Wireless power transfer transmitter, system and method for wirelessly transferring power

Abstract

An apparatus for use in a magnetic induction wireless power transfer system includes at least one boost coil positioned proximate to a primary coil of a magnetic induction wireless power transfer system and a capacitor electrically connected to the boost coil. A capacitance of the capacitor is selected such that a current in the boost coil is approximately equal to a current in the primary coil during wireless power transfer. The apparatus can include at least one shield coil positioned proximate to the primary coil of the magnetic induction wireless power transfer system, a capacitor electrically connected to the shield coil, and a conductor positioned proximate to the shield coil opposite the primary coil. The conductor encloses the shield coil.

Description

Technical Field

[0001] This disclosure generally relates to wireless power transmission, and more particularly to apparatus, wireless power transmission system and method for use in magnetic induction wireless power transmission systems. Background Technology

[0002] Wireless power transfer systems, such as wireless chargers, are becoming an increasingly important technology for enabling next-generation devices. With more and more manufacturers and companies investing in this technology, the potential benefits and advantages it offers are evident.

[0003] Various wireless power transmission systems are known. A typical wireless power transmission system consists of a power source electrically connected to the wireless power transmitter and a wireless power receiver electrically connected to the load.

[0004] In a magnetic induction system, the transmitter has a transmitter coil with a certain inductance that transfers electrical energy from a power source to a receiver, which has a receiver coil with a certain inductance. Power transfer occurs due to the magnetic field coupling between the coils or inductors of the transmitter and receiver. These magnetic induction systems are limited in scope, and the coils or inductors of the transmitter and receiver must be tightly coupled, i.e., have a coupling factor greater than 0.5 and be optimally aligned for efficient power transfer.

[0005] There are also resonant magnetic systems, where power is transferred due to magnetic field coupling between the coils or inductors of the transmitter and receiver. The transmitter and receiver inductors can be loosely coupled, i.e., with a coupling factor less than 0.5. However, in a resonant magnetic system, at least one capacitor is used to resonate the inductor. Furthermore, in a resonant magnetic system, both the transmitter and receiver are self-resonant. The power transfer range in a resonant magnetic system is increased compared to that in a magnetic induction system, and alignment issues are corrected. Although electromagnetic energy is generated in both magnetic induction and resonant magnetic systems, most power transfer occurs via the magnetic field. Very little (if any) power is transferred via induction or resonant induction.

[0006] The Qi wireless charging standard is an exemplary implementation of a magnetic induction system. It is used in low-power consumer electronics, such as smartphones and wearable devices. Furthermore, low-cost power converters, coils, and integrated circuits are available for the Qi wireless charging standard. The Qi wireless charging standard operates in the kHz frequency range. Devices operating according to the Qi wireless charging standard have a limited coupling range, require precise coil alignment, and use ferrite-based coils, which can be heavy and fragile. Therefore, the application scope of the Qi wireless charging standard is limited.

[0007] In an inductive system, the transmitter and receiver have capacitive electrodes. Power transfer occurs due to electric field coupling between the capacitive electrodes of the transmitter and receiver. Similar to a resonant magnetic system, there exists a resonant electrical system in which at least one inductor is used to resonate the capacitive electrodes of the transmitter and receiver. The inductor can be a coil. In a resonant electrical system, the transmitter is self-resonant, and the receiver is self-resonant. Compared to an inductive system, a resonant electrical system has an increased power transfer range and corrects for alignment problems. Although electromagnetic energy is generated in both inductive and resonant electrical systems, most power transfer occurs via the electric field. Very little power (if any) is transferred via magnetic induction or resonant magnetic induction.

[0008] While wireless power transmission systems are known, they require improvement. Therefore, one objective is to provide a novel wireless power transmission transmitter, receiver, system, and method for wirelessly transmitting power.

[0009] This background is provided merely to set the scene and allow those skilled in the art to better understand the following description. Therefore, the above discussion should not be construed as an admission that it is part of the prior art or common knowledge. Summary of the Invention

[0010] It should be understood that this summary is provided to introduce some concepts in a simplified form, which will be further described in the detailed description below. This summary is not intended to limit the scope of the claimed subject matter.

[0011] Therefore, in one aspect, an apparatus for a magnetic induction wireless power transmission system is provided. This apparatus can shield components outside the system from magnetic fields originating from or generated by the system. The apparatus can further amplify the magnetic field originating from or generated by the system. The apparatus can also maintain the impedance of the active coil of the magnetic induction wireless power transmission system without affecting it. This system can provide the benefit that, due to the introduction of this apparatus, the inverter associated with the active coil does not need to be retuned.

[0012] The device may include a field shielding unit.

[0013] The device may include at least one shielded coil positioned adjacent to the active coil of the magnetic induction wireless power transmission system.

[0014] For the purposes of this disclosure, a plane defined as substantially parallel can be considered adjacent. The shielded coil can be adjacent to the active coil because the main surface of the shielded coil is parallel to the plane defined by the main surface of the active coil.

[0015] The device may also include a capacitor electrically connected to the shielded coil. The capacitor can be configured to set the resonant frequency of the device.

[0016] A capacitor can be electrically connected to the shielded coil. The capacitance of the capacitor is selected such that the impedance or reactance of the effective coil and the field shielding unit or device is the same as the impedance or reactance of the effective coil without the field shielding unit at the same operating frequency.

[0017] The field-shielded coil and capacitor can generate net positive reactance. The conductive plate can generate negative reactance. The capacitance of the capacitor can be chosen such that the net positive reactance equals the negative reactance. Therefore, net zero reactance can exist, and the impedance or reactance of the transmitter coil does not change with or without the field-shielded unit.

[0018] Maintaining the same impedance or reactance ensures that the wireless power transmission system does not need to be retuned. Retuning can increase cost and system setup time.

[0019] The device may include a conductor positioned adjacent to the shielding coil opposite to the active coil. The conductor may surround the shielding coil.

[0020] Conductors may include conductive plates. Conductive plates are typically planar.

[0021] The resonant frequency of this device can be greater than the resonant frequency of the effective coil.

[0022] The resonant frequency of the shielded coil can be less than or equal to the self-resonant frequency of the shielded coil.

[0023] The phase of the current in the shielded coil is approximately equal to the phase of the current in the active coil. In contrast, in existing shielded units, the current in the shielded unit or coil is typically out of phase (e.g., 180 degrees out of phase) with the current in the active coil of a wireless power transmission system (e.g., a magnetic induction wireless power transmission system).

[0024] The shielding coil is configured to amplify the magnetic field originating from or generated by the effective coil. Compared to existing shielding units, the combination of the shielding coil and conductor ensures that the impedance of the effective coil is unaffected by the introduction of the device.

[0025] The conductor can be configured to attenuate the magnetic field originating from or generated by the effective coil.

[0026] When the device is removed, the impedance of the effective coil can remain approximately constant. Similarly, when using a device with a magnetic induction wireless power transmission system, the impedance of the effective coil can remain approximately constant.

[0027] The parameters of the device can be determined based on the following:

[0028]

[0029] Where ω is the resonant frequency of the device.

[0030] Where M 12 It is the mutual inductance between the shielded coil and the active coil.

[0031] Where r L2 It is the resistance of the shielding coil.

[0032] Where L2 is the inductance of the shielded coil.

[0033] Where C is the capacitance of the capacitor.

[0034] Z 1gnd It is the reflected impedance of the conductor toward the effective coil, and

[0035] Z 2gnd It is the reflected impedance of the conductor toward the shielding coil.

[0036] The device may include two shielded coils. Specifically, the device may include a first shielded coil positioned adjacent to the active coil of the magnetic induction wireless power transmission system. The device may also include a second shielded coil located between the first shielded coil and the conductor.

[0037] The capacitor can be electrically connected to the first shielding coil, and the terminals of the second shielding coil can be electrically shorted together to generate capacitive reflected impedance.

[0038] The capacitor may be electrically connected to the first shielding coil. The device may also include a second capacitor electrically connected to the second field shielding coil.

[0039] The parameters of the device can be determined based on the following:

[0040]

[0041] Where ω is the resonant frequency of the device.

[0042] Where M 12 It is the mutual inductance between the effective coil and the first shielding coil.

[0043] Where M 13 It is the mutual inductance between the active coil and the second shielding coil.

[0044] Where M 23 It is the mutual inductance between the first shielding coil and the second shielding coil.

[0045] Where r L2 It is the resistance of the first shielding coil.

[0046] Where L2 is the inductance of the first shielding coil,

[0047] Where C is the capacitance of the capacitor.

[0048] Z 1gnd It is the reflected impedance of the conductor toward the effective coil.

[0049] Z 2gnd It is the reflected impedance of the conductor toward the first shielding coil, and

[0050] Z 3gnd It is the reflected impedance of the conductor toward the second shielding coil.

[0051] The parameters of the device can be determined based on the following:

[0052]

[0053] Where ω is the resonant frequency of the device.

[0054] Where M 12 It is the mutual inductance between the effective coil and the first shielding coil.

[0055] Where M 13 It is the mutual inductance between the active coil and the second shielding coil.

[0056] Where M 23 It is the mutual inductance between the first shielding coil and the second shielding coil.

[0057] Where r L2 It is the resistance of the first shielding coil.

[0058] Where L2 is the inductance of the first shielding coil,

[0059] Where C is the capacitance of the capacitor.

[0060] Z 1gnd It is the reflected impedance of the conductor toward the effective coil.

[0061] Z 2gnd It is the reflected impedance of the conductor toward the first shielding coil, and

[0062] Z 13gnd It is the reflected impedance of the conductor toward the second shielding coil.

[0063] The active coil can be either a transmitter coil or a receiver coil. A transmitter coil can form part of the transmitter in a magnetic induction wireless power transmission system. A receiver coil can form part of the receiver in a magnetic induction wireless power transmission system.

[0064] The wireless power system can be a high-frequency magnetic wireless power transmission system.

[0065] According to another aspect, a wireless power transmission system for transmitting power via magnetic field coupling is provided. The system may include a transmitter coil for transmitting power via magnetic field coupling and a receiver coil for extracting power from the transmitter coil via magnetic field coupling. The system may also include at least one of the described devices. The shielding coil of the device may be positioned adjacent to at least one of the transmitter coil and the receiver coil.

[0066] According to another aspect, a method for shielding the effective coil of a magnetic induction wireless power transmission system is provided. This method can shield external components from magnetic fields originating from or generated by the system. The method can further amplify the magnetic field originating from or generated by the system. Furthermore, this method can also maintain the impedance of the effective coil of the magnetic induction wireless power transmission system without affecting it; that is, the inverter associated with the effective coil does not need to be retuned due to the introduction of the device.

[0067] The method may include positioning at least one shielding coil adjacent to an effective coil of a magnetic induction wireless power transmission system, with a conductor electrically connected to the shielding coil; and positioning a conductor adjacent to the shielding coil relative to the effective coil such that the conductor surrounds the shielding coil.

[0068] The shielding coil can be as described above. The conductor can be as described above.

[0069] According to another approach, a method for wirelessly transmitting power via magnetic induction is provided.

[0070] The method may include generating a magnetic field at the transmitter coil to transfer power to the receiver coil via magnetic field coupling.

[0071] The method may also include amplifying the generated magnetic field via at least one shielding coil positioned adjacent to the transmitter coil relative to the receiver coil.

[0072] The method may also include attenuating the generated magnetic field via a conductor positioned adjacent to the shielding coil relative to the transmitter coil, the conductor surrounding the shielding coil.

[0073] According to another aspect, an apparatus for use in a magnetic induction wireless power transmission system is provided, the apparatus comprising: at least one boost coil positioned adjacent to the effective coil of the magnetic induction wireless power transmission system; and a capacitor electrically connected to the boost coil, the capacitance of the capacitor being selected such that the current in the boost coil is approximately equal to the current in the effective coil during wireless power transmission.

[0074] The capacitance of the capacitor can be selected such that the device generates a net positive reactance.

[0075] The capacitance of a capacitor can be selected such that the impedance or reactance of the effective coil increases.

[0076] The plane of the active coil can be parallel to the plane of the boost coil. This plane can be defined as the major object plane of the active coil, and similarly as the major object plane of the boost coil.

[0077] The device may also include a conductor positioned adjacent to the boost coil relative to the active coil, the conductor surrounding the boost coil.

[0078] The plane of the conductor may be parallel to the plane of the active coil and / or the step-up coil. This plane can be defined as the principal plane of the conductor.

[0079] The conductor can be configured to attenuate the magnetic field originating from the effective coil.

[0080] The conductor can be a conductive plate.

[0081] The distance between the boost coil and the effective coil, as well as the distance between the boost coil and the conductor, can be selected such that the desired capacitance of the capacitor and the eddy current losses in the conductor are optimized.

[0082] The device can be configured to increase the magnetic field generated by the effective coil by approximately two times.

[0083] The effective coil can be either a transmitter coil or a receiver coil.

[0084] The wireless power system can be a high-frequency magnetic wireless power transmission system.

[0085] The resonant frequency of this device can be higher than the operating frequency of the wireless power transmission system.

[0086] The boost coil has the same shape and size as the active coil. The boost coil may have a different shape and / or size than the active coil. For example, the active coil may have a generally square planar shape, and the boost coil may have a generally circular planar shape.

[0087] The device may include multiple boost coils. For example, the device may include four (4) boost coils.

[0088] The boost coil can be configured to be surrounded by an effective coil.

[0089] The boost coil can be configured to increase the magnetic field generated by the effective coil according to the magnetic field distribution.

[0090] According to another aspect, an apparatus for use in a magnetic induction wireless power transmission system is provided, the apparatus comprising: at least one shielding coil positioned adjacent to an effective coil of the magnetic induction wireless power transmission system; a capacitor electrically connected to the shielding coil; and a conductor positioned adjacent to the shielding coil relative to the effective coil, the conductor surrounding the shielding coil.

[0091] According to another aspect, a wireless power transmission system for transmitting power via magnetic field coupling is provided, the system comprising: a transmitter coil for transmitting power via magnetic field coupling, a receiver coil for extracting power from the transmitter coil via magnetic field coupling, and at least one means comprising: at least one shielding coil positioned adjacent to the transmitter coil or the receiver coil; a capacitor electrically connected to the shielding coil; and a conductor positioned adjacent to the shielding coil relative to the transmitter coil or the receiver coil, the conductor surrounding the shielding coil.

[0092] According to another aspect, a method for shielding an effective coil of a magnetic induction wireless power transmission system is provided, the method comprising: positioning at least one shielding coil adjacent to the effective coil of the magnetic induction wireless power transmission system, wherein a conductor is electrically connected to the shielding coil; and positioning a conductor adjacent to the shielding coil relative to the effective coil such that the conductor surrounds the shielding coil.

[0093] According to another aspect, a method for wirelessly transmitting power via magnetic induction is provided, the method comprising: generating a magnetic field at a transmitter coil to transmit power to a receiver coil via magnetic field coupling; reinforcing the generated magnetic field via at least one shielding coil positioned relative to the receiver coil adjacent to the transmitter coil; and attenuating the generated magnetic field via a conductor positioned relative to the transmitter coil adjacent to the shielding coil, the conductor surrounding the shielding coil.

[0094] According to another aspect, a method for wirelessly transmitting power via magnetic induction is provided, the method comprising: generating a magnetic field at a transmitter coil to transmit power to a receiver coil via magnetic field coupling; and reinforcing the generated magnetic field via at least one boost coil positioned adjacent to the transmitter coil relative to the receiver coil, a capacitor electrically connected to the boost coil, the capacitance of the capacitor being selected such that the current in the boost coil is approximately equal to the current in the active coil during wireless power transmission.

[0095] It should be understood that any feature described with respect to one aspect, example, or embodiment may also be used with respect to any other aspect, example, or embodiment of this disclosure. Other advantages of this disclosure will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0096] The embodiments will now be described more fully with reference to the accompanying drawings, in which:

[0097] Figure 1 This is a block diagram of a wireless power transmission system;

[0098] Figure 2 This is a block diagram of an inductive wireless power transmission system;

[0099] Figure 3A yes Figure 2 A perspective view of the transmitter coil of a wireless power transmission system;

[0100] Figure 3B Along without field shielding Figure 3A The magnetic field diagram intercepted by the transmitter coil along the x and y axes;

[0101] Figure 3C Along without field shielding Figure 3A The finite element method (FEM) simulation of the magnetic field diagram intercepted by the xz axis of the transmitter coil;

[0102] Figure 4A This is a perspective view of the shielding unit and transmitter coil according to aspects of this disclosure;

[0103] Figure 4B This is an end view of the shielding unit and transmitter coil according to aspects of this disclosure;

[0104] Figure 4C It is an FEM simulation of a magnetic field diagram with a shielding unit and transmitter coil configuration according to aspects of this disclosure;

[0105] Figure 4D It is a graph of the current waveform in the shielding unit and the transmitter coil according to aspects of this disclosure;

[0106] Figure 4E It is the equivalent circuit of the shielding unit and transmitter coil according to aspects of this disclosure;

[0107] Figure 5A This is a perspective view of another shielding unit and transmitter coil according to an aspect of this disclosure;

[0108] Figure 5B This is an end view of the shielding unit and transmitter coil according to aspects of this disclosure;

[0109] Figure 5C It is an FEM simulation of a magnetic field diagram with a shielding unit and transmitter coil configuration according to aspects of this disclosure;

[0110] Figure 5DIt is a graph of the current waveform in the shielding unit and the transmitter coil according to aspects of this disclosure;

[0111] Figure 5E It is the equivalent circuit of the shielding unit and transmitter coil according to aspects of this disclosure;

[0112] Figure 6A This is a perspective view of another shielding unit and transmitter coil according to an aspect of this disclosure;

[0113] Figure 6B This is an end view of the shielding unit and transmitter coil according to aspects of this disclosure;

[0114] Figure 6C It is an FEM simulation of the magnetic field diagram of the shielding unit and the transmitter coil according to aspects of this disclosure;

[0115] Figure 6D It is a graph of the current waveform in the shielding unit and the transmitter coil according to aspects of this disclosure;

[0116] Figure 6E This is an elevated perspective view of the shielding unit and transmitter coil according to another aspect of this disclosure;

[0117] Figure 6F It is the equivalent circuit of the shielding unit and transmitter coil according to aspects of this disclosure;

[0118] Figure 7 This is a perspective view of the transmitter coil and apparatus according to aspects of this disclosure;

[0119] Figure 8A A perspective view of a portion of the transmitter coil and apparatus according to aspects of this disclosure; and

[0120] Figure 8B yes Figure 8A A side view of a portion of the transmitter and device. Detailed Implementation

[0121] The foregoing description of the invention and certain examples will be better understood when read in conjunction with the accompanying drawings. As used herein, elements or features introduced in the singular and preceded by the words "a" or "an" should be understood to not necessarily exclude multiple elements or features. Furthermore, references to "an example" or "an embodiment" are not intended to be construed as excluding the existence of additional examples or embodiments that also include the described elements or features. Moreover, unless explicitly stated otherwise, examples or embodiments that "comprise," "have," or "include" elements or features having a particular property may include additional elements or features that do not have that property. Furthermore, it should be understood that the terms "comprise," "have," and "include" mean "including but not limited to," and the terms "comprise," "have," and "include" have equivalent meanings. It should also be understood that throughout the specification and drawings, the same reference numerals will be used to refer to the same elements.

[0122] As used herein, the terms “suitable” and “configurable” mean that an element, component, or other subject is designed and / or intended to perform a given function. Therefore, the use of the terms “suitable” and “configurable” should not be construed as meaning that a given element, component, or other subject is simply “capable” of performing a given function, but rather that the element, component, and / or other subject is specifically selected, created, implemented, utilized, and / or designed to perform that function. Also within the scope of this subject matter disclosure, an element, component, and / or other subject described as suitable for performing a particular function may additionally or alternatively be described as configured to perform that function, and vice versa. Similarly, a subject described as configured to perform a particular function may additionally or alternatively be described as operable to perform that function.

[0123] It should be understood that when a component is referred to as being "on", "attached to", "connected to", "coupled to", "in contact with" another component, it can be directly on, attached to, connected to, coupled to, or in contact with the other component, or there may be an intermediate component.

[0124] It should be understood that, unless otherwise stated, the use of the word "exemplary" means "as an example" or "an example," and does not indicate a preferred or best design or implementation.

[0125] As used herein, the terms “approximately,” “about,” “roughly,” “substantially,” etc., indicate a quantity or characteristic that is close to the stated quantity or characteristic, while still performing the desired function or achieving the desired result. For example, the terms “approximately” and “about” with respect to a stated quantity will include quantities within engineering or design tolerances that are readily understood by those skilled in the art. Similarly, for example, the term “substantially” with respect to a stated characteristic will include elements that provide almost entirely the stated characteristic, and the term “roughly” with respect to a stated characteristic will include elements that primarily provide the stated characteristic.

[0126] Unless otherwise stated, the terms “first,” “second,” etc., are used merely as labels herein and are not intended to impose any order, position, or hierarchy requirements on the elements referred to by these terms. Furthermore, reference to a “second” element does not require or exclude the presence of a lower-numbered element (e.g., a “first” element) and / or a higher-numbered element (e.g., a “third” element).

[0127] Now go to Figure 1 A wireless power transfer system is illustrated, generally identified by reference numeral 100. The wireless power transfer system 100 includes a transmitter 110 and a receiver 120. The transmitter 110 includes a power supply 112 electrically connected to a transmitting element 114, and the receiver 120 includes a receiving element 124 electrically connected to a load 122. Power is transferred from the power supply 112 to the transmitting element 114. Power is then transferred from the transmitting element 114 to the receiving element 124 via high-frequency, resonant, or non-resonant electric or magnetic field coupling. Power is then transferred from the receiving element 124 to the load 122.

[0128] Figure 2 A magnetic induction (h field) wireless power transmission system, generally identified as reference numeral 200, is shown.

[0129] The wireless power transmission system 200 includes a transmitter 202 and a receiver 204. As will be described, the wireless power system 200 operates by transmitting power from the transmitter 202 to the receiver 204. The transmitter 202 is configured to wirelessly transmit power via magnetic field or magnetic induction coupling, as will be described. Although an electric field can also be generated, very little power (if any) is transmitted via electric field coupling.

[0130] Transmitter 202 includes a power supply 206, a transmitter DC / DC converter 208, a DC / AC inverter 210, and a transmitter coil or inductor 212. Power supply 206 is electrically connected to transmitter DC / DC converter 208. Power supply 206 is configured to generate a DC power signal. Power supply 206 is configured to output the DC power signal to transmitter DC / DC converter 208. In this embodiment, the DC power signal is between 24V and 48V. Transmitter DC / DC converter 208 is electrically connected to power supply 206. Transmitter DC / DC converter 208 is electrically connected to DC / AC inverter 210. Transmitter DC / DC converter 208 connects power supply 206 to DC / AC inverter 210. Transmitter DC / DC converter 208 is configured to convert the DC power signal from power supply 206 into a voltage level for transmission to DC / AC inverter 210.

[0131] DC / AC inverter 210 is electrically connected to transmitter DC / DC converter 208. DC / AC inverter 210 is also electrically connected to transmitter coil 212. DC / AC inverter 210 is configured to convert a DC power signal from transmitter DC / DC converter 208 into a sinusoidal radio frequency (RF) power signal. The sinusoidal RF power signal is output from DC / AC converter 210 to transmitter coil 212.

[0132] Receiver 204 is configured to extract power from transmitter 202 via magnetic inductive coupling, as will be described. Although an electric field can also be generated, very little power (if any) is extracted via electric field coupling.

[0133] Receiver 204 includes receiver coil 214, AC / DC rectifier 216, receiver DC / DC converter 218, and load 220. Receiver coil 214 is electrically connected to AC / DC rectifier 216. Receiver coil 214 is configured to receive power from transmitter 202 via transmitter coil 212 using high-frequency magnetic induction coupling.

[0134] For the purposes of this disclosure, high frequency is defined as a frequency of 6.78 MHz or higher. This includes frequencies of 13.56 MHz and higher. Furthermore, frequency refers to the operating frequency of a wireless power transmission system. Therefore, a high-frequency magnetic induction system transmits power from transmitter coil 212 to receiver coil 214 via magnetic induction coupling at a frequency of, for example, 13.56 MHz. Those skilled in the art will understand that the system frequency does not need to be precisely 6.78 MHz or 13.56 MHz. High frequency includes frequencies in the megahertz (MHz) range and above. High frequency also includes frequencies in the International Telecommunication Union (ITU) Band 7 (HF), which ranges from 3 to 30 MHz and above.

[0135] AC / DC rectifier 216 is electrically connected to receiver coil 214. AC / DC rectifier 216 is also electrically connected to receiver DC / DC converter 218. AC / DC rectifier 216 is configured to convert a sinusoidal RF power signal from receiver coil 214 into a DC power signal. AC / DC rectifier 216 is configured to output the DC power signal to receiver DC / DC converter 218.

[0136] Receiver DC / DC converter 218 is electrically connected to AC / DC rectifier 216. Receiver DC / DC converter 218 is also electrically connected to load 220. A DC power signal is output from AC / DC rectifier 216 to receiver DC / DC converter 218. Receiver DC / DC converter 218 connects AC / DC rectifier 216 to load 220. Receiver DC / DC converter 218 is configured to convert the received DC power signal. The converted DC power signal is output from receiver DC / DC converter 218 to load 220. Load 220 is electrically connected to receiver DC / DC converter 218. Load 220 can be a fixed or variable load.

[0137] Although receiver 204 has been described as including receiver DC / DC converter 218, those skilled in the art will understand that other configurations are possible. In another embodiment, receiver 204 does not include receiver DC / DC converter 218. In this embodiment, AC / DC rectifier 216 is electrically connected to load 220. AC / DC rectifier 216 is configured to generate a DC power signal acceptable to load 220.

[0138] Receiver 204 operates at a given frequency. In this embodiment, the operating frequency of receiver 204 is the operating frequency of transmitter 202. In this embodiment, the operating frequency of receiver 204 is 13.56 MHz, which makes the system a high-frequency system as previously defined.

[0139] Now go to Figure 3A The transmitter coil 202 of system 200 is shown. In this embodiment, the transmitter coil 212 is circular and consists of two turns of copper traces on an FR4 printed circuit board (PCB). The transmitter coil 212 has an inductance of approximately 1.50uH. The transmitter coil has two capacitors 228 electrically connected between its terminals. Although a generally rectangular transmitter coil 212 with rounded corners is described, those skilled in the art will understand that other shapes, such as square, spiral, rectangular, or circular, can be used.

[0140] Figure 3B This shows the effect of no field shielding or cancellation from Figure 3AThe magnetic field diagram of the transmitter coil 212 of system 200 is shown. The transmitter coil 212 is shown as having a magnetic field indicated by circular lines. The direction of the magnetic field is indicated by arrows. As shown, the magnetic field is emitted from the coil in two directions, at the top and bottom. The magnetic field is not limited to the area within the transmitter coil 212, thus allowing the magnetic field to radiate around the magnetic coil 212 in multiple directions. Although not shown in the figure, the magnetic field radiates around the transmitter 212 in all directions in three-dimensional space.

[0141] Figure 3C This is an FEM simulation of the transmitter coil 212 without a field shielding unit. For the purposes of this simulation, the transmitter coil 212 consists of two copper rails 213. Those skilled in the art will recognize that the coil 212 can have any number of turns. The simulation shows the magnetic field diagram from the transmitter coil 212 without field shielding or cancellation. Figure 3C The magnetic field is shown to be emitted from either side of the transmitter coil 212. The transmitter coil 212 is shown as having a magnetic field indicated by circular lines.

[0142] In the described magnetic induction (h-field) wireless power transmission system 200, field shielding of the magnetic field generated by the wireless power system 200 is likely an important aspect of the system 200 design. For example... Figure 3C As shown, without field shielding, the magnetic fields generated by the transmitter and receiver coils (or inductors) 212 and 214, respectively, radiate in all directions away from the coils or inductors. Although some of the magnetic field remains confined to the region between transmitter coil 212 and receiver coil 214, most of it is unconfined and thus coupled to the surrounding environment. This can lead to undesirable coupling and transfer of energy to other objects, inducing eddy currents in conductive objects and heating tissue. All of this results in energy loss and may lead to failure to meet EMI / EMC requirements and ICNIRP / IEEE field exposure limits. Conventional solutions, such as the Qi system, rely on ferrite for field shielding due to the high permeability of ferrite. However, ferrite is a heavy and brittle material and is inefficient at MHz frequencies. It is generally understood by those skilled in the art that the two main loss mechanisms in ferrite and magnetism are eddy current losses and hysteresis losses, both of which are frequency- and permeability-dependent. The higher the frequency, the higher the losses. Specifically, the permeability of ferrite is inefficient at MHz frequencies and may require a larger air gap between the ferrite and the coil. This could increase the system size by 200. Furthermore, eddy current and hysteresis losses in ferrite increase with frequency. At MHz frequencies, these losses can lead to system inefficiency and may render the system unusable for power transmission.

[0143] Those skilled in the art generally know that to cancel current or voltage, equal and opposite currents or voltages can be applied, in which case the opposite current or voltage must be 180 degrees out of phase with the current or voltage to be canceled. This is true, for example, of sound waves, frequencies, or forces. Similarly, current magnetic field cancellation methods involve changing the phase of the magnetic field emitted by the transmitter coil 212 such that the phase of the current in the cancellation coil is 180 degrees out of phase with the current in the transmitter coil 212. Utilizing known magnetic field cancellation techniques and methods in magnetic induction systems, the current in the field cancellation coil is 180 degrees out of phase with the current in the transmitter coil 212. This method is often referred to as "field cancellation" because the current in the cancellation coil is 180 degrees out of phase with the current in the transmitter coil 212 and effectively cancels the field from the transmitter coil 212 toward the field cancellation coil.

[0144] A field shielding unit or device for a wireless power transmission system is disclosed. The field shielding unit confines the radiated magnetic field to the area or volume required for wireless power transmission, as will be described.

[0145] Field shielding units are used in magnetically inductive wireless power transmission systems. Examples of such systems include non-resonant magnetic systems, resonant magnetic systems, and high-frequency magnetically inductive systems. Magnetic field (magnetically inductive) wireless power transmission systems use magnetic coils to transfer power from the transmitter to the receiver using magnetic inductive coupling. While an electric field can also be generated, very little power (if any) is transferred using inductive coupling.

[0146] In this embodiment, the field shielding unit is implemented using a high-frequency magnetic induction wireless power transmission system. In another embodiment, the system is a low-frequency magnetic induction wireless power transmission system. In yet another embodiment, the system is a resonant magnetic induction wireless power transmission system. In still another embodiment, the system is a magnetic induction system.

[0147] Now go to Figure 4A This illustration shows a field shielding unit 430 or device for a magnetically inductive wireless power transmission system according to one aspect of the present disclosure. In this embodiment, the field shielding unit 430 includes a single field shielding coil 422 and a conductive plate or conductor 426. The field shielding coil 422 is electrically connected to a discrete capacitor 428. The capacitor 428 is located outside the field shielding coil 422. The capacitor 428 is electrically connected between two terminals of the field shielding coil 422.

[0148] The field shielding coil 422 is configured to amplify or increase the magnetic field generated by the transmitter coil 412. Specifically, the field shielding coil 422 is configured to increase the magnitude of the magnetic field generated by the transmitter coil 412. The conductive plate 426 is configured to at least partially attenuate or block the magnetic field generated by the transmitter coil 412 in a direction substantially opposite to the receiver coil relative to the transmitter coil 412. The size and position of the conductive plate 426 are designed to surround the field shielding coil 422.

[0149] For the purposes of this disclosure, the conductive plate 426 is considered to surround the field shielding coil 422 when at least one of the following conditions is met: (i) if the area defined by the periphery of the field shielding coil 422 is projected onto the area of ​​the conductive plate 426, the projection is entirely within the area of ​​the conductive plate 426; (ii) the projected area of ​​the field shielding coil 422 is constrained by the area of ​​the conductive plate 426; and (iii) the area of ​​the conductive plate 426 is larger than the total area defined by the periphery of the field shielding coil 422 by at least the distance between the field shielding coil 422 and the conductive plate 426.

[0150] The field shielding device 430 is positioned such that the plane formed by the field shielding coil 422 is parallel to the plane formed by the transmitter coil 412. The plane formed by the field shielding coil 422 is also parallel to the plane formed by the conductive plate 426. The plane formed by the conductive plate 426 is parallel to the plane formed by the transmitter coil 412. Therefore, the planes formed by coils 412, 422, and plate 426 are all parallel.

[0151] The plane of any one of coils 412, 422 and plate 426 can be defined as the master plane of a particular element.

[0152] The field shielding device 430 is positioned such that the field shielding coil 422 is opposite the transmitter coil 412 and the receiver coil. The receiver coil is part of a wireless power transmission system in which the transmitter coil 412 forms a portion. The field shielding device 430 is positioned such that the field shielding coil 422 is adjacent to one side of the transmitter coil 412, while the receiver coil is adjacent to the opposite side of the transmitter coil 412. The transmitter coil 412 is adjacent to one side of the shielding coil 422, and the conductive plate 426 is adjacent to the other side of the shielding coil 422.

[0153] Capacitor 428 is configured to set the resonant frequency of the field shielding coil 422. The field shielding coil 422 is tuned to a frequency different from the operating frequency of the transmitter coil 412 of the wireless power transmission system 200. Specifically, the field shielding coil 422 is tuned to a frequency higher than the operating frequency of the transmitter coil 412. Calculate the capacitance of capacitor 428 so that the resonant frequency of field shielding coil 422 is higher than the operating frequency of wireless power transmission system 200.

[0154] The field shielding coil 430 is in phase with the transmitter coil 412. Tuning the field shielding coil 422 to a higher frequency than the transmitter coil 412 ensures that the current in the shielding coil 422 is in phase with the current in the transmitter coil 412, rather than 180 degrees out of phase. The higher frequency of the field shielding coil 422 compared to the transmitter coil 412 ensures that the current in the field shielding coil 422 is in phase with the current in the transmitter coil 412. The field shielding coil 422 is not tuned to the same frequency as the transmitter coil 412. Tuning the field shielding coil 422 to the frequency of the transmitter coil 412 may cause a short-circuit load, in which case the field shielding unit 430 or the device may not function as expected.

[0155] Furthermore, since the current in the shielding coil 422 is in phase with the current in the transmitter coil 412, the magnetic field strength available for coupling with the corresponding receiver coil of the magnetic induction system is increased. This contrasts with shielding or canceling units or systems where the currents are 180 degrees out of phase. In out-of-phase systems, the magnetic field strength coupled to the receiver coil is smaller due to the shielding or canceling units or systems. This reduces power transmission efficiency. In contrast, the shielding coil 422 with in-phase current improves power transmission efficiency.

[0156] The capacitance of capacitor 428 is selected such that the impedance or reactance of transmitter coil 412 and field shielding unit 430 or the device is the same as the impedance or reactance of transmitter coil 412 without field shielding unit 430. Specifically, field shielding coil 422 and capacitor 428 produce a net positive reactance, while conductive plate 426 produces a negative reactance. The capacitance of capacitor 428 is selected such that the net positive reactance is equal to the negative reactance. Therefore, there is a net zero reactance, and the impedance or reactance of transmitter coil 412 does not change with or without field shielding unit 430. As will be described, the capacitance of capacitor 428 is selected according to the equation described below. Specifically, as will be described, the capacitance of capacitor 428 is selected based on equation (7).

[0157] During operation, the field shielding unit 430 is positioned on the side of the transmitter coil 412 opposite to the receiver coil. In this embodiment, unless otherwise stated, the transmitter coil 412 is identical to the transmitter coil 212. The field shielding coil 422 amplifies the magnetic field originating from or generated by the transmitter coil 412 toward the receiver coil, and the conductive plate 426 positioned on the side of the field shielding coil 422 opposite to the transmitter coil 412 attenuates residual magnetic fields originating from or generated by the transmitter coil 412 toward or away from the conductive plate 426. As will be understood, using the field shielding coil 422 without the conductive plate 426 would amplify the magnetic field; however, the field shielding coil 422 would also increase the impedance of the transmitter coil 412. Furthermore, using the conductive plate 426 without the field shielding coil 422 would attenuate the magnetic field; however, the conductive plate 426 would also decrease the impedance of the transmitter coil 412. The use of field shielding coil 422 and conductive plate 426 ensures that the impedance of transmitter coil 412 remains approximately constant. The tuning and positioning of field shielding coil 422 and conductive plate 426 are configured such that the total impedance of transmitter coil 412 remains constant with or without field shielding unit 430. The capacitance of capacitor 428 of field shielding unit 430 is selected to keep the impedance of transmitter coil 412 constant.

[0158] The mathematical model of the field shielding unit 430 can be described by the impedance seen by the transmitter coil 412. The impedance seen by the transmitter coil 412 (Z) in the absence of any field shielding coil 422 or receiver coil (not shown) TX (Given by Equation 1)

[0159]

[0160] Where r L1 ω is the equivalent series resistance (ESR) of transmitter coil 412, and ωL1 is the reactance of transmitter coil 412, where ω is the operating frequency (radians / second) and L1 is the inductance of transmitter coil.

[0161] As previously described, the impedance (Z) seen by the inverter circuit connected to the transmitter coil 412 (e.g., the DC / AC inverter 210 described with reference to the wireless power transmission system 200) TX The impedance will remain the same before and after the addition of the field shielding unit 430, or with and without the field shielding unit 430. Maintaining the same impedance value with and without the field shielding unit 430 ensures that the inverter circuit (e.g., DC / AC inverter 210) does not need to be retuned when the field shielding unit 430 is added or removed. This is much more advantageous than field cancellation systems that require inverter retuning after the field cancellation coil is added or removed.

[0162] When the field shielding unit 430 is added to the wireless power transmission system 200, the impedance seen by the transmitter coil 412 is given by Equation 2:

[0163]

[0164] Z ref2 It is the reflective impedance of a single field-shielded coil 422 with inductance L2 similar to that of capacitor C, and Z gnd It is the reflected impedance from the conductive plate 426 to the field shielding coil 422.

[0165] To ensure the impedance (Z) of the transmitter coil 412 is sufficient when the field shielding unit 430 is added to the wireless power transmission system. TX ) No change, Z ref2 Add Z gnd It must be equal to zero, as shown in Equation 3:

[0166] Z ref2 +Z gnd =0 (3)

[0167] Based on the known relationship between reflection impedance and impedance, the above equation can be extended based on the relationship between the reflection impedance of the coil and the impedance of the coil, as shown in Equation 4:

[0168]

[0169] Where M xx It is the mutual inductance between the transmitter coil 412 and the field shielding coil 422 and the conductive plane (e.g. Figure 4E (as shown), and Z 2gnd It is the reflected impedance of the equivalent AC resistance and inductance of the conductive plate 426.

[0170] It should be noted that the resistance and inductance of the ground plane depend on the mutual inductance, position, and size of the transmitter coil 412 and the field shielding coil 422. From an electromagnetic perspective, the conductive plate 426 acts as a reflector to reflect the impedance of the conductive plate 426. The reflected impedance of the conductive plate 426 is always capacitive, therefore, the second term in equation (4) is negative. Therefore, in this embodiment, the first term of equation (4) should be inductive to satisfy equation (4). Now, the value of C is applied to produce the inductive reflected impedance. Therefore, it can be further concluded that the value of C makes the reflected impedance Z from the single field shielding coil 422... ref2 The reflected impedance from the field shielding coil 422 is inductive to counteract the negative reflected impedance of the conductive plate 426, which means that the resonant frequency of the field shielding coil 422 must be higher than the operating frequency of the transmitter 412 of the wireless power transmission system 200.

[0171] Therefore, for a given parameter of a specific wireless power transmission system, the capacitance of capacitor 428 is selected according to equation (7).

[0172] An unintended effect of implementing the field shielding unit 430 is that the field shielding coil 422 will also produce a slight attenuation of the magnetic field in the direction toward the receiver coil. This attenuation of the magnetic field toward the receiver coil is due to the asymmetric field generated by the field shielding unit 430. The asymmetric field typically reduces the strength of the magnetic field compared to an unshielded magnetic field. As current flows through the single field shielding coil 422, this attenuation of the magnetic field toward the receiver coil results in an efficiency loss. This efficiency loss represents a reduction in efficiency ranging from 1% to 5% in power transfer from the transmitter coil 412 to the receiver coil. This efficiency loss is negligible compared to the efficiency losses found with 180-degree out-of-phase cancellation or shielding units or systems.

[0173] The placement of the field shielding unit will now be described. Now proceed to... Figure 4B The field shielding coil 422 is positioned at a fixed distance on the side of the transmitter coil 412 opposite to the receiver coil. The spacing between the field shielding coil 422 and the transmitter 412 is uniform across both the transmitter coil 412 and the receiver coil 422. In this embodiment, the distance (d1) between the transmitter coil 412 and the field shielding coil 422 is 12 mm. The conductive plate 426 is placed at a fixed distance from the field shielding coil 422. In this embodiment, the distance (d2) between the field shielding coil 422 and the conductive plate 426 is 22 mm. In this embodiment, the field shielding coil 422 consists of two turns, with a track width of 15 mm, a track spacing of 6.5 mm, an inner coil radius of 65 mm, and an outer coil radius of 102.5 mm. The conductive plate 426 can be made of any conductive material, including, for example, copper, aluminum, and steel. In this embodiment, the conductive plate 426 is made of copper strip. Although a specific field shielding coil configuration has been described, those skilled in the art will recognize that the field shielding coil configuration does not need to be the same as the transmitter coil configuration, and therefore the coils may differ in size, shape, number of turns, track width, track spacing, and may also have different inner and outer radii than those described herein.

[0174] FEM simulations were performed to verify the operating principle of the field shielding unit 430. In this embodiment, the simulation was based on a transmitter coil 412 consisting of two turns, a track width of 15 mm, a track spacing of 6.5 mm, an inner coil radius of 65 mm, and an outer coil radius of 102.5 mm. In this embodiment, the current in the transmitter coil 412 is 1 A, and the operating frequency of the transmitter coil 412 is 13.56 MHz.

[0175] Those skilled in the art will recognize that transmitter coil 412 may be used with more or fewer turns, different track widths, different track spacings, different inner coil radii, or different outer coil radii. Those skilled in the art will also recognize that transmitter coil 412 may have a different current or operating frequency than those mentioned in the embodiments described for these simulation purposes.

[0176] Now go to Figure 4C and Figure 4D The image shows an FEM simulation of the transmitter coil 412, with a field shielding unit 430 or device positioned on the side of the transmitter coil 412 opposite to the receiver coil. In this embodiment, the field shielding unit 430 includes a single field shielding coil 422 and a conductive plate 426, the single field shielding coil 422 having an external / discrete capacitor 428 connected between the terminals of the transmitter coil 412. The conductive plate is typically 10% to 25% larger in diameter than the outer radius of the transmitter and the diameter of the shielding coil. In this embodiment, the conductive plate is made of copper and has dimensions of approximately 240 mm × 240 mm.

[0177] For the purposes of this particular simulation, the distance (d1) between the transmitter coil 412 and the first field shielding coil 422 is 12 mm. The distance (d2) between the field shielding coil 422 and the conductive plate 426 is 22 mm. Referring to equation (4), the value (C) of the capacitor 428 is 93 pF. Figure 4D The diagram illustrates a scenario where the field shielding unit 430 is positioned on the side of the transmitter coil 412 opposite to the receiver coil. The magnetic field emitted from the transmitter coil 412 is now only in one direction and is blocked by the field shielding unit 430 from emitting from the other side of the transmitter coil 412. The ratio of distance (d1) to the outer radius of the transmitter coil 412 yields approximately 11.7% for this single-coil field shielding unit 430 configuration. This ratio can typically be used to determine the distance of the field shielding coil 422 from the transmitter coil 412 based on its size. Similarly, the ratio of distance (d2) to the outer radius of the transmitter coil 412 yields approximately 21.5% for this single-coil field shielding unit 430 configuration. This ratio can typically be used to determine the distance of the conductive plate 426 from the single field shielding coil 422 based on its size.

[0178] like Figure 4CAs shown, the magnetic field is emitted in two directions from the top and bottom of the transmitter coil. With the field shielding unit 430 positioned as shown, most of the magnetic field is attenuated by the field shielding coil 422, while the remaining magnetic field terminates on the conductive plate 426. Using the field shielding unit 430, the magnetic field is confined to the area surrounding the transmitter coil 412 in front of the field shielding unit 430, thereby preventing the magnetic field from radiating around the transmitter coil 412 in multiple directions. Because the magnetic field is confined to propagate toward the receiver in the intended direction, power transmission via the magnetic field becomes safer.

[0179] Figure 4D The current waveforms in transmitter coil 412 and field shielding coil 422 are shown. The current is normalized to the current in transmitter coil 412. The current in field shielding coil 422 is in phase with the current in transmitter coil 412. The residual magnetic field originating from transmitter coil 412 terminates on conductive plate 426. Figure 4D As clearly shown, the normalized current in the field shielding coil 422 is always less than the normalized current in the transmitter coil 412. The current in the field shielding coil 422 increases the magnetic field generated by the transmitter coil 412, thereby increasing wireless power transmission and / or wireless power transmission efficiency.

[0180] Figure 4E An equivalent circuit diagram of a field shielding unit according to one aspect of this disclosure is shown. The field shielding unit includes a field shielding coil 422, a capacitor 428, and a conductive plate 426. L1 represents the inductance of the transmitter coil 412 or the receiver coil (not shown). L2 represents the inductance of a single field shielding coil 422, and C is the capacitance of a single capacitor 428 connected between the terminals of the field shielding coil 422. The field shielding coil 422 is positioned at a fixed distance on the side of the transmitter coil 412 opposite to the receiver coil. The conductive plate 426 is positioned at a fixed distance on the side of the field shielding coil 422 opposite to the transmitter coil 412. Figure 4E The diagram shows the mutual inductance between the transmitter coil 412, the field shielding coil 422, and the conductive plate 426.

[0181] The transmitter coil 412 may form part of the described wireless power transmission system 200. The wireless power transmission system 200 may include an inverter 210. The inverter 210 may be configured for current-mode output (constant current output) as described in U.S. Patent Application No. 17 / 018,328, the relevant portions of which are incorporated herein by reference.

[0182] Although an apparatus 430 with one field shielding coil 422 has been described, those skilled in the art will recognize that other embodiments of the field shielding unit 430 with more than one field shielding coil 422 are also possible. For example, in another embodiment, the field shielding unit includes two field shielding coils. While adding a second field shielding coil to the field shielding unit increases the overall size (i.e., thickness) of the field shielding unit, an added benefit is a more efficient field shielding unit with a thinner, lighter conductive plate, which in turn reduces the weight of the field shielding unit and, by extension, reduces the weight of the magnetic induction system implementing the field shielding unit. Reducing the thickness of the conductive plate also reduces the thickness of the field shielding unit by an equal amount.

[0183] Now go to Figure 5A The image shows a transmitter coil 512 with a field shielding unit 530 according to one aspect of this disclosure. Unless otherwise stated, the transmitter coil 512 is identical to the transmitter coil 412. In this embodiment, the field shielding unit 530 includes a first field shielding coil 522, a second field shielding coil 524, and a conductive plate 526. The two terminals of the first field shielding coil 522 are electrically connected to a capacitor 528. The capacitor 528 is external to the first field shielding coil 522. The second field shielding coil 524 has a direct electrical short across its terminals. The shorting of the terminals of the second field shielding coil 524 ensures that the reflected impedance of the second shielding coil 524 is capacitive.

[0184] Field shielding coils 522 and 524 are configured to amplify the magnetic field generated by transmitter coil 512. Conductive plate 526 is configured to at least partially attenuate or block the magnetic field generated by transmitter coil 512 in a direction substantially opposite to the receiver coil relative to transmitter coil 512. The size and position of conductive plate 526, or conductor, are designed to surround first field shielding coil 522 and second field shielding coil 524. First field shielding coil 522 and second field shielding coil 524 are tuned to a frequency different from the operating frequency of transmitter coil 512 of wireless power transmission system 200. Field shielding coils 522 and 524 are not tuned to the same frequency as transmitter coil 512. Tuning field shielding coils 522 and 524 to the frequency of transmitter coil 512 may cause a short-circuit load, in which case field shielding unit 530 may not function as intended. First field shielding coil 522 and second field shielding coil 524 may be tuned to different frequencies, respectively. Each corresponding frequency may not be equal to the operating frequency of transmitter coil 512. Tuning the first field shielding coil 522 and the second field shielding coil 524 to different frequencies allows for increased flexibility in the current and voltage flowing in the field shielding coils 522 and 524. In this embodiment, the first field shielding coil 522 and the second field shielding coil 524 are tuned to frequencies higher than the operating frequency of the transmitter coil 512.

[0185] The first field shielding coil 522 is placed at a fixed distance from the transmitter coil 512. The second field shielding coil 524 is placed at a fixed distance from the first field shielding coil 524. In this embodiment, the distance between the first field shielding coil 522 and the second field shielding coil 524 is 15 mm. The conductive plate 526 is placed at a fixed distance from the second field shielding coil 524.

[0186] The field shielding unit or device 530 is positioned such that the plane formed by the first field shielding coil 512 is parallel to the plane formed by the transmitter coil 512. The plane formed by the first field shielding coil 512 is also parallel to the plane formed by the second field shielding coil 524. The plane formed by the second field shielding coil 524 is parallel to the plane formed by the conductive plate 526. Therefore, the planes formed by the transmitter coil 512, the first field shielding coil 522, the second field shielding coil 524, and the conductive plate 526 are all parallel. The plane of any one of the transmitter coil 512, the first field shielding coil 522, the second field shielding coil 524, and the conductive plate 526 can be defined as the main plane of a particular element.

[0187] The first field shielding coil 522 is located near one side of the transmitter coil 512, while the receiver coil is located near the opposite side of the transmitter coil 512. The transmitter coil 512 is located near one side of the first field shielding coil 522, and the second field shielding coil 524 is located near the opposite side of the first field shielding coil 522. The first field shielding coil 522 is located near one side of the second field shielding coil 524, and the conductive plate 526 is located near the opposite side of the second field shielding coil 524.

[0188] In this embodiment, the distance (d3) between the second shielding coil 524 and the conductive plate 526 is 7 mm. The conductive plate 526 can be made of any conductive material, including, for example, copper, aluminum, and steel. In this embodiment, the conductive plate 526 is made of copper foil.

[0189] The tuning and positioning of the first field shielding coil 522, the second field shielding coil 524, and the conductive plate 526 are configured such that the total impedance of the transmitter coil 512 remains constant with or without the field shielding unit 530.

[0190] For example, in one embodiment, the inductance of the transmitter coil 512, the first field shielding coil 522, the second field shielding coil 524, and the conductive plate 526 is 1 μH. When the field shielding unit 530, which includes the first field shielding coil 522, the second field shielding coil 524, and the conductive plate 526, is placed near the transmitter coil 512, the inductance of the transmitter coil 512 will remain at 1 μH. The capacitance of the capacitor 528 is selected such that the inductance of the transmitter coil 512 remains unchanged with or without the field shielding unit 530. Since the inductance remains unchanged, the impedance also remains unchanged. In other words, the introduction of the field shielding unit 530 does not affect the impedance.

[0191] Figure 5B A more detailed view is shown of an example configuration of a first field shielding coil 522, a second field shielding coil 524, and a conductive plate 526 relative to a transmitter coil 512. In this embodiment, the field shielding coil 522 is positioned 12 mm from the transmitter coil 512. The field shielding coil 522 is electrically connected to a capacitor 528. The capacitor 528 is connected between the terminals of the first field shielding coil 522. The capacitor 528 has a capacitance of 132 pF. In this embodiment, the second field shielding coil 524 is positioned 15 mm from the first field shielding coil 522. The terminals of the second field shielding coil 524 are electrically shorted together to generate capacitive reflected impedance. In this embodiment, the conductive plates 526 are positioned at fixed distances from the second field shielding coil 524. In this embodiment, the fixed distance between the second field shielding coil 524 and the conductive plates is 7 mm.

[0192] Now go to Figure 5C and Figure 5D The image shows an FEM simulation of the transmitter coil 512, with a field shielding unit 530 positioned on the side of the transmitter coil 512 opposite to the receiver coil. In this embodiment, the field shielding unit 530 includes a first field shielding coil 522, a second field shielding coil 524, and a conductive plate 526. The first field shielding coil 522 has an external / discrete capacitor 528 connected between its terminals, and the two terminals of the second field shielding coil 524 are electrically shorted together to generate capacitive reflected impedance. Unless otherwise stated, the conductive plate 526 is identical to the conductive plate 426.

[0193] For the purposes of these specific simulations, the distance (d1) between the transmitter coil 512 and the first field shielding coil 522 is 12 mm. The distance (d2) between the first field shielding coil 522 and the second field shielding coil 524 is 15 mm. The distance (d3) between the second field shielding coil 524 and the conductive plate 526 is 7 mm. Referring to equation (7) described below, the value (C) of capacitor 428 is 132 pF. Figure 5CThe diagram shows that with the field shielding unit 530 positioned on the side of the transmitter coil 512 opposite to the receiver coil, the magnetic field emitted from the transmitter coil 512 is now only in one direction and is blocked by the field shielding unit 530 from being emitted from the other side of the transmitter coil 512. The ratio of distance (d1) to the outer radius of the transmitter coil 512 yields approximately 11.7% for this dual-coil, single-capacitor field shielding unit 530 configuration. This ratio can typically be used to determine the distance of the first shielding coil 522 from the transmitter coil 512 based on the size of the transmitter coil 512. The ratio of distance (d2) to the outer radius of the transmitter coil 512 yields approximately 14.6% for this dual-coil, single-capacitor field shielding unit 530 configuration. This ratio can typically be used to determine the distance of the second shielding coil 524 from the first field shielding coil 522 based on the size of the transmitter coil 512. The ratio of distance (d3) to the outer radius of transmitter coil 512 yields approximately 6.83% for this dual-coil, single-capacitor field shielding unit 530 configuration. This ratio can typically be used to determine the distance of conductive plate 526 from the second field shielding coil 524 based on the size of transmitter coil 512. When added together, the ratio of (d2) and (d3) is approximately equal to distance (d2) in the single-coil field shielding unit 430 configuration. In this embodiment, the field shielding coil consists of two turns with a track width of 15 mm, a track spacing of 6.5 mm, an inner coil radius of 65 mm, and an outer coil radius of 102.5 mm. Conductive plate 526 can be made of any conductive material, including, for example, copper, aluminum, and steel. In this embodiment, conductive plate 526 is made of copper strip. In this embodiment, the field shielding coil consists of two turns with a track width of 15 mm, a track spacing of 6.5 mm, an inner coil radius of 65 mm, and an outer coil radius of 102.5 mm. Although a specific field shielding coil configuration has been described, those skilled in the art will recognize that the field shielding coil configuration does not need to be the same as the transmitter coil configuration, and therefore the coils may differ in size, shape, number of turns, track width, track spacing, and may also have different inner and outer radii than those described herein.

[0194] Figure 5C The magnetic field diagram of the transmitter coil 512 of the wireless power transmission system is shown. In this embodiment, the wireless power transmission system is as described above. Figure 5AThe field shielding unit 530 is a magnetic induction system. The transmitter coil 512 is shown having a magnetic field indicated by circular lines. As shown, the magnetic field is emitted from the coil in both top and bottom directions. With the field shielding unit 530 positioned as shown, the magnetic field is attenuated by the first field shielding coil 522 and the second field shielding coil 524, where any residual magnetic field terminates on the conductive plate 526. Using the field shielding unit 530, the magnetic field is confined to the area around the transmitter coil 512 in front of the field shielding unit 530, thereby preventing the magnetic field from radiating around the transmitter coil 512 in multiple directions. Because the magnetic field is configured to propagate toward the receiver in the desired direction by using the field shielding unit 530, power transmission via the magnetic field becomes safer.

[0195] Figure 5D The current waveforms in transmitter coil 512, first shielding coil 522, and second shielding coil 524 are shown respectively. The current is normalized to the current in transmitter coil 512. The currents in shielding coils 522 and 524 are in phase with the current in transmitter coil 512.

[0196] Figure 5E An equivalent circuit is shown for a field shielding unit 530 configuration comprising two field shielding coils 522 and 524 and a conductive plate 526. The first field shielding coil 522 has a single discrete / external capacitor 528 connected between its terminals. The capacitor 528 is used to set the resonant frequency of the first field shielding coil 522. The terminals of the second field shielding coil 524 are shorted together to generate a capacitive reflective impedance (Z). ref3 L3 represents the inductance of the second shielded coil 524.

[0197] An additional advantage of the dual-coil field shielding unit 530 configuration over the single-coil field shielding unit 430 configuration is that the conductive plate 526 can now be much thinner and potentially lighter than the conductive plate 426 in the single-coil field shielding unit 430. Most of the current that does not flow in the conductive plate 526 is now conducted in the second field shielding coil 524, thus allowing the conductive plate 426 to be thinner. Furthermore, overall conduction losses are reduced. This means that a thin conductive plate, such as copper foil or aluminum foil, can be used instead of a thick conductive material plate. Since the most expensive and heaviest part of the field shielding unit 530 is the conductive plate 526, adding the second field shielding coil 524 allows the conductive plate 526 to be thinner, resulting in a lighter field shielding unit 530 compared to the weight of the added second coil 524. Adding the second coil 524 also has the benefit of reducing the cost of the conductive plate 526, and by extension, reducing the cost of the field shielding unit 530.

[0198] Figure 5EThe equivalent circuit of a field shielding unit 530 with a first field shielding coil 522, a capacitor 528, and a second field shielding coil 524 is shown. The reflection impedance (Z) is shown as seen from the transmitter coil 512. TX As shown in Equation 5:

[0199] Z TX =r TX +jωL1+Z ref2 +Z 1gnd (5)

[0200] The equation above now includes the reflection impedance Z of the second field shielding coil 524. ref3 Similarly, when a field shielding unit 530 is added to the side of the transmitter coil 512 opposite to the receiver coil, the impedance (Z) of the transmitter coil 512 before the field shielding unit is added... TX The equation must remain the same, as shown in Equation 6:

[0201] Z ref2 +Z ref3 +Z 1gnd =0 (6)

[0202] The above equation can be extended to Equation 7 as follows:

[0203]

[0204] The reflection impedance Z of the second shielding coil 524 ref3 It is capacitive because its terminals are shorted together to create a capacitive reflected impedance. The reflected impedance of the conductive plate is always capacitive, which means that the second and third terms in equation (7) are negative. Therefore, the first term of the equation is inductive to satisfy equation (7). Now the value of C is crucial for creating an inductive reflected impedance. Similar to the previous configuration, the conclusion is: the value of C makes the reflected impedance Z from the first field shielding coil 522... ref2 It is positive, i.e., inductive, to counteract the negative reflective impedance from the second field shielding coil 524 and the conductive plate 526. This means that the resonant frequency of the first field shielding coil 522 with inductance L2 must be higher than the operating frequency of the transmitter coil 512 of the wireless power transmission system, which in this embodiment is a magnetic induction system.

[0205] An unintended effect of implementing the field shielding unit 530 is that the field shielding coils 522 and 524 will also produce a slight attenuation of the magnetic field in the direction toward the receiver coil. Since current flows in the first field shielding coil 522 and the second field shielding coil 524, respectively, this attenuation of the magnetic field toward the receiver coil results in an efficiency loss. This efficiency loss represents a reduction in efficiency ranging from 1% to 5% in power transfer from the transmitter coil 512 to the receiver coil. This efficiency loss is negligible compared to the efficiency losses found when using a 180-degree out-of-phase cancellation or shielding unit or system.

[0206] and Figure 4E Same, Figure 5E The transmitter coil 512 depicted herein may form part of the described wireless power transmission system 200. The wireless power transmission system 200 may include an inverter 210. The inverter 210 may be configured for current-mode output (constant current output), as described in U.S. Patent Application No. 17 / 018,328, which is incorporated above.

[0207] Figure 6A A transmitter coil 612 with a field shielding unit 630 according to one aspect of this disclosure is shown. Unless otherwise stated, the transmitter coil 612 is identical to transmitter coil 512. In this embodiment, the field shielding unit 630 includes a first field shielding coil 622, a second field shielding coil 624, and a conductive plate 626. The first field shielding coil 622 and the second field shielding coil 624 are respectively tuned to frequencies different from the operating frequency of the transmitter coil 612 of the wireless power transmission system 200. The first field shielding coil 622 and the second field shielding coil 624 are not tuned to the same frequency as the transmitter coil 612. Tuning the first field shielding coil 622 and the second field shielding coil 624 to the frequency of the transmitter coil 612 may cause a short-circuit load, in which case the field shielding unit 630 may not function as intended. In this embodiment, the first field shielding coil 622 and the second field shielding coil 624 are tuned to frequencies higher than the operating frequency of the transmitter coil 612. The conductive plate 626 can be made of any conductive material, including, for example, copper, aluminum, or steel. In this embodiment, the conductive plate 626 is made of copper foil.

[0208] A first shielding coil 622 is positioned at a fixed distance from the transmitter coil 612 on the side opposite to the receiver coil. A second shielding coil 624 is positioned at a fixed distance from the first shielding coil 622 on the side opposite to the transmitter coil 612. A conductive plate 626 is placed on the respective sides of the first and second shielding coils 622 and 624 opposite to the transmitter coil 612 to completely attenuate or block any residual magnetic field that has not been canceled by the first and second shielding coils 622 and 624, respectively. The same configuration can be applied to the receiver coil.

[0209] The tuning and positioning of the first field shielding coil 622, the second field shielding coil 624, and the conductive plate 626 are configured such that the total impedance of the transmitter coil 612 remains constant with or without the field shielding unit 630.

[0210] For example, in one embodiment, the inductance of the transmitter coil 612, the first field shielding coil 622, the second field shielding coil 624, and the conductive plate 626 is 1 μH. When the field shielding unit 630, which includes the first field shielding coil 622, the second field shielding coil 624, and the conductive plate 626, is placed near the transmitter coil 612, the inductance of the transmitter coil 612 will remain at 1 μH. Since the inductance remains unchanged, the impedance also remains unchanged. In other words, the introduction of the field shielding unit 630 does not affect the impedance.

[0211] The first field shielding coil 622 has a discrete / external capacitor 628 connected between its terminals, and the second field shielding coil 624 has a discrete / external capacitor 629 connected between its terminals. The main purpose of capacitors 628 and 629 is to set the impedance and resonant frequency of the first field shielding coil 622 and the second field shielding coil 624, respectively. The difference between this configuration using capacitors 628 and 629, which are electrically connected between the terminals of the first field shielding coil 622 and the second field shielding coil 624, and the configuration of the two previous field shielding units 430 and 530, is that... Figure 6A The configuration allows for increased control over the impedance reflected to the transmitter coil 612, and thus can result in a thinner, more compact field shielding unit 630, in which the first field shielding coil 622 and the second field shielding coil 624, as well as the conductive plate 626, can be positioned closer to the transmitter coil 612, thereby reducing the overall size of the field shielding unit 630 while maintaining performance and reducing the weight of the field shielding unit compared to conventional field shielding materials (such as ferrite), and thus reducing the weight of the entire system.

[0212] Figure 6BEnd views of an example configuration of a first field shielding coil 622, a second field shielding coil 624, and a conductive plate 626 relative to a transmitter coil 612 are shown. In this embodiment, the first field shielding coil 622 is positioned 12 mm on the side of the transmitter coil 612 opposite to the receiver coil. The first field shielding coil 622 is electrically connected to a first capacitor 628. The first capacitor 628 is connected between the terminals of the first field shielding coil 622. In this embodiment, the first capacitor 628 has a capacitance of 89 pF. In this embodiment, the second field shielding coil 624 is positioned 15 mm on the side of the first field shielding coil 622 opposite to the transmitter coil 612. The second field shielding coil 624 is electrically connected to a second capacitor 629. The second capacitor 629 is connected between the terminals of the second field shielding coil 624. In this embodiment, the second capacitor 629 has a capacitance of 89 pF. In this embodiment, the conductive plate 626 is positioned at a fixed distance of 7 mm on the side of the second field shielding coil 624 opposite to the first shielding coil. In this embodiment, each field shielding coil 622 and 624 consists of two turns, with a track width of 15 mm, a track spacing of 6.5 mm, an inner coil radius of 65 mm, and an outer coil radius of 102.5 mm. The conductive plate 626 can be made of any conductive material, including, for example, copper, aluminum, and steel. In this embodiment, the conductive plate 626 is made of copper strip. Although a specific field shielding coil configuration has been described, those skilled in the art will recognize that the field shielding coil configuration does not need to be the same as the transmitter coil configuration, and therefore, the coils can differ in size, shape, number of turns, track width, track spacing, and can also have different inner and outer radii than those described herein.

[0213] Now go to Figure 6C and Figure 6D The image shows an FEM simulation of the transmitter coil 612, with a field shielding unit 630 positioned on the side of the transmitter coil 612 opposite to the receiver coil. In this embodiment, the field shielding unit 630 includes a first field shielding coil 622, a second field shielding coil 624, and a conductive plate 626. The first field shielding coil 622 has a first discrete / external capacitor 628 connected between its terminals, and the second field shielding coil 624 has a second discrete / external capacitor 629 connected between its terminals. Unless otherwise stated, the conductive plate 626 is identical to the conductive plate 526.

[0214] For the purposes of these specific simulations, the distance (d1) between the transmitter coil 612 and the first field shielding coil 622 is 12 mm. The distance (d2) between the first field shielding coil 622 and the second field shielding coil 624 is 15 mm. The distance (d3) between the second field shielding coil 624 and the conductive plate 626 is 7 mm. Referring to equation (10) described below for this embodiment, the value (C1) of the first capacitor 628 is 89 pF.

[0215] The ratio of distance (d1) to the outer radius of transmitter coil 612 yields approximately 11.7% for this dual-coil, dual-capacitor field shielding unit 630 configuration. This ratio is typically used to determine the distance of the first shielding coil 622 from transmitter coil 612 based on its size. The ratio of distance (d2) to the outer radius of transmitter coil 612 yields approximately 14.6% for this dual-coil, dual-capacitor field shielding unit 630 configuration. This ratio is typically used to determine the distance of the second shielding coil 624 from the first field shielding coil 622 based on its size. The ratio of distance (d3) to the outer radius of transmitter coil 612 yields approximately 6.83% for this dual-coil, dual-capacitor field shielding unit 630 configuration. This ratio is typically used to determine the distance of the conductive plate 626 from the second field shielding coil 624 based on its size.

[0216] Figure 6C The magnetic field diagram of the transmitter coil 612 of the wireless power transmission system is shown. In this embodiment, the wireless power transmission system has... Figure 6A The field shielding unit 630 is a magnetic induction system. The transmitter coil 612 is shown having a magnetic field indicated by circular lines. As shown, the magnetic field is emitted from the coil in both top and bottom directions. With the field shielding unit 630 positioned as shown, the magnetic field is attenuated by the first field shielding coil 622 and the second field shielding coil 624, where any residual magnetic field terminates on the conductive plate 626. Using the field shielding unit 630, the magnetic field is confined to the area around the transmitter coil 612 in front of the field shielding unit 630, thereby preventing the magnetic field from radiating around the transmitter coil 612 in multiple directions. Because the magnetic field is confined to propagate toward the receiver in the intended direction by using the field shielding unit 530, power transmission via the magnetic field becomes safer.

[0217] Figure 6D The current waveforms in transmitter coil 612, first shielding coil 622, and second shielding coil 624 are shown respectively. The current is normalized to the current in transmitter coil 612. The currents in first shielding coil 622 and second shielding coil 624 are in phase with the current in transmitter coil 612.

[0218] Figure 6E An exemplary illustration of a field shielding unit 630 is shown, which comprises a first field shielding coil 622, a second field shielding coil 624, and a conductive plate 626 located on the side of the transmitter coil 612 opposite to the receiver coil. In this embodiment, the coils are printed circuit board (PCB) coils. While a specific embodiment of the field shielding unit 630 positioned on the side of the transmitter coil 612 opposite to the receiver coil has been described, those skilled in the art will recognize that the same figure can also depict a field shielding unit 630 placed on the side of the receiver coil of a wireless power transmission system opposite to the transmitter coil 612, in which embodiment the wireless power transmission system is a magnetic induction system.

[0219] and Figure 4E Same, Figure 6E The transmitter coil 612 depicted herein may form part of the described wireless power transmission system 200. The wireless power transmission system 200 may include an inverter 210. The inverter 210 may be configured for current-mode output (constant current output), as described in U.S. Patent Application No. 17 / 018,328, which is incorporated above.

[0220] Figure 6F An equivalent circuit of a field shielding unit 630 with a first field shielding coil 622, a second field shielding coil 624, and two capacitors 628 and 629 is shown.

[0221] The reflected impedance seen from transmitter coil 612 is:

[0222] Z TX =r TX +jωL1+Z ref2 +Z ref3 +Z 1gnd (8)

[0223] The reflection impedance is similar to the previous configuration. It should also meet the same criteria:

[0224] Z ref2 +Z ref3 +Z 1gnd =0 (9)

[0225] However, extending the above equation now yields the following result:

[0226]

[0227] In the equation above, we can see that the first and second terms can now be controlled by adjusting the values ​​of C1 and C2. Therefore, we can draw the following conclusion:

[0228] The values ​​of C1 and C2 make the reflection impedance Z from the first field shielding coil 622 and the second field shielding coil 624, respectively. ref2 and Z ref3 It is positive, i.e., inductive, to counteract the negative reflective impedance of the conductive plate 626. This means that the resonant frequencies of the first field shielding coil 622 and the second field shielding coil 624 must be higher than the operating frequency of the transmitter coil 612 of the wireless power transmission system, which in this embodiment is a magnetic induction system.

[0229] In this embodiment, the field shielding unit 630 includes a first field shielding coil 622 and a second field shielding coil 624, which are positioned to attenuate the magnetic field strength on the side of the transmitter coil 612 opposite to the receiver coil. A conductive plate 626 is then added to the side of the field shielding coils 622 and 624 opposite to the transmitter coil 612 to eliminate any residual magnetic field. An unintended effect of implementing the field shielding unit 630 is that the field shielding coils 622 and 624 will also produce a small attenuation of the magnetic field in the direction toward the receiver coil. This attenuation of the magnetic field toward the receiver coil results in an efficiency loss as current flows in the first field shielding coil 622 and the second field shielding coil 624, respectively. The efficiency loss is a reduction in efficiency ranging from 1% to 5% in power transfer from the transmitter coil 612 to the receiver coil. This efficiency loss is negligible compared to the efficiency loss found with 180-degree out-of-phase cancellation or shielding units or systems.

[0230] While various configurations of field shielding units for use with a particular wireless power transmission system have been described, those skilled in the art will recognize that various wireless power systems can be used with various field shielding unit configurations. For example, the previously described wireless power system 200 may include a non-resonant system in which the transmitter 202 and receiver 204 are not self-resonant and / or do not operate at a resonant frequency. The wireless power transmission system 200 may include a resonant system in which both the transmitter 202 and receiver 204 are self-resonant and / or operate at the same resonant frequency. The wireless power transmission system 200 may include a high-frequency inductive wireless power transmission system, as described in U.S. Patent Application No. 17 / 018,328, which is incorporated above.

[0231] Furthermore, while specific embodiments of the field shielding unit have been described, those skilled in the art will recognize that other embodiments and configurations are possible. For example, although the embodiments described herein relate to the transmitter coil of a wireless power transmission system, those skilled in the art will recognize that the disclosed field shielding unit configurations can also be applied to receiver coils in wireless power transmission systems, and such embodiments of receivers having the various field shielding units disclosed herein are supported by the accompanying drawings and descriptions. The wireless power transmission system may be a magnetic induction system or a resonant magnetic system.

[0232] Although the field shielding unit 430 or device has been described, those skilled in the art will understand that other implementations are possible. [Go to...] Figure 7 This diagram illustrates a device 1430 for use in a magnetic induction wireless power transmission system. The device 1430 is used to increase the magnetic field generated by the effective coil of the magnetic induction wireless power transmission system. The magnetic induction wireless power transmission system can be the described wireless power transmission system 200.

[0233] In the illustrated arrangement, device 1430 includes a single boost coil 1422 and a conductive plate 1426. The boost coil 1422 is electrically connected to a discrete capacitor 1428. The capacitor 1428 is located outside the boost coil 1422. The capacitor 1428 is electrically connected between the two terminals of the boost coil 1422.

[0234] The boost coil 1422 is configured to amplify or increase the magnetic field generated by the transmitter coil 1412 of the magnetic induction wireless power transmission system. Specifically, the boost coil 1422 is configured to increase the magnitude of the magnetic field generated by the transmitter coil 1412. The conductive plate 1426 is configured to at least partially attenuate or block the magnetic field generated by the transmitter coil 1412 in a direction generally opposite to the receiver coil relative to the transmitter coil 1412. The size and position of the conductive plate 1426 or conductor are designed to surround the boost coil 1422.

[0235] For the purposes of this disclosure, the conductive plate 1426 is considered to surround the boost coil 1422 when at least one of the following conditions is met: (i) if the area defined by the periphery of the boost coil 1422 is projected onto the area of ​​the conductive plate 1426, the projection is entirely within the area of ​​the conductive plate 1426; (ii) the projected area of ​​the boost coil 1422 is constrained by the area of ​​the conductive plate 1426; and (iii) the area of ​​the conductive plate 1426 is larger than the total area defined by the periphery of the boost coil 1422 by at least the distance between the boost coil 1422 and the conductive plate 1426.

[0236] In the illustrated arrangement, the conductive plate 1426 is an elongated plate. The conductive plate 1426 can be made of any conductive material, including, for example, copper, aluminum, and steel.

[0237] In the arrangement shown, the boost coil 1422 has the same configuration as the transmitter coil 1412. The boost coil 1422 has the same dimensions, size, and shape as the transmitter coil 1412.

[0238] The device 1430 is positioned such that the boost coil 1422 is opposite the transmitter coil 1412 and the receiver coil. The receiver coil is part of a wireless power transmission system in which the transmitter coil 1412 forms a portion. The device 1430 is positioned such that the boost coil 1422 is adjacent to one side of the transmitter coil 1412, while the receiver coil is adjacent to the opposite side of the transmitter coil 1412. The transmitter coil 1412 is adjacent to one side of the boost coil 1422, and the conductive plate 1426 is adjacent to the other side of the boost coil 1422.

[0239] Device 1430 is positioned such that the plane formed by field shielding coil 1422 is parallel to the plane formed by transmitter coil 1412. The plane formed by field shielding coil 1422 is also parallel to the plane formed by conductive plate 1426. The plane formed by conductive plate 1426 is parallel to the plane formed by transmitter coil 1412. Therefore, the planes formed by transmitter coil 1412, boost coil 1422, and conductive plate 1426 are all parallel. The plane of any one of transmitter coil 1412, boost coil 1422, and conductive plate 1426 can be defined as the master plane of a particular element.

[0240] Although device 1430 is shown as including conductive plate 1426, those skilled in the art will appreciate that other configurations are possible. In another embodiment, device 1430 does not include the described conductive plate 1426.

[0241] The boost coil 1422 and capacitor 1428 are configured such that the current in the transmitter coil 1412 remains approximately constant due to the introduction of device 1430. For example, if the current in the transmitter coil 1412 is approximately 1A before the introduction of device 1430, the current in the transmitter coil 1412 will still be approximately 1A after the introduction of device 1430. Furthermore, the current in the boost coil 1422 is equal to the current in the transmitter coil 1412. Therefore, in the described example, as will be described, the current in the boost coil is approximately 1A during use.

[0242] The capacitance of capacitor 1428 is chosen such that the boost coil 1422 and capacitor 1428 produce a net positive reactance. Therefore, a net positive reactance exists, and the impedance or reactance of transmitter coil 1412 increases. Consequently, a wireless power system including transmitter coil 1412 may require retuning upon introduction of the device (specifically, boost coil 1422 and capacitor 1428).

[0243] The capacitance of capacitor 1428 is given by equation (11):

[0244]

[0245] Where C is the capacitance of capacitor 1428.

[0246] ω is the operating frequency of the wireless power transmission system.

[0247] L2 is the inductance of the boost coil 1422, and

[0248] M 12 It is the mutual inductance between the transmitter coil 1412 and the boost coil 1422.

[0249] The current in the boost coil 1422 increases the magnitude of the magnetic field generated by the transmitter coil 1412, thereby increasing the power transmitted to the receiver without increasing the current in the transmitter coil 1412. It is likely preferable not to increase the current in the transmitter coil 1412, as increasing the current in the transmitter coil 1412 may increase losses in the transmitter coil 1412. For example, increasing the current in the transmitter coil 1412 may increase conduction and ohmic losses proportional to the square of the current. Therefore, increasing the current in the transmitter coil 1412 to increase the strength or magnitude of the magnetic field generated by the transmitter coil 1412 may result in increased losses, which may be undesirable.

[0250] The boost coil 1422 does not increase the current in the transmitter coil 1412; instead, it maintains the current in the boost coil 1422, which is approximately the same as the current in the transmitter coil 1412. This additional current can increase the voltage induced at the receiver by the transmitter coil 1412.

[0251] The resonant frequency of device 1430, particularly the resonant frequency of boost coil 1422 and capacitor 1428, is higher than the operating frequency of the wireless power transmission system.

[0252] The current in the boost coil 1422 is in phase with the current in the transmitter coil 1412. Therefore, the magnetic field generated by the current in the boost coil 1422 is in phase with the magnetic field generated by the transmitter coil 1412. Consequently, the magnetic field generated by the boost coil 1422 is effectively added to the magnetic field generated by the transmitter coil 1412. This increased magnetic field induces a larger voltage in the receiver, thereby increasing power transfer between the transmitter and receiver.

[0253] As previously described, the boost coil 1422 is adjacent to the transmitter coil 1412 of the wireless power transmission system. The distance between the transmitter coil 1412 and the boost coil 1422 is generally uniform. Furthermore, the distance between the boost coil 1422 and the conductive plate 1426 is generally uniform. An optimal spacing exists between the boost coil 1422 and the transmitter coil 1412, depending on the parameters of the wireless power transmission system.

[0254] Positioning the boost coil 1422 away from the transmitter coil 1412 increases the required capacitance of the capacitor 1428 to induce a current in the boost coil that is approximately the same as the current in the transmitter coil 1412. Furthermore, positioning the boost coil 1422 too close to the conductive plate 1426 could result in large eddy current losses. These losses could reduce power delivery and power delivery efficiency. Positioning the boost coil 1422 as close as possible to the transmitter coil 1412 reduces the required capacitance at the capacitor 1428, making it impractical to achieve the desired capacitance value.

[0255] Therefore, the device 1430 is positioned such that the boost coil 1422 is as close as possible to the transmitter coil 1412 within the practical constraints of the required capacitance value of the capacitor 1428, and such that the boost coil 1422 is as close as possible to the conductive plate 1426, without significant eddy current losses.

[0256] In operation, device 1430 is positioned relative to transmitter coil 1412 and receiver coil of wireless power transmission system. Wireless power transmission system includes a transmitter and a receiver; the transmitter includes transmitter coil 1412, and the receiver includes receiver coil. Boost coil 1422 and capacitor 1428 reinforce the magnetic field originating from or generated by transmitter coil 412 toward receiver coil. Because the capacitance of capacitor 1428 is chosen such that the current in boost coil 1422 is approximately equal to the current in transmitter coil 1412 during wireless power transmission, the transmitter, including transmitter 1412, needs to be retuned upon introduction into device 1430. However, the magnetic field strength is significantly increased. Specifically, the magnetic field generated by transmitter coil 1412 is doubled or tripled by device 1430.

[0257] The conductive plate 1426, positioned on the side of the field shielding coil 1422 opposite to the transmitter coil 1412, attenuates the residual magnetic field originating from or generated by the transmitter coil 1412 when facing away from the receiver coil. As will be understood, the magnetic field will still be amplified when using a device 1430 without the conductive plate 1426.

[0258] While device 1430 has been described as including a single boost coil 1422, those skilled in the art will understand that other configurations are possible. In another embodiment, the device includes more than one boost coil. The device also includes more than one capacitor. As previously described, each capacitor is electrically connected to a corresponding boost coil. As previously described, the capacitance of the capacitors is selected such that during wireless power transmission, the current in each boost coil is approximately equal to the current in the active coil.

[0259] In another embodiment, the plurality of boost coils 1422 are coplanar. Specifically, the principal planes of the plurality of boost coils 1422 are collinear. The plurality of boost coils 1422 may define a principal plane parallel to the principal plane of the transmitter coil 1412. In this embodiment, each boost coil 1422 increases the magnitude of the magnetic field generated by the transmitter coil 1412 in a certain region of the transmitter coil 1412, the region corresponding to a location of one of the boost coils 1422. In this way, the plurality of boost coils 1422 can be used to generate a magnetic field distribution or pattern generated by the transmitter coil 1422, which has an increased magnetic field magnitude at specific locations.

[0260] Although the boost coil 1422 has been described as having the same configuration as the transmitter coil 1412, those skilled in the art will understand that other configurations are possible. In another embodiment, the boost coil 1422 has a different configuration than the transmitter coil 1412. Specifically, the boost coil 1422 has a different size, shape, and / or dimensions than the transmitter coil 1412. Having different configurations for the boost coil 1422 can strengthen or increase the magnetic field at certain locations of the transmitter coil. Specific magnetic field distributions can be achieved by arranging the boost coil 1422 and the transmitter coil 1412 with specific shapes. This may be advantageous in certain use cases.

[0261] Now go to Figure 8A and Figure 8B This illustrates another embodiment of the device 2430 used in a magnetic induction wireless power transmission system. The device 2430 is used to increase the magnetic field generated by the effective coil of the magnetic induction wireless power transmission system. The magnetic induction wireless power transmission system can be the described wireless power transmission system 200.

[0262] In the illustrated arrangement, device 2430 includes a plurality of boost coils and a conductive plate 2426. In the illustrated arrangement, device 2430 includes four (4) boost coils, but those skilled in the art will understand that more or fewer boost coils can be used. Specifically, device 2430 includes: a first boost coil 2432, a second boost coil 2434, a third boost coil 2436, and a fourth boost coil 2438. Each boost coil is electrically connected to discrete capacitors 2442, 2444, 2446, and 2448. Each capacitor 2442, 2444, 2446, and 2448 is external to the corresponding boost coil 2432, 2434, 2436, and 2438. Each capacitor 2442, 2444, 2446, and 2448 is electrically connected between two terminals of the corresponding boost coil 2432, 2434, 2436, and 2438. As shown in the side view of device 2430, capacitors 2442 and 2444 are... Figure 8B It is not visible in the middle.

[0263] Unless otherwise stated, boost coils 2432, 2434, 2436, and 2438 function in the same manner as the described boost coil 1422.

[0264] Unless otherwise stated, conductive plate 2426 is configured in the same manner as conductive plate 1426 described.

[0265] Device 2430 is positioned such that boost coils 2432, 2434, 2436, and 2438 are opposite to transmitter coil 2412 and receiver coil. The receiver coil is part of a wireless power transmission system in which transmitter coil 2412 forms a part. Device 2430 is positioned such that boost coils 2432, 2434, 2436, and 2438 are adjacent to one side of transmitter coil 2412, while receiver coil is adjacent to the opposite side of transmitter coil 2412.

[0266] As previously described, device 2430 includes four (4) boost coils 2432, 2434, 2436, and 2438. Each capacitor 2442, 2444, 2446, and 2448 is located outside the corresponding boost coil 2432, 2434, 2436, and 2438. Furthermore, each capacitor 2442, 2444, 2446, and 2448 is electrically connected between two terminals of the corresponding boost coil 2432, 2434, 2436, and 2438. In the arrangement shown, the first capacitor 2442 is electrically connected between the two terminals of the first boost coil 2432. The second capacitor 2444 is electrically connected between the two terminals of the second boost coil 2434. The third capacitor 2446 is electrically connected between the two terminals of the third boost coil 2436. The fourth capacitor 2448 is electrically connected between the two terminals of the fourth boost coil 2438.

[0267] The first boost coil 2432 is arranged alongside the second boost coil 2434 on one side and alongside the third boost coil 2436 on the other side. The first boost coil 2432 is diagonally opposite to the fourth boost coil 2438. The second boost coil 2434 is arranged alongside the first boost coil 2432 on one side and alongside the fourth boost coil 2438 on the other side. The second boost coil 2434 is diagonally opposite to the third boost coil 2436. The third boost coil 2436 is arranged alongside the first boost coil 2432 on one side and alongside the fourth boost coil 2438 on the other side. The third boost coil 2436 is diagonally opposite to the second boost coil 2434. The fourth boost coil 2438 is arranged alongside the second boost coil 2434 on one side and alongside the third boost coil 2436 on the other side. The fourth boost coil 2438 is diagonally opposite to the first boost coil 2432.

[0268] In the arrangement shown, boost coils 2432, 2434, 2436, and 2438 are enclosed within transmitter coil 2412.

[0269] For the purposes of this disclosure, transmitter coil 2412 is referred to as surrounding boost coils 2432, 2434, 2436, 2438 when at least one of the following conditions is met: (i) if the region defined by the periphery of boost coils 2432, 2434, 2436, 2438 is projected onto the region of transmitter coil 2412, the projection is entirely within the region of transmitter coil 2412; (ii) the projected region of boost coils 2432, 2434, 2436, 2438 is constrained by the region of transmitter coil 2412; and (iii) the region of transmitter plate 1412 is larger than the total region defined by the periphery of boost coils 2432, 2434, 2436, 2438.

[0270] In the arrangement shown, as Figure 8A As best shown, the transmitter coil 2412 is typically a square shape with rounded corners. In the illustrated arrangement, each boost coil 2432, 2434, 2436, 2438 of the device 2430 does not have the same size or shape as the transmitter coil 2412. Each boost coil 2432, 2434, 2436, 2438 has a diameter smaller than the length or width of the transmitter coil 2412. Furthermore, each boost coil 2432, 2434, 2436, 2438 has a generally circular shape compared to the square shape of the transmitter coil 2412.

[0271] In the arrangement shown, as Figure 8BAs shown in the optimal configuration, the boost coils 2432, 2434, 2436, and 2438 are parallel. Accordingly, parallelism is defined as the plane defined by the main surface of each boost coil 2432, 2434, 2436, and 2438 being parallel to the plane defined by the main surface of each of the other boost coils 2432, 2434, 2436, and 2438. Therefore, the boost coils 2432, 2434, 2436, and 2438 define a single plane. This single plane defined by the boost coils 2432, 2434, 2436, and 2438 is parallel to the plane defined by the main surface of the transmitter coil 2412 and the plane defined by the main surface of the conductive plate 2426.

[0272] During operation, the magnetic field at positions corresponding to the boost coils 2432, 2434, 2436, and 2438 of device 2430 can be strengthened or increased. Therefore, a specific magnetic field pattern or distribution can be achieved by using multiple boost coils 2432, 2434, 2436, and 2438.

[0273] Although the device for increasing the magnetic field generated by the effective coil of the magnetic induction wireless power transmission system has been described as having a conductive plate, in any embodiment of the described device, the conductive plate may be absent.

[0274] Although devices 1430 and 2430 have been described with respect to transmitter coils, those skilled in the art will understand that these devices can be used similarly with receiver coils of receivers in wireless power transfer systems. Devices can be used with both transmitter and receiver coils, or with only a single coil from the transmitter and receiver coils. For example, a device including a boost coil can be used with a transmitter coil to increase the magnetic field generated by the transmitter coil, thereby increasing power transfer to the receiver coil. A device including a field-shielding coil can be used with a receiver coil to ensure that retuning is not required at the receiver.

Claims

1. An apparatus for a magnetic induction wireless power transmission system, the apparatus comprising: At least one shielded coil is positioned adjacent to the effective coil of the magnetic induction wireless power transmission system such that the main surface of the at least one shielded coil is parallel to the plane defined by the main surface of the effective coil; A capacitor electrically connected to the shielding coil; as well as A conductor is positioned adjacent to the shielding coil relative to the effective coil, such that the main surface of the conductor is parallel to the plane defined by the main surface of the effective coil, and the conductor surrounds the shielding coil. The parameters of the device are determined based on the following: Where ω is the resonant frequency of the device. Where M 12 It is the mutual inductance between the shielded coil and the effective coil. Where r L2 It is the resistance of the shielding coil. Where L2 is the inductance of the shielding coil. Where C is the capacitance of the capacitor. Z 1gnd It is the reflected impedance of the conductor toward the effective coil, and Z 2gnd It is the reflected impedance of the conductor toward the shielding coil.

2. The apparatus according to claim 1, wherein the resonant frequency of the apparatus is greater than the resonant frequency of the effective coil.

3. The apparatus according to claim 1, wherein the resonant frequency of the shielding coil is less than or equal to the self-resonant frequency of the shielding coil.

4. The apparatus according to claim 1, wherein the phase of the current in the shielding coil and the phase of the current in the effective coil are approximately equal.

5. The apparatus according to any one of claims 1 to 4, wherein at least one of the following: (i) the shielding coil is configured to enhance the magnetic field originating from the effective coil, and (ii) the conductor is configured to attenuate the magnetic field originating from the effective coil.

6. The apparatus according to any one of claims 1 to 4, comprising two shielding coils, a first shielding coil positioned adjacent to the effective coil of the magnetic induction wireless power transmission system, and a second shielding coil positioned between the first shielding coil and the conductor.

7. The apparatus of claim 6, wherein the capacitor is electrically connected to the first shielding coil, and the terminals of the second shielding coil are electrically shorted together to generate capacitive reflective impedance; or The capacitor is electrically connected to the first shielding coil, and a second capacitor is also electrically connected to the second shielding coil.

8. A wireless power transmission system for transmitting power via magnetic field coupling, the system comprising: The transmitter coil is used to transmit power via magnetic field coupling. A receiver coil, used to extract power from the transmitter coil via magnetic field coupling, and At least one device, comprising: At least one shielding coil is positioned adjacent to the transmitter coil or the receiver coil such that the main surface of the at least one shielding coil is parallel to the plane defined by the main surface of the transmitter coil or the receiver coil; A capacitor electrically connected to the shielding coil; and A conductor, positioned adjacent to the shielding coil opposite to the transmitter coil or the receiver coil, such that the main surface of the conductor is parallel to the plane defined by the main surface of the transmitter coil or the receiver coil, the conductor surrounding the shielding coil. The parameters of the device are determined based on the following: Where ω is the resonant frequency of the device. Where M 12 It is the mutual inductance between the shielding coil and the transmitter coil. Where r L2 It is the resistance of the shielding coil. Where L2 is the inductance of the shielding coil. Where C is the capacitance of the capacitor. Z 1gnd It is the reflected impedance of the conductor toward the transmitter coil, and Z 2gnd It is the reflected impedance of the conductor toward the shielding coil.

9. A method for shielding the effective coil of a magnetic induction wireless power transmission system, the method comprising: At least one shielding coil is positioned adjacent to the effective coil of the magnetic induction wireless power transmission system, and a conductor is electrically connected to the shielding coil such that the main surface of the at least one shielding coil is parallel to the plane defined by the main surface of the effective coil; as well as The conductor is positioned adjacent to the shielding coil relative to the effective coil, such that the main surface of the conductor is parallel to the plane defined by the main surface of the effective coil and the conductor surrounds the shielding coil. The parameters of the shielding coil and the effective coil are determined based on the following: Where ω is the resonant frequency of the shielding coil and the effective coil. Where M 12 It is the mutual inductance between the shielded coil and the effective coil. Where r L2 It is the resistance of the shielding coil. Where L2 is the inductance of the shielding coil. Where C is the capacitance of the capacitor electrically connected to the shielding coil. Z 1gnd It is the reflected impedance of the conductor toward the effective coil, and Z 2gnd It is the reflected impedance of the conductor toward the shielding coil.

10. A method for wirelessly transmitting power via magnetic induction, the method comprising: A magnetic field is generated at the transmitter coil to transfer power to the receiver coil via magnetic field coupling; The generated magnetic field is amplified by at least one shielding coil, which is positioned relative to the receiver coil and adjacent to the transmitter coil, such that the main surface of the at least one shielding coil is parallel to the plane defined by the main surface of the transmitter coil; as well as The generated magnetic field is attenuated by a conductor positioned adjacent to the shielding coil opposite to the transmitter coil, such that the main surface of the conductor is parallel to the plane defined by the main surface of the transmitter coil, and the conductor surrounds the shielding coil. The parameters of the transmitter coil and the shielding coil are determined based on the following: Where ω is the resonant frequency of the transmitter coil and the shielding coil. Where M 12 It is the mutual inductance between the shielding coil and the transmitter coil. Where r L2 It is the resistance of the shielding coil. Where L2 is the inductance of the shielding coil. Where C is the capacitance of the capacitor electrically connected to the shielding coil. Z 1gnd It is the reflected impedance of the conductor toward the transmitter coil, and Z 2gnd It is the reflected impedance of the conductor toward the shielding coil.

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