Wireless charging system with object detection

Abstract

The wireless power transmission device transmits a wireless power signal to a wireless power receiving device using an output circuit including a wireless power transmission coil. The measurement circuit is coupled to the output circuit to help determine whether the wireless power receiving device is present and ready to receive the transmission of wireless power. The measurement circuit includes a measurement circuit that is coupled to the output circuit and measures the signal, and an oscillator circuit provides a signal to the output circuit at a detection frequency. The measurement circuit also includes a measurement circuit that is coupled to the output circuit and measures the signal, and the oscillator circuit scans the signal applied to the output circuit between a first frequency and a second frequency to detect sensitive devices such as radio frequency identification devices. The pulse response circuit in the measurement circuit is used to perform inductance and Q factor measurements.

Description

[0001] This application is a divisional application of the invention patent application with international application number PCT / US2018 / 015778, international application date January 29, 2018, and Chinese application number 201880009061.0.

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 15 / 804,145 filed on November 6, 2017, U.S. Provisional Patent Application No. 62 / 526,285 filed on June 28, 2017, and U.S. Provisional Patent Application No. 62 / 453,850 filed on February 2, 2017, which are hereby incorporated by reference in their entirety. Technical Field

[0003] The present invention relates generally to wireless systems and, more particularly, to systems in which devices are charged wirelessly. Background Art

[0004] In a wireless charging system, a wireless power transfer device, such as a device with a charging surface, wirelessly transfers power to a portable electronic device. The portable electronic device receives the wirelessly transferred power and uses the power to charge an internal battery or to power the device. In some cases, foreign objects may be accidentally placed on the charging surface. This may create challenges when performing wireless power transfer operations. Summary of the invention

[0005] The wireless power transmission device transmits a wireless power signal to a wireless power receiving device. The wireless power transmission device has an inverter that provides a signal to an output circuit including a wireless power transmission coil. The wireless power transmission coil may be part of a wireless power transmission coil array covering a wireless charging surface associated with the wireless power transmission device.

[0006] The signal measurement circuit is coupled to the output circuit to help determine whether the wireless power receiving device is present and ready to accept the transmission of wireless power. The measurement circuit includes a measurement circuit that is coupled to the output circuit and measures the signal, and an oscillator circuit provides a signal to the output circuit at a detection frequency. Using measurements at one or more detection frequencies from the measurement circuit, the wireless power transmission device determines whether an external object is present on the coil.

[0007] The pulse response circuit in the measurement circuit is coupled to the output circuit and is used to measure the response of the output circuit to the pulse signal provided by the inverter in the wireless power transmission device. The pulse response circuit is used to perform inductance and Q factor measurements.

[0008] During operation, information from the pulse response circuit and measurements at the probing frequency may be used to determine whether a wireless receiving device is present over a particular coil in the wireless charging surface and may therefore be used to regulate wireless power transfer with the wireless power transmitting device.

[0009] The measurement circuit also includes a measurement circuit coupled to the output circuit and measuring the signal while the oscillator circuit sweeps the AC output signal between a first frequency and a second frequency. The measurements generated by the frequency sweep operation are used to detect sensitive devices, such as radio frequency identification devices. If a sensitive device is detected, potentially destructive wireless power transfer operations can be avoided.

[0010] Switching circuitry is used to dynamically switch selected coils from the coil array that overlaps the charging surface into the output circuitry so that the appropriate coils in the coil array can be detected for the presence of external objects and sensitive devices such as radio frequency identification devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of an exemplary wireless charging system according to some embodiments.

[0012] Figure 2 is a top view of an illustrative wireless power transfer device having an array of coils forming a wireless charging surface according to one embodiment.

[0013] Figure 3 is a circuit diagram of an exemplary wireless power transmission circuit according to one embodiment, wherein an output circuit signal measurement circuit is provided in a wireless power transmission device.

[0014] Figure 4 is a graph showing responses of various exemplary objects on a surface of a wireless power transmission device according to one embodiment.

[0015] Figure 5 is a graph of an exemplary impulse response that may be used to characterize a type of object on a wireless power transmission device according to an embodiment.

[0016] Figure 6 is a graph illustrating an output signal trace of the type that may be associated with placing a sensitive object, such as a radio frequency identification device, on the surface of a wireless power transmission device, according to one embodiment.

[0017] Figure 7 is a cross-sectional side view of an exemplary portable electronic device having a wireless power receiving coil and an auxiliary coil forming a resonant circuit according to one embodiment.

[0018] Figure 8is a graph in which output circuit signal measurements as a function of frequency are plotted for various types of exemplary objects on a surface of a wireless power transfer device, according to one embodiment.

[0019] Fig. 9 According to one embodiment, a wireless power transmission system such as Figure 1 Flowchart of illustrative operations involved in a wireless charging system.

[0020] Fig.10 is a graph illustrating signals associated with performing impulse response measurements in a noisy wireless charging environment, according to an embodiment.

[0021] Fig.11 is a flow chart of example operations associated with making impulse response measurements, according to an embodiment. DETAILED DESCRIPTION

[0022] The wireless power system has a wireless power transmission device that wirelessly transmits power to a wireless power receiving device. The wireless power transmission device is a device such as a wireless charging pad, a wireless charging plate, a wireless charging stand, a wireless charging station, or other wireless power transmission devices. The wireless power transmission device has one or more coils for transmitting wireless power to one or more wireless power receiving coils in a wireless power receiving device. The wireless power receiving device is a device such as a cellular phone, a watch, a media player, a tablet, a pair of earbuds, a remote control, a laptop computer, other portable electronic devices, or other wireless power receiving devices.

[0023] During operation, the wireless power transmission device provides an AC signal to one or more wireless power transmission coils. This causes the coils to transmit an AC electromagnetic signal (sometimes referred to as a wireless power signal) to one or more corresponding coils in the wireless power receiving device. The rectifier circuit in the wireless power receiving device converts the received wireless power signal into direct current (DC) power for powering the wireless power receiving device.

[0024] Figure 1 An exemplary wireless power system (wireless charging system) is shown in FIG. Figure 1 As shown, wireless power system 8 includes wireless power transmission device 12 and one or more wireless power receiving devices, such as wireless power receiving device 10. Device 12 may be a stand-alone device such as a wireless charging pad, may be built into furniture, or may be other wireless charging equipment. Device 10 is a portable electronic device such as a watch, a cellular phone, a tablet computer, or other electronic device. Exemplary configurations in which device 12 is a pad or other device that forms a wireless charging surface and device 10 is a portable electronic device that rests on the wireless charging surface during wireless power transmission operations may sometimes be described herein as embodiments.

[0025] During operation of system 8, a user places one or more devices 10 on a charging surface of device 12. Power transmission device 12 is coupled to an AC power source, such as AC power source 50 (e.g., a wall outlet that supplies line power or other mains power), has a battery such as battery 38 for powering, and / or is coupled to another power source. A power converter such as AC-DC power converter 40 can convert power from the mains or other AC power source to DC power for powering control circuit 42 and other circuits in device 12. During operation, control circuit 42 transmits an AC electromagnetic signal 48 to device 10 using wireless power transmission circuit 34 and one or more coils 36 coupled to circuit 34, and thereby transmits wireless power to wireless power receiving circuit 46 of device 10.

[0026] The power transmission circuit 34 has switching circuits (e.g., transistors in an inverter circuit) that are turned on and off based on control signals provided by the control circuit 42 to generate AC current signals through the appropriate coils 36. When the AC current passes through the coils 36 driven by the inverter circuit, an AC electromagnetic field (wireless power signal 48) is generated that is received by one or more corresponding coils 14 coupled to the wireless power receiving circuit 46 in the receiving device 10. When the AC electromagnetic field is received by the coils 14, a corresponding AC current and voltage are induced in the coils 14. The rectifier circuit 46 in the circuit 46 converts the received AC signal (the received AC current and voltage associated with the wireless power signal) from the one or more coils 14 into a DC voltage signal for powering the device 10. The DC voltage is used to power components in device 10, such as display 52, touch sensor components and other sensors 54 (e.g., accelerometers, force sensors, temperature sensors, light sensors, pressure sensors, gas sensors, humidity sensors, magnetic sensors, etc.), wireless communication circuitry 56 for wirelessly communicating with control circuitry 42 of device 12 and / or other devices, audio components and other components (e.g., input-output devices 22 and / or control circuitry 20), and for charging an internal battery in device 10 (such as battery 18).

[0027] Devices 12 and 10 include control circuits 42 and 20. Control circuits 42 and 20 include storage and processing circuits, such as a microprocessor, a power management unit, a baseband processor, a digital signal processor, a microcontroller, and / or an application-specific integrated circuit with processing circuits. Control circuits 42 and 20 are configured to execute instructions for implementing desired control and communication features in system 8. For example, control circuits 42 and / or 20 may be used to determine power transfer levels, process sensor data, process user input, process other information from transmission circuits 34 such as information about wireless coupling efficiency, process information from receiving circuits 46, use information from circuits 34 and / or 46, such as signal measurements on output circuits in circuits 34 and other information from circuits 34 and / or 46 to determine when to start and stop wireless charging operations, adjust charging parameters such as charging frequency, coil alignment in a multi-coil array, and wireless power transfer levels, and perform other control functions. The control circuit 42 and / or 20 may be configured to perform these operations using hardware (e.g., dedicated hardware or circuits) and / or software (e.g., code running on the hardware of the system 8). The software code for performing these operations is stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium). The 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, other computer-readable media, or a combination of these computer-readable media or other storage devices. The software stored on the non-transitory computer-readable storage medium may be executed on the processing circuit of the control circuit 42 and / or 20. The processing circuit may include a dedicated integrated circuit having a processing circuit, one or more microprocessors, or other processing circuits.

[0028] Device 12 and / or device 10 may communicate wirelessly. Devices 10 and 12 may, for example, communicate with each other in control circuits 42 and 20 (and / or wireless communication circuits such as Figure 1 The circuit 56 of the device 10 has a wireless transceiver circuit, which allows wireless transmission of signals between the devices 10 and 12 (for example, using an antenna separate from the coils 36 and 14 to transmit and receive one-way or two-way wireless signals, using the coils 36 and 14 to transmit and receive one-way or two-way wireless signals, etc.).

[0029] With one exemplary configuration, the wireless transmission device 12 is a wireless charging pad or other wireless power transmission device that includes an array of coils 36 configured to provide wireless power through a wireless charging surface. This type of arrangement is Figure 2 In Figure 2In the example of , device 12 has an array of coils 36 located in an XY plane. Coils 36 of device 12 are covered by a planar dielectric structure such as a plastic member or other structure that forms a charging surface 60. The lateral dimensions (X and Y dimensions) of the array of coils 36 in device 36 can be 1 to 1000 cm, 5 to 50 cm, greater than 5 cm, greater than 20 cm, less than 200 cm, less than 75 cm, or other suitable sizes. Coils 36 can overlap or can be arranged in a non-overlapping configuration. Coils 36 can be placed in a rectangular array with rows and columns, and / or can be tiled using a hexagonal tile pattern or other pattern.

[0030] During operation, a user places one or more devices 10 on the charging surface 60. Foreign objects, such as coins, paper clips, fragments of metal foil, and / or other external conductive objects may be accidentally placed on the surface 60. The system 8 automatically detects whether the conductive objects located on the surface 60 correspond to the device 10 or incompatible external objects and takes appropriate action. With one exemplary arrangement, the system 8 checks whether the objects located on the surface 60 include sensitive items such as radio frequency identification (RFID) devices or other potentially sensitive electronic devices that may be damaged when exposed to large fields from the coil 36 before the system 36 allows wireless power to be transferred to these objects.

[0031] like Figure 2 As shown in the example of , external objects such as external object 62 and object 64 may overlap with one or more coils 36. In some cases, objects 62 and 64 will be portable electronic devices 10. In other cases, one or more of objects 62 and 64 will be incompatible external objects (e.g., conductive external objects such as metal coins, sensitive devices such as RFID devices, etc.). It is also possible that such a situation occurs in which an incompatible external object and a portable electronic device overlap with the same one or more coils 36.

[0032] Figure 3 An exemplary wireless power transfer circuit 34 is shown, which includes circuitry for detecting and characterizing external objects on a surface 60. Figure 2 As shown, the circuit 34 may include an inverter such as inverter 72 or other drive circuit that generates a wireless power signal that is transmitted through an output circuit including one or more coils 36. Figure 236 is shown in the example. In general, device 12 may have any suitable number of coils 36 (1-100, greater than 5, greater than 10, less than 40, less than 30, 5-25, etc.). Switching circuitry MX (sometimes referred to as multiplexer circuitry) controlled by control circuitry 42 may be located before and / or after each coil 36 and / or before and / or after other components of output circuitry 71 and may be used to switch a desired set of one or more coils 36 (desired output circuitry 71) into or out of use. For example, if it is determined that Figure 2 If the object 62 is the wireless power receiving device 10 and the object 64 is an incompatible external object such as a coin, the coils overlapping the object 62 can be activated during the wireless power transmission operation, and the coils under the object 64 can be deactivated so that these coils do not transmit wireless power. If desired, other coils 36 (e.g., coils not overlapped by the object 64 in this example) can also be turned off during the wireless power transmission operation.

[0033] Continue to refer Figure 3 During wireless power transfer operation, transistor 74 of inverter 72 is driven by an AC control signal from control circuit 42. Control circuit 42 may also apply square wave pulses or other pulses to coil 36 using transistor 74 of inverter 72 (e.g., during pulse response measurement). Coil 36 (e.g., a coil that has been selected using multiplexing circuit MX) has an inductance L. Capacitor 96 has a capacitance C1 coupled in series with the inductance L in output circuit 90. When an AC drive signal is provided by inverter 72 when switch (transistor) TP is closed, the output circuit formed by coil 36 and capacitor 96 generates an AC electromagnetic field that is received by one or more coils 14 in device 10. The inductance L of each coil 36 is affected by magnetic coupling with external objects, so measurements of the inductance L of one or more coils 36 in device 12 at various frequencies can reveal information about objects on charging surface 60.

[0034] To save power, device 12 may operate in a standby mode to supply wireless power to device 10 while awaiting use. Figure 3 The signal measurement circuit (sometimes referred to as an output circuit signal measurement circuit, an external or foreign object detection circuit, etc.) monitors the presence of external objects during standby. During standby operation, the power consumption of the measurement circuit in transmitter circuit 34 may be less than 50 mW, less than 200 mW, greater than 1 mW, or other suitable value.

[0035] In standby mode, device 12 periodically scans coil 36 (e.g., device 12 scans each of coils 36) to determine if an external object (e.g., device 10, a foreign object such as a coin, etc.) is present. To detect the selected coil for a change in inductance L due to a measured value, a detection signal is driven to node N1 using oscillator circuit 84 when control circuit 42 turns off inverter 72 (e.g., transistor 74 is not used to drive a signal to node N2). Control circuit 42 may, for example, use oscillator circuit 84 (e.g., one or more voltage-controlled oscillators, one or more other adjustable oscillators, and / or other oscillation circuits) to generate an AC detection signal (e.g., a sine wave, a square wave, etc.) at a detection frequency fr (e.g., 4 MHz or other suitable frequencies, such as at least 500 kHz, at least 1 MHz, at least 2 MHz, less than 10 MHz, between 1 MHz and 10 MHz, or other suitable frequencies). The detection frequency fr used during the standby mode is a frequency different from the RFID frequency such as 13.56 MHz, and different from the normal AC frequency provided by the inverter 72 to the output circuit 71 during the wireless charging operation, and the frequency may be, for example, 100-500 kHz, greater than 50 kHz, greater than 100 kHz, greater than 200 kHz, less than 450 kHz, less than 400 kHz, less than 300 kHz or other suitable wireless power AC drive frequencies.

[0036] The signal at frequency fr is applied to node N1 via capacitor 86 and coupled to coil 36 via capacitor 96, while inverter 72 is kept in the off state by control circuit 42. Control circuit 42 controls multiplexer MX to select Figure 2 The array of coils 36 of the device 12 shown is selected to apply a signal at a frequency fr (e.g., Figure 3 36). Capacitor C1 may have 150 μF, greater than 10 μF, less than 1000 μF, or other suitable values. Transistor TP may have a parasitic capacitance Cp (e.g., 80 pF, greater than 10 pF, less than 800 pF, or other suitable values ​​of capacitance) when turned on. For standby operation, control circuit 42 turns on transistor TP so that the detection signal is routed through coil 36. When transistor TP is turned on, parasitic capacitance Cp is coupled in series with capacitor C1. This effectively removes capacitor C1 from the series circuit formed with inductor L, because the capacitance of capacitors C1 (which is in the microfarad range) and Cp (which is in the picofarad range) in the series circuit will be approximately Cp.

[0037] With TP open, the output circuit 71 (coil 36 in series with C1 and Cp) will be characterized by resonance at the frequency fres of Eq. 1.

[0038] fres=1 / (2π(LCp)1 / 2 ) (1)

[0039] Figure 4 Curve 102 of FIG. 1 shows the expected measured signal (output voltage OUT(N1)) at node N1 as a function of the applied signal frequency f in the absence of an external object on coil 36. In the presence of an electronic device such as device 10 that includes one or more coils 14 overlapping coil 36, curve 102 may be shifted to a lower frequency as shown by curve 100. In the presence of a coin or other incompatible foreign object overlapping coil 36, curve 102 may be shifted to a higher frequency as shown by curve 104. The change in load may be achieved by using Figure 3 The measurement circuit 78 of the embodiment can be used to monitor the value of OUT(N1) at one or more detection frequencies to detect. For example, the oscillator circuit 84 can be used to apply a detection signal to the node N1 at a frequency fr that has been selected to match the resonant frequency fres of Formula 1. If desired, multiple detection signals can be applied to the output circuit 72, and the measurement circuit can be used to evaluate the resulting signal at the node N1. For example, the direction of change of the curve 102 (shifting higher or lower) can be detected by Figure 4 The detection is performed by performing multiple measurements of OUT(N1) at two or more frequencies near the frequency fr.

[0040] To measure OUT(N1), measurement circuit 78 includes a peak detector 80 and an analog-to-digital converter 82. Circuit 78 measures the signal at node N1 and provides a corresponding digital version of the signal to control circuit 42. In the presence of an object overlapping coil 36 (whether from device 10, a sensitive RFID device, or a coin or other incompatible foreign object), signal OUT(N1) will decrease. For example, due to the presence of the foreign object, the signal at node N1 may decrease from a value of P1d when coil 36 is unloaded (e.g., a peak value associated with curve 102) to a value of P2 when coil 36 is loaded (a reduced value associated with offset curve 100).

[0041] During standby operation, control circuit 42 may scan coils 36 using multiplexer circuit MX or other switching circuitry in circuit 34. In some embodiments, this sequentially couples each of coils 36 to node N1, and circuit 78 measures OUT(N1) for each selected coil 36. If no change in OUT(N1) is detected, control circuit 42 may conclude that no object is present on device 12 (e.g., no object is resting on charging surface 60). If a change in OUT(N1) is detected, control circuit 42 performs additional operations to confirm that device 10 is present and not an incompatible foreign object such as a coin.

[0042] Using an exemplary method, the control circuit 42 uses a pulse response measurement circuit 76 (sometimes referred to as an inductance measurement circuit and / or a Q-factor measurement circuit) to perform low-frequency measurements of the inductance L and the quality factor Q in response to detecting a load on one or more coils 36 during standby. During the pulse response measurement, the control circuit 42 directs the inverter 72 to provide one or more excitation pulses (pulses) to the coil 36, while turning on the transistor TP so that L and C1 in the output circuit 71 form a resonant circuit. The pulse can be, for example, a square wave pulse with a duration of 1μ. If desired, longer or shorter pulses can be applied. The resonant circuit can resonate at a frequency close to the normal wireless charging frequency of the coil 36 (e.g., about 320kHz, 100-500kHz, greater than 50kHz, greater than 100kHz, greater than 200kHz, less than 450kHz, less than 400kHz, less than 300kHz, or other suitable wireless charging frequencies).

[0043] The pulse response of circuit 71 to the applied pulse (signal OUT(N1)) is as follows: Figure 5 shown. Figure 5 The frequency of the impulse response signal is proportional to 1 / sqrt(LC), so L can be obtained from the known value of C1 and the measured frequency of the impulse response signal. Q can be derived from L and the measured attenuation of the impulse response signal. Figure 5 As shown, if the signal OUT(N1) decays slowly, Q is high (e.g., HQ), and if the signal OUT(N1) decays faster, Q is low (e.g., SQ). Figure 5 The decay envelope of the impulse response signal OUT(N1) and the frequency of OUT(N1) will allow the control circuit 42 to determine Q and L.

[0044] If the measured value L of a given coil matches the expected normal L value for each of the coils 36 in the array of coils 36 overlapping the surface 60 (e.g., when the measured L value is not affected by the presence of a device 10 or other external object on the surface 60), the control circuit 42 can conclude that there are no external objects suitable for wireless charging. If the given measured value of L is greater than the expected value for an unloaded coil, the control circuit 42 can infer that there are external objects suitable for wireless charging, and can perform additional measurement operations. For example, the control circuit 42 can perform a scanning frequency measurement (sometimes referred to as an RFID check measurement) on the node N1 to check whether a sensitive device such as an RFID device is present on the surface 60.

[0045] The measurements made by circuit 76 are performed on one or more coils 36 (e.g., these measurements may be performed on each of the coils 36 in the coil array in device 12). Circuit 42 uses these impulse response measurements to identify spatial patterns in the L values ​​(and / or Q factor values) measured across surface 60. Analysis of the pattern of measured inductance (L) changes can help determine whether a device 10 of a known type is present on coil 36. Analysis of the spatial pattern of measured inductance L (and, if desired, Q factor, which has an inverse relationship with respect to L) as a function of coil position in the XY plane of surface 60 can be used in determining when to transfer wireless power from device 12 to device 10. For example, if the L value of each of coils 36 remains unchanged from its nominal state, circuit 42 may conclude that no external device suitable for wireless charging is present. If the L value of one of a given coil 36 increases or other suitable pattern of measured L values ​​is detected, circuit 42 may conclude that an external device suitable for wireless charging is present on that coil and may be prepared to transfer wireless power using that coil.

[0046] Before transmitting wireless power, it may be desirable to check whether a sensitive device, such as an RFID device, is present on the surface 60. Sensitive devices may be damaged by excessive wireless power levels, so checking for sensitive devices helps avoid damage to the sensitive device during subsequent wireless power transmission operations. In some cases, both the portable device 10 and the sensitive device may be present on the same coil 36 in the array of coils 36 in the device 12. For example, the sensitive device may be present under a cellular phone, watch, or other portable device 10 that includes a wireless power receiving coil 14. Although the presence of the portable device 10 may be detected by making inductance measurements using the coil 36, it is desirable to check whether the sensitive device is also present to avoid damaging the sensitive device by exposure to wireless power transmission.

[0047] Radio frequency identification (RFID) devices typically have RFID coil circuits that resonate at relatively high frequencies, such as 13.56 MHz. In some embodiments, to determine whether an RFID is present on surface 60, an RFID detection measurement is performed using measurement circuit 94 ( Figure 3) is performed by measuring the signal OUT(N1) on the node N1. During these check measurements, the control circuit 42 directs the oscillator circuit 84 to sweep the frequency of the signal provided to the node N1 between a first frequency f1 and a second frequency f2 that cover the expected resonant frequency of the popular RFID coil. The transistor TP can be kept on so that the current from the oscillator circuit 84 flows through each coil 36 that has been selected during the measurement operation. The value of f1 can be, for example, 10 MHz, greater than 5 MHz, less than 11 MHz, less than 12 MHz, less than 15 MHz or other suitable values. The value of f2 can be 30 MHz, greater than 14 MHz, greater than 15 MHz, greater than 20 MHz, less than 45 MHz or other suitable values.

[0048] like Figure 3 As shown, scanning frequency measurement circuit 94 includes a peak detector, such as peak detector 88 that measures the voltage on node N1, a bandpass filter 90, and analog-to-digital converter circuit 92. Analog-to-digital converter circuit 92 provides control circuit 42 with a digital version of its input.

[0049] When no RFID device is present on the charging surface 60 of the device 12, the peak detector 88 will detect a signal such as Figure 6 When the RFID device overlaps the charging surface 60, the signal OUT(N1) (see, for example, curve 110) will display a resonant signal, such as signal 112, when the frequency f sweeps between f1 and f2. The resonant signal 112 may correspond to a resonant frequency, such as the RFID resonant frequency of 13.56 MHz, for example.

[0050] The frequency f is swept between f1 and f2 at a predetermined rate. For example, the control circuit 42 may sweep the frequency from f1 to f2 at intervals of 2 milliseconds, at least 1 millisecond, less than 3 milliseconds, or other suitable time periods. The pass frequency of the bandpass filter 90 is selected so that when the frequency f changes between f1 and f2 at a predetermined rate (e.g., when the entire sweep range is covered at intervals of 2 milliseconds, etc.), the resonant frequency 112 will pass through the bandpass filter 90 as a bandpass filtered signal 112' of the bandpass output curve 114. The use of the bandpass filter 90 helps to remove non-resonant signal fluctuations (e.g., Figure 610). The resulting bandpass filtered signal (curve 114 and filtered signal resonance 112') may be processed by the control circuit 42 to confirm that an RFID resonance at a particular frequency has been detected. The control circuit 42 may then take appropriate action. For example, if no RFID signature is detected, the control circuit 42 may conclude that the external object detected on the surface 60 is likely to be a portable device (device 14 with coil 10) without any intervening (overlapping) sensitive RFID device. If an RFID signature is detected (e.g., a resonant signal 112' at an RFID frequency such as 13.56 MHz), the control circuit 42 may reduce the level of wireless power transmitted by the coil 36, or may prevent wireless power from being transmitted by the coil 36 (or at least by a coil overlapped by a sensitive RFID device) to mitigate damage to the RFID device. Optionally, the control circuit 42 may issue a warning to the user.

[0051] In some arrangements, it may be desirable to Figure 6 Sensitive frequencies may be avoided during the frequency sweep operation of . For example, it may be desirable to skip a narrow frequency band, such as band 113, centered around an impermissible frequency fnp. For example, the impermissible frequency fnp may be a frequency of 13.56 MHz. Band 113 may cover frequencies within + / - 20 kHz of 13.56 MHz (as an example). Skipping band 113 during the frequency sweep from f1 to f2 may ensure compliance with regulations in jurisdictions where the use of frequencies in band 113 is restricted. To facilitate skipping band 113, oscillator 84 may be implemented using a circuit that allows for quick skipping of unwanted frequencies during a frequency sweep, such as a direct digital sine wave generator. Other types of oscillators may be used if desired.

[0052] Figure 7 1 is a cross-sectional side view of device 10 in an exemplary configuration, wherein device 10 has a power receiving coil (coil 14) located in a lower portion of device housing 116. The device may also have one or more additional coils, such as coil PR. Each optional coil PR may form part of a corresponding resonant circuit (e.g., a passive resonant circuit having a known frequency resonance at a frequency between 10 MHz and 30 MHz or other suitable frequency). When scanning the frequency f of each coil 36, the measurement circuitry of device 12 may detect the presence and position of a coil such as coil PR, as combined with Figure 6 Incorporating known passive resonators into device 10 may help allow device 12 to accurately identify the location, orientation, and type of device 10.

[0053] Different devices may also have different known frequencies that resonate when placed on surface 60. For example, consider Figure 8Scenario. In the absence of external objects, the coil 36 may exhibit a frequency response of the type shown in curve FS. When a first type of device 10 (e.g., a cellular phone) is placed on the surface 60, the curve FS may shift to curve D1. When a second type of device 10 (e.g., a watch) is placed on the surface 60, the curve FS may shift to curve D2. By scanning the measurement OUT (N1) across a predetermined frequency range (e.g., from a low frequency of 1kHz, 10kHz, greater than 100kHz, greater than 1MHz, greater than 10MHz, less than 100MHz, less than 10MHz, less than 1MHz or other suitable low frequencies to a high frequency of 10kHz, greater than 100kHz, greater than 1MHz, greater than 10MHz, greater than 10MHz, less than 10MHz, less than 1GHz, less than 100MHz, less than 10MHz or other suitable high frequencies), the device 12 may determine what type of power receiving device 10 is present and may use this information to take appropriate action (e.g., by providing wireless power to a device having a setting suitable for the device, etc.). If desired, circuit 42 may also use a smaller set of measurements (eg, a set of 2-10 data points, greater than 2 data points, less than 5 data points, etc.) to differentiate between curves such as curves FS, D1, and D2.

[0054] Fig. 9 1 is a flow chart of illustrative operations involved in using system 8. During operation at block 120, system 8 performs standby measurements. For example, device 12 may use circuitry such as Figure 3 Circuitry 78 is provided to monitor one or more coils 36 (e.g., each coil 36 in an array of coils 36 in device 12) for the presence of an external object that may be compatible with wireless power transfer, such as one of device 10, or an incompatible object such as a coin or magnetic card. A single measurement may be made at frequency fr to determine if OUT(N1) is lower than expected for any coil 36, or multiple measurements may be made at different frequencies near fr if desired (e.g., to determine the direction in which the coil resonance is shifted due to an external object, thereby helping to determine whether the object is an electronic device or a coin or other incompatible foreign object). The standby operation of block 120 consumes low power (e.g., 50 milliwatts or less, 100 milliwatts or less, greater than 1 milliwatt, or other suitable amount).

[0055] In response to detecting the external object with the control circuit 42 during the operation of block 120, the control circuit 42 performs additional detection operations, such as low-frequency pulse response measurements (block 122). During the operation of block 122, the control circuit 42 may, for example, use the inverter 72 or other resonant circuit drive circuit to apply an excitation (e.g., a square wave or other signal pulse) to a circuit formed by one or more coils 36 (e.g., each coil 36 in an array of coils 36 in the device 12, a subset of these coils, such as those coils for which the presence of a foreign object has been detected during the operation of block 120, and / or other suitable subset of one or more of the coils 36), thereby causing the circuit (and the coils 36) to resonate while using a measurement unit such as Figure 3 The pulse response measurement circuit 76 measures the response of the resonant circuit. Figure 5 As described, the characteristics of the resulting circuit resonance may then be measured and analyzed. For example, control circuit 42 may use information about the measured resonant frequency to measure inductance, and may use information about signal resonance attenuation to determine resistance R and Q factor. If desired, the measurements of blocks 120 and / or 122 may be mapped out in dimensions X and Y across surface 60 to aid in identifying device 10 and foreign objects.

[0056] If the operations of block 122 indicate that no foreign object is present and the electronic device 10 is present, additional inspection operations may be performed during block 124. Specifically, a circuit such as Figure 3 The oscillator circuit 84 and the frequency scanning measurement circuit 94 are used to detect whether a sensitive RFID device exists, such as the combination of Figure 6 described.

[0057] During operation at block 126, appropriate actions are taken based on measurement results, such as those of blocks 120, 122, and / or 124. For example, if a sensitive RFID device is detected during operation at block 124, or if a foreign object is detected, wireless charging operations utilizing all coils 36 or an appropriate subset of coils 36 may be prevented. In response to detecting an electronic device 10 having a known characteristic L response (and / or Q response), and in response to the absence of an RFID device after detecting one or more coils 36 utilizing 94 (if applicable) (e.g., coils 36 indicated by L and / or Q measurements and / or other measurements may be overlapped by an object or all coils 36), control circuitry 42 may utilize wireless power transmission circuitry 42 to transmit wireless power to wireless power reception circuitry 46.

[0058] In some operating environments, signal measurement accuracy may be adversely affected by noise. For example, in an arrangement where multiple power receiving devices are located on a common wireless charging mat, the process of transmitting wireless power to one of the devices using the coil in the mat overlapped by the device may generate noise when making a measurement, such as a pulse response measurement on another device that overlaps a different coil in the mat. With one exemplary arrangement, potential interference may be avoided by stopping charging of the first device long enough to allow measurements such as pulse response measurements to be made on the device in the absence of noise. With another exemplary arrangement, noise may be removed from measurements such as pulse response measurements.

[0059] Fig.10 1 is a schematic diagram showing how a measurement signal at node N1 (or other suitable node), such as signal OUT, may suppress noise when attempting to make a measurement of a coil overlapped by a wireless power receiving device. As shown by curve 150, signal OUT may initially be measured by pulse response measurement circuit 76 during time period T1 in the absence of any pulses applied by pulse response measurement circuit 76. During time period T1, noise may be present in signal OUT due to charging of one or more additional wireless power receiving devices elsewhere on device 12 (e.g., other coils other than coil / coil 36 overlapped by the wireless power receiving device). During time period T2, pulse response measurement circuit 76 applies pulses to coil 36 and measures the resulting ringing and exponential decay of the resulting signal OUT. Noise is present in the measurement signal due to wireless power being transmitted to one or more other devices on device 12. As shown in conjunction with Figure 5 As described above, the frequency and decay rate of the impulse response signal can reveal information such as the coil inductance value L. To enhance measurement accuracy, the noise measured during period T1 can be removed from the signal measured during period T2 before processing the signal measured during period T2 to produce a measurement result such as inductance L.

[0060] A flow chart of exemplary operations involved in measuring the inductance L in a potentially noisy environment, such as a charging environment where multiple devices 10 are located on a common wireless power transmission device 12, is shown in FIG. Fig.11 In. Fig.11 As shown, power transfer from device 12 to first device 10 may be initiated at step 152 .

[0061] With one exemplary method, power transmission to the first device is briefly suspended to allow measurement of L of the coil overlapped by the second device. The method is illustrated by the operations of blocks 154, 156, and 158. During the operation of block 154, the device 12 stops power transmission to the first device. During the operation of block 156, the impulse response measurement circuit 76 is used to make impulse response measurements to obtain L of the coil overlapped by the second device (e.g., in the case where the first device is not receiving power). During the operation of block 158, power transmission from the device 12 to the first device 10 is resumed. Power may also be transmitted wirelessly to the second device 10.

[0062] Using another exemplary method shown in blocks 160, 162 and 164, noise is removed from the measured signal without interrupting power delivery to the first device. During operation of block 160, the measurement circuit 76 or other measurement circuit measures the signal OUT (e.g., Fig.10 During operation of block 162, the pulse response measurement circuit 76 applies a pulse to the coil overlapped by the second device and measures the signal OUT (e.g., see Fig.10 The first device is then subjected to a period T2 of the period T2 measured by the impulse response measurement circuit 76 (e.g., by repeatedly subtracting the measured noise at various trial phase values ​​until satisfactory noise removal is achieved). The impulse response measurement is completed and the wireless power transmission operation can continue. As shown by line 166, if the noise is not satisfactorily removed during the operation of block 164, the processing can return to block 160 to perform additional noise and impulse response measurements.

[0063] If a foreign object such as a radio frequency identification (RFID) device is overlapped by the device 10 and is therefore inserted between the device 10 and one or more coils 36 in the device 12, the system 8 allows the device 12 to abandon charging of the device 10. Because the coils 36 can be independently controlled, if an RFID device or other sensitive device is detected on one portion of the device 12 (e.g., overlapping with the first set of one or more coils) and the device 10 is detected on another portion of the device 12 (e.g., overlapping with a second set of one or more coils different from the first set of coils), the device 12 can use only the second set of coils and not the first set of coils to wirelessly transmit power. In this way, power is not wirelessly transmitted to the RFID device, but only to the wireless power receiving device 10.

[0064] According to one embodiment, a wireless power transmission device having a charging surface is provided, which includes a plurality of coils, a measurement circuit coupled to the coils, a wireless power transmission circuit coupled to the coils and configured to transmit a wireless power signal to a wireless power receiving device having one or more coils, and a control circuit configured to control the transmission of the wireless power signal, the control circuit being configured to operate in the following modes: a first mode, wherein the control circuit uses the wireless power transmission circuit and a first group of one or more coils of the coils to transmit the wireless power signal to the wireless power receiving device without transmitting wireless power to a radio frequency identification device detected using the measurement circuit, the radio frequency identification device overlapping with a second group of one or more coils of the coils different from the first group of coils; and a second mode, wherein when the measurement circuit detects that the radio frequency identification device is overlapped by the wireless power receiving device, the control circuit abandons using the wireless power transmission circuit to transmit the wireless power signal to the wireless power receiving device.

[0065] According to another embodiment, the control circuit is further configured to detect a foreign object using the coil based at least in part on the coil inductance information from the measurement circuit.

[0066] According to another embodiment, the measurement circuit includes: an output circuit, the output circuit including a selected one of the coils; an oscillator circuit, the oscillator circuit coupled to the output circuit; a first measurement circuit, the first measurement circuit configured to measure a signal in the output circuit when the oscillator circuit generates an output at a detection frequency; and a second measurement circuit, the second measurement circuit configured to measure the signal in the output circuit when the oscillator circuit generates a frequency sweep output ranging from a first frequency to a second frequency.

[0067] According to another embodiment, the measurement circuit further includes a pulse response measurement circuit, which is configured to measure a response of the output circuit including the selected one of the coils to a pulse signal, the wireless power transmission circuit includes an inverter, the control circuit is configured to provide the pulse signal to the selected one of the coils using the inverter, and the control circuit is configured to use the pulse response measurement circuit to measure the inductance associated with the selected one of the coils.

[0068] According to another embodiment, the control circuit is configured to measure a Q factor associated with the selected coil using the pulse response measurement circuit.

[0069] According to another embodiment, the frequency of 13.56 MHz is between the first frequency and the second frequency.

[0070] According to another embodiment, the measurement circuit includes a pulse response measurement circuit, which is coupled to the output circuit and configured to perform inductance and Q factor measurements, and the control circuit is configured to control the transmission of wireless power to the wireless power receiving device using the wireless power transmission circuit based at least in part on information from the pulse response measurement circuit.

[0071] According to another embodiment, the control circuit is configured to detect a foreign object overlapping the coil array based at least in part on information from the first measurement circuit.

[0072] According to another embodiment, the control circuit is configured to detect the radio frequency identification device overlapped by the wireless power receiving device based at least in part on information from the second measurement circuit.

[0073] According to another embodiment, the wireless power receiving device is configured to overlap an area on the coil, and the control circuit is configured to identify the area based at least in part on information from the first measurement circuit.

[0074] According to another embodiment, the first measurement circuit includes a first peak detector and the second measurement circuit includes a second peak detector and a bandpass filter.

[0075] According to another embodiment, the wireless power transmission circuit includes an inverter, the control circuit is configured to apply a pulse signal to the output circuit including the selected one of the coils using the inverter, the wireless power transmission device includes a pulse response measurement circuit, the control circuit is configured to measure a resonant frequency associated with the output circuit using the pulse response measurement circuit when applying the pulse signal, and the control signal is configured to control the transmission of wireless power to the wireless power receiving device using the wireless power transmission circuit based at least in part on the measured resonant frequency.

[0076] According to one embodiment, there is provided a method of using a wireless power transmission device having a wireless power transmission circuit, wherein the wireless power transmission circuit uses a coil to transmit a wireless power signal to a wireless power receiving device, the method comprising: operating the wireless power transmission device in a first mode, wherein the wireless power transmission device uses a first group of one or more coils of the coils to transmit the wireless power signal to the wireless power receiving device without transmitting wireless power to a radio frequency identification device that overlaps with a second group of one or more coils of the coils that is different from the first group of coils; and operating the wireless power transmission device in a second mode, wherein upon detecting that the radio frequency identification device is overlapped by the wireless power receiving device, the wireless power transmission device abandons transmitting the wireless power signal to the wireless power receiving device.

[0077] According to another embodiment, the method includes detecting a foreign object on the wireless power transfer device based at least in part on coil inductance information collected from the coil.

[0078] According to another embodiment, the method includes measuring a signal in the wireless power transmission device when an oscillator circuit in the wireless power transmission device generates an output at a detection frequency; and measuring a signal in the wireless power transmission device when the oscillator circuit generates a frequency sweep output ranging from a first frequency to a second frequency.

[0079] According to another embodiment, the method includes measuring a response of the coil to the pulse signal.

[0080] According to another embodiment, the wireless power transmission device includes an inverter, and the method includes: providing the pulse signal to a selected one of the coils using the inverter; and measuring the inductance associated with the selected one of the coils using a pulse response measurement circuit.

[0081] According to one embodiment, a non-transitory computer-readable storage medium is provided, comprising instructions for: transmitting a wireless power signal to a wireless power receiving device using a wireless power transmission circuit coupled to a coil; operating a control circuit in a first mode, wherein the control circuit uses the wireless power transmission circuit and a first group of one or more coils of the coils to transmit the wireless power signal to the wireless power receiving device without transmitting wireless power to a radio frequency identification device, the radio frequency identification device overlapping with a second group of one or more coils of the coils that is different from the first group of coils; and operating the control circuit in a second mode, wherein upon detecting that the radio frequency identification device is overlapped by the wireless power receiving device, the control circuit abandons using the wireless power transmission circuit to transmit the wireless power signal to the wireless power receiving device.

[0082] According to another embodiment, a non-transitory computer-readable storage medium includes instructions for detecting a foreign object based at least in part on coil inductance information acquired from the coil.

[0083] According to another embodiment, a non-transitory computer readable storage medium includes instructions for measuring a response of a selected one of the coils to a pulse signal.

[0084] The foregoing is merely illustrative and various modifications may be made to the embodiments described. The foregoing embodiments may be implemented independently or in any combination.

Claims

1. A wireless power transmission device having a charging surface, comprising: Coil; an output circuit coupled to the coil and configured to transmit a wireless power signal to a wireless power receiving device using the coil; an oscillator circuit providing an oscillator output signal to the output circuit; a measurement circuit coupled to the output circuit; as well as A control circuit, the control circuit being configured to: performing a frequency sweep of the oscillator output signal from a first frequency to a second frequency using the measurement circuit to detect a resonant signal between the first frequency and the second frequency, A determination is made based on the frequency scan whether an object is present at the charging surface. 2 . The wireless power transmission device of claim 1 , wherein the control circuit is configured to use the measurement circuit to collect coil inductance measurements to determine whether a foreign object is present at the charging surface. 3 . The wireless power transmission device of claim 2 , wherein the control circuit is configured to determine whether a radio frequency identification (RFID) device is present at the charging surface based on the frequency scan. 4 . The wireless power transmission device according to claim 3 , wherein the control circuit is configured to perform the frequency scan within a frequency range including 13.56 MHz.

5. The wireless power transmission device of claim 3, wherein the control circuit is configured to: in response to determining that the RFID device is present at the charging surface, forgo using the wireless power transmission circuit to transmit the wireless power signal.

6. The wireless power transmission device according to claim 5, wherein the control circuit is configured to: determine whether the wireless power receiving device is present at the charging surface based on the coil inductance measurement result, and wherein the control circuit is configured to: in response to determining that the wireless power receiving device is present at the charging surface, control the output circuit to transmit the wireless power signal to the wireless power receiving device.

7. The wireless power transmission device according to claim 2, wherein the control circuit is configured to determine whether a radio frequency identification (RFID) device or a foreign object such as the following is present at the charging surface based on the coil inductance measurement result, the foreign object being not an RFID device and not the wireless power receiving device. 8 . The wireless power transmission device of claim 7 , wherein the wireless power signal is configured to charge a battery on the wireless power receiving device. 9 . The wireless power transmission apparatus according to claim 1 , wherein the first frequency is equal to 5 MHz and the second frequency is equal to 30 MHz. 10 . The wireless power transmission device of claim 2 , wherein the control circuit is configured to determine whether the object is present at the charging surface by comparing the coil inductance measurement result with a predetermined coil inductance.

11. A wireless power transmission device having a charging surface, comprising: Coil; an output circuit coupled to the coil and configured to transmit a wireless power signal to a wireless power receiving device using the coil; an oscillator circuit providing an oscillator output signal to the output circuit; a measurement circuit coupled to the output circuit; as well as A control circuit, the control circuit being configured to: performing a frequency sweep of the oscillator output signal from a first frequency to a second frequency using the measurement circuit to obtain a frequency response, and A determination is made based on the frequency response whether a radio frequency identification (RFID) device overlaps the coil. 12 . The wireless power transmission device of claim 11 , wherein the control circuit is configured to abandon using the wireless power transmission circuit to transmit the wireless power signal in response to determining that the RFID device is present and overlaps with the coil.

13. The wireless power transmission device of claim 12, wherein the control circuit is configured to: use the measurement circuit to collect coil inductance measurement results, and wherein the control circuit is configured to: determine whether the wireless power receiving device overlaps with the coil based on the coil inductance measurement results. 14 . The wireless power transmission device according to claim 13 , wherein the control circuit is configured to: in response to determining that the wireless power receiving device overlaps the coil, control the output circuit to transmit the wireless power signal to the wireless power receiving device. 15 . The wireless power transmission apparatus according to claim 11 , wherein the first frequency is equal to 5 MHz and wherein the second frequency is equal to 30 MHz. 16 . The wireless power transmission device of claim 11 , wherein the control circuit is configured to reduce a transmission power level of the wireless power signal in response to determining that the RFID device overlaps the coil. 17 . The wireless power transmission device of claim 13 , wherein the control circuit is configured to determine whether the RFID device overlaps the coil by comparing the coil inductance measurement result with a predetermined coil inductance.

18. A wireless power transmission device having a charging surface, comprising: Coil; an output circuit coupled to the coil and configured to transmit a wireless power signal to a wireless power receiving device using the coil; an oscillator circuit providing an oscillator output signal to the output circuit; a measurement circuit coupled to the output circuit; as well as A control circuit, the control circuit being configured to: Using the measurement circuit to collect coil inductance measurements, performing a frequency sweep of the oscillator output signal from a first frequency to a second frequency using the measurement circuit to determine if a sensitive device is present, determining whether a foreign object other than the wireless power receiving device overlaps the coil based on the coil inductance measurement result, In response to determining that the foreign object and the sensitive device do not overlap the coil, and controlling the output circuit to transmit the wireless power signal to the wireless power receiving device, and In response to determining that the foreign object or the sensitive device overlaps the coil, using the wireless power transmission circuit to transmit the wireless power signal is abandoned. 19 . The wireless power transmission apparatus according to claim 18 , wherein the control circuit is configured to determine whether the foreign object overlaps the coil by comparing the coil inductance measurement result with a predetermined coil inductance.

20. The wireless power transmission device of claim 18, wherein the sensitive device comprises a radio frequency identification (RFID) device.

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