Apparatus, system and method for detecting foreign matter

Abstract

Devices, systems, and methods for detecting foreign matter are disclosed. A detection device (100) includes a detection pad (102) having a plurality of detection coils (106) and at least one pair of detection coil groups (106), the pair of detection coil groups (106) including a first detection coil group (106) and a second detection coil group (106). The first detection coil set (106) and the second detection coil set (106) comprise a first impedance value and a second impedance value. The detection device (100) comprises one or more drive subsystems (112) and a comparison subsystem (112). The drive subsystem (112) is operably coupled to the detection pad (102) and is configured to energize the at least one pair of detection coil sets (106).

Description

[0001] This application is a divisional application of the Chinese national stage application of the PCT application with the filing date of April 17, 2019, international application number PCT / US2019 / 027789, and invention title "Devices, Systems, and Methods for Detecting Foreign Objects". The entry date of this Chinese national stage application into the Chinese national stage is October 15, 2020, and the application number is 201980026147.9. Technical Field

[0002] Embodiments of this specification relate to a detection device, and more particularly, embodiments of this specification relate to a detection device for detecting foreign objects in the operating environment of a system. Background Art

[0003] Traditional wireless power transfer (WPT) systems wirelessly transfer electrical energy from one device to another based on the principle of inductive power transfer. Generally, in a WPT system, a main power device (e.g., a transmitter) wirelessly transfers power to a slave power device called a receiver. The transmitter and the receiver include corresponding coils that are disposed in proximity during the operation of the WPT system. When current passes through the transmitter coil, the generated magnetic field induces an electromotive force in the receiver coil, thereby wirelessly transferring power from the transmitter to the receiver.

[0004] In such a WPT system, if there is any metal object, such as a metal can or aluminum foil, between the transmitter and receiver coils during wireless power transfer, the metal object may be undesirably heated due to eddy currents. This can lead to safety hazards, such as fire safety hazards. In addition, the efficiency of the wireless power transfer process may be inadvertently affected, or the entire process may be completely interrupted.

[0005] There are various different methods for detecting foreign objects in a WPT system. These include detecting the presence of foreign objects by a change in the current frequency in the primary coil, detecting the unbalanced difference between the current and voltage in the primary coil based on the measurement of the power drawn from the primary coil, etc. In addition, in some detection methods, there may be some delay in detecting foreign objects after starting wireless power transfer. During this period, the foreign object continues to draw power, resulting in power waste. Summary of the Invention

[0006] In one embodiment, the detection device includes a detection pad having a plurality of detection coils and at least a pair of detection coil groups, wherein the pair of detection coil groups includes a first detection coil group and a second detection coil group. The first detection coil group includes a first impedance value, and the second detection coil group includes a second impedance value. Additionally, the detection device includes one or more drive subsystems and a comparison subsystem. The drive subsystem is operably coupled to the detection pad and is configured to excite at least the pair of detection coil groups. The comparison subsystem is operably coupled to the detection pad and is configured to receive differential current signals from at least the pair of detection coil groups, wherein the comparison subsystem is configured to generate a control signal based on the differential current signals.

[0007] In another embodiment, the detection system includes a detection device and a wireless power transfer (WPT) system. The detection device includes a detection pad having a plurality of detection coils and at least a pair of detection coil groups, wherein the pair of detection coil groups includes a first detection coil group and a second detection coil group. The first detection coil group includes a first impedance value, and the second detection coil group includes a second impedance value. Additionally, the detection device includes one or more drive subsystems and a comparison subsystem. The drive subsystem is operably coupled to the detection pad and is configured to excite at least the pair of detection coil groups. The comparison subsystem is operably coupled to the detection pad and is configured to receive differential current signals from at least the pair of detection coil groups, wherein the comparison subsystem is configured to generate a control signal based on the differential current signals. The WPT system includes a main power supply configured to supply power in the form of an alternating current (AC) voltage signal. The WPT system further includes a transmitter unit having at least one transmitter coil, wherein the transmitter unit is configured to receive the AC voltage signal from the main power supply. Additionally, the transmitter unit is configured to generate a main magnetic field in response to the received AC voltage signal, and wherein the detection pad is operably coupled to the transmitter unit. The WPT system further includes a receiver unit that includes at least one receiver coil and is configured to receive at least a portion of the main magnetic field generated by the transmitter unit. Additionally, the WPT system includes a control unit that is operably coupled to the detection device and is configured to receive the control signal from the detection device and control the power supply to the transmitter unit based on the control signal.

[0008] In yet another embodiment, a method includes utilizing a detection device that includes a detection pad having a plurality of detection coils and at least a pair of detection coil groups, wherein the pair of detection coil groups includes a first detection coil group and a second detection coil group. The first detection coil group includes a first impedance value, and the second detection coil group includes a second impedance value. The method further includes exciting at least the pair of detection coil groups and determining differential current signals from at least the pair of detection coil groups. Additionally, the method includes generating a control signal based on the differential current signals and transmitting the control signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features and aspects of embodiments of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout all the figures, wherein:

[0010] Figure 1 is a schematic diagram of an example detection device for detecting the presence of foreign objects according to aspects of the present specification;

[0011] Figures 2A to 2B is a graphical representation of an example pair of detection coil sets according to aspects of the present specification;

[0012] Figures 3A to 3B is a graphical representation of a portion of a detection device including a pair of detection coil sets coupled to a drive subsystem according to aspects of the present specification;

[0013] Figures 3C to 3E is a schematic representation of a portion of a detection device having one or more drive subsystems coupled to several pairs of detection coil sets according to aspects of the present specification;

[0014] Figure 4 is a graphical representation of an example detection system having a detection device for detecting the presence of foreign objects in the operating environment of a WPT system according to aspects of the present specification;

[0015] Figure 5 is a graphical representation of an example comparison subsystem of a detection device according to aspects of the present specification;

[0016] Figures 6 to 7 is an example method for detecting the presence of foreign objects in the operating environment of a WPT system according to aspects of the present specification; and

[0017] Figure 8 is a cross-sectional view of a detection pad according to aspects of the present specification. DETAILED DESCRIPTION

[0018] Embodiments of the present specification relate to detection devices, detection systems, and methods for detecting foreign objects. In certain embodiments, the detection device can be used to detect foreign objects in a wireless power transfer (WPT) system. As used herein, the term "foreign object" refers to an electrically conductive or magnetically permeable object that is not part of the system but is inadvertently present in the operating environment of the system. Non-limiting examples of foreign objects can include iron-containing objects, tin cans, or other conductive or iron-containing objects. In one example, in the operating environment of a WPT system, a can or a bunch of keys is considered a foreign object.

[0019] As used herein, the term "main magnetic field" refers to the magnetic field induced by a transmitter unit (e.g., the transmitting unit of a WPT system). The term "operating environment" is defined by the main magnetic field in the system, where the main magnetic field of the transmitter unit is detectably present and detectably interacts with foreign objects. For example, a foreign object present in the operating environment of a WPT system may experience a temperature increase due to its interaction with the main magnetic field.

[0020] As used herein, the term "detection coil set" refers to a single detection coil or two or more coils, where each individual set of detection coils is electrically coupled to each other. Additionally, the term "pair of detection coil sets" refers to two such detection coil sets.

[0021] Some electric vehicles (EVs) and hybrid vehicles use WPT systems for charging via wireless power transfer or inductive power transfer. A WPT system mainly consists of two parts, namely, a transmitter that is part of a charging station and a receiver that is installed in an electric vehicle (EV). The transmitter unit of the charging station is inductively coupled to the receiver unit of the EV. Generally, when the receiver coil of the EV is introduced into the operating environment of the transmitter coil and starts to supply power to the transmitter unit, power transfer begins between the coils of the transmitter and receiver units.

[0022] When a foreign object made of a conductive material or an iron-containing material is inadvertently placed in the operating environment of a WPT, the foreign object may interact with the magnetic field generated by the transmitter unit. As a result, the foreign object may inadvertently intercept the magnetic field and draw power from the transmitter unit via the magnetic field. Thus, the power drawn by the foreign object results in power waste and undesired heating of the foreign object. If not dealt with promptly, or if not noticed, the temperature of the foreign object may rise to a value that may make the foreign object unsafe to handle and may also pose a safety risk. Therefore, it is desirable to detect the presence of foreign objects to prevent power waste and avoid the risk of an unsafe environment.

[0023] Figure 1 A detection device 100 having a detection pad 102 is shown, the detection pad 102 having a plurality of detection coils 106 and at least one pair ( Figure 1The detection coil group 106 (not shown in the figure) is detected. At least one pair of detection coil groups 106 includes a first detection coil group 106 and a second detection coil group 106. Among them, the first detection coil group 106 has a first impedance value, and the second detection coil group 106 has a second impedance value. The detection device 100 further includes one or more drive subsystems 112, which are operatively coupled to the detection pad 102 and are configured to excite at least one pair of detection coil groups 106. In addition, the detection device 100 includes a comparison subsystem 114, which is operatively coupled to the detection pad 102 and is configured to receive a differential current signal from at least one pair of detection coil groups 106. The comparison subsystem 114 is configured to generate a control signal based on the differential current signal.

[0024] In some embodiments, the detection device 100 is configured to detect the presence of foreign objects in the operating environment of a wireless power transfer (WPT) system ( Figure 1 not shown in the figure). The presence of foreign objects in the operating environment of the WPT system may cause a change in the impedance value of one or more detection coils 106. This change in the impedance value of the detection coil 106 is used to determine the presence of foreign objects. Reference will be made to Figures 2A to 2B and Figures 3A to 3B to explain the detection coil group 106 in more detail.

[0025] In addition, the detection pad 102 may include several geometric positions, also referred to as "detection zones" 104. The detection zone 104 defines a discrete area of the detection pad 102, where each detection zone 104 includes one or more detection coil groups 106. It can be noted that the detection zones 104 may not be physically separated or insulated from each other, and the detection zones 104 may be electrically insulated from each other. In addition, the detection zones 104 may have geometric or non-geometric shapes.

[0026] The detection pad 102 can be a flexible pad, a conformable pad, a rigid pad, or a plug-and-play pad, a stand-alone pad, or a combination thereof. It can be noted that the surface area of the detection pad 102 can be greater than or equal to the surface area of the transmitter unit on which the detection pad 102 is provided. The substrate of the detection pad 102 can be made of an electrically insulating material. The detection pad 102 can also include a mechanically wear-resistant material to withstand the movement of the electric vehicle thereon. The detection pad 102 can be further designed for outdoor applications and is designed to withstand temperature, humidity, and be waterproof.

[0027] In some embodiments, for the safety and aesthetics of the user, the detection coil 106 can be disposed on the substrate of the detection pad 102, or can be embedded in the substrate of the detection pad 102. In some other embodiments, the detection coil 106 can be printed, molded, woven, or otherwise manufactured on the substrate of the detection pad 102.

[0028] The detection coil 106 is an electromagnetic coil. In Figure 1In the illustrated embodiment, the sense coils 106 are for representative purposes and it may be noted that each sense coil 106 may include a spiral or other coil topology. Additionally, each sense region 104 may have one or more sense coils 106. In some embodiments, the sense coil sets 106 may include various coil topologies, shapes, and geometric arrangements of sense coils 106. Non-limiting examples of the shape of the sense coils 106 may include spiral coils, helical coils, non-circular coils, etc. The different sense coils 106 or sense coil sets 106 present on the sense pad 102 may have the same or different impedance values.

[0029] Each pair of sense coil sets 106 includes two sets disposed at the same or different geometric locations on the sense pad 102 to form the pair of sense coil sets 106. By way of example, the two sets in the pair may be disposed in the same sense region 104 or may be disposed in two different sense regions 104. In a non-limiting example, each sense coil set 106 may include concentric coils, adjacent coils, or coils arranged side by side. Additionally, one or more sense coil sets 106 may be disposed in a single plane or in two or more layers. The sense coils 106 in a sense coil set 106 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0030] In some embodiments, a pair of sense coil sets 106 includes concentric coils. In a non-limiting example, the inductance value of one of the two concentric coils is different from the inductance value of the other concentric coil. By way of example, while the inductance value of one concentric coil in the pair of concentric coils may be represented by L, the inductance value of the other concentric coil in the pair of concentric coils may be represented by nL.

[0031] The drive subsystem 112 includes one or more drive units and a drive controller. The drive subsystem 112 is operatively coupled to the sense pad 102 and is configured to excite one or more pairs of sense coil sets 106. The drive subsystem 112 may be configured to intermittently or periodically excite a determined sense coil set 106 of the detection device 100, where the determined sense coil set forms one or more pairs of sense coil sets 106. The drive subsystem 112 may be configured to excite pairs of sense coil sets 106 belonging to the same or different sense regions 104. In some embodiments, the drive subsystem 112 may be configured to excite sense coil sets 106 that are symmetrically positioned with respect to the primary magnetic field ( Figure 1 not shown) of the WPT system.

[0032] In one example, the drive subsystem 112 can be configured to energize the groups in a pair of detection coil sets 106 simultaneously or sequentially. Additionally or alternatively, the drive subsystem 112 can be configured to energize two or more pairs of detection coil sets 106 of the detection pad 102 simultaneously or sequentially. In one example, the drive subsystem 112 can be configured to scan the detection pad 102 to look for the presence of foreign objects. The detection of the presence of foreign objects can be completed before the start of wireless power transfer of a device (e.g., an EV). Additionally, the detection of the presence of foreign objects can also be performed periodically or intermittently during the wireless power transfer of the device (e.g., an EV).

[0033] As will be described in reference to Figures 3A to 3E the detailed description, in one example, each pair of detection coil sets 106 can be coupled to a corresponding drive subsystem, and in another example, two or more pairs of detection coil sets 106 can be coupled to different drive units sharing a common drive controller.

[0034] In some embodiments, the drive units of the drive subsystem 112 are configured to provide voltage signals to one or more detection coil sets 106, and the drive controller is configured to control the operation of the drive units. To this end, the drive controller turns on the drive subsystem 112 to energize one or more detection coil sets 106 and turns off the drive subsystem 112 when the detection coil sets 106 do not need to be energized. In certain embodiments, the drive subsystem 112 includes one or more of an inverter, a converter, a linear amplifier, an electronic switch, or a combination thereof. The switching of the drive subsystem 112 can be performed by an electronic switch, e.g., a bidirectional switch, a semiconductor switch, a mechanical switch, e.g., a relay, a contractor, or a combination thereof. In certain embodiments, the drive subsystem 112 can draw power from a main power source configured to power the transmitter unit of the WPT system. Optionally, the drive subsystem 112 can have a separate power source, such as but not limited to a battery.

[0035] It can be noted that in operation, if present on the detection pad 102, a foreign object can inductively couple to one or more detection coils 106, thereby affecting the combined impedance value of those particular groups of detection coils 106. Additionally, it can be noted that in the absence of a foreign object, the inherent impedance values of different detection coil sets 106 of the detection device 100 can be the same or different. Additionally, in the absence of a foreign object, the inherent impedance values of the two sets of a pair of detection coil sets 106 can be the same or different. In some of these embodiments, the detection pad 102 further includes a compensator element( Figure 1(not shown in the figure), the compensator element is operably coupled to at least one of a pair of detection coil sets 106 to provide similar synthetic impedance values from each of the two sets of the pair of detection coil sets 106 in the absence of foreign objects. In some other embodiments, a drive controller may be used to provide voltage compensation for one of the pair of detection coil sets 106. For example, the drive controller of the drive subsystem 112 provides different voltage signals to the two sets of the pair of detection coil sets 106 such that in the absence of foreign objects, the two sets of the pair of detection coil sets 106 are driven by the same current with similar amplitude and phase.

[0036] The comparison subsystem 114 is operably coupled to the detection pad 102 and is configured to receive one or more differential current signals from the detection pad 102. The comparison subsystem 114 is configured to determine a detection voltage signal based on the differential current signals. It can be noted that the value of the differential current signal may be very small and undetectable in the absence of foreign objects. Additionally, due to the inductive coupling between the foreign object and one or more detection coils 106, the value of the differential current signal can be a detectable non-zero value in the presence of foreign objects.

[0037] The detection device 100 can be an independent device that can be used to detect the presence of foreign objects in a system, such as but not limited to a WPT system. For this purpose, the detection device 100 can be used with an existing WPT system to detect the presence of foreign objects before and / or during wireless power transfer. In addition to the detection pad 102, the drive subsystem 112, and the comparison subsystem 114, the detection device 100 may further include a communication unit ( Figure 1 (not shown in the figure), which enables the detection device 100 to communicate with the system using it. For example, the communication unit can enable the detection device 100 to communicate with the WPT system according to the Society of Automotive Engineers (SAE) standard. The communication unit can be used to transmit the detection voltage signal to the control unit of the WPT system to evaluate whether to continue powering the transmitter unit of the WPT system.

[0038] Advantageously, the detection device 100 of the present technology is configured to detect the presence of even relatively small foreign objects in the operating environment of the WPT system. In one example, the foreign object can have a surface area of 2 square centimeters or larger.

[0039] Now refer to Figures 2A to 2B , in certain embodiments, one or more pairs of detection coil sets of the detection device can be excited to determine the differential current signal from the detection pad, where the differential current signal is used to determine the presence or absence of foreign objects. It can be noted that each of the two separate sets of the pair of detection coils can include one or more detection coils.

[0040] In some embodiments, the first and second sets of a pair of detection coil sets are symmetrically arranged with respect to the main magnetic field. Additionally, the first and second sets of the pair of detection coil sets are arranged in the same geometric region on the detection pad. In some embodiments, the first and second sets of the pair of detection coil sets include structurally similar arrangements of detection coils. Further, in certain embodiments, in the absence of foreign objects in the operating environment of the WPT system, the first impedance value and the second impedance value of the sets of the pair of detection coil sets are similar. As used herein, similar impedance values refer to impedance values that vary from each other by less than or equal to 0.5%. By way of example, the impedance value of the first set can be within -0.5% of the impedance value of the second set, where the first and second sets form a pair of detection coil sets.

[0041] In some other embodiments, in the absence of foreign objects, the first impedance value and the second impedance value are different. In some embodiments of these embodiments, the detection pad can include a compensator element that is operably coupled to one of the first and second sets of the pair of detection coil sets to compensate for the difference in the impedance values of the first detection coil set and the second detection coil set 106. In some embodiments, in the absence of foreign objects, the first impedance value and the second impedance value are different, and wherein one or more drive subsystems further include a drive controller configured to provide different voltage signals to the first detection coil set and the second detection coil set such that, in the absence of foreign objects, the first and second sets of the pair of detection coil sets are driven by the same current having similar amplitude and phase.

[0042] As will be referenced Figure 2A and described, the detection coils of a particular pair of detection coil sets are symmetrically arranged with respect to the main magnetic field and thus are subjected to a main magnetic field of similar intensity. As will be referenced Figure 2B and described, the sets of a pair of detection coil sets can be arranged in the same geometric region of the detection pad and thus these sets can be subjected to a main magnetic field of similar intensity. In some embodiments, in the absence of foreign objects in the operating environment of the WPT system, each of the sets of the pair of detection coil sets includes the same impedance value. In some other embodiments, the two sets of the pair of detection coil sets have different impedance values. In these embodiments, the two sets of a pair of detection coils can provide a negligible and non-detectable differential current amount either in association with a compensator element or with the aid of a drive controller. However, in the presence of a foreign object, it is provided when one or more detection coils in one of the sets belonging to the pair of detection coil sets are electrically coupled to the foreign object and change the net impedance of that set of detection coils, which results in a difference in the currents drawn by the two sets of the pair of detection coil sets. Thus, the differential current reaches a detectable value, which is the difference between the input current of one of the two sets of the pair and the input current of the other set of the pair of detection coil sets.

[0043] Figure 2A An exemplary detection pad 200 having a plurality of detection zones 202 is shown, and the detection zones 202 have groups 204 of detection coils 205. In the non - limiting exemplary embodiment shown, the detection pad 200 is shown as having a 4×4 array of detection zones 202, and each detection zone 202 is shown as having 4 groups 204 of detection coils 205. However, it can be noted that the number of detection zones 202 in the detection pad 200 and the number of groups 204 in each detection zone 202 can vary and are for illustrative purposes only. Further, although the detection pad 200 is shown as having 16 detection zones 202 in the example shown, it can be noted that the number of detection zones 202 in a detection pad (e.g., detection pad 200) can be one or more. Further, each group 204 can include one or more detection coils 205. Further, the helical shape of the detection coils 205 of the group 204 is for illustrative purposes, and the detection coils 205 can be of various shapes such as, but not limited to, circular, non - circular, coiled, helical, or combinations thereof. The detection pad 200 can be disposed on a transmitter unit ( Figure 2A not shown). Further, the dashed - line circle 206 represents the transmitter coil of the transmitter unit disposed below the detection pad 200.

[0044] Any two groups 204 of detection coils can be subjected to a main magnetic field of similar intensity and can be paired to form a pair of detection coil groups for detecting the presence of foreign objects. Several plausible pairs of the groups 204 of detection coils 205 are denoted by n - n'. For example, the group 204 denoted by the reference numeral 208 is symmetrically disposed with respect to the main magnetic field of the transmitter coil 206 or the transmitter unit and forms a pair 212 of detection coil groups 208. Similarly, the group 210 is symmetrically disposed with respect to the main magnetic field of the transmitter unit and forms another pair 214 of detection coil groups 210. It can be noted that in addition to 212, 214, n - n', other pairs of the groups 204 of detection coils 205 are possible.

[0045] In certain embodiments, when the detection pad 200 is disposed on the transmitter unit, one or more pairs of the groups 204 of detection coils 205 can be excited to detect the presence of foreign objects in the operating environment of a WPT system ( Figure 2A not shown). For example, one of the two pairs 212 or 214 can be excited by a drive subsystem. Further, in the case where the impedance values of the two groups in a pair are different, a compensator element 218 can be operatively coupled to at least one of the groups 204 of a pair of detection coils 205 to provide similar combined impedance values from each of the two groups 204 of a pair of detection coil groups 205 in the absence of foreign objects.

[0046] Figure 2BDenotes a detection pad 220 having a plurality of detection zones 224, the detection zones 224 having two or more detection coils 222. The detection device 220 may be disposed on a transmitter unit ( Figure 2B not shown in the figure). In the illustrated embodiment, the dashed circle 225 represents the transmitter coil of the transmitter unit disposed below the detection device 220. In addition, each zone 224 includes a plurality of sets of concentric detection coils 222 disposed in each detection zone 224. It can be noted that within the scope of the present application, it is conceivable that each zone 224 has a greater number of detection coils 222 or detection coils 222 having different shapes and geometries, and Figure 2B the illustrated embodiment is a representative embodiment presented for illustrative purposes only. Sets 228 and 230 of a pair 226 of detection coils 222 are formed in the manner shown. The respective sets 228 and 230 are disposed in the same geometric region such that the detection coils 222 of the sets 228 and 230 experience a main magnetic field of similar intensity.

[0047] Figure 3A A portion 300 of the detection device of the present specification is shown. The portion 300 includes sets 304 and 306 of a pair 302 of detection coils 308 disposed on the detection pad of the detection device. In the presently contemplated embodiment, both sets 304 and 306 of detection coils 308 are excited by a single drive subsystem 310. The drive subsystem 310 includes a drive unit 311 and a drive controller 314. In addition, a single drive unit 311 of the drive subsystem 310 is used to excite the sets 304 and 306 of detection coils 308. The drive unit 311 includes an inverter / converter 312, capacitors 309 and 311, one or more compensator elements 315 and 317. It can be noted that the capacitance values of the capacitors 309 and 311 may be fixed or variable. The drive controller 314 of the drive subsystem 310 is configured to control the excitation voltage of the two sets 304 and 306 of detection coils 308. As shown, the detection coils 308 within each of the sets 304 and 306 may be coupled to each other in series, in parallel, or a combination of both. The capacitors 309 and 311 are coupled to the sets 304 and 306 and form a resonant circuit with the detection coils 308 of the sets 304 and 306. The capacitors 309 and 311 help to regulate the current driven in the detection coils 308 and thus change the magnetic field strength for detecting foreign objects on the detection pad of the detection device.

[0048] One or more detection coils 308 in the vicinity of a foreign object can be electromagnetically coupled to the foreign object, and this inductive coupling can cause a change in the value of the current drawn by the detection coils 308. In one embodiment, in the absence of a foreign object, two sets 304 and 306 of a pair 302 of detection coils 308 can have detectable similar impedance values. To detect the presence of a foreign object, a differential current signal for the pair 302 is calculated based on the return current signal I1 318 of set 304 and the ongoing current signal I2 320 of set 306, and vice versa. In another embodiment, wherein, in the absence of a foreign object, the two sets 304 and 306 have detectable different impedances, one or more compensator elements 315 and 317 are used to ensure that the currents drawn by the two sets are similar in the absence of a foreign object. Non-limiting examples of the compensator elements 315 and 317 can include inductors, resistors, capacitors in series or parallel or both.

[0049] Figure 3B Another embodiment is shown, wherein a portion 330 of the detection device of this specification includes a pair 332 of a first set 334 and a second set 336 of detection coils 338 disposed on a detection pad of the detection device. The two sets 334 and 336 are coupled to a drive subsystem 340. The drive subsystem 340 includes two drive units 342 and 344, which are configured to excite the first set 334 and the second set 336, respectively. The two drive units 342 and 344 include inverters 348 and 350, DC / DC converters 352 and 354, and capacitors 333 and 335. Although not shown, one or both of the drive units 342 and 244 can also include one or more compensator elements. The capacitors 333 and 335 coupled to the sets 334 and 336 form a resonant circuit with the detection coils 338 of the sets 334 and 336 and help regulate the current driven in the coils, thereby regulating the magnetic field strength in the detection pad. The inverters 348 and 350 receive inputs from the two DC / DC converters 352 and 354 that drive the two sets 334 and 336, wherein, in the absence of a foreign object, the two sets 334 and 336 can have similar or different impedance values.

[0050] The drive subsystem 340 also includes a drive controller 346 that can be configured to compensate for any differences in the current values of the first set 334 and the second set 336, regardless of the differences in the impedance values of the first set 334 and the second set 336. In embodiments where the sets 334 and 336 have different impedance values, the drive controller 346 can be configured to adjust the current used to drive the two sets 334 and 336 by one or more methods. In one embodiment, the drive controller 346 can be configured to change the voltage signals V1 and V2 of the inverters 348 and 350 by controlling the DC / DC stage converters 352 and 354. In another embodiment, the duty cycles of the inverters 348 and 350 can be changed without changing the operating frequency of the inverters 348 and 350 such that in the absence of foreign objects, the first set 334 and the second set 336 of sense coils 338 can be driven by the same current with similar amplitude and phase. A differential current signal for 332 is calculated based on the return current signal I1 356 of the first set 334 and the ongoing current signal I2 358 of the second set 336, and vice versa.

[0051] Turning now to Figures 3C to 3E , Figures 3C to 3E an embodiment showing the operational coupling between the drive subsystem and the sense coil sets. During detection, the sense coil sets are coupled to one or more drive subsystems of the detection system and draw current from one or more drive units of the drive subsystem. When the impedance values of the two sets of a pair of sets are similar, the current drawn by the two sets of the pair of sense coil sets causes the value of the differential current to be negligible in the absence of foreign objects. However, in the case where the impedances of the two sets in a pair of sense coil sets are different, the drive controller provides compensation for one or both of the pair of sense coils to ensure that the two sets are driven by similar current signals in the absence of foreign objects. The drive controller also controls the excitation voltage, frequency, and excitation duration of the sense coils. The drive controller turns on the drive units to excite the sense coil sets and turns off the drive units when the sense coil sets do not need to be excited. The drive controller can use an electronic circuit to control the drive units. Non-limiting examples of electronic circuits include microcontrollers, field-programmable gate arrays (FPGAs), semiconductor devices, logic gates, device drivers, oscillators, and timers or combinations thereof.

[0052] Figure 3C shows a portion 360 of a detection device ( Figure 3C not shown in ) having a drive subsystem 362, the drive subsystem 362 being coupled to a plurality 364 of sense coil sets 366 disposed on a detection pad. The drive subsystem 362 includes a plurality of drive units 368, where each drive unit 368 is coupled to a corresponding sense coil set 366. The drive subsystem 362 also includes a drive controller 370 that controls the operation of the drive units 368.

[0053] Figure 3D shows a portion 380 of a detection device having a drive subsystem 382 (not shown in Figure 3D ), the drive subsystem 382 being coupled to a plurality 384 of detection coil sets 386 disposed on a detection pad. The drive subsystem 382 includes a plurality of drive units 387. The drive subsystem 382 further includes a drive controller 389 that controls the operation of the drive units 387. Several pairs 388 of detection coil sets are coupled to the drive subsystem 382 such that each pair 388 is coupled to a corresponding single drive unit 387.

[0054] Figure 3E shows a portion 390 of a detection device (not shown in Figure 3E ), wherein the detection device employs two drive subsystems 391 and 392 coupled to a plurality 393 of detection coil sets 394. The detection coils are disposed on a detection pad. Pairs 395 and 397 of the detection coil sets 394 are coupled to the drive subsystems 391 and 392, respectively. The drive subsystem 391 includes a drive unit 399 and a drive controller 401, and the drive subsystem 392 includes a drive unit 403 and a drive controller 405.

[0055] Figure 4 shows an exemplary detection system 400 for detecting the presence of foreign objects in an operating environment 402 of a WPT system 404. The system 400 includes a detection device 406 and a WPT system 404. The detection device 406 includes a detection pad 408 having a plurality of detection coils and at least one pair of detection coil sets for detecting the presence of foreign objects in the operating environment 402 of the WPT system 404.

[0056] The detection device 406 further includes a drive subsystem 410. The drive subsystem 410 includes a drive unit 411 and a drive controller 412. Although not shown, the detection system 400 may include two or more drive subsystems 410. Additionally, the drive subsystem 410 may include a plurality of drive units 411 or a plurality of drive controllers 412 or both. The drive subsystem 410 is operatively coupled to the detection pad 408 and is configured to energize two or more detection coil sets of the detection pad 408. The detection device 406 further includes a comparison subsystem 414 that is operatively coupled to the detection pad 408 and is configured to receive a differential current signal from the detection pad. Additionally, the comparison subsystem 414 is configured to provide a control signal based on the differential current signal.

[0057] The WPT system 404 of the detection system 400 includes a main power supply 418 that is configured to supply power to a transmitter unit 420 of the WPT system 404 in the form of an alternating current (AC) voltage signal. The transmitter unit 420 includes at least one transmitter coil ( Figure 4(not shown in the figure). The transmitter unit 420 is configured to receive an AC voltage signal from the main power supply 418 and generate a main magnetic field or operating environment 402 in response to the received AC voltage signal.

[0058] The detection pad 408 is operatively coupled to the transmitter unit 420. In particular, the detection pad 408 is disposed on the transmitter unit 420. In some embodiments, the detection pad 408 is directly disposed on the surface 422 of the transmitter unit 420. In some other embodiments, the detection pad 408 is located above the transmitter unit 408 such that the detection pad 408 is disposed in the operating environment of the WPT system 404. The detection pad 408 may be arranged and aligned relative to the transmitter coil of the transmitter unit 420. The detection pad 408 may be arranged such that the transmitter coil is geometrically symmetrically positioned relative to the detection pad 408. Additionally, the detection pad 408 may be a stand-alone pad 408, a plug-and-play pad, and may have one or more of a flexible, conformable, and rigid structure.

[0059] The WPT system 404 further includes a receiver unit 424 having at least one receiver coil configured to receive at least a portion of the main magnetic field 402 generated by the transmitter unit 420. The receiver unit 424 may be disposed on the underside 426 of the device to be charged. In the illustrated embodiment, the receiver unit 424 is disposed on the underside 426 of an electric vehicle (EV) 416 that will be charged using the WPT system 404. The EV 416 may include an external power source, e.g., a battery 417. The WPT system 404 further includes a control unit 426 that controls the operation of the main power supply 418 and is also operatively coupled to the detection device 406. The control unit 426 receives a control signal from the detection device 406. Additionally, the control unit 426 controls the power supply from the main power supply 418 to the transmitter unit 420 based on the control signal.

[0060] In certain embodiments, the detection device 406 includes a communication unit 428 that is operatively coupled to the comparison subsystem 414 and is configured to receive a control signal from the comparison subsystem 414. Additionally, the communication unit 428 is configured to communicate with the control unit 426 of the WPT system 404. In certain embodiments, the communication unit 428 may transmit a control signal, for example, to the user of the EV 416 or the operator of the corresponding EV charging station via a mobile phone network to convey the presence and / or absence of a foreign object.

[0061] The differential current signal received by the comparator subsystem 414 from the sense coils of the sense pad 408 is converted into a voltage signal, referred to as the sense voltage signal. In some embodiments, the sense voltage signal is compared to a threshold or threshold voltage signal. The threshold or threshold value can be defined, for example, by the user based on the parameters and design of the sensing device 406. If the value of the sense voltage signal is greater than the value of the threshold voltage signal, it indicates that the currents drawn by the two sets of the pair of sense coils are different, which indicates the presence of a foreign object in the operating environment of the WPT system 404. Optionally, if the value of the voltage signal is less than or equal to the value of the threshold voltage signal, it indicates that the currents drawn by the two sets of the pair of sense coils are suitably similar, which indicates the absence of a foreign object or the presence of a very small foreign object (e.g., a coil, etc.) in the operating environment of the WPT system 404 that may not have an adverse effect on WPT operation.

[0062] In addition, in the case where the value of the sense voltage signal is greater than the value of the threshold voltage signal, a control signal can be transmitted by the sensing device 406 to the WPT system 404 to interrupt the power supply to the transmitter unit 420. In some embodiments, the communication unit 428 communicates with the control unit 426, and the control unit 426 in turn interrupts the power supply from the main power source 418 to the transmitter unit 420. In another embodiment, in the case where the transmitter unit 420 consists of a coil array, the control signal transmitted by the sensing device 406 to the control unit 426 will cause the control unit 426 to energize only a subset of the coil array in the transmitter unit 420, thus avoiding the area where the foreign object is detected.

[0063] Figure 5 An exemplary comparator subsystem 500 is shown that is operably coupled to a pair 502 of sense coils 504 and 506 of a sense pad. Figure 5 The example shown is a non-limiting example of measuring differential current, and it should be noted that other methods for measuring differential current can also be employed in this specification, where the other methods can include sensing individual currents and using electronic devices (such as but not limited to differential amplifiers) to find the difference between the individual currents. The differential current signal from the pair 502 can be determined by using the ongoing current signal to one set and the return current signal from the other set of the pair. In the illustrated embodiment, the return current signal I1 508 from set 504 and the ongoing current signal I2 510 from set 506 are used to derive the differential current signal for the pair 502 of sets 504 and 506.

[0064] When two current signals 508 and 510 pass through the magnetic core 512, the difference between the current signals 508 and 510 generates a magnetic flux in the magnetic core and induces a corresponding detected voltage signal in the electrical winding 514 wound around the magnetic core 512, which signal is typically denoted by reference numeral 516. Under the condition that the magnetic core is not magnetically saturated, this detected voltage is proportional to the difference between the current signals 508 and 510 and represents a measured value of the differential current between the two sets 504 and 506 of the pair 502.

[0065] Comparator subsystem 500 also includes a rectifier 518 that receives and rectifies the detected voltage signal. Optional filter 520 filters the voltage signal before sending the voltage signal to comparator 522. In one example, filter 520 is configured to filter out high-frequency components from the measurement. Comparator 522 compares the filtered voltage signal with a threshold voltage signal and thus transmits a control signal to the WPT system, e.g., Figure 4 WPT system 404.

[0066] Figure 6 Is an example method flowchart 600 for detecting the presence of foreign objects in a system operating environment. In one example, the system can be a WPT system. At block 602, a detection device is utilized by placing a detection pad of the detection device on the transmitter unit of the WPT system. The detection pad can be placed directly on the transmitter unit, or the detection pad can be placed above the transmitter unit such that it does not physically contact the transmitter unit. The detection pad includes a plurality of detection coils and at least one pair of detection coil sets, wherein the at least one pair of detection coil sets includes a first detection coil set and a second detection coil set, and wherein the first detection coil set includes a first impedance value and the second detection coil set includes a second impedance value.

[0067] At block 604, at least one pair of detection coil sets is excited. In some embodiments, the sets of the pair can be symmetrically arranged with respect to the main magnetic field. In some other embodiments, the sets of the pair are arranged in the same geometric position. In certain embodiments, the sets of the pair can be arranged in two different detection zones, and the detection zones can be selected such that the two detection zones in the pair of detection zones are symmetrically placed with respect to the magnetic field of the transmitter unit.

[0068] In certain embodiments, more than one pair of detection coil sets can be excited. In one example, multiple pairs of detection coil sets can be excited simultaneously for detecting the presence of foreign objects. In one embodiment, different pairs of detection coil sets can be selected such that the entire surface of the detection pad is excited to detect the presence of foreign objects. In some embodiments, different pairs can be excited at different times. In another embodiment, two or more pairs can be excited simultaneously. In one embodiment, different pairs of sets can be excited in chronological order.

[0069] In addition, the pair of groups can be excited before starting the wireless power transfer operation of the WPT system for the receiver unit and during the wireless power transfer operation of the WPT system. The pair of groups can be excited intermittently or at periodic intervals. In addition, the detection coils corresponding to different pairs of detection zones are excited at different times. In addition, different voltage signals are provided to the detection coils in the pair of detection coils having different impedance values, such that in the absence of foreign objects, the detection coils in the pair of detection coils are driven by the same current signal having similar amplitude and phase.

[0070] At block 606, a differential current signal is determined for the excited detection coils. In one embodiment, the differential current signal is determined using the ongoing current signal of one of the pair of detection coil groups and the return current signal of the other of the pair of detection coil groups. In embodiments where two or more pairs are excited simultaneously, corresponding individual differential current signals can be determined to detect the presence of foreign objects. Based on the differential current signal, it is determined whether there is a foreign object in the operating environment of the WPT system.

[0071] Subsequently, at block 608, a control signal is generated based on the differential current signal. At block 610, the generated control signal is transmitted. In one example, the control signal is transmitted to the control unit of the WPT system. In some embodiments, based on the control signal received by the control unit of the WPT system, the power supply to the transmitter unit of the WPT system is continued, adjusted, or interrupted.

[0072] Figure 7 FIG. 700 is a method flowchart of a method for controlling the power supply of the transmitter unit based on a control signal. At block 702, a detection voltage signal proportional to the differential current signal is generated using, for example, an electric winding and a magnetic core of a comparison subsystem. At block 704, the detection voltage signal is compared with a threshold. In some embodiments, the threshold can be a threshold or a threshold voltage signal. The threshold voltage signal can be a predetermined voltage signal based on the characteristics of the WPT system.

[0073] At decision block 706, if it is found that the detection voltage signal is greater than the threshold voltage signal, a control signal is transmitted to the WPT system to not start, adjust, or interrupt the power supply to the transmitter unit (block 708). Alternatively, at decision block 706, if the detection voltage signal is lower than the threshold voltage signal, no communication is made to the WPT system, or a control signal indicating the continuation or start of the power supply to the transmitter unit can be transmitted to the WPT system (block 710).

[0074] Detection can be performed in real-time or near real-time. Near real-time detection can be performed such that control signals are generated and transmitted within a time period of a few microseconds to a few milliseconds from the start of detection. In some embodiments, any foreign object can be scanned on the detection pad at periodic intervals at a determined rate, for example, once per second. Once a foreign object is detected, a communication signal is sent to the transmitter unit.

[0075] Figure 8 is a cross-sectional view of the detection pad 800 according to aspects of the present specification. In some embodiments, the detection pad 800 can be a stand-alone structure detachably coupled to the transmitter unit, for example, Figure 4 the transmitter unit 420. In one example, the detection pad 800 can be a plug-and-play structure. The detection pad 800 includes a substrate 802 having one or more printed circuit boards (PCBs) 804. The substrate 802 can include an electrically insulating material. In some embodiments, the substrate 802 itself can be a printed circuit board (PCB).

[0076] In addition, a group 806 of detection coils 808 can be provided on the substrate 802. In one embodiment, the group 806 of detection coils 808 can be provided on the respective PCB 804. In some embodiments, for user safety and aesthetics, the detection coils 808 can be provided on the substrate 802 or can be embedded in the substrate 802. The detection coils 808 can also be printed on a flexible or regular printed circuit board. In certain embodiments, the detection coils 808 can be printed, molded, woven, or otherwise fabricated on the substrate 808 or the PCB 804. It can be noted that each detection coil 808 can be compact and wound within a fine-gauge wire.

[0077] A cover layer 810 can be provided on the detection coils 808. The cover layer 810 has a first side 812 and a second side 814. In certain embodiments, the detection coils 808 can be directly provided on the second side 814 of the cover layer 810. In some of these embodiments, the detection coils 808 can be not provided on the PCB 804. In addition, suitable electronic devices 816 can be provided to the substrate 802 to enable the detection pad 800 to be operatively coupled to the drive subsystem and the comparison subsystem of the detection device.

[0078] The substrate 802 and the cover layer 810 can include flexible materials, rigid materials, or a combination thereof. The cover layer 810 includes a thermally and electrically insulating (TCEI) material. In one embodiment, the thermally and electrically insulating (TCEI) material can include an elastomer or a thermoplastic with wear-resistant fillers. In one embodiment, the elastomer can be silicone rubber. The filler can be a TCEI filler, such as, for example, alumina, aluminum nitride, beryllium oxide, boron nitride, graphene oxide, silicon carbide, and silicon nitride. Similarly, the thermoplastic can be a polyolefin, polycarbonate, poly(methyl methacrylate) (PMMA), and polyester. Additionally, in some embodiments, the substrate 802 and the cover layer 810 can be folded together with the detection coil 808. In one embodiment, the detection pad 800 can be a conforming structure. To this end, when the detection pad 800 is disposed on the transmitter unit, the detection pad 800 can be configured to generally conform to the gradient and curve of the surface of the transmitter unit. In some embodiments, the cover layer 810 can form a housing around the substrate 802, the detection coil 808, and can surround the electronic device 816.

[0079] In one embodiment, the detection pad 800 can be integrated with a standard SAE transmitter system. In some embodiments, the size of the detection pad 800 can range from about 0.5 m to about 2.2 m. The detection pad 800 can be sized appropriately to cover the surface area of the transmitter coil. In some examples, the detection pad 800 can have a length in the range from about 0.5 m to about 2.2 m and a width in the range from about 0.5 m to about 2.2 m. Additionally, the detection pad 800 can have a thickness in the range from about 1 mm to about 20 mm. In one embodiment, the detection pad 800 can be a monolithic structure. In another embodiment, the detection pad 800 can be formed by integrating separate discrete pieces.

[0080] Advantageously, the devices, systems, and methods of the present technology are simple in construction and do not require any complex assembly. Additionally, the present technology is very sensitive and is capable of detecting the presence of foreign objects shortly after the start of wireless power transfer. This helps to minimize power wastage. The embodiments of the present specification provide a highly sensitive, simple, and accurate system to detect foreign objects placed in the operating environment of a WPT system. Additionally, the detection device of the present specification can be deployed in an existing WPT system with minimal changes or adjustments, or without any changes or adjustments. Advantageously, the devices, systems, and methods of the present specification enable a safe operating environment during wireless power transfer of an electric vehicle (EV), but stop the wireless transmission of the EV when a foreign object is detected, or issue an alert when a foreign object is detected in the operating environment of the WPT system.

[0081] Although only certain features of the present invention have been shown and described herein, many modifications and variations will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and variations as fall within the scope of the present invention.

Claims

1. A detection device (100), comprising: A detection pad (102) having a plurality of detection coils (106) and at least a pair of detection coil groups (106), wherein the at least a pair of detection coil groups (106) includes a first detection coil group (106) and a second detection coil group (106), and wherein the first detection coil group (106) includes a first impedance value and the second detection coil group (106) includes a second impedance value; One or more drive subsystems (112) operatively coupled to the detection pad (102) and configured to excite at least a pair of detection coil groups (106); and A comparison subsystem (114) operatively coupled to the detection pad (102) and configured to receive differential current signals from the at least a pair of detection coil groups (106), wherein the comparison subsystem (114) is configured to generate a control signal based on the differential current signals.

2. The detection device (100) according to claim 1, wherein, The first detection coil group (106) and the second detection coil group (106) are symmetrically arranged with respect to the main magnetic field of the wireless power transfer system, and wherein the detection device (100) is configured to detect the presence of foreign objects in the operating environment of the wireless power transfer system based on the differential current signals.

3. The detection device (100) according to claim 1, wherein, The first detection coil group (106) and the second detection coil group (106) include structurally similar arrangements of detection coils (106).

4. The detection device (100) according to claim 1, wherein, The first detection coil group (106) and the second detection coil group (106) are disposed in the same geometric region on the detection pad (102).

5. The detection device (100) according to claim 1, wherein, The first impedance value and the second impedance value are similar to each other.

6. The detection device (100) according to claim 1, wherein, The first impedance value and the second impedance value are different from each other, and wherein the detection pad (102) further includes a compensator element operatively coupled to one of the first detection coil group (106) and the second detection coil group (106) to compensate for the difference in impedance values between the first detection coil group (106) and the second detection coil group (106).

7. The detection device (100) according to claim 1, wherein, The first impedance value and the second impedance value are different from each other, and wherein the one or more drive subsystems (112) further includes a drive controller configured to provide different voltage signals to the first detection coil group (106) and the second detection coil group (106) such that the first detection coil group (106) and the second detection coil group (106) are driven by the same current with similar amplitude and phase.

8. The detection device (100) according to claim 1, wherein, The one or more drive subsystems (112) includes two drive units respectively coupled to the first detection coil group (106) and the second detection coil group (106) and at least one drive controller, and wherein the drive controller is coupled to the drive units.

9. A detection system (400), comprising: A detection device (406), comprising: A detection pad (102) having a plurality of detection coils (106) and at least one pair of detection coil groups (106), wherein the at least one pair of detection coil groups (106) includes a first detection coil group (106) and a second detection coil group (106), and wherein the first detection coil group (106) includes a first impedance value and the second detection coil group (106) includes a second impedance value; One or more drive subsystems (112) operatively coupled to the detection pad (102) and configured to excite at least one pair of detection coil groups (106); and A comparison subsystem (114) operatively coupled to the detection pad (102), And configured to receive differential current signals from the at least one pair of detection coil groups (106), wherein the comparison subsystem (114) is configured to generate a control signal based on the differential current signals, and A wireless power transfer system, comprising: A main power supply configured to supply power in the form of an alternating voltage signal; A transmitter unit including at least one transmitter coil, wherein the transmitter unit is configured to receive the alternating voltage signal from the main power supply, wherein the transmitter unit is configured to generate a main magnetic field in response to the received alternating voltage signal, and wherein the detection pad (102) is operatively coupled to the transmitter unit; A receiver unit including at least one receiver coil and configured to receive at least a portion of the main magnetic field generated by the transmitter unit; A control unit operatively coupled to the detection device and configured to: Receive the control signal from the detection device; and Control the power supply to the transmitter unit based on the control signal.

10. A detection method (600), comprising: Utilizing (602) a detection device including a detection pad having a plurality of detection coils and at least one pair of detection coil groups, wherein the at least one pair of detection coil groups includes a first detection coil group and a second detection coil group, and wherein the first detection coil group includes a first impedance value and the second detection coil group includes a second impedance value; Exciting (604) at least one pair of detection coil groups; Determining (606) differential current signals from the at least one pair of detection coil groups; and Generating (608) a control signal based on the differential current signals; and Transmitting (610) the control signal.

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