Power transmission equipment, methods and programs used by power transmission equipment

Abstract

To suppress the generation of electromagnetic noise in a method for detecting an object different from a power reception device on the basis of voltage and current during a period in which a power transmission device restricts power transmission.SOLUTION: The power transmission device performs a detection process to detect an object different from the power reception device on the basis of the values of voltage or current at least at two points in time within a predetermined period during which power transmission is restricted, according to the coupling state between an antenna of the power transmission device and an antenna of the power reception device.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a power transmission device , methods and programs performed by power transmission equipment .

Background Art

[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 (WPC) standard. Further, Patent Document 2 discloses a foreign object detection method for detecting the presence of an object based on the attenuation amount of the voltage value of the power transmitter in a period where the voltage of the power transmitter gradually decreases after power transmission is restricted. Note that the foreign object herein refers to an object different from the power receiving device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0004] In the method of detecting the presence of an object by the method described in Patent Document 2, power transmission by the power transmission device is restricted, so electromagnetic noise may occur. In suppressing the occurrence of such electromagnetic noise, it is desirable that the number of times power transmission by the power transmission device is restricted is as small as possible.

[0005] An object of the present disclosure is to provide a technique for suppressing the occurrence of electromagnetic noise in a method of detecting an object different from a power receiving device based on voltage and current in a period during which the power transmission device restricts power transmission.

Means for Solving the Problems

[0006] One aspect of this disclosure is the wireless transmission of power to a power receiving device. The power transmission device comprises a power transmission means, an acquisition means for acquiring information on received power from the power receiving device, a calculation means for calculating an index relating to the coupling state with the power receiving device, and a detection means for performing a first foreign object detection process relating to the Quality Factor and a second foreign object detection process relating to power loss. The detection means performs the first foreign object detection process during a period of limiting power transmission if predetermined conditions are met after the calculation of the index, and if no foreign object is detected by the first foreign object detection process, it performs calibration related to the second foreign object detection process based on the information on received power acquired by the acquisition means. [Effects of the Invention]

[0007] According to this disclosure, in a method for detecting an object different from a power receiving device based on voltage and current during a period when a power transmission device limits power transmission, the generation of electromagnetic noise can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing an example configuration of a wireless power transmission system. [Figure 2] This is a diagram illustrating foreign object detection using the power loss method. [Figure 3] This figure shows an example of the configuration of a power transmission device. [Figure 4] This figure shows an example of the configuration of a power receiving device. [Figure 5] This is a block diagram showing an example of the functional configuration of the control unit of a power transmission device. [Figure 6] This is a sequence diagram showing an example of processing for wireless power transmission. [Figure 7] This is a diagram illustrating foreign object detection using the waveform attenuation method. [Figure 8] This is a diagram illustrating foreign object detection using the waveform attenuation method. [Figure 9] This is an equivalent circuit diagram of a transmitting antenna and a receiving antenna. [Figure 10] This is a flowchart to explain the operation of a power transmission device. [Figure 11] This is a flowchart to explain the operation of the power receiving device. [Figure 12A] This sequence diagram shows an example of the Calibration phase process. [Figure 12B] This sequence diagram shows an example of the Calibration phase process. [Figure 12C] This sequence diagram shows an example of the Calibration phase process. [Figure 13] This is a flowchart for explaining the operation of the power transmission device. [Figure 14] This is a flowchart for explaining the operation of the power reception device. [Figure 15A] This is a sequence diagram showing a processing example of the Calibration phase. [Figure 15B] This is a sequence diagram showing a processing example of the Calibration phase. [Figure 15C] This is a sequence diagram showing a processing example of the Calibration phase. [Description of Embodiments]

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. Although a plurality of features are described in the embodiments, not all of these plurality of features are necessarily essential. Further, the plurality of features may be arbitrarily combined. Furthermore, in the drawings, the same reference numerals are assigned to the same or similar configurations.

[0010] (First Embodiment) [Configuration of Wireless Power Transmission System] Figure 1 is a diagram showing a configuration example of a wireless power transmission system (wireless charging system) 100 according to the first embodiment. In one example, the wireless power transmission system 100 includes a power reception device 101 and a power transmission device 102. The charging stand 103 is a part of the power transmission device 102. Detailed configurations of the power transmission device 102 and the power reception device 101 will be described later with reference to Figures 3 and 4. The power reception device 101 is an electronic apparatus that receives power from the power transmission device 102 and charges a built-in battery. The power transmission device 102 is an electronic apparatus that wirelessly transmits power to the power reception device 101 placed on the charging stand 103 that is a part of the power transmission device 102. A range 104 is a range in which the power reception device 101 can receive power from the power transmission device 102.

[0011] The power receiving device 101 and the power transmitting device 102 may also have functions to perform applications other than wireless charging. An example of the power receiving device 101 is a smartphone. An example of the power transmitting device 102 is an accessory device for charging that smartphone. The wireless power transmission system 100 may be a tablet, a storage device such as a hard disk drive or memory device, or an information processing device such as a personal computer (PC). Furthermore, the wireless power transmission system 100 may be, for example, an imaging device (camera, video camera, etc.), an automobile, a robot, medical equipment, or a printer.

[0012] The wireless power transmission system 100 performs wireless power transmission using an electromagnetic induction method for wireless charging, based on the WPC (Wireless Power Consortium) standard. Specifically, the receiving device 101 and the transmitting device 102 perform wireless power transmission for wireless charging based on the WPC standard between the receiving antenna 405 of the receiving device 101 (Figure 4) and the transmitting antenna 305 of the transmitting device 102 (Figure 3). The wireless power transmission method applied to the wireless power transmission system 100 is not limited to the method specified in the WPC standard, but may also be other methods such as electromagnetic induction, magnetic field resonance, electric field resonance, microwave, or laser. Furthermore, although this embodiment describes an example in which wireless power transmission is used for wireless charging, wireless power transmission may also be used for purposes other than wireless charging.

[0013] The WPC standard specifies that the amount of power guaranteed when the receiving device 101 receives power from the transmitting device 102 is defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP represents the power value at which the output to the load of the receiving device 101 is guaranteed, even if, for example, the positional relationship between the receiving device 101 and the transmitting device 102 changes and the power transmission efficiency between the receiving antenna 405 and the transmitting antenna 305 decreases. The load of the receiving device 101 is, for example, the charging unit 406 and the battery 407 in Figure 4. For example, if the GP is 5 watts, even if the positional relationship between the receiving antenna 405 and the transmitting antenna 305 changes and the power transmission efficiency decreases, the transmitting device 102 will be controlled to output 5 watts to the load in the receiving device 101 and will transmit power.

[0014] Furthermore, when transmitting power from the power transmission device 102 to the power receiving device 101, if there is a foreign object other than the power receiving device 101 near the power transmission device 102, the electromagnetic waves used for power transmission may affect the foreign object, potentially raising its temperature or destroying it. Therefore, the WPC standard specifies a method for the power transmission device 102 to detect the presence of a foreign object on the charging base 103, so as to prevent the foreign object from overheating or being destroyed by stopping power transmission if a foreign object is present. Specifically, the Power Loss method is specified, which detects the foreign object based on the difference between the power transmitted by the power transmission device 102 and the power received by the power receiving device 101. In addition, the Q-value measurement method is specified, which detects the foreign object based on the change in the quality coefficient (Q-value) of the power transmission antenna (power transmission coil) 305 of the power transmission device 102. Note that the foreign object detected by the power transmission device 102 in this embodiment is not limited to objects present on the charging base 103. The power transmission device 102 only needs to detect foreign objects located in its vicinity. For example, it may detect foreign objects located within the range 104 from which it can transmit power.

[0015] Figure 2 is a diagram illustrating foreign object detection based on the Power Loss method specified in the WPC standard. The horizontal axis of Figure 2 represents the power transmitted by the power transmission device 102, and the vertical axis represents the power received by the power receiving device 101. A foreign object is an object different from the power receiving device 101 that may affect the transmission of power from the power transmission device 102 to the power receiving device 101, such as a conductive metal piece. Such metal pieces include, for example, paper clips or IC cards. Objects that are essential to the power receiving device and the product into which the power receiving device is incorporated, or to the product into which the power transmission device and power receiving device are incorporated, and that may unintentionally generate heat when exposed to the radio power transmitted by the power transmission antenna, are not considered foreign objects.

[0016] First, the power transmission device 102 transmits power with transmission power value Pt1 to the power receiving device 101. The power receiving device 101 then receives power with received power value Pr1. The power transmission device 102 then stores the transmission power value Pt1. Here, the transmission power value Pt1 or the received power value Pr1 is a predetermined minimum transmission power or received power. At this time, the power receiving device 101 controls the load (for example, the charging unit 406 and battery 407 in Figure 4) so ​​that the power received is the minimum power. This load state is called the Light Load state. For example, the power receiving device 101 may disconnect the load from the receiving antenna 405 so that the received power is not supplied to the load. Subsequently, the power receiving device 101 transmits the received power value Pr1 to the power transmission device 102. Upon receiving the power value Pr1 from the power receiving device 101, the power transmitting device 102 calculates that the power loss Ploss1 between the power transmitting device 102 and the power receiving device 101 is Pt1-Pr1, and can create a calibration point 200 that shows the correspondence between Pt1 and Pr1.

[0017] Next, the power transmission device 102 changes the power transmission value to power transmission value Pt2 and transmits power of power transmission value Pt2 to the power receiving device 101. The power receiving device 101 then receives power of power received value Pr2. The power transmission device 102 then stores the power transmission value Pt2. Here, the power transmission value Pt2 or power received value Pr2 is a predetermined maximum power transmission or power reception. At this time, the power receiving device 101 controls the load (for example, the charging unit 406 and battery 407 in Figure 4) so ​​that the power received is the maximum power. This state of the load is called the Connected Load state (load connection state). For example, the power receiving device 101 connects the power receiving antenna 405 to the load so that the received power is supplied to the load. Next, the power receiving device 101 transmits the power received value Pr2 to the power transmission device 102. Upon receiving the power value Pr2 from the power receiving device 101, the power transmitting device 102 calculates that the power loss Ploss2 between the power transmitting device 102 and the power receiving device 101 is Pt2-Pr2, and can create a calibration point 201 that shows the correspondence between Pt2 and Pr2.

[0018] The power transmission device 102 then creates a straight line 202 by linear interpolation between calibration point 200 and calibration point 201. The straight line 202 shows the relationship between transmitted power and received power when there are no foreign objects in the vicinity of the power transmission device 102. Based on the straight line 202, the power transmission device 102 can predict the power value that the power receiving device 101 will receive when it transmits power of a predetermined transmitted power value in the absence of foreign objects. For example, if the power transmission device 102 transmits power of a transmitted power value Pt3, the power transmission device 102 can infer from point 203 on the straight line 202, which corresponds to the transmitted power value Pt3, that the power received by the power receiving device 101 will be Pr3.

[0019] The power transmission device 102 can determine the amount of power loss between the power transmission device 102 and the power reception device 101 according to the load of the power reception device 101, based on multiple combinations of the power transmission power value of the power transmission device 102 and the power reception power value of the power reception device 101, measured while varying the load of the power reception device 101. Furthermore, the power transmission device 102 can estimate the amount of power loss between the power transmission device 102 and the power reception device 101 according to the load of the power reception device 101 by interpolation from the above multiple combinations. In this way, the calibration process performed by the power transmission device 102 and the power reception device 101 in order for the power transmission device 102 to obtain combinations of power transmission power value and power reception power value will be referred to below as the "Power Loss Method Calibration Process (CAL Process)".

[0020] After the calibration described above, let's assume that when the power transmission device 102 actually transmits power of transmission power value Pt3 to the power receiving device 101, the power transmission device 102 receives the power received power value Pr3' from the power receiving device 101. The power transmission device 102 calculates a value Ploss_FO = Pr3 - Pr3' by subtracting the power received power value Pr3' actually received from the power receiving device 101 from the power received power value Pr3 when no foreign objects are present in the vicinity of the power transmission device 102. This Ploss_FO can be considered as the amount of power loss due to the power consumed by foreign objects when they are present in the vicinity of the power transmission device 102 and the power receiving device 101. Therefore, if the power value Ploss_FO, which is the power that would have been consumed by the foreign objects, exceeds a predetermined threshold, the power transmission device 102 can determine that foreign objects are present in the vicinity of the power transmission device 102.

[0021] Alternatively, the power transmission device 102 may first determine the amount of power loss between the power transmission device 102 and the power receiving device 101, Ploss3 = Pt3 - Pr3, from the received power value Pr3 when no foreign objects are present in the vicinity of the power transmission device 102. Next, the power transmission device 102 may determine the amount of power loss between the power transmission device 102 and the power receiving device 101, Ploss3' = Pt3 - Pr3', from the received power value Pr3' received from the power receiving device 101 when foreign objects are present in the vicinity of the power transmission device 102. Then, the power transmission device 102 may estimate the amount of power value Ploss_FO that would have been consumed by the foreign object using Ploss3' - Ploss3 (= Ploss_FO).

[0022] As described above, the power value Ploss_FO, which is estimated to have been consumed by the foreign object, can be calculated as either Pr3-Pr3'(=Ploss_FO) or Ploss3'-Ploss3(=Ploss_FO). In the following, we will primarily describe the method of calculating Ploss3'-Ploss3(=Ploss_FO), but this embodiment can also be applied to the method of calculating Pr3-Pr3'(=Ploss_FO). This concludes the explanation of foreign object detection based on the power loss method.

[0023] Foreign object detection using the Power Loss method is performed during power transmission (the Power Transfer phase described later) based on data obtained in the Calibration phase described later. Foreign object detection using the Q-value measurement method is performed before power transmission (the Negotiation phase or Renegotiation phase before Digital Ping transmission described later).

[0024] The power receiving device 101 and power transmitting device 102 in this embodiment communicate for power transmission and reception control based on the WPC standard. The WPC standard defines multiple phases, including the Power Transfer phase in which power transmission is performed and one or more phases prior to actual power transmission, and necessary power transmission and reception control communication is performed in each phase. The phases prior to power transmission include the Selection phase, Ping phase, Identification and Configuration phase, Negotiation phase, and Calibration phase. In the following, the Identification and Configuration phase will be referred to as the I&C phase. The processing of each phase will be described below.

[0025] In the Selection phase, the power transmission device 102 intermittently transmits Analog Pings to detect that an object has been placed on the charging base 103 of the power transmission device 102 (for example, that a power receiving device 101 or a conductive piece has been placed on the charging base 103). The power transmission device 102 detects at least one of the voltage value and current value of the power transmission antenna 305 when it transmits the Analog Ping, and if the voltage value falls 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.

[0026] In the Ping phase, the power transmitter 102 transmits a Digital Ping with higher power than the Analog Ping. The power of the Digital Ping is sufficient to activate the control unit 401 (Figure 4) of the power receiving device 101, which is placed on the charging base 103 of the power transmitter 102. The power receiving device 101 notifies the power transmitter 102 of the received voltage value. In this way, the power transmitter 102 recognizes that the object detected in the Selection phase is the power receiving device 101 by receiving the response from the power receiving device 101 that received the Digital Ping. Upon receiving notification of the received voltage value, the power transmitter 102 transitions to the I&C phase. In addition, before transmitting the Digital Ping, the power transmitter 102 measures the Q-factor of the power transmitting antenna 305. This measurement result is used when performing foreign object detection processing using the Q-factor measurement method.

[0027] In the I&C phase, the power transmission device 102 identifies the power receiving device 101 and obtains equipment configuration information (capacity information) from the power receiving device 101. The power receiving device 101 transmits an ID Packet and a Configuration Packet. The ID Packet contains the identifier information of the power receiving device 101, and the Configuration Packet contains the equipment configuration information (capacity information) of the power receiving device 101. Upon receiving the ID Packet and Configuration Packet, the power transmission device 102 responds with an acknowledgment (ACK). The I&C phase then ends.

[0028] In the Negotiation phase, the GP value is determined based on the GP value requested by the receiving device 101 and the transmission capacity of the transmission device 102. The transmission device 102 also receives an FOD Status Packet from the receiving device 101, which includes the Reference Quality Factor Value. This Reference Quality Factor Value is the Q value that can be measured at the terminal of the transmission antenna of the test transmission device when the receiving device is mounted on the test transmission device and no foreign objects are nearby. In the Q value measurement method, the presence or absence of foreign objects is determined based on a threshold value that uses this Reference Quality Factor Value as a reference. The transmission device 102 then performs foreign object detection processing using the Q value measurement method according to the request from the receiving device 101. Furthermore, the WPC standard specifies that the transmission device 102 will first transition to the Power Transfer phase and then, at the request of the receiving device 101, perform the same processing as in the Negotiation phase again. The phase in which these processes are performed after transitioning from the Power Transfer phase is called the Renegotiation phase.

[0029] In the Calibration phase, the power transmission device 102 and the power receiving device 101 perform calibration based on the WPC standard. The power receiving device 101 also notifies the power transmission device 102 of a predetermined power received value (power received value under light load conditions / power received value under maximum load conditions), and the power transmission device 102 makes adjustments to efficiently transmit power. The power received value notified to the power transmission device 102 is used for foreign object detection processing using the Power Loss method.

[0030] During the Power Transfer phase, control is performed for starting and continuing power transmission, as well as stopping power transmission due to errors or full charge. For this power transmission and reception control, the power transmission device 102 and the power receiving device 101 communicate by superimposing signals onto electromagnetic waves transmitted from the power transmission antenna 305 or the power receiving antenna 405, using the power transmission antenna 305 and the power receiving antenna 405, respectively, in accordance with the WPC standard. The range in which communication based on the WPC standard is possible between the power transmission device 102 and the power receiving device 101 is approximately the same as the power transmission range 104 of the power transmission device 102.

[0031] [Configuration of power transmission device 102 and power receiving device 101] Next, the configurations of the power transmission device 102 and the power receiving device 101 in this embodiment will be described. Note that the configuration described below is merely an example, and some (or all) of the described configurations may be replaced or omitted by other configurations that perform similar functions, and further configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block. Also, each functional block shown below is assumed to be implemented as a software program, but some or all of the components included in this functional block may be implemented in hardware.

[0032] Figure 3 is a block diagram showing an example of the functional configuration of the power transmission device 102 according to this embodiment. The power transmission device 102 includes a control unit 301, a power supply unit 302, a power transmission unit 303, a communication unit 304, a power transmission antenna 305, a memory 306, a resonant capacitor 307, a switch unit 308, and a communication unit 309. In Figure 3, the control unit 301, power supply unit 302, power transmission unit 303, communication unit 304, memory 306, and communication unit 309 are shown as separate blocks, but any multiple functional blocks among these may be implemented on the same chip.

[0033] The control unit 301 controls the entire power transmission device 102, for example, by executing a control program stored in the memory 306. The control unit 301 also performs control related to power transmission control, including communication for equipment authentication in the power transmission device 102. Furthermore, the control unit 301 may perform control for executing applications other than wireless power transmission. The control unit 301 is configured to include one or more processors, such as a CPU (Central Processing Unit) or an MPU (MicroProcessor Unit). The control unit 301 may also be configured to include hardware such as an Application Specific Integrated Circuit (ASIC). Additionally, the control unit 301 may include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processes. The control unit 301 stores information that should be stored during the execution of various processes in the memory 306. The control unit 301 also measures time using a timer (not shown).

[0034] The power supply unit 302 supplies DC or AC power to each functional block. The power supply unit 302 is, for example, a commercial power source or a battery. The battery stores power supplied from the commercial power source.

[0035] The power transmission unit 303 converts the DC or AC power input from the power supply unit 302 into AC power in the frequency band used for wireless power transmission, and inputs this AC power to the power transmission antenna 305 to generate electromagnetic waves for power reception to the power receiving device 101. Therefore, the power transmission unit 303 includes an inverter. For example, the power transmission unit 303 converts the DC voltage supplied by the power supply unit 302 into an AC voltage using a switching circuit in a half-bridge or full-bridge configuration with a FET (Field Effect Transistor). In this case, the power transmission unit 303 includes a gate driver that controls the on / off state of the FET.

[0036] The power transmission unit 303 controls the intensity of the electromagnetic waves output by adjusting the voltage (transmission voltage) or current (transmission current), or both, input to the power transmission antenna 305. Increasing the transmission voltage or transmission current increases the intensity of the electromagnetic waves, while decreasing the transmission voltage or transmission current decreases the intensity of the electromagnetic waves. The power transmission unit 303 also controls the output of AC power so that power transmission from the power transmission antenna 305 is started or stopped based on instructions from the control unit 301. The power transmission unit 303 also has the capacity to supply enough power to output 15 watts (W) of power to the charging unit 406 of the power receiving device 101, which complies with the WPC standard.

[0037] The communication unit 304 communicates with the power receiving device 101 for power transmission control based on the WPC standard. The communication unit 304 modulates the electromagnetic waves output from the power transmitting antenna 305 and transmits information to the power receiving device 101 to perform communication. The communication unit 304 also demodulates the electromagnetic waves transmitted from the power transmitting antenna 305, which have been modulated by the power receiving device 101, to obtain the information transmitted by the power receiving device 101. In other words, the communication performed by the communication unit 304 is carried out by superimposing a signal onto the electromagnetic waves transmitted from the power transmitting antenna 305.

[0038] In addition to storing the control program, the memory 306 also stores the status of the power transmission device 102 and the power receiving device 101 (such as the power transmission value and power reception value). For example, the status of the power transmission device 102 is acquired by the control unit 301. The status of the power receiving device 101 is acquired by the control unit 401 of the power receiving device 101 (Figure 4) and received by the control unit 301 via the communication unit 304.

[0039] The switch unit 308 is controlled by the control unit 301. The power transmitting antenna 305 is connected to the resonant capacitor 307. When the switch unit 308 is turned on and short-circuited, the power transmitting antenna 305 and the resonant capacitor 307 form a series resonant circuit and resonate at a specific frequency f1. At this time, current flows through the closed circuit formed by the power transmitting antenna 305, the resonant capacitor 307, and the switch unit 308. When the switch unit 308 is turned off and opened, power is supplied to the power transmitting antenna 305 and the resonant capacitor 307 from the power transmitting unit 303.

[0040] The communication unit 309 communicates with the communication unit 412 (Figure 4) of the power receiving device 101 using a communication standard different from the WPC standard, using a different antenna from the power transmitting antenna 305. Examples of communication standards include wireless LAN, Bluetooth® Low Energy (BLE), and NFC (Near Field Communication). The power transmitting device 102 may also selectively use the communication unit 304 and the communication unit 309 to communicate with the power receiving device 101.

[0041] Figure 4 is a block diagram showing an example configuration of the power receiving device 101 according to this embodiment. The power receiving device 101 includes a control unit 401, a UI (user interface) unit 402, a power receiving unit 403, a communication unit 404, a power receiving antenna 405, a charging unit 406, a battery 407, a memory 408, and a switch unit 409. Furthermore, the power receiving device 101 includes a switch unit 410, a resonant capacitor 411, a communication unit 412, and a switch unit 413. Note that the multiple functional blocks shown in Figure 4 may be implemented as a single hardware module.

[0042] The control unit 401 controls the entire power receiving device 101 by executing a control program stored in, for example, the memory 408. That is, the control unit 401 controls each of the functional units shown in Figure 4. Furthermore, the control unit 401 may also perform control for executing applications other than wireless power transmission. An example of the control unit 401 is configured to include one or more processors such as a CPU or MPU. The control unit 401 may also control the entire power receiving device 101 (or the entire smartphone if the power receiving device 101 is a smartphone) in cooperation with the OS (Operating System) that the control unit 401 is running.

[0043] Furthermore, the control unit 401 may be composed of hardware such as an ASIC. Alternatively, the control unit 401 may include an array circuit such as an FPGA compiled to perform predetermined processing. The control unit 401 stores information that should be stored while various processing is being performed in the memory 408. The control unit 401 also measures time using a timer (not shown).

[0044] The UI unit 402 provides various outputs to the user. These outputs include screen displays, flashing and color changes of LEDs (Light Emitting Diodes), audio output from the speaker, and vibration of the main body of the power receiving device 101. The UI unit 402 is realized by a liquid crystal panel, a speaker, a vibration motor, etc.

[0045] The power receiving unit 403 acquires AC power (AC voltage and AC current) generated by electromagnetic induction based on electromagnetic waves radiated from the power transmitting antenna 305 of the power transmitting device 102 via the power receiving antenna 405. The power receiving unit 403 then converts the AC power into DC power or AC power of a predetermined frequency and outputs power to the charging unit 406, which performs processing for charging the battery 407. In other words, the power receiving unit 403 includes a rectifier and a voltage control unit necessary to supply power to the load in the power receiving device 101. The above GP is the amount of power guaranteed to be output from the power receiving unit 403. The power receiving unit 403 has the capacity to supply enough power for the charging unit 406 to charge the battery 407 and to output 15 watts of power to the charging unit 406.

[0046] The communication unit 404 communicates with the communication unit 304 of the power transmission device 102 for power receiving control based on the WPC standard as described above. The communication unit 404 demodulates the electromagnetic waves input from the power receiving antenna 405 and acquires information transmitted from the power transmission device 102. Then, the communication unit 404 communicates with the power transmission device 102 by superimposing a signal related to the information to be transmitted to the power transmission device 102 onto the electromagnetic waves by load modulation or amplitude modulation.

[0047] In addition to storing the control program, the memory 408 also stores the status of the power transmission device 102 and the power receiving device 101. For example, the status of the power receiving device 101 is acquired by the control unit 401. The status of the power transmission device 102 is acquired by the control unit 301 of the power transmission device 102 and received by the control unit 401 via the communication unit 404 or the communication unit 412.

[0048] Switch units 409 and 410 are controlled by the control unit 401. The receiving antenna 405 is connected to the resonant capacitor 411. When switch unit 410 is turned ON and short-circuited, the receiving antenna 405 and the resonant capacitor 411 form a series resonant circuit and resonate at a specific frequency f2. At this time, current flows through the closed circuit formed by the receiving antenna 405, the resonant capacitor 411, and the switch unit 410, but no current flows to the receiving unit 403. When switch unit 410 is turned OFF and opened, the power received by the receiving antenna 405 and the resonant capacitor 411 is supplied to the receiving unit 403.

[0049] The switch unit 410 may be placed between the receiving antenna 405 and the resonant capacitor 411. When the switch unit 413 is ON and the switch unit 410 is also ON, the terminals of the receiving antenna 405 are short-circuited.

[0050] The switch unit 409 controls whether or not the received power is supplied to the load, which is the battery 407. The switch unit 409 also has the function of controlling the value of the load. When the switch unit 409 is in the off state and open, the received power is not supplied to the battery 407. When the switch unit 409 is in the on state and short-circuited, the received power is supplied to the battery 407.

[0051] In Figure 4, the switch unit 409 is positioned between the charging unit 406 and the battery 407, but it may also be positioned between the power receiving unit 403 and the charging unit 406. Alternatively, the switch unit 409 may be positioned between the closed circuit formed by the power receiving antenna 405, the resonant capacitor 411, and the switch unit 410, and the power receiving unit 403. In other words, the switch unit 409 may be used to control whether or not the received power is supplied to the power receiving unit 403. Also, although the switch unit 409 is shown as a single block in Figure 4, it is also possible to implement the switch unit 409 as part of the charging unit 406 or as part of the power receiving unit 403. Furthermore, although the switch unit 409 is inserted in series between the charging unit 406 and the battery 407, it may also be inserted in parallel between the charging unit 406 and the battery 407. In this case, when the switch unit 409 is turned off and opened, the received power is supplied to the battery 407. If the switch unit 409 is turned ON and short-circuited, the power received will not be supplied to the battery 407.

[0052] The switch unit 413 controls whether or not the terminals of the receiving antenna 405 are open. When the switch unit 413 is in the off state, the terminals of the receiving antenna 405 are open. When the switch unit 413 is in the on state, the receiving antenna 405 is connected to the receiving unit 403 via the resonant capacitor 411. In Figure 4, the switch unit 413 is positioned between the receiving antenna 405 and the resonant capacitor 411, but it may also be positioned between the resonant capacitor 411 and the receiving unit 403.

[0053] Figure 5 is a block diagram showing an example of the functional configuration of the control unit 301 of the power transmission device 102 shown in Figure 3. The control unit 301 includes a communication control unit 501, a power transmission control unit 502, a measurement unit 503, a setting unit 504, and a state detection unit 505. The communication control unit 501 performs control communication with the power receiving device 101 based on the WPC standard via the communication unit 304. Alternatively, the communication control unit 501 performs control communication with the power receiving device 101 via the communication unit 309.

[0054] The power transmission control unit 502 controls the power transmission unit 303 and controls the power transmission to the power receiving device 101. The measurement unit 503 measures the waveform attenuation index, which will be described later. The measurement unit 503 also measures the power transmitted to the power receiving device 101 via the power transmission unit 303 and measures the average transmitted power value per unit time. The measurement unit 503 also measures the Q value of the power transmission antenna 305. The measurement unit 503 also measures the coupling state (e.g., coupling coefficient) between the power transmission antenna 305 and the power receiving antenna 405, which will be described later.

[0055] The setting unit 504 sets a threshold value to be used for foreign object detection based on the waveform attenuation index measured by the measurement unit 503, for example, by a calculation process. Alternatively, the setting unit 504 sets a threshold value to be used for foreign object detection or for detecting misalignment between the power transmission device 102 and the power receiving device 101, for example, by a calculation process, based on the coupling state between the power transmission antenna 305 and the power receiving antenna 405 measured by the measurement unit 503. The coupling state is, for example, the coupling coefficient.

[0056] The state detection unit 505 detects the state between the power transmission device 102 and the power receiving device 101. For example, the state detection unit 505 detects foreign objects present between the power transmission device 102 and the power receiving device 101, or detects misalignment between the power transmission antenna 305 and the power receiving antenna 405. For example, the state detection unit 505 implements foreign object detection functions using the Power Loss method, Q value measurement method, waveform attenuation method, or coupling state (e.g., coupling coefficient) between the power transmission antenna 305 and the power receiving antenna 405, as well as misalignment detection functions between the power transmission antenna 305 and the power receiving antenna 405. The state detection unit 505 may also have functions for performing foreign object detection or misalignment detection processing between the power transmission antenna 305 and the power receiving antenna 405 using other methods. For example, in a power transmission device 102 equipped with NFC (Near Field Communication) communication functionality, the state detection unit 505 may perform foreign object detection processing using the NFC standard's peer detection function. In addition to detecting foreign objects, the state detection unit 505 can also detect changes in the state of the power transmission device 102. For example, the power transmission device 102 can also detect increases or decreases in the number of power receiving devices 101 on the power transmission device 102.

[0057] The setting unit 504 sets a threshold value that serves as a criterion for determining the presence or absence of foreign objects when the power transmission device 102 performs foreign object detection using the Power Loss method, Q-value measurement method, waveform attenuation method, or coupling state (e.g., coupling coefficient) between the power transmission antenna 305 and the power receiving antenna 405. The setting unit 504 may also have a function to set a threshold value that serves as a criterion for determining the presence or absence of foreign objects, which is necessary when performing foreign object detection processing using other methods. Furthermore, the state detection unit 505 can perform foreign object detection processing or positional misalignment detection processing based on the threshold value set by the setting unit 504 and the waveform attenuation index, power transmission power, Q-value, and coupling state between the power transmission antenna 305 and the power receiving antenna 405 measured by the measurement unit 503. The coupling state is, for example, the coupling coefficient. The positional misalignment detection processing is the process of detecting positional misalignment between the power transmission antenna 305 and the power receiving antenna 405.

[0058] The communication control unit 501, power transmission control unit 502, measurement unit 503, setting unit 504, and state detection unit 505 all function when the control unit 301 executes a program. Each processing unit is configured as an independent program and can operate in parallel while synchronizing the programs through event processing, etc. However, two or more of these processing units may be incorporated into a single program.

[0059] [Processing flow for power transmission in accordance with WPC standards] The WPC standard specifies the Selection phase, Ping phase, I&C phase, Negotiation phase, Calibration phase, and Power Transfer phase. Below, the operation of the power transmission device 102 and the power receiving device 101 in these phases will be explained using the sequence diagram in Figure 6.

[0060] Figure 6 is a sequence diagram for power transmission in accordance with the WPC standard. Here, a power transmission device 102 and a power receiving device 101 are used as examples. In step F601, the power transmission device 102 repeatedly and intermittently transmits Analog Ping according to the WPC standard to detect objects within the transmittable range 104. The power transmission device 102 performs the processes defined as the Selection phase and Ping phase of the WPC standard and waits for the power receiving device 101 to be placed on the charging stand 103.

[0061] In step F602, the power receiving device (e.g., a smartphone) 101 is placed on the charging cradle 103 to charge it. This places the power receiving device 101 within the range 104 to which the power transmitting device 102 can transmit power. In step F603, the power receiving device 101 receives an Analog Ping. In step F604, the power transmitting device 102 detects the presence of an object within the power transmission range 104. Then, in step F605, the power transmitting device 102 sends a Digital Ping according to the WPC standard. In step F606, when the power receiving device 101 receives the Digital Ping, it understands that the power transmitting device 102 has detected the power receiving device 101 and responds. When the power transmitting device 102 receives a predetermined response to the Digital Ping, it determines that the detected object is the power receiving device 101 and that the power receiving device 101 has been placed on the charging cradle 103.

[0062] In step F607, when the power transmission device 102 detects the placement of the power receiving device 101, it obtains identification information and capability information of the power receiving device 101 from the power receiving device 101 via I&C phase communication as defined in the WPC standard. Here, the identification information of the power receiving device 101 includes the Manufacturer Code and Basic Device ID. The capability information of the power receiving device 101 includes information elements that can identify the corresponding WPC standard version, the Maximum Power Value, and information indicating whether it has the WPC standard Negotiation function. The Maximum Power Value is a value that identifies the maximum power value that the power receiving device 101 can supply to the load. The power transmission device 102 may also obtain the identification information and capability information of the power receiving device 101 by a method other than the I&C phase communication of the WPC standard. Furthermore, the identification information may be any other identification information that can identify an individual power receiving device 101, such as a Wireless Power ID. The capability information may include information other than that described above.

[0063] Next, in step F608, the power transmission device 102 determines the value of GP with the power receiving device 101 through communication in the Negotiation phase as defined in the WPC standard. In this embodiment, GP = 5 watts. Note that in step F608, other procedures for determining GP may be performed, not limited to communication in the Negotiation phase as defined in the WPC standard. Also, the power transmission device 102 can obtain information indicating that the power receiving device 101 does not support the Negotiation phase, for example in step F607. In that case, the power transmission device 102 may not perform communication in the Negotiation phase and may set the value of GP to a small value predetermined in the WPC standard, for example.

[0064] From step F609 onward, the power transmission device 102 and the power receiving device 101 perform calibration based on the GP after it has been determined. In step F609, the power receiving device 101 transmits information to the power transmission device 102 that includes the received power value Pr1 in a light load state (a state where the transmitted power value is less than or equal to the first threshold) (hereinafter referred to as the first reference received power information). For example, the first reference received power information is the information of the received power value Pr1 of the power receiving device 101 when the transmitted power value Pt1 of the power transmission device 102 is 250 milliwatts. The first reference received power information is a Received Power Packet (mode 1) as defined in the WPC standard, but other messages may be used. The power transmission device 102 determines whether or not to accept the transmitted power value Pt1 and the received power value Pr1 as calibration points 200. The power transmission device 102 sends an acknowledgment (ACK) to the power receiving device 101 if it accepts the signal, and a negative response (NAK) to the power receiving device 101 if it does not accept the signal.

[0065] In step F610, the receiving device 101 receives an ACK from the transmitting device 102. From step F611 onward, the receiving device 101 performs processing to transmit information including the received power value Pr2 in the load-connected state (hereinafter referred to as the second reference received power information) to the transmitting device 102. The load-connected state is the Connected Load state, the maximum load state, or the load state in which the transmitted power value is greater than or equal to the second threshold. In this embodiment, since GP is 5 watts, the second reference received power information is the information of the received power value Pr2 of the receiving device 101 when the transmitted power value Pt2 of the transmitting device 102 is 5 watts. Here, the second reference received power information is the Received Power Packet (mode2) as defined in the WPC standard, but other messages may be used.

[0066] In step F611, the receiving device 101 sends a power output change instruction containing a positive value to increase the power transmitted from the power transmitting device 102 to 5 watts. In step F612, the power transmitting device 102 receives the power output change instruction and determines whether it is able to increase the power transmitted. In step F613, if the power transmitting device 102 is able to increase the power transmitted, it responds with an ACK and increases the power transmitted.

[0067] In step F614, the receiving device 101 sends another transmission output change instruction containing a positive value to increase the transmission power from the transmission device 102 to 5 watts. The transmission device 102 receives the above transmission output change instruction and determines whether it is able to handle the increase in transmission power. The second reference received power information is the received power information when the transmission power of the transmission device 102 is 5 watts. Therefore, in step F615, if the transmission power is 5 watts, the transmission device 102 responds to the above transmission output change instruction with NAK. As a result, the transmission device 102 suppresses the transmission of power exceeding 5 watts. In step F616, the receiving device 101 determines that the transmission power has reached 5 watts upon receiving NAK from the transmission device 102 and sends information including the received power value Pr2 in the load-connected state to the transmission device 102 as the second reference received power information.

[0068] In step F617, the power transmission device 102 calculates the amount of power loss in light load and load-connected states based on the power transmission values ​​Pt1 and Pt2 of the power transmission device 102, and the power reception values ​​Pr1 and Pr2 included in the first and second reference power reception information. The amount of power loss is the amount of power loss Ploss1 and Ploss2 between the power transmission device 102 and the power reception device 101. By interpolating between these power loss amounts Ploss1 and Ploss2, the power transmission device 102 can calculate the amount of power loss between the power transmission device 102 and the power reception device 101 for all possible power transmission values ​​(from 250 milliwatts to 5 watts). In step F618, the power transmission device 102 sends an ACK to the second reference power reception information from the power reception device 101, completing the calibration process.

[0069] In step F619, the power transmission device 102 and the power receiving device 101 communicate for equipment authentication and determine whether their respective devices can handle a larger GP. In step F620, if the power transmission device 102 and the power receiving device 101 determine that they can handle a larger GP, they re-determine the GP to a larger value (e.g., 15 watts).

[0070] In step F621, the receiving device 101 sends a power output change instruction containing a positive value to increase the power transmitted from the power transmitting device 102 to 15 watts. In step F622, the power transmitting device 102 receives the power output change instruction and, if it is able to increase the power transmitted, responds with an ACK and increases the power transmitted.

[0071] In step F623, the receiving device 101 again sends a transmission output change instruction containing a positive value in order to increase the transmission power from the transmission device 102 to 15 watts. In step F624, the transmission device 102 receives the above transmission output change instruction, and if the transmission power is 15 watts, it responds with NAK to the above transmission output change instruction. In step F625, the receiving device 101 determines that the transmission power has reached 15 watts upon receiving NAK from the transmission device 102, and sends information including the received power value in the load-connected state to the transmission device 102 as third reference received power information. That is, the calibration process for the case GP=15 watts is performed again. The third reference received power information is information including the received power value of the receiving device 101 in the load-connected state when the transmission power of the transmission device 102 is 15 watts.

[0072] In step F626, the power transmission device 102 calculates three power loss amounts based on the power transmission power values ​​of the power transmission device 102 (250 milliwatts, 5 watts, 15 watts) and the power received power values ​​included in the first, second, and third reference power received information. The three power loss amounts are the power loss amounts between the power transmission device 102 and the power receiving device 101. By interpolating between these power loss amounts, the power transmission device 102 can calculate the power loss amounts between the power transmission device 102 and the power receiving device 101 for all possible power transmission powers of the power transmission device 102 (from 250 milliwatts to 15 watts). In step F627, the power transmission device 102 sends an ACK to the third reference power received information from the power receiving device 101, completing the calibration process. In step F628, the power transmission device 102 determines that it is ready to start charging the power receiving device 101, starts transmitting power to the power receiving device 101, and moves to the Power Transfer phase.

[0073] In the Power Transfer phase, the power transmission device 102 transmits power to the power receiving device 101. The power transmission device 102 also performs foreign object detection using the Power Loss method. In the Power Loss method, the power transmission device 102 first calculates the amount of power loss between the power transmission device 102 and the power receiving device 101 in a state without foreign objects, based on the difference between the power transmission value of the power transmission device 102 and the power reception value of the power receiving device 101, as determined by the Calibration described above. The calculated amount of power loss is the amount of power loss in a normal state (without foreign objects) during power transmission. Then, if the amount of power loss between the power transmission device 102 and the power receiving device 101 measured during power transmission after Calibration deviates by a threshold from the amount of power loss in the normal state described above, the power transmission device 102 determines that "foreign objects are present" or "there is a possibility of foreign objects being present".

[0074] The above is an explanation of the Power Loss method. The Power Loss method detects foreign objects based on the measurement results of power loss during power transmission from the power transmission device 102 to the power receiving device 101. While the Power Loss method has the disadvantage that the accuracy of foreign object detection decreases when the power transmission device 102 is transmitting a large amount of power, it has the advantage that foreign object detection can be performed while power transmission continues, thus maintaining high power transmission efficiency.

[0075] Thus, foreign object detection can be performed during the Power Transfer phase using the Power Loss method. However, relying solely on the Power Loss method for foreign object detection carries the risk of false detection of foreign objects or incorrect determination of the absence of foreign objects when they are present. In particular, the Power Transfer phase is the phase in which the power transmission device 102 transmits power. If foreign objects are present near the power transmission device 102 and the power receiving device 101 during power transmission, heat generation from the foreign objects will increase, so it is necessary to improve the accuracy of foreign object detection in this phase. Therefore, in this embodiment, we consider implementing a foreign object detection method different from the Power Loss method in order to improve the accuracy of foreign object detection.

[0076] [Foreign object detection method using waveform attenuation] In the Power Transfer phase, the power transmission device 102 transmits power to the power receiving device 101. 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 will be possible without using newly defined foreign object detection signals, etc. A method for detecting foreign objects based on the attenuation state of the transmitted radio waves (hereinafter referred to as the waveform attenuation method) will be explained with reference to Figure 7.

[0077] Figure 7 is a diagram illustrating the principle of foreign object detection using the waveform attenuation method. Here, foreign object detection using the transmission waveform related to power transmission from the power transmission device 102 to the power receiving device 101 is explained as an example. In Figure 7, the waveform shows the change over time of the voltage value 700 (hereinafter simply referred to as the voltage value) of the high-frequency voltage applied to the power transmission antenna 305 of the power transmission device 102. The horizontal axis of Figure 7 represents time, and the vertical axis of Figure 7 represents the voltage value. The power transmission device 102, which transmits power to the power receiving device 101 via the power transmission antenna 305, stops transmitting power at time T0. That is, at time T0, the power supply for power transmission from the power supply unit 302 is stopped. The frequency of the transmitted radio wave related to power transmission from the power transmission device 102 is a predetermined frequency, for example, a fixed frequency between 85 kHz and 205 kHz used in the WPC standard. Point 701 is a point on the envelope of the high-frequency voltage and is the voltage value at time T1. In Figure 7, (T1, A1) indicates that the voltage value at time T1 is A1. Similarly, point 702 is a point on the envelope of the high-frequency voltage and represents the voltage value at time T2. In Figure 7, (T2, A2) indicates that the voltage value at time T2 is A2. The quality factor (Q value) of this transmitting antenna 305 can be determined based on the time change of the voltage value from time T0 onward. For example, the Q value can be calculated using (Equation 1) based on the time, voltage value, and frequency f of the high-frequency voltage at points 701 and 702 on the envelope of the voltage value. Q = πf(T2 - T1) / ln(A1 / A2) (Equation 1)

[0078] If foreign matter is present near the power transmission device 102 and the power receiving device 101, the Q value decreases. This is because, when foreign matter is present, energy loss occurs due to that foreign matter. Therefore, focusing on the slope of voltage attenuation, when foreign matter is present, more energy loss occurs due to the foreign matter than when it is absent, so the slope of the line connecting points 701 and 702 becomes steeper, and the attenuation rate of the waveform amplitude increases. In other words, the waveform attenuation method determines the presence or absence of foreign matter based on the voltage attenuation state between points 701 and 702, and in actual determination of the presence or absence of foreign matter, it is possible to make the determination by comparing some numerical value that represents this attenuation state. For example, the determination can be made using the Q value described above. A lower Q value means that the waveform attenuation rate (the degree of decrease in waveform amplitude per unit time) is higher. Alternatively, the determination may be made using the slope of the line connecting points 701 and 702 obtained from (A1-A2) / (T2-T1). Alternatively, if the time (T1 and T2) for observing the voltage decay state is fixed, the determination can also be made using a value representing the difference in voltage values ​​(A1-A2) or a value representing the ratio of voltage values ​​(A1 / A2). Alternatively, if the voltage value A1 immediately after the power transmission is stopped is constant, the determination can also be made using the value of voltage value A2 after a predetermined time has elapsed. Alternatively, the determination may be made using the value of the time (T2-T1) until the voltage value A1 becomes a predetermined voltage value A2.

[0079] Furthermore, even if the vertical axis of Figure 7 represents the current value flowing through the power transmission antenna 305, the attenuation state of the current value during the power transmission stop period changes depending on the presence or absence of foreign matter, similar to the case of the voltage value. When foreign matter is present, the waveform attenuation rate is higher than when there is no foreign matter. Therefore, foreign matter can be detected by applying the above method to the time change of the current value flowing through the power transmission antenna 305. That is, the presence or absence of foreign matter can be determined and detected by using the Q value obtained from the current waveform, the slope of the current value attenuation, the difference in current values, the ratio of current values, the absolute value of the current value, and the time until a predetermined current value is reached, etc., as waveform attenuation indices. Alternatively, foreign matter 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 foreign matter using an evaluation value calculated from the waveform attenuation index of the voltage value and the waveform attenuation index of the current value. In the above example, the waveform attenuation index is measured during the period when the power transmission device 102 temporarily stopped power transmission, but it is not limited to this. The waveform attenuation index may be measured during the period when the power transmission device 102 temporarily reduces the power supplied from the power supply unit 302 from a predetermined power level to a lower power level.

[0080] This section describes a method for detecting foreign objects based on the power transmission waveform during power transmission using the waveform attenuation method. During the transient response period immediately after the power transmission device 102 starts transmitting power, the power transmission waveform is unstable. Therefore, during this transient response period when the power transmission waveform is unstable, the power receiving device 101 controls itself to refrain from communicating (communication by load modulation) with the power transmission device 102. In addition, the power transmission device 102 controls itself to refrain from communicating (communication by frequency shift modulation) with the power receiving device 101.

[0081] When it is time to detect a foreign object, the power transmission device 102 temporarily stops power transmission. During the foreign object detection period when power transmission is stopped, the amplitude of the transmitted wave is attenuated, so the power transmission device 102 calculates the waveform attenuation rate of this attenuated waveform. The power transmission device 102 then determines that a foreign object is present if the calculated waveform attenuation rate exceeds a predetermined threshold. After the predetermined foreign object detection period has elapsed, if no foreign object is detected, the power transmission device 102 resumes power transmission. After resuming power transmission, the power transmission device 102 repeatedly performs the above-described transient response period waiting, foreign object detection timing determination, power transmission stop, and foreign object detection process. The above is the basic process of foreign object detection using the waveform attenuation method. Note that if the waveform attenuation rate can be obtained, it is not necessary to completely stop power transmission. For example, the power of transmission can be limited to a value close to zero.

[0082] When measuring the waveform attenuation rate of a transmitting signal, if elements such as the receiving unit 403, charging unit 406, and battery 407 are connected to the receiving antenna 405 and resonant capacitor 411 of the receiving device 101, the waveform attenuation rate of the attenuated waveform will be affected by the load from these elements. In other words, the waveform attenuation rate will change depending on the state of the receiving unit 403, charging unit 406, and battery 407. Therefore, even if the waveform attenuation rate is large, it becomes difficult to distinguish whether it is due to the influence of foreign objects or due to changes in the state of the receiving unit 403, charging unit 406, and battery 407. For this reason, when observing the waveform attenuation rate to detect foreign objects, the switch unit 409 may be disconnected. This makes it possible to eliminate the influence of the battery 407. Alternatively, the switch unit 410 may be turned on to short-circuit the circuit, allowing current to flow through the closed loop formed by the receiving antenna 405, resonant capacitor 411, and switch unit 410. This makes it possible to eliminate the influence of the power receiving unit 403, the charging unit 406, and the battery 407. As described above, by performing foreign object detection with the switch unit 409 disconnected or with the switch unit 410 turned on and short-circuited (connected), highly accurate foreign object detection is possible. Furthermore, by performing both disconnection of the switch unit 409 and short-circuiting (connection) of the switch unit 410, highly accurate foreign object detection is also possible. In addition, the same effect can be obtained by replacing the load with the "Light Load state" described above, instead of the "state with the switch unit 409 disconnected" described above.

[0083] Furthermore, when measuring the waveform attenuation rate of a transmitted wave, if elements such as the power transmission unit 303, communication unit 304, and power supply unit 302 are connected to the power transmission antenna 305 and resonant capacitor 307 of the power transmission device 102, the waveform attenuation rate of the attenuated waveform will be affected by these elements. In other words, the waveform attenuation rate will change depending on the state of the power transmission unit 303, communication unit 304, and power supply unit 302. Therefore, even if the waveform attenuation rate is large, it becomes difficult to distinguish whether it is due to the influence of foreign objects or to the power transmission unit 303, communication unit 304, and power supply unit 302. For this reason, when measuring the waveform attenuation rate, the switch unit 308 may be turned on to short-circuit it, so that current flows through the closed loop formed by the power transmission antenna 305, resonant capacitor 307, and switch unit 308. This makes it possible to eliminate the influence of the power transmission unit 303, communication unit 304, and power supply unit 302. Alternatively, a switch may be provided between the closed-loop circuit formed by the transmitting antenna 305, the resonant capacitor 307, and the switch unit 308, and the transmitting unit 303. When detecting foreign objects, the switch unit disconnects the closed-loop circuit from the transmitting unit 303, thereby eliminating the influence of the transmitting unit 303, the communication unit 304, and the power supply unit 302. As described above, by turning on the switch unit 308 to create a short circuit (connection), or by disconnecting the closed-loop circuit from the transmitting unit 303 with the switch unit, foreign object detection can be performed with high accuracy. Furthermore, by performing both turning on the switch unit 308 to create a short circuit (connection) and disconnecting the closed-loop circuit from the transmitting unit 303 with the switch unit, high accuracy foreign object detection can also be achieved.

[0084] [Method for setting the foreign object detection threshold in waveform attenuation method] This section describes how to set the threshold value for the waveform attenuation index used to determine the presence or absence of foreign objects when detecting foreign objects using the waveform attenuation method described above.

[0085] Figure 8 is a diagram illustrating foreign object detection in the waveform attenuation method. First, the power receiving device 101 controls the load of the power receiving device 101 to a light load state so that when power is transmitted from the power transmitting device 102, no power or only a very small amount of power is supplied to the load of the power receiving device 101. Let the power transmission value of the power transmitting device 102 at this time be Pt1. Then, the power transmitting device 102 stops transmitting power in that state and measures the waveform attenuation rate. Let the waveform attenuation rate at this time be δ1. At this time, the power transmitting device 102 recognizes the power transmission value Pt1 that it is transmitting and stores a calibration point 800 in memory 306 that associates the power transmission value Pt1 with the waveform attenuation rate δ1. Next, the power receiving device 101 controls the load of the power receiving device 101 so that, when power is transmitted from the power transmitting device 102, the load of the power receiving device 101 is connected to the load so that the maximum power is supplied to the load of the power receiving device 101, or power exceeding a predetermined threshold is supplied. The power transmitted by the power transmitting device 102 at this time is denoted as Pt2. Then, the power transmitting device 102 stops transmitting power in this state and measures the waveform attenuation rate. The waveform attenuation rate at this time is denoted as δ2. At this time, the power transmitting device 102 stores a calibration point 801 in memory 306 that associates the transmitted power value Pt2 with the waveform attenuation rate δ2. Subsequently, the power transmitting device 102 linearly interpolates between calibration point 800 and calibration point 801 to create a line 802. The line 802 shows the relationship between the transmitted power value and the waveform attenuation rate of the transmitted radio wave when there are no foreign objects around the power transmitting device 102 and the power receiving device 101. Therefore, the power transmission device 102 can estimate the waveform attenuation rate of the transmitted radio wave for each power transmission value in the absence of foreign matter from the straight line 802. For example, when the power transmission value is Pt3, the waveform attenuation rate can be estimated to be δ3 from point 803 on the straight line 802 corresponding to the power transmission value Pt3. Based on the above estimation results, the power transmission device 102 can then calculate a threshold value used to determine the presence or absence of foreign matter for each power transmission value. For example, a waveform attenuation rate that is larger by a predetermined value (a value corresponding to the measurement error) than the estimated waveform attenuation rate in the absence of foreign matter for a given power transmission value may be set as the threshold value for determining the presence or absence of foreign matter.The calibration process performed by the power transmission device 102 and the power receiving device 101 in order for the power transmission device 102 to acquire a combination of the transmitted power value and the waveform attenuation rate will be referred to below as the "waveform attenuation method calibration process (CAL process)".

[0086] Furthermore, the power receiving device 101 may perform the control to result in no power being supplied to the load / a light load state, and the control to result in a load connection state, after notifying the power transmission device 102 of its intention to perform these controls. Also, either of these two controls may be performed first.

[0087] Furthermore, the operation described in this embodiment for calculating the threshold used to determine the presence or absence of foreign matter for each load (each transmitted power value) may be performed in the Calibration phase. As described above, in the Calibration phase, the power transmission device 102 acquires data necessary for detecting foreign matter using the Power Loss method. At that time, the power transmission device 102 acquires data on the amount of power loss when the load state of the power receiving device 101 is a light load state and when it is a load connected state. The measurement of calibration point 800 and calibration point 801 in Figure 8 may be performed in the Calibration phase described above, together with the measurement of the amount of power loss when the power receiving device 101 is in a light load state and when it is in a load connected state. That is, when the power transmission device 102 receives the first reference received power information from the power receiving device 101, it measures calibration point 800 in addition to the predetermined processing that should be performed in the Calibration phase. Furthermore, when the power transmission device 102 receives the second reference power information from the power receiving device 101, it performs a measurement of the calibration point 801 in addition to the predetermined processing that should be performed in the Calibration phase. This eliminates the need to set aside a separate period for measuring calibration point 800 and calibration point 801, making it possible to measure calibration point 800 and calibration point 801 in a shorter time.

[0088] Furthermore, when using the Q value obtained by (Equation 1), for example, as the "waveform attenuation index," a threshold can be set based on the Reference Quality Factor Value mentioned above. The Reference Quality Factor Value is transmitted by the power receiving device 101 to the power transmitting device 102 in the FOD Status Packet. This Reference Quality Factor Value is the Q value that can be measured at the terminal of the power transmitting antenna of the test power transmitting device when the power receiving device is mounted on the test power transmitting device and no foreign objects are nearby. Since the Reference Quality Factor Value and the Q value calculated by (Equation 1), which is the waveform attenuation index, are physically equivalent, it is possible to set a threshold using them.

[0089] [First method for measuring the coupling state of a transmitting antenna and a receiving antenna] Wireless power transmission transmits power by electromagnetically coupling a transmitting antenna 305 and a receiving antenna 405. That is, by passing an alternating current through the transmitting antenna 305 and changing the magnetic flux passing through the receiving antenna 405, a voltage is induced in the receiving antenna 405, thereby transmitting power. The coupling coefficient is an index that represents the coupling state between the transmitting antenna 305 and the receiving antenna 405. For example, when all (100%) of the magnetic flux generated by the transmitting antenna 305 passes through the receiving antenna 405, the coupling coefficient k is "k=1". Also, for example, when 70% of the magnetic flux generated by the transmitting antenna 305 passes through the receiving antenna 405, the coupling coefficient k is "k=0.7". In this case, the remaining magnetic flux (30%) generated by the transmitting antenna 305 becomes leakage flux, which is the magnetic flux generated by the transmitting antenna 305 that did not pass through the receiving antenna 405.

[0090] In other words, when the coupling state is good and the coupling coefficient value is large, the transmission efficiency of power transmitted from the power transmission device 102 to the power receiving device 101 is high. On the other hand, when the coupling state is poor and the coupling coefficient value is small, the transmission efficiency of power transmitted from the power transmission device 102 to the power receiving device 101 is low.

[0091] Factors that can lead to poor coupling (a decrease in the coupling coefficient) include the presence of foreign matter (such as metal fragments) between the transmitting antenna 305 and the receiving antenna 405, and misalignment between the transmitting antenna 305 and the receiving antenna 405. If foreign matter is present between the transmitting antenna 305 and the receiving antenna 405, heat generation may occur in the foreign matter. Furthermore, if misalignment occurs between the transmitting antenna 305 and the receiving antenna 405, as mentioned above, leakage flux will increase, potentially generating significant noise in the surrounding environment. Therefore, when the coupling is poor (the coupling coefficient is small), appropriate control can be implemented to achieve safer and higher-quality wireless power transmission.

[0092] In this embodiment, in order to improve the accuracy of detecting foreign objects between the transmitting antenna 305 and the receiving antenna 405 and to detect positional misalignment between the transmitting antenna 305 and the receiving antenna 405, the coupling state between the transmitting antenna 305 and the receiving antenna 405 is detected. The coupling state is, for example, the coupling coefficient. The method for measuring the coupling state (coupling coefficient) between the transmitting antenna 305 and the receiving antenna 405 is described below.

[0093] Figure 9 shows an example of an equivalent circuit of a transmitting antenna (coil) 305 and a receiving antenna (coil) 405. Resistance r1 is the winding resistance of the transmitting antenna 305. Self-inductance L1 is the self-inductance of the transmitting antenna 305. Voltage V1 is the input voltage of the transmitting antenna 305. Resistance r2 is the winding resistance of the receiving antenna 405. Self-inductance L2 is the self-inductance of the receiving antenna 405. Voltage V2 is the output voltage of the receiving antenna 405. In this case, the coupling coefficient k, which represents the coupling state between the transmitting antenna 305 and the receiving antenna 405, can be obtained by (Equation 2). k = (V2 / V1)√(L1 / L2) (Equation 2)

[0094] Therefore, when the power transmission device 102 calculates the coupling coefficient, the power receiving device 101 notifies the power transmission device 102 of the voltage V2 applied to the power receiving antenna 405 measured by the power receiving device 101, and the value of the self-inductance L2 of the power receiving antenna 405 that the power receiving device 101 has previously stored. The power transmission device 102 then obtains the voltage V1 applied to the power transmitting antenna 305 measured by the power transmission device 102, and the value of the self-inductance L1 of the power transmitting antenna 305 that the power transmission device 102 has previously stored. The power transmission device 102 can calculate the coupling coefficient k using the voltage V1, the value of the self-inductance L1, the voltage V2 received from the power receiving device 101, and the value of the self-inductance L2 of the power receiving antenna 405. Alternatively, the power receiving device 101 may notify the power transmitting device 102 of a constant calculated using all or any of the voltage V1 and self-inductances L1 and L2, and the power transmitting device 102 may calculate the coupling coefficient k using the constant and the voltage V2.

[0095] On the other hand, when the receiving device 101 calculates the coupling coefficient, the transmitting device 102 notifies the receiving device 101 of the voltage V1 applied to the transmitting antenna 305 measured by the transmitting device 102, and the value of the self-inductance L1 of the transmitting antenna 305 that the transmitting device 102 has previously stored. The receiving device 101 then obtains the voltage V2 applied to the receiving antenna 405 measured by the receiving device 101, and the value of the self-inductance L2 of the receiving antenna 405 that the receiving device 101 has previously stored. The receiving device 101 can calculate the coupling coefficient k using the voltage V1, the value of the self-inductance L2, and the voltage V1 and self-inductance L1 values ​​received from the transmitting device 102. Alternatively, the transmitting device 102 may notify the receiving device 101 of a constant calculated using all or any of the voltage V2 and self-inductances L1 and L2, and the receiving device 101 may calculate the coupling coefficient k using this constant and the voltage V1.

[0096] The voltage V1 applied to the transmission antenna 305 may be determined by the transmission device 102 actually measuring the voltage V1 applied to the transmission antenna 305, or by calculating the voltage V1 from the set value of the power transmission power transmitted by the transmission device 102. Alternatively, the set value of the transmission voltage at the time of transmission may be used as the voltage V1. Furthermore, the voltage V1 applied to the transmission antenna 305 may be determined from the voltage V3 applied to the circuit (e.g., inverter) included in the transmission unit 303 of the transmission device 102 and the voltage across the resonant capacitor 411. In this case, the voltage V3 applied to the circuit (e.g., inverter) included in the transmission unit 303 of the transmission device 102 may also be calculated from the set value of the power transmission power transmitted by the transmission device 102.

[0097] Furthermore, when the power transmission device 102 or the power receiving device 101 performs the above-mentioned measurements, the power receiving device 101 may control the switch unit 413 to turn off, so that the terminals of the power receiving antenna 405 are open. This makes it possible to open both ends of the power receiving antenna 405, as shown in Figure 9.

[0098] Furthermore, this eliminates the influence of the resonant capacitor 411, the power receiving unit 403, the charging unit 406, and the battery 407 when performing the above-mentioned measurements. As a result, it becomes possible to measure the coupling state (coupling coefficient) between the power transmitting antenna 305 and the power receiving antenna 405 with higher precision.

[0099] In the above, the "coupling coefficient" was used as an indicator representing the coupling state between the transmitting antenna 305 and the receiving antenna 405. However, there are multiple values ​​that represent the coupling state between the transmitting antenna 305 and the receiving antenna 405, not just the "coupling coefficient." In this embodiment, these values ​​that represent the coupling state between the transmitting antenna 305 and the receiving antenna 405 are called "coupling state indices." For example, the "coupling coefficient" mentioned above is included in the "coupling state indices." All coupling state indices are values ​​that correspond to the coupling state between the transmitting antenna 305 and the receiving antenna 405. The contents of this embodiment can be applied similarly when using coupling state indices other than the coupling coefficient.

[0100] The coupling state index representing the coupling state between the transmitting antenna 305 and the receiving antenna 405 may be calculated by other methods. For example, the coupling state between the transmitting antenna 305 and the receiving antenna 405 may be calculated using the voltage V3 applied to the circuit (e.g., inverter) included in the transmitting unit 303 of the power transmission device 102 and the voltage V4 applied to the circuit (e.g., rectifier) ​​included in the receiving unit 403 of the power receiving device 101. In this case, the power transmission device 102 notifies the power receiving device 101 of the voltage V3, enabling the power receiving device 101 to calculate an index representing the coupling state between the transmitting antenna 305 and the receiving antenna 405. At this time, the power transmission device 102 may also notify the power receiving device 101 of constants including the characteristics of the self-inductance L1, and based on these, the power receiving device 101 may calculate an index representing the coupling state between the transmitting antenna 305 and the receiving antenna 405.

[0101] Similarly, when the receiving device 101 notifies the transmitting device 102 of the voltage V4, the transmitting device 102 can calculate the coupling state index between the transmitting antenna 305 and the receiving antenna 405. At this time, the receiving device 101 may also notify the transmitting device 102 of constants including the characteristics of the self-inductance L2, and based on this, the transmitting device 102 may calculate the coupling state index between the transmitting antenna 305 and the receiving antenna 405.

[0102] Furthermore, when the power transmission device 102 or the power receiving device 101 performs the above-mentioned measurements, the power receiving device 101 may control the switch unit 413 to turn off, so that the terminals of the circuit consisting of the power receiving antenna 405 and the resonant capacitor 411 are open. This eliminates the influence of the power receiving unit 403, the charging unit 406, and the battery 407 when performing the above-mentioned measurements, making it possible to measure the coupling state (coupling coefficient) between the power transmission antenna 305 and the power receiving antenna 405 with higher accuracy.

[0103] [Second method for measuring the coupling state of a transmitting antenna and a receiving antenna] The following describes a second method for measuring the coupling state (coupling coefficient) between the transmitting antenna 305 and the receiving antenna 405. The coupling coefficient k, which represents the coupling state between the transmitting antenna 305 and the receiving antenna 405, is calculated using (Equation 3). k = √(1 - Lsc / Lopen) (Equation 3)

[0104] Here, Lsc is the inductance value of the transmitting antenna 305 when both ends of the receiving antenna 405 are short-circuited. For example, Lsc can be measured by measuring the inductance value of the transmitting antenna 305 with the switch unit 413 turned ON (short-circuited) and the switch unit 410 located between the switch unit 413 and the resonant capacitor 411 also turned ON (short-circuited). The inductance value of the transmitting antenna 305 can be determined from the voltage V5 input to the transmitting antenna 305 and the current I1 flowing through the transmitting antenna 305.

[0105] Furthermore, Lopen is the inductance value of the transmitting antenna 305 when both ends of the receiving antenna 405 are open. For example, Lopen can be measured by measuring the inductance value of the transmitting antenna 305 with the switch unit 413 in the off state (open state). The inductance value of the transmitting antenna 305 can be determined from the voltage V6 input to the transmitting antenna 305 and the current I2 flowing through the transmitting antenna 305.

[0106] The coupling state index between the transmitting antenna 305 and the receiving antenna 405 can be determined by the voltage input to the transmitting antenna 305 and the current flowing through the transmitting antenna 305 when both ends of the receiving antenna 405 are short-circuited and when they are open-circuited.

[0107] Furthermore, the power transmission device 102 can calculate an index (including the coupling coefficient) representing the coupling state between the power transmission antenna 305 and the power receiving antenna 405 based on the voltage applied to the circuit (e.g., inverter) included in the power transmission unit 303 and the current flowing through the circuit (e.g., inverter) included in the power transmission unit 303. The voltage V5 or V6 mentioned above may be the voltage applied to the circuit (e.g., inverter) included in the power transmission unit 303, or the voltage applied to the power transmission antenna 305. Alternatively, the voltage V5 or V6 mentioned above may be the voltage applied to both terminals of a series resonant circuit consisting of the power transmission antenna 305 and the resonant capacitor 307. Alternatively, the voltage applied to the circuit (e.g., inverter) included in the power transmission unit 303 and the voltage across the resonant capacitor 411 may be measured, and the voltage applied to the power transmission antenna 305 may be calculated from the results. In other words, it is possible to determine the coupling state index (coupling coefficient) between the power transmission antenna 305 and the power receiving antenna 405 from the measurement results of the voltage applied to the circuit (e.g., inverter) included in the power transmission unit 303 and the voltage across the resonant capacitor 411. In this case, the voltage applied to the circuit (e.g., inverter) included in the power transmission unit 303 may also be calculated from the set value of the power transmitted by the power transmission device 102.

[0108] Furthermore, the currents I1 or I2 mentioned above may be currents flowing through the circuit (e.g., inverter) included in the power transmission unit 303, or currents flowing through the power transmission antenna 305. Also, the "open" and "short-circuit" states of the power receiving antenna 405 may be realized by the switch units 410 and 413 controlled by the control unit 401, or by the power receiving unit 403. Alternatively, the "short-circuit" state of the power receiving antenna 405 may be the Light Load state mentioned above.

[0109] In this measurement method, the power transmission device 102 measures voltages V5 and V6 and currents I1 and I2, enabling it to calculate an index (including the coupling coefficient) representing the coupling state between the power transmission antenna 305 and the power receiving antenna 405. In other words, the voltage values ​​measured by the power receiving device 101, the inductance values ​​of the power receiving antenna 405, etc., are not necessary, and the power receiving device 101 does not need to notify the power transmission device 102 of this information. However, when the power transmission device 102 measures voltage V5 and current I1, the power receiving device 101 needs to open both terminals of the circuit containing the power receiving antenna 405. Also, when the power transmission device 102 measures voltage V6 and current I2, the power receiving device 101 needs to short-circuit both terminals of the circuit containing the power receiving antenna 405. In other words, depending on the timing of the voltage and current measurements by the power transmission device 102, the power receiving device 101 needs to appropriately control the circuit containing the power receiving antenna 405 so that both terminals are open or short-circuited. The timing may be determined by the power transmission device 102 and notified to the power receiving device 101, or it may be determined by the power receiving device 101 and notified to the power transmission device 102. This notification is carried out by communication based on the WPC standard between the communication unit 304 of the power transmission device 102 and the communication unit 404 of the power receiving device 101. Alternatively, the notification may be carried out by communication using a standard different from the WPC standard between the communication unit 309 of the power transmission device 102 and the communication unit 412 of the power receiving device 101. Examples of such different communication standards include wireless LAN, Bluetooth® Low Energy (BLE), NFC (Near Field Communication), etc.

[0110] [Method for setting an abnormal state detection threshold using the coupling state between the transmitting antenna and the receiving antenna] The wireless power transmission system 100 performs abnormal state detection, such as detecting foreign objects between the transmitting antenna 305 and the receiving antenna 405, and detecting positional misalignment between the transmitting antenna 305 and the receiving antenna 405. This document describes how to set a threshold for the coupling state (including coupling coefficient) between the transmitting antenna 305 and the receiving antenna 405 in order to determine whether or not an abnormal state exists.

[0111] The following describes how to set the threshold. The coupling state index used to detect the presence or absence of abnormal conditions between the transmitting antenna 305 and the receiving antenna 405 is used to make judgments such as abnormal condition present, possible abnormal condition, or no abnormal condition. In this case, the threshold for the coupling state index is the coupling state index when there is no abnormal condition. For example, when the receiving device is mounted on the test power transmission device and there is no abnormal condition between the transmitting antenna and the receiving antenna, the coupling state index between the test power transmission device including the transmitting antenna and the receiving device including the receiving antenna can be used as the threshold. In other words, the receiving device 101 stores the coupling state index measured in advance in the memory 408 and notifies the power transmission device 102 of the coupling state index, so that the power transmission device 102 can use the coupling state index as the threshold.

[0112] [Processing of power transmission equipment when the waveform attenuation method is applied to the WPC standard] Figure 10 is a flowchart showing the processing method of the power transmission device 102 when foreign object detection is performed by applying the waveform attenuation method to the WPC standard. The main points that differ from the WPC standard will be explained.

[0113] When measuring the coupling state between the transmitting antenna 305 and the receiving antenna 405 to determine whether or not to perform foreign object detection, a threshold value is required as a criterion for determining whether or not there is a change in the coupling state. Here, we show an example in which the coupling coefficient is used as an indicator of the coupling state between the transmitting antenna 305 and the receiving antenna 405, and we show how to calculate the initial value k0 of that coupling coefficient.

[0114] In step S1001, the power transmission device 102 performs the above-described Selection phase and Ping phase processing. In the Ping phase, the power transmission device 102 measures the voltage value Vtx0 of the power transmission antenna 305 while transmitting a Digital Ping and records it in memory 306. The power transmission device 102 also obtains the power receiving voltage value Vrx0 of the power receiving device 101, which is notified by the power receiving device 101, by receiving a predetermined packet and records it in memory 306. A Signal Strength Packet can be used as the predetermined packet. The Signal Strength Packet may include not only the power receiving voltage value of the power receiving device 101 but also the power receiving value, or the power receiving value of the power receiving device 101 may be notified to the power transmission device 102 in a separate Signal Strength Packet.

[0115] In step S1002, the power transmission device 102 receives an Identification Packet and a Configuration Packet from the power receiving device 101 during the I&C phase. During the I&C phase, the power transmission device 102 obtains the inductance value Lrx of the power receiving antenna 405 notified by the power receiving device 101 by receiving a predetermined packet and records it in the memory 306. The predetermined packet can be an Identification Packet or an Extended Identification Packet.

[0116] In step S1003, the power transmission device 102 negotiates the GP value with the power receiving device 101 during the Negotiation phase and determines the GP value. In step S1004, the power transmission device 102 transitions to the Calibration phase. In step S1005, the power transmission device 102 performs calibration. In step S1006, the power transmission device 102 transitions to the Power Transfer phase.

[0117] The power transmission device 102 calculates the initial state of the coupling between the transmitting antenna 305 and the receiving antenna 405. The power transmission device 102 uses Vtx0, Vrx0, Lrx, and the inductance value Ltx of the power transmission device 102, which has been previously recorded in the memory 306, to calculate the initial value k0 of the coupling coefficient between the transmitting antenna 305 and the receiving antenna 405. The power transmission device 102 records the initial value k0 of the coupling coefficient in the memory 306. This calculation only needs to be performed before the power transmission device 102 starts the process of calculating the coupling state between the transmitting antenna 305 and the receiving antenna 405.

[0118] Furthermore, when performing foreign object detection using the waveform attenuation method, a threshold value is required as a criterion for determining whether or not a foreign object is present. Here, the power transmission device 102 is shown to pre-measure the waveform attenuation rate when no foreign object is present and calculate the threshold value based on that. The power transmission device 102 performs foreign object detection using the waveform attenuation method. Then, if the measured waveform attenuation rate is greater than the threshold value, the power transmission device 102 determines that "a foreign object is present" or "there is a possibility of a foreign object being present," and if the measured waveform attenuation rate is less than the threshold value, it determines that "there is no foreign object" or "there is a high possibility that there is no foreign object."

[0119] This section explains the timing for pre-measuring the waveform attenuation rate in the absence of foreign matter. In the WPC standard, as mentioned above, the power transmission device 102 performs foreign matter detection using the Q-value measurement method in step S1003 of the Negotiation phase. If the power transmission device 102 determines that there is no foreign matter as a result of the foreign matter detection, it proceeds to steps S1004 and S1005 of the Calibration phase and step S1006 of the Power Transfer phase. In other words, proceeding to the Negotiation phase or later means that the foreign matter detection using the Q-value measurement method has determined that there is no foreign matter. Therefore, measuring the waveform attenuation rate in any of the Negotiation phase, Calibration phase, or Power Transfer phase has a high probability of determining the waveform attenuation rate in the absence of foreign matter. Thus, the timing for measuring the waveform attenuation rate in the absence of foreign matter can be any of the Negotiation phase, Calibration phase, or Power Transfer phase.

[0120] In this embodiment, the timing for measuring the waveform attenuation rate in the absence of foreign matter is set to step S1007, the first step of the Power Transfer phase. The reason is that the longer the time elapsed since it was determined that there was no foreign matter using the Q-value measurement method, the higher the probability that foreign matter will be placed near the power transmission device 102 and the power receiving device 101. Then, at the timing for foreign matter detection specified by the power receiving device 101 or the power transmission device 102, the power transmission device 102 measures the waveform attenuation rate of the transmitted radio wave in the absence of foreign matter and calculates a threshold Q0. The power transmission device 102 then compares the Q-value measured thereafter with the threshold Q0 calculated from the waveform attenuation rate in the absence of foreign matter described above to determine the presence or absence of foreign matter.

[0121] However, the waveform attenuation method has the disadvantage of causing a decrease in transmission efficiency due to the temporary suspension of power transmission, as it requires the power transmission device 102 to temporarily stop transmitting power and observe the attenuation rate of the transmitted radio waves to detect foreign objects. On the other hand, the waveform attenuation method has the advantage of enabling highly accurate foreign object detection even when foreign object detection processing is performed while a large amount of power is being transmitted. In other words, even in situations where it is difficult to accurately detect foreign objects using the Power Loss method, foreign objects can be detected by using the waveform attenuation method.

[0122] In step S1007, the power transmission device 102 measures the waveform attenuation rate of the transmitted radio wave in the absence of foreign matter, calculates the Q value of the power transmission antenna 305 from the waveform attenuation rate using (Equation 1), and sets this Q value as the threshold Q0.

[0123] In step S1008, the power transmission device 102 determines whether it has received an instruction from the power receiving device 101 to perform foreign object detection. This instruction to perform foreign object detection can be implemented with Received Power Packet (mode0). In the WPC standard, Received Power Packet includes information on the power received by the power receiving device 101, but here it includes information on the power received voltage value Vrx of the power receiving device 101. The power received voltage value Vrx is the voltage across the receiving antenna 405 of the power receiving device (RX) 101. The power transmission device 102 receives a Received Power Packet (mode0) packet from the power receiving device 101 and obtains the power received voltage value Vrx of the power receiving device 101. The power transmission device 102 records the obtained power received voltage value Vrx in memory 306, and also measures the power transmission voltage value Vtx of the power transmission device 102 and records it in memory 306. The transmission voltage value Vtx is the voltage across the terminals of the transmission antenna 305.

[0124] In step S1009, the power transmission device 102 calculates the current coupling state. Here, the power transmission device 102 calculates the coupling coefficient k between the transmitting antenna 305 and the receiving antenna 405. The power transmission device 102 uses Vtx, Vrx and Ltx, Lrx to calculate the coupling coefficient k using (Equation 2) and records it in memory 306.

[0125] In step S1010, the power transmission device 102 determines whether the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient already calculated is greater than or equal to a preset threshold k_diff. If the difference is greater than or equal to the threshold k_diff (YES in S1010), the process proceeds to step S1011. If the difference is less than the threshold k_diff (NO in S1010), the process proceeds to step S1031.

[0126] In step S1011, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the Q value of the power transmission antenna 305 using (Equation 1). In step S1012, the power transmission device 102 compares the measured Q value with a threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 is greater than or equal to a preset threshold Q_diff. If the difference is greater than or equal to the threshold Q_diff (YES in S1012), the process proceeds to step S1013. If the difference is less than the threshold Q_diff (NO in S1012), the process proceeds to step S1021.

[0127] In step S1013, the power transmission device 102 determines that a foreign object is present between the power transmission antenna 305 and the power receiving antenna 405. In step S1014, the power transmission device 102 notifies the power receiving device 101 of the presence of a foreign object using a predetermined packet. For example, the power transmission device 102 sends a negative response (NAK) to the power receiving device 101. In step S1015, the power transmission device 102 receives an EPT (End Power Transfer) packet from the power receiving device 101, which is a power transmission stop command requesting the cessation of power transmission. In step S1041, the power transmission device 102 stops power transmission.

[0128] In step S1021, the power transmission device 102 determines that there has been a change in the relative position between the power transmission antenna 305 and the power receiving antenna 405. In step S1022, the power transmission device 102 notifies the power receiving device 101 that there has been a change in the relative position between the power transmission antenna 305 and the power receiving antenna 405. For example, the power transmission device 102 first sends an acknowledgment (ACK) to the power receiving device 101, then a request packet, and then a request operation identification packet. This request packet indicates that the power transmission device 102 is requesting an action from the power receiving device 101. The request operation identification packet contains identification information that identifies the action that the power transmission device 102 is requesting from the power receiving device 101. Here, the identification information is a request to perform calibration again. The power transmission device 102 may perform the processing in step S1022 in a single packet. In other words, the power transmission device 102 may send to the power receiving device 101 a packet that indicates that the power transmission device 102 is requesting an action from the power receiving device 101, and that includes identification information to identify the requested action.

[0129] Next, in step S1023, the power transmission device 102 updates the measured coupling coefficient k as the initial value k0 of the coupling coefficient. In step S1024, the power transmission device 102 transitions to the Calibration phase. In step S1025, the power transmission device 102 performs calibration. In step S1026, the power transmission device 102 transitions to the Power Transfer phase. After that, the process returns to step S1008.

[0130] In step S1031, the power transmission device 102 determines that neither foreign matter contamination nor relative position change has occurred, and notifies the power receiving device 101 of this fact using a predetermined packet. For example, the power transmission device 102 sends an acknowledgment (ACK) to the power receiving device 101 and continues power transmission. In step S1032, the power transmission device 102 determines whether or not it has received an EPT packet from the power receiving device 101. If the power transmission device 102 has received an EPT packet (YES in S1032), the process proceeds to step S1041. If the power transmission device 102 has not received an EPT packet (NO in S1032), the process returns to step S1008. In step S1041, the power transmission device 102 stops power transmission.

[0131] [Processing of power receiving equipment when the waveform attenuation method is applied to the WPC standard] Figure 11 is a flowchart showing the processing method of the power receiving device 101 when foreign object detection is performed by applying the waveform attenuation method to the WPC standard. The main points that differ from the WPC standard will be explained.

[0132] When measuring the coupling state between the transmitting antenna 305 and the receiving antenna 405 to determine whether or not to perform foreign object detection, a threshold is required as a criterion for determining whether or not there is a change in the coupling state. Here, we show an example in which the coupling coefficient is used as an indicator of the coupling state between the transmitting antenna 305 and the receiving antenna 405, and we show the method of exchanging information necessary for calculating the initial value k0 of the coupling coefficient.

[0133] In step S1101, the power receiving device 101 performs the above-described Selection phase and Ping phase processing. In the Ping phase, the power receiving device 101 receives a Digital Ping from the power transmitting device 102 and measures the received voltage value Vrx0. The power receiving device 101 then notifies the power transmitting device 102 of the received voltage value Vrx0 using a predetermined packet. A Signal Strength Packet can be used as the predetermined packet. The Signal Strength Packet may include not only the received voltage value of the power receiving device 101 but also the received power value, or the power receiving device 101 may be notified to the power transmitting device 102 using a separate Signal Strength Packet.

[0134] In step S1102, the power receiving device 101 transmits an Identification Packet and a Configuration Packet to the power transmitting device 102 during the I&C phase. During the I&C phase, the power receiving device 101 notifies the power transmitting device 102 of the inductance value Lrx of the power receiving antenna 405 using a predetermined packet. The predetermined packet can be either an Identification Packet or an Extended Identification Packet.

[0135] In step S1103, the power receiving device 101 negotiates the GP value with the power transmitting device 102 during the Negotiation phase. As mentioned above, foreign matter detection is performed during the Negotiation phase using the Q value measurement method. If the power transmitting device 102 determines that there is no foreign matter as a result of the foreign matter detection, the process proceeds to step S1104.

[0136] In step S1104, the power receiving device 101 transitions to the Calibration phase. In step S1105, the power receiving device 101 performs calibration. In step S1106, the power receiving device 101 transitions to the Power Transfer phase.

[0137] In step S1108, the power receiving device 101 transitions to the Power Transfer phase and then notifies the power transmitting device 102 of an instruction to perform foreign object detection. This instruction to perform foreign object detection can be implemented in Received Power Packet (mode 0). In the WPC standard, Received Power Packet includes information on the power received by the power receiving device 101, but here it includes information on the power received voltage value Vrx of the power receiving device 101.

[0138] In step S1151, the power receiving device 101 determines whether it has been notified by the power transmitting device (TX) 102 in a predetermined packet that foreign matter is present. The predetermined packet is, for example, a NACK, which is a negative response. If it has been notified that foreign matter is present (YES in S1151), the process proceeds to step S1162. If it has not been notified that foreign matter is present (NO in S1151), the process proceeds to step S1153.

[0139] In step S1153, the receiving device 101 determines whether it has been notified by the transmitting device 102, in a predetermined manner, that there has been a change in the relative position between the transmitting antenna 305 and the receiving antenna 405. In the predetermined manner, the receiving device 101 receives an acknowledgment (ACK), followed by a request packet, and then a request operation identification packet. Note that the request packet and the request operation identification packet may be a single packet. If it has been notified that the above change has occurred (YES in S1153), the process proceeds to step S1154. If it has not been notified that the above change has occurred (NO in S1153), the process proceeds to step S1161.

[0140] In step S1154, the power receiving device 101 transitions to the Calibration phase. In step S1155, the power receiving device 101 performs calibration. In step S1156, the power receiving device 101 transitions to the Power Transfer phase. After that, the process returns to step S1108.

[0141] In step S1161, the power receiving device 101 determines whether or not to stop the power transmission from the power transmitting device 102. If the power transmission is to be stopped (YES in S1161), the process proceeds to step S1162. If the power transmission is not to be stopped (NO in S1161), the process returns to step S1108. In step S1162, the power receiving device 101 sends an EPT packet to the power transmitting device 102 requesting that the power transmission be stopped.

[0142] In the embodiment described above, when the power transmission device 102 performs foreign object detection by the waveform attenuation method, it measures the waveform attenuation rate in the absence of foreign objects before starting power transmission and calculates a threshold Q0 based on that. The power transmission device 102 then determines that "foreign objects are present" or "there is a possibility of foreign objects being present" if the Q value measured when performing foreign object detection by the waveform attenuation method is greater than the threshold Q0. The power transmission device 102 also determines that "there are no foreign objects" or "there is a high possibility that there are no foreign objects" if the measured Q value is less than the threshold Q0.

[0143] Furthermore, the power transmission device 102 may perform foreign object detection using a threshold value obtained from the waveform attenuation rate measured at a time when it is presumed that there are no foreign objects after the start of power transmission. For example, the power transmission device 102 confirms the absence of foreign objects using the Power Loss method during power transmission. Next, the power transmission device 102 performs the first waveform attenuation rate measurement and calculates a threshold value based on the measured waveform attenuation rate. Since this first waveform attenuation rate measurement is performed immediately after it has been confirmed that there are no foreign objects using the Power Loss method, the measured waveform attenuation rate is presumed to be the waveform attenuation rate when there are no foreign objects. Next, the power transmission device 102 restarts power transmission and performs a second waveform attenuation rate measurement at a time when it is determined that foreign object detection should be performed. Then, the power transmission device 102 can determine the presence or absence of foreign objects by comparing the measurement result of the second waveform attenuation rate measurement with the measurement result of the first waveform attenuation rate measurement or the threshold value calculated based on it. In other words, when the power transmission device 102 performs foreign object detection using the waveform attenuation method, it may compare the waveform attenuation rate measured at that time with the waveform attenuation rate or threshold measured previously in the absence of foreign objects.

[0144] Furthermore, in the embodiments described above, the frequency of the transmitted radio waves from the power transmission device 102 was assumed to be a fixed frequency, but this is not limited to this. The power transmission device 102 may perform the foreign object detection processing described in this embodiment for each of the multiple frequencies and determine the presence or absence of foreign objects by combining the results. By using the waveform attenuation rates at multiple frequencies, not just one frequency, the power transmission device 102 can perform more accurate foreign object detection.

[0145] Furthermore, in this embodiment, a waiting time is provided before each operation because the power transmission waveform is unstable due to transient response immediately after the power transmission device 102 stops or starts transmitting power. However, the cause of this instability in the power transmission waveform is caused by suddenly starting or suddenly stopping power transmission. Therefore, to mitigate this, the power transmission device 102 may be controlled to gradually increase the power transmission when starting power transmission. Alternatively, the power transmission device 102 may be controlled to gradually decrease the power transmission when stopping power transmission.

[0146] As described above, the power transmission device 102 wirelessly transmits power to the power receiving device 101. Prior to the transition to step S1006, the power transmission device 102 functions as an acquisition unit and acquires the coupling state between the power transmission antenna 305 of the power transmission device 102 and the power receiving antenna 405 of the power receiving device 101. This coupling state is, for example, the coupling coefficient between the power transmission antenna 305 of the power transmission device 102 and the power receiving antenna 405 of the power receiving device 101, and the initial value k0 of the coupling coefficient.

[0147] The initial value k0 of the coupling coefficient is a coefficient based on the inductance Ltx of the transmitting antenna 305, the voltage value Vtx0 of the transmitting antenna 305, the inductance Lrx of the receiving antenna 405, and the voltage value Vrx0 of the receiving antenna 405, as shown in (Equation 2). Alternatively, the initial value k0 of the coupling coefficient may be a coefficient based on the number of turns of the transmitting antenna 305, the voltage value Vtx0 of the transmitting antenna 305, the number of turns of the receiving antenna 405, and the voltage value Vrx0 of the receiving antenna 405.

[0148] For example, the voltage value Vrx0 of the receiving antenna 405 and the inductance Lrx or number of turns of the receiving antenna 405 are received from the power receiving device 101. At least the voltage value Vrx0 of the receiving antenna 405 is received from the power receiving device 101.

[0149] In step S1007, the power transmission device 102 functions as an acquisition unit and acquires the Q value of the power transmission antenna 305 using the waveform attenuation method of (Equation 1), and sets that Q value as the threshold Q0.

[0150] In step S1009, the power transmission device 102 functions as an acquisition unit and acquires the coupling state between the power transmission antenna 305 of the power transmission device 102 and the power receiving antenna 405 of the power receiving device 101. This coupling state is, for example, the coupling coefficient k between the power transmission antenna 305 of the power transmission device 102 and the power receiving antenna 405 of the power receiving device 101.

[0151] The coupling coefficient k is a coefficient based on the inductance Ltx of the transmitting antenna 305, the voltage value Vtx of the transmitting antenna 305, the inductance Lrx of the receiving antenna 405, and the voltage value Vrx of the receiving antenna 405, as shown in (Equation 2). Alternatively, the coupling coefficient k may be a coefficient based on the number of turns of the transmitting antenna 305, the voltage value Vtx of the transmitting antenna 305, the number of turns of the receiving antenna 405, and the voltage value Vrx of the receiving antenna 405.

[0152] For example, the voltage value Vrx of the receiving antenna 405 and the inductance Lrx or number of turns of the receiving antenna 405 are received from the receiving device 101. At least the voltage value Vrx of the receiving antenna 405 is received from the receiving device 101.

[0153] The initial value k0 of the coupling coefficient is the coupling coefficient between the transmitting antenna 305 and the receiving antenna 405 at a time prior to the coupling coefficient k. The coupling coefficient k is the coupling coefficient after transitioning to the Power Transfer phase in step S1006. The initial value k0 of the coupling coefficient is the coupling coefficient before transitioning to the Power Transfer phase in step S1006.

[0154] In step S1011, the power transmission device 102 functions as a foreign object detection unit and performs foreign object detection processing using the waveform attenuation method according to the coupling coefficient k obtained in step S1009. Specifically, the power transmission device 102 performs foreign object detection processing using the waveform attenuation method if the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient is greater than the threshold k_diff. Also, the power transmission device 102 does not perform foreign object detection processing using the waveform attenuation method if the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient is less than the threshold k_diff. The above foreign object detection processing is a detection process that detects an object different from the power receiving device 101 based on the voltage or current value at at least two points in time during a predetermined period in which the power transmission device 102 restricts power transmission.

[0155] In step S1011, the power transmission device 102 acquires the Q value of the power transmission antenna 305 using the waveform attenuation method (Equation 1). The threshold Q0 in step S1007 is the Q value of the power transmission antenna 305 at a time earlier than the Q value acquired in step S1011.

[0156] In step S1012, the power transmission device 102 determines the presence or absence of foreign matter based on the Q value obtained in step S1011. In step S1013, the power transmission device 102 determines that there is foreign matter if the difference between the Q value obtained in step S1011 and the threshold Q0 is greater than the threshold Q_diff. In step S1021, the power transmission device 102 determines that there has been a change in the relative positional relationship between the power transmission antenna 305 and the power receiving antenna 405 if the difference between the Q value obtained in step S1011 and the threshold Q0 is less than the threshold Q_diff.

[0157] In step S1023, if the difference between the Q value obtained in step S1011 and the threshold Q0 is smaller than the threshold Q_diff, the power transmission device 102 updates the coupling coefficient k as the new initial value k0 of the coupling coefficient. In step S1025, if the difference between the Q value obtained in step S1011 and the threshold Q0 is smaller than the threshold Q_diff, the power transmission device 102 is calibrated.

[0158] As described above, when transmitting wireless power, the power transmission device 102 performs detection of objects different from those detected by the power receiving device 101 (foreign object detection). In this case, the power transmission device 102 appropriately determines the necessity of performing foreign object detection using the change in the coupling state between the power transmission antenna 305 and the power receiving antenna 405 based on the change in the attenuation of the transmitted energy, and reduces the number of times foreign object detection is performed. This reduces the generation of electromagnetic noise associated with stopping power transmission for foreign object detection.

[0159] (Second embodiment) In the first embodiment, if foreign matter is introduced between the transmitting antenna 305 and the receiving antenna 405 during the calibration phase, it may not be possible to obtain appropriate calibration results. In light of this possibility, the transmitting device 102 and the receiving device 101 of the second embodiment perform foreign matter detection using the waveform attenuation method during calibration. The processing of the transmitting device 102 and the receiving device 101 of the second embodiment will be described, focusing on the differences from the first embodiment.

[0160] Figure 12A is a sequence diagram of the Calibration phase of the power transmission device 102 and power receiving device 101 according to the second embodiment. When the power transmission device 102 measures the coupling state between the power transmission antenna 305 and the power receiving antenna 405 and determines whether or not to perform foreign object detection, a threshold value is required as a criterion for determining whether or not there is a change in the coupling state. Here, an example is shown in which the coupling coefficient is used as an indicator for the coupling state between the power transmission antenna 305 and the power receiving antenna 405. The method for calculating the initial value k0 of the coupling coefficient is the same as in the first embodiment, so the explanation is omitted.

[0161] Furthermore, when the power transmission device 102 performs foreign object detection using the waveform attenuation method, a threshold value is required as a criterion for determining whether or not a foreign object is present. Here, we show a method in which the power transmission device 102 pre-measures the waveform attenuation rate when no foreign object is present and calculates the threshold value based on that. Subsequently, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the waveform attenuation rate. If the measured waveform attenuation rate is greater than the threshold value, the power transmission device 102 determines that "a foreign object is present" or "there is a possibility of a foreign object being present," and if the measured waveform attenuation rate is less than the threshold value, it determines that "there is no foreign object" or "there is a high possibility that there is no foreign object."

[0162] In step F1201, the power transmission device 102 and the power receiving device 101 set the timing for measuring the waveform attenuation rate in the absence of foreign objects to the first stage of the Calibration phase. This is because the longer the time elapsed since the Q-value measurement method determined that there are no foreign objects, the higher the probability that foreign objects will be placed near the power transmission device 102 and the power receiving device 101. In step F1202, the power transmission device 102 measures the waveform attenuation rate of the transmitted radio wave in the absence of foreign objects at the timing of foreign object detection specified by the power receiving device 101 or the power transmission device 102, and calculates a threshold Q0 based on the measured waveform attenuation rate.

[0163] In step F1203, the power receiving device 101 transmits information including the power received value and power received voltage value Vrx under light load conditions (hereinafter referred to as the first reference power received voltage information) to the power transmitting device 102. Light load conditions are Light Load conditions, load disconnection conditions, and load conditions in which the power transmitted value is below the first threshold. The first reference power received voltage information is the power received voltage information of the power receiving device 101 when the power transmitted by the power transmitting device 102 is 250 milliwatts. The first reference power received voltage information is Received Power Packet (mode 1) as defined in the WPC standard, but other messages may be used. Upon receiving the Received Power Packet, the power transmitting device 102 acquires the power received voltage value Vrx and records it in memory 306, and also measures the power transmitted voltage value Vtx of the power transmitting device 102 and records it in memory 306.

[0164] In step F1204, the power transmission device 102 calculates the current coupling state. Here, the power transmission device 102 calculates the coupling coefficient k between the transmitting antenna 305 and the receiving antenna 405. For example, the power transmission device 102 uses Vtx, Vrx and Ltx, Lrx to calculate the coupling coefficient k using (Equation 2) and records it in memory 306.

[0165] In step F1205, the power transmission device 102 determines whether the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient already calculated exceeds a preset threshold k_diff. If the difference exceeds the threshold k_diff, the process proceeds to step F1206.

[0166] In step F1206, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the Q value of the power transmission antenna 305. In step F1207, the power transmission device 102 compares the measured Q value with a threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 exceeds the threshold Q_diff. If the difference exceeds the threshold Q_diff, the process proceeds to step F1208.

[0167] In step F1208, the power transmission device 102 determines that a foreign object is present between the power transmission antenna 305 and the power receiving antenna 405. In step F1209, the power transmission device 102 notifies the power receiving device 101 of the presence of a foreign object using a predetermined packet. For example, the power transmission device 102 sends a negative response (NAK) to the power receiving device 101. In step F1210, the power transmission device 102 notifies the power receiving device 101 to cancel the calibration process and return to the Selection phase. In step F1211, the power transmission device 102 and the power receiving device 101 return to the Selection phase.

[0168] Figure 12B is a sequence diagram showing a different process for step F1207 in Figure 12A. Steps F1201 to F1206 are the same as in Figure 12A.

[0169] In step F1207, the power transmission device 102 compares the measured Q value with the threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 exceeds the threshold Q_diff. If the difference does not exceed the threshold Q_diff, the process proceeds to step F1231.

[0170] In step F1231, the power transmission device 102 determines that there has been a change in the relative position between the power transmission antenna 305 and the power receiving antenna 405. In step F1232, the power transmission device 102 notifies the power receiving device 101 that there has been a change in the relative position between the power transmission antenna 305 and the power receiving antenna 405 and that the calibration should be redone. For example, the power transmission device 102 sends a negative response (NAK) to the power receiving device 101, then a request packet, and then a request action identification packet. This request packet indicates that the power transmission device 102 is requesting an action from the power receiving device 101. The request action identification packet contains identification information that identifies the action that the power transmission device 102 is requesting from the power receiving device 101. Here, the identification information is a request to redo the calibration from the beginning. Note that the processing in step F1232 may be performed in a single packet. In other words, the power transmission device 102 may send a packet to the power receiving device 101 that indicates a request for action and includes identification information to identify the requested action.

[0171] In step F1233, the power transmission device 102 updates the calculated coupling coefficient k as the initial value k0 of the coupling coefficient. In step F1234, the power transmission device 102 and the power receiving device 101 return to step F1203 and repeat the calibration.

[0172] Figure 12C is a sequence diagram showing a different process for step F1205 in Figure 12A. Steps F1201 to F1204 are the same as in Figure 12A.

[0173] In step F1205, the power transmission device 102 determines whether the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient already calculated exceeds the threshold k_diff. If the difference does not exceed the threshold k_diff, the process proceeds to step F1251.

[0174] In step F1251, the power transmission device 102 determines that neither foreign matter contamination nor relative position change has occurred. In step F1252, the power transmission device 102 notifies the power receiving device 101 of this fact using a predetermined packet. For example, the power transmission device 102 sends an acknowledgment (ACK) to the power receiving device 101.

[0175] From this point onward, the power transmission device 102 and the power receiving device 101 perform calibration in the connected load state (connected load state, maximum load state, load state where the transmitted power value is equal to or greater than the second threshold). Since this calibration is the same process as the calibration in the light load state, the explanation will be omitted.

[0176] As described above, in the Calibration phase, the power transmission device 102 performs detection of objects different from those of the power receiving device 101 (foreign object detection) when performing wireless power transmission. In this case, the power transmission device 102 appropriately determines the necessity of performing foreign object detection using the change in the coupling state between the power transmission antenna 305 and the power receiving antenna 405 based on the change in the attenuation of the energy transmitted by the power transmission device 102, and reduces the number of times foreign object detection is performed. This makes it possible to reduce the generation of electromagnetic noise associated with stopping power transmission for foreign object detection.

[0177] (Third embodiment) The first embodiment is an example in which the power transmission device 102 measures the coupling state between the power transmission antenna 305 and the power receiving antenna 405 and determines whether or not to perform foreign object detection using the waveform attenuation method. The third embodiment shows an example in which the power receiving device 101 measures the coupling state between the power transmission antenna 305 and the power receiving antenna 405 and performs foreign object detection using the waveform attenuation method. The processing of the power transmission device 102 and the power receiving device 101 in the third embodiment will be explained, focusing on the differences from the first embodiment.

[0178] [Processing of power transmission equipment when the waveform attenuation method is applied to the WPC standard] Figure 13 is a flowchart showing the processing method of the power transmission device 102 when the waveform attenuation method is applied to the WPC standard.

[0179] When measuring the coupling state between the transmitting antenna 305 and the receiving antenna 405 to determine whether or not to perform foreign object detection, a threshold value is required as a criterion for determining whether or not there is a change in the coupling state. Here, an example is shown in which the coupling coefficient is used as an indicator of the coupling state between the transmitting antenna 305 and the receiving antenna 405, and the processing method of the power transmission device 102 for calculating the initial value k0 of the coupling coefficient is shown.

[0180] In step S1301, the power transmission device 102 performs the above-described Selection phase and Ping phase processing. In the Ping phase, the power transmission device 102 measures the voltage value Vtx0 of the power transmission antenna 305 while transmitting a Digital Ping and records it in the memory 306. Also, if the power transmission device 102 receives a request for information on the voltage value Vtx0 from the power receiving device 101 via a predetermined packet, the power transmission device 102 notifies the power receiving device 101 of the information on the voltage value Vtx0. The predetermined packets can be a General Request Packet or a Specific Request Packet.

[0181] In step S1302, the power transmission device 102 receives an Identification Packet and a Configuration Packet from the power receiving device 101 during the I&C phase. If the power transmission device 102 receives a request from the power receiving device 101 for information on the inductance value Ltx of the power transmission antenna 305 via a predetermined packet during the I&C phase, the power transmission device 102 notifies the power receiving device 101 of the inductance value Ltx. The predetermined packets can be a General Request Packet or a Specific Request Packet. The power receiving device 101 calculates the initial value k0 of the coupling coefficient using Vtx0 and Ltx notified to the power receiving device 101 by the power transmission device 102.

[0182] In step S1303, the power transmission device 102 negotiates the GP value with the power receiving device 101 in the Negotiation phase and determines the GP value. In step S1304, the power transmission device 102 transitions to the Calibration phase. In step S1305, the power transmission device 102 performs calibration. In step S1306, the power transmission device 102 transitions to the Power Transfer phase.

[0183] When detecting foreign objects using the waveform attenuation method, a threshold value is required as a criterion for determining whether or not foreign objects are present. Here, as in the first embodiment, the power transmission device 102 pre-measures the waveform attenuation rate in the absence of foreign objects and uses this as a criterion to calculate the threshold value. Also, as in the first embodiment, the power transmission device 102 sets the timing for measuring the waveform attenuation rate in the absence of foreign objects to the first stage of the Power Transfer phase. In step S1307, the power transmission device 102 measures the waveform attenuation rate of the transmitted radio waves in the absence of foreign objects and calculates the threshold value Q0 from that waveform attenuation rate.

[0184] In step S1308, the power transmission device 102 measures the voltage value Vtx of the power transmission antenna 305 while transmitting power and records it in memory 306. Furthermore, if the power transmission device 102 receives a request for information on the voltage value Vtx from the power receiving device 101 via a predetermined packet, it notifies the power receiving device 101 of the voltage value Vtx. The predetermined packets can be a General Request Packet or a Specific Request Packet. After this, the power receiving device 101 calculates the coupling coefficient k between the power transmission antenna 305 and the power receiving antenna 405 based on the voltage value Vtx notified by the power transmission device 102. The power receiving device 101 determines whether the difference between the coupling coefficient k and the previously calculated initial value k0 exceeds a preset threshold k_diff. If the difference exceeds the threshold k_diff, it determines that the power transmission device 102 should perform foreign object detection using the waveform attenuation method.

[0185] In step S1310, the power transmission device 102 determines whether or not it has received an instruction from the power receiving device 101 to perform foreign object detection. This instruction to perform foreign object detection can be implemented using Received Power Packet (mode 0). If the instruction to perform foreign object detection is received (YES in S1310), the process proceeds to step S1311. If the instruction to perform foreign object detection is not received (NO in S1310), the process proceeds to step S1332.

[0186] In step S1311, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the Q value of the power transmission antenna 305. In step S1312, the power transmission device 102 compares the measured Q value with a threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 is greater than or equal to a preset threshold Q_diff. If the difference is greater than or equal to the threshold Q_diff (YES in S1312), the power transmission device 102 performs the processing in steps S1313 to S1315. If the difference is less than the threshold Q_diff (NO in S1312), the power transmission device 102 performs the processing in steps S1321 to S1326. The processing in steps S1313 to S1315 is the same as the processing in steps S1013 to S1015 in Figure 10. The processes in steps S1321, S1322, and S1324-S1326 are the same as the processes in steps S1021, S1022, and S1024-S1026 in Figure 10. However, the power transmission device 102 does not perform the process in step S1023, which updates the initial value k0 of the coupling coefficient in Figure 10.

[0187] In step S1332, the power transmission device 102 determines whether or not it has received an EPT packet from the power receiving device 101. If the power transmission device 102 has received an EPT packet (YES in S1332), the process proceeds to step S1341. If the power transmission device 102 has not received an EPT packet (NO in S1332), the process returns to step S1308. In step S1341, the power transmission device 102 stops transmitting power.

[0188] [Processing of power receiving equipment when the waveform attenuation method is applied to the WPC standard] Figure 14 is a flowchart showing the processing method of the power receiving device 101 when foreign object detection is performed by applying the waveform attenuation method to the WPC standard. The main points that differ from the WPC standard will be explained.

[0189] When measuring the coupling state between the transmitting antenna 305 and the receiving antenna 405 to determine whether or not to perform foreign object detection, a threshold is required as a criterion for determining whether or not there is a change in the coupling state. Here, we show an example in which the coupling coefficient is used as an indicator of the coupling state between the transmitting antenna 305 and the receiving antenna 405, and we show the method of exchanging information necessary for calculating the initial value k0 of the coupling coefficient.

[0190] In step S1401, the power receiving device 101 performs the above-described Selection phase and Ping phase processing. In the Ping phase, the power receiving device 101 receives a Digital Ping from the power transmitting device 102 and measures the received voltage value Vrx0. The power receiving device 101 then notifies the power transmitting device 102 of the received voltage value Vrx0 using a predetermined packet. A Signal Strength Packet can be used as the predetermined packet. The Signal Strength Packet may include not only the received voltage value of the power receiving device 101 but also the received power value, or the power receiving device 101 may notify the power transmitting device 102 of the received power value using a separate Signal Strength Packet. The power receiving device 101 also requests information on the voltage value Vtx0 of the power transmitting antenna 305 of the power transmitting device 102 from the power transmitting device 102 using a predetermined packet. A General Request Packet and a Specific Request Packet can be used as the predetermined packets.

[0191] In step S1402, the receiving device 101 transmits an Identification Packet and a Configuration Packet to the transmitting device 102 during the I&C phase. During the I&C phase, the receiving device 101 requests information on the inductance value Ltx of the transmitting antenna 305 of the transmitting device 102 from the transmitting device 102 using a predetermined packet. The predetermined packet can be either an Identification Packet or an Extended Identification Packet. The receiving device 101 calculates the initial value k0 of the coupling coefficient using the voltage value Vtx0 and the inductance value Ltx obtained from the transmitting device 102.

[0192] In step S1403, the power receiving device 101 negotiates the GP value with the power transmitting device 102 in the Negotiation phase. In step S1404, the power receiving device 101 transitions to the Calibration phase. In step S1405, the power receiving device 101 performs calibration. In step S1406, the power receiving device 101 transitions to the Power Transfer phase.

[0193] In step S1407, the receiving device 101 requests information on the voltage value Vtx from the transmitting device 102 using a predetermined packet. The predetermined packet can be a General Request Packet or a Specific Request Packet. In step S1408, the receiving device 101 calculates the coupling coefficient k between the transmitting antenna 305 and the receiving antenna 405 based on the voltage value Vtx notified by the transmitting device 102.

[0194] In step S1409, the power receiving device 101 compares the coupling coefficient k with the initial value k0 of the coupling coefficient that has already been calculated, and determines whether the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient is greater than or equal to a preset threshold k_diff. If the difference is greater than or equal to the threshold k_diff (YES in S1409), the process proceeds to step S1410. If the difference is less than the threshold k_diff (NO in S1409), it is determined that neither foreign matter contamination nor relative position change has occurred, and the process proceeds to step S1461.

[0195] In step S1410, the power receiving device 101 determines that the power transmitting device 102 will perform foreign object detection using the waveform attenuation method, and notifies the power transmitting device 102 of an instruction to perform foreign object detection. This instruction to perform foreign object detection can be implemented in Received Power Packet (mode0). In step S1451, the power receiving device 101 determines whether or not it has been notified by the power transmitting device 102 in a predetermined packet that foreign objects are present. The predetermined packet is, for example, NCK, which is a negative response. If it has been notified in the predetermined packet that foreign objects are present (YES in S1451), the process proceeds to step S1462. If it has been notified in a predetermined way that foreign objects are not present (NO in S1451), the process proceeds to step S1453. The predetermined method is, for example, ACK, which is an acknowledgment.

[0196] In step S1453, the power receiving device 101 determines that a change in the relative position between the transmitting antenna 305 and the receiving antenna 405 has occurred. Also in step S1453, the power receiving device 101 updates the coupling coefficient k calculated in step S1408 as the new initial value k0 of the coupling coefficient.

[0197] In step S1454, the power receiving device 101 transitions to the Calibration phase. In step S1455, the power receiving device 101 performs calibration. In step S1456, the power receiving device 101 transitions to the Power Transfer phase. After that, the process returns to step S1407.

[0198] In step S1461, the power receiving device 101 determines whether or not to stop the power transmission from the power transmitting device 102. If the power transmission is to be stopped (YES in S1461), the process proceeds to step S1462. If the power transmission is not to be stopped (NO in S1461), the process returns to step S1407. In step S1462, the power receiving device 101 sends an EPT packet to the power transmitting device 102 requesting that the power transmission be stopped.

[0199] As described above, the power receiving device 101 receives power wirelessly from the power transmitting device 102. In step S1402, the power receiving device 101 functions as an acquisition unit and acquires the coupling state between the power transmitting antenna 305 of the power transmitting device 102 and the power receiving antenna 405 of the power receiving device 101. This coupling state is, for example, the coupling coefficient between the power transmitting antenna 305 of the power transmitting device 102 and the power receiving antenna 405 of the power receiving device 101, and the initial value k0 of the coupling coefficient.

[0200] The initial value k0 of the coupling coefficient is a coefficient based on the inductance Ltx of the transmitting antenna 305, the voltage value Vtx0 of the transmitting antenna 305, the inductance Lrx of the receiving antenna 405, and the voltage value Vrx0 of the receiving antenna 405, as shown in (Equation 2). Alternatively, the initial value k0 of the coupling coefficient may be a coefficient based on the number of turns of the transmitting antenna 305, the voltage value Vtx0 of the transmitting antenna 305, the number of turns of the receiving antenna 405, and the voltage value Vrx0 of the receiving antenna 405.

[0201] For example, the voltage value Vtx0 of the transmitting antenna 305 and the inductance Ltx or number of turns of the transmitting antenna 305 are received from the power transmitting device 102. At least the voltage value Vtx0 of the transmitting antenna 305 is received from the power transmitting device 102.

[0202] In step S1408, the power receiving device 101 functions as an acquisition unit and acquires the coupling state between the transmitting antenna 305 of the power transmitting device 102 and the receiving antenna 405 of the power receiving device 101. This coupling state is, for example, the coupling coefficient k between the transmitting antenna 305 of the power transmitting device 102 and the receiving antenna 405 of the power receiving device 101.

[0203] The coupling coefficient k is a coefficient based on the inductance Ltx of the transmitting antenna 305, the voltage value Vtx of the transmitting antenna 305, the inductance Lrx of the receiving antenna 405, and the voltage value Vrx of the receiving antenna 405, as shown in (Equation 2). Alternatively, the coupling coefficient k may be a coefficient based on the number of turns of the transmitting antenna 305, the voltage value Vtx of the transmitting antenna 305, the number of turns of the receiving antenna 405, and the voltage value Vrx of the receiving antenna 405.

[0204] For example, the voltage value Vtx of the transmitting antenna 305 and the inductance Ltx or number of turns of the transmitting antenna 305 are received from the power transmitting device 102. At least the voltage value Vtx of the transmitting antenna 305 is received from the power transmitting device 102.

[0205] The initial value k0 of the coupling coefficient in step S1402 is the coupling coefficient between the transmitting antenna 305 and the receiving antenna 405 at a time prior to the coupling coefficient k. The coupling coefficient k is the coupling coefficient after transitioning to the Power Transfer phase in step S1406. The initial value k0 of the coupling coefficient is the coupling coefficient before transitioning to the Power Transfer phase in step S1406.

[0206] In step S1410, the power receiving device 101 functions as a transmitting unit and sends an instruction to the power transmitting device 102 to execute the foreign object detection process using the waveform attenuation method, according to the coupling coefficient k obtained in step S1408. Specifically, if the difference between the coupling coefficient k obtained in step S1408 and the initial value k0 of the coupling coefficient is greater than the threshold k_diff, the power receiving device 101 sends an instruction to the power transmitting device 102 to execute the foreign object detection process using the waveform attenuation method. If the difference between the coupling coefficient k obtained in step S1408 and the initial value k0 of the coupling coefficient is less than the threshold k_diff, the power receiving device 101 does not send an instruction to the power transmitting device 102 to execute the foreign object detection process using the waveform attenuation method.

[0207] In step S1451, the power receiving device 101 functions as a receiving unit and responds to the transmission of the instruction to execute the foreign object detection process using the waveform attenuation method in step S1410, receiving information from the power transmitting device 102 regarding the presence or absence of foreign objects. In step S1462, if the power receiving device 101 receives information that a foreign object is present in step S1451, it transmits a power transmission stop instruction (EPT packet) to the power transmitting device 102.

[0208] In step S1453, if the receiving device 101 receives confirmation in step S1451 that there is no foreign object, it determines that there has been a change in the relative position between the transmitting antenna 305 and the receiving antenna 405. Also in step S1453, if the receiving device 101 receives confirmation in step S1451 that there is no foreign object, it updates the coupling coefficient k as the new initial value k0 of the coupling coefficient. In step S1455, if the receiving device 101 receives confirmation in step S1451 that there is no foreign object, it is instructed to perform calibration of the receiving device 101.

[0209] As described above, the power transmission device 102 performs detection of objects different from those detected by the power receiving device 101 (foreign object detection) when performing wireless power transmission. In this case, the power receiving device 101 appropriately determines the necessity of performing foreign object detection using the change in the coupling state between the power transmission antenna 305 and the power receiving antenna 405 based on the change in the attenuation of the transmitted energy, and reduces the number of times foreign object detection is performed. This reduces the generation of electromagnetic noise associated with stopping power transmission for foreign object detection.

[0210] (Fourth embodiment) The second embodiment involves performing foreign object detection using the waveform attenuation method during calibration. In this embodiment, the power transmission device 102 measures the coupling state between the power transmission antenna 305 and the power receiving antenna 405 and determines whether or not to perform foreign object detection using the waveform attenuation method. The fourth embodiment shows an example where the power receiving device 101 measures the coupling state between the power transmission antenna 305 and the power receiving antenna 405 and performs foreign object detection using the waveform attenuation method. The processing of the power transmission device 102 and the power receiving device 101 in the fourth embodiment will be explained, focusing on the differences from the second embodiment.

[0211] Figure 15A is a sequence diagram of the Calibration phase of the power transmission device 102 and power receiving device 101 according to the fourth embodiment. When measuring the coupling state between the power transmission antenna 305 and the power receiving antenna 405 to determine whether or not to perform foreign object detection, a threshold value is required as a criterion for determining whether or not there is a change in the coupling state. Here, an example is shown in which the coupling coefficient is used as an indicator for the coupling state between the power transmission antenna 305 and the power receiving antenna 405. The method for calculating the initial value k0 of the coupling coefficient is the same as in the first and second embodiments, so the explanation is omitted.

[0212] Furthermore, when performing foreign object detection using the waveform attenuation method, a threshold value is required as a criterion for determining whether or not a foreign object is present. Here, the power transmission device 102 is shown to pre-measure the waveform attenuation rate when no foreign object is present and calculate the threshold value based on that. Subsequently, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the waveform attenuation rate. If the measured waveform attenuation rate is greater than the threshold value, the power transmission device 102 determines that "a foreign object is present" or "there is a possibility of a foreign object being present," and if the measured waveform attenuation rate is less than the threshold value, it determines that "there is no foreign object" or "there is a high possibility that there is no foreign object."

[0213] In step F1501, the power transmission device 102 and the power receiving device 101 set the timing for measuring the waveform attenuation rate in the absence of foreign matter to the first stage of the Calibration phase, similar to the second embodiment. In step F1502, the power transmission device 102 measures the waveform attenuation rate of the transmitted radio wave in the absence of foreign matter at the timing for detecting foreign matter specified by the power receiving device 101 or the power transmission device 102, and calculates a threshold Q0 based on the measured waveform attenuation rate.

[0214] In step F1551, the receiving device 101 requests information about the voltage value Vtx of the transmitting antenna 305 from the transmitting device 102 using a predetermined packet. The predetermined packet can be a General Request Packet or a Specific Request Packet.

[0215] In step F1504, the receiving device 101 calculates the coupling coefficient k between the transmitting antenna 305 and the receiving antenna 405 using (Equation 2) based on the voltage value Vtx notified by the transmitting device 102. In step F1505, the receiving device 101 compares the coupling coefficient k with the initial value k0 of the coupling coefficient already calculated and determines whether the difference between the coupling coefficient k and the initial value k0 exceeds a preset threshold k_diff. If the difference exceeds the threshold k_diff, the process proceeds to step F1552.

[0216] In step F1552, the power receiving device 101 decides to perform foreign object detection using the waveform attenuation method and requests the power transmitting device 102 to perform foreign object detection using the waveform attenuation method. In step F1503, the power receiving device 101 transmits a first reference power receiving information (or second reference power receiving information) including the power received value to the power transmitting device 102. The first or second reference power receiving information is a Received Power Packet (mode 1 or mode 2) as defined in the WPC standard, but other messages may be used. In addition, the request to perform foreign object detection using the waveform attenuation method in step F1552 can use a General Request Packet or a Specific Request Packet. Furthermore, the request information to perform foreign object detection using the waveform attenuation method in step F1552 may be included in the Received Power Packet (mode 1 or mode 2) mentioned above.

[0217] In step F1506, the power transmission device 102 performs foreign object detection using the waveform attenuation method and measures the Q value of the power transmission antenna 305. In step F1507, the power transmission device 102 compares the measured Q value with a threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 exceeds the threshold Q_diff. If the difference exceeds the threshold Q_diff, the process proceeds to step F1508.

[0218] In step F1508, the power transmission device 102 determines that there is foreign matter between the power transmission antenna 305 and the power receiving antenna 405. In step F1509, the power transmission device 102 notifies the power receiving device 101 of the presence of foreign matter using a predetermined packet. For example, the power transmission device 102 sends a negative response, NAK, to the power receiving device 101. In step F1510, the power transmission device 102 notifies the power receiving device 101 to cancel the calibration process and return to the Selection phase. In step F1511, the power transmission device 102 and the power receiving device 101 return to the Selection phase.

[0219] Figure 15B is a sequence diagram showing a different process for step F1507 in Figure 15A. Steps F1501 to F1506 are the same as those in Figure 15A.

[0220] In step F1507, the power transmission device 102 compares the measured Q value with the threshold Q0 and determines whether the difference between the measured Q value and the threshold Q0 exceeds the threshold Q_diff. If the difference does not exceed the threshold Q_diff, the process proceeds to step F1531.

[0221] In step F1531, the power transmission device 102 determines that no foreign matter is present between the power transmission antenna 305 and the power receiving antenna 405, and notifies the power receiving device 101 in a predetermined packet that no foreign matter is present between the power transmission antenna 305 and the power receiving antenna 405. For example, the power transmission device 102 sends an acknowledgment (ACK) to the power receiving device 101.

[0222] In step F1532, upon receiving an ACK, the receiving device 101 determines that there has been a change in the relative position between the transmitting antenna 305 and the receiving antenna 405. In step F1533, the receiving device 101 updates the calculated coupling coefficient k as the initial value k0 of the coupling coefficient. In step F1534, the transmitting device 102 and the receiving device 101 return to step F1551 and repeat the calibration.

[0223] Figure 15C is a sequence diagram showing a different process for step F1505 in Figure 15A. Steps F1501, F1502, F1551, and F1504 are the same as those in Figure 15A.

[0224] In step F1505, the power receiving device 101 compares the coupling coefficient k with the initial value k0 of the coupling coefficient that has already been calculated, and determines whether the difference between the coupling coefficient k and the initial value k0 of the coupling coefficient exceeds the threshold k_diff. If the difference does not exceed the threshold k_diff, the power receiving device 101 decides not to perform foreign object detection using the waveform attenuation method, and determines that neither foreign object contamination nor relative position change has occurred, and proceeds to step F1503.

[0225] In step F1503, the receiving device 101 transmits a first reference power received information (or second reference power received information) including the power received value to the transmitting device 102. The first or second reference power received information is a Received Power Packet (mode 1 or mode 2) as defined in the WPC standard, but other messages may be used. In step F1553, the transmitting device 102 calculates the amount of power loss between the transmitting device 102 and the receiving device 101 and sends an ACK to the receiving device 101.

[0226] From this point onward, the power transmission device 102 and the power receiving device 101 perform calibration in the connected load state (connected load state, maximum load state, load state where the transmitted power value is equal to or greater than the second threshold). Since this calibration is the same process as the calibration in the light load state, the explanation will be omitted.

[0227] As described above, in the Calibration phase, the power transmission device 102 performs detection of objects different from those detected by the power receiving device 101 (foreign object detection) when performing wireless power transmission. In this case, the power receiving device 101 appropriately determines the necessity of performing foreign object detection using the change in the coupling state between the power transmission antenna 305 and the power receiving antenna 405, based on the change in the attenuation of the energy transmitted by the power transmission device 102, and reduces the number of times foreign object detection is performed. This reduces the generation of electromagnetic noise associated with stopping power transmission for foreign object detection.

[0228] (Other embodiments) In the first to fourth embodiments, when detecting foreign matter using the waveform attenuation method and determining whether or not there is a change in the Q value, a threshold Q0 calculated using the waveform attenuation method in the absence of foreign matter was used, but this is not limited to this. For example, in the Ping phase, the results of the Q value measurement performed by the power transmission device 102 may be used. Also, in the Negotiation phase, the Reference Quality Factor Value notified from the power receiving device 101 to the power transmission device 102 by the FOD Status Packet may be used.

[0229] Furthermore, while the first to fourth embodiments describe an example where the device for calculating the coupling state and the device for determining whether or not to perform foreign object detection using the waveform attenuation method are the same, the system is not limited to this. That is, either the power transmission device 102 or the power receiving device 101 may calculate the coupling state, while the other determines whether or not to perform foreign object detection using the waveform attenuation method.

[0230] The power receiving device and power transmitting device may have functions to perform applications other than wireless charging. An example of a power receiving device is an information processing terminal such as a smartphone, and an example of a power transmitting device is an accessory device for charging that information processing terminal. For example, an information terminal device has a display unit that displays information to the user, and is supplied with power received from a power receiving coil (antenna). The power received from the power receiving coil is stored in a power storage unit (battery), and power is supplied to the display unit from the battery. In this case, the power receiving device may have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may support communication standards such as NFC (Near Field Communication) or 5th generation mobile communication system (5G). In this case, the communication unit may perform communication by being powered by the battery. The power receiving device may also be a tablet terminal, a storage device such as a hard disk drive and memory device, or an information processing device such as a personal computer (PC). The power receiving device may also be, for example, an imaging device (camera, video camera, etc.). Furthermore, the power receiving device may be an image input device such as a scanner, or an image output device such as a printer, copier, or projector. The power receiving device may also be a robot, medical equipment, etc. The power transmitting device may be a device for charging the aforementioned equipment.

[0231] Furthermore, the power transmission device may be a smartphone. In this case, the power receiving device may be another smartphone or wireless earphones.

[0232] Furthermore, the power receiving device in this embodiment may be a vehicle such as an automobile or an automated guided vehicle (AGV). For example, an automobile acting as a power receiving device may receive power from a charger (power transmission device) via a power transmission antenna installed in a parking lot. Alternatively, a vehicle acting as a power receiving device may receive power from a charger (power transmission device) via a power transmission coil (antenna) embedded in the road or driving path. In such a vehicle, the received power is supplied to a battery. The battery's power may be supplied to a drive unit (motor, electric unit) that drives the wheels, or it may be used to drive sensors used for driving assistance or a communication unit that communicates with external devices. In other words, in this case, the power receiving device may have a battery, motors and sensors that are driven using the received power, and a communication unit that communicates with devices other than the power transmission device, in addition to the wheels. Furthermore, the power receiving device may have a dwelling for accommodating people. For example, sensors may be used to measure the distance between vehicles or the distance to other obstacles. The communication unit may, for example, be compatible with the Global Positioning System (Global Positioning Satellite, GPS). The communication unit may also be compatible with communication standards such as 5G. Furthermore, the vehicle may be a bicycle or a motorcycle. The power receiving device is not limited to a vehicle; it may be a mobile or flying object having a power unit that operates using electricity stored in a battery.

[0233] Furthermore, the power receiving device in this embodiment may be a power tool, a home appliance, or the like. These power receiving devices may have a battery, as well as a motor driven by the power stored in the battery. These devices may also have a notification means for notifying the remaining battery level, etc. These devices may also have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may support communication standards such as NFC or fifth-generation mobile communication systems (5G).

[0234] Furthermore, the power transmission device in this embodiment may be an in-vehicle charger that transmits power to portable information terminal devices such as smartphones and tablets that support wireless power transmission within the vehicle. Such an in-vehicle charger may be installed anywhere in the vehicle. For example, the in-vehicle charger may be installed on the vehicle's console, on the instrument panel (dashboard), between passenger seats, on the ceiling, or on the doors. However, it is preferable not to install it in a location that would interfere with driving. In addition, although the power transmission device has been described using the example of an in-vehicle charger, such chargers are not limited to those installed in vehicles, but may also be installed in transport vehicles such as trains, aircraft, and ships. In this case, the charger may also be installed between passenger seats, on the ceiling, or on the doors.

[0235] Alternatively, a vehicle such as an automobile equipped with an on-board charger may also serve as a power transmission device. In this case, the power transmission device has wheels and a battery, and uses the power from the battery to supply power to the power receiving device via a power transmission circuit and a power transmission coil (antenna).

[0236] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the embodiments described above to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions.

[0237] Furthermore, the embodiments described above are merely examples illustrating how to implement this disclosure, and they should not be interpreted as limiting the technical scope of this disclosure. In other words, this disclosure can be implemented in various ways without departing from its technical concept or its main features. [Explanation of Symbols]

[0238] 101 Power receiving device, 102 Power transmitting device, 301 Control unit, 305 Power transmitting antenna, 401 Control unit, 405 Power receiving antenna

Claims

1. A power transmission means for wirelessly transmitting power to a power receiving device, An acquisition means for acquiring information on the received power from the power receiving device, A calculation means for calculating an index relating to the coupling state with the power receiving device, It has detection means that perform a first foreign object detection process related to the Quality Factor and a second foreign object detection process related to power loss, The detection means is If predetermined conditions are met after the calculation of the aforementioned indicator, the first foreign object detection process is performed during the period in which power transmission is restricted. A power transmission device that, if no foreign object is detected by the first foreign object detection process, performs calibration related to the second foreign object detection process based on the power reception information acquired by the acquisition means.

2. The power transmission device according to claim 1, wherein the index relating to the coupling state is calculated based on the voltage of the power receiving device and the voltage of the power transmission device.

3. The power transmission device according to claim 2, wherein the voltage information of the power receiving device is received from the power receiving device, and the voltage of the power transmission device is the voltage of the inverter of the power transmission device.

4. A method used by power transmission equipment, The power transmission process involves wirelessly transmitting power to the power receiving device, The acquisition process involves acquiring information on the received power from the power receiving device, A calculation step for calculating an index related to the coupling state with the power receiving device, The detection process includes a first foreign object detection process related to the Quality Factor and a second foreign object detection process related to power loss, In the detection step, If the predetermined conditions are met after the calculation of the aforementioned indicator, the first foreign object detection process related to the Quality Factor will be performed during the period in which power transmission is restricted. A method comprising performing a calibration related to a second foreign object detection process based on the power reception information acquired in the acquisition step, if no foreign object is detected by the first foreign object detection process.

5. A program for causing a computer to function as one of the means of a power transmission device described in any one of claims 1 to 3.

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