Sensor arrangement structure for foreign body detection device

Abstract

A sensor arrangement structure for a foreign object detection device in a wireless power transmission system includes multiple detection units, each of which includes a sensing coil having a winding spirally wound in a plane and having multiple turns. Multiple input leads and one or more output leads are provided, so that each detection unit can be connected to a current input terminal and a current output terminal directly or through a selection circuit. The selection circuit is adapted to selectively establish an electrical connection between the current input terminal and one or more of the input leads, or between one or more of the output leads and the current output terminal. To achieve relatively uniform foreign object detection sensitivity near a particular detection unit, the sensing coil of the detection unit includes an outer coil segment and an inner coil segment arranged within the outer coil segment, wherein a first distance between the outermost turn of the inner coil segment and the innermost turn of the outer coil segment is at least twice the maximum distance between two turns of the outer coil segment.

Description

Technical Field

[0001] The present invention relates to a sensor arrangement for a foreign object detection device for a wireless power transmission system, the sensor arrangement comprising: a current input and a current output; a plurality of detection units, each detection unit comprising a sensing coil having a winding spirally wound in a plane and having a plurality of turns; a plurality of input leads and one or more output leads, wherein each detection unit is connected between one of the input leads and one of the output leads, and wherein each detection unit is connected to a different combination of the input leads and the output leads; and an input selection circuit adapted to selectively establish an electrical connection between the current input and the one or more input leads. The present invention also relates to a foreign object detection device for a primary portion of a wireless power transmission system for transmitting power across an air gap to a nearby receiver, the foreign object detection device comprising such a sensor arrangement; and the present invention also relates to a primary portion of a wireless power transmission system for transmitting power across an air gap to a nearby receiver, the primary portion comprising such a sensor arrangement or such a foreign object detection device. Background Art

[0002] Electrical energy is used in many different applications. In order to power electrically driven devices, items or objects that are not constantly connected to a power source, these devices, items or objects are usually equipped with one or more batteries for storing energy to power such devices, items or objects when they are not connected to a power source. Examples are: mobile devices such as cell phones, laptops, cordless screwdrivers, etc.; household appliances; motor vehicles such as cars, trucks, motorcycles, trains, boats, ships, airplanes, helicopters, etc.; and industrial vehicles such as forklifts, automated guided vehicles (AGVs), cleaning machines, elevators, etc., or electrically powered equipment for lifting, moving or transporting any type of goods. All of these devices, items or objects usually include batteries to enable them to operate.

[0003] If the energy stored in such a battery has been fully or partially consumed by a device, item or object that operates with it, the battery can be recharged. Charging can be performed by connecting a power source to the battery with a wire.

[0004] Another way to charge these batteries is wireless charging, typically using inductive power transfer via a magnetic field.

[0005] The power levels of wireless charging systems have a wide range, with output power ranging from 1W to hundreds of kW.

[0006] However, one of the problems with wireless charging is that it is usually impossible to mechanically prevent objects placed in the magnetic field used to transfer energy from being placed in the vicinity of the primary and / or secondary units of the power transmission device. In particular, magnetic and conductive objects, such as coins, keys, tools, cans or other objects, heat up rapidly in the magnetic field due to induced eddy currents and hysteresis losses. This unintentional conversion of electrical energy into thermal energy leads to additional losses and is particularly dangerous for the system and for people or animals in the system environment. Due to the laws of physics, this effect and the resulting heat cannot be avoided. Therefore, it is important to detect the presence of such foreign objects in order to mitigate the risk. This method is also known as foreign object detection (FOD).

[0007] There are various approaches to solving this problem. In some cases, the curved shape of the transmitting pad ensures that the object leaves the pad with the help of gravity. Another approach is to use sensors to detect the presence of metal objects. For example, capacitive sensors and optical sensors can be used, but they are easily interfered with by environmental influences and non-metallic objects. Inductive sensors are more commonly used because they are robust to environmental influences such as dirt, while providing accurate results at close range. An inductive sensor detects the reduction in the inductance of the coil due to eddy currents induced in the object to be detected, where the eddy currents cancel out the primary magnetic field of the coil. Due to the finite conductivity of the object, ohmic losses also occur, which can also be detected. In order to evaluate these changes, several methods have been established in the prior art, which are also used in the prior art described below. It is well known to use arrays of sensor coils to increase the detection area while achieving sufficient detection sensitivity.

[0008] One known technique for FOD consists in measuring the impedance of a coil that is arranged in a matrix of several coils and that changes due to the presence of foreign matter.

[0009] For example, document EP 3 734 801 discloses such a foreign object detection device. The foreign object detection device comprises a sensor arrangement, a stimulation unit, a measurement unit, and a signal processing and control unit. The sensor arrangement comprises a plurality of detection units that can be individually enabled by a multiplexer. Each detection unit comprises a sensing coil and, in order to improve the accuracy and anti-interference capability of object detection, also a capacitor to form a resonant circuit. The detection units are typically arranged in a matrix having rows and columns so that a larger area can be monitored. The specific detection units can be connected to the stimulation unit and the measurement unit respectively via an input multiplexer and an output multiplexer using the following connecting lines, which are fed along the rows and columns of the matrix formed by the detection units, and these connecting lines are connected to the input and output terminals via controllable switches.

[0010] Foreign matter is detected in the following manner: a stimulation signal provided by a stimulation unit is applied to a selected detection unit, the resulting response is measured, and the resulting response is compared with a previously recorded response of the detection unit to the same stimulation signal when ensuring that no foreign matter is located in the magnetic field. If the resulting response is different from the previously recorded response, it is known that a foreign matter is present in the magnetic field.

[0011] The stimulus signal can be, for example, a current step. The resulting step response caused by the current step is an oscillation of the voltage. This oscillation can be defined by several parameters, which can be affected by foreign matter. For example, foreign matter can change the inductance L and resistance R of the sensing coil.

[0012] The stimulus signal may also be a rectangular pulse, or any other signal that allows the necessary or desired characteristics for foreign body detection to be determined.

[0013] If the area to be covered by the foreign body detection is large, a single coil is usually not sufficient to cover the entire area. As shown in EP3 734 801, for example, this problem is solved by using a plurality of detection units arranged in a matrix-like structure.

[0014] However, the sensing coil of each of these multiple detection units does not have the same sensitivity over the entire surface covered by the particular sensing coil. For example, the sensing coil has a substantially square shape with its turns evenly distributed, such as in EP 3 734 801. Figure 8 a and Figure 8 As shown in Figure 2b, the sensitivity of the sensing coil reaches its maximum value at the center of the coil and decreases almost linearly towards the edges of the coil. Therefore, a foreign object located between the edges of two adjacent sensing coils may not be detected due to the reduced sensitivity of the sensing coil in this area.

[0015] In another example, the sensing coil has a generally square shape, with the turns concentrated in the outer region of the coil, such as that of EP 3 734 801. Figure 8 As shown in c, the sensitivity of the sensing coil reaches a maximum at about half the distance between the center of the coil and the edge of the coil, decreases around the center of the coil, and decreases almost linearly from the maximum toward the edge of the coil.

[0016] Therefore, due to the reduced sensitivity of such a sensing coil at its center, a foreign object, for example, located in the center of the sensing coil may not be detected and the signal indicating the detection of a foreign object may be difficult to interpret, which is why systems are usually designed for the worst case scenario and therefore usually have to be oversized. Summary of the Invention

[0017] The object of the present invention is therefore to create a sensor arrangement belonging to the initially mentioned technical field, which ensures relatively uniform sensitivity for foreign object detection over the entire surface of a transmitting unit. A further object of the present invention is to create a corresponding foreign object detection device and a corresponding primary part (primary part) for a wireless power transmission system for transmitting power via an air gap to a nearby receiver.

[0018] An embodiment of the present invention provides a sensor arrangement structure for a foreign object detection device for a wireless power transmission system, comprising: a current input terminal and a current output terminal; a plurality of detection units, each detection unit comprising a sensing coil having a winding spirally wound in a plane and having a plurality of turns; a plurality of input leads and one or more output leads, wherein each detection unit is connected between one of the input leads and one of the output leads, and each detection unit is connected to a different combination of the input leads and the output leads; and an input selection circuit adapted to selectively establish an electrical connection between the current input terminal and the one or more input leads. According to the present invention, the sensing coil of at least one detection unit comprises an outer coil segment and an inner coil segment arranged within the outer coil segment, wherein a first distance between the outermost turn of the inner coil segment and the innermost turn of the outer coil segment is at least twice the maximum distance between two turns of the outer coil segment.

[0019] Preferably, the sensing coils of all detection units include an outer coil segment and an inner coil segment arranged within the outer coil segment, wherein a first distance between an outermost turn of the inner coil segment and an innermost turn of the outer coil segment is at least three times a maximum distance between two turns of the outer coil segment.

[0020] By dividing the turns of the sensing coil into outer and inner coil segments that are spaced apart from one another, the sensitivity of the sensing coil can be made more uniform around the center of the sensing coil. Thus, the outer coil segments correspond to concentrated windings in the outer region, while the inner coil segments ensure that the sensitivity does not drop, or does not drop significantly, around the center of the sensing coil.

[0021] Therefore, the present invention not only ensures that a single sensing coil has a relatively uniform sensitivity to foreign object detection, but also ensures that the sensitivity to foreign object detection has a relatively uniform sensitivity over the entire surface of the transmitting unit.

[0022] In addition to the sensor arrangement of the present invention, the FOD device according to the present invention further comprises a stimulation circuit for generating a predetermined stimulation signal, such as a current step or a current pulse. The stimulation signal may also be a sinusoidal signal. The stimulation circuit is connected to a current input of the sensor arrangement. Accordingly, the current input is a connection point of the sensor arrangement at which the current of the stimulation signal flows into the sensor arrangement. Similarly, the current output is a connection point of the sensor arrangement at which the current of the stimulation signal flows out of the sensor arrangement. Typically, the current output is grounded.

[0023] Input leads are electrical connectors that connect the detection unit to an input selection circuit, as described further below, which in turn establishes an electrical connection between the current input and one or more input leads. Similarly, output leads are electrical connectors that connect the detection unit directly to the current output of the sensor arrangement or to an output selection circuit, as described further below, which in turn establishes an electrical connection between one or more output leads and the current output. The input and output leads can be formed from any suitable electrical conductor, such as a wire. However, the input leads are typically formed from traces on a PCB.

[0024] The FOD device further comprises a measuring unit adapted to sense an electrical signal applied to the current input terminal, wherein the measuring unit comprises an analog-to-digital converter for acquiring sampled data representing the sensed electrical signal. The FOD device further comprises a signal processing unit configured to determine time response data of the selected detection unit based on the sampled data acquired by the measuring unit. Furthermore, the measuring unit preferably comprises a filter for filtering the electrical signal.

[0025] The sensing coil is, for example, arranged as a flat structure, such as a pad or plate, which is positioned above a primary pad for generating a power transfer field, and is arranged between the primary pad and the secondary pad when a device including the secondary pad is positioned to receive power through the power transfer field.

[0026] In the context of this application, a wireless power transfer system is a system that allows power to be transferred in space via a time-varying electromagnetic field without the need for wires as a physical link. The power transfer system comprises a primary part, a transmitter device, which is driven by power from a power source and generates an electromagnetic field; and a secondary part, a receiver device, which extracts power from the magnetic field and supplies it to an electrical load. In a specific form, the wireless power transfer system is an inductive power transfer system.

[0027] An electromagnetic field, also known as a power transfer field, is generated by at least one resonator arranged in the primary part of a power transmission system. The shape of the power transfer field depends on the components of the resonator and their arrangement and interconnection. Such a resonator typically comprises a resonant circuit with at least one coil and a capacitor. A resonator may also include other components, such as an additional inductor and one or more flux-guiding elements. A so-called double-D arrangement is often used in resonators to generate the power transfer field. This arrangement consists of two D-shaped (or similarly shaped) coils arranged adjacent to each other and positioned above a ferrite sheet, for example. When the two coils are fed with current in opposite directions, a magnetic field is generated in which the magnetic field lines pass through the center of the coils but are generally parallel to the plane of the coils in the region between them. If the secondary part is located near the primary part, for example, above it, the magnetic field lines of the primary magnetic field are deformed by the secondary part. The shape of the generated power transfer field depends largely on the arrangement of the secondary part relative to the primary part, as well as the currents in the primary and secondary windings and the power they transmit.

[0028] In the context of this application, a foreign object is defined as any conductive and / or magnetic object, in particular any metallic object, located in the vicinity of but not part of the wireless power transfer system and which may cause losses in the power transfer of the power transfer system.

[0029] The term "active area" refers to the area through which the majority of the primary magnetic field's flux lines extend when the primary is powered at its nominal current and frequency, in the absence of a secondary and foreign objects. This majority can be, for example, 10%, 25%, 50%, 75%, 80%, 90%, 95%, or 99% of the total magnetic flux. The active area defines the area around which the secondary must be placed to transfer power. For wireless charging applications, the active area may also be designated as the "charging area."

[0030] Similarly, the term "power transfer area" refers to the area through which the majority of the primary magnetic field's flux lines extend when the secondary is arranged in its nominal position, but without transferring power through the air gap between the primary and secondary parts. In other words, the active area and power transfer area define the surface exposed to the primary's magnetic field in the space near the primary.

[0031] In the context of the present application, the term "time response data of the selected detection unit" is understood to include a data set representing the time response of the selected detection unit to a predefined stimulation signal, wherein the time response data is obtained based on sampled data of the electrical signal representing the excited oscillation of the selected detection unit.

[0032] The data may simply comprise the raw sampled data of the electrical signal representing the excited oscillation caused by the predetermined stimulus signal, acquired by the analog-to-digital converter of the FOD device for the selected detection unit. The data may also comprise values ​​obtained after applying a digital processing step to the raw sampled data, such as downsampling, upsampling, scaling, filtering, data compression, application of correlation functions, parameter identification, etc. This list is not exclusive. The time response data of the selected detection unit may specifically comprise a single parameter, such as the series resistance, series inductance or more generally the series impedance of the detection unit, the relative change of the series impedance of the selected detection unit, the attenuation rate, the change of the attenuation rate, the resonant frequency or the change of the resonant frequency. The time response data may also comprise a combination of these parameters.

[0033] In general, both the inner and outer coil segments can have any number of turns. The number of turns for both segments can be selected to best suit a particular application, including a particular number and arrangement of detection units and a particular shape of sensing coil.

[0034] However, in a preferred embodiment of the invention, the sensing coil comprises multiple turns in the outer coil section and a single turn in the inner coil section. Experiments have shown that a single turn of the inner coil section is sufficient in many cases to achieve a sufficiently uniform distribution of the sensitivity of the sensing coil.

[0035] If the inner coil segment has a single turn, the first distance is preferably equal to the distance between the single turn in the inner coil segment of the sensing coil of the at least one detection unit and the center of the sensing coil. In other words, the distance between the single turn and the center of the sensing coil is preferably the same as the distance between the single turn and the innermost turn of the outer coil segment. Experiments have shown that this position of the single turns of the inner coil segment results in a sufficiently uniform distribution of the sensitivity of the sensing coil.

[0036] In another preferred embodiment of the present invention, the distance between the center of the sensing coil of at least one detection unit and the innermost turn of the inner coil segment is less than two-thirds of the distance between the center of the sensing coil and the outermost turn of the outer coil segment. Accordingly, the turns of the outer coil segment are concentrated in an outer region of the sensing coil, while the turns of the inner coil segment are arranged within but spaced apart from the outer coil segment.

[0037] In an even more preferred embodiment of the invention, the distance between the center of the sensing coil of the at least one detection unit and the innermost turn of the inner coil segment is smaller than half the distance between the center of the sensing coil and the outermost turn of the outer coil segment.

[0038] Although the turns of the outer coil segment may be chosen to have different distances from one another, it is preferably chosen so as to be arranged equidistant from one another.

[0039] Similarly, if the inner coil segment comprises three or more turns, these turns may be chosen to have different distances from one another, but preferably they are also chosen to be arranged equidistant from one another.

[0040] Thus, the equal distances between the turns of the outer coil segment and the equal distances between the turns of the inner coil segment may be different, but they are preferably the same.

[0041] Preferably, the planes in which the sensing coils of the detection unit are wound are at least parallel to each other, and more preferably are arranged in a single layer.

[0042] Such a single layer of sensing coils preferably do not overlap each other. Depending on the outer shape of the sensing coils and the position of the center of the sensing coils, there may be gaps between the sensing coils, where detection sensitivity may be reduced or even impossible to detect, thereby creating blind spots.

[0043] However, the sensing coils may also be arranged in more than one layer, wherein the layers are arranged parallel to each other.

[0044] In this case, it is preferable to arrange the sensing coils of different layers so that the sensing coils of one layer overlap with the sensing coils of another layer. This allows blind spots or gaps where detection sensitivity is reduced in one layer to be covered by the sensing coils of the other layer. This avoids blind spots or areas where detection sensitivity is reduced. This increases the coverage of the overall detection area and provides higher and more uniform detection sensitivity.

[0045] Therefore, in another preferred embodiment of the present invention, the sensing coils are arranged in one or more layers.

[0046] To further improve the uniformity of detection sensitivity, the sensing coils on each layer are preferably arranged in a regular pattern. To achieve the most uniform sensitivity possible, the sensing coils on each layer are arranged in the same regular pattern but staggered so that blind spots or gaps with reduced detection sensitivity on one layer are covered as closely as possible by the sensing coils on another layer.

[0047] In a preferred embodiment of the present invention, the regular pattern is a matrix-like structure. Thus, the sensing coils of a layer are arranged in a matrix-like structure with multiple rows and columns. The term "matrix" generally means that the individual elements of the matrix are precisely arranged adjacent to and between each other.

[0048] In contrast, in the context of this application, the term "matrix-like" is intended to mean that the individual elements of the matrix are arranged adjacent to and between each other, but they do not necessarily have to be arranged exactly adjacent to and between each other. For example, in the context of this application, an arrangement of individual detection units in columns or rows that are slightly staggered from each other, such as a honeycomb arrangement, would also be considered a matrix-like structure, regardless of the shape of the sensing coils of the detection units.

[0049] By arranging the sensing coils in a single layer, a larger total detection area can be covered by a sensor arrangement with a minimal number of sensing coils. Furthermore, a flat structure can be achieved. For example, the sensing coils can be arranged, for example, by vapor deposition, on a flat support structure such as a plate made of non-electrical material, a single PCB, or a flexible foil.

[0050] The sensing coil may also be mounted in a recess in the support structure.

[0051] In the context of the present application, the term "flat support structure" is intended to designate a flat structure such as a coil mat or plate, wherein flat means that the thickness of the mat or plate is less than one fifth of its greatest lateral extension.

[0052] In a preferred embodiment, the support structure is a multi-layer PCB and the sensing coil layers are realized by traces belonging to different layers of the PCB.

[0053] While the sensing coil of the detection unit must be arranged on the flat structure, other components of the detection unit may or may not be located on the flat structure. For example, the capacitor that forms a resonant circuit with the sensing coil and the decoupling element may be arranged outside the flat structure, for example, on a control board connected to the flat structure.

[0054] In another preferred aspect of the present invention, the sensing coils are arranged in one or more layers, and the sensing coils of a particular layer are arranged in a matrix-like structure having a plurality of rows and columns.

[0055] In a first example of this preferred aspect of the invention, the sensor arrangement includes an input selection circuit and an output selection circuit. An input lead of a particular detection cell is routed from the input selection circuit to the sensing coil of that detection cell, and an output lead of that detection cell is routed from the sensing coil of that detection cell to the output selection circuit.

[0056] A particular detection unit can be connected to the stimulation unit and the measurement unit respectively via an input multiplexer and an output multiplexer using connection lines that are fed along the rows and columns of the matrix formed by the detection units and that are connected to the input and output via controllable switches.

[0057] Another possibility for routing the input and output leads to the detection cells is to provide a separate connection from the input selection circuit to each detection cell, and to provide a separate connection from each detection cell to the output selection circuit.

[0058] However, according to this first example of this aspect of the invention, each input lead of a particular layer interconnects all detection units of a particular row of the matrix-like structure, and each output lead of the particular layer interconnects all detection units of a particular column of the matrix-like structure; or, each input lead of a particular layer interconnects all detection units of a particular column of the matrix-like structure, and each output lead of the particular layer interconnects all detection units of a particular row of the matrix-like structure.

[0059] In this manner, as long as the number of detection units is equal to or greater than six, the total number of input leads and output leads is less than the number of detection units. Therefore, the number of detection units in the sensor arrangement is preferably six or more. Accordingly, this embodiment is suitable for sensor arrangements with a relatively high number of detection units (e.g., more than 50 detection units). However, it can also be used for sensor arrangements with fewer than 50 detection units.

[0060] Thus, as described above, each detection unit may be connected to a different combination or pairing of input and output leads.

[0061] It should be noted that this aspect of the present invention can be applied to a sensor arrangement for foreign object detection regardless of the other features of the sensor arrangement described above, such as the distribution of the turns of the sensing coil. Furthermore, the preferred embodiments for routing the input and output leads described below can be applied to a sensor arrangement for foreign object detection regardless of the other features of the sensor arrangement described above.

[0062] By routing the input and output leads of a particular layer in this manner, the number of output terminals of the input selection circuit and the number of input terminals of the output selection circuit can be minimized. In addition, the total length of the input and output leads can be reduced because certain portions of the leads can be used to connect multiple detection units.

[0063] The preferred routing of the input and output leads of the detection unit achieves the goal of minimizing the hardware effort and minimizing the overall length of the input and output leads.

[0064] In a second example of this preferred aspect of the invention, the sensor arrangement comprises an input selection circuit but does not comprise an output selection circuit. An output selection circuit is not necessary because the sensor arrangement comprises only a single output lead that interconnects all detection units and connects them directly to the current output. In this example, each detection unit comprises its own input lead. Accordingly, the input lead of a particular detection unit is routed from the input selection circuit to the sensing coil of that detection unit. A particular detection unit can be connected to the stimulation unit and the measurement unit via an input multiplexer, wherein connecting lines are fed to the detection units from the input multiplexer along the rows and columns of the matrix formed by the detection units. The input multiplexer, for example, comprises a plurality of controllable switches that are controlled to connect one or more detection units to the current input.

[0065] In this manner, the total number of input leads and output leads is greater than the number of detection units, i.e., the total number of input leads and output leads is the number of detection units plus one. Therefore, this embodiment is suitable for sensor arrangements with a relatively low number of detection units, for example, fewer than 200 detection units. However, it can also be used for sensor arrangements with more than 200 detection units.

[0066] Furthermore, the input and output leads of the detection unit form a loop. If this loop is exposed to a magnetic field, such as that generated by a wireless power transfer system for wireless power transfer, and this exposure causes magnetic field lines to pass through the area spanned by the loop, a voltage is induced at the terminals of the loop. This induced voltage may interfere with the impedance measurement or distort the detection unit's response to a stimulus signal or a foreign object positioned near the detection unit. This distortion may be negligible, but it may also be so large that the measurement is unreliable.

[0067] In another aspect of the invention, the input and output leads of at least one sensing coil are therefore routed close to each other through the matrix-like structure to which the at least one sensing coil belongs to reduce the area spanned by the input and output leads.

[0068] By routing the input and output leads of the sensing coil of a particular detection unit to reduce the area spanned by the input and output leads, the voltage induced by external magnetic fields can be reduced or minimized. This, in turn, minimizes the interference and distortion that external magnetic fields (e.g., the magnetic field used for energy transmission in a wireless power transmission system) may have on foreign object detection.

[0069] Preferably, the input leads and the output leads of each sensing coil of the sensor arrangement are routed through the matrix-like structure in this way.

[0070] In this way, the area surrounded by the input and output leads and through which the power transfer field passes can be significantly reduced.

[0071] Accordingly, to reduce the area through which magnetic field lines may pass, the area spanned by the input and output leads should be aligned and as parallel to the magnetic field lines as possible. Therefore, based on the direction of the magnetic field lines of the power transmission field in the area where the input and output leads are arranged, the input and output leads should be routed so that the area spanned between them is parallel to the magnetic field lines.

[0072] In an embodiment where the magnetic field lines of the magnetic field extend perpendicular to the matrix-like structure, the input leads and the output leads are preferably arranged one above the other. In an embodiment where the magnetic field lines of the magnetic field extend parallel to the matrix-like structure, the input leads and the output leads are preferably arranged in the same plane parallel to the matrix-like structure.

[0073] For example, in the double-D arrangement described above, the magnetic field lines in the region between the two coils generally extend parallel to the sensing coils. Therefore, by arranging the sensor arrangement so that the input and output leads are positioned above the region between the coils, the magnetic field lines of the power transfer field extend parallel to the plane of the matrix-like structure. Consequently, the region spanned by the input and output leads of the detection unit is parallel to the magnetic field lines of the power transfer field, i.e., the region through which the magnetic field lines of the power transfer field may pass is minimized.

[0074] More generally, the input and output leads are typically routed through a matrix-like structure, and the matrix-like structure is typically arranged so that the input and output leads are positioned in regions where the magnetic field lines of the power transfer field extend parallel to the plane of the matrix-like structure. In such regions, the magnetic field lines are also less densely distributed, and therefore the magnetic field strength is weaker. This reduces the voltage induced in the loop formed by the input and output leads of the detection unit. The precise arrangement of the input and output leads within the matrix-like structure, as well as its placement above the resonators generating the power transfer field, depends largely on the specific application and must be selected accordingly.

[0075] Furthermore, by reducing these induced voltages, the noise in the system can also be reduced. Lower noise means less effort is required to analyze the measured response of the detection unit to the stimulus signal to detect the presence of a foreign object. This reduces the manufacturing cost of the foreign object detection device according to the present invention.

[0076] Accordingly, the object achieved by this aspect of the present invention is to reduce interference effects and distortion in foreign object detection, thereby also reducing the manufacturing costs of the foreign object detection device.

[0077] The input and output leads of each sensing coil of a particular layer may be routed together along an edge of the matrix-like structure, wherein the input and output leads of a particular row or column are routed into the matrix-like structure through gaps between corresponding rows or columns.

[0078] However, in another preferred embodiment of the present invention, the input leads and the output leads of each sensing coil of a particular layer are generally routed through the same gap between two columns or two rows of the matrix-like structure.

[0079] This wiring produces an arrangement in which all input leads and output leads of a particular layer are arranged close to each other, thereby not only reducing the total length of the leads, but also reducing the area enclosed by the loops of the input leads and output leads of each detection unit, and reducing the voltage induced in each of these loops.

[0080] In an even more preferred embodiment of the present invention, the input and output leads of each sensing coil of a particular layer are routed through the gap between two central columns or two central rows of the matrix-like structure to minimize the total length of the input and output leads.

[0081] The term "center" in this connection means that in the case of even rows or columns, the leads are routed through the gap between the two middle rows or columns, while in the case of odd rows or columns, the leads are routed through one of the gaps near the middle row or column.

[0082] In another preferred embodiment of the present invention, the distance between the input lead and the output lead of the at least one sensing coil is less than the distance between two rows or columns of the matrix structure. Thus, the input lead and the output lead are routed in a small spatial area from the input selection circuit to the sensing coil and from the sensing coil to the output selection circuit, respectively. Preferably, this distance is less than one-third of the distance between two rows or columns.

[0083] In another preferred embodiment of the present invention, the input leads and the output leads of at least one sensing coil are arranged one above the other. This means that the input leads and the output leads of the sensing coil are not arranged in the same plane, but in different planes, which are preferably parallel to each other and to the layer to which the sensing coil belongs.

[0084] For example, the input leads may be arranged in a first layer of a multi-layer PCB, and the output leads may be arranged in a second layer of the multi-layer PCB.

[0085] The input and output leads of the detection unit may be routed parallel along their entire length. However, in a preferred embodiment, the input and output leads of the detection unit are twisted at least once.

[0086] Due to the twisting of the leads, the loops formed by the leads include regions where the voltages induced by the external magnetic field cancel or cancel each other out. This also results in lower voltages induced in these loops.

[0087] In another preferred embodiment, the sensor arrangement comprises not only an input selection circuit but also an output selection circuit adapted to selectively establish an electrical connection between one or more output leads and the current output terminal.

[0088] In this way, as long as the number of detection units is equal to or greater than six, the total number of input leads and output leads can be reduced to be smaller than the number of detection units.

[0089] The sensing coil may generally have any suitable shape, such as an ellipse, a circle, a hexagon, an arbitrary polygon, or any other suitable shape, wherein the shape may be regular or irregular.

[0090] In another preferred embodiment of the present invention, the sensing coil of at least one detection unit is rectangular, and even more preferably square. Rectangular or square in this context does not exclude the possibility that one or more turns of the coil have rounded corners.

[0091] Hexagonal coils, particularly regular hexagonal coils, fully utilize the available space in a given layer, reducing or even minimizing the area of ​​reduced detection sensitivity between coils. However, input and output leads must be routed in a zigzag pattern between the detection units, resulting in longer input and output leads and potentially making routing more difficult.

[0092] Rectangular or square coils also make good use of the available space and allow for direct wiring between detection units, making them a good compromise.

[0093] In another preferred embodiment of the present invention, each detection unit includes a capacitive element forming a resonant circuit together with the sensing coil.

[0094] In a further preferred embodiment of the present invention, at least one detection unit comprises a decoupling element connected in series to its resonant tank, wherein the decoupling element is preferably a diode.

[0095] An embodiment of the present invention further provides a foreign object detection device. According to the present invention, the foreign object detection device includes: a sensor arrangement structure as described above; a stimulation circuit for generating a predetermined stimulation signal, connected to a current input terminal of the sensor arrangement structure; a measurement unit adapted to sense an electrical signal applied to the current input terminal and including an analog-to-digital converter for acquiring sampled data representing the sensed electrical signal; and a signal processing unit configured to determine time response data of a selected detection unit based on the sampled data acquired by the measurement unit.

[0096] Preferably, the measuring unit comprises a filter for filtering the electrical signal, for example to remove disturbing or interfering components of the signal or to prepare the signal to be more easily analyzed.

[0097] Embodiments of the present invention also provide a primary section for a wireless power transmission system, wherein the wireless power transmission system transmits power across an air gap to a nearby receiver. According to the present invention, the primary section is configured to generate a magnetic field at a transmission frequency within an active area, and the primary section includes a sensor arrangement as described above or a foreign object detection device as described above, wherein the sensing coils are arranged such that a sensing area defined by the sensing coils at least partially covers the active area, and preferably, the sensing area completely covers the active area.

[0098] Further advantageous embodiments and feature combinations emerge from the following detailed description and from the entire claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The accompanying drawings are used to illustrate the embodiments and show:

[0100] Figure 1a and Figure 1b is a schematic diagram of a hexagonal sensing coil with a linear turn distribution and the magnitude of the magnetic field generated according to the prior art;

[0101] Figure 2a and Figure 2b is a schematic diagram of a hexagonal sensing coil with turns concentrated in an outer region of the coil and the magnitude of the magnetic field generated according to the prior art;

[0102] Figure 3a and Figure 3b is a schematic diagram of a hexagonal sensing coil and the magnitude of the magnetic field generated according to the present invention;

[0103] Figure 4 Is for Figure 1a A schematic diagram showing the effect of a foreign object on the coil shown in FIG. 1 in relation to the location of the foreign object;

[0104] Figure 5 Is for Figure 2a A schematic diagram showing the effect of a foreign object on the coil shown in FIG. 1 in relation to the location of the foreign object;

[0105] Figure 6 Is for Figure 3a A schematic diagram showing the effect of a foreign object on the coil shown in FIG. 1 in relation to the location of the foreign object;

[0106] Figure 7 is a schematic diagram of another embodiment of a sensing coil according to the present invention;

[0107] Figure 8 is a schematic diagram of another embodiment of a sensing coil according to the present invention;

[0108] Figure 9 is a schematic diagram of another embodiment of a sensing coil according to the present invention;

[0109] Figure 10 is a schematic diagram of a sensor arrangement according to the present invention;

[0110] Figure 11 is a schematic diagram of another sensor arrangement structure according to the present invention;

[0111] Figure 12 is a schematic diagram of a single-layer sensor arrangement structure in which leads are arranged one above the other;

[0112] Figure 13 It is a schematic diagram of the double-layer sensor arrangement structure;

[0113] Figure 14 is a schematic diagram of a foreign body detection device according to the present invention;

[0114] Figure 15 is a schematic diagram of a sensor arrangement according to the present invention; and

[0115] Figure 16 is a schematic diagram of yet another sensor arrangement structure according to the present invention.

[0116] In the drawings, the same components are given the same reference numerals. DETAILED DESCRIPTION

[0117] Figure 1a A hexagonal sensing coil 1 with a linear turns distribution as known in the prior art is shown. The sensing coil 1 has a length of approximately 56 mm and a width of approximately 50 mm, with a distance between adjacent turns of the coil of approximately 5 mm. Figure 1b A qualitative illustration of the corresponding total magnetic field amplitude generated by the hexagonal sensing coil 1, for example, when a stimulation signal comprising a step is applied, is shown. The horizontal axis shows the distance from the center of the sensing coil 1 in meters (m), and the vertical axis shows the magnetic field strength as a percentage of the corresponding maximum value. The absolute value of the generated magnetic field strength depends on various parameters of the specific application.

[0118] It can be seen that the magnetic field strength H has a maximum value at the center of the sensing coil 1 and decreases to 0 toward the edge of the sensing coil 1. Accordingly, the magnetic field strength of such a sensing coil 1 is far from being uniformly distributed over the area covered by the sensing coil 1.

[0119] Figure 2aA hexagonal sensing coil 2 is shown with turns concentrated in the outer region of the sensing coil 2. The sensing coil 2 also has a length of approximately 56 mm and a width of approximately 50 mm and comprises 5 turns in the outer region of the sensing coil 2 with a distance of approximately 2 mm between adjacent turns. Figure 2b A qualitative illustration of the generated magnetic field strength is shown. Likewise, the horizontal axis shows the distance from the center of the sensing coil 2 in m, and the vertical axis shows the magnetic field strength H as a percentage of the respective maximum value.

[0120] It can be seen that the magnetic field strength H has a maximum value at a distance of about 15 mm from the center of the sensing coil 2, decreases to 0 toward the edge of the sensing coil 2, and further decreases to a minimum value of about 80% toward the center of the sensing coil 2. Likewise, the magnetic field strength of such a sensing coil 2 may not be considered uniform over the area covered by the sensing coil 2.

[0121] Figure 3a A hexagonal sensing coil 3 according to the present invention is shown. Sensing coil 3 also has a length of approximately 56 mm and a width of approximately 50 mm, and includes an outer coil segment 3a having multiple turns and an inner coil segment 3b having a single turn. In this example, outer coil segment 3a includes four turns with a distance of approximately 2 mm between adjacent turns, while inner coil segment 3b has a single turn.

[0122] Figure 3b A qualitative illustration of the generated magnetic field strength is shown. Likewise, the horizontal axis shows the distance from the center of the sensing coil 3 in m, and the vertical axis shows the magnetic field strength H as a percentage of the respective maximum value.

[0123] It can be seen that the magnetic field strength H has a maximum value in a region with a radius of approximately 4 mm around the center of the sensing coil 3. From this region, the magnetic field strength drops slightly to a local minimum value of approximately 85% at a distance of approximately 13 mm, rises again to a local maximum value of approximately 90% at a distance of approximately 20 mm from the center of the sensing coil 3, and then drops to 0 toward the edge of the sensing coil 3.

[0124] The resulting magnetic field strength is therefore significantly more uniform. In a region of radius around the centre of the sensing coil 3 , of approximately 22 mm, the magnetic field strength varies only slightly before dropping off sharply towards the edge of the sensing coil 3 .

[0125] The absolute value of the magnetic field strength generated when measuring the detection unit's response to the stimulus signal also depends significantly on the presence of foreign matter in the magnetic field. For example, the foreign matter used to measure the magnetic field strength in the examples shown in Figures 1 to 3 is a square copper plate with a side length of 20 mm and a thickness of 0.3 mm.

[0126] In another example (not shown), the sensing coil has a hexagonal shape with four turns in the outer coil segment and a single turn in the inner coil segment, so that it appears to be Figure 3a The sensing coil 3 shown in FIG is identical. However, the dimensions are different. In this case, the sensing coil is slightly larger, which is, for example, better suited to covering a larger active area of ​​the primary field and / or detecting larger foreign objects. The width between two parallel sides (the smaller side of the rectangle enclosing the hexagon) is approximately 76.5 mm, resulting in a length of approximately 88.5 mm (the larger side of the rectangle enclosing the hexagon). The four turns of the outer coil segment are spaced approximately 3 mm apart from one another, while the width of the single turn of the inner coil segment is approximately 30 mm (the smaller side of the rectangle enclosing the hexagon) and its length is approximately 35.5 mm (the larger side of the rectangle enclosing the hexagon). Accordingly, the distance between the single turn of the inner coil segment and the innermost turn of the outer coil segment is approximately 13 mm, which is more than four times the 3 mm distance between the two turns of the outer coil segment.

[0127] Figure 4 Shown for Figure 1a FIG2 is a schematic diagram showing the influence of foreign objects on the sensing coil 1 in relation to the location of the foreign objects.

[0128] Figure 4 The figure shows the changes in resistance R and inductance L of the sensing coil 1 as a function of the displacement of the object from the center of the sensing coil 1 for a standard object (aluminum ring). The horizontal axis shows the displacement from the center of the sensing coil 1 in millimeters (mm), the vertical axis on the left shows the change in resistance R in percentage, and the vertical axis on the right shows the change in inductance L in percentage.

[0129] A set of lines 10 shows the change in resistance R of sensing coil 1 for three frequencies: 800 kHz, 850 kHz, and 900 kHz. It can be seen that if the standard object is located at the center of sensing coil 1, the change in resistance R of sensing coil 1 is approximately 16%. The change in resistance R then decreases to approximately 2% at a displacement of approximately 18 mm from the center. The change in resistance R then decreases further and approaches zero at a distance of 28 mm or greater.

[0130] A set of lines 11 shows the variation in inductance L of sensing coil 1 for the same three frequencies: 800 kHz, 850 kHz, and 900 kHz. It can be seen that these three lines are nearly identical over the entire range of displacement from the center of coil 1. If the standard object is located at the center of sensing coil 1, the variation in inductance L of sensing coil 1 is approximately 15%. The variation in inductance L decreases to approximately 2% at a displacement of approximately 20 mm from the center. The variation in inductance L then decreases further, approaching zero at a distance of 28 mm or greater.

[0131] Figure 5 Shown for Figure 2a FIG. 1 is a schematic diagram showing the influence of foreign matter on the sensing coil 2 in relation to the location of the foreign matter.

[0132] Similar to Figure 4 , Figure 5 The figure shows the changes in the resistance R and inductance L of the sensing coil 2 as a function of the displacement of the object from the center of the sensing coil 2 for a standard object (aluminum ring). The horizontal axis shows the displacement from the center of the sensing coil 2 in mm, the left vertical axis shows the change in resistance R in percentage, and the right vertical axis shows the change in inductance L in percentage.

[0133] A set of lines 12 shows the change in resistance R of the sensing coil 2 for three frequencies of 800 kHz, 850 kHz, and 900 kHz. It can be seen that if the standard object is located at the center of the sensing coil 2, the change in resistance R of the sensing coil 2 is about 5%, then the change in resistance R increases until it reaches a maximum value at a displacement of about 22 mm, and then rapidly decreases to a value of about 3% toward the edge of the sensing coil 2.

[0134] A set of lines 13 shows the variation in inductance L of sensing coil 2 for the same three frequencies: 800 kHz, 850 kHz, and 900 kHz. It can be seen that these three lines are nearly identical over the entire range of displacement from the center of coil 2. If the standard object is located at the center of sensing coil 2, the variation in inductance L of sensing coil 2 is approximately 1%. The variation in inductance L then increases to a value of approximately 2.5% at a displacement of approximately 24 mm from the center. The variation in inductance L then decreases again, approaching zero toward the edges of sensing coil 2.

[0135] Figure 6 Shown for Figure 3a For the coil shown, the impact of foreign matter is related to the location of the foreign matter.

[0136] Similar to Figure 4 and Figure 5 , Figure 6 The figure shows the changes in resistance R and inductance L of the sensing coil 3 according to the present invention, for a standard object (aluminum ring), as a function of the displacement of the object from the center of the sensing coil 3. The horizontal axis shows the displacement from the center of the sensing coil 3 in mm, the vertical axis on the left shows the change in resistance R in percentage, and the vertical axis on the right shows the change in inductance L in percentage.

[0137] A set of lines 14 shows the change in resistance R of the sensing coil 3 for three frequencies of 800 kHz, 850 kHz, and 900 kHz. It can be seen that if the standard object is located at the center of the sensing coil 3, the change in resistance R of the sensing coil 3 is about 9%, then slightly increases to a value of about 10% at a displacement of about 6 mm, then decreases to a value of about 7% at a displacement of about 16 mm, increases again to a value between about 8% and 10% at a displacement of about 22 mm, and then decreases again to a value of about 3% toward the edge of the sensing coil 3.

[0138] A set of lines 15 shows the variation in the inductance L of the sensing coil 3 for the same three frequencies of 800 kHz, 850 kHz, and 900 kHz. It can be seen that these three lines are almost identical over the entire range of displacement from the center of the coil 3. If the standard object is located at the center of the sensing coil 3, the variation in the inductance L of the sensing coil 3 is approximately 2%, then increases slightly to a value of approximately 2.5% at a displacement of approximately 6 mm, decreases to a value of approximately 1.5% at a displacement of approximately 16 mm, increases again to a value of approximately 2% at a displacement of approximately 26 mm, and finally decreases to approximately 0% toward the edge of the sensing coil 3.

[0139] from Figures 4 to 6 As can be seen from the figure, the change in resistance R and the change in inductance L of the sensing coil 3 according to the present invention are significantly more uniform than those of the sensing coils 1 and 2 known in the prior art. Therefore, compared with the existing method, the sensing coil 3 according to the present invention shows a significantly more uniformly distributed sensitivity.

[0140] Figure 7 Another embodiment of a sensing coil 20 according to the present invention is shown. The sensing coil 20 has a rectangular shape and includes an outer coil segment 20a having four turns and an inner coil segment 20b having a single turn. The outer coil segment 20a and the inner coil segment 20b are arranged on a coil layer. Figure 7 Also shown are output connection wires 20c leading from the ends of the single turns of the inner coil segment 20b to the outside of the coil 20. In this case, the output connection wires 20c are arranged on a different layer than the coil layer and are arranged above the coil layer.

[0141] Figure 8 Another embodiment of a sensing coil 22 according to the present invention is shown. The sensing coil 22 has a circular shape and includes an outer coil segment 22a having three turns and an inner coil segment 22b having a single turn. The outer coil segment 22a and the inner coil segment 22b are arranged on a coil layer. Figure 8 Also shown are output connection wires 22c leading from the ends of the single turns of the inner coil segment 22b to the outside of the coil 22. Also in this case, the output connection wires 22c are arranged on a different layer than the coil layer and are arranged above the coil layer.

[0142] Figure 9 Another embodiment of a sensing coil 24 according to the present invention is shown. The sensing coil 24 has a rectangular shape and includes an outer coil segment 24a having four turns and an inner coil segment 24b having two turns. The outer coil segment 24a and the inner coil segment 24b are arranged on a coil layer. Figure 9 Also shown are output connection wires 24c leading from the ends of the innermost turns of the inner coil segment 24b to the outside of the coil 24. In this case, the output connection wires 24c are arranged on a different layer than the coil layer and are arranged below the coil layer.

[0143] Figure 10 A sensor arrangement 29 according to the present invention is shown. The sensor arrangement 29 comprises 12 detection units 30-41 arranged in a matrix-like structure with three rows R1, R2 and R3 and four columns C1, C2, C3 and C4, wherein:

[0144] - a first row R1 comprising detection cells 30, 31, 32 and 33,

[0145] - the second row R2 comprises detection cells 34, 35, 36 and 37,

[0146] - the third row R3 comprises detection cells 38, 39, 40 and 41,

[0147] - a first column C1 comprising detection cells 30 , 34 and 38 ,

[0148] - the second column C2 comprises detection cells 31 , 35 and 39 ,

[0149] - the third column C3 comprises detection cells 32, 36 and 40, and

[0150] The fourth column C4 comprises detection cells 33 , 37 and 41 .

[0151] Each detection unit comprises any sensing coil as described above or known in the art, preferably a sensing coil according to the present invention as described above.

[0152] Sensor arrangement 29 also includes a plurality of input leads 50, 51, 52, and 53. Input leads 50 enter the matrix-like structure between the two central columns C2 and C3 and interconnect the input terminals of all detection cells 30, 34, and 38 in the first column C1. Input leads 51 also enter the matrix-like structure between the two central columns C2 and C3 and interconnect the input terminals of all detection cells 31, 35, and 39 in the second column C2. Input leads 52 also enter the matrix-like structure between the two central columns C2 and C3 and interconnect the input terminals of all detection cells 32, 36, and 40 in the third column C3. Input leads 53 also enter the matrix-like structure between the two central columns C2 and C3 and interconnect the input terminals of all detection cells 33, 37, and 41 in the fourth column C4.

[0153] Sensor arrangement 29 also includes a plurality of output leads 56, 57, and 58. Output lead 56 exits the matrix-like structure between the two center columns C2 and C3 and interconnects the output terminals of all detection cells 30, 31, 32, and 33 in first row R1. Output lead 57 also exits the matrix-like structure between the two center columns C2 and C3 and interconnects the output terminals of all detection cells 34, 35, 36, and 37 in second row R2. Output lead 58 also exits the matrix-like structure between the two center columns C2 and C3 and interconnects the output terminals of all detection cells 38, 39, 40, and 41 in third row R3.

[0154] Accordingly, a particular detection cell can be enabled by connecting the input lead of the column to which the detection cell belongs to the current input terminal via the input selection circuit, and connecting the output lead of the row to which the detection cell belongs to the current output terminal via the output selection circuit. For example, to enable detection cell 36, input lead 52 is connected to the current input terminal via the input selection circuit, and output lead 57 is connected to the current output terminal via the output selection circuit.

[0155] Figure 10 Not shown are: a current input and a current output of the sensor arrangement 29; an input selection circuit interconnecting the current input with one or more of the input leads 50, 51, 52, or 53 via a controllable switch; and an output selection circuit interconnecting one or more of the output leads 56, 57, or 58 with the current output via a controllable switch.

[0156] It should be noted that the arrangement, size, and spacing of the various elements (e.g., detection cells, input leads, and output leads) of the sensor arrangement 29 are not to scale. For example, the size of the detection cells is typically selected so that as large a portion of the area of ​​the sensor arrangement 29 as possible is covered by the detection cells.

[0157] like Figure 10As shown, all input leads 50, 51, 52, or 53 and all output leads 56, 57, or 58 are routed through the gap between the two center columns C2 and C3. They are arranged so that the input leads and output leads of a particular detection cell are adjacently arranged as close to each other as possible to minimize the area enclosed by the loop formed by the input leads and output leads of the detection cell.

[0158] Since all input and output leads are routed through the same gap between columns C2 and C3, the area enclosed by the loop formed by the input and output leads of the detection unit is as small as possible.

[0159] It is clear to a person skilled in the art that the roles of rows and columns of sensor arrangement 29 can also be reversed.

[0160] This sensor arrangement 29 can, for example, be used in conjunction with the double-D coil arrangement described above for generating a power transfer field. This coil arrangement generates a magnetic field with two poles: one at the center of the first coil and one at the center of the second coil. For example, the sensor arrangement 29 is positioned above the coil arrangement such that the detection elements 30, 34, and 38 of the first column C1 are positioned above the first pole of the power transfer field, and the detection elements 33, 37, and 41 of the fourth column C4 are positioned above the second pole of the power transfer field. In this manner, the magnetic field lines of the power transfer field in the region between the second column C2 and the third column C3 extend generally parallel to the plane of the detection elements. Accordingly, by arranging the input leads 50, 51, 52, and 53 and the output leads 56, 57, and 58 in the same layer, parallel to the plane of the detection element's coils, the area of ​​the detection element's coils spanned by the input and output leads, which is perpendicular to the magnetic field lines, is minimized. Furthermore, the magnetic field lines are less densely distributed, resulting in a weaker magnetic field.

[0161] Figure 11 Another sensor arrangement 59 according to the present invention is shown. The sensor arrangement 59 comprises six detection units 30-35 arranged in a matrix-like structure having two rows R1, R2 and three columns C1, C2 and C3, wherein

[0162] - a first row R1 comprising detection cells 30, 31 and 32,

[0163] - the second row R2 comprises detection cells 33, 34 and 35,

[0164] - the first column C1 comprises detection cells 30 and 33,

[0165] - the second column C2 comprises detection cells 31 and 34, and

[0166] The third column C3 comprises detection cells 32 and 35 .

[0167] Each detection unit comprises any sensing coil as described above or known in the art, preferably a sensing coil according to the present invention as described above.

[0168] The sensor arrangement 59 further includes a plurality of input leads 60, 61, and 62. Input leads 60 enter the matrix structure at an edge of the sensor arrangement 59 near the third column C3 and interconnect the input terminals of all detection cells 30 and 33 in the first column C1. Input leads 61 also enter the matrix structure at an edge of the sensor arrangement 59 near the third column C3 and interconnect the input terminals of all detection cells 31 and 34 in the second column C2. Input leads 62 also enter the matrix structure at an edge of the sensor arrangement 59 near the third column C3 and interconnect the input terminals of all detection cells 32 and 35 in the third column C3.

[0169] The sensor arrangement 59 further includes a plurality of output leads 66 and 67. The output leads 66 exit the matrix-like structure at an edge of the sensor arrangement 59 near the third column C3 and interconnect the output terminals of all the detection units 30, 31, and 32 of the first row R1; the output leads 67 also exit the matrix-like structure at an edge of the sensor arrangement 59 near the third column C3 and interconnect the output terminals of all the detection units 33, 34, and 35 of the second row R2.

[0170] Figure 11 Not shown are: a current input and a current output of the sensor arrangement 59; an input selection circuit interconnecting the current input with one or more of the input leads 60, 61, 62 via a controllable switch; and an output selection circuit interconnecting one or more of the output leads 66 or 67 with the current output via a controllable switch.

[0171] Note also that the arrangement, size, and spacing of the various elements of the sensor arrangement 59 (eg, detection cells, input leads, and output leads) are not to scale.

[0172] like Figure 11As shown, all input leads 60, 61, and 62 and all output leads 66 and 67 are routed at the edge of the sensor arrangement 59 near the third column C3. However, in this case, the input leads and output leads of the detection cells in the first column C1 are longer than in a sensor arrangement in which the input leads and output leads are routed through the gap between the two center columns (or rows). In other words, if the input leads and output leads are routed through the center gap, the variation in the length of the input leads and output leads of different detection cells is less than in a case in which the input leads and output leads are routed along the edge or routed through the gap between the two outer columns or rows.

[0173] It is clear to a person skilled in the art that the roles of rows and columns of sensor arrangement 59 can also be reversed.

[0174] Figure 12 A single-layer sensor arrangement 69 is shown in side view, in which leads are arranged one above the other. The sensor arrangement 69 is disposed on a support structure, such as a multi-layer PCB 75, such that the detection units 30, 31, 32, and 33 of the sensor arrangement 69 are disposed on the upper surface of the PCB 75 or are embedded in corresponding recesses. A plurality of input and output leads 70, 71, 72, and 73 are provided to connect the detection units 30, 31, 32, and 33 to current input terminals and current output terminals, respectively.

[0175] Figure 12 The black dots in indicate that the corresponding lines are perpendicular to the drawing plane.

[0176] Figure 12 The sensor arrangement 69 is shown with some input and / or output leads arranged one above the other to minimize voltages induced in the leads by external magnetic fields. In the sensor arrangement 69, a multilayer PCB 75 comprises three conductive layers on which input and output leads 70, 71, 72, 73 are provided.

[0177] Figure 13 A two-layer sensor arrangement 79 is shown in side view. Sensor arrangement 79 is disposed on a support structure, such as a multi-layer PCB 85, ​​and includes two layers of detection units, where each layer comprises a matrix of detection units. The first layer includes detection units 30, 31, 32, and 33 disposed on the upper surface of PCB 85 or embedded in corresponding recesses. The second layer includes detection units 34, 35, and 36 disposed on the lower surface of PCB 85 or embedded in corresponding recesses.

[0178] A plurality of input and output leads 80, 81, 82, 83, and 84 are provided to connect the detection units 30, 31, 32, and 33 to the current input and current output terminals, respectively. Similarly, the input and output leads are provided on different conductive layers of a multilayer PCB 85. Black dots also indicate that the corresponding lines are perpendicular to the drawing plane.

[0179] like Figure 13 As shown, the two layers of detection units are arranged to be staggered with each other, so that the detection units of one layer cover the gaps between the detection units of the other layer, so as to reduce blind spots or areas where the detection sensitivity is reduced.

[0180] Figure 14 A simplified block diagram of a foreign object detection (FOD) device 119 having a sensor arrangement 120 according to the present invention is shown. The FOD device 119 further includes a stimulation unit 121, a measurement unit 122, and a signal processing and control unit 123. The sensor arrangement 120 includes a sensing coil pad 124 having a PCB as a support structure; a detection unit selection circuit 134 having a first multiplexing unit 125 as an input selection circuit and a second multiplexing unit 126 as an output selection circuit. The sensor arrangement 120 includes a current input terminal 135 and a current output terminal 136.

[0181] First multiplexing unit 125 is a demultiplexer having one input and five outputs. The demultiplexer's output is connected to input lead 127 of sensor arrangement 120. The demultiplexer's input is connected to current input 135 of sensor arrangement 120. Second multiplexing unit 126 is a multiplexer having five inputs and one output. The multiplexer's input is connected to output lead 128 of sensor arrangement 120. The output of multiplexing unit 126 is connected to current output 136 of sensor arrangement 120, which is connected to ground 137.

[0182] The sensing coil pad 124 comprises an array of 5×5 detection elements. Each detection element can be selected via two multiplexing elements 125 and 126. The output of the stimulation element 121 is connected to the input of the first multiplexing element 125. The filter input of the bandpass filter 129 of the measuring element 122 is connected to the current input 135. The measuring element 122 also includes an analog-to-digital converter (ADC) 130, which is connected to the output of the bandpass filter 129. The passband of the bandpass filter 129 includes the resonant frequency of the resonant circuit of the detection elements of the sensor arrangement, which is approximately 900 kHz in this case. The stopband eliminates frequencies related to the operating frequency of the power transmission field, which is, for example, 45 kHz in this case.

[0183] The bandpass filter 129 is optional and may also be replaced by a high-pass filter. In addition to or as an alternative to the bandpass filter 129, the measuring unit 122 may also include a signal conditioning module, for example for scaling or converting the signal.

[0184] The input of the signal processing and control unit 123 is connected to the output of the ADC 130. The signal processing and control unit also has a row selection control output 131 connected to the first multiplexing unit 125, a column selection control output 132 connected to the second multiplexing unit 126, and a trigger control output 133 connected to the input of the stimulation unit 121.

[0185] The signal processing and control unit 123 includes a microcontroller, for example, a digital signal controller, an FPGA and / or an ASIC. The functions of the microcontroller can be implemented by the FPGA and / or the ASIC. The signal processing and control unit 123 includes a memory for the sampled data acquired by the ADC 130. It preferably includes means for reproducing the stimulation signal, for example, a memory for the timestamp of the triggering event of the stimulation signal. Alternatively, the measurement unit 122 may include another signal channel for acquiring the stimulation signal. The signal processing and control unit 123 then also includes a data memory for the acquired samples of the stimulation signal.

[0186] The signal processing and control unit 123 is configured to calculate parameters related to the series impedance of the selected detection unit based on the sampled electrical signal and the stimulation signal.

[0187] Figure 15 A schematic circuit diagram of an embodiment of a sensor arrangement 140 according to the present invention, together with a stimulation unit 141, is shown. Sensor arrangement 140 includes a current input 142 and a current output 143, which is connected to ground. Current input 142 is connected to the output of stimulation unit 141. Sensor arrangement 140 includes four detection units, namely a first detection unit 144.1, a second detection unit 144.2, a third detection unit 144.3, and a fourth detection unit 144.4, arranged in a matrix structure comprising two rows and two columns.

[0188] Each of the four detection units 144.1, 144.2, 144.3, and 144.4 includes, for example, a sensing coil and a capacitor arranged in parallel, the sensing coil and the capacitor forming a parallel resonant circuit. Each of the detection units 144.1, 144.2, 144.3, and 144.4 may also include a diode whose cathode is connected in series to a first terminal of the parallel resonant circuit of the corresponding detection unit 144.1, 144.2, 144.3, and 144.4.

[0189] First detection cell 144.1 and second detection cell 144.2 are part of the first row, while third detection cell 144.3 and fourth detection cell 144.4 are part of the second row. First input lead 148a is connected to the input of first detection cell 144.1, which is part of the first row, and to the input of third detection cell 144.3, which is part of the second row. Similarly, second input lead 148b is connected to second detection cell 144.2, which is part of the first row, and to fourth detection cell 144.4, which is part of the second row. The second terminals of the detection cells in the first row are connected to first output lead 150a. Similarly, the second terminals of the detection cells in the second row are connected to second output lead 150b.

[0190] The number of detection units and the total number of input leads and output leads in this embodiment are both four, so the number of detection units is the same as the total number of input leads and output leads.

[0191] The sensor arrangement further includes an input selection circuit 152, which includes a first switch Q1 and a second switch Q2. Switches Q1 and Q2 can be implemented, for example, as MOSFETs. The first switch Q1 is connected between the current input terminal 142 and the first input lead 148a, and the second switch Q2 is connected between the current input terminal 142 and the second input lead 148b. By addressing either the first switch Q1 or the second switch Q2, a column of the 2×2 sensor matrix can be selected.

[0192] Furthermore, the sensor arrangement 140 includes an output selection circuit 153, which includes a third switch Q3 and a fourth switch Q4. The third switch Q3 is connected between the first output lead 150a and the current output terminal 143. In this embodiment, the current output terminal 143 is connected to ground. The fourth switch Q4 is connected between the second output lead 150b and the current output terminal 143. By addressing the third switch Q3 or the fourth switch Q4, a row of the 2×2 sensor matrix can be selected.

[0193] The input selection circuit 152 and the output selection circuit 153 each include two control inputs 154, 155, 156, and 157, which are connected to the control inputs of the corresponding switches Q1, Q2, Q3, and Q4. These control inputs 154-157 can be used to address different switches Q1, Q2, Q3, and Q4, thereby selecting a detection unit.

[0194] The stimulation unit 141 is configured to generate rectangular current pulses to stimulate electrical oscillations in the parallel circuit of the selected detection unit. The stimulation unit includes a current source and an internal switch. Figure 15 Not shown in the figure.

[0195] The excited electrical oscillation in the selected detection cell generates an oscillating voltage between the current input terminal 142 and the current output terminal 143 (ground), which can be sensed, for example, by an ADC having terminals connected between the current input terminal and ground.

[0196] Figure 16 FIG2 shows a schematic diagram of another sensor arrangement 229 according to the present invention. The sensor arrangement 229 comprises eight detection units 30-37 arranged in a matrix structure having two rows R1 and R2 and four columns C1, C2, C3 and C4, wherein:

[0197] - a first row R1 comprising detection cells 30, 31, 32 and 33,

[0198] - the second row R2 comprises detection cells 34, 35, 36 and 37,

[0199] - The first column C1 comprises detection cells 30 and 34

[0200] - the second column C2 comprises detection cells 31 and 35,

[0201] - the third column C3 comprises detection cells 32 and 36, and

[0202] The fourth column C4 comprises detection cells 33 and 37 .

[0203] Each detection unit comprises any sensing coil as described above or known in the art, preferably a sensing coil according to the present invention as described above.

[0204] In this embodiment of the invention, each detection cell of the sensor arrangement 229 comprises its own input leads 251 - 258 which are fed into a matrix-like structure and fed to each detection cell separately from the input leads of the other detection cells.

[0205] All input leads 251 - 258 enter the matrix-like structure between the two center columns C2 and C3 and run in parallel until they are connected to the corresponding detection units.

[0206] The sensor arrangement 229 also includes only a single output lead 259 that interconnects the output terminals of all detection cells 30-37 and then exits the matrix-like structure between the two center columns C2 and C3. Specifically, the single output lead 259 is arranged in the center of the input leads 251-258, in this case between input leads 257 and 258.

[0207] Since there is only a single output lead 259, this sensor arrangement typically does not include output selection circuitry to connect one or more output leads to the current output. In this case, the single output lead 259 is connected directly to the current output.

[0208] Accordingly, a specific detection unit can be enabled by connecting the input lead of the detection unit to the current input terminal through the input selection circuit, and the output lead of the detection unit is permanently connected to the current output terminal.

[0209] Figure 16 Not shown are: the current input and current output of the sensor arrangement 229; and input selection circuitry interconnecting the current input with one or more of the input leads 251-258 via controllable switches.

[0210] Note that the arrangement, size, and spacing of the various elements of the sensor arrangement 229 (eg, detection cells, input leads, and output leads) are not to scale.

[0211] like Figure 16 As shown, all input leads 251-258 and a single output lead 259 are routed through the gap between the two center columns C2 and C3. Furthermore, they are arranged so that the input and output leads of a particular detection cell are adjacently positioned as close to each other as possible, minimizing the area enclosed by the loop formed by the input and output leads of that detection cell. In the case of a double-D arrangement, this could be, for example, midway between the two magnetic poles.

[0212] It is clear to a person skilled in the art that the roles of rows and columns of sensor arrangement 229 may also be reversed.

[0213] In summary, it is to be noted that the present invention enables the creation of a sensor arrangement for a foreign object detection device which ensures a relatively uniform sensitivity for foreign object detection over the surface of the transmitting unit.

[0214] It is also noted that the present invention enables the creation of a sensor arrangement structure for a foreign object detection device that minimizes hardware effort and minimizes the total length of the input and output leads, as well as a sensor arrangement structure for a foreign object detection device that reduces the voltage induced in the input and output leads of a single detection unit by reducing the area surrounded by the input and output leads of the detection unit and potentially passed through by an external magnetic field. The reduction in the voltage induced in the input and output leads minimizes the interference effects and distortion of external magnetic fields (e.g., the power transmission field of a wireless power transmission system) on foreign object detection.

Claims

1. A sensor arrangement structure for use in a foreign object detection device of a wireless power transmission system, the sensor arrangement structure comprising: Current input terminal and current output terminal; a plurality of detection units, each detection unit comprising a sensing coil, wherein a winding of the sensing coil is spirally wound in a plane and has a plurality of turns; a plurality of input leads and one or more output leads, wherein each detection unit is connected between one of the input leads and one of the output leads, and wherein each detection unit is connected to a different combination of input leads and output leads; and an input selection circuit adapted to selectively establish an electrical connection between the current input terminal and one or more of the input leads; It is characterized by: The sensing coil of at least one detection unit comprises an outer coil segment and an inner coil segment arranged within the outer coil segment, wherein a first distance between an outermost turn of the inner coil segment and an innermost turn of the outer coil segment is at least twice a maximum distance between two turns of the outer coil segment; The distance between the center of the sensing coil of the at least one detection unit and the innermost turn of the inner coil segment is equal to or less than two-thirds of the distance between the center of the sensing coil and the outermost turn of the outer coil segment.

2. The sensor arrangement according to claim 1, wherein: The sensing coil of the at least one detection unit comprises a plurality of turns in the outer coil segment and a single turn in the inner coil segment.

3. The sensor arrangement according to claim 2, wherein: The first distance is equal to a distance between a single turn of the inner coil segment and a center of the sensing coil of the at least one detection unit.

4. The sensor arrangement according to any one of claims 1 to 3, wherein: The turns of the outer coil segment of the at least one detection unit are arranged equidistant from one another.

5. The sensor arrangement according to any one of claims 1 to 3, wherein: The sensing coils are arranged in one or more layers, and wherein the sensing coils of each layer are arranged in a regular pattern.

6. A sensor arrangement structure for use in a foreign object detection device of a wireless power transmission system, the sensor arrangement structure being the sensor arrangement structure according to any one of claims 1 to 5, comprising: Current input terminal and current output terminal; a plurality of detection units, each detection unit comprising a sensing coil having a winding helically wound in a plane and having a plurality of turns; wherein the sensing coils of the plurality of detection units are arranged in one or more layers, and wherein the sensing coils of a particular layer are arranged in a matrix-like structure having a plurality of rows and a plurality of columns; a plurality of input leads and one or more output leads, wherein each detection unit is connected between one of the input leads and one of the output leads, and wherein each detection unit is connected to a different combination of input leads and output leads; and an input selection circuit adapted to selectively establish an electrical connection between the current input terminal and one or more of the input leads; It is characterized by: Input leads and output leads of at least one sensing coil are routed close to each other through the matrix structure to which the at least one sensing coil belongs to reduce an area parallel to the matrix structure and surrounded by the input leads and the output leads.

7. The sensor arrangement according to claim 6, wherein: The input leads and output leads of each sensing coil of a particular layer are routed through the gaps between two columns or two rows of the matrix-like structure, and through the gaps between the two center columns or two center rows.

8. The sensor arrangement according to claim 6, wherein: The distance between the input lead and the output lead of the at least one sensing coil is smaller than the distance between two rows or two columns of the matrix structure.

9. The sensor arrangement according to any one of claims 6 to 8, wherein: The input lead and the output lead of the at least one sensing coil are arranged one above the other.

10. The sensor arrangement according to any one of claims 6 to 8, wherein: The input lead and the output lead of the at least one sensing coil are twisted at least once.

11. The sensor arrangement according to any one of claims 6 to 8, comprising: An output selection circuit is adapted to selectively establish an electrical connection between one or more of the output leads and the current output terminal.

12. The sensor arrangement according to any one of claims 6 to 8, wherein: The sensing coil of the at least one detection unit has a rectangular shape.

13. A foreign object detection device for use in a primary portion of a wireless power transmission system, the wireless power transmission system being configured to transmit power across an air gap to a nearby receiver, the foreign object detection device comprising: The sensor arrangement according to any one of claims 1 to 12; a stimulation circuit configured to generate a predetermined stimulation signal and connected to a current input terminal of the sensor arrangement; a measuring unit adapted to sense the electrical signal applied to the current input terminal, the measuring unit comprising an analog-to-digital converter configured to acquire sampled data representing the sensed electrical signal; as well as A signal processing unit is configured to determine time response data of the selected detection unit based on the sampling data acquired by the measurement unit.

14. A primary part for a wireless power transmission system for transmitting power across an air gap to a nearby receiver, the primary part being configured to generate a magnetic field at a transmission frequency in an active area, the primary part comprising the sensor arrangement according to any one of claims 1 to 12 or the foreign object detection device according to claim 13, wherein: The sensing coils are arranged such that a sensing area defined by the sensing coils at least partially covers the active area, and the sensing area completely covers the active area.

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