Wireless Power System with Object Detection

Abstract

The present disclosure relates to a wireless power system with object detection. The wireless power system has a wireless power transmission device and a wireless power reception device. The wireless power transmission device can be a wireless charging pad or other device having one or more wireless power transmission coils for transmitting a wireless power signal. The wireless power reception device can be a portable electronic device having one or more wireless power reception coils for receiving the transmitted wireless power signal. The wireless power transmission device may have an external object detection coil. During wireless power transmission, a quality factor measurement may be performed on the transmission coil, and / or a voltage measurement may be performed using the external object detection coil to detect the presence of an external object. The external object detection coil may include overlapping coils having different winding patterns to enhance the external object detection coverage.

Description

[0001] This patent application claims priority to U.S. Non - Provisional Patent Application No. 16 / 867,460, filed on May 5, 2020, and U.S. Provisional Patent Application No. 62 / 889,162, filed on August 20, 2019, the entireties of which are hereby incorporated by reference herein. Technical Field

[0002] The present disclosure relates generally to power systems, and more particularly, to wireless power systems for charging electronic devices. Background Art

[0003] In a wireless charging system, a wireless power transfer device such as a charging pad wirelessly transfers power to a wireless power receiving device such as a portable electronic device. The portable electronic device has a coil and a rectifier circuit. The coil of the portable electronic device receives an alternating - current wireless power signal from the wireless charging pad. The rectifier circuit converts the received signal into direct - current power. To ensure satisfactory operation, the wireless charging system may have a circuit for detecting foreign objects. Summary of the Invention

[0004] A wireless power system has a wireless power transfer device and a wireless power receiving device. The wireless power transfer device can be a wireless charging pad or other device having one or more wireless power transfer coils for transmitting a wireless power signal. The wireless power receiving device can be a portable electronic device having one or more wireless power receiving coils for receiving the transmitted wireless power signal.

[0005] The wireless power transfer device has foreign - object detection coils of one or more winding types. During wireless power transfer, a quality - factor measurement can be performed on the transfer coil and / or a magnetic - field measurement can be performed using the foreign - object detection coils to detect the presence of foreign objects.

[0006] The foreign - object detection coils can include different types of overlapping coils. For example, the foreign - object detection coils can include a first set of coils having a spiral winding and a second set of coils having a figure - eight winding. By overlapping the first and second coils, the foreign - object detection accuracy can be improved. Brief Description of the Drawings

[0007] Figure 1 is a schematic diagram of an exemplary wireless power system including a wireless power transfer device and a wireless power receiving device, according to one embodiment.

[0008] Figure 2 is a graph of an exemplary wireless power transmitter signal, according to one embodiment.

[0009] Figure 3is a circuit diagram showing an exemplary measurement circuit in a wireless power transmitter according to one embodiment.

[0010] Figure 4 , Figure 5 , Figure 6 and Figure 7 are illustrations of an exemplary wireless power transmitter coil and an external object detection coil according to one embodiment.

[0011] Figure 8 is a cross-sectional side view of an exemplary wireless power system according to one embodiment.

[0012] Figure 9 is an illustration of an exemplary external object detection coil having a spiral winding according to one embodiment.

[0013] Figure 10 is an illustration of an exemplary external object detection coil according to one embodiment, the external object detection coil having an 8-shaped winding forming a pair of sub-coils having respective clockwise and counterclockwise winding senses.

[0014] Figure 11 is a cross-sectional side view of a portion of overlapping sub-coils in an exemplary wireless power transfer coil and an external object detection coil according to one embodiment.

[0015] Figure 12 is a graph showing possible output readings from overlapping spiral and 8-shaped external object detection coils varying with the position of an external object according to one embodiment. DETAILED DESCRIPTION

[0016] The wireless power system includes a wireless power transfer device, such as a wireless charging pad. The wireless power transfer device wirelessly transfers power to a wireless power receiving device (such as a wristwatch, cellular phone, tablet computer, laptop computer, or other electronic device). The wireless power receiving device uses the power from the wireless power transfer device to power the device and to charge an internal battery.

[0017] One or more wireless power transfer coils are used to transfer wireless power from the wireless power transfer device to the wireless power receiving device to charge a battery in the wireless power receiving device and / or to power other load circuits. The wireless power receiving device has one or more wireless power receiving coils coupled to a rectifier circuit that converts the received wireless power signal to DC power.

[0018] Figure 1 An exemplary wireless power system (wireless charging system) is shown in Figure 1As shown, the wireless power system 8 includes a wireless power transmission device (such as the wireless power transmission device 12), and includes a wireless power receiving device (such as the wireless power receiving device 24). The wireless power transmission device 12 includes a control circuit 16. The wireless power receiving device 24 includes a control circuit 30. The control circuits in the system 8, such as the control circuit 16 and the control circuit 30, are used to control the operation of the system 8. Such control circuits may include processing circuits associated with a microprocessor, a power management unit, a baseband processor, a digital signal processor, a microcontroller, and / or an application specific integrated circuit having a processing circuit. The processing circuits implement desired control and communication features in the devices 12 and 24. For example, the processing circuits may be used to select coils, determine the power transmission level, process sensor data and other data to detect foreign objects and perform other tasks, process user input, handle negotiations between the devices 12 and 24, send and receive in-band and out-of-band data, make measurements, and otherwise control the operation of the system 8. In an illustrative configuration, the processing circuit of the device 12 uses a foreign object detection coil to monitor the presence of foreign objects such as coins, paper clips, credit cards, etc., and takes appropriate actions (e.g., stops power transmission) in response to detecting the presence of a foreign object.

[0019] The control circuits in the system 8 may be configured to perform operations in the system 8 using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. The software code for performing operations in the system 8 is stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium) in the control circuit 8. Such software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer-readable storage medium may include non-volatile memory such as non-volatile random access memory (NVRAM), one or more hard disk drives (e.g., a disk drive or a solid state drive), one or more removable flash drives, or other removable media, etc. The software stored on the non-transitory computer-readable storage medium may be executed on the processing circuits of the control circuit 16 and / or 30. The processing circuits may include an application specific integrated circuit having a processing circuit, one or more microprocessors, a central processing unit (CPU), or other processing circuits.

[0020] The power transmission device 12 may be a standalone power adapter (e.g., a wireless charging pad or charging puck including a power adapter circuit), may be a wireless charging pad or stand coupled to a power adapter or other equipment via a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other systems, may be a removable battery case, or may be other wireless power transfer equipment. An illustrative configuration in which the wireless power transmission device 12 is a wireless charging pad is sometimes described as an example herein.

[0021] The power receiving device 24 can be a portable electronic device, such as a wristwatch, a cellular phone, a laptop computer, a tablet computer, an accessory such as earbuds, or other electronic equipment. The power transmission device 12 can be coupled to a wall outlet (e.g., an AC power source), can have a battery for supplying power, and / or can have another power source. The power transmission device 12 can have an alternating current (AC)-direct current (DC) power converter, such as the AC-DC power converter 14, for converting AC power from the wall outlet or other power source into DC power. The DC power can be used to power the control circuit 16. During operation, a controller in the control circuit 16 uses the power transmission circuit 52 to transmit wireless power to the power receiving circuit 54 of the device 24. The power transmission circuit 52 can have a switching circuit (e.g., an inverter circuit 61 formed by transistors), which is turned on or off based on a control signal provided by the control circuit 16 to form an AC current signal through one or more wireless power transmission coils such as the wireless power transmission coil 36. These coil drive signals cause the coil 36 to transmit wireless power. The coil 36 can be arranged as a planar coil array (e.g., in a configuration where the device 12 is a wireless charging pad) or can be arranged to form a coil cluster (e.g., in a configuration where the device 12 is a wireless charging stand). In some arrangements, the device 12 (e.g., a charging pad, a charging stand, etc.) can have only a single coil. In other arrangements, the wireless charging device can have multiple coils (e.g., two or more coils, 5 - 10 coils, at least 10 coils, 10 - 30 coils, fewer than 35 coils, fewer than 25 coils, or other suitable numbers of coils).

[0022] When an AC current passes through one or more coils 36, an alternating current electromagnetic (e.g., magnetic) field (wireless power signal 44) is generated, and these alternating current electromagnetic fields are received by one or more corresponding receiver coils, such as one or more coils 48 in the power receiving device 24. The device 24 can have a single coil 48, at least two coils 48, at least three coils 48, at least four coils 48, or other suitable numbers of coils 48. When the alternating current electromagnetic field is received by the coil 48, a corresponding alternating current is induced in the coil 48. A rectifier circuit such as the rectifier circuit 50 (which includes rectifying components, such as synchronous rectifier metal oxide semiconductor transistors arranged in a bridge network) converts the AC signal received from one or more coils 48 (the received alternating current signal associated with the electromagnetic signal 44) into a DC voltage signal for powering the device 24.

[0023] The DC voltage generated by the rectifier circuit 50 (sometimes referred to as the rectifier output voltage Vrect) can be used to charge a battery such as battery 58 and can also be used to power other components in the device 24. For example, the device 24 can include input-output devices 56 such as a display, a touch sensor, a communication circuit, an audio component, a sensor, a light-emitting diode status indicator, other light-emitting and light-detecting components, and other components, and these components (which form the load of the device 24) can be powered by the DC voltage generated by the rectifier circuit 50 (and / or the DC voltage generated by the battery 58).

[0024] The device 12 and / or the device 24 can perform wireless communication using in-band or out-of-band communication. The device 12 can, for example, have a wireless transceiver circuit 40 that uses an antenna to wirelessly transmit an out-of-band signal to the device 24. The wireless transceiver circuit 40 can be used to wirelessly receive an out-of-band signal from the device 24 using the antenna. The device 24 can have a wireless transceiver circuit 46 that transmits an out-of-band signal to the device 12. The receiver circuit in the wireless transceiver 46 can use the antenna to receive an out-of-band signal from the device 12. In-band transmission between the devices 12 and 24 can be performed using the coils 36 and 48. In one exemplary configuration, frequency-shift keying (FSK) is used to transmit in-band data from the device 12 to the device 24, and amplitude-shift keying (ASK) is used to transmit in-band data from the device 24 to the device 12. During these FSK and ASK transmissions, power can be wirelessly transmitted from the device 12 to the device 24.

[0025] It is desirable for the power transmission device 12 and the power receiving device 24 to be able to communicate information such as received power, charge status, etc. to control wireless power transfer. However, the above techniques can function without involving the transmission of personally identifiable information. Out of an abundance of caution, it should be noted that to the extent that any implementation of this charging technology involves the use of personally identifiable information, the implementer should follow privacy policies and practices that are generally considered to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of inadvertent or unauthorized access or use, and the nature of the authorized use should be clearly explained to the user.

[0026] The control circuit 16 includes an external object measurement circuit 41 that can be used to detect external objects on the charging surface of the device 12 (e.g., on top of a charging pad, or if desired, to detect objects adjacent to the coupling surface of a charging dock). The circuit 41 can detect foreign objects such as coils, paper clips, and other metallic objects, and can detect the presence of a wireless power receiving device 24 (e.g., the circuit 41 can detect the presence of one or more coils 48). During object detection and characterization operations, the external object measurement circuit 41 can be used to make measurements on the coil 36 and / or the foreign object detection coil 70 to determine whether any device 24 is present on the device 12.

[0027] In an exemplary arrangement, the measurement circuit 41 of the control circuit 16 includes a signal generator circuit (e.g., an oscillator circuit for generating an AC probe signal at one or more probe frequencies, a pulse generator that can generate pulses to enable measurement of the pulse response to acquire inductance information, quality factor (Q-Factor) information, etc.) and a signal detection circuit (e.g., a filter, an analog-to-digital converter, a pulse response measurement circuit, etc.). In some configurations, quality factor measurements and other measurements can be made during wireless power transfer operations. A switching circuit in the device 12 can be used to switch the desired coil into use during wireless power transfer and / or foreign object detection operations.

[0028] The measurement circuit 43 in the control circuit 30 and / or the measurement circuit 41 in the control circuit 16 can be used to make current and voltage measurements. Based on this information or other information, the control circuit 30 can configure the rectifier circuit 50 to help enhance wireless power reception by the coil 48.

[0029] Figure 2 is a graph showing an exemplary wireless power transfer signal during wireless power transfer. The wireless power transfer coil signal 72 (e.g., coil voltage) is characterized by an AC waveform that is created by the inverter 61 when the inverter 61 drives the wireless power transfer coil. In Figure 2 example, the waveform is a square wave. If desired, other types of alternating current (AC) waveforms can be provided. The frequency of the AC drive signal can be 10 kHz to 1 MHz, at least 50 kHz, less than 300 kHz, or other suitable frequencies.

[0030] As Figure 2As shown, oscillations 74 can be induced in the wireless power transfer coil signal 72 (e.g., oscillations caused by each square wave period of the AC drive signal and / or oscillations caused by pulses individually applied to the wireless power transfer coil by the control circuit 16 during wireless power transfer). Using the analog-to-digital converter circuit, peak detection circuit, envelope detection circuit, and / or other measurement circuits 41 in the control circuit 16, the magnitude and frequency of the oscillatory components of the wireless power transfer coil signal and the decay envelope 76 can be measured, thereby allowing measurement of coil parameters such as inductance L and quality factor. When no foreign object is present, the decay envelope can have a shape of the type shown by the exemplary decay envelope 76 (by way of example). When a foreign object is present, a damped response can be exhibited (see, for example, damped envelope 76').

[0031] Figure 3 is a circuit diagram of an exemplary transmission coil circuit. As Figure 3 shown, the measurement circuit 41 can have a voltage sensor configured to measure the signal 72 on the wireless power transfer coil 36 (including the oscillatory portion of the signal 72). Figure 3 The components of Figure 3 (e.g., coil 36 and capacitor C) form a parallel resonant circuit that is tuned to a measurable frequency (e.g., a frequency of at least 0.2 MHz, at least 0.5 MHz, about 1 MHz, less than 2 MHz, less than 1.5 MHz, or other suitable frequency). The capacitor C can be used to reduce the frequency of the oscillations 74. The value of the capacitor C can be at least 0.2 nF, at least 2 nF, 22 nF, less than 200 nF, less than 400 nF, or other suitable value. In the absence of the capacitor C, the frequency of the oscillations 74 can be in the tens of MHz, which can pose measurement challenges. In the presence of the capacitor C coupled across the coil 36, the frequency of the oscillations 74 can be reduced (e.g., to hundreds of kHz, 1 MHz, or other suitable frequency), thereby facilitating measurement of the oscillations 74 using the measurement circuit 41.

[0032] During operation, the control circuit 16 can use the measurement circuit 41 to measure coil characteristics such as the quality factor (e.g., by measuring the decay envelope 76) to determine whether a foreign object is present on the coil 36. In the presence of a foreign object s (e.g., a metallic object), the wireless power signal will induce eddy currents in the foreign object, and these eddy currents will result in a lower quality factor value. In response to detecting that the measured Q value is less than a predetermined threshold (or using other suitable detection criteria), the control circuit 16 can conclude that a foreign object may be present and can take appropriate action (e.g., by notifying the user of the system 8, by stopping wireless power transfer, by reducing the amount of power being transferred to a relatively low level, etc.). Analysis of the oscillatory signal can be performed during the power transfer operation, so there is no need to interrupt power transfer to detect foreign objects.

[0033] If desired, the control circuit 16 may use the foreign object detection coil 70 to detect foreign objects. The coil 70 may be arranged to overlap fully or partially with one or more of the coils 36. Figure 4 , Figure 5 , Figure 6 and Figure 7 show how the coil 70 may include four overlapping coil layers configured to provide foreign object detection for the overlapping transmission coils 36. In Figure 4 and Figure 5 's example, the coil 70 forms a section of a loop. The layout of the coil 70 varies between Figure 4 and Figure 5 to enhance detection sensitivity. In Figure 6 and Figure 7 's example, the coil 70 has a fan-shaped (e.g., wedge-shaped) shape. Figure 6 and Figure 7 's coil 70 patterns are different from each other and from the coil patterns of the coil 70 in Figure 4 and Figure 5 to create sensitivity in different regions and thus enhance foreign object detection coverage. In Figure 4 , Figure 5 , Figure 6 and Figure 7 's exemplary configuration, there are a total of four layers of coils 70 and 16 coils 70. Generally, there may be one layer of coils 70, at least two layers of coils 70, at least three layers of coils 70, at least four layers of coils 70, or other suitable numbers of foreign object detection coil layers. The coil 70 may be formed by signal lines such as metal traces, metal wires, or other signal paths on a flexible printed circuit board and / or other substrates. In some configurations, the coil 70 may include spiral coils and / or figure-eight coils.

[0034] Figure 8 is a cross-sectional side view of the system 8. In Figure 8 's exemplary configuration, the device 12 has a single wireless power transmission coil 36 that overlaps with the flexible printed circuit 78. A magnetic material layer such as a ferrite layer 80 may overlap with the coil 36 and the flexible printed circuit 78. The foreign object detection coil 70 is formed by metal traces in the flexible printed circuit 78. The flexible printed circuit 78 is interposed between the coil 36 and the magnetic material layer (e.g., layer 80). The misalignment of the wireless power receiving device 24 creates an imbalance between the detection coil voltages, which in some cases may simulate the presence of a foreign object. By placing the printed circuit 78 below the coil 36, the printed circuit 78 and the coil 70 are interposed between the wireless power transmission coil 36 and the ferrite layer 80 to reduce sensitivity to misalignment of the wireless power receiving device 24 relative to the wireless power transmission coil 36.

[0035] The circuitry of device 12 can be formed by components 82 mounted to printed circuit 84. Connector 86 electrically couples the circuitry on printed circuit 84 to foreign object detection coil 70 in printed circuit 78. Conductive wires (e.g., lengths of litz wire) electrically couple inverter 61 to respective terminals of coil 36.

[0036] A foreign object such as foreign object 90 can be located above coil 36 (e.g., at a distance R from the center of coil 36). Control circuit 16 uses foreign object detection coil 70 to measure magnetic field B to monitor the presence of an object such as object 90.

[0037] To enhance detection sensitivity, foreign object detection coil 70 can include coils of different winding types. For example, some of the coils in coil 70 can have a helical winding pattern, and some of the coils in coil 70 can have a figure-eight winding pattern. Each type of coil can exhibit different peaks and valleys in sensitivity to a foreign object, and thus by overlapping coils having different types of winding patterns, blind spots can be avoided.

[0038] Figure 9 is an exemplary foreign object detection coil having a helical winding. Figure 9 The conductive path (trace) 92 of the winding of exemplary coil 70 has a helical shape adapted within a desired coil profile. Figure 9 Coil 70 of has the shape of a quarter toroidal segment. The distance (radius) R is associated with the distance from the center of coil 36. If desired, a wedge coil shape and other coil profiles can be used. Terminals 94 are electrically coupled to control circuit 16 (e.g., measurement circuit 41). During operation, the voltage change (ΔV) across terminals 94 is monitored by circuit 41 to determine the presence of foreign object 90. In Figure 9 the helical coil winding of any suitable number of turns (e.g., at least one, at least two, at least three, at least five, at least 10, less than 20, etc.) can be present.

[0039] Figure 10 is an exemplary foreign object detection coil having a figure-eight winding. Figure 10 The conductive path (trace) 96 of exemplary coil 70 of has a profile having the shape of a quarter toroidal segment (as an example). Using a common shape for Figure 10 coil 70 of and Figure 9 coil 70 of (e.g., matching the coil profile) allows Figure 10 coil 70 of to overlap and match the profile of Figure 9 coil 70 of. If desired, other shapes (e.g., other shapes such as the wedge shape of Figure 6 or other shapes that match the shape of the overlapping helical coil) can be used.

[0040] The conductive path 96 is coupled to the measurement circuit 41 through the terminal 98. Figure 10 A first portion of the coil 70 forms a first sub - coil C1 having a first winding sense (e.g., clockwise), while Figure 10 A second portion of the coil 70 forms a second sub - coil C2 having a second winding sense (e.g., clockwise winding sense). Since the sub - coils C1 and C2 have opposite winding senses, Figure 10 the coil 70 of Figure 10 tends to be sensitive to perturbations in the transverse magnetic field. This sensitivity is complementary to Figure 9 the sensitivity of the coil 70 of Figure 9 , so by using Figure 9 the coil 70 of Figure 9 and Figure 10 the coil 70 of Figure 10 both, foreign object detection blind spots are avoided. Coil C1 and / or C2 may each have a single turn (as Figure 10 shown) and / or coil C1 and / or coil C2 may have two or more turns.

[0041] Figure 11 is an illustration showing how the coil 36 can generate transverse magnetic fields B1, B1', B2, and B2' during wireless power transfer. The figure - eight coil 70 has a first sub - coil C1 and a second sub - coil C2 in regions that overlap corresponding portions of the coil 36 (e.g., the coil 70 may have Figure 4 and Figure 5 the quarter - toroidal segment shape of the type shown in Figure 5 ). The performance of the magnetic field associated with the coil 36 during operation depends on the presence of a foreign object 90. In the absence of the object 90, the coil 36 generates magnetic fields B1 and B2. The magnetic field B1 has a first portion that passes upward through the first part of the coil C1 and a second portion that passes downward through the coil C2. This induces two voltage contributions that add constructively to produce a resulting ΔV value at the terminals of the coil 70. The magnetic field B2 passes through the coil C1 but not through the coil C2, so in this example, the contribution of the magnetic field B2 to the induced voltage ΔV is smaller.

[0042] In the presence of a magnetic foreign object such as a paper clip formed of magnetic steel or other objects formed of magnetic materials (e.g., Figure 11 the foreign object 90 of Figure 11 ), the magnetic field is perturbed. In Figure 11 the example of Figure 11 , the magnetic field B1 in the presence of the foreign object 90 may follow Figure 11 the path of the magnetic field B1' of Figure 11 , which induces a voltage similar to that induced in the absence of the foreign object 90. On the other hand, the magnetic field B2 now follows Figure 11 the path of the magnetic field B2' of Figure 11 because Figure 11The magnetic material of the foreign object 90 forms a bridge. Thus, the magnetic field B2' passes upward through the coil C1 and downward through the coil C2, thereby inducing a voltage ΔV that is greater than the magnetic field B2. Using the measurement circuit 41, the circuit 16 measures the difference in the value of ΔV caused by the presence of the object 90, thereby detecting when the object 90 is present.

[0043] Figure 12 is a graph showing the response (ΔV1) of a helical foreign object detection coil (e.g., Figure 9 the coil 70) and the response (ΔV2) of an overlapping figure-eight coil having the same profile when a foreign object such as a magnetic foreign object is located at a central distance R from the coil 36. As shown in the graph, the helical coil can exhibit a minimum sensitivity to the presence of a foreign object at a distance XM. At this position, the figure-eight coil has a maximum sensitivity, so the responses of coils with different winding patterns are complementary and avoid detection blind spots. As shown in this example, using the overlapping detection coil 70 helps the device 12 detect magnetic foreign objects.

[0044] In the presence of a non-magnetic foreign object, the foreign object may perturb the magnetic field in a different way. Specifically, a non-magnetic foreign object may tend to block the magnetic flux rather than form a bridge of the magnetic field like a magnetic foreign object. Therefore, the induced voltage in the coils 70 such as the helical coil and the figure-eight shaped coil will tend to decrease relative to the other coils in the group where there is no foreign object. When the flux in a part of the transmitter is blocked, the flux in the other part (the detection coil) whose voltage increases in this case increases (the net flux remains the same). But in the presence of a magnetic foreign object, the flux is only perturbed around the immediate vicinity of the foreign object because it is bridged rather than blocked.

[0045] In Figure 9 、 Figure 10 、 Figure 11 and Figure 12 's example, the foreign object detection coil 70 includes a first set of coils of a first type (e.g., a set of four or more helical coils) and a second set of coils of a second type different from the first type (e.g., a set of four or more figure-eight coils). These coils can have a quarter-ring segment shape or other suitable shapes. If desired, other types of coils 70 and / or other coil shapes can be used. The profiles of the coils 70 can overlap completely or partially with each other and can overlap completely or partially with the windings of the coil 36. Figure 4 and Figure 5 's exemplary quarter-ring segment coils 70 overlap completely with the windings of the coil 36 (e.g., no windings of the coils 70 fall outside the occupied area of the coil 36), while Figure 6 and Figure 7The exemplary wedge-shaped coil 70 partially overlaps with the winding of the coil 36 and partially overlaps with the empty central portion of the toroidal coil 36. The coil 70 may include only one layer of coils (e.g., Figure 4 coil layer), may include only two layers of coils (e.g., having Figure 4 pattern and the first layer of the spiral winding and having Figure 4 pattern and the second layer of the matching figure-eight winding), may include three or more layers of coils, may include coil layers with different coil shapes and / or orientations (see, for example, Figure 4 、 Figure 5 、 Figure 6 and Figure 7 layers), and / or may include other arrangements of coils.

[0046] According to one embodiment, there is provided a wireless power transmission device for transmitting wireless power to a wireless power receiving device, comprising: a wireless power transmission circuit including a wireless power transmission coil configured to transmit a wireless power signal; an external object detection coil having at least a first winding pattern and a second winding pattern different from each other and overlapping with the wireless power transmission coil; and a control circuit configured to monitor the presence of an external object using the external object detection coil.

[0047] According to another embodiment, the first winding pattern includes a spiral winding pattern.

[0048] According to another embodiment, the second winding pattern includes a figure-eight winding pattern.

[0049] According to another embodiment, the external object detection coil includes a first group of external object detection coils having the first winding pattern and a second group of external object detection coils having the second winding pattern.

[0050] According to another embodiment, there are at least four external object detection coils having the first winding pattern in the first group.

[0051] According to another embodiment, there are at least four external object detection coils having the second winding pattern in the second group.

[0052] According to another embodiment, the first winding pattern includes one or more spiral coil winding patterns, and the second winding pattern includes one or more figure-eight winding patterns.

[0053] According to another embodiment, each external object detection coil in the external object detection coil has a quarter-ring segment profile.

[0054] According to another embodiment, each foreign object detection coil in the first group of foreign object detection coils overlaps with a corresponding foreign object detection coil in the second group of foreign object detection coils.

[0055] According to another embodiment, the wireless power transfer coil has a plurality of turns, and each foreign object detection coil in the foreign object detection coils overlaps completely with the turns and does not overlap with the central opening in the wireless power transfer coil.

[0056] According to another embodiment, each foreign object detection coil having the first winding pattern overlaps with a corresponding foreign object detection coil having the second winding pattern and shares a common shape.

[0057] According to one embodiment, there is provided a wireless power transfer device for transferring wireless power to a wireless power receiving device, comprising: a wireless power transfer circuit; a coil; and a control circuit configured to acquire a quality factor measurement of the coil to detect a foreign object when the wireless power transfer circuit drives the coil with a coil drive signal to transfer wireless power to the wireless power receiving device.

[0058] According to another embodiment, the wireless power transfer device includes a foreign object detection coil, and the wireless power transfer circuit includes: a wireless power transfer coil through which the coil drive signal flows; and an inverter configured to provide the coil drive signal to the wireless power transfer coil, the coil drive signal including an alternating current signal.

[0059] According to another embodiment, the control circuit includes a measurement circuit configured to acquire the quality factor measurement by measuring the resonant characteristics in the coil drive signal.

[0060] According to another embodiment, the wireless power transfer circuit includes a capacitor coupled across the coil.

[0061] According to another embodiment, the control circuit is configured to stop the wireless power transfer in response to detecting that one of the quality factor measurements is lower than a predetermined threshold.

[0062] According to one embodiment, there is provided a wireless power transfer device for transferring wireless power to a wireless power receiving device, comprising: a wireless power transfer circuit including a wireless power transfer coil configured to transfer a wireless power signal; a spiral winding foreign object detection coil having a spiral winding pattern; and a figure-eight winding foreign object detection coil having a figure-eight winding pattern.

[0063] According to another embodiment, the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil overlap each other.

[0064] According to another embodiment, the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil at least partially overlap the wireless power transfer coil.

[0065] According to another embodiment, there is provided the wireless power transfer device, comprising: a magnetic material layer; and a printed circuit having metal traces forming the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil, the printed circuit being interposed between the wireless power transfer coil and the magnetic material layer.

[0066] According to another embodiment, there is provided the wireless power transfer device, comprising: a magnetic material layer; and a printed circuit having metal traces forming the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil, the printed circuit being interposed between the wireless power transfer coil and the magnetic material layer to reduce the sensitivity to misalignment of the wireless power receiving device relative to the wireless power transfer coil.

[0067] The foregoing is merely illustrative and various modifications may be made to the described embodiments. The foregoing embodiments may be implemented independently or in any combination.

Claims

1. A wireless power transfer device for transferring wireless power to a wireless power receiving device, comprising: A wireless power transfer circuit, the wireless power transfer circuit including a wireless power transfer coil configured to transfer a wireless power signal; A magnetic material layer; A printed circuit having metal traces, the printed circuit forming an external object detection coil, the external object detection coil having at least a first winding pattern and a second winding pattern that are different and overlapping with the wireless power transfer coil, wherein the first winding pattern includes a spiral winding pattern, and wherein the second winding pattern includes an 8-shaped winding pattern, and wherein the printed circuit is between the wireless power transfer coil and the magnetic material layer; And A control circuit, the control circuit being configured to monitor the presence of an external object using the external object detection coil, Wherein the external object is a metal object other than the wireless power receiving device.

2. The wireless power transfer device according to claim 1, wherein, The external object detection coil of the first winding pattern has a first winding type and is formed in a first layer, and wherein the external object detection coil of the second winding pattern has a second winding type different from the first winding type and is formed in a second layer different from the first layer.

3. The wireless power transfer device according to claim 1, wherein the external object detection coil includes a first group of external object detection coils having the first winding pattern and a second group of external object detection coils having the second winding pattern.

4. The wireless power transfer device according to claim 3, wherein there are at least four external object detection coils having the first winding pattern in the first group.

5. The wireless power transfer device according to claim 4, wherein there are at least four external object detection coils having the second winding pattern in the second group.

6. The wireless power transfer device according to claim 5, wherein the first winding pattern includes one or more spiral coil winding patterns, and wherein the second winding pattern includes one or more 8-shaped winding patterns.

7. The wireless power transfer device according to claim 6, wherein each external object detection coil of the external object detection coils has a quarter-annular segment profile.

8. The wireless power transfer device according to claim 7, wherein each external object detection coil in the first group overlaps with a corresponding external object detection coil in the second group.

9. The wireless power transfer device according to claim 8, wherein the wireless power transfer coil has a plurality of turns, and wherein each external object detection coil of the external object detection coils overlaps completely with the turns and does not overlap with the central opening in the wireless power transfer coil.

10. The wireless power transfer device according to claim 1, wherein each of the foreign object detection coils having the first winding pattern overlaps and shares a common shape with a corresponding one of the foreign object detection coils having the second winding pattern.

11. A wireless power transfer device for transferring wireless power to a wireless power receiving device, comprising: a wireless power transfer circuit; a coil; a magnetic material layer; a printed circuit having metal traces, the printed circuit forming a spiral winding foreign object detection coil and an eight-shaped winding foreign object detection coil, the spiral winding foreign object detection coil having a spiral winding pattern, the eight-shaped winding foreign object detection coil having an eight-shaped winding pattern, wherein the printed circuit is interposed between the coil and the magnetic material layer; and a control circuit configured to collect a quality factor measurement for the coil to detect a foreign object when the wireless power transfer circuit drives the coil with a coil drive signal to transfer wireless power to the wireless power receiving device, wherein the foreign object is a metal object other than the wireless power receiving device.

12. The wireless power transfer device according to claim 11, wherein the wireless power transfer circuit comprises: a wireless power transfer coil through which the coil drive signal flows; and an inverter configured to provide the coil drive signal to the wireless power transfer coil, wherein the coil drive signal comprises an alternating current signal.

13. The wireless power transfer device according to claim 12, wherein the control circuit comprises a measurement circuit configured to collect the quality factor measurement by measuring a resonance characteristic in the coil drive signal.

14. The wireless power transfer device according to claim 13, wherein the wireless power transfer circuit comprises a capacitor coupled across the coil.

15. The wireless power transfer device according to claim 14, wherein the control circuit is configured to stop the transfer of wireless power in response to detecting that one of the quality factor measurements is below a predetermined threshold.

16. A wireless power transfer device for transferring wireless power to a wireless power receiving device, comprising: a wireless power transfer circuit comprising a wireless power transfer coil configured to transfer a wireless power signal; a magnetic material layer; and a printed circuit having metal traces, the printed circuit forming a spiral winding foreign object detection coil and an eight-shaped winding foreign object detection coil, the spiral winding foreign object detection coil having a spiral winding pattern, the eight-shaped winding foreign object detection coil having an eight-shaped winding pattern, wherein the printed circuit is interposed between the wireless power transfer coil and the magnetic material layer to reduce the sensitivity of the wireless power receiving device to misalignment with respect to the wireless power transfer coil, and wherein the foreign object is a metal object other than the wireless power receiving device.

17. The wireless power transfer device according to claim 16, wherein the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil overlap each other, and wherein the spiral winding foreign object detection coil and the figure-eight winding foreign object detection coil at least partially overlap the wireless power transfer coil.

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