Power transmission device and method performed by power transmission device

Abstract

To suppress lowering of the detection accuracy of foreign substance detection.SOLUTION: A power reception device can receive power transmitted from a power transmission device that can execute first foreign substance detection and second foreign substance detection. The power reception device transmits, to the power transmission device, data used for the power transmission device to execute the first foreign substance detection, determines, before transmitting the data, whether a predetermined condition for the power transmission device to execute the second foreign substance detection different from the first foreign substance detection is satisfied, and transmits, to the power transmission device, a signal for executing the second foreign substance detection according to the determination.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power receiving device.

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. In Patent Document 1, a power transmission device and a power receiving device compliant with the standard (hereinafter referred to as the Wireless Power Consortium standard (WPC standard)) formulated by the wireless charging standardization organization Wireless Power Consortium are disclosed. Further, Patent Document 2 discloses foreign object detection in the WPC standard.

[0003] The WPC standard adopts a foreign object detection method called the Power Loss method. In the Power Loss method, first, the power loss in a state where there is no foreign object between the power transmission device and the power receiving device is calculated in advance from the difference between the power transmitted from the power transmission device and the power received by the power receiving device. Then, the power transmission device executes calibration processing assuming that the calculated value is the power loss in the normal state (state without foreign object) during power transmission. Moreover, when the power loss between the power transmission device and the power receiving device calculated during subsequent power transmission exceeds a threshold value from the reference power loss in the normal state, it is determined that "there is a foreign object".

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in reality, there may be a case where, despite the presence of a foreign object between the power transmission device and the power reception device, the calibration process described above is executed as if no foreign object is present. In this case, since the presence or absence of the foreign object is determined based on the power loss in the state where the foreign object is present, there is a problem that the detection accuracy of foreign object detection by the power transmission device decreases.

[0006] The present invention has been made in view of the above problems, and an object thereof is to suppress a decrease in the detection accuracy of foreign object detection.

Means for Solving the Problems

[0007] In order to solve the above problems, one aspect of the power reception device according to the present invention is a power reception device capable of receiving power transmitted from a power transmission device capable of performing first foreign object detection and second foreign object detection, and includes a first transmission means for transmitting data used by the power transmission device to perform the first foreign object detection to the power transmission device; a determination means for determining whether or not a predetermined condition for the power transmission device to perform the second foreign object detection, which is different from the first foreign object detection, is satisfied before the first transmission means transmits the data; and a second transmission means for transmitting a signal for causing the power transmission device to perform the second foreign object detection in accordance with the determination of the determination means.

Effects of the Invention

[0008] According to the present invention, it is possible to suppress a decrease in the detection accuracy of foreign object detection.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and duplicate explanations are omitted.

[0011] <First Embodiment> <1. Foreign Object Detection Based on the Power Loss Method> Foreign object detection based on the Power Loss method defined in the Wireless Power Consortium standard (WPC standard) (hereinafter referred to as the first foreign object detection) will be described with reference to FIG. 11. The horizontal axis in FIG. 11 is the power transmitted by the power transmission device, and the vertical axis is the power received by the power receiving device. Note that a foreign object is an object that is not a power receiving device, and is, for example, an object such as a metal piece having conductivity.

[0012] First, the power transmission device transmits power to the power receiving device at the first power transmission value Pt1. Here, it is assumed that the power receiving device receives power at the first power reception value Pr1 (referred to as the Light Load state). Here, the power transmission device stores the first power transmission value Pt1. Here, the first power transmission value Pt1, or the first power reception value Pr1, is the minimum power. Also, here, the power receiving device controls the load so that the received power becomes the minimum power. For example, the power receiving device may disconnect the load so that the received power is not supplied to the load (such as a charging circuit and a battery).

[0013] Subsequently, the power receiving device reports the power value Pr1 of the first received power to the power transmission device. The power transmission device that has received Pr1 from the power receiving device calculates that the power loss between the power transmission device and the power receiving device is Pt1 - Pr1 (Ploss1), and can create a calibration point 1100 (point 1100) indicating the correspondence between Pt1 and Pr1.

[0014] Subsequently, the power transmission device changes the power transmission value to the second power transmission value Pt2 and transmits power to the power receiving device. Here, it is assumed that the power receiving device receives power at the second power reception value Pr2 (referred to as the Connected Load state). Here, the power transmission device stores the first power transmission value Pt2. Here, the first power transmission value Pt2, or the first power reception value Pr2, is the maximum power. Also, here, the power receiving device controls the load so that the received power becomes the maximum power. For example, the power receiving device connects the load so that the received power is supplied to the load.

[0015] Subsequently, the power receiving device reports Pr2 to the power transmission device. The power transmission device that has received Pr2 from the power receiving device calculates that the power loss between the power transmission device and the power receiving device is Pt2 - Pr2 (Ploss2), and can create a calibration point 1101 (point 1101) indicating the correspondence between Pt2 and Pr2.

[0016] Then, the power transmission device linearly interpolates point 1100 and point 1101 to create line 1102. Line 1102 shows the relationship between the transmitted power and the received power when there is no foreign object around the power transmission device and the power reception device. Thereby, based on line 1102, the power transmission device can predict the power value received by the power reception device when transmitting power at a predetermined transmitted power in a state without a foreign object. For example, when the power transmission device transmits power at the third transmitted power value Pt3, it can be inferred that from point 1103 on line 1102 where the transmitted power value is Pt3, the third received power value received by the power reception device when transmitting power at Pt3 is Pr3.

[0017] As described above, based on a plurality of combinations of the transmitted power values of the power transmission device and the received power values of the power reception device under different loads, the power loss between the power transmission device and the power reception device under different loads can be obtained. Also, by interpolating the plurality of combinations, the power loss between the power transmission device and the power reception device at all loads can be estimated. In this way, the calibration process performed by the power transmission device and the power reception device to obtain the combination of the transmitted power value and the received power value is hereinafter referred to as the Calibration process (CAL process).

[0018] Here, assume that when the power transmission device actually transmits power to the power receiving device at Pt3, the power transmission device receives a value Pr3' of the received power from the power receiving device. The power transmission device calculates a value Pr3 - Pr3' (= Ploss_FO) obtained by subtracting the actually received power value Pr3' from the power receiving device from the received power value Pr3 in the state where the foreign object does not exist. This Ploss_FO can be considered as the power loss consumed by the foreign object when a foreign object exists between the power transmission device and the power receiving device. Therefore, when the power Ploss_FO that would have been consumed by the foreign object exceeds a predetermined threshold value, it can be determined that a foreign object exists. Alternatively, the power transmission device may previously obtain the power loss Pt3 - Pr3 (Ploss3) between the power transmission device and the power receiving device from the received power value Pr3 in the state where no foreign object exists. Then, next, from the received power value Pr3' received from the power receiving device in the state where a foreign object exists, the power loss Pt3 - Pr3' (Ploss3') between the power transmission device and the power receiving device in the state where a foreign object exists is obtained. And the power Ploss_FO that would have been consumed by the foreign object may be estimated by Ploss3' - Ploss3 (= Ploss_FO).

[0019] As described above, as a method for obtaining the power Ploss_FO that would have been consumed by the foreign object, it may be obtained as Pr3 - Pr3' (= Ploss_FO), or it may be obtained as Ploss3' - Ploss3 (= Ploss_FO). In the following description of this specification, basically, the method of obtaining it as Ploss3' - Ploss3 (= Ploss_FO) will be described, but it is also applicable to the method of obtaining it as Pr3 - Pr3' (= Ploss_FO). The above is the description of foreign object detection based on the Power Loss method.

[0020] In the above CAL process, the power receiving device transmits the received power value received from the power transmitting device to the power transmitting device. This received power value needs to be the received power value in a state where there is no foreign object between the power transmitting device and the power receiving device. Only in the case of a state without a foreign object can foreign object detection by the highly accurate Power Loss method be enabled. However, in reality, when the power receiving device measures the received power value, there may be a foreign object between the power transmitting device and the power receiving device. In that case, the accuracy of foreign object detection deteriorates. Therefore, in the present embodiment, a method for preventing a decrease in the accuracy of foreign object detection by the Power Loss method when performing the CAL process in a state where there is a foreign object between the power transmitting device and the power receiving device will be described.

[0021] <2. System Configuration> Fig. 12 shows a configuration example of a wireless power transmission system (wireless charging system) according to this embodiment. This system includes a power receiving device 1 and a power transmitting device 2 in one example. Hereinafter, the power receiving device 1 is also referred to as RX1, and the power transmitting device 2 is also referred to as TX2. RX1 is a device capable of receiving power transmitted from TX2. In one example, it is an electronic device that charges a built-in battery with the received power. TX2 is an electronic device that wirelessly transmits power to RX1 placed on a charging stand 3 which is a part of TX2. Hereinafter, since the charging stand 3 is a part of TX2, the case of "placed on the charging stand 3" may be referred to as "placed on TX2". 4 is the range within which RX1 can receive power from TX2. Note that RX1 and TX2 may have functions to execute applications other than wireless charging. One example of RX1 is a smartphone, and one example of TX2 is an accessory device for charging the smartphone. RX1 and TX2 may be storage devices such as tablets, hard disk devices, and memory devices, or information processing devices such as personal computers (PCs). Also, RX1 and TX2 may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) and scanners, or image output devices such as printers, copiers, projectors, etc. Also, TX2 may be a smartphone. In this case, RX1 may be another smartphone or a wireless earphone. Also, RX1 may be a vehicle such as an automobile, and TX2 may be a charger installed in a console of an automobile, etc.

[0022] This system performs wireless power transmission using an electromagnetic induction method for wireless charging based on the WPC standard. That is, RX1 and TX2 perform wireless power transmission for wireless charging based on the WPC standard between the power receiving antenna of RX1 and the power transmitting antenna of TX2. Note that the wireless power transmission method applied to this system is not limited to the method defined by the WPC standard, and other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, methods using lasers, etc. may be used. Also, in this embodiment, it is assumed that wireless power transmission is used for wireless charging, but wireless power transmission may be performed for uses other than wireless charging.

[0023] <3. Control Flow for Power Transmission> RX1 and TX2 according to this embodiment perform communication for power transmission and reception control based on the WPC standard. In the WPC standard, a plurality of phases are defined, including a Power Transfer phase in which power transmission is executed and one or more phases before actual power transmission, and communication for power transmission and reception control required in each phase is performed.

[0024] FIG. 13 shows a sequence for performing power transmission. The phases before power transmission may include a Selection phase (S1301), a Ping phase (S1302), an Identification and Configuration phase (S1303), a Negotiation phase (S1304), and a Calibration phase (S1305) after RX1 is placed on TX2. Hereinafter, the Identification and Configuration phase is referred to as the I&C phase.

[0025] In the Selection phase (S1301), TX2 intermittently transmits an Analog Ping and detects that an object is placed on the charging stand 3 of TX2 (for example, RX1 or a conductor piece is placed on the charging stand 3). TX2 detects at least one of the voltage value and the current value of the power transmission antenna when transmitting the Analog Ping, and determines that an object exists when the voltage value is below a certain threshold or the current value exceeds a certain threshold, and then transitions to the Ping phase.

[0026] In the Ping phase, TX2 transmits a Digital Ping with more power than the Analog Ping. The magnitude of the Digital Ping is sufficient power for the control unit of RX1 mounted on TX2 to start up. RX1 notifies TX2 of the magnitude of the received power voltage. In this way, TX2 recognizes that the object detected in the Selection phase is RX1 by receiving the response from RX1 that has received its Digital Ping. When receiving the notification of the received power voltage value, TX2 transitions to the I&C phase. Also, before transmitting the Digital Ping, TX2 may measure the Q-Factor of the power transmission antenna (power transmission coil). This measurement result is used when performing foreign object detection processing (secondary foreign object detection) using the Q-value measurement method (Quality Factor method).

[0027] In the I&C phase, TX2 identifies RX1 and acquires device configuration information (capability information) from RX1. Therefore, RX1 transmits an ID Packet and a Configuration Packet to TX2. The ID Packet contains the identifier information of RX1, and the Configuration Packet contains the device configuration information (capability information) of RX1. TX2 that has received the ID Packet and the Configuration Packet responds with an acknowledge (ACK, positive response). Then, the I&C phase ends.

[0028] In the Negotiation phase, the value of the Guaranteed Power (hereinafter referred to as "GP") is determined based on the value of GP required by RX1, the power transmission capability of TX2, etc. Also, TX2 performs foreign object detection (secondary foreign object detection) using the Q-value measurement method (Quality Factor method) according to the request from RX1. Also, in the WPC standard, after once transitioning to the Power Transfer phase, a method of performing the same processing as in the Negotiation phase again according to the request of RX1 is defined. The phase of performing these processes after transitioning from the Power Transfer phase is called the Renegotiation phase.

[0029] In the calibration phase, based on the WPC standard, the above-described CAL process is performed. Also, RX1 notifies TX2 of a predetermined received power value (the received power value in the light load state / the received power value in the maximum load state), and TX2 performs adjustments for efficient power transmission. The received power value notified to TX2 can be used for foreign object detection processing (primary foreign object detection) by the Power Loss method.

[0030] In the Power Transfer phase, control for starting, continuing power transmission, and stopping power transmission due to errors or full charge is performed. Also, in this embodiment, even in the Power Transfer phase, as will be described later, the CAL process is executed as necessary. TX2 and RX1 perform communication that superimposes a signal on the electromagnetic wave transmitted from the power transmission antenna or the power reception antenna, using the same power transmission antenna (power transmission coil) and power reception antenna (power reception coil) as those used when performing wireless power transmission for these power transmission and reception controls. Note that the range in which communication is possible between TX2 and RX1 is substantially the same as the power transmission range of TX2. In one example, the communication between TX2 and RX1 is based on the WPC standard.

[0031] In the WPC standard, the magnitude of the power guaranteed when RX1 receives power from TX2 is defined by a value called GP. GP indicates a power value that guarantees the output to the load (for example, a charging circuit, battery, etc.) of RX1 even if the positional relationship between RX1 and TX2 changes and the power transmission efficiency between the power reception antenna and the power transmission antenna decreases. For example, when GP is 5 watts, even if the positional relationship between the power reception antenna and the power transmission antenna changes and the power transmission efficiency decreases, TX2 controls power transmission so that it can output 5 watts to the load in RX1.

[0032] In addition, the WPC standard stipulates a method for TX2 to detect the presence of an object (foreign object) that is not a power receiving device (near the power receiving antenna) around TX2. Specifically, there are a Power Loss method (primary foreign object detection) for detecting foreign objects based on the difference between the power transmission value of TX2 and the power reception value of RX1, and a Q-value measurement method (secondary foreign object detection) for detecting foreign objects based on the change in the quality factor (Q-value) of the power transmission antenna of TX2. The detection of foreign objects by the Power Loss method is performed during power transmission (power transfer phase, described later) based on the above-mentioned CAL processing and its data. Also, the detection of foreign objects by the Q-value measurement method is performed before power transmission (before Digital Ping transmission, Negotiation phase or Renegotiation phase, described later).

[0033] <4. Processing Sequence for Power Transmission> Next, the operations of TX2 and RX1 in S1301 to S1306 in FIG. 3 will be described using the sequence diagram in FIG. 4.

[0034] TX2 repeatedly transmits Analog Ping of the WPC standard intermittently to detect objects existing within the power transmission range (S401). TX2 executes the processes defined as the Selection phase and Ping phase of the WPC standard and waits for RX1 to be placed.

[0035] The user of RX1 brings RX1 closer to TX2 (S402) to charge RX1 (for example, a smartphone). Specifically, methods such as placing RX1 on TX2 can be considered. When TX2 detects the presence of an object within the power transmission range (S403, S404), it transmits Digital Ping of the WPC standard (S405). When RX1 receives the Digital Ping, it can recognize that TX2 has detected RX1 (S406). Also, when there is a predetermined response to the Digital Ping, TX2 determines that the detected object is RX1 and that RX1 has been placed on charging stand 3.

[0036] When TX2 detects the placement of RX1, it acquires identification information and capability information from the RX1 through communication in the I&C phase defined by the WPC standard (S407). Here, the identification information of RX1 includes the Manufacturer Code and the Basic Device ID. In addition, the capability information of RX1 includes information that can identify the corresponding version of the WPC standard, a value indicating the maximum power that RX1 can receive (Maximum Power Value), and information indicating whether RX1 has the Negotiation function of the WPC standard. Note that TX2 may acquire the identification information and capability information of RX1 by methods other than communication in the I&C phase of the WPC standard. Also, the identification information may be any other identification information that can identify the individual of RX1, such as Wireless Power ID. As the capability information, information other than the above may be included.

[0037] Subsequently, TX2 determines the value of GP with RX1 through communication in the Negotiation phase defined by the WPC standard (S408). Note that in S408, not only the communication in the Negotiation phase of the WPC standard but also other procedures for determining GP may be executed. Also, when TX2 acquires information indicating that RX1 does not support the Negotiation phase (for example, in S407), the communication in the Negotiation phase is not performed, and the value of GP may be set to a small value (for example, predefined in the WPC standard). In this embodiment, GP = 5 watts (5W).

[0038] After the GP is determined, TX2 performs the CAL process described above based on the GP. In the CAL process, RX1 transmits information including the received power in the light load state to TX2 (hereinafter referred to as first received power information) (S409). The first received power information in this embodiment is assumed to be data corresponding to the received power of RX1 when the transmission power of TX2 is 250 mW. The first received power information will be described as a received power packet (RP packet) including Received Power (mode1) defined by the WPC standard, but other messages may be used. TX2 determines whether to accept the first received power information based on the transmission state of TX2. Here, when TX2 receives the first received power information including data corresponding to the received power exceeding the transmission power, TX2 may determine not to accept the first received power information. Or, when the ratio of the received power to the transmission power is less than the threshold value, TX2 may determine not to accept the first received power information. When TX2 accepts the first received power information, it transmits an affirmative response (ACK) to RX1, and when it does not accept it, it transmits a negative response (NAK) to RX1 (S410).

[0039] Subsequently, when RX1 receives an ACK from TX2 (S410), RX1 determines whether it is possible to receive a larger power. If it is possible, in order to increase the transmission power from TX2, it transmits a transmission output change instruction including a positive value (S411). TX2 receives the above-described transmission output change instruction and, if it is possible to increase the transmission power, responds with an ACK and increases the transmission power (S412, S413). Since the GP is set to 5W in S408, the transmission of transmission output change requests (+) such as S411 and S414 is repeated until the transmission power reaches 5W.

[0040] When TX2 receives a power increase request from RX1 that exceeds GP (S414), it responds with a NAK to the power transmission output change instruction to suppress power transmission above the specified level (S415). When RX1 determines that it has reached the predetermined received power upon receiving a NAK from TX2, it transmits data including the received power in the load connection state to TX2 as second received power information (S417). In this embodiment, since GP is 5 W, the second received power information is the received power information of RX1 when the transmission power of TX2 is 5 watts. Here, the second received power information is a received power packet including Received Power (mode2) defined in the WPC standard, but other messages may be used.

[0041] TX2 calculates the power loss between TX2 and RX1 based on the received power values included in the first and second received power information and the transmission power values corresponding to each of the first and second received power information (S416). By interpolating these power losses, it is possible to calculate the power loss values between TX2 and RX1 at all transmission powers of TX2 (in this case, TX2 transmission power from 250 mW to 5 W). TX2 transmits an ACK to the second received power information from RX1 (S418), completes the Calibration phase, and transitions to the Power Transfer phase. TX2, which has determined that it can start the charging process, starts the power transmission process to RX1, and the charging of RX1 is started.

[0042] Subsequently, TX2 and RX1 perform device authentication processing (S419). If it is determined that the mutual devices are capable of supporting a larger GP, the GP may be reset to a larger value, here 15W (S420). As described above in S411 - S413, RX1 and TX2 use a transmission power change instruction, ACK, and NAK to change the transmission power in order to increase the transmission power of TX2 up to 15W (S421 - S424, S508). TX2 and RX1 execute the CAL process again for GP = 15W. Specifically, RX1 transmits a received power packet (hereinafter referred to as third received power information) including data corresponding to the received power in the load connection state of RX1 when the transmission power of TX2 is 15W (S425).

[0043] TX2 calculates the power loss between TX2 and RX1 based on the received power values included in the first, second, and third received power information and the corresponding transmission power values (S426). As a result, the power loss at all transmission powers of TX2 (in this case, TX2 transmission power from 250mW to 15W) can be estimated. When TX2 creates a calibration point using the third received power from RX1, it transmits an ACK to RX1 (S427) and completes the CAL process. TX2, having determined that it can start the charging process, starts the power transmission process to RX1 (S428).

[0044] <5. Configuration of Power Transmission Device and Power Reception Device> Subsequently, the configurations of the power transmission device and the power reception device according to this embodiment will be described. Note that the configurations described below are merely examples, and a part (in some cases, all) of the described configurations may be replaced with or omitted by other configurations that perform similar functions, and additional configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into a plurality of blocks, or a plurality of blocks may be integrated into one block. Also, each functional block shown below is assumed to have its functions implemented as a software program, but a part or all of the functions included in this functional block may be implemented in hardware.

[0045] FIG. 1 is a functional block diagram showing a configuration example of TX2 according to the present embodiment. TX2 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, and an antenna switching unit 107. In FIG. 1, the control unit 101, the power supply unit 102, the power transmission unit 103, the communication unit 104, the memory 106, and the antenna switching unit 107 are described as separate entities, but any plurality of these functional blocks may be implemented within the same chip.

[0046] The control unit 101 controls the entire TX2 by executing, for example, a control program stored in the memory 106. The control unit 101 also performs control related to power transmission control including communication for device authentication in TX2. Further, the control unit 101 may perform control for executing applications other than wireless power transmission. The control unit 101 includes, for example, one or more processors such as a CPU (Central Processor Unit) or an MPU (Microprocessor Unit). Note that the control unit 101 may be configured by dedicated hardware for specific processing such as an ASIC (Application Specific Integrated Circuit). Also, the control unit 101 may include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 101 stores information to be stored during the execution of various processes in the memory 106. Also, the control unit 101 can measure time using a timer (not shown).

[0047] The power supply unit 102 supplies power to each functional block. The power supply unit 102 is, for example, a commercial power supply or a battery. Electric power supplied from the commercial power supply is stored in the battery.

[0048] 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 generates an electromagnetic wave for power reception by the RX1 by inputting the AC frequency power to the power transmission antenna 105. 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 FETs (Field Effect Transistors). In this case, the power transmission unit 103 includes a gate driver that controls the ON / OFF of the FETs.

[0049] The power transmission unit 103 controls the intensity of the power of the electromagnetic wave to be 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 power of the electromagnetic wave, and decreasing the transmission voltage or transmission current decreases the intensity of the power of the electromagnetic wave. Also, the power transmission unit 103 performs output control of the AC frequency power so that power transmission from the power transmission antenna 105 is started or stopped based on an instruction from the control unit 101. Also, it is assumed that the power transmission unit 103 has the ability to supply power sufficient to output 15 watts (W) of power to the charging unit 206 (Fig. 2) of the RX1 compliant with the WPC standard.

[0050] The communication unit 104 communicates with the RX1 for power transmission control based on the WPC standard as described above. The communication unit 104 modulates the electromagnetic wave transmitted from the power transmission antenna 105, transmits information to the RX1, and performs communication. Also, the communication unit 104 demodulates the electromagnetic wave transmitted from the power transmission antenna 105 modulated by the RX1 to acquire the information transmitted by the RX1. That is, the communication performed by the communication unit 104 is performed with a signal superimposed on the electromagnetic wave transmitted from the power transmission antenna 105. Also, the communication unit 104 may communicate with the RX1 by communication according to a standard different from the WPC standard using an antenna different from the power transmission antenna 105, or may communicate with the RX1 by selectively using a plurality of communications.

[0051] In addition to storing the control program, the memory 106 can also store the states of TX2 and RX1 (such as the power transmission value, the power reception value, etc.). For example, the state of TX2 is acquired by the control unit 101, and the state of RX1 can be acquired by the control unit 201 of RX1 (Fig. 2) and received via the communication unit 104.

[0052] The power transmission antenna 105 has a plurality of antennas (coils). The antenna switching unit 107 selects and switches one of the plurality of antennas (coils). Alternatively, the power transmission antenna 105 may have a single power transmission antenna 105 instead of a plurality of antennas. In that case, the antenna switching unit 107 is not necessary.

[0053] Fig. 2 is a block diagram showing a configuration example of RX1 according to the present embodiment. RX1 has a control unit 201, a UI (user interface) unit 202, a power reception unit 203, a communication unit 204, a power reception antenna 205, a charging unit 206, a battery 207, a memory 208, and a switch unit 209. Note that the plurality of functional blocks shown in Fig. 2 may be realized as one hardware module.

[0054] The control unit 201 controls the entire RX1 by executing, for example, the control program stored in the memory 208. That is, the control unit 201 controls each functional unit shown in Fig. 3. Further, the control unit 201 may 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 an MPU. Note that the entire RX1 (when RX1 is a smartphone, the entire smartphone) may be controlled in cooperation with the OS (Operating System) executed by the control unit 201.

[0055] Further, the control unit 201 may be configured by hardware dedicated to specific processing such as an ASIC. Further, the control unit 201 may be configured to include an array circuit such as an FPGA compiled to execute predetermined processing. The control unit 201 causes the memory 208 to store information to be stored during the execution of various processes. Further, the control unit 201 can measure time using a timer (not shown).

[0056] The UI unit 202 performs various outputs to the user. The various outputs here refer to operations such as screen display, blinking or color change of an LED, voice output by a speaker, and vibration of the RX1 main body. The UI unit 202 is realized by a liquid crystal panel, a speaker, a vibration motor, and the like.

[0057] The power receiving unit 203 obtains, at the power receiving antenna 205, the alternating current power (alternating current voltage and alternating current) generated by electromagnetic induction caused by the electromagnetic wave radiated from the power transmitting antenna 105 of TX2. Then, the power receiving unit 203 converts the alternating current power into direct current or alternating current power of a predetermined frequency, and outputs the power to the charging unit 206 that performs a process for charging the battery 207. That is, the power receiving unit 203 supplies power to the load in RX1. The above-mentioned GP is the power that is guaranteed to be output from the power receiving unit 203. Assume that the power receiving unit 203 has the ability to supply the power for the charging unit 206 to charge the battery 207 and to supply the power sufficient to output 15 watts of power to the charging unit 206. The switch unit 209 is for controlling whether or not to supply the received power to the battery (load). If the switch unit 209 connects the charging unit 206 and the battery 207, the power received via the power receiving antenna 205 is supplied to the battery 207. That is, the switch unit 209 is a switching unit that switches whether or not to disconnect the connection between the power receiving antenna 205 and the battery 207 which is the load. If the switch unit 209 disconnects the connection between the charging unit 206 and the battery 207 with a switch, the received power is not supplied to the battery 207. Note that, in FIG. 2, the switch unit 209 is arranged between the charging unit 206 and the battery 207, but it may be arranged between the power receiving unit 203 and the charging unit 206. Alternatively, although the switch unit 209 is described as one block in FIG. 2, it is also possible to implement the switch unit 209 as a part of the charging unit 206. The communication unit 204 performs communication for power receiving control based on the WPC standard as described above with the communication unit 104 of TX2. The communication unit 204 demodulates the electromagnetic wave input from the power receiving antenna 205 to obtain the information transmitted from TX2. Then, the communication unit 204 performs communication with TX2 by superimposing a signal related to the information to be transmitted to TX2 on the electromagnetic wave by load-modulating the input electromagnetic wave. Note that the communication unit 204 may communicate with TX2 by a standard different from the WPC standard using an antenna different from the power receiving antenna 205, or may communicate with TX2 by selectively using a plurality of communications.

[0058] In addition to storing the control program, the memory 208 also stores the states of TX2 and RX1, etc. For example, the state of RX1 is acquired by the control unit 201, and the state of TX2 is acquired by the control unit 101 of TX2 and can be received via the communication unit 204.

[0059] Next, with reference to Fig. 3(A), the functional block diagram of the control unit 101 of TX2 will be described. The control unit 101 includes a communication control unit 301, a power transmission control unit 302, a foreign object detection unit 303, a power measurement unit 304, and a detection determination unit 305. The communication control unit 301 performs control communication with RX1 based on the WPC standard via the communication unit 104. For example, the communication control unit 301 receives a power reception packet including data indicating the power reception power of RX1 from RX1 and transmits a response to the power reception packet. The power transmission control unit 302 controls the power transmission unit 103 to control the power transmission to RX1.

[0060] The foreign object detection unit 303 performs first foreign object detection based on the power loss between the power transmission device and the power reception device, and second foreign object detection by measuring the Q value of the power transmission antenna 105. In the present embodiment, the foreign object detection unit 303 will be described as performing foreign object detection by the Q value measurement method as the second foreign object detection, but foreign object detection processing may be performed using other methods. For example, in TX2 equipped with an NFC (Near Feald Communication) communication function, foreign object detection may be performed using the opposing device detection function according to the NFC standard. In addition, as a function other than detecting foreign objects, the foreign object detection unit 303 can also detect that the state on TX2 has changed. For example, the increase or decrease in the number of RX1s on TX2 may be detected. Alternatively, it may be detected that RX1 on TX2 has moved.

[0061] The power measurement unit 304 measures the power output to RX1 via the power transmission unit 103, and calculates the average output power value for each unit time. The foreign object detection unit 303 performs foreign object detection processing by the Power Loss method based on the measurement result by the power measurement unit 304 and the received power information received from the power receiving device via the communication control unit 301. The detection determination unit 305 determines whether to execute foreign object detection based on at least one of the information received from RX1 and the power measured by the power measurement unit 304. Further, the detection determination unit 305 may determine at least one of which foreign object detection (at least one of the first foreign object detection and the second foreign object detection) to execute.

[0062] The communication control unit 301, the power transmission control unit 302, the foreign object detection unit 303, the power measurement unit 304, and the foreign object detection determination unit 305 have their functions realized as programs operating in the control unit 101. Each processing unit is configured as an independent program and can operate in parallel while taking synchronization between programs by event processing or the like.

[0063] Next, with reference to FIG. 3(B), a functional block diagram of the control unit 201 of RX1 will be described. The control unit 201 includes a communication control unit 351, a power measurement unit 352, a detection determination unit 353, and a power reception control unit 354.

[0064] The communication control unit 351 performs control communication with TX2 via the communication unit 204. The power measurement unit 352 measures the power received from TX2, and transmits data indicating the received power to TX2 by the communication control unit 351. The detection determination unit 353 determines at least one of whether it is necessary to execute foreign object detection on TX2 and whether to execute at least one of the first foreign object detection and the second foreign object detection, and transmits a signal for executing foreign object detection to TX2 via the communication control unit 351. The power reception control unit 354 controls the power reception unit 203 and controls the power transmission with TX2. Further, the power reception control unit 354 controls the communication unit 204 and controls the phase and parameters of the power transmission.

[0065] The functions of the communication control unit 351, the power measurement unit 352, the detection and determination unit 353, and the power reception control unit 354 are realized as programs that run in the control unit 201. Each processing unit is configured as an independent program, and can run in parallel while synchronizing the programs by event processing or the like.

[0066] <6. Example of Power Transfer Phase Processing> In the power transfer phase, power is transmitted from TX2 to RX1. A foreign object is detected by the first foreign object detection. In the first foreign object detection, the power loss (power loss in a normal state) between TX2 and RX1 in a state where there is no foreign object is calculated in advance from the difference between the power transmitted by TX2 and the power received by RX1 by the above-mentioned CAL process. Then, TX2 determines that there is a foreign object when the power loss between TX2 and RX1 calculated during the subsequent power transmission is greater than or equal to a threshold value from the power loss in the normal state that is the reference.

[0067] However, even though a foreign object actually exists between the power transmitting device and the power receiving device, the CAL process may be executed as if no foreign object exists. In this case, the presence or absence of a foreign object is determined based on the power loss in the state where the foreign object exists, and the accuracy of foreign object detection decreases. Therefore, in this embodiment, a process for preventing the accuracy of foreign object detection by the power loss method from decreasing due to the CAL process being executed even though a foreign object exists between TX2 and RX1 will be described.

[0068] In order to execute the first foreign object detection, a CAL process is executed to obtain data necessary for the first foreign object detection. Before executing this CAL process, RX1 controls TX2 to check whether a foreign object is present on the power transmitting device using the second foreign object detection method. This makes it possible to execute the CAL process in an appropriate state (a state without a foreign object). The operations of TX2 and RX1 to achieve this will be described with reference to the sequence in FIG. 5, the flow chart of the power receiving device in FIG. 6, and the flow chart of the power transmitting device in FIG. 7.

[0069] In this embodiment, consider the case where CAL processing is required again during the Power Transfer phase in which power is transmitted from TX2 to RX1. After starting power reception (S501, S601, S701), RX1 determines whether CAL processing is necessary (S502, S602). For example, when changing the transmission power to a higher power, since it is necessary to create new calibration points (e.g., 1100, 1103, 1101 in FIG. 11), it is determined that CAL processing needs to be executed. Alternatively, due to power transmission from TX2 to RX1 or the like, the temperature of TX2 or RX1 may increase, and characteristics of the circuits and components of TX2 or RX1 may change. In such a case, since fluctuations occur in the line or curve connecting the calibration points (e.g., the line connecting points 1100, 1103, 1101 in FIG. 11), RX1 may determine that CAL processing needs to be executed to update the calibration points. That is, RX1 may include a temperature sensor (not shown) and determine whether CAL processing needs to be executed based on the value of the temperature sensor. In this case, it may be determined that CAL processing needs to be executed when the value of the temperature sensor has changed by a predetermined value or more from the value at the time of the previous execution of CAL processing. Alternatively, RX1 may include a timer (not shown) and determine whether CAL processing needs to be executed according to the passage of time since power reception started or the passage of time since the previous execution of CAL processing.

[0070] Next, RX1 judges whether a predetermined condition is satisfied (S503, S603). This judges whether there is a high possibility that a foreign object is present between TX2 and RX1 (whether the predetermined condition is satisfied). For example, if a predetermined time has elapsed since the previous foreign object detection performed by the foreign object detection unit 303 shown in FIG. 3, RX1 judges that there is a high possibility that a foreign object is present between TX2 and RX1. On the other hand, if the predetermined time has not elapsed, RX1 judges that there is a low possibility that a foreign object is present between TX2 and RX1. If it is judged that there is a low possibility that a foreign object is present between TX2 and RX1 (No in S603), RX1 transmits the received power value (fourth received power information) of the received power received by RX1 to TX2 in a received power packet (RP packet) (S504, S604, S702). TX2, which has received the RP packet, judges whether the RP packet instructs the execution of CAL processing (S703). In one example, TX2 judges whether the RP packet is an instruction to execute CAL processing based on the presence or absence of an instruction to execute CAL processing or an instruction to execute first foreign object detection, which is included in the RP packet or is included in a signal different from the RP packet. TX2 creates a calibration point based on the received fourth received power information and the corresponding transmission power (S505, S704), and transmits an ACK to TX2 (S506, S705). If TX2 judges that the RP packet is an instruction to execute first foreign object detection, TX2 executes first foreign object detection (S706), and if a foreign object is detected (Yes in S707), TX2 notifies RX1 of that fact (S709) and stops power transmission (S710). If it judges that no foreign object was detected in the first foreign object detection in S706 (No in S707), TX2 notifies RX1 of that fact (S708), and returns to the process of S702.

[0071] After S604, RX1 determines whether it is necessary to perform the CAL process again after a predetermined time has elapsed (S502, S607), and determines whether certain conditions are met (S503, S608). This is to determine whether there is a high possibility of foreign matter mixing between the power transmission device and the power reception device. For example, when a predetermined time has elapsed since the previous CAL process was executed, it is determined that there is a high possibility of foreign matter mixing. Before performing the CAL process, the power transmission device uses a foreign matter detection method different from the first foreign matter detection to check whether foreign matter has mixed between TX2 and RX1. RX1 transmits, for example, an EPT packet (End Power Transfer packet) to TX2 in order to cause TX2 to execute a foreign matter detection method different from the first foreign matter detection (S505, S609, S711).

[0072] As a result, TX2 ends the Power Transfer phase and shifts to the Selection phase (S712). That is, it is reset to the state before power transmission. As a result, since the power transmission device starts processing again from the Selection phase, foreign matter detection (second foreign matter detection) by the Q value measurement method, which is executed in the Negotiation phase or the Renegotiation phase, will be executed. In this way, it is possible to perform second foreign matter detection different from the first foreign matter detection before executing the CAL process. This reduces the possibility of foreign matter mixing between TX2 and RX1 when executing the CAL process, and makes it possible to execute the first foreign matter detection with higher accuracy.

[0073] In this embodiment, in order to perform the second foreign matter detection, RX1 transmits an EPT (End Power Transfer) packet to TX2. However, signals other than the EPT packet may be used to perform the second foreign matter detection. For example, RX1 may transmit a signal instructing TX2 to shift to the Renegotiation phase. Alternatively, RX1 may instruct TX2 to transition to the Selection phase so as not to change the reference value for the second foreign matter detection.

[0074] As described above, before executing the CAL process for the first foreign object detection, the RX according to the present embodiment determines whether or not a predetermined condition for executing the second foreign object detection is satisfied. Further, when it is determined that the predetermined condition is satisfied, the TX is controlled to execute the second foreign object detection. As a result, in a state where there is a high possibility that a foreign object exists between TX2 and RX1, the possibility of executing the CAL process for the first foreign object detection is reduced, and it is possible to prevent the detection accuracy of the foreign object by the first foreign object detection from decreasing.

[0075] <Second Embodiment> In the first embodiment, when it is determined that the second foreign object detection is to be executed before executing the CAL process for the first foreign object detection, a method of controlling the power transmission device to perform the second foreign object detection by ending the Power Transfer phase has been described. In the second embodiment, a method of controlling the power transmission device to execute the second foreign object detection within a shorter time when it is determined that the CAL process necessary for executing the first foreign object detection is required will be described. Note that descriptions of the same configurations, functions, and processes as those in the first embodiment are omitted.

[0076] For the first foreign object detection, the CAL process is necessary. Before executing the CAL process, RX1 controls TX2 to check whether a foreign object has been mixed on the power transmission device using the second foreign object detection method. When the CAL process is executed during the Power Transfer phase, by also performing the second foreign object detection during the Power Transfer phase, it becomes possible to check whether a foreign object exists on the power transmission device in a shorter time compared to the first embodiment.

[0077] The operations of TX2 and RX1 for realizing this will be described with reference to the sequence of FIG. 8, the flowchart of the power receiving device in FIG. 9, and the flowchart of the power transmission device in FIG. 10.

[0078] First, TX2 starts power transmission to RX1, and RX1 starts power reception (S801, S901, S1001). After starting power reception, RX1 determines whether it is necessary to perform CAL processing (S802, S902). For example, when there is a change such as the transmission power becoming higher, it is necessary to create new calibration points (e.g., 1100, 1103, 1101 in FIG. 11), so it is determined that CAL processing is necessary. Alternatively, due to power transmission, the temperature of TX2 or RX1 rises, and fluctuations occur in the characteristics of the circuits and components of TX2 or RX1, and fluctuations may occur in the line or curve connecting the calibration points (e.g., the line connecting 1100, 1103, 1101 in FIG. 11). In this case, since it is necessary to update the calibration points, it is determined that CAL processing is necessary.

[0079] Next, it is determined whether a predetermined condition for executing the second foreign object detection is satisfied (S803, S903). This is to determine whether there is a high possibility that a foreign object exists between TX2 and RX1. For example, if a predetermined time has passed since the previous foreign object detection performed by the foreign object detection unit 303 shown in FIG. 3, it is determined that there is a high possibility that a foreign object exists between TX2 and RX1, and if the predetermined time has not passed, it is determined that there is a low possibility that a foreign object exists. If it is determined that there is a low possibility that a foreign object exists (No in S903), RX1 transmits data (fourth received power information) corresponding to the received power received by RX1 to TX2 in a received power packet (RP packet) (S804, S904). When TX2 receives the RP packet (S1002), it executes CAL processing (S805, S1003), and if there is no problem as a result of the CAL processing, it transmits ACK to TX2 (S806, S1004). Then, based on the result of the CAL process, TX2 performs foreign object detection at a predetermined timing during power transmission by the first foreign object detection (S807, S1005). After a certain time has passed, RX1 judges whether it is necessary to perform the CAL process again (S808, S902) and judges whether a predetermined condition is satisfied (S903, S809). This judges whether there is a high possibility that a foreign object exists between TX2 and RX1. In this case, if the elapsed time exceeds a predetermined time, it is judged that there is a high possibility of a foreign object being mixed in, and before performing the CAL process, TX2 confirms that there is no foreign object between TX2 and RX1 using a foreign object detection method other than the power loss method. To do this, RX1 instructs TX2 to suspend power transmission (S905, S810). When TX2 receives the instruction to suspend power transmission (S1006), it suspends power transmission (S1007, S811). Then, RX1 requests TX2 to perform foreign object detection (second foreign object detection) using the Q-value measurement method (S906, S812). Then, RX1 controls the switch unit 209 to disconnect the load (battery, etc.) (S907, S813). This is because if the load of RX1 is connected when the second foreign object detection is performed, foreign object detection cannot be performed or the accuracy of foreign object detection decreases.Then, when TX2 receives an execution instruction for foreign object detection by the Q - factor measurement method (S1008, S812), it performs foreign object detection by the Q - factor measurement method (S1009, S814). After a predetermined time has elapsed for TX2 to perform foreign object detection by the Q - factor measurement method, RX1 connects a load (S908, S815). If as a result of the second foreign object detection, TX2 does not detect a foreign object (No in S1010), TX2 notifies RX1 that no foreign object has been detected (S1011, S816). When RX1 receives a notification from TX2 that no foreign object has been detected (No in S909), it instructs TX2 to resume power transmission (S910, S817). When TX2 receives the power transmission resume instruction (S1012), it resumes power transmission (S1013). If it is confirmed in the second foreign object detection that there is no foreign object between TX2 and RX1, RX1 returns the process to S902, determines whether to perform the CAL process (S902, S818), and determines whether a predetermined condition is satisfied (S903, S819). When RX1 determines that the predetermined condition is satisfied, it decides to perform the CAL process, and RX1 transmits data (fifth received power information) for executing the CAL process to TX2 via RP (S904, S820). When TX2 receives the RP (S1002, S820), it calculates the power loss and executes the CAL process (S1003, S821), and transmits an ACK to RX1 (S1004, S822). If TX2 detects a foreign object in S1010, it notifies RX1 that a foreign object has been detected (S1015) and stops power transmission (S1016). When RX1 receives a notification that a foreign object has been detected from the power transmission device (Yes in S909), it transmits an EPT packet to TX2 (S911) and may stop power transmission. As described above, according to this embodiment, it is possible to perform a second foreign object detection different from the first foreign object detection in a shorter time before performing the CAL process for the first foreign object detection. Thereby, it is possible to prevent a foreign object from being mixed between TX2 and RX1 when the CAL process is executed and the accuracy of the first foreign object detection from decreasing.

[0080] <Third Embodiment> In the second embodiment, when performing foreign object detection by the Power Loss method, a stop packet that requests a temporary stop (momentary interruption) of power transmission is transmitted to the power transmission device, and the power transmission device is controlled to perform the Q-value measurement method before performing the CAL process required for foreign object detection. In the third embodiment, without adding a new packet (protocol) to the existing WPC standard, control is performed so that the second foreign object detection is performed during the Power Transfer phase, and a method for checking whether a foreign object has entered the power transmission device in a shorter time is described. Thereby, compatibility can be ensured while reducing the verification required by adding a new packet (protocol). Note that descriptions of configurations, functions, or processes similar to those of the first or second embodiment are omitted.

[0081] Hereinafter, the operations of TX2 and RX1 according to this embodiment will be described using the flowchart of RX1 in FIG. 15, the flowchart of TX2 in FIG. 16, and the processing sequence in FIG. 14.

[0082] First, TX2 starts power transmission to RX1, and RX1 starts power reception (S1501, S1601, S1401). After starting power reception, RX1 determines whether it is necessary to execute the CAL process (S1502, S1402). For example, when there is a change such that the transmission power becomes higher, it is necessary to create new Calibration points (e.g., 1100, 1103, 1101 in FIG. 11), so it is determined that it is necessary to execute the CAL process. Alternatively, due to power transmission, the temperature of TX2 or RX1 may rise, causing variations in the characteristics of the circuit and components, and there may be variations in the line or curve connecting the calibration points (e.g., the line connecting 1100, 1103, 1101 in FIG. 11). In this case, RX1 determines that it is necessary to execute the CAL process to update the calibration points. Next, RX1 determines whether a predetermined condition for performing the second foreign object detection is satisfied (S1503, S1403). This determines whether there is a high possibility that a foreign object has entered between TX2 and RX1. For example, if the predetermined time has not elapsed since the previous foreign object detection (first or second foreign object detection) performed by the foreign object detection unit 303 shown in FIG. 3, RX1 determines that the possibility of a foreign object entering between TX2 and RX1 is low. And if the predetermined time or more has elapsed since the previous foreign object detection, RX1 determines that the possibility of a foreign object entering between TX2 and RX1 is high.

[0083] When it is determined that the possibility of foreign matter intrusion is low, RX1 transmits the received power value (fourth received power information) of the received power received by RX1 to TX2 via RP (S1504, S1404). TX2 receives RP (S1602) and executes CAL processing (S1603, S1405). Then, TX2 determines whether the received power value in the received Received Power Packet and the calculated power loss value are appropriate (S1604, S1506). This determination is made based on, for example, whether the received power value in the received RP is greater than a predetermined threshold, whether the value of the calculated power loss value is greater than a predetermined threshold, etc. As a result of the determination, if TX2 determines that there is no problem with the received power value in the received RP, TX2 transmits an ACK to RX1 (S1605, S1507). Then, during power transmission, TX2 performs first foreign matter detection based on the Power Loss method, which is the first foreign matter detection method, at a predetermined timing (S1606, S1422). After a predetermined time, RX1 determines again whether it is necessary to execute CAL processing (S1502, S1408). If it is determined that CAL processing needs to be performed, next, it is determined whether a predetermined condition is satisfied (S1503, S1409). If it is determined that the possibility of foreign matter intrusion is high, such as when a long time has elapsed since the previous foreign matter detection was performed, RX1 transmits a signal to cause TX2 to perform second foreign matter detection. For example, instead of the received power value of the received power received by RX1, an RP packet is transmitted to TX2 with a value determined to be inappropriate for TX2 as the received power value. This value may be, for example, the maximum value or the minimum value of the received power value that can be set in the RP packet, or a predetermined value for causing TX2 to perform second foreign matter detection. Alternatively, it is also possible to cause TX2 to perform second foreign matter detection by continuously transmitting RP packets to TX2 a plurality of times within a predetermined time.

[0084] Then, based on the information included in the received RP, TX2 performs a CAL process (power loss value calculation) (S1603, S1411). Then, TX2 determines whether the received power value in the received RP or the calculated power loss value is appropriate (S1604, S1412). At this time, as described above, when RX1 transmits the RP with a value that TX2 determines is inappropriate as the received power value, TX2 will determine that the received power value in the RP or the calculated power loss value is inappropriate. That is, by RX1 transmitting to TX2 in the RP a clearly abnormal value as the received power value, TX2 can recognize that RX1 is requesting the execution of the second foreign object detection. Similarly, when RX1 transmits to TX2 in the RP a predetermined value as the received power value to cause TX2 to execute the second foreign object detection, TX2 can also recognize that RX1 is requesting the execution of the second foreign object detection. Alternatively, by RX1 causing TX2 to hold information for requesting the execution of the second foreign object detection in a location in the RP that holds information other than the received power value, TX2 can recognize that RX1 is requesting the execution of the second foreign object detection. Then, TX2 transmits a NAK for the received RP to RX1 (S1607, S1413). Thereby, RX1 can recognize that TX2 is about to perform the second foreign object detection by the Q - factor measurement method.

[0085] RX1, having recognized that TX2 is about to perform the second foreign object detection, controls the switch unit 209 to disconnect the load (such as a battery) (S1506, S1414). This is because when performing foreign object detection by the Q - factor measurement method, if the load of RX1 is in a connected state, the foreign object detection by the Q - factor measurement method cannot be performed or the accuracy of the foreign object detection decreases. Therefore, when TX2 performs foreign object detection other than the Q - factor measurement method where load disconnection is not required, the process of S1414 is not necessary.

[0086] Then, TX2 performs foreign object detection by the Q - factor measurement method, which is the second foreign object detection method (S1608, S1415). Then, after RX1 waits for a predetermined time for TX2 to perform foreign object detection by the Q - factor measurement method, it controls the switch unit 209 to reconnect the load (such as a battery) (S1507, S1416). Then, as a result of performing foreign object detection by the Q - factor measurement method, TX2 determines whether a foreign object has been detected (S1609, S1417). If TX2 does not detect a foreign object, it starts power transmission. At this time, TX2 may notify RX1 that no foreign object has been detected. RX1 determines whether there is a notification from TX2 that a foreign object has been detected (S1507). If there is no notification within a predetermined time, it determines that no foreign object has been detected and returns to S1502. Alternatively, if there is a notification from TX2 that no foreign object has been detected, it may determine that no foreign object has been detected and return to S1502. Here, if TX2 detects a foreign object in S1609, TX2 notifies RX1 that a foreign object has been detected (S1610). When RX1 receives a notification from TX2 that a foreign object has been detected, it may transmit EPT to TX2 (1509) and stop power transmission.

[0087] RX1 determines that CAL processing needs to be performed at S1502. When TX2 determines that there is no foreign object as a result of performing the second foreign object detection, it determines at S1503 that a predetermined condition is satisfied (the possibility of foreign object mixing is low). Then, again at S1504, RP (the fifth received power information) is transmitted to TX2 (S1504, S1418). The received power value of the received power received by RX1 is stored in the RP at this time. TX2 receives the RP (S1602, S1418), performs CAL processing based on the received RP (S1603, S1419), and determines whether the value of the received power value in the received RP or the calculated power loss value is appropriate (S1604, S1420). When it is determined to be appropriate and the CAL processing is completed, TX2 transmits an ACK to RX1 (S1605, S1421). Then TX2 performs power transmission to RX1 and executes the first foreign object detection based on the result of the above-described CAL processing at a predetermined timing (S1606).

[0088] In the above-described embodiment, TX2 determined whether to perform the first foreign object detection or the second foreign object detection based on the RP information from RX1 at S1604. However, TX2 may determine which foreign object detection to perform. That is, TX2 may make a determination in the same manner as in S1502 and S1503, and transmit an ACK when it determines to perform the first foreign object detection (S1605), and transmit a NAK when it determines to perform the second foreign object detection (S1607).

[0089] From the above, it becomes possible to check in a short time whether a foreign object has entered the power transmission device by performing the second foreign object detection before executing the CAL processing without adding a new packet (protocol) type to the existing WPC standard.

[0090] <Fourth Embodiment> In the second and third embodiments, before executing the CAL process used in the first foreign object detection, a method for checking the presence or absence of a foreign object between TX2 and RX1 by a second foreign object detection different from the first foreign object detection was described. In one example, the order of executing the CAL process and the second foreign object detection may be reversed, and after executing the CAL process for the first foreign object detection, the presence or absence of a foreign object between TX2 and RX1 may be checked by a second foreign object detection different from the first foreign object detection. This is because when the second foreign object detection is executed after the execution of the CAL process and it is determined that there is a foreign object between TX2 and RX1, by re-executing the CAL process, it is possible to prevent the first foreign object detection from being executed using the result of the CAL process in a state where there is a foreign object.

[0091] The operations of TX2 and RX1 when the order of executing the CAL process and the second foreign object detection in the second embodiment according to this embodiment is reversed are shown in the processing sequence diagram of RX1 and TX2 in FIG. 17 and the flowchart of RX1 in FIG. 18. Regarding the processing of TX2, it is the same as the flowchart of TX2 according to the second embodiment shown in FIG. 8. Also, in the processing sequence diagram of FIG. 17 and the flowchart of FIG. 18, the same processing as in FIGS. 8 and 9 uses the same reference numerals and the description is omitted.

[0092] When RX1 determines that a predetermined condition for executing the second foreign object detection is satisfied (Yes in S903), it transmits a Received Power Packet (RP) including received power information for the CAL process to TX2 (S1801, S820). TX2 that has received the RP calculates a power loss value based on the received power information (fifth received power information) included in the RP and executes the CAL process (S821). Also, RX1 performs a process of requesting TX2 to perform the second foreign object detection (S906, S812), and when TX2 detects a foreign object by the second foreign object detection (Yes in S909), it transmits an EPT (S911) and causes the CAL process to be executed again. Thereby, it is possible to prevent the first foreign object detection from being performed based on the reference power by the CAL process in a state where a foreign object exists between TX2 and RX1.

[0093] In this embodiment, although the CAL process is executed immediately when TX2 receives RP in S1801, as an example, the execution of the CAL process may be waited for a predetermined time. For example, if TX2 does not receive a request to suspend power transmission or execute second foreign object detection from RX1 within a predetermined time after receiving RP, the CAL process may be executed using the received RP. And when TX2 receives a request to suspend power transmission or execute second foreign object detection from RX1, the CAL process may be executed after the second foreign object detection. Note that in this case, TX2 calculates the power loss value and transmits ACK before the second foreign object detection, but the creation of the calibration point may be after the second foreign object detection. That is, the creation of the calibration point may be after the process of S1010 when no foreign object is detected by the second foreign object detection (No in S1010).

[0094] Also, as an example, RX1 that has received a notification from TX2 indicating that a foreign object has been detected in S909 may delete the calibration point created in S1801 in S911.

[0095] Alternatively, TX2 that has transmitted a notification to RX1 indicating that a foreign object has been detected in S816 of FIG. 17 may perform control so as not to perform the first foreign object detection using the area corresponding to the calibration point created in S821. For example, in the example of FIG. 11, after creating the calibration point 1101 in S821 of FIG. 17, TX2 that has detected a foreign object in S816 may not transmit power at a transmission power greater than Pt3 until the CAL process for Pt2 is re-executed. Alternatively, TX2 may not perform the first foreign object detection while transmitting power at a transmission power greater than Pt3.

[0096] Thereby, it is possible to prevent the detection accuracy of the first foreign object detection from decreasing because the first foreign object detection can be prevented from being performed based on the CAL process executed in a state where there is a high possibility that a foreign object exists between TX2 and RX1.

[0097] <Fifth Embodiment> In the fourth embodiment, the order of performing the CAL process and the second foreign object detection in the second embodiment is reversed. After executing the CAL process for the first foreign object detection, the process of confirming the presence or absence of a foreign object between TX2 and RX1 by the second foreign object detection different from the first foreign object detection was described. In this embodiment, the processing of TX2 and RX1 when the order of performing the CAL process and the second foreign object detection in the third embodiment is reversed will be described.

[0098] The operations of TX2 and RX1 when the order of executing the CAL process and the second foreign object detection in the third embodiment according to this embodiment is reversed are shown in the processing sequence diagrams of RX1 and TX2 in FIG. 19 and the flowchart of RX1 in FIG. 20. Regarding the processing of TX2, it is the same as the flowchart of TX2 according to the third embodiment shown in FIG. 16. Also, in FIGS. 19 and 20, the same processing as in FIGS. 14 and 15 of the third embodiment uses the same reference numerals and the description thereof is omitted.

[0099] When RX1 determines that a predetermined condition for executing the second foreign object detection is satisfied (Yes in S1503), it transmits a Received Power Packet (RP) including received power information for the CAL process to TX2 (S2001, S1418). TX2 that has received the RP calculates a power loss value based on the received power information (the fifth received power information) included in the RP and executes the CAL process (S1419). Also, RX1 transmits an RP or a predetermined signal requesting the second foreign object detection to TX2 (S1505, S1410). When TX2 detects a foreign object by the second foreign object detection (Yes in S1508), it transmits an EPT (S1509) to cause the CAL process to be executed again. This can prevent the first foreign object detection from being performed based on the reference power by the CAL process in a state where a foreign object exists between TX2 and RX1.

[0100] Note that in this embodiment, it is assumed that the CAL process is executed immediately when TX2 receives the RP in S1411. However, as an example, the execution of the CAL process may be waited for a predetermined time. Since this is the same as in the fourth embodiment, the description thereof is omitted.

[0101] Also, in this embodiment as well, when TX2 is configured to perform second foreign object detection when receiving power reception power packets continuously within a predetermined time, similar to the third embodiment, it is not necessary to include an instruction to execute second foreign object detection in the power reception power packet.

[0102] <Sixth Embodiment> In the second embodiment, before instructing the execution of the CAL process used in the first foreign object detection, the process of confirming the presence or absence of a foreign object between TX2 and RX1 by second foreign object detection different from the first foreign object detection was described.

[0103] In the fourth embodiment, after instructing the execution of the CAL process used in the first foreign object detection, the process of confirming the presence or absence of a foreign object between TX2 and RX1 by second foreign object detection different from the first foreign object detection was described.

[0104] In this embodiment, by combining the second embodiment and the fourth embodiment, the process of confirming the presence or absence of a foreign object between TX2 and RX1 by second foreign object detection different from the first foreign object detection is described before and after instructing the execution of the CAL process used in the first foreign object detection.

[0105] Note that the same reference numerals are used for the same processes, configurations, and functions as in the first to fifth embodiments, and the description thereof is omitted.

[0106] The processes of S2101 to S2108 in FIG. 21 are the same as the processes of S810 to S817, so the description thereof is omitted. Also, the processes of 2201 to S2206 in FIG. 22 are the same as the processes of S905 to S910, so the description thereof is omitted.

[0107] As shown in FIGS. 21 and 22, by performing second foreign object detection before and after TX2 executes the CAL process, it becomes possible to detect that a foreign object has entered or been removed between TX2 and RX1 during the execution of the CAL process. As a result, the validity of the result of the CAL process can be judged with higher accuracy.

[0108] <Seventh Embodiment> In the third embodiment, before instructing the execution of the CAL process used in the first foreign object detection, the process of checking for the presence or absence of a foreign object between TX2 and RX1 in the second foreign object detection different from the first foreign object detection was described.

[0109] In the fifth embodiment, after instructing the execution of the CAL process used in the first foreign object detection, the process of checking for the presence or absence of a foreign object between TX2 and RX1 in the second foreign object detection different from the first foreign object detection was described.

[0110] In this embodiment, by combining the third and fifth embodiments, the process of checking for the presence or absence of a foreign object between TX2 and RX1 in the second foreign object detection different from the first foreign object detection is described before and after instructing the execution of the CAL process used in the first foreign object detection.

[0111] Note that the same reference numerals are used for the same processes, configurations, and functions as in the first to fifth embodiments, and the description thereof is omitted.

[0112] The processes of S2301 and S2302 in FIG. 23 are the same as the processes of S1610 and S1510, so the description thereof is omitted. Also, S2303 to S2309 in FIG. 23 are the same as the processes of S1410 to S1416 and S2301, S2302, so the description thereof is omitted. Also, the processes of S2401 to S2405 in FIG. 24 are the same as the processes of S1505 to S1510, so the description thereof is omitted.

[0113] As shown in FIGS. 23 and 24, by performing the second foreign object detection before and after TX2 executes the CAL process, it becomes possible to detect that a foreign object has entered or been removed between TX2 and RX1 while the CAL process is being executed. As a result, the validity of the CAL process result can be determined with higher accuracy.

[0114] <Other Embodiments> The above-described first to seventh embodiments can be arbitrarily combined. For example, the second embodiment and the third embodiment may be combined, and the power receiving device may be instructed to perform second foreign object detection in different ways according to the model of the power transmitting device, the version of the corresponding WPC standard, and the like.

[0115] In the above-described embodiments, as the second foreign object detection different from the first foreign object detection, the Q-value measurement method (Q-FACTOR MEASUREMENT) was cited. As a method for measuring the Q-value of the power transmission antenna (power transmission coil), there is a method of transmitting a signal of a resonance frequency (for example, a sine wave, a rectangular wave, etc.) for a predetermined time and measuring the Q-value at the resonance frequency. Alternatively, there is a method of transmitting signals of a plurality of frequencies near the resonance frequency a plurality of times and measuring their Q-values. Alternatively, there is a method of transmitting a signal (for example, a pulse wave) having at least a part of the frequency components of a plurality of frequencies to be measured once, and performing arithmetic processing (for example, Fourier transform) on the measurement result to measure the Q-values at a plurality of frequencies. Alternatively, the above-described signal (electromagnetic wave) may be output, and then the output of the signal may be stopped, and foreign object detection may be performed based on the attenuation state of the signal waveform (electromagnetic wave waveform) (hereinafter referred to as the waveform attenuation method). When the attenuation state of the waveform is large, it is possible to determine that there is a foreign object. For example, after the output of the electromagnetic wave is stopped, when the waveform amplitude at time T1 is A1 and the waveform amplitude at time T2 after a predetermined time has elapsed is A2, the second foreign object detection may be performed based on whether the ratio of the waveform amplitudes A1 and A2 is larger than a predetermined value. Alternatively, the second foreign object detection may be performed using the difference between the waveform amplitudes A1 and A2, the slope of the waveform attenuation (A1 - A2) / (T2 - T1), the time until the waveform becomes equal to or less than a predetermined amplitude, and the like. Alternatively, when the frequency of the electromagnetic wave waveform is f, Q = πf(T2 - T1) / ln(A1 / A2) Since it is obtained from the above, foreign object detection may be performed based on this. Alternatively, the sharpness of resonance (Q-value) may be obtained from the measurement results at the above-described respective frequencies, and foreign object detection may be performed based on this.

[0116] On the other hand, for the second foreign object detection, it is only necessary to check that there is no foreign object between TX2 and RX1 so as not to execute the first foreign object detection (foreign object detection by the Power Loss method) using the Calibration result in a state where there is a foreign object between TX2 and RX1. Therefore, a foreign object detection method other than the Q value measurement method (Q-FACTOR MEASUREMENT) may be applied as the second foreign object detection.

[0117] For example, in addition to the Q value of the power transmission antenna, measurement results such as the resonance frequency of the power transmission antenna, the sharpness of the resonance curve, or the inductor value, the coupling coefficient between the power transmission antenna and the object placed on the power transmission device, and the electrical characteristics of the power transmission unit including the power transmission antenna of the power transmission device may be used. Also, they may determine the presence or absence of a foreign object based on the measurement results of the electrical characteristics at one frequency, or may determine the presence or absence of a foreign object based on the measurement results of the electrical characteristics at a plurality of frequencies.

[0118] Note that as a method for measuring the electrical characteristics at a plurality of frequencies, it is possible to realize by transmitting signals (for example, sine waves, rectangular waves, etc.) at each frequency for which the electrical characteristics are to be measured a plurality of times and measuring the electrical characteristics in the signals at each frequency. This method has the effect that measurement can be performed with relatively little arithmetic processing in the power transmission device.

[0119] Alternatively, by transmitting a signal (for example, a pulse wave) having all frequency components at a plurality of frequencies for which the electrical characteristics are to be measured once and performing arithmetic processing (for example, Fourier transform) on the measurement result, the electrical characteristics at a plurality of frequencies can be calculated.

[0120] Alternatively, by transmitting signals having some frequency components at a plurality of frequencies for which the electrical characteristics are to be measured a plurality of times and performing arithmetic processing (for example, Fourier transform) on the measurement results, the electrical characteristics at a plurality of frequencies can be calculated. This method has the effect that measurement can be performed in a relatively short time because the number of times of transmitting the signal for measurement can be reduced.

[0121] Alternatively, as a second foreign object detection method, measurement results of sensors such as a photoelectric sensor, an eddy current displacement sensor, a contact displacement sensor, an ultrasonic sensor, an image discrimination sensor, and a weight sensor mounted on the power transmission device may be used.

[0122] Also, in the first to seventh embodiments, a method of confirming the presence or absence of a foreign object between TX2 and RX1 by a second foreign object detection different from the first foreign object detection before executing the calibration process for the first foreign object detection during the Power Transfer phase was described. However, during the Calibration phase, before executing the calibration process, confirming the presence or absence of a foreign object between TX2 and RX1 by a second foreign object detection different from the first foreign object detection described in the first to seventh embodiments can also obtain the same effect. That is, by applying the first to seventh embodiments to the calibration process during the Calibration phase, the possibility of a foreign object being mixed between TX2 and RX1 during the CAL process can be reduced. Also, in the first to seventh embodiments, the Power Loss method was cited as the first foreign object detection. And the Calibration process (CAL process) was described as estimating the power loss between the power transmission device and the power reception device at different loads when there is no foreign object between the power transmission device and the power reception device. However, this Calibration process is, in a broad sense, a process for acquiring parameters between the power transmission device and the power reception device necessary for foreign object detection in a state where there is no foreign object between the power transmission device and the power reception device. Therefore, a foreign object detection other than the Power Loss method may be applied as the first foreign object detection. For example, foreign object detection by the Q-value measurement method (Q-FACTOR MEASUREMENT) or the waveform attenuation method described above may be used as the first foreign object detection. And in the Calibration process, the Q-value and the waveform attenuation state in a state where there is no foreign object may be measured. And based on the results, the threshold value etc. of the first foreign object detection may be determined, and the same effect can be obtained even when performing foreign object detection.

[0123] The present invention can also be realized by supplying a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, an ASIC) that implements one or more functions.

[0124] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0125] 1: Power receiving device, 2: Power transmitting device, 3: Charging stand, 4: Power transmission range

Claims

Claim 1 A power receiving device capable of receiving power transmitted from a power transmitting device capable of performing first foreign object detection and second foreign object detection, first transmission means for transmitting data used by the power transmitting device to perform the first foreign object detection to the power transmitting device; determination means for determining whether a predetermined condition for the power transmitting device to perform the second foreign object detection, which is different from the first foreign object detection, is satisfied before the first transmission means transmits the data; second transmission means for transmitting a signal for causing the power transmitting device to perform the second foreign object detection according to the determination of the determination means; A power receiving device characterized by comprising the same.

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