Power receiving device, power transmitting device, wireless power transmission method, and program

Abstract

To make it possible to more quickly perform re-detection processing, according to a result of detection processing for detecting an object different from a power transmitting device and a power receiving device.SOLUTION: A power receiving device 401 includes: a coil 205 that wirelessly receives power from a power transmitting device; a communication unit 204 that transmits at predetermined intervals a signal for executing detection processing for detecting an object different from the power transmitting device and the power receiving device, based on values of voltage or current at at least two time points during a predetermined time period during which the power transmitting device restricts transmission, and receives, from the power transmitting device, a response signal that includes a detection result based on the detection processing executed according to the transmitted signal; and a control unit 201 that performs control so that the signal is transmitted at intervals shorter than the predetermined intervals when the detection result included in the received response signal satisfies a predetermined condition.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In recent years, technical development of wireless power transmission systems has been widely carried out. Patent Document 1 discloses a method of foreign object detection in the Wireless Power Consortium standard (WPC standard). Patent Document 2 discloses a foreign object detection method for detecting the presence of an object (hereinafter referred to as a foreign object) different from a power receiving device and a power transmitting device based on a change in energy attenuation or a change in resonance frequency of a power transmitting coil and a resonance circuit integrated or coupled with the power transmitting coil. Patent Document 3 discloses a foreign object detection method in which a power transmitting device transmits a signal for foreign object detection to a power receiving device and determines the presence or absence of a foreign object using an echo signal from the power receiving device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-70074 A [Patent Document 2] Special Publication No. 2018-512036 [Patent Document 3] JP 2015-27172 A Summary of the Invention [Problem to be solved by the invention]

[0004] In wireless power transmission, when it is determined that a foreign object is present, the power transmitting device stops power transmission, thereby suppressing the possibility of the foreign object generating heat due to power transmission to the foreign object. In addition, the foreign object detection process is assumed to be performed in response to a predetermined signal received by the power transmitting device from the power receiving device. However, depending on the result of the foreign object detection process, there may be cases where it is not clear whether or not a foreign object is present. In this case, there is a problem that the possibility of the foreign object generating heat due to continued power transmission increases, or power transmission is stopped even when no foreign object is present, resulting in a decrease in power transmission efficiency.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to enable a re-detection process to be performed more quickly depending on the results of a detection process for detecting an object other than a power transmitting device and a power receiving device. [Means for solving the problem]

[0006] A power receiving device according to the present disclosure includes a power receiving means for wirelessly receiving power from a power transmitting device, a transmitting means for transmitting packets including information on received power at time intervals in a power transfer phase, a receiving means for receiving a response to the packets from the power transmitting device, and a control means for switching to a first mode if the received response is a predetermined response, and for switching to a second mode if the received response is not the predetermined response, wherein the packets are transmitted at a first time interval in the first mode, and the packets are transmitted at a second time interval in the second mode, and the first time interval is shorter than the second time interval. The predetermined response is a response including information indicating that the probability of the presence of a foreign object is higher than a threshold and lower than another threshold higher than the threshold. . Effect of the Invention

[0007] According to the present disclosure, a detection process is performed again more quickly depending on the result of the detection process for detecting an object other than the power transmitting device and the power receiving device. [Brief description of the drawings]

[0008] [Figure 1]FIG. 2 is a diagram illustrating a configuration example of a power transmitting device. [Diagram 2] FIG. 2 is a diagram illustrating a configuration example of a power receiving device. [Diagram 3] 4 is a block diagram showing an example of a functional configuration of a control unit of the power transmitting device. FIG. [Figure 4] FIG. 1 is a diagram illustrating a configuration example of a wireless power transmission system. [Diagram 5] FIG. 11 is a diagram illustrating an example of a process for performing wireless power transmission. [Figure 6] 11A and 11B are diagrams for explaining foreign object detection by a waveform attenuation method. [Figure 7] 11A and 11B are diagrams for explaining a method of detecting a foreign object based on a power transmission waveform during power transmission. [Figure 8] 5 is a flowchart for explaining the operation of the power receiving device in the first embodiment. [Figure 9] 4 is a diagram for explaining the operation of a power receiving device and a power transmitting device in the first embodiment. FIG. [Figure 10] 10 is a flowchart for explaining the operation of a power receiving device in the second embodiment. [Figure 11] 11 is a diagram for explaining the operation of a power receiving device and a power transmitting device in the second embodiment. FIG. [Figure 12] 11 is a diagram for explaining a method of setting a threshold value in foreign object detection by the Power Loss method. FIG. [Figure 13] 11A and 11B are diagrams for explaining a method of setting a threshold value in foreign object detection using a waveform attenuation method. [Figure 14] FIG. 13 is a diagram for explaining a process when a plurality of waveform attenuation methods are performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Embodiment 1> Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Although the embodiments include a number of features, not all of these features are essential, and the features may be combined in any manner. In addition, in the accompanying drawings, the same reference numerals are used to refer to the same or similar features.

[0010] (Configuration of wireless power transmission system) FIG. 4 shows a configuration example of a wireless power transmission system (wireless charging system) in this embodiment. In one example, this system includes a power receiving device 401 and a power transmitting device 402. Detailed configurations of the power receiving device 401 and the power transmitting device 402 will be described later with reference to FIG. 2 and FIG. 1. In the following, the power receiving device 401 may be called RX401, and the power transmitting device 402 may be called TX402. The RX401 is an electronic device that receives power from the TX402 and charges an internal battery. The TX402 is an electronic device that wirelessly transmits power to the RX401 placed on a charging stand 403, which is a part of the TX402. Hereinafter, since the charging stand 403 is a part of the TX402, "placed on the charging stand 403" may be referred to as "placed on the TX402 (power transmitting device 402)". A range 404 surrounded by a dotted line is a range in which the RX401 can receive power from the TX402. In addition, the state of being “placed” does not necessarily mean that the RX 401 and the TX 402 are in contact with each other, but refers to a state in which the RX 401 is included in the range 404 .

[0011] In addition, RX401 and TX402 may have a function of executing applications other than wireless charging. An example of RX401 is an information processing terminal such as a smartphone, and an example of TX402 is an accessory device for charging the information processing terminal. For example, the information terminal device has a display unit (display) that displays information to a user and is supplied with power received from a receiving coil (antenna). Also, the power received from the receiving coil is stored in a power storage unit (battery), and power is supplied from the battery to the display unit. In this case, RX401 may have a communication unit that communicates with other devices different from TX402. The communication unit may be compatible with communication standards such as NFC communication and the fifth generation mobile communication system (5G). Also, in this case, the communication unit may perform communication by receiving power from the battery to the communication unit. Also, RX401 may have a function of notifying the remaining battery level. Also, RX401 may be a tablet terminal, or a storage device such as a hard disk device and a memory device, or an information processing device such as a personal computer (PC). The RX 401 may be, for example, an imaging device (such as a camera or a video camera). The RX 401 may be an image input device such as a scanner, or an image output device such as a printer, a copier, or a projector. The RX 401 may be a robot, a medical device, or the like. The TX 402 may be a device for charging the above-mentioned devices.

[0012] In addition, the TX 402 may be a smartphone. In this case, the RX 401 may be another smartphone or a wireless earphone.

[0013] Also, the RX401 in this embodiment may be a vehicle such as an automobile. For example, the automobile as the RX401 may receive power from a charger (TX402) via a power transmission antenna installed in a parking lot. Also, the automobile as the RX401 may receive power from the charger (TX402) via a power transmission coil (antenna) embedded in a road. In such an automobile, the received power is supplied to a battery. The power of the battery may be supplied to a driving unit (motor, electric unit) that drives the wheels, or may be used to drive a sensor used for driving assistance or a communication unit that communicates with an external device. That is, in this case, the RX401 may have a battery, a motor or sensor that is driven using the received power, and a communication unit that communicates with devices other than the TX402, in addition to the wheels.

[0014] Furthermore, the RX401 may have a storage unit for storing a person. For example, the sensor may be a sensor used to measure the distance between vehicles or the distance between other obstacles. The communication unit may be compatible with the Global Positioning System (GPS, Global Positioning Satellite). The communication unit may be compatible with communication standards such as the fifth generation mobile communication system (5G). The vehicle may be a bicycle or a motorcycle. The RX401 is not limited to a vehicle, and may be a moving object or an aircraft having a motor unit that is driven using power stored in a battery. The TX402 may be a charger installed in a console or the like in a vehicle, or may be a charging device that charges an electric vehicle. The RX102 may not have a built-in battery.

[0015] In addition, the RX 401 and the TX 402 in this embodiment perform processing based on the Wireless Power Consortium standard (WPC standard). Details of the processing will be described later.

[0016] (Configuration of power transmitting device 402 and power receiving device 401) Next, the configuration of the power transmitting device 402 (TX402) and the power receiving device 401 (RX401) in this embodiment will be described. Note that the configuration described below is merely an example, and a part (or in some cases, the whole) of the configuration described may be replaced with another configuration having a similar function or may be omitted, and further configuration may be added to the configuration described. Furthermore, one block described below may be divided into multiple blocks, or multiple blocks may be integrated into one block. Furthermore, although the functions of each functional block described below are implemented as a software program, some or all of the functional blocks included in this functional block may be implemented as hardware.

[0017] Fig. 1 is a functional block diagram showing an example of the configuration of the TX 402 according to this embodiment. The TX 402 has a control unit 101, a power supply unit 102, a power transmission unit 103, a communication unit 104, a power transmission antenna 105, a memory 106, a resonant capacitor 107, and a switch 108. In Fig. 1, the control unit 101, the power supply unit 102, the power transmission unit 103, the communication unit 104, and the memory 106 are depicted as separate entities, but any of a plurality of these functional blocks may be implemented in the same chip.

[0018] The control unit 101 controls the entire TX 402 by executing a control program stored in the memory 106, for example. The control unit 101 also controls power transmission control including communication for device authentication in the TX 402. The control unit 101 may also control the execution of applications other than wireless power transmission. The control unit 101 includes one or more processors, such as a central processing unit (CPU) or a microprocessor unit (MPU). The control unit 101 may also be configured with hardware such as an application specific integrated circuit (ASIC). The control unit 101 may also be configured with an array circuit such as a field programmable gate array (FPGA) compiled to execute a predetermined process. The control unit 101 stores information to be stored during the execution of various processes in the memory 106. The control unit 101 may also measure time using a timer (not shown).

[0019] The power supply unit 102 supplies power to each functional block. The power supply unit 102 is, for example, a commercial power supply or a battery. The battery stores power supplied from the commercial power supply.

[0020] The power transmitting unit 103 converts the DC or AC power input from the power supply unit 102 into AC frequency power in a frequency band used for wireless power transmission, and generates electromagnetic waves for receiving power in the RX 401 by inputting the AC frequency power to a power transmitting antenna (coil) 105. For example, the power transmitting unit 103 converts the DC voltage supplied by the power supply unit 102 into an AC voltage by a switching circuit in a half-bridge or full-bridge configuration using a FET (Field Effect Transistor). In this case, the power transmitting unit 103 includes a gate driver that controls ON / OFF of the FET.

[0021] The power transmitting unit 103 controls the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmission voltage) or current (power transmission current), or both, input to the power transmitting antenna 105. Increasing the power transmission voltage or power transmission current increases the intensity of the electromagnetic waves, and decreasing the power transmission voltage or power transmission current decreases the intensity of the electromagnetic waves. Furthermore, the power transmitting unit 103 performs output control of AC frequency power so that power transmission from the power transmitting antenna 105 is started or stopped based on an instruction from the control unit 101. Furthermore, the power transmitting unit 103 is assumed to have a capacity to supply enough power to output 15 watts (W) to the charging unit 206 of the power receiving device 401 (RX401) that complies with the WPC standard.

[0022] The communication unit 104 communicates with the RX401 for power transmission control based on the WPC standard. The communication unit 104 performs frequency shift keying on the electromagnetic waves output from the power transmitting antenna 105, transmits information to the RX401, and performs communication. The communication unit 104 also demodulates the electromagnetic waves transmitted from the power transmitting antenna 105 that have been amplitude modulated or load modulated by the RX401, and acquires information transmitted by the RX401. That is, the communication performed by the communication unit 104 is performed by superimposing a signal on the electromagnetic waves transmitted from the power transmitting antenna 105. The communication unit 104 may also communicate with the RX401 by communication based on a standard other than the WPC standard using an antenna other than the power transmitting antenna 105, or may selectively use multiple communications to communicate with the RX401. Examples of this communication standard include Bluetooth (registered trademark) Low Energy (BLE) and NFC (Near Field Communication).

[0023] The memory 106 can store the control program and also the states of the TX 402 and the RX 401 (transmitted power value, received power value, etc.). For example, the state of the TX 402 is acquired by the control unit 101, and the state of the RX 401 is acquired by the control unit 201 of the RX 401, and can be received via the communication unit 104.

[0024] The switch 108 is controlled by the control unit 101. The power transmitting antenna 105 is connected to the resonant capacitor 107, and when the switch 108 is turned on and short-circuited, the power transmitting antenna 105 and the resonant capacitor 107 form a series resonant circuit and resonate at a specific frequency f1. At this time, a current flows through a closed circuit formed by the power transmitting antenna 105, the resonant capacitor 107, and the switch 108. When the switch 108 is turned off and opened, power is supplied from the power transmitting unit 103 to the power transmitting antenna 105 and the resonant capacitor 107.

[0025] Fig. 2 is a block diagram showing an example of the configuration of a power receiving device 401 (RX401) according to this embodiment. The RX401 includes a control unit 201, a UI (user interface) unit 202, a power receiving unit 203, a communication unit 204, a power receiving antenna 205, a charging unit 206, a battery 207, a memory 208, a first switch unit 209, a second switch unit 210, and a resonance capacitor 211. Note that a plurality of functional blocks shown in Fig. 2 may be realized as one hardware module.

[0026] The control unit 201 controls the entire RX401 by executing a control program stored in the memory 208, for example. That is, the control unit 201 controls each functional unit shown in FIG. 2. Furthermore, the control unit 201 may perform control for executing applications other than wireless power transmission. An example of the control unit 201 includes one or more processors such as a CPU or an MPU. Note that the control unit 201 may control the entire RX401 (the entire smartphone when the RX401 is a smartphone) in cooperation with an OS (Operating System) being executed.

[0027] The control unit 201 may be configured with hardware such as an ASIC. The control unit 201 may be configured to include an array circuit such as an FPGA compiled to execute a predetermined process. The control unit 201 stores information to be stored during execution of various processes in the memory 208. The control unit 201 may measure time using a timer (not shown).

[0028] The UI unit 202 performs various outputs to the user. The various outputs referred to here include screen display, blinking or color changes of LEDs (Light Emitting Diodes), audio output from a speaker, vibration of the RX401 main body, etc. The UI unit 202 is realized by a liquid crystal panel, a speaker, a vibration motor, etc.

[0029] The power receiving unit 203 acquires AC power (AC voltage and AC current) generated by electromagnetic induction based on electromagnetic waves radiated from the power transmitting antenna 105 of the TX 402 through the power receiving antenna (coil) 205. The power receiving unit 203 then converts the AC power into DC or AC power of a predetermined frequency, and outputs the power to the charging unit 206 that performs processing for charging the battery 207. That is, the power receiving unit 203 includes a rectification unit and a voltage control unit that are necessary for supplying power to the load in the RX 401. The above-mentioned GP is the amount of power guaranteed to be output from the power receiving unit 203. The power receiving unit 203 is assumed to have the capacity to supply power for the charging unit 206 to charge the battery 207 and to output 15 watts of power to the charging unit 206.

[0030] The communication unit 204 communicates with the communication unit 104 of the TX402 for power reception control based on the WPC standard. The communication unit 204 demodulates the electromagnetic wave input from the power receiving antenna 205 to obtain information transmitted from the TX402. The communication unit 204 then performs amplitude modulation or load modulation on the input electromagnetic wave to superimpose a signal related to information to be transmitted to the TX402 on the electromagnetic wave, thereby communicating with the TX402. Note that the communication unit 204 may communicate with the TX402 using a communication standard other than the WPC standard using an antenna other than the power receiving antenna 205, or may selectively use multiple communications to communicate with the TX402. Examples of this communication standard include Bluetooth (registered trademark) Low Energy (BLE) and NFC (Near Field Communication).

[0031] The memory 208 stores the control program and also stores the states of the TX 402 and the RX 401. For example, the state of the RX 401 is acquired by the control unit 201, and the state of the TX 402 is acquired by the control unit 101 of the TX 402, and can be received via the communication unit 204.

[0032] The first switch unit 209 and the second switch unit 210 are controlled by the control unit 201. The power receiving antenna 205 is connected to the resonant capacitor 211, and when the second switch unit 210 is turned on and short-circuited, the power receiving antenna 205 and the resonant capacitor 211 form a series resonant circuit and resonate at a specific frequency f2. At this time, a current flows through a closed circuit formed by the power receiving antenna 205, the resonant capacitor 211, and the second switch unit 210, and no current flows through the power receiving unit. When the second switch unit 210 is turned off and opened, the power received by the power receiving antenna 205 and the resonant capacitor 211 is supplied to the power receiving unit 203.

[0033] The first switch unit 209 is for controlling whether or not the received power is supplied to the battery, which is a load. It also has a function of controlling the value of the load. When the first switch unit 209 connects the charging unit 206 and the battery 207, the received power is supplied to the battery 207. When the first switch unit 209 disconnects the connection between the charging unit 206 and the battery 207, the received power is not supplied to the battery 207. Note that the first switch unit 209 is disposed between the charging unit 206 and the battery 207 in FIG. 2, but may be disposed between the power receiving unit 203 and the charging unit 206. Alternatively, the first switch unit 209 may be disposed between the closed circuit formed by the power receiving antenna 205, the resonant capacitor 211, and the second switch unit 210, and the power receiving unit 203. In other words, the first switch unit 209 may be for controlling whether or not the received power is supplied to the power receiving unit 203. In addition, while first switch unit 209 is illustrated as one block in FIG. 2, first switch unit 209 can also be realized as part of charging unit 206 or as part of power receiving unit 203 .

[0034] Next, the function of the control unit 101 of the TX 402 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the functional configuration of the control unit 101 of the power transmitting device 402 (TX 402). The control unit 101 has a communication control unit 301, a power transmission control unit 302, a measurement unit 303, a setting unit 304, and a foreign object detection unit 305.

[0035] The communication control unit 301 performs control communication with the RX 401 based on the WPC standard via the communication unit 104. The power transmission control unit 302 controls the power transmitting unit 103 to control power transmission to the RX 401. The measurement unit 303 measures a waveform attenuation index, which will be described later. Also, the measurement unit 303 measures the power transmitted to the RX 401 via the power transmitting unit 103, and measures the average transmitted power per unit time. Also, the measurement unit 303 measures the Q value of the power transmitting antenna 105. The setting unit 304 sets a threshold value used for foreign object detection based on the waveform attenuation index measured by the measurement unit 303, for example, by a calculation process.

[0036] The foreign object detection unit 305 performs processing for detecting a foreign object within the power transmission range of the TX 402. Here, the foreign object in this embodiment refers to an object other than the power receiving device and the power transmitting device. The foreign object detection unit 305 can realize a foreign object detection function using a power loss method, a foreign object detection function using a Q value measurement method, and a foreign object detection function using a waveform attenuation method, which will be described later. The foreign object detection unit 305 may also have a function for performing foreign object detection processing using other methods. For example, NFC (Near Field Communication) iel In the TX402 having a NFC (Near Field Communication) communication function, the foreign object detection unit 305 may perform foreign object detection processing using a function for detecting an opposing device according to the NFC standard. In addition, the foreign object detection unit 305 can also detect changes in the state of the TX402 as a function other than detecting foreign objects. For example, the TX402 can detect an increase or decrease in the number of RX401 on the TX402.

[0037] The setting unit 304 sets a threshold value that is a reference for determining the presence or absence of a foreign object when the TX 402 detects a foreign object using the power loss method, the Q value measurement method, or the waveform attenuation method. The setting unit 304 may also have a function of setting a threshold value that is a reference for determining the presence or absence of a foreign object, which is necessary when performing foreign object detection processing using other methods. The foreign object detection unit 305 can perform foreign object detection processing based on the threshold value set by the setting unit 304 and the waveform attenuation index, transmission power, and Q value measured by the measurement unit 303.

[0038] The functions of the communication control unit 301, the power transmission control unit 302, the measurement unit 303, the setting unit 304, and the foreign object detection unit 305 are realized as programs that run in the control unit 101. Each processing unit is configured as an independent program, and can run in parallel while synchronizing the programs through event processing or the like. However, two or more of these processing units may be incorporated into one program.

[0039] In this embodiment, the RX401 and the TX402 perform wireless power transmission using an electromagnetic induction method for wireless charging based on the WPC standard. That is, the RX401 and the TX402 perform wireless power transmission for wireless charging based on the WPC standard between the power receiving antenna 205 of the RX401 and the power transmitting antenna 105 of the TX402. Note that the wireless power transmission method applied to this system is not limited to the method defined by the WPC standard, and may be a method using other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, lasers, etc. Also, in this embodiment, the wireless power transmission is used for wireless charging, but the wireless power transmission may be performed for purposes other than wireless charging.

[0040] In the WPC standard, the magnitude of power guaranteed to be output to a load (battery) of a power receiving device when the power receiving device receives power from a power transmitting device is specified by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates a power value that is guaranteed to be output to a load (e.g., a charging circuit, a battery, etc.) of RX401 even if the positional relationship between RX401 and TX402 fluctuates and the power transmission efficiency between the power receiving antenna 205 and the power transmitting antenna 105 decreases. For example, when GP is 5 watts, TX402 performs power transmission by controlling so as to output 5 watts to the load in RX401, even if the positional relationship between the power receiving antenna 205 and the power transmitting antenna 105 fluctuates and the power transmission efficiency decreases.

[0041] Furthermore, when transmitting power from the TX402 to the RX401, if a foreign object other than the RX401 is present near the TX402, there is a risk that the electromagnetic waves for transmitting power will affect the foreign object, raising the temperature of the foreign object or destroying the foreign object. Therefore, the WPC standard specifies a method for the TX402 to detect the presence of a foreign object on the charging base 403 so that the temperature rise and destruction of the foreign object can be prevented by stopping power transmission when the foreign object is present. Specifically, the power loss method is specified to detect a foreign object based on the difference between the power transmitted by the TX402 and the power received by the RX401. In addition, the Q-factor measurement method is specified to detect a foreign object based on a change in the quality factor (Q-factor) of the power transmitting antenna 105 in the TX402. Note that the foreign object detected by the TX402 in this embodiment is not limited to an object present on the charging base 403. The TX402 only needs to detect a foreign object located near the TX402, and may detect a foreign object located within a range where the TX402 can transmit power, for example.

[0042] (Processing based on WPC standards) The process based on the WPC standard performed by the RX401 and TX402 according to this embodiment will be described. The WPC standard specifies a number of phases including a power transfer phase in which power transfer is performed and one or more phases before the actual power transfer, and communication for necessary power transmission and reception control is performed in each phase. The phase before the power transfer may include a selection phase, a ping phase, an identification and configuration phase, a negotiation phase, and a calibration phase. In the following, the identification and configuration phase is called an I&C phase. The process of each phase will be described below.

[0043] In the Selection phase, the TX402 transmits Analog Pings intermittently to detect that an object has been placed on the charging stand of the TX402 (for example, that the RX401 or a conductor piece has been placed on the charging stand). The TX402 detects at least one of the voltage value and current value of the power transmitting antenna 105 when the Analog Ping is transmitted, and if the voltage value is below a certain threshold or the current value exceeds a certain threshold, it determines that an object is present and transitions to the Ping phase.

[0044] In the Ping phase, the TX402 transmits a Digital Ping with a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start the control unit of the RX401 placed on the TX402. The RX401 notifies the TX402 of the magnitude of the received voltage. In this way, the TX402 recognizes that the object detected in the Selection phase is the RX401 by receiving a response from the RX401 that received the Digital Ping. When the TX402 receives the notification of the received voltage value, it transitions to the I&C phase. In addition, the TX402 measures the Q value of the power transmitting antenna 105 before transmitting the Digital Ping. This measurement result is used when executing a foreign object detection process using the Q value measurement method.

[0045] In the I&C phase, the TX402 identifies the RX401 and obtains device configuration information (capability information) from the RX401. The RX401 transmits an ID packet and a configuration packet. The ID packet contains the identifier information of the RX401, and the configuration packet contains the device configuration information (capability information) of the RX401. Upon receiving the ID packet and the configuration packet, the TX402 responds with an acknowledgement (ACK, positive response). Then the I&C phase ends.

[0046] In the Negotiation phase, the GP value is determined based on the GP value requested by RX401 and the power transmission capability of TX402. TX402 also receives an FOD Status Packet containing information on the Reference Quality Factor Value from RX401, and adjusts and determines the threshold value in the Q-factor measurement method. Then, TX402 executes foreign object detection processing using the Q-factor measurement method according to the request from RX401. The WPC standard also specifies a method of once transitioning to the Power Transfer phase, and then performing the same processing as in the Negotiation phase again at the request of RX401. The phase transitioning from the Power Transfer phase and performing these processes is called the Renegotiation phase.

[0047] In the calibration phase, calibration is performed based on the WPC standard. In addition, the RX401 notifies the TX402 of a predetermined receiving power value (receiving power value in a light load state / receiving power value in a maximum load state), and the TX402 performs adjustments to transmit power efficiently. The receiving power value notified to the TX402 can be used for foreign object detection processing using the Power Loss method.

[0048] In the power transfer phase, control is performed for starting and continuing power transmission, and stopping power transmission due to an error or full charge. For this power transmission and reception control, the TX402 and the RX401 use the power transmitting antenna 105 and the power receiving antenna 205 to communicate by superimposing a signal on the electromagnetic wave transmitted from the power transmitting antenna 105 or the power receiving antenna 205. The range in which communication based on the WPC standard is possible between the TX402 and the RX401 is almost the same as the power transmission range of the TX402.

[0049] The above is an explanation of the processing performed by the RX401 and TX402 in this embodiment. In the following, the operations of the RX401 and TX402 in each of the above-mentioned phases will be explained using the sequence diagram of Fig. 5. Fig. 5 is a sequence diagram for power transmission according to the WPC standard. Here, the explanation will be given taking the power transmitting device 402 (TX402) and the power receiving device 401 (RX401) as examples.

[0050] The TX402 repeatedly and intermittently transmits Analog Pings of the WPC standard to detect objects present within the power transmission range (F501). The TX402 executes processes defined as the Selection phase and Ping phase of the WPC standard, and waits for the RX401 to be placed on it. The user of the RX401 brings the RX401 (e.g., a smartphone) close to the TX402 to charge the RX401 (F502). For example, the user places the RX401 on the TX402, thereby bringing the RX401 close to the TX402.

[0051] When the TX402 detects the presence of an object within the power transmission range using Analog Ping (F503, F504), it transmits a Digital Ping of the WPC standard (F505). When the RX401 receives the Digital Ping, it knows that the TX402 has detected the RX401 (F506). Furthermore, when there is a predetermined response to the Digital Ping, the TX402 determines that the detected object is the RX401 and that the RX401 has been placed on the charging stand 403. When the TX402 detects that the RX401 has been placed, it acquires identification information and capability information from the RX401 through communication in the I&C phase defined by the WPC standard (F507). Here, the identification information of the RX401 includes the Manufacturer Code and Basic Device ID. The capability information of the RX401 includes the following information: That is, the information includes an information element capable of identifying the version of the supported WPC standard, a Maximum Power Value that is a value that identifies the maximum power that the RX401 can supply to a load, and information indicating whether the RX402 has a negotiation function of the WPC standard. The TX402 may obtain the identification information and capability information of the RX401 by a method other than communication in the I&C phase of the WPC standard. The identification information may be any other identification information capable of identifying an individual unit of the RX401, such as a Wireless Power ID. The capability information may include information other than the above.

[0052] Next, TX402 determines the value of GP with RX401 through communication in the negotiation phase defined by the WPC standard (F508). Note that in F508, other procedures for determining GP may be executed, not limited to communication in the negotiation phase of the WPC standard. Also, when TX402 acquires information indicating that RX401 does not support the negotiation phase (for example, in F507), it may not perform communication in the negotiation phase. In this case, TX402 may set the value of GP to a small value (for example, predefined by the WPC standard). In this embodiment, GP=5 watts.

[0053] After determining the GP, the TX402 performs calibration based on the GP. In the calibration process, first, the RX401 transmits information (hereinafter referred to as first reference received power information) including the received power in a light load state (load disconnected state, or a load state in which the transmitted power is equal to or less than a first threshold) to the TX402 (F509). The first reference received power information in this embodiment is the received power information of the RX401 when the transmitted power of the TX402 is 250 milliwatts. The first reference received power information is the Received Power Packet (mode1) defined in the WPC standard, but other messages may be used. Note that Received Power Packet (mode1) is also referred to as "RP1" below. The TX402 determines whether or not to accept the first reference received power information based on the power transmission state of its own device. The TX402 transmits an acknowledgement (ACK) to the RX401 if it accepts, and a negative acknowledgement (NAK) if it does not accept.

[0054] Next, when RX401 receives an ACK from TX402 (F510), it performs processing for transmitting information (hereinafter referred to as second reference received power information) including the received power in a load connection state (maximum load state or a load state in which the transmitted power is equal to or greater than a second threshold) to TX402. In this embodiment, since GP is 5 watts, the second reference received power information is the received power information of RX401 when the transmitted power of TX402 is 5 watts. Here, the second reference received power information is Received Power Packet (mode 2) defined in the WPC standard, but other messages may be used. Note that Received Power Packet (mode 2) is also referred to as "RP2" below. RX401 transmits a transmission power output change request including a positive value to increase the transmitted power from TX402 to 5 watts (F511).

[0055] When the TX402 receives the above-mentioned transmission output change request and is able to increase the transmission power, it responds with an ACK and increases the transmission power (F512, F513). Since the second reference received power information is received power information when the transmission power of the TX402 is 5 watts, when the TX402 receives a power increase request exceeding 5 watts from the RX401 (F514), it responds with a NAK to the transmission output change request. This prevents the transmission of power above the specified level (F515).

[0056] When the RX401 determines that the predetermined transmission power has been reached by receiving a NAK from the TX402, it transmits information including the received power in the load-connected state to the TX402 as second reference received power information (F516). The TX402 is able to calculate the amount of power loss between the TX402-RX401 in the load-disconnected state and the load-connected state based on the transmission power value of the TX402 and the received power value included in the first and second reference received power information. In addition, by interpolating between these power loss amounts, it is possible to calculate an estimate of the power loss between the TX402-RX401 for all possible transmission powers of the TX402 (between 250 milliwatts and 5 watts in this case) (F517). The TX402 transmits an ACK in response to the second reference received power information from the RX401 (F518) and completes the calibration process.

[0057] When the TX402, which has determined that charging processing can be started, starts power transmission processing to the RX401, charging of the RX401 is started. Note that before starting power transmission processing, the TX402 and RX401 perform device authentication processing (F519), and if it is determined that the other device can support a higher GP, the GP may be reset to a higher value, for example, 15 watts (F520).

[0058] In this case, RX401 and TX402 increase the transmission power using a transmission power change request, ACK, and NAK to increase the transmission power of TX402 to 15 watts (F521 to F524). Then, TX402 and RX401 perform calibration processing again for GP=15 watts. Specifically, RX401 transmits information including the received power in the load-connected state of RX401 when the transmission power of TX402 is 15 watts (hereinafter referred to as third reference received power information) (F525). TX402 performs calibration based on the received power included in the first, second, and third reference received power information. This allows TX402 to calculate the amount of power loss between TX402 and RX401 for all possible transmission powers of TX402 (in this case, 250 milliwatts to 15 watts) (F526). The TX402 transmits an ACK in response to the third reference received power information from the RX401 (F527) and completes the calibration process. When the TX402 determines that charging can be started, it starts power transmission to the RX401 and transitions to the power transfer phase (F528). Note that the processes from F519 to F527 are not essential.

[0059] In the power transfer phase, the TX402 transmits power to the RX401. In addition, foreign object detection is performed using the power loss method. In the power loss method, the TX402 first calculates the amount of power loss between the TX402 and RX401 in a state where there is no foreign object, based on the difference between the power transmitted by the TX402 and the power received by the RX401, using the above-mentioned calibration. The calculated value corresponds to the reference amount of power loss in a normal state (a state where there is no foreign object) during power transmission processing. Then, the TX402 determines that there is a foreign object when the amount of power loss between the TX402 and RX401 measured during power transmission after calibration deviates from the amount of power loss in the normal state by a threshold value or more. A more detailed explanation of the power loss method will be given later.

[0060] The power loss method detects foreign objects based on the results of measuring power loss while transmitting power from the TX402 to the RX401. Foreign object detection using the power loss method has the disadvantage that the accuracy of foreign object detection decreases when the TX402 is transmitting large power, but has the advantage that foreign object detection can be performed while continuing power transmission, thereby maintaining high power transmission efficiency.

[0061] The above is the flow of processing based on the WPC standard. In the power transmission processing of F528, when power transmission is to be terminated because the battery of RX401 is fully charged, a foreign object is detected, or the like, RX401 transmits a power transmission stop request command to TX402 to request the TX402 to stop power transmission. In this embodiment, the power transmission stop request command is an EPT (End Power Transfer) command (packet). This ends the power transmission processing.

[0062] (Power Loss Method) Foreign object detection based on the power loss method defined in the WPC standard will be explained with reference to Fig. 12. The horizontal axis of Fig. 12 is the power transmitted by the TX 402, and the vertical axis is the power received by the RX 401. A foreign object is an object other than the RX 401 that may affect the power transmission from the TX 402 to the RX 401, such as a metal piece having electrical conductivity.

[0063] First, the TX402 transmits power to the RX401 at a first transmission power value Pt1. The RX401 receives power at a first reception power value Pr1 (this state is called a light load state). Then, the TX402 stores the first transmission power value Pt1. Here, the first transmission power value Pt1 or the first reception power value Pr1 is a predetermined minimum transmission power or reception power. At this time, the RX401 controls the received power to be the minimum power. For example, the RX401 may control the first switch unit 209 to disconnect the receiving antenna 205 from the load so that the received power is not supplied to a load (such as a charging circuit and a battery). Next, the RX401 notifies the TX402 of the power value Pr1 of the first reception power. Upon receiving Pr1 from RX401, TX402 calculates that the power loss between TX402 and RX401 is Pt1-Pr1 (Ploss1), and is able to create a calibration point 1200 (which indicates the correspondence between Pt1 and Pr1).

[0064] Next, the TX402 changes the transmission power value to the second transmission power value Pt2 and transmits power to the RX401. The RX401 receives power at the second receiving power value Pr2 (this state is called a connected load state). Then, the TX402 stores the second transmission power value Pt2. Here, the second transmission power value Pt2 or the second receiving power value Pr2 is a predetermined maximum transmission power or receiving power. At this time, the RX401 controls so that the received power becomes the maximum power. For example, the RX401 controls the first switch unit 209 to connect the receiving antenna 205 and the load so that the received power is supplied to the load. Next, the RX401 notifies the TX402 of Pr2. Upon receiving Pr2 from RX401, TX402 calculates that the power loss between TX402 and RX401 is Pt2-Pr2 (Ploss2), and is able to create a calibration point 1001 that indicates the correspondence between Pt2 and Pr2.

[0065] Then, the TX402 creates a straight line 1202 that linearly interpolates between the calibration point 1200 and the calibration point 1201. The straight line 1202 indicates the relationship between the transmitted power and the received power in a state where there is no foreign object near the TX402 and the RX401. Based on the straight line 1202, the TX402 can predict the power value that the RX401 receives when transmitting power at a predetermined transmitted power in a state where there is no foreign object. For example, when the TX402 transmits power at a third transmitted power value Pt3, it can be estimated from a point 1203 on the straight line 1202 that corresponds to Pt3 that the third received power value that the RX401 receives will be Pr3.

[0066] As described above, the power loss between the TX402 and RX401 according to the load can be obtained based on multiple combinations of the transmission power value of the TX402 and the reception power value of the RX401 measured while changing the load. In addition, the power loss between the TX402 and RX401 according to all loads can be estimated by interpolating from multiple combinations. In this way, the calibration process performed by the TX402 and RX401 for the TX402 to obtain combinations of the transmission power value and the reception power value is hereinafter referred to as "calibration process of the power loss method (CAL process)".

[0067] After the calibration, when the TX402 actually transmits power to the RX401 at Pt3, the TX402 receives a received power value Pr3' from the RX401. The TX402 calculates a value Pr3-Pr3' (=Ploss_FO) by subtracting the received power value Pr3' actually received from the RX401 from the received power value Pr3 in a state where no foreign object exists. This Ploss_FO can be considered as a power loss due to the power consumed by a foreign object when a foreign object exists near the TX402 and the RX401. Therefore, when the power Ploss_FO that would have been consumed by the foreign object exceeds a predetermined threshold, it can be determined that a foreign object exists. Alternatively, the TX402 calculates the power loss Pt3-Pr3 (Ploss3) between the TX402 and the RX401 in advance from the received power value Pr3 in a state where no foreign object exists. Next, the power loss Pt3-Pr3' (Ploss3') between the TX402 and the RX401 in the presence of a foreign object is calculated from the received power value Pr3' received from the RX401 in the presence of a foreign object. Then, the power Ploss_FO that would have been consumed by the foreign object may be estimated using Ploss3'-Ploss3 (=Ploss_FO).

[0068] As described above, the power Ploss_FO that would have been consumed by a foreign object may be calculated as Pr3-Pr3' (=Ploss_FO) or as Ploss3'-Ploss3 (=Ploss_FO). In the following specification, the method of calculating Ploss3'-Ploss3 (=Ploss_FO) will basically be described, but the contents of this embodiment are also applicable to the method of calculating Pr3-Pr3' (=Ploss_FO). This concludes the description of foreign object detection based on the Power Loss method.

[0069] After the straight line 1002 is acquired by the calibration process, the foreign object detection unit 305 of the TX402 periodically receives the current received power value (for example, the above Pr3') from the RX401 via the communication unit 104. The current received power value periodically transmitted by the RX401 is transmitted to the TX402 as a Received Power Packet (mode0). The foreign object detection unit 305 of the TX402 performs foreign object detection based on the received power value stored in the Received Power Packet (mode0) and the straight line 1002. Note that Received Power Packet (mode0) will be referred to as "RP0" below.

[0070] Foreign object detection using the Power Loss method is performed during power transmission (Power Transfer phase described below) based on data obtained in the Calibration phase described below. Foreign object detection using the Q-value measurement method is performed before power transmission (before sending a Digital Ping, Negotiation phase or Renegotiation phase described below).

[0071] During the power transfer phase in the WPC standard, foreign object detection is performed using the power loss method. However, foreign object detection using only the power loss method may result in erroneous detection of a foreign object or erroneous determination that there is no foreign object even though there is one. In particular, the power transfer phase is a phase in which the TX402 transmits power, and if there is a foreign object near the TX402 and the RX401 during power transmission, heat generation from the foreign object increases, so it is necessary to improve the accuracy of foreign object detection in this phase. Therefore, in this embodiment, in order to improve the accuracy of foreign object detection, a foreign object detection method other than the power loss method is considered.

[0072] (Foreign object detection method using waveform attenuation method) In the power transfer phase, the TX402 transmits power to the RX401. Therefore, if foreign object detection can be performed using the power transmission waveform (voltage waveform or current waveform) related to this power transmission, foreign object detection can be performed without using a newly defined foreign object detection signal or the like. A method of detecting foreign objects based on the attenuation state of a transmitted wave (hereinafter referred to as the waveform attenuation method) will be described with reference to FIG. 6. FIG. 6 is a diagram for explaining the principle of foreign object detection using the waveform attenuation method. Here, foreign object detection using a power transmission waveform related to power transmission from the TX402 (TX402) to the RX401 (RX401) will be described as an example.

[0073] In Fig. 6, the waveform shows the change over time in the voltage value 600 (hereinafter simply referred to as the voltage value) of the high frequency voltage applied to the power transmitting antenna 105 of the TX402. The horizontal axis of Fig. 6 represents time, and the vertical axis represents the voltage value. The TX402, which is transmitting power to the RX401 via the power transmitting antenna 105, limits the power transmission at time T0. That is, at time T0, the power supply for power transmission from the power supply unit 102 is limited. Note that limiting the power means stopping the power or reducing the power to a predetermined value or below.

[0074] The frequency of the transmitting wave for power transmission from the TX 402 is a predetermined frequency, for example, a fixed frequency between 85 kHz and 205 kHz used in the WPC standard. Point 601 is a point on the envelope of the high frequency voltage, and is a voltage value at time T1. (T1, A1) in the figure indicates that the voltage value at time T1 is A1. Similarly, point 602 is a point on the envelope of the high frequency voltage, and is a voltage value at time T2. (T2, A2) in the figure indicates that the voltage value at time T2 is A2. The quality factor (Q value) of this power transmitting antenna 105 can be obtained based on the time change of the voltage value after time T0. For example, the Q value is calculated by Equation 1 based on the time, voltage value, and frequency f of the high frequency voltage at points 601 and 602 on the envelope of the voltage value. Q = πf(T2-T1) / ln(A1 / A2) (Equation 1) When a foreign object is present near the TX402 and the RX401, the Q value decreases. This is because the presence of a foreign object causes a loss of energy due to the foreign object. Therefore, when focusing on the slope of the attenuation of the voltage value, the slope of the line connecting the points 601 and 602 becomes steeper and the attenuation rate of the waveform amplitude becomes higher when a foreign object is present than when there is no foreign object, because the foreign object causes a loss of energy compared to when there is no foreign object. In other words, the waveform attenuation method judges the presence or absence of a foreign object based on the attenuation state of the voltage value between the points 601 and 602, and it is possible to actually judge the presence or absence of a foreign object by comparing some numerical value that represents this attenuation state. For example, the judgment can be made using the above-mentioned Q value. A lower Q value means a higher waveform attenuation rate (a degree of reduction in the waveform amplitude per unit time). Alternatively, the judgment may be made using the slope of the line connecting the points 601 and 602, which is calculated from (A1-A2) / (T2-T1). Alternatively, if the time (T1 and T2) for observing the attenuation state of the voltage values ​​is fixed, the judgment can be made using the value of (A1-A2) representing the difference in the voltage values ​​or the value of the ratio of the voltage values ​​(A1 / A2). Alternatively, if the voltage value A1 immediately after the power transmission is stopped is constant, the judgment can be made using the value of the voltage value A2 after a predetermined time has elapsed. Alternatively, the judgment can be made using the value of the time (T2-T1) until the voltage value A1 reaches the predetermined voltage value A2.

[0075] As described above, the presence or absence of a foreign object can be determined by the attenuation state of the voltage value during the power transmission stop period, and there are multiple values ​​that represent the attenuation state. In this embodiment, the values ​​that represent these attenuation states are called "waveform attenuation indexes." For example, as described above, the Q value calculated by Equation 1 is a value that represents the attenuation state of the voltage value related to power transmission, and is included in the "waveform attenuation index." All waveform attenuation indexes are values ​​that correspond to the waveform attenuation rate. Note that in the waveform attenuation method, the waveform attenuation rate itself may be measured as the "waveform attenuation index." The following description will focus on the case where the waveform attenuation rate is used as the waveform attenuation index, but the contents of this embodiment can be applied to the case where other waveform attenuation indexes are used.

[0076] 6 is the current value flowing through the power transmitting antenna 105, the attenuation state of the current value during the power transmission stop period changes depending on the presence or absence of a foreign object, as in the case of the voltage value. When a foreign object is present, the waveform attenuation rate is higher than when no foreign object is present. Therefore, a foreign object can be detected by applying the above-mentioned method to the change over time in the current value flowing through the power transmitting antenna 105. That is, the Q value obtained from the current waveform, the slope of the attenuation of the current value, the difference in the current values, the ratio of the current values, the absolute value of the current values, the time until a predetermined current value is reached, and the like can be used as waveform attenuation indicators to determine the presence or absence of a foreign object and detect the foreign object.

[0077] Furthermore, foreign object detection may be performed based on both the attenuation state of the voltage value and the attenuation state of the current value, such as determining the presence or absence of a foreign object using an evaluation value calculated from a waveform attenuation index of the voltage value and a waveform attenuation index of the current value. In the above example, the waveform attenuation index is measured during the period when the TX402 temporarily stops power transmission, but this is not limited to the above. For example, the waveform attenuation index may be measured during the period when the TX402 temporarily reduces the power supplied from the power supply unit 102 from a predetermined power level to a power level lower than the predetermined power level. In the above example, the voltage or current values ​​are measured at two points in time during the period when the TX402 limits power transmission, but measurements may be performed at three or more points in time.

[0078] A method of detecting a foreign object based on a power transmission waveform during power transmission using the waveform attenuation method will be described with reference to Fig. 7. Fig. 7 shows a power transmission waveform when detecting a foreign object using the waveform attenuation method, with the horizontal axis representing time and the vertical axis representing the voltage value of the power transmitting antenna 105. Note that the vertical axis may represent the voltage value of the power transmitting antenna 105, similarly to Fig. 6.

[0079] During the transient response period immediately after TX402 starts transmitting power, the transmission waveform is not stable. Therefore, during this transient response period when the transmission waveform is not stable, RX401 controls TX402 not to communicate (communication by amplitude modulation or load modulation). Also, TX402 controls RX401 not to communicate (communication by frequency shift keying) with RX401. Hereinafter, this period is called the communication prohibited period. Note that during this communication prohibited period, TX402 transmits power to RX401. After the communication prohibited period, TX402 transmits power to RX401. Hereinafter, this period is called the power transmission period. When TX402 receives a foreign object detection execution request (command) from RX401, it suspends power transmission after a predetermined period has elapsed. Alternatively, it temporarily reduces the transmission power. Hereinafter, this predetermined period is called the preparation period. The foreign object detection execution request may be the above-mentioned Received Power Packet (mode 0), Received Power Packet (mode 1), or Received Power Packet (mode 2). Then, the power transmission control unit 302 of the TX402 stops power transmission or temporarily reduces the power transmission. Then, the amplitude of the transmitted wave attenuates. The period from when the TX402 temporarily suspends or temporarily reduces the power transmission until the power transmission is resumed is hereinafter referred to as the power transmission power control period. The TX402 calculates a waveform attenuation index of this attenuated waveform, and compares the calculated waveform attenuation index with a predetermined threshold to determine the presence or absence of a foreign object, or the possibility (probability of existence) of a foreign object. The determination may be performed during the power transmission power control period, the communication prohibition period, or the power transmission period.

[0080] If no foreign object is detected after the transmission power control period has elapsed, the TX402 resumes power transmission. During the transient response period immediately after resuming power transmission, the transmission waveform is not stable, and communication is prohibited again. Then, the TX402 transitions to a power transmission period in which stable power transmission is performed from the TX402 to the RX401.

[0081] As described above, the TX402 repeatedly executes the power transmission start, communication prohibition period, power transmission period, and power transmission power control period. The TX402 then calculates a waveform attenuation index of the attenuated waveform at a predetermined timing, compares the calculated waveform attenuation index with a predetermined threshold, and determines the presence or absence of a foreign object, or the possibility (probability of presence) of a foreign object. That is, in the waveform attenuation method, the presence or absence of a foreign object is determined based on the voltage or current values ​​at at least two points in time during the predetermined period during which the TX402 limits power transmission. The above is the basic process of foreign object detection using the waveform attenuation method.

[0082] In addition, during the transmission power control period, if elements such as the power receiving antenna 205 and the resonant capacitor 211 of the RX401 are connected to the power receiving unit 203, the charging unit 206, and the battery 207, the waveform attenuation index of the attenuated waveform is affected by the load of these elements. That is, the waveform attenuation index changes depending on the states of the power receiving unit 203, the charging unit 206, and the battery 207. Therefore, even if the waveform attenuation index is large, it is difficult to distinguish whether it is due to the influence of a foreign object or due to a change in the state of the power receiving unit 203, the charging unit 206, the battery 207, etc. Therefore, when detecting a foreign object by observing the waveform attenuation index, the RX401 may turn off the first switch unit 209 during the preparation period. This makes it possible to eliminate the influence of the battery 207. Alternatively, the second switch unit 210 may be turned on to short-circuit the power receiving antenna 205, the resonant capacitor 211, and the second switch unit 210, so that a current flows through a closed loop formed by the power receiving antenna 205, the resonant capacitor 211, and the second switch unit 210. This makes it possible to eliminate the influence of the power receiving unit 203, the charging unit 206, and the battery 207. When the RX401 transmits a foreign object detection execution request (command) to the TX402, it executes the above process. This enables highly accurate foreign object detection by detecting a foreign object based on the waveform attenuation index of the waveform observed in a state in which the first switch unit 209 or the second switch unit 210 is turned on and short-circuited (connected). Alternatively, the RX401 may be controlled to transition to a low power consumption mode or to keep the power consumption constant during the above preparation period in a state in which the first switch unit 209 is turned on and short-circuited, and the second switch unit 210 is turned off and disconnected. That is, when the power consumed by the RX401 is not constant or when a large amount of power is consumed, the waveform attenuation index of the attenuated waveform is affected by the fluctuations in the power consumption. Therefore, in order to eliminate this, the following process may be executed. That is, the power consumed by the RX401 is controlled by limiting or stopping the operation of software applications running on the RX401, putting the hardware function blocks of the RX401 into a low power consumption mode or into a stopped mode, etc. Highly accurate foreign object detection is possible by detecting foreign objects based on the waveform attenuation index of the waveform observed under such conditions.

[0083] Similarly, the TX402 may be configured to turn on the switch unit 108 to short-circuit it during the preparation period upon receiving a foreign object detection execution request (command) from the RX401. That is, the TX402 may be configured to cause a current to flow through a closed loop formed by the power transmitting antenna 105, the resonant capacitor 107, and the switch unit 108. This makes it possible to eliminate the influence of the power supply unit 102, the power transmitting unit 103, and the communication unit 104. Alternatively, a switch (not shown) may be provided between the power transmitting antenna and the power transmitting unit, and the influence of the power supply unit 102, the power transmitting unit 103, and the communication unit 104 may be eliminated by turning off the switch during the preparation period.

[0084] (How to set the foreign object detection threshold in the waveform attenuation method) A method for setting a threshold value for determining the presence or absence of a foreign object or the possibility (probability of the presence) of a foreign object when detecting a foreign object by the waveform attenuation method will be described. As described above, in the waveform attenuation method, foreign object detection is performed based on a "waveform attenuation index." The measured "waveform attenuation index" is compared with a predetermined threshold value, and the presence or absence of a foreign object or the possibility of the presence of a foreign object is determined based on the result. There are the following methods for setting this threshold value. The first method is a method in which the TX402 holds a predetermined value as a common value that does not depend on the RX401 to which power is transmitted. Note that this value may be the same in any case, or may be a value determined by the TX402 depending on the situation. As described above, the waveform attenuation rate of the transmission waveform during the transmission power control period increases when a foreign object is present. Therefore, a "waveform attenuation index" when it is considered that "no foreign object is present" is held as a predetermined value in advance, and this is used as a threshold value to compare with the result of the measured "waveform attenuation index." If the measured waveform attenuation index results in a waveform attenuation rate greater than the threshold value, it is determined that "a foreign object is present" or "there is a high possibility that a foreign object is present." For example, if the "waveform attenuation index" is the Q value, the Q value measured by the TX402 is compared with a predetermined Q value (threshold value) at which it is considered that no foreign object is present. If the measured Q value is smaller than the threshold Q value, it is determined that "foreign object is present" or "there is a high possibility that a foreign object is present." If the measured Q value is larger than or approximately equal to the threshold Q value, it is determined that "no foreign object is present" or "there is a low possibility that a foreign object is present." By doing as described above, foreign object detection using the waveform attenuation method can be achieved using the first method.

[0085] The second method is that the TX402 adjusts and determines the threshold value based on the information transmitted from the RX401. As described above, if a foreign object is present, the waveform attenuation rate of the transmission waveform during the transmission power control period increases. Therefore, the "waveform attenuation index" when it is considered that "no foreign object is present" is stored as a predetermined value in advance, and this is used as a threshold value to compare with the measured "waveform attenuation index". If the measured waveform attenuation index shows a waveform attenuation rate greater than the threshold value, it is determined that "foreign object is present" or that "there is a high possibility that a foreign object exists". Here, the value of the "waveform attenuation index" may differ depending on the RX401 that is the transmission target placed on the TX402. This is because the electrical characteristics of the RX401 that is coupled via the power transmission coil of the TX402 affect the value of the waveform attenuation index.

[0086] For example, if the "waveform attenuation index" is the Q value, the Q value measured by the TX402 when no foreign object is present may differ depending on the RX401 placed on the TX402. Therefore, the RX401 holds, for each TX402, Q value information when the RX401 is placed on the TX402 when no foreign object is present, and communicates and notifies the TX402 of the Q value. The TX402 then adjusts and determines the threshold based on the Q value information received from the RX401. More specifically, in the negotiation phase, the TX402 receives an FOD Status Packet containing information on the Reference Quality Factor Value, and adjusts and determines the threshold in the Q value measurement method. This Reference Quality Factor Value corresponds to "Q value information when the RX401 is placed on the TX402 when no foreign object is present". Therefore, the TX402 also adjusts and determines the threshold in foreign object detection using the waveform attenuation method based on this Reference Quality Factor Value. In addition, the Reference Quality Factor Value transmitted from the RX 401 to the TX 402 in the negotiation phase is information used for foreign object detection in the Q-factor measurement method, which originally measures the Q-factor in the frequency domain. However, when the "waveform attenuation index" is the Q-factor, the method of deriving the Q-factor is different, but even with the waveform attenuation method that measures the Q-factor in the time domain, for example, from the waveform in Figure 6, Q = πf(T2-T1) / ln(A1 / A2) Since it is possible to obtain the Q value in this way, it is possible to set the Q value threshold for the waveform attenuation method based on the Reference Quality Factor Value. In this way, the TX402 sets the Q value threshold for the waveform attenuation method based on the information already sent from the RX401 to the TX402 in the negotiation phase, eliminating the need for new measurement or other processing to set the threshold. As a result, it becomes possible to set the threshold in a shorter time.

[0087] The Q value measured by the TX402 is compared with the threshold determined by the above method, and if the measured Q value is smaller than the threshold Q value, it is determined that "foreign object is present" or "possibility of foreign object being present" If the measured Q value is larger than or approximately equal to the threshold Q value, it is determined that "no foreign object is present" or "the possibility of foreign object being present is low."

[0088] By doing as described above, it becomes possible to use the second method to detect foreign objects using the waveform attenuation method.

[0089] The third method is for the TX402 to measure the waveform attenuation index when there is no foreign object, and adjust and determine the threshold value based on the information from the measurement result. The value of the "waveform attenuation index" may differ depending on the transmission power of the TX402. This is because the amount of heat generated and the various characteristics of the electrical circuit of the TX402 change depending on the transmission power of the TX402, and these affect the value of the "waveform attenuation index." Therefore, by having the TX402 measure the waveform attenuation index for each transmission power and adjust and determine the threshold value based on the results, more accurate foreign object detection becomes possible.

[0090] FIG. 13 is a diagram for explaining a method of setting a foreign object detection threshold for each transmission power of the TX402 in the waveform attenuation method. First, the RX401 controls the load of the RX401 to be in a light load state so that no power is supplied to the load of the RX401 or only a very small amount of power is supplied when power is transmitted from the TX402. The transmission power of the TX402 at this time is Pt1. Then, the TX402 stops transmitting power in this state and measures the waveform attenuation index. The waveform attenuation index at this time is δ1. At this time, the TX402 recognizes the transmission power Pt1 that the TX402 is transmitting, and stores in a memory a calibration point 1300 that associates the transmission power Pt1 with the waveform attenuation index δ1. Next, the RX401 controls the load of the RX401 to be in a load connection state so that the load of the RX401 is supplied with maximum power or with power equal to or greater than a predetermined threshold when power is transmitted from the TX402. The transmission power of the TX402 at this time is Pt2. Then, the TX402 stops the power transmission in this state and measures the waveform attenuation index. At this time, the TX402 stores in the memory a calibration point 1301 that associates the transmission power Pt2 with the waveform attenuation index δ2. Next, the TX402 linearly interpolates between the calibration point 1300 and the calibration point 1301 to create a straight line 1302. The straight line 1302 shows the relationship between the transmission power and the waveform attenuation index of the transmission wave in a state where there is no foreign object around the TX402 and the RX401. Therefore, the TX402 can estimate the waveform attenuation index of the transmission wave for each transmission power value in a state where there is no foreign object from the straight line 1302. For example, when the transmission power value is Pt3, it can be estimated that the waveform attenuation index is δ3 from a point 1303 on the straight line 1302 corresponding to the transmission power value Pt3. Based on the above estimation result, the TX402 can calculate a threshold value for each transmission power value to be used for determining the presence or absence of a foreign object. For example, a waveform attenuation index that is larger than the estimation result of the waveform attenuation index when there is no foreign object at a certain transmission power value by a predetermined value (a value corresponding to a measurement error) may be set as the threshold value for determining the presence or absence of a foreign object.The calibration process performed by the TX402 and the RX401 for the TX402 to acquire a combination of the transmission power value and the waveform attenuation index is hereinafter referred to as "calibration process of the waveform attenuation index (CAL process)." Note that, in the above example, the measurement was performed at two points, Pt1 and Pt2, of the transmission power of the TX402, but in order to improve accuracy, the measurement may be performed at three or more points to calculate the waveform attenuation index of each transmission power.

[0091] The RX401 may perform the control to set the load to a no power supply / light load state and the control to set the load to a connected state after notifying the TX402 of the control to be performed. Also, either of the two controls may be performed first.

[0092] Note that the operation for calculating the threshold value used to determine the presence or absence of a foreign object for each load (each transmission power value) described in this embodiment may be performed in the calibration phase. As described above, in the calibration phase, the TX402 acquires data required for foreign object detection using the power loss method. At that time, the TX402 acquires data related to power loss when the load state of the RX401 is a light load state and when the load is connected. Therefore, the measurement of the calibration point 1300 and the calibration point 1301 in FIG. 13 may be performed in the above-mentioned calibration phase when the RX401 is in a light load state and when the RX401 is in a load connected state. That is, when the TX402 receives the first reference received power information from the RX401, in addition to the predetermined processing to be performed in the calibration phase, the TX402 measures the calibration point 1300. Also, when the TX402 receives the second reference received power information from the RX401, in addition to the predetermined processing to be performed in the calibration phase, the TX402 measures the calibration point 1301. This eliminates the need to provide a separate period for measuring the calibration points 1300 and 1301, and therefore allows the measurements of the calibration points 1300 and 1301 to be performed in a shorter time.

[0093] In this way, based on the information on the waveform attenuation index measured by the TX402 at each transmission power, the TX402 adjusts and sets the threshold value of the waveform attenuation index of the waveform attenuation method for each transmission power. For example, if the waveform attenuation index is a Q value, the Q value measured by the TX402 is compared with the threshold value determined by the above method, and if the measured Q value is smaller than the threshold Q value, it is determined that "foreign object is present" or "foreign object may be present." If the measured Q value is larger than or approximately equal to the threshold Q value, it is determined that "foreign object is not present" or "foreign object is unlikely to be present." By doing so, it becomes possible to set a threshold value for each transmission power of the TX402, enabling more accurate foreign object detection.

[0094] By doing as described above, it becomes possible to use the third method to detect foreign objects using the waveform attenuation method.

[0095] Furthermore, when detecting a foreign object, there is a possibility that accurate foreign object detection cannot be performed by executing the process for detecting a foreign object only once. For example, when detecting a foreign object using the waveform attenuation method, if a single transmission power control is performed and the presence or absence of a foreign object or the possibility (probability of presence) of a foreign object is determined from the waveform attenuation index, there is a possibility that the transmission waveform may be disturbed during the transmission power control period. Possible reasons for disturbance of the transmission waveform during the transmission power control period include the intrusion of other noise during the transmission power control period, or the position of the RX401 placed on the TX402 being shifted for some reason. The waveform attenuation index found from the transmission waveform during one transmission power control period is Sending Due to disturbances in the radio wave waveform, the value may not be accurate, which may result in an erroneous judgment in the detection of a foreign object. In order to prevent this, it is conceivable to carry out transmission power control multiple times, measure the waveform attenuation index from the transmission waveform during multiple transmission power control periods, and perform foreign object detection from the results.

[0096] (Foreign object detection using multiple waveform attenuation method) In the above-mentioned waveform attenuation method, the TX402 is configured to perform a single Q-value measurement and perform foreign object detection processing based on the result. Here, the TX402 may perform multiple Q-value measurements and perform foreign object detection processing based on the result. The process of detecting foreign objects based on the results of multiple Q-value measurements will be described with reference to FIG. 14. In FIG. 14, the TX402 performs two Q-value measurements using the waveform attenuation method and performs foreign object detection processing based on the result.

[0097] First, RX401 transmits RP0 to TX (F636). When TX402 receives RP0, it performs a Q-factor measurement using the waveform attenuation method (F637). Here, it is clear that the Q-factor measurement performed by TX402 (F637) is the first of two that will be performed. Therefore, in response to RP0 (F636), TX402 transmits to RX401 a packet indicating that it is "not determining" whether or not there is a foreign object at this time (F638).

[0098] RX401 transmits CE(0) to TX402 (F639). Here, CE stands for Control Error Packet, which requests TX402 to increase or decrease the receiving voltage (or receiving current, receiving power). CE can include a + integer to increase the receiving voltage, a - integer to decrease the receiving voltage, or 0 to leave the receiving voltage unchanged. CE(0) is a packet that requests to maintain the receiving voltage.

[0099] The RX401 transmits RP0 again (F640). When the TX402 receives RP0, it performs Q-factor measurement using the waveform attenuation method (F641).

[0100] Here, it can be seen that the Q value measurement (F641) performed on TX402 was the second of two measurements. window Assume that the transmission power value during this period is stable and that the third foreign object detection determines that there is a high possibility that there is no foreign object. In this case, the TX 402 determines the presence or absence of a foreign object, and transmits a response signal including the possibility (probability) of the presence of a foreign object to the RX 401 based on the determination result (F642).

[0101] Here, an example of a method for deriving the possibility (existence probability) of the presence of a foreign object using multiple waveform attenuation methods will be described. For example, the possibility (existence probability) of the presence of a foreign object is derived based on the difference between the Q value obtained by one waveform attenuation method and a threshold value. This process is performed for multiple waveform attenuation methods to derive the average value of the existence probability. In this way, the possibility (existence probability) of the presence of a foreign object based on the results of multiple waveform attenuation methods is acquired. The second example is a method for weighting the total value of the possibility (existence probability) of the presence of a foreign object for multiple times. The third example is a method for measuring the number of waveform attenuation methods in which a certain value or more of the possibility (existence probability) of the presence of a foreign object is detected. In this embodiment, when the possibility (existence probability) of the presence of a foreign object is notified to the RX401, "no foreign object" is replaced with a numerical value of 0 and "foreign object present" is replaced with a numerical value of 10, and the average value of the multiple existence probability values ​​is notified to the RX401. In addition, a process of rounding up the decimal point of the average value may be performed.

[0102] In addition, in this embodiment, the RX401 controls the interval for transmitting RP0, which is a foreign object detection execution request, in order to control the timing at which the TX402 limits power transmission related to the multiple waveform attenuation methods. When the RX401 transmits RP0 as a foreign object detection execution request multiple times to the TX402, the RX401 waits for a predetermined interval after transmitting RP0 and then transmits the next RP0. However, if the possibility of the presence of a foreign object (probability of presence) satisfies a predetermined condition, the RX401 controls the timing from transmitting RP0 to transmitting the next RP0. This process will be described later.

[0103] (Processing of power receiving device 401 and power transmitting device 402) The flow of processing by the power receiving device 401 (RX 401) in this embodiment will be described with reference to the flowchart in Fig. 8. Fig. 8 is a flowchart illustrating the operation of the RX 401 that is executed after the start of the power transmission process of F528 in Fig. 5.

[0104] The RX401 starts receiving power transmitted from the TX402 (S801). After starting power reception, the RX401 determines a threshold value of the presence probability (S802). Here, the threshold value of the presence probability is a threshold value for determining whether or not there is a possibility that a foreign object exists. For example, when the presence probability obtained by the foreign object detection process is greater than the threshold value of the presence probability, it is determined that "there is a high possibility that a foreign object exists". Also, for example, when the presence probability obtained by the foreign object detection process is smaller than the threshold value of the presence probability, it is determined that "there is a low possibility that a foreign object exists". Also, the threshold value of the presence probability is a value for determining whether or not to adjust the interval at which the RX401 waits for transmission of a foreign object detection execution request, which will be described later. The threshold value of the presence probability may be determined by using a value previously determined for each RX401 or a value determined by the power transmission output from the TX402.

[0105] The RX401 waits for a predetermined interval before transmitting a request to execute foreign object detection to the TX402 (S803). In this embodiment, the TX402 performs foreign object detection based on the waveform attenuation method multiple times, so as described above, the RX401 waits for a predetermined interval (predetermined time length) after transmitting a request to execute foreign object detection until transmitting the next request to execute foreign object detection. If the predetermined interval is short, the TX402 executes transmission power control in a short period of time, and the RX401 also receives a load due to an increase in processing related to the foreign object detection request, so it is desirable to set the waiting time long. After waiting for the predetermined interval in S803, the RX401 transmits a request to execute foreign object detection to the TX402 (S804). This foreign object detection request may be the Received Power Packet (mode 0), Received Power Packet (mode 1), or Received Power Packet (mode 2) described above. After transmitting the foreign object detection execution request in S804, RX401 judges whether the response packet from TX402 includes the possibility of the presence of a foreign object (probability of presence) (S805). The judgment in S805 corresponds to a process of determining the possibility of the presence of a foreign object (probability of presence) from a predetermined number of transmission power controls. If the transmission power control has not been reached a predetermined number of times, the response from TX402 does not include the probability of the presence of a foreign object. This is realized by TX402 transmitting an ND (Not-Defined) packet representing "no judgment" as a response to RX401. RX401 judges whether the transmission power control has been completed a predetermined number of times based on the ND packet. If it is an ND packet, it judges that the transmission power control has not been completed a predetermined number of times (NO in S805), returns to S803, and waits for a predetermined interval until the transmission of the foreign object detection execution request is transmitted again. If the response from TX402 includes the possibility of the presence of a foreign object (probability of presence) (YES in S805), it is determined whether the notified possibility of the presence of a foreign object (probability of presence) is equal to or greater than the threshold of the probability of presence (S806). If the probability of presence is not equal to or greater than the threshold of the probability of presence (NO in S806), the process returns to S803 and waits for a predetermined interval to transmit a request to detect a foreign object again.

[0106] If the existence probability is equal to or greater than the threshold (YES in S806), it is determined whether the notified possibility of the presence of a foreign object (existence probability) is definitely "foreign object present" (S807). In this embodiment, the existence probability is expressed by a value of 0 for "no foreign object" and 10 for "foreign object present". Therefore, when the existence probability value is 10, it is definitely determined that "foreign object present", and when it is not 10, it is not definitely determined that "foreign object present". Note that this is not limited to this, and a value of 8, for example, may be set as the threshold used to definitely determine whether "foreign object present" is present. In this case, when the existence probability value is greater than 8, it is definitely determined that "foreign object present", and when it is equal to or less than 8, it is not definitely determined that "foreign object present". In this case, the threshold for definitely determining whether "foreign object present" is a threshold value greater than the existence probability threshold. In addition, the expression of the existence probability is not limited to the above, and a value or range other than 0 to 10 may be used.

[0107] If the result of the determination is that there is a clear "foreign object" (YES in S807), power reception is stopped (S808). Note that S808 can be achieved by the RX 401 transmitting an EPT (End Power Transfer) command (packet), which is a power transmission stop request command requesting the TX 402 to stop power transmission.

[0108] If it is not clearly determined that "foreign object presence" as a result of the determination in S807, the current standby interval is determined in order to adjust the standby interval for transmitting the foreign object detection execution request (S809). Specifically, it is determined whether the standby time length until the next foreign object detection execution request is transmitted can be made shorter than the current time length. If the standby time for transmitting the foreign object detection execution request is not the shortest time length that the RX401 can realize (NO in S809), the standby time for transmitting the foreign object detection execution request is shortened (S810), and the transmission of the foreign object detection execution request is put on hold until the shortened time has elapsed (S811). On the other hand, if the standby time for transmitting the foreign object detection execution request is already the shortest time length (YES in S809), the standby time for transmitting the foreign object detection execution request is not shortened, and the transmission of the foreign object detection execution request is put on hold until the current standby time has elapsed (S811).

[0109] In addition, a method of determining the predetermined interval (length of standby time) for transmitting the foreign object detection execution request may be a method of using a value previously determined for at least one of the RX401 and TX402. In addition, for example, a method of determining the predetermined interval (length of standby time) may be a method of using a value determined by the power transmission output from the TX402. In addition, the shortest time length may be determined based on, for example, the shortest time length in which the TX402 can execute the waveform attenuation method or the shortest time length in which the RX401 can transmit the foreign object detection execution request. In addition, for example, the predetermined interval may be determined by negotiation between the RX401 and the TX402. In addition, this negotiation may be configured to be performed in the negotiation phase.

[0110] In addition, the method of shortening the time length may include shortening it by a predetermined time length, shortening it to the shortest time length in one processing, or shortening it by a time length according to the transmission output from TX402.

[0111] The process from S811 to S813 is the same as the process from S803 to S805, and the description will be omitted. If the response from TX402 includes the possibility of the presence of a foreign object (probability of presence) (YES in S813), RX401 judges whether the notified possibility of the presence of a foreign object (probability of presence) is clearly "foreign object present" (S814). If the result of the judgment is clearly "foreign object present" (YES in S814), power reception is stopped (S808).

[0112] On the other hand, if the result of the judgment is not clearly "foreign object presence" (NO in S814), RX401 judges whether or not "foreign object absence" (S815). Here, "foreign object absence" is clearly the case where the value of the presence probability is 0. If "foreign object absence" is clearly the case (YES in S815), RX401 restores the shortened waiting time for transmission of the foreign object detection execution request to the time length before shortening, returns to S803, and continues receiving power (S816). On the other hand, if "foreign object absence" is not clearly the case (NO in S815), RX401 judges whether or not the transmission of the foreign object detection execution request with the shortened waiting time for transmission of the foreign object detection execution request has been performed a predetermined number of times in succession (S817). If the transmission has been performed a predetermined number of times in succession (YES in S817), since there is a possibility of suspecting a device failure, RX401 stops receiving power (S808). If the predetermined number of times has not been executed consecutively (NO in S817), the process returns to S809, and the current waiting interval is determined in order to adjust the length of the waiting time for transmitting the foreign object detection execution request. Here, the method of determining the predetermined number of times may be a method using a value previously determined for each RX 401, a method using a value determined based on the power transmission output from the TX 402, or the like.

[0113] As described above, when the possibility of a foreign object being present (probability of presence) is higher than the threshold for the probability of presence and lower than the threshold for clearly determining whether a foreign object is present, RX401 controls the transmission of requests to perform foreign object detection at shorter intervals.

[0114] Note that the configuration may be such that the determination in S807 is not performed, and the processes from S809 onwards are performed if the presence probability is equal to or greater than the threshold in S806. With this configuration, if the presence probability is equal to or greater than the threshold, the transmission of the foreign object detection execution request is expedited and foreign object detection is performed again, thereby making it possible to quickly and reliably confirm the presence or absence of a foreign object.

[0115] Next, the power receiving device 401 (RX401) and Power transmission equipmentThe flow of processing in this embodiment of 402 (TX402) will be described with reference to the sequence diagram of Fig. 9. Fig. 9 shows processing that is executed after the start of power transmission processing in F528 in Fig. 5. As an example of processing, processing when foreign matter is mixed in between transmission power control in the waveform attenuation method when TX402 performs the waveform attenuation method three times will be described here.

[0116] The TX402 and RX401 start power transmission processing (F901). After starting power reception, the RX401 determines the presence probability threshold (F902). Here, it is assumed that the 15 watts of power transmission determined in F527 is being performed, and the RX401, which has determined that the received power is high, determines the threshold so as to adjust the length of time to wait before transmitting a foreign object detection execution request even in the case where the "possibility of the presence of a foreign object is low."

[0117] After determining the threshold in F902, the RX401 waits for the waiting interval for sending a foreign object detection execution request (F903). Here, the default waiting time for the RX401 is 2 seconds. The shortest waiting time for sending a foreign object detection execution request is 0.5 seconds. After the waiting time in F903 has elapsed, the RX401 transmits a foreign object detection execution request to the TX402 (F904). Foreign object detection execution request in F904 of The TX 402 that has received the signal from the RX 401 performs transmission power control and executes foreign object detection (F905). Here, three times is set as the number of times of transmission power control that the TX 402 uses to detect the possibility (probability) of the presence of a foreign object.

[0118] In the transmission power control of F905, since no foreign object is present, the possibility of the presence of a foreign object (probability of presence) is clearly determined to be "no foreign object". In the transmission power control of F905, since the predetermined number of transmission power controls has not been reached, TX402 notifies RX401 of an ND packet (F906). Upon receiving the notification of F906, RX401 waits until the waiting time has elapsed before sending the next foreign object detection execution request (F907). The processing from F908 to F911 is similar to the processing from F904 to F907, and therefore description thereof will be omitted.

[0119] Here, assume that a foreign object is introduced within the power transmission range of TX402 during standby in F911 (F912). After the standby time of F911 has elapsed, RX401 transmits a foreign object detection execution request to TX402 (F913). TX402, which has received the foreign object detection execution request from RX401 in F913, performs transmission power control and executes foreign object detection (F914). In the transmission power control in F914, since a foreign object is present, the possibility of foreign object presence (probability of presence) is clearly detected as "foreign object present".

[0120] Since the number of times (=3) of the waveform attenuation method has been reached in the transmission power control of F914, TX402 determines the possibility (probability of presence) of the foreign object to be notified to RX401 from the results of the transmission power control of F905, F909, and F914 (F915). TX402 notifies RX401 of the possibility (probability of presence) of the foreign object determined in F915 (F916). Upon receiving the notification of F916, RX401 determines whether the notified possibility (probability of presence) of the foreign object is equal to or greater than the threshold of the presence probability determined in F902 (F917). Here, RX401 compares the notified possibility (probability of presence) of the foreign object with the threshold and determines that the probability of presence is equal to or greater than the threshold.

[0121] From the result of the determination in F917, the RX401 checks the current waiting time for transmission of a foreign object detection execution request in order to shorten the waiting time for transmission of the foreign object detection execution request (F918). As a result of F918, the current waiting time for transmission of a foreign object detection execution request is 2 seconds, which is longer than the shortest waiting time for transmission of a foreign object detection execution request, which is 0.5 seconds, so the RX401 shortens the waiting time for the foreign object detection execution request (F919). Here, the RX401 determines the waiting time to be 0.5 seconds, which is the shortest waiting time. Note that, although in this embodiment, the value is changed to the shortest value in a single shortening, a configuration in which the waiting time is gradually shortened is also possible.

[0122] The RX401 waits for the waiting time for sending a foreign object detection execution request determined in F919 (F920). After the shortened waiting time in F920 has elapsed, the RX401 transmits a foreign object detection execution request to the TX402 (F921). As a result, if the possibility of a foreign object being present (probability of presence) based on foreign object detection is higher than the threshold and it is not clearly determined that a foreign object is present, the TX402 receives the next foreign object detection execution request at an earlier timing than when these conditions are not met. The TX402 that has received the foreign object detection execution request transmitted in F921 performs transmission power control and executes foreign object detection (F922). Here, the number of times of transmission power control that the TX402 uses to detect the possibility of a foreign object being present (probability of presence) is set to three, the same as in F905.

[0123] In the transmission power control of F922, since a foreign object is present, the possibility of a foreign object being present (probability of presence) is clearly determined to be "foreign object present." In the transmission power control of F922, since the predetermined number of transmission power controls has not been reached, TX402 notifies RX401 of an ND packet (F923). Upon receiving the notification of F923, RX401 waits again for the waiting interval for transmission of a foreign object detection execution request (F924). The processing from F925 to F930 is the same as the processing from F921 to F926, and therefore a description thereof will be omitted.

[0124] Since the transmission power control of F930 has reached a predetermined number of transmission power controls, TX402 determines the possibility (existence probability) of the presence of a foreign object to be notified to RX401 from the results of the transmission power controls of F922, F926, and F930 (F931). Here, TX402 determines to notify the presence probability indicating "foreign object present" from the results of "foreign object present" of F922, "foreign object present" of F926, and "foreign object present" of F930. TX402 notifies RX401 of the possibility (existence probability) of the presence of a foreign object determined in F931 (F932). Upon receiving the notification from F932, RX401 confirms that the notified possibility (existence probability) of the presence of a foreign object is "foreign object present" and transmits an EPT (End Power Transfer) command (packet) to TX402 to stop power reception (F933). The above is an example of the process to be performed when a foreign object is detected based on the multiple waveform attenuation method.

[0125] In this embodiment, there are two types of intervals to be adjusted for waiting for transmission of a foreign object detection execution request: "interval until first execution of foreign object detection" represented by F903, and "interval between multiple transmission power controls" represented by F907. In this embodiment, a method of adjusting both at the same time is described, but only one of them may be adjusted.

[0126] With the above configuration, when the RX401 is notified by the TX402 that "there is a high possibility that a foreign object exists", the RX401 can shorten the transmission interval of the foreign object detection execution request. As a result, when the RX401 is notified that the foreign object exists, the RX401 can shorten the time until the foreign object detection process is performed again. As a result, the RX401 can quickly clarify the presence or absence of a foreign object. Furthermore, when there is no foreign object and when the RX401 is notified that there is a clear "no foreign object", the RX401 sets the transmission time of the foreign object detection execution request to be longer than the shortest time length. As a result, the processing load related to the waveform attenuation method can be reduced, and a safer and more efficient wireless power transmission system can be realized.

[0127] <Embodiment 2> In the first embodiment, an example of applying the multiple waveform attenuation method for foreign object detection in the WPC standard is described. In the present embodiment, a method for performing safer power transmission using the method described in the first embodiment is described.

[0128] (Processing of power transmitting device 402 and power receiving device 401) The flow of processing by the power receiving device 401 (RX401) in this embodiment will be described with reference to the flowchart in Fig. 10. Fig. 10 is a flowchart showing the operation of the RX401 that is executed after the start of the power transmission process of F528 in Fig. 5. Note that the description of the same processing content as in the first embodiment will be omitted.

[0129] The process from S1001 to S1015 is the same as the process from S801 to S815, and therefore the description will be omitted. If it is not clear that "no foreign object is present" (NO in S1015), it is determined whether the foreign object detection execution request with the shortened waiting time for sending the foreign object detection execution request has been sent a predetermined number of times in succession (S1017). If it has not been sent a predetermined number of times in succession (NO in S1016), the process returns to S1009, and RX401 determines the current waiting time in order to adjust the waiting time for sending the foreign object detection execution request. The method for determining the predetermined number of times is the same as in the first embodiment.

[0130] On the other hand, if the operation has been performed a predetermined number of times in succession (YES in S1016), the RX401 judges whether the current power transmission from the TX402 is the lower limit that can be taken between the TX402 and the RX401 (S1017). If the power transmission from the TX402 is the lower limit (YES in S1017), the process returns to S1009, and the RX401 judges the current waiting time in order to adjust the waiting time for transmitting a request to perform foreign object detection. If the power transmission from the TX402 is not the lower limit (NO in S1017), the RX401 transmits a request to change the power transmission to the TX402 to lower the power transmission (S1018).

[0131] After the transmission power change process in S1018 is completed, the process returns to S1009, and the RX 401 determines the current waiting time in order to adjust the waiting time for transmitting the foreign object detection execution request.

[0132] If it is clearly determined in S1015 that there is no foreign object (YES in S1015), the shortened waiting time for sending a request to detect a foreign object is returned to the time length before the shortening (S1019), and it is determined whether the transmission power has been changed in S1018 (S1020). If the transmission power output has not been changed (NO in S1020), 10 Returning to S803, RX401 continues receiving power. On the other hand, if the transmission power has been changed (YES in S1020), RX401 transmits a transmission output change request to TX402 to return the changed transmission power to the transmission power before the change (S1021), and returns to S803 to continue receiving power.

[0133] The above-described processing has the following effects. That is, when it is highly likely that a foreign object exists, the transmission power is reduced, thereby avoiding the risk of transmitting power to the foreign object and raising the temperature of the foreign object. In addition, the higher the transmission power, the greater the influence of noise related to the power transmission. Therefore, when foreign object detection is performed using the waveform attenuation method, there is a high possibility that a foreign object is erroneously detected, that is, a foreign object is determined to be "present" when no foreign object exists, or a foreign object is determined to be "not present" when a foreign object exists. Therefore, when it is determined that a foreign object exists "highly likely," the transmission power is reduced and foreign object detection is performed again, thereby enabling the presence or absence of a foreign object to be confirmed with higher accuracy.

[0134] Next, the flow of processing in the power receiving device 401 (RX401) and the power transmitting device 402 (TX402) in this embodiment will be described with reference to the sequence diagram of Fig. 11. Fig. 11 shows processing executed after the start of power transmission processing in F528. As an example of processing, processing in the case where a disturbance occurs in the power transmission waveform during the power transmission power control period due to temporary noise when performing power transmission control in the waveform attenuation method will be described here. The processing from F1101 to F1104 is the same as the processing from S901 to S904, and therefore description thereof will be omitted.

[0135] The TX402, which has received the foreign object detection execution request from the RX401 in F1104, performs transmission power control and executes foreign object detection (F1105). Here, one time is the number of times of transmission power control that the TX402 uses to detect the possibility (existence probability) of the presence of a foreign object. In the transmission power control in F1105, even if no foreign object exists, it is assumed that the possibility (existence probability) of the presence of a foreign object is detected as "low possibility of the presence of a foreign object" due to the disturbance of the transmission wave form during the transmission power control period caused by the influence of noise. The TX402 notifies the RX401 of the detection result in F1105 (F1106). The RX401, which has received the notification in F1106, judges whether the notified possibility (existence probability) of the presence of a foreign object is equal to or greater than the threshold of the existence probability determined in F1102 (F1107). Here, the RX401 compares the notified possibility (existence probability) of the presence of a foreign object with the threshold and judges that it is equal to or greater than the threshold of the existence probability.

[0136] The processes from F1108 to F1111 are similar to the processes from F918 to F921, and therefore explanations thereof will be omitted. The processes from F1112 and F1113 are similar to the processes from F1105 and F1106, and therefore explanations thereof will be omitted. While foreign object detection is repeatedly performed by the same processes as from F1110 to F1113 in which the transmission waiting interval of the foreign object detection execution request is shortened, RX401 judges whether the predetermined number of repetitions has been reached (F1114). After it is judged in F1114 that the predetermined number of repetitions has been reached, RX401 judges whether the current transmission power is set to the lower limit (F1115). In this embodiment, the lower limit of the transmission power is set to 5 watts, and the current transmission power output is set to 15 watts. Therefore, in the judgment at F1115, it is judged that the current transmission power is not the lower limit, and the RX401 transmits a transmission power change request to the TX402 to set the transmission power to the lower limit of 5 watts (F1116).

[0137] The TX402, which has received the transmission power output change request of F1116, changes the transmission power to 5 watts (F1117), and notifies the RX401 that the change in transmission power output has been completed by sending an ACK (F1118). Note that, in this embodiment, the RX401 changes the transmission power to the lower limit value in one change, but the transmission power may be gradually decreased.

[0138] By changing the transmission power to the lower limit, the noise that has been affecting the transmission waveform disappears (F1119). After the noise disappears in F1119, RX401 transmits a foreign object detection execution request to TX402 (F1120). TX402, which has received the foreign object detection execution request from RX401 in F1120, performs transmission power control using the waveform attenuation method and executes foreign object detection (F1121). Here, since the noise that has been affecting the disturbance of the transmission wave waveform during the transmission power control period in S1119 has disappeared, the possibility of the presence of a foreign object (probability of existence) is clearly determined to be "no foreign object". TX402 notifies RX401 of the presence probability based on the determination result of F1121 (F1122).

[0139] Upon receiving the notification of F1122, RX401 repeats the execution of foreign object detection using the same processing as from F1120 to F1122, and determines that no foreign object is present (F1123). In this embodiment, since the transmission power control was performed once for the processing of F1123, RX401 makes the determination based on the results of multiple foreign object detection executions in consideration of the effects of noise, etc., but the determination may also be made based on the results of one foreign object detection execution. Having determined that no foreign object is present in F1123, RX401 returns the shortened transmission standby time for a foreign object detection execution request to the time length before the shortening ( F 1124), and determine whether the transmission power has been changed ( F In this embodiment, since the transmission power has been changed from 15 watts to 5 watts, the RX 401 transmits a transmission power change request to the TX 402 to return the transmission power output to 15 watts ( F The TX 402, which has received the transmission power output change request of F1126, changes the transmission power to 15 watts (F1127), and notifies the RX 401 that the change in transmission power has been completed by sending an ACK (F1128).

[0140] In this way, when the RX401 is notified by the TX402 that "there is a possibility of a foreign object being present," the RX401 shortens the transmission time of the foreign object detection execution request and reduces the transmission power. This allows the RX401 and TX402 to prevent the power transmission from being stopped due to erroneous detection while reducing the possibility of the foreign object generating heat, and to continue the power transmission. Furthermore, by continuing the state in which the transmission time of the foreign object detection execution request is shortened, the intrusion of a foreign object can be detected as soon as possible, and a safer and more efficient wireless power transmission system can be realized.

[0141] <Other embodiments> The contents of the above-mentioned first and second embodiments may be combined as appropriate. In the above-mentioned embodiment, the TX402 controls the transmission power and detects a foreign object from the waveform attenuation index. As another method for measuring the Q value, which is one of the waveform attenuation indexes, the following method is conceivable. That is, there is also a method for measuring the Q value by transmitting a signal (e.g., a pulse wave) having multiple frequency components, measuring the amplitude or attenuation state of the waveform, and performing arithmetic processing (e.g., a Fourier transform) on the result, and this method can also be applied to the above-mentioned embodiment.

[0142] The present disclosure can also be realized by a process in which a program for realizing one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC, etc.) that realizes one or more functions. The program may also be provided by recording it on a computer-readable recording medium. [Explanation of symbols]

[0143] 401 Power receiving device 201 Control section 204 Communications Department 205 Coil

Claims

1. A power receiving means for wirelessly receiving power from a power transmitting device; A transmitting means for transmitting a packet including information on received power at time intervals in a power transfer phase; A receiving means for receiving a response to the packet from the power transmitting device; a control means for switching to a first mode when the received response is a predetermined response, and for switching to a second mode when the received response is not the predetermined response; the packets are transmitted in the first mode at first time intervals; the packets are transmitted in the second mode at second time intervals; the first time interval is shorter than the second time interval; The predetermined response is a response including information indicating that the probability of the presence of a foreign object is higher than a threshold and lower than another threshold that is higher than the threshold.

2. The power receiving device according to claim 1 , wherein the time interval is determined by negotiation between the power receiving device and the power transmitting device.

3. The power receiving device according to claim 1 , wherein the transmission means transmits a packet for changing power when the response is the predetermined response.

4. The power receiving device according to claim 3 , wherein the transmission means transmits a request to stop power transmission when the response includes information indicating that the probability is higher than the other threshold value.

5. A method performed by a power receiving device, comprising: In the Power Transfer phase, a packet including information on the received power is transmitted; receiving a response to the packet from the power transmitting device; switching to a first mode if the received response is a predetermined response; switching to a second mode if the received response is not a predetermined response; the packets are transmitted in the first mode at first time intervals; the packets are transmitted in the second mode at second time intervals; the first time interval is shorter than the second time interval; A method according to claim 1, wherein the predetermined response is a response containing information indicative of a probability that a foreign object is present that is greater than a threshold and less than another threshold that is greater than the threshold.

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