Power transmission apparatus, method for power transmission apparatus, storage medium, and computer program product

Abstract

The invention relates to a power transmission device, a method used by the power transmission device, a storage medium and a computer program product. A power transmission device capable of wirelessly transmitting power to a power receiving device via a power transmission coil and communicating with the power receiving device determines the presence or absence of an object different from the power receiving device on the basis of a Q factor of the power transmission coil measured in a stage for transmitting power from the power transmission device to the power receiving device. The power transmission device controls, on the basis of information indicating whether or not the power reception device can execute a predetermined process received from the power reception device by communication, whether or not to execute a determination of the presence or absence of an object different from the power reception device on the basis of the measurement of the Q factor of the power transmission coil. Wherein the predetermined process is associated with a determination of the presence or absence of an object different from the power receiving device based on a measurement of a Q factor of the power transmission coil.

Description

[0001] (This application is a divisional application of application No. 2021800267307, filed on March 3, 2021, entitled “Power Transmitting Device, Power Receiving Device, Control Method, and Computer-Readable Storage Medium.”) Technical Field

[0002] The present invention relates to a power transmitting device, a power receiving device, a control method, and a computer-readable storage medium, and more particularly to a foreign object detection technology in wireless power transmission. Background Art

[0003] Technical development of wireless power transmission systems has been widely carried out, and the standard (WPC standard) established by the Wireless Power Consortium (WPC: Wireless Power Consortium), a standardization organization, as a standard for wireless power charging is well known. In such wireless power transmission, it is important to detect foreign objects and control power transmission / reception when there are foreign objects within the range in which the power transmitting device can transmit power. Foreign objects are objects that are different from the power receiving device. Patent document 1 describes a method for detecting foreign objects and limiting power transmission / reception when there are foreign objects near a power transmitting / transmitting device that complies with the WPC standard. Patent document 2 describes a technology for detecting foreign objects by short-circuiting a coil in a wireless power transmission system. Patent document 3 describes a technology for detecting foreign objects based on changes in the Q factor (quality factor) of a power transmitting coil in a wireless power transmission system measured by applying a high-frequency signal to the coil over a predetermined time period.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-070074

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-034972

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2013-132133 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The present invention provides a technology capable of accurately performing detection of an object different from a power receiving device in a power transmitting device and a power receiving device conforming to the WPC standard.

[0011] Solutions for solving problems

[0012] According to an aspect of the present invention, there is provided a power transmitting device comprising: power transmitting means for wirelessly transmitting power to a power receiving device via a power transmitting coil; communication means for communicating with the power receiving device; measurement means for measuring a Q factor of the power transmitting coil during a phase of power transmission from the power transmitting device to the power receiving device; determination means for determining the presence or absence of an object different from the power receiving device based on the Q factor of the power transmitting coil; and control means for controlling whether to perform determination of the presence or absence of an object different from the power receiving device based on measurement of the Q factor of the power transmitting coil, based on information indicating whether the power receiving device can perform predetermined processing associated with determination of the presence or absence of an object different from the power receiving device based on measurement of the Q factor of the power transmitting coil, wherein the information is received by the communication means from the power receiving device.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to more accurately perform detection of an object different from a power receiving device in a power transmitting device and a power receiving device that conform to the WPC standard.

[0015] Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals represent the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0017] Figure 1 is a diagram showing an example of a configuration of a wireless power transmission system;

[0018] Figure 2 is a block diagram showing an example of a configuration of a power receiving device;

[0019] Figure 3 is a block diagram showing an example of a configuration of a power transmitting device;

[0020] Figure 4 is a block diagram showing an example of a functional configuration of a control unit of a power transmitting device;

[0021] Figure 5 is a block diagram showing an example of a functional configuration of a control unit of a power receiving device;

[0022] Figure 6A is a sequence diagram showing an example of a procedure of processing performed by a conventional power transmitting device and a conventional power receiving device;

[0023] Figure 6Bis a sequence diagram illustrating an example of a procedure of processing performed by a power transmitting apparatus and a power receiving apparatus according to the embodiment;

[0024] Figure 7 is a flowchart illustrating an example of a procedure of a third foreign object detection process using a power transmitting device;

[0025] Figure 8 is a flowchart illustrating an example of a procedure of a third foreign object detection process using a power receiving device;

[0026] Figure 9 is a flowchart illustrating an example of a procedure of a second Q-factor measurement process using a power transmitting device;

[0027] Figure 10 is a flowchart illustrating an example of a procedure of a second Q-factor measurement process using a powered device;

[0028] Figure 11 This is a diagram for explaining foreign object detection using a power loss method;

[0029] Figure 12A is a diagram for explaining a Q factor measurement method in the time domain;

[0030] Figure 12B is a diagram for explaining a Q factor measurement method in the time domain; and

[0031] Figure 13 is a diagram showing the frame format of a configuration packet. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. A plurality of features are described in the embodiments, but the invention is not limited to requiring all of these features, and a plurality of such features may be appropriately combined. Furthermore, in the accompanying drawings, identical or similar structures are given the same reference numerals, and redundant descriptions thereof are omitted.

[0033] (System Configuration)

[0034] Figure 1An example of a configuration of a wireless power transmission system according to this embodiment is shown. In this example, the wireless power transmission system is configured to include a power transmitting device 100 and a power receiving device 102. It is assumed that the power transmitting device 100 and the power receiving device 102 comply with the WPC (Wireless Power Consortium) standard. The power transmitting device 100 is, for example, an electronic device that wirelessly transmits power to the power receiving device 102 placed on its own device. The power transmitting device 100 wirelessly transmits power to the power receiving device 102 via a power transmission coil 101. The power receiving device 102 is, for example, an electronic device that receives power from the power transmitting device 100 and charges its internal battery. The power receiving device 102 can be configured to be incorporated into other devices (cameras, smartphones, tablet PCs, laptops, cars, robots, medical devices, or printers) and supply power to these devices. The power transmitting device 100 can be a smartphone, etc. In this case, the power receiving device 102 can be, for example, another smartphone or a wireless headset. The power receiving device 102 may be a transport aircraft or a vehicle such as a car, and the power transmitting device 100 may be a charger installed in a console of the transport aircraft or the vehicle such as a car.

[0035] Figure 1 The present embodiment illustrates a situation in which a conductive foreign object 103 is present within the range (operating volume) affected by the wireless power output from the power transmitting coil 101. If foreign object 103 is present within the operating volume, power transmission / reception efficiency decreases, and in some cases, problems such as heat generation may occur. Therefore, it is important for the power transmitting device 100 and the power receiving device 102 to detect foreign object 103 and perform power transmission / reception control. In this embodiment, the power transmitting device 100 and the power receiving device 102 measure the Q factor (quality factor) based on the temporal variation of the power transmitting coil voltage within a control range that complies with the WPC standard, detect foreign object 103, and control power transmission / reception. An example of the configuration of the device used to perform this process and the processing procedure will be described in detail below. Note that foreign object 103 is an object different from the power receiving device. For example, foreign object 103 is a conductive object such as a metal piece or an IC card.

[0036] (Device Configuration)

[0037] Figure 2An example configuration of the power receiving device 102 is shown. The power receiving device 102 is configured to include, for example, 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 208. The control unit 200 controls the entire power receiving device 102. The control unit 200 is configured to include, for example, one or more processors such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). Note that the control unit 200 may include, for example, one or more storage devices such as RAM (Random Access Memory) and ROM (Read Only Memory). The control unit 200 may be configured such that, for example, the processor executes programs stored in the storage device to perform various processes described later. The power receiving coil 201 is a coil for receiving power from the power transmitting coil 101 of the power transmitting device 100. The rectifier unit 202 converts the AC voltage and AC current received via the power receiving coil 201 into DC voltage and DC current. Voltage control unit 203 converts the DC voltage input from rectifier unit 202 to a DC voltage level suitable for the operation of control unit 200, charging unit 205, and the like (neither too high nor too low). Voltage control unit 203 also supplies the converted voltage to charging unit 205. Charging unit 205 charges battery 206 using the voltage supplied from voltage control unit 203. Communication unit 204 performs control communication for wireless charging based on the WPC standard with power transmitting device 100. This control communication is performed by load modulating the AC voltage and AC current received by power receiving coil 201.

[0038] Furthermore, the power receiving coil 201 is connected to the resonant capacitor 207 and is configured to resonate at a specific frequency F2. The switch 208 is configured to short-circuit the power receiving coil 201 and the resonant capacitor 207 and is controlled by the control unit 200. If the switch 208 is turned on, the power receiving coil 201 and the resonant capacitor 207 form a series resonant circuit. In this case, current flows only through the closed circuit of the power receiving coil 201, the resonant capacitor 207, and the switch 208, and no current flows to the rectifier unit 202 and the voltage control unit 203. On the other hand, if the switch 208 is turned off, current flows to the rectifier unit 202 and the voltage control unit 203 via the power receiving coil 201 and the resonant capacitor 207.

[0039] Figure 3An example configuration of the power transmitting device 100 is shown. The power transmitting device 100 is configured to include, for example, a control unit 300, a power supply unit 301, a power transmitting unit 302, a power transmitting coil 303, a communication unit 304, a memory 305, a resonant capacitor 306, and a switch 307. The control unit 300 controls the entire power transmitting device 100. The control unit 300 is configured to include, for example, one or more processors such as a CPU and an MPU. Note that the control unit 300 can be configured such that, for example, the processor executes a program stored in the memory 305 or a storage device incorporated into the control unit 300, which will be described later, thereby executing the various processes described later. The power supply unit 301 supplies power to the various functional blocks. The power supply unit 301 is, for example, a commercial power supply or a battery. The battery can store power supplied from, for example, a commercial power supply.

[0040] The power transmission unit 302 converts the DC or AC power input from the power supply unit 301 into AC power in the frequency band used for wireless power transmission and inputs the AC power to the power transmission coil 303, causing the power transmission coil 303 to generate electromagnetic waves to be received by the power receiving device 102. For example, the power transmission unit 302 converts the DC voltage supplied from the power supply unit 301 into AC voltage using a switching circuit having a half-bridge or full-bridge configuration using FETs (field-effect transistors). In this case, the power transmission unit 302 includes a gate driver that controls the on / off switching of the FETs. Furthermore, the power transmission unit 302 adjusts at least one of the voltage (transmission voltage) and current (transmission current) input to the power transmission coil 303, or the frequency, to control the intensity or frequency of the electromagnetic waves to be output. For example, the power transmission unit 302 increases the intensity of the electromagnetic waves by increasing the transmission voltage or current, and decreases the intensity of the electromagnetic waves by decreasing the transmission voltage or current. Here, it is assumed that power transmission unit 302 is capable of supplying 15 watts (W) of power to charging unit 205 of power receiving device 102 compliant with the WPC standard. Furthermore, power transmission unit 302 controls the output of AC power based on instructions from control unit 300, thereby starting or stopping the output of electromagnetic waves from power transmission coil 303.

[0041] The communication unit 304 communicates with the power receiving device 102 via the power transmitting 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 transmitting unit 302 using frequency modulation (FSK (Frequency Shift Keying)) and transmits the information to the power receiving device 102. Furthermore, the communication unit 304 demodulates the AC voltage and AC current modulated by load modulation by the communication unit 204 of the power receiving device 102 to obtain the information transmitted from the power receiving device 102. In other words, the communication unit 304 superimposes the information to be transmitted to the power receiving device 102 on the electromagnetic wave transmitted from the power transmitting unit 302, and the power receiving device 102 detects the power reception signal superimposed on the electromagnetic wave, thereby communicating with the power receiving device 102. Furthermore, the communication unit 304 can communicate with the power receiving device 102 using a coil (or antenna) different from the power transmitting coil 303 according to a standard different from the WPC standard. Furthermore, the communication unit 304 can selectively utilize multiple communication functions to communicate with the power receiving device 102. The memory 305 stores, for example, a control program to be executed by the control unit 300 and information such as the status of the power transmitting device 100 and the power receiving device 102. For example, the control unit 300 obtains the status of the power transmitting device 100. The status of the power receiving device 102 is obtained by the control unit 200 of the power receiving device 102 and transmitted from the charging unit 205. The power transmitting device 100 obtains information indicating this status via the communication unit 304.

[0042] The power transmission coil 303 is connected to the resonant capacitor 306 and is configured to resonate at a specific frequency F1. Switch 307 is configured to short-circuit the power transmission coil 303 and the resonant capacitor 306 and is controlled by the control unit 300. When switch 307 is turned on, the power transmission coil 303 and the resonant capacitor 306 form a series resonant circuit. In this case, current flows only through the closed circuit of the power transmission coil 303, the resonant capacitor 306, and the switch 307. When switch 307 is turned off, power is supplied from the power transmission unit 302 to the power transmission coil 303 and the resonant capacitor 306.

[0043] Figure 4An example of the functional configuration implemented by the control unit 300 of the power transmitting device 100 is shown. The control unit 300 can operate as a functional unit including, for example, a first Q-factor measurement unit 400, a second Q-factor measurement unit 401, a calibration processing unit 402, a first foreign object detection processing unit 403, a second foreign object detection processing unit 404, a third foreign object detection processing unit 405, and a power transmission processing unit 406. As will be described later, the first Q-factor measurement unit 400 measures the Q-factor in the frequency domain (first Q-factor measurement). As will be described later, the second Q-factor measurement unit 401 measures the Q-factor in the time domain (second Q-factor measurement). As will be described later, the calibration processing unit 402 acquires calibration data points and creates a calibration curve. The first foreign object detection processing unit 403 performs foreign object detection processing (first foreign object detection processing) based on the first Q-factor measured by the first Q-factor measurement unit 400. The second foreign object detection processing unit 404 performs foreign object detection processing (second foreign object detection processing) based on the power loss method described later. The third foreign object detection processing unit 405 performs foreign object detection processing (third foreign object detection processing) based on the second Q factor measured by the second Q factor measurement unit 401. The power transmission processing unit 406 performs processing related to starting and stopping power transmission in the power transmission unit 302 and increasing / decreasing the transmitted power. Figure 4 The illustrated processing unit is configured as, for example, a plurality of independent programs, and can operate concurrently while performing synchronization between the plurality of programs through event processing or the like.

[0044] Figure 5 This figure shows an example of the functional configuration implemented by the control unit 200 of the power receiving device 102. The control unit 200 can operate as a functional unit including, for example, a second Q-factor measurement unit 500 and a power reception processing unit 501. As will be described later, the second Q-factor measurement unit 500 measures the Q factor in the time domain (second Q-factor measurement). The power reception processing unit 501 performs processing related to starting and stopping power reception by the power receiving device 102 and increasing / decreasing the power requested from the power transmitting device 100. Figure 5 The processing units shown are configured as independent programs, and can operate concurrently while performing synchronization between the programs through event processing or the like.

[0045] (Foreign matter detection method in WPC standard)

[0046] Next, we will describe the foreign object detection method defined by the WPC (Wireless Power Consortium) standard, using power transmitting device 100 and power receiving device 102 as examples. We will describe a foreign object detection method based on the Q factor measured in the frequency domain (a first foreign object detection method) and a foreign object detection method based on power loss (a second foreign object detection method).

[0047] (1) Foreign matter detection method based on Q factor measured in the frequency domain (first foreign matter detection method)

[0048] In the first foreign object detection method, first, the power transmitting device 100 measures the Q factor changed by the influence of foreign objects in the frequency domain (first Q factor measurement). This measurement is performed after the power transmitting device 100 sends an analog ping (Analog Ping) until a digital ping (Digital Ping) is sent (see Figure 6A F601 in FIG. For example, to measure the Q factor, the power transmission unit 302 sweeps the frequency of the wireless power output from the power transmission coil 303, and the first Q-factor measurement unit 400 measures the voltage value at the end of the resonant capacitor 306 connected in series (or in parallel) with the power transmission coil. The first Q-factor measurement unit 400 searches for a resonant frequency at which the voltage value exhibits a peak, and calculates the Q factor of the power transmission coil 303 based on the resonant frequency and a frequency indicating a voltage value that is 3 dB lower than the peak voltage value measured at the resonant frequency.

[0049] The Q factor can be measured using other methods. For example, the power transmission unit 302 sweeps the frequency of the wireless power output from the power transmission coil 303, and the first Q factor measurement unit 400 measures the voltage value at the ends of the resonant capacitor 306 connected in series with the power transmission coil 303, searching for the resonant frequency at which the voltage value exhibits a peak. The first Q factor measurement unit 400 then measures the voltage value at both ends of the resonant capacitor 306 at the resonant frequency and calculates the Q factor of the power transmission coil 303 based on the ratio of the voltage values ​​at both ends.

[0050] After calculating the Q factor of the power transmitting coil 303, the first foreign object detection processing unit 403 of the power transmitting device 100 obtains the Q factor, which serves as a reference for foreign object detection, from the power receiving device 102 via the communication unit 304. For example, the first foreign object detection processing unit 403 receives the Q factor (first characteristic value) of the power transmitting coil when the power receiving device is placed on the power transmitting coil as defined in the WPC standard from the power receiving device 102. The Q factor is stored in a FOD (Foreign Object Detection) status packet transmitted from the power receiving device 102, and the power transmitting device 100 receives the FOD status packet to obtain the Q factor. Based on the obtained Q factor, the first foreign object detection processing unit 403 estimates the Q factor of the power transmitting coil 303 when the power receiving device 102 is placed on the power transmitting device 100. In this embodiment, the estimated Q factor will be represented as a first reference Q factor. Note that the Q factor stored in the FOD status packet can be pre-stored in the non-volatile memory (not shown) of the power receiving device 102. That is, the power receiving apparatus 102 may notify the power transmitting apparatus 100 of the pre-stored Q factor. Note that the Q factor corresponds to Q1 which will be described later.

[0051] The first foreign object detection processing unit 403 of the power transmitting device 100 compares the first reference Q factor with the Q factor measured by the first Q-factor measurement unit 400 and determines the presence of a foreign object based on the comparison result. For example, a Q factor that is a percentage lower than the first reference Q factor (a first ratio) is used as a threshold. If the measured Q factor is below the threshold, the first foreign object detection processing unit 403 determines that there is a high probability of a foreign object being present. Otherwise, there is a high probability of the absence of a foreign object.

[0052] (2) Foreign matter detection method based on power loss method (second foreign matter detection method)

[0053] Next, we will refer to Figure 11 This article describes the foreign object detection method based on the power loss method defined in the WPC standard. Figure 11 This is a conceptual diagram of foreign object detection using the power loss method. The horizontal axis represents the transmitted power of the power transmitting device 100, and the vertical axis represents the received power of the power receiving device 102. Note that the power transmitted by the power transmission unit 302 of the power transmitting device 100 can be controlled by the power transmission processing unit 406.

[0054] First, the power transmission unit 302 of the power transmitting device 100 sends a digital Ping to the power receiving device 102. The communication unit 304 of the power transmitting device 100 receives the received power value Pr1 (referred to as light load) of the power receiving device 102 through a received power packet (Received Power Packet) (mode 1). Note that the received power packet (mode 1) will be referred to as "RP1" hereinafter. Pr1 is the received power value when the power receiving device 102 does not supply received power to the load (charging unit 205 and battery 206). The control unit 300 of the power transmitting device 100 compares the received Pr1 with the transmitted power value Pt1 when Pr1 was obtained ( Figure 11 The point 1100 shown is stored in the memory 305. Therefore, the power transmitting device 100 can recognize that the power loss amount between the power transmitting device 100 and the power receiving device 102 when Pt1 is transmitted as the transmission power is Pt1 - Pr1 (Ploss1).

[0055] Next, the communication unit 304 of the power transmitting device 100 receives the value of the received power value Pr2 (referred to as the connected load) of the power receiving device 102 from the power receiving device 102 via the received power packet (mode 2). Note that the received power packet (mode 2) will be referred to as "RP2" hereinafter. Pr2 is the received power value when the power receiving device 102 supplies received power to the load. The control unit 300 of the power transmitting device 100 calculates the relationship between the received Pr2 and the transmitted power value Pt2 when Pr2 was obtained ( Figure 11 The point 1101 shown is stored in the memory 305. Therefore, the power transmitting device 100 can recognize that the power loss amount between the power transmitting device 100 and the power receiving device 102 when Pt2 is transmitted as the transmission power is Pt2 - Pr2 (Ploss2).

[0056] The calibration processing unit 402 of the power transmitting device 100 performs linear interpolation on points 1100 and 1101 to create a line 1102. Line 1102 corresponds to the relationship between the transmitted and received power when there are no foreign objects around the power transmitting device 100 and the power receiving device 102. Therefore, the power transmitting device 100 can predict the received power when there is a high probability that no foreign objects are present based on the transmitted power value and line 1102. For example, if the transmitted power value is Pt3, the power transmitting device 100 can predict the received power value to be Pr3 based on point 1103 on line 1102 corresponding to the transmitted power value Pt3.

[0057] Here, it is assumed that if the power transmitting unit 302 of the power transmitting device 100 transmits power to the power receiving device 102 using the transmitted power Pt3, then the communication unit 304 receives the received power value Pr3' from the power receiving device 102. The second foreign object detection processing unit 404 of the power transmitting device 100 calculates Pr3-Pr3' (=Ploss_FO), which is the value obtained by subtracting the received power value Pr3' actually received from the power receiving device 102 from the received power value Pr3 when no foreign object is present. Ploss_FO can be considered as the power loss consumed by the foreign object when it is present between the power transmitting device 100 and the power receiving device 102. Therefore, if the power consumed by the foreign object, Ploss_FO, exceeds a predetermined threshold, the second foreign object detection processing unit 404 can determine that a foreign object is present. This threshold can be derived, for example, based on the relationship between point 1100 and point 1101.

[0058] Furthermore, the second foreign object detection processing unit 404 of the power transmitting device 100 predetermines the power loss amount Pt3-Pr3 (Ploss3) between the power transmitting device 100 and the power receiving device 102 from the received power value Pr3 when no foreign object is present. The second foreign object detection processing unit 404 calculates the power loss amount Pt3-Pr3' (Ploss3') between the power transmitting device 100 and the power receiving device 102 when a foreign object is present, based on the received power value Pr3' received from the power receiving device 102 when the presence of a foreign object is unclear. The second foreign object detection processing unit 404 then calculates Ploss3'-Ploss3. If this value exceeds a predetermined threshold, it is determined that a foreign object is present. Note that Ploss3'-Ploss3 = Pt3-Pr3'-Pt3 + Pr3 = Pr3-Pr3'. Therefore, by comparing the power loss amounts, the power Ploss_FO, which is expected to be consumed by the foreign object, can be estimated.

[0059] As described above, the power Ploss_FO to be consumed by the foreign object can be calculated as Pr3 - Pr3 ' which is the difference in received power, or can be calculated as Ploss3 ' - Ploss3 (= Ploss_FO) which is the difference in power loss.

[0060] After the calibration processing unit 402 obtains line 1102, the second foreign object detection processing unit 404 of the power transmitting device 100 periodically receives the current received power value (e.g., Pr3' described above) from the power receiving device 102 via the communication unit 304. The current received power value periodically transmitted from the power receiving device 102 is transmitted to the power transmitting device 100 as a received power packet (mode 0). The second foreign object detection processing unit 404 of the power transmitting device 100 performs foreign object detection based on line 1102 and the received power value stored in the received power packet (mode 0). Note that the received power packet (mode 0) will be referred to as (RP0) below.

[0061] Note that in this embodiment, points 1100 and 1101 used to obtain a line 1102 representing the relationship between the transmitted and received power when no foreign objects are present around the power transmitting device 100 and the power receiving device 102 are referred to as "calibration data points." Furthermore, the line segment (line 1102) obtained by interpolating at least two calibration data points is referred to as a "calibration curve." The calibration data points and the calibration curve (second reference) are used for foreign object detection processing by the second foreign object detection processing unit 404.

[0062] (Q factor measurement method in the time domain)

[0063] Will refer to Figure 12A and Figure 12B Describe the Q-factor measurement method in the time domain. Figure 12A and Figure 12B This is a conceptual diagram illustrating a method for measuring the Q factor in the time domain (second Q factor measurement). In this embodiment, the foreign object detection method based on the second Q factor will be referred to as the third foreign object detection method. The second Q factor measurement is performed by the second Q factor measurement unit 401. Furthermore, the control of the transmitted power by the power transmission unit 302 of the power transmitting device 100 is performed by the power transmission control unit 406. During the second Q factor measurement, the power transmitting device 100 and the power receiving device 102 turn on their switches during the same period to momentarily shut off power transmission, thereby preventing the load from receiving power. Consequently, for example, the voltage applied to the coil gradually decreases. The second Q factor is calculated based on how the voltage decreases.

[0064] Figure 12A The waveform 1200 shown represents the elapsed time of the high frequency voltage value (hereinafter referred to as “voltage value of the power transmission coil”) applied to the end of the power transmission coil 303 or the resonant capacitor 306 of the power transmission device 100. Figure 12A and Figure 12B In FIG, the horizontal axis represents time, and the vertical axis represents voltage value. At time T0, application of high frequency voltage (power transmission) is stopped. Point 1201 is a point on the envelope of high frequency voltage, and represents the high frequency voltage at time T1. Figure 12A In , (T1, A1) indicates that the voltage value at time T1 is A1. Similarly, point 1202 is a point on the envelope of the high-frequency voltage and indicates the high-frequency voltage at time T2. Figure 12A In the figure, (T2, A2) indicates that the voltage value at time T2 is A2.

[0065] The Q factor is measured based on the temporal change in the voltage value from time T0. For example, based on the time and voltage values ​​of points 1201 and 1202 as the envelope of the voltage value, and the angular velocity ω of the high-frequency voltage (ω = 2πf, where f is the operating frequency of the high-frequency voltage), the Q factor is calculated by the following formula:

[0066]

[0067] Next, we will refer to Figure 12BThe following describes the process of measuring the Q factor in the time domain by the power transmitting device 100 in this embodiment. Waveform 1203 represents the value of the high-frequency voltage applied to the power transmitting coil 303, and its frequency falls within the range of 110 kHz to 148.5 kHz used in the Qi standard. Furthermore, each of points 1204 and 1205 is a portion of the envelope of the voltage value. The power transmitting unit 302 of the power transmitting device 100 stops power transmission during the period from time T0 to T5. The second Q-factor measurement unit 401 of the power transmitting device 100 measures the Q factor based on the voltage value A3 at time T3 (point 1204), the voltage value A4 at time T4 (point 1205), the operating frequency of the high-frequency voltage, and equation (1). Note that the power transmitting unit 302 of the power transmitting device 100 resumes power transmission at time T5. As described above, the second Q-factor measurement is performed by the power transmitting device 100 momentarily stopping power transmission and measuring the Q factor based on the elapsed time, voltage value, and operating frequency.

[0068] Note that in the third foreign matter detection method, measuring (T3, A3) and (T4, A4) is sufficient, and measuring the second Q factor is unnecessary. That is, as shown in equation (1), an indicator based on the value of (T4 - T3) and the ratio of A4 to A3 (A4 / A3) or the ratio of A3 to A4 (A3 / A4) can be used to detect the presence of foreign matter. More specifically, this indicator is compared with a threshold value to detect the presence of foreign matter.

[0069] Furthermore, in the third foreign object detection method, current values ​​can be measured instead of voltage values, and the presence of foreign matter can be detected using an indicator based on the ratio of current values. Specifically, the current value at time T3 and the current value at time T4 are measured. A second Q factor can be obtained based on the current values.

[0070] (Operation of conventional power transmission and receiving equipment)

[0071] Will refer to Figure 6A The operation of the conventional power transmitting device 100 and the conventional power receiving device 102 is described. Figure 6A In the description, it is assumed that the power transmitting device 100 and the power receiving device 102 are power transmitting devices and power receiving devices that comply with the WPC standard v1.2.3.

[0072] The power transmitting device 100 transmits an analog ping to detect an object near the power transmitting coil 303 (F600). The analog ping is a pulsed power used to detect an object. Even if the power receiving device 102 receives the analog ping, the power is too low to activate the control unit 200. Using the analog ping, the power transmitting device 100 detects the object based on the shift in the resonant frequency of the voltage value in the power transmitting coil 303 or the change in the voltage and current flowing through the power transmitting coil 303 caused by the object near the power transmitting coil 303. When the object is detected using the analog ping, the power transmitting device 100 measures the Q factor of the power transmitting coil 303 using the first Q factor measurement described above (F601). After the first Q factor measurement, the power transmitting device 100 begins transmitting a digital ping (F602). The digital ping is a power used to activate the control unit 200 of the power receiving device 102 and is greater than the power of the analog ping. From then on, the digital ping is continuously transmitted. That is, the power transmitting apparatus 100 continuously transmits power equal to or greater than the digital ping after starting to transmit the digital ping ( F602 ) until receiving an EPT packet (End Power Transfer packet) from the power receiving apparatus 102 ( F622 ).

[0073] Upon being activated by receiving a digital ping, the power receiving device 102 stores the voltage value of the received digital ping in a signal strength packet and transmits it to the power transmitting device 100 (F603). Next, the power receiving device 102 transmits an ID packet storing an ID including the version information of the WPC standard to which the power receiving device 102 complies and device identification information to the power transmitting device 100 (F604). Furthermore, the power receiving device 102 transmits a configuration packet to the power transmitting device 100, including information such as the maximum value of the power to be supplied from the voltage control unit 203 to the load (charging unit 205) (F605). The power transmitting device 100 receives the ID packet and configuration packet. Upon determining, based on these packets, that the power receiving device 102 supports the extended protocol after WPC standard v1.2 (including negotiation, which will be described later), the power transmitting device 100 responds with an ACK (F606).

[0074] The power receiving device 102 receives the ACK and transitions to the negotiation phase to negotiate the power to be transmitted and received. First, the power receiving device 102 sends a FOD status packet to the power transmitting device 100 (F607). In this embodiment, the FOD status packet will be referred to as "FOD(Q1)." The power transmitting device 100 performs foreign object detection using the first foreign object detection method based on the Q factor (Q factor measured in the frequency domain) stored in the received FOD(Q1) and the Q factor measured by the first Q factor measurement. If it is determined that there is a high probability that a foreign object is not present, the power transmitting device 100 sends an ACK indicating the determination result to the power receiving device 102 (F608).

[0075] Upon receiving the ACK, the power receiving device 102 negotiates a guaranteed power (GP), which is the maximum value of the power that the power receiving device 102 requests to receive. The guaranteed power represents the load power of the power receiving device 102 (the power to be consumed by the battery 206) agreed upon between the power transmitting device 100 and the power receiving device 102. This negotiation is achieved by sending a packet storing the guaranteed power value requested by the power receiving device 102 to the power transmitting device 100 in a specific request (Specific Request) defined in the WPC standard (F609). In this embodiment, this packet will be referred to as "SRQ(GP)." The power transmitting device 100 responds to the SRQ(GP) based on its own power transmission capabilities. If it determines that the guaranteed power is acceptable, the power transmitting device 100 sends an ACK indicating that the request has been accepted (F610). In this embodiment, it is assumed that the power receiving device 102 requests 15W as the guaranteed power through the SRQ(GP). When negotiation of multiple parameters, including guaranteed power, is complete, the power receiving device 102 sends a "SRQ(EN)" requesting the end of negotiation (End Negotiation) to the power transmitting device (F611). The power transmitting device 100 sends an ACK (F612) in response to the SRQ(EN), ending the negotiation and transitioning to the power transmission phase to transmit and receive power as defined by the guaranteed power.

[0076] Next, the power transmitting device 100 performs foreign object detection based on the above-mentioned power loss method (second foreign object detection method). First, the power transmitting device 100 receives RP1 from the power receiving device 102 (F613). The power transmitting device 100 receives the received power value stored in RP1 and the transmitted power value of the power transmitting device 100 when the received power value is obtained as a calibration data point (with the power receiving device 102). Figure 11 The power transmitting device 100 transmits an ACK indicating acceptance of the calibration data point to the power receiving device 102 ( F614 ).

[0077] After receiving the ACK, the power receiving device 102 transmits a control error (hereinafter referred to as CE) to the power transmitting device 100, requesting the power transmitting device 100 to increase or decrease the power receiving voltage (or power receiving current or power receiving). CE stores a sign and a value. A positive sign indicates a request to increase power. A negative sign indicates a request to decrease power. A zero value indicates a request to maintain power. Here, the power receiving device 102 transmits CE(+) indicating a power increase to the power transmitting device 100 (F615).

[0078] Upon receiving CE(+), the power transmitting device 100 changes the setting value of the power transmitting unit 302 to increase the transmitted power (F616). When the received power increases in response to CE(+), the power receiving device 102 supplies the received power to the load (charging unit 205 and battery 206) and transmits RP2 to the power transmitting device 100 (F617). The power transmitting device 100 accepts the received power value stored in RP2 and the transmitted power value of the power transmitting device 100 at this time as a calibration data point (with the calibration data point). Figure 11 The power transmitting device 100 sends an ACK (F618) indicating that it has accepted the calibration data point to the power receiving device 102. Since the power transmitting device 100 has obtained two calibration data points ( Figure 11 Points 1100 and 1101 in ), so the calibration curve can be derived ( Figure 11 line 1102 in FIG.

[0079] At this point, the power transmitting device 100 and the power receiving device 102 have transitioned to the power transmission phase, and the power transmitting device 100 is transmitting power sufficient to enable the power receiving device 102 to receive the maximum power of 15W negotiated in the negotiation phase. The power receiving device 102 periodically transmits a CE packet requesting the power transmitting device 100 to maintain the transmitted power and an RP0 packet storing the current received power value to the power transmitting device 100 (F619 and F620). Upon receiving the RP0 packet from the power receiving device 102, the power transmitting device 100 performs foreign object detection based on the second foreign object detection method described above. If the foreign object detection result indicates a high probability of the absence of a foreign object, the power transmitting device 100 transmits an ACK packet to the power receiving device 102 (F621). Subsequently, when charging of the battery 206 is complete, the power receiving device 102 transmits an EPT (End Power Transmission) packet to the power transmitting device 100 requesting the termination of power transmission (F622).

[0080] In the above-described manner, wireless power transmission is performed between the power transmitting device 100 and the power receiving device 102 compliant with the WPC standard v1.2.3.

[0081] like Figure 6AAs shown in the processing example, foreign object detection using the power loss method is performed during the power transmission phase. However, if only one foreign object detection method is used, there is still a possibility to a certain extent that a foreign object is detected despite its absence, or conversely, a foreign object is judged to be absent despite its presence. On the other hand, if foreign object detection is performed by combining multiple foreign object detection methods, the accuracy of foreign object detection can be expected to be improved. In particular, the power transmission phase is the phase in which TX transmits power. If a foreign object is present between TX and RX during power transmission, the heat generated from the foreign object increases. Note that even if a foreign object is not between TX and RX but is present within the power transmittable range, power is received and heat is generated. Therefore, in this phase, a great advantage can be obtained by executing multiple foreign object detection methods and improving the accuracy of foreign object detection. In this embodiment, a foreign object detection method different from the power loss method is introduced in the power transmission phase.

[0082] Here, in foreign object detection based on the Q factor (first Q factor) measured in the frequency domain (first foreign object detection method), the frequency is swept to search for a resonant frequency each time a measurement is performed. If this sweep is performed while the power transmitting device 100 is transmitting relatively high power during the digital ping or power transmission phase, switching noise in the power transmitting unit 302 may increase. On the other hand, foreign object detection based on the Q factor (second Q factor) measured in the time domain (third foreign object detection method) can be performed using a single frequency, eliminating the need for frequency sweeping. To this end, this method can be performed at the operating frequency during power transmission during the digital ping or power transmission phase, with minimal impact on switching noise. In this embodiment, in the second Q factor measurement, control is performed to close the switch 208 when the power transmitting device stops transmitting power, forming a closed circuit including the power receiving coil 201 and the resonant capacitor 207. The second Q factor is measured in a state where the effects of load changes in the power receiving device 102 are eliminated.

[0083] When applying the third foreign object detection method to the WPC standard, it is assumed that the device configuration of the power receiving device 102 adopts various modes. To this end, the power transmitting device 100 needs to appropriately control the processing to be performed based on the capabilities of the power receiving device 102. For example, if the power transmitting device 100 performs the second Q factor measurement on a power receiving device 102 that cannot be controlled to form a closed circuit, the measurement is affected by changes in the load on the power receiving device 102, and the Q factor cannot be accurately measured. It is also possible to perform the second Q factor measurement on the power receiving device 102. However, if the capabilities of the power receiving device 102 are unknown, the power transmitting device 100 cannot determine whether to perform the second Q factor measurement on its own. For example, if the power receiving device 102 can form a closed circuit but cannot perform the second Q factor measurement, the power transmitting device 100 cannot determine the presence of a foreign object unless it measures the second Q factor. Similarly, if the capabilities of the power receiving device 102 are unknown, the power transmitting device 100 cannot determine whether to receive the second Q factor measurement results from the power receiving device 102. For example, if the power receiving device 102 is unable to measure the second Q factor, but the power transmitting device 100 is about to receive the measurement result from the power receiving device 102, unnecessary waiting time is generated. On the other hand, if the power receiving device 102 can measure the second Q factor, but the power transmitting device 100 does not receive the measurement result from the power receiving device 102, a state deviation occurs between the power transmitting device 100 and the power receiving device 102. Therefore, in this embodiment, a control method for appropriately applying the third foreign object detection method based on the second Q factor measurement to the WPC standard is used. This control method will be described below.

[0084] (Description of Operation in Case Where the Third Foreign Matter Detection Method is Applied to the WPC Standard)

[0085] Figure 6B An example of the procedure of the processing performed by the power transmitting device 100 and the power receiving device 102 according to this embodiment is shown. Figure 6AIdentical reference numerals in the figure denote identical processing, and their description will be omitted. After executing the processing from F600 to F604, the power receiving device 102 sends a configuration packet to the power transmitting device 100 (F623). In this embodiment, the configuration packet notifies the power transmitting device 100 of the capability information of the power receiving device 102. In this embodiment, the configuration packet defines a short-circuit capability bit and a measurement capability bit as the capability information to be notified. The short-circuit capability bit indicates whether the power receiving device 102 can control the formation of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for second Q-factor measurement. For example, if the power receiving device 102 has the capability to form a closed circuit for second Q-factor measurement, the power receiving device 102 stores a "1" in the short-circuit capability bit. Otherwise, a "0" is stored. The measurement capability bit indicates whether the power receiving device 102 can perform second Q-factor measurement of the power receiving circuit. For example, if the power receiving device 102 has the ability to measure the second Q factor of the power receiving circuit, it stores a "1" in the measurement capability bit. Otherwise, it stores a "0." Note that this information may indicate whether the power receiving device 102 can perform a predetermined process associated with foreign object detection based on the second Q factor measurement performed by the power transmitting device 100. In other words, whether a closed circuit can be formed or whether the second Q factor of the power receiving circuit can be measured is merely one predetermined process, and information bits related to other processes may be transmitted from the power receiving device 102 to the power transmitting device 100.

[0086] Figure 13The configuration of the configuration package for the WPC standard v1.2.3 is shown. Note that descriptions of portions not relevant to this embodiment will be omitted here. The configuration package for the WPC standard v1.2.3 includes multiple reserved regions. Specifically, region 1300 from bit 0 to bit 7 of Bank 1, region 1301 from bits 4 to 6 of Bank 2, and region 1302 from bits 0 to 2 of Bank 4 are reserved regions. In this embodiment, as an example, the short-circuit capability bit is placed in bit 2 of Bank 4, and the measurement capability bit is placed in bit 1 of Bank 4. Note that these bits can be placed in other reserved regions. Instead of these bits, information indicating the version of the WPC standard, etc., can be placed in the reserved regions. In this case, the version can indicate whether the powered device 102 can control the formation of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for second Q-factor measurement, and whether the powered device 102 can perform second Q-factor measurement of the powered circuit. For example, it may be possible to define that, in a future version of the WPC standard, it is essential for powered devices 102 that comply with that version to possess certain features. In this case, by notifying the powered device 102 of its version information via a configuration packet, the power transmitting device 100 can specify whether the powered device 102 possesses these features. Note that in WPC standard v1.2.3, all bits in the reserved area are set to 0. Furthermore, a power transmitting device 100 that cannot use the third foreign object detection method disregards the values ​​stored in these reserved areas.

[0087] Note that this description describes a case where the short-circuit capability bit and the measurement capability bit are set in a configuration packet and transmitted from the powered device 102 to the powered device 100. However, the present invention is not limited to this. For example, this information may be included in a new packet not defined by the WPC standard and transmitted / received. Alternatively, this information may be included in another packet defined by the WPC standard and transmitted / received.

[0088] In this embodiment, it is assumed that the power receiving device 102 can control the closed circuit including the power receiving coil 201 and the resonant capacitor 207 for second Q-factor measurement, and that the power receiving device 102 can measure the second Q-factor of the power receiving circuit. Therefore, in F623, the power receiving device 102 transmits a configuration packet with the short-circuit capability bit set to "1" and the measurement capability bit also set to "1." The power transmitting device 100 references the short-circuit capability bit and the measurement capability bit included in the received configuration packet and stores these values ​​in the memory 305.

[0089] After receiving the configuration packet, the power transmitting device 100 responds with an ACK (F606). Upon receiving the ACK for the configuration packet, the power receiving device 102 transitions to the negotiation phase. In the negotiation phase, the power transmitting device 100 and the power receiving device 102 negotiate regarding the third foreign object detection. In the second Q-factor measurement, the power receiving device 102 negotiates the measurement start time, which is the time until the power transmission unit 302 of the power transmitting device 100 stops transmitting power. This negotiation is completed by the power receiving device 102 sending a packet storing the requested measurement start time in a specific request defined in the WPC standard to the power transmitting device 100 (F631). The power receiving device 102 determines the value of the requested measurement start time based on its own processing capabilities and sends a packet storing the measurement start time value to the power transmitting device 100. This packet will be referred to herein as "SRQ (M1)." The power transmitting device 100 responds to the SRQ (M1) taking into account its own device processing capabilities. If the power transmitting device 100 determines that the measurement start time indicated by the SRQ (M1) is acceptable, it sends an ACK. If it determines that the measurement start time is unacceptable, it sends a NAK. Here, it is assumed that the power transmitting device 100 determines that the measurement start time is acceptable and sends an ACK (F632). Note that, as an example, it is assumed that the power receiving device 102 requests a 50 ms Q-factor measurement start time in the SRQ (M1).

[0090] The power receiving device 102 negotiates the window length, which is the length of the interval (from time T0 to time T5) during which the power transmitting unit 302 of the power transmitting device 100 stops power transmission during the second Q-factor measurement. This negotiation is completed by the power receiving device 102 sending a packet storing the requested window length value in a specific request defined in the WPC standard to the power transmitting device 100 (F633). This packet will be referred to herein as "SRQ(M2)." The power receiving device 102 determines the window length value based on its own processing capabilities and sends a packet storing the determined window length value to the power transmitting device 100. The power transmitting device 100 responds to the SRQ(M2) taking into account its own processing capabilities. If the window length indicated by the SRQ(M2) is acceptable, the power transmitting device 100 sends an ACK. If the window length is unacceptable, the power transmitting device 100 sends a NAK. It is assumed here that the power transmitting device 100 determines that the window length is acceptable and sends an ACK (F634). Note that, here, as an example, it is assumed that the powered device 102 requests 100 ms as the window length in the SRQ ( M2 ).

[0091] Furthermore, the power receiving device 102 negotiates a timeout length, which is the duration during which the power transmitting device 100 receives the Q factor measured by the power receiving device 102 in the second Q-factor measurement. This negotiation is completed by the power receiving device 102 sending a packet storing the requested timeout value in a specific request defined in the WPC standard to the power transmitting device 100 (F635). This packet will be referred to herein as "SRQ (M3)." The power receiving device 102 determines the timeout value based on its own processing capabilities and sends the packet storing the determined timeout value to the power transmitting device 100. The power transmitting device 100 responds to the SRQ (M3) taking into account its own processing capabilities. If the timeout length is determined to be acceptable, the power transmitting device 100 sends an ACK. If the timeout length is determined to be unacceptable, the power transmitting device 100 sends a NAK. It is assumed here that the power transmitting device 100 determines that the timeout length is acceptable and sends an ACK (F636). In this embodiment, it is assumed that the powered device 102 requests 500 ms as the timeout length in the SRQ ( M3 ).

[0092] Here, in the example, a type (Type) in a specific request that is not defined by v1.2.3 can be assigned to the negotiation of the measurement start time, window length, and timeout length. Measure Delay Req (Measure Delay Req) is a packet requesting the power transmitting device 100 to change the measurement start time. Window Length Req (Window Length Req) is a packet requesting the power transmitting device 100 to change the window length. Timeout Req (Timeout Req) is a packet requesting the power transmitting device 100 to change the timeout length. These three packets are reserved packets, whose packet types are not defined by the WPC standard v1.2.3. In this embodiment, among these reserved packets, the packet with a packet header of 0×40 is defined as a Measurement Delay Req packet. Similarly, the packet with a packet header of 0×41 is defined as a Window Length Req packet, and the packet with a packet header of 0×42 is defined as a Timeout Req packet.

[0093] Alternatively, in the packets defined in WPC standard v1.2.3, packets with undefined types other than specific requests or general requests may be defined as the three packets described above. For example, reserved packets or proprietary packets with undefined packet types other than specific requests or general requests may be defined as the three packets described above. Furthermore, in general requests or specific requests defined in WPC standard v1.2.3, packets with undefined packet types may be defined as the three packets described above. That is, in general requests or specific requests, reserved packets or proprietary packets with undefined packet types may be defined as the three packets described above.

[0094] Return Reference Figure 6BIf the processes from F607 to F612 are executed during the negotiation phase, the negotiation phase ends and the phase transitions to the power transmission phase. During the power transmission phase, the processes from F613 to F617 are executed. Here, it is assumed that a foreign object is placed on the operating volume immediately after the power receiving device 102 receives the simulated ping in F618. The power receiving device 102 transmits CE, requesting the power transmitting device 100 to maintain the transmitted power, and RP0, which stores the current received power value (F619 and F620).

[0095] Upon receiving RP0 from the power receiving device 102, the power transmitting device 100 performs foreign object detection based on the second foreign object detection method described above. As a result of the foreign object detection, the power transmitting device 100 determines that there is a high probability of a foreign object being present and sends a NAK to the power receiving device 102 (F624). Upon receiving the NAK from the power transmitting device 100, the power receiving device 102 sends a Q2R packet (F625) to the power transmitting device 102 to more specifically determine the presence of a foreign object. This Q2R packet is a packet in which a value indicating a Q2R packet is set in a reserved bit of a reserved power packet in the WPC standard. However, the present invention is not limited to this. For example, the power receiving device 102 may request the start of the third foreign object detection using a mode that does not define a reserved power packet, or may request the start of the third foreign object detection by defining a new packet. In this embodiment, a case is described in which the power receiving device 102 uses a Q2R packet to request the start of the third foreign object detection. However, the third foreign matter detection may be started based on the NAK response to RP2 without using the Q2R packet.

[0096] Upon receiving the Q2R, the power transmitting device 100 determines whether to perform the third foreign object detection. If it determines to perform, the power transmitting device 100 sends an ACK to the power receiving device 102. If it determines not to perform, the power transmitting device 100 sends a NAK to the power receiving device 102. Here, it is assumed that the power transmitting device 100 determines to perform the third foreign object detection. In this case, the power transmitting device 100 sends an ACK to the power receiving device 102 (F626). If the ACK is sent, the power transmitting device 100 and the power receiving device 102 begin the third foreign object detection. During the third foreign object detection, the power transmitting device 100 and the power receiving device 102 measure the second Q factor (F629 and F630). After measuring the second Q factor, the power receiving device 102 stores the second Q factor measured by its own device in a packet (QRS) and sends the QRS to the power transmitting device 100 (F627). Note that the QRS is a packet that includes at least the second Q factor measured by the power receiving device 102, but may also include other information such as the current received power value. Upon receiving the QRS from the power receiving device 102, the power transmitting device 100 determines the presence of a foreign object based on the received second Q factor of the power receiving device 102 and the second Q factor measured by the power transmitting device 100 itself. By using the second Q factor measured by the power receiving device 102 in addition to the second Q factor measured by the power transmitting device 100 to determine the presence of a foreign object, the presence of a foreign object can be determined more accurately. If a foreign object is determined to be present, the power transmitting device 100 sends a NAK to the power receiving device 102. If a foreign object is determined not to be present, the power transmitting device 100 sends an ACK to the power receiving device 102. Here, it is assumed that the power transmitting device 100 determines that a foreign object is present. In this case, the power transmitting device 100 sends a NAK to the power receiving device 102 (F628). Thereafter, the power transmitting device 100 stops power transmission.

[0097] (Procedure of the Third Foreign Object Detection Process Using the Power Transmitting Device 100)

[0098] Next, we will refer to Figure 7 An example of the process of the third foreign object detection process using the power transmitting device 100 will be described. After receiving the third foreign object detection request, the power transmitting device 100 determines whether the power receiving device 102 is capable of controlling the formation of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for the second Q-factor measurement (step S701). For example, the power transmitting device 100 refers to the short-circuit capability bit stored in memory during the configuration phase. If the value is 1, the power transmitting device 100 determines that this control is possible ("Yes" in step S701) and proceeds to step S702. On the other hand, if the value of the short-circuit capability bit is 0, the power transmitting device 100 determines that this control is not possible ("No" in step S701), transmits a NAK (step S708), and ends the process.

[0099] In step S702, the power transmitting device 100 determines whether the power receiving device 102 is capable of measuring the second Q factor of the power receiving circuit. The power transmitting device 100, for example, refers to the measurement capability bit stored in memory during the configuration phase. If the value is 0, the power transmitting device 100 determines that the second Q factor cannot be measured ("No" in step S702) and proceeds to step S709. The power transmitting device 100 then measures the second Q factor in its own device (step S709) and proceeds to step S706. On the other hand, if the value of the measurement capability bit is 1, the power transmitting device 100 determines that the second Q factor can be measured ("Yes" in step S702) and proceeds to step S703.

[0100] In step S703, the power transmitting device 100 determines whether the second Q factor of the power transmission circuit is being measured by the device itself. If it determines that the second Q factor is being measured by the device itself ("Yes" in step S703), the power transmitting device 100 measures the second Q factor (step S704) and proceeds to step S705. On the other hand, if it determines that the second Q factor is not being measured by the device itself ("No" in step S703), the power transmitting device 100 proceeds to step S705 without measuring the second Q factor. In step S705, the power transmitting device 100 receives the second Q factor from the power receiving device and proceeds to step S706. At this time, if the second Q factor cannot be received from the power receiving device after sending an ACK in F626 and before the timeout period has elapsed, the power transmitting device 100 terminates the process and stops power transmission. By setting the timeout period, the process can be appropriately advanced or stopped if the second Q factor is not transmitted from the power receiving device 102. Furthermore, at this time, if an appropriate timeout length according to the processing capability of the power receiving apparatus 102 is decided and set by negotiation as described above, even a power receiving apparatus 102 with low processing capability can complete transmission of the second Q factor before timeout.

[0101] In step S706, the power transmitting device 100 uses at least one of the second Q factor measured in step S704 and the second Q factor received in step S705 to determine the presence of a foreign object. If it determines that a foreign object is present ("Yes" in step S706), the power transmitting device 100 sends a NAK to the power receiving device 102 (step S708). On the other hand, if it determines that no foreign object is present ("No" in step S706), the power transmitting device 100 sends an ACK to the power receiving device 102 (step S707), and the process ends.

[0102] In reference Figure 7In the described processing example, in step S701, the power transmitting device 100 confirms that the value of the short-circuit capability bit is 1, determines that the power receiving device 102 can execute control to form a closed circuit, and proceeds to step S702. In step S702, the power transmitting device 100 confirms that the value of the measurement capability bit is 1, determines that the power receiving device 102 can measure the second Q factor, and proceeds to step S703. In step S703, the power transmitting device 100 also determines that it will measure the second Q factor, and proceeds to step S704. The power transmitting device 100 measures the second Q factor in step S704, receives the second Q factor measured by the power receiving device 102 in step S705, and proceeds to step S706. Next, in step S706, the power transmitting device 100 determines that a foreign object is present, using the second Q factor received from the power receiving device 102 and the second Q factor measured by the power transmitting device 100. In step S708 , the power transmitting device 100 transmits a NAK to the power receiving device 102 and ends the process.

[0103] exist Figure 7 In the illustrated process, in step S701, the power transmitting device 100 determines whether the power receiving device 102 is capable of performing control to form a closed circuit, thereby preventing the power receiving device 102, which is unable to perform such control, from measuring the second Q factor. As a result, the power transmitting device 100 can prevent erroneous control from being performed by measuring the Q factor under inappropriate conditions.

[0104] Note that in this embodiment, when it is determined in step S701 that the power receiving device 102 is unable to perform control to form a closed circuit, the power transmitting device 100 transmits a NAK and terminates the process. However, the present invention is not limited to this. For example, the power transmitting device 100 may measure the second Q factor when the power receiving device 102 does not form a closed circuit and determine the presence of a foreign object based on the measured second Q factor. However, if the second Q factor is measured when a closed circuit is not formed, it is assumed that the measured value is affected by changes in the load on the power receiving device. Therefore, if such second Q factor measurement is used, the presence of a foreign object is determined using a different criterion than the criterion for determining the presence of a foreign object based on the second Q factor measurement result when a closed circuit can be formed.

[0105] Furthermore, in step S702, the power transmitting device 100 determines whether the power receiving device 102 is capable of measuring the second Q factor of the power transmitting circuit. This prevents the power transmitting device 100 from failing to detect a foreign object due to the fact that the power receiving device 102 is unable to measure the second Q factor, but the power transmitting device 100 itself is not measuring the second Q factor. Furthermore, this prevents the power transmitting device 100 from needlessly waiting for the second Q factor measurement result to be transmitted from the power receiving device 102, despite the power receiving device 102 being unable to measure the second Q factor. Furthermore, if the power receiving device 102 is capable of measuring the second Q factor, the power transmitting device 100 can prevent a state deviation from occurring, and the power transmitting device 100 does not receive the second Q factor transmitted from the power receiving device 102.

[0106] Furthermore, in step S704, the power transmitting device 100 measures the second Q factor using its own device in addition to the power receiving device 102, thereby enabling accurate foreign object detection with minimal noise influence. Furthermore, in step S703, the power transmitting device 100 decides not to measure the second Q factor itself, thereby omitting its own second Q factor measurement and using the second Q factor received from the power receiving device 102 to determine foreign object presence. This can prevent unnecessary Q factor measurements from occurring when both the power transmitting device 100 and the power receiving device 102 measure the Q factor simultaneously.

[0107] (Procedure of the Third Foreign Object Detection Processing by the Power Receiving Device 102)

[0108] Next, we will refer to Figure 8An example of the procedure for the third foreign object detection process using the power receiving device 102 will be described. The power receiving device 102 determines whether it can control the formation of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for second Q-factor measurement (step S801). If it is determined that control to form a closed circuit can be performed ("Yes" in step S801), the power receiving device 102 proceeds with the process to step S802. If it is determined that control to form a closed circuit cannot be performed ("No" in step S801), the power receiving device 102 proceeds with the process to step S805. In step S802, the power receiving device 102 determines whether it can measure the second Q-factor of the power receiving circuit. If the second Q-factor can be measured ("Yes" in step S802), the power receiving device 102 proceeds with the process to step S803. If the second Q-factor cannot be measured ("No" in step S802), the power receiving device 102 proceeds with the process to step S805. In step S803, the power receiving device 102 measures the second Q factor. Subsequently, in step S804, the power receiving device 102 transmits the Q factor measured in step S803 to the power transmitting device 100 and proceeds to step S805. In step S805, the power receiving device 102 receives the result of foreign object detection from the power transmitting device 100 and ends the process.

[0109] In reference Figure 8 In the processing example described above, in step S801, the power receiving device 102 determines that it is possible to perform control to form a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for the second Q factor measurement. In addition, in step S802, the power receiving device 102 determines that it can measure the second Q factor of the power receiving circuit. Then, the power receiving device 102 performs the processing of steps S803 to S805 and ends. Figure 8 The processing shown.

[0110] (Procedure of Second Q-Factor Measurement Processing by Power Transmitting Device 100)

[0111] Will refer to Figure 9An example of the process for the second Q-factor measurement process performed by the power transmitting device 100 in step S704 or S709 described above will be described. For example, after completing the transmission of the ACK (completing the transmission of the trailing edge in the time domain of the ACK) in F626, the power transmitting device 100 stops power transmission for 50 ms, which is the value agreed upon in the negotiation of the measurement start time (step S901). The power transmitting device 100 measures the voltage value A3 of the power transmitting coil at time T3 (step S902), and measures the voltage value A4 of the power transmitting coil at time T4 (step S903). The power transmitting device 100 calculates the Q factor in the manner described above based on the operating frequency, measurement time, and voltage value (step S904). Then, after a time of 100 ms or more, which is the value agreed upon in the negotiation of the window length, has passed since the power transmission was stopped in step S901, the power transmitting device 100 resumes power transmission (step S905), and the process ends.

[0112] (Procedure of Second Q-Factor Measurement Processing by Power Receiving Device 102)

[0113] Will refer to Figure 10 An example of the process for the second Q-factor measurement process performed by the power receiving device 102 in step S803 will be described. After the ACK is received (the trailing edge of the ACK is received) in F626, the power receiving device 102 detects that power transmission has stopped within 50 ms of the value agreed upon in the negotiation, which is the measurement start time. The power receiving device 102 controls the circuit to form a closed circuit including the power receiving coil 201 and the resonant capacitor 207 (step S1001). The power receiving device 102 measures the voltage value A3 of the power receiving coil at time T3 (step S1002) and the voltage value A4 of the power receiving coil at time T4 (step S1003). The power receiving device 102 calculates the Q-factor based on the operating frequency, the measurement time, and the voltage value (step S1004). Thereafter, the power receiving device 102 reconnects the load before 100 ms of the window length agreed upon in the negotiation has elapsed since the power transmission was detected to have stopped in step S1001 (step S1005), and the process ends. Note that reconnection of the load is performed by opening switch 208 .

[0114] Figures 7 to 10 The processing described can be implemented, for example, by the control unit 300 of the power transmitting device 100 or the control unit 200 of the power receiving device 102 reading out a pre-stored program and executing it. However, the present invention is not limited to this, and at least a portion of the processing can be implemented in hardware. When implementing the processing in hardware, for example, a predetermined compiler can be used to automatically generate a dedicated circuit on an FPGA based on a program configured to implement the processing steps. Here, FPGA stands for field-programmable gate array. Furthermore, similar to FPGAs, gate array circuits can be formed to implement hardware configured to perform at least a portion of the above-described processing.

[0115] In this embodiment, since the measurement start time is negotiated in advance, the powered device 102 can identify the timing at which the power transmitting device 100 stops power transmission and can appropriately start the second Q-factor measurement. Since the measurement start time is negotiated to set an appropriate measurement start time based on the processing performed by the powered device 102 or its processing capabilities, the second Q-factor measurement can be started at a timing suitable for the powered device 102. For example, if the powered device 102 needs to transmit other packets near the time of the second Q-factor measurement, the measurement start time can be negotiated so that the second Q-factor measurement can be completed before the start of packet transmission. This avoids the momentary disconnection of power transmission used for the second Q-factor measurement while the powered device 102 is transmitting other packets, preventing degradation in power transmission efficiency. If the powered device 102 takes time to start the second Q-factor measurement due to its hardware configuration or processing capabilities, the measurement start time can be determined at a later time based on the capabilities of the powered device 102. This enables the power transmitting apparatus 100 to stop power transmission at a timing when, for example, the power receiving apparatus 102 completes formation of a closed circuit and can start the second Q-factor measurement process.

[0116] Furthermore, in this embodiment, because the window length is negotiated in advance, the power receiving device 102 can reconnect the power receiving coil 201 to the load at the appropriate timing. This means that if power transmission is resumed while a closed circuit is forming in the power receiving device 102, an overcurrent could flow into the power receiving coil 201 and resonant capacitor 207. However, in this embodiment, because the window length is predetermined through negotiation, this situation can be prevented. Furthermore, the time required for the second Q-factor measurement can vary depending on the performance of the power receiving device 102 or the requested measurement accuracy. However, according to this embodiment, the power receiving device 102 negotiates the window length based on its own performance or the requested measurement accuracy, thereby ensuring sufficient measurement time and preventing measurement failures or a decrease in measurement accuracy.

[0117] Note that in the above description, all of the measurement start timing, measurement period length, and time period (timeout period) until the second Q-factor measurement report in the powered device are determined by negotiation. At least some of these can be negotiated. That is, for example, only one of these can be negotiated, or only two of these can be negotiated. In other words, these elements can be used independently, and it is not necessary to always use all of them.

[0118] (Other embodiments)

[0119] The present invention can also be implemented by supplying a program for implementing one or more functions in the above-described exemplary embodiments to a system or device via a network or storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. The present invention can also be implemented by a circuit (e.g., an ASIC) for implementing one or more functions.

[0120] The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, the following claims are made to inform the public of the scope of the present invention.

[0121] This application claims the benefit of Japanese Patent Application No. 2020-064204, filed on March 31, 2020, which is hereby incorporated by reference herein in its entirety.

Claims

1. A power transmission device, comprising: a power transmitting unit configured to wirelessly transmit power to a powered device; a communication unit configured to communicate with the powered device; a negotiation unit configured to negotiate a length of a time period during which power transfer is restricted; as well as The detection unit is configured to perform foreign object detection during a time period in which power transmission is restricted after power transmission starts in the power transmission phase.

2. The power transmission device according to claim 1, wherein: The detection unit performs the foreign matter detection based on a Q factor.

3. The power transmission device according to claim 1, wherein: The communication unit receives information related to the time period from the powered apparatus.

4. The power transmission device according to claim 1, wherein The information is information about the length of the time period.

5. A method for use with a power transmission device, the method comprising: Communicate with powered devices; Negotiating the length of the period during which power delivery is restricted; as well as After power transmission is started in the power transmission phase, foreign object detection is performed during a time period in which the power transmission is restricted.

6. The method according to claim 5, wherein: The foreign matter detection is performed based on the Q factor.

7. The method according to claim 5, wherein: Information related to the time period is received from the powered device.

8. The method according to claim 5, wherein The information is information about the length of the time period.

9. A computer-readable storage medium storing a program for causing a computer to execute a method used by a power transmitting device, the method comprising: Communicate with powered devices; Negotiating the length of the period during which power delivery is restricted; as well as After power transmission is started in the power transmission phase, foreign object detection is performed during a time period in which the power transmission is restricted.

10. A computer program product comprising a program for causing a computer to execute a method used by a power transmitting device, the method comprising: Communicate with powered devices; Negotiating the length of the period during which power delivery is restricted; as well as After power transmission is started in the power transmission phase, foreign object detection is performed during a time period in which the power transmission is restricted.

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