Method performed by power transmission device, and power transmission device

Abstract

To provide a method for improving calculation accuracy of a parameter used for determining whether a foreign object exists, and to provide a power transmission device.SOLUTION: A method performed by a power transmitter device comprises: A first reception step of receiving, from a power receiving apparatus, a first received power packet including information indicating a value of first received power; A second reception step of receiving a second received power packet including information indicating a value of second received power from the power receiving apparatus after the acknowledgement is transmitted in the first transmission step; A second transmission step of transmitting a positive response or a negative response to the second received power packet based on the values indicated by the plurality of ControlError 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.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

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

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

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-070074 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the transmitted power of a power transmitter and the power loss between the transmitter and receiver are not always constant. For example, the transmitter unit of a power transmitter uses a switching circuit composed of switching elements (e.g., field-effect transistors, hereafter referred to as FETs) to convert DC voltage or current to AC voltage or current. Switching circuits include half-bridge circuits composed of two FETs and full-bridge circuits composed of four FETs. It is widely known that the switching circuit of the power transmitter operates by switching between these two circuits depending on the magnitude of the transmitted power. This operation can cause the power consumed by the switching circuit of the power transmitter and the power transmitted by the transmitting antenna to temporarily fluctuate significantly and become unstable. Furthermore, for example, if the receiver device placed on the power transmitter is a smartphone, it is possible that the device may shift position due to vibration or other factors, resulting in unstable received power. When detecting foreign objects during power transmission, using the above parameters calculated using the transmitted power and received power under such conditions could result in the foreign object being undetectable or being erroneously detected.

[0006] An object of the present invention is to improve the accuracy of calculating parameters used to determine whether 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. [Effects 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 explanation 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. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a power receiving device according to the embodiment. [Figure 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. [Figure 5] 10 is a flowchart showing a process executed by the power transmitting device. [Figure 6] 10 is a flowchart showing a process executed by the power transmitting device. [Figure 7] 10 is a flowchart showing a process executed by a power receiving device. [Figure 8] FIG. 4 is a diagram showing an example of an operation sequence of the wireless power transmission system according to the embodiment. [Figure 9]FIG. 4 is a diagram showing an example of an operation sequence of the wireless power transmission system according to the embodiment. [Figure 10] FIG. 10 is a diagram showing an estimated received power graph created by the power transmitting device. [Figure 11] 10 is a flowchart showing a foreign object detection process executed by the power transmitting device. [Figure 12] 10A and 10B are diagrams showing the relationship between the measurement cycle and the measurement period of the power transmission power measurement process in the power transmitting device. DETAILED DESCRIPTION OF THE INVENTION

[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 concept 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 an example of the configuration of a wireless power transmission system (contactless 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 its 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 need to be placed on the charging stand as long as it is within the power transmission range of the TX100 (for example, the range indicated by the dashed line in FIG. 4).

[0012] The RX200 and the TX100 may also have a function for 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 hard disk drives or memory devices, or information processing devices such as tablets or personal computers (PCs). The RX200 and the TX100 may also be image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, and projectors. The RX200 may also be a vehicle such as an automobile, and the TX100 may also be a charging stand installed in the console of the automobile.

[0013] In this system, wireless power transmission is performed using an electromagnetic induction method for wireless charging based on the WPC standard. That is, the RX200 and the TX100 perform wireless power transmission for wireless charging based on the WPC standard between the power receiving antenna of the RX200 and the power transmitting antenna of the TX100. Note that the wireless power transmission method (contactless power transmission method) applied to this system is not limited to the method specified by the WPC standard, and may be other methods such as electromagnetic induction, magnetic field resonance, electric field resonance, microwave, or laser. Furthermore, in this embodiment, wireless power transmission is used for wireless charging, but wireless power transmission may also 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 defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value that is guaranteed to be output to the RX200's load (e.g., a charging circuit) even if the relative positions of the RX200 and TX100 change and the power transmission efficiency between the receiving antenna and the transmitting antenna decreases. For example, if the GP is 5 watts, the TX100 will transmit power by controlling it so that it can output 5 watts to the load within the RX200, even if the relative positions of the receiving antenna and the transmitting antenna change 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) near the transmitting antenna that is not the target of power transmission. More specifically, it specifies a power loss method that detects foreign objects by measuring the difference between the transmitted power of the TX100 and the received power of the RX200, and a Q-factor measurement method that detects foreign objects by measuring changes in the quality factor (Q-factor) of the transmitting coil of the TX100. Foreign object detection using the power loss method is performed during power transmission (the power transfer phase, described below). Foreign object detection using the Q-factor measurement method is performed before power transmission (the negotiation or renegotiation phase, described below).

[0016] Furthermore, the RX200 and TX100 according to this embodiment communicate for power transmission and reception control based on the WPC standard. The WPC standard defines multiple phases, including a power transfer phase in which power transmission is performed and one or more phases before the actual power transmission, and communication for the necessary power transmission and reception control is performed in each phase. Phases before power transmission may include a selection phase, a ping phase, an identification and configuration phase, a negotiation phase, and a calibration phase. Note that the identification and configuration phase will be referred to as the I&C phase below.

[0017] In the Selection phase, the TX100 transmits Analog Pings intermittently to detect that an object has been placed on the charging base of the TX100 (for example, that the RX200 or a piece of conductor has been placed on the charging base). The TX100 detects at least one of the voltage and current values ​​of the power transmitting antenna when it transmits Analog Pings, 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 base 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 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 then 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 in which the system transitions to the Power Transfer phase, and then performs the same processing as the Negotiation phase again at the request of the RX200. The phase in which the system transitions from the Power Transfer phase and performs these processing is called the Renegotiation phase.

[0021] In the calibration phase, based on the WPC standard, 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) and requests 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 using 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 processing for acquiring received power, acquiring transmitted power corresponding to the received power, calculating the power loss, and storing the transmitted power and power loss in association with each other. The calibration processing also includes processing for calculating parameters for foreign object detection processing performed by the TX100 from two or more pairs of transmitted power and power loss. Note that the power loss is the power lost when power is transmitted from the TX100 to the RX200. For example, if the transmitted power is 1 watt and the received power is 0.9 watts, the power loss is 0.1 watts. Note that the power loss may be measured not by the actual power loss value but by the loss rate (10% in the above example).

[0022] In the power transfer phase, control is performed to start and continue power transmission, and to stop power transmission due to foreign object detection or 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, and 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 approximately 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 configurations of the power transmitting device 100 (TX100) and the power receiving device 200 (RX200) according to this embodiment will be described. Note that the configurations described below are merely examples, and part (or in some cases all) of the described configurations may be replaced with other configurations that perform similar functions or may be omitted, or additional configurations may be added to the described configurations. Furthermore, a block described below may be divided into multiple blocks, or multiple blocks may be integrated into a single block. Furthermore, although the functions of each functional block described below are implemented as a software program, some or all of the components included in the functional blocks may be implemented in hardware.

[0025] Fig. 1 is a functional block diagram showing an example 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 two or more of these functional blocks may be implemented on the same chip.

[0026] The control unit 101 controls the entire TX100 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 controls power transmission control, including communication for device authentication in the TX100. The control unit 101 may also control the execution of 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 also be configured with hardware dedicated to specific processing, such as an Application Specific Integrated Circuit (ASIC). The control unit 101 may also be configured to include an array circuit such as a field programmable gate array (FPGA) compiled to execute predetermined processes. The control unit 101 stores information to be stored while executing various processes in the memory 106. The control unit 101 may also measure time using a timer (not shown).

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

[0028] The power transmitting unit 103 converts 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 with a half-bridge or full-bridge configuration using FETs (Field Effect Transistors). In this case, the power transmitting unit 103 includes a gate driver that controls the ON / OFF of the FETs. The power transmitting unit 103 can change the transmission power by switching between these two switching circuits.

[0029] Furthermore, the power transmitting unit 103 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 will be described later, the power transmitting unit 103 can control the transmission power by changing the power transmission voltage in accordance with a Control Error packet (hereinafter, referred to as a CE packet) periodically transmitted from the RX200. The intensity of the electromagnetic waves to be output may be controlled by adjusting the current (transmission current) input to the power transmitting antenna 105, or by adjusting both the transmission voltage and the transmission current. Furthermore, the power transmitting unit 103 controls the output of AC frequency power so as to start or stop power transmission from the power transmitting antenna 105 based on instructions from the control unit 101. Furthermore, the power transmitting unit 103 is assumed to be capable of supplying enough power to output 15 watts (W) to the charging unit 206 (FIG. 2) of the RX200, which complies with the WPC standard.

[0030] The communication unit 104 communicates with the RX200 for power transmission control based on the WPC standard as described above. The communication unit 104 modulates electromagnetic waves output from the power transmitting antenna 105 and transmits information to the RX200 to perform communication. The communication unit 104 also acquires information transmitted by the RX200 by demodulating the electromagnetic waves output from the power transmitting antenna 105 and modulated by the RX200. That is, the communication performed by the communication unit 104 is performed by superimposing a signal on the electromagnetic waves transmitted from the power transmitting antenna 105. The communication unit 104 may also communicate 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, or NFC (Near Field Communication). The communication unit 104 may also communicate with the RX200 by selectively using a plurality of communication methods.

[0031] The memory 106 stores the control program and also stores the status (received power value, etc.) of the TX 100 and the RX 200. For example, the status of the TX 100 is acquired by the control unit 101, and the status of the RX 200 is acquired by the control unit 201 (FIG. 2) of the RX 200, 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 (or the entire smartphone if the RX200 is a smartphone) in cooperation with an operating system (OS) running on the control unit 201. 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 predetermined process. The control unit 201 stores information to be stored during execution of various processes in the memory 208. The control unit 201 may also measure time using a timer (not shown).

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

[0035] The power receiving unit 203 acquires, 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. The power receiving unit 203 then converts the AC power into DC or AC power of a predetermined frequency and outputs the power to the charging unit 206, which performs processing to charge the battery 207. In other words, the power receiving unit 203 supplies power to a load in the RX200. The above-mentioned GP is a power value 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 at the RX200, also changes accordingly. Here, the charging unit 206 is a load at the RX200. Therefore, causing the charging unit 206 to start charging the battery 207 is equivalent to connecting the load to the power receiving unit 203. Similarly, stopping charging is equivalent to disconnecting the load from the power receiving unit 203.

[0037] The communication unit 204 communicates with the communication unit 104 of the TX100 for power reception control based on the WPC standard as described above. The communication unit 204 demodulates electromagnetic waves input from the power receiving antenna 205 to acquire information transmitted from the TX100. The communication unit 204 then performs load modulation on the input electromagnetic waves to superimpose a signal related to information to be transmitted to the TX100 onto the electromagnetic waves, thereby communicating with the TX100. Note that the communication unit 204 may communicate with the TX100 using another communication method that uses an antenna different from the power receiving antenna 205. For example, communication may be performed using 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 also communicate with the TX100 by selectively using a plurality of communication methods.

[0038] The memory 208 stores the control program and also stores the status of the TX100 and RX200. For example, the status of the RX200 is acquired by the control unit 201, and the status 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 processor 303 performs a process to detect foreign objects. The foreign objects detected here include foreign objects within the power transmission range of the TX100 and foreign objects placed on the mounting surface (contact surface) on which the RX200 is placed. The detection range is not limited as long as foreign objects located in a position that will be affected when power is transmitted from the TX100 to the RX200 can be detected. The foreign object detection processor 303 can implement 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 processor 303 may also perform foreign object detection using other methods. For example, in a TX100 equipped with an NFC communication function, foreign object detection may be performed using an opposing 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 the average transmitted power value per 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 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 maintaining synchronization between the programs through event processing or the like.

[0044] [Power receiving device operation] Next, the operation of the RX200 of this embodiment will be described using the flowchart in Fig. 7. This processing can be realized, for example, by the control unit 201 of the RX200 reading a program from the memory 208 and executing it.

[0045] 7 is a flowchart showing the processing executed by the RX200, and illustrates the processing procedure for making the TX100 calculate an estimated value of power loss (hereinafter, also 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 RX200 completes the above-mentioned negotiation phase and before charging the battery 207. More specifically, the processing is started after the RX200 transmits a packet requesting 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 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. Then, the RX200 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 reference power information, and information "Mode=1" indicating that the first calibration will be performed.

[0047] Although not shown, after the Negotiation phase is complete, the RX200 periodically transmits CE packets to control the transmission voltage (transmission power) of the TX100. For example, the CE packet may issue instructions such as +1 volt, -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 remains at a constant value (for example, 500 mW).

[0048] When the RX200 receives a NAK packet in response to the 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 terminates 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 using a CE packet in order to calculate the received power value under high load conditions (S706). Note that the high load condition here refers to a state in which the power receiving unit 203 is connected to a load and the received power is at its maximum. In this case, the power output to the power receiving unit 203 is set to approximately 15 W, which is the maximum power within the WPC standard. Note that the maximum received power is set to either the maximum power that the RX200 can supply to the load, the maximum power expected to be required by the load 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. Upon receiving this CE packet, the TX100 switches the switching circuit to enable transmission of large power.

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

[0051] When the RX200 receives a NAK packet in response to the second calibration request from the TX100 (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 terminates 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 complete, the RX200 periodically notifies the TX100 of its own received power value using an RP packet. In this way, an RP packet sent when no calibration is requested contains information that Mode=0. As will be described later, the TX100 uses the received power value contained in the RP packet with Mode=0 received from the RX200 to detect foreign objects using the power loss method.

[0053] [Power transmission device operation] Next, the operation of the TX 100 of this embodiment will be described using the flowcharts in Figures 5 and 6. This processing can be realized by, for example, the control unit 101 of the TX 100 reading out 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 the 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 the processing procedure for calculating the estimated power loss used in the foreign object detection processing by the power loss method in the TX100. The processing in FIGS. 5 and 6 is executed when the above-mentioned negotiation phase is completed in the TX100. More specifically, it is started after the TX100 receives a packet from the RX200 requesting completion of negotiation and transmits an acknowledgment (ACK packet) to the RX200. The processing in FIGS. 5 and 6 operates independently and in parallel.

[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 "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) for a measurement period T2 (No in S504) every measurement period T1 (Yes in S502). Here, the relationship between the measurement period T1 and the measurement period T2 will be described with reference to FIG. 12.

[0058] 12, the horizontal axis represents time and the vertical axis represents the transmitted power of the TX 100, and a curve 1210 represents the actual measured value of the transmitted power. The straight line at the bottom of the figure represents the measurement period T2 of the transmitted 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 of 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 the present embodiment, T1 = 3 msec and T2 = 8 msec. Note that it may be set such that the relationship of T1 ≥ T2 holds. Thus, the TX100 periodically measures the transmission power value. Thereby, as will be described later, even if the reception power value is notified from the 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 elapses (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, sometimes 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 the transmission power data calculated in S505 in the memory 106 in 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 determines whether a CE packet transmitted from the RX200 requests a change in the transmission voltage equal to or greater than a predetermined threshold (S507). A change in the transmission voltage equal to or greater than the threshold can occur in several cases, such as when the RX200 transmits a CE packet in S706. In this case, the first calibration (calculation of the estimated power loss) is complete, and the transmission power value before the change in the transmission voltage is no longer needed. Therefore, the transmission power data stored in S506 is deleted (S508). Another possible case is when the received power becomes unstable during the first calibration due to factors such as misalignment of the RX200, resulting in a large change in the voltage specified in the CE packet periodically transmitted from the RX200. This can also occur during the second calibration. In such a case, the transmission power must be measured again, and the previous measurement results are no longer needed. Therefore, the stored transmission power data is deleted in S508.

[0062] If a change in the transmission voltage equal to or greater than the threshold value 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 also deletes the transmission power data stored in the memory 106 in S506 (S509). By deleting the data in S508 and S509, it is possible to reduce the amount of data stored in the memory 106, and the process of this embodiment can be performed even in a hardware configuration in which the memory 106 has a small capacity.

[0063] In this way, the TX100 in this embodiment constantly measures and calculates the transmitted power, which makes it possible to identify the transmitted power value corresponding to the received power value when the received power value is acquired from the RX200 in the processing of Fig. 6 and Fig. 11 described later.

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

[0065] The processing of S602 to S620 is continuously performed after the Negotiation phase is completed in the TX100 until the power transmission processing to the RX200 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 it receives a calibration request (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 sends 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 most recent CE packet 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 at the RX200 is unstable, and the communication processing unit 301 sends a NAK packet to the RX200 (S616). If the amount of change is less than the predetermined threshold (No in S604), the TX100 determines that the received power at the RX200 is stable. Note that the value checked in S604 may be determined based on values ​​specified in multiple CE packets received most recently. For example, the TX100 may determine that the received power at the RX200 is stable if the sum of the amounts of change specified in multiple CE packets is equal to or greater than a threshold, and that it is unstable 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 it is not stable if the threshold value has been exceeded 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 calculating the power loss from the transmitted power data (average value and standard deviation of transmitted power values) stored by the calculation processing unit 304 in S506 (S605). Specifically, the transmitted power data with the calculation completion time closest to the time T3 before the time the RP packet was received is used. Here, T3 is an estimated value of the time from when the RX200 completes the calculation of the received power until the value is notified to the TX100 in 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 value (Yes in S606), the TX100 determines that the transmission power is unstable, 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 value (No in S606), the foreign object detection processing unit 303 calculates the standard deviation between the average transmission power value adopted in S605 and n average transmission power values ​​calculated before calculating this data (S607). Note that n here is a predetermined integer value equal to or greater than 1 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 unstable, and the communication processing unit 301 transmits a NAK packet to the RX200 (S616). Also, 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 and minimum values, or the total amount of change in each calculated value, and determine that the transmission power is unstable if each value is equal to or greater than the threshold, or stable if each value is less than the threshold. Also, the transmission power may be determined to be 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 calculating the relevant data have never exceeded the threshold, or determined to be unstable if they have exceeded the threshold even once.

[0072] If the TX100 determines that the transmitted 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 by subtracting the received power value included in the RP packet received in S602 from the average transmitted power value included in the transmitted 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 transmitted power value adopted in S605 (S610).

[0073] Here, the TX100 determines 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 TX100 may not be in a stable power transmission state with the RX200, and therefore 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 m or more power losses have been stored (Yes in S611), the foreign object detection processing unit 303 calculates the standard deviation of the power losses calculated over the most recent m times (S612). Because the processing in S606 to S608 stabilizes the power transmitted by the TX100, a large standard deviation of the power loss occurs when there is variation in the power received by the RX200. This may occur due to a problem in the RX200 itself, or due to some change in the power transmission status (power transmission environment) between the TX100 and RX200. If the standard deviation is greater than or equal to the threshold (Yes in S612), it is determined that the power received by the RX200 or the power transmission status between the TX100 and RX200 is unstable, 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). More specifically, the average power transmission power value (Av tp ) and power loss (Av loss ) and calculate the average value of each, and the transmitted 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 and minimum values, or 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, or 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 over the most recent m times has never exceeded the threshold, or unstable if it has exceeded the threshold even once. In addition, in S612, the case where the stability of the power transmission state is determined based on the standard deviation of the calculated power loss, etc., has been described, but the determination may also be based on the standard deviation of the acquired received power, etc.

[0077] Thereafter, 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 average transmission power value stored in the memory 106 in S610 because it is no longer needed (S615), and the process returns to S601.

[0078] When the communication 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 in accordance with 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 TX100 to the RX200 is completed (Yes in S601), the foreign object detection processing unit 303 clears the information on the power loss and 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. If the situation does not allow stable measurement, the TX100 responds with a NAK, and once stable measurement is possible, it stores the estimated power loss and responds with an ACK. This allows for accurate calculation of the estimated power loss, making it possible to improve the accuracy of foreign object detection.

[0081] Next, the operation of the foreign object detection process using the power loss method in the TX100 of this embodiment will be described with reference to FIGS.

[0082] 10 is a graph showing an estimated received power graph 1000 created by the TX 100. The estimated received power graph 1000 is a graph of the transmitted power (horizontal axis) versus the estimated received power (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 transmitted power value Av stored in the memory 106 in S613 of FIG. 6 described above. tp and 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 estimated power loss Av loss The plot is based on the horizontal axis, and the value 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, 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 calculation formula (graph) for determining the value is created. In this embodiment, the slope and intercept of the linear function expressed 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 received power value (1040). If the difference between the received power value notified from the RX200 and the expected received power value is equal to or greater than a predetermined threshold, the TX100 determines that a foreign object is present near the power transmitting antenna 105 (power transmission range).

[0085] The method for creating the graph is not limited to the linear interpolation method between the measurement points described above, and can be any method such as linear interpolation between the measurement points. tp One Av for each 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 two mentioned above, and a graph may be created by linearly interpolating between three or more measurement points. Also, if there are three or more measurement points, a graph may be created using an approximation curve.

[0086] Fig. 11 is a flowchart of foreign object detection processing performed by the TX 100 using the estimated received power graph 1000. The processing in Fig. 11 is executed continuously while the TX 100 is in the power transfer phase after the processing in Fig. 6 has been performed. This processing 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 transmitted 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 using 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 value (Yes in S1104), the TX100 determines that a foreign object has been detected, stops power transmission processing to the RX200, and transitions to the Selection phase (S1105). If the difference found in S1103 is less than the threshold value (No in S1104), the TX100 remains in the Power Transfer phase and continues power transmission processing. The threshold value used for the determination in S1104 may be a single fixed value, or may be a value determined according to dynamically changing measured values ​​such as the transmission power value and temperature.

[0090] In addition, in S1101, it has been described that 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 before the time the RP packet is received may be used.

[0091] [Sequence of wireless power transmission system] Next, the sequence of a wireless power transmission system including the TX100 and the RX200 will be described with reference to Figures 8 and 9. Figures 8 and 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 settings have been made in the RX200 to execute the charging function using WPC.

[0092] FIG. 8 shows an example of a communication sequence when 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 the measurement and calculation process of 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) under a light load to the TX100 as a first calibration request (S803). The TX100 identifies the transmitted power data corresponding to the received power value contained in the RP packet. The TX100 then calculates the power loss from the difference between the average transmitted power value contained in the transmitted power data and the received power value contained 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 sends 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 the result as the second calculation (S807), and sends a NAK packet to the RX200 (S808). Next, when the RX200 sends an RP packet to the TX100 again (S809), the TX100 calculates the power loss (S810) and calculates and records the estimated power loss when transmitting 500 mW from the average of the first to third calculation results (S811). Next, the TX100 sends 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 sending a CE packet to the TX100 in order to calculate the 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 since 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 (approximately 15 W) under high load 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 power transmission is stable, calculates the power loss, and stores the calculation result as the first calculation result in a high-load state (S817). Then, the TX100 transmits a NAK packet to the RX200 (S818). Thereafter, 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 sends an ACK packet to the RX200 notifying that the calculation of the estimated power loss was successful in response to the second calibration request (S825).

[0102] Fig. 9 shows an example of a communication sequence when 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 an unstable condition in which 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.

[0103] The processing in steps S901 to S915 is the same as steps S801 to S815 described with reference to FIG. 8, and therefore a description thereof will be omitted.

[0104] Immediately after sending the CE packet in S913, the RX200 sends an RP packet (Mode=2) specifying the received power value under high load conditions (approximately 15 W) to the TX100 (S916). At this time, the TX100 determines that 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 sends a NAK packet to the RX200 without calculating or recording the power loss (S918).

[0105] Thereafter, when an RP packet is sent from RX200 after the timer started in S915 has expired (S919), 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 processing in steps S921 to S928 is the same as steps S818 to S825 described with reference to FIG. 8, and therefore a description thereof will be omitted.

[0107] As described above, according to this embodiment, the TX100 can measure and calculate the estimated power loss between the RX200 in a stable environment. In other words, the transmitted power or received power, which may vary when a sudden environmental change occurs, can be excluded from the original data used to calculate the estimated power loss. As a result, the transmitted power and received power 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 subsequent power transmission process, thereby improving the accuracy of foreign object detection during the power transmission process.

[0108] In the above embodiment, a method was shown in which the transmission power value measured and calculated immediately after switching 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 calculating the estimated power loss. Also, a method was shown in which the calculation processing unit 304 calculates the standard deviation of the transmission power continuously measured and calculated, and if the value is equal to or greater than a threshold, the data is not used in calculating the estimated power loss. By adopting such a configuration, it is possible to take into account variations in the measured and calculated data due to factors inside the TX100.

[0109] In the above-described embodiment, the TX100 calculates power loss based on the received power value specified in the RP packet transmitted from the RX200, and averages the calculated results to calculate the estimated power loss. The method also calculates the standard deviation of the most recently calculated power loss or received power, and if the value is equal to or greater than a threshold, does not use that data in the calculation of the estimated power loss. This configuration allows for consideration of variations in measured and calculated data due to environmental factors between the TX100 and the RX200. For example, this avoids the problem of a value calculated in a situation where the contact surfaces of the TX100 and the RX200 are slightly misaligned due to slight vibrations being used as an estimated value in a stationary state.

[0110] In the above embodiment, a method was shown in which, if the voltage change amount instructed by the RX200 in a CE packet is equal to or greater than a threshold, the TX100 does not use the transmission power value measured and calculated at that time and the received power value corresponding to that transmission power value in calculating the estimated power loss. Because the voltage change amount in response to a 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 this 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 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 a certain number of times or for a certain period of time, it can determine that the environment is one in which 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 in which the transmission power output is not always stable.

[0113] Furthermore, 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 variation in the calculated values ​​is normal and change the aforementioned thresholds to larger values ​​before determining whether the state is stable. In this case, the threshold (the difference from the estimated power loss) used when actually performing foreign object detection processing can also be changed. This configuration makes it possible to perform power transmission processing and foreign object detection processing in an optimal state even in an environment with constant vibration, such as inside a moving vehicle.

[0114] In this embodiment, the method for determining whether the power transmission process from the TX100 to the RX200 is stable uses the variations in the transmitted power, power loss, and received power, the amount of change in the specified power, and the like. However, the present invention is not limited to this. For example, the TX100 may be equipped with hardware such as a vibration sensor or a magnetic sensor, and if each sensor detects vibration or magnetism above a threshold, the TX100 may determine that the power transmission process is unstable and return a NAK to the RP packet. Alternatively, the TX100 may be connected to an external device other than the RX200 via wireless or other means, and may obtain information from the external device indicating whether the power transmission process is stable. Combining these methods, including the method described in this embodiment, can further improve the accuracy of the calculation process of the estimated power loss.

[0115] In the present embodiment, an example has been described in which the estimated power loss is calculated at two power receiving states of the power receiving device, a low load state and a high load state, but the present invention is not limited to this. For example, the above-described method may also be used when calculating the estimated power loss at three or more states. Furthermore, the present invention is not limited to this example, but the present invention is not limited to this example. 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 has been 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 has been shown in which an RP packet is used as a signal for notifying the TX100 of a 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] Although the various thresholds and timeout values ​​shown in this embodiment have been described as being predetermined fixed values, 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 through negotiation between the TX100 and RX200 in the negotiation phase, for example.

[0118] In addition, in the present embodiment, the transmitted power and the estimated power loss are stored in association with each other in S613 of FIG. 6 , and the graph of FIG. 10 is created using this 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. Alternatively, the transmitted power and the received power may be stored in association with each other and a graph may be created. Furthermore, all 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 is described with the transmitted power on the horizontal axis and the received power on the vertical axis. However, any combination of the transmitted power, the received power, or the power loss may be used as the horizontal and vertical axis. Regardless of which 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 implemented by hardware. When implementing by hardware, for example, a specific compiler may be used to automatically generate a dedicated circuit on an FPGA from a program for implementing each step. Also, a gate array circuit may be formed in the same manner as an FPGA and implemented as hardware.

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

[0121] 100 Power transmission device 200 Powered Device

Claims

1. A method performed by a power transmission device, 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 transmitting step of 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; a second receiving step of receiving, after the positive response is transmitted in the first transmitting step, a second received power packet including information indicating a value of a second received 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; A method comprising:

2. A method performed by a power transmission device, 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 transmitting step of transmitting an acknowledgment to the first received power packet when a value indicated by a Control Error packet received from the power receiving device is equal to a predetermined value; a second receiving step of receiving, after the first transmitting step, a second received power packet including information indicating a value of a second received 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; A method comprising:

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

4. A power transmission device, power transmission 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; 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, power transmission 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, and 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 transmission device characterized by:

Images