Power receiving device and its control method, power transmitting device and its control method, program

Abstract

To provide a technology that enables detection of objects different from a power receiving device with higher accuracy.SOLUTION: A wireless power transmission system includes a power transmission device 100 and a power reception device 101. The power transmission device 100 transmits power with a power transmission coil, and the power reception device 101 receives power with a power reception coil. The power reception device 101 associates information such as a positional relationship between the power transmission coil and the power reception coil when the power reception device 101 is placed on a predetermined power transmission coil, the presence or absence and a position of an object different from the power transmission device 100 and the power reception device 101, an operation frequency, and a received power value with a predetermined physical quantity. The predetermined physical quantity is a Q-value related to the power transmission coil, a resonance frequency, a coupling coefficient between the power transmission coil and the power reception coil, and power consumption in the object. The power reception device 101 transmits the associated information to the power transmission device 100. The power transmission device 100 executes detection processing of the object in accordance with the information received from the power reception device 101.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] This disclosure relates to wireless power transmission technology. [Background technology]

[0002] The standard developed by the Wireless Power Consortium (hereinafter referred to as the WPC standard) as a wireless charging standard is widely known. In wireless power transmission systems that utilize wireless power transmission technology, it is necessary to detect the presence or absence of objects between the power transmitting device and the power receiving device. These objects (hereinafter sometimes referred to as foreign objects) are objects that are neither power transmitting devices nor power receiving devices, and which may generate heat when exposed to power signals. Power transmission and reception are controlled based on the detection results of objects that may be present within the range to which the power transmitting device can transmit power.

[0003] Patent Document 1 discloses a technology for detecting foreign objects and restricting power transmission and reception when foreign objects are present near a power transmission and reception device compliant with the WPC standard. Patent Document 2 discloses a technology for detecting foreign objects by short-circuiting the coils of a wireless power transmission system. Furthermore, Patent Document 3 discloses a technology for detecting foreign objects by applying a high-frequency signal to the transmission coil of a wireless power transmission system over a certain period of time and measuring the change in the Q value (Quality factor) of the transmission coil. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-070074 [Patent Document 2] Japanese Patent Publication No. 2017-034972 [Patent Document 3] Japanese Patent Publication No. 2017-022999 [Overview of the project] [Problems that the invention aims to solve]

[0005] With conventional technology, a decrease in the accuracy of state detection or foreign object detection in a wireless power transmission system compliant with the WPC standard could potentially disrupt the control of wireless power transmission. This disclosure aims to provide a technology that enables more accurate detection of objects other than power receiving devices. [Means for solving the problem]

[0006] The power receiving device of the embodiment of the present disclosure is a power receiving device that receives power from a power transmitting device by wireless power transmission, and comprises communication means for communicating with the power transmitting device, and physical quantities used for detecting the state of the power receiving device relative to the power transmitting device, or for detecting objects other than the power transmitting device and the power receiving device. and information indicating the positional relationship between the power transmission coil of the power transmission device and the power receiving coil of the power receiving device or the object. Related hair, The system includes control means for performing control to transmit associated information to the power transmission device via the communication means. [Effects of the Invention]

[0007] This disclosure provides a technology that enables more accurate detection of objects other than power receiving devices. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the system configuration and position on the power transmission coil of the embodiment. [Figure 2] This figure shows an example of the configuration of a power receiving device. [Figure 3] This figure shows an example of the configuration of a power transmission device. [Figure 4] This figure shows an example of the functional configuration of the control unit of a power transmission device. [Figure 5] This figure shows an example of the functional configuration of the control unit of a power receiving device. [Figure 6] This is a conceptual diagram explaining foreign object detection using the power loss method. [Figure 7] This is a conceptual diagram illustrating the method for measuring the Q-value in the time domain. [Figure 8] This is a sequence diagram illustrating the operation of the power transmission and receiving equipment. [Figure 9] It is an explanatory diagram of the FOD Status packet transmitted by the power receiving device. [Figure 10] It is a flowchart for explaining the operation of the power receiving device. [Figure 11] It is an explanatory diagram of the Configuration packet transmitted by the power receiving device. [Figure 12] It is a flowchart for explaining the operation of the power transmitting device. [Figure 13] It is a diagram showing an example of associating various types of information used for detection.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the embodiments, as an example of a wireless charging system to which a wireless power transmission system is applied, wireless power transmission conforming to the WPC standard will be described.

[0010] Referring to FIG. 1, the configuration of the system according to the embodiment will be described. FIG. 1(A) is a diagram showing a configuration example of a wireless power transmission system. The wireless power transmission system includes a power transmitting device 100 and a power receiving device 101. The power transmitting device 100 is an electronic device that wirelessly transmits power via a power transmission antenna to, for example, a power receiving device 101 placed on its own device. The power receiving device 101 is an electronic device that, for example, receives power from the power transmitting device 100 and charges a built-in battery. There are embodiments in which the power transmitting device 100 and the power receiving device 101 are separate devices, and embodiments in which those devices are incorporated into other devices. The other devices include imaging devices, smartphones, tablet PCs, laptop PCs, automobiles, robots, medical devices, printers, etc., and power supply to various devices is possible.

[0011] Figure 1(B) is a schematic diagram showing a power transmission coil and a position on the coil. It shows a power transmission device (test power transmitter, hereafter referred to as TPT) 1000 and its power transmission coil 1001 used for compliance testing of power receiving equipment according to the WPC standard. In a planar coordinate system consisting of the X and Y axes, point 102 indicates the center of the power transmission coil 1001. Point 103 is a point located a predetermined distance from point 102 in the +X direction in the figure. Point 104 is a point located a predetermined distance from point 102 in the +Y direction in the figure. Point 105 is a point located a predetermined distance from point 102 in the -X direction in the figure. Point 106 is a point located a predetermined distance from point 102 in the -Y direction in the figure. The predetermined distance is, for example, 5 millimeters, but other distance values ​​may be used.

[0012] The configuration of the power receiving device 101 will be explained with reference to Figure 2. Figure 2 is a diagram showing an example of the configuration of the power receiving device 101. The power receiving device 101 includes a control unit 200, a power receiving coil 201, a rectifier unit 202, a voltage control unit 203, a communication unit 204, a charging unit 205, a battery 206, a resonant capacitor 207, and a switch unit 208.

[0013] The control unit 200 controls the entire power receiving device 101. The control unit 200 is composed of one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 200 may also include one or more storage devices, such as RAM (Random Access Memory) or ROM (Read Only Memory). The control unit 200 performs the processes described later by having the processor execute programs stored in the storage devices.

[0014] The receiving coil 201 receives power from the transmitting coil (Figure 3:303) of the power transmission device 100. A resonant capacitor 207 is connected to the receiving coil 201. The rectifier 202 converts the AC voltage and AC current received via the receiving coil 201 into DC voltage and DC current.

[0015] The voltage control unit 203 converts the DC voltage level input from the rectifier unit 202 to a DC voltage level suitable for the operation of the control unit 200, the charging unit 205, etc. The voltage control unit 203 supplies the converted voltage level to the control unit 200, the charging unit 205, etc. The charging unit 205 charges the battery 206 based on the voltage supplied from the voltage control unit 203.

[0016] The communication unit 204 is connected to the control unit 200 and the receiving coil 201. The communication unit 204 performs control communication for wireless charging based on the WPC standard with the power transmission device 100. This control communication is performed by load modulation of the AC voltage and AC current received by the receiving coil 201.

[0017] The receiving coil 201 is connected to the resonant capacitor 207 and configured to resonate at a specific frequency F2. The switch unit 208 has the function of short-circuiting the receiving coil 201 and the resonant capacitor 207 and is controlled by a control signal from the control unit 200. When the switch unit 208 is turned on, the receiving coil 201 and the resonant capacitor 207 form a series resonant circuit. At this time, current flows through the closed circuit formed by the receiving coil 201, the resonant capacitor 207, and the switch unit 208, and no current flows to the rectifier unit 202 or the voltage control unit 203. On the other hand, when the switch unit 208 is turned off, current flows to the rectifier unit 202 and the voltage control unit 203 via the receiving coil 201 and the resonant capacitor 207.

[0018] The configuration of the power transmission device 100 will be explained with reference to Figure 3. Figure 3 is a diagram showing an example of the configuration of the power transmission device 100. The power transmission device 100 includes a control unit 300, a power supply unit 301, a power transmission unit 302, a power transmission coil 303, a communication unit 304, a memory 305, a resonant capacitor 306, and a switch unit 307.

[0019] The control unit 300 controls the entire power transmission device 100. The control unit 300 is composed of one or more processors, such as a CPU or MPU. The control unit 300 performs the processes described later by having the processor execute programs stored in the memory 305 or a storage device built into the control unit 300.

[0020] The power supply unit 301 supplies power to each part of the power transmission device 100. The power supply unit 301 includes, for example, a connection circuit to the commercial power supply and a battery. For example, the battery is charged by power supplied from the commercial power supply.

[0021] The power transmission unit 302 converts the DC power or AC power input from the power supply unit 301 into AC power in the frequency band used for wireless power transmission. The power transmission unit 302 inputs the converted AC power to the power transmission coil 303, generating electromagnetic waves from the power transmission coil 303 for the power receiving device 101 to receive power. For example, the power transmission unit 302 converts the DC voltage supplied by the power supply unit 301 into an AC voltage using a switching circuit in a half-bridge or full-bridge configuration. The bridge-configured switching circuit is made up of multiple FETs (Field Effect Transistors), and the power transmission unit 302 includes a gate driver that controls the ON / OFF state of the multiple FETs. The power transmission unit 302 controls the intensity and frequency of the output electromagnetic waves by adjusting the voltage (transmission voltage) or current (transmission current), or both, input to the power transmission coil 303, or by adjusting their frequencies. For example, the power transmission unit 302 controls the strength of the electromagnetic waves by adjusting the magnitude of the transmission voltage or transmission current. The power transmission unit 302 shall have the capacity to supply at least 15 watts (W) of power to the charging unit 205 of the power receiving device 101, which complies with the WPC standard. In addition, the power transmission unit 302 controls the output of AC power so that the output of electromagnetic waves from the power transmission coil 303 is started or stopped based on instructions from the control unit 300.

[0022] The communication unit 304 is connected to the control unit 300 and the power transmission unit 302, and communicates with the power receiving device 101 via the power transmission coil 303 for power transmission control based on the WPC standard. The communication unit 304 modulates the AC voltage and AC current output from the power transmission unit 302 using frequency shift keying (FSK) and transmits information to the power receiving device 101. The communication unit 304 also demodulates the AC voltage and AC current that have been load-modulated by the communication unit 204 of the power receiving device 101 and acquires the information transmitted by the power receiving device 101.

[0023] In this embodiment, the communication between the communication unit 304 and the communication unit 204 of the power receiving device 101 is performed by superimposing a signal of information to be transmitted to the power receiving device 101 onto the electromagnetic waves output from the power transmission unit 302. The power receiving device 101 acquires the information transmitted from the power receiving device 101 by detecting the signal superimposed on the electromagnetic waves. Not limited to this example, the communication unit 304 can communicate with the power receiving device 101 using a different coil (or antenna) than the power transmission coil 303 and according to a standard other than the WPC standard. Examples of communication standards include Bluetooth® Low Energy (BLE) and NFC (Near Field Communication). Furthermore, the communication unit 304 may selectively use multiple communication functions according to the WPC standard and standards other than the WPC standard to communicate with the power receiving device 101.

[0024] Memory 305 is connected to the control unit 300 and stores information such as the control program executed by the processor of the control unit 300 and the status of the power transmission device 100 and the power receiving device 101. For example, information regarding the status of the power transmission device 100 is acquired by the control unit 300. Information regarding the status of the power receiving device 101 is acquired by the control unit 200 and transmitted to the power transmission device 100 from the communication unit 204. The power transmission device 100 acquires information regarding the status of the power receiving device 101 via the communication unit 304. The control unit 300 and the control unit 200 communicate with each other to acquire information and execute status detection and determination processes.

[0025] The power transmission coil 303 is connected to the resonant capacitor 306 and configured to resonate at a specific frequency F1. The switch unit 307 has the function of short-circuiting the power transmission coil 303 and the resonant capacitor 306 and is controlled by a control signal from the control unit 300. When the switch unit 307 is turned on, the power transmission coil 303 and the resonant capacitor 306 form a series resonant circuit. At this time, current flows through the closed circuit of the power transmission coil 303, the resonant capacitor 306, and the switch unit 307. On the other hand, when the switch unit 208 is turned off, power is supplied to the power transmission coil 303 and the resonant capacitor 306 from the power transmission unit 302.

[0026] Figure 4 shows the functional block elements implemented by the control unit 300 of the power transmission device 100. The functional block elements of the control unit 300 include the first Q value measurement unit 400, the second Q value measurement unit 401, the calibration processing unit 402, the first foreign object detection processing unit 403, the second foreign object detection processing unit 404, the third foreign object detection processing unit 405, and the power transmission control processing unit 406.

[0027] The first Q-value measurement unit 400 and the second Q-value measurement unit 401 measure physical quantities used for detecting the state of a wireless power transmission system, etc. The first Q-value measurement unit 400 measures the Q-value in the frequency domain (hereinafter referred to as the first Q-value measurement). This Q-value will be denoted as the first Q-value. The second Q-value measurement unit 401 measures the Q-value in a different way than the first Q-value measurement unit 400. Specifically, the second Q-value measurement unit 401 measures the Q-value in the time domain (hereinafter referred to as the second Q-value measurement). This Q-value will be denoted as the second Q-value. Details of the first Q-value measurement and the second Q-value measurement will be described later.

[0028] The Calibration processing unit 402 performs the process of acquiring Calibration Data Points and creating Calibration curves. Details of the process will be described later.

[0029] The first foreign object detection processing unit 403, the second foreign object detection processing unit 404, and the third foreign object detection processing unit 405 each perform foreign object detection based on the acquired measurement results. A foreign object is an object that is neither a power transmission device nor a power receiving device, and which may generate heat when exposed to a power signal. Specifically, metals and the like fall into this category. If a foreign object is present near the power transmission device 100, the electromagnetic waves for power transmission may affect the foreign object, potentially causing a temperature rise or destruction of the foreign object. However, objects that are essential parts of a power receiving device, a product incorporating a power receiving device, or a power transmission device, or a product incorporating a power transmission device, and which may unintentionally generate heat when exposed to the wireless power transmitted by the power transmission antenna, are not considered foreign objects.

[0030] The first foreign object detection processing unit 403 acquires the first Q value and executes the first foreign object detection process. The second foreign object detection processing unit 404 executes the second foreign object detection process based on the power loss method described later. The third foreign object detection processing unit 405 executes the third foreign object detection process based on the second Q value.

[0031] The power transmission control processing unit 406 controls the power transmitted by the power transmission unit 302. For example, it controls the start and stop of power transmission by the power transmission unit 302, and increases and decreases in power transmission.

[0032] Figure 5 shows an example of the configuration of a functional block element realized by the control unit 200 of the power receiving device 101. The functional block elements of the control unit 200 are shown as a second Q value measurement unit 501 and a third foreign object detection processing unit 500. The second Q value measurement unit 501 performs a second Q value measurement, which is a measurement of the Q value in the time domain. The third foreign object detection processing unit 500 acquires the second Q value measured by the second Q value measurement unit 501 and performs a third foreign object detection process.

[0033] Each processing unit shown in Figures 4 and 5 is configured as an independent program and can operate in parallel while synchronizing with other programs through event handling, etc.

[0034] Next, we will explain examples of foreign object detection methods in the WPC standard. Here, we will describe a foreign object detection method based on the first Q value (hereinafter referred to as the first detection method) and a foreign object detection method based on the power loss method (hereinafter referred to as the second detection method).

[0035] In the first detection method, the power transmission device 100 first performs a measurement (first Q value measurement) in the frequency domain of the Q value that changes due to the influence of foreign matter. The first Q value measurement is performed between the time the power transmission device 100 transmits Analog Ping and the time it transmits Digital Ping (see F601 in Figure 8). For example, the power transmission unit 302 sweeps the frequency of the radio power output by the power transmission coil 303 in order to measure the first Q value. The first Q value measurement unit 400 measures the voltage value at the end of the resonant capacitor 306 connected in series (or parallel) with the power transmission coil. The first Q value measurement unit 400 searches for the resonant frequency at which the measured voltage value peaks, and calculates the first Q value from the frequency showing a voltage value 3 dB lower than the peak voltage value measured at the resonant frequency and that resonant frequency.

[0036] There is also another method for measuring the first Q value. For example, the power transmission unit 302 sweeps the frequency of the radio power output by the power transmission coil 303. The first Q value measurement unit 400 measures the voltage value at the ends of the resonant capacitor 306 connected in series with the power transmission coil 303 and searches for the resonant frequency at which that voltage value peaks. At the searched resonant frequency, the first Q value measurement unit 400 measures the voltage value across the resonant capacitor 306 and calculates the first Q value from the ratio of the voltage values ​​across its ends.

[0037] After calculating the first Q value, the first foreign object detection processing unit 403 obtains the Q value, which serves as the criterion for foreign object detection, from the power receiving device 101 via the communication unit 304. For example, the first foreign object detection processing unit 403 receives the Q value (first characteristic value) related to the power transmission coil when the power receiving device is placed on a certain power transmission coil, as defined in the WPC standard, from the power receiving device 101. This Q value is stored in the FOD (Foreign Object Detection) Status packet transmitted by the power receiving device 101. The power transmission device 100 obtains the Q value by receiving the FOD Status packet from the power receiving device 101. Details of the FOD Status packet will be described later.

[0038] The first foreign object detection processing unit 403 estimates the Q value of the power transmission coil 303 when the power receiving device 101 is placed on the power transmission device 100, based on the acquired Q value. Hereinafter, the estimated Q value will be referred to as the first reference Q value. The Q value stored in the FOD Status packet is pre-stored in, for example, the non-volatile memory (not shown) of the power receiving device 101. The power receiving device 101 can notify the power transmission device 100 of the Q value that it has previously stored. This Q value corresponds to Q1, which will be described later. The first foreign object detection processing unit 403 compares the first reference Q value (first reference) with the measurement result of the first Q value and determines the presence or possibility of a foreign object based on the comparison result. For example, the first foreign object detection processing unit 403 sets a threshold value obtained by reducing the first reference Q value by a predetermined percentage. If the predetermined percentage is denoted as a%, the threshold value corresponds to the product of the first reference Q value and a / 100. The first foreign object detection processing unit 403 determines that if the measurement result of the first Q value is lower than a set threshold, there is a high probability that the Q value has decreased due to a foreign object. Also, if the measurement result of the first Q value is equal to or greater than the set threshold, the first foreign object detection processing unit 403 determines that there is a high probability that no foreign object is present.

[0039] Next, the second detection method will be explained with reference to Figure 6. Figure 6 is a conceptual diagram for explaining the second detection method, where the horizontal axis represents the power transmitted by the power transmission device 100 and the vertical axis represents the power received by the power receiving device 101. On the graph lines shown by the straight line segments 1202 and 1205, point 1200 corresponds to the first power transmitted value Pt1 and the first power received value Pr1. On the graph line shown by line segment 1202, point 1201 corresponds to the second power transmitted value Pt2 and the second power received value Pr2, and point 1203 corresponds to the third power transmitted value Pt3 and the third power received value Pr3. Also, on the graph line shown by line segment 1205, point 1204 corresponds to the power transmitted value Pt2 * This corresponds to the second power received value Pr2. The power transmission unit 302 controls the transmitted power, which is performed by the power transmission control processing unit 406. The foreign objects to be detected are conductive metal pieces, etc.

[0040] First, the power transmission unit 302 of the power transmission device 100 sends a Digital Ping to the power receiving device 101. The communication unit 304 of the power transmission device 100 receives information on the power received value in the light load state of the power receiving device 101 via Received Power Packet (mode 1). Hereafter, Received Power Packet (mode 1) will be abbreviated as "RP1". The information in RP1 represents the power received value when the power receiving device 101 is not supplying power to the load (charging unit 205, battery 206, etc.).

[0041] The control unit 300 of the power transmission device 100 stores a Calibration Data Point in the memory 305 that represents the relationship between the received RP1 and the transmitted power value Pt1 when RP1 was obtained. Hereinafter, the Calibration Data Point will be abbreviated as CDP. Hereinafter, CDP corresponds to point 1200 in Figure 6. The power transmission device 100 recognizes that the amount of power loss between the power transmission device 100 and the power receiving device 101 when transmitting power value Pt1 is Pt1-Pr1. Pt1-Pr1 will be denoted as Ploss1.

[0042] Next, the communication unit 304 of the power transmission device 100 receives the power received value Pr2 in the connected load state of the power receiving device 101 from the power receiving device 101 via Received Power Packet (mode 2). Hereinafter, Received Power Packet (mode 2) will be abbreviated as "RP2". The power received value Pr2 is the power received value when the power receiving device 101 is supplying power to the load. The control unit 300 of the power transmission device 100 then stores in memory 305 a CDP that represents the relationship between the received Pr2 and the power transmitted value Pt2 when Pr2 was obtained. Here, CDP corresponds to point 1201 in Figure 6. As a result, the power transmission device 100 recognizes that when it transmits power at the power transmitted value Pt2, the amount of power loss between the power transmission device 100 and the power receiving device 101 is Pt2-Pr2. Pt2-Pr2 will be denoted as Ploss2.

[0043] The Calibration Processing Unit 402 of the power transmission device 100 performs linear interpolation between two CDPs, points 1200 and 1201, to generate a line segment 1202. The line segment 1202 represents the relationship between transmitted power and received power when there are no foreign objects around the power transmission device 100 and the power receiving device 101. Therefore, the power transmission device 100 can predict the received power value when there is a high probability that no foreign objects are present, based on the transmitted power value and the line segment 1202. For example, consider the case where the transmitted power value is Pt3. The power transmission device 100 can predict the received power value Pr3 from point 1203 on the line segment 1202 corresponding to the transmitted power value Pt3.

[0044] Here, assuming that the power transmission unit 302 of the power transmission device 100 transmits power to the power receiving device 101 with a power transmission value Pt3, the communication unit 304 receives the power reception value Pr3 from the power receiving device 101. * Assume that the following information has been received. The second foreign object detection processing unit 404 of the power transmission device 100 calculates the received power value Pr3 in a state where there is a high probability that no foreign object is present, and then calculates the received power value Pr3 that was actually received from the power receiving device 101. * Subtract this. That is, Pr3-Pr3 *(=Ploss_FO) is calculated. Ploss_FO corresponds to the amount of power loss consumed by the foreign object when a foreign object exists between the power transmission device 100 and the power reception device 101. When the amount of power loss Ploss_FO that would have been consumed by the foreign object exceeds a predetermined threshold, the second foreign object detection processing unit 404 can determine that a foreign object exists. This threshold is derived, for example, based on the relationship between point 1200 and point 1201.

[0045] Also, in advance, the second foreign object detection processing unit 404 of the power transmission device 100 obtains the power loss amount Pt3 - Pr3 (= Ploss3) between the power transmission device 100 and the power reception device 101 from the received power value Pr3 in a state where there is a high possibility that no foreign object exists. Then, in a state where the presence or absence of a foreign object is unknown, from the received power value Pr3 received from the power reception device 101, the power loss amount Pt3 - Pr3 * between the power transmission device 100 and the power reception device 101 in a state where a foreign object exists * (=Ploss3 * ) is calculated. The second foreign object detection processing unit 404 calculates Ploss3 * - Ploss3. Ploss3 * - Ploss3 = Pt3 - Pr3 * - Pt3 + Pr3 = Pr3 - Pr3 * which corresponds to Ploss_FO. When this value exceeds a predetermined threshold, the second foreign object detection processing unit 404 can determine that a foreign object exists (or the possibility of its existence is high). By calculating the difference in the power loss amount in this way, the power loss amount Ploss_FO can be estimated.

[0046] As described above, in the method for calculating Ploss_FO, there are a method of calculating Ploss_FO from Pr3 - Pr3 * and a method of calculating Ploss_FO from Ploss3 * - Ploss3.

[0047] After the Calibration Processing Unit 402 generates the line segment 1202 in Figure 6, the second foreign object detection processing unit 404 periodically receives the power received value (e.g., Pr3) from the power receiving device 101 via the communication unit 304. * The information of the received power value that the power receiving device 101 periodically transmits to the power transmitting device 100 is transmitted to the power transmitting device 100 as Received Power Packet (mode0). Hereinafter, Received Power Packet (mode0) will be abbreviated as "RP0". The second foreign object detection processing unit 404 performs foreign object detection based on the received power value stored in RP0 and the line segment 1202.

[0048] In this embodiment, points 1200 and 1201 are used as the CDP for generating the line segment 1202 in Figure 6, and the line segment 1202 is obtained by linear interpolation. Note that the line segment 1202 is referred to as the "Calibration curve," including curves, and is not limited to this example. The CDP and Calibration curve are used as a reference (second reference) for the second foreign object detection process.

[0049] Next, the second Q value measurement method will be explained with reference to Figure 7. Figures 7(A) and 7(B) are conceptual diagrams illustrating the second Q value measurement method. In this embodiment, the foreign object detection method based on the measured second Q value (Q2) is called the third foreign object detection method.

[0050] In the second Q value measurement, the power transmission device 100 and the power receiving device 101 are switched on at the same time to momentarily interrupt power transmission, and then controlled so that the received power is not applied to the load. As a result, for example, the voltage applied to the power transmission coil decreases exponentially. The second Q value corresponding to the attenuation state of the transmission type can be calculated. The power transmission waveform is either a voltage waveform or a current waveform, and the second Q value is calculated according to how the voltage value or current value decreases.

[0051] Figure 7(A) shows an example of the time variation of waveform 1100. In Figure 7(A), the horizontal axis is the time axis and the vertical axis is the voltage axis. Waveform 1100 shows the time variation of the value of the high-frequency voltage applied to the end of the transmission coil 303 or resonant capacitor 306 of the power transmission device 100 (hereinafter simply referred to as "voltage value of the transmission coil"). The power transmission device 100 stops applying the high-frequency voltage (transmission) at time T0. Point 1101 is a point on the envelope of the high-frequency voltage (in other words, a point of maximum value). At point 1101, (T1, A1) indicates that the voltage value at time T1 is A1. Point 1102 is a point on the envelope of the high-frequency voltage. At point 1102, (T2, A2) indicates that the voltage value at time T2 is A2.

[0052] The second Q value measurement is performed based on the time change of the voltage value after time T0. For example, the Q value can be calculated using Equation 1 based on the time, voltage value, and frequency of the high-frequency voltage (hereinafter denoted as f, and referred to as the operating frequency) at points 1101 and 1102 shown in Figure 7(A). Q=π·f·(T2-T1) / ln(A1 / A2) (Equation 1)

[0053] In Equation 1, ln represents the natural logarithm function. The second Q value represents the electrical characteristics determined by the relationship between the elapsed time after power transmission is restricted and the voltage drop across the transmission coil 303. In this disclosure, power transmission restriction includes the cessation of power transmission.

[0054] Next, an example of the measurement process for the second Q value will be explained with reference to Figure 7(B). In Figure 7(B), the settings for the horizontal and vertical axes are the same as in Figure 7(A). Waveform 1103 shows the value of the high-frequency voltage applied to the transmission coil 303, and its frequency is between 110kHz and 148.5kHz, which are used in the Qi standard. Points 1104, 1105, 1106, and 1107 are all points on the envelope of the high-frequency voltage and correspond to (T3,A3), (T4,A4), (T6,A6), and (T7,A7), respectively. <T6<T7<T4」および「A3> The relationship is A6 > A7 > A4.

[0055] In the example shown in Figure 7(B), the power transmission unit 302 of the power transmission device 100 stops transmitting power during the period from time T0 to time T5. The second Q value measuring unit 401 calculates the second Q value using Equation 1, for example, from the voltage value A3 (point 1104) at time T3, the voltage value A4 (point 1105) at time T4, and the operating frequency f of the high-frequency voltage. Subsequently, the power transmission unit 302 resumes transmitting power at time T5. Thus, the second Q value measurement is performed based on the elapsed time from the moment the power transmission device 100 momentarily interrupted power transmission, the voltage value of the waveform, and the operating frequency. Similarly, in the power receiving device 101, the second Q value can be calculated as an electrical characteristic determined by the relationship between the elapsed time after power transmission is restricted and the voltage drop of the power receiving coil 201.

[0056] In the examples in Figures 7(A) and 7(B), the vertical axis represents the voltage value, but the vertical axis may also represent the current value flowing through the transmission coil. Similar to the case of voltage values, it is possible to calculate the second Q value according to the decay state of the current value during the power transmission restriction period.

[0057] Referring in part to Figure 8, an example of operation when the power transmission device 100 and the power receiving device 101 perform the first foreign object detection process, the second foreign object detection process, and the third foreign object detection process will be described. In Figure 8, the operation of the power transmission device 100 is shown on the left, and the operation of the power receiving device 101 is shown on the right. F600 to F632 in the figure are symbols and numbers used to distinguish the operation at each stage.

[0058] At F600, the power transmission device 100 transmits an Analog Ping to detect an object in the vicinity of the power transmission coil 303. The Analog Ping is a pulsed power signal used to detect an object. Furthermore, the Analog Ping is such a small amount of power that even if the power receiving device 101 receives it, it cannot start the control unit 200.

[0059] The power transmission device 100 performs object detection processing using Analog Ping. The detection processing is based on a shift in the resonant frequency of the voltage inside the power transmission coil 303 caused by an object in the vicinity of the power transmission coil 303, or on a change in the voltage value or current value of the power transmission coil 303.

[0060] When the power transmission device 100 detects an object using Analog Ping, it measures the Q value (Q1) of the power transmission coil 303 by measuring the first Q value at F601. Then, at F602, the power transmission device 100 starts transmitting Digital Ping. Digital Ping is the power required to activate the control unit 200 of the power receiving device 101, and it is a higher power than Analog Ping. Furthermore, Digital Ping is transmitted continuously from this point onward. That is, from the start of Digital Ping transmission until the reception of the EPT (End Power Transfer) packet (see F622), the power transmission device 100 continues to transmit power equal to or greater than Digital Ping.

[0061] The power receiving device 101 starts up when it receives a Digital Ping. At F603, the power receiving device 101 stores the voltage value of the received Digital Ping in a Signal Strength packet and sends it to the power transmitting device 100. Subsequently, at F604, the power receiving device 101 sends an ID packet to the power transmitting device 100 containing an ID that includes version information of the WPC standard to which the power receiving device 101 conforms and device identification information. Furthermore, at F605, the power receiving device 101 sends a Configuration packet to the power transmitting device 100 containing information such as the maximum value of power that the voltage control unit 203 will supply to the load (charging unit 205).

[0062] The power transmission device 100 receives an ID packet and a Configuration packet. Based on these packets, the power transmission device 100 determines that the power receiving device 101 supports the WPC standard v1.2 or later (including the Negotiation protocol described below). In this case, the power transmission device 100 responds to the power receiving device 101 with an acknowledgment (ACK) at F606. Upon receiving the ACK, the power receiving device 101 transitions to the Negotiation phase, where negotiations regarding the amount of power to be transmitted and received take place.

[0063] At F607, the power receiving device 101 sends an FOD Status packet to the power transmitting device 100. In this embodiment, this FOD Status packet is denoted as "FOD(Q1)". Based on the Q value (first characteristic value) stored in the received FOD(Q1) and the measured first Q value, the power transmitting device 100 performs foreign object detection using the first foreign object detection method. At F608, if the power transmitting device 100 determines that there is a high probability that no foreign object is present, it sends an ACK indicating the determination result to the power receiving device 101.

[0064] When the power receiving device 101 receives an ACK, it negotiates the Guaranteed Power (hereinafter referred to as GP), which is the maximum power value that the power receiving device 101 requests to receive. GP represents the load power of the power receiving device 101 agreed upon between the power receiving device 101 and the power transmitting device 100. Load power corresponds to the power consumed by the battery 206, etc. This negotiation is realized by the power receiving device 101 sending a packet containing the requested GP value to the power transmitting device 100, as defined in the Specific Request of the WPC standard. In this embodiment, this packet is called "SRQ(GP)". At F609, the power receiving device 101 sends SRQ(GP) to the power transmitting device 100.

[0065] The power transmission device 100 responds to the SRQ(GP) from the power receiving device 101 based on its own power transmission capacity, etc. If the power transmission device 100 determines in F610 that it can accept the GP value, it sends an ACK to the power receiving device 101 indicating that it has accepted the request. In this embodiment, it is assumed that the power receiving device 101 has requested 15 watts as the GP value via SRQ(GP).

[0066] Once the power receiving device 101 has finished negotiating multiple parameters, including the GP, it requests the end of negotiation (End Negotiation) via F611. The Specific Request for End Negotiation is denoted as "SRQ(EN)". After the power receiving device 101 sends SRQ(EN) to the power transmitting device 100, the power transmitting device 100 sends an ACK in response to SRQ(EN) via F612. Once negotiation is complete, the system transitions to the Power Transfer phase, where power is transmitted and received as defined by the GP.

[0067] Next, the power transmission device 100 generates a calibration curve for executing the second foreign object detection method based on the power loss method. At F613, the power transmission device 100 receives RP1 from the power receiving device 101. This RP1 contains information elements that the power receiving device 101 requests from the power transmission device 100 to perform the second Q value measurement. For example, the Reserved area of ​​the Received Power Packet is provided with a 1-bit field indicating whether or not the second Q value measurement is requested. If the power receiving device 101 requests the second Q value measurement, it stores "1" in the field; if it does not request the second Q value measurement, it stores "0" in the field. In this embodiment, the bit in the field is called the "request bit". RP1 with a request bit value of "1" is denoted as RP1(FOD).

[0068] When the power transmission device 100 receives RP1(FOD) from the power receiving device 101, it performs a second Q value measurement using F614. Based on the measurement result Q2, a third foreign object detection process is performed. Here, the response to RP1(FOD) is determined based on two elements. The first element is the result of the third foreign object detection process. The second element is a Control Error Packet (hereinafter abbreviated as CE) in which the power receiving device 101 requests the power transmission device 100 to increase or decrease the received voltage (or received current, or received power). The Control Error Value is stored in the CE. The Control Error Value is a measure that indicates the difference between the actual operating point of the power receiving device and the target operating point, and is represented as an 8-bit signed integer. Here, the operating point refers to the combination of frequency, duty cycle, and amplitude of the voltage applied to the power transmission unit. A positive Control Error Value indicates that the actual operating point is below the target operating point, and that the receiving device 101 is requesting the transmitting device 100 to increase the strength of the power signal. Specifically, the receiving device 101 is requesting the transmitting device 100 to increase the transmission voltage or transmission current. Conversely, a negative Control Error Value indicates that the actual operating point is above the target operating point, and that the receiving device 101 is requesting the transmitting device 100 to decrease the strength of the power signal. Specifically, the receiving device 101 is requesting the transmitting device 100 to decrease the transmission voltage or transmission current. Furthermore, a Control Error Value of 0 indicates that the receiving device 101 is requesting the transmitting device 100 to maintain the current operating point.

[0069] The power transmission device 100 promptly controls power transmission based on the sign and integer stored in CE. Specifically, if an integer with a positive sign is stored in CE, the power transmission device 100 promptly increases the transmission voltage. If an integer with a negative sign is stored in CE, the power transmission device 100 promptly decreases the transmission voltage. If "0" is stored in CE, the power transmission device 100 maintains the current transmission voltage.

[0070] At F615, the power transmission device 100 decides to accept the received power value stored in RP1(FOD) and the transmitted power value of the power transmission device 100 when that received power was obtained as data for the CDP (corresponding to point 1200 in Figure 6). The power transmission device 100 sends an acknowledgment (ACK) to the power receiving device 101. Subsequently, at F616, the power receiving device 101 sends CE(+) to the power transmission device 100, indicating an increase in power. CE(+) represents CE, which stores an integer with a + sign.

[0071] When the power transmission device 100 receives CE(+), it changes the setting value of the power transmission unit 302 to increase the power transmission. When the power reception device 101 receives an increase in power in response to CE(+), it supplies the received power to the load (charging unit 205 or battery 206). Subsequently, at F617, the power reception device 101 sends an RP2(FOD) with a "1" stored in the request bit to the power transmission device 100. When the power transmission device 100 receives the RP2(FOD) from the power reception device 101, it performs a second Q value measurement at F618. A third foreign object detection process is performed based on the measurement result of the second Q value. The power transmission device 100 then decides to accept the power received value stored in the RP2(FOD) and the power transmission value of the power transmission device 100 when that power was obtained as data for the CDP (corresponding to point 1201 in Figure 7). At F619, the power transmission device 100 sends an acknowledgment (ACK) to the power receiving device 101.

[0072] At F620, the receiving device 101 transmits RP0 to the transmitting device 100. Upon receiving RP0, the transmitting device 100 performs foreign object detection based on the second foreign object detection method. If the transmitting device 100 determines that there is a high probability that no foreign object is present as a result of the foreign object detection, it transmits an ACK at F621 to the receiving device 101. Subsequently, when the charging of the battery 206 is complete, the receiving device 101 requests the transmitting device 100 to stop power transmission at F622. At F622, the receiving device 101 transmits an EPT (End Power Transfer) packet to the transmitting device 100 requesting the cessation of power transmission.

[0073] Next, with reference to Figure 1(B), the Q1 value and the accuracy of the first and third foreign object detection will be explained. The Q1 value is the Q value related to the power transmission coil of the TPT when the power receiving device 101 is placed on the TPT. The Q value changes depending on whether the center of the power receiving coil 201 of the power receiving device 101 is located at point 102 to point 106, and generally the greater the overlap between the power transmission and receiving coils, the larger the Q value. Since the relative positional relationship between the power transmission coil and the power receiving coil varies when the power receiving device 101 is placed on the power transmission device, differences in the positional relationship of the two coils can be a factor in decreasing the Q value. The presence of foreign objects is also a factor in decreasing the Q value. Here, we will explain the challenges of detecting foreign objects based on the above Q1 using two case examples. Case 1) Assume the center of the receiving coil 201 is at point 102, and foreign matter is present near both the transmitting and receiving coils. If the transmitting and receiving coils are approximately the same size, the overlap between the transmitting and receiving coils is greater compared to the case where the center of the receiving coil 201 is at other points (points 103 to 106), so the measured Q value will be higher. The presence of foreign matter will lower the Q value. In this case, since foreign matter is present, power transmission and reception should be restricted. Case 2) Assume the center of the receiving coil 201 is at point 103, and there are no foreign objects in the vicinity of the transmitting and receiving coils. If the transmitting and receiving coils are approximately the same size, a lower Q value will be observed compared to the case where the center of the receiving coil 201 is at point 102. Furthermore, there is no decrease in the Q value due to the presence of foreign objects. In this case, since there are no foreign objects, power transmission and reception should not be restricted. However, when detecting foreign objects based on the average Q value Q1, it is possible that the Q value measured in Case 2 may be lower than the Q value measured in Case 1. In that case, a false negative may occur in the power transmission equipment, where a foreign object is present in Case 1 but is judged as "not present." Also, a false positive may occur in Case 2, where a foreign object is not present but is judged as "present." If foreign object detection is performed based solely on the average Q1, the detection result may impair the reliability of the system. This disclosure describes a method that enables more accurate detection.

[0074] The power receiving device 101 of this embodiment associates one or more physical quantities when the power receiving device is placed on the power transmission coil of the TPT and transmits the associated information to the power transmission device 100. The power transmission device 100 performs foreign object detection based on the associated information. The one or more physical quantities are, for example, as follows: • The position on which the receiving device (receiving coil) is placed on the TPT's transmitting coil, the Q value of the transmitting coil when it is placed, and the resonant frequency of the transmitting coil when it is placed (this is different from the resonant frequency of the transmitting coil alone). • Coupling coefficient between the transmitting coil and the receiving coil; the position of the receiving device and foreign object when a foreign object is placed on the transmitting coil of the TPT together with the receiving device; the AC voltage value and AC current value transmitted from the transmitting coil, their frequency (referred to as the operating frequency), and the transmitted power. - AC voltage and AC current values ​​received by the receiving coil, operating frequency and received power, and power consumed by foreign objects due to wireless power transmitted from the transmitting coil at the said operating frequency. In this disclosure, unless otherwise specified, physical quantities refer to any or more of the above. Referring to Figure 9, the FOD Status packet transmitted by the power receiving device 101 will be explained in detail. Figure 9 is an explanatory diagram of the FOD Status packet in this embodiment. Bank0 stores FO (Foreign object) alignment, PRx alignment, and type data, while Bank1 stores FOD support data. In the conventional WPC standard, the area from bit 2 to bit 7 of Bank0 is a reserved area where "0" is stored. In this embodiment, unlike the conventional WPC standard, PRx alignment is stored in the area from bit 2 to bit 4 of Bank0. PRx alignment indicates the positional relationship between the power transmitting coil and the power receiving coil (power receiving device).

[0075] Refer to Figures 9(E) and 1(B) to explain PRx alignment. When the PRx alignment value is 001, it indicates that the center of the receiving coil is approximately on point 102. When the PRx alignment value is 010, it indicates that the center of the receiving coil is approximately on point 103. When the PRx alignment value is 011, it indicates that the center of the receiving coil is approximately on point 104. When the PRx alignment value is 100, it indicates that the center of the receiving coil is approximately on point 105. And when the PRx alignment value is 101, it indicates that the center of the receiving coil is approximately on point 106.

[0076] The FO alignment stored in the region from bit 5 to bit 7 of Bank0 indicates the positional relationship between the foreign object and the power transmission coil. In Figure 9(E), when the FO alignment value is 001, it indicates that the center of the foreign object is approximately on point 102. When the FO alignment value is 010, it indicates that the center of the foreign object is approximately on point 103. When the FO alignment value is 011, it indicates that the center of the foreign object is approximately on point 104. When the FO alignment value is 100, it indicates that the center of the foreign object is approximately on point 105. And when the FO alignment value is 101, it indicates that the center of the foreign object is approximately on point 106. Note that when the FO alignment value is 000, it indicates that there is no foreign object.

[0077] The bit0 and bit1 areas of Bank0 are, as before, the storage area for type, and the value corresponding to type is stored in Bank1. Refer to Figure 9(D) for a detailed explanation. In the conventional WPC standard, if the value of type is 00, it indicates that the FOD support data in Bank1 is FOD / qf, that is, the Q value (Q1 above). If the value of type is 01, it indicates that the FOD support data in Bank1 is FOD / rf (resonant frequency), that is, the resonant frequency of the TPT's transmitting coil. If the value of type is 10, it indicates that the FOD support data in Bank1 is FOD / kf (k-factor), that is, the coupling coefficient between the TPT's transmitting coil and receiving coil. If the value of type is 11, the FOD support data in Bank1 is data indicating the power consumption that is consumed by foreign matter and converted into heat, and this is denoted as FOD / FO_loss.

[0078] In Figure 9(B), Bank 2 and Bank 3 are added compared to Figure 9(A). Bank 2 and Bank 3 store the Received Power Value. In Figure 9(C), Bank 4 is added compared to Figure 9(B). Bank 4 stores the Operating Frequency of the power transmission circuit of the power transmission device. Furthermore, Bank 5, Bank 6, etc. may be added to store AC voltage values, AC current values, and transmitted power transmitted from the transmission coil, as well as AC voltage values, AC current values, and values ​​based on them received by the receiving coil.

[0079] The power receiving device of this embodiment can associate physical quantities corresponding to the presence or possibility of foreign matter in each state with the region corresponding only to the Q value and resonant frequency in the conventional WPC standard, and transmit them to the power transmitting device. The physical quantities are one or more quantities from among the Q value, resonant frequency, coupling coefficient, and power consumption of the foreign matter, which are used for detecting the state of wireless power transmission, etc. The control unit 200 of the power receiving device 101 associates the physical quantities and controls the communication unit 204 to transmit the associated information to the power transmitting device 100. Furthermore, the control unit 200 associates information such as the positional relationship between the power transmitting coil and the power receiving coil in each state, the positional relationship between the power transmitting coil and the foreign matter, the operating frequency, and the power received value. Upon receiving this information, the power transmitting device 100 can detect the presence or probability of foreign matter with higher accuracy based on the current Q value, resonant frequency, and coupling coefficient.

[0080] The operation of the power receiving device 101 will be explained with reference to Figure 10. Figure 10 is a flowchart illustrating the operation of the power receiving device 101. The following processes are realized by the processor of the control unit 200 executing a control program. At S700, the power receiving device 101 sends FOD(Q1) to the power transmitting device (see F607 in Figure 8). At S701, the control unit 200 determines whether or not it has received an ACK from the power transmitting device. If an ACK is received (Yes at S701), the process proceeds to S702; if an ACK is not received (No at S701), the process ends.

[0081] In S702, the power receiving device 101 sends a GRQ (CAP) to the power transmitting device (see F623 in Figure 8) and requests Capability information. GRQ stands for "General Request packet". In S703, the control unit 200 determines whether or not it has received a Capability packet from the power transmitting device 100 (see F624 in Figure 8). If a Capability packet is received (Yes in S703), the process proceeds to S704; if a Capability packet is not received (No in S703), the process ends.

[0082] Referring to Figure 11, the Capability packet of the power transmission device in this embodiment will be explained. In Figure 11(A), Improved FOD data is stored in Bank0. The data in bits 6 and 7 related to Improved FOD indicates whether or not it corresponds to the "improved foreign object detection" of this embodiment. Figure 11(B) is a diagram illustrating the 2-bit values ​​of Improved FOD. For Improved FOD provided in Bank0, if the values ​​of bits 6 and 7 are 00, it indicates Incompatible, i.e., it does not support Improved FOD. If the values ​​of bits 6 and 7 are 01, it indicates Compatible, i.e., it supports Improved FOD.

[0083] In S704 of Figure 10, the power receiving device 101 determines whether the power transmitting device supports the foreign object detection method (Improved FOD) of this embodiment. If it is determined that the power transmitting device supports Improved FOD (Yes in S704), the process proceeds to S705. If it is determined that the power transmitting device does not support Improved FOD (No in S704), the process ends.

[0084] In S705, the power receiving device 101 transmits data to the power transmitting device that associates the predetermined physical quantities described above with the position information of the power receiving device relative to the power transmitting device and the received power value. Specifically, the power transmitting device receives data that associates the positional relationship between the power transmitting coil and the power receiving coil, information indicating the presence and location of foreign matter, and the operating frequency and received power value with the Q value, resonant frequency, coupling coefficient, and power consumption of the foreign matter. Examples of communication are shown in F625 to F632 of Figure 8.

[0085] In S706, the power receiving device 101 determines whether or not it has received an ACK. This ACK is a response from the power transmitting device 100 indicating that, based on the data associated in S705, foreign object detection has been performed and it is highly likely that no foreign object is present. If an ACK is received (Yes in S706), the process proceeds to S707; if an ACK is not received (No in S706), the process ends.

[0086] In S707, the receiving device 101 sends a GRQ (GP) to the transmitting device to negotiate the power transmission (GP). Next, in S708, the receiving device 101 determines whether or not it has received an ACK from the transmitting device. If an ACK is received (Yes in S708), the process proceeds to S709; if an ACK is not received (No in S708), the process ends.

[0087] In S709, the receiving device 101 sends a GRQ(EN) to the transmitting device to terminate the negotiation. Next, in S710, the receiving device 101 determines whether or not it has received an ACK from the transmitting device. If an ACK is received (Yes in S710), the negotiation phase ends at the time of ACK reception. If an ACK is not received (No in S710), the series of processes ends.

[0088] The operation of the power transmission device 100 will be explained with reference to Figure 12. Figure 12 is a flowchart illustrating the operation of the power transmission device 100. The following processes are realized by the processor of the control unit 300 executing a control program.

[0089] In S800, the power transmission device 100 performs object detection processing using Analog Ping. The control unit 300 determines whether or not an object has been detected. If it is determined that an object has been detected (Yes in S800), the process proceeds to S801; if it is determined that no object has been detected (No in S800), the process ends.

[0090] In S801, the power transmission device 100 measures the Q value, resonant frequency, and coupling coefficient k related to the power transmission coil. In S802, the power transmission device 100 receives a Configuration packet from the power receiving device.

[0091] Figure 11(C) is an explanatory diagram of the Configuration packet in this embodiment. The Improved FOD bit is provided in bit 5 of bank2. If the power receiving device supports Improved FOD, the Improved FOD bit is set to "1". If the power receiving device does not support Improved FOD, the Improved FOD bit is set to "0".

[0092] Upon receiving the Configuration packet in S802, the power transmission device 100 determines in S803 whether the power receiving device supports Improved FOD. If it is determined that the power receiving device supports Improved FOD (Yes in S803), the process proceeds to S804. If it is determined that the power receiving device does not support Improved FOD (No in S803), the process proceeds to S805.

[0093] In S804, the power transmission device 100 receives information from the power receiving device 101 that associates a predetermined number of physical quantities, and performs a first foreign object detection process, a second foreign object detection process, or a third foreign object detection process based on the received information. In S805, the power transmission device 100 performs foreign object detection based on predetermined physical quantities. For example, as in the past, foreign object detection is performed based on the Q value and resonant frequency. In addition, when the power transmission device performs a second Q value measurement based on the reception of RPx(FOD) (where x is 0, 1, or 2), it measures not only the Q value but also the resonant frequency and coupling coefficient, or one or more of them. It is possible to perform foreign object detection by comparing each of the measured Q value, resonant frequency, and coupling coefficient with a threshold value.

[0094] After S804 or S805, the series of processes is terminated. The power transmission device 100 takes necessary measures based on the foreign object detection result. Necessary measures include restricting power transmission, changing the power transmission value or frequency, and processing to request the power receiving device to take notification to prompt the removal of the foreign object.

[0095] In the wireless power transmission system of this embodiment, the power receiving device associates information such as the positional relationship between the power transmitting coil and the power receiving coil, the presence and location of foreign matter, the operating frequency, and the power received value with predetermined physical quantities (Q value, resonant frequency, coupling coefficient, power consumption in the foreign matter).

[0096] Figure 13 shows an example of associating FO alignment, PRx alignment, Q value, k value, FO_loss, RPV (receiving power value), and operating frequency. Here, FO alignment is information indicating the position of foreign matter on the transmission coil. PRx alignment is information indicating the position of the receiving coil (receiving device). k value is information indicating the coupling coefficient. FO_loss is information indicating power loss due to foreign matter. Operating frequency is information indicating the frequency of transmitted power (Operating Frequency). The receiving device transmits this information to the transmission device in one or more packets. The transmission device then stores the associated information and can improve detection accuracy by performing foreign matter detection processing according to that information.

[0097] [Modified Embodiment 1] The transmission unit can correct the calibration curve based on one or more of the measured Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf). Specifically, after the calibration curve is created, the receiving unit periodically sends RPx(FOD) (where x is 0, 1, or 2) request bits to request a measurement from the transmission unit. This measurement is one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf). The transmission unit then compares the measurement results measured and stored between the Analog Ping transmission and the Digital Ping transmission with the measurement results measured based on the receipt of RPx(FOD). In other words, one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf) obtained in each measurement are compared. The transmission unit then shifts the calibration curve up or down based on the difference resulting from this comparison. For example, suppose one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf) are larger than those used when the calibration curve was created. The power transmission device moves the calibration curve, composed of line segments 1202 and 1205 in Figure 6, upwards (or downwards) by a predetermined amount. Also, suppose one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf) are smaller than those used when the calibration curve was created. The power transmission device moves the calibration curve, composed of line segments 1202 and 1205 in Figure 6, downwards (or upwards) by a predetermined amount. This movement corresponds to the process of moving the calibration curve in the direction of the received power (vertical axis) in Figure 6. The power transmission device determines whether one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf) are different from the values ​​stored when the calibration curve was created. The shift in the calibration curve, which occurs when the values ​​differ, is equivalent to the power transmission equipment correcting the received power value received at RPx(FOD) by a predetermined amount. In this way, the power transmission device appropriately corrects the created calibration curve based on one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf) measured when PRx(FOD) is received. By correcting the calibration curve, the accuracy of foreign object detection can be improved. Furthermore, although the above description describes a method for correcting a created calibration curve, this method may also be used when creating a new calibration curve. Furthermore, the power transmission device is requested by the power receiving device to measure one or more of the Q value (FOD / qf), K (FOD / kf), and resonant frequency (FOD / rf). When measuring these physical quantities, the power transmission device corrects the measured physical quantities based on the internal temperature of the power transmission device. This makes it possible to detect foreign objects with higher accuracy when physical quantities change with temperature.

[0098] [Modified Embodiment 2] The receiving device stored the planar position of the receiving coil (receiving device) on the transmitting coil using the PRx alignment or FO (Foreign object) alignment of the FOD Status packet. Furthermore, the vertical position of the receiving coil (receiving device) on the transmitting coil may also be added. Doing so can further improve the accuracy of foreign object detection.

[0099] [Modified Embodiment 3] The power receiving device in the above embodiment transmits FO_loss to the power transmitting device in association with other physical quantities using an FOD Status Packet. In addition, the power receiving device in the modified embodiment stores and transmits the physical quantities in an FOD Status Packet when the temperature of the foreign object or FO_loss reaches a threshold, with the power receiving device and the foreign object placed on the power transmitting coil of the TPT. For example, the threshold temperature of the foreign object is 85°C, and the threshold for FO_loss is 500 milliwatts. To explain in detail, first, with the center of the receiving coil positioned at point 103 in Figure 1(B), the TPT and the power receiving device begin the charging process. At this point, no foreign matter is yet placed on the TPT. The power receiving device then stores the physical quantities measured in this state in its non-volatile memory. Next, the foreign matter is placed on the outer circumference of the transmitting coil 1001, and the foreign matter is moved toward point 102, which is the center of the transmitting coil 1001, while measuring the temperature of the foreign matter (especially the highest temperature when the temperature reaches a steady state) and FO_loss. The power receiving device stores the physical quantities measured at the point where the temperature or FO_loss of the foreign matter reaches a threshold in its non-volatile memory. The power receiving device then stores the physical quantities when no foreign matter is placed on the TPT, and the physical quantities when foreign matter is placed on the TPT and the temperature or FO_loss of the foreign matter reaches a threshold, in an FOD Status Packet and transmits it to the power transmitting device. The power transmitting device that receives the FOD Status Packet has a configuration that allows it to correct the judgment threshold in addition to the configuration already described. The threshold for determining the possibility of foreign matter presence in the third foreign matter detection process based on the second Q value measurement is corrected using the FOD Status Packet, which contains physical quantities that occur when a foreign matter is placed on the TPT and the temperature or FO_loss of the foreign matter reaches a threshold. Specifically, the thresholds for the Q value, resonant frequency, and coupling coefficient in the third foreign matter detection process can be corrected. Furthermore, the above explanation described the case where the power receiving device is placed at point 103. The power receiving device may be placed at multiple different points on the TPT, and the physical quantities in the absence of foreign matter and the physical quantities measured at the location where the temperature of the foreign matter or FO_loss reaches the threshold may be associated with each other, stored in the FOD Status Packet, and transmitted to the power transmitting device. In this way, the power transmitting device can estimate the position of the power receiving device when it receives the Q value (F625 in Figure 8), the resonant frequency f (F627 in Figure 8), and the coupling coefficient k (F629 in Figure 8). By correcting the threshold of the third foreign matter detection process based on the physical quantities measured at the location where the temperature of the foreign matter or FO_loss reaches the threshold, associated with the estimated position of the power receiving device, it becomes possible to detect foreign matter with higher accuracy.

[0100] [Modified Embodiment 4] In this modified embodiment, in addition to the configuration already described, the power receiving device is configured to correct the threshold value in the third foreign object detection process based on the operating frequency. First, with the center of the power receiving coil placed at point 103 in Figure 1(B), the power receiving device is charged at operating frequencies of, for example, 100kHz, 125kHz, and 148kHz, and the physical quantities measured at each operating frequency are stored in the non-volatile memory. Then, the power receiving device stores the physical quantities measured at different operating frequencies in FOD Status Packets and transmits them to the power transmitting device. The power transmitting device can compare the operating frequency at which the physical quantities contained in the FOD Status Packet were measured with the current operating frequency, and predict and correct the threshold value at the current operating frequency.

[0101] [Other modified embodiments] In the modified embodiments of this disclosure, at least a portion of the processing shown in the flowcharts of Figures 10 and 12 is implemented in hardware. For example, by using a predetermined compiler, a dedicated circuit can be automatically generated on the FPGA from a program to implement each step. FPGA stands for "Field Programmable Gate Array". Alternatively, a Gate Array circuit may be formed in a similar manner to an FPGA and implemented as hardware.

[0102] Furthermore, while this disclosure describes Improved FOD, which means "improved foreign object detection," the name is not limited to this. For example, it could also be Enhanced FOD, which means "enhanced foreign object detection."

[0103] Furthermore, the power transmission and power reception devices may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, or projectors. They may also be storage devices such as hard disk drives or memory devices, or information processing devices such as personal computers (PCs) or smartphones. Furthermore, the power receiving device in this disclosure may also be an information terminal device. For example, an information terminal device has a display unit that displays information to the user and is supplied with power received from a power receiving antenna. The power received from the power receiving antenna is stored in a power storage unit (battery), and power is supplied to the display unit from the battery. In this case, the power receiving device may also have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may support communication standards such as NFC communication or fifth-generation mobile communication systems (5G). Furthermore, the power receiving device in this disclosure may be a vehicle such as an automobile. For example, an automobile that is a power receiving device may receive power from a charger (power transmission device) via a power transmission antenna installed in a parking lot. Alternatively, an automobile that is a power receiving device may receive power from a charger (power transmission device) via a power transmission antenna embedded in the road. In such an automobile, the received power is supplied to a battery. The power from the battery may be supplied to a drive unit (motor, electric unit) that drives the wheels, or it may be used to drive sensors used for driving assistance or a communication unit that communicates with external devices. In other words, in this case, the power receiving device may have a battery, motors and sensors that are driven using the received power, and a communication unit that communicates with devices other than the power transmission device, in addition to the wheels. Furthermore, the power receiving device may have a dwelling for accommodating people. For example, sensors may be used to measure the distance between vehicles or the distance to other obstacles. The communication unit may be compatible with, for example, the Global Positioning System (Global Positioning Satellite, GPS). Furthermore, the communication unit may support communication standards such as the fifth-generation mobile communication system (5G). Also, the vehicle may be a bicycle or a motorcycle. Furthermore, the power receiving device in this disclosure may be a power tool, a home appliance, etc. These devices, which are power receiving devices, may have a battery, as well as a motor driven by the power received from the battery. These devices may also have a notification means for notifying the remaining battery level, etc. These devices may also have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may support communication standards such as NFC or fifth-generation mobile communication systems (5G). Furthermore, the power transmission device of this disclosure may also be an in-vehicle charger that transmits power to portable information terminal devices such as smartphones and tablets that support wireless power transmission within a vehicle. Such an in-vehicle charger may be installed anywhere in the vehicle. For example, the in-vehicle charger may be installed on the vehicle's console, on the instrument panel (dashboard), between passenger seats, on the ceiling, or on the doors. However, it is preferable not to install it in a location that would interfere with driving. In addition, although the power transmission device has been described using the example of an in-vehicle charger, such chargers are not limited to those installed in vehicles, but may also be installed in transport vehicles such as trains, airplanes, and ships. In this case, the chargers may also be installed between passenger seats, on the ceiling, or on the doors. Alternatively, a vehicle such as an automobile equipped with an on-board charger may also serve as a power transmission device. In this case, the power transmission device has wheels and a battery, and uses the power from the battery to supply power to the power receiving device via a power transmission circuit and a power transmission antenna.

[0104] This embodiment includes the following configurations, methods, and programs. (Composition 1) A power receiving device that receives power from a power transmission device via wireless power transmission, A communication means for communicating with the aforementioned power transmission device, The system includes control means that performs control to detect the state of the power receiving device relative to the power transmitting device, or to associate a physical quantity used for detecting an object different from the power transmitting device and the power receiving device, and to transmit the associated information to the power transmitting device via the communication means. A power receiving device characterized by the following features.

[0105] (Configuration 2) The physical quantity is one or more of the following: the Q value of the power transmission coil of the power transmission device, the resonant frequency, the coupling coefficient between the power transmission coil and the power receiving coil of the power receiving device, and the power consumption in the object. The control means associates information indicating the positional relationship between the power transmitting coil and the power receiving coil or the object with the physical quantity. The power receiving device according to configuration 1, characterized in that it is a power receiving device.

[0106] (Composition 3) The control means associates the physical quantities in each state corresponding to the presence or possibility of the object. A power receiving device according to configuration 1 or configuration 2, characterized in that it is a power receiving device.

[0107] (Composition 4) The control means associates the operating frequency or received power value related to the power transmitted from the power transmission device with the physical quantity. A power receiving device according to any one of configurations 1 to 3, characterized by the above.

[0108] (Composition 5) The control means performs the object detection process using the measurement result of the Q value based on the attenuation state of the transmitted radio wave type. A power receiving device according to configuration 2 or configuration 3, characterized in that it is a power receiving device.

[0109] (Composition 6) A power transmission device that transmits power to the power receiving device described in Configuration 1, A communication means for communicating with the aforementioned power receiving device, The system includes a control means that, when the communication means receives information associated with the physical quantity when the power receiving device is placed on a predetermined power transmission coil, performs object detection processing based on the received information. A power transmission device characterized by the following features.

[0110] (Composition 7) The control means performs, as an object detection process executed in response to the received information, a first detection process based on the measurement result of the Q value related to the power transmission coil, or a second detection process based on the amount of power loss in wireless power transmission. The power transmission device according to configuration 6, characterized in that it is a power transmission device.

[0111] (Composition 8) The control means performs the first detection process using the measurement result of a first Q value that changes due to the influence of the object, or a second Q value based on the attenuation state of the transmitted radio wave type. The power transmission device according to configuration 7, characterized by the features described above.

[0112] (Method 1) A control method performed in a power receiving device that receives power from a power transmitting device via wireless power transmission, A step of communicating with the power transmission device by means of communication, The control means performs a step of controlling the detection of the state of the power receiving device relative to the power transmitting device, or an association with a physical quantity used for detecting an object different from the power transmitting device and the power receiving device, and transmitting the associated information to the power transmitting device via the communication means. A control method for a power receiving device, characterized by the following:

[0113] (Method 2) A control method performed by a power transmission device that transmits power to the power receiving device described in Configuration 1, A step of communicating with the power receiving device by means of communication, The process includes the step of the control means performing an object detection process based on the received information when the communication means receives information relating the physical quantity when the power receiving device is placed on a predetermined power transmission coil. A method for controlling a power transmission device, characterized by the following features.

[0114] (program) Have a computer perform each step described in Method 1 or Method 2. A program characterized by the following features.

[0115] According to this disclosure, state detection or foreign object detection can be performed with higher accuracy in power transmission and power receiving equipment compliant with the WPC standard.

[0116] [Other embodiments] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of Symbols]

[0117] 100 Power transmission equipment 101 Power receiving device

Claims

1. A power receiving device that receives power from a power transmission device via wireless power transmission, A communication means for communicating with the aforementioned power transmission device, The system includes a control means that associates a physical quantity used to detect the state of the power receiving device with respect to the power transmitting device, or to detect an object different from the power transmitting device and the power receiving device, with information indicating the positional relationship between the power transmitting coil of the power transmitting device and the power receiving coil of the power receiving device or the object, and performs control to transmit the associated information to the power transmitting device via the communication means. A power receiving device characterized by the following features.

2. The aforementioned physical quantity is one or more of the following: the Q value of the power transmission coil, the resonant frequency, the coupling coefficient between the power transmission coil and the power receiving coil, and the power consumption in the object. The power receiving device according to feature 1.

3. The control means associates the physical quantities in each state corresponding to the presence or possibility of the object. The power receiving device according to feature 1.

4. The control means associates the operating frequency or received power value related to the power transmitted from the power transmission device with the physical quantity. The power receiving device according to any one of claims 1 to 3.

5. The control means performs object detection processing using the measurement result of the Q value based on the attenuation state of the transmitted radio wave type. The power receiving device according to claim 2 or 3, characterized by the feature described above.

6. A power transmission device for transmitting power to a power receiving device according to claim 1, A communication means for communicating with the aforementioned power receiving device, The system includes a control means that, when the communication means receives information relating the physical quantity when the power receiving device is placed on a predetermined power transmitting coil to information indicating the positional relationship between the power transmitting coil and the power receiving coil or the object, performs object detection processing based on the received information. A power transmission device characterized by the following features.

7. The control means performs, as an object detection process executed in response to the received information, a first detection process based on the measurement result of the Q value related to the power transmission coil, or a second detection process based on the amount of power loss in wireless power transmission. The power transmission device according to claim 6.

8. The control means performs the first detection process using the measurement result of a first Q value that changes due to the influence of the object, or a second Q value based on the attenuation state of the transmitted radio wave type. The power transmission device according to feature 7.

9. A control method performed in a power receiving device that receives power from a power transmitting device via wireless power transmission, A step of communicating with the power transmission device by means of communication, The control means performs a process of associating a physical quantity used for detecting the state of the power receiving device with respect to the power transmitting device, or for detecting an object different from the power transmitting device and the power receiving device, with information indicating the positional relationship between the power transmitting coil of the power transmitting device and the power receiving coil of the power transmitting device or the object, and transmitting the associated information to the power transmitting device via the communication means. A control method for a power receiving device, characterized by the following:

10. A control method performed by a power transmission device that transmits power to a power receiving device according to claim 1, A step of communicating with the power receiving device by means of communication, The system includes a step in which, when the communication means receives information relating the physical quantity when the power receiving device is placed on a predetermined power transmitting coil with information indicating the positional relationship between the power transmitting coil and the power receiving coil or the object, the control means performs an object detection process based on the received information. A method for controlling a power transmission device, characterized by the following features.

11. To cause a computer to perform each step described in claim 9 or claim 10. A program characterized by the following features.

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