Apparatus and method for detecting foreign objects in a wireless power transfer system

Abstract

An apparatus for detecting a foreign object (112) in a WPT system is disclosed. The apparatus includes an injection unit (122) to receive a DC power signal and to generate a first AC power signal having a first frequency. Also, the apparatus includes a coil array (120) to receive the first AC power signal having the first frequency and to generate a first electromagnetic field at the first frequency. Further, the apparatus includes a detection unit (124) to measure a parameter of at least one of the DC power signal received by the injection unit (122) and the first AC power signal generated by the injection unit (122) and to detect the foreign object (112) within the first electromagnetic field based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil of the coil array (120).

Description

Technical Field

[0001] The embodiments of the present invention generally relate to a wireless power transmission system, and more specifically to an apparatus and method for detecting foreign objects in a wireless power transmission system. Background Technology

[0002] Electric or hybrid vehicles include one or more batteries that supply electricity to drive the vehicle. For example, a battery supplies energy to a motor to drive a shaft in the vehicle, which in turn drives the vehicle. Batteries are used to supply electricity, and therefore their power may be depleted and they need to be recharged from an external power source.

[0003] In general, power transmission systems are widely used to transfer electricity from a power source to one or more electrical loads, such as a battery in a vehicle. Typically, power transmission systems can be either contact-based or contactless. In a contact-based power transmission system, components such as plugs, socket connectors, and wires are physically coupled to the battery for charging. However, these connectors and wires can be adversely affected by environmental factors. Furthermore, charging the battery uses high current and high voltage. Therefore, establishing a physical connection between the power source and the battery in the vehicle can involve cumbersome safety measures. Moreover, such power transmission systems can be larger and heavier compared to contactless power transmission systems.

[0004] In contactless power transmission systems, a charging device converts input power received from a power source into transferable power, which is then transmitted to charge one or more batteries in a receiver device (such as an electric vehicle). However, if a foreign object (such as a coin or metal can) is present in the power transmission path between the charging device and the receiver device, the transmitted power may be received by the foreign object. Consequently, the foreign object may be substantially heated and affect components in the charging device. Furthermore, additional power loss exists in the system due to the power consumption of the foreign object, which in turn affects the efficiency of the power transmission system.

[0005] Therefore, there is a need for an improved system and method for detecting foreign objects in wireless power transmission systems. Summary of the Invention

[0006] According to one embodiment of the present invention, an apparatus for detecting foreign objects in a wireless power transmission system is disclosed. The apparatus includes an injection unit configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal. Furthermore, the apparatus includes a coil array operatively coupled to the injection unit and configured to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency. Further, the apparatus includes a detection unit operatively coupled to the coil array and configured to: measure a parameter of at least one of the DC power signal received by the injection unit and the first AC power signal generated by the injection unit, and detect foreign objects within the first electromagnetic field based on changes in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil in the coil array.

[0007] According to another embodiment of the present invention, a method for detecting foreign objects in a wireless power transmission system is disclosed. The method includes receiving a direct current (DC) power signal by an injection unit. Furthermore, the method includes generating a first AC power signal having a first frequency by the injection unit based on the DC power signal. Further, the method includes generating a first electromagnetic field at the first frequency by a coil array operatively coupled to the injection unit. Additionally, the method includes measuring a parameter of at least one of the DC power signal received by the injection unit and the first AC power signal generated by the injection unit by a detection unit. Furthermore, the method includes detecting foreign objects within the first electromagnetic field of the wireless power transmission system by the detection unit based on changes in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil in the coil array.

[0008] According to another embodiment of the present invention, a wireless power transmission system is disclosed. The wireless power transmission system includes a foreign object detection subsystem, which includes an injection unit configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal. Furthermore, the foreign object detection subsystem includes a coil array operatively coupled to the injection unit and configured to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency. Additionally, the foreign object detection subsystem includes a detection unit operatively coupled to the coil array and configured to: measure a parameter of at least one of the DC power signal received by the injection unit and the first AC power signal generated by the injection unit, and detect a foreign object within the first electromagnetic field of the wireless power transmission system based on changes in the parameters of at least one of the DC power signal and the first AC power signal across at least one coil in the coil array. Furthermore, the wireless power transmission system includes a power transmission subsystem including a power drive unit configured to generate a second AC power signal having a second frequency, wherein the power of the second AC power signal is greater than the power of the first AC power signal. Furthermore, the wireless power transmission system includes a primary coil operatively coupled to the power drive unit and configured to transmit a second AC power signal having a second frequency to the power receiving subsystem, wherein the primary coil generates a second electromagnetic field at the second frequency. Additionally, the wireless power transmission system includes a control unit operatively coupled to the power drive unit and configured to send a stop signal to the power drive unit to halt the transmission of the second AC power signal if a foreign object is detected. Attached Figure Description

[0009] These and other features, aspects, and advantages of this disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings, in which the same characters throughout the drawings denote the same parts, wherein:

[0010] Figure 1 This is a schematic representation of a wireless power transmission system for charging a vehicle according to various aspects of the present invention;

[0011] Figure 2 This is a block diagram of a wireless power transmission system according to various aspects of the present invention;

[0012] Figure 3 This is a block diagram of a foreign object detection (FOD) subsystem according to various aspects of the present invention;

[0013] Figures 4 to 6 A schematic representation of the electrical coupling between the coil and the injection unit according to various aspects of the present invention is shown;

[0014] Figure 7 This is a schematic representation of a coil coupled to an injection unit via a switch according to various aspects of the present invention;

[0015] Figures 8 to 9 A graphical representation of parameters measured for detecting foreign objects according to various aspects of the present invention is shown;

[0016] Figures 10 to 11 This is a schematic representation of the flexible pad used in the FOD subsystem according to various aspects of the present invention;

[0017] Figure 12 This is a cross-sectional view of a flexible pad according to various aspects of the present invention;

[0018] Figures 13 to 14 This is a schematic representation of a flexible pad positioned on a power transmission subsystem according to various aspects of the invention; and

[0019] Figures 15 to 18 Schematic representations of different arrangements of coils in a FOD subsystem according to various aspects of the present invention are shown. Detailed Implementation

[0020] Embodiments of an apparatus and method for detecting foreign objects in a wireless power transmission system are disclosed below in detail. Specifically, the embodiments of the apparatus and method disclose the use of low-power signals and the detection of foreign objects without affecting power transmission in the wireless power transmission system. Furthermore, the apparatus and method ensure that the wireless power transmission system complies with the Society of Automotive Engineers (SAE) standards. Moreover, foreign objects are detected with good detection sensitivity.

[0021] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this specification pertains. The terms “first,” “second,” etc., as used herein, do not indicate any order, quantity, or importance, but are used to distinguish one element from another. The terms “including,” “comprising,” or “having,” and variations thereof, as used herein, mean that they cover the items listed below and their equivalents, as well as additional items. The terms “connection” and “coupled” are not limited to physical or mechanical connections or couplings and may include electrical connections or electrical couplings, whether direct or indirect. Furthermore, the terms “circuit,” “circuitry,” and “control unit” may include single or multiple components that are active and / or passive and connected or otherwise coupled together to provide the described functionality. Additionally, the term “operably coupled,” as used herein, includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software-based communication, or combinations thereof.

[0022] Figure 1 This is a schematic representation of a wireless power transfer system 100 for charging a vehicle 106 according to various aspects of the present invention. The vehicle 106 may be an electric vehicle or a hybrid vehicle. The wireless power transfer (WPT) system 100 is used to transfer power from a power source 102 to one or more electrical loads 104 of the vehicle 106. The one or more electrical loads 104 may include a battery. In one embodiment, the wireless power transfer system 100 may also refer to a contactless power transfer system.

[0023] Wireless power transfer (WPT) system 100 includes a power transmission subsystem 108 and a power receiving subsystem 110. The power transmission subsystem 108 is configured to be magnetically or wirelessly coupled to the power receiving subsystem 110 to transmit power from a power source 102 to the power receiving subsystem 110. In one embodiment, the electrical power can range from about 100W to about 22kW. In one example, the power can be transmitted at frequencies ranging from about 80kHz to about 90kHz to comply with SAE standards. In one embodiment, the power transmission subsystem 108 may be part of a charging station. It can be noted that the power transmission subsystem 108 may be located below ground 118 (e.g., Figure 1 (as depicted in the text) or positioned above ground level 118.

[0024] Furthermore, the power receiving subsystem 110 is configured to receive power from the power transmitting subsystem 108 and supply the received power to one or more electrical loads 104. In one embodiment, the power receiving subsystem 110 may be located within an electric and / or hybrid vehicle 106. It should be noted that the power transmitting subsystem 108 may refer to a wireless charging device, and the power receiving subsystem 110 may refer to a wireless receiver device.

[0025] If a foreign object 112 (such as a coin or a can) is present in the power transmission path 114 between the power transmission subsystem 108 and the power receiving subsystem 110, the transmitted power may be received or consumed by the foreign object 112. Furthermore, if the foreign object 112 remains undetected in the power transmission path 114, it may be substantially heated and could affect components in the power transmission subsystem 108. Moreover, as the foreign object 112 is heated, the temperature in the system may rise above 80 degrees Celsius, exceeding the limits specified according to SAE standards. In some embodiments, the presence of a foreign object 112, such as a coin or a can, may not significantly affect the power transmitted by the power transmission subsystem 108. Therefore, it will be difficult to detect the foreign object 112 based on the power transmitted by the power transmission subsystem 108.

[0026] To overcome the above problems / disadvantages, an exemplary wireless power transmission system 100 includes a foreign object detection (FOD) subsystem 116 configured to detect foreign objects 112 within the wireless power transmission system 100. Foreign object 112 may refer to a current-conducting object or a magnetically permeable object that intercepts or alters the electromagnetic field of the wireless power transmission system 100. In one example, foreign object 112 includes a metal coin, a metal can, a metal nail, foil, a metal plate, and ferrite.

[0027] In one embodiment, the FOD subsystem 116 may be a flexible pad placed on the power transmission subsystem 108. In one example, the flexible pad 116 may include a thermally conductive and electrically insulating material that helps to conform to a shape corresponding to the position of the power transmission subsystem 108 on the ground 118. Further, the FOD subsystem 116 includes a coil array 120, an injection unit 122, and a detection unit 124. The injection unit 122 is operatively coupled to the coil array 120 and the detection unit 124. Further, a first transceiver 126 is operatively coupled to the detection unit 124.

[0028] The injection unit 122 is configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal. In one embodiment, the injection unit 122 may include an internal power source (such as a battery that provides the DC power signal). In another embodiment, the injection unit 122 may receive a DC power signal from an external power source 102. The DC power signal may represent electrical power in the range of about 5V to about 20V.

[0029] Furthermore, the injection unit 122 includes one or more converters configured to operate at a defined switching frequency to convert a DC power signal into a first AC power signal having a first frequency. In one example, the first frequency may be in the range from about 150 kHz to about 10 MHz. In another example, the first frequency may be in the range from about 10 kHz to about 75 kHz. Moreover, the first AC power signal is in the range from about 5 V to about 20 V. In one embodiment, the injection unit 122 may include a bridging circuit and a local controller that provides control pulses to the bridging circuit to convert the DC power signal into a first AC power signal having the first frequency. In another embodiment, the injection unit 122 may include digital circuitry or a processor that performs one or more functions based on pre-stored instructions or programs to convert the DC power signal into a first AC power signal having the first frequency. The injection unit 122 is further configured to transmit the first AC power signal having the first frequency to the coil array 120.

[0030] Furthermore, the coil array 120 is configured to receive a first AC power signal having a first frequency and generate a first electromagnetic field at the first frequency. Specifically, the coil array 120 can be tuned to be excited at the first frequency to generate the first electromagnetic field at the first frequency. It can be noted that the coil array 120 can be activated simultaneously or sequentially to generate the first electromagnetic field. Moreover, the coil array 120 can be arranged in one or more predetermined patterns to improve the sensitivity of detecting the foreign object 112. It can be noted that each coil in the coil array 120 can be compact and wound within a fine-gauge wire.

[0031] Furthermore, the detection unit 124 is configured to measure parameters of the DC power signal received by the injection unit 122 and parameters of the first AC power signal generated by the injection unit 122. In one example, the parameters of the DC power signal may be the power, current, or voltage of the DC power signal. In another example, the parameters of the AC power signal may be the power, current, voltage, or phase angle between the current and voltage of the first AC power signal. In one embodiment, if the power transmission subsystem 108 is transmitting power at 85 kHz, the coil array 120 in the FOD subsystem 116 may transmit power at 500 kHz to avoid interfering with the power transmitted by the power transmission subsystem 108. Moreover, the power of the first AC power signal is less than the power transmitted by the power transmission subsystem 108. In one example, 10 W of power is sufficient for the FOD subsystem 116 to detect or scan the foreign object 112.

[0032] Furthermore, the detection unit 124 is configured to detect the foreign object 112 based on changes in parameters of the DC power signal and / or the first AC power signal across at least one coil in the coil array 120. In one embodiment, the coil array 120 may generate a first electromagnetic field corresponding to the first AC power signal. If the foreign object 112 is present within the first electromagnetic field, the coil array 120 consumes more power of the first AC power signal. Therefore, parameters (such as the power of the first AC power signal and the power of the DC power signal) change from predetermined values ​​or baseline values. This predetermined value may refer to the value of the parameters determined in the absence of the foreign object 112 within the first electromagnetic field.

[0033] The detection unit 124 detects changes in the power of the first AC power signal or the power of the DC power signal. Further, if the change in the power of the first AC power signal or the change in the power of the DC power signal exceeds a threshold, the detection unit 124 detects a foreign object 112 between the power transmission subsystem 108 and the power receiving subsystem 110. In one example, if the power of the first AC power signal is 5% greater than a predetermined value, the detection unit 124 detects the presence of a foreign object 112. It can be noted that the detection unit 124 can also be used to detect other parameters such as current and voltage, and is not limited to the power of the DC power signal and / or the first AC power signal. (Reference) Figure 2To explain in more detail the various aspects of detecting foreign object 112. Furthermore, upon detection of foreign object 112, detection unit 124 transmits a control signal to power transmission subsystem 108 via first transceiver 126 to stop power transmission from power transmission subsystem 108 to power receiving subsystem 110. In one embodiment, a wired connection between detection unit 124 and power transmission subsystem 108 can be used to transmit the control signal. By stopping power transmission from power transmission subsystem 108, overheating of foreign object 112 can be avoided, thereby preventing any adverse effects on components in system 100. Moreover, the power consumption of foreign object is significantly reduced, which in turn reduces power loss and improves the efficiency of system 100. (Refer to...) Figure 2 A more detailed explanation of the various aspects of detecting foreign object 112.

[0034] refer to Figure 2 A block diagram of a wireless power transfer (WPT) system 100 according to various aspects of the present invention is shown. The wireless power transfer system 100 includes a power transmission subsystem 108, a power receiving subsystem 110, and a foreign object detection (FOD) subsystem 116.

[0035] In the illustrated embodiment, the power transmission subsystem 108 includes a power drive unit 202, a control unit 204, a primary coil 206, and a second transceiver 208 coupled to the control unit 204. The power drive unit 202 is electrically coupled to a power supply 102 and the control unit 204. The power supply 102 is configured to supply a direct current (DC) power signal to the power drive unit 202. In some embodiments, the power of the DC power signal can be in the range of about 100 W to about 22 kW. In one embodiment, the power supply 102 may be part of the wireless power transmission system 100. In another embodiment, the power supply 102 may be located external to the wireless power transmission system 100.

[0036] The power drive unit 202 is configured to receive a direct current (DC) power signal from the power supply 102. Further, the power drive unit 202 is configured to operate at a determined switching frequency to convert the DC power signal into a second alternating current (AC) power signal having a second frequency. Specifically, the control unit 204 may determine the switching frequency of the power drive unit 202 based on the electrical load 104. In one embodiment, the control unit 204 may include digital circuitry or a processor that performs one or more functions based on pre-stored instructions or programs. In one example, the second AC power signal represents power in the range from about 100W to about 22kW. Moreover, according to the SAE standard, the second frequency may be in the range from about 80kHz to about 90kHz. The power drive unit 202 is further configured to transmit the second AC power signal having the second frequency to a primary coil 206. Furthermore, the primary coil 206 is used to wirelessly transmit the second AC power signal having the second frequency from the power drive unit 202 to the power receiving subsystem 110.

[0037] Furthermore, the power receiving subsystem 110 includes a secondary coil 210, a rectifier 212, and a load 104. The secondary coil 210 is magnetically coupled to the primary coil 206 and configured to receive a second AC power signal having a second frequency from the primary coil 206. More specifically, when the primary coil 206 receives the second AC power signal having a second frequency, the primary coil 206 generates a second electromagnetic field at the second frequency. The second electromagnetic field is intercepted by the secondary coil 210 in the power receiving subsystem 110. Therefore, a voltage corresponding to the second AC power signal is induced in the secondary coil 210 and received by the rectifier 212 in the power receiving subsystem 110. The rectifier 212 is configured to convert the second AC power signal having a second frequency into output power having a DC voltage. Furthermore, the rectifier 212 is configured to deliver the output power having a DC voltage to the electrical load 104. In one example, the output power can be used to charge the electrical load 104, which includes one or more batteries located in the vehicle 106.

[0038] During operation of the wireless power transmission system 100, the power drive unit 202 drives the primary coil 206 to transmit a second AC power signal having a second frequency to the power receiving subsystem 110. Specifically, the primary coil 206 generates a second electromagnetic field corresponding to the second AC power signal having the second frequency. While the primary coil 206 transmits the second AC power signal having the second frequency, the injection unit 122 of the FOD subsystem 116 receives a DC power signal and converts it into a first AC power signal having a first frequency. The DC power signal can be received from an internal source (such as a battery) or from an external source (such as a power supply 102). Further, the injection unit 122 drives the coil array 120 to generate a first electromagnetic field corresponding to the first AC power signal. Specifically, each coil in the coil array 120 generates a first electromagnetic field corresponding to the first AC power signal having the first frequency. In another embodiment, only a subset of the coil array 120 generates the first electromagnetic field corresponding to the first AC power signal having the first frequency.

[0039] The detection unit 124 measures the parameters of the DC power signal received by the injection unit 122 and / or the parameters of the first AC power signal generated by the injection unit 122 when the first electromagnetic field is generated. In one example, the parameters of the DC power signal include the current, voltage, or power of the DC power signal. In another example, the parameters of the first AC power signal include the current, voltage, power, or phase angle between the voltage and current of the first AC power signal.

[0040] Figure 3 This is a block diagram of a foreign object detection (FOD) subsystem 116 according to various aspects of the present invention. The detection unit 124 includes a sensing subunit 302, a processor 304, a memory 306, and a communication subunit 308. The sensing subunit 302 includes one or more first sensors 310 coupled to an input terminal of the injection unit 122 to measure parameters of a DC power signal received by the injection unit 122. Similarly, the sensing subunit 302 includes one or more second sensors 312 coupled to an output terminal of the injection unit 122 to measure parameters of a first AC power signal generated by the injection unit 122.

[0041] Furthermore, the processor 304 is coupled to the sensing subunit 302 to receive parameters measured from the first sensor 310 and the second sensor 312. Moreover, the processor 304 is configured to compare the measured parameters with a predetermined value to determine a change in the parameter of at least one of the DC power signal and the first AC power signal. This predetermined value may refer to the condition where there is no foreign object 112 in the first electromagnetic field (…). Figure 1The value of the parameter is determined as shown. In one example, the processor 304 can compare the power of the first AC power signal with a predetermined power value. In another example, the processor 304 can compare the current of the DC power signal with a corresponding predetermined current value.

[0042] Subsequently, the processor 304 detects the foreign object 112 based on changes in parameters of at least one of the DC power signal and the first AC power signal of at least one coil in the coil array 120. Specifically, if the change in parameters of at least one of the DC power signal and the first AC power signal is greater than a threshold, the detection unit 124 detects the foreign object 112. For example, if the power of the first AC power signal is 5% greater than a predetermined power value, the detection unit 124 detects the presence of a foreign object 112 in the first electromagnetic field. Similarly, if the current of the DC power signal is 5% greater than a predetermined current value, the detection unit 124 detects the presence of a foreign object 112 in the first electromagnetic field.

[0043] Upon detecting a foreign object 112, processor 304 generates a control signal to indicate the presence of the foreign object 112. Furthermore, processor 304 transmits the control signal to communication subunit 308, which in turn transmits it via first transceiver 126 (in...). Figure 2 (As shown in the figure) the control signal is transmitted to the power transmission subsystem 108.

[0044] Refer again Figure 2 The control unit 204 of the power transmission subsystem 108 receives control signals via a second transceiver 208 communicatively coupled to the first transceiver 126. Further, the control unit 204 stops transmitting a second AC power signal from the primary coil 206. In one example, the control unit 204 may stop transmitting pulse width modulation signals or switching pulses to the power drive unit 202, thereby preventing the power drive unit 202 from transmitting the second AC power signal. In another example, the control unit 204 may turn off the power supply 102 to completely disable the power transmission subsystem 108. In yet another example, the primary coil 206 may include a coil array, and the control unit 204 may alternatively activate a subset of the coil array such that the array of coils near the foreign object 112 is not energized.

[0045] Thus, by employing the exemplary FOD subsystem 116, foreign object 112 located between the power transmission subsystem 108 and the power receiving subsystem 110 is detected.

[0046] refer to Figure 4 The diagram illustrates a schematic representation of the coil array 402 and injection unit 404 employed in the FOD subsystem 400 according to an embodiment of the present invention. The coil array 402 is similar to... Figure 1The coil array 120. Similarly, the injection unit 404 is similar to... Figure 1 The injection unit 122. In the illustrated embodiment, each coil in the coil array 402 is provided with a dedicated injection circuit to drive the corresponding coil to generate a first electromagnetic field. Specifically, the injection unit 404 includes a first injector 406, a second injector 408, a third injector 410, and a fourth injector 412. It can be noted that the injection unit 404 may include any number of injectors and is not limited to them. Figure 4 The number of injectors shown is as follows. Further, each coil of the coil array 402 is individually coupled to a corresponding injector of the injection unit 404. For example, the first coil 414 is coupled to the first injector 406, the second coil 416 to the second injector 408, the third coil 418 to the third injector 410, and the fourth coil 420 to the fourth injector 412. Further, each of the injectors 406, 408, 410, and 412 can independently drive the corresponding coil of the coil array 402 to generate a first electromagnetic field. Injectors 406-412 can operate in either a continuous injection mode or an intermittent injection mode. In continuous injection mode, coil 402 is continuously driven by injectors 406-412, resulting in high power consumption, which in turn facilitates rapid detection of foreign objects. In intermittent injection mode, coil 402 is intermittently driven by injectors 406-412, resulting in low power consumption, which in turn facilitates slow detection of foreign objects.

[0047] Figure 5 This is a schematic representation of a coil array 502 and an injection unit 504 used in a FOD subsystem 500 according to another embodiment of the present invention. The coil array 502 is similar to... Figure 1 The coil array 120. Similarly, the injection unit 504 is similar to... Figure 1 The injection unit 122. In this embodiment, the coil array 502 includes a first group of coils 506 and a second group of coils 508. The first group of coils 506 are connected in parallel and electrically coupled to each other and to a first injector 510 of the injection unit 504. Moreover, the first injector 510 simultaneously drives the first group of coils 506 to generate a first electromagnetic field. Similarly, the second group of coils 508 are connected in parallel and electrically coupled to a second injector 512 of the injection unit 504. Moreover, the second injector 512 simultaneously drives the second group of coils 508 to generate a first electromagnetic field. It can be noted that the coil array 502 may include any number of coil groups and is not limited to such a number. Figure 5 The first group of coils 506 and the second group of coils 508 are shown.

[0048] Figure 6This is a schematic representation of the coil array 602 and injection unit 608 used in the FOD subsystem 600 according to another embodiment of the present invention. The coil array 602 is similar to Figure 1 The coil array 120. Similarly, the injection unit 608 is similar to... Figure 1 The injection unit 122. In this embodiment, the coil array 602 includes a first group of coils 604 and a second group of coils 606. The first group of coils 604 are connected in series with each other and electrically coupled to a first injector 610 of the injection unit 608. Moreover, the first injector 610 drives the first group of coils 604 to generate a first electromagnetic field. Similarly, the second group of coils 606 are connected in series with each other and electrically coupled to a second injector 612 of the injection unit 608. Moreover, the second injector 612 drives the second group of coils 606 to generate a first electromagnetic field. In one embodiment, the first group of coils 604 and the second group of coils 606 may be driven sequentially or simultaneously by the respective injectors 610, 612. It can be noted that the coil array 602 may include any number of coil groups and is not limited to such a number. Figure 6 The first group of coils 604 and the second group of coils 606 are shown.

[0049] refer to Figure 7 The illustration depicts a schematic representation of a coil array 702 and an injection unit 704 employed in a FOD subsystem 700 according to an embodiment of the present invention. The coil array 702 is similar to... Figure 1 The coil array 120. Similarly, the injection unit 704 is similar to... Figure 1 The injection unit 122. Furthermore, the detection unit 708 is similar to... Figure 1 The detection unit 124. The FOD subsystem 700 includes one or more switches 706 coupled to the injection unit 704 and the coil array 702. Moreover, each of the switches 706 is coupled to a corresponding coil in the injection unit 704 and the coil array 702. Further, the detection unit 708 is electrically coupled to these switches 706 and is configured to activate each of the switches 706 to transmit a first AC power signal from the injection unit 704 to the corresponding coil in the coil array 702.

[0050] Furthermore, the detection unit 708 is configured to select and drive one or more coils in the coil array 702 by activating corresponding switches among a plurality of switches 706 for transmitting a first AC power signal. One or more coils 702 are selected and driven to simultaneously generate a first electromagnetic field corresponding to the first AC power signal. Specifically, the processor 304 of the detection unit 708 ( Figure 3(As shown in the diagram) A switching pulse is transmitted to activate or deactivate switch 706. If switch 710 is activated, the corresponding coil 712 is electrically coupled to injection unit 704 to receive the first AC power signal. If switch 710 is deactivated, the corresponding coil 712 is electrically decoupled from injection unit 704.

[0051] Furthermore, the detection unit 708 can activate the switches 706 in a predetermined sequence to minimize mutual interference between the coils 702. For example, as depicted in Table 714, the detection unit 708 can activate the switches 706 corresponding to coils numbered 1, 5, and 9 during a first time period. Furthermore, the detection unit 708 can activate the switches 706 corresponding to coils numbered 2, 6, and 10 during a second time period. Moreover, the detection unit 708 can activate the switches 706 corresponding to coils numbered 3, 7, and 11 during a third time period. Similarly, the detection unit 708 can activate the switches 706 corresponding to coils numbered 4, 8, and 12 during a fourth time period. Furthermore, the detection unit 708 can repeat this sequence of activation of the switches 706 for detecting foreign objects. It can be noted that the detection unit 708 can use any predefined sequence to activate the switches 706 and cyclically switch between coils to detect or scan for foreign objects. In one example, the switches 706 are activated in a predefined sequence, thereby cyclically selecting and driving the corresponding coils of the coil array.

[0052] Figure 8 This is a graphical representation 800 of parameters measured by the detection unit in the absence of foreign matter, according to various aspects of the present invention. The parameters are plotted considering time along the x-axis 801 and amplitude along the y-axis 803. Curve 802 represents the change in current of the DC power signal received by the injection unit. Curve 804 represents the change in current of the first AC power signal transmitted by the injection unit. Similarly, curve 806 represents the change in power of the first AC power signal transmitted by the injection unit.

[0053] Figure 9 This is a graphical representation 900 of parameters measured by the detection unit in the presence of a foreign object, according to various aspects of the present invention. The parameters are plotted considering time along the x-axis 901 and amplitude along the y-axis 903. Curve 902 represents the change in current of the DC power signal received by the injection unit. Curve 904 represents the change in current of the first AC power signal transmitted by the injection unit. Similarly, curve 906 represents the change in power of the first AC power signal transmitted by the injection unit. Clearly, parameters such as current and power change when a foreign object is present in the system. This change in parameters is monitored by the detection unit to detect the foreign object.

[0054] Figure 10 and Figure 11A schematic representation of a FOD subsystem 116 having a pad 1000 according to one embodiment of the present invention is shown. In one embodiment, the pad 1000 may be a separate structure detachably coupled to a power transmission subsystem. Figure 1 (As shown in the diagram). In one example, pad 1000 can be used as a plug-and-play structure with a wireless power transmission system. Pad 1000 may include flexible materials, rigid materials, or a combination thereof. For ease of understanding, pad 1000 refers to a flexible pad. The flexible pad 1000 includes a thermally conductive and electrically insulating (TCEI) material that forms a housing 1002 for the coil array 1004 and electronic devices such as injection and detection units. In one embodiment, the thermally conductive and electrically insulating (TCEI) material may include an elastomer or thermoplastic with abrasion-resistant filler. In one embodiment, the elastomer may be silicone rubber. The filler may be a TCEI filler (such as alumina, aluminum nitride, beryllium oxide, boron nitride, graphene oxide, silicon carbide, and silicon nitride). Similarly, the thermoplastic may be a polyolefin, polycarbonate, poly(methyl methacrylate) (PMMA), and polyester. Furthermore, the housing 1002 may be folded together with the coil array 1004. In one embodiment, the pad 1000 can be integrated with any type of standard SAE transmitter system. In one embodiment, the flexible pad 1000 can have a length ranging from about 0.5m to about 2.2m and a width ranging from about 0.5m to about 2.2m. Furthermore, the flexible pad 1000 can have a thickness ranging from about 1mm to about 20mm. In one embodiment, the flexible pad 1000 can be a monolithic structure. In another embodiment, as... Figure 11 As shown, the flexible pad 1000 can be formed by integrating smaller pad structures 1006. These pad structures 1006 can have predefined designs (such as a jigsaw puzzle design) to facilitate integration with each other. Due to the use of smaller pad structures, the size of the flexible pad 1000 can be varied to any desired size. It can be noted that each of these coils 1004 can be compact and wound within fine-gauge wires. The coils 1004 can also be printed on flexible or conventional printed circuit boards. Furthermore, due to the low power consumption of the coils 1004, any changes in the transmitted power are detected by the coils 1004 compared to the large primary coils of the power transmission subsystem.

[0055] Figure 12This is a cross-sectional view of the flexible pad 1000 of the FOD subsystem according to an embodiment of the present invention. Reference numeral 1002 denotes the housing of the flexible pad 1000. Reference numeral 1004 denotes a coil array printed on a PCB board 1008. In one embodiment, without using the PCB board 1008, the coil array 1004 may include wound coils placed toward the top surface of the housing 1002. Reference numeral 1010 denotes electronic devices such as injection units and detection units, which are positioned at locations where the first and second electromagnetic fields are minimal.

[0056] Figures 13 to 14 This is a schematic representation of a flexible pad 1000 positioned on a power transmission subsystem 108 according to an embodiment of the present invention. (See reference) Figure 13 The power transmission subsystem 108 is positioned above the ground 118. Furthermore, the flexible mat 1000 conforms to the shape of the power transmission subsystem 108 to cover the entire surface area of ​​the power transmission subsystem 108 and the portion of the ground 118 adjacent to it. (Reference) Figure 14 The power transmission subsystem 108 is positioned below the ground 118. Furthermore, a flexible mat 1000 is placed on the ground 118 to cover at least a portion of the ground 118 above the power transmission subsystem 108.

[0057] Figures 15 to 18 Different schematic representations of the arrangement of the coil array 120 of the FOD subsystem 116 according to an embodiment of the present invention are shown. Figure 15 In this embodiment, the coils 120 are arranged in a square pattern. Furthermore, the coils 120 can be coupled to the injection unit 122 (e.g., ...) in parallel or series. Figure 1 (As shown). In one embodiment, coils 120 may be arranged to form a subset 1502 of coils 120, wherein each subset 1502 has a predetermined number of coils 120. In one example, four adjacent coils 1504 are coupled in parallel or in series with each other to form a subset 1502 of coils 120. Figure 16 In this embodiment, the coils 120 are arranged in a hexagonal pattern to reduce or minimize the gaps or blank spaces 1602 between the coils 120, thereby improving the sensitivity to foreign object detection. Furthermore, the coils 120 can be coupled to the injection unit in parallel or series. It is worth noting that the coils 120 can be arranged in any desired pattern, and are not limited to this. Figure 15 and Figure 16 The pattern shown is illustrated. Furthermore, in one embodiment, the coil 120 can be formed on a PCB board. Additionally, the coil 120 can be of any shape (e.g., circular, rectangular, triangular, spiral, and elliptical). It can be noted that the coil can have any desired shape and size, and is not limited to any particular shape. Figure 15and Figure 16 The shapes and sizes shown.

[0058] In addition, Figure 17 In one embodiment, the coil 120 is arranged in two layers (e.g., a first layer 1702 and a second layer 1704). Furthermore, each layer 1702, 1704 may include coils 120 arranged in one or more patterns (e.g., square patterns or hexagonal patterns). Figure 17 In this embodiment, the coils 120 are arranged in a square pattern. Further, the first layer 1702 and the second layer 1704 are shifted relative to each other, such that the coils 120 in the second layer 1704 are positioned below the gaps between the coils 120 in the first layer 1702. This shifted arrangement of the coil layers 1702 and 1704 minimizes the gaps between the coils 120, thereby improving the sensitivity for foreign object detection. In addition to the three layers 1802, 1804, and 1806 of the coil 120 being shown as shifted relative to each other, Figure 18 The implementation method is similar to Figure 17 The implementation method is to further improve the sensitivity of foreign object detection.

[0059] The methods and systems described above facilitate the detection of one or more foreign objects (FODs) in wireless power transmission systems. Furthermore, they detect FODs using low-power signals and without affecting the primary power transmission within the system. Additionally, the methods and systems described above ensure that the wireless power transmission system complies with Society of Automotive Engineers (SAE) standards. Moreover, the coils can be printed on a PCB board, enabling simple and low-cost implementation of the FOD system.

[0060] While only certain features of this disclosure have been shown and described herein, many modifications and changes will occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and changes falling within the true spirit of this disclosure.

Claims

1. An apparatus for detecting a foreign object (112) in a wireless power transfer system (100), the apparatus comprising: an injection unit (122) configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal; a coil array (120) operably coupled to the injection unit (122) and configured to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency; and a detection unit (124) operably coupled to the coil array (120) and configured to: measure a parameter of at least one of the DC power signal received by the injection unit (122) and the first AC power signal generated by the injection unit (122); and detect the foreign object (112) within the first electromagnetic field based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil of the coil array (120), the detection unit comprising a sensing subunit comprising one or more first sensors coupled to an input terminal of the injection unit to measure a parameter of the DC power signal received by the injection unit and one or more second sensors coupled to an output terminal of the injection unit to measure a parameter of the first AC power signal generated by the injection unit; wherein a second AC power signal having a second frequency is generated by a power transfer sub-system (108) of the wireless power transfer system (100) and transmitted to the foreign object detection sub-system, the transmitted second AC power signal having the second frequency having a power greater than a power of the first AC power signal, wherein the wireless power transfer system (100) comprises a pad (1000) enclosing the coil array (120) and the pad is independent of the power transfer sub-system (108), and wherein the pad (1000) is detachably coupled to the power transfer sub-system, and wherein the pad forms an enclosure (1002) for the coil array (120) other than a primary coil (206), the enclosure being folded with the coil array (120).

2. The apparatus of claim 1, wherein, the parameter of the DC power signal comprises at least one of a current, a voltage and a power of the DC power signal, and wherein the parameter of the first AC power signal comprises at least one of a current, a voltage, a power and a phase angle between the voltage and the current of the first AC power signal.

3. The apparatus of claim 1, wherein, the detection unit (124) further comprises a processor (304) electrically coupled to the sensing subunit (302) and configured to: compare the measured parameter with a predetermined value to determine a change in the parameter of at least one of the DC power signal and the first AC power signal; detecting the foreign object (112) if the variation in the parameter of at least one of the DC power signal and the first AC power signal is greater than a threshold; and generating a control signal if the foreign object (112) is detected.

4. The apparatus of claim 3, wherein, The detection unit (124) further includes a communication subunit (308) operably coupled to the processor (304) and configured to communicate the generated control signal to the power transfer sub-system (108) of the wireless power transfer system (100) to stop the transfer of the second AC power signal having the second frequency to the power receiving sub-system (110).

5. The apparatus of claim 4, wherein, The coil array (120) is positioned within a second electromagnetic field corresponding to the second AC power signal generated by the power transfer sub-system (108).

6. The apparatus of claim 1, wherein, The coils in the coil array (120) are arranged to form at least one of a square pattern, a hexagonal pattern, one or more hierarchical structures, and wherein the coils are coupled to each other in series, in parallel, or a combination of series and parallel.

7. The apparatus of claim 1, wherein, Each coil in the coil array (120) is individually coupled to the injection unit (122).

8. The apparatus of claim 7, further comprising a plurality of switches (706), wherein, Each of the switches (706) is coupled to the injection unit (122) and a corresponding coil in the coil array (120).

9. The apparatus of claim 8, wherein, The detection unit (124) is electrically coupled to the plurality of switches (706) and configured to activate each of the switches (706) to transfer the first AC power signal from the injection unit (122) to the corresponding coil in the coil array (120).

10. The apparatus of claim 9, wherein, The detection unit (124) is configured to select and drive one or more coils in the coil array (120, 702) for transferring the first AC power signal by activating a corresponding switch in the plurality of switches (706), and wherein the one or more coils are selected to simultaneously generate the first electromagnetic field corresponding to the first AC power signal.

11. The apparatus of claim 9, wherein, The detection unit (124) is configured to activate each of the switches (706) in a predefined order, thereby selecting and driving a corresponding coil in the coil array (120, 702) in a cyclic manner.

12. A method for detecting a foreign object (112) in a wireless power transfer system (100), the method comprising: receiving, by an injection unit (122), a direct current (DC) power signal; generating, by the injection unit (122), a first AC power signal having a first frequency based on the DC power signal; generating, by a coil array (120) operably coupled to the injection unit (122), a first electromagnetic field at the first frequency; and measuring, by a detection unit (124), a parameter of at least one of the DC power signal received by the injection unit (122) and the first AC power signal generated by the injection unit (122); and detecting the foreign object (112) if the variation in the parameter of at least one of the DC power signal and the first AC power signal is greater than a threshold; and generating a control signal if the foreign object (112) is detected. detecting, by the detection unit (124), the foreign object (112) within the first electromagnetic field of the wireless power transfer system (100) based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil of the coil array (120), the detection unit comprises a sensing subunit comprising: one or more first sensors coupled to an input terminal of the injection unit to measure a parameter of a DC power signal received by the injection unit; and one or more second sensors coupled to an output terminal of the injection unit to measure a parameter of the first AC power signal generated by the injection unit; wherein a second AC power signal having a second frequency is generated by a power transfer subsystem (108) of the wireless power transfer system (100) and transmitted to a power receiving subsystem (110), the transmitted second AC power signal having the second frequency having a power greater than a power of the first AC power signal, wherein the wireless power transfer system (100) comprises a pad (1000) enclosing the coil array (120), and the pad is independent of the power transfer subsystem (108), and wherein the pad (1000) is detachably coupled to the power transfer subsystem, and wherein the pad forms an enclosure (1002) for the coil array (120) other than a primary coil (206), the enclosure being folded with the coil array (120).

13. The method of claim 12, wherein, the parameter of the DC power signal comprises at least one of a current, a voltage, and a power of the first power signal, and wherein the parameter of the first AC power signal comprises at least one of a current, a voltage, a power, and a phase angle between the voltage and the current of the first AC power signal.

14. The method of claim 12, wherein, detecting the foreign object (112) comprises: comparing, by a processor (304) of the detection unit (124), the measured parameter with a predetermined value to determine a change in the parameter of at least one of the DC power signal and the first AC power signal; detecting, by the processor (304), the foreign object (112) if the change in the parameter of at least one of the DC power signal and the first AC power signal is greater than a threshold value; and generating a control signal if the foreign object (112) is detected.

15. The method of claim 13, further comprising: communicating, by a communication subunit (308) of the detection unit (124), the generated control signal from the processor (304) to the power transfer subsystem (108) of the wireless power transfer system (100) to stop the transfer of the second AC power signal having the second frequency to the power receiving subsystem (110).

16. The method of claim 15, further comprising: communicating, by a plurality of switches (706), the first AC power signal from the injection unit (122) to corresponding coils of the coil array (120).

17. The method of claim 16, further comprising: selecting and driving, by the detection unit (124), one or more coils in the coil array (120) for transmitting the first AC power signal by activating corresponding ones of the plurality of switches (706), and wherein the one or more coils are selected to transmit the first AC power signal simultaneously.

18. A wireless power transmission system (100), comprising: a foreign object (112) detection subsystem, comprising: an injection unit (122) configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal; and a coil array (120) operably coupled to the injection unit (122) and configured to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency; a detection unit (124) operably coupled to the coil array (120) and configured to: measure a parameter of at least one of the DC power signal received by the injection unit (122) and the first AC power signal generated by the injection unit (122); and detect a foreign object (112) within the first electromagnetic field of the wireless power transmission system based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one coil in the coil array (120), the detection unit comprises a sensing subunit comprising: one or more first sensors coupled to an input terminal of the injection unit to measure a parameter of the DC power signal received by the injection unit; and one or more second sensors coupled to an output terminal of the injection unit to measure a parameter of the first AC power signal generated by the injection unit; and a power transfer subsystem (108), comprising: a power drive unit (202) configured to generate a second AC power signal having a second frequency, wherein a power of the second AC power signal is greater than a power of the first AC power signal; a primary coil (206) operably coupled to the power drive unit (202) and configured to transmit the second AC power signal having the second frequency to a power receiving subsystem (110), wherein the primary coil (206) generates a second electromagnetic field at the second frequency; and a control unit (204) operably coupled to the power drive unit (202) and configured to send a termination signal to the power drive unit (202) to stop transmission of the second AC power signal if the foreign object (112) is detected, wherein the wireless power transfer system (100) includes a mat (1000) that encloses the coil array (120), and the mat (1000) is independent of the power transfer subsystem (108), and wherein the mat (1000) is detachably coupled to the power transfer subsystem, and wherein the mat forms an enclosure (1002) for the coil array (120) but not for the primary coil (206), the enclosure being foldable with the coil array (120).

19. The wireless power transfer system (100) of claim 18, wherein, The detection unit (124) further includes a processor (304) electrically coupled to the sensing subunit (302) and configured to: compare the measured parameter with a predetermined value to determine a change in the parameter of at least one of the DC power signal and the first AC power signal; detect the foreign object (112) if the change in the parameter of at least one of the DC power signal and the first AC power signal is greater than a threshold value; and generate a control signal if the foreign object (112) is detected.

20. The wireless power transfer system (100) of claim 19, wherein, The processor (304) is further configured to transmit the control signal to the control unit to stop the transmission of the second AC power signal having the second frequency if the foreign object (112) is detected.

21. The wireless power transfer system (100) of claim 18, wherein, The mat (1000) includes a thermally and electrically insulating material, and wherein the mat includes at least one of a flexible material and a rigid material.

22. The wireless power transfer system (100) of claim 18, wherein, The mat (1000) is configured to conform to a shape corresponding to a location of the power transfer subsystem (108).

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