Method performed by power transmission device, and power transmission device

Abstract

To improve the accuracy of calculating a parameter used for a determination as to whether a foreign substance is present.SOLUTION: A method includes: a first reception step of receiving, from a power receiving device, a first received power packet including information indicating the value of first received power; a first transmission step of transmitting acknowledgement or negative acknowledgement to the first received power packet on the basis of values indicated by a plurality of control error packets received from the power receiving device; a second reception step of, after the acknowledgement is transmitted in the first transmission step, receiving, from the power receiving device, a second received power packet including information indicating the value of second received power; a second transmission step of transmitting acknowledgement or negative acknowledgement to the second received power packet on the basis of values indicated by a plurality of control error packets received after the acknowledgement is transmitted in the first transmission step; and processing step of performing foreign substance detection processing after the second transmission step.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method performed by a power transmitting device and to a power transmitting device. [Background technology]

[0002] In recent years, technological development of wireless power transmission systems such as wireless charging systems has been widely carried out. Patent Document 1 discloses a power transmission device that complies with a standard (hereinafter referred to as the "WPC standard") established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging. Patent Document 1 also describes that the WPC standard specifies a calibration process in order to improve the accuracy of detection of conductive objects (hereinafter referred to as foreign objects) such as metal pieces that are not targets of power transmission near a power transmission antenna (coil).

[0003] In the calibration process, the transmission power of the power transmitting device and the corresponding received power of the power receiving device are acquired in each of two different states of the power receiving device. Then, using these two sets of transmission power and received power, a parameter for calibrating the received power or the transmitted power when the power is actually transmitted wirelessly is calculated. This parameter is used in the detection process of a foreign object. That is, for example, the received power calibrated using the above-mentioned parameter can be estimated for the received power when the power is transmitted wirelessly by the power transmitting device, and the power loss, which is the difference between the actual transmission power of the power transmitting device and the estimated received power, can be calculated. Then, if this power loss exceeds a predetermined value, it is possible to determine that there is a power loss due to a foreign object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-070074 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the transmission power in the power transmitting device and the power loss between the power transmitting device and the power receiving device are not always constant. For example, the power transmitting unit of the power transmitting device uses a switching circuit composed of switching elements (for example, field effect transistors, hereinafter referred to as FETs) to convert DC voltage or current into AC voltage or current. The switching circuit includes a half-bridge circuit composed of two FETs and a full-bridge circuit composed of four FETs, and it is widely known that the switching circuit of the power transmitting unit operates by switching between these two circuits depending on the magnitude of the transmission power. Then, due to this operation, the power consumed by the switching circuit of the power transmitting unit or the power transmitted by the power transmitting antenna may temporarily fluctuate greatly and become unstable. In addition, for example, when the power receiving device placed on the power transmitting device is a smartphone, it is assumed that the position shift occurs due to vibration or the like, and the received power becomes unstable. When the above parameters calculated using the transmission power and the received power under such a situation are used for foreign object judgment during power transmission processing, there is a possibility that the foreign object cannot be detected or the foreign object may be erroneously detected.

[0006] An object of the present invention is to improve the accuracy of calculating parameters used to determine whether or not a foreign object is present. [Means for solving the problem]

[0007] In order to solve the above problem, the present invention is a method performed by a power transmitting device, comprising: a first receiving step of receiving a first received power packet from a power receiving device, the first received power packet including information indicating a value of a first received power; a first transmitting step of transmitting a positive or negative response to the first received power packet based on values ​​indicated by multiple Control Error packets received from the power receiving device; a second receiving step of receiving a second received power packet from the power receiving device after the positive response is transmitted in the first transmitting step, the second transmitting step of transmitting a positive or negative response to the second received power packet based on values ​​indicated by multiple Control Error packets received after the positive response is transmitted in the first transmitting step; and a processing step of performing a foreign object detection process after the second transmitting step. Effect of the Invention

[0008] According to the present invention, it is possible to improve the accuracy of calculating parameters used to determine whether or not a foreign object is present. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a power transmitting device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a configuration example of a power receiving device according to the embodiment. [Diagram 3] FIG. 2 is a functional block diagram of a power transmitting device according to an embodiment. [Figure 4] FIG. 1 is a diagram showing an example of the configuration of a wireless power transmission system according to an embodiment. [Diagram 5] 5 is a flowchart showing a process executed by the power transmitting device. [Figure 6] 5 is a flowchart showing a process executed by the power transmitting device. [Figure 7] 6 is a flowchart showing a process executed by a power receiving device. [Figure 8] 5 is a diagram showing an example of an operation sequence of the wireless power transmission system according to the embodiment. [Figure 9]5 is a diagram showing an example of an operation sequence of the wireless power transmission system according to the embodiment. [Figure 10] 13 is a diagram showing an estimated received power graph created by the power transmitting device. [Figure 11] 6 is a flowchart showing a foreign object detection process executed by the power transmitting device. [Figure 12] 6 is a diagram showing the relationship between a measurement cycle and a measurement period of a transmission power measurement process in a power transmitting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples for explaining the technical idea of ​​the present invention, and are not intended to limit the present invention to the configurations and methods described in the embodiments.

[0011] [System configuration] FIG. 4 shows a configuration example of a wireless power transmission system (non-contact charging system) according to this embodiment. This system includes a power transmitting device 100 and a power receiving device 200. Hereinafter, the power transmitting device may be referred to as TX, and the power receiving device may be referred to as RX. The TX100 is an electronic device that wirelessly transmits power to the RX200 placed on its own charging stand. The RX200 is an electronic device that receives power from the TX100 and charges a battery. The following description will be given taking as an example a case where the RX200 is placed on the charging stand. However, when the TX100 transmits power to the RX200, the RX200 does not have to be placed on the charging stand as long as it is within the power transmitting range of the TX100 (for example, the range indicated by the dashed line in FIG. 4).

[0012] Furthermore, the RX200 and the TX100 may have a function of executing applications other than wireless charging. An example of the RX200 is a smartphone, and an example of the TX100 is an accessory device for charging the smartphone. The RX200 and the TX100 may be storage devices such as a hard disk device or a memory device, or may be information processing devices such as a tablet or a personal computer (PC). The RX200 and the TX100 may be image input devices such as an imaging device (camera, video camera, etc.) or a scanner, or may be image output devices such as a printer, a copier, or a projector. The RX200 may be a vehicle such as an automobile, and the TX100 may be a charging stand installed in the console of the automobile, etc.

[0013] In this system, wireless power transmission is performed using an electromagnetic induction method for wireless charging based on the WPC standard. That is, between the RX200 and the TX100, wireless power transmission for wireless charging based on the WPC standard is performed between the power receiving antenna of the RX200 and the power transmitting antenna of the TX100. Note that the wireless power transmission method (non-contact power transmission method) applied to this system is not limited to the method defined by the WPC standard, and may be a method using other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, lasers, etc. Also, in this embodiment, wireless power transmission is used for wireless charging, but wireless power transmission may be performed for purposes other than wireless charging.

[0014] In the WPC standard, the amount of power guaranteed when the RX200 receives power from the TX100 is stipulated by a value called Guaranteed Power (hereafter referred to as "GP"). GP indicates the power value that is guaranteed to be output to the load of the RX200 (e.g., a charging circuit, etc.) even if the positional relationship between the RX200 and the TX100 fluctuates and the power transmission efficiency between the receiving antenna and the transmitting antenna decreases. For example, if the GP is 5 watts, the TX100 controls and transmits power so that it can output 5 watts to the load in the RX200, even if the positional relationship between the receiving antenna and the transmitting antenna fluctuates and the power transmission efficiency decreases.

[0015] The WPC standard also specifies a method for the TX100 to detect the presence of an object (foreign object) that is not a target for power transmission near the power transmitting antenna. More specifically, the standard specifies a power loss method for detecting a foreign object based on the difference between the power transmitted by the TX100 and the power received by the RX200, and a Q-factor measurement method for detecting a foreign object based on a change in the quality factor (Q-factor) of the power transmitting coil in the TX100. Foreign object detection using the power loss method is performed during power transmission (Power Transfer phase, described below). Foreign object detection using the Q-factor measurement method is performed before power transmission (Negotiation phase or Renegotiation phase, described below).

[0016] Moreover, the RX200 and the TX100 according to this embodiment perform communication for power transmission and reception control based on the WPC standard. The WPC standard specifies a plurality of phases including a power transfer phase in which power transmission is performed and one or more phases before the actual power transmission is performed, and communication for the necessary power transmission and reception control is performed in each phase. The phases before the power transmission may include a selection phase, a ping phase, an identification and configuration phase, a negotiation phase, and a calibration phase. In the following, the identification and configuration phase is referred to as an I&C phase.

[0017] In the Selection phase, the TX100 transmits Analog Pings intermittently to detect that an object has been placed on the charging stand of the TX100 (for example, that the RX200 or a conductor piece has been placed on the charging stand). The TX100 detects at least one of the voltage value and current value of the power transmitting antenna when the Analog Ping is transmitted, and if the voltage value is below a certain threshold or the current value exceeds a certain threshold, it determines that an object is present and transitions to the Ping phase.

[0018] In the Ping phase, the TX100 transmits a Digital Ping with a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start up the control unit of the RX200 placed on the charging stand of the TX100. The RX200 notifies the TX100 of the magnitude of the received voltage. In this way, the TX100 recognizes that the object detected in the Selection phase is the RX200 by receiving a response from the RX200 that received the Digital Ping. When the TX100 is notified of the received voltage value, it transitions to the I&C phase.

[0019] In the I&C phase, the TX100 identifies the RX200 and obtains device configuration information (capability information) from the RX200. To do this, the RX200 transmits an ID packet and a configuration packet to the TX100. The ID packet contains the identification information of the RX200, and the configuration packet contains the device configuration information (capability information) of the RX200. Upon receiving the ID packet and the configuration packet, the TX100 responds with an acknowledgement (ACK, positive response). Then, the I&C phase ends.

[0020] In the negotiation phase, the GP value is determined based on the GP value requested by the RX200 and the power transmission capability of the TX100. The TX100 also performs foreign object detection processing using the Q-factor measurement method in response to a request from the RX200. The WPC standard also specifies a method of transitioning to the power transfer phase once, and then performing the same processing as in the negotiation phase again at the request of the RX200. The phase in which these processing are performed after transitioning from the power transfer phase is called the renegotiation phase.

[0021] In the calibration phase, the RX200 notifies the TX100 of a predetermined received power value (received power value in a light load state / received power value in a high load state) based on the WPC standard and requests the execution of calibration. The TX100 acquires a transmitted power value corresponding to the received power value, calculates a power loss based on the transmitted power value and the received power value, and stores the calculated power loss in association with the transmitted power. The TX100 then calculates parameters for foreign object detection processing by the power loss method based on at least two pairs of transmitted power and power loss. These parameters will be described later. In this way, the calibration processing includes a process of acquiring the received power, acquiring the transmitted power corresponding to the received power and calculating the power loss, and storing the transmitted power and power loss in association with each other. The calibration processing also includes a process of calculating parameters for the foreign object detection processing performed by the TX100 from two or more pairs of transmitted power and power loss. The power loss is the power lost when transmitting power from the TX100 to the RX200. For example, if the transmitted power is 1 W and the received power is 0.9 W, the power loss is 0.1 W. Note that instead of using the lost power value as the power loss, the loss rate (10% in the above example) may be used.

[0022] In the power transfer phase, control is performed for starting and continuing power transmission, as well as stopping power transmission due to foreign object detection and full charge.

[0023] To control power transmission and reception, the TX100 and RX200 use the same antenna (coil) as for wireless power transmission based on the WPC standard to communicate by superimposing a signal on the electromagnetic waves transmitted from the antenna. Note that the range in which communication based on the WPC standard is possible between the TX100 and RX200 is almost the same as the power transmission range of the TX100 (for example, the range indicated by the dashed line in Figure 4).

[0024] [Device configuration] Next, the configuration of the power transmitting device 100 (TX100) and the power receiving device 200 (RX200) according to this embodiment will be described. Note that the configuration described below is merely an example, and a part (or in some cases the whole) of the described configuration may be replaced with another configuration having a similar function or omitted, and further configuration may be added to the described configuration. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block. Also, although the function of each functional block shown below is implemented as a software program, some or all of the components included in this functional block may be implemented as hardware.

[0025] Fig. 1 is a functional block diagram showing an example of the configuration of a TX 100 according to this embodiment. The TX 100 has a control unit 101, a power supply unit 102, a power transmission unit 103, a communication unit 104, a power transmission antenna 105, and a memory 106. In Fig. 1, the control unit 101, the power supply unit 102, the power transmission unit 103, the communication unit 104, and the memory 106 are depicted as separate entities, but any of a plurality of these functional blocks may be implemented in the same chip.

[0026] The control unit 101 controls the entire TX 100 by executing a control program stored in the memory 106, for example. That is, the control unit 101 controls each functional unit shown in FIG. 1. The control unit 101 also performs control related to power transmission control including communication for device authentication in the TX 100. Furthermore, the control unit 101 may perform control for executing applications other than wireless power transmission. The control unit 101 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (MicroProcessor Unit). The control unit 101 may be configured with hardware dedicated to a specific process, such as an application specific integrated circuit (ASIC). The control unit 101 may also be configured with an array circuit, such as a field programmable gate array (FPGA) compiled to execute a specific process. The control unit 101 stores information to be stored during execution of various processes in the memory 106. The control unit 101 may measure time using a timer (not shown).

[0027] The power supply unit 102 supplies power required for the control of the TX 100 by the control unit 101 and for power transmission and communication to the entire TX 100. The power supply unit 102 is, for example, a commercial power source or a battery. The battery stores power supplied from the commercial power source.

[0028] The power transmitting unit 103 converts the DC or AC power input from the power supply unit 102 into AC frequency power in a frequency band used for wireless power transmission, and inputs the AC frequency power to the power transmitting antenna 105 to generate electromagnetic waves for receiving power at the RX200. For example, the power transmitting unit 103 converts the DC voltage supplied by the power supply unit 102 into an AC voltage using a switching circuit in a half-bridge or full-bridge configuration using a FET (Field Effect Transistor). In this case, the power transmitting unit 103 includes a gate driver that controls ON / OFF of the FET. The power transmitting unit 103 can change the transmission power by switching between these two switching circuits.

[0029] The power transmitting unit 103 also controls the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmission voltage) input to the power transmitting antenna 105. Increasing the power transmission voltage increases the intensity of the electromagnetic waves, and decreasing the power transmission voltage decreases the intensity of the electromagnetic waves. As described later, the power transmitting unit 103 can control the transmission power by changing the power transmission voltage according to a control error packet (hereinafter, CE packet) periodically transmitted from the RX200. Note that the intensity of the electromagnetic waves to be output may be controlled by adjusting the current (power transmission current) input to the power transmitting antenna 105, or both the power transmission voltage and the power transmission current. The power transmitting unit 103 also performs output control of the AC frequency power so that the power transmission from the power transmitting antenna 105 is started or stopped based on an instruction from the control unit 101. It is also assumed that the power transmitting unit 103 has the capacity to supply power to the charging unit 206 (FIG. 2) of the RX200 that complies with the WPC standard, so as to output 15 watts (W).

[0030] The communication unit 104 performs communication with the RX200 for power transmission control based on the WPC standard as described above. The communication unit 104 modulates the electromagnetic wave output from the power transmitting antenna 105 and transmits information to the RX200 to perform communication. The communication unit 104 also demodulates the electromagnetic wave output from the power transmitting antenna 105 and modulated in the RX200 to acquire information transmitted by the RX200. That is, the communication performed by the communication unit 104 is performed by superimposing a signal on the electromagnetic wave transmitted from the power transmitting antenna 105. The communication unit 104 may also perform communication with the RX200 by another communication method using an antenna different from the power transmitting antenna 105. For example, the communication may be performed by a wireless LAN (e.g., Wi-Fi (registered trademark)) of the IEEE802.11 standard series, Bluetooth (registered trademark), ZigBee, NFC (Near Field Communication), or the like. The communication unit 104 may also perform communication with the RX200 by selectively using a plurality of communications.

[0031] The memory 106 can store the control program and also the statuses (received power value, etc.) of the TX100 and the RX200. For example, the status of the TX100 is acquired by the control unit 101, and the status of the RX200 is acquired by the control unit 201 (FIG. 2) of the RX200, and can be received via the communication unit 104.

[0032] 2 is a block diagram showing an example of the configuration of a power receiving device 200 (RX200) according to this embodiment. The RX200 includes a control unit 201, a UI (user interface) unit 202, a power receiving unit 203, a communication unit 204, a power receiving antenna 205, a charging unit 206, a battery 207, and a memory 208.

[0033] The control unit 201 controls the entire RX200 by executing a control program stored in the memory 208, for example. That is, the control unit 201 controls each functional unit shown in FIG. 2. Furthermore, the control unit 201 may perform control for executing applications other than wireless power transmission. The control unit 201 includes one or more processors, such as a CPU or an MPU. Note that the control unit 201 may control the entire RX200 (if the RX200 is a smartphone, the entire smartphone) in cooperation with an OS (Operating System) that the control unit 201 is executing. The control unit 201 may also be configured with hardware dedicated to a specific process, such as an ASIC. The control unit 201 may also be configured with an array circuit, such as an FPGA, compiled to execute a specific process. The control unit 201 stores information to be stored during execution of various processes in the memory 208. The control unit 201 may measure time using a timer (not shown).

[0034] The UI unit 202 outputs various information to the user. The various outputs referred to here include screen display, blinking or color change of LED, audio output by a speaker, vibration of the RX200 main body, and other operations. The UI unit 202 includes an LCD panel, an LED, a speaker, a vibration motor, and other notification devices. The UI unit 202 may also have a reception function for receiving operations on the RX200 from the user. In this case, the UI unit 202 includes, for example, a voice input device such as a button, a keyboard, or a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, or other input device. Note that a device capable of both outputting information to the user and receiving operations from the user, such as a touch panel, may be used.

[0035] The power receiving unit 203 obtains, at the power receiving antenna 205, AC power (AC voltage and AC current) generated by electromagnetic induction caused by electromagnetic waves radiated from the power transmitting antenna 105 of the TX100. Then, the power receiving unit 203 converts the AC power into DC or AC power of a predetermined frequency, and outputs the power to the charging unit 206 that performs processing for charging the battery 207. That is, the power receiving unit 203 supplies power to the load in the RX200. The above-mentioned GP is a power value that is guaranteed to be output from the power receiving unit 203. The power receiving unit 203 is assumed to have the capacity to supply power for the charging unit 206 to charge the battery 207 and to output 15 watts of power to the charging unit 206. Furthermore, the power receiving unit 203 notifies the control unit 201 of the current received power value, thereby enabling the control unit 201 to know the received power value at any time.

[0036] The charging unit 206 charges the battery 207 with power supplied from the power receiving unit 203. The charging unit 206 also starts or stops charging the battery 207 based on the control of the control unit 201, and further adjusts the power used to charge the battery 207 based on the charging state of the battery 207. When the power used by the charging unit 206 changes, the power supplied from the power receiving unit 203, i.e., the received power in the RX200, also changes accordingly. Here, the charging unit 206 is a load in the RX200. Therefore, making the charging unit 206 start charging the battery 207 means connecting the load to the power receiving unit 203. Similarly, stopping charging means disconnecting the load from the power receiving unit 203.

[0037] The communication unit 204 performs communication for power reception control based on the WPC standard with the communication unit 104 of the TX100. The communication unit 204 demodulates the electromagnetic wave input from the power receiving antenna 205 to obtain information transmitted from the TX100. The communication unit 204 performs communication with the TX100 by load modulating the input electromagnetic wave to superimpose a signal related to information to be transmitted to the TX100 on the electromagnetic wave. The communication unit 204 may perform communication with the TX100 using another communication method using an antenna different from the power receiving antenna 205. For example, the communication may be performed by a wireless LAN (e.g., Wi-Fi (registered trademark)) of the IEEE802.11 standard series, Bluetooth (registered trademark), ZigBee, NFC, or the like. The communication unit 204 may selectively use a plurality of communications to perform communication with the TX100.

[0038] The memory 208 stores the control program and also stores the states of the TX100 and the RX200. For example, the state of the RX200 is acquired by the control unit 201, and the state of the TX100 is acquired by the control unit 101 of the TX100, and can be received via the communication unit 204.

[0039] Next, a functional block diagram of the control unit 101 of the TX 100 will be described with reference to Fig. 3. The control unit 101 has a communication processing unit 301, a power transmission processing unit 302, a foreign object detection processing unit 303, and a calculation processing unit 304.

[0040] The communication processing unit 301 performs processing related to control communication with the RX200 based on the WPC standard via the communication unit 104. The power transmission processing unit 302 controls the power transmission unit 103 and performs processing related to power transmission to the RX200.

[0041] The foreign object detection processing unit 303 performs a process of detecting a foreign object. The foreign object detected here is a foreign object present within the power transmission range of the TX100 or a foreign object placed on the mounting surface (contact surface) on which the RX200 is placed. It is sufficient to detect a foreign object in a position that is affected when transmitting power from the TX100 to the RX200, and the detection range is not limited. The foreign object detection processing unit 303 can realize a foreign object detection function using a power loss method and a foreign object detection function using a Q value measurement method. The foreign object detection processing unit 303 may also perform the foreign object detection process using other methods. For example, in the TX100 having an NFC communication function, the foreign object detection process may be performed using a counterpart device detection function according to the NFC standard.

[0042] The calculation processing unit 304 measures the power output to the RX 200 via the power transmitting unit 103, and calculates an average transmission power value for each unit time. The foreign object detection processing unit 303 performs foreign object detection processing using a power loss method based on the calculation result by the calculation processing unit 304 and the received power information received from the power receiving device via the communication processing unit 301.

[0043] The functions of the communication processing unit 301, the power transmission processing unit 302, the foreign object detection processing unit 303, and the calculation processing unit 304 are realized as programs that run in the control unit 101. Each processing unit is configured as an independent program, and can run in parallel while synchronizing the programs through event processing or the like.

[0044] [Power receiving device operation] Next, the operation of the RX 200 of this embodiment will be described using the flowchart in Fig. 7. This process can be realized, for example, by the control unit 201 of the RX 200 reading a program from the memory 208 and executing it.

[0045] 7 is a flowchart showing the processing executed by the RX200, and shows the processing procedure for making the TX100 calculate an estimated value of power loss (hereinafter, may be referred to as estimated power loss) used for foreign object detection by the power loss method. The processing in FIG. 7 is executed after the above-mentioned negotiation phase is completed in the RX200, and before the charging processing for the battery 207. More specifically, it is started after the RX200 transmits a packet requesting the completion of negotiation to the TX100 and receives an acknowledgment (ACK packet) from the TX100.

[0046] First, the RX200 calculates the received power value in a low load (light load) state as the reference received power information (S701). Note that the low load state here refers to a state in which the power receiving unit 203 is not connected to a load, i.e., a state in which the received power is minimized, and the power output to the power receiving unit 203 is approximately 500 mW. The RX200 then requests the TX100 to perform calibration using a Received Power packet (hereinafter, RP packet) in the WPC standard (S702). The RP packet includes the received power value in a low load state calculated as the reference power information, and information Mode=1 indicating that a first calibration is to be performed.

[0047] Although not shown, after the completion of the negotiation phase, the RX200 periodically transmits a CE packet to control the transmission voltage (transmission power) of the TX100. For example, the CE packet issues instructions such as +1 volts, -2 volts, or 0 (maintain voltage). When performing calibration, the CE packet is used to request fine adjustment of the transmission power so that the received power is kept at a constant value (for example, 500 mW).

[0048] When the RX200 receives a NAK packet in response to a calibration request from the TX100 (No in S703), it calculates the time since the RP packet was first sent in S702, and checks whether a timeout has occurred (S704). If a timeout has occurred (Yes in S704), the RX200 notifies the user that an error has occurred (S705), and ends the charging process. If a timeout has not occurred (No in S704), the RX200 recalculates the received power value (S701) and sends an RP packet (S702).

[0049] When receiving an ACK packet in response to the calibration request from the TX100 (Yes in S703), the RX200 instructs the TX100 to increase the transmission voltage by a CE packet in order to calculate the received power value in a high-load state (S706). Note that the high-load state here refers to a state in which the power receiving unit 203 is connected to a load and the received power is maximized. In this case, the power output to the power receiving unit 203 is approximately 15 W, which is the maximum power within the range of the WPC standard. Note that when the received power is maximized, it is either the maximum power that the RX200 can supply to the load, the maximum power expected to be required by the load during the period from placement to charging completion, or the power based on the GP. The RX200 may measure the power output to the power receiving unit 203 and transmit a CE packet multiple times to adjust the output to approximately 15 W. When the TX100 receives this CE packet, it switches the switching circuit so that it can transmit a large amount of power.

[0050] After transmitting the CE packet, when it is confirmed that the received power has increased to approximately 15 W, the RX200 calculates the received power value as the reference received power information (S707) and requests calibration using an RP packet (S708), just as in the case of a low load state. The RP packet transmitted here contains, in addition to the received power value in a high load state, information called Mode=2, which indicates that a second calibration will be performed.

[0051] When the RX200 receives a NAK packet from the TX100 in response to the second calibration request (No in S709), it calculates the time since the RP packet was sent in S708 and checks whether a timeout has occurred (S710). If a timeout has occurred (Yes in S710), the RX200 notifies the user that an error has occurred (S711) and ends the charging process. If a timeout has not occurred (No in S710), the RX200 recalculates the received power value (S707) and sends an RP packet (S708).

[0052] When the RX200 receives an ACK packet in response to the second calibration request from the TX100 (Yes in S709), it starts charging the battery 207 (S712). After the second calibration is completed, the RX200 periodically notifies the TX100 of its own received power value by using an RP packet. In this way, an RP packet sent when not requesting the execution of calibration contains information Mode=0. As will be described later, the TX100 performs foreign object detection by the power loss method using the received power value contained in the RP packet of Mode=0 received from the RX200.

[0053] [Power transmission device operation] Next, the operation of the TX 100 of this embodiment will be described with reference to the flowcharts of Figures 5 and 6. This process can be realized, for example, by the control unit 101 of the TX 100 reading a program from the memory 106 and executing it.

[0054] FIG. 5 is a flowchart showing the processing operation of the calculation processing unit 304 operating in the control unit 101, and shows a processing procedure for calculating and storing the transmission power when the TX100 transmits power to the RX200. FIG. 6 is a flowchart showing the processing operation of each processing unit operating in the control unit 101, and shows a processing procedure for calculating an estimated power loss used in the foreign object detection processing by the power loss method in the TX100. The processing in FIG. 5 and FIG. 6 is executed when the above-mentioned negotiation phase is completed in the TX100. More specifically, the processing is started after the TX100 receives a packet requesting completion of the negotiation from the RX200 and transmits an acknowledgment (ACK packet) to the RX200. The processing in FIG. 5 and FIG. 6 are executed in parallel independently of each other.

[0055] First, the measurement and storage process of the transmitted power in FIG. 5 will be described in detail.

[0056] The processes of S502 to S508 are continuously performed after the Negotiation phase is completed in the TX 100 until the power transmission process to the RX 200 is completed (Yes in S501). More specifically, these processes are repeatedly performed until the communication processing unit 301 receives an End Power Transfer packet (hereinafter, referred to as an "EPT packet") from the RX 200 or until the power transmission process cannot be continued due to an environmental abnormality such as a temperature rise.

[0057] The calculation processing unit 304 of the TX 100 measures the transmission power value (S503) during a measurement period T2 (No in S504) every measurement cycle T1 (Yes in S502). Here, the relationship between the measurement cycle T1 and the measurement period T2 will be described with reference to FIG.

[0058] 12, the horizontal axis represents time and the vertical axis represents the transmission power of the TX 100, and a curve 1210 represents the actual measurement value of the transmission power. The straight line at the bottom of the figure represents the measurement period T2 of the transmission power value in the calculation processing unit 304 (the period during which S503 is executed).

[0059] 1220 represents the time to start the first measurement (the timing to shift to Yes in S502), and 1221 represents the time to end the first measurement (the timing to shift to Yes in S504). 1230 represents the time to start the second measurement, and 1231 represents the time to end the second measurement. Here, the time intervals from 1220 to 1221 and from 1230 to 1231 are the measurement period T2, and the time interval from 1220 to 1230 is the measurement cycle T1. As shown in FIG. 12, by setting the measurement cycle T1 and the measurement period T2 such that the relationship T1 < T2 holds, the calculation processing unit 304 executes a plurality of measurement processes of the transmission power in parallel while shifting the timing. In this embodiment, T1 = 3 msec and T2 = 8 msec. Note that it may be set such that the relationship T1 ≥ T2 holds. In this way, TX100 periodically measures the transmission power value. Thereby, as will be described later, even if the reception power value is notified from RX200 at any timing, the transmission power value corresponding to the reception power value can be derived.

[0060] Return to the description of FIG. 5. When the measurement period T2 has elapsed (Yes in S504), the calculation processing unit 304 calculates the average value of the plurality of transmission power values measured within T2 and the standard deviation as information indicating the degree of variation of the transmission power values (S505). Then, the calculation processing unit 304 associates the calculated average value of the transmission power values (hereinafter, may also be referred to as the average transmission power value) with the standard deviation and stores them in the memory 106 as transmission power data (S506). Here, the case where the standard deviation is used as information indicating the degree of variation of the transmission power values has been described. However, for example, the variance or the difference value between the maximum value and the minimum value may be used as information indicating the degree of variation. Further, the calculation processing unit 304 stores a plurality of pieces of transmission power data calculated in S505 in the memory 106 in the order of measurement time. The data to be stored is managed as a ring buffer, and when the maximum storage number of the buffer is exceeded, the old data is overwritten and stored in order.

[0061] The calculation processing unit 304 judges whether or not a change in the transmission voltage to a value equal to or greater than a predetermined threshold has been requested by the CE packet transmitted from the RX200 (S507). Here, there are several cases in which a change in the transmission voltage to a value equal to or greater than the threshold is requested, for example, when the CE packet is transmitted from the RX200 in S706. In this case, the first calibration (calculation of the estimated power loss) is completed, and the transmission power value before the change in the transmission voltage becomes unnecessary, so the transmission power data stored in S506 is erased (S508). In another case, during the execution of the first calibration, the received power is not stable due to the influence of the positional deviation of the RX200, etc., and the change amount of the voltage specified in the CE packet periodically transmitted from the RX200 becomes large. This can also occur during the execution of the second calibration. In such a case, it is necessary to measure the transmission power again, and the measurement results up to that point become unnecessary, so the transmission power data stored in S508 is erased.

[0062] If a change in the transmission voltage to be equal to or greater than the threshold is not requested in S507, or if the transmission power data stored in the memory 106 is deleted in S508, the process returns to S501. Similarly, when the power transmission process for the RX200 is completed (Yes in S501), the calculation processing unit 304 deletes the transmission power data stored in the memory 106 in S506 (S509). By deleting data in S508 and S509, it is possible to suppress the amount of data stored in the memory 106, and it is possible to implement the process of this embodiment even in a hardware configuration in which the capacity of the memory 106 is small.

[0063] In this way, the TX100 in this embodiment constantly performs measurement and calculation processing of the transmitted power. As a result, when a received power value is acquired from the RX200 in the processing of Fig. 6 and Fig. 11 described later, it becomes possible to identify the transmitted power value corresponding to the received power value.

[0064] Next, the process of calculating the estimated power loss in FIG. 6 will be described in detail.

[0065] The processes of S602 to S620 are continuously performed after the Negotiation phase is completed in the TX 100 until the power transmission process to the RX 200 is completed (YES in S601).

[0066] In this process, the communication processing unit 301 of the TX 100 waits for reception of an RP packet (Mode=1 or 2) as reference received power information transmitted from the RX 200 in S702 or S708 in FIG. 7, and a CE packet as a transmission voltage change instruction.

[0067] When the communication processing unit 301 receives an RP packet, that is, when a calibration request is received (Yes in S602), the foreign object detection processing unit 303 checks the time since the switching circuit of the power transmitting unit 103 was last switched (S603). If a predetermined time has not passed since the switching circuit was switched (Yes in S603), the TX100 determines that the power transmission output is not stable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616).

[0068] If a predetermined time has passed since the switching circuit was switched (No in S603), the foreign object detection processing unit 303 checks the amount of change in voltage requested in the CE packet most recently received from the RX200 (S604). If the amount of change is equal to or greater than a predetermined threshold (Yes in S604), the TX100 determines that the received power in the RX200 is not stable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616). If the amount of change is less than a predetermined threshold (No in S604), the TX100 determines that the received power in the RX200 is stable. Note that the value checked in S604 may be determined based on values ​​specified in multiple CE packets most recently received. For example, the TX100 may determine that the received power in the RX200 is stable if the total amount of change specified in multiple CE packets is equal to or greater than a threshold, and that the received power is not stable if it is less than the threshold. In addition, TX100 may determine that the received power at RX200 is stable if the specified value (voltage change amount) of the CE packets received most recently has not exceeded the threshold value even once, and that the received power is unstable if the specified value has exceeded the threshold value even once.

[0069] If it is determined that the received power in the RX200 is stable (No in S604), the foreign object detection processing unit 303 determines the data to be used for the power loss calculation from among the transmitted power data (average value and standard deviation of transmitted power value) stored by the calculation processing unit 304 in S506 (S605). Specifically, the transmitted power data with the closest calculation completion time and the time T3 back from the time the RP packet was received is used. Here, T3 is an estimated value of the time from the completion of the calculation of the received power in the RX200 to the time the value is notified to the TX100 by the RP packet. In this embodiment, T3=8 msec.

[0070] If the standard deviation of the transmission power values ​​included in the transmission power data determined in S605 is equal to or greater than the threshold (Yes in S606), the TX100 determines that the transmission power is not stable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616). If the standard deviation included in the transmission power data determined in S605 is less than the threshold (No in S606), the foreign object detection processing unit 303 calculates the standard deviation of the average transmission power value adopted in S605 and the n average transmission power values ​​calculated before the calculation of the data (S607). Here, n is an integer value equal to or greater than 1 that is determined in advance, and is equal to or less than the number of buffers in the ring buffer that stores the transmission power data described above. In this embodiment, n=5.

[0071] If the standard deviation calculated in S607 is equal to or greater than the threshold (Yes in S608), the TX100 determines that the transmission power is not stable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616). If the standard deviation calculated in S607 is less than the threshold (No in S608), the TX100 determines that the transmission power is stable. Note that the value calculated and confirmed in S607 and S608 does not have to be the standard deviation. For example, the TX100 may calculate the variance, the difference between the maximum value and the minimum value, and the total of the change in the calculated values ​​each time, and determine that the transmission power is not stable if each value is equal to or greater than the threshold, and that the transmission power is stable if each value is less than the threshold. Also, it may be determined that the transmission power is stable if the average transmission power value of the transmission power data adopted in S605 and the average transmission power value of the n pieces of transmission power data calculated before the calculation of the data have never exceeded the threshold, and that the transmission power is not stable if it has exceeded the threshold even once.

[0072] When the TX100 judges that the transmission power is stable (No in S608), the foreign object detection processing unit 303 calculates the power loss between the TX100 and the RX200 (S609). Specifically, the power loss is determined as a value obtained by subtracting the received power value included in the RP packet received in S602 from the average transmission power value included in the transmission power data adopted in S605. Next, the foreign object detection processing unit 303 stores the calculated power loss in the memory 106 in association with the average transmission power value adopted in S605 (S610).

[0073] Here, the TX100 judges whether or not m or more power losses have been stored. If m or more power losses have not been stored (No in S611), the power transmission state between the TX100 and the RX200 may not be stable, so the communication processing unit 301 transmits a NAK packet to the RX200 (S616). Here, m is a predetermined integer value of 2 or more, and in this embodiment, m=3.

[0074] If the power loss is stored m times or more (Yes in S611), the foreign object detection processing unit 303 calculates the standard deviation of the power loss calculated in the most recent m times (S612). Since the power transmission power in the TX100 is stable due to the processes in S606 to S608, the case where the standard deviation of the power loss is large is when the power reception power in the RX200 varies. This may occur due to a problem in the RX200 itself, or due to some change in the power transmission state (power transmission environment) between the TX100 and the RX200. If the standard deviation is equal to or greater than the threshold (Yes in S612), it is determined that the power reception by the RX200 or the power transmission state between the TX100 and the RX200 is not stable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616).

[0075] If the standard deviation is less than the threshold value (No in S612), the TX 100 determines that the power transmission state between the TX 100 and the RX 200 has stabilized, and the foreign object detection processing unit 303 stores the estimated power loss in the memory 106 (S613). tp ) and power loss (Av loss ) and calculate the average value of each, and the transmission power is Av tp The estimated power loss when loss It is stored as being.

[0076] The value calculated and confirmed in S612 does not have to be the standard deviation. For example, the TX100 may calculate the variance, the difference between the maximum value and the minimum value, and the total amount of change in the calculated values ​​each time, and determine that the power transmission state with the RX200 is unstable if each value is equal to or greater than a threshold, and stable if it is less than the threshold. The TX100 may also determine that the power transmission state with the RX200 is stable if the power loss calculated the most recent m times has never exceeded the threshold, and that the power transmission state is unstable if it has exceeded the threshold even once. In addition, in S612, the case where the power transmission state is determined to be stable based on the standard deviation of the calculated power loss, etc. has been described, but the determination may also be made based on the standard deviation of the acquired received power, etc.

[0077] After that, the communication processing unit 301 transmits an ACK packet to the RX 200 (S614). Furthermore, the foreign object detection processing unit 303 clears the information on the power loss and the average transmission power value stored in the memory 106 in S610 since it is no longer necessary (S615), and the process returns to S601.

[0078] When the communications processing unit 301 receives a CE packet (Yes in S617), the power transmission processing unit 302 changes the voltage applied to the power transmitting unit 103 according to the value instructed in the CE packet (S618). If the amount of change in the voltage instructed in the CE packet is equal to or greater than a predetermined threshold (Yes in S619), the received power at the RX 200 is unstable and calibration must be performed again. Therefore, the foreign object detection processing unit 303 clears the information on the power loss and average transmitted power value stored in the memory 106 in S610 (S620).

[0079] When the power transmission process from the TX 100 to the RX 200 is completed (Yes in S601), the foreign object detection processing unit 303 clears the information on the power loss and the average transmission power value stored in the memory 106 in S610 and the estimated power loss information stored in S613 (S621).

[0080] In this way, when the TX100 in this embodiment receives a calibration request from the RX200, it checks whether the situation allows stable measurement of the estimated power loss. Specifically, it checks whether the transmission power in the TX100 is stable, whether the received power in the RX200 is stable, etc. Then, the TX100 responds with a NAK if the situation does not allow stable measurement, and stores the estimated power loss and responds with an ACK after the situation allows stable measurement. Therefore, it is possible to accurately calculate the estimated power loss, and improve the accuracy of foreign object detection.

[0081] Next, the operation of the foreign object detection process using the power loss method in the TX 100 of this embodiment will be described with reference to FIG. 10 and FIG.

[0082] FIG. 10 is a graph showing an estimated power reception graph 1000 created by the TX 100. The estimated power reception graph 1000 is a graph of the transmission power (horizontal axis) versus the estimated power reception (vertical axis) when power is transmitted from the TX 100 to the RX 200 in a state where no foreign object is placed. This graph is based on the transmission power value Av stored in the memory 106 in S613 of FIG. 6 described above. tp and the estimated power loss Av loss The calculation processing unit 304 generates the signal based on the above.

[0083] 1010 and 1020 are the transmission output Av stored in S613, respectively. tp and the estimated power loss Av loss The plot is based on the horizontal axis, and the value on the horizontal axis is Av tp , the vertical axis value is Av tp -Av loss That is, 1010 is plotted based on the calibration result in the low load state described above, and 1020 is plotted based on the calibration result in the high load state. The calculation processing unit 304 linearly interpolates between the measurement points plotted in S613 to obtain a specific Av tp Av for value rpA formula (graph) for determining the value is created. In this embodiment, the slope and intercept of the linear function represented by this graph correspond to the parameters for the foreign object detection process described above.

[0084] The calculation processing unit 304 continuously measures its own transmission power (1030) and calculates the corresponding expected receiving power value (1040). When the difference between the receiving power value notified from the RX200 and the expected receiving power value is equal to or greater than a predetermined threshold, the TX100 determines that a foreign object is present in the vicinity of the transmitting antenna 105 (power transmission range).

[0085] The method of creating the graph is not limited to the linear interpolation method between the measurement points described above, and may be any method such as one Av tp One Av for the value rp It is sufficient to derive a graph from which values ​​can be obtained. For example, calibration may be performed at points other than the above two points, and a graph may be created by linearly interpolating between three or more measurement points. Also, when there are three or more measurement points, a graph may be created using an approximation curve.

[0086] Fig. 11 is a flowchart for performing a foreign object detection process using an estimated received power graph 1000 in the TX 100. The process in Fig. 11 is executed continuously while the TX 100 is in the power transfer phase after the process in Fig. 6 is executed. This process can be realized, for example, by the control unit 101 of the TX 100 executing a program read from the memory 106.

[0087] The calculation processing unit 304 of the TX 100 continuously calculates the estimated received power value in the RX 200 relative to its own transmission power according to the estimated received power graph 1000 (S1101).

[0088] As described above, after completing the second calibration, the RX200 periodically notifies the TX100 of its own received power value by an RP packet (Mode=0). When the communication processing unit 301 receives the RP packet from the RX200 (Yes in S1102), the calculation processing unit 304 calculates the difference between the expected received power value calculated in S1101 and the received power value received in the RP packet (S1103).

[0089] If the difference found in S1103 is equal to or greater than the threshold (Yes in S1104), the TX100 determines that a foreign object has been detected, stops the power transmission process to the RX200, and transitions to the Selection phase (S1105). If the difference found in S1103 is less than the threshold (No in S1104), the TX100 remains in the Power Transfer phase and continues the power transmission process. The threshold used for the determination in S1104 may be a single fixed value, or may be a value determined according to a dynamically changing measurement value such as the transmission power value or temperature.

[0090] In addition, in S1101, the expected received power value in RX200 for its own transmitted power is continuously calculated, but in S1102, the corresponding transmitted power may be calculated when an RP packet of Mode=0 is received. Specifically, as in S605 in Fig. 6, the transmitted power value whose calculation completion time is closest to the time T3 back from the time when the RP packet is received may be used.

[0091] [Sequence of wireless power transmission system] Next, a sequence of a wireless power transmission system including the TX100 and the RX200 will be described with reference to Fig. 8 and Fig. 9. Fig. 8 and Fig. 9 show an example of a communication sequence until calibration between the TX100 and the RX200 is completed when the RX200 is placed on the TX100 after setting the RX200 to execute a charging function by WPC.

[0092] FIG. 8 shows an example of a communication sequence in the case where the calculation process of the estimated power loss in the TX 100 can be performed under stable conditions.

[0093] First, the TX100 and RX200 perform processing from the Selection phase to the Negotiation phase in accordance with the WPC standard (S801).

[0094] When the Negotiation phase ends, the calculation processing unit 304 of the TX 100 starts the measurement and calculation process of the transmission power described with reference to Fig. 5 (S802). After that, the TX 100 continues to measure and calculate the transmission power until the Power Transfer phase ends.

[0095] The RX200 transmits an RP packet (Mode=1) specifying a received power value (approximately 500 mW) in a light load state to the TX100 as a first calibration request (S803). The TX100 identifies the transmitted power data corresponding to the received power value included in the RP packet. The TX100 then calculates the power loss from the difference between the average transmitted power value included in the transmitted power data and the received power value included in the RP packet, stores this as the first calculation result (S804), and transmits a NAK packet to the RX200 (S805).

[0096] Upon receiving the NAK packet, the RX200 measures the received power value again and transmits an RP packet (Mode=1) to the TX100 (S806). Upon receiving the RP packet, the TX100 calculates the power loss in the same way, stores it as the second calculation result (S807), and transmits a NAK packet to the RX200 (S808). Next, when the RX200 transmits an RP packet to the TX100 again (S809), the TX100 calculates the power loss (S810), calculates the estimated power loss at 500 mW transmission from the average of the first to third calculation results, and records it (S811). Next, the TX100 transmits an ACK packet to the RX200, notifying it that it has successfully calculated the estimated power loss in response to the first calibration request (S812).

[0097] Upon receiving the ACK packet, the RX200 instructs the TX100 to increase the transmission voltage by transmitting a CE packet to the TX100 in order to calculate an estimated power loss under high load conditions (received power of about 15 W) (S813).

[0098] Upon receiving the CE packet, the TX100 controls the power transmitting unit 103 to increase the transmission voltage by the instructed change amount (S814). At this time, the power transmitting unit 103 controls the ON / OFF of the FET to switch the circuit from a half-bridge configuration to a full-bridge configuration. The TX100 starts a timer that measures the elapsed time from the circuit switching of the power transmitting unit 103 (S815).

[0099] Thereafter, as a second calibration request, the RX200 transmits an RP packet (Mode=2) specifying the received power value under high load (approximately 15 W) to the TX100 (S816).

[0100] At the time when the TX100 receives the RP packet, the timer started in S815 expires, and a predetermined time has passed since the circuit switching of the power transmitting unit 103. Therefore, the TX100 determines that the power transmission is stable, calculates the power loss, and stores the calculation result as the first calculation result in the high load state (S817). Then, the TX100 transmits a NAK packet to the RX200 (S818). After that, the second and third power losses are calculated and recorded in the same manner as in S806 to S810 (S819 to S823).

[0101] The TX100 calculates and records the estimated power loss when transmitting 15 W from the average of the first to third calculation results (S824). Next, the TX100 transmits an ACK packet to the RX200 notifying that it has successfully calculated the estimated power loss in response to the second calibration request (S825).

[0102] Fig. 9 shows an example of a communication sequence in the case where the calculation process of the estimated power loss in the TX 100 is performed under unstable conditions. Fig. 9 shows an example of a communication sequence assuming a case where an RP packet is transmitted from the RX 200 immediately after circuit switching is performed in the power transmitting unit 103 of the TX 100, as an unstable situation.

[0103] The processes in S901 to S915 are the same as those in S801 to S815 described with reference to FIG. 8, and therefore the description thereof will be omitted.

[0104] Immediately after transmitting the CE packet in S913, the RX200 transmits an RP packet (Mode=2) specifying the receiving power value under high load (about 15 W) to the TX100 (S916). At this time, the TX100 determines that the power transmission is not stable because a certain amount of time has not passed since the circuit switching of the power transmitting unit 103 (S917), and transmits a NAK packet to the RX200 without calculating or recording the power loss (S918).

[0105] Thereafter, when an RP packet is transmitted from the RX200 after the timer started in S915 has expired (S919), the TX100 calculates the power loss for the first time and stores the calculation result as the first calculation result in a high-load state (S920).

[0106] The processes in S921 to S928 are the same as those in S818 to S825 described with reference to FIG. 8, and therefore will not be described.

[0107] In this way, according to this embodiment, the TX100 can perform measurement and calculation processing of the estimated power loss between the RX200 in a stable environment. In other words, the transmission power or the reception power that varies when a sudden environmental change occurs can be excluded from the original data used to calculate the estimated power loss. As a result, the transmission power and the reception power as described above are not used to calculate the parameters for foreign object detection. This makes it possible to estimate with high accuracy the power that is steadily lost during the power transmission processing that is performed thereafter, and improves the accuracy of foreign object detection during the power transmission processing.

[0108] In the above embodiment, a method has been shown in which the transmission power value measured and calculated immediately after switching of the internal circuit in the power transmitting unit 103 of the TX100 and the received power value corresponding to the transmission power value are not used in the calculation of the estimated power loss. Also, a method has been shown in which the standard deviation of the transmission power continuously measured and calculated by the calculation processing unit 304 is calculated, and if the value is equal to or greater than a threshold, the data is not used in the calculation of the estimated power loss. By adopting such a configuration, it is possible to take into account the variation in the measured and calculated data due to factors inside the TX100.

[0109] In the above embodiment, the TX100 calculates the power loss based on the received power value specified in the RP packet transmitted from the RX200, and calculates the estimated power loss by averaging the calculation results. In addition, the method of calculating the standard deviation of the most recently calculated power loss or received power and not using the data for the calculation of the estimated power loss if the value is equal to or greater than a threshold value is shown. By adopting such a configuration, it is possible to take into account the variation in the measured and calculated data due to environmental factors between the TX100 and the RX200. For example, it is possible to avoid the problem of a value calculated in a situation where the contact surfaces of the TX100 and the RX200 are gradually shifted due to small vibrations being used as an estimated value in a stationary state.

[0110] Also, in the above embodiment, a method was shown in which, when the voltage change amount instructed by the RX200 in a CE packet is equal to or greater than a threshold, the transmission power value measured and calculated by the TX100 at that time and the received power value corresponding to that transmission power value are not used in the calculation of the estimated power loss. Since the voltage change amount instructed by the CE packet is determined as a result of processing and judgment within the RX200, this configuration makes it possible to take into account variations in the measured and calculated data due to factors within the RX200.

[0111] The above is an example of a typical embodiment, but the present embodiment is not limited to the embodiment shown in the specification and drawings, and may be modified as appropriate within the scope that does not change the gist of the present embodiment.

[0112] In this embodiment, when the TX100 receives an RP packet, if it cannot stably calculate the estimated power loss, it continues to return a NAK, but this is not limited to this. For example, if the TX100 does not return an ACK for a certain number of times or for a certain period of time, it can determine that the environment is such that foreign object detection cannot be performed normally, stop power transmission, and return to the Selection phase. By adopting such a configuration, it is possible to avoid continuing the calculation process of the estimated power loss under conditions where the transmission power output is not always stable.

[0113] Also, if the TX100 does not receive an ACK for a certain number of times or for a certain period of time, it can determine that the state in which the calculated values ​​vary is normal, and change each of the above-mentioned thresholds to larger values ​​before determining whether the state is stable. In that case, the threshold value (the difference from the estimated power loss) used when actually performing the foreign object detection process can be changed. By adopting such a configuration, it becomes possible to perform the power transmission process and the foreign object detection process in an optimal state in an environment that is constantly vibrating, such as inside a moving vehicle.

[0114] In the present embodiment, the method of determining whether the power transmission process from the TX100 to the RX200 is stable is based on the variation of the transmission power, the power loss, and the received power, the change in the specified power, or the like, but is not limited thereto. For example, the TX100 may be provided with hardware such as a vibration sensor or a magnetic sensor, and when each sensor detects vibration or magnetism above a threshold, the power transmission process may be determined to be unstable, and a NAK may be returned to the RP packet. In addition, the TX100 may be connected to an external device other than the RX200 by wireless or the like, and information indicating whether the power transmission process can be performed stably may be obtained from the external device to determine whether the power transmission process can be performed stably. By combining these methods, including the method shown in the present embodiment, the accuracy of the calculation process of the estimated power loss can be further improved.

[0115] In the present embodiment, an example has been described in which the estimated power loss is calculated at two points, a low load state and a high load state, as the power receiving state of the power receiving device, but the present invention is not limited to this. For example, the above-mentioned method may be used when calculating the estimated power loss at three or more points. In addition, the example has been described in which the process of FIG. 6 is performed after the completion of the negotiation phase and before the start of the charging process, but the present invention is not limited to this. For example, the TX100 may perform the process of FIG. 6 when calculating the estimated power loss at the third point after transitioning to the power transfer phase.

[0116] In this embodiment, an example is shown in which a CE packet is used as a request signal for controlling the transmission power of the TX100, but the present invention is not limited to this. Also, an example is shown in which an RP packet is used as a signal for notifying the TX100 of the received power value from the RX200, but the present invention is not limited to this. In either case, instructions and notifications may be given using any other packet. Also, instructions and notifications may be given in multiple packets, or two instructions and notifications may be given in one packet.

[0117] In addition, although the various thresholds and timeout values ​​shown in this embodiment have been described as being fixed values ​​determined in advance, they are not limited to this. They may be dynamically changed depending on changes in the surrounding environment or the execution status of software and hardware processing, or may be determined by negotiation between the TX100 and RX200 in the negotiation phase, for example.

[0118] In the present embodiment, the transmitted power and the estimated power loss are stored in association with each other in S613 in FIG. 6, and the graph in FIG. 10 is created using these pieces of information. However, other combinations may be used. For example, the received power and the estimated power loss may be stored in association with each other and a graph may be created using these pieces of information, or the transmitted power and the received power may be stored in association with each other and a graph may be created. All of these three pieces of information may be stored. That is, at least two of the transmitted power, the received power, and the power loss may be stored in association with each other. In addition, in FIG. 10, the graph in which the horizontal axis is the transmitted power and the vertical axis is the received power is described, but any of the transmitted power, the received power, and the power loss may be used as the combination of the horizontal axis and the vertical axis. In any case where any graph is used, the constants in the calculation formula representing the graph correspond to parameters for foreign object detection.

[0119] At least a part of the processes shown in the flowcharts of Figures 5 to 7 and 11 may be realized by hardware. When the processes are realized by hardware, for example, a specific compiler may be used to automatically generate a dedicated circuit on an FPGA from a program for realizing each step. Also, a gate array circuit may be formed in the same manner as an FPGA, and the processes may be realized as hardware.

[0120] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0121] 100 Power transmission equipment 200 Powered Device

Claims

1. A method performed by a power transmitting device, comprising: a first receiving step of receiving a first received power packet including information indicating a value of a first received power from the power receiving device; a first transmission step of transmitting a positive response or a negative response to the first receiving power packet based on values ​​indicated by a plurality of Control Error packets received from the power receiving device; a second receiving step of receiving, after an acknowledgment is transmitted in the first transmitting step, a second receiving power packet including information indicating a value of a second receiving power from the power receiving device; a second transmission step of transmitting a positive response or a negative response to the second receiving power packet based on values ​​indicated by a plurality of Control Error packets received after the positive response is transmitted in the first transmission step; a processing step of performing a foreign object detection process after the second transmission step; The method according to claim 1, further comprising:

2. A method performed by a power transmitting device, comprising: a first receiving step of receiving a first received power packet including information indicating a value of a first received power from the power receiving device; a first transmission step of transmitting an acknowledgment to the first receiving power packet when a value indicated by a Control Error packet received from the power receiving device is a predetermined value; a second receiving step of receiving, after the first transmitting step, a second receiving power packet including information indicating a value of a second receiving power from the power receiving device; a second transmission step of transmitting an acknowledgment to the second receiving power packet when a value indicated by a Control Error packet received after the first transmission step is a predetermined value; a processing step of performing a foreign object detection process after the second transmission step; The method according to claim 1, further comprising:

3. The method of claim 2 , wherein the predetermined value is a value not exceeding a predetermined threshold value.

4. A power transmission device, A power transmitting means for wirelessly transmitting power to a power receiving device; a communication means for receiving from the power receiving device a first received power packet including information indicating a value of a first received power, transmitting a positive response or a negative response to the first received power packet based on values ​​indicated by a plurality of Control Error packets received from the power receiving device, receiving a second received power packet including information indicating a value of a second received power from the power receiving device after transmitting the positive response, and transmitting a positive response or a negative response to the second received power packet based on values ​​indicated by a plurality of Control Error packets received after transmitting the positive response; and a processing unit configured to perform a foreign object detection process after the communication unit transmits an acknowledgment to the second received power packet.

5. A power transmission device, A power transmitting means for wirelessly transmitting power to a power receiving device; a communication means for receiving from a power receiving device a first received power packet including information indicating a value of a first received power, transmitting an acknowledgment to the first received power packet if a value indicated by a Control Error packet received from the power receiving device is a predetermined value, receiving from the power receiving device a second received power packet including information indicating a value of a second received power after transmitting the acknowledgment, and transmitting an acknowledgment to the second received power packet if a value indicated by a Control Error packet received after transmitting the acknowledgment is a predetermined value; a processing unit that performs a foreign object detection process after the communication unit transmits an acknowledgment to the second received power packet. A power transmitting device comprising:

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