Power receiving device, method performed by the power receiving device, and program

Abstract

To prevent a reduction in the accuracy of foreign substance detection processing based on power loss even though input of voltage to a power transmission part is changed in a power transmission device.SOLUTION: A power reception device has power receiving means that receives power wirelessly transmitted from a power transmission device, communication means that communicates with the power transmission device, and changing means that changes the voltage of the power reception device. The communication means transmits, to the power transmission device, a first received power packet including information indicating the value of first received power. The changing means changes the voltage of the power reception device on the basis of authentication of the power transmission device after the first received power packet is transmitted. The communication means transmits, to the power transmission device, a second received power packet including information indicating the value of second received power after the first received power packet is transmitted and the voltage of the power reception device is changed. The communication means transmits, to the power transmission device, a third received power packet including information indicating the value of third received power after the second received power packet is transmitted. The communication means transmits identification information to the power transmission device.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power receiving device for wireless power transmission, a method performed by the power receiving device, and a program.

Background Art

[0002] In recent years, technical development of wireless power transmission systems such as wireless charging systems has been widely carried out. Patent Document 1 describes a power transmission device and a power receiving device compliant with a standard (hereinafter referred to as the "WPC standard") formulated by the wireless charging standardization organization Wireless Power Consortium (WPC). Further, Patent Document 1 describes a calibration process defined in the WPC standard for enhancing the accuracy of detection of a conductive object (foreign object) such as a metal piece.

[0003] In the calibration process, the received power of the power receiving device and the power loss at that time are acquired in each of two different states. The power loss is obtained as the difference between the transmitted power in the power transmission device and the received power in the power receiving device. Then, by using the pair of the received power and the power loss in these two states as a parameter, the power loss expected for the received power notified from the power receiving device in wireless power transmission is obtained. When the difference between the actual power loss and the expected power loss exceeds a predetermined value, it is possible to determine that there is a power loss due to a foreign object, that is, a foreign object is present.

[0004] On the other hand, Universal Serial Bus Power Delivery (USB PD) is widespread as a standard for supplying power for rapid charging to a battery by wire. In USB PD, when the power supplied to a load increases, control is performed to increase the voltage output to the load accordingly. Thereby, even when the supplied power increases, the current is kept low, so that losses and heat generation in the circuit can be suppressed, and power can be supplied to the load while maintaining high efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a power transmission device for wireless power transmission, when changing the input voltage to a power transmission unit including a power transmission coil to change the transmitted power, the power loss in each state of the power reception device changes before and after changing the input voltage. Therefore, when attempting to perform foreign object detection in a state after changing the input voltage using the set of received power and power loss obtained in the state before changing the input voltage to the power transmission unit as parameters, the detection accuracy of foreign objects decreases.

[0007] The present invention provides a technique for suppressing a decrease in the accuracy of foreign object detection processing based on power loss even when the input voltage to the power transmission unit is changed in the power transmission device.

Means for Solving the Problems

[0008] A power reception device according to an aspect of the present invention has the following configuration. That is, Power reception means for receiving power wirelessly transmitted from a power transmission device, Communication means for communicating with the power transmission device, Changing means for changing the voltage of the power reception device, and has The communication means transmits a first received power packet including information indicating a value of first received power to the power transmission device, The changing means changes the voltage of the power reception device based on authentication with the power transmission device after the first received power packet is transmitted, The communication means transmits a second received power packet including information indicating a value of second received power to the power transmission device after the first received power packet is transmitted and after the voltage of the power reception device is changed, After the second received power packet is transmitted, the communication means transmits a third received power packet including information indicating a value of a third received power to the power transmission device. The communication means transmits identification information to the power transmission device.

Advantages of the Invention

[0009] According to the present invention, even when the input voltage to the power transmission unit in the power transmission device is changed, it is possible to suppress a decrease in the accuracy of the foreign object detection process based on power loss.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] 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 the present invention is not intended to be limited to the configurations and methods described in the embodiments.

[0012] <First Embodiment> (Configuration of the System) FIG. 1 shows a configuration example of a wireless charging system (wireless power transmission system) according to the present embodiment. This system includes a power transmission device 101 and a power reception device 102. Hereinafter, the power transmission device may be referred to as TX, and the power reception device may be referred to as RX. TX101 is an electronic device that wirelessly transmits power to RX102 placed on the charging stand 103. RX102 is an electronic device that receives the power wirelessly transmitted from TX101 and charges the built-in battery. Hereinafter, the case where RX102 is placed on the charging stand 103 will be described as an example. However, in order for TX101 to transmit power to RX102, RX102 only needs to be within the power transmission range of TX101, and it is not necessarily required that RX102 be placed on the charging stand 103.

[0013] Note that TX101 and RX102 may each have a function to execute applications other than wireless charging. An example of RX102 is a mobile information device that operates on a rechargeable battery, such as a laptop PC (Personal Computer), a tablet PC, or a smartphone. Also, an example of TX101 is an accessory device for charging the mobile information device. Note that TX101 and RX102 may be storage devices such as a hard disk device or a memory device, or may be information processing devices such as a personal computer (PC). Also, TX101 and RX102 may be, for example, image input devices such as an imaging device (a camera, a video camera, etc.) or a scanner, or may be image output devices such as a printer, a copier, or a projector. Also, TX101 may be a mobile information device. In this case, RX102 may be another mobile information device or may be a wireless earphone. Also, RX102 may be an automobile. Also, TX101 may be a charger installed in a console or the like inside an automobile.

[0014] Also, in the wireless charging system of the present embodiment, one TX101 and one RX102 are shown, but the present invention is not limited to this. The present invention can also be applied to a configuration in which a plurality of RX102 receive power transmitted from one TX101 or from separate TX101s.

[0015] This system performs wireless power transmission using an electromagnetic induction method for wireless charging based on the Wireless Power Consortium standard (hereinafter, the WPC standard). That is, TX101 and RX102 perform wireless power transmission for wireless charging based on the WPC standard between the power transmission coil of TX101 and the power reception coil of RX102. 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 other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, methods using lasers, or the like. Also, in the present embodiment, it is assumed that wireless power transmission is used for wireless charging, but wireless power transmission may be performed for uses other than wireless charging.

[0016] In the WPC standard, the amount of power guaranteed when RX102 receives power from TX101 is defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value guaranteed for the output to the load of RX102 (for example, a charging circuit, etc.), even if the positional relationship between TX101 and RX102 changes and the power transmission efficiency between the power receiving coil and the power transmitting coil decreases. For example, when GP is 5 watts, even if the positional relationship between the power receiving coil and the power transmitting coil changes and the power transmission efficiency decreases, TX101 controls the power transmission so that it can output 5 watts to the load in RX102.

[0017] TX101 and RX102 according to this embodiment perform communication for power transmission and reception control based on the WPC standard. In the WPC standard, a plurality of phases are defined, including a Power Transfer phase in which power transmission is executed and a phase before power transmission is executed, and communication for power transmission and reception control is performed in each phase. The phases before power transmission include a Selection phase, a Ping phase, an Identification and Configuration phase, a Negotiation phase, and a Calibration phase. Hereinafter, the Identification and Configuration phase is referred to as the I&C phase.

[0018] In the Selection phase, TX101 intermittently repeats sending an Analog Ping to detect that an object has been placed on the charging stand 103 (for example, RX102, a conductor piece, etc. has been placed on the charging stand 103). The Analog Ping is a detection signal for detecting the presence of an object. TX101 sends the Analog Ping by applying a voltage or current to the power transmission coil. When the state changes from a state where no object is placed on the charging stand 103 to a state where an object is placed, a change occurs in the voltage or current applied to the power transmission coil. TX101 detects at least one of the voltage value and the current value of the power transmission coil when sending the Analog Ping, and determines that an object is present when the voltage value is below a certain threshold or the current value exceeds a certain threshold, and then transitions to the Ping phase.

[0019] In the Ping phase, TX101 sends a Digital Ping with higher power than the Analog Ping. The power of the Digital Ping is sufficient to activate the control unit of RX102 placed on the charging stand 103. RX102 notifies TX101 of the magnitude of the received power voltage. In this embodiment, RX102 sends a Signal Strength packet (hereinafter referred to as "SS packet") to TX101. TX101 recognizes that the object detected in the Selection phase is RX102 by receiving the response (SS packet) from RX102 that has received the Digital Ping sent by itself. When receiving the notification of the received power voltage value, TX101 transitions to the I&C phase.

[0020] In the I&C phase, TX101 identifies RX102 and acquires device configuration information (capability information) from RX102. Therefore, RX102 transmits an Identification Packet (ID Packet) and a Configuration Packet to TX101. The ID Packet contains the identification information of RX102, and the Configuration Packet contains the device configuration information (capability information) of RX102. TX101 that has received the ID Packet and the Configuration Packet responds with an acknowledgement (ACK). Then, the I&C phase ends. In the subsequent Negotiation phase, the value of GP is determined based on the value of GP requested by RX102, the power transmission capability of TX101, etc.

[0021] In the Calibration phase, RX102 notifies TX101 of the received power using a Received Power Packet. At this time, RX102 notifies at least two different received powers. For example, RX102 notifies two received powers: the received power in a state where no load is connected and the received power in a state where a load is connected and power close to the value of GP is being received. Accordingly, TX101 acquires the power transmission power of its own device when each of those received powers is notified, obtains the power loss from the difference between the power transmission power and the received power, and stores it in association with the received power. In the subsequent Power Transfer phase, TX101 performs a foreign object detection process for detecting foreign objects other than the power receiving device using the pair of received power and power loss stored as described above as parameters.

[0022] Here, a method for performing a foreign object detection process using two sets of received power and power loss as parameters in TX101 will be described. TX101 stores two sets of received power and power loss through communication in the Calibration phase. Assume that one set of these two sets is "received power = RP1, power loss = PL1", and the other set is "received power = RP2, power loss = PL2".

[0023] When performing foreign object detection processing in the Power Transfer phase, TX101 first obtains the current received power = P from RX102. received Subsequently, TX101 determines the expected value of power loss PL cal at this time by linear interpolation between two points (RP1, PL1) and (RP2, PL2). It is assumed that RP1 < RP2. Specifically, it can be obtained by the following Equation 1. [Equation 1] PL cal = (PL2 - PL1) / (RP2 - RP1) · (P received - RP1) + PL1

[0024] Here, the current power loss PL is obtained from the current transmission power P in TX101 transmitted and the received power = P notified from RX102 received by the following Equation 2. When the current power loss PL exceeds the expected value PL cal by a predetermined threshold, TX101 determines that the power is consumed more than the foreign object value, resulting in an increase in power loss, that is, a foreign object is detected. [Equation 2] PL = P transmitted - P received

[0025] In the above method, the expected value of the current power loss is obtained by linear interpolation using the previously obtained power loss value as a parameter. This is expressed as calibrating the power loss. Note that the object to be calibrated may be, for example, the received power of RX102 or the transmitted power of TX101 instead of the power loss of RX102. Also, the method for obtaining the expected value of the power loss, that is, the calibration method, is not limited to linear interpolation, and may be, for example, non-linear interpolation using a power series or the like. Further, three or more sets of information (for example, a set of received power and transmitted power) may be used as parameters. An example of using three or more sets of information as parameters is a piecewise linear interpolation connecting (RP1, PL1) and (RP2, PL2), and (RP2, PL2) and (RP3, PL3). Here, (RP3, PL3) is the information of the third set of received power and power loss, and RP2 < RP3.

[0026] In the Power Transfer phase, control for starting, continuing power transmission, and stopping power transmission due to foreign object detection or full charge is performed. In the present embodiment, in the Power Transfer phase, further, processing for changing GP, changing the transmission voltage of the power transmission device, changing the output voltage to the load of the power reception device, and processing for re-acquiring or additionally requesting parameters for foreign object detection processing are performed. Details of these processes will be described later.

[0027] TX101 and RX102 perform communication for these power transmission and reception controls based on the WPC standard by superimposing a signal on the power transmission power using the same antenna (coil) as the wireless power transmission. Note that TX101 and RX102 may perform communication for power transmission and reception control using an antenna (coil) different from the wireless power transmission. As an example of communication using an antenna (coil) different from the wireless power transmission, a communication method compliant with the Bluetooth (registered trademark) Low Energy standard can be cited. Also, it may be performed by other communication methods such as wireless LAN of the IEEE802.11 standard series (for example, Wi-Fi (registered trademark)), ZigBee, NFC (Near Field Communication). Communication using an antenna (coil) different from the wireless power transmission may be performed at a frequency different from the frequency used in the wireless power transmission.

[0028] (Device Configuration) Subsequently, the configurations of the power transmission device 101 (TX101) and the power reception device 102 (RX102) according to the present embodiment will be described. Note that the configurations described below are merely examples, and a part (in some cases, all) of the described configurations may be replaced with or omitted by other configurations that perform the same functions, and further configurations may be added to the configurations described below. Furthermore, one block shown in the following description may be divided into a plurality of blocks, or a plurality of blocks may be integrated into one block.

[0029] FIG. 2 is a block diagram showing a configuration example of TX101 according to the present embodiment. In one example, TX101 includes a control unit 201, a power supply unit 202, a power transmission unit 203, a placement detection unit 204, a power transmission coil 205, a communication unit 206, a notification unit 207, an operation unit 208, a memory 209, a timer 210, an input voltage setting unit 211, and a re-acquisition request unit 212.

[0030] The control unit 201 controls the entire TX101 by executing, for example, a control program stored in the memory 209. That is, the control unit 201 controls each functional unit shown in FIG. 2. Also, the control unit 201 performs control related to power transmission control in the TX101. Further, the control unit 201 may perform control for executing applications other than wireless power transmission. The control unit 201 includes, for example, one or more processors such as a CPU or an MPU. Note that the control unit 201 may include dedicated hardware for specific processing such as an application specific integrated circuit (ASIC), or an array circuit such as an FPGA compiled to execute predetermined processing. The control unit 201 stores in the memory 209 information to be stored during the execution of various processes. Also, the control unit 201 can measure time using the timer 210.

[0031] The power supply unit 202 supplies power necessary for the control of the TX101 by the control unit 201, power transmission, and communication to the entire TX101. The power supply unit 202 is, for example, a commercial power supply or a battery. In the battery, power supplied from the commercial power supply is stored.

[0032] The power transmission unit 203 converts the DC or AC power input from the power supply unit 202 into AC frequency power in the frequency band used for wireless power transmission, and generates an electromagnetic wave for causing RX102 to receive power by inputting the AC frequency power to the power transmission coil 205. Note that the frequency of the AC power generated by the power transmission unit 203 is, for example, about several hundreds of kHz (for example, 110 kHz to 205 kHz). The power transmission unit 203 inputs the AC frequency power to the power transmission coil 205 so as to output an electromagnetic wave for performing power transmission to RX102 based on an instruction from the control unit 201. Further, the power transmission unit 203 controls the intensity of the output electromagnetic wave by adjusting the voltage (transmission voltage) or current (transmission current), or both, input to the power transmission coil 205. When the transmission voltage or transmission current is increased, the intensity of the electromagnetic wave becomes stronger, and when the transmission voltage or transmission current is decreased, the intensity of the electromagnetic wave becomes weaker. Also, the power transmission unit 203 performs output control of the AC frequency power so that power transmission from the power transmission coil 205 is started or stopped based on an instruction from the control unit 201. Furthermore, the power transmission unit 203 notifies the control unit 201 of the current transmission power. Thereby, the control unit 201 can know the current transmission power at an arbitrary timing. Note that the measurement of the transmission power and the notification to the control unit 201 may be configured to be performed by other than the power transmission unit 203.

[0033] The placement detection unit 204 detects whether an object is placed on the charging stand 103 based on the WPC standard. Specifically, the placement detection unit 204 detects whether an object is placed on the Interface Surface of the charging stand 103. For example, the placement detection unit 204 detects at least one of the voltage value and the current value of the power transmission coil 205 when the power transmission unit 203 transmits an Analog Ping of the WPC standard via the power transmission coil 205. Note that the placement detection unit 204 may detect a change in impedance. When the voltage is below a predetermined voltage value or the current value exceeds a predetermined current value, the placement detection unit 204 may determine that an object is placed on the charging stand 103. Whether this object is a power receiving device or other foreign object is determined by the presence or absence of a predetermined response from RX102 to the Digital Ping subsequently transmitted by the communication unit 206. That is, when TX101 receives a predetermined response, it is determined that the object is a power receiving device (RX102), and otherwise, it is determined that the object is an object different from the power receiving device.

[0034] The communication unit 206 performs control communication based on the WPC standard as described above with RX102. The communication unit 206 modulates the electromagnetic wave output from the power transmission coil 205, transmits information to RX102, and performs communication. Also, the communication unit 206 demodulates the electromagnetic wave output from the power transmission coil 205 and modulated at RX102 to acquire the information transmitted by RX102. That is, the communication performed by the communication unit 206 is performed by being superimposed on the electromagnetic wave transmitted from the power transmission coil 205.

[0035] The notification unit 207 notifies the user of information by any method such as visual, auditory, or tactile. The notification unit 207 notifies the user of, for example, the charging state of TX101 or the state regarding power transmission of the wireless power transmission system including TX101 and RX102 as shown in FIG. 1. The notification unit 207 is configured to include, for example, a liquid crystal display, an LED, a speaker, a vibration generation circuit, and other notification devices.

[0036] The operation unit 208 has a reception function for receiving operations on the TX101 from the user. The operation unit 208 includes, for example, buttons, a keyboard, a voice input device such as a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, or other input devices. Note that a device in which the notification unit 207 and the operation unit 208 are integrated, such as a touch panel, may be used.

[0037] The memory 209 stores various information such as identification information and capability information, and control programs. Note that the memory 209 may store information obtained by a functional unit different from the control unit 201. The timer 210 measures time, for example, by an up-counter timer that measures the elapsed time from the start time, or a down-counter timer that counts down from the set time. The input voltage setting unit 211 sets an input voltage for supplying power from the power supply unit 202 to the power transmission unit 203 based on the control of the control unit 201. The input voltage setting unit 211 includes a variable voltage circuit.

[0038] The re-acquisition request unit 212 requests the re-acquisition of the foreign object detection processing parameters for the RX102 using the communication unit 206. The foreign object detection processing parameters are one or more pairs of received power and power loss described in the above description of the Calibration phase. The re-acquisition request unit 212 may be configured to operate on a processor separate from the control unit 201 for all or part of it, or may be executed by a program operating on the control unit 201. The re-acquisition request unit 212 can perform its function, for example, by executing a program stored in the memory 209.

[0039] Here, the power supply unit 202 and the input voltage setting unit 211 may exist as separate devices outside the TX101. Examples of such external devices include a power adapter that supplies power based on the USB PD standard. In that case, the control of the input voltage setting unit 211 by the control unit 201 may be performed by USB PD standard communication.

[0040] FIG. 3 is a block diagram showing a configuration example of RX102 according to the present embodiment. RX102 includes a control unit 301, a battery 302, a power receiving unit 303, a placement detection unit 304, a power receiving coil 305, a communication unit 306, a notification unit 307, an operation unit 308, a memory 309, and a timer 310. Further, RX102 includes an output voltage setting unit 311, a re-acquisition instruction unit 312, and a charging unit 313.

[0041] The control unit 301 controls the entire RX102 by executing, for example, a control program stored in the memory 309. That is, the control unit 301 controls each functional unit shown in FIG. 3. Further, the control unit 301 performs control related to power reception control in RX102. Furthermore, the control unit 301 may perform control for executing applications other than wireless power transmission. The control unit 301 includes, for example, one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Note that the control unit 301 may be configured by hardware dedicated to specific processing such as an ASIC (Application Specific Integrated Circuit). Further, the control unit 301 may include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 301 stores information to be stored during execution of various processes in the memory 309. Also, the control unit 301 can measure time using the timer 310.

[0042] The battery 302 supplies power necessary for controlling each part of RX102 by the control unit 301, power reception, and communication to the entire RX102. Further, the battery 302 stores the power received via the power receiving coil 305.

[0043] In the power receiving coil 305, an induced electromotive force is generated by the electromagnetic wave radiated from the power transmission coil 205 of TX101. The power receiving unit 303 acquires the power generated in the power receiving coil 305. The power receiving unit 303 acquires the AC power generated by electromagnetic induction in the power receiving coil 305, converts the AC power into DC power or AC power of a predetermined frequency, and outputs it to a charging unit 313 that performs a process of charging the battery 302. That is, the power receiving unit 303 supplies power to the load in RX102, and the charging unit 313 and the battery 302 are an example of such a load. The above-mentioned GP is the power guaranteed to be output from the power receiving unit 303. Further, the power receiving unit 303 notifies the control unit 301 of the current received power. Thereby, the control unit 301 can know the received power at that timing at an arbitrary timing. Note that the measurement of the received power and the notification of the received power to the control unit 301 may be configured to be performed outside the power receiving unit 303.

[0044] The placement detection unit 304 detects that RX102 is placed on the charging stand 103 based on the WPC standard. The placement detection unit 304 detects, for example, at least one of the voltage value and the current value of the power receiving coil 305 when the power receiving unit 303 receives a Digital Ping of the WPC standard via the power receiving coil 305. The placement detection unit 304 determines that RX102 is placed on the charging stand 103, for example, when the voltage value is lower than a predetermined voltage threshold or when the current value exceeds a predetermined current threshold.

[0045] The communication unit 306 performs control communication based on the WPC standard as described above with TX101. The communication unit 306 demodulates the electromagnetic wave input from the power receiving coil 305 to acquire the information transmitted from TX101, and superimposes the information to be transmitted to TX101 on the electromagnetic wave by load modulating the electromagnetic wave, thereby performing communication with TX101. That is, the communication performed by the communication unit 306 is performed by being superimposed on the electromagnetic wave transmitted from the power transmission coil of TX101.

[0046] The notification unit 307 notifies the user of information by any method such as visual, auditory, tactile, etc. The notification unit 307 notifies the user of, for example, the charging state of the RX102 or the state related to the power transmission of the wireless power transmission system including the TX101 and RX102 as shown in FIG. 1. The notification unit 307 is configured to include, for example, a liquid crystal display, an LED, a speaker, a vibration generation circuit, and other notification devices. The operation unit 308 has a reception function of receiving an operation on the RX102 from the user. The operation unit 308 is configured to include, for example, a button, a keyboard, a voice input device such as a microphone, a motion detection device such as an acceleration sensor and a gyro sensor, or other input devices. Note that a device in which the notification unit 307 and the operation unit 308 are integrated, such as a touch panel, may be used. The memory 309 stores various information such as identification information and device configuration information, and control programs as described above. Note that the memory 309 may store information obtained by a functional unit different from the control unit 301. The timer 310 measures time, for example, by an up-counter that measures the elapsed time from the start time, a down-counter that counts down from the set time, or the like.

[0047] The charging unit 313 charges the battery 302 with the power supplied from the power receiving unit 303. Also, based on the control of the control unit 301, the charging unit 313 starts or stops charging the battery 302, and further adjusts the power used for charging the battery 302 based on the charging state of the battery 302. When the power used by the charging unit 313 changes, the power supplied from the power receiving unit 303 accordingly, that is, the received power in RX102 also changes. As described above, the charging unit 313 is a load in RX102. Note that the charging unit 313 and the battery 302 may exist as separate devices outside RX102. That device may be, for example, a device that operates with power supplied based on the USB PD standard. In that case, the control unit 301 may acquire information on the magnitude of the power required by the charging unit 313 from the charging unit 313 through USB PD standard communication. The output voltage setting unit 311 sets the output voltage for supplying power from the power receiving unit 303 to the charging unit 313, that is, to the load, based on the control by the control unit 301. The output voltage setting unit 311 includes a variable voltage circuit.

[0048] The re-acquisition instruction unit 312 uses the communication unit 306 to instruct the start of re-acquisition of the foreign object detection processing parameters at TX101. The foreign object detection processing parameters are the pair of received power and power loss described in the above explanation of the Calibration phase. Note that the re-acquisition instruction unit 312 may be configured to operate with all or part of it on a processor separate from the control unit 301, or may be executed by a program operating on the control unit 301. The re-acquisition instruction unit 312 can perform its function, for example, by executing a program stored in the memory 309.

[0049] (Flow of processing) Subsequently, an example of the flow of processing executed by TX101 and RX102 will be described.

[0050] [Processing in the power transmission device] FIG. 4 is a flowchart showing an example of the processing flow executed by TX101. This processing can be realized, for example, by the control unit 201 of TX101 executing a program read from the memory 209. This processing also includes the processing in the re-acquisition request unit 212. Note that at least a part of the following procedures may be realized by hardware. In this case, the hardware can be realized, for example, by automatically generating a dedicated circuit using a gate array circuit such as an FPGA from a program for realizing each processing step using a predetermined compiler. Also, this processing can be started in response to the power of TX101 being turned on, in response to the user of TX101 inputting an instruction to start the wireless charging application, or in response to TX101 being connected to a commercial power supply and receiving power supply. However, this processing may be started by other triggers.

[0051] In the processing related to power transmission and reception, TX101 first executes the processing defined as the Selection phase and Ping phase of the WPC standard and waits for the placement of RX102 (S401). Specifically, TX101 repeatedly and intermittently transmits the Analog Ping of the WPC standard, and the placement detection unit 204 detects the presence or absence of an object placed on the charging stand 103 based on the change in current or voltage in the power transmission coil 205. When TX101 detects that an object is placed on the charging stand 103, it transmits a Digital Ping. Then, when there is a predetermined response (Signal Strength Packet) to the Digital Ping, TX101 determines that the detected object is RX102 and RX102 is placed on the charging stand 103. When TX101 detects the placement of RX102, the communication unit 206 executes the processing defined as the I&C phase of the WPC standard to acquire the identification information and device configuration information (capability information) from the RX102 (S402).

[0052] Figure 7(A) shows the communication flow in the I&C phase. In the I&C phase, RX102 transmits an Identification Packet (ID Packet) to TX101 (F701). The ID Packet stores, in addition to the Manufacturer Code and Basic Device ID which are the identification information of RX102, information elements that can identify the version of the WPC standard corresponding to the capability information of RX102. RX102 further transmits a Configuration Packet to TX101 (F702). The Configuration Packet includes, as the capability information of RX102, a Maximum Power Value which is a value specifying the maximum power that RX102 can supply to the load, and information indicating whether it has the Negotiation function of the WPC standard.

[0053] When TX101 receives these packets, it transmits an ACK (F703), and the I&C phase ends. Note that TX101 may obtain the identification information and device configuration information (capability information) of RX102 from RX102 by a method other than the communication in the I&C phase of the WPC standard. Also, the identification information of RX102 may be the Wireless Power ID of the WPC standard, or any other identification information that can identify the individual of RX102. As the capability information, information other than the above may be included.

[0054] Returning to Figure 4, TX101 negotiates with RX102 to determine the GP through the communication in the Negotiation phase (S403). Figure 7(B) shows an example of the flow in the Negotiation phase. The determination of the GP is made by a Specific Request Packet from RX102 and the response from TX101 thereto. First, RX102 notifies the value of the requested GP by transmitting a Specific Request Packet to TX101 (F711). RX102 determines the value of the requested GP based on the power required by its own device. In this embodiment, an example of the value of the GP requested at this stage is 5 watts.

[0055] TX101 determines whether to accept a request from RX102 based on its own power transmission capacity. If it accepts, it sends an ACK (positive response) to RX102; if it does not accept, it sends a NAK (negative response) to RX102. In FIG. 7(B), an example where TX101 sends an ACK is shown (F712). When TX101 sends an ACK, the value of GP is determined to be the same as the value requested by RX102 and stored in the memories of both TX101 and RX102. On the other hand, when TX101 sends a NAK, the value of GP becomes a default small value, for example, a value of 5 watts or less. The default value is stored in the memories of both TX101 and RX102 in advance in one example. Note that the method for determining GP described above is just an example, and GP may be determined by other methods.

[0056] Returning to FIG. 4, the input voltage setting unit 211 of TX101 determines the input voltage for supplying power from the power supply unit 202 to the power transmission unit 203 based on the GP determined at S403 and sets it in the power transmission unit 203 (S404). Note that this process also includes a process of waiting for the voltage to stabilize and be input to the power transmission unit 203 after the input voltage setting unit 211 sets the input voltage in the power transmission unit 203. An example of the input voltage determined based on GP is shown in Table 1001 in FIG. 10(A). By referring to Table 1001, the input voltage setting unit 211 can set, for example, the input voltage to 5 volts when the determined GP is 5 watts, and the input voltage to 9 volts when the determined GP is 15 watts. Here, each value in Table 1001 is a value of the input voltage determined in advance to efficiently transmit the determined power based on the electrical characteristics of the power transmission unit 203 of TX101, and is held in the memory 209, for example. Note that when the power supply unit 202 and the input voltage setting unit 211 are external devices operating based on the USB PD standard, the input voltage setting unit 211 may obtain the values in Table 1001 from the control unit 201 through communication. Alternatively, Table 1001 may be held in the memory 209 as a table defined by the USB PD standard.

[0057] Returning to FIG. 4, after setting the input voltage, TX101 acquires the parameters for foreign object detection processing through the processing in the Calibration phase (S405). FIG. 7(C) shows the communication in the Calibration phase. RX102 transmits a Received Power Packet via the communication unit 306 (F721). The Received Power Packet includes a Received Power Value indicating the current received power. TX101 stores the information on the received power included in the Received Power Packet as parameters for foreign object detection processing and then returns an ACK (F722). As shown below, F721 and F722 are repeated at least twice.

[0058] For example, RX102 notifies the received power in two different states: a state where no load is connected, i.e., a state close to 0 watts, and a state where a load is connected and power close to the GP value is being received. For these notifications, the communication of the Received Power Packet and ACK occurs twice, and TX101 stores the information on the two received powers. In addition to the above, the received power in the middle between the state close to 0 watts and the state where power close to the GP value is being received may also be notified. In this embodiment, when the value of GP exceeds 5 watts, the received power is notified at power value intervals of approximately 5 watts. For example, when the value of GP is 15 watts, the received power is notified in four received power states of approximately 0 watts, approximately 5 watts, approximately 10 watts, and approximately 15 watts. Note that the power value interval does not have to be constant and does not have to be 5 watts. TX101 stores all the notified received powers as parameters for foreign object detection processing in the memory 209.

[0059] Also, RX102 attaches information indicating this to the first Received Power Packet when starting the Calibration phase. Specifically, the value of Mode included in the Received Power Packet is set to 1. Also, for Received Power Packets after the second time in the Calibration phase, the value of Mode is set to a value other than 1, for example, 2. Thereby, TX101 can identify the start of the Calibration phase based on the value of Mode. Note that the method of identifying the start of the Calibration phase described above is just an example, and the Mode may be set to other values, or it may be identified using a value other than Mode. Also, the start may be identified using another packet.

[0060] When TX101 identifies the start of the Calibration phase by receiving a Received Power Packet with a Mode value of 1, it discards the foreign object detection processing parameters already stored in the memory 209. Then, TX101 stores in the memory 209 the received power included in the Received Power Packet received from RX102 in association with the power loss, which is the difference between the received power and the transmitted power at the transmission unit 203 at that time. Note that instead of the power loss, the transmitted power may be stored in association with the received power, or both the power loss and the transmitted power may be stored in association with the received power. After that, when TX101 receives a Received Power Packet with a Mode value of 2, TX101 stores in the memory 209 by adding the received power included in the packet in association with the power loss at that time.

[0061] Table 800 in FIG. 8 shows an example of the content of the foreign object detection processing parameters stored in the memory 209. For example, the information in row 801 indicates that when the received power at RX102 is 0.1 watt, the power loss is 0.6 watt, and it is stored by receiving a Received Power Packet (Mode = 1) from RX102. Thereafter, each time a Received Power Packet (Mode = 2) is received from RX102, TX101 adds a row to Table 800 (for example, row 802). However, when a Received Power Packet with Mode = 1 is received as described above, TX101 clears the previous content and then starts storing again from row 801.

[0062] Returning to FIG. 4, TX101 starts the foreign object detection process and power transmission (S406, S407). The foreign object detection process in TX101 is performed as follows. First, TX101 periodically acquires information on the current received power from RX102. The notification of the received power from RX102 for the foreign object detection process is made, for example, by a Received Power Packet with a Mode value of 0. When TX101 receives a Received Power Packet (Mode = 0), it does not update the foreign object detection processing parameters (Table 800). Then, TX101 obtains the expected value of the power loss at the acquired received power by linear interpolation at each point using the foreign object detection processing parameters in Table 800 of FIG. 8. Equation 1 above can be used for linear interpolation.

[0063] After obtaining the received power, TX101 calculates the power loss from the difference between the transmitted power measured first (the current transmitted power) and the obtained received power. Then, TX101 compares the difference between the calculated power loss and the expected value with a threshold value. If the difference between the calculated power loss and the expected value exceeds the threshold value, TX101 determines that there is a power loss due to a foreign object such as a metal piece, and determines that there is a foreign object in the transmission range. When it is determined that there is a foreign object in the transmission range, TX101 restricts the power transmission by the control unit 201. Specifically, the control unit 201 controls the power transmission unit 203 to stop the power transmission or reduce the transmitted power. Further, the control unit 201 may notify RX102 of the presence of a foreign object via the communication unit 206. Additionally, the control unit 201 may notify RX102 of restricting the transmitted power.

[0064] Here, taking the case where the content of the foreign object detection processing parameter is the content shown in rows 801 and 802 of Table 800 in FIG. 8 as an example, the foreign object detection processing will be specifically described. When plotting rows 801 and 802 on a graph with the received power and the power loss as axes, they become points A and B in FIG. 9(A) respectively. TX101 obtains the expected value of the power loss at the current received power by linear interpolation using the straight line connecting points A and B. For example, when the value of the current received power (RP) is 2.5 watts, substitute the numerical values of row 801 (RP1 = 0.1 watt, PL1 = 0.6 watt) and row 802 (RP1 = 4.9 watts, PL2 = 1.6 watts) into the above formula 1. In this case, the expected value PL of the power loss is 1.1 as follows. PL=(1.6 - 0.6) / (4.9 - 0.1)*(2.5 - 0.1)+0.6 = 1.1

[0065] Then, after obtaining the received power, TX101 calculates the power loss from the difference between the currently transmitted power, which is the transmitted power measured first after obtaining the received power, and the current received power (RP = 2.5 watts). If the difference between the value of the power loss calculated in this way and the expected value (PL), which is 1.1 watts, exceeds a predetermined threshold, it is determined that power is being lost in the foreign object, and it is determined that the foreign object is within the transmission range. Here, the threshold value may be an absolute value such as 1 watt, for example, or a relative value such as 50 percent with respect to the expected value, for example. Information regarding this threshold value is stored in the memory 209. Also, the threshold value may change stepwise according to the received power or the expected value of the power loss.

[0066] In FIG. 4, TX101 accepts the negotiation of GP from RX102 even during power transmission (S408). As a result of the negotiation, if GP changes, TX101 determines the input voltage to the power transmission unit 203 with reference to Table 1001 in FIG. 10(A). If it is to be changed from the current input voltage (if the determined input voltage is different from the current input voltage) (YES in S409), the input voltage setting unit 211 changes the input voltage (S410). The re-acquisition request unit 212 waits for the input voltage to stabilize (S410) and then transmits a re-acquisition request for the foreign object detection processing parameters to RX102 (S411). On the other hand, if it is not to be changed from the current input voltage (if the determined input voltage is the same as the current input voltage) (NO in S409), the processes of S410 and S411 are skipped. Subsequently, TX101 waits for a re-acquisition instruction for the foreign object detection processing parameters from RX102 for a predetermined time (S412). Here, waiting for the re-acquisition instruction from RX102 for a predetermined time is to give time for RX102, which has received the re-acquisition request, to perform the process of transmitting the re-acquisition instruction for the foreign object detection processing parameters.

[0067] When an instruction to re-acquire the foreign object detection processing parameters is received from RX102 (YES in S413), the process returns to S405, and TX101 re-acquires the foreign object detection processing parameters through the processing in the Calibration phase. Note that the reception of the re-acquisition instruction from RX102 is constantly monitored while TX101 is transmitting power. When a re-acquisition instruction is received from RX102, the process proceeds from S413 to S405, and TX101 executes the re-acquisition of the foreign object detection processing parameters. That is, regardless of whether the input voltage has been changed, when an instruction to re-acquire the foreign object detection processing parameters is received from RX102 (YES in S413), TX101 starts the re-acquisition of the foreign object detection processing parameters. Also, the process of S412 (the process of waiting for the reception of the re-acquisition instruction) may be skipped when it is determined in S408 that the GP is not updated and in S409 that the input voltage is not changed. In S409, the input voltage is changed based on the GP value determined through negotiation with RX102, but it is not limited to this. For example, the control unit 201 may acquire the power transmission power to RX102, and based on this, set and change the input voltage to the power transmission unit 203. Also, in this case as well, the input voltage may be configured to be changed based on the USB PD standard.

[0068] When an instruction to re-acquire the foreign object detection processing parameters has not been received from RX102 (NO in S413), power transmission is continued for a predetermined time (S414). Here, the predetermined time is, for example, 1 second. During this power transmission, if a power transmission stop request is not received and no foreign object is detected (NO in S415), the process returns to S408, and the above process is repeated. When a power transmission stop request is received, or when a foreign object is detected (YES in S415), TX101 stops the power transmission (S416). Then, TX101 determines whether to end the process (S417). When it is determined not to end the process (NO in S417), the process returns to S401, and the above process is repeated. When it is determined to end the process (YES in S417), this process ends. Whether to end the process is determined based on, for example, the operation content of the user's operation unit 208.

[0069] [Processing in the power receiving device] Next, an example of the processing flow executed by RX102 will be described with reference to FIG. 5. This processing can be realized, for example, by the control unit 301 of RX102 executing a program read from the memory 309. This processing also includes the processing in the reacquisition instruction unit 312. Note that at least a part of the procedure of this processing described below may be realized by hardware. In this case, the hardware can be realized, for example, by automatically generating a dedicated circuit using a gate array circuit such as an FPGA from a program for realizing each processing step using a predetermined compiler. Further, this processing can be started in response to the power of RX102 being turned on, RX102 being activated by power supply from the battery 302 or TX101, or the user of RX102 inputting an instruction to start a wireless charging application. Note that this processing may be started by other triggers.

[0070] After starting the processing related to power transmission and reception, RX102 executes the processing defined as the Selection phase and Ping phase of the WPC standard, and waits for the own device to be placed on TX101 (S501). Then, RX102 detects that it is placed on the charging stand 103 of TX101, for example, by detecting a Digital Ping from TX101. Then, when RX102 detects a Digital Ping, it transmits an SS packet including the power reception voltage value to TX101.

[0071] When RX102 detects that the own device is placed on the charging stand 103 of TX101, it executes the communication in the aforementioned I&C phase by the communication unit 306, and transmits identification information and device configuration information (capability information) to TX101 (S502). Then, RX102 negotiates with TX101 through the communication in the Negotiation phase to determine the GP (S503). The communication in the Negotiation phase is specifically performed by the Specific Request Packet shown in FIG. 7(B) and the response thereto, as described in the processing of the power transmission device.

[0072] The output voltage setting unit 311 determines an output voltage for supplying power from the power receiving unit 303 to the charging unit 313 based on the GP determined in S503, and sets it in the charging unit 313 (S504). This process also includes a process in which after the output voltage setting unit 311 sets the output voltage, it waits for the voltage to be stably output to the charging unit 313.

[0073] An example of the output voltage determined based on the GP is shown in Table 1002 of FIG. 10(B). By referring to Table 1002, the output voltage setting unit 311 can determine, for example, that the output voltage is 5 volts when the GP is 5 watts, and the output voltage is 9 volts when the GP is 15 watts. Here, each value in Table 1002 is a value determined in advance for efficient charging based on the electrical characteristics of the charging unit 313 of the RX102 and is assumed to be held in the memory 309. When the charging unit 313 is an external device that operates based on the USB PD standard, the value of the output voltage may be obtained from the charging unit 313 by communication, or may be held in the memory 309 as a table defined by the USB PD standard. In this embodiment, it is assumed that the content of Table 1002 held by the RX102 is the same as the content of Table 1001 held by the TX101. For example, when both the TX101 and the RX102 comply with the USB PD standard, they may be the same. Note that it may also be content that complies with other standards.

[0074] Subsequently, the RX102 notifies the TX101 of the received power information for acquiring the foreign object detection processing parameters by the communication in the above-described Calibration phase (S505). Subsequently, the RX102 connects the charging unit 313, which is a load, to the power receiving unit 303 and starts power reception in the Power Transfer phase (S506).

[0075] While receiving wireless power from TX101, RX102 obtains the necessary power at the charging unit 313 (S507). This value may be pre-held in the memory 309, or may be obtained by communication from an external device when the charging unit 313 is an external device. If the power required by the charging unit 313 is within the current GP range (NO in S508), power reception for a predetermined time is continued without changing the GP (S515). The predetermined time is, for example, 1 second. After that, if the charging unit 313 has completed charging the battery 302, power reception is stopped (YES in S516, S517), and this process ends. Otherwise (NO in S516), the process returns to S507 to continue charging.

[0076] Here, while continuing power reception in S515, RX102 repeatedly and periodically notifies TX101 of the current power reception power. TX101 performs foreign object detection based on this power reception power information. The Received Power Packet of the WPC standard is used for notification of the current power reception power. Here, the Received Power Packet is also used for the communication in the above-mentioned Calibration phase. For this reason, RX102 enables identification of whether it is a notification for causing TX101 to store foreign object detection processing parameters in the Calibration phase or a notification of the current power reception power for performing foreign object detection processing in TX101. Specifically, this is done by setting the Mode value of the Received Power Packet to 0. Note that it may be another value different from the Mode value in the Calibration phase, or the above identification may be performed other than by the Mode value. For example, identification may be enabled by using different types of packets in the Calibration phase and the Power Transfer phase.

[0077] On the other hand, if it becomes necessary to change the GP as a result of obtaining the necessary power at the charging unit 313 (YES in S508), the RX102 negotiates with the TX101 to change the GP (S509). Here, when the GP is set to a size equal to or greater than a predetermined value, the RX102 may authenticate the TX101 through communication. By performing device authentication, power can be received at a power level equal to or greater than a predetermined value only from the TX101 that is guaranteed to meet the conditions of the WPC standard and other standards. An example of device authentication is challenge-response type communication using an electronic certificate.

[0078] Subsequently, the RX102 determines the output voltage to the charging unit 313 based on the updated GP. The output voltage is determined by referring to Table 1002 in FIG. 10(B). If it is necessary to change from the current output voltage (YES in S510), the output voltage setting unit 311 changes the output voltage to the charging unit 313 and waits for the voltage to stabilize (S511). If it is not necessary to change from the current output voltage (NO in S510), the process of S511 is skipped.

[0079] Subsequently, the RX102 waits for a re-acquisition request for the foreign object detection processing parameters from the TX101 for a predetermined period of time (S512). The predetermined period of time in S512 is, for example, longer than the time required to complete the processes of S410 and S411 when the TX101 becomes YES in S409 of FIG. 4 after the communication for updating the GP described in FIG. 7(B) is completed. It is assumed that the value of this predetermined period of time is stored in advance in the memory 309.

[0080] When a request for re-acquiring the parameters for foreign object detection is received from TX101 or when the output voltage is changed in S511 (YES in S513), RX102 transmits an instruction to TX101 to re-acquire the parameters for foreign object detection (S514). Then, the process proceeds to S505, and the Calibration phase process is performed again between TX101 and RX102. On the other hand, when a request for re-acquiring the parameters for foreign object detection from TX101 is not received and the output voltage has not been changed in S511 (NO in S513), the process proceeds to S515. The processes after S515 are as described above.

[0081] Here, the instruction to re-acquire the parameters for foreign object detection transmitted by RX102 may be a packet conforming to the WPC standard or another packet recognizable by TX101. Alternatively, when RX102 receives a request for re-acquiring the parameters for foreign object detection from TX101, the positive response (ACK) thereto may be used as the instruction to re-acquire the parameters. Furthermore, the instruction to re-acquire the parameters for foreign object detection transmitted by RX102 may be the same as the packet indicating the start of the Calibration phase. That is, RX102 may use the transmission of F721 in FIG. 7(C) as the instruction to re-acquire the parameters for foreign object detection. Thereby, TX101 clears the parameters for foreign object detection already stored therein and starts the communication in the Calibration phase. That is, the parameters for foreign object detection are re-acquired.

[0082] Also, in FIG. 5, although the processing in which an instruction to re-acquire the foreign object detection processing parameters can be issued when GP is changed is shown, it is not limited to this. For example, when it is determined in S508 that GP is not changed (NO in S508), the processing may skip S509 and proceed to S510. In this way, regardless of the change in GP, RX102 issues a re-acquisition instruction in response to receiving a re-acquisition request from TX101 during power reception, and the re-acquisition of the foreign object detection processing parameters is executed (YES in S513). As a result, even when TX101 changes the input voltage without updating GP and issues a re-acquisition request for the foreign object detection processing parameters, RX102 can issue a re-acquisition instruction. In this case, since RX102 monitors the reception of the re-acquisition request during power reception, S511 and S512 may be configured to be skipped when it is determined as NO in S510.

[0083] [System Operation] The operation sequence of TX101 and RX102 described with reference to FIGS. 4 and 5 will be described more specifically with reference to FIG. 6. FIG. 6 is a diagram showing an example of the flow of processing executed in the wireless charging system according to the first embodiment. In FIG. 6, it is assumed that time progresses in the downward direction from top to bottom. As an initial state, it is assumed that RX102 is not placed on TX101, and the load (charging unit 313) of RX102 is not connected to the power reception unit 303. Also, the power required by the charging unit 313 of RX102 is initially 5 watts and increases to 15 watts after the Power Transfer phase is started.

[0084] First, TX101 sends an Analog Ping and waits for an object to be placed on the charging stand 103 (F601, S501). When RX102 is placed (F602), a change occurs in the voltage or current of the Analog Ping (F603). The placement detection unit 204 of TX101 detects the placement of the object based on this change (F604). When the placement of the object is detected, TX101 sends a Digital Ping (F605). By receiving this Digital Ping, RX102 detects that its own device has been placed on TX101 (F606). Also, TX101 detects that the object placed on the charging stand 103 is RX102 based on the response to the Digital Ping. Subsequently, through communication in the I&C phase, identification information and device configuration information (capability information) are sent from RX102 to TX101 (F607, S402, S502).

[0085] Subsequently, a GP is determined between TX101 and RX102 (F608, S403, S503). Since RX102 initially requests 5 watts which is necessary, the GP here is 5 watts. Since the GP is 5 watts, TX101 refers to Table 1001 and sets the input voltage (the voltage input by the input voltage setting unit 211 to the power transmission unit 203) to 5 volts (F609, S404). Similarly, RX102 refers to Table 1002 and sets the output voltage (the voltage output by the output voltage setting unit 311 to the charging unit 313) to 5 volts (F610, S504).

[0086] Subsequently, through the processing in the Calibration phase, TX101 acquires the parameters for foreign object detection processing from 0 watt to 5 watts which is the GP, and stores them in the memory 209 (F611, S405, S505). This processing in the Calibration phase is executed with the input voltage of TX101 being 5 volts and the output voltage of RX102 being 5 volts. As a result, the parameters for foreign object detection processing acquired and held by TX101 are, for example, the content corresponding to FIG. 9(A).

[0087] Subsequently, foreign object detection processing and power transmission are started with TX101 (F612, S406, S407), power reception is started with RX102 (F612, S506), and power transmission / reception and foreign object detection processing continue with GP = 5 watts. This corresponds to the loop of NO → S412 → S413 → NO → S414 → S415 → NO → 408 in S408 → S409 of FIG. 4. It also corresponds to the loop of NO → S515 → S516 → NO → S507 in S507 → S508 of FIG. 5. When 15 watts are required at the charging unit 313 during power transmission / reception (YES in F613, S507, S508), GP is updated to 15 watts between TX101 and RX102 (F614, S408, S509). When GP is updated to 15 watts, TX101 changes the input voltage to 9 volts with reference to Table 1001 (YES in F615, S409, S410) and transmits a request for reacquisition of foreign object detection processing parameters (F617, S411). On the other hand, RX102 also changes the output voltage to 9 volts with reference to Table 1002 (YES in F616, S510, S511) and transmits an instruction for reacquisition of foreign object detection processing parameters (YES in F618, S512, S513, S514).

[0088] Since TX101 has received an instruction for reacquisition of foreign object detection processing parameters (YES in F618, S412, S413), it starts the processing in the Calibration phase (S405). On the other hand, RX102 also starts the processing in the Calibration phase (S514, S505). Therefore, the processing in the Calibration phase is performed again between TX101 and RX102, and the foreign object detection processing parameters from 0 watt to 15 watts, which is GP at this point, are acquired and held by TX101 (F619, S405, S505). The processing in this Calibration phase is executed in a state where the input voltage set by the input voltage setting unit 211 of TX101 is 9 volts and the output voltage set by the output voltage setting unit 311 of RX102 is 9 volts.

[0089] As described above, at the beginning of the Calibration phase, TX101 clears the foreign object detection processing parameters it has held so far. Also, in this embodiment, it is assumed that the foreign object detection processing parameters are acquired in 5-watt increments. Therefore, the information at each point of 0 watts, 5 watts, 10 watts, and 15 watts is acquired as the parameters for the foreign object detection processing. Further, at this time, the input voltage setting unit 211 of TX101 and the output voltage setting unit 311 of RX102 are in a state where a voltage of 9 volts, which is the voltage based on GP, is set respectively. That is, it is in a state electrically different from the state where 5 volts is set by F611 respectively. For this reason, as a result of the calibration process of F619, points A', B', C', and D' in FIG. 9(B), which are different from points A and B in FIG. 9(A), are obtained and held in TX101 as the foreign object detection processing parameters. Thereafter, between TX101 and RX102, power transmission / reception and foreign object detection are performed at GP = 15 watts using the foreign object detection processing parameters in FIG. 9(B) (F620, S406, S407, S506).

[0090] In the operation described above, when GP changes from 5 watts to 15 watts, the input voltage and the output voltage change to 9 volts in TX101 and RX102 (F614 to F616), and re-acquisition of the foreign object detection processing parameters is performed in that state (F619). That is, when the electrical states of both TX101 and RX102 change, the parameters updated according to the state after the change are used for the foreign object detection processing. Thereby, foreign objects can be detected more accurately.

[0091] Note that, in the above embodiment, TX101 is configured to send a request for re-acquiring the foreign object detection processing parameters after changing the input voltage (S410, S411), but it is not limited to this. After sending the request for re-acquiring the foreign object detection processing parameters, the input voltage may be changed within a predetermined time. At this time, after receiving the request for re-acquiring the foreign object detection processing parameters (YES in S513), RX102 waits for a predetermined time until the change of the input voltage is completed on the TX101 side, and then sends an instruction for re-acquiring the foreign object detection processing parameters (S514). This predetermined time includes the time from the setting of the new input voltage until it stabilizes. Even in such an implementation, it is possible to re-acquire the foreign object detection processing parameters in a state where the input voltage is changed, that is, in a state where the electrical state of TX101 has changed. Note that, instead of waiting for the predetermined time as described above, it may be configured to wait for a notification of completion of the input voltage change from TX101. Alternatively, in RX102, the received power voltage from TX101 may be monitored, and when this changes significantly, it may be determined that the input voltage change of TX101 is completed. In this case, a notification of completion of the input voltage change from TX101 is not required. In any case, it is possible to re-acquire the foreign object detection processing parameters in a state where the input voltage is changed, that is, in a state where the electrical state of TX101 has changed, and in that state.

[0092] Also, TX101 may store the foreign object detection processing parameters in Table 800 of FIG. 8 in the memory 209 in association with the information on the input voltage set when it acquired them. At this time, when TX101 identifies the start of the Calibration phase, it keeps the foreign object detection processing parameters in Table 800 without clearing them. After changing the input voltage (S410), if TX101 already holds the foreign object detection processing parameters associated with that input voltage, it replaces the foreign object detection processing parameters with those held in association with the changed input voltage. Thereby, it is possible to prevent re-acquiring the foreign object detection processing parameters multiple times in the same input voltage state, and accordingly, the time until charging is completed while continuing power transmission can be shortened.

[0093] Also, when TX101 re-acquires the parameters for foreign object detection processing, it may be configured to notify the user via the notification unit 207. Through this notification, the user can know that the power transmission for charging has temporarily stopped for re-acquiring the parameters for foreign object detection processing. For example, in the case of a power receiving device where an LED lights up during charging of RX102, the LED may turn off when the power transmission for charging temporarily stops. At this time, the user can know that the turning off of the LED is not a failure.

[0094] <Second Embodiment> In the first embodiment, the case where the content of Table 1002 held by RX102 is the same as the content of Table 1001 held by TX101 has been described. In the second embodiment, the case where the relationship between GP and the input voltage to the power transmission unit 203 in TX101 is different from the relationship between GP and the output voltage to the power receiving unit 303 in RX102 will be described. For example, instead of Table 1002 in FIG. 10, RX102 holds Table 1102 in FIG. 11 in the memory 309. Also, hereinafter, the case where the power required by the charging unit 313 of RX102 is initially 5 watts, then increases to 10 watts after the Power Transfer phase is started, and then further increases to 15 watts will be described. Note that other configurations are the same as those in the first embodiment.

[0095] The operation sequence of TX101 and RX102 in the second embodiment will be described with reference to FIG. 12. FIG. 12 is a diagram showing an example of the flow of processing executed in the wireless charging system according to the second embodiment. In FIG. 12, it is assumed that time progresses in the downward direction from top to bottom. The operations from placement detection to power transmission / reception and foreign object detection processing with GP at 5 watts are the same as those in FIG. 6 (F601 to F612, S401 to S407, S501 to S506). In F612, the input voltage of TX101 is 5 volts and the output voltage of RX102 is 5 volts.

[0096] When 10 watts are required at the charging unit 313 (YES in F1201, S507, S508), GP is updated to 10 watts between TX101 and RX102 (F1202, S408, S509). When GP is updated to 10 watts, TX101 maintains the input voltage at 5 volts with reference to Table 1001 (NO in F1203, S409) and waits for a re-acquisition instruction for the foreign object detection processing parameters from RX102 (S412). On the other hand, RX102 changes the output voltage to 9 volts with reference to Table 1102 (YES in F1204, S510, S511) and transmits a re-acquisition instruction for the foreign object detection processing parameters (YES in F1205, S512, S513, S514).

[0097] When TX101 receives a re-acquisition instruction for the foreign object detection processing parameters, it starts the processing in the Calibration phase (YES in S412, S413, S405). On the other hand, RX102, which has transmitted the re-acquisition instruction for the foreign object detection processing parameters, also starts the processing in the Calibration phase (S514, S505). Therefore, the processing in the Calibration phase is performed again between TX101 and RX102, and the foreign object detection processing parameters from 0 watts to 10 watts, which is the current GP, are acquired and held by TX101 (F1206, S405, S505). The processing in this Calibration phase is executed with the input voltage set by the input voltage setting unit 211 of TX101 at 5 volts and the output voltage set by the output voltage setting unit 311 of RX102 at 9 volts. The foreign object detection processing parameters obtained in this Calibration phase processing are used for the foreign object detection processing by TX101 during power transmission and reception at GP = 10 watts (F1207, S406, S407, S506).

[0098] After that, when 15 watts are required at the charging unit 313 (YES in F1208, S507, S508), GP is updated to 15 watts between TX101 and RX102 (F1209, S408, S509). When GP is updated to 15 watts, TX101 changes the input voltage to 9 volts with reference to Table 1001 (YES in F1210, S409, S410), and sends a request for re-acquisition of the foreign object detection processing parameters (F1212, S411). On the other hand, RX102 maintains the input voltage at 9 volts with reference to Table 1102 (NO in F1211, S510), and waits for a request for re-acquisition of the foreign object detection processing parameters from TX101 (S512).

[0099] Since RX102 has received a request for re-acquisition of the foreign object detection processing parameters (YES in F1212, S512, S513), it sends an instruction for re-acquisition of the foreign object detection processing parameters (F1213, S514). Since TX101 has received an instruction for re-acquisition of the foreign object detection processing parameters (YES in F1213, S412, S413), it starts the processing in the Calibration phase (S405). On the other hand, RX102, which has sent an instruction for re-acquisition of the foreign object detection processing parameters, also starts the processing in the Calibration phase (S514, S505). For this reason, the processing in the Calibration phase is performed again between TX101 and RX102, and the foreign object detection processing parameters from 0 watts to 15 watts, which is the current GP, are acquired and held by TX101 (F1214, S405, S505). The processing in this Calibration phase is executed in a state where the input voltage of TX101 is 9 volts and the output voltage of RX102 is 9 volts. Using the obtained foreign object detection processing parameters, power transmission and reception at 15 watts of GP and foreign object detection are performed between TX101 and RX102 (F1215, S406, S407, S506).

[0100] As described above, according to the second embodiment, when the GP changes from 5 watts to 10 watts (F1202), the input voltage of TX101 remains at 5 volts, while the input voltage of RX102 changes to 9 volts (F1203, F1204). The re-acquisition of the foreign object detection processing parameters is performed when the input voltage of TX101 is 5 volts and the input voltage of RX102 is 9 volts (F1206). Also, when the GP changes from 10 watts to 15 watts (F1209), the input voltage of TX101 changes to 9 volts, while the input voltage of RX102 remains at 9 volts (F1210, F1211). Then, the re-acquisition of the foreign object detection processing parameters is performed when the input voltages of TX101 and RX102 are both 9 volts (F1214). That is, when the electrical state changes in either TX101 or RX102, foreign object detection is performed using the parameters updated according to that state. Thereby, foreign objects can be detected more accurately.

[0101] <Third Embodiment> In the third embodiment, when the GP is updated, even if neither the input voltage of TX101 nor the output voltage of RX102 changes, additional foreign object detection processing parameters are added. The processing of TX101 and RX102 in the third embodiment is shown in FIGS. 13 and 14, respectively. The difference from the first embodiment is that S1301 is added to the processing of TX101 in FIG. 4 and S1401 is added to the processing of RX102 in FIG. 5. Other configurations are the same as those in the first embodiment.

[0102] In the third embodiment, the process when the GP is updated from 5 watts to 10 watts will be described. First, the communication in FIG. 7(B) is executed between TX101 and RX102, and thus the GP is updated (YES in S408, S508, S509). In this case, from Table 1001 in FIG. 10(A) and Table 1002 in FIG. 10(B), neither the input voltage of TX101 nor the output voltage of RX102 is changed (NO in S409, NO in S510). Therefore, a request for re-acquiring the foreign object detection processing parameters is not transmitted from TX101, and an instruction for re-acquiring the foreign object detection processing parameters is not transmitted from RX102. At this time, RX102 transmits a request for adding the foreign object detection processing parameters based on the updated GP (NO in S513, S1401). Also, TX101 adds the foreign object detection processing parameters based on the addition request (NO in S413, S1301).

[0103] Here, the addition of the foreign object detection processing parameters will be described. RX102 temporarily increases the received power in the power receiving unit 303, receives power at approximately 10 watts, which is the updated GP, and notifies TX101 of the received power at that time together with the request for adding the foreign object detection processing parameters. Note that the notification of the received power and the request for adding the foreign object detection processing parameters may be transmitted in one packet or divided into different packets. For example, the Received Power Packet with a Mode value of 2 described in the first embodiment can be used. When TX101 receives the Received Power Packet with a Mode value of 2, it adds the pair of the received power and the power loss to Table 800 (FIG. 8).

[0104] TX101 calculates the power loss from the value of the received power received together with the additional requirement for the foreign object detection process parameter and the value of the transmitted power in its own device at that time, and adds it as a foreign object detection process parameter. To explain with a specific example, TX101 acquires lines 801 and 802 in FIG. 8 in the first Calibration phase of S405, and assumes that FIG. 9(A) is obtained. After that, for example, in S1301, it is assumed that the received power of 9.9 watts is received together with the additional requirement for the foreign object detection process parameter, and the transmitted power at that time is 13.4 watts. In this case, 3.5 watts of the difference between them is used as the power loss, and line 803 is added to the foreign object detection process parameter. Line 803 corresponds to point C in FIG. 9(C). Thereby, TX101 can perform foreign object detection more accurately when the received power and power loss in RX102 change non-linearly.

[0105] Here, when GP changes from 5 watts to 10 watts, since neither the input voltage of TX101 nor the output voltage of RX102 changes, the electrical state does not change. Therefore, it is not necessary to re-acquire all the foreign object detection process parameters from 0 watts as shown in FIG. 9(B), and the already acquired parameters can be reused. In this case, as shown in the third embodiment, by completing the additional process without re-acquiring the parameters, the time for stopping power transmission for charging can be shortened, and charging can be completed in a shorter time.

[0106] Note that when the updated GP becomes very large, RX102 may notify a plurality of received power values, for example, in increments of about 5 watts. TX101 may obtain the power loss in each of the received plurality of received powers and add a plurality of foreign object detection process parameters. Thereby, since the accuracy of linear interpolation is improved, foreign object detection can be performed more accurately.

[0107] <Other Embodiments> The present invention can also be realized by supplying a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that implements one or more functions.

[0108] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to publicize the scope of the present invention, the following claims are attached.

Explanation of Reference Numerals

[0109] 101: Power transmission device, 102: Power reception device, 201: Control unit, 203: Power transmission unit, 204: Mounting detection unit, 205: Power transmission coil, 206: Communication unit, 211: Input voltage setting unit, 212: Re-acquisition request unit

Claims

1. A power receiving device, A power receiving unit that receives power wirelessly transmitted from a power transmitting device; A communication means for communicating with the power transmitting device; A voltage changing means for changing the voltage of the power receiving device; having The communication means transmits a first received power packet including information indicating a value of a first received power to the power transmitting device; the change means changes a voltage of the power receiving device based on authentication of the power transmitting device after the first received power packet is transmitted; the communication means transmits, after the first received power packet is transmitted and after a voltage of the power receiving device is changed, a second received power packet including information indicating a value of a second received power to the power transmitting device; After the second received power packet is transmitted, the communication means transmits a third received power packet including information indicating a value of a third received power to the power transmitting device; The communication means transmits identification information to the power transmitting device. A power receiving device comprising:

2. 2. The power receiving device according to claim 1, wherein the change unit changes the voltage to be supplied to the load based on power required by the load that consumes the power received by the power receiving unit.

3. 3. The power receiving device according to claim 2, further comprising a negotiation unit for negotiating with the power transmitting device based on the power required by the load to change the transmitted power.

4. 4. The power receiving device according to claim 1, wherein a calibration process is started by transmitting the first received power packet.

5. The power receiving device according to claim 4 , wherein the transmission of the second received power packet restarts a calibration process.

6. 6. The power receiving device according to claim 4, wherein the calibration process acquires parameters used in a foreign object detection process performed by the power transmitting device.

7. The power receiving device according to claim 1 , wherein the authentication is based on an electronic certificate.

8. A method performed by a power receiving device, comprising: a first transmission step of transmitting a first received power packet including information indicating a value of the first received power to the power transmitting device; a change step of changing a voltage of the power receiving device based on authentication of the power transmitting device after the first transmission step; a second transmission step of transmitting a second received power packet including information indicating a value of a second received power to the power transmitting device after the change step; a third transmission step of transmitting, after the second transmission step, a third received power packet including information indicating a value of a third received power to the power transmitting device; a fourth transmission step of transmitting identification information to the power transmitting device; The method according to claim 1, further comprising:

9. 9. The method of claim 8, wherein transmitting the first received power packet initiates a calibration process.

10. 10. The method of claim 9, wherein transmitting the second received power packet initiates a calibration process again.

11. 11. The method according to claim 9, wherein the calibration process acquires parameters used in a foreign object detection process performed by the power transmitting device.

12. A program for causing a computer to function as the power receiving device according to claim 1 .

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