Power transmission device, power receiving device, control method, and program

Abstract

The present invention provides a power transmission device that appropriately controls the process of measuring voltage and current multiple times during periods when the power transmission device restricts power transmission. [Solution] In a wireless power transmission system, the power transmission device 402 transmits power wirelessly to the power receiving device using the power transmission antenna 105 and performs a plurality of measurement processes, including a first measurement process and a second measurement process, which measure at least one of the voltage and current at the power transmission antenna 105 at at least two points in time during a power transmission restriction period in which the power transmitted to the power receiving device 401 is limited. Here, the processing period for the first measurement process and the processing period for the second measurement process are controlled to be of different lengths.

Description

Technical Field

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

Background Art

[0002] In recent years, the technical development of wireless power transmission systems has been widely carried out. Patent Document 1 discloses a method for foreign object detection in the Wireless Power Consortium (WPC) standard. Further, Patent Document 2 discloses a method for determining whether an object exists in the vicinity of a power transmitter based on the attenuation amount of the voltage value of the power transmitter during a period in which the voltage of the power transmitter gradually decreases after the power transmission is stopped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When determining the presence or absence of an object using the method described in Patent Document 2, the measurement results obtained by the process of measuring the voltage or current during the period in which the power transmission device restricts power transmission may be data unsuitable for determination. Therefore, it is assumed that by performing the process of measuring the voltage or current during the period in which the power transmission device restricts power transmission a plurality of times, data suitable for determination can be obtained and more reliable determination can be made. However, in Patent Documents 1 and 2, control in the case of performing the process of measuring the voltage or current during the power transmission period in which the power transmission device restricts power transmission a plurality of times is not considered.

[0005] This disclosure has been made in view of the above-mentioned problems and aims to enable appropriate control when a power transmission device performs a process to measure voltage or current multiple times during a period in which it limits power transmission. [Means for solving the problem]

[0006] As one means to solve the above problems, the power transmission device of this disclosure has the following configuration. The power transmission device includes a power transmission means that transmits power wirelessly to a power receiving device using an antenna, a measurement means that performs a measurement process to measure at least one of the voltage and current at the antenna at at least two or more points in time during a power transmission restriction period in which the power transmitted to the power receiving device by the power transmission means is restricted, and a control means that, when a first measurement process and a second measurement process are performed by the measurement means, controls the processing period for the first measurement process and the processing period for the second measurement process to be of different lengths. [Effects of the Invention]

[0007] According to this disclosure, appropriate control becomes possible when a power transmission device performs the process of measuring voltage or current multiple times during a period when power transmission is restricted. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of the configuration of a power transmission device. [Figure 2] This figure shows an example of the configuration of a power receiving device. [Figure 3] This is a block diagram showing an example of the functional configuration of the control unit of a power transmission device. [Figure 4] This is a diagram showing an example configuration of a wireless power transmission system. [Figure 5] This is a sequence diagram showing an example of processing for wireless power transmission. [Figure 6] This is a diagram illustrating foreign object detection using the waveform attenuation method. [Figure 7] This diagram illustrates a method for detecting foreign objects based on the power transmission waveform during power transmission. [Figure 8]It is a flowchart for explaining the operation of the power transmission device in Embodiment 1. [Figure 9] It is a flowchart for explaining the operation of the power receiving device in Embodiment 1. [Figure 10] It is a diagram for explaining a method of setting a threshold value in foreign object detection by the Power Loss method. [Figure 11] It is a diagram for explaining a method of setting a threshold value in foreign object detection by the waveform attenuation method. [Figure 12] It is a flowchart for explaining the operation of the power transmission device in Embodiment 2. [Figure 13] It is a flowchart for explaining the operation of the power receiving device in Embodiment 2. [Figure 14] It is a flowchart for explaining the operation of the power transmission device in Embodiment 3. [Figure 15] It is a flowchart for explaining the operation of the power receiving device in Embodiment 3. [Figure 16] It is a diagram for explaining a method of measuring an index indicating the first coupling state of the power transmission antenna and the power reception antenna in Embodiment 1. [Figure 17] It is a diagram for explaining a method of measuring an index indicating the second coupling state of the power transmission antenna and the power reception antenna in Embodiment 1. [Figure 18] It is a diagram for explaining a method of setting a threshold value for state abnormality detection using the coupling state of the power transmission antenna and the power reception antenna in Embodiment 1. [Mode for Carrying Out the Invention]

[0009] [Embodiment 1] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the embodiments, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals.

[0010] [Configuration of Wireless Power Transmission System] FIG. 4 shows a configuration example of the wireless power transmission system in the present embodiment. In one example, this system includes a power receiving device 401 and a power transmitting device 402. The detailed configurations of the power receiving device 401 and the power transmitting device 402 will be described later with reference to FIGS. 2 and 1. Hereinafter, the power receiving device may be referred to as RX, and the power transmitting device may be referred to as TX. RX401 is an electronic device that receives power from TX402 and charges its built-in battery.

[0011] TX402 is an electronic device that wirelessly transmits power to RX401 placed on a charging stand 403 which is a part of TX402. Hereinafter, since the charging stand 403 is a part of TX402, the statement that "RX401 is placed on the charging stand 403" may be expressed as "RX401 is placed on TX402". The range 404 surrounded by the dotted line is the range in which RX401 can receive power from TX402. That is, it can also be said that the range 404 is the range in which TX402 can transmit power to RX401. The state where RX401 is placed on TX402 does not necessarily require RX401 to be in contact with TX402 or the charging stand 403. For example, a state where RX401 is included in the range 404 without contact with TX402 (charging stand 403) shall also be regarded as the state where "RX401 is placed on TX402".

[0012] Furthermore, RX401 and TX402 may have functions to perform applications other than wireless power transmission. An example of RX401 is a smartphone, and an example of TX402 is an accessory device for charging that smartphone. RX401 and TX402 may also be tablets, storage devices such as hard disk drives and memory devices, or information processing devices such as personal computers (PCs). Additionally, RX401 and TX402 may be, for example, imaging devices (cameras, video cameras, etc.). RX401 may also be an image input device such as a scanner, or an image output device such as a printer, copier, or projector. TX402 may also be a smartphone. In this case, RX401 may be a different smartphone or wireless earphones. Furthermore, RX401 may be an automobile. TX402 may also be a charger installed in the console of an automobile.

[0013] In this system, RX401 and TX402 perform wireless power transmission using an electromagnetic induction method based on the Wireless Power Consortium (WPC) standard. Specifically, RX401 and TX402 perform wireless power transmission based on the WPC standard between the receiving antenna (receiving coil) of RX401 and the transmitting antenna (transmitting coil) of TX402. The wireless power transmission method applied to this system is not limited to the method specified in the WPC standard, but may also be other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, laser methods, etc. Furthermore, in this embodiment, wireless power transmission is used for wireless charging, but wireless power transmission may be performed for purposes other than wireless charging.

[0014] Here, we will explain the processing of power receiving and transmitting devices in the WPC standard. The WPC standard specifies the amount of power that the power receiving device is guaranteed to be able to output to the load (e.g., charging circuit, battery, etc.). Specifically, this is a value called Guaranteed Power or Guaranteed Load Power (hereinafter referred to as "GP"). GP indicates the power value that guarantees the output to the load of the power receiving device even if the relative positions of the power receiving and transmitting devices change and the transmission efficiency between the receiving and transmitting antennas decreases. For example, if the GP is 5 watts, even if the relative positions of the receiving and transmitting antennas change and the transmission efficiency decreases, the transmitting device will control the power receiving device so that it can output 5 watts of power to the load and transmit power. The GP is determined by negotiations between the transmitting and receiving devices in the Negotiation phase, which will be described later. In addition, the WPC standard specifies the maximum amount of power that the power receiving device can output to the load (e.g., charging circuit, battery, etc.) in the Power Transfer phase. Specifically, this value is called Maximum Power or Reference Power (hereinafter referred to as "MP").

[0015] Furthermore, the WPC standard specifies the amount of power that a power transmission device can transmit to an appropriate reference receiving device during the Power Transfer phase. Specifically, this value is called Potential Power or Potential Load Power (hereinafter referred to as "PP"). In other words, PP is the maximum GP that the power transmission device can negotiate with the receiving device. Note that this embodiment is applicable to any configuration in which power is transmitted and received at a power level determined through negotiation between the power transmission device and the receiving device, not limited to GP, MP, or PP.

[0016] Furthermore, when transmitting power from a power transmission device to a power receiving device, there may be objects other than the power receiving device (hereinafter referred to as "foreign objects") present near the power transmission device. In this case, if the foreign object is, for example, a piece of metal, the electromagnetic waves used for power transmission may affect the foreign object, causing its temperature to rise or even destroying it. Therefore, the WPC standard specifies methods for detecting the presence or possibility of foreign objects within the range that the power transmission device can transmit power to. Specifically, the Power Loss method is specified, which detects foreign objects by the difference between the power transmitted by the power transmission device and the power received by the power receiving device. In addition, the Q-value measurement method is specified, which detects foreign objects by the change in the quality coefficient (Q-value) of the power transmission antenna (power transmission coil) in the power transmission device. By detecting foreign objects using these methods, the power transmission device can stop power transmission if foreign objects are present, preventing the foreign objects from overheating or being destroyed.

[0017] In this disclosure, foreign matter refers to, for example, metal fragments, paper clips, or IC cards. Objects that are essential parts of a power receiving device and a product incorporating a power receiving device, or a power transmitting device and a product incorporating a power receiving device, and that may unintentionally generate heat when exposed to the radio power transmitted by the power transmitting antenna, are not considered foreign matter.

[0018] In this embodiment, RX401 and TX402 perform a process to detect the presence of foreign objects as described above (hereinafter referred to as "foreign object detection process"). Note that the foreign objects detected by TX402 in this embodiment are not limited to objects located on the charging base 403. TX402 only needs to detect foreign objects located in its vicinity, for example, it may detect foreign objects located within the power transmission range 404.

[0019] The foreign object detection method based on the Power Loss method specified in the WPC standard will be explained using Figure 10. In Figure 10, the horizontal axis represents the power transmitted by TX402, and the vertical axis represents the power received by RX401. The graph in Figure 10 can be obtained through a calibration process (Calibration process (CAL process)). The calibration process will be explained below.

[0020] First, TX402 transmits power to RX401 at a first transmission power value Pt1. RX401 receives power at a first reception power value Pr1 (this state is called the Light Load state). TX402 then stores the first transmission power value Pt1. Here, the first transmission power value Pt1, or the first reception power value Pr1, is the minimum transmission or reception power predetermined between RX401 and TX402. At this time, RX401 controls the load so that the received power is the minimum possible. For example, RX401 may disconnect the connection between the receiving antenna and the load so that the received power is not supplied to the load (such as a charging circuit and battery).

[0021] Next, RX401 notifies TX402 of the power value Pr1 of the first received power. Upon receiving the notification of Pr1 from RX401, TX402 calculates that the power loss between TX402 and RX401 is Pt1-Pr1 (=Ploss1), and can create calibration point 1000 that shows the correspondence between Pt1 and Pr1.

[0022] Next, TX402 changes the transmission power value to the second transmission power value Pt2 and transmits power to RX401. At this time, RX401 receives power at the second received power value Pr2 (this state is called the Connected Load state). Then, TX402 stores the second transmission power value Pt2. Here, the second transmission power value Pt2 or the second received power value Pr2 is a predetermined maximum transmission power or received power. At this time, RX401 controls the load so that the power received is the maximum power. Alternatively, it controls the load so that power above a predetermined threshold is supplied to the load. For example, RX401 connects the receiving antenna and the load so that the received power is supplied to the load. Next, RX401 notifies TX402 of Pr2. Upon receiving the notification of Pr2 from RX401, TX402 calculates that the power loss between TX402 and RX401 is Pt2-Pr2 (=Ploss2), and can create a calibration point 1001 that shows the correspondence between Pt2 and Pr2.

[0023] The TX402 then creates a linear interpolation line 1002 between calibration point 1000 and calibration point 1001. Line 1002 represents the relationship between transmitted power and received power when there are no foreign objects in the vicinity of the TX402 and RX401. Based on line 1002, the TX402 can predict the power value that the RX401 will receive when transmitting power at a predetermined transmission power in the absence of foreign objects. For example, if the TX402 transmits power at a third transmission power value Pt3, the third received power value that the RX401 will receive can be estimated to be Pr3 from point 1003 on line 1002, which corresponds to Pt3.

[0024] As described above, based on multiple combinations of the transmitted power value of TX402 and the received power value of RX401 measured while varying the load, the relationship between power loss between TX402 and RX401 depending on the load can be determined. Furthermore, by interpolation from multiple combinations, the power loss between TX402 and RX401 for all loads can be estimated.

[0025] Using the graph in Figure 10, we will explain how to perform foreign object detection using the Power Loss method. After calibration processing, assume that TX402 transmits power to RX401 at Pt3, and TX402 receives notification from RX401 of a power value called Pr3'.

[0026] TX402 calculates Pr3-Pr3' (=Ploss_FO) by subtracting the actual power received from RX401, Pr3', from the power received in the absence of foreign objects, Pr3. This Ploss_FO is assumed to represent power loss due to the presence of foreign objects near TX402 and RX401, and the power consumed by those objects.

[0027] Therefore, if the power Ploss_FO that would have been consumed by the foreign object is greater than a predetermined threshold, it can be determined that a foreign object is present. Alternatively, TX402 may pre-calculate the power loss Pt3-Pr3 (=Ploss3) between TX402 and RX401 from the received power value Pr3 when no foreign object is present. Then, from the received power value Pr3' received from RX401 when a foreign object is present, it may calculate the power loss Pt3-Pr3' (=Ploss3') between TX402 and RX401 when a foreign object is present. Finally, Ploss3'-Ploss3 (=Ploss_FO) may be used to estimate the power Ploss_FO that would have been consumed by the foreign object.

[0028] As described above, the power Ploss_FO, which is estimated to have been consumed by the foreign object, can be calculated as Pr3-Pr3'(=Ploss_FO) or as Ploss3'-Ploss3(=Ploss_FO). In this disclosure below, we will primarily describe the method of calculating Ploss3'-Ploss3(=Ploss_FO), but the contents of 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.

[0029] After the linear 1002 is acquired through the calibration process, the foreign object detection unit 305 of TX402 periodically receives the current power received value (e.g., Pr3' above) from RX401 via the communication unit 104. The current power received value transmitted periodically by RX401 is sent to TX402 as Received Power Packet (mode0). The foreign object detection unit 305 of TX402 performs foreign object detection based on the power received value stored in Received Power Packet (mode0) and the linear 1002.

[0030] 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 (before Digital Ping transmission described later, in the Negotiation phase or Renegotiation phase).

[0031] Next, we will describe the communication between the power receiving device and the power transmitting device based on the WPC standard. In this embodiment, RX401 and TX402 perform control communication 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 before actual power transmission, and necessary power transmission and reception control communication is performed in each phase. The phases before power transmission may include the Selection phase, Ping phase, Identification and Configuration phase, Negotiation phase, and Calibration phase. Hereafter, the Identification and Configuration phase will be referred to as the I&C phase. The processing of each phase will be described below.

[0032] In the Selection phase, the TX402 intermittently transmits Analog Pings to detect when an object is placed on the TX402's charging base (for example, when an RX401 or a conductive piece is placed on the charging base). The TX402 detects at least one of the voltage and current values ​​of the transmitting antenna when the Analog Ping is transmitted. 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.

[0033] In the Ping phase, TX402 transmits a Digital Ping with higher power than the Analog Ping. The power of the Digital Ping is sufficient to activate the control unit of the RX401 mounted on top of TX402. RX401 notifies TX402 of the magnitude of the received voltage. In this way, TX402 recognizes that the object detected in the Selection phase is RX401 by receiving the response from RX401, which received the Digital Ping. Upon receiving notification of the received voltage value, TX402 transitions to the I&C phase. Also, before transmitting the Digital Ping, TX402 measures the Q-factor of the transmitting antenna. This measurement result is used when performing foreign object detection processing using the Q-factor measurement method.

[0034] In the I&C phase, TX402 identifies RX401 and obtains equipment configuration information (capability information) from RX401. RX401 sends an ID Packet and a Configuration Packet. The ID Packet contains the identifier information of RX401, and the Configuration Packet contains the equipment configuration information (capability information) of RX401. Upon receiving the ID Packet and Configuration Packet, TX402 responds with an acknowledgment (ACK). The I&C phase then ends.

[0035] In the Negotiation phase, the GP value is determined based on the GP value requested by RX401 and the transmission capacity of TX402. The MP and PP values ​​are also determined in the Negotiation phase. TX402 receives an FOD Status Packet containing Reference Quality Factor Value information from RX401, adjusts and determines the threshold for the Q-value measurement method. Then, TX402 performs foreign object detection processing using the Q-value measurement method according to the request from RX401. The WPC standard also specifies a method in which, after transitioning to the Power Transfer phase, the same processing as the Negotiation phase is performed again at the request of RX401. The phase in which the same processing as the Negotiation phase is performed again from the Power Transfer phase, as described later, is called the Renegotiation phase.

[0036] In the Calibration phase, the calibration process described above is performed based on the WPC standard. The RX401 also notifies the TX402 of a predetermined power reception value (power reception value under light load conditions / power reception value under maximum load conditions), and the TX402 performs adjustments for efficient power transmission. The power reception value notified to the TX402 may be used for foreign object detection processing using the Power Loss method.

[0037] During the Power Transfer phase, control is performed for initiating, continuing, and stopping power transmission due to errors or full charge. The TX402 and RX401 communicate by superimposing signals onto electromagnetic waves transmitted from the transmitting or receiving antennas, using the transmitting and receiving antennas used for wireless power transmission based on the WPC standard. The range over which communication based on the WPC standard is possible between the TX402 and RX401 is approximately the same as the power transmission range of the TX402.

[0038] [Configuration of power transmission device 402 and power receiving device 401] Next, the configurations of the power transmission device 402 (TX402) and the power receiving device 401 (RX401) in this embodiment will be described. Note that the configuration described below is merely an example, and some (or all) of the described configurations may be replaced by other configurations performing similar functions, or omitted, 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.

[0039] Figure 1 is a functional block diagram showing an example configuration of the TX402 according to this embodiment. The TX402 includes a control unit 101, a power supply unit 102, a power transmission unit 103, a communication unit 104, a power transmission antenna 105, a memory 106, a resonant capacitor 107, and a switch 108. In Figure 1, the control unit 101, power supply unit 102, power transmission unit 103, communication unit 104, and memory 106 are shown as separate components, but any multiple functional blocks among these may be implemented on the same chip.

[0040] The control unit 101 controls the entire TX402, for example, by executing a control program stored in memory 106. The control unit 101 also performs control related to power transmission control, including communication for device authentication in the TX402. Furthermore, the control unit 101 may perform control for executing applications other than wireless power transmission. The control unit 101 is configured to include one or more processors, such as a CPU (Central Processing Unit) or an MPU (MicroProcessor Unit). The control unit 101 may also be configured to include hardware such as an Application Specific Integrated Circuit (ASIC). Additionally, the control unit 101 may include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processes. The control unit 101 stores information that should be stored during the execution of various processes in memory 106. The control unit 101 can also measure time using a timer (not shown).

[0041] The power supply unit 102 supplies power to each functional block. The power supply unit 102 is, for example, a commercial power source or a battery. The battery stores power supplied from the commercial power source.

[0042] The power transmission unit 103 transmits power wirelessly to the RX401 using the power transmission antenna 105. The power transmission unit 103 converts the DC or AC power input from the power supply unit 102 into AC frequency power in the frequency band used for wireless power transmission, and inputs this AC frequency power to the power transmission antenna 105 to generate electromagnetic waves for the RX401 to receive power. For example, the power transmission unit 103 converts the DC voltage supplied by the power supply unit 102 into an AC voltage using a switching circuit with a half-bridge or full-bridge configuration using an FET (Field Effect Transistor). In this case, the power transmission unit 103 includes a gate driver that controls the ON / OFF state of the FET.

[0043] The power transmission unit 103 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 105. 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 103 also controls the output of AC frequency power so that power transmission from the power transmission antenna 105 is started or stopped based on instructions from the control unit 101. Furthermore, the power transmission unit 103 is assumed to have the capacity to supply enough power to output 15 watts (W) of power to the charging unit 206 of the RX401, which complies with the WPC standard.

[0044] The communication unit 104 communicates with the RX401 for power transmission control based on the WPC standard described above. The communication unit 104 modulates the electromagnetic waves output from the power transmission antenna 105 by frequency shift modulation and transmits information to the RX401 to perform communication. The communication unit 104 also demodulates the electromagnetic waves transmitted from the power transmission antenna 105, which have been amplitude-modulated or load-modulated by the RX401, to obtain the information transmitted by the RX401. In other words, the communication performed by the communication unit 104 is carried out by superimposing a signal onto the electromagnetic waves transmitted from the power transmission antenna 105. The communication unit 104 may also communicate with the RX401 using a different antenna than the power transmission antenna 105 and a different standard than the WPC standard, or it may selectively use multiple communication methods to communicate with the RX401. Examples of such communication standards include Bluetooth® Low Energy (BLE) and NFC (Near Field Communication).

[0045] In addition to storing the control program, memory 106 can also store the status of TX402 and RX401 (transmitted power value, received power value, etc.). For example, the status of TX402 can be acquired by the control unit 101, and the status of RX401 can be acquired by the control unit 201 of RX401 and received via the communication unit 104.

[0046] Switch 108 is controlled by control unit 101. The transmitting antenna 105 is connected to the resonant capacitor 107. When switch 108 is turned ON and short-circuited, the transmitting antenna 105 and the resonant capacitor 107 form a series resonant circuit and resonate at a specific frequency f1. At this time, current flows through the closed circuit formed by the transmitting antenna 105, the resonant capacitor 107, and switch 108. When switch 108 is turned OFF and opened, power is supplied to the transmitting antenna 105 and the resonant capacitor 107 from the power transmission unit 103.

[0047] Figure 2 is a block diagram showing an example configuration of the RX401 according to this embodiment. The RX401 includes a control unit 201, a UI (user interface) unit 202, a power receiving unit 203, a communication unit 204, a power receiving antenna 205, a charging unit 206, a battery 207, a memory 208, a first switch unit 209, a second switch unit 210, and a resonant capacitor 211. Note that the multiple functional blocks shown in Figure 2 may be implemented as a single hardware module.

[0048] The control unit 201 controls the entire RX401 by executing a control program stored, for example, in the memory 208. In other words, the control unit 201 controls each of the functional units shown in Figure 2. Furthermore, the control unit 201 may also perform control for executing applications other than wireless power transmission. An example of the control unit 201 is configured to include one or more processors such as a CPU or MPU. In addition, the control unit 201 may control the entire RX401 (or the entire smartphone if the RX401 is a smartphone) in cooperation with the OS (Operating System) it is running.

[0049] Furthermore, the control unit 201 may be composed of hardware such as an ASIC. Alternatively, the control unit 201 may include an array circuit such as an FPGA compiled to perform predetermined processing. The control unit 201 stores information that should be stored during the execution of various processes in the memory 208. The control unit 201 may also measure time using a timer (not shown).

[0050] The UI unit 202 provides various outputs to the user. These outputs include screen displays, blinking and color changes of LEDs (Light Emitting Diodes), audio output from the speaker, and vibration of the RX401 unit. The UI unit 202 is implemented using an LCD panel, speaker, vibration motor, etc.

[0051] The power receiving unit 203 receives power wirelessly from the TX402 using the power receiving antenna 205. The power receiving unit 203 acquires AC power (AC voltage and AC current) generated by electromagnetic induction based on electromagnetic waves radiated from the power transmitting antenna 105 of the TX402 via the power receiving antenna 205. The power receiving unit 203 then converts the AC power into DC or AC power of a predetermined frequency and outputs power to the charging unit 206, which performs processing for charging the battery 207. In other words, the power receiving unit 203 includes a rectifier and a voltage control unit necessary to supply power to the load in the RX401. The above GP is the amount of power guaranteed to be output from the power receiving unit 203. The power receiving unit 203 is assumed to have the capacity to supply enough power to the charging unit 206 to charge the battery 207 and to output 15 watts of power to the charging unit 206.

[0052] The communication unit 204 communicates with the communication unit 104 of the TX402 for power receiving control based on the WPC standard as described above. The communication unit 204 demodulates the electromagnetic waves input from the power receiving antenna 205 and obtains the information transmitted from the TX402. Then, the communication unit 204 communicates with the TX402 by superimposing a signal related to the information to be transmitted to the TX402 onto the electromagnetic waves by amplitude modulation or load modulation. The communication unit 204 may also communicate with the TX402 using a different antenna than the power receiving antenna 205 and a communication standard different from the WPC standard, or it may selectively use multiple communication methods to communicate with the TX402. Examples of such communication standards include Bluetooth® Low Energy (BLE) and NFC (Near Field Communication).

[0053] In addition to storing the control program, memory 208 also stores the states of TX402 and RX401. For example, the state of RX401 is acquired by the control unit 201, and the state of TX402 is acquired by the control unit 101 of TX402, and can be received via the communication unit 204.

[0054] The first switch section 209 and the second switch section 210 are controlled by the control unit 201. The receiving antenna 205 is connected to the resonant capacitor 211. When the second switch section 210 is turned ON and short-circuited, the receiving antenna 205 and the resonant capacitor 211 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 205, the resonant capacitor 211, and the second switch section 210, but no current flows through the receiving section. When the second switch section 210 is turned OFF and opened, the power received by the receiving antenna 205 and the resonant capacitor 211 is supplied to the receiving section 203.

[0055] The first switch unit 209 controls whether or not the received power is supplied to the load, which is the battery. The first switch unit 209 also has the function of controlling the value of the load. When the charging unit 206 and the battery 207 are connected by the first switch unit 209, the received power is supplied to the battery 207. When the connection between the charging unit 206 and the battery 207 is disconnected by the first switch unit 209, the received power is not supplied to the battery 207.

[0056] In Figure 2, the first switch unit 209 is positioned between the charging unit 206 and the battery 207, but it may also be positioned between the power receiving unit 203 and the charging unit 206. Alternatively, it may be positioned between the power receiving antenna 205, the resonant capacitor 211, and the closed circuit formed by the second switch unit 210 and the power receiving unit 203. In other words, the first switch unit 209 may be used to control whether or not to supply the received power to the power receiving unit 203. Furthermore, although the first switch unit 209 is shown as a single block in Figure 2, it is also possible to implement the first switch unit 209 as part of the charging unit 206 or as part of the power receiving unit 203.

[0057] Next, the functions of the control unit 101 of the TX402 will be described with reference to Figure 3. Figure 3 is a block diagram showing an example of the functional configuration of the control unit 101 of the TX402. The control unit 101 includes a communication control unit 301, a power transmission control unit 302, a measurement unit 303, a setting unit 304, and a foreign object detection unit 305. The communication control unit 301 performs control communication with the RX401 based on the WPC standard via the communication unit 104. The power transmission control unit 302 controls the power transmission unit 103 and controls the power transmission to the RX401. The measurement unit 303 measures the waveform attenuation index used in the waveform attenuation method described later. It also measures the power transmitted to the RX401 via the power transmission unit 103 and measures the average transmitted power per unit time. The measurement unit 303 also measures the Q value of the power transmission antenna 105.

[0058] The setting unit 304 sets a threshold value to be used for foreign object detection based on the waveform attenuation index measured by the measurement unit 303, for example, by a calculation process.

[0059] The foreign object detection unit 305 can implement foreign object detection functions using the Power Loss method, the Q-value measurement method, and the waveform attenuation method. The foreign object detection unit 305 may also have functions for performing foreign object detection processing using other methods. For example, if the TX402 has an NFC (Near Field Communication) communication function, the foreign object detection unit 305 may perform foreign object detection processing using the NFC standard's opposing device detection function. In addition to detecting foreign objects, the foreign object detection unit 305 can also detect changes in the state on the TX402. For example, the TX402 can also detect increases or decreases in the number of RX401s on the TX402. The setting unit 304 sets thresholds that serve as criteria for determining the presence or absence of foreign objects when the TX402 performs foreign object detection using the Power Loss method, the Q-value measurement method, or the waveform attenuation method described later. The setting unit 304 may also have functions for setting thresholds that serve as criteria for determining the presence or absence of foreign objects, which are necessary when performing foreign object detection processing using other methods. Furthermore, the foreign object detection unit 305 can perform foreign object detection processing based on the threshold set by the setting unit 304 and the waveform attenuation index, power transmission power, and Q value measured by the measurement unit 303.

[0060] The communication control unit 301, power transmission control unit 302, measurement unit 303, setting unit 304, and foreign object detection unit 305 are implemented as programs that operate in the control unit 101. 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.

[0061] [Processing flow for power transmission in accordance with WPC standards] The WPC standard defines the following phases: Selection phase, Ping phase, I&C phase, Negotiation phase, Calibration phase, and Power Transfer phase. Below, the operation of the TX402 and RX401 in these phases will be explained using the sequence diagram in Figure 5. Figure 5 is a sequence diagram for power transmission in accordance with the WPC standard. Here, the TX402 (TX402) and RX401 will be used as examples.

[0062] TX402 repeatedly and intermittently transmits WPC-compliant Analog Pings to detect objects within its power transmission range (F501). TX402 performs the processes defined as the Selection and Ping phases of the WPC standard and waits for RX401 to be placed on it. The user of RX401 brings RX401 (e.g., a smartphone) close to TX402 to charge it (F502). For example, by loading RX401 onto TX402, RX401 is brought close to TX402. When TX402 detects the presence of an object within its power transmission range (F503, F504), it transmits a WPC-compliant Digital Ping (F505). Upon receiving the Digital Ping, RX401 understands that TX402 has detected it (F506).

[0063] Furthermore, when TX402 receives a predetermined response to Digital Ping, it determines that the detected object is RX401 and that RX401 has been placed on the charging stand 403.

[0064] When TX402 detects the placement of RX401, it obtains identification and capability information from RX401 via I&C phase communication as defined by the WPC standard (F507). Here, the identification information of RX401 includes the Manufacturer Code and Basic Device ID. The capability information of RX401 includes the following information: for example, information elements that can identify the version of the WPC standard it supports, the Maximum Power Value which is a value that identifies the maximum power that RX401 can supply to the load, and information indicating whether it has the WPC standard negotiation function. Note that TX402 may obtain the identification and capability information of RX401 by means other than the WPC standard I&C phase communication. Also, the identification information may be any other identification information that can identify an individual RX401, such as the Wireless Power ID. Capability information may include information other than that listed above.

[0065] Next, TX402 determines the value of GP with RX401 through communication in the Negotiation phase as defined in the WPC standard (F508). The values ​​of MP and PP are also determined in the Negotiation phase. Note that in F508, other procedures for determining GP, MP, and PP may be performed in addition to the communication in the Negotiation phase as defined in the WPC standard. Furthermore, if TX402 obtains information in F507 indicating that RX401 does not support the Negotiation phase, it may not perform the Negotiation phase communication and may set the values ​​of GP, MP, and PP to predetermined values. In this embodiment, the predetermined values ​​set as GP, MP, and PP may be relatively small values, for example, those predetermined in the WPC standard.

[0066] After determining the GP, TX402 performs calibration based on that GP. In the calibration process, RX401 first transmits information to TX402 including the received power under light load conditions (load disconnection state, load condition where the transmitted power is below the first threshold) (hereinafter referred to as "first reference received power information") (F509). In this embodiment, the first reference received power information is the received power information of RX401 when the transmitted power of TX402 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. Based on the power transmission status of its own device, TX402 determines whether or not to accept the first reference received power information. If it accepts, TX402 sends an acknowledgment (ACK) to RX401; otherwise, it sends a negative acknowledgment (NAK).

[0067] Next, when RX401 receives an ACK from TX402 (F510), it performs processing to send information to TX402 that includes the received power under load connection conditions (maximum load conditions, load conditions where the transmitted power exceeds the second threshold) (hereinafter referred to as "second reference received power information"). In this embodiment, since the GP is 5 watts, the second reference received power information is the received power information of RX401 when the transmitted power of TX402 is 5 watts. Here, the second reference received power information is Received Power Packet (mode2) as defined in the WPC standard, but other messages may be used. RX401 sends a transmission output change instruction (F511) containing a positive value to increase the transmitted power from TX402 to 5 watts.

[0068] TX402 receives the above-mentioned power output change instruction and, if it is able to handle the increase in power, responds with an ACK and increases the power (F512, F513). Since the second reference received power information is the received power information when TX402's power output is 5 watts, if TX402 receives a power increase request from RX401 that exceeds 5 watts (F514), it responds with an NAK to the power output change instruction. This prevents the transmission of power exceeding the specified limit (F515).

[0069] When RX401 receives a NAK from TX402 and determines that it has reached the predetermined transmission power, it transmits information including the received power in the load-connected state to TX402 as second-reference received power information (F516). Based on the transmission power value of TX402 and the received power values ​​included in the first and second-reference received power information, TX402 can calculate the amount of power loss between TX402 and RX401 in the load-disconnected and load-connected states. Furthermore, by interpolating between these power loss amounts, it is possible to calculate the power loss value between TX402 and RX401 for all transmission power values ​​that TX402 can take (in this case, from 250 milliwatts to 5 watts) (F517). TX402 sends an ACK to RX401 for the second-reference received power information (F518) and completes the calibration process. When TX402 determines that it is ready to start charging and begins transmitting power to RX401, charging of RX401 begins. Furthermore, before the power transmission process begins, TX402 and RX401 perform equipment authentication (F519), and if they determine that the equipment can handle a larger GP, they may reset the GP to a larger value, for example, 15 watts (F520).

[0070] In this case, RX401 and TX402 increase the transmission output of TX402 to 15 watts using transmission output change instructions, ACK, and NAK (F521~F524). Then TX402 and RX401 perform calibration again for GP=15 watts. Specifically, RX401 transmits information including the received power in the load-connected state of RX401 when TX402's transmission power is 15 watts (hereinafter referred to as "third reference received power information") (F525). TX402 performs calibration based on the received power included in the first, second, and third reference received power information. This calculates the power loss between TX402 and RX401 for all possible transmission power levels of TX402 (from 250 milliwatts to 15 watts in this case) (F526). TX402 sends an ACK to RX401 for the third reference power information (F527) and completes the calibration process. Having determined that it is ready to start charging, TX402 begins the power transmission process to RX401 and moves to the Power Transfer phase (F528).

[0071] In the Power Transfer phase, TX402 transmits power to RX401. Foreign object detection is also performed using the Power Loss method. In the Power Loss method, TX402 first calculates the amount of power loss between TX402 and RX401 in a state without foreign objects, based on the difference between the power transmitted by TX402 and the power received by RX401, as described in the Calibration section above. This calculated value corresponds to the standard amount of power loss in a normal state (without foreign objects) during power transmission. Then, TX402 determines that "foreign object present" if the amount of power loss between TX402 and RX401 measured during power transmission after Calibration deviates by a threshold from the power loss in the normal state.

[0072] 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 TX402 to RX401. While the Power Loss method has the disadvantage that the accuracy of foreign object detection decreases when TX402 is transmitting a large amount of power, it has the advantage that it can maintain high power transmission efficiency because foreign object detection can be performed while power transmission continues.

[0073] 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 TX402 transmits power, and if foreign objects are present near TX402 and RX401 during power transmission, heat generation from these objects will increase. Therefore, improving the accuracy of foreign object detection in this phase is required. Accordingly, in this embodiment, in order to improve the accuracy of foreign object detection, we consider implementing the waveform attenuation method in addition to the Power Loss method as a foreign object detection method different from the Power Loss method.

[0074] [Foreign object detection method using waveform attenuation] The following describes a method for detecting foreign objects based on the attenuation state of the transmitted signal (hereinafter referred to as the "waveform attenuation method"), using Figure 6. Here, "transmitted waveform" refers to the voltage waveform or current waveform at the transmitting antenna 105 of TX402. Figure 6 is a diagram illustrating the principle of foreign object detection using the waveform attenuation method. Here, we will explain using foreign object detection using the transmitted waveform related to power transmission from TX402 to RX401 as an example.

[0075] In Figure 6, the waveform shows the change over time of the high-frequency voltage value 600 (hereinafter simply referred to as "voltage value") applied to the transmitting antenna 105 of TX402. In Figure 6, the horizontal axis represents time, and the vertical axis represents the voltage value. TX402, which transmits power to RX401 via the transmitting antenna 105, stops transmitting power at time T0. That is, at time T0, the power supply for power transmission from the power supply unit 102 is stopped. The frequency of the transmitted radio waves from TX402 is a predetermined frequency, for example, a fixed frequency between 85kHz and 205kHz used in the WPC standard.

[0076] Point 601 is a point on the envelope of the high-frequency voltage and represents the voltage value at time T1. In the figure, (T1, A1) indicates that the voltage value at time T1 is A1. Similarly, point 602 is a point on the envelope of the high-frequency voltage and represents the voltage value at time T2. In the figure, (T2, A2) indicates that the voltage value at time T2 is A2. The quality factor (Q value) of this transmitting antenna (transmitting coil) 105 can be determined based on the time change of the voltage value of the transmitting antenna 105 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 601 and 602 on the envelope of the voltage value. Q = πf(T2 - T1) / ln(A1 / A2) (Equation 1) If foreign matter is present near TX402 and RX401, the Q value decreases. This is because energy loss occurs due to the presence of foreign matter. Therefore, focusing on the slope of voltage attenuation, the slope of the line connecting points 601 and 602 becomes steeper when foreign matter is present than when it is absent, as more energy is lost due to the foreign matter. This results in a higher attenuation rate (amount of attenuation) of the waveform amplitude. In other words, the waveform attenuation method determines the presence or absence of foreign matter based on the voltage attenuation state between points 601 and 602. In practice, the presence or absence of foreign matter can be determined by using a predetermined numerical index that represents this attenuation state.

[0077] For example, the Q value mentioned above can be used for the determination. A lower Q value means that the waveform attenuation rate (the degree to which the amplitude of the waveform decreases per unit time) is higher. Alternatively, the determination may be made using the slope of the line connecting points 601 and 602, which can be obtained from (A1-A2) / (T2-T1). Alternatively, if the time (T1 and T2) for observing the voltage attenuation state is fixed, the determination can also be made using the difference in voltage values ​​(A1-A2) or 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 the voltage value A2 after a predetermined time has elapsed. Alternatively, the determination may be made using the time (T2-T1) until the voltage value A1 becomes the predetermined voltage value A2. In this way, TX402 can measure the voltage of the power transmission antenna 105 at at least two or more points in time during the period when power transmission is restricted, and determine the presence or absence of foreign matter by obtaining values ​​such as the voltage attenuation amount, attenuation rate, and Q value based on the measurement results. Note that TX402 may be configured to measure the voltage at three or more points in time.

[0078] As described above, the presence or absence of foreign matter can be determined by the voltage attenuation state during the power transmission outage period, and there are multiple values ​​that represent this attenuation state. In this embodiment, these values ​​representing the attenuation state are called "waveform attenuation indices." For example, as mentioned above, the Q value calculated by Equation 1 is a value that represents the voltage attenuation state related to power transmission and is included in the "waveform attenuation indices." All waveform attenuation indices are values ​​that correspond to the waveform attenuation rate or waveform attenuation amount. In addition, in the waveform attenuation method, the waveform attenuation rate and attenuation amount themselves may be measured as "waveform attenuation indices." In the following, we will mainly explain the case in which the waveform attenuation rate is used as the waveform attenuation index, but the contents of this embodiment can be applied similarly when other waveform attenuation indices are used.

[0079] Furthermore, even if the vertical axis of Figure 6 represents the current value flowing through the power transmission antenna 105, 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 105. That is, indicators representing the current attenuation state, such as the Q value obtained from the current waveform, the slope of current 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, can be used as waveform attenuation indicators to determine the presence or absence of foreign matter and to detect it. 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 indicator of the voltage value and the waveform attenuation indicator of the current value.

[0080] In the above example, the waveform attenuation index is measured during the period when TX402 temporarily stops power transmission, but this is not limited to this. For example, the waveform attenuation index may be measured during the period when TX402 temporarily reduces the power supplied from the power supply unit 102 from a predetermined power level to a lower power level. In other words, in the waveform attenuation method, foreign object detection is performed based on the attenuation state of at least one of the voltage and current of the power transmission antenna 105 during the period when TX402 stops power transmission or limits it to a predetermined value.

[0081] A method for detecting foreign objects based on the power transmission waveform during power transmission using the waveform attenuation method will be explained with reference to Figure 7. Figure 7 shows the power transmission waveform when foreign object detection is performed using the waveform attenuation method, with the horizontal axis representing time and the vertical axis representing the voltage value of the power transmission antenna 105. As with Figure 6, the vertical axis may also represent the current value of the current flowing through the power transmission antenna 105. Although Figure 7 shows the waveform when the waveform attenuation method is performed multiple times, here we will refer to Figure 7 and explain the case when the waveform attenuation method is performed only once.

[0082] If TX402 receives a foreign object detection execution request packet (command) from RX401 during the power transmission period, it will temporarily suspend power transmission after a predetermined period of time has elapsed, or it will limit the transmitted power to a temporary reduction. The predetermined period from the receipt of this foreign object detection execution request packet (hereinafter referred to as the "execution request packet") until the start of the power transmission limit will be referred to as the preparation period. In this embodiment, the signal used as the execution request packet is a signal that represents the magnitude of the power received by RX401 from TX402. The signals that represent the magnitude of the received power are, for example, Received Power Packet (mode0), Received Power Packet (mode1), and Received Power Packet (mode2) for TX402. When TX402 receives these signals, it will treat them as having received an execution request packet and will perform waveform attenuation. Note that the execution request packet is not limited to these, and a dedicated packet for the request may be used.

[0083] When the power transmission control unit 302 of TX402 receives an execution request packet, it stops power transmission or temporarily reduces the power transmission. As a result, the amplitude of the transmitted signal is attenuated. The period during which power transmission is restricted, from when TX402 temporarily stops or reduces the power transmission until power transmission is resumed, is hereafter referred to as the power transmission control period. More specifically, the power transmission control period is the period from when the slope of the envelope of the transmitted signal transmitted by TX402 to RX401 becomes a negative slope below a predetermined value until the slope becomes zero or a positive slope above a predetermined value.

[0084] TX402 calculates a waveform attenuation index for this attenuated waveform, compares the calculated waveform attenuation index with a predetermined threshold, and determines the presence or absence of foreign matter, or the probability of foreign matter being present. This determination may be performed during the power transmission control period, or during the communication ban period or power transmission period described later.

[0085] After the power transmission control period has elapsed, if no foreign objects are detected, TX402 will resume power transmission. During the transient response period immediately after TX402 starts transmitting power, the transmitted waveform is unstable. Therefore, during this transient response period when the transmitted waveform is unstable, RX401 is controlled not to communicate with TX402 (communication by amplitude modulation or load modulation). In turn, TX402 is controlled not to communicate with RX401 (communication by frequency shift modulation). Hereafter, this communication restriction period will be referred to as the communication prohibition period.

[0086] Specifically, the period from the moment when the slope of the envelope of the transmitted radio waves transmitted by TX402 to RX401 becomes greater than or equal to a predetermined positive value after power transmission is resumed, until the moment when communication becomes possible, is called the communication restriction period. The moment when communication becomes possible is the moment when RX401 and TX402 are allowed to communicate, or the moment when TX402 or RX401 transmits a packet. Alternatively, the communication restriction period may be the period from the moment when the slope of the envelope of the transmitted radio waves transmitted by TX402 to RX401 becomes zero after power transmission is resumed, until the moment when communication becomes possible. Alternatively, the communication restriction period may be the period from the moment TX402 resumes power transmission, that is, the moment when the power transmission control unit 302 increases the supply of power, until the moment when communication becomes possible. Alternatively, the communication restriction period may be the period from the moment TX402 receives a foreign object detection execution request packet (command) from RX401 until the moment when communication becomes possible. Alternatively, the communication restriction period may be the time from when RX401 sends a foreign object detection execution request packet (command) to TX402 until communication becomes possible.

[0087] During this communication ban period, power will be supplied to RX401 by TX402. The period during which TX402 supplies power to RX401 after the communication ban period will hereafter be referred to as the power supply period.

[0088] As described above, TX402 determines the preparation period, power transmission control period, communication ban period, and power transmission period. Based on each determined period, TX402 calculates a waveform attenuation index of the attenuated waveform at predetermined timings, compares the calculated waveform attenuation index with a predetermined threshold, and determines the presence or absence of foreign objects, or the probability of foreign objects being present. This is the basic process of foreign object detection using the waveform attenuation method. In the following explanation, the series of periods including the communication ban period, power transmission period, preparation period, and power transmission control period will also be referred to as the detection processing period in the waveform attenuation method.

[0089] The detection processing period does not necessarily have to include all of the communication prohibition period, power transmission period, preparation period, and power transmission control period. The detection processing period shall represent a period that includes at least the power transmission control period. In other words, the detection processing period is the processing period related to measurement processing that measures voltage or current at at least two or more points in time within the period in which power transmission is restricted. The detection processing period is determined by the power transmission control unit 302 of TX402.

[0090] Furthermore, if elements such as the power receiving unit 203, charging unit 206, and battery 207 are connected to the power receiving antenna 205 and resonant capacitor 211 of the RX401 during the power transmission control period, the waveform attenuation index of the attenuated waveform will be affected by the load from these elements. In other words, the waveform attenuation index will change depending on the state of the power receiving unit 203, charging unit 206, and battery 207. Therefore, even if the waveform attenuation index is large, it may be difficult to distinguish whether it is due to the influence of foreign objects or due to changes in the state of the power receiving unit 203, charging unit 206, battery 207, etc. For this reason, when foreign object detection is performed by observing the waveform attenuation index, the first switch unit 209 of the RX401 may be disconnected during the above preparation period. This makes it possible to eliminate the influence of the battery 207. Alternatively, the RX401 may control the load so that the power received is the minimum power, resulting in the Light Load state described above. Alternatively, the RX401 may control the load to achieve the Connected Load state (load connected state) described above, such that the power received is the maximum power received, or that power above a predetermined threshold is supplied to the load. By setting the load state to a predetermined state in this way, it becomes possible to eliminate the influence of changes in the state of the power receiving unit 203, charging unit 206, battery 207, etc.

[0091] Alternatively, the second switch unit 210 may be turned ON to short-circuit the circuit, allowing current to flow through the closed loop formed by the receiving antenna 205, the resonant capacitor 211, and the second switch unit 210. This eliminates the influence of the receiving unit 203, the charging unit 206, and the battery 207. In other words, when RX401 sends an execution request packet (command) to TX402, it performs the above process and turns ON either the first switch unit 209 or the second switch unit 210 to short-circuit (connect) the circuit. By performing foreign object detection based on the waveform attenuation index of the waveform observed in this state, highly accurate foreign object detection becomes possible.

[0092] Furthermore, during the above preparation period, the RX401 may switch to a low-power mode or be controlled to maintain a constant power consumption when the first switch unit 209 is turned ON to short-circuit and the second switch unit 210 is turned OFF to disconnect. If the power consumed by the RX401 is not constant or if a large amount of power is consumed, the waveform attenuation index of the attenuated waveform will be affected by these fluctuations in power consumption. Therefore, to eliminate this, the operation of software applications running on the RX401 may be restricted or stopped, or the hardware function blocks of the RX401 may be put into a low-power mode or an operation stop mode. In this way, the RX401 controls the power it consumes. By performing foreign object detection based on the waveform attenuation index of the waveform observed in such a state, highly accurate foreign object detection becomes possible.

[0093] Furthermore, when TX402 receives an execution request packet (command) from RX401, it turns on the switch unit 108 to short-circuit it during the preparation period. In other words, TX402 may be configured to allow current to flow through the closed loop formed by the transmitting antenna 105, the resonant capacitor 107, and the switch unit 108. This makes it possible to eliminate the influence of the power supply unit 102, the transmitting unit 103, and the communication unit 104. Alternatively, a switch (not shown) can be provided between the transmitting antenna and the transmitting unit, and this switch can be turned off during the above preparation period to eliminate the influence of the power supply unit 102, the transmitting unit 103, and the communication unit 104.

[0094] [Method for measuring an indicator showing the first coupling state of a transmitting antenna and a receiving antenna] Wireless power transmission transmits power by electromagnetically coupling a transmitting antenna 105 and a receiving antenna 205. That is, by passing an alternating current through the transmitting antenna 105, an alternating current is passed through the receiving antenna 205, changing the magnetic flux passing through the receiving antenna 205, thereby inducing a voltage in the receiving antenna 205 and transmitting power. The coupling coefficient is an index that represents the coupling state between the transmitting antenna 105 and the receiving antenna 205. For example, when all (100%) of the magnetic flux generated by the transmitting antenna passes through the receiving antenna 205, the coupling coefficient k is "k=1". Also, for example, when 70% of the magnetic flux generated by the transmitting antenna 105 passes through the receiving antenna 205, the coupling coefficient k is "k=0.7". In this case, the remaining (30%) of the magnetic flux generated by the transmitting antenna 105 becomes leakage flux, which is the magnetic flux generated by the transmitting antenna 105 that did not pass through the receiving antenna 205. In other words, when the coupling state is good and the coupling coefficient value is large, the power transmission efficiency from TX402 to RX401 is high. On the other hand, when the coupling state is poor and the coupling coefficient value is small, the power transmission efficiency from TX402 to RX401 is low.

[0095] Factors that can cause poor coupling (low coupling coefficient) include the presence of foreign matter between the transmitting antenna 105 and the receiving antenna 205, and misalignment between the transmitting antenna 105 and the receiving antenna 205. If foreign matter is present between the transmitting antenna 105 and the receiving antenna 205, heat generation may occur in the foreign matter. Also, if the receiving antenna 205 of the transmitting antenna 105 is misaligned, as mentioned above, the leakage flux will increase, which may generate significant noise in the surroundings. Therefore, it is necessary to detect poor coupling (low coupling coefficient) and control it appropriately. In this embodiment, TX402 and RX401 may perform the measurement of the coupling state (including the coupling coefficient) between the transmitting antenna 105 and the receiving antenna 205 as described above.

[0096] Figure 16 shows the equivalent circuits of the transmitting antenna 105 and the receiving antenna 205. In this case, the coupling coefficient k, which represents the coupling state between the transmitting antenna 105 and the receiving antenna 205, can be calculated using the following formula.

[0097]

number

[0098] Therefore, for example, when TX402 calculates the coupling coefficient, RX401 notifies TX402 of the measured receiving voltage V2 applied to the receiving antenna 205 and the pre-stored value of the self-inductance L2 of the receiving antenna 205. Then, TX402 can calculate k using the measured transmitting voltage V1 applied to the transmitting antenna 105, the pre-stored value of the self-inductance L1 of the transmitting antenna 105, and the values ​​of V2 and L2. Alternatively, RX401 may notify TX402 of a constant calculated using all or any of V1, L1, and L2, and TX402 may calculate k using this constant and V2.

[0099] On the other hand, for example, when RX401 calculates the coupling coefficient, TX402 notifies RX401 of the measured transmission voltage V1 applied to the transmission antenna 105 and the pre-stored value of the transmission antenna 105's self-inductance L1. Then, RX401 can calculate k using the measured receiving voltage V2 applied to the receiving antenna 205, the pre-stored value of the receiving antenna 205's self-inductance L2, and the values ​​of V1 and L1. Alternatively, TX402 may notify RX401 of a constant calculated using all or any of V2, L1, and L2, and RX401 may calculate k using this constant and V1.

[0100] The transmission voltage V1 applied to the transmission antenna 105 may be actually measured by the TX402, calculated from the set value of the transmission power transmitted by the TX402, or set to the transmission voltage setting value at the time of transmission. Alternatively, the transmission voltage V1 applied to the transmission antenna 105 may be determined from the transmission voltage (let's call it V3) applied to the circuit included in the transmission unit 103 (e.g., an inverter) and the voltage across the resonant capacitor 211. In this case, the transmission voltage (let's call it V3) applied to the circuit included in the transmission unit 103 (e.g., an inverter) may also be calculated by the TX402 from the set value of the transmission power transmitted.

[0101] Furthermore, when TX402 or RX401 performs the above-mentioned measurements, RX401 may control the system to turn OFF a switch (not shown) located between the receiving antenna 205 and the resonant capacitor 211, so that the terminals of the receiving antenna 205 are open. This makes it possible to open both ends of the receiving antenna, as shown in Figure 16. As a result, the above-mentioned measurements are not affected by the resonant capacitor 211, the receiving unit 203, the charging unit 206, and the battery 207, making it possible to measure the coupling state (coupling coefficient) of the transmitting antenna and the receiving antenna with higher accuracy.

[0102] Furthermore, when TX402 or RX401 performs the above measurements, the load on RX401 may be controlled to be in a light load state. Alternatively, the load on RX401 may be controlled to be in a connected load state. By doing so, the load state of RX401 can be kept constant, making it possible to measure the coupling state (coupling coefficient) of the transmitting and receiving antennas with higher accuracy.

[0103] In the above, the "coupling coefficient" was used as an indicator to represent the coupling state of the transmitting antenna 105 and the receiving antenna 205. However, there are multiple values ​​that represent the coupling state of the transmitting antenna 105 and the receiving antenna 205, not just the "coupling coefficient". In this embodiment, these values ​​that represent the coupling state of the transmitting antenna 105 and the receiving antenna 205 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 of the transmitting antenna 105 and the receiving antenna 205. The contents of this embodiment can be applied similarly when using coupling state indices other than the coupling coefficient.

[0104] For example, the coupling state index representing the coupling state of the transmitting antenna 105 and the receiving antenna 205 may be the following index: that is, an index calculated using the transmitting voltage (let's call it V3) applied to the circuit included in the transmitting unit 103 (e.g., an inverter) and the receiving voltage (let's call it V4) applied to the circuit included in the receiving unit 203 (e.g., a rectifier). Alternatively, the coupling state index may be calculated using the output voltage (let's call it V5) output by the circuit included in the receiving unit 203 (e.g., a rectifier). This output voltage V5 is the voltage applied to the load (charging unit, battery). In this case, by notifying RX401 of the transmitting voltage V3 from TX402, RX401 can calculate the coupling state index of the transmitting antenna 105 and the receiving antenna 205. Alternatively, TX402 may notify RX401 of constants (e.g., L1) including the electrical characteristics of the transmitting antenna 105, and based on this, RX401 may calculate an index of the coupling state between the transmitting antenna 105 and the receiving antenna 205.

[0105] Alternatively, RX401 may notify TX402 of the receiving voltage V4 or output voltage V5, allowing TX402 to calculate the coupling state index of the transmitting antenna 105 and the receiving antenna 205. In this case, RX401 may notify TX402 of constants (e.g., L2) including the electrical characteristics of the receiving antenna 105, and TX402 may calculate the coupling state index of the transmitting antenna 105 and the receiving antenna 205 based on these constants.

[0106] As mentioned above, the TX402 and RX401 exchange information including voltage values, self-inductance values, constants including the electrical characteristics of the transmitting antenna (e.g., L1), and constants including the electrical characteristics of the receiving antenna (e.g., L2). The timing of these voltage value measurements and the timing of the exchange of information will be described below.

[0107] First, the measurement timing for each voltage value may be performed during the Ping phase. During the Ping phase, TX402 sends a Digital Ping to RX401. Then, TX402 and RX401 measure one of the V1 to V5 values ​​mentioned above and store it in memory 106 or memory 208. TX402 receives a predetermined packet containing information on one of the voltage values ​​V2, V4, or V5 notified by RX401 and records that information in memory.

[0108] The predetermined packet may include not only the receiving voltage of RX401 but also the received power. Furthermore, the predetermined packet may include information on the self-inductance values ​​of L1 and L2, or constants including the electrical characteristics of the transmitting antenna (e.g., L1) and the receiving antenna (e.g., L2). A Signal Strength Packet can be used as the predetermined packet. Note that the Signal Strength Packet may also notify TX402 of the received power of RX401 in another Signal Strength Packet. The predetermined packet may also be an Identification Packet, Extended Identification Packet, or Configuration Packet in the I&C phase. Furthermore, the predetermined packet may be a Received Power Packet (mode1) in the Calibration or Power Transfer phase. Finally, the predetermined packet may be a Received Power Packet (mode2) or Received Power Packet (mode0).

[0109] The above describes the case where the voltage value generated when TX402 transmits a Digital Ping is used, but any of the voltage values ​​V1 to V5 generated when TX402 transmits an Analog Ping during the Selection phase may also be used. Furthermore, when TX402 or RX401 performs the above measurement, RX401 turns ON (short-circuits) the switch 210 located between the resonant capacitor 211 and the power receiving unit 203. The circuit consisting of the power receiving antenna 205 and the resonant capacitor 211 may then be controlled to become a closed circuit. This eliminates the influence of the power receiving unit 203, the charging unit 206, and the battery 207 when performing the above measurement, making it possible to measure the coupling state index of the power transmitting antenna 105 and the power receiving antenna 205 with higher accuracy.

[0110] [Measurement method for an indicator showing the second coupling state of the transmitting and receiving antennas] The following describes a method for measuring another indicator that shows the coupling state between the transmitting antenna 105 and the receiving antenna 205. In Figure 17, when there is a transmitting antenna 105 and a receiving antenna 205, the coupling coefficient k, which represents the coupling state between the transmitting antenna 105 and the receiving antenna 205, can be calculated using the following formula.

[0111]

number

[0112] Here, Lsc is the inductance value of the transmitting antenna 105 when both ends of the receiving antenna 205 are short-circuited. This can be measured by measuring the inductance value of the transmitting antenna 105 with, for example, the switch 210 located between the resonant capacitor 211 and the receiving unit 203 turned ON (short-circuited). In this case, a switch (not shown) may be placed in series between the resonant capacitor 211 and the receiving unit 203 and the switch turned OFF (open). This eliminates the influence of the receiving unit 203, the charging unit 206, and the battery 207, making it possible to measure Lsc with higher accuracy. The inductance value Lsc of the transmitting antenna 105 can be determined from the input voltage (V6) input to the transmitting antenna 105 and the current (I1) flowing through the transmitting antenna 105. Lopen is the inductance value of the transmitting antenna 105 when both ends of the receiving antenna 205 are open-circuited. This involves, for example, placing a switch (not shown) in series between the resonant capacitor 211 and the receiving unit 203, and setting the switch to the OFF state (open state). Then, with the switch 210 between the resonant capacitor 211 and the receiving unit 203 in the OFF (open) state, the RX401 can measure Lopen by measuring the inductance value of the transmitting antenna 105. The inductance value Lopen of the transmitting antenna 105 can be determined from the input voltage (V7) input to the transmitting antenna 105 and the current (I2) flowing through the transmitting antenna 105. In other words, the coupling state index (coupling coefficient) of the transmitting antenna 105 and the receiving antenna 205 can be determined from the input voltage input to the transmitting antenna 105 and the current flowing through the transmitting antenna 105, respectively, when the ends of the receiving antenna 205 are short-circuited and when they are open-circuited.

[0113] Furthermore, TX402 may calculate an index representing the coupling state of the transmitting antenna 105 and the receiving antenna 205 based on the transmission voltage applied to the circuit (e.g., inverter) included in the transmitting unit 103 and the current flowing through the circuit (e.g., inverter) included in the transmitting unit 103. In other words, the input voltage V6 or V7 used when calculating the index representing the coupling state of the transmitting antenna 105 and the receiving antenna 205 as shown in Figure 8 may be the transmission voltage applied to the circuit (e.g., inverter) included in the transmitting unit 103. Also, V6 or V7 may be the voltage applied to the transmitting antenna 105, or the voltage applied to both terminals of the series resonant circuit consisting of the transmitting antenna 105 and the resonant capacitor. Alternatively, the transmission voltage applied to the circuit (e.g., inverter) included in the transmitting unit 103 and the voltage across the resonant capacitor 211 may be measured, and the voltage applied to the transmitting antenna may be calculated from the results. In other words, the coupling state index of the transmitting antenna 105 and the receiving antenna 205 may be determined from the measurement results of the transmission voltage applied to the circuit included in the transmitting unit 103 (e.g., an inverter) and the voltage across the resonant capacitor 211. Alternatively, the transmission voltage applied to the circuit included in the transmitting unit 103 (e.g., an inverter) may also be calculated from the set value of the transmission power transmitted by TX402.

[0114] Furthermore, the current I1 or I2 shown in Figure 17, which is used when calculating an index representing the coupling state of the transmitting antenna 105 and the receiving antenna 205, may be any of the following currents. That is, it may be the current flowing through the circuit (e.g., inverter) included in the transmitting unit 103, or it may be the current flowing through the transmitting antenna 105. Also, the "OPEN" and "SHORT" states of the receiving antenna shown in Figure 17 may be realized by the aforementioned switch controlled by the control unit 201, or by the receiving unit 203. Alternatively, the "SHORT" state may be the Light Load state described above.

[0115] In this measurement method, the TX402 can calculate an index representing the coupling state by measuring the input voltages V6 and V7 and currents I1 and I2. In other words, the voltage values ​​measured by the RX401 and the inductance value of the receiving antenna 205 are not necessary, and it is not necessary for the RX401 to notify the TX402 of this information. However, when the TX402 measures the input voltage V6 and current I1, the RX401 needs to open both terminals of the circuit containing the receiving antenna 205. Also, when the TX402 measures the input voltage V7 and current I2, the RX401 needs to short both terminals of the circuit containing the receiving antenna 205. In other words, the RX401 appropriately controls the terminals of the circuit containing the receiving antenna 205 to be open or short depending on the timing when the TX402 measures the input voltage or current. This timing may be determined by TX402 and notified to RX401, or determined by RX401 and notified to TX402. The notification method is carried out by communication based on the WPC standard between the communication unit 104 of TX402 and the communication unit 204 of RX401. Alternatively, it may be carried out by communication using a standard other than the WPC standard (for example, wireless LAN, Bluetooth® Low Energy (BLE), NFC (Near Field Communication), etc.).

[0116] Alternatively, the TX402 may measure the voltage values ​​V6 and V7 and the current values ​​I1 and I2 during the Ping phase. During the Ping phase, the TX402 sends a Digital Ping to the RX401. Therefore, it measures either the voltage value V6 or V7 generated when the Digital Ping is sent. It also measures either the current value I1 or I2 generated when the Digital Ping is sent. During the Ping phase, the TX402 measures one of the above values ​​of V6, V7, I1, and I2, stores them in memory 106, and calculates the coupling coefficient.

[0117] The above describes the case where the voltage and current values ​​generated when the TX402 sends a Digital Ping are used, but the voltage and current values ​​of V6, V7, I1, or I2 generated when the TX402 sends an Analog Ping may also be used.

[0118] In the following, when the phrase "measurement method for an indicator showing the coupling state of the transmitting antenna and the receiving antenna" is used, it means that either of the two measurement methods described above is applicable. That is, in this case, either "measurement method for an indicator showing the first coupling state of the transmitting antenna and the receiving antenna" or "measurement method for an indicator showing the second coupling state of the transmitting antenna and the receiving antenna" is applicable.

[0119] [Method for setting a threshold for detecting abnormal conditions using an indicator that shows the coupling state of the transmitting and receiving antennas] This document describes methods for detecting abnormal conditions, such as detecting foreign objects between the transmitting antenna 105 and the receiving antenna 205, and detecting misalignment between the transmitting and receiving antennas. Below, based on the "Measurement Method for Indicators Showing the Coupling State of the Transmitting and Receiving Antennas," the method for setting thresholds used to determine the presence or absence of abnormal conditions is described.

[0120] First, let's describe the first method for setting a threshold. The threshold used to detect abnormal conditions between the transmitting antenna 105 and the receiving antenna 205 can be the coupling state index used when there are no abnormal conditions. For example, if RX401 is mounted on a test power transmission device and there are no abnormal conditions between the transmitting antenna and the receiving antenna 205 of the test power transmission device, the coupling state index of the transmitting antenna and the receiving antenna 205 can be used as the threshold. In other words, RX401 stores an index indicating the coupling state that has been measured in advance in its memory, and RX401 notifies TX402 of the coupling state index, so that TX402 can use the coupling state index as the threshold. This coupling state index that serves as the threshold may also be transmitted by RX401 to TX402 in the FOD Status Packet as defined in the WPC standard.

[0121] Next, we will describe the second threshold setting method. In this case, the coupling state index measured when there are no abnormalities is used as the threshold. That is, when there are no abnormalities between the transmitting antenna 105 and the receiving antenna 205, the coupling state index measured by TX402 and RX401 using the "method for measuring the index indicating the coupling state of the transmitting antenna and the receiving antenna" described above is used as the threshold. Methods for confirming that there are no abnormalities include foreign object detection using the Power Loss method described above, and Q value measurement methods. In other words, to confirm that there are no abnormalities, a "means for detecting abnormalities between the transmitting antenna and the receiving antenna" other than the "method for measuring the index indicating the coupling state of the transmitting antenna and the receiving antenna" is performed. If the result is determined to be "no abnormalities," the coupling state index is measured using the "method for measuring the index indicating the coupling state of the transmitting antenna and the receiving antenna," and the measurement result is used as the threshold.

[0122] For example, the WPC standard performs foreign object detection using the Q-factor measurement method during the Negotiation or Renegotiation phase. If the result of this foreign object detection using the Q-factor measurement method is determined to be "no foreign objects," the coupling state index is measured using the "method for measuring an index indicating the coupling state of the transmitting and receiving antennas" after the Negotiation or Renegotiation phase. By using the measurement result as a threshold, it becomes possible to set an appropriate threshold. Alternatively, foreign object detection using the Power Loss method may be performed during the Power Transfer phase. That is, after performing the Power Loss method during the Power Transfer phase, the coupling state index may be measured using the "method for measuring an index indicating the coupling state of the transmitting and receiving antennas," and the measurement result may be used as a threshold. Or, foreign object detection may be performed using Q-Factor, etc., during the Selection phase or Ping phase. In this case, the coupling state index may be measured using the "method for measuring an index indicating the coupling state of the transmitting and receiving antennas" after the phase in which the foreign object detection process was performed, and the measurement result may be used as a threshold.

[0123] Next, we will describe the third threshold setting method. Figure 18 is a diagram illustrating this threshold setting method. The following is an example in which the receiving voltage V4 applied to the circuit (e.g., rectifier) ​​included in the receiving unit 203, or the output voltage V5 output by that circuit, is used to calculate the coupling state index in the "Method for measuring the index indicating the first coupling state of the transmitting antenna and the receiving antenna" described above. In this case, the receiving unit 203 is connected to the loads of the charging unit 206 and the battery 207, so the calculated coupling state index changes depending on the state of these loads. Therefore, a threshold for the coupling state (including the coupling coefficient) between the transmitting antenna 105 and the receiving antenna 205 is set to determine whether or not there is a state abnormality depending on the state of the load. The method for doing so is described below. First, when power is transmitted from TX402, RX401 is controlled so that the load of RX401 is in a light load state, such that no power is supplied to the load of RX401, or only a very small amount of power is supplied. The power transmitted by TX402 at this time is Pt1. Then, TX402 and RX402 measure the input voltage on the TX402 side and the received voltage on the RX401 side as described above, exchange information on the input and received voltages, and either TX402 or RX401 calculates a coupling state index. This coupling state index is denoted as k1. At this time, TX402 recognizes the transmitted power Pt1 that TX402 is transmitting and stores a calibration point 1800 in memory that associates the transmitted power Pt1 with the coupling state index k1. Next, RX401 controls the load of RX401 to be in a load-connected state so that when power is transmitted from TX402, the load of RX401 is supplied with maximum power or power above a predetermined threshold. In this case, the transmitted power of TX402 is denoted as Pt2. Then, in that state, TX402 measures the input voltage on the TX402 side and the received voltage on the RX401 side as described above, and TX402 or RX401 exchanges information on the input voltage and received voltage, and TX402 or RX401 calculates the coupling state index. At this time, TX402 stores a calibration point 1801 in memory that associates the transmitted power Pt2 with the coupling state index k2.Next, TX402 performs linear interpolation between calibration point 1800 and calibration point 1801 to create line 1802. Line 1802 shows the relationship between transmitted power and coupling state index when there are no abnormalities around TX402 and RX401. Therefore, TX402 can estimate the coupling state index for each transmitted power value from line 1802 when there are no abnormalities around TX402 and RX401. For example, if the transmitted power value is Pt3, the coupling state index can be estimated to be k3 from point 1803 on line 1802 corresponding to the transmitted power value Pt3. Based on the above estimation results, TX402 can then calculate a threshold used to determine the presence or absence of abnormalities for each transmitted power value. For example, a coupling state index that is a predetermined value (a value corresponding to the measurement error) larger than the estimated coupling state index for a given transmitted power value when there are no abnormalities may be set as the threshold for determining the presence or absence of foreign matter. The calibration process performed by TX402 and RX401 to obtain a combination of transmission power value and coupling state index is hereafter referred to as the "Coupling State Measurement Method Calibration Process (CAL Process)". Note that RX401 may perform control to set the load to a state where no power is supplied / light load state, and control to set the load to a connected state, after notifying TX402 of the control. Furthermore, either of these two controls may be performed first. Note that the operation for calculating the threshold used to determine the presence or absence of abnormal state for each load (for each transmission power value), as described in this embodiment, may be performed in the Calibration phase. As described above, in the Calibration phase, TX402 obtains data necessary for foreign object detection using the Power Loss method. At that time, TX402 obtains data on power loss when the load state of RX401 is a light load state and when it is a connected load state. Therefore, the measurements at calibration point 1800 and calibration point 1801 in Figure 18 may be performed together with the measurement of power loss during the light load state and load-connected state in the Calibration phase.In other words, when TX402 receives the first reference power information from RX401, in addition to the predetermined processing to be performed in the Calibration phase, it measures calibration point 1800. Here, the first reference power information is Received Power Packet (mode 1) as defined in the WPC standard, but other messages may be used. Also, when TX402 receives the second reference power information from RX401, in addition to the predetermined processing to be performed in the Calibration phase, it measures calibration point 1801. Here, the second reference power information is Received Power Packet (mode 2) as defined in the WPC standard, but other messages may be used. Therefore, it is no longer necessary to set aside a separate period for measuring calibration point 1800 and calibration point 1801, and thus calibration point 1800 and calibration point 1801 can be measured in a shorter time. This concludes the explanation of the third threshold setting method.

[0124] The fourth threshold setting method is described below. The fourth threshold setting method involves the TX402 or RX401 pre-setting a threshold for a coupling state index that has a value within a predetermined range. For example, if the coupling state index is the "coupling coefficient," the coupling coefficient k will be a value within the range of 0 to 1, as described above. Therefore, the TX402 or RX401 will determine, for example, "0≦k<0.3 indicates a state abnormality," "0.3≦k<0.6 indicates a possible state abnormality," and "0.6≦k≦1 indicates no state abnormality." Specifically, the coupling coefficient k and its determination conditions are stored in memory beforehand, and the determination is made based on this. This concludes the explanation of the fourth threshold setting method.

[0125] Similarly, a threshold may be set in the "setting of a state abnormality detection threshold using the coupling state of the transmitting and receiving antennas." In other words, a waveform attenuation rate that is greater or less than a predetermined value (a value corresponding to the measurement error) than the "coupling state index" calculated based on the measured or received information as described above may be set as the threshold for determining the presence or absence of foreign matter. Furthermore, there may be multiple thresholds in stages. The first threshold may be set as "state abnormality present," the second threshold as "possibility of state abnormality," and the third threshold as "no state abnormality," and so on.

[0126] [Method for setting each period when using the waveform attenuation method as a foreign object detection method] The following describes an example of how to set each period in the waveform attenuation method in this embodiment, and how to determine an appropriate duration for each period.

[0127] The method for determining the preparation period is described below. In this embodiment, the preparation period is set to a predetermined value (time length) by TX402. However, it is not limited to this, and for example, TX402 may determine a predetermined value (time) according to its own state and notify RX401 of it. Alternatively, RX401 may determine a predetermined value (time) according to its own state and notify TX402 of it. Alternatively, TX402 and RX401 may communicate with each other and exchange information to determine a predetermined value (time). Alternatively, TX402 may notify RX401 of the maximum time length it has determined, and RX401 may notify TX402 of the minimum time length it has determined, and RX401 may determine the preparation period within the range of values ​​(time length) set by TX402 and RX401 and notify TX402 of it. Furthermore, the relationship between TX402 and RX401 may be reversed. By setting the preparation period to an appropriate length of time, it is possible to prevent the waveform during the power transmission control period from being disturbed.

[0128] Next, the method for determining the power transmission control period will be described. In this embodiment, the power transmission control period is determined through negotiation between RX401 and TX402. The negotiation method is as follows, for example: TX402 determines the minimum time length that can be set as the power transmission control period and notifies RX401 of it. RX401 also determines the maximum time length that can be set as the power transmission control period and notifies TX402 of it. TX402 and RX401 then determine a time length within the range that can be set using the time lengths they have notified each other of, and set it as the power transmission control period. In this case, TX402 or RX401 will determine the minimum time length within the range set by TX402 and RX401 as the power transmission control period. Note that the content of the negotiation is not limited to this. For example, one of TX402 or RX401 may notify the other of the range of time lengths that it can set, and the notified party may then determine the time length. Alternatively, the TX402 may notify the maximum time duration, and the RX401 may notify the minimum time duration. Furthermore, information for determining the power transmission control period may be included in the execution request packet (e.g., Received Power Packet).

[0129] Alternatively, a predetermined value (duration) may be set as the power transmission control period. Alternatively, TX402 may determine a predetermined value (duration) according to its state and notify RX401 of it. Alternatively, RX401 may determine a predetermined value (duration) according to its state and notify TX402 of it. Alternatively, TX402 or RX401 may determine the maximum time within the range set by TX402 and RX401 as the power transmission control period. In this way, the waveform attenuation state of the transmitted radio waves can be observed for a long period of time, enabling highly accurate detection of foreign objects.

[0130] Next, we will discuss the relationship between the power transmitted from TX402 and the power transmission control period. In addition to the method described above, TX402 or RX401 determines that the power transmission control period is shorter when the power transmitted by TX402 is greater than when it is smaller. When power transmission is resumed after the power transmission control period, ringing occurs in the transmission waveform at the time of resumption. The greater the difference in peak power between the power immediately before resumption and the power transmitted at the time of resumption, the greater the ringing. Therefore, in order to reduce ringing, it is necessary to reduce the difference in peak power between the power immediately before resumption and the power transmitted at the time of resumption. To achieve this, the power transmission control period is shortened. As a result, power transmission is resumed with less waveform attenuation, and consequently, the difference in peak power between the power immediately before resumption and the power transmitted at the time of resumption becomes smaller, making it possible to suppress ringing. Similarly, the greater the transmitted power, the shorter the transmission power control period can be, thereby reducing the difference in power levels between the power level immediately before power transmission is resumed and the power level at the time of resumption, and thus suppressing ringing.

[0131] Furthermore, as explained above, in order to suppress ringing, the transmission power control period should be shortened as the transmission power increases. On the other hand, if the accuracy of measuring the waveform attenuation index in the waveform attenuation method is prioritized, the transmission power control period may be made longer as the transmission power increases. For example, as the transmission power increases, the risk of foreign matter being present increases, requiring highly accurate foreign matter detection. Therefore, when the transmission power is greater than a predetermined value, the transmission power control period is made longer to observe the attenuation state for a longer period. This improves the accuracy of measuring the attenuation state, and thus the accuracy of the attenuation index also improves. Thus, when prioritizing the accuracy of measuring the waveform attenuation index, the transmission power control period is made longer when the transmission power is greater than a predetermined value than when it is smaller. It is also possible to configure the system so that the transmission power control period is made longer as the transmission power increases. Alternatively, the system may be configured to determine whether to lengthen or shorten the transmission power control period depending on the magnitude of the transmission power, based on user specifications or other factors. As described above, the TX402 and RX401 can determine the length of the power transmission control period based on the magnitude of the transmitted power.

[0132] The above describes a case where the length of the power transmission control period is determined based on the magnitude of the power transmitted by TX402 to RX401. However, it is not limited to this, and the power transmitted by TX402 as described above may be replaced with GP, MP, or PP. In other words, the length of the power transmission control period may be determined based on the magnitude of the setting value for power transmission determined through negotiations between TX402 and RX401. Alternatively, the length of the power transmission control period may be determined based on the information stored in the Received Power Packet (mode0) that RX401 transmits to TX402. Furthermore, the length of the power transmission control period may be determined based on the information stored in the Received Power Packet (mode1) or Received Power Packet (mode2). These Received Power Packets contain received power value information indicating the magnitude of the power received by RX401 from TX402. The power transmitted by TX402 may also be replaced with this received power value information.

[0133] Next, we will describe the relationship between the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 and the power transmission control period. The coupling state index between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 can be measured, for example, by "a method for measuring an index indicating the coupling state of a transmitting antenna and a receiving antenna." Alternatively, the coupling state index may be measured by other methods for measuring the coupling state of a transmitting antenna and a receiving antenna.

[0134] In addition to the method described above, the TX402 or RX401 determines that the power transmission control period is longer when the coupling state between the transmitting antenna 105 and the receiving antenna 205 is worse than when it is good. Here, "good coupling state" refers to a case where, for example, as described above, the measured coupling coefficient is compared with a predetermined threshold and determined to be "no abnormality." "Poor coupling state" refers to a case where, for example, as described above, the measured coupling coefficient is compared with a predetermined threshold and determined to be "possible abnormality" or "abnormality present."

[0135] The worse the coupling condition, the greater the possibility that foreign matter may be present between the transmitting antenna 105 and the receiving antenna 205, thus requiring highly accurate detection of foreign matter. Therefore, if the coupling condition is worse than a predetermined value, the power transmission control period is extended to observe the attenuation state for a longer period. This improves the accuracy of the attenuation index because it increases the accuracy of the measurement of the attenuation state. In this way, when prioritizing the accuracy of the waveform attenuation index measurement, if the coupling state is worse than a predetermined value, the power transmission control period is made longer than when it is good. In fact, a configuration may be used where the power transmission control period is made longer the worse the coupling state is.

[0136] Furthermore, as explained above, in order to improve the accuracy of measuring the waveform attenuation index, the worse the coupling state, the longer the power transmission control period should be. On the other hand, if power transmission efficiency is prioritized, the worse the coupling state, the shorter the power transmission control period should be. Power transmission efficiency decreases as the coupling state worsens. Therefore, when the coupling state is poor, the power transmission control period should be shortened to ensure a longer period during which power can be transmitted. This improves power transmission efficiency. Thus, when prioritizing power transmission efficiency, if the coupling state is worse than a predetermined value, the power transmission control period should be shortened compared to when it is good. It should also be configured so that the power transmission control period is shortened as the coupling state worsens. In addition, the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 described above may be measured before TX402 starts transmitting power, or it may be measured multiple times at predetermined timings after TX402 starts transmitting power. If multiple measurements are taken at predetermined intervals after TX402 has started transmitting power, the power transmission control period may be changed based on the results of each measurement. For example, if three measurements are taken at predetermined intervals after TX402 has started transmitting power, and the measured coupling state values ​​are all different, the power transmission control period will be changed three times.

[0137] Furthermore, the configuration may determine whether to lengthen or shorten the power transmission control period based on the coupling state, based on user specifications or other factors. As described above, TX402 and RX401 can determine the length of the power transmission control period based on the coupling state.

[0138] Next, we will describe the relationship between the frequency of electromagnetic waves radiated from the transmitting antenna 105 of TX402 to the receiving antenna 205 of RX401 for power transmission and the power transmission control period. In addition to the method described above, TX402 or RX401 is configured such that the power transmission control period is longer when the frequency of electromagnetic waves radiated from the transmitting antenna 105 to the receiving antenna 205 of RX401 for power transmission is lower than when the frequency is higher. Here, the frequency of electromagnetic waves radiated for power transmission is the frequency of electromagnetic waves radiated from the transmitting antenna 105 to the receiving antenna 205 of RX401 for power transmission during the power transmission period.

[0139] Generally, the higher the frequency of electromagnetic waves, the greater the loss. Therefore, the higher the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the greater the attenuation rate of the electromagnetic waves during the power transmission control period, resulting in a steeper attenuation. On the other hand, the lower the frequency of the electromagnetic waves, the smaller the attenuation rate of the electromagnetic waves during the power transmission control period, resulting in a more gradual attenuation. Also, the higher the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the shorter the wavelength of the electromagnetic waves during the power transmission control period, making it possible to calculate the attenuation rate in a shorter period. Conversely, the lower the frequency of the electromagnetic waves, the longer the wavelength of the electromagnetic waves during the power transmission control period, requiring a longer period to calculate the attenuation rate. Therefore, the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the longer the power transmission control period is allowed to observe the attenuation state for a longer period. This improves the accuracy of the measurement of the attenuation state, and thus improves the accuracy of the attenuation index. Thus, in order to improve the accuracy of the waveform attenuation index measurement, when the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission is lower than a predetermined value, the power transmission control period is made longer than when the frequency is higher. Furthermore, a configuration may be used where the power transmission control period is made longer the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission.

[0140] Furthermore, as explained above, in order to improve the accuracy of measuring the waveform attenuation index, the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the longer the power transmission control period should be. On the other hand, if power transmission efficiency is prioritized, the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the shorter the power transmission control period should be. The lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the more stable the waveform of the electromagnetic waves becomes. Conversely, the higher the frequency of the electromagnetic waves, the more susceptible they become to the influence of objects around the transmitting antenna 105, and there is a risk that the waveform of the electromagnetic waves will become unstable. Therefore, when the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission is high, the power transmission control period should be made longer to observe the attenuation state for a longer period of time. This improves the accuracy of measuring the attenuation state, and thus improves the accuracy of the attenuation index. Thus, in order to improve the accuracy of the waveform attenuation index measurement, if the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission is higher than a predetermined value, the power transmission control period is made longer than when the frequency is higher. Furthermore, a configuration may be used where the power transmission control period is made longer the higher the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission.

[0141] Furthermore, as mentioned above, for example, the frequency of electromagnetic waves used for power transmission in the WPC standard is between 85 kHz and 205 kHz. If the frequency of electromagnetic waves radiated from the transmission antenna 105 for power transmission varies between 85 kHz and 205 kHz, the power transmission control period may be controlled accordingly. Alternatively, if the frequency of electromagnetic waves radiated from the transmission antenna 105 for power transmission is within a first predetermined frequency band, such as 85 kHz to 205 kHz, the power transmission control period may be set to the first power transmission control period. If it is within a second predetermined frequency band different from the first predetermined frequency band, the power transmission control period may be set to a second power transmission control period different from the first power transmission control period.

[0142] Furthermore, the system may be configured to determine whether to lengthen or shorten the power transmission control period based on the frequency of the electromagnetic waves radiated from the power transmission antenna 105 for power transmission, based on user specifications or other factors. As described above, the TX402 and RX401 can determine the length of the power transmission control period based on the frequency of the electromagnetic waves radiated from the power transmission antenna 105 for power transmission.

[0143] Next, the method for determining the communication ban period will be described. The purpose of the communication ban period is to ensure stable communication by preventing communication during periods of ringing, as ringing occurs in the power transmission waveform after power transmission is resumed. In this embodiment, the communication ban period is determined by RX401 and notified to TX402. However, it is not limited to this, and for example, TX402 may determine a predetermined value (time) according to the state of TX402 and notify RX401 of it. Alternatively, RX401 may determine a predetermined value (time) according to the state of RX401 and notify TX402 of it. Alternatively, TX402 and RX401 may communicate with each other and exchange information to determine a predetermined value (duration).

[0144] Alternatively, TX402 may notify RX401 of the maximum time duration it has determined, and RX401 may notify TX402 of the minimum time duration it has determined. RX401 may then determine the communication ban period within the range (time duration) set by TX402 and RX401, and notify TX402 of this. The relationship between TX402 and RX401 may also be reversed. In this case, TX402 or RX401 may determine the minimum time within the range set by TX402 and RX401 as the communication ban period. Alternatively, TX402 or RX401 may determine the maximum time within the range set by TX402 and RX401 as the communication ban period. Furthermore, information for determining the communication ban period may be included in the execution request packet (e.g., Received Power Packet).

[0145] Next, we will discuss the relationship between the power transmitted from TX402 and the communication blackout period. In addition to the method described above, TX402 or RX401 determines that the communication blackout period is longer when the power transmitted by TX402 is greater than when it is smaller. When power transmission is resumed after the power transmission control period, ringing occurs in the transmission waveform at the time of resumption. The greater the difference in the peak and trough of the transmitted power at the time of resumption, the greater the ringing. In other words, the greater the transmitted power, the greater the ringing. Therefore, by making the communication blackout period longer when the transmitted power is large, communication can be performed after the ringing has subsided or become sufficiently small, enabling stable communication between TX402 and RX401. Note that, for example, if it is desired to shorten the period related to communication as much as possible, the communication blackout period may be made even shorter. As described above, TX402 and RX401 can determine the length of the communication blackout period based on the magnitude of the transmitted power.

[0146] The above describes a case where the length of the communication blackout period is determined based on the magnitude of the power transmitted by TX402 to RX401. However, the power transmitted by TX402 may be replaced with GP, MP, or PP. In other words, the length of the communication blackout period may be determined based on the magnitude of the setting value for power transmission determined through negotiations between TX402 and RX401. Alternatively, the length of the communication blackout period may be determined based on the information stored in the Received Power Packet (mode0) transmitted by RX401 to TX402. Furthermore, the length of the communication blackout period may be determined based on the information stored in Received Power Packet (mode1) and Received Power Packet (mode2). These Received Power Packets contain received power value information indicating the magnitude of the power received by RX401 from TX402. The power transmitted by TX402 may be replaced with this received power value information.

[0147] Furthermore, the relationship between the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 and the communication blackout period will be described. In addition to the method described above, TX402 or RX401 is configured such that the communication blackout period is longer when the coupling state between the transmitting and receiving antennas is worse than when it is good. The worse the coupling state, the greater the possibility that foreign matter is present between the transmitting and receiving antennas. The presence of foreign matter can have adverse effects on communication between TX402 and RX401, such as causing waveform distortion, thus increasing the likelihood of communication errors between TX402 and RX401. Therefore, if the coupling state is worse than a predetermined value, the communication blackout period is made longer. This allows communication to be performed only after the ringing of the transmitted signal type has converged or become sufficiently small when power transmission is resumed, thus reducing the likelihood of communication errors. Thus, if the coupling state is worse than a predetermined value, the communication blackout period is made longer than when it is good. Note that a configuration in which the communication blackout period is longer the worse the coupling state is is also possible.

[0148] Furthermore, as explained above, to improve communication quality, the worse the coupling state, the longer the communication blackout period should be. On the other hand, to improve communication quality, the worse the coupling state, the shorter the communication blackout period should be. The worse the coupling state, the higher the possibility of errors occurring in communication between TX402 and RX401. Therefore, when the coupling state is poor, the communication blackout period should be shortened to ensure a longer period of communication. In addition, communication between TX402 and RX401 should be slower than when the coupling state is good. Alternatively, communication between TX402 and RX401 should be at a greater modulation depth. In other words, when the coupling state is poor, TX402 transmits communication data using slower frequency shift modulation. Alternatively, it transmits communication data using frequency shift modulation with a greater modulation depth. Also, when the coupling state is poor, RX401 transmits communication data using slower amplitude modulation or load modulation. Alternatively, communication data can be transmitted using amplitude modulation or load modulation with a larger modulation depth.

[0149] This reduces the probability of communication errors and improves communication quality. Thus, when the coupling state is worse than a predetermined value, the communication blackout period is shortened compared to when the coupling state is good. Furthermore, communication between TX402 and RX401 is performed at a slower speed or with a higher modulation index than when the coupling state is good. Alternatively, the worse the coupling state, the shorter the communication blackout period may be, resulting in even slower communication or communication with a higher modulation index between TX402 and RX401.

[0150] Furthermore, the above described a scenario where, in the event of poor coupling, the communication blackout period is shortened to ensure a longer period of communication, and communication between TX402 and RX401 is performed at a slower speed or using a larger modulation depth. However, in the event of poor coupling, it is also acceptable to simply perform communication between TX402 and RX401 at a slower speed or using a larger modulation depth compared to the case of good coupling. In other words, in the event of poor coupling, TX402 transmits communication data using a slower frequency shift modulation, or uses a frequency shift modulation with a larger modulation depth. Similarly, in the event of poor coupling, RX401 transmits communication data using a slower amplitude modulation or load modulation, or uses an amplitude modulation or load modulation with a larger modulation depth. This reduces the probability of communication errors and improves communication quality.

[0151] Furthermore, the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 described above may be measured before TX402 starts transmitting power, or it may be measured multiple times at predetermined timings after TX402 starts transmitting power. If multiple measurements are taken at predetermined timings after TX402 starts transmitting power, the communication blackout period, or the communication speed or modulation index may be changed based on the results of each measurement. For example, if three measurements are taken at predetermined timings after TX402 starts transmitting power, and the measured coupling state values ​​are all different, the communication blackout period, or the communication speed or modulation index will be changed three times. Alternatively, the configuration may be such that the length of the communication blackout period is determined based on the state of the coupling, based on user specification or the like. As described above, TX402 and RX401 can determine the length of the communication blackout period based on the coupling state.

[0152] Furthermore, we will discuss the relationship between the frequency of electromagnetic waves radiated from the transmitting antenna 105 of TX402 to the receiving antenna 205 of RX401 for power transmission and the communication blackout period. In addition to the method described above, TX402 or RX401 determines that the communication blackout period is shorter when the frequency of electromagnetic waves radiated from the transmitting antenna 105 to the receiving antenna 205 of RX401 for power transmission is lower than when the frequency is higher. Here, "frequency of electromagnetic waves radiated for power transmission" refers to the frequency of electromagnetic waves radiated from the transmitting antenna 105 to the receiving antenna 205 of RX401 for power transmission during the power transmission period. When power transmission is resumed after the power transmission control period, ringing occurs in the transmission waveform of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission at the time of resumption of power transmission. The higher the frequency of the transmitted wave, the greater the risk of ringing occurring. In other words, the higher the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the greater the risk of ringing. Therefore, by increasing the communication blackout period as the frequency of the electromagnetic waves radiated from the antenna 105 for power transmission increases, communication can be initiated only after the ringing has subsided or become sufficiently small. This makes stable communication between TX402 and RX401 possible. Thus, to improve the stability of communication between TX402 and RX401, when the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission is higher than a predetermined value, the communication blackout period is made longer than when the frequency is lower. It is also possible to configure the system so that the communication blackout period is longer as the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission increases.

[0153] Furthermore, as explained above, in order to improve the stability of communication between TX402 and RX401, the higher the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the longer the communication blackout period should be. On the other hand, the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the longer the power transmission control period should be. When power transmission is resumed after the power transmission control period, ringing occurs in the transmission waveform of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission at the time of resumption of power transmission. And the lower the frequency of the transmitted wave waveform, the greater the risk of ringing occurring for a long period of time. In other words, the lower the frequency of the electromagnetic waves radiated from the transmitting antenna 105 for power transmission, the greater the risk of ringing occurring for a long period of time. Therefore, by making the communication blackout period longer as the frequency of the electromagnetic waves radiated from the antenna 105 for power transmission decreases, communication can be performed after the ringing has converged or become sufficiently small. This enables stable communication between TX402 and RX401. In order to improve the stability of communication between TX402 and RX401, the communication blackout period is made longer when the frequency of electromagnetic waves radiated from the power transmission antenna 105 for power transmission is lower than a predetermined value, compared to when the frequency is higher. Alternatively, the lower the frequency of electromagnetic waves radiated from the power transmission antenna 105 for power transmission, the longer the communication blackout period may be configured.

[0154] Furthermore, as mentioned above, for example, the frequency of electromagnetic waves used for power transmission in the WPC standard is between 85 kHz and 205 kHz. If the frequency of electromagnetic waves radiated from the power transmission antenna 105 for power transmission varies between 85 kHz and 205 kHz, the communication blackout period may be controlled accordingly. Alternatively, if the frequency of electromagnetic waves radiated from the power transmission antenna 105 for power transmission is within a first predetermined frequency band, such as 85 kHz to 205 kHz, the communication blackout period may be set to a first communication blackout period. If it is within a second predetermined frequency band different from the first predetermined frequency band, the communication blackout period may be set to a second communication blackout period different from the first communication blackout period.

[0155] Furthermore, the configuration may determine whether to lengthen or shorten the communication ban period based on the frequency of the electromagnetic waves radiated from the power transmission antenna 105 for power transmission, based on user specifications or other factors. As described above, the TX402 and RX401 can determine the length of the communication ban period based on the frequency of the electromagnetic waves radiated from the power transmission antenna 105 for power transmission.

[0156] Furthermore, the relationship between the power transmission control period and the communication ban period will be discussed. In addition to the method described above, the TX402 or RX401 will determine that the longer the power transmission control period, the longer the communication ban period. As mentioned above, the greater the difference between the power immediately before power transmission is resumed and the power transmitted at the time of resumed transmission, the greater the ringing that occurs. As the power transmission control period lengthens, the attenuation of the transmitted signal also increases, resulting in a larger difference between the power immediately before power transmission is resumed and the power transmitted at the time of resumed transmission, thus causing significant ringing. Therefore, by setting a longer communication ban period as the power transmission control period lengthens, communication can be initiated after the ringing has subsided or become sufficiently small, enabling stable communication between the TX402 and RX401. As described above, the TX402 and RX401 can determine the length of the communication ban period based on the length of the power transmission control period.

[0157] Next, the method for determining the power transmission period will be described. In this embodiment, the length of the power transmission period is determined by RX401 and notified to TX402. However, it is not limited to this, and the power transmission period may be set to a predetermined value (time length) by TX402. Alternatively, TX402 may determine a predetermined value (time) according to its state and notify RX401 of it. Or RX401 may determine a predetermined value (time length) according to its state and notify TX402 of it. Alternatively, TX402 and RX401 may communicate with each other and exchange information to determine a predetermined value (time length). Alternatively, TX402 may determine the maximum time length that can be set as the power transmission period and notify RX401 of it, and RX401 may determine the minimum time length that can be set as the power transmission period and notify TX402 of it. Based on this notification, RX401 may determine the power transmission control period within the range (time) set by TX402 and RX401, and notify TX402 of that value. Alternatively, the relationship between TX402 and RX401 may be reversed.

[0158] Next, we will discuss the relationship between the power transmitted from TX402 and the transmission period. In addition to the method described above, TX402 or RX401 will determine the transmission period to be shorter when the power transmitted by TX402 is greater than when it is smaller. The higher the power transmitted, the higher the accuracy required for foreign object detection. Therefore, by shortening the transmission period as the power transmitted increases, it is possible to increase the number of power transmission control periods within a predetermined time, increase the number of times the attenuation state of the transmitted radio wave is observed, and increase the opportunities for foreign object detection, thereby enabling highly accurate foreign object detection. Alternatively, the transmission period may be set to be longer as the power transmitted increases. By setting a longer transmission period, it becomes possible to transmit power from TX402 to RX401 without reducing the power transmission efficiency. Note that the above describes the case where the length of the transmission period is determined based on the amount of power transmitted by TX402 to RX401. However, the power transmitted by TX402 may also be replaced with GP, MP, or PP. In other words, the length of the power transmission period may be determined based on the magnitude of the setting value for the power transmitted, which is determined through negotiations between TX402 and RX401.

[0159] Furthermore, the relationship between the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 and the power transmission period will be described. In addition to the method described above, TX402 or RX401 is determined such that the power transmission period is shorter when the coupling state between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 is worse than when it is good. A poorer coupling state suggests a higher possibility of foreign matter being present between the transmitting and receiving antennas, thus requiring high accuracy in detecting foreign matter.

[0160] Therefore, the worse the coupling state, the shorter the power transmission period, which increases the number of power transmission control periods within a predetermined time, thereby increasing the number of times the attenuation state of the transmitted radio waves is observed and increasing the opportunities for foreign object detection, thus enabling highly accurate foreign object detection. Alternatively, the worse the coupling state, the longer the power transmission period may be set. Although the power transmission efficiency decreases as the coupling state worsens, setting a longer power transmission period makes it possible to transmit power from TX402 to RX401 without reducing the power transmission efficiency.

[0161] If TX402 does not receive an execution request packet during the power transmission period, the power transmission period as a detection processing period will not be set, and power transmission will continue.

[0162] The above describes how to set each period. Note that each period does not necessarily have to be set individually. For example, the length of the entire detection processing period, which includes at least the power transmission control period, may be determined. In this case, TX402 and RX401 may be configured to determine the length of the entire detection processing period based on the magnitude of the power transmission. Alternatively, the length of the entire detection processing period may be determined based on the magnitude of the setting value related to power transmission, which is determined by negotiation between TX402 and RX401. Alternatively, the length of the entire detection processing period may be determined based on the coupling state between the power transmission antenna 105 of TX402 and the power receiving antenna 205 of RX401.

[0163] [Method for setting the foreign object detection threshold in waveform attenuation method] This section describes how to set a threshold for determining the presence or absence of a foreign object, or the probability of its presence, when performing foreign object detection using the waveform attenuation method. As mentioned above, the waveform attenuation method performs foreign object detection based on a waveform attenuation index. In the foreign object detection process in this embodiment, the measured waveform attenuation index is compared with a predetermined threshold, and the presence or absence of a foreign object, or the probability of its presence, is determined based on the result. The following methods can be used to set this threshold.

[0164] The first method involves the TX402 maintaining a predetermined threshold value, which is a common value independent of the RX401 being transmitted to. This threshold value may be the same in all cases, or it may be a value determined by the TX402 depending on the situation. As mentioned above, the waveform attenuation rate of the transmitted waveform during the power transmission control period is higher when foreign matter is present compared to when no foreign matter is present. Therefore, a predetermined value for the waveform attenuation index when it is considered that "no foreign matter is present" is maintained in advance, and this is used as a threshold value to compare with the measured waveform attenuation index result. If the measured waveform attenuation index is greater than the threshold value, it is determined that "foreign matter is present" or "there is a high possibility that foreign matter is present." For example, if the Q value is used as the waveform attenuation index, the Q value measured by the TX402 is compared with a predetermined Q value (threshold) when it is considered that no foreign matter is present. If the measured Q value is smaller than the threshold Q value, it is determined that "foreign matter is present" or "there is a possibility that foreign matter is present." If the measured Q value is greater than or nearly equal to the threshold Q value, it is determined that there is "no foreign object" or "the possibility of foreign object presence is low." In this way, foreign object detection using the waveform attenuation method becomes possible using the first method.

[0165] The second method involves the TX402 adjusting and determining a threshold based on information transmitted from the RX401. As mentioned above, the waveform attenuation rate of the transmitted waveform during the power transmission control period is higher when foreign objects are present compared to when they are not. Therefore, a predetermined value for the waveform attenuation index when "no foreign objects are present" is stored in advance, and this is used as a threshold to compare with the measured "waveform attenuation index" result. If the measured waveform attenuation index is greater than the threshold value, it is determined that "foreign objects are present" or "there is a high probability that foreign objects are present." Here, the value of the waveform attenuation index may differ depending on the RX401 being transmitted, which is mounted on the TX402. This is because the electrical characteristics of the RX401 coupled via the TX402's transmission antenna (transmission coil) affect the value of the waveform attenuation index.

[0166] For example, if the waveform attenuation index is defined as the Q value, the Q value measured by the TX402 when no foreign objects are present may differ depending on the RX401 placed on the TX402. Therefore, the RX401 stores the Q value information for each TX402 when the RX401 is placed on the TX402 when no foreign objects are present, and notifies the TX402 of this Q value. The TX402 then adjusts and determines the threshold based on the Q value information received from the RX401. More specifically, in the Negotiation phase, the TX402 receives an FOD Status Packet containing information on the Reference Quality Factor Value, and adjusts and determines the threshold in the Q value measurement method. This Reference Quality Factor Value corresponds to "the Q value information when the RX401 is placed on the TX402 when no foreign objects are present within the power transmission range of the TX402."

[0167] Therefore, the threshold for foreign object detection using the waveform attenuation method is also adjusted and determined by TX402 based on this Reference Quality Factor Value. The Reference Quality Factor Value transmitted from RX401 to TX402 during the Negotiation phase is originally information used for foreign object detection in the Q-value measurement method, which measures the Q value in the frequency domain. However, if the "waveform attenuation index" is used as the Q value, although the method of deriving the Q value is different, it is possible to determine the Q value using (Equation 1) from the waveform in Figure 6, for example, even when using the waveform attenuation method which measures the Q value in the time domain.

[0168] Therefore, it is possible to set the Q value threshold for the waveform attenuation method based on the Reference Quality Factor Value. In this way, by having TX402 set the Q value threshold for the waveform attenuation method based on the information already transmitted from RX401 to TX402 during the Negotiation phase, new measurements and other processing for threshold setting become unnecessary. As a result, it becomes possible to set the threshold in a shorter time.

[0169] The Q value measured by TX402 is compared with the threshold value determined by the method described above. If the measured Q value is smaller than the threshold Q value, it is determined that "foreign object is present" or "there is a possibility of foreign object being present." If the measured Q value is larger than or approximately the same as the threshold Q value, it is determined that "there is no foreign object" or "there is a low possibility of foreign object being present." In this way, foreign object detection using the waveform attenuation method becomes possible using the second method.

[0170] The third method involves the TX402 measuring the waveform attenuation index in the absence of foreign matter, and then adjusting and determining the threshold based on the measurement results. The value of the waveform attenuation index may vary depending on the power transmission of the TX402. This is because the amount of heat generated, the characteristics of the TX402's electrical circuit, etc., change depending on the power transmission of the TX402, and these affect the value of the waveform attenuation index. Therefore, by having the TX402 measure the waveform attenuation index for each power transmission level and adjusting and determining the threshold based on the results, more accurate foreign matter detection becomes possible.

[0171] Figure 11 illustrates the method for setting foreign object detection thresholds for each power transmission level of TX402 in the waveform attenuation method. First, when power is transmitted from TX402, RX401 controls itself so that no power or only very little power is supplied to the load of RX401, thereby reducing the load of RX401 to a light load state. The power transmission level of TX402 at this time is denoted as Pt1. Then, TX402 stops transmitting power in this state and measures the waveform attenuation index. The waveform attenuation index at this time is denoted as δ1. At this time, TX402 recognizes the power transmission level Pt1 that TX402 is transmitting and stores a calibration point 1100 in memory that associates the power transmission level Pt1 with the waveform attenuation index δ1.

[0172] Next, RX401 controls itself so that when power is transmitted from TX402, the load of RX401 is supplied with maximum power, or power exceeding a predetermined threshold, and so that the load of RX401 is in a load-connected state. The power transmitted by TX402 at this time is denoted as Pt2. Then, TX402 limits the power transmission for a predetermined period in this state and measures the waveform attenuation index. At this time, TX402 stores a calibration point 1101 in memory that associates the transmitted power Pt2 with the waveform attenuation index δ2.

[0173] Next, TX402 performs linear interpolation between calibration point 1100 and calibration point 1101 to create a line 1102. Line 1102 shows the relationship between the transmitted power and the waveform attenuation index of the transmitted signal type when there are no foreign objects around TX402 and RX401. Therefore, TX402 can estimate the waveform attenuation index of the transmitted signal type for each transmitted power value in the absence of foreign objects from line 1102. For example, if the transmitted power value is Pt3, the waveform attenuation index can be estimated to be δ3 from point 1103 on line 1102 corresponding to the transmitted power value Pt3. Based on the above estimation results, TX402 can then calculate a threshold value used to determine the presence or absence of foreign objects for each transmitted power value. For example, a waveform attenuation index that is larger by a predetermined value (a value corresponding to the measurement error) than the estimated waveform attenuation index in the absence of foreign objects for a certain transmitted power value may be set as the threshold value for determining the presence or absence of foreign objects. The calibration process performed by TX402 and RX401 to obtain a combination of transmission power value and waveform attenuation index will be referred to below as "waveform attenuation index calibration process (CAL process)". In the example above, measurements were taken at two points, Pt1 and Pt2, of the TX402's transmission power. However, to improve accuracy, measurements may be taken at three or more points to calculate the waveform attenuation index for each transmission power.

[0174] Furthermore, RX401 may notify TX402 of its intention to perform control actions such as reducing power supply to the load / creating a light load state, and connecting the load, before performing these actions. Also, the order in which these two controls are performed does not matter.

[0175] Furthermore, the operation for calculating the threshold used to determine the presence or absence of foreign matter for each load (each transmitted power value), as described in this embodiment, may be performed in the Calibration phase. As mentioned above, in the Calibration phase, TX402 acquires data necessary for detecting foreign matter using the Power Loss method. At that time, TX402 acquires data on power loss when the load state of RX401 is a light load state and when it is a load connected state. Therefore, the measurement of calibration point 1100 and calibration point 1101 in Figure 11 may be performed in the Calibration phase described above, when RX401 is in a light load state and when it is a load connected state. That is, when TX402 receives first reference received power information from RX401, it measures calibration point 1100 in addition to the predetermined processing to be performed in the Calibration phase. Also, when TX402 receives second reference received power information from RX401, it measures calibration point 1101 in addition to the predetermined processing to be performed in the Calibration phase. This eliminates the need to set aside a separate period for measuring calibration point 1100 and calibration point 1101, allowing measurements of calibration point 1100 and calibration point 1101 to be performed in a shorter time.

[0176] In this way, the TX402 adjusts and sets the threshold value for the waveform attenuation index of the waveform attenuation method for each power transmission based on the waveform attenuation index information measured by the TX402 for each power transmission. For example, if the waveform attenuation index is the Q value, the TX402 compares the Q value measured by the TX402 with the threshold value determined by the method described above. If the measured Q value is smaller than the threshold Q value, it determines that "foreign matter is present" or "there is a possibility of foreign matter being present." Also, if the measured Q value is larger than or approximately the same as the threshold Q value, the TX402 determines that "there is no foreign matter" or "there is a low possibility of foreign matter being present." By doing so, it becomes possible to set the threshold value for each power transmission of the TX402, enabling more accurate foreign matter detection.

[0177] In the method described above, the waveform attenuation index used as the threshold is assumed to be a predetermined value, but it is not limited to this. For example, the waveform attenuation index used as the threshold may be a value with a predetermined width (range). This width may be set, for example, based on the measurement error expected in the measurement of the attenuation rate. When such a threshold is set, the TX402 may be configured to determine "no foreign matter" or "low probability of foreign matter presence" if the waveform attenuation index obtained by measurement is within the range set as the threshold.

[0178] [Processing of power receiving device 401 and power transmitting device 402] The processing flow of RX401 and TX402 to execute the above-described content will be explained using Figures 8 and 9. Figure 8 is a flowchart representing the processing of TX402, and Figure 9 is a flowchart representing the processing of RX401. The processing in Figures 8 and 9 is realized by the control units of TX402 and RX401 executing programs stored in memory.

[0179] When the TX402 is powered on, it detects the RX401 (S801) after going through the Selection phase and Ping phase described above. The TX402 then starts supplying power to the detected RX401 (S802). This power supply is performed during the I&C phase, Negotiation phase, Calibration phase, Power Transfer phase, etc.

[0180] Furthermore, once RX401 is mounted on TX402 (S901), it is detected by TX402 after going through the Selection phase and Ping phase. RX401 also begins receiving power from TX402 (S902). The power received here is the same power transmitted from TX402 during the I&C phase, Negotiation phase, Calibration phase, Power Transfer phase, etc.

[0181] RX401 decides to request foreign object detection from TX402 if the predetermined conditions are met (Yes in S903). On the other hand, if the predetermined conditions are not met, RX401 decides not to request foreign object detection from TX402 (No in S903) and continues to receive power.

[0182] Here, the predetermined conditions are, for example, the following: an error occurs in communication between TX402 and RX401, a decrease in power transmission from TX402 to RX401 is observed, the acquired calibration data is an abnormal value, a temperature rise is observed in TX402 or RX401, etc. These conditions indicate the presence of a foreign object. Alternatively, the predetermined conditions include increasing the power transmission from TX402 to RX401. Alternatively, the predetermined conditions include performing calibration (Calibration process of the Power Loss method), which is a measurement to set the threshold used in foreign object detection. Alternatively, the predetermined conditions include RX401 notifying TX402 of the status of RX401 (for example, the power received by RX401). RX401 pre-sets the predetermined conditions as described above and decides to perform foreign object detection when at least one of the set predetermined conditions is met. Note that conditions other than those described above may also be set as predetermined conditions. Furthermore, any of the above-mentioned conditions may be set as predetermined conditions.

[0183] If RX401 decides to request foreign object detection from TX402 (Yes in S903), RX401 determines the detection processing period related to the foreign object detection process (S904). The detection processing period includes the preparation period, the power transmission control period, the communication prohibition period, and the power transmission period. Then, RX401 sends an execution request packet to TX402 containing information for determining each period related to power transmission control (S905). In this embodiment, the information included in the execution request packet includes, for example, information for determining the length of the power transmission control period and the length of the communication prohibition period. The execution request packet may be, for example, Received Power Packet (mode0), Received Power Packet (mode1), or Received Power Packet (mode2). Alternatively, individual packets may be used as the execution request packet.

[0184] If TX402 receives a foreign object detection request packet from RX401 (Yes in S803), it sets the periods related to power transmission control based on the information in the execution request packet (S804). Then, it executes power transmission control based on the set periods (S805). Next, it measures the waveform attenuation index and compares the result with the thresholds mentioned above to determine the presence or absence of a foreign object, or the probability of its presence (probability of presence) (S806). If the determination result is "foreign object present" or "high probability of foreign object presence" (Yes in S807), TX402 notifies RX401 of this fact using a predetermined packet (S808). This can be achieved by TX402 sending a negative response, such as NAK, to RX401. If the determination result is "no foreign object" or "low probability of foreign object presence" (No in S807), TX402 notifies RX401 of this fact using a predetermined packet (S809). This can be achieved by TX402 sending, for example, an acknowledgment (ACK) to RX401. TX402 then continues transmitting power.

[0185] Furthermore, TX402 may notify RX401 of the "possibility of foreign object presence" determined by the judgment, using an index corresponding to the level of possibility (probability of presence). For example, it may identify the probability of foreign object presence, determined based on the difference between the measured waveform attenuation index and a set threshold, and notify RX401 of this. Therefore, when foreign object detection is performed, TX402 transmits a predetermined packet to RX401 that includes at least one of the following: foreign object present, foreign object absent, possibility of foreign object presence, and the probability of foreign object presence.

[0186] RX401 receives a packet from TX402 containing the result of the foreign object detection (S906). If the received result is "Foreign object present" or "High probability of foreign object presence" (Yes in S907), RX401 sends a power stop command to TX402 requesting the cessation of power transmission (S908). This power stop command may be an EPT (End Power Transfer) command (packet). At this time, TX402 may include information requesting the transmission of an EPT (End Power Transfer) command (packet) in the packet containing the foreign object detection result and send the packet containing the foreign object detection result to RX401. If the result of S907 is "No foreign object" or "Low probability of foreign object presence" (No in S907), RX401 performs a predetermined process (S909). Here, the predetermined process is, for example, the following process. Specifically, this involves increasing the power transmitted from TX402 to RX401, performing measurement processing to set thresholds used in foreign object detection, and notifying TX402 of the status of RX401 (such as the power received by RX401).

[0187] When TX402 receives an EPT (End Power Transfer) command (packet), which is a power transmission stop command, from RX401 (S810), it stops supplying power to RX401 (S811). Alternatively, in S811, TX402 may reduce the power supplied to RX401. At this time, TX402 may include information requesting a specific operation from RX401 in the packet containing the foreign object detection result and send it to RX401 in the packet containing the foreign object detection result. The above describes the processing flow of RX401 and TX402.

[0188] <Embodiment 2> Embodiment 1 described the application method for detecting foreign objects using the waveform attenuation method in accordance with the WPC standard, the method for setting each period of the power transmission waveform when using the waveform attenuation method, and the method for setting the foreign object detection threshold in the waveform attenuation method. However, when performing foreign object detection, it is possible that accurate foreign object detection cannot be achieved by performing the processing for foreign object detection only once. For example, when performing a single power transmission control and determining the presence or absence of foreign objects, or the possibility (probability of presence) of foreign objects, from the waveform attenuation index, it is possible that an appropriate waveform attenuation index cannot be obtained due to the following factors. For example, disturbances may occur in the power transmission waveform during the power transmission control period due to factors such as the introduction of other noise during the power transmission control period, or a shift in the position of the RX401 mounted on the TX402. In this case, it is possible that an appropriate waveform attenuation index cannot be obtained.

[0189] Furthermore, an appropriate waveform attenuation index may not be obtained, potentially leading to misidentification in foreign object detection.

[0190] To suppress false detections, the TX402 in this embodiment performs power transmission control multiple times, measures waveform attenuation indices from the power transmission waveforms during multiple power transmission control periods, and performs foreign object detection based on the results. In such cases, measuring multiple waveform attenuation indices and performing foreign object detection based on the results makes foreign object detection more reliable. In this embodiment, we will describe a case in which foreign object detection is performed using the waveform attenuation method multiple times in order to perform foreign object detection more reliably while using the method described in Embodiment 1. We will also describe the method for determining foreign object detection in that case.

[0191] In this embodiment, the power transmission waveform when foreign object detection is performed by measuring multiple waveform attenuation indices will be explained using Figure 7. As shown in Figure 7, when the waveform attenuation method is performed multiple times, the communication prohibition period, power transmission period, preparation period, and power transmission control period will be repeated multiple times. In this embodiment, each of these periods is set to be the same length. That is, for the communication prohibition period, the 1st communication prohibition period, the 2nd communication prohibition period, the 3rd communication prohibition period, ..., the Nth communication prohibition period are all set to be the same length. Similarly, for the power transmission period, the 1st power transmission period, the 2nd power transmission period, the 3rd power transmission period, ..., the Nth power transmission period are all set to be the same length. Similarly, for the preparation period, the 1st preparation period, the 2nd preparation period, the 3rd preparation period, ..., the Nth preparation period are all set to be the same length. Similarly, for the power transmission control period, the 1st power transmission control period, the 2nd power transmission control period, the 3rd power transmission control period, ..., the Nth power transmission control period are all set to be the same length. The method for setting each period is as described in Embodiment 1, and based on the method described in Embodiment 1, TX402 and RX401 determine the optimal time for each period. As described above, by setting each period to the optimal time and repeating this multiple times, it becomes possible to measure the waveform attenuation index multiple times. Furthermore, by setting each period to the optimal length and performing the waveform attenuation method multiple times with the same length for each period, it becomes possible to suppress distortion of the transmitted radio wave form, suppress ringing, and perform highly accurate foreign object detection while maintaining stable communication.

[0192] In the example above, the communication prohibition period, power transmission period, preparation period, and power transmission control period within the detection processing period were controlled to have the same length as each of the other periods within the detection processing period. However, the TX402 is not limited to this. For example, the TX402 may be configured to control the length of the entire detection processing period, including at least the power transmission control period, to be the same as the length of the other detection processing periods. Alternatively, for example, the TX402 may be configured to control at least one of the communication prohibition period, power transmission period, preparation period, and power transmission control period to have the same length as the other periods within the detection processing period.

[0193] Next, as described above, we will explain how the TX402 determines the presence or absence of foreign matter, or the probability of foreign matter being present, based on the multiple measurement results when it measures waveform attenuation indices (e.g., Q value) multiple times. The TX402 performs power transmission control during a predetermined multiple power transmission control period and can obtain multiple waveform attenuation indices from the measurement results of the attenuation state of the transmitted radio wave. The TX402 makes a determination based on predetermined thresholds for these multiple waveform attenuation indices. For example, when the Q value is used as the waveform attenuation index, the TX402 determines that "foreign matter is present" if, in multiple waveform attenuation methods, the number of Q values ​​obtained that are smaller than the threshold Q value is greater than a predetermined number. Also, for example, when the waveform attenuation amount or waveform attenuation rate is used as the waveform attenuation index, the TX402 determines that "foreign matter is present" if, in multiple waveform attenuation methods, the number of indicators obtained that are larger than the threshold is greater than a predetermined number.

[0194] The threshold in this case may be set as a predetermined range having an upper threshold and a lower threshold. In this case as well, the presence or absence of foreign matter is determined according to the number of indicators among the multiple indicators obtained by multiple waveform attenuation methods that fall within the predetermined range represented by the threshold, or the number of indicators that fall outside the predetermined range. The "predetermined number" mentioned above is the number obtained by multiplying the number of times the power transmission control is performed by a predetermined ratio. For example, if TX402 performs five waveform attenuation methods, it sets the predetermined number to 40% of five (=2). If TX402 obtains multiple Q values ​​by multiple waveform attenuation methods, it determines that there is foreign matter if the number of Q values ​​smaller than the threshold Q value is greater than 2. The same applies when indicators other than Q values ​​are used. Furthermore, the ratio used to determine the predetermined number can be set to any number. Also, the method for determining the predetermined number is not limited to this, and any number can be set.

[0195] Furthermore, TX402 may determine the probability of foreign matter presence by comparing it with a predetermined threshold and express it using a predetermined index. The index that indicates the probability of foreign matter presence will be hereinafter referred to as the "foreign matter presence probability index." For example, TX402 sets the "foreign matter presence probability index" according to the number of waveform attenuation indices that fall within a predetermined range having an upper threshold and a lower threshold, and notifies RX401 of this index. In other words, the more waveform attenuation indices that fall within the predetermined range, the lower the probability of foreign matter presence, and the fewer waveform attenuation indices that fall within the predetermined range, the higher the probability of foreign matter presence. TX402 sets the index according to the magnitude of the probability of foreign matter presence identified by this method and notifies RX401. Note that the criteria for judgment can be arbitrarily changed depending on the type of waveform attenuation index. Also, the probability of foreign matter presence itself may be used as the foreign matter presence probability index.

[0196] Alternatively, the TX402 compares each of several waveform attenuation indices with a predetermined threshold to determine the probability of foreign matter being present and expresses it using a predetermined index. In this way, the TX402 obtains multiple "foreign matter presence probability indices" that indicate the probability of foreign matter being present.

[0197] Then, TX402 determines the final presence or absence of a foreign object, or the probability of its presence, based on an index indicating the likelihood (probability of presence) of multiple foreign objects. Based on the probability of presence, TX402 determines the presence or absence of a foreign object and transmits a signal (e.g., ACK or NAK) based on the determination result to RX401. Alternatively, TX402 may notify RX401 of the probability of the foreign object's presence itself using a predetermined packet.

[0198] Furthermore, RX401 may receive information on multiple waveform attenuation indices or multiple foreign object presence probability indices from TX402, and RX401 may perform the above-described determination. Also, in the above-described embodiment, the waveform attenuation index was calculated by TX402 from the measurement results. However, since the transmitting antenna and the receiving antenna are electromagnetically coupled, the attenuation state of the transmitted radio wave can also be observed by RX401. Therefore, the waveform attenuation index may be calculated by RX401 from the measurement results. Also, RX401 may perform the above-described determination based on the waveform attenuation index calculated by RX401.

[0199] As described above, by having the TX402 perform power transmission control multiple times, calculate multiple waveform attenuation indices from the resulting waveform attenuation state, and use these indices to determine whether or not to detect foreign objects, more accurate foreign object detection becomes possible. The TX402 or RX401 may also have a configuration to determine whether or not to perform the waveform attenuation method multiple times. For example, if the TX402 determines "no foreign object" after the first waveform attenuation method, it may not perform the waveform attenuation method again. If the TX402 determines "foreign object present" after the first waveform attenuation method, it may perform the second waveform attenuation method. Alternatively, the TX402 may identify the probability of foreign object presence, and if the probability falls within a predetermined range, it may perform the second waveform attenuation method. In this case, the RX401 may obtain the value of the probability of presence identified by the TX402 and send an execution request packet according to the value.

[0200] The processing flow of RX401 and TX402 to perform the above-mentioned actions will be explained using Figures 12 and 13. Figure 12 is a flowchart of the processing performed by TX402, and Figure 13 is a flowchart of the processing performed by RX401.

[0201] When the TX402 is powered on, it detects the RX401 (S1201) after going through the Selection phase and Ping phase described above. The TX402 then starts supplying power to the detected RX401 (S1202). This power supply is the same as that performed in the I&C phase, Negotiation phase, Calibration phase, Power Transfer phase, etc.

[0202] Furthermore, once RX401 is mounted on TX402 (S1301), it is detected by TX402 after going through the Selection phase and Ping phase. RX401 also begins receiving power transmitted from TX402 (S1302). The power received here is the same power transmitted from TX402 during the I&C phase, Negotiation phase, Calibration phase, Power Transfer phase, etc.

[0203] RX401 decides to request foreign object detection from TX402 if certain conditions are met (Yes in S1303). If certain conditions are not met, RX401 decides not to request foreign object detection from TX402 (No in S1303) and continues to receive power. The certain conditions are, for example, the following: an error occurs in communication between TX402 and RX401, a decrease in power transmitted from TX402 to RX401 is observed, the acquired calibration data is an abnormal value, a temperature increase is observed in TX402 or RX401, etc. Another example of a certain condition is when the power transmitted from TX402 to RX401 is increased. Another example of a certain condition is when calibration (Calibration process of the Power Loss method) is performed, which is a measurement to set the threshold used in foreign object detection. Another example is when RX401 notifies TX402 of the status of RX401 (such as the power received by RX401). The RX401 decides to perform foreign object detection if at least one of the above conditions is met.

[0204] If RX401 decides to request foreign object detection from TX402 (Yes in S1303), RX401 determines the detection processing period related to power transmission control in the manner described in Embodiment 1 (S1304). The detection processing period includes the preparation period, the power transmission control period, the communication period, and the power transmission period. Then, RX401 sends an execution request packet to TX402 containing information for determining the length of the detection processing period (S1305).

[0205] The execution request packets used include Received Power Packet (mode0), Received Power Packet (mode1), or Received Power Packet (mode2). When TX402 receives a foreign object detection request packet from RX401 (Yes in S1203), it sets the periods related to power transmission control based on the information in the execution request packet (S1204). Alternatively, TX402 may notify RX401 in advance of the information necessary for RX401 to set the information in the execution request packet. That is, RX401 receives information related to TX402 from TX402 that is necessary for setting the periods related to power transmission control. Then, TX402 may include the information for setting the periods related to power transmission control, determined based on this information, in the execution request packet and send the execution request packet to TX402.

[0206] TX402 performs power transmission control based on each set period (S1205). Then TX402 determines whether it has completed power transmission control a predetermined number of times (S1206). The number of times power transmission control is performed may be determined in advance by TX402, or it may be determined in advance by RX401 and notified to TX402. Alternatively, if TX402 determines it in advance, it may also notify RX401 of this. Next, if TX402 determines that power transmission control has not been completed a predetermined number of times (No in S1206), TX402 sends a predetermined signal to RX401 (S1207). The predetermined signal may be, for example, an ND (Not-Defined) packet. By transmitting a predetermined signal, TX402 can notify RX401 that a predetermined number of power transmission control operations are incomplete and that it is requesting RX401 to send additional execution request packets.

[0207] RX401 receives a predetermined signal from the received packet indicating whether a predetermined number of power transmission control operations have been completed (S1306). Also, if RX401 obtains information indicating that a predetermined number of power transmission control operations have not been completed (No in S1307), it returns to S1304 and performs power transmission control again. At this time in S1304, RX401 sets the length of each period related to the power transmission control to be performed now to the same length as the period related to the power transmission control that was set during the previous power transmission control operation. In other words, TX402 sets the length of each period related to the second power transmission control to be the same as the length of each period related to the first power transmission control. Then, RX401 sends an execution request packet containing each period related to the power transmission control to TX402 again (S1305). This execution request packet may be, for example, Received Power Packet (mode0), Received Power Packet (mode1), or Received Power Packet (mode2).

[0208] If TX402 receives a second foreign object detection request packet from RX401 (Yes in S1203), it sets the length of each period related to power transmission control again based on the information in the execution request packet (S1204). Then, it executes power transmission control based on the set length of each period (S1205). TX402 then determines whether the power transmission control has been completed a predetermined number of times (S1206). If TX402 determines that the power transmission control has not yet been completed a predetermined number of times (No in S1206), it repeats the process from S1203 onwards.

[0209] When the TX402 completes a predetermined number of power transmission control cycles, the TX402 proceeds to Yes in S1206. Then, in S1208, the TX402 sends a packet to the RX401 containing information indicating that the predetermined number of power transmission control cycles has been completed. The RX401 receives the packet in S1306, determines from the information in the packet that the predetermined number of power transmission control cycles has been completed, and proceeds to Yes in S1307. By controlling the TX402 and RX401 in this manner, the length of each period related to power transmission control is set to be the same for at least a predetermined number of power transmission control cycles.

[0210] Next, S1209 determines the presence or absence of foreign matter, or the probability of foreign matter being present, based on the results of multiple waveform attenuation indices, etc. The detailed method for this determination is as described above. If the determination result is "foreign matter present" or "high probability of foreign matter being present" (Yes in S1210), TX402 notifies RX401 of this fact in a predetermined packet (S1211).

[0211] This can be achieved by TX402 sending a negative response (NAK) to RX401. If the result of the determination is "no foreign object" or "low probability of foreign object presence" (No in S1210), TX402 notifies RX401 of this in a predetermined packet (S1212). This can be achieved by TX402 sending an acknowledgment (ACK) to RX401, for example. TX402 then continues power transmission. Alternatively, TX402 may express the "probability of foreign object presence" determined by the determination result using a predetermined index corresponding to the probability level (probability of presence), and notify RX401 by sending a predetermined packet containing that index to RX401. RX401 receives a packet from TX402 containing the determination result of foreign object detection (S1308). Furthermore, if the received determination result is "Foreign object present" or "High probability of foreign object presence" (Yes in S1309), RX401 sends an EPT command (packet) to TX402 (S1310).

[0212] If the result of the S1309 determination is "no foreign object" or "low probability of foreign object presence" (No in S1309), RX401 performs a predetermined process (S1311). Here, the predetermined process is, for example, the following: increasing the power transmitted from TX402 to RX401, performing calibration, which is a measurement to set the threshold used in foreign object detection, etc. Alternatively, the predetermined process is for RX401 to notify TX402 of the status of RX401 (such as the power received by RX401). When TX402 receives an EPT (End Power Transfer) command (packet), which is a power transmission stop command, from RX401 (S1213), it stops transmitting power to RX401 (S1214). Alternatively, in S1214, TX402 may reduce the power transmitted to RX401.

[0213] In the above-described embodiment, when TX402 performs multiple power transmission control operations, it receives notification from RX401 each time to set information for determining the detection processing period. However, it is not limited to this, and TX402 may be configured to receive notification only once before performing the first power transmission control, rather than receiving notification from RX401 each time. For example, RX401 may send information to TX402 only once to determine the length of the detection processing period, and TX402 may set the length of the detection processing period for a predetermined number of times determined by TX402 according to that information. Also, when TX402 performs multiple power transmission control operations, it receives notification from RX401 each time to set an execution request packet. However, instead of receiving notification from RX401 each time, it may be configured to receive notification only once before performing the first power transmission control. For example, RX401 may send an execution request packet to TX402 only once, and TX402 may perform a predetermined number of power transmission control operations determined by TX402 accordingly.

[0214] Furthermore, while TX402 is configured to determine the length of the detection processing period based on information obtained from RX401, it is not limited to this. For example, TX402 may control the power transmission for at least one of the periods included in the detection processing period, for a predetermined detection processing period length. However, if TX402 is configured to control the power transmission each time it receives an execution request packet from RX401, the length of the detection processing period may vary depending on the timing of receiving the execution request packet. For example, if the timing of receiving the execution request packet in the power transmission period differs each time, the power transmission period may also vary. Therefore, in this configuration, RX401 is controlled to send execution request packets so that the detection processing period is the same for multiple detection processes. For example, if multiple detection processes are performed, RX401 sends execution request packets at regular intervals.

[0215] The interval in this case is assumed to be the same length as the detection processing period for TX402 to perform detection processing. In this way, even when the detection processing period may fluctuate, the length of the detection processing period can be kept constant by controlling the timing at which RX401 sends the execution request packet.

[0216] Furthermore, the execution request packet does not need to include all the information necessary to determine the communication ban period, power transmission period, preparation period, and power transmission control period. For example, the execution request packet may include information to determine the power transmission control period, and for the other periods, predetermined values ​​may be used for the TX402. Alternatively, the execution request packet may include information to determine the communication ban period, and for the other periods, predetermined values ​​may be used for the TX402. Thus, the execution request packet may include information to determine the length of any of the periods. It is also possible to configure the execution request packet to include information to determine the length of the entire detection processing period.

[0217] <Embodiment 3> Embodiment 2 described a case where the time intervals related to power transmission control were the same, and foreign object detection was performed using multiple waveform attenuation methods. This embodiment describes a case where the time intervals related to power transmission control were different, and foreign object detection was performed using multiple waveform attenuation methods.

[0218] As described in Embodiment 2, when performing foreign object detection using the waveform attenuation method, it may not be possible to accurately detect foreign objects by performing the foreign object detection process only once. Therefore, more reliable foreign object detection is achieved by performing the foreign object detection process multiple times and determining the presence of foreign objects from multiple results. In Embodiment 2, high-precision foreign object detection was achieved by setting each time related to power transmission control to an optimal value (time length) and repeating the process multiple times.

[0219] However, in the method of Embodiment 2, there is a problem that noise may be generated in a specific frequency band because the transmission waveform becomes periodic during multiple power transmission control cycles. Since a periodic waveform is separated into a fundamental wave and harmonics, high-power electromagnetic waves will be observed in several specific frequency bands. In other words, if multiple detection processing periods are set to the same length and repeated multiple times in multiple power transmission control cycles, relatively high-power electromagnetic waves may be generated in specific frequency bands other than the frequency band used for power transmission, between 85kHz and 205kHz. In this case, for example, if the power transmitted from TX402 to RX401 is lower than a predetermined value, the electromagnetic waves in the specific frequency band will not be very large, and no problem may occur. Therefore, when the transmitted power is lower than a predetermined value, high-precision foreign object detection can be performed by setting multiple detection processing periods to the same optimal length, as described in Embodiment 2. However, for example, if the transmitted power is higher than a predetermined value, the generated electromagnetic waves may become noise that causes malfunctions in other equipment. Furthermore, while each country's radio wave regulations set limits on power consumption in each frequency band, depending on the power transmission conditions, electromagnetic waves generated at frequencies other than those between 85kHz and 205kHz may exceed the aforementioned limits.

[0220] To compensate for the shortcomings of the method of Embodiment 2 described above, in this embodiment, each time involved in power transmission control is controlled to be of a different length. Details are described below. The power transmission waveform when foreign object detection is performed by measuring multiple waveform attenuation indices in this embodiment will be explained with reference to Figure 7. As shown in Figure 7, when measuring multiple waveform attenuation indices, the communication ban period, power transmission period, preparation period, and power transmission control period are repeated multiple times. In this embodiment, each of these periods is set to be of a different length. That is, for the communication ban period, the 1st communication ban period, the 2nd communication ban period, the 3rd communication ban period, ..., the Nth communication ban period are all set to be of different lengths. Alternatively, at least one communication ban period may be set to be of a different length from the other communication ban periods. Similarly, for the power transmission period, the 1st power transmission period, the 2nd power transmission period, the 3rd power transmission period, ..., the Nth power transmission period are all set to be of different lengths. Alternatively, at least one power transmission period may be set to be of a different length from the other power transmission periods. Furthermore, regarding the preparation period, the first, second, third, ..., and Nth preparation periods are all set to different lengths. Alternatively, at least one preparation period may be set to a different length from the other preparation periods. Furthermore, regarding the power transmission control period, the first, second, third, ..., and Nth power transmission control periods are all set to different lengths. Alternatively, at least one power transmission control period may be set to a different length from the other power transmission control periods.

[0221] In the example above, the lengths of each period were set to be different, but this is not limited to this. For example, the length of at least one period included in the detection processing period may be controlled to be different from the lengths of periods in other detection processing periods. Alternatively, the length of the entire detection processing period may be set to be different from the lengths of other detection processing periods.

[0222] The methods described in Embodiments 1 and 2 can be applied to setting each period. For example, based on the method described in Embodiment 1, the optimal length of each period is determined for TX402 and RX401. However, in order to vary the length of the detection processing period, it is not always necessary to set the optimal length each time. For example, during the first detection of a foreign object, the length of the detection processing period may be determined by the method described in Embodiment 1, and from the second time onward, the detection processing period may be adjusted to be different from the length of the first detection processing period. Furthermore, the method for adjusting the length of the period at this time may be any method.

[0223] For example, TX402 determines the detection processing period based on the information contained in the execution request packet received from RX401. In this case, RX401 sends an execution request packet to TX402 that contains information to determine the length of the detection processing period, but the length of the detection processing period represented by this information will be different for each detection process.

[0224] As described above, by setting each period to a different value (duration) and repeating this multiple times, it becomes possible to suppress noise in a specific frequency band and perform highly accurate foreign object detection.

[0225] The processing flow of RX401 and TX402 to perform the above-mentioned actions will be explained using Figures 14 and 15. Figure 14 is a flowchart of the processing performed by TX402, and Figure 15 is a flowchart of the processing performed by RX401.

[0226] Since the flowchart diagrams for the power transmission device in Figure 12 and the power receiving device in Figure 13 are largely the same as those described in Embodiment 2, the explanation of the identical parts will be omitted, and only the differences will be explained. The difference from Embodiment 2 is S1504 in the flowchart diagram of RX401 in Figure 15. When determining the time for each step related to power transmission control, a different time is set than the time for the previous power transmission control. For example, when performing the second power transmission control, a different time is set for each step related to power transmission control than the time set during the first power transmission control.

[0227] For example, TX402 and RX401 communicate and exchange information to determine the maximum (maximum time) and minimum (minimum time) values ​​for each time period related to power transmission control. Within the range of the determined maximum (maximum time) and minimum (minimum time) values ​​for each time period related to power transmission control, RX401 sets a time that is different from the time period related to power transmission control of the previous period. In this way, as described in Embodiment 1, it becomes possible to suppress disturbances in the transmitted radio wave pattern, suppress ringing, and perform stable communication while implementing highly accurate foreign object detection, and it also becomes possible to suppress large noises that occur in a specific frequency band.

[0228] Then, in S1505, RX401 sends an execution request packet to TX402 that includes the time periods related to power transmission control. Meanwhile, TX402 receives the execution request packet sent from RX401 (Yes in S1403) and sets the time periods related to power transmission control based on the information in the execution request packet. At this time, the time periods related to power transmission control will be set to be different from the time periods related to power transmission control in the previous instance. By controlling TX402 and RX401 in this way, for at least a predetermined number of power transmission control operations, the length of each period related to power transmission control will be set to be different from the time periods related to power transmission control in the previous instance.

[0229] As described above, when power transmission control is performed multiple times, the transmission waveform does not become periodic, making it possible to perform foreign object detection without generating large noise in a specific frequency band. Regarding the method for determining the presence or absence of a foreign object, or the probability of its presence, from the waveform attenuation index obtained from multiple foreign object detections performed using the method described above, the determination method described in Embodiment 2 can also be applied to this embodiment. Furthermore, this embodiment differs from Embodiment 2 in that the lengths of the multiple detection processing periods are different. Therefore, for configurations other than those that differ from Embodiment 2, the configuration of Embodiment 2 can be applied.

[0230] Furthermore, in the flowchart described above, foreign object detection is performed each time RX401 sends an execution request packet. However, this is not the only option; for example, a configuration in which an execution request packet is sent only once is also possible. In this case, for example, the execution request packet may include information to specify the length of the detection processing period for multiple foreign object detections.

[0231] Furthermore, while TX402 is configured to determine the length of the detection processing period based on information obtained from RX401, it is not limited to this. For example, TX402 may control the power transmission for at least one of the periods included in the detection processing period, with a predetermined detection processing period length. However, if TX402 is configured to control the power transmission each time it receives an execution request packet from RX401, the length of the detection processing period may vary depending on the timing of receiving the execution request packet. For example, if the timing of receiving the execution request packet in the power transmission period differs each time, the power transmission period may also vary. Therefore, in this configuration, RX401 is controlled to send execution request packets so that the detection processing periods for multiple detection processes are of different lengths. For example, when multiple detection processes are performed, RX401 sends execution request packets at random intervals so that the detection processing periods are of different lengths. In this way, by controlling the timing of when RX401 sends execution request packets, the detection processing periods for multiple detection processes can be made to be of different lengths.

[0232] <Embodiment 4> Embodiment 2 describes a case where the time intervals related to power transmission control are the same, and foreign object detection is performed using multiple waveform attenuation methods. Embodiment 3 describes a case where the time intervals related to power transmission control are different, and foreign object detection is performed using multiple waveform attenuation methods. This embodiment describes a method for switching between the method described in Embodiment 2 and the method described in Embodiment 3 when predetermined conditions are met.

[0233] In Embodiment 2, when the time intervals related to power transmission control are set to the same value and foreign object detection is performed multiple times using the waveform attenuation method, the TX402 sets the time intervals related to power transmission control to optimal values ​​and performs power transmission control multiple times. Therefore, Embodiment 2 has the effect of enabling more accurate foreign object detection, enabling foreign object detection in a shorter time, enabling more stable communication, and enabling faster communication compared to Embodiment 3. On the other hand, in Embodiment 3, when the time intervals related to power transmission control are set to different values ​​(times) and foreign object detection is performed multiple times using the waveform attenuation method, there is the effect of being able to suppress noise in a specific frequency band compared to Embodiment 2.

[0234] Here, for example, if the power transmitted from TX402 to RX401 is lower than a predetermined value, even if the method of Embodiment 2 is used, the noise in a specific frequency band may not be very large, and no problems may arise. Therefore, if the power transmitted from TX402 to RX401 is lower than a predetermined value, the method of Embodiment 2 may be used, and if the power transmitted from TX402 to RX401 is higher than a predetermined value, the method of Embodiment 3 may be used.

[0235] Furthermore, for example, if the coupling between the transmitting antenna of TX402 and the receiving antenna of RX401 is strong enough to meet the standard, and the power leaking between the antennas is judged to be less than the standard, the method of Embodiment 2 may be used. This is because there are cases where noise in a specific frequency band is not a problem. Therefore, if the coupling strength between the transmitting antenna of TX402 and the receiving antenna of RX401 meets the standard and the leakage power is less than the standard, TX402 will use the method of Embodiment 2. On the other hand, if the coupling strength between the transmitting antenna of TX402 and the receiving antenna of RX401 does not meet the standard and the leakage power is greater than the standard, TX402 will use the method of Embodiment 3.

[0236] The strength of the coupling between the TX402's transmitting antenna and the RX401's receiving antenna can vary due to the following two factors. The first is a factor related to the inherent performance of the TX402's transmitting antenna and the RX401's receiving antenna. For example, the larger the difference between the size (antenna diameter) of the TX402's transmitting antenna and the size (antenna diameter) of the RX401's receiving antenna, the weaker the coupling may become. Since there are multiple types of TX402's transmitting antenna and RX401's receiving antenna, the detection processing period performed by the TX402 may be switched between the method of Embodiment 2 and the method of Embodiment 3 depending on the RX401 mounted on the TX402.

[0237] The second factor concerns the misalignment of the RX401 mounted on the TX402. For example, if the RX401 shifts position from its initial position for any reason, a change occurs in the relative position of the transmitting and receiving antennas, potentially resulting in a weaker coupling between the antennas than before the misalignment. Therefore, when the TX402 or RX401 detects a change in the relative position of the TX402 and RX401, the time setting related to the power transmission control performed by the TX402 may be configured to switch between the method of Embodiment 2 and the method of Embodiment 3. Methods for detecting a change in the relative position of the TX402 and RX401 include using measurement results from sensors such as photoelectric sensors, eddy current displacement sensors, contact displacement sensors, ultrasonic sensors, image discrimination sensors, and weight sensors mounted on the TX402 or RX401. Alternatively, the change in the Q value of the TX402 antenna or RX401 antenna measured in the time domain, or the change in the Q value of the TX402 antenna or RX401 antenna measured in the frequency domain, may be observed. Alternatively, the change in the coupling state (e.g., coupling coefficient) between the transmitting antenna 105 of TX402 and the receiving antenna 205 of RX401 may be observed.

[0238] Methods for measuring the Q-factor used to detect misalignment include the following: Transmitting a signal at the resonant frequency (e.g., a sine wave, square wave, etc.) and measuring the Q-factor at that resonant frequency; Transmitting signals at multiple frequencies near the resonant frequency multiple times and measuring their Q-factors; Transmitting a signal (e.g., a pulse wave) containing all or some of the frequency components of multiple frequencies whose electrical characteristics are to be measured once, and performing calculations (e.g., Fourier transform) on the measurement results to measure the Q-factors at multiple frequencies; Alternatively, measurement results such as the resonant frequency of the transmission antenna, the sharpness of the resonance curve, the inductor value of the transmission antenna, the coupling coefficient between the transmission antenna and an object placed on the transmission device, and the electrical characteristics of the transmission section including the transmission antenna of the transmission device may be used. Furthermore, these may be determined based on the measurement results of the electrical characteristics at a single frequency, or based on the measurement results of the electrical characteristics at multiple frequencies. Furthermore, to measure the electrical characteristics at multiple frequencies, it is possible to transmit signals at each frequency whose electrical characteristics are to be measured (e.g., sine waves, square waves, etc.) multiple times and measure the electrical characteristics of the signal at each frequency. This method has the effect of allowing measurement with relatively little computational processing in the power transmission device. Alternatively, the electrical characteristics at multiple frequencies can be calculated by transmitting a signal containing all frequency components of the multiple frequencies whose electrical characteristics are to be measured (e.g., a pulse wave) once and performing computational processing (e.g., Fourier transform) on the measurement result. Alternatively, the electrical characteristics at multiple frequencies can be calculated by transmitting signals containing some of the frequency components of the multiple frequencies whose electrical characteristics are to be measured multiple times and performing computational processing (e.g., Fourier transform) on the measurement result. This method has the effect of allowing measurement in a relatively short time because it reduces the number of times the signal for measurement is transmitted. Alternatively, the change in the power value received by RX401 from TX402 can be observed to detect the change in the relative position of TX402 and RX401.

[0239] Furthermore, TX402 and RX401 may perform wireless communication using a standard different from the WPC standard (for example, Bluetooth® Low Energy (BLE), NFC (Near Field Communication), etc.). In this case, if the method of Embodiment 1 is used, noise generated by the power transmission control of TX402 may adversely affect communication. Therefore, the method of Embodiment 1 may be used when TX402 and RX401 do not communicate, and the method of Embodiment 2 may be used when TX402 and RX401 do communicate. Alternatively, the method of Embodiment 2 may be used when TX402 and RX401 do not perform wireless communication using a standard different from the WPC standard, and the method of Embodiment 3 may be used when TX402 and RX401 perform wireless communication using a standard different from the WPC standard.

[0240] Furthermore, in the cases described above, the methods of Embodiment 1, Embodiment 2, and Embodiment 3 are used interchangeably, and the decision of which method to use may be made by either TX402 or RX401.

[0241] <Other Embodiments> The contents of Embodiments 1 to 4 described above may be implemented in any combination. In the embodiments described above, the TX402 performed power transmission control and detected foreign objects from its waveform attenuation index. Another method for measuring the Q value, which is one of the waveform attenuation indices, is as follows: That is, a signal having multiple frequency components (e.g., a pulse wave) is transmitted, the amplitude or attenuation state of the waveform is measured, and the Q value is measured by performing calculation processing (e.g., Fourier transform) on the result. This method can also be applied to the embodiments described above.

[0242] Furthermore, the embodiments described above may be carried out by devices other than RX401 and TX402. For example, at least one of the following may be carried out by another device: measuring the voltage or current during the period when TX402 restricts power transmission, and determining the presence or absence of foreign matter based on the measurement results. Also, the determination of the duration of the detection processing period may be carried out by another device. Furthermore, another device may control RX401 and TX402 to carry out the processing described in the embodiments described above.

[0243] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions. Furthermore, the program may be recorded on a recording medium readable by a computer and provided.

[0244] Furthermore, at least a portion of the flowcharts shown in Figures 8, 9, and 12-15 may be implemented in hardware. When implemented in hardware, for example, a dedicated circuit can be automatically generated on the FPGA from a program to implement each step by using a predetermined compiler. FPGA stands for Field Programmable Gate Array. Alternatively, a Gate Array circuit may be formed in a similar manner to an FPGA and implemented as hardware.

[0245] Furthermore, the power transmission and power reception devices may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, or projectors. They may also be storage devices such as hard disk drives or memory devices, or information processing devices such as personal computers (PCs) or smartphones.

[0246] Furthermore, the power receiving device in this disclosure may also be an information terminal device. For example, an information terminal device has a display unit that displays information to the user and is supplied with power received from a power receiving antenna. The power received from the power receiving antenna is stored in a power storage unit (battery), and power is supplied to the display unit from the battery. In this case, the power receiving device may also have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may support communication standards such as NFC communication or fifth-generation mobile communication systems (5G).

[0247] Furthermore, the power receiving device in this disclosure may be a vehicle such as an automobile. For example, an automobile that is a power receiving device may receive power from a charger (power transmission device) via a power transmission antenna installed in a parking lot. Alternatively, an automobile that is a power receiving device may receive power from a charger (power transmission device) via a power transmission antenna embedded in the road. In such an automobile, the received power is supplied to a battery. The power from the battery may be supplied to a drive unit (motor, electric unit) that drives the wheels, or it may be used to drive sensors used for driving assistance or a communication unit that communicates with external devices. In other words, in this case, the power receiving device may have a battery, motors and sensors that are driven using the received power, and a communication unit that communicates with devices other than the power transmission device, in addition to the wheels. Furthermore, the power receiving device may have a dwelling unit for accommodating people. For example, sensors may be used to measure the distance between vehicles or the distance to other obstacles. The communication unit may be compatible with, for example, the Global Positioning System (Global Positioning Satellite, GPS). Furthermore, the communication unit may support communication standards such as the fifth-generation mobile communication system (5G). The vehicle may also be a bicycle or a motorcycle.

[0248] Furthermore, the power receiving device in this disclosure may also 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 received from the battery. These devices may also have a notification means for notifying the remaining battery level, etc. These devices may also have a communication unit for communicating 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).

[0249] Furthermore, the power transmission device of this disclosure may also be an in-vehicle charger that transmits power to portable information terminal devices such as smartphones and tablets that support wireless power transmission within a vehicle. Such an in-vehicle charger may be installed anywhere in the vehicle. For example, the in-vehicle charger may be installed on the vehicle's console, on the instrument panel (dashboard), between passenger seats, on the ceiling, or on the doors. However, it is preferable not to install it in a location that would interfere with driving. In addition, although the power transmission device has been described using the example of an in-vehicle charger, such chargers are not limited to those installed in vehicles, but may also be installed in transport vehicles such as trains, airplanes, and ships. In this case, the chargers may also be installed between passenger seats, on the ceiling, or on the doors.

[0250] Alternatively, a vehicle such as an automobile equipped with an on-board charger may also serve as a power transmission device. In this case, the power transmission device has wheels and a battery, and uses the power from the battery to supply power to the power receiving device via a power transmission circuit and a power transmission antenna.

[0251] <Other> The above-described embodiments include the following configurations, methods, and programs.

[0252] (Composition 1) A power transmission means that transmits power wirelessly to a power receiving device using an antenna, A measuring means that performs a measurement process to measure at least one of the voltage and current at the antenna at at least two or more points in time during a power transmission restriction period in which the power transmitted to the power receiving device by the power transmission means is restricted, When the measurement means performs a first measurement process and a second measurement process, a control means controls the processing period for the first measurement process and the processing period for the second measurement process to be of different lengths. A power transmission device characterized by having the following features.

[0253] (Configuration 2) It has communication means for communicating with the aforementioned power receiving device, The measurement means performs the measurement process in response to the reception of a predetermined signal from the power receiving device via the communication means. The power transmission device according to configuration 1, characterized in that it is a power transmission device.

[0254] (Composition 3) The measurement means performs the measurement process each time the predetermined signal is received by the communication means. The power transmission device according to configuration 2, characterized in that it is a power transmission device.

[0255] (Composition 4) The measurement means performs a plurality of measurement processes, including the first measurement process and the second measurement process, in response to the reception of the predetermined signal by the communication means. A power transmission device according to configuration 2 or 3, characterized by the above.

[0256] (Composition 5) The predetermined signal includes information for determining the power transmission restriction period. A power transmission device according to any one of configurations 2 to 4, characterized by the features described above.

[0257] (Composition 6) The predetermined signal includes information for determining a communication restriction period during which communication performed by the communication means is restricted. A power transmission device according to any one of configurations 2 to 5, characterized in that it is a power transmission device.

[0258] (Configuration 7) The predetermined signal is a signal indicating the magnitude of the power received by the power receiving device from the power transmitting device. The power transmission device according to any one of Configurations 2 to 6, characterized in that.

[0259] (Configuration 8) The control means determines the length of the processing period based on the predetermined signal. The power transmission device according to any one of Configurations 2 to 7, characterized in that.

[0260] (Configuration 9) The processing period includes a communication restriction period during which communication performed by the communication means is restricted, and the control means controls so that the communication restriction period related to the first measurement process and the communication restriction period related to the second measurement process have different lengths. The power transmission device according to any one of Configurations 2 to 8, characterized in that.

[0261] (Configuration 10) The processing period includes a predetermined period from when the predetermined signal is received by the communication means until the restriction of the power transmitted by the power transmission means is started. The control means controls so that the predetermined period related to the first measurement process and the predetermined period related to the second measurement process have different lengths. The power transmission device according to any one of Configurations 2 to 9, characterized in that.

[0262] (Configuration 11) The processing period includes the power transmission restriction period. The control means controls so that the power transmission restriction period related to the first measurement process and the power transmission restriction period related to the second measurement process have different lengths. The power transmission device according to any one of Configurations 1 to 10, characterized in that.

[0263] (Configuration 12) The system has a detection means for detecting an object different from the power receiving device based on the results of a plurality of measurement processes, including the first measurement process and the second measurement process. A power transmission device according to any one of configurations 1 to 11, characterized by the features described herein.

[0264] (Composition 13) The detection means detects an object different from the power receiving device when, among a plurality of measurement results in a plurality of measurement processes including the first measurement process and the second measurement process, the number of measurement results that satisfy a predetermined condition is greater than a predetermined number. The power transmission device according to configuration 12, characterized in that it is a power transmission device.

[0265] (Composition 14) The predetermined condition is that at least one of the voltage attenuation amount and attenuation rate obtained based on the measurement result is greater than a threshold. The power transmission device according to configuration 13, characterized by the features described above.

[0266] (Composition 15) The predetermined condition is that at least one of the current attenuation amount and attenuation rate obtained based on the measurement results is greater than a threshold. A power transmission device according to configuration 13 or 14, characterized by the above.

[0267] (Composition 16) The predetermined condition is that the quality factor obtained based on the measurement results is smaller than the threshold. A power transmission device according to any one of configurations 13 to 15, characterized by the features described herein.

[0268] (Composition 17) An output means outputs at least one of the following, depending on the result of the detection process by the detection means: that an object different from the power receiving device exists, that there is a possibility that an object different from the power receiving device exists, and the probability that an object different from the power receiving device exists. has A power transmission device according to any one of the configurations 12 to 16, characterized by the features described herein.

[0269] (Composition 18) A power receiving device, A power receiving means that receives power wirelessly from a power transmission device using an antenna, A communication means for communicating with the aforementioned power transmission device, A determination means for determining the length of the processing period for a predetermined process performed by the power transmission device, which is for detecting an object different from the power receiving device, The system includes a control means that controls the transmission of a predetermined signal to the power transmission device via the communication means to notify the power transmission device of the length of the processing period determined by the determination means, The determination means determines the length of the processing period such that, when the power transmission device performs the first predetermined processing and the second predetermined processing, the processing period for the first predetermined processing and the processing period for the second predetermined processing are of different lengths. A power receiving device characterized by the following features.

[0270] (Composition 19) The processing period includes a power transmission restriction period during which the power transmitted by the power transmission device is restricted in the predetermined processing. The determination means determines the length of the processing period such that the power transmission restriction period for the first predetermined processing and the power transmission restriction period for the second predetermined processing are of different lengths. The power receiving device according to configuration 18, characterized in that...

[0271] (Composition 20) The processing period includes a communication restriction period during which communication performed by the communication means in the predetermined processing is restricted. The determination means determines the length of the processing period such that the communication restriction period for the first predetermined processing and the power transmission restriction period for the second predetermined processing are of different lengths. A power receiving device according to configuration 18 or 19, characterized by the above.

[0272] (Method 21) A method for controlling a power transmission device, A measuring step of performing a measuring process for measuring at least one of the voltage and current in the antenna at at least two time points of a power transmission limit period during which power wirelessly transmitted from the power transmission device to the power receiving device using the antenna is limited; When a first measurement process and a second measurement process are performed in the measurement step, a control step of controlling so that a processing period related to the first measurement process and a processing period related to the second measurement process have different lengths; A control method characterized by comprising the above.

[0273] (Method 22) A control method for a power receiving device, A determining step of determining the length of a processing period related to a predetermined process for detecting an object different from the power receiving device that wirelessly receives power from a power transmission device using an antenna; A control step of controlling so that a predetermined signal for notifying the power transmission device of the length of the processing period determined in the determining step is transmitted to the power transmission device; In the determining step, when a first predetermined process and a second predetermined process are performed by the power transmission device, the length of the processing period is determined so that the processing period related to the first predetermined process and the processing period related to the second predetermined process have different lengths. A control method characterized by the above.

[0274] (Program) A program for causing a computer to function as the power transmission device according to any one of configurations 1 to 17 or the power receiving device according to any one of configurations 18 to 20.

Explanation of Signs

[0275] 402 Power transmission device 101 Control unit 103 Power transmission unit

Claims

1. Negotiation means for negotiating power with a power receiving device in the Negotiation phase, After the Negotiation phase, a power transmission means performs a Power Transfer phase in which power is transmitted wirelessly to the power receiving device based on the power, In the Power Transfer phase, when predetermined information is received from the power receiving device, a limiting means is provided to limit the power transmission. During the period when power transmission was restricted, a detection means for detecting objects, A receiving means for receiving information from the power receiving device indicating the period during which power transmission is restricted, It has, The power transmission means is a power transmission device that, after the end of the period during which power transmission was restricted, resumes power transmission in the Power Transfer phase without going through the Negotiation phase again.

2. The power transmission device according to Claim 1, wherein the period during which power transmission is restricted is determined by negotiation with the power receiving device.

3. The power transmission device according to claim 1, wherein the detection means detects the object based on a Quality factor.

4. A method performed by a power transmission device, The negotiation phase involves negotiating with the power receiving equipment regarding power, After the Negotiation phase, the process involves wirelessly transmitting power to the power receiving device in the Power Transfer phase based on the power, In the Power Transfer phase, when predetermined information is received from the power receiving device, the process of restricting the power transmission is performed. During the period when power transmission was restricted, the process of detecting an object, After the period during which power transmission was restricted ends, the process involves restarting power transmission in the Power Transfer phase without going through the Negotiation phase again. A method comprising the step of receiving information from the power receiving device indicating the period during which power transmission is restricted.

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