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

Abstract

To enable appropriate object detection processing according to the power transmission and reception status. [Solution] A power transmission device comprising a power transmission means for wirelessly transmitting power to a power receiving device, A power transmission device comprising: detection means for performing detection processing to detect foreign objects based on a Quality Factor measured during a restricted period in which the power transmitted by the power transmission means is limited; a power receiving device; and communication means for communicating a change in the restricted period, wherein the communication means communicates a change in the restricted period based on a change in the power or voltage state of at least one of the power transmission device and the power receiving device.

Description

Technical Field

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

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. In Patent Document 1, a method for detecting an object different from a power transmission device and a power reception device that transmit and receive power (Foreign Object Detection) is disclosed in the Wireless Power Consortium (WPC) standard. Further, in Patent Document 2, a method for detecting an object based on the attenuation amount of the voltage value of the power transmission device during a period in which the voltage of the power transmission device gradually decreases after the power transmission is stopped is disclosed.

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 detecting an object using the method described in Patent Document 2, it is assumed that a stop time for stopping power transmission is set in advance between the power reception device and the power transmission device. However, for example, due to factors such as changes in the state related to power transmission and reception, such as the temperature of the power transmission device or the power reception device, and the transmission power, the processing for detecting an object may not be appropriately performed with the preset stop time. This problem was not considered in Patent Documents 1 and 2.

[0005] The present disclosure has been made in view of the above problems. The objective is to enable appropriate processing for object detection according to the state related to power transmission and reception. [Means for solving the problem]

[0006] The power transmission device according to this disclosure is a power transmission device comprising: a power transmission means for wirelessly transmitting power to a power receiving device; a detection means for performing detection processing to detect foreign matter based on a Quality Factor measured during a restricted period in which the power transmitted by the power transmission means is restricted; the power receiving device; and a communication means for communicating a change in the restricted period, wherein the communication means communicates a change in the restricted period based on a change in the power or voltage state of at least one of the power transmission device and the power receiving device. [Effects of the Invention]

[0007] According to this disclosure, appropriate processing for object detection can be performed according to the state of power transmission and reception. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing an example configuration of a wireless power transmission system. [Figure 2] This figure shows an example of the configuration of a power receiving device. [Figure 3] This figure shows an example of the configuration of a power transmission device. [Figure 4] This figure shows an example of the functional configuration of the control unit of a power transmission device. [Figure 5] This figure shows an example of the processing flow performed by the power transmission device and power receiving device according to the first embodiment. [Figure 6] This flowchart shows an example of the processes performed by power transmission equipment. [Figure 7] This figure shows an example of the processing flow performed by the power transmission device and power receiving device according to the second embodiment. [Figure 8] This is a flowchart showing an example of the processes performed by a power receiving device. [Figure 9] This is a flowchart explaining the method for measuring the Q-value in the time domain. [Figure 10]This flowchart shows an example of the process for detecting a third foreign object using a power transmission device. [Figure 11] This diagram illustrates foreign object detection using the power loss method. [Figure 12] This diagram illustrates the measurement of the Q-value in the time domain. [Figure 13] This diagram illustrates the control process based on the WPC standard. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. Note that the components described in the following embodiments are merely examples of embodiments, and this disclosure is not limited to them.

[0010] (First embodiment) <System Configuration> Figure 1 shows an example of the configuration of the wireless power transmission system (wireless charging system) in this embodiment. In one example, this system is configured to include a power receiving device 102 and a power transmitting device 100. The detailed configurations of the power receiving device 102 and the power transmitting device 100 will be described later.

[0011] The power transmission device 100 is an electronic device that wirelessly transmits power to a power receiving device 102 placed on the power transmission device 100. When the power receiving device 102 is placed on it, the power transmission device 100 wirelessly transmits power to the power receiving device 102 via the power transmission coil 101 (corresponding to the power transmission coil 304 in Figure 3, which will be described later). In the following description, "the power receiving device 102 being placed on the power transmission device 100" means "the state in which the power receiving device 102 is included within the power transmission range of the power transmission device 100." The power transmission range of the power transmission device 100 is the range in which power can be transmitted to the power receiving device 102 using the power transmission coil 101. Furthermore, the state in which the power receiving device 102 is placed on the power transmission device 100 does not require that the power receiving device 102 and the power transmission device 100 are in contact. For example, a state in which the power receiving device 102 is within the range of power transmission without contact with the power transmitting device 100 shall also be considered as a state in which "the power receiving device 102 is placed on the power transmitting device 100". Furthermore, the power receiving device 102 may be configured to be placed on the side of the power transmitting device 100, for example, rather than being placed on top of the power transmitting device 100.

[0012] Note that the power receiving device 102 and the power transmitting device 100 may have functions to execute applications other than wireless charging. An example of the power receiving device 102 is an information processing terminal such as a smartphone, and an example of the power transmitting device 100 is an accessory device for charging the information processing terminal. For example, the information terminal device has a display unit (display) that displays information to the user, to which power received from the power receiving coil (antenna) is supplied. Also, the power received from the power receiving coil is stored in a power storage unit (battery), and power is supplied from the battery to the display unit. In this case, the power receiving device 102 may have a communication unit that communicates with another device different from the power transmitting device 100. The communication unit may conform to communication standards such as NFC communication or the fifth generation mobile communication system (5G). Also in this case, the communication unit may communicate by being supplied with power from the battery. Also, the power receiving device 102 may be a tablet terminal, or a storage device such as a hard disk device and a memory device, or an information processing device such as a personal computer (PC). Also, the power receiving device 102 may be, for example, an imaging device (such as a camera or a video camera). Also, the power receiving device 102 may be an image input device such as a scanner, or an image output device such as a printer, a copy machine, or a projector. Also, the power receiving device 102 may be a robot, a medical device, or the like. The power transmitting device 100 may be a device for charging the above-described devices.

[0013] Also, the power transmitting device 100 may be a smartphone. In this case, the power receiving device 102 may be another smartphone or a wireless earphone.

[0014] Also, the power receiving device 102 in the present embodiment may be a vehicle such as an automobile. For example, the automobile as the power receiving device 102 may receive power from a charger (power transmission device 100) via a power transmission antenna installed in a parking lot. Also, the automobile as the power receiving device 102 may receive power from a charger (power transmission device 100) via a power transmission coil (antenna) embedded in the road. In such an automobile, the received power is supplied to the battery. The power of the battery may be supplied to an engine unit (motor, electric unit) that drives the wheels, or may be used to drive sensors used for driving assistance or a communication unit that communicates with an external device. That is, in this case, the power receiving device 102 may have, in addition to the wheels, a battery, a motor, a sensor that is driven using the received power, and further a communication unit that communicates with a device other than the power transmission device 100. Furthermore, the power receiving device 102 may have a housing unit that houses people. For example, as sensors, there are sensors used to measure the distance between vehicles and the distance to other obstacles. The communication unit may, for example, support the Global Positioning System (GPS). Also, the communication unit may support a communication standard such as the 5th generation mobile communication system (5G). Also, as the vehicle, it may be a bicycle or a motorcycle. Also, the power receiving device 102 is not limited to a vehicle, and may be a moving body, a flying body, etc. that have an engine unit driven using the power stored in the battery.

[0015] Also, the power receiving device 102 in the present embodiment may be a power tool, a household electrical appliance, etc. These devices as the power receiving device 102 may have, in addition to the battery, a motor driven by the received power stored in the battery. Also, these devices may have a notification means for notifying the remaining amount of the battery, etc. Also, these devices may have a communication unit that communicates with another device different from the power transmission device 100. The communication unit may support a communication standard such as NFC or the 5th generation mobile communication system (5G).

[0016] Furthermore, the power transmission device 100 in this embodiment may be an in-vehicle charger that transmits power to portable information terminal devices such as smartphones and tablets that support wireless power transmission within the vehicle. Such an in-vehicle charger may be installed anywhere in the vehicle. For example, the in-vehicle charger may be installed on the vehicle's console, on the instrument panel (dashboard), between passenger seats, on the ceiling, or on the doors. However, it is preferable not to install it in a location that would interfere with driving. In addition, although the power transmission device 100 has been described using the example of an in-vehicle charger, such chargers are not limited to those installed in vehicles, but may also be installed in transport vehicles such as trains, aircraft, and ships. In this case, the charger may also be installed between passenger seats, on the ceiling, or on the doors.

[0017] Alternatively, the power transmission device 100 may be a vehicle such as an automobile equipped with an on-board charger. In this case, the power transmission device 100 has wheels and a battery, and uses the power from the battery to supply power to the power receiving device 102 via a power transmission circuit and a power transmission coil (antenna).

[0018] In this embodiment, the power receiving device 102 and the power transmitting device 100 shall perform processing in accordance with the WPC (Wireless Power Consortium) standard.

[0019] <Device Configuration> Figure 2 is a block diagram showing an example configuration of the power receiving device 102. The power receiving device 102 includes a control unit 200, a power receiving coil 201, a flow control unit 202, a voltage suppression unit 203, a communication unit 204, a charging unit 205, a battery 206, a resonant capacitor 207, and a switch 208.

[0020] The control unit 200 controls the entire power receiving device 102. The control unit 200 is composed of, for example, one or more CPUs (Central Processing Units). The power receiving coil 201 is an antenna (coil) for receiving power and receives power from the power transmitting device 100.

[0021] The rectifier unit 202 converts the AC voltage and AC current received via the power receiving coil 201 into DC voltage and DC current. The voltage control unit 203 converts the level of the DC voltage input from the rectifier unit 202 into a DC voltage level for the operation of the control unit 200 and the charging unit 205, etc. The voltage control unit 203 also supplies the converted voltage level to the charging unit 205.

[0022] The charging unit 205 charges the battery 206. The communication unit 204 performs control communication for wireless charging based on the WPC standard with the communication unit 305 of the power transmission device 100. This control communication is achieved by load modulation of the AC voltage and AC current received by the receiving coil 201.

[0023] The receiving coil 201 is connected to the resonant capacitor 207 and resonates at a specific frequency F2. Switch 208 is a switch for short-circuiting the power receiving coil 201 and the resonant capacitor 207, and is controlled by the control unit 200. When switch 208 is turned on, the power receiving coil 201 and the resonant capacitor 207 form a series resonant circuit. At this time, current flows only through the closed circuit of the power receiving coil 201, the resonant capacitor 207 and switch 208, and no current flows to the rectifier unit 202 and the voltage control unit 203. When switch 208 is turned off, current flows to the rectifier unit 202 and the voltage control unit 203 via the power receiving coil 201 and the resonant capacitor 207. Memory 209 stores the control program executed by the control unit 200, as well as various settings, information, etc.

[0024] Figure 3 is a block diagram showing an example configuration of the power transmission device 100. The power transmission device 100 includes a control unit 301, a power supply unit 302, a power transmission unit 303, a power transmission coil 304, a communication unit 305, a memory 306, a resonant capacitor 307, and a switch 308.

[0025] The control unit 301 controls the entire power transmission device 100. The control unit 301 is composed of, for example, one or more CPUs. The power supply unit 302 supplies power to each functional block. The power supply unit 302 is, for example, a commercial power source or a battery. If the power supply unit 302 is a battery, power supplied from the commercial power source can be stored in the battery.

[0026] The power transmission unit 303 converts the DC or AC power input from the power supply unit 302 into AC power in the frequency band used for wireless power transmission, and inputs this AC power to the power transmission coil 304 to generate electromagnetic waves for power reception to the power receiving device 102. For example, the power transmission unit 303 converts the DC voltage supplied by the power supply unit 302 into an AC voltage using a switching circuit with a half-bridge or full-bridge configuration using a FET (Field Effect Transistor). In this case, the power transmission unit 303 includes a gate driver that controls the ON / OFF state of the FET.

[0027] Furthermore, the power transmission unit 303 controls the intensity of the electromagnetic waves to be output by adjusting the voltage (transmission voltage) or current (transmission current), or both, or the frequency, input to the power transmission coil 304. Increasing the transmission voltage or transmission current increases the intensity of the electromagnetic waves, and decreasing the transmission voltage or transmission current decreases the intensity of the electromagnetic waves. In addition, the power transmission unit 303 controls the power transmission unit 303 to start or stop the power transmission coil 304 based on instructions from the control unit 301, thereby controlling the output of AC power. Furthermore, the power transmission unit 303 in this embodiment is assumed to have the capacity to supply enough power to output at least 15 watts (W) of power to the charging unit 205 of the power receiving device 102.

[0028] The communication unit 305 communicates with the power receiving device 102 via the power transmission coil 304 for power transmission control based on the WPC standard. The communication unit 305 frequency modulates (FSK (Frequency Shift Keying)) the AC voltage and AC current output from the power transmission unit 303 and transmits information to the power receiving device 102. The communication unit 305 also demodulates the modulated AC voltage and AC current in the communication unit 204 of the power receiving device 102 to obtain the information transmitted by the power receiving device 102. In other words, the communication performed by the communication unit 305 is carried out by superimposing a signal on the electromagnetic waves transmitted from the power transmission unit 303.

[0029] Furthermore, the communication unit 305 may be configured to communicate with the power receiving device 102 using a different coil or antenna than the power transmission coil 304 and a communication method that conforms to a standard different from the WPC standard. Alternatively, the communication unit 305 may be configured to communicate with the power receiving device 102 by selectively using multiple communication methods.

[0030] The memory 306 stores control programs executed by the control unit 301, as well as the states of the power transmission device 100 and the power receiving device 102. For example, the state of the power transmission device 100 is acquired by the control unit 301, and the state of the power receiving device 102 is acquired by the control unit 200 of the power receiving device 102, and can be received via the communication unit 305.

[0031] The transmission coil 304 is an antenna (coil) for transmitting power to the power receiving device 102, and is connected to the resonant capacitor 307, resonating at a specific frequency F1. The switch 308 is a switch for short-circuiting the transmission coil 304 and the resonant capacitor 307, and is controlled by the control unit 301. When the switch 308 is turned on, the transmission coil 304 and the resonant capacitor 307 form a series resonant circuit. At this time, current flows only in the closed circuit of the transmission coil 304, the resonant capacitor 307 and the switch 308. When the switch 308 is turned off, power is supplied to the transmission coil 304 and the resonant capacitor 307 from the power transmission unit 303.

[0032] FIG. 4 is a block diagram showing the functional configuration of the control unit 301 of the power transmission device 100 according to the present embodiment. The control unit 301 includes a first Q-value measurement unit 400, a second Q-value measurement unit 401, a Calibration processing unit 402, a first foreign object detection processing unit 403, a second foreign object detection processing unit 404, a third foreign object detection processing unit 405, and a power transmission control processing unit 406. Note that the foreign object in the present embodiment refers to an object different from the power transmission device 100 and the power reception device 102. The foreign object can be, for example, a metal piece such as a clip, an NFC tag, and an IC card. The power transmission device 100 in the present embodiment performs a process of determining whether a foreign object exists within the range where the power transmission device 100 can transmit power. This process is also referred to as foreign object detection or foreign object detection processing in the following description.

[0033] The first Q-value measurement unit 400 measures the Q-value in the frequency domain (first Q-value measurement). The second Q-value measurement unit 401 measures the Q-value in the time domain (second Q-value measurement). The Calibration processing unit 402 performs acquisition of Calibration data Point and creation processing of a Calibration curve. The first foreign object detection processing unit 403 performs foreign object detection processing (first foreign object detection processing) based on the first Q-value measured by the first Q-value measurement unit 400. The second foreign object detection processing unit 404 performs foreign object detection processing (second foreign object detection processing) based on the power loss method. The third foreign object detection processing unit 405 performs foreign object detection processing (third foreign object detection processing) based on the second Q-value measured by the second Q-value measurement unit 401. The power transmission control unit 406 performs processing related to start, stop, and increase / decrease of the power transmission power of the power transmission unit 303. Each processing unit shown in FIG. 4 is configured as an independent program and can operate in parallel while taking synchronization between programs by event processing or the like. Note that the details of the processing performed by each block in FIG. 4 will be described later.

[0034] <Control based on the WPC standard> The control flow between the power transmission device 100 and the power receiving device 102 in this embodiment will be described. First, the control of wireless power transmission in accordance with the WPC standard will be described. Figure 13 is a sequence diagram showing the control flow of the power transmission device and power receiving device in accordance with the WPC standard v1.2.3. The sequence shown in Figure 13 is control performed by a power transmission device having a configuration that conforms to the WPC standard. In the following description, the case in which the power transmission device and power receiving device conform to the WPC standard v1.2.3 will be described, but it is not limited to this. In other words, the power transmission device and power receiving device of this disclosure may conform to the WPC standard v1.2.3 or later versions of the WPC standard, or they may conform to versions earlier than the WPC standard v1.2.3.

[0035] The WPC standard defines multiple phases, including the Power Transfer phase in which power transmission for charging takes place, and the phases preceding power transmission for charging. The phases preceding power transmission include (1) Selection phase, (2) Ping phase, (3) Identification & Configuration phase, (4) Negotiation phase, and (5) Calibration phase. In the following, the Identification and Configuration phase will be referred to as the I&C phase.

[0036] In the Selection phase, the power transmission device 100 transmits an Analog Ping (hereinafter referred to as A-Ping) (F500) to detect an object present in the vicinity of the power transmission coil 304. The A-Ping is pulsed power, used for detecting objects. Furthermore, even if the power receiving device receives the A-Ping, the power is so small that it cannot activate the control unit 301 of the power receiving device 102. The power transmission device 100 transmits the A-Ping intermittently. Here, the voltage and current applied to the power transmission coil 209 change depending on whether an object is placed within the power transmission range of the power transmission device 100 or not. Therefore, the control unit 301 of the power transmission device 100 detects at least one of the voltage value and current value of the power transmission coil 304 when the A-Ping is transmitted. The control unit 201 determines that an object is present if the detected voltage value falls below a certain threshold or the current value exceeds a certain threshold, and transitions to the Ping phase.

[0037] In the Ping phase, when the presence of an object is detected by A-Ping, the first Q-value measuring unit 400 of the power transmission device 100 measures the Q-value (Quality Factor) of the power transmission coil 304 (F501). The Q-value obtained here is a measurement of the Q-value in the frequency domain (first Q-value measurement). Once the Q-value measurement is complete, the power transmission device 100 starts transmitting Digital Ping (hereinafter referred to as D-Ping) (F502). D-Ping is the power required to activate the control unit 200 of the power receiving device 102, and is greater than A-Ping power. From then on, the power transmission device 100 continues to transmit power equal to or greater than D-Ping power from the start of D-Ping transmission (F502) until it receives an EPT (End Power Transfer) packet from the power receiving device 102 requesting a halt to power transmission (F522). When the control unit 200 of the power receiving device 102 receives a D-Ping and starts up, it sends a Signal Strength packet, which is data containing the voltage value of the received D-Ping, to the power transmitting device 100 (F503). The power transmitting device 100 recognizes that the object detected in the Selection phase is the power receiving device by receiving the Signal Strength packet from the power transmitting device 101 that received the D-Ping. When the power transmission device 100 receives a Signal Strength packet, it transitions to the I&C phase.

[0038] In the I&C phase, the receiving device 102 transmits data containing an ID that includes version information of the WPC standard to which the receiving device 102 conforms and device identification information (F504). The receiving device 102 also transmits a Configuration packet to the transmitting device 100 that includes information such as the maximum power that the receiving device 102 will supply to the load (battery 206) (F505). Upon receiving the ID and Configuration packet, the transmitting device 100 determines whether the receiving device 102 is conforming to a version of the WPC standard it conforms to and sends an ACK. Specifically, if the transmitting device 100 determines that the receiving device 102 is compatible with the WPC standard v1.2 or later extension protocol (including the processing in the Negotiation phase described later), it responds with an ACK (F506). Upon receiving the ACK, the receiving device 101 transitions to the Negotiation phase, where it negotiates the amount of power to transmit and receive.

[0039] In the negotiation phase, the power receiving device 102 sends an FOD Status packet to the power transmitting device 100 (F507). In this embodiment, the FOD Status packet is referred to as FOD(Q). The first foreign object detection processing unit 403 of the power transmitting device 100 performs foreign object detection based on the Q value stored in the received FOD(Q) and the Q value measured by the Q value measurement, and sends an ACK to the power receiving device 102 indicating that it has determined there is a high probability that there is no foreign object (F508).

[0040] When the receiving device 102 receives an ACK, it sends a General Request (Capability) packet (F535), which is data querying the capabilities of the transmitting device 100 and is one of the General Requests defined in the WPC standard. Hereafter, the General Request (Capability) packet will be referred to as the GRQ (CAP) packet. When the transmitting device 100 receives the GRQ (CAP) packet, it sends a Capability packet (hereinafter referred to as CAP) (F536), which contains the capability information it supports.

[0041] The power receiving device 102 negotiates the Guaranteed Power (hereinafter referred to as GP), which is the maximum value of power it requests to receive. GP represents the amount of power available to the power receiving device 102, as agreed upon in negotiations with the power transmitting device 100. In other words, GP is the maximum amount of power that can be used to supply power to the load of the power receiving device 102 (power consumed by the charging unit 205 and the battery 206). Alternatively, GP may be the power that the power receiving device is guaranteed to be able to output to the load (e.g., a charging circuit, battery, etc.). In this case, GP indicates the power value at which the power receiving device's output to the load is guaranteed, even if, for example, the positional relationship between the power receiving device and the power transmitting device changes and the power transmission efficiency between the power receiving coil and the power transmitting coil decreases. For example, if GP is 5 watts, even if the positional relationship between the power receiving coil and the power transmitting coil changes and the power transmission efficiency decreases, the power transmitting device will control the power receiving device so that it can output 5 watts of power to the load.

[0042] Negotiation is achieved by sending a packet containing the GP value requested by the power receiving device to the power transmitting device 100, which is one of the Specific Request packets defined in the WPC standard (F509). In this embodiment, this data is expressed as an SRQ(GP) packet. The power transmitting device 100 responds to the SRQ(GP) packet, taking into consideration its own power transmission capacity, etc. If the power transmitting device 100 determines that it can accept Guaranteed Power, it sends an ACK indicating that it has accepted the request (F510). Once negotiation of multiple parameters, including GP, is complete, the power receiving device 102 sends an SRQ(EN) packet to the power transmitting device requesting the end of negotiation (End Negotiation) from the Specific Request (F511). The power transmitting device 100 sends an ACK to the SRQ(EN) packet (F512), ends the negotiation, and transitions to the Calibration phase, where it creates criteria for implementing foreign object detection based on the power loss method. Foreign object detection is a process that determines whether or not an object different from the power receiving device (hereinafter referred to as a foreign object) exists within the power transmission range of the power transmission device 100, or whether or not there is a possibility that a foreign object exists.

[0043] During the Calibration phase, the receiving device 102, without supplying power to the load (charging unit 205 and battery 207), notifies the transmitting device 100 of the received power value R1 when the receiving device 102 receives a D-Ping. At this time, the receiving device 102 transmits a Received Power packet (mode1) (hereinafter referred to as PR1) containing the received power value R1 to the transmitting device 100. Upon receiving PR1, the transmitting device 100 transmits an ACK to the receiving device 101 (F514). At this time, the transmitting device 100 measures its own transmitted power value T1 and calculates the difference Δ1 between T1, which is the power loss, and R1. After receiving the ACK, the receiving device 102, while supplying power to the load, transmits a Control Error packet (hereinafter referred to as CE) to the transmitting device 100 requesting an increase or decrease in the received voltage. The CE stores a sign and a numerical value. A positive sign in the numerical value stored in the CE indicates a request to increase the receiving voltage, a negative sign indicates a request to decrease the receiving voltage, and a zero value indicates a request to maintain the receiving voltage. In this case, the receiving device 102 transmits CE(+) to the transmitting device 100, indicating an increase in the receiving voltage (F515).

[0044] When the power transmission device 100 receives CE(+), it changes the setting value of the power transmission circuit and increases the power transmission voltage (F516). When the power received by the power receiving device 102 increases in response to CE(+), it supplies the received power to the load (charging unit 205 and battery 206). The power receiving device 102 also transmits RP2 (Received Power packet (mode2) (hereinafter referred to as RP2)) to the power transmission device 100 (F517). Here, RP2 stores the power received value R2 when the power receiving device 102 is supplying power to the load.

[0045] When the power transmission device 100 receives RP2, it sends an ACK to the power receiving device (F514). At this time, the power transmission device 100 measures its own transmitted power value T2 and calculates the difference Δ2 between the power loss T2 and R2. The power transmission device 100 performs foreign object detection based on power loss, using the power loss Δ1 when no power is supplied to the load and the load's power consumption is 0, and the power loss Δ2 when power is supplied to the load and the load's power consumption is not 0 as references. Specifically, the power transmission device 100 predicts the power loss in a state where there is no foreign object at an arbitrary received power value from Δ1 and Δ2. The Calibration processing unit 402 generates a calibration curve based on this predicted value. The second foreign object detection processing unit 404 performs foreign object detection by comparing the relationship between the actually received power value and the transmitted power value with the calibration curve. When the power transmission device 100 sends an ACK to RP2, it transitions to the Power Transfer phase.

[0046] In the Power Transfer phase, the power transmission device 100 transmits power that can be received up to a maximum of 15 watts, as negotiated by the power receiving device in the Negotiation phase. The power receiving device 102 periodically sends RP0 (Received Power packet (mode0) (hereinafter referred to as RP0)) containing CE and the current received power value to the power transmission device 100 (F519, F520). Note that RP0 may be sent at regular intervals or randomly. When the power transmission device 100 receives RP0 from the power receiving device, it predicts the power loss at any given received power from Δ1 and Δ2 and performs foreign object detection. If the power transmission device 100 determines that there is a high probability that there is no foreign object, it sends an ACK to the power receiving device (F521). If it determines that there is a high probability that there is a foreign object, the power transmission device 100 sends a NAK to the power receiving device.

[0047] When the power receiving device 101 has finished charging the battery 307, it sends an EPT (End Power Transfer) packet (F522) to the power transmitting device 100 requesting that it stop transmitting power. The above describes the control flow of the power transmitting device 100 and the power receiving device in accordance with the WPC standard v1.2.3.

[0048] <Third foreign object detection process> The processing performed by the first Q-value measurement unit 400, the calibration processing unit 402, the first foreign object detection processing unit 403, and the second foreign object detection processing unit 404 in this embodiment is as described in the processing flow of the WPC standard described above. Here, the foreign object detection method performed by the second Q-value measurement unit 401 and the third foreign object detection processing unit 405 will be described.

[0049] The waveform 1200 in Figure 12(a) shows the time course of the high-frequency voltage applied to the terminals of the power transmission coil 304 or a resonant capacitor (not shown) of the power transmission device 100 (hereinafter simply referred to as the voltage value of the power transmission coil), with the horizontal axis representing time and the vertical axis representing the voltage value. At time T0, the application of the high-frequency voltage (power transmission) is stopped. Point 1201 is a point on the envelope of the high-frequency voltage and is the high-frequency voltage at time T1. (T1, A1) in the figure indicates that the voltage value at time T1 is A1. Note that power transmission is stopped at T0, but is not limited to this. For example, at T0, power transmission may be restricted so that the power transmitted is below a predetermined value.

[0050] Similarly, point 1202 is a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T2. In the figure, (T2, A2) indicates that the voltage value at time T2 is A2. The Q value measurement is performed based on the time change of the voltage value from time T0 onward. Specifically, the Q value is calculated using (Equation 1) based on the time, voltage value, and frequency f of the high-frequency voltage (hereinafter referred to as the operating frequency) of points 1201 and 1202, which are the envelope of the voltage value.

[0051]

number

[0052] Next, the process by which the power transmission device 100 measures the Q value in the time domain in this embodiment will be described with reference to Figure 12(b). Waveform 1203 shows the value of the high-frequency voltage applied to the power transmission coil 304, and its frequency is assumed to be between 120 kHz and 148.5 kHz as used in the WPC standard. Points 1204 and 1205 are part of the envelope of the voltage value. The power transmission unit 303 of the power transmission device 100 stops power transmission or limits power transmission so that the power being transmitted is below a predetermined value during the interval from time T0 to T5.

[0053] The second Q-value measuring unit 401 of the power transmission device 100 measures the Q-value based on the voltage value A3 (point 1204) at time T3, the voltage value A4 (point 1204) at time T4, the operating frequency of the high-frequency voltage, and (Equation 1). The power transmission unit 303 of the power transmission device 100 resumes power transmission at time T5. Thus, the second Q-value measurement is achieved by measuring the Q-value based on the elapsed time, voltage value, and operating frequency during a predetermined period in which the power transmission device 100 restricts power transmission. From now on, the period in which power transmission is stopped or restricted so that the power transmitted is below a predetermined value (in the example of Figure 12(b), the period from time T0 to T5) is called the power transmission restriction period.

[0054] The power transmission restriction period is determined between the power transmission device 100 and the power receiving device 102 before the second Q-value measurement is performed. The shorter the power transmission restriction period, the shorter the period during which conductivity is restricted, allowing power to be transmitted to the power receiving device without reducing power transmission efficiency. However, the length of the power transmission restriction period that can be achieved varies depending on the capabilities of, for example, the switches 308 and control unit 301 of the power transmission device 100. For this reason, if the power transmission restriction period is set to a length shorter than the minimum period during which the power transmission device 100 can restrict power transmission, the second Q-value measurement may not be performed properly. Also, depending on the type of power receiving device 102, it may not be able to function properly if the received power is restricted for a certain period of time or longer. For example, the power receiving device may determine that power transmission has ended and terminate the power receiving process because power transmission has been restricted for a certain period of time or longer, or it may become unable to perform processes that rely on power transmitted from the power transmission device 100.

[0055] For the reasons stated above, the power transmission restriction period in this embodiment shall be set to be longer than the minimum length that the power transmission device 100 can achieve. Furthermore, the power transmission restriction period in this embodiment shall be set to be shorter than the maximum length that the power receiving device 102 can tolerate. The method for setting the power transmission restriction period will be described later.

[0056] The third foreign object detection processing unit 405 determines whether foreign objects are present within the power transmission range of the power transmission device 100 based on the second Q value measured by the second Q value measurement unit 401. The determination method is as follows, for example. If foreign objects are present near the power transmission device 100, the second Q value will be lower than when no foreign objects are present. This is because energy loss occurs due to the foreign objects when they are present. Focusing on the slope of voltage attenuation, more energy loss occurs due to foreign objects when they are present than when they are absent. Therefore, the slope of the straight line connecting points 1204 and 1205 in the example of Figure 12(b) becomes steeper, and the attenuation rate (amount of attenuation) of the waveform amplitude increases. A lower Q value means that the waveform attenuation rate (the degree of decrease in waveform amplitude per unit time) is higher. Therefore, the third foreign object detection processing unit 405 can determine that foreign objects are present, or that there is a high probability of their presence, if the second Q value obtained by measurement is smaller than a predetermined threshold.

[0057] In this embodiment, an example of detecting foreign objects using the second Q value has been described, but the method is not limited to this. For example, the determination may be made using the slope of the line connecting points 1204 and 1205, which can be obtained from (A3-A4) / (T3-T4). Alternatively, if the time (T3 and T4) for observing the voltage decay state is fixed, the determination can also be made using the value of (A3-A4) representing the difference in voltage values, or the value of the voltage ratio (A3 / A4). Alternatively, if the voltage value A3 immediately after the power transmission is stopped is constant, the determination can also be made using the value of the voltage value A4 after a predetermined time has elapsed. Alternatively, the determination may be made using the value of the time (T4-T3) until the voltage value A3 becomes a predetermined voltage value A4.

[0058] In this way, the power transmission device 100 can determine the presence or absence of foreign matter by measuring the voltage at the power transmission coil 304 at at least two points in time during the period in which power transmission is restricted, and 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.

[0059] Furthermore, even if the vertical axis of Figure 12 represents the current value flowing through the transmission coil 304, the decay state of the current value during the power transmission restriction 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 decay rate is higher than when there is no foreign matter. Therefore, the presence or absence of foreign matter can be determined by applying the above method to the time change of the current value flowing through the transmission coil 304. That is, the presence or absence of foreign matter can be determined and detected using indicators that represent the decay state of the current, such as the second Q value obtained from the measured current, the slope of the current decay, 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. Alternatively, foreign matter detection may be performed based on both the measured voltage and the measured current.

[0060] <Method for determining the period of power transmission restrictions> In this embodiment, the method for setting the power transmission restriction period to measure the second Q value will be explained using Figure 5. Figure 5(a) is a diagram showing the sequence when the control process based on the WPC standard and the third foreign object detection process are combined. Processes similar to those in Figure 13 are denoted by the same reference numerals and their explanations are omitted.

[0061] At F528, the power transmission device 100 and the power receiving device 102 negotiate to determine the power transmission restriction period. An example of the negotiations conducted at F528 is shown in Figure 5(b). The power receiving device 102 sends a negotiation packet to the power transmission device 100 that includes the length of the power transmission restriction period desired by the power receiving device 102 (F540). If the power transmission device 100 accepts the length of the power transmission restriction period obtained from the power receiving device 102, it returns an ACK; otherwise, it returns a NAK (F541).

[0062] In this embodiment, a negotiation packet containing an identifier requesting no downtime is expressed as power transmission restriction period (0). A negotiation packet containing an identifier requesting a power transmission restriction period of 100 microseconds is expressed as power transmission restriction period (1). A negotiation packet containing an identifier requesting a power transmission restriction period of 120 microseconds is expressed as power transmission restriction period (2). A negotiation packet containing an identifier requesting a power transmission restriction period of 140 microseconds is expressed as power transmission restriction period (3). These identifiers are examples, and other identifiers may be used. The power receiving device 102 repeatedly transmits negotiation packets, excluding power transmission restriction period (0), in order of increasing power transmission restriction period length until an ACK is returned from the power transmitting device 100 (F540, 542). When an ACK is sent from the power transmitting device 100, the power receiving device 102 sets the length of the power transmission restriction period determined by negotiation to the length of the power transmission restriction period included in the negotiation packet when the power transmitting device 100 sent the ACK. The power receiving device 102 stores the determined length of the power transmission restriction period in memory 209 and terminates negotiations regarding the power transmission restriction period (F543). If the power receiving device 102 has sent all possible negotiation packets other than the power transmission restriction period (0) but has not received an ACK from the power transmission device 100, the power receiving device 102 sends a downtime (0) to the power transmission device 100. The power receiving device 102 also decides not to perform the third foreign object detection and terminates negotiations regarding the power transmission restriction period.

[0063] For example, the operation when the power transmission device 100 can perform third-party foreign object detection with a power transmission restriction period of 120 μs or longer will be explained using Figure 5(b). The power receiving device 102 transmits a power transmission restriction period (1) to the power transmission device 100 (F540). At this point, the power transmission device 100 determines that it cannot accept the length of the power transmission restriction period obtained from the power receiving device 102 and returns NAK (F541).

[0064] Next, the receiving device 102 transmits a power transmission restriction period (2) to the receiving device (F542). The transmitting device 100 decides to accept a downtime of 120 microseconds and returns an ACK (F543). The receiving device 102 and the transmitting device 100 decide that 120 microseconds is the length of the power transmission restriction period and conclude negotiations regarding the power transmission restriction period.

[0065] This embodiment illustrates an example of negotiation regarding the power transmission restriction period in a case where the power transmission device 100 does not transmit the length of the power transmission restriction period it requests to the power receiving device 102 during negotiations. In this case, the power receiving device 102 transmits the shortest to the power transmission device 100 downtimes in order, and determines the length of the power transmission restriction period based on the value for which the first ACK is returned. This allows the length of the power transmission restriction period to be determined by negotiation even in a configuration where the power transmission device 100 does not transmit the length of the power transmission restriction period to the power receiving device 102. Furthermore, the length of the power transmission restriction period set at this time will satisfy the minimum length that the power transmission device 100 can achieve, and will be shorter than the length of the power transmission restriction period requested by the power receiving device 102.

[0066] The negotiation regarding the power transmission restriction period performed in this embodiment is an example. For example, the receiving device 102 may request the power transmission device 100 to transmit information for determining the length of the power transmission restriction period, and the power transmission device 100 may transmit to the receiving device 102 the length of the power transmission restriction period that the power transmission device 100 requests. Alternatively, the power transmission device 100 may transmit information representing the minimum length that the power transmission device 100 can achieve.

[0067] As an example of negotiation regarding the power transmission restriction period, the power transmission device sends a CAP to the power receiving device in response to the GRQ(CAP), which contains information indicating the length of the power transmission restriction period. For example, the information indicating the length of the power transmission restriction period is recorded in the Reserved field specified in the CAP packet. By including information indicating the length of the power transmission restriction period in the CAP, the power transmission device 100 can reduce the number of packets required for negotiation. Furthermore, the power transmission device 100 may have a means to determine whether or not to include information indicating the length of the power transmission restriction period in the CAP in response to the GRQ(CAP). If it is determined not to include it, the Reserved field is filled with zeros. The decision of whether or not to include information indicating the length of the power transmission restriction period in the CAP may be based, for example, on whether or not the power receiving device supports third-party foreign object detection processing. The decision of whether or not the power receiving device supports third-party foreign object detection processing may be based, for example, on the version information of the power receiving device included in the Configuration packet, and on the version that supports third-party foreign object detection processing. Alternatively, the decision may be based on the version information included in the Identification packet, for example, to determine whether or not the version supports third-party foreign object detection processing. Alternatively, for example, whether or not the device supports the third foreign object detection process may be determined based on information contained in the Configuration packet or other packets indicating whether or not it supports the third foreign object detection process. If the device does not support the third foreign object detection process, the Reserved field can be filled with zeros to reduce the risk of the power receiving device 102 malfunctioning if it does not support the third foreign object detection process.

[0068] Returning to Figure 5(a), at F520, the power transmission device 100 performs third foreign object detection processing in response to receiving RP0 from the power receiving device 102 (F529). Here, if the length of the power transmission restriction period has been determined at F528, the power receiving device 102 transmits to the power transmission device 100 information requesting third foreign object detection in RP0. In this embodiment, the information requesting third foreign object detection includes information indicating the length of the power transmission restriction period determined in negotiations, which is transmitted as RP0. The power transmission device 100 performs third foreign object detection in response to receiving RP0 containing the length of the power transmission restriction period.

[0069] Figure 10 shows an example of the flow of the third foreign object detection process performed in F529. The power transmission device 100 determines whether or not third foreign object detection is possible (S1001). If foreign object detection is possible, proceed to S1002. If foreign object detection is not possible, terminate the process. Next, the power transmission device 100 measures the value of the second Q (S1002). The second Q value measurement process will be explained with reference to Figure 9. Figure 9 is a flowchart of the second Q value measurement process performed by the power transmission device 100. In Figure 9, the power transmission control unit 406 stops power transmission by the power transmission unit 303, or limits power transmission so that the power transmitted is less than a predetermined value (S900). Next, the second Q value measurement unit 401 controls the switch 308 to perform a short circuit between the power transmission coil 304 and the resonant capacitor 307. Then, the second Q-value measuring unit 401 measures the voltage value A3 of the power transmission coil 304 at time T3 (S901), and further measures the voltage value A4 of the power transmission coil 304 at T4 after a certain period of time has elapsed (S902).

[0070] The second Q-value measuring unit 401 calculates the second Q-value from the frequency, time, and voltage value of the transmitted power (waveform 1203) based on the measurement results and (Equation 1) (S903). Here, the frequency of the transmitted power is the resonant frequency F1 of the transmission coil 304 and the resonant capacitor 307. When the voltage value measurement is completed, the second Q-value measuring unit 401 terminates the short-circuit process and releases the power transmission restriction (S904). Releasing the restriction here means returning the transmitted power to the amount of energy before it was restricted in S900.

[0071] Returning to Figure 10, the power transmission device 100 determines the presence or absence of a foreign object based on the value of the second Q value and the result of the second foreign object detection method, and then terminates the process. If the power transmission device 100 determines that a foreign object is present or that there is a high probability of a foreign object being present, it sends an NAK to the power receiving device 102. If it determines that no foreign object is present or that there is a low probability of a foreign object being present, the power transmission device 100 sends an ACK to the power receiving device 102. In the example of Figure 5(a), it is determined that there is no foreign object, and an ACK is sent at F521. Thereafter, each time the power receiving device 102 receives an RP0 containing information requesting the execution of the third foreign object detection, the power transmission device 100 performs the third foreign object detection using the same process as described above. In this embodiment, an example has been described in which an RP0 is used as a packet containing information requesting the execution of the third foreign object detection, but it may also be included in a CE packet or other proprietary packets. Furthermore, information requesting the execution of third-party foreign object detection may be included in RP1 and RP2. In this case, the power transmission device 100 will perform third-party foreign object detection processing in the Calibration phase.

[0072] <Changes to the period of power transmission restrictions> The third foreign object detection process is carried out by negotiating to determine the length of the power transmission restriction period, as described above, and using the determined length. As explained earlier, the length of the power transmission restriction period is determined based on the capabilities of the power transmission equipment 100 and the power receiving equipment 102. However, after the length of the power transmission restriction period has been determined through negotiation, the state of at least one of the power transmission equipment 100 and the power receiving equipment 102 may change. For example, after F528, the characteristics of the power transmission equipment 100 may change due to changes in GP, ​​changes in transmitted power, changes in transmitted voltage, temperature changes of the power transmission equipment 100, changes in the power transmission circuit configuration, etc. As an effect of such changes in characteristics, for example, the ratio of the voltage drop amount appearing in the waveform 1203 used for the second Q value measurement to noise may change. If the ratio of noise increases further, the judgment result of foreign object detection may become incorrect, or foreign object detection itself may become impossible. In such cases, it is conceivable that the length of the power transmission restriction period should be made longer in order to perform foreign object detection with the same accuracy as before the state of the power transmission equipment 100 changed. Conversely, if the noise ratio decreases due to a change in the state of the power transmission device 100 compared to before the change, foreign object detection can be performed with the same accuracy even if the downtime is shortened. In such cases, it is expected that shortening the length of the power transmission restriction period will improve power transmission efficiency.

[0073] Furthermore, depending on the combination of the power transmission device 100 and the power receiving device 102, if communication does not occur properly, or due to device settings, negotiation may not take place at F528. If negotiation does not take place, even if the power transmission device 100 receives a packet from the power receiving device 102 requesting the execution of the third foreign object detection process, it will not be able to perform the third foreign object detection. In addition, changes in the state of the power receiving device 102, such as changes in received power, changes in received voltage, or changes in the temperature of the power receiving device 102, may also change the length of the power transmission restriction period that the power receiving device 102 can tolerate.

[0074] To solve the above problems, the power transmission device 100 and power receiving device 102 of this embodiment perform a process to change the length of the power transmission restriction period when the state of at least one of the power transmission device or power receiving device changes. The process for changing the length of the power transmission restriction period will be explained using Figure 5(a).

[0075] In Figure 5(a), at F520, the power transmission device 100 receives RP0, which includes the length of the power transmission restriction period. The length of the power transmission restriction period included in RP0 is the length determined by negotiation. Here, we will explain the case where the power transmission device 100 decides to change the length of the power transmission restriction period determined by negotiation due to a change in the state of at least one of the power transmission device 100 and the power receiving device 102. Here, as an example, let's assume that the power transmission device 100 decides to change the length to 130 microseconds or longer than the 120 microseconds determined by negotiation. Here, an example of a case in which the power transmission device 100 decides to change the length of the power transmission restriction period to be longer is as follows: That is, when the temperature of at least one of the power transmission device 100 and the power receiving device 102 changes to a temperature higher than a certain level from the temperature at the time the negotiation took place. Also, for example, when the temperature of at least one of the power transmission device 100 and the power receiving device 102 changes to a temperature higher than a predetermined threshold after the negotiation took place. Another example is when at least one of the values ​​of the power transmitted by the power transmission device 100 and the power (GP) that the power receiving device 102 is guaranteed to be able to output to the load changes to a value that is a certain amount smaller than the value that was determined at the time of negotiation. Note that changes to the transmitted power and GP can be made by a process that repeats the negotiation phase (renegotiation phase). In the above case, the power transmission device 100 decides to change the length of the transmission restriction period determined in the negotiation to be longer.

[0076] Figure 6 shows the flow of processing related to changing the length of the power transmission restriction period. The power transmission device 100 determines whether to change the length of the power transmission restriction period (S601). If it determines to change it, it sends a signal to the power receiving device 102 requesting communication for the change (hereinafter referred to as a change request) (S602, F530). If it determines not to change it, no change processing is performed, and the third foreign object detection processing is performed based on the length of the power transmission restriction period obtained from the power receiving device 102 (F529).

[0077] When the power receiving device 102 receives a change request, it transmits information to the power transmitting device 100 indicating that it is waiting for parameter reception from the power transmitting device 100 (F531). Here, the parameter transmitted from the power transmitting device 100 is, for example, information representing the minimum length of the power transmission restriction period during which the power transmitting device 100 can perform the third foreign object detection process. The power transmitting device 100 transmits a predetermined signal to the power receiving device 102, triggered by the signal transmitted by the power receiving device 102 indicating that it is waiting for parameter reception (S603, F532). Note that the signal transmitted from the power receiving device 102 in F531 may be a "signal that permits the transmission of parameters by the power transmitting device 100" and a "signal that prompts the transmission device 100 to transmit parameters," etc.

[0078] In this instance, at F532, the power transmission device 100 sends a packet to the power receiving device 102 containing information (parameters) representing 130 microseconds as the length of the power transmission restriction period. The power transmission device 100 and the power receiving device 102 then decide that 130 microseconds is the new length of the power transmission restriction period. The power receiving device 102 transmits RP0 to the power transmitting device, which contains information indicating that the length of the power transmission restriction period is 130 microseconds (F533). In S1001, the power transmitting device 100 confirms that the length of the power transmission restriction period included in RP0 is 130 microseconds and is at least 130 microseconds, which is the minimum length for which the third foreign object detection process can be executed. The power transmitting device 100 determines that the third foreign object detection can be executed and performs the third foreign object detection process (S1002, S1003, F529). Thus, in this embodiment, the power transmitting device 100 transmits a packet requesting communication to change the length of the power transmission restriction period, and then transmits a packet containing information regarding the length of the power transmission restriction period. This makes it possible to perform the third foreign object detection even if, for example, the state of the power transmitting device 100 changes during power transmission.

[0079] The above example illustrates a case where the length of the power transmission restriction period is changed to be longer than the length determined by negotiation. However, it is also possible to change it to be shorter by performing a similar process. Examples of cases in which the power transmission restriction period is decided to be shortened include the following: when the temperature of at least one of the power transmission equipment 100 and the power receiving equipment 102 changes to a temperature that is a certain amount lower than the temperature at the time of negotiation. Also, for example, when the temperature of at least one of the power transmission equipment 100 and the power receiving equipment 102 changes to a temperature that is a certain amount lower than the value determined at the time of negotiation. Also, for example, when the value of the power transmitted by the power transmission equipment 100 and the value of the power (GP) that the power receiving equipment 102 is guaranteed to be able to output to the load change to a value that is a certain amount higher than the value determined at the time of negotiation. In the above cases, the power transmission equipment 100 decides to change the length of the power transmission restriction period determined by negotiation to be shorter.

[0080] If it is decided to shorten the length of the power transmission restriction period, the power transmission device 100 sends a packet to the power receiving device 102 in F532 that represents, for example, 110 microseconds as the length of the power transmission restriction period. This makes it possible to shorten the length of the power transmission restriction period by 10 microseconds from the length decided by negotiation, and improves power transmission efficiency compared to not changing the length of the power transmission restriction period. The above-described process for changing the power transmission restriction period may be executed repeatedly each time it is determined that a change should be made. In this embodiment, the power transmission device 100 sends a change request in S802 and F530 when it determines that it should change the length of the power transmission restriction period, but this step may be omitted. That is, the power transmission device 200 may send a signal that includes information representing the length of the power transmission control period when it determines that it should change the length of the power transmission restriction period. Alternatively, the change request may include information representing the length of the power transmission control period.

[0081] Furthermore, in this embodiment, the parameter transmission process is executed upon receiving a specific packet, but it may be executed at other times. The power transmission device 100 may, for example, execute a change process when it determines that it cannot perform third-party foreign object detection within the length of the power transmission restriction period requested by the power receiving device 102. This is effective, for example, when the system proceeds to the PowerTransfer phase without negotiation.

[0082] For example, the power transmission device 100 may decide to perform the change process when a predetermined amount of time has elapsed since it last transmitted a parameter related to the length of the power transmission restriction period to the power receiving device 102. For example, if the power transmission device 100 has two or more power transmission circuits and can switch between power transmission circuits depending on the power transmission or voltage, it may decide to perform the parameter transmission process when the power transmission circuit is switched. For example, the power transmission device 100 may decide to perform parameter transmission when the processing load of the control unit 301 changes by more than a predetermined value. Alternatively, the system may be configured to determine whether to perform the change process by combining at least one of the above-mentioned criteria.

[0083] Alternatively, for example, in F530 or F531, the power transmission device 100 may be configured to transmit a packet containing an identifier requesting renegotiation to change the length of the power transmission restriction period. After the power receiving device 102 receives the packet containing the identifier requesting renegotiation, it transmits a Renegotiate Packet (hereinafter referred to as "RN packet") to the power transmission device 100. Then, after transitioning to the Renegotiation phase, the power receiving device 102 requests the power transmission device 100 to transmit information representing the length of the power transmission restriction period. Subsequently, the power transmission device 100 transmits a signal to the power receiving device 102 containing information regarding the length of the power transmission restriction period.

[0084] As explained above, when the state of at least one of the power transmission device 100 and the power receiving device 102 changes, communication is made to change the length of the power transmission restriction period, making it possible to perform appropriate foreign object detection processing in accordance with the state change.

[0085] In the example described above, the power transmission device 100 communicates to change the length of the power transmission restriction period in response to a change in the state of at least one of the power transmission device 100 and the power receiving device 102, but it is not limited to this. For example, the power transmission device 100 may decide to communicate to change the length of the power transmission restriction period in response to a change in the state of the power transmission device 100 and the power receiving device 102 after the length of the power transmission restriction period has been determined. For example, the power transmission device 100 may decide to communicate to change the length of the power transmission restriction period if the temperature of at least one of the power transmission device 100 and the power receiving device 102 is higher than a predetermined threshold. Alternatively, the power transmission device 100 may decide to communicate to change the length of the power transmission restriction period if at least one of the values ​​of the transmitted power and the value of the power that the power receiving device 102 is guaranteed to be able to output to the load is smaller than a predetermined threshold. In these cases, the length of the power transmission restriction period is changed to be longer.

[0086] For example, the power transmission device 100 may determine to communicate to change the length of the power transmission restriction period if the temperature of at least one of the power transmission device 100 and the power receiving device 102 is below a predetermined threshold. For example, the power transmission device 100 may also determine to communicate to change the length of the power transmission restriction period if at least one of the value of the transmitted power and the value of the power that the power receiving device 102 is guaranteed to be able to output to the load is greater than a predetermined threshold. In these cases, the length of the power transmission restriction period is changed to be shorter.

[0087] As described above, if it is determined to change the length of the power transmission restriction period based on the state of the power transmission equipment 100 and the power receiving equipment 102 after the length of the power transmission restriction period has been determined, the determination may be made at the following timing, for example. That is, when the power transmission equipment 100 receives a signal (e.g., RP0) containing information representing the length of the power transmission restriction period, it identifies the state of the power transmission equipment 100 and the power receiving equipment 102, such as the temperature and the magnitude of the power transmitted. The power transmission equipment 100 considers the identified state and determines that it is necessary to change the length of the power transmission restriction period requested by the power receiving equipment 102, and then decides to change the length of the power transmission restriction period.

[0088] (Second embodiment) In this embodiment, we will describe an example in which negotiations to determine the length of the power transmission restriction period are not conducted at timing F528 in Figure 5(a), and negotiations are conducted during the Power Transfer phase. Note that the functional configurations of the power transmission device 100 and the power receiving device 102 are the same as in the first embodiment, so the same reference numerals are used and their explanation is omitted.

[0089] The processing in this embodiment will be explained using Figures 7 and 8. Figure 7(a) shows the processing sequence of the power transmission device 100 and the power receiving device 102 in this embodiment. Note that in the example in Figure 7(a), it is shown that negotiation F528 in Figure 5(a) did not take place. Figure 8 is a flowchart showing the processing performed by the power receiving device 102. In Figure 7(a), the same reference numerals are used for the same processing as in Figure 5(a). Possible reasons why negotiation does not take place include, for example, initial settings of the power transmission device 100 and the power receiving device 102, or when communication for negotiation does not take place properly and the system proceeds to the Power Transfer phase.

[0090] In F700, the power receiving device 102 determines whether negotiation is necessary to determine the power transmission restriction period (S801). At this time, the power receiving device 102 determines that negotiation is necessary, for example, if the length of the power transmission restriction period is not stored in the memory 209 (YES in S801). On the other hand, if it determines that negotiation is not necessary, for example, by not performing the third foreign object detection process, it does not perform negotiation (NO in S801).

[0091] If the power receiving device 102 determines that negotiation will take place, it sends a signal to the power transmitting device 100 at F700 to request negotiation (S802). In this embodiment, a Renegotiate Packet (RN) is used as the signal to request negotiation. An RN is a packet that requests to repeat the negotiation phase (renegotiation). A packet other than an RN may also be used as the signal to request negotiation. When the power transmitting device 100 receives an RN from the power receiving device 102, it sends an ACK if it accepts the negotiation, and a NAK if it does not accept the negotiation. At F701, the power transmitting device 100 determines that it accepts the request for negotiation and sends an ACK.

[0092] When the power receiving device 102 receives an ACK, it transitions to the Renegotiation phase and negotiates regarding the power transmission restriction period (F702). If a packet other than an RN is used as the signal to request negotiation, the following processing may be performed without transitioning to the Renegotiation phase. Furthermore, if the device transitions to the Renegotiation phase, in addition to negotiating to determine the power transmission restriction period, processing such as determining the GP value and notifying the settings of the power receiving device 102 may be performed.

[0093] An example of processing in F702 will be explained using Figure 7(b). The power receiving device 102 sends a packet to the power transmitting device 100 indicating a request for a specific length of power transmission control period (F711). In response to receiving the packet requesting a specific length of power transmission restriction period, the power transmitting device 100 sends a signal to the power receiving device 102 containing information representing the length of the power transmission restriction period (F712). Here, as an example, a packet for power transmission restriction period (1) is sent. When the power receiving device 102 receives a packet from the power transmitting device 100 containing information representing the length of the power transmission restriction period (S803), it stores the received length of the power transmission restriction period in the memory 209 (S804). Here, based on the power transmission restriction period (1) sent from the power transmitting device 100, 100 microseconds is stored in the memory 209. Note that the configuration may also store a length determined considering the state of the power receiving device 102, rather than the length of the power transmission restriction period itself sent from the power transmitting device 100. Alternatively, F702 may be configured to perform the processing shown in Figure 5(b).

[0094] Returning to Figure 7(a), once the length of the power transmission restriction period is stored in F702, the power receiving device 102 transmits an RP0 containing information representing the length of the power transmission restriction period stored in memory 209 to the power transmitting device 100 in F520. Thereafter, the third foreign object detection process is performed in the same manner as in Figure 5(a).

[0095] Through the process described above, if negotiations to determine the length of the power transmission restriction period have not yet taken place, the power receiving device 102 can send a signal requesting negotiations to determine the length of the power transmission restriction period. In this embodiment, the example was given where no negotiations took place in F528, but even if negotiations have taken place, the power receiving device 102 may send a signal requesting negotiations as necessary. The determination of whether negotiations are necessary may be made by the power receiving device 102 using the same determination criteria as in the first embodiment.

[0096] Furthermore, after negotiations are conducted using the method in the second embodiment, a modification process to change the length of the power transmission restriction period may be performed, similar to the first embodiment. In this way, it is also possible to combine the first and second embodiments as appropriate.

[0097] (Other embodiments) This disclosure can also be implemented by supplying a program that implements one or more of the functions of the embodiments described above to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of symbols]

[0098] 100 Power transmission equipment 301 Control Unit 303 Power Transmission Section 305 Communications Department

Claims

1. A power transmission device, A power transmission means for wirelessly transmitting power to a power receiving device, A detection means performs a detection process to detect foreign objects based on a Quality Factor measured during a restricted period in which the power transmitted by the aforementioned power transmission means is limited. The power receiving device and communication means for communicating about the change of the restriction period. It has, The power transmission device is characterized in that the communication means performs communication regarding the change of the restriction period based on a change in the power or voltage state of at least one of the power transmission device and the power receiving device.

2. A power transmission device, A power transmission means for wirelessly transmitting power to a power receiving device, A detection means performs a detection process to detect foreign objects based on a Quality Factor measured during a restricted period in which the power transmitted by the aforementioned power transmission means is limited. The power receiving device and communication means for communicating about the change of the restriction period. It has, The power transmission device is characterized in that the communication means performs communication regarding a change in the restriction period based on a change in the temperature state of at least one of the power transmission device and the power receiving device.

3. The power transmission device according to claim 1 or 2, characterized in that the communication relating to the change of the restriction period is communication of information representing the length of the restriction period.

4. The power transmission device according to claim 1 or 2, characterized in that the communication relating to the change of the restriction period is a communication of information requesting negotiation with the power receiving device to determine the length of the restriction period.

5. A power receiving device A power receiving means that receives power wirelessly from a power transmission device, A communication means for communicating changes to the restriction period during which the power transmitted from the power transmission device is restricted, and during which the power transmission device measures the Quality Factor. It has, The power receiving device is characterized in that the communication means performs communication regarding the change of the restriction period based on a change in the power or voltage state of at least one of the power transmitting device and the power receiving device.

6. A power receiving device A power receiving means that receives power wirelessly from a power transmission device, A communication means for communicating changes to the restriction period during which the power transmitted from the power transmission device is restricted, and during which the power transmission device measures the Quality Factor. It has, The power receiving device is characterized in that the communication means performs communication regarding the change of the restriction period based on a change in the temperature state of at least one of the power transmitting device and the power receiving device.

7. The power receiving device according to claim 5 or 6, characterized in that the communication relating to the change of the restriction period is the communication of information representing the length of the restriction period.

8. The power receiving device according to claim 5 or 6, characterized in that the communication relating to the change of the restriction period is a signal communication requesting negotiation with the power receiving device to determine the length of the restriction period.

9. A method used by power transmission equipment, A detection process that performs detection of foreign objects based on a Quality Factor measured during a restricted period in which the transmitted power is limited, A power receiving device and a communication process that performs communication regarding the change of the restriction period. It has, A method characterized in that, in the communication step, communication relating to a change in the restriction period is performed based on a change in the power or voltage state of at least one of the power transmitting device and the power receiving device.

10. A method used by power transmission equipment, A detection process that performs detection of foreign objects based on a Quality Factor measured during a restricted period in which the transmitted power is limited, A power receiving device and a communication process that performs communication regarding the change of the restriction period. It has, A method characterized in that, in the communication step, communication relating to a change in the restriction period is made based on a change in the temperature state of at least one of the power transmission device and the power receiving device.

11. A method performed by a power receiving device, The power receiving process involves receiving power wirelessly from the power transmission equipment, A communication process which involves communication regarding a change in the restriction period during which the power transmitted from the power transmission device is restricted, and the power transmission device measures the Quality Factor. It has, A method characterized in that, in the communication step, communication relating to a change in the restriction period is performed based on a change in the power or voltage state of at least one of the power transmitting device and the power receiving device.

12. A method performed by a power receiving device, The power receiving process involves receiving power wirelessly from the power transmission equipment, A communication process which involves communication regarding a change in the restriction period during which the power transmitted from the power transmission device is restricted, and the power transmission device measures the Quality Factor. It has, A method characterized in that, in the communication step, communication relating to a change in the restriction period is made based on a change in the temperature state of at least one of the power transmission device and the power receiving device.

13. A program for causing a computer to perform the method described in claim 9 or 10.

14. A program for causing a computer to perform the method according to claim 11 or 12.

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