Power transmission equipment, power reception equipment, control method, and computer-readable storage medium

Abstract

A power transmission device that can wirelessly transmit power to and communicate with a power receiving device via a power transmission coil determines the presence or absence of an object different from the power receiving device based on the Q factor of the power transmission coil measured in a stage for performing power transmission from the power transmission device to the power receiving device. The power transmission device controls whether to perform the determination of the presence or absence of an object different from the power receiving device based on the Q factor of the power transmission coil based on information received from the power receiving device through communication indicating whether the power receiving device can perform a predetermined process, where the predetermined process is associated with the determination of the presence or absence of an object different from the power receiving device based on the Q factor of the power transmission coil.

Description

Technical Field

[0001] The present invention relates to a power transmission device, a power reception device, a control method, and a computer-readable storage medium, and more particularly to a foreign object detection technique in wireless power transmission. Background Art

[0002] The technology development of wireless power transmission systems has been widely carried out, and the standard (WPC standard) standardized by the Wireless Power Consortium (WPC), a standardization organization, as a wireless power charging standard is well known. In such wireless power transmission, it is important to detect a foreign object and control power transmission / reception when there is a foreign object within the range where the power transmission device can transmit power. A foreign object is an object different from the power reception device. Patent Document 1 describes a method of detecting a foreign object and restricting power transmission / reception when there is a foreign object near a power transmission / power transmission device conforming to the WPC standard. Patent Document 2 describes a technique for foreign object detection by short-circuiting a coil in a wireless power transmission system. Patent Document 3 describes a technique for detecting a foreign object based on a change in the Q factor (quality factor) of a power transmission coil in a wireless power transmission system measured by applying a high-frequency signal to the coil for a predetermined period of time.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-070074

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-034972

[0007] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2013-132133 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The present invention provides a technique capable of accurately performing detection of an object different from a power reception device in a power transmission device and a power reception device conforming to the WPC standard.

[0010] Solutions to the Problems

[0011] According to an aspect of the present invention, there is provided a power transmission device including: a power transmission component for wirelessly transmitting power to a power receiving device via a power transmission coil; a communication component for communicating with the power receiving device; a measurement component for measuring the Q factor of the power transmission coil in a stage of performing power transmission from the power transmission device to the power receiving device; a determination component for determining the presence or absence of an object different from the power receiving device based on the Q factor of the power transmission coil; and a control component for controlling whether to perform the determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil, based on information indicating whether the power receiving device can perform a predetermined process associated with the determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil, wherein the information is received by the communication component from the power receiving device.

[0012] Effects of the Invention

[0013] 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 transmission device and a power receiving device compliant with the WPC standard.

[0014] Other features and advantages of the present invention will be apparent from the following description in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals denote the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings, which are included in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0016] Figure 1 is a diagram showing an example of the configuration of a wireless power transmission system;

[0017] Figure 2 is a block diagram showing an example of the configuration of a power receiving device;

[0018] Figure 3 is a block diagram showing an example of the configuration of a power transmission device;

[0019] Figure 4 is a block diagram showing an example of the functional configuration of a control unit of a power transmission device;

[0020] Figure 5 is a block diagram showing an example of the functional configuration of a control unit of a power receiving device;

[0021] Figure 6A is a sequence diagram showing an example of a process of processing performed by a conventional power transmission device and a conventional power receiving device;

[0022] Figure 6Bis a sequence diagram showing an example of a process of processing performed by a power transmission device and a power reception device according to an embodiment;

[0023] Figure 7 is a flowchart showing an example of a process of a third foreign object detection process using a power transmission device;

[0024] Figure 8 is a flowchart showing an example of a process of a third foreign object detection process using a power reception device;

[0025] Figure 9 is a flowchart showing an example of a process of a second Q factor measurement process using a power transmission device;

[0026] Figure 10 is a flowchart showing an example of a process of a second Q factor measurement process using a power reception device;

[0027] Figure 11 is a diagram for explaining foreign object detection using a power loss method;

[0028] Figure 12A is a diagram for explaining a Q factor measurement method in the time domain;

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

[0030] Figure 13 is a diagram showing the frame format of a configuration packet. Detailed Description of the Invention

[0031] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. In the embodiments, a plurality of features are described, but the invention is not limited to an invention that requires all of these features, and a plurality of such features can be appropriately combined. In addition, in the drawings, the same reference numerals are given to the same or similar structures, and redundant descriptions thereof are omitted.

[0032] (System Configuration)

[0033] Figure 1An example of the configuration of the wireless power transmission system according to this embodiment is shown. In the example, the wireless power transmission system is configured to include a power transmission device 100 and a power reception device 102. It is assumed that the power transmission device 100 and the power reception device 102 conform to the WPC (Wireless Power Consortium) standard. The power transmission device 100 is, for example, an electronic device that wirelessly transmits power to the power reception device 102 placed on its own device. The power transmission device 100 wirelessly transmits power to the power reception device 102 via a power transmission coil 101. The power reception device 102 is, for example, an electronic device that receives power from the power transmission device 100 and charges an internal battery. The power reception device 102 can be configured to be incorporated into other devices (camera, smartphone, tablet PC, laptop computer, automobile, robot, medical device, or printer) and supply power to these devices. The power transmission device 100 can be a smartphone or the like. In this case, for example, the power reception device 102 can be another smartphone or wireless earphones. The power reception device 102 can be a transport vehicle or a conveyance such as an automobile, and the power transmission device 100 can be a charger installed in the console of the transport vehicle or a conveyance such as an automobile.

[0034] Figure 1 A situation is shown in which a conductive foreign object 103 exists in the range (operating volume) affected by the wireless power output from the power transmission coil 101. If the foreign object 103 exists in the operating volume, the power transmission / reception efficiency decreases, and in some cases, problems such as heat generation may occur. Therefore, it is important for the power transmission device 100 and the power reception device 102 to detect the foreign object 103 and perform power transmission / reception control. In this embodiment, the power transmission device 100 and the power reception device 102 measure the Q factor (quality factor) based on the time variation of the voltage of the power transmission coil within the control range conforming to the WPC standard, detect the foreign object 103, and control the power transmission / reception. An example of the configuration of the device for performing such a process and the processing procedure will be described in detail below. Note that the foreign object 103 is an object different from the power reception device. The foreign object 103 is, for example, a conductive object such as a metal sheet or an IC card.

[0035] (Configuration of the device)

[0036] Figure 2An example of the 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 rectifying 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 a RAM (Random Access Memory) and a ROM (Read Only Memory). The control unit 200 may be configured to execute programs stored in the storage device by the processor, thereby performing 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 rectifying unit 202 converts the AC voltage and AC current received via the power receiving coil 201 into a DC voltage and a DC current. The voltage control unit 203 converts the level of the DC voltage input from the rectifying unit 202 into a level of a DC voltage (neither too high nor too low) suitable for the operations of the control unit 200, the charging unit 205, etc. The voltage control unit 203 also supplies the voltage at the converted level to the charging unit 205. The charging unit 205 charges the battery 206 with the voltage supplied from the voltage control unit 203. The communication unit 204 performs control communication for wireless charging based on the WPC standard with respect to the power transmitting device 100. This control communication is performed by load modulation of the AC voltage and AC current received by the power receiving coil 201.

[0037] In addition, 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 a switch 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. At this time, current only flows through the closed circuit of the power receiving coil 201, the resonant capacitor 207, and the switch 208, and no current flows through the rectifying unit 202 and the voltage control unit 203. On the other hand, if the switch 208 is turned off, current flows through the rectifying unit 202 and the voltage control unit 203 via the power receiving coil 201 and the resonant capacitor 207.

[0038] Figure 3An example of the configuration of the power transmission device 100 is shown. The power transmission device 100 is configured to include, for example, 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 307. The control unit 300 controls the entire power transmission 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 may be configured to execute, for example, a program stored in the memory 305 described later or a storage device incorporated in the control unit 300 by the processor, thereby performing various processes described later. The power supply unit 301 supplies power to each functional block. The power supply unit 301 is, for example, a commercial power supply or a battery. The battery can store, for example, electric power supplied from the commercial power supply.

[0039] The power transmission unit 302 converts the DC or AC power input from the power supply unit 301 into AC power in a frequency band for wireless power transmission, and inputs the AC power to the power transmission coil 303, so that the power transmission coil 303 generates an electromagnetic wave 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 an AC voltage through 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 performs ON / OFF control of the FETs. In addition, the power transmission unit 302 adjusts at least one of the voltage (transmission voltage) and current (transmission current) or the frequency input to the power transmission coil 303, thereby controlling the intensity or frequency of the electromagnetic wave to be output. For example, the power transmission unit 302 increases the intensity of the electromagnetic wave by making the transmission voltage or transmission current large, and decreases the intensity of the electromagnetic wave by making the transmission voltage or transmission current small. Here, it is assumed that the power transmission unit 302 has the ability to supply power to output 15 watts (W) of power to the charging unit 205 of the power receiving device 102 corresponding to the WPC standard. In addition, the power transmission unit 302 performs output control of the AC power based on an instruction from the control unit 300, so as to start or stop outputting the electromagnetic wave from the power transmission coil 303.

[0040] The communication unit 304 communicates with the power receiving device 102 via the power transmission coil 303 for power transmission control based on the WPC standard. The communication unit 304 uses frequency modulation (FSK (Frequency Shift Keying)) to modulate the AC voltage and AC current output from the power transmission unit 302 and transmits information to the power receiving device 102. In addition, the communication unit 304 demodulates the AC voltage and AC current modulated by the load modulation of the communication unit 204 of the power receiving device 102 to obtain the information transmitted from the power receiving device 102. That is, the communication unit 304 superimposes the information to be transmitted to the power receiving device 102 on the electromagnetic wave transmitted from the power transmission unit 302, and the power receiving device 102 detects the power receiving signal superimposed on the electromagnetic wave, thereby communicating with the power receiving device 102. In addition, the communication unit 304 may use a coil (or antenna) different from the power transmission coil 303 to communicate with the power receiving device 102 according to a standard different from the WPC standard. In addition, the communication unit 304 may communicate with the power receiving device 102 by selectively using multiple communication functions. The memory 305 stores, for example, the control program to be executed by the control unit 300 and information such as the states of the power transmission device 100 and the power receiving device 102. For example, the state of the power transmission device 100 is obtained by the control unit 300. The state of the power receiving device 102 is obtained by the control unit 200 of the power receiving device 102 and is transmitted from the charging unit 205. The power transmission device 100 obtains the information indicating the state via the communication unit 304.

[0041] The power transmission coil 303 is connected to the resonance capacitor 306 and is configured to resonate at a specific frequency F1. The switch 307 is a switch configured to short-circuit the power transmission coil 303 and the resonance capacitor 306 and is controlled by the control unit 300. If the switch 307 is turned on, the power transmission coil 303 and the resonance capacitor 306 form a series resonance circuit. At this time, current only flows through the closed circuit of the power transmission coil 303, the resonance capacitor 306, and the switch 307. If the switch 307 is turned off, power is supplied from the power transmission unit 302 to the power transmission coil 303 and the resonance capacitor 306.

[0042] Figure 4An example of the functional configuration implemented by the control unit 300 of the power transmission 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 performs acquisition of calibration data points and calibration curve creation processing. 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 to be 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 the start of power transmission, stop of power transmission, and increase / decrease of transmission power in the power transmission unit 302. Figure 4 The processing units shown are configured as, for example, multiple independent programs, and can operate concurrently while synchronizing among multiple programs through event processing or the like.

[0043] Figure 5 An example of the functional configuration implemented by the control unit 200 of the power reception device 102 is shown. 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 the start of power reception and stop of power reception of the power reception device 102 and the increase / decrease of the power requested from the power transmission device 100. Figure 5 The processing units shown are configured as independent programs, and can operate concurrently while synchronizing among the programs through event processing or the like.

[0044] (Foreign Object Detection Method in WPC Standard)

[0045] Next, the foreign object detection method defined by the WPC (Wireless Power Consortium) standard will be described using the power transmission device 100 and the power reception device 102 as examples. Here, the foreign object detection method based on the Q-factor measured in the frequency domain (first foreign object detection method) and the foreign object detection method based on the power loss method (second foreign object detection method) will be described.

[0046] (1) Foreign object detection method based on Q factor measured in the frequency domain (first foreign object detection method)

[0047] In the first foreign object detection method, first, the power transmission device 100 measures the Q factor (first Q factor measurement) changed due to the influence of foreign objects in the frequency domain. This measurement is performed after the power transmission device 100 sends an Analog Ping until a Digital Ping is sent (see F601 in Figure 6A . For example, to measure the Q factor, the power transmission unit 302 scans 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 the resonant frequency at which the voltage value exhibits a peak, and calculates the Q factor of the power transmission coil 303 based on this resonant frequency and the frequency indicating a voltage value 3 dB lower than the peak voltage value measured at this resonant frequency.

[0048] The Q factor can be measured by other methods. For example, the power transmission unit 302 scans 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 with the power transmission coil 303 and searches for the resonant frequency at which the voltage value exhibits a peak. Then, the first Q factor measurement unit 400 measures the voltage values 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.

[0049] After calculating the Q factor of the power transmission coil 303, the first foreign object detection processing unit 403 of the power transmission device 100 obtains the Q factor used as a determination 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 transmission coil when the power receiving device is placed on the power transmission coil defined by the WPC standard from the power receiving device 102. The Q factor is stored in the FOD (foreign object detection) status packet sent from the power receiving device 102, and the power transmission device 100 receives the FOD status packet to obtain the Q factor. The first foreign object detection processing unit 403 estimates the Q factor of the power transmission coil 303 when the power receiving device 102 is placed on the power transmission device 100 based on the obtained Q factor. In this embodiment, the estimated Q factor will be expressed as the 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 device 102 can notify the power transmission device 100 of the pre-stored Q factor. Note that the Q factor corresponds to Q1 described later.

[0050] The first foreign object detection and processing unit 403 of the power transmission 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 or absence of a foreign object based on the comparison result. For example, a Q factor that is a% (the first ratio) lower than the first reference Q factor is used as a threshold. If the measured Q factor is lower than the threshold, the first foreign object detection and processing unit 403 determines that there is a high possibility of the presence of a foreign object; otherwise, it determines that there is a high possibility of the absence of a foreign object.

[0051] (2) Foreign object detection method based on power loss method (second foreign object detection method)

[0052] Next, reference will be made to Figure 11 Describe a foreign object detection method based on the power loss method defined by the WPC standard. Figure 11 is a conceptual diagram of foreign object detection using the power loss method. The abscissa represents the transmitted power of the power transmission device 100, and the ordinate represents the received power of the power receiving device 102. Note that the control of the transmitted power of the transmission unit 302 of the power transmission device 100 can be performed by the transmission processing unit 406.

[0053] First, the transmission unit 302 of the power transmission device 100 sends a digital Ping to the power receiving device 102. The communication unit 304 of the power transmission device 100 receives the received power value Pr1 (referred to as Light Load) of the power receiving device 102 through a Received Power Packet (mode 1). Note that hereinafter, the Received Power Packet (mode 1) will be referred to as "RP1". Pr1 is the received power value when the power receiving device 102 does not supply the received power to the load (charging unit 205 and battery 206). The control unit 300 of the power transmission device 100 stores the relationship between the received Pr1 and the transmitted power value Pt1 when Pr1 is obtained ( Figure 11 the point 1100 shown) in the memory 305. Therefore, the power transmission device 100 can identify that the power loss amount between the power transmission device 100 and the power receiving device 102 when Pt1 is transmitted as the transmitted power is Pt1 - Pr1 (Ploss1).

[0054] Next, the communication unit 304 of the power transmission device 100 receives the received power value Pr2 (referred to as "Connected Load") of the power receiving device 102 from the power receiving power pack (mode 2) of the power receiving device 102. Note that hereinafter, the power receiving power pack (mode 2) will be referred to as "RP2". Pr2 is the received power value when the power receiving device 102 supplies the received power to the load. The control unit 300 of the power transmission device 100 stores the relationship between the received Pr2 and the transmitted power value Pt2 when Pr2 is obtained ( Figure 11 the point 1101 shown) in the memory 305. Therefore, the power transmission device 100 can recognize that the power loss amount between the power transmission device 100 and the power receiving device 102 when Pt2 is transmitted as the transmitted power is Pt2 - Pr2 (Ploss2).

[0055] The calibration processing unit 402 of the power transmission device 100 performs linear interpolation on the points 1100 and 1101 to create the line 1102. The line 1102 corresponds to the relationship between the transmitted power and the received power in a state where there is no foreign object around the power transmission device 100 and the power receiving device 102. Therefore, the power transmission device 100 can predict the received power in a state where the possibility of no foreign object is high based on the transmitted power value and the line 1102. For example, for the case where the transmitted power value is Pt3, the power transmission device 100 can predict the received power value Pr3 based on the point 1103 on the line 1102 corresponding to the case where the transmitted power value is Pt3.

[0056] Here, it is assumed that: if the transmission unit 302 of the power transmission device 100 transmits power to the power receiving device 102 using the transmitted power Pt3, 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 transmission device 100 calculates Pr3 - Pr3' (= Ploss_FO), which is a value obtained by subtracting the actually received received power value Pr3' from the received power value Pr3 in a state where there is no foreign object. Ploss_FO can be considered as the power loss consumed by the foreign object when there is a foreign object between the power transmission device 100 and the power receiving device 102. Therefore, if the power Ploss_FO consumed by the foreign object exceeds a predetermined threshold, the second foreign object detection processing unit 404 can determine that there is a foreign object. For example, the threshold is derived based on the relationship between the point 1100 and the point 1101.

[0057] In addition, the second foreign object detection processing unit 404 of the power transmission device 100 obtains, in advance from the received power value Pr3 in a state where no foreign object exists, the power loss amount Pt3 - Pr3 (Ploss3) between the power transmission device 100 and the power reception device 102. The second foreign object detection processing unit 404 calculates, based on the received power value Pr3' received from the power reception device 102 in a state where it is not clear whether a foreign object exists, the power loss amount Pt3 - Pr3' (Ploss3') between the power transmission device 100 and the power reception device 102 in a state where a foreign object exists. Then, the second foreign object detection processing unit 404 calculates Ploss3' - Ploss3. If this value exceeds a predetermined threshold, it can be determined that a foreign object exists. Note that Ploss3' - Ploss3 = Pt3 - Pr3' - Pt3 + Pr3 = Pr3 - Pr3'. Therefore, the power Ploss_FO consumed by the predicted foreign object can be estimated by comparing the power loss amounts.

[0058] As described above, the power Ploss_FO 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.

[0059] After the calibration processing unit 402 obtains the line 1102, the second foreign object detection processing unit 404 of the power transmission device 100 periodically receives the current received power value (for example, the above Pr3') from the power reception device 102 via the communication unit 304. The current received power value periodically transmitted from the power reception device 102 is transmitted to the power transmission device 100 as a received power packet (mode 0). The second foreign object detection processing unit 404 of the power transmission device 100 performs foreign object detection based on the received power value stored in the line 1102 and the received power packet (mode 0). Note that hereinafter, the received power packet (mode 0) will be referred to as (RP0).

[0060] Note that in this embodiment, the points 1100 and 1101 of the line 1102 for obtaining the relationship between the transmitted power and the received power in a state where no foreign object exists around the power transmission device 100 and the power reception device 102 will be referred to as "calibration data points". In addition, the line segment (line 1102) obtained by interpolating at least two calibration data points will be referred to as a "calibration curve". The calibration data points and the calibration curve (second reference) are used for the foreign object detection processing by the second foreign object detection processing unit 404.

[0061] (Q - factor measurement method in the time domain)

[0062] Reference will be made to Figure 12A and Figure 12B describe the Q - factor measurement method in the time domain. Figure 12A andFigure 12B It is a conceptual diagram of a method for explaining the measurement of 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. In addition, the control of the transmission power of the transmission unit 302 of the power transmission device 100 is performed by the transmission control unit 406. In the second Q factor measurement, the power transmission device 100 and the power reception device 102 turn on the switch within the same time period to instantaneously cut off the power transmission, so that the received power is not supplied to the load. Accordingly, for example, the voltage applied to the coil gradually decreases. The second Q factor is calculated based on how the voltage decreases.

[0063] Figure 12A The waveform 1200 shown represents the elapsed time of the high-frequency voltage value (hereinafter simply referred to as the "voltage value of the power transmission coil") applied to the end of the power transmission coil 303 or the resonance capacitor 306 of the power transmission device 100. Note that in Figure 12A and Figure 12B , the abscissa represents time, and the ordinate represents the voltage value. At time T0, the application (power transmission) of the high-frequency voltage is stopped. Point 1201 is a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T1. In Figure 12A , (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 represents the high-frequency voltage at time T2. In Figure 12A , (T2, A2) indicates that the voltage value at time T2 is A2.

[0064] The Q factor measurement is performed based on the time change of the voltage value starting from time T0. For example, based on the time and voltage values of points 1201 and 1202, which are the envelopes of the voltage values, and the angular velocity ω of the high-frequency voltage (ω = 2πf, f is the operating frequency of the high-frequency voltage), the Q factor is calculated by the following formula:

[0065]

[0066] Next, reference will be made to Figure 12BDescribe the process of the power transmission device 100 measuring the Q factor in the time domain. The waveform 1203 represents the value of the high-frequency voltage applied to the power transmission coil 303, and its frequency falls within the range of 110 kHz to 148.5 kHz used in the Qi standard. In addition, each of the points 1204 and 1205 is a part of the envelope of the voltage value. The power transmission unit 302 of the power transmission device 100 stops power transmission in the period from time T0 to T5. The second Q factor measurement unit 401 of the power transmission 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 transmission unit 302 of the power transmission device 100 resumes power transmission at time T5. As described above, the second Q factor measurement is performed by the power transmission device 100 instantaneously disconnecting power transmission and measuring the Q factor based on the elapsed time, voltage value, and operating frequency.

[0067] Note that in the third foreign object detection method, it is sufficient to measure (T3, A3) and (T4, A4), and it is not necessary to measure the second Q factor. That is, as shown in Equation (1), an index 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 or absence of a foreign object. More specifically, this index is compared with a threshold value to detect the presence or absence of a foreign object.

[0068] In addition, in the third foreign object detection method, the current value can be measured instead of the voltage value, and an index based on the ratio of the current values can be used to detect the presence or absence of a foreign object. That is, the current value at T3 and the current value at time T4 are measured. The second Q factor can be obtained based on the current value.

[0069] (Operations of Conventional Power Transmission and Power Reception Devices)

[0070] Reference will be made to Figure 6A describe the operations of the conventional power transmission device 100 and the conventional power reception device 102. In Figure 6A the description, it is assumed that the power transmission device 100 and the power reception device 102 are power transmission and power reception devices compliant with the WPC standard v1.2.3.

[0071] The power transmission device 100 transmits an analog Ping to detect an object present near the power transmission coil 303 (F600). The analog Ping is pulsed power and is power for detecting an object. Even if the power receiving device 102 receives the analog Ping, the power is too small to activate the control unit 200. Using the analog Ping, the power transmission device 100 detects an object based on the shift in the resonance frequency of the voltage value in the power transmission coil 303 caused by the object present near the power transmission coil 303, or the change in the voltage value / current value flowing through the power transmission coil 303. When an object is detected by the analog Ping, the power transmission device 100 measures the Q factor of the power transmission coil 303 by the above-described first Q factor measurement (F601). After the first Q factor measurement, the power transmission device 100 starts transmitting the digital Ping (F602). The digital Ping is power for activating the control unit 200 of the power receiving device 102 and is greater than the analog Ping. The digital Ping is continuously transmitted from then on. That is, the power transmission device 100 continuously transmits power equal to or greater than the digital Ping after starting to transmit the digital Ping (F602) until an EPT packet (End Power Transfer packet) is received from the power receiving device 102 (F622).

[0072] When activated by receiving the 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 transmission device 100 (F603). Next, the power receiving device 102 transmits an ID packet (ID Packet) storing an ID including version information of the WPC standard and device identification information that the power receiving device 102 complies with to the power transmission device 100 (F604). In addition, the power receiving device 102 transmits a Configuration Packet 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) to the power transmission device 100 (F605). The power transmission device 100 receives the ID packet and the configuration packet. When it is determined based on these packets that the power receiving device 102 supports the extended protocol (including negotiation described later) of WPC standard v1.2, the power transmission device 100 responds with an ACK (F606).

[0073] The power receiving device 102 receives the ACK and transitions to the negotiation phase to negotiate the power to be transmitted / received. First, the power receiving device 102 sends an FOD status packet (F607) to the power transmitting device 100. In this embodiment, the FOD status packet will be referred to as "FOD(Q1)". The power transmitting device 100 performs foreign object detection by the first foreign object detection method based on the Q factor stored in the received FOD(Q1) (the Q factor measured in the frequency domain) and the Q factor measured by the first Q factor measurement. When it is determined that the possibility of the absence of foreign objects is high, the power transmitting device 100 sends an ACK (F608) indicating the determination result to the power receiving device 102.

[0074] Upon receiving the ACK, the power receiving device 102 negotiates the Guaranteed Power (GP), which is the maximum value of the power value requested by the power receiving device 102 for power reception. The guaranteed power represents the load power of the power receiving device 102 (the power to be consumed by the battery 206) agreed between the power transmitting device 100 and the power receiving device 102. This negotiation is achieved by sending a packet storing the value of the guaranteed power requested by the power receiving device 102 to the power transmitting device 100 in a Specific Request defined by 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) considering its own power transmission capacity, etc. When it is determined that the guaranteed power is acceptable, the power transmitting device 100 sends an ACK (F610) indicating that the request is accepted. In this embodiment, it is assumed that the power receiving device 102 requests 15W as the guaranteed power through the SRQ(GP). If the negotiation of multiple parameters including the guaranteed power is completed, the power receiving device 102 sends an "SRQ(EN)" (End Negotiation) that requests the end of the negotiation in the specific request to the power transmitting device (F611). The power transmitting device 100 sends an ACK (F612) for the SRQ(EN), ends the negotiation, and transitions to the power transmission phase to transmit / receive the power defined by the guaranteed power.

[0075] Next, the power transmitting device 100 performs foreign object detection (the second foreign object detection method) based on the above power loss method. First, the power transmitting device 100 receives RP1 from the power receiving device 102 (F613). The power transmitting device 100 accepts the received power value stored in the RP1 and the power transmission value of the power transmitting device 100 when obtaining the received power value as calibration data points (corresponding to point 1100 in Figure 11 . The power transmitting device 100 sends an ACK (F614) indicating the acceptance of the calibration data points to the power receiving device 102.

[0076] After receiving the ACK, the power receiving device 102 sends a control error (CE) (hereinafter referred to as CE) to the power transmitting device 100 requesting the power transmitting device 100 to increase / decrease the received voltage (or received current or received power). CE stores a sign and a value. If the sign is positive, it means a request to increase power. If the sign is negative, it means a request to decrease power. If the value is zero, it means a request to maintain power. Here, the power receiving device 102 sends a CE (+) (F615) indicating an increase in power to the power transmitting device 100.

[0077] Upon receiving the CE (+), the power transmitting device 100 changes the setting value of the power transmission unit 302 to increase the transmitted power (F616). When the received power increases in response to the CE (+), the power receiving device 102 supplies the received power to the load (charging unit 205 and battery 206) and sends 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 calibration data points (corresponding to point 1101 in Figure 11 . The power transmitting device 100 sends an ACK (F618) indicating acceptance of the calibration data point to the power receiving device 102. Since the power transmitting device 100 obtains two calibration data points (points 1100 and 1101 in Figure 11 ) at this time point, a calibration curve (line 1102 in Figure 11 ) can be derived.

[0078] The power transmitting device 100 and the power receiving device 102 have transitioned to the power transmission stage at this time point, and the power transmitting device 100 is transmitting power such that the power receiving device 102 can receive the maximum power of 15W negotiated in the negotiation stage. The power receiving device 102 periodically sends a CE requesting the power transmitting device 100 to maintain the transmitted power and RP0 storing the current received power value to the power transmitting device 100 (F619 and F620). When receiving RP0 from the power receiving device 102, the power transmitting device 100 performs foreign object detection based on the above-mentioned second foreign object detection method. When it is determined as a result of the foreign object detection that the possibility of the presence of a foreign object is low, the power transmitting device 100 sends an ACK to the power receiving device 102 (F621). Thereafter, if the charging of the battery 206 is completed, the power receiving device 102 sends an EPT (End Power Transfer) packet requesting the stop of power transmission to the power transmitting device 100 (F622).

[0079] In the above 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.

[0080] As Figure 6AAs shown in the processing example, foreign object detection using the power loss method is performed during the power transmission stage. However, if only one foreign object detection method is used, there is still, to some extent, the possibility of detection errors where a foreign object is detected even though there is no foreign object, or conversely, the possibility of judgment errors where it is determined that there is no foreign object even though there is a foreign object. On the other hand, if foreign object detection is performed by combining multiple foreign object detection methods, an improvement in the accuracy of foreign object detection can be expected. In particular, the power transmission stage is the stage where TX performs power transmission. If there is a foreign object between TX and RX during power transmission, the heat generated from the foreign object increases. Note that even if the foreign object does not exist between TX and RX but exists within the power transmission range, power is received and heat is generated. Therefore, in this stage, significant advantages can be obtained by performing multiple foreign object detection methods and improving the accuracy of foreign object detection. In this embodiment, during the power transmission stage, a foreign object detection method different from the power loss method is introduced.

[0081] Here, in foreign object detection based on the Q factor (first Q factor) measured in the frequency domain (first foreign object detection method), each time a measurement is made, the frequency is scanned to search for the resonance frequency. If such a scan is performed when the power transmission device 100 is sending relatively large power during digital Ping or the power transmission stage, the switching noise in the power transmission 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, and frequency scanning is not required. For this reason, this method can be performed at the operating frequency during the power transmission period of digital Ping or the power transmission stage, and has little impact on the switching noise. In this embodiment, during the second Q factor measurement, control is performed to turn on the switch 208 and form a closed circuit including the power receiving coil 201 and the resonance capacitor 207 when the power transmission device stops power transmission. In a state where the influence of the load change in the power receiving device 102 is thus removed, the second Q factor is measured.

[0082] 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 takes various modes. For this reason, the power transmitting device 100 needs to appropriately control the processes to be performed according to the capabilities of the power receiving device 102. For example, if the power transmitting device 100 performs the second Q factor measurement for the power receiving device 102 that cannot be controlled to form a closed circuit, the measurement is affected by changes in the load in the power receiving device 102, and the Q factor cannot be measured correctly. It can also be assumed that the second Q factor measurement is performed on the power receiving device 102 side. 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 in its own device. For example, if the power receiving device 102 can form a closed circuit but cannot perform the second Q factor measurement, it is impossible to determine the presence or absence of a foreign object unless the power transmitting device 100 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 measurement result of the second Q factor from the power receiving device 102. For example, if the power receiving device 102 cannot perform the second Q factor measurement, but the power transmitting device 100 will 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. The control method will be described below.

[0083] (Description of operations in the case where the third foreign object detection method is applied to the WPC standard)

[0084] Figure 6B An example of the process of the processes performed by the power transmitting device 100 and the power receiving device 102 according to this embodiment is shown. Note that Figure 6ALike reference numerals represent like processes and their description will be omitted. After performing the processes of F600 to F604, the power receiving device 102 transmits a configuration packet (F623) to the power transmitting device 100. In the present embodiment, the ability information of the power receiving device 102 is notified to the power transmitting device 100 by the configuration packet. In the present embodiment, as the ability information to be notified, a short - circuit ability bit and a measurement ability bit are defined in the configuration packet. The short - circuit ability bit is information indicating whether the power receiving device 102 can be controlled to form a closed circuit including the power receiving coil 201 and the resonance capacitor 207 for the second Q - factor measurement. For example, if the own device has the ability to form a closed circuit for the second Q - factor measurement, the power receiving device 102 stores "1" in the short - circuit ability bit. Otherwise, "0" is stored. The measurement ability bit is information indicating whether the power receiving device 102 can perform the measurement of the second Q - factor of the power receiving circuit. For example, if the own device has the ability to measure the second Q - factor of the power receiving circuit, the power receiving device 102 stores "1" in the measurement ability bit. Otherwise, "0" is stored. Note that this information may be information indicating whether the power receiving device 102 can perform a predetermined process associated with the foreign object determination based on the second Q - factor measurement performed by the power transmitting device 100. That is, whether to form a closed circuit or whether to perform the measurement of the second Q - factor of the power receiving circuit is merely a predetermined process, and information bits related to processes other than these can be transmitted from the power receiving device 102 to the power transmitting device 100.

[0085] Figure 13Shows the configuration of the configuration package of the WPC standard v1.2.3. Note that the description of the parts not relevant to this embodiment will be omitted here. The configuration package of the WPC standard v1.2.3 includes multiple reserved regions. That is, the region 1300 from bit 0 to bit 7 of Bank 1, the region 1301 from bit 4 to bit 6 of Bank 2, and the region 1302 from bit 0 to bit 2 of Bank 4 are reserved regions. In this embodiment, as an example, the short-circuit capability bit is arranged in bit 2 of Bank 4, and the measurement capability bit is arranged in bit 1 of Bank 4. Note that these bits can be arranged in other reserved regions. Instead of these bits, information indicating the version of the WPC standard, etc. can be arranged in the reserved region. In this case, the version can indicate whether the power receiving device 102 can be controlled to form a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for the second Q-factor measurement, and whether the power receiving device 102 can perform the measurement of the second Q-factor of the power receiving circuit. For example, it can be defined that in a future version of the WPC standard, it is essential for the power receiving device 102 compliant with this version to have these functions. In this case, if the version information of the power receiving device 102 is notified through the configuration package, the power transmitting device 100 can specify whether the power receiving device 102 has these functions. Note that in the WPC standard v1.2.3, all bits of the above-mentioned reserved regions are 0. In addition, the power transmitting device 100 that cannot use the third foreign object detection method ignores the values stored in these reserved regions.

[0086] Note that the case where the short-circuit capability bit and the measurement capability bit are set in the configuration package and sent from the power receiving device 102 to the power transmitting device 100 will be described here. However, the present invention is not limited to this. For example, this information can be included in a new package not defined by the WPC standard and sent / received. Alternatively, this information can be included in other packages defined by the WPC standard and sent / received.

[0087] In this embodiment, the following is assumed: The power receiving device 102 can be controlled to form a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for the second Q-factor measurement, and the power receiving device 102 can perform the measurement of the second Q-factor of the power receiving circuit. Therefore, in F623, the power receiving device 102 sends a configuration package with "1" set in the short-circuit capability bit and also "1" set in the measurement capability bit. The power transmitting device 100 refers to the short-circuit capability bit and the measurement capability bit included in the received configuration package and stores these values in the memory 305.

[0088] After receiving the configuration packet, the power transmission device 100 responds with an ACK (F606). When receiving the ACK for the configuration packet, the power reception device 102 transitions to the negotiation phase. In the negotiation phase, the power transmission device 100 and the power reception device 102 conduct negotiation related to the third foreign object detection. In the second Q-factor measurement, the power reception device 102 negotiates the measurement start time, which is the time until the power transmission unit 302 of the power transmission device 100 stops power transmission. This negotiation is completed by the power reception device 102 sending a packet storing the requested measurement start time in a specific request defined by the WPC standard to the power transmission device 100 (F631). The power reception device 102 determines the value of the requested measurement start time based on its own processing capacity and sends a packet storing the value of the measurement start time to the power transmission device 100. Here, this packet will be referred to as "SRQ(M1)". The power transmission device 100 responds to SRQ(M1) considering its own device's processing capacity. When determining that the measurement start time indicated by SRQ(M1) can be accepted, the power transmission device 100 sends an ACK. When determining that the measurement start time cannot be accepted, the power transmission device 100 sends a NAK. Here, it is assumed that the power transmission device 100 determines that the measurement start time can be accepted and sends an ACK (F632). Note that here, as an example, it is assumed that the power reception device 102 requests 50 ms as the Q-factor measurement start time in SRQ(M1).

[0089] The power reception device 102 negotiates the window length, which is the length of the interval during which the power transmission unit 302 of the power transmission device 100 stops power transmission in the second Q-factor measurement (the interval from time T0 to time T5). This negotiation is completed by the power reception device 102 sending a packet storing the value of the requested window length in a specific request defined by the WPC standard to the power transmission device 100 (F633). Here, this packet will be referred to as "SRQ(M2)". The power reception device 102 determines the value of the window length based on its own device's processing capacity and sends a packet storing the determined value of the window length to the power transmission device 100. The power transmission device 100 responds to SRQ(M2) considering its own device's processing capacity. When determining that the window length indicated by SRQ(M2) can be accepted, the power transmission device 100 sends an ACK. When determining that the window length cannot be accepted, the power transmission device 100 sends a NAK. Here, it is assumed that the power transmission device 100 determines that the window length can be accepted and sends an ACK (F634). Note that here, as an example, it is assumed that the power reception device 102 requests 100 ms as the window length in SRQ(M2).

[0090] In addition, the power receiving device 102 negotiates the timeout length, which is the duration for 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 value of the requested timeout length in a specific request defined by the WPC standard to the power transmitting device 100 (F635). Here, this packet will be referred to as "SRQ (M3)". The power receiving device 102 determines the value of the timeout length based on the processing capacity of its own device, and sends a packet storing the determined value of the timeout length to the power transmitting device 100. The power transmitting device 100 responds to the SRQ (M3) considering the processing capacity of its own device. When it determines that the timeout length is acceptable, the power transmitting device 100 sends an ACK. When it determines that the timeout length is unacceptable, the power transmitting device 100 sends a NAK. Here, it is assumed 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 power receiving device 102 requests 500 ms as the timeout length in the SRQ (M3).

[0091] Here, in the example, a type (Type) not defined by v1.2.3 in the specific request can be assigned to the negotiation of the measurement start time, window length, and timeout length. The Measure Delay Req is a packet requesting the power transmitting device 100 to change the measurement start time. The Window Length Req is a packet requesting the power transmitting device 100 to change the window length. The Timeout Req is a packet requesting the power transmitting device 100 to change the timeout length. These three packets are reserved packets, and their 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 0x40 is defined as the Measure Delay Req packet. Similarly, the packet with a packet header of 0x41 is defined as the Window Length Req packet, and the packet with a packet header of 0x42 is defined as the Timeout Req packet.

[0092] Alternatively, among the packets defined by the WPC standard v1.2.3, packets that are not specific requests or general requests and whose types are not defined can be defined as the above three packets. For example, reserved packets or proprietary packets whose packet types are not defined, rather than specific requests or general requests, can be defined as the above three packets. In addition, among the general requests or specific requests defined by the WPC standard v1.2.3, packets whose packet types are not defined can be defined as the above three packets. That is, among the general requests or specific requests, reserved packets or proprietary packets whose packet types are not defined can be defined as the above three packets.

[0093] Return reference Figure 6B, if the processing from F607 to F612 is executed during the negotiation phase, the negotiation phase ends and the phase transitions to the power transmission phase. During the power transmission phase, the above-described processing from F613 to F617 is executed. Here, it is assumed that a foreign object is placed on the operation volume immediately after the power receiving device 102 receives an analog Ping in F618. The power receiving device 102 sends a CE for requesting the power transmission device 100 to maintain the power transmission power and an RP0 storing the current received power value to the power transmission device 100 (F619 and F620).

[0094] When receiving the RP0 from the power receiving device 102, the power transmission device 100 performs foreign object detection based on the above-described second foreign object detection method. The power transmission device 100 determines that there is a high possibility of a foreign object as a result of the foreign object detection and sends a NAK to the power receiving device 102 (F624). When receiving the NAK from the power transmission device 100, in order to more specifically measure the presence or absence of a foreign object, the power receiving device 102 sends a Q2R (F625) to the power transmission device 100. The Q2R is a packet for requesting the start of a third foreign object detection. The Q2R packet is a packet in which a value indicating the Q2R packet is set in a reserved bit of a reserved power packet in the WPC standard, for example. However, the present invention is not limited thereto. For example, the power receiving device 102 may use a mode in which a reserved power packet is not defined to request the start of a third foreign object detection, or may request the start of a third foreign object detection by defining a new packet. In this embodiment, a case where the power receiving device 102 requests the start of a third foreign object detection using the Q2R packet is described. However, the third foreign object detection may be started based on a NAK response for RP2 without using the Q2R packet.

[0095] When receiving Q2R, the power transmission device 100 determines whether to perform the third foreign object detection. When it is determined to perform, the power transmission device 100 sends an ACK to the power reception device 102. When it is determined not to perform, the power transmission device 100 sends a NAK to the power reception device 102. Here, it is assumed that the power transmission device 100 determines to perform the third foreign object detection. In this case, the power transmission device 100 sends an ACK (F626) to the power reception device 102. If the transmission of the ACK is completed, the power transmission device 100 and the power reception device 102 start the third foreign object detection. In the third foreign object detection, the power transmission device 100 and the power reception device 102 measure the second Q factors (F629 and F630). After the measurement of the second Q factor, the power reception device 102 stores the second Q factor measured by its own device in a packet (QRS) and sends the QRS to the power transmission device 100 (F627). Note that the QRS is a packet including at least the second Q factor measured by the power reception device 102, but may also include other information such as the current received power value. When receiving the QRS from the power reception device 102, the power transmission device 100 determines the presence or absence of a foreign object based on the second Q factor of the power reception device 102 received and the second Q factor measured by its own device. By using the second Q factor measured by the power reception device 102 in addition to the second Q factor measured by the power transmission device 100 to determine the presence or absence of a foreign object, the presence or absence of a foreign object can be determined more accurately. When it is determined that there is a foreign object, the power transmission device 100 sends a NAK to the power reception device 102. When it is determined that there is no foreign object, the power transmission device 100 sends an ACK to the power reception device 102. Here, it is assumed that the power transmission device 100 determines that there is a foreign object. In this case, the power transmission device 100 sends a NAK (F628) to the power reception device 102. After that, the power transmission device 100 stops power transmission.

[0096] (Process of the third foreign object detection process using the power transmission device 100)

[0097] Next, an example of the process of the third foreign object detection process using the power transmission device 100 will be described with reference to Figure 7 After receiving the third foreign object detection request, the power transmission device 100 determines whether the power reception device 102 can be controlled to form a closed circuit including the power reception coil 201 and the resonant capacitor 207 for the second Q factor measurement (step S701). For example, the power transmission device 100 refers to the short-circuit ability bit stored in the memory in the configuration phase. If the value is 1, the power transmission device 100 determines that the control can be performed ("Yes" in step S701), and advances the process to step S702. On the other hand, if the value of the short-circuit ability bit is 0, the power transmission device 100 determines that the control cannot be performed ("No" in step S701), sends a NAK (step S708), and ends the process.

[0098] In step S702, the power transmission device 100 determines whether the power reception device 102 can measure the second Q factor of the power reception circuit. The power transmission device 100 refers to, for example, the measurement ability bit stored in the memory during the configuration phase. If the value is 0, the power transmission device 100 determines that the second Q factor cannot be measured ("No" in step S702), and advances the process to step S709. Then, the power transmission device 100 measures the second Q factor in its own device (step S709), and advances the process to step S706. On the other hand, if the value of the measurement ability bit is 1, the power transmission device 100 determines that the second Q factor can be measured ("Yes" in step S702), and advances the process to step S703.

[0099] In step S703, the power transmission device 100 determines whether to measure the second Q factor of the power transmission circuit by its own device. When it is determined that the second Q factor is to be measured by its own device ("Yes" in step S703), the power transmission device 100 performs the measurement of the second Q factor (step S704), and advances the process to step S705. On the other hand, when it is determined that the second Q factor is not to be measured by its own device ("No" in step S703), the power transmission device 100 advances the process to step S705 without performing the measurement of the second Q factor. In step S705, the power transmission device 100 receives the second Q factor from the power reception device, and advances the process to step S706. At this time, if the second Q factor cannot be received from the power reception device until the timeout length time has elapsed after the ACK is sent in F626, the power transmission device 100 ends the process and stops power transmission. By setting the timeout length, if the second Q factor is not sent from the power reception device 102, the process can be appropriately advanced or stopped. In addition, at this time, if an appropriate timeout length according to the processing ability of the power reception device 102 is determined and set through negotiation as described above, even a power reception device 102 with low processing ability can complete the transmission of the second Q factor before the timeout.

[0100] In step S706, the power transmission device 100 determines the presence or absence of a foreign object using at least one of the second Q factor measured in step S704 and the second Q factor received in step S705. When it is determined that a foreign object is present ("Yes" in step S706), the power transmission device 100 sends a NAK to the power reception device 102 (step S708). On the other hand, when it is determined that no foreign object is present ("No" in step S706), the power transmission device 100 sends an ACK to the power reception device 102 (step S707) and ends the process.

[0101] In reference Figure 7In the described processing example, in step S701, the power transmission device 100 confirms that the value of the short-circuit capability bit is 1, determines that the power reception device 102 can perform control to form a closed circuit, and advances the processing to step S702. In step S702, the power transmission device 100 confirms that the value of the measurement capability bit is 1, determines that the power reception device 102 can measure the second Q factor, and advances the processing to step S703. In step S703, the power transmission device 100 also decides to measure the second Q factor by its own device and advances the processing to step S704. The power transmission device 100 measures the second Q factor by its own device in step S704, receives the second Q factor measured by the power reception device 102 in step S705, and advances the processing to step S706. Next, in step S706, using the second Q factor received from the power reception device 102 and the second Q factor measured by its own device, the power transmission device 100 determines that there is a foreign object. In step S708, the power transmission device 100 sends a NAK to the power reception device 102 and ends the processing.

[0102] In Figure 7 In the processing shown, in step S701, the power transmission device 100 determines whether the power reception device 102 can perform control to form a closed circuit, thereby preventing the power reception device 102 that cannot perform such control from measuring the second Q factor. As a result, the power transmission device 100 can prevent incorrect control from being performed by measuring the Q factor under inappropriate conditions.

[0103] Note that in this embodiment, when it is determined in step S701 that the power reception device 102 cannot perform control to form a closed circuit, the power transmission device 100 sends a NAK and ends the processing. However, the present invention is not limited to this. For example, the power transmission device 100 can measure the second Q factor in a state where the power reception device 102 does not form a closed circuit and determine the presence or absence of a foreign object based on the measured second Q factor. However, if the second Q factor is measured in a state where the closed circuit is not formed, it is assumed that the measured value is affected by changes in the load in the power reception device. For this reason, if such a second Q factor measurement is used, a different criterion from the criterion for determining the presence or absence of a foreign object based on the measurement result of the second Q factor in the case where a closed circuit can be formed is used to determine the presence or absence of a foreign object.

[0104] In addition, in step S702, the power transmission device 100 determines whether the power reception device 102 has the ability to measure the second Q factor of the power transmission circuit. Therefore, the power transmission device 100 can prevent the foreign object detection process from failing because although the power reception device 102 cannot measure the second Q factor, its own device does not measure the second Q factor. In addition, it is possible to prevent the power transmission device 100 from unnecessarily waiting for the measurement result of the second Q factor sent from the power reception device 102 although the power reception device 102 cannot measure the second Q factor. Further, in the case where the power reception device 102 can measure the second Q factor, the power transmission device 100 can prevent the occurrence of a state deviation, and the power transmission device 100 does not receive the second Q factor sent from the power reception device 102.

[0105] In addition, in step S704, in addition to the power reception device 102, the power transmission device 100 also measures the second Q factor by its own device, thereby performing accurate foreign object detection with little noise influence. Further, in step S703, the power transmission device 100 decides not to measure the second Q factor by its own device, thereby omitting the measurement of the second Q factor of its own device and using the second Q factor received from the power reception device 102 to determine a foreign object. This can suppress unnecessary measurements that occur because the power transmission device 100 and the power reception device 102 measure the Q factor simultaneously.

[0106] (Process of the third foreign object detection process using the power reception device 102)

[0107] Next, with reference to Figure 8An example of the process of the third foreign object detection process using the power receiving device 102 is described. The power receiving device 102 determines whether the power receiving device 102 can perform control to form a closed circuit including the power receiving coil 201 and the resonance capacitor 207 for the second Q factor measurement (step S801). When it is determined that the control to form the closed circuit can be performed (\"Yes\" in step S801), the power receiving device 102 advances the process to step S802. When it is determined that the control to form the closed circuit cannot be performed (\"No\" in step S801), the power receiving device 102 advances the process to step S805. In step S802, the power receiving device 102 determines whether its own device 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 advances the process to step S803. If the second Q factor cannot be measured (\"No\" in step S802), the power receiving device 102 advances the process to step S805. In step S803, the power receiving device 102 measures the second Q factor. Thereafter, in step S804, the power receiving device 102 sends the Q factor measured in step S803 to the power transmitting device 100, and advances the process to step S805. In step S805, the power receiving device 102 receives the result of the foreign object detection from the power transmitting device 100, and ends the process.

[0108] In the process example described with reference to Figure 8 In step S801, the power receiving device 102 determines that it can perform control to form a closed circuit including the power receiving coil 201 and the resonance capacitor 207 for the second Q factor measurement. In addition, in step S802, the power receiving device 102 determines that its own device can measure the second Q factor of the power receiving circuit. Then, the power receiving device 102 executes the processes of steps S803 to S805, and ends Figure 8 the process shown.

[0109] (Process of the second Q factor measurement process using the power transmitting device 100)

[0110] Reference will be made to Figure 9Describe an example of the process of performing the second Q-factor measurement process using the power transmission device 100 in the above step S704 or S709. For example, after the transmission of ACK is completed in F626 (the transmission of the trailing edge in the time domain of ACK is completed), the power transmission device 100 stops power transmission for 50 ms, which is the value negotiated in the negotiation at the measurement start time (step S901). The power transmission device 100 measures the voltage value A3 of the power transmission coil at time T3 (step S902), and measures the voltage value A4 of the power transmission coil at time T4 (step S903). The power transmission device 100 calculates the Q factor based on the operating frequency, the measurement time, and the voltage value in the above manner (step S904). Then, the power transmission device 100 resumes power transmission after 100 ms or more of the value negotiated in the negotiation as the window length has elapsed since the power transmission stopped in step S901 (step S905), and ends the process.

[0111] (Process of the second Q-factor measurement process using the power receiving device 102)

[0112] Refer to Figure 10 Describe an example of the process of performing the second Q-factor measurement process using the power receiving device 102 in step S803. After the reception of ACK is completed in F626 (the reception of the trailing edge in the time domain of ACK is completed), the power receiving device 102 detects that the power transmission stops within 50 ms, which is the value negotiated in the negotiation at the measurement start time. The power receiving device 102 performs control 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 measures 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 value negotiated in the negotiation as the window length has elapsed since the power transmission stop detected in step S1001 (step S1005), and ends the process. Note that the load is reconnected by disconnecting the switch 208.

[0113] Figures 7 to 10 The processes shown can be implemented, for example, by the control unit 300 of the power transmission device 100 or the control unit 200 of the power receiving device 102 reading a pre-stored program and executing the program. However, the present invention is not limited thereto, and at least a part of the processes can be implemented by hardware. When the processes are implemented by hardware, for example, a dedicated circuit can be automatically generated on an FPGA according to a program configured to implement the process steps using a predetermined compiler. Here, FPGA is an abbreviation for Field Programmable Gate Array. In addition, similarly to an FPGA, a gate array circuit can be formed to implement the hardware configured to execute at least a part of the above processes.

[0114] In this embodiment, since the measurement start time is negotiated in advance, the power receiving device 102 can identify the timing at which the power transmission device 100 stops power transmission, and can appropriately start the second Q factor measurement. At this time, since an appropriate measurement start time is set through negotiation of the measurement start time according to the processing performed by the power receiving device 102 or its processing ability, the second Q factor measurement can be started at a timing suitable for the power receiving device 102. For example, if the power receiving device 102 needs to transmit other packets near the time of performing 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 can avoid an instantaneous disconnection of power transmission for the second Q factor measurement during the transmission of other packets by the power receiving device 102, and prevent deterioration of power transmission efficiency. If it takes time for the power receiving device 102 to start the second Q factor measurement due to the hardware configuration or processing ability of the power receiving device 102, the measurement start time is determined to be a later timing according to the ability of the power receiving device 102. This enables the power transmission device 100 to stop power transmission at a timing when, for example, the power receiving device 102 has completed the formation of a closed circuit and can start the second Q factor measurement process.

[0115] In addition, in this embodiment, since the window length is negotiated in advance, the power receiving device 102 can reconnect the power receiving coil 201 to the load at an appropriate timing. That is, if power transmission is restored while a closed circuit is being formed in the power receiving device 102, an overcurrent may flow through the power receiving coil 201 and the resonance capacitor 207. On the other hand, in this embodiment, since the window length is determined in advance through negotiation, such a situation can be prevented. In addition, the time required for the second Q factor measurement may vary according to the performance of the power receiving device 102 or the requested measurement accuracy. On the other hand, the power receiving device 102 according to this embodiment negotiates the window length according to the performance of its own device or the requested measurement accuracy, thereby ensuring sufficient measurement time and preventing measurement failure or reduction in measurement accuracy.

[0116] Note that in the above description, all the measurement start timing, the measurement period length, and the period (timeout time) until the second Q factor measurement report in the power receiving device are determined through 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. That is, these elements can be used independently, and it is not always necessary to use all of these elements.

[0117] (Other embodiments)

[0118] The present invention can also be implemented by supplying, via a network or a storage medium, a program for implementing one or more functions in the above-described exemplary embodiments to a system or a device, and causing one or more processors in a computer of the system or the device to read and execute the program. The present invention can also be implemented by a circuit (e.g., ASIC) for implementing one or more functions.

[0119] 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 appended claims are made to inform the public of the scope of the present invention.

[0120] This application claims priority to Japanese Patent Application No. 2020-064204 filed on Mar. 31, 2020, the entire contents of which are incorporated herein by reference.

Claims

1. A power transmission device, comprising: A power transmission component for wirelessly transmitting power to a power receiving device via a power transmission coil; A communication component for communicating with the power receiving device; A measurement component for measuring the Q factor of the power transmission coil during the stage of transmitting power from the power transmission device to the power receiving device; A determination component for determining the presence or absence of an object different from the power receiving device based on the Q factor of the power transmission coil; And A control component for controlling whether to perform a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil, based on information indicating whether the power receiving device can perform a predetermined process associated with the determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil, where the information is received by the communication component from the power receiving device, wherein, based on information indicating that the power receiving device cannot perform the predetermined process, the control component controls not to perform a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil.

2. The power transmission device according to claim 1, wherein, Based on information indicating that the power receiving device can perform the predetermined process, the control component controls to perform a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil.

3. The power transmission device according to claim 1, wherein, The predetermined process is a process for forming a closed circuit by a power receiving coil and a resonant capacitor in the power receiving device.

4. The power transmission device according to claim 1, wherein, The information further indicates whether the power receiving device has the ability to measure the Q factor of the power receiving coil of the power receiving device.

5. The power transmission device according to claim 4, wherein, Based on information indicating that the power receiving device does not have the ability to measure the Q factor of the power receiving coil of the power receiving device, the control component controls to perform a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil.

6. The power transmission device according to claim 4, wherein, When the information indicates that the power receiving device has the ability to measure the Q factor of the power receiving coil of the power receiving device, the communication component receives the measurement result of the Q factor of the power receiving coil.

7. The power transmission device according to claim 6, wherein, When the information indicates that the power receiving device does not have the ability to measure the Q factor of the power receiving coil of the power receiving device, the communication component does not perform a process for receiving the measurement result of the Q factor of the power receiving coil.

8. The power transmission device according to claim 6, wherein, The determination component is configured to be able to perform a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil, a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmission coil and the measurement result of the Q factor of the power receiving coil received from the power receiving device, and a determination of the presence or absence of an object different from the power receiving device based on the measurement result of the Q factor of the power receiving coil received from the power receiving device rather than based on the measurement of the Q factor of the power transmission coil.

9. The power transmission device according to claim 8, wherein, Based on information indicating that the power receiving device has the ability to measure the Q factor of the power receiving coil of the power receiving device, the control component performs control to execute a determination of the presence or absence of an object different from the power receiving device based on the measurement result of the Q factor of the power transmitting coil and the Q factor of the power receiving coil.

10. The power transmission device according to claim 8, wherein, Based on information indicating that the power receiving device has the ability to measure the Q factor of the power receiving coil of the power receiving device, the control component performs control to execute a determination of the presence or absence of an object different from the power receiving device based on the measurement result of the Q factor of the power receiving coil received from the power receiving device rather than based on the measurement of the Q factor of the power transmitting coil.

11. The power transmission device according to claim 1, wherein, The information is represented by a value indicating a version in the standard of the Wireless Power Consortium.

12. The power transmission device according to claim 1, wherein, The information is included in and received from a configuration packet in the standard of the Wireless Power Consortium.

13. The power transmission device according to claim 1, wherein, The communication component performs communication for negotiating with the power receiving device regarding the measurement start time of the measurement component.

14. The power transmission device according to claim 1, wherein, The communication component performs communication for negotiating with the power receiving device regarding the time length from the start to the end of the measurement by the measurement component.

15. The power transmission device according to claim 6, wherein, The communication component performs communication for negotiating with the power receiving device regarding the period for receiving the measurement result of the Q factor of the power receiving coil of the power receiving device.

16. A computer-readable storage medium storing a program configured to cause a computer to function as the power transmitting device according to any one of claims 1 to 15.

17. A control method executed by a power transmitting device that can wirelessly transmit power to a power receiving device via a power transmitting coil and can communicate with the power receiving device, wherein the power transmitting device is configured to be able to measure the Q factor of the power transmitting coil in a stage for performing power transmission from the power transmitting device to the power receiving device, and determine the presence or absence of an object different from the power receiving device based on the Q factor of the power transmitting coil, and the control method includes: receiving from the power receiving device information indicating whether the power receiving device can execute a predetermined process associated with determining the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmitting coil; and controlling, based on the information, whether to execute a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmitting coil, wherein the power transmitting device, based on information indicating that the power receiving device cannot execute the predetermined process, performs control not to execute a determination of the presence or absence of an object different from the power receiving device based on the measurement of the Q factor of the power transmitting coil.

18. A computer program product including a program configured to cause a computer to function as the power transmitting device according to any one of claims 1 to 15.

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