameters.

The next step: the width of the core of the transmitting (TX) inductor and the number of N turns should be optimized based on the following considerations. Increasing N allows one to achieve better coupling uniformity for different offsets of the receiving (RX) block 120, while N is limited by the minimum width of the core of the inductor, i.e. reducing the line width directly reduces the average coupling coefficient and Q1, resulting in reduced maximum efficiency. An increase in the width of the inductor leads to an increase in Q1, while the variation in the inductance of the transmitting (TX) inductor increases when the receiving (RX) unit 120 is placed close to the edges of the active charging region.

The decrease in active losses of the transmitting (TX) inductor due to the increase in the width of the core is relatively small, as a result of which the quality factor is independent of the width of the core. This phenomenon is associated with an inhomogeneous current distribution over the surface of the core, while the bulk of the current flows along the edges of the core. The mutual inductance between the transmitting (TX) inductor 112 and the receiving (RX) inductor 121 is invariant to the width of the core. As a result, the efficiency is increased in accordance with equation (2) due to a decrease in the resistance of the transmitting (TX) inductor.

The next step: the external turns of the transmitting (TX) inductor 112 should be rounded with the maximum possible radius of curvature to increase the average coupling coefficient. For the one shown in FIG. 2 examples: maximally rounded turns provide k = 0.157; angles rounded in accordance with r1 = rN = 15 mm provide a decrease in the coupling coefficient to k = 0.129.

The next stage: matching circuits of optimal impedances should be calculated using equations (5), (6), (8), (9). The calculated impedance matching circuits 113 and 122 provide optimum matching and maximum PTE efficiency.

In conclusion, the effect of matching impedances and varying PTE efficiencies due to a change in position of the receiving (RX) block 120 should be estimated based on equation (13).

Experimental test results

FIG. 17A-F depict experimental test results for a prototype transmit (TX) unit (as an example, integrated in a mobile phone). In accordance with the control results:

- Maximum PTE efficiency = 90%, PTE efficiency> 84% for all positions and orientation of the receiving (RX) unit 120 on the transmitting (TX) inductor 112.

- Available cellphone positions:

- The phone is located vertically, the dX position is from -37 mm to +37 mm (positions 1201, 1202, 1203).

- The phone is located horizontally, position dY from -30 mm to +30 mm (positions 1204, 1205, 1206).

является коэффициентом стоячей волны напряжения, при этом коэффициент Г отражения является мерой отклонения ZTX_IN от оптимального значения, определенный посредством уравнения (12), (13).In this case

is the coefficient of the standing voltage wave, and the reflection coefficient G is a measure of the deviation ZTX_IN from the optimal value, determined by equation (12), (13).

Although illustrative embodiments of the present invention have been disclosed herein, it should be noted that any various changes and modifications may be made to the embodiments of the present invention within the scope of legal protection as determined by the appended claims. In the appended claims, reference to the singular does not exclude the presence of a plurality of such elements unless otherwise indicated.

Claims (50)

1. A wireless charging system comprising: - a wireless power transmission unit comprising: source of energy; a transmitting inductor connected to an energy source and configured to emit electromagnetic radiation; a first shielding element configured such that electromagnetic radiation emitted by the transmitting inductor is suppressed outside the active charging region determined by the structure of the transmitting inductor; and a first impedance matching circuit connected between the energy source and the transmitting inductor and configured to provide impedance matching between the transmitting inductance and the energy source; and - a wireless power reception unit comprising: a receiving inductor inductively coupled to the transmitting inductor so that electromagnetic radiation emitted by the transmitting inductor induces charging currents in the receiving inductor; a load connected to a receiving inductor and configured to be charged by means of charging currents; and a second impedance matching circuit connected between the receiving inductor and the load and configured to provide matching impedances between the receiving inductor and the load; moreover, the first and second matching circuits are additionally configured to provide resonance between the transmitting inductor and the receiving inductor in order to maximize the efficiency of energy transfer; wherein the active charging region, determined by the structure of the transmitting inductor, provides a constant impedance regardless of the position and orientation of the load in it; the transmitting inductor is a flat inductor made on a single-layer or multilayer PCB, moreover, a flat inductor is made of groups of layers, with each layer of one group of layers having the same structure of turns, all layers of one group of layers are connected to each other through many interlayer connections and implemented as a continuous conductive inductor having a thickness equal to the thickness of said one group of layers. 2. The system of claim 1, wherein the transmitting inductance coil has a plurality of conductive turns separated by gaps, the gaps being reduced in the direction of removal from the central region of the transmitting inductance. 3. The system of claim 1, wherein the first shielding element is made of conductive and / or ferrite materials. 4. The system of claim 1, wherein the first impedance matching circuit is further configured to bypass common-mode currents to the first screening element to suppress spurious radiation emitted by the transmitting inductance coil. 5. The system of claim 4, wherein the first impedance matching circuit of the wireless power transmission unit comprises: at least two shunt capacitors connected in parallel to the transmitting inductor, the shunt capacitors connecting the transmitting inductor to the first shielding element and grounding the power source, whereby this common-mode current bypass is provided; and at least two series capacitors connecting the contacts of the transmitting inductor with the corresponding terminals of the energy source. 6. The system of claim 5, wherein the shunt and series capacitors of the first impedance matching circuit are further selected so as to convert the impedance of the transmitter inductance into an optimal impedance for the energy source. 7. The system of claim 1, wherein the first impedance matching circuit is balanced with respect to the output of the energy source and has a contact connected to the ground of the energy source. 8. The system of claim 1, wherein the wireless power transmission unit further comprises absorbing resonant elements that are located below the transmitting inductor and are used to suppress peaks of electromagnetic radiation emitted by the transmitting inductor. 9. The system of claim 8, wherein the resonant frequencies of the absorbing resonant elements are tuned to be equal to the frequencies of the peaks of the electromagnetic radiation emitted by the transmitting inductor, whereby the absorbing resonant elements are capable of absorbing the peaks of electromagnetic radiation at these resonant frequencies. 10. The system according to claim 8, in which the absorbing resonant elements are made as resonators in the form of split rings, resonators in the form of complementary split rings, resonant helices, complementary resonant helices or other types of metamaterial structures. 11. The system of claim 1, wherein the turns of the transmitter inductance have maximum radii of curvature at the outer edges of the transmitter inductance and minimum radii of curvature in the central region of the transmitter inductance. 12. The system of claim 1, wherein the transmitting inductor has a central tap connected to the first shield element, the central tap being used to bypass common-mode currents to the first shield element. 13. The system of claim 12, wherein the central tap is connected to the first shielding element through galvanic or capacitive connections, said capacitive coupling being formed as lumped capacitive elements or mutual capacitance between the central tap and the first shielding element. 14. The system of claim 1, wherein between the transmitting inductance coil and the first shielding element, a plurality of connecting taps are formed by capacitive connections. 15. The system according to claim 1, in which the structure of the transmitting inductor is defined as follows:

where lx _N , ly _N and lx ₁ , ly ₁ are the external and internal dimensions of the transmitting inductor, respectively, N is the number of turns, r _i is the radius of curvature of the i-th turn, and α is a parameter of the ratio of the turns. 16. The system of claim 1, wherein the wireless power receiving unit is integrated in the electronic device, and the load is a battery or battery pack of the electronic device. 17. The system of claim 16, wherein the electronic device is a mobile and portable device selected from the group consisting of smartphones, smart watches, smart glasses, tablet computers and laptops. 18. The system of claim 16, wherein the transmitting inductance coil allows one or more electronic devices to be charged within the active charging region. 19. The system of claim 1, wherein the second impedance matching circuit of the wireless power receiving unit comprises: at least two shunt capacitors connected in parallel with the receiving inductor, and at least two series capacitors connecting the receiving inductor to the terminals of the load; moreover, the capacitors of the second impedance matching circuit are configured to provide, together with the capacitors of the first impedance matching circuit, a resonance between the transmitting inductor and the receiving inductor, which also maximizes the efficiency of energy transfer. 20. The system of claim 18, wherein the capacitors of the second impedance matching circuit are further selected so as to convert the impedance of the receiving inductor to the optimal impedance for the load. 21. The system of claim 1, wherein the transmitting inductance coil is configured to emit substantially uniform electromagnetic radiation within the active charging region. 22. The system of claim 1, wherein the transmitting inductor is further configured to provide substantially constant mutual inductance and intrinsic inductance of the transmitting inductor and the receiving inductor whenever the wireless power receiving unit is randomly located within the active charging area. 23. The system of claim 1, wherein the first impedance matching circuit is further configured to: changes in the impedance of the transmitting inductance coil depending on the load of the wireless power reception unit. 24. The system of claim 1, configured to operate in a frequency range from 100 kHz to 100 MHz. 25. The system of claim 1, wherein the wireless power receiving unit further comprises a rectifier that is located in front of the load and is configured to convert AC to DC in relation to the induced charging currents. 26. The system of claim 1, wherein the inductance inductor has a plurality of conductive turns, the density and geometry of said turns depending on the geometry and power consumption of the wireless power receiving unit. 27. The system of claim 16, wherein the wireless power receiving unit further comprises a second shielding element mounted beneath the receiving inductor to isolate the internal components of the electronic device from electromagnetic radiation emitted by the transmitting inductor and the receiving inductor. 28. The system of claim 16, wherein the battery or battery pack isolates the internal components of the electronic device.

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