Foreign object detection in wireless power transmission systems

Abstract

This invention provides a system, method, and apparatus for foreign object detection (FOD) in wireless power transmission (WPT) systems. [Solution] In a wireless power transmission system 200, the FOD mat 150 determines that a foreign object is in the vicinity of one of the detection coils 170, which form a coil pair including at least two detection coils 171, 172, compared to one or more other detection coils. The present disclosure provides several options for the design, structure, layout, and operation of detection coils to improve foreign object detection.

Description

Technical Field

[0001] Cross-Reference to Related Applications This patent application claims the priority benefit of Indian Patent Application No. 202111006541, filed on February 16, 2021, entitled "FOREIGN OBJECT DETECTION IN A WIRELESS POWER TRANSFER SYSTEM", and assigned to the assignee of the present application. The disclosure of the prior application is considered part of this patent application and is incorporated herein by reference.

[0002] The present disclosure relates generally to wireless power. More specifically, the present application relates to foreign object detection in a wireless power transfer system.

Background Art

[0003] Technologies have been developed to enable wireless transmission of power from a wireless power transfer device to a wireless power receiving device. Examples of wireless power receiving devices may include, among other examples, several types of mobile devices, small electronic devices, computers, tablets, gadgets, appliances (such as cordless blenders, water kettles, mixers), and several types of large electronic devices. Wireless power transfer is sometimes referred to as contactless power transfer or non-contact power transfer. Wireless power may be transmitted using inductive coupling or resonant coupling between a primary coil of the wireless power transfer device and a secondary coil of the wireless power receiving device. For example, a wireless power transfer device may include a primary coil that generates an electromagnetic field. The electromagnetic field may induce an electromotive force in the secondary coil of the wireless power receiving device when the secondary coil is placed in proximity to the primary coil. In this configuration, the electromagnetic field may wirelessly transmit power to the secondary coil.

[0004] In contactless power transfer systems, if metallic foreign objects (such as keys, coins, metal cans, or aluminum foil, among other examples) are in close proximity to an electromagnetic field, eddy currents can cause the objects to overheat undesirably. This can pose safety hazards, including the risk of fire. Furthermore, the efficiency of the wireless power transfer process can be affected or interrupted due to inattention. Conventional techniques for detecting foreign objects in wireless power transfer systems may be insufficient or ineffective in preventing such safety hazards. [Overview of the project]

[0005] The systems, methods, and apparatus of this disclosure each have several innovative aspects, and none of them alone are solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of the subject matter described herein can be implemented as a detection device for a wireless power transmission (WPT) system. The detection device may include a plurality of detection coils, including at least a first detection coil and a second detection coil. The detection device may include a first driver configured to simultaneously energize the first detection coil and the second detection coil during a first foreign object detection (FOD) period. The detection device may include a differential current sensing device configured to detect a first differential current associated with the first detection coil and the second detection coil during the FOD period. The detection device may include a control unit configured to generate a foreign object detection signal based at least in part on the first differential current.

[0007] Another innovative aspect of the subject matter described herein can be implemented as a detection device for a WPT system. The detection device may include a plurality of detection coils arranged to form an FOD scanning area with a threshold size greater than the potential combined surface area of ​​at least a plurality of power transmission coils of the WPT system. The detection device may include a control unit configured to generate a foreign object detection signal based at least partially on the detection of foreign objects within the FOD scanning area.

[0008] Another innovative aspect of the subject matter described herein can be implemented as a WPT system. A WPT system may include a wireless power transmission device comprising at least one primary coil and a first plurality of detection coils arranged to form a first FOD scanning area having at least a first size greater than the size of the primary coil. A WPT system may include a wireless power receiving device comprising at least one secondary coil and a second plurality of detection coils arranged to form a second FOD scanning area having at least a second size greater than the size of the secondary coil.

[0009] Another innovative aspect of the subject matter described herein can be implemented as a method for a detection device in a WPT system. The method may include simultaneously exciting at least a first detection coil and a second detection coil during a first FOD period. The method may include detecting a first differential current associated with the first detection coil and the second detection coil during the FOD period using a differential current sensing device. The method may include generating a foreign object detection signal based at least in part on the first differential current. [Brief explanation of the drawing]

[0010] Details of one or more implementations of the subject matter described herein are given in the accompanying drawings and the following specification. Other features, embodiments, and advantages will become apparent from the specification, drawings, and claims. Note that the relative dimensions in the following figures may not be drawn to scale.

[0011] [Figure 1] This shows a block diagram of an exemplary wireless power transmission system. [Figure 2] This shows a block diagram of an exemplary detection device in a wireless power transmission system. [Figure 3] A block diagram of an exemplary detection device configured to excite a pair of detection coils to measure differential current is shown. [Figure 4]The chart shows an example of the magnitude of the differential current. [Figure 5] This shows a block diagram of an exemplary detection device based on a detection voltage induced by differential current. [Figure 6] The circuit diagram shows an example of the electrical configuration of a pair of coils. [Figure 7] The circuit diagram shows an exemplary electrical configuration of multiple coil pairs. [Figure 8A] This shows an exemplary timing diagram for a detection device having multiple coil pairs. [Figure 8B] This shows another exemplary timing diagram for a detection device having multiple coil pairs. [Figure 8C] This shows another exemplary timing diagram for a detection device having multiple coil pairs. [Figure 9A] This diagram shows multiple coil pairs within the associated detection zone. [Figure 9B] Figure 9A shows an exemplary detection of foreign matter using multiple coil pairs. [Figure 10] Another diagram shows multiple coil pairs within the associated detection zone. [Figure 11] An illustrative diagram of the detection coil is shown. [Figure 12] This diagram shows an exemplary detection coil with features designed to reduce the influence of the power transmission coil field. [Figure 13] The diagram shows multiple pairs of coils that can distinguish between the movement of a wireless power receiving device or foreign objects. [Figure 14] This chart illustrates the comparison of detection voltages induced by the differential current in a coil pair as a result of the movement of a wireless power receiver or foreign object. [Figure 15] A block diagram of an exemplary detection device configured to adapt the detection voltage of a coil pair based on the movement of a wireless power receiving device is shown. [Figure 16] An example diagram of a foreign object detection scanning area is shown. [Figure 17]1 is a flowchart diagram of an exemplary process for detecting foreign matter according to some implementations. [Figure 18] is a block diagram of an exemplary apparatus for use in a wireless power transmission system.

[0012] Like reference numerals and designations in different drawings indicate like elements.

Mode for Carrying Out the Invention

[0013] A wireless power transmission (WPT) system may include a wireless power transmission device and a wireless power receiving device. The wireless power transmission device may include one or more primary coils that transmit wireless energy (as a wireless power signal) to one or more corresponding secondary coils in the wireless power receiving device. A primary coil refers to a source of wireless energy (such as induction or magnetic resonance energy that generates an electromagnetic field) in the wireless power transmission device. A secondary coil disposed in the wireless power receiving device may receive wireless energy via the electromagnetic field. In some cases, foreign matter (sometimes referred to as metallic foreign matter) may be in proximity to the electromagnetic field. A foreign matter may be any object that is conductive, has detectable magnetic permeability, is not part of the WPT system, but is inadvertently present in the operating environment of the WPT system. Non-limiting examples of foreign matter may include iron objects, metal cans, coins, metal spoons, keys, aluminum foil, or other conductive or ferrous objects. When foreign matter is in proximity to the electromagnetic field, the foreign matter may adversely affect wireless power transmission, or may be undesirably heated by eddy currents.

[0014] There are various technologies for detecting foreign objects in wireless power transmission systems. Some technologies may include detecting the presence of a foreign object based on variations in the frequency of the current of a primary coil, detecting current and voltage imbalance in the primary coil, performing power loss calculation based on measured values of power drawn from the primary coil, and the like. In some detection technologies, there may be some delay in foreign object detection after wireless power transmission is started. A foreign object may absorb energy from a wireless power signal during this period, which may result in power waste or unsafe heating. As WPT systems are being developed for higher power levels, the potential risk of foreign objects rapidly heating to unsafe temperatures is increasing.

[0015] This disclosure provides systems, methods, and apparatus for foreign object detection (FOD) in wireless power transmission systems. Several implementations generally relate to the use of detection coils in a detection device (such as one integrated with a detection mat or a component of a WPT system). A pair of detection coils may be energized during the FOD period to measure and compare the differential current flowing through the pair of detection coils. The differential current may be the result of a difference in impedance associated with one detection coil as a result of the presence of a foreign object in the operating environment of the WPT system. For example, a foreign object may cause a change in the impedance of one or more detection coils compared to one or more other detection coils. As a result of different impedances, different detection coils may draw different amounts of current when energized. For brevity, this disclosure includes a description of a coil pair comprising at least two detection coils. The difference in the amount of current associated with the detection coils of a coil pair may be called the differential current. By detecting the differential current of a coil pair, the detection device may determine that a foreign object is in proximity to one of the detection coils of the coil pair. In addition to the description of foreign object detection based on differential current, this disclosure provides several options for the design and layout of detection coils to improve foreign object detection. Furthermore, this disclosure provides exemplary circuit design options, layout design options, detection coil design options, and techniques for improving foreign object detection. For example, some of the design options provided may improve the accuracy of foreign object detection by using a unique detection coil design and a comparison of differential currents associated with different coil pairs within the detection device. When a wireless power receiver moves during wireless power transmission, it can cause impedance changes even in the absence of foreign objects. Advantageously, some of the techniques of this disclosure can distinguish impedance changes caused by foreign objects from those caused by the movement of the wireless power receiver.

[0016] A coil pair refers to two or more detection coils that can be excited (also called energized) simultaneously during the FOD period. Two or more detection coils may be located in each foreign object detection zone (referred to as a “detection zone” for brevity) within the interface space of the WPT system. In some implementations, the detection zones may be symmetrically arranged with respect to the primary magnetic field of the WPT system. For example, the detection zones may cover the scanning area relative to the primary coil of the radio power transmission device. In some implementations, the detection zones may be symmetrically arranged with respect to the secondary coil of the radio power receiver. Alternatively or additionally, detection zones may be located relative to both the primary and secondary coils. The primary magnetic field refers to the magnetic field induced by a transmission unit, such as the radio power transmission device, in the WPT system. Detection coils may reside within a detection device (such as a detection mat or other device) configured for use in the primary magnetic field. For example, the detection device may be used in the interface space between the radio power transmission device and the radio power receiver. In some implementations, the detection device may be part of the radio power transmission device. In some implementations, the detection device may be part of the radio power receiver. In some implementations, the detection device can be a standalone device independent of the wireless power transmission device and the wireless power receiving device.

[0017] A pair of coils may be coupled in parallel to a driver that simultaneously energizes the detection coils of the coil pair using a high-frequency signal (e.g., 200 kHz or higher) during the FOD period. The differential current of the coil pair may be measured during the FOD period. The detection device may have several such coil pairs and measure the differential current of each coil pair. In some implementations, this disclosure includes exemplary layouts of detection coils within a detection zone so that non-adjacent coil pairs can be energized simultaneously. Alternatively, each coil pair may be energized during different FOD periods to prevent cross-interference. By measuring the differential current associated with each coil pair and comparing the various differential currents of the coil pairs, the detection device may determine whether foreign matter is present. In some implementations, the detection device may also determine the location of foreign matter relative to one or more coil pairs.

[0018] In some implementations, a differential current sensor may be used to determine the differential current associated with a pair of coils. For example, a differential current sensor may generate a detection voltage (or other detectable output value) that has an magnitude that increases as the differential current of a pair of coils increases, and vice versa. This disclosure describes an exemplary differential current sensor comprising a magnetic core (such as a toroid) and a differential current sensor circuit. One leg of each detection coil of a pair of coils may pass through the magnetic core in opposite directions. The currents associated with the detection coils generate a magnetic flux coupling with the magnetic core. If the currents of the detection coils are the same or similar, their magnetic flux couplings cancel each other out (or nearly cancel each other out), resulting in a lower combined magnetic flux generated in the magnetic core. If the currents are dissimilar (indicating a larger differential current), a higher combined magnetic flux is generated in the magnetic core.

[0019] In some implementations, a differential current sensing circuit may include a sensor coil wound around a magnetic core. The magnetic flux generated within the magnetic core can induce a voltage signal within the differential current sensing circuit. This electrical signal can be rectified and filtered to produce a DC voltage (called the sensing voltage) whose magnitude depends on the differential current in the sensing coil. Thus, for all coil pairs, the sensing voltage can represent the differential current in those coil pairs during the FOD period.

[0020] In some implementations, the detection device may include multiple pairs of coils distributed across detection zones. In some implementations, the detection zones may be non-overlapping (or partially overlapping) and symmetrically arranged with respect to the primary magnetic field of the WPT system. For example, a circular detection area (also called a scanning area) may be divided into detection zones having a sector shape relative to the circular detection area. The detection device may control which pairs of coils are excited during each FOD period. For example, the detection device may excite each pair of coils during different FOD periods. Alternatively, the detection device may excite two or more pairs of coils in non-adjacent detections. Thus, the detection device may prevent adjacent detection coils from interfering with the differential current measurement of a particular pair of coils during each FOD period.

[0021] In some implementations, the detection device may determine the detection voltage (corresponding to the differential current) associated with multiple coil pairs. Typically, the radio receiver is large enough to simultaneously span multiple coil pairs. Conversely, the foreign object may be smaller than the radio receiver. The foreign object may span only one coil pair or two coil pairs. The detection device can distinguish between the movement of the radio receiver and the introduction of the foreign object based on the number of coil pairs having a change in differential current. For example, if the detection voltage of multiple coil pairs of a threshold amount indicates a change in differential current, the detection device may determine that such a change is the result of the movement of the radio receiver. If the detection voltage for one coil pair (or less than a threshold amount) indicates a change in differential current, the detection device may determine that such a change is the result of the introduction of the foreign object. In some implementations, the detection device may change or offset the detection voltage of multiple coil pairs in response to determining that the radio receiver has moved. Thus, for subsequent comparison of the detection voltages, the detection device may adjust the detection voltage to take into account the current position of the radio receiver in the magnetic field of the WPT system. Therefore, while still providing accurate techniques for detecting foreign objects introduced during wireless power transmission, the accuracy of subsequent FOD treatment can be improved by taking into account the effects of the normal impedance of the wireless power receiver.

[0022] This disclosure provides exemplary designs for detection coils used in detection devices. For example, the options provided for the size, shape, structure, and position of the detection coils can improve the accuracy of foreign object detection based on differential current. The size of the detection coil may be selected based on the difference between the size of the radio receiver and the size of the foreign object, which is relatively smaller in comparison to the radio receiver. In some implementations, the size and shape of the detection coils in each coil pair may be uniform, thereby normalizing the impedance difference of the coils themselves. In some implementations, the detection coil may be composed of a capacitor to increase the impedance of the detection coil at power transmission frequencies (e.g., 50 kHz) while providing low impedance when the detection coil is excited at higher frequencies (e.g., 200 kHz or higher).

[0023] In some implementations, coil pairs may be structured for use in polygonal or circular scanning areas. For example, detection coils may have a triangular or sector shape so as to form a polygonal or circular scanning area when positioned in their respective non-overlapping detection zones. In some implementations, some coil pairs may be configured to prevent a narrow detection area in the center of the scanning area, while other coil pairs may be configured to have a larger detection area to cover the central area of ​​the scanning area. For example, the detection coils of one or more coil pairs may have a triangular or sector shape with an additional portion to cover the central area, while the detection coils of other coil pairs may have a trapezoidal or annular sector shape to fill the remaining portion of the polygonal or circular scanning area.

[0024] In some implementations, each detection coil may be configured as a collection of smaller subcoils connected in series to form a single detection coil. The smaller size of the subcoils allows the detection coil to better capture the impedance effects of smaller foreign objects. Furthermore, in some implementations, the subcoils may be wound in opposite directions so that the primary magnetic field of the WPT system (such as during wireless power transmission) induces less voltage, or no voltage at all, in the detection coil as a whole. Thus, the detection device can remain within the primary magnetic field during wireless power transmission between the wireless power transmission device and the wireless power receiving device. The voltages induced in the subcoils by the primary magnetic field may cancel each other out or reduce the overall voltage induced in the detection coil.

[0025] This disclosure describes the use of detection coils in the FOD scanning area. In some implementations, the size of the FOD scanning area may be larger than the combined surface area of ​​the power transmission coils of the WPT system. For example, the primary coil of the wireless power transmission device may have a first diameter, and the secondary coil of the wireless power receiver may have a second diameter. The optimal arrangement of the wireless power receiver and wireless power transmission device may be when the centers of the primary and secondary coils are perfectly aligned. However, this is not always the case in actual operating environments. The WPT system may tolerate a misalignment tolerance where the secondary and primary coils are misaligned, but wireless power transmission is still possible. On the other hand, foreign matter may be introduced into the area just outside the surface area of ​​the misaligned primary and secondary coils. Even in that location, the foreign matter may absorb energy from the primary magnetic field during wireless power transmission, reducing the efficiency of wireless power transmission or causing heat to reach dangerous temperatures. Therefore, in some implementations, the FOD scanning area may have a threshold size larger than the combined surface area of ​​the power transmission coils, taking into account the misalignment tolerance. In some implementations, the FOD scanning area may have a diameter at least 10% larger than the larger of the primary and secondary coil diameters. In some implementations, the FOD scanning area may have a diameter at least 10% larger than the larger power transmission coil plus the misalignment tolerance allowed by the WPT system.

[0026] In some implementations, the FOD scanning area may be dynamically determined based on the characteristics of the primary coil, secondary coil, their current alignment, or any combination thereof. For example, in a detection device with multiple detection zones, the detection zones may be dynamically selected or disabled based on the current operating conditions. The dynamic FOD scanning area size may be based on a threshold size (such as a 10% larger diameter or a 20% larger radius) that is at least greater than the potential combined surface area or footprint of the power transmission coil plus a misalignment tolerance.

[0027] In some implementations, the detection device may comprise two parts, such that a first part detects foreign objects related to the primary coil of a wireless power transmission device, and a second part detects foreign objects related to the secondary coil of a wireless power receiving device. Each of the parts is capable of detecting foreign objects within an FOD scanning area with a threshold size at least larger than the diameter of its respective power transmission coils. In such a configuration, the detection device can detect foreign objects in the primary magnetic field relative to the primary and secondary coils, even if there is a misalignment between the primary and secondary coils. Although described as two parts of the detection device, in some implementations, each part may be configured as a separate detection mat. For example, the first detection mat may be configured, mounted, or integrated with the wireless power transmission device, and the second detection mat may be configured, mounted, or integrated with the wireless power receiving device.

[0028] Certain implementations of the subject matter described herein may be implemented to achieve one or more of the following potential advantages: The detection device can detect foreign objects during the FOD period before or during wireless power transmission. The technology of this disclosure favorably minimizes the impact of the detection device on wireless power transmission, and vice versa. Furthermore, the exemplary detection coil design in this disclosure favorably enables accurate foreign object detection using differential current in the coil pair. The exemplary layout of the detection zone may enable rapid and accurate detection of foreign objects within the FOD scanning area. The FOD scanning area may be large enough to ensure that foreign objects around the wireless power transmission do not overheat beyond a safe level.

[0029] The following description relates to specific implementations for the purpose of illustrating innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in numerous different ways. The described implementations can be implemented in any means, apparatus, system, or method for wireless power transmission.

[0030] Figure 1 shows a block diagram of an exemplary wireless power transmission system 100. The wireless power transmission system may include a wireless power transmission device 102 and a wireless power receiving device 118. The wireless power transmission device includes a primary coil 110. The primary coil 110 may be associated with a power signal generator 106. The primary coil 110 may be a wire coil that transmits wireless power (also called wireless energy). The primary coil 110 may transmit wireless energy using induction or a magnetic resonance field. The power signal generator and the primary coil together may generate a primary magnetic field during wireless power transmission. The power signal generator 106 may include components (not shown) that supply power to the primary coil 110, causing the primary coil 110 to generate a wireless power signal. For example, the power signal generator 106 may include one or more switches, drivers, series capacitors, rectifiers or other components. The wireless power transmission device 102 may also include a transmission controller 108 that controls the components of the power signal generator 106. For example, the transmission controller 108 can determine the operating point (such as voltage or current) and control the power signal generator 106 according to the operating point.

[0031] In some implementations, the power signal generator 106, the transmission controller 108, and other components (not shown) may be collectively referred to as the power transmission circuit. Some or all of the power transmission circuit may be embodied as an integrated circuit (IC) that implements features of the present disclosure for controlling and transmitting radio power to one or more radio-powered devices. The transmission controller 108 may be implemented as a microcontroller, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), or any other suitable electronic device.

[0032] The power supply 112 can supply power to the power transmission circuit within the wireless power transmission device 102. The power supply 112 can convert alternating current (AC) power to direct current (DC) power. For example, the power supply 112 may include a converter that receives AC power from an external power source (such as a power line) and converts the AC power to DC power used by the power signal generator 106.

[0033] In some implementations, the first communication unit 142 may be coupled to components of the power signal generator 106 or primary coil 110 to transmit or receive communications over a radio power signal. The first communication unit 142 may include logic for controlling one or more switches and other components that cause radio signals to be transmitted and received over the radio power signal. For example, the first communication unit 142 may include a modulator or demodulator that converts information into a modulated signal added to the radio power signal. In one example, the first communication unit 142 may convert data from the transmission controller 108 into a frequency shift key (FSK) modulated signal that is combined with the radio power signal for communication from the radio power transmission device 102 to the radio power receiving device 118. In another example, the first communication unit 142 may detect a load modulation amplitude shift key (ASK) signal from the power signal generator 106 or primary coil 110, demodulate the ASK signal to obtain data that the first communication unit 142 will supply to the transmission controller 108.

[0034] In some implementations, the wireless power transmission device 102 may include a wireless communication interface 114. The wireless communication interface 114 may be connected to a first communication coil 116 (which may be a coil or loop antenna). The wireless communication interface 114 may include logic to control one or more switches and other components that transmit and receive wireless communication signals via the first communication coil 116. In some implementations, the wireless communication interface 114 may support short-range radio frequency communication (such as Bluetooth®) or near-field communication (NFC). NFC is a technology that performs data transfer at a carrier frequency of 13.56 MHz. The wireless communication unit 114 may also support any suitable communication protocol.

[0035] The transmission controller 108 may detect the presence or proximity of the wireless power receiver 118. In some implementations, the presence or proximity of the wireless power receiver 118 may be detected based on load changes in response to periodic low-power signals generated by the power signal generator 106 and the primary coil 110. In some implementations, the presence or proximity of the wireless power receiver 118 may occur during the periodic ping process of the wireless communication interface 114 within the wireless power transmission device 102.

[0036] The transmission controller 108 can control the characteristics of the radio power supplied by the radio power transmission device 102 to the radio power receiver 118. After detecting the radio power receiver 118, the transmission controller 108 can receive information from the radio power receiver 118. For example, the transmission controller 108 may receive information during the handshake process with the radio power receiver 118. The information may include information about the radio power receiver 118 (among other examples, power rating, manufacturer, model, or receiver parameters when operating with a standard transmitter). The transmission controller 108 can use this information to determine at least one operational control parameter (e.g., frequency, duty cycle, voltage) for the radio power to be supplied to the radio power receiver 118. To configure the radio power, the transmission controller 108 can modify the frequency, duty cycle, voltage, or any other appropriate characteristics of the power signal generator 106.

[0037] The wireless power receiver 118 may include a secondary coil 120, a rectifier 126, and a receiver controller 128. When the secondary coil 120 is aligned with the primary coil 110, the secondary coil 120 can generate an induced voltage based on the wireless power signal received from the primary coil 110. A capacitor may be in series between the secondary coil 120 and the rectifier 126. The rectifier 126 can rectify the induced voltage and provide it to a load 130. In some implementations, the load 130 may be outside the wireless power receiver 118 and coupled via wires from the rectifier 126.

[0038] The receiver controller 128 may be connected to a rectifier 126 and a second communication unit 152. The second communication unit 152 may be coupled to components of the secondary coil 120 or rectifier 126 to transmit or receive communications over radio power signals. The second communication unit 152 may include logic for controlling one or more switches and other components that cause communication signals to be transmitted and received over radio power signals. For example, the second communication unit 152 may include a modulator or demodulator that converts information into an ASK or FSK modulated signal. In one example, the second communication unit 152 may convert data from the receiver controller 128 into an ASK modulated signal used to load modulate the radio power signal for communication from the radio power receiving device 118 to the radio power transmission device 102. In another example, the second communication unit 152 may detect an FSK signal in the radio power signal in the secondary coil 120 or rectifier 126, demodulate the FSK signal to obtain data that the second communication unit 152 provides to the receiver controller 128.

[0039] In some implementations, the wireless power receiver 118 may include a wireless communication interface 132. The wireless communication interface 132 may include modulation and demodulation circuits for wireless communication via a second communication coil 134 (which may be a coil or loop antenna). Thus, the receiver controller 128 may wirelessly communicate with the transmission controller 108 via the wireless communication interface 132 and the wireless communication interface 114 using NFC communication or Bluetooth.

[0040] In some conventional wireless power systems, the primary coil can transmit wireless energy to the secondary coil up to a rating predetermined by the wireless standard. For example, low-power wireless power signals can transmit 5 watts (5W), 9W, 12W, or 15W. Low-power wireless power systems can supply up to 15 watts of energy, suitable for many electronic devices. Higher-power wireless systems are being developed to support wireless power transmission to equipment or devices that require higher power. For example, high-power cordless kitchen transmitters can supply as much power as 2.2 kW.

[0041] The interface space 180 may define the spatial boundary between the wireless power transmission device and the wireless power receiving device. For example, the interface space may include the surface of the wireless power transmission device, which may also include the surface on which the wireless power receiving device may be placed. The distance between the primary coil 110 and the secondary coil may include the thickness of the surface in the interface space. During wireless power transmission, the primary coil 110 may induce a magnetic field (called the primary magnetic field) through the interface space into the operating environment in which the secondary coil is located. Thus, the “operating environment” is defined by the primary magnetic field in the system, which is detectably present and can detectably interact with the secondary coil or foreign object 190 (indicated as FO190). Foreign object 190 present in the operating environment of the WPT system may experience a temperature increase due to interaction with the primary magnetic field. Therefore, if foreign object is detected, the wireless power transmission device may interrupt the generation of the primary magnetic field or otherwise prevent the wireless power transmission device from transferring a sufficient amount of energy through the foreign object, causing the foreign object to heat beyond a safe level. Conventional techniques for detecting foreign objects may be based on power loss calculations, where the amount of power received by a wireless power receiving device is compared with the amount of power output by a wireless power transmission device, and power loss is attributed to the foreign object 190. However, such techniques, when used alone, may be too slow, inaccurate, or insufficient for detecting foreign objects, especially in higher-power wireless power transmission systems.

[0042] Figure 2 shows a block diagram of an exemplary detection device in a wireless power transmission system 200. The wireless power transmission system 200 includes a wireless power transmission device 102 (having a primary coil 110), an interface space 180, and a wireless power receiving device 118 (having a secondary coil 120), as described with reference to Figure 1. For brevity, other components of the wireless power transmission device 102 and the wireless power receiving device 118 are not shown in Figure 2. The detection device (e.g., the FOD mat 150 shown in Figure 2, or a variation thereof) may include a plurality of detection coils 170 capable of detecting the presence of foreign matter according to several embodiments of this disclosure. The detection coils 170 may be arranged in a pattern that covers an area of ​​at least a threshold, which is larger than the overlapping relative potential surface area of ​​the primary coil 110 and the secondary coil 120. In some implementations, the detection device may include a FOD mat 150, and the detection coils may be configured in or on the FOD mat 150. Although not shown in Figure 2, in some implementations, the FOD mat may extend over the entire area of ​​the interface space. Alternatively, the size of the FOD mat (and the number or configuration of the detection coils within it) may be determined based on technical specifications that define the size of the primary coil 110, the secondary coil, or both. An example in Figure 2 shows a detection device deployed as an FOD mat 150 in or on a surface, but in some implementations, the detection device may be deployed on or within any surface or structure in the space between the transmitting coil 110 and the receiving coil 120.

[0043] The FOD mat 150 may be associated with a control unit 155. In some implementations, the control unit 155 may communicate with a wireless power transmission device 102 (shown as a dashed arrow 157) to enable or disable the wireless power transmission operation of the wireless power transmission device 102 based on whether the control unit 155 has detected a foreign object 190 adjacent to the detection coil 170. In some implementations, the control unit 155 may communicate with a wireless power receiving device 118 (not shown) to enable or disable the wireless power transmission operation of the wireless power receiving device 118 based on whether the control unit 155 has detected a foreign object 190 adjacent to the detection coil 170. Although only one FOD mat 150 is shown in Figure 2, in some implementations, two or more FOD mats may be deployed in the WPT system. For example, the control unit 155 may perform foreign object detection using FOD mats (not shown) positioned in relation to different primary coils of different wireless power transmission devices in a stovetop or other wireless power equipment. Alternatively or additionally, one FOD mat may be positioned in association with a wireless power transmission device, and another FOD mat may be positioned in association with a wireless power receiving device. Each of the FOD mats may be connected to the same or different foreign object control units (performing the functions described with reference to control unit 155 in Figure 2).

[0044] The technology by which the control unit 155 communicates with the wireless power transmission device or wireless power receiving device may vary. For example, the control unit 155 may have a wired communication link (not shown) with the transmitting controller (not shown) of the wireless power transmission device 102 or the receiving controller (not shown) of the wireless power receiving device 118. In some implementations, the control unit 155 may communicate with the wireless power transmission device 102 or the wireless power receiving device 118, or both, by a wireless communication link (not shown). In some implementations, the control unit 155 may communicate with the wireless power transmission device 102 or the wireless power receiving device 118 using pin lines or other control signals without requiring a communication protocol.

[0045] The FOD mat 150 may be a flexible mat, a adaptable mat, a rigid mat or a plug-and-play mat, a standalone mat, or a combination thereof. The substrate of the FOD mat 150 may be made from an electrically insulating material. In some implementations, the FOD mat 150 may further include a mechanically abrasion-resistant material to withstand the movement of the wireless power receiving device covering it (for example, if the wireless power receiving device 118 is a large piece of equipment). In some implementations, the FOD mat 150 may be further designed for outdoor use, and may be designed to withstand temperature and humidity, and may be resistant to water ingress. The detection coil 170 may be placed on the substrate of the FOD mat 150, or may be embedded within the substrate of the FOD mat 150 for user safety and aesthetics. In some other embodiments, the detection coil 170 may be printed, molded, woven, or laminated on the substrate of the FOD mat 150.

[0046] The detection coils 170 may operate in pairs. For example, a first detection coil 171 and a second detection coil 172 may form a coil pair. The control unit may excite the first detection coil 171 and the second detection coil 172 using a high frequency (higher than the frequency typically used for the primary magnetic field). If present, foreign matter may cause the first detection coil 171 to experience a different impedance than the second detection coil 172 (if no foreign matter is present). The control unit may determine the presence of foreign matter near either the first detection coil 171 or the second detection coil 172 by comparing the currents flowing through the first detection coil 171 and the second detection coil 172. The difference in current drawn by the coil pair is sometimes called the differential current. If the control unit determines, based on the differential current, that foreign matter is present, it may cause the wireless power transmission device to stop wireless power transmission.

[0047] Figure 3 shows a block diagram 300 of an exemplary FOD mat configured to energize a pair of sensing coils to measure differential current. Figure 3 shows a coil pair comprising a first sensing coil 171 and a second sensing coil 172. The coil pair is connected in parallel to the driver 305. Therefore, when one of the sensing coils in the coil pair is energized, the other sensing coil is also energized. For brevity, the example in Figure 3 is described as a coil pair having two sensing coils. Each sensing coil 171 and 172 may be a single coil or may consist of two or more sub-coils connected in series (as further described with reference to Figures 11 and 12).

[0048] The driver 305 can be operably coupled to a coil pair (in this example, a first detection coil 171 and a second detection coil 172). The driver 305 can be configured to simultaneously excite the detection coils 171 and 172 of the coil pair using AC signals through coil connectors 311 and 312. In some implementations, the impedance values ​​of the first detection coil 171 and the second detection coil 172 may be the same or similar in the absence of foreign matter 190. However, in the presence of foreign matter 190, it may cause an impedance change in one of the detection coils 171 and 172 such that the first detection coil 171 has a first impedance value and the second detection coil 172 has a second impedance value. The impedance difference may result in different amounts of current drawn through coil connectors 311 and 312. The differential current 350 may refer to a comparison of the currents drawn through coil connectors 311 and 312. If the foreign object 190 is not present and the impedances of the detection coils 171 and 172 are the same or similar, the amount of current drawn through the coil connections 311 and 312 may be the same or similar. Therefore, the differential current 350 may be a low value indicating little or no difference. Conversely, if the foreign object 190 is present near one of the first detection coils 171, the impedance of that first detection coil 171 changes, causing the differential current 350 to show a greater difference in the current drawn through the coil connections 311 and 312.

[0049] Figure 4 shows Chart 400 with exemplary magnitudes of differential currents. For example, Figure 4 schematically shows exemplary magnitudes of differential currents 350A and 350B (as an example of differential current 350 in Figure 3), and how differential currents can be used to determine whether foreign matter is present. If no foreign matter is present (shown in Graph 411), the magnitude of differential current 350A may be lower than the differential current threshold level 420. If foreign matter is present (shown in Graph 412), the magnitude of differential current 350B may be higher than the differential current threshold level. The differential current threshold level may be a configurable parameter based on the desired sensitivity of the detection device.

[0050] In the example shown in Figure 4, foreign matter is detected when the differential current exceeds the differential current threshold. In some implementations, foreign matter is detected based on the change in differential current. For example, the differential current may be higher during the baseline state and then decrease below the threshold amount when foreign matter is detected. If foreign matter is present, the differential current may be larger or smaller (compared to previous or baseline measurements). Therefore, in some implementations, the change in differential current can indicate the presence of foreign matter. The change in the amount of differential current may be compared to a delta threshold to determine whether the change is due to the introduction of foreign matter.

[0051] Figure 5 shows a block diagram of an exemplary detection device 500 based on a detection voltage induced by a differential current. The exemplary detection device may include detection coils arranged in pairs as described herein. For example, the exemplary detection device may include a pair of detection coils 171 and 172 (referred to as a coil pair), as described with reference to Figure 3. For brevity, the driver and other components of the WPT system are not shown in Figure 5. However, the detection device includes a driver (not shown) configured to simultaneously excite the coil pair during the FOD period. The presence (or absence) of foreign matter 190 may cause a measurable differential current in the coil connections 311 and 312. Figure 5 provides an example of a differential current detection device that can be used to measure the differential current. The differential current detection device may include a magnetic core 510, a differential current detection circuit 501, and a control unit 155. The control unit 155 may be configured to generate a foreign matter detection signal 580 based on the differential current in the coil connections 311 and 312.

[0052] As currents on coil connections 311 and 312 pass through the magnetic core 510, the difference in currents generates magnetic flux coupling in the magnetic core. Coil connections 311 and 312 pass through the magnetic core in opposite directions such that equal currents in coil connections 311 and 312 generate smaller magnetic flux coupling, while a difference in currents between coil connections 311 and 312 generates larger magnetic flux coupling. The magnetic flux coupling in the magnetic core 510 can induce an electrical signal corresponding to the sensor coil 520 wound around the magnetic core 510. This induced electrical signal, under conditions of a magnetically unsaturated magnetic core 510, has an induced voltage 522 that depends on (is related to or proportional to, for example) the difference between the currents in coil connections 311 and 312 and represents a measure of the differential current between the coil pair of detection coils 171 and 172.

[0053] The differential current sensing circuit 501 may also include a rectifier 530 that receives and rectifies an induced voltage signal to generate a DC sensing voltage 545 (referred to as the sensing voltage 545). An optional filter 540 may filter the sensing voltage before sending it to the control unit 155. In one example, the filter 540 is configured to remove high-frequency components from the measurement. In some implementations, the control unit 155 may include a comparator 560 configured to compare the absolute value of the sensing voltage with a sensing threshold 565. Based on the comparison of the sensing voltage with the sensing threshold 565, the control unit 155 may communicate a foreign object detection signal 580 or other control signals to components of the WPT system (such as a wireless power transmission device or wireless power receiving device). For example, if the absolute value of the sensing voltage is greater than the sensing threshold 565, the control unit 155 may indicate the presence of a foreign object. Alternatively, the sensing voltage in the presence of a foreign object may be lower than the sensing voltage in the absence of a foreign object. Therefore, in some implementations, the change in the absolute value of the detected voltage (from a previous or baseline measurement to the current measurement) may be compared to a delta threshold, and if the amount of change is greater than the delta threshold, a foreign object may be detected.

[0054] The control unit 155 may include a component 555 for generating the absolute value (called magnitude) of the detected voltage.

[0055] In some implementations, the control unit may also include a calibration unit 550 configured to add or subtract an offset value (sometimes referred to simply as "offset") to the detection voltage. For example, the offset value may be based on the normal difference in impedance between the coil pair of detection coils 171 and 172, or on a baseline measurement of the detection device. In some implementations, the offset value may be determined during or after the manufacture of the detection coils 171 and 172. Alternatively or additionally, the offset value may be determined by the control unit or another test device (not shown) during a baseline measurement of the detection device when no foreign matter is present. For example, the offset value may constitute a small difference in impedance caused by an FOD mat, a radio power transmission device, or other components of the radio power receiver, depending on where the detection device is installed. Alternatively or additionally, the offset value may be based on a determination of the resulting impedance difference of the radio power receiver in the operating environment of the WPT system, determined during a previous measurement.

[0056] Figure 6 shows a circuit diagram of an exemplary electrical configuration 600 of a single coil pair. A power supply 602 may supply power to a driver 690. The driver 690 may be configured to simultaneously energize a first detection coil 171 and a second detection coil 172 during the FOD period. As shown in Figure 6, the detection coils 171 and 172 may be connected in parallel to the driver. The detection coils 171 and 172 may have capacitors C1 and C2. In some implementations, the detection coils 171 and 172 may be called inductors L1 and L2, respectively. The driver controller 680 may be part of the control unit of the detection device or may be implemented as a separate logic component of the detection device. The driver may be a full-bridge inverter. During the FOD period when the coil pair is energized and the differential current is measured, the driver controller may control gates (A, B, C, and D) in the driver to cause the driver to generate AC electrical signals to the detection coils 171 and 172. In some implementations, the FOD period may occur before the wireless power transmission between the wireless power transmission device and the wireless power receiver. Alternatively or additionally, the FOD period may be associated with a measurement gap period during which the ongoing wireless power transmission is interrupted for the purpose of performing a foreign object detection procedure. Figure 6 shows a configuration in which the detection coils 171 and 172 have coil connections that pass through the magnetic core 510 of the differential current sensing device. The coil connections may pass through the magnetic core in opposite directions (as shown in Figure 6).

[0057] Figure 7 shows a circuit diagram 700 of an exemplary electrical configuration of multiple coil pairs. As described herein, a detection device may utilize multiple coil pairs associated with corresponding detection zones. In some implementations, the detection device may energize two or more coil pairs simultaneously, particularly when the coil pairs are associated with non-adjacent detection zones. The circuit diagram shows four coil pairs. The first coil pair comprises the first and second detection coils 171 and 172. The second coil pair comprises the third and fourth detection coils 173 and 174. The third coil pair comprises the fifth and sixth detection coils 175 and 176. The fourth coil pair comprises the seventh and eighth detection coils 177 and 178. The example in Figure 7 is provided for educational purposes, and it is clear that the detection device may have any variety of coil pairs.

[0058] Circuit diagram 700 includes a power supply 602 configured to supply power to the driver unit 790. The driver unit 790 may include one or more drivers. As shown in Figure 7, the driver unit 790 may include two drivers represented as half-bridge inverters. The first driver includes devices 712 and 714 that form the first half-bridge inverter. The second driver includes devices 716 and 718 that form the second half-bridge inverter. The driver controller 780 may control the operation of the devices using control signals A, B, C, and D so that the first and second drivers may work together to excite coil pairs at different times.

[0059] Each coil pair may pass through the corresponding magnetic cores 722, 724, 726, and 728. Although shown as separate magnetic cores in Figure 7, in some implementations the number of magnetic cores can be reduced by having several coil pairs sharing the same magnetic core, as long as only one coil pair per magnetic core is energized during the FOD period. During the first FOD period, the driver controller 780 may energize a first coil pair (detection coils 171 and 172) or a third coil pair (detection coils 175 and 176). Differential current sensing circuits (not shown) associated with each of the magnetic cores 722 and 724 may measure the detection voltages associated with the first and third coil pairs during the first FOD period. During the second FOD period, the driver controller 780 may energize a second coil pair (detection coils 173 and 174) or a fourth coil pair (detection coils 177 and 178). Differential current sensing circuits (not shown) associated with the magnetic cores 726 and 728, respectively, can measure the sensing voltages associated with the second and fourth coil pairs during the second FOD period. Thus, the circuit diagram allows the driver controller 780 to manage the excitation of multiple coil pairs by the driver unit 790 according to the pattern.

[0060] Figure 8A shows an exemplary timing diagram 801 for a detection device having multiple coil pairs. Timing diagram 801 shows the timing of radio power transmission 860 and foreign object handling of the detection device 880 in a WPT system. In some implementations, foreign object handling may be performed before radio power transmission 870. Alternatively or additionally, foreign object handling may be performed during a measurement gap 850 in which radio power transmission 805 is interrupted, to allow foreign object detection to be performed with less interference caused by the primary magnetic field of radio power transmission. Figure 8A shows a continuous pattern in which different coil pairs 810, 820, 830, and 840 are excited during each FOD period 851, 852, 853, and 854. For example, the first coil pair 810 may be excited and its differential current may be measured during the first FOD period 851. Subsequently, the detection device may discontinue the excitation of the first coil pair 810 and energize the second coil pair 820 during the second FOD period 852 so that the differential current of the second coil pair 820 can be measured. The third coil pair 830 may be energized during the third FOD period 853, and the fourth coil pair 840 may be energized during the fourth FOD period 854. In this way, each coil pair may be energized during different FOD periods, and as a result, its associated differential current can be measured without interference from other coil pairs.

[0061] Figure 8B shows another exemplary timing diagram 802 for a detection device having multiple coil pairs. Similar to Figure 8A, timing diagram 802 shows the timing 860 for radio power transmission in a WPT system. Unlike Figure 8A, the detection device may energize multiple coil pairs during each FOD period. For example, during the first FOD period 851, the detection device may energize the first coil pair 810 and the third coil pair 830 and measure their respective differential currents. During the second FOD period 852, the detection device may energize the second coil pair 820 and the fourth coil pair 840 and measure their respective differential currents. Thus, the measurement gap 850 can be shortened, allowing for faster foreign object detection. In some implementations, the detection device may energize various coil pairs using the circuit diagram described with reference to Figure 7. One consideration regarding which coil pairs to energize during the same FOD period is the proximity or adjacency of the detection coils in the coil pairs. The example in Figure 8B is based on a design in which the first coil pair 810 and the third coil pair 830 are in non-adjacent detection zones (and the second coil pair 820 and the fourth coil pair 840 are in non-adjacent detection zones). Figures 9A, 9B, and 10 provide several exemplary layouts using non-adjacent coil pairs in the pattern described with reference to Figure 8B.

[0062] Figure 8C shows another exemplary timing diagram 803 for a detection device having multiple coil pairs. Similar to Figure 8B, timing diagram 803 in Figure 8C shows the timing 860 for radio power transmission in a WPT system. The coil arrangement used in Figure 8C may be the same as that described with reference to Figure 8B. Figure 8C shows an implementation where FOD periods may be intervened during the radio power transmission period. For example, during a first FOD period 853, the detection device may energize a first coil pair 810 and a third coil pair 830 and measure their respective differential currents. Following the first FOD period 853, the WPT system may have a radio power transmission period 871 before the next FOD period (indicated as a second FOD period 854). During the second FOD period 854, the detection device may energize a second coil pair 820 and a fourth coil pair 840 and measure their respective differential currents. Another period 872 of wireless power transmission may follow the second FOD period 854. FOD periods 853 and 854 may be interposed between periods 871 and 872 of wireless power transmission.

[0063] Figure 9A shows multiple coil pairs within an associated detection zone. Coil pairs can be associated with detection zones. In some implementations, a detection mat may contain several detection zones. Detection zones may resemble geometric shapes so that detection coils can cover circular or polygonal scanning areas. Detection zones may define separate areas of the detection mat. Detection zones do not have to be physically separated or isolated from one another. However, detection zones may be electrically insulated from one another and further insulated based on the FOD period in which they are used. Geometric shapes are described for brevity in this disclosure, but other shapes may be used in some implementations. An example in Figure 9A shows triangular detection coils 171, 172, 173, 174, 175, 176, 177 and 178. For simplicity, detection coils 171, 172, 173, 174, 175, 176, 177, and 178 are referred to as L1, L2, L3, L4, L5, L6, L7, and L8, respectively. The detection coils are triangular and may be positioned in detection zones that form polygons (such as an octagon in the example in Figure 9A). In some implementations, the detection coils may have a sector shape to form a circular FOD scanning area. In some implementations, the coils may have other shapes. The coils may have a uniform shape, size, and structural material, resulting in a cost-effective design.

[0064] Figure 9A also shows a coil pair 901 formed in this arrangement. The first coil pair 810 may include coils L1 and L2. As shown in Figure 9A, coils L1 and L2 may be located in detection zones arranged symmetrically with respect to the primary magnetic field (not shown) of the WPT system. The second coil pair 820 may include coils L3 and L4. The third coil pair 830 may include coils L5 and L6. The fourth coil pair 840 may include coils L7 and L8. The first coil pair 810 is sometimes referred to as adjacent to these coil pairs because at least one detection coil (first detection coil 171) is adjacent to the detection coils of the second coil pair 820 and the fourth coil pair 840 (e.g., fourth detection coil 174 and seventh detection coil 177). Conversely, the first coil pair 810 and the third coil pair 830 may be non-adjacent coil pairs because coils L1, L2, L5, and L6 of those coil pairs are not adjacent. Therefore, similar to the pattern described with reference to Figure 8, the first coil pair 810 and the third coil pair 830 can be utilized during the same first FOD period. The second coil pair 820 and the fourth coil pair 840 are non-adjacent coil pairs that can be utilized during the same second FOD period.

[0065] Figure 9B illustrates exemplary detection of foreign matter using the exemplary coil pairs of Figure 9A. In one example, foreign matter 960 may be located near coil L3. When the coil pair of coils L3 and L4 is energized, their detection coils draw different currents, and the differential current may indicate that the foreign matter is located near one of those coils. In another example, foreign matter 970 may be located on the adjacent edges of coils L5 and L7. However, since the coil pair including those adjacent coils is energized during different FOD periods, the foreign matter can still be detected. When the coil pair of coils L5 and L6 is energized, the foreign matter generates a differential current in that coil pair. When the coil pair of coils L7 and L8 is energized (during different FOD periods), the foreign matter generates a differential current in that coil pair.

[0066] Multiple detection coils may be located in close proximity within the central region 980 of the FOD scanning area. Therefore, when multiple coil pairs are excited, the magnetic flux from one coil pair may affect the magnetic flux from another simultaneously excited coil pair, potentially leading to an incorrect determination of the presence of an FO. Furthermore, the detection coils themselves may absorb energy from the primary magnetic field of the WPT system. A concentration of detection coils near the center 980 can result in heating caused by interference with the primary magnetic field or radio power transmission. Therefore, in some implementations, the detection coils may be designed to reduce the concentration of coil material within the central region 980.

[0067] Figure 10 shows another diagram of multiple coil pairs within an associated detection zone. This layout diagram includes detection coils 171, 172, 173, 174, 175, 176, 177, and 178 (let's call them L1, L2, L3, L4, L5, L6, L7, and L7) as described above. Unlike Figures 9A and 9B, the first and second detection coils 171 and 172 may have different shapes to address the concentration of coils within the central region 980 as described with reference to Figure 9B. For example, the first coil pair (coils L1 and L2) may be configured to cover a triangular or sectoral portion of the FOD scanning area and the central region of the FOD scanning area. The other coils (L3, L4, L5, L6, L7, and L8) may cover a trapezoidal or annular sectoral detection area within the FOD scanning area. It should be understood that the shapes of the detection coils in Figure 10 are provided as examples. Other shapes are possible. For example, two or more coil pairs may have unique designs to cover the central region. In some implementations, the central region may be covered by a coil pair in which the sensing coils are of the same shape. Alternatively, only one sensing coil of the coil pair may cover the central region, and the impedance difference caused by the additional portion of that sensing coil may be taken into account by the control unit of the sensing device using an offset value.

[0068] Figure 11 shows an exemplary diagram of a detection coil. The first diagram 1110 shows an exemplary detection coil composed of multiple subcoils connected in series. The subcoils together form a single detection coil. The first diagram may be examples of detection coils L3, L4, L5, L6, L7, and L8 as described with reference to Figure 10. The first diagram shows eight subcoils combined to form the detection coil. Using subcoils allows the detection coil to be made larger, and smaller subcoils can be used for smaller foreign object impedance responses, while reducing the cost and complexity of the detection device. The second diagram 1120 shows an exemplary detection coil composed of multiple subcoils connected in series. The second diagram may be examples of detection coils L1 and L2 as described with reference to Figure 10. The second diagram shows ten subcoils combined to form the detection coil. The second diagram includes the same eight subcoils as the first diagram, as well as two subcoils that cover a portion of the central area of ​​the FOD scanning region.

[0069] Figure 12 shows an exemplary diagram of a detection coil with features to reduce the influence of the power transmission coil field. The first and second diagrams are the same as those described with reference to Figure 11. Figure 12 shows that adjacent subcoils within each detection coil may be wound in opposite directions to reduce the influence of the primary magnetic field of the WPT system. For example, the first subcoil 1211 may be wound in a first direction (e.g., counterclockwise), and its adjacent subcoil 1212 may be wound in a second direction (e.g., clockwise). The subcoil layout can increase the likelihood that the voltages induced in the subcoils (from the primary magnetic field of the WPT system) will nearly cancel each other out, resulting in a small overall voltage across the detection coil terminals. This can protect some electronic components within the detection device, reduce power loss, or minimize subcoil heating, among other advantages. Figure 12 also shows how adjacent subcoils can be wound in opposite directions in the second diagram.

[0070] Additionally or alternatively, the detection coil shown in Figure 12 may include a capacitor 1230 at one or both terminals of the detection coil. Capacitor 1230 may be examples of capacitors C1, C2, C3, C4, C5, C6, C7, and C8 shown in Figures 6 and 7, respectively. Some WPT systems can transmit radio power using frequencies up to a maximum power frequency of 50 kHz. According to some implementations of this disclosure, the detection coil may be excited using higher frequencies (such as 200 kHz or higher). Capacitor 1230 can reduce the effects of circulating currents due to the primary magnetic field (below 50 kHz) passing through the detection coil. The series capacitance of capacitor 1230 can introduce high impedance to the 50 kHz radio power signal while still enabling high-frequency operation of the detection device.

[0071] Figure 13 shows a diagram of multiple coil pairs that can distinguish the movement of a wireless power receiver or foreign object. The layout of Figure 13 utilizes an exemplary configuration of multiple coil pairs described with reference to Figure 10. Primary coils (not shown) may be located in the center and below the detection zone covered by coils L1-L8. The first example 1301 shows a secondary coil (shown as a single circle for brevity) moving from a first position 1310 to a second position 1320 on an array of detection coils. Because the secondary coil contains metallic and ferrite components, it can cause a change in the impedance of the detection coil. Therefore, if the differential current of a coil pair is measured, the secondary coil itself can cause a differential current in various coil pairs. However, because the secondary coil is relatively large compared to the size of the detection coil, multiple coil pairs measure the change in differential current. By comparison, the second example 1302 shows a foreign object 1330 introduced into the operating environment of a WPT system. The foreign object is relatively small compared to the size of the detection coil. Therefore, perhaps only one or two coil pairs can measure the change in differential current resulting from the introduction of foreign objects. In some implementations, the sizes of the detection coils L1-L8 (and their sub-coils) may be selected based on a standardized size (or multiple sizes) of the secondary coil that conforms to the technical specifications. Similarly, the sizes of the detection coils L1-L8 may be selected based on the potential size of foreign objects that may be introduced into the operating environment. For example, a detection device for use in a kitchen WPT system may have its detection coils appropriately sized to detect spoons, forks, coins, keys, tin cans, or metal plates, among other examples. A detection device for use in an EV WPT system may be appropriately sized to detect wrenches, aluminum cans, gas tanks, washers, nuts, or screws, among other examples. A detection device for use in a desktop WPT system may be appropriately sized to detect foreign objects (among other examples, pens, keys, computer components, rings, or thumb drives, etc.).

[0072] Figure 14 shows an exemplary chart 1400 comparing detection voltages induced by the differential current of a coil pair as a result of the movement of a wireless power receiver or foreign object. In the first example 1410, the detection device may establish a baseline calibration of the detection voltages. For example, the detection device may add an offset value to the detection voltage of each coil pair based on a test calibration or baseline offset value. Detection voltages 1411, 1412, 1413 and 1414 represent the detection voltages induced by the differential current of a plurality of coil pairs (e.g., coil pairs 810, 820, 830, and 840 described herein). The detection device may determine that no foreign object is present based on the detection voltages. For example, the detection device may compare each detection voltage to a detection threshold and determine that no foreign object is present for each coil pair. Alternatively or additionally, the detection device may compare the change in each detection voltage to a delta threshold and determine that no foreign object is present if the change is below the delta threshold. Based on the determination that no foreign object is present, the WPT system may initiate wireless power transmission. The detection device may determine a set of calibration values ​​(also called offset values) based on the presence of a wireless power receiver in the WPT system. This set of calibration values ​​may be used to adjust the detection voltage of the coil pair during subsequent foreign object detection procedures.

[0073] In the second example 1420 (such as a subsequent measurement), the radio receiving device may have moved from its previous position relative to the previous measurement. This movement may cause a change in the detected voltage of a coil pair. For example, detected voltages 1421, 1422, 1423, and 1424 represent the detected voltages induced by the differential current of multiple coil pairs. In the second example, the detected voltages 1422, 1423, and 1424 corresponding to the second, third, and fourth coil pairs have changed. The changes in detected voltages 1422, 1423, and 1424 are enclosed in 1426, 1427, and 1428, respectively, for the sake of this explanation. Although shown as a decrease in detected voltage (enclosed in 1426, 1427, and 1428) for educational purposes, in some implementations the change may be an increase in detected voltage. Whether the change is an increase or decrease, the detection device may determine how many coil pairs have a change in detected voltage that exceeds the delta threshold. The detection device may determine that a change in the detected voltage of a pair of coils exceeding a threshold amount is a result of movement of the radio-powered device. The threshold amount may be a configurable parameter or may be predetermined. In some implementations, changes in three or more pairs of coils may be considered a result of movement of the radio-powered device during radio power transmission. Once the detection device determines that a change in detected voltage is a result of movement of the radio-powered device, it may adjust a set of offset values ​​for the detected voltage to constitute the new position of the radio-powered device. In some implementations, the offset values ​​may be adjusted continuously during radio power transmission as the detection device detects movement of the radio-powered device. When radio power transmission is completed or interrupted, the detection device may reset the offset values ​​to return to baseline calibration.

[0074] In the third example 1430, a foreign object may be introduced into the operating environment during wireless power transmission. As illustrated with reference to Figure 9, the foreign object may affect the differential current of only one or two coil pairs. The detection voltages 1431, 1432, 1433, and 1434 represent the detection voltages induced by the differential currents of multiple coil pairs. In the third example, the detection voltage 1432 of the second coil pair is changing. The change in detection voltage 1432 is enclosed in 1436 for illustrative purposes. Since the amount of the coil pair with a change in detection voltage is less than a threshold amount, the detection device can determine that the change is the result of a foreign object introduced in close proximity to the detection coil of the second coil pair. The detection device may send a foreign object detection signal or control signal to the WPT system to stop wireless power transmission to prevent the foreign object from overheating.

[0075] Figure 15 shows a block diagram 1500 of an exemplary detection device configured to adapt the detection voltages of a coil pair based on the movement of a radio-powered device. Block diagram 1500 may illustrate the features of a control unit in a detection device having multiple coil pairs. The control unit may be configured to receive detection voltages 1511, 1512, 1513, and 1514 from the first, second, third, and fourth coil pairs, respectively. Each of the detection voltages may be acquired using different differential current sensing circuits associated with the coil pair. The detection voltages 1511, 1512, 1513, and 1514 may be adjusted using a set of offset values ​​1521, 1522, 1523, and 1524, respectively. Initially, the set of offset values ​​(collectively called offset value 1570) may be obtained based on the baseline calibration of the detection device. The absolute values ​​(magnitudes) of the detected voltages 1511, 1512, 1513, and 1514 may be determined by the components 1551, 1552, 1553, and 1554, respectively. The comparator 1560 may compare each adjusted detected voltage with a detection threshold 1565 to determine whether a foreign object is located near the detection coil of a particular coil pair. In some implementations, if any one of the detected voltages exceeds the detection threshold, the comparator may transmit an FOD signal 1580 indicating that a foreign object has been detected. Alternatively or additionally, the comparator may determine the amount by which the detected voltage has changed since the previous iteration of the foreign object detection procedure. For example, the comparator may determine a change count indicating how many detected voltages have changed. If the change count exceeds the change threshold, the comparator may determine that the change is the result of movement of the radio receiver and adjust the offset value 1570 for subsequent iterations of the foreign object detection procedure. Alternatively, if the change count falls below the change threshold, the FOD signal 1580 may be based solely on a comparison between each detected voltage and the detection threshold.

[0076] Figure 16 shows an illustrative diagram of a foreign object detection scanning region. In the first example 1601, the FOD scanning region 1632 may be based on the combined overlapping surface region of the primary coil 1610 and the secondary coil 1620. In some implementations, the FOD scanning region may be larger than the combined overlapping surface region, including any potential misalignment tolerance. For example, the first example shows several possible arrangements of the secondary coil within the misalignment tolerance. The FOD scanning region may have a threshold size larger than the potential region of the primary coil 1610 and the secondary coil 1620, taking into account the maximum allowable misalignment between the primary and secondary coils. In some implementations, the FOD scanning region may be a circular region with a diameter at least 10% larger than the potential region of the primary coil and the most misaligned secondary coil. For example, if the primary coil diameter is 210 mm, the secondary coil diameter is 235 mm, and the allowable misalignment tolerance is 50 mm, the FOD scanning area 1632 could be 358.5 mm (2 * ((235 / 2) + (0.1 * (235 / 2)) + (50))). The value of 358.5 mm for the FOD scanning area 1632 can be based on the largest of the primary and secondary coils. In this example, the secondary coil is larger (235 mm). This formula involves determining the diameter of the FOD scanning area 1632 by multiplying the sum of the secondary coil radius (235 / 2), 10% of the secondary coil radius (0.2 * 235), and the misalignment tolerance (50) by a value of 2. The illustrative calculation is provided for educational purposes only, and it should be understood that other calculations or formulas can be performed to determine the size of the FOD scanning area based on various power transmission coil sizes.

[0077] In the second example 1602, the detection device may utilize two FOD scanning regions: a first FOD scanning region 1612 associated with the primary coil and a second FOD scanning region 1622 associated with the secondary coil. The FOD scanning regions 1612 and 1622 may have threshold sizes at least larger than their respective power transmission coils (the primary and secondary coils, respectively). For example, the first FOD scanning region may have a diameter at least 10% larger than the diameter of the primary coil. The second FOD scanning region 1622 may have a diameter at least 10% larger than the diameter of the secondary coil. The opportunity to use two FOD scanning regions allows for the detection of foreign objects on the power transmission coils despite any potential misalignment. In some implementations, the first detection device may be used with the primary coil, and the second detection device may be used with the secondary coil.

[0078] Figure 17 shows a flowchart of an exemplary process 1700 for detecting metallic foreign objects, relating to several implementation configurations. The operation of process 1700 can be implemented by a detection device described herein. For example, the operation of process 1700 can be implemented by a detection device described with reference to Figures 2 to 16. The detection device may have a detection coil of any configuration and structure described herein. For brevity, the operation is described as being performed by the device. In block 1710, the device may simultaneously energize at least a first detection coil and a second detection coil during a first FOD period. In block 1720, the device may detect a first differential current associated with the first detection coil and the second detection coil during the FOD period by a differential current sensing device. In block 1730, the device may generate a foreign object detection signal based at least in part on the first differential current.

[0079] Figure 18 shows a block diagram of an exemplary device 1800 for use in a wireless power transmission system. In some implementations, device 1800 may be a detection device, such as one of the detection devices described herein. Device 1800 may include a processor 1802 (which may include multiple processors, multiple cores, multiple nodes, or multithreading, depending on the circumstances). Device 1800 may also include memory 1806. Memory 1806 may be one or more of system memory or possible implementations of computer-readable media described herein. Device 1800 may also include a bus 1811 (such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus®, AHB, AXI, etc.).

[0080] The device 1800 may include one or more controllers 1862 configured to manage the excitation of multiple detection coils (such as a coil array 1864). In some implementations, the controllers 1862 may be distributed within the processor 1802, memory 1806, and bus 1811. The controllers 1862 may perform some or all of the operations described herein. For example, the controllers 1862 may implement the features of the driver controller described herein.

[0081] Memory 1806 may contain computer instructions that can be executed by processor 1802 to implement the functions of the implementation configurations described with reference to Figures 1 to 17. Any of these functions may be partially (or entirely) implemented in hardware or on processor 1802. For example, the functions may be implemented by application-specific integrated circuits, logic implemented on processor 1802, peripheral devices, or coprocessors on cards. Furthermore, the implementation may include fewer or additional components not shown in Figure 18. Processor 1802, memory 1806, and controller 1862 may be coupled to bus 1811. Although shown as coupled to bus 1811, memory 1806 may be coupled to processor 1802.

[0082] Figures 1 to 18 and the operations described herein are examples intended to aid in understanding exemplary implementations and should not be used to limit potential implementations or the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in different orders, and several different operations.

[0083] The foregoing disclosures provide examples and explanations, but are not intended to be exhaustive or to limit the embodiments to the exact forms disclosed. Modifications and alterations may be made in light of the foregoing disclosures or obtained from the practice of embodiments. While embodiments of this disclosure have been described in relation to various examples, any combination of embodiments from any example is also within the scope of this disclosure. The examples of this disclosure are provided for educational purposes. Alternatively, or in addition to other examples described herein, the examples include any combination of the following implementation options:

[0084] One innovative aspect of the subject matter described herein can be implemented as a detection device for a wireless power transmission (WPT) system. The detection device may include a plurality of detection coils, including at least a first detection coil and a second detection coil. The detection device may include a first driver configured to simultaneously energize the first detection coil and the second detection coil during a first foreign object detection (FOD) period. The detection device may include a differential current sensing device configured to detect a first differential current associated with the first detection coil and the second detection coil during the FOD period. The detection device may include a control unit configured to generate a foreign object detection signal based on the first differential current.

[0085] In some implementations, the detection device may include a mat containing multiple detection coils. The mat may be configured for use in the interface space between a wireless power transmission device and a wireless power receiving device.

[0086] In some implementations, the first differential current is based on the difference between the first current of the first detection coil and the second current of the second detection coil during the FOD period.

[0087] In some implementations, the differential current sensing device includes at least a first magnetic core through which a first current from a first sensing coil passes in a first direction and a second current from a second sensing coil passes in a second direction, such that the difference between a first current and a second current generates a flux coupling in the first magnetic core that represents the first differential current.

[0088] In some implementations, the differential current sensing device further includes a first differential current sensing circuit, which includes a first sensor coil wound around a first magnetic core. The first magnetic core may be configured to induce a first electrical signal in the first sensor coil based on magnetic flux coupling. The magnitude of the induced voltage of the first electrical signal may be based on the magnitude of the first differential current.

[0089] In some implementations, the differential current sensing circuit further includes a rectifier configured to rectify a first electrical signal into a direct current (DC) signal having a first detection voltage. The differential current sensing circuit may also include a filter configured to stabilize the first detection voltage of the DC signal.

[0090] In some implementations, the control unit is configured to add or subtract a first offset to a first sense voltage in order to generate a first calibrated sense voltage.

[0091] In some implementations, the control unit is configured to compare the absolute value of a first calibrated detection voltage with a detection threshold. The foreign object detection signal may indicate the presence of a foreign object when the first calibrated detection voltage exceeds the detection threshold. The foreign object detection signal may indicate the absence of a foreign object when the first calibrated detection voltage falls below the detection threshold.

[0092] In some implementations, the foreign object detection signal may indicate the presence of a foreign object when the change in the first calibrated detection voltage exceeds a delta threshold. The foreign object detection signal may indicate the absence of a foreign object when the change in the first calibrated detection voltage falls below a delta threshold.

[0093] In some implementations, the first and second detection coils are located in their respective detection zones within the interface space of the WPT system.

[0094] In some implementations, the detection zones are arranged symmetrically with respect to either the primary coil or the secondary coil of the WPT system, or both.

[0095] In some implementations, the multiple detection coils include one or more coil pairs, each coil pair having at least two associated detection coils connected in parallel to the driver. The first coil pair may include a first detection coil and a second detection coil.

[0096] In some implementations, each coil pair is associated with at least two detection zones within the interface space of the WPT system.

[0097] In some implementations, one or more coil pairs include a first coil pair containing a first detection coil and a second detection coil in a first detection zone and a second detection zone, respectively. In some implementations, the detection device includes a second coil pair containing a third detection coil and a fourth detection coil in a third detection zone and a fourth detection zone, respectively.

[0098] In some implementations, one or more coil pairs further include a third coil pair, each containing a fifth detection coil and a sixth detection coil in a fifth detection zone and a sixth detection zone, respectively.

[0099] In some implementations, one or more coil pairs further include a fourth coil pair, each containing a seventh detection coil and an eighth detection coil in a seventh detection zone and an eighth detection zone, respectively.

[0100] In some implementations, the detection device may include a driver controller configured to control drivers associated with one or more coil pairs so that the drivers simultaneously energize at least two associated detection coils of each coil pair during each FOD period. A differential current detection device may be configured to detect the corresponding differential current associated with each coil pair during each FOD period. A control unit may be configured to generate a foreign object detection signal based on the corresponding differential current associated with each coil pair.

[0101] In some implementations, the driver controller is configured to energize one or more coil pairs in a continuous pattern to the driver, such that one coil pair is energized during each respective FOD period.

[0102] In some implementations, the driver controller is configured to cause the driver to energize one or more coil pairs in a predetermined pattern so that two or more coil pairs are energized during each FOD period. The two or more coil pairs within each FOD period may be located in non-adjacent detection zones.

[0103] In some implementations, the differential current sensing device includes multiple differential current sensing circuits configured to acquire multiple sensing voltages, each sensing voltage corresponding to the differential current of a respective coil pair. The multiple sensing voltages may include at least a first sensing voltage whose magnitude is based on a first differential current of a first coil pair, and a second sensing voltage whose magnitude is dependent on a second differential current of a second coil pair.

[0104] In some implementations, the control unit is configured to adjust multiple detection voltages based on a set of offset values. The set of offset values ​​may include at least a first offset value for a first detection voltage and a second offset value for a second detection voltage.

[0105] In some implementations, the set of offset values ​​is initially based on baseline measurements of the impedance difference between at least two associated sensing coils in each coil pair.

[0106] In some implementations, the control unit is configured to detect multiple changes in detection voltages over a successive FOD period for each detection voltage. The control unit may also be configured to determine a change count representing the amount of change in multiple detection voltages over a successive FOD period for each detection voltage.

[0107] In some implementations, the control unit is configured to determine, based on the change count, whether a change in multiple detected voltages was caused by movement of a wireless power receiver within the WPT system.

[0108] In some implementations, the control unit is configured to determine that if the change count is above a count threshold, the changes in multiple detected voltages are caused by the movement of the wireless power receiver. If the change count is below the count threshold, the control unit may determine that the changes in multiple detected voltages are due to the presence of a foreign object.

[0109] In some implementations, the control unit is configured to determine the ratio between the count of changes in multiple detected voltages and the total count. The control unit may be configured to determine that the changes in multiple detected voltages are due to the movement of the wireless power receiver if the ratio is greater than or equal to a ratio threshold. The control unit may determine that the changes in multiple detected voltages are due to the presence of a foreign object if the ratio is less than the ratio threshold.

[0110] In some implementations, the control unit is configured to change a set of offset values ​​based on the changes in multiple detected voltages if the control unit determines that the changes in multiple detected voltages were caused by the movement of a wireless power receiver within the WPT system.

[0111] In some implementations, the control unit is configured to continuously calibrate a set of offset values ​​to account for the movement of the wirelessly charged device within the WPT system.

[0112] In some implementations, multiple detection coils include detection coils of the same shape.

[0113] In some implementations, each of the at least two associated detection coils within each coil pair has a triangular or sectoral shape when multiple detection coils are arranged in the corresponding detection zone. Multiple detection coils may form a polygonal or circular FOD scanning area.

[0114] In some implementations, the multiple detection coils include one or more pairs of coils having a first shape and one or more other pairs of coils having a second shape.

[0115] In some implementations, the first shape is substantially trapezoidal or annular sector such that, when positioned in a corresponding detection zone, one or more coil pairs of the first shape form a portion of a polygonal or circular FOD scanning area excluding the central region of the FOD scanning area. The second shape may be substantially triangular or sectoral in combination with a polygon or sector such that, when positioned in a corresponding detection zone, one or more other coil pairs of the second shape complete a polygonal or circular FOD scanning area including the central region of the FOD scanning area.

[0116] In some implementations, the first and second detection coils of the first coil pair are configured to cover a triangular or sectoral portion of the FOD scanning area and the central region of the FOD scanning area. The remaining detection coils of the plurality of detection coils may cover a trapezoidal or annular sectoral portion such that the central region forms part of a polygonal or circular FOD scanning area associated with the first coil pair.

[0117] In some implementations, each detection coil in a set of multiple detection coils is larger than the size of the reference foreign object.

[0118] In some implementations, each detection coil in a set of multiple detection coils is large enough that a reference foreign object cannot simultaneously span three or more coil pairs.

[0119] In some implementations, each of the multiple detection coils is formed from sub-coils connected in series to form a single detection coil.

[0120] In some implementations, each subcoil is adjacent to one or more other subcoils to form the overall coverage area of ​​a single detection coil.

[0121] In some implementations, a single detection coil is configured such that adjacent subcoils are wound in opposite directions, thereby reducing the influence of the WPT system's primary magnetic field on the single detection coil.

[0122] In some implementations, each of the multiple detection coils includes a series capacitance configured to reduce the influence of the primary magnetic field of the WPT system.

[0123] In some implementations, multiple detection coils are made of Litz wire.

[0124] In some implementations, multiple detection coils are configured on a printed circuit board (PCB).

[0125] In some implementations, when multiple detection coils are excited, they operate at an FOD scanning frequency that exceeds the power transmission frequency of the WPT system.

[0126] In some implementations, the FOD scanning frequency is 200 kilohertz (kHz) or higher. The power transmission frequency of the WPT system may be 50 kHz or lower.

[0127] In some implementations, multiple detection coils are arranged to cover multiple detection zones. These multiple detection zones can form an FOD scanning area with a threshold size at least larger than the combined surface area of ​​the primary and secondary coils of the WPT system.

[0128] In some implementations, the threshold size is determined based on the larger of the two diameters of the primary and secondary coils.

[0129] In some implementations, the threshold size is based on the maximum secondary coil diameter supported by the WPT system.

[0130] In some implementations, the threshold size is at least 10% larger than the larger of the primary coil and the largest secondary coil supported by the WPT system.

[0131] In some implementations, the threshold size is further based on the maximum allowable misalignment between the primary and secondary coils before wireless power transmission is disabled.

[0132] In some implementations, multiple detection coils are arranged to cover multiple detection zones. These detection zones can be selectively enabled or disabled by the control unit to form a dynamic FOD scanning area.

[0133] In some implementations, the control unit is further configured to determine the dynamic FOD scanning area based on the potential combined surface area of ​​the primary and secondary coils of the WPT system.

[0134] In some implementations, the dynamic FOD scanning area is large enough to cover the maximum allowable misalignment between the primary and secondary coils, as well as additional adjacent surface areas.

[0135] In some implementations, the additional adjacent surface area makes the diameter of the dynamic FOD scanning area at least 10% larger than the maximum diameter in the primary and secondary coils supported by the WPT system, including the maximum misalignment tolerance.

[0136] In some implementations, a first subset of multiple detection coils is located on the wireless power transmission device of the WPT system, and a second subset of multiple detection coils is located on the wireless power receiving device of the WPT system.

[0137] Another innovative aspect of the subject matter described herein can be implemented as a detection device for a wireless power transmission (WPT) system. The detection device may include a plurality of detection coils arranged to form a foreign object detection (FOD) scanning area having a threshold size greater than the potential surface area of ​​a plurality of power transmission coils of the wireless power transmission (WPT) system. The detection device may include a control unit configured to generate a foreign object detection signal based on the detection of a foreign object within the FOD scanning area.

[0138] In some implementations, the multiple power transmission coils include a primary coil for the wireless power transmission device and a secondary coil for the wireless power receiving device. The threshold size may be determined based on the larger of the two coil diameters.

[0139] In some implementations, the threshold size is based on the maximum secondary coil diameter supported by the WPT system.

[0140] In some implementations, the threshold size is at least 10% larger than the larger of the primary coil and the largest secondary coil supported by the WPT system.

[0141] In some implementations, the threshold size is further based on the maximum misalignment tolerance that the WPT system allows between the primary and secondary coils.

[0142] In some implementations, a first subset of multiple detection coils is located on or within the wireless power transmission device of the WPT system, and a second subset of multiple detection coils is located on or within the wireless power receiving device of the WPT system.

[0143] Another innovative aspect of the subject matter described herein can be implemented as a system. The system includes a wireless power transmission device comprising at least one primary coil and a first plurality of detection coils arranged to form a first foreign object detection (FOD) scanning area which is at least a first size larger than the size of the primary coil. The system may include a wireless power receiving device comprising at least one secondary coil and a second plurality of detection coils arranged to form a second FOD scanning area which is at least a second size larger than the size of the secondary coil.

[0144] In some implementations, the first size of the first FOD scanning region is based on the diameter of the primary coil. The second size of the second FOD scanning region may be based on the diameter of the secondary coil.

[0145] In some implementations, the first size is at least 10% larger than the diameter of the primary coil, and the second size is at least 10% larger than the diameter of the secondary coil.

[0146] Another innovative aspect of the subject matter described herein can be implemented as a method for a detection device for use in a wireless power transmission (WPT) system. The method may include simultaneously exciting at least a first detection coil and a second detection coil during a first foreign object detection (FOD) period. The method may include detecting a first differential current associated with the first detection coil and the second detection coil during the FOD period using a differential current sensing device. The method may include generating a foreign object detection signal based on the first differential current.

[0147] In some implementations, the first differential current is based on the difference between the first current of the first detection coil and the second current of the second detection coil during the FOD period.

[0148] In some implementations, detecting a first differential current involves passing a first current from a first detection coil through the first magnetic core in a first direction and a second current from a second detection coil through the first magnetic core in a second direction, such that the difference between the first current and the second current generates a flux coupling in the first magnetic core that represents the first differential current.

[0149] In some implementations, the first magnetic core is configured to induce a first electrical signal in a first sensor coil based on magnetic flux coupling. The magnitude of the induced voltage of the first electrical signal may be based on the magnitude of the first differential current.

[0150] In some implementations, the method may include rectifying a first electrical signal into a direct current (DC) signal having a first detection voltage. The method may also include stabilizing the first detection voltage of the DC signal using a filter.

[0151] In some implementations, the method may include adding or subtracting a first offset to a first sense voltage in order to generate a first calibrated sense voltage.

[0152] In some implementations, the method may include determining a foreign object detection signal by comparing the absolute value of a first calibrated detection voltage with a detection threshold. The foreign object detection signal may indicate the presence of a foreign object when the first calibrated detection voltage exceeds the detection threshold. The foreign object detection signal may indicate the absence of a foreign object when the first calibrated detection voltage falls below the detection threshold.

[0153] In some implementations, the first and second detection coils are located in their respective detection zones within the interface space of the WPT system.

[0154] In some implementations, the detection zones are arranged symmetrically with respect to either the primary coil or the secondary coil of the WPT system, or both.

[0155] In some implementations, the detection device includes a plurality of detection coils organized as one or more coil pairs, each coil pair having at least two associated detection coils connected in parallel to a driver. A first coil pair may include a first detection coil and a second detection coil.

[0156] In some implementations, each coil pair is associated with at least two detection zones within the interface space of the WPT system.

[0157] In some implementations, the method may include simultaneously exciting at least two associated detection coils of each coil pair during each FOD period. The method may also include detecting the corresponding differential current associated with each coil pair during each FOD period. The method may also include generating a foreign object detection signal based on the corresponding differential current associated with each coil pair.

[0158] In some implementations, this method may include exciting one or more coil pairs in a continuous pattern such that one coil pair is excited during each respective FOD period.

[0159] In some implementations, the method may include exciting one or more coil pairs in a predetermined pattern such that two or more coil pairs are excited during each FOD period. The two or more coil pairs may be in detection zones that are not adjacent to each other during each FOD period.

[0160] In some implementations, the method may include obtaining multiple detection voltages using multiple differential current sensing circuits. Each detection voltage may correspond to the differential current of each coil pair. The multiple detection voltages may include at least a first detection voltage whose magnitude is based on the first differential current of the first coil pair, and a second detection voltage whose magnitude is dependent on the second differential current of the second coil pair.

[0161] In some implementations, the method may include adjusting multiple detection voltages based on a set of offset values. The set of offset values ​​may include at least a first offset value for a first detection voltage and a second offset value for a second detection voltage.

[0162] In some implementations, the set of offset values ​​is initially based on baseline measurements of the impedance difference between at least two associated sensing coils in each coil pair.

[0163] In some implementations, the method may include detecting changes in multiple detection voltages over consecutive FOD periods for each detection voltage. The method may also include determining a change count representing the amount of change in multiple detection voltages over consecutive FOD periods for each detection voltage.

[0164] In some implementations, the method may include determining, based on change counts, whether multiple changes in detected voltages were caused by movement of a wireless power receiver within the WPT system.

[0165] In some implementations, the method may include determining that multiple changes in detected voltages were caused by the movement of the wireless power receiver if the change count is greater than or equal to a count threshold. The method may also include determining that multiple changes in detected voltages were caused by the presence of a foreign object if the change count is less than or equal to a count threshold.

[0166] In some implementations, the method may include determining the ratio of the number of changes in multiple detected voltages to the total count. If the ratio is greater than or equal to a ratio threshold, the method may include determining that the changes in multiple detected voltages are due to the movement of the wireless power receiver. If the ratio is less than the ratio threshold, the method may include determining that the changes in multiple detected voltages are caused by the presence of a foreign object.

[0167] In some implementations, the method may include modifying a set of offset values ​​based on the changes in multiple detected voltages if the control unit determines that the changes in multiple detected voltages were caused by the movement of a wireless powered device within the WPT system.

[0168] In some implementations, this method may include continuously calibrating a set of offset values ​​to account for the movement of wireless power receivers within the WPT system.

[0169] The figures, operations, and components described herein are examples intended to aid in understanding exemplary implementations and should not be used to limit potential implementations or the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in different sequences, and several different operations.

[0170] As used herein, the phrases “at least one of” or “one or more of” the list of items refer to any combination of those items, including a single member. For example, “at least one of a, b, or c” is intended to cover the possibilities of a only, b only, c only, a and b combination, a and c combination, b and c combination, and a, b, and c combination.

[0171] The various exemplary components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in relation to the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware, or software, including the structures disclosed herein and their structural equivalents. Hardware, firmware, and software compatibility is generally described with respect to functionality and is shown in the various exemplary components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0172] Hardware and data processing devices used to implement the various exemplary components, logic, logic blocks, modules, and circuits described in relation to the embodiments disclosed herein may be implemented or run using general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices (PLDs), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. In some implementations, specific processes, operations, and methods may be performed by circuits specific to a given function.

[0173] As described above, some aspects of the subject matter described herein can be implemented as software. For example, various functions of the components disclosed herein, or various blocks or steps of the methods, operations, processes, or algorithms disclosed herein, can be implemented as one or more modules of one or more computer programs. Such computer programs may include non-temporary processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by or control of a data processing device including the components of the devices described herein. Such storage media may include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other media that can be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0174] Various modifications to the implementations described herein will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Accordingly, the claims are not intended to be limited to the implementations shown herein, but should be given the broadest scope that is consistent with the disclosures, principles, and novel features disclosed herein.

[0175] Furthermore, various features described herein in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented separately or in any suitable subcombination in multiple implementations. Thus, features are described above as acting in a particular combination and may initially be claimed as such, but one or more features from the claimed combination may, in some cases, be removed from that combination, and the claimed combination may cover a partial combination or a variation of a partial combination.

[0176] Similarly, while actions are shown in a specific order in the diagrams, this should not be understood as requiring that such actions be performed in a specific order or sequentially, or that all shown actions be performed, in order to achieve the desired result. Furthermore, the diagrams may schematically represent one or more exemplary processes in the form of flowcharts or flow charts. However, other actions not illustrated can be incorporated into the schematicly represented exemplary processes. For example, one or more additional actions can be performed before, after, simultaneously with, or in between any of the illustrated actions. In some situations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementation forms described above should not be understood as requiring such separation in all implementation forms, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged in multiple software products.

Claims

1. A detection device for foreign object detection (FOD), A plurality of detection coils that collectively form an FOD scanning region, wherein the plurality of detection coils are arranged as pairs of detection coils symmetrically positioned with respect to the primary coil of a wireless power transmission device, and each pair of detection coils includes two detection coils that have the same shape as each other and have the same or similar impedance when no foreign matter is present, One or more sensors configured to detect the differential current associated with the two detection coils of each detection coil pair when the two detection coils of each detection coil pair are simultaneously excited by the same voltage, A control unit configured to detect the presence of a foreign object based on one or more of the differential currents exceeding a differential current threshold, A detection device equipped with the following features.

2. The detection device according to claim 1, wherein each pair of detection coils is associated with at least two detection zones in the FOD scanning region.

3. The aforementioned pair of detection coils A first detection coil pair, including a first detection coil (L1) and a second detection coil (L2) in the first detection zone and the second detection zone, A second pair of detection coils, each including a third detection coil (L3) and a fourth detection coil (L4) in the third and fourth detection zones, A third pair of detection coils, each including a fifth detection coil (L5) and a sixth detection coil (L6) in the fifth and sixth detection zones, respectively. A fourth pair of detection coils, each including a seventh detection coil (L7) and an eighth detection coil (L8) in the seventh and eighth detection zones, respectively. The detection device according to claim 2, including the following:

4. The detection device according to claim 1, wherein the plurality of detection coils collectively form a polygon or a circle so as to cover the FOD scanning area.

5. The detection device according to claim 4, wherein each of the plurality of detection coils has a triangular or sector shape.

6. The detection device according to claim 4, wherein the plurality of detection coils include one or more pairs of detection coils having a first shape and one or more other pairs of detection coils having a second shape.

7. The first shape is substantially trapezoidal or annular sector, such that when the first shape is placed in the corresponding detection zone, the detection coil of the first shape forms part of a polygonal or circular region excluding the central region of the FOD scanning area. The second shape is substantially triangular or sector-shaped, combined with a polygon or sector, such that when the second shape is positioned in the corresponding detection zone, the detection coil of the second shape completes the polygonal or circular region and forms the central region of the FOD scanning area. The detection device according to claim 6.

8. The detection device according to claim 1, wherein each of the plurality of detection coils is larger than the size of a reference foreign object.

9. The detection device according to claim 1, wherein each of the plurality of detection coils is large enough that a reference foreign object cannot simultaneously span three or more pairs of detection coils.

10. The detection device according to claim 1, wherein each of the plurality of detection coils is formed from sub-coils connected in series to form a single detection coil.

11. The detection device according to claim 10, wherein each subcoil is adjacent to one or more other subcoils to form the overall coverage area of ​​the single detection coil.

12. The detection device according to claim 10, wherein the single detection coil is configured such that adjacent sub-coils are wound in opposite directions, thereby reducing the influence of the primary magnetic field of the wireless power transmission device on the single detection coil.

13. The detection device according to claim 1, wherein each of the plurality of detection coils includes a series capacitance configured to reduce the influence of the primary magnetic field of the wireless power transmission device on each detection coil.

14. The detection device according to claim 1, wherein the plurality of detection coils are configured on a printed circuit board (PCB) or using Litz wire.

15. The driver further comprises one or more drivers configured to excite the detection coil pair at an excitation frequency exceeding the power transmission frequency, The excitation frequency is 200 kilohertz (kHz) or higher. The detection device according to claim 1.

16. A foreign object detection (FOD) system, The FOD mat includes multiple detection coils associated with multiple corresponding detection zones within the FOD scanning area, The plurality of detection coils are arranged as detection coil pairs that are symmetrically positioned with respect to the primary coil of the wireless power transmission device, and each detection coil pair includes at least a first detection coil pair and a second detection coil pair. The first detection coil pair comprises two detection coils having the same first shape as each other, and the first detection coil pair forms a part of the FOD scanning region excluding the central region of the FOD scanning region. The second detection coil pair comprises two other detection coils having the same second shape as each other, and the second detection coil pair forms another portion of the FOD scanning region, including the central region of the FOD scanning region. The plurality of detection coils collectively form the FOD scanning region. Foreign object detection system.

17. The first shape is substantially trapezoidal or annular sector, The second shape is substantially a triangle or sector combined with a polygon or sector so as to include the central region. The foreign object detection system according to claim 16.

18. The foreign object detection system according to claim 16, wherein the first shape and the second shape are designed to reduce the concentration of detection coils in the central region of the FOD scanning area.

19. Each of the detection coils of the plurality of detection coils A plurality of subcoils connected in series, wherein each subcoil is positioned adjacent to one or more other subcoils, and adjacent subcoils are wound in opposite directions, A series capacitance configured to reduce the influence of the primary magnetic field of the wireless power transmission device on each detection coil, A foreign object detection system according to claim 16, including the above.

20. One or more sensors configured to detect the differential current associated with the two detection coils of each detection coil pair when the two detection coils of each detection coil pair are simultaneously excited by the same voltage, A control unit configured to detect the presence of a foreign object based on one or more of the differential currents exceeding a differential current threshold, The foreign object detection system according to claim 16, further comprising:

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