Power receiving apparatus, method performed by power receiving apparatus, and storage medium

Abstract

To suppress deterioration of accuracy of foreign matter detection processing based on power loss even when output voltage to a load is changed in a power receiving device.SOLUTION: A power receiving device comprising: a power receiving unit configured to receive power wirelessly transmitted from a power transmitting device; a communication unit configured to communicate with the power transmitting device; and a changing unit configured to change an output voltage to be output to a load of the power receiving device, the communication unit transmits a first received power packet including information indicating a value of first received power to the power transmitting apparatus, and after the first received power packet is transmitted, the changing unit changes the GuaranteedPower and changes the output voltage after authentication with the power transmitting apparatus, and the communication unit transmits a second received power packet including information indicating a value of second received power to the power transmitting apparatus after the first received power packet is transmitted and after the output voltage is changed. The communication unit transmits identification information to the power transmitting apparatus.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power receiving device for wireless power transmission, and a method and program performed by the power receiving 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 describes a power transmitting device and a power receiving device that comply with the standard (hereinafter referred to as the "WPC standard") established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging. Patent Document 1 also describes a calibration process specified in the WPC standard to improve the accuracy of detecting conductive objects (foreign objects) such as metal pieces.

[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 calculated as the difference between the transmitted power of the power transmitting device and the received power of the power receiving device. Then, using the pair of received power and power loss in these two states as parameters, the power loss expected from the received power notified by the power receiving device during wireless power transmission is calculated, and the actual power loss is compared with the expected power loss. If the difference between the actual power loss and the expected power loss exceeds a predetermined value, it can be determined that a foreign object has caused power loss, i.e., that a foreign object is present.

[0004] Meanwhile, Universal Serial Bus Power Delivery (USB PD) is becoming popular as a standard for supplying power via a wired connection for purposes such as rapid battery charging. With USB PD, when the power supplied to the load increases, the voltage output to the load is increased accordingly. This keeps the current low even when the power supplied increases, reducing losses and heat generation in the circuit and enabling power to be supplied to the load while maintaining high efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-070074 Summary of the Invention [Problem to be solved by the invention]

[0006] In a power receiving device for wireless power transmission, when the output voltage to a load is changed in response to a change in the received power, the state of power loss in the power receiving device changes before and after the output voltage is changed. Therefore, if a pair of received power and power loss acquired before the output voltage is changed is used as a parameter for foreign object detection and then foreign object detection is performed after the output voltage is changed, the accuracy of foreign object detection may decrease.

[0007] The present invention provides a technique for suppressing a decrease in the accuracy of foreign object detection processing due to power loss even when the output voltage to a load in a power receiving device is changed. [Means for solving the problem]

[0008] A power receiving device according to one aspect of the present invention has the following configuration: A power receiving device, power receiving means for receiving power wirelessly transmitted from a power transmitting device; a communication means for communicating with the power transmitting device; a change unit for changing an output voltage to be output to a load of the power receiving device; and 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 the Guaranteed Power and the output voltage after the first received power packet is transmitted and after authentication of the power transmitting device; the communication means transmits, after the first received power packet has been transmitted and after the output voltage has been changed, a second received power packet including information indicating a value of a second received power to the power transmitting device; The communication means transmits the identification information to the power transmitting device. [Effects of the Invention]

[0009] According to the present invention, even if the output voltage to the load in the power receiving device is changed, it is possible to suppress a decrease in the accuracy of the foreign object detection process due to power loss. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of the configuration of a wireless charging system according to an embodiment; [Figure 2] FIG. 1 is a block diagram illustrating an example of the configuration of a power receiving device according to a first embodiment. [Figure 3] FIG. 1 is a block diagram showing an example of the configuration of a power transmitting device according to a first embodiment. [Figure 4A] 5 is a flowchart showing an example of the flow of processing of the power receiving device according to the first embodiment. [Figure 4B] 5 is a flowchart showing an example of the flow of processing of the power receiving device according to the first embodiment. [Figure 5A] 5 is a flowchart showing an example of the flow of processing by the power transmitting device according to the first embodiment. [Figure 5B] 5 is a flowchart showing an example of the flow of processing by the power transmitting device according to the first embodiment. [Figure 6A] FIG. 4 is a diagram showing an example of a flow of processing executed in the wireless charging system. [Figure 6B] FIG. 4 is a diagram showing an example of a flow of processing executed in the wireless charging system. [Figure 7] (A) is a diagram showing the communication sequence of the I&C phase, (B) is a diagram showing the communication sequence of the Negotiation phase, and (C) is a diagram showing the communication sequence of the Calibration phase. [Figure 8] FIG. 3 is a diagram showing the contents of parameters for foreign object detection processing according to the first embodiment. [Figure 9] 5A and 5B are diagrams illustrating linear interpolation in the foreign object detection process according to the first embodiment. [Figure 10](A) is a diagram showing the relationship between the GP and the output voltage to the charging unit, and (B) is a diagram showing the relationship between the GP and the input voltage to the power transmission unit. [Figure 11] 10 is a flowchart showing an example of the flow of processing by a power receiving device according to the second embodiment. [Figure 12] FIG. 10 is a diagram showing the relationship between the power consumption of a charging unit and the output voltage to the charging unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0012] First Embodiment (System configuration) FIG. 1 shows an example of the configuration of a wireless charging system (wireless power transmission system) according to this embodiment. This system includes a power receiving device 101 and a power transmitting device 102. Hereinafter, the power receiving device may be referred to as RX, and the power transmitting device may be referred to as TX. The TX102 is an electronic device that wirelessly transmits power to the RX101 placed on a charging stand 103. The RX101 is an electronic device that receives power wirelessly transmitted from the TX102 and charges its built-in battery. The following description will be given taking as an example a case where the RX101 is placed on the charging stand 103. However, for the TX102 to transmit power to the RX101, the RX101 only needs to be within the power transmission range of the TX102, and the RX101 does not necessarily have to be placed on the charging stand 103.

[0013] Note that RX101 and TX102 may each have a function to execute applications other than wireless charging. An example of RX101 is a mobile information device that runs on a rechargeable battery, such as a laptop PC (Personal Computer), a tablet PC, or a smartphone. An example of TX102 is an accessory device for charging the mobile information device. Note that RX101 and TX102 may be storage devices such as a hard disk drive or a memory device, or may be information processing devices such as a personal computer (PC). RX101 and TX102 may be 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. TX102 may also be a mobile information device. In this case, RX101 may be another mobile information device or a wireless earphone. RX101 may also be an automobile. TX102 may also be a charger installed in a console or the like inside the automobile.

[0014] Furthermore, although one RX 101 and one TX 102 are shown in this embodiment, the present invention is not limited to this. The present invention can also be applied to a configuration in which multiple RX 101 receive power transmitted from one TX 102 or from separate TXs 102.

[0015] This system performs wireless power transmission using an electromagnetic induction method for wireless charging based on the WPC standard. That is, RX101 and TX102 perform wireless power transmission for wireless charging based on the WPC standard between the receiving coil of RX101 and the transmitting coil of TX102. 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.

[0016] In the WPC standard, the amount of power guaranteed when the RX101 receives power from the TX102 is specified by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value guaranteed for the output of the RX101 to a load (such as a charging circuit) even if, for example, the relative positions of the RX101 and TX102 change and the power transmission efficiency between the receiving coil and the transmitting coil decreases. For example, if the GP is 5 watts, the TX102 controls power transmission so that it can output 5 watts to the load in the RX101, even if the relative positions of the receiving coil and the transmitting coil change and the power transmission efficiency decreases.

[0017] The RX101 and TX102 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 a phase before power transmission is performed, and communication for power transmission and reception control is performed in each phase. The phase before power transmission includes 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.

[0018] In the Selection phase, the TX102 repeatedly transmits Analog Pings intermittently to detect that an object has been placed on the charging base 103 (for example, that the RX101, a conductor piece, or the like has been placed on the charging base 103). Analog Pings are detection signals for detecting the presence of an object. The TX102 transmits Analog Pings by applying a voltage or current to the transmitting coil. When the charging base 103 changes from a state in which no object is placed to a state in which an object is placed, a change occurs in the voltage or current applied to the transmitting coil. The TX102 detects at least one of the voltage value and current value of the transmitting coil when transmitting 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.

[0019] In the Ping phase, the TX102 transmits a Digital Ping with higher power than the Analog Ping. The power of the Digital Ping is sufficient to start up the control unit of the RX101 placed on the charging stand 103. The RX101 notifies the TX102 of the magnitude of the received voltage. That is, the RX101 transmits a Signal Strength packet (hereinafter referred to as an "SS packet") to the TX102. The TX102 recognizes that the object detected in the Selection phase is the RX101 by receiving a response from the RX101 that received the Digital Ping it transmitted. When the TX102 is notified of the received voltage value, it transitions to the I&C phase.

[0020] In the I&C phase, the TX102 identifies the RX101 and acquires device configuration information (capability information) from the RX101. To do this, the RX101 transmits an ID packet and a configuration packet to the TX102. The ID packet contains the identification information of the RX101, and the configuration packet contains the device configuration information (capability information) of the RX101. Upon receiving the ID packet and configuration packet from the RX101, the TX102 responds by transmitting an acknowledgement (ACK) to the RX101. The I&C phase then ends. When the I&C phase ends, the TX102 transitions to the negotiation phase. In the negotiation phase, the GP value is determined based on the GP value requested by the RX101, the power transmission capability of the TX102, and other factors. When the negotiation phase ends, the TX102 transitions to the calibration phase.

[0021] In the calibration phase, the RX101 notifies the TX102 of the received power using a Received Power Packet. At this time, at least two different received powers are notified. For example, the received power when no load is connected and the received power when a load is connected and power close to GP is received are notified. The TX102 acquires the transmitted power of its own device corresponding to the two received powers, calculates the power loss from the difference between the notified received power and the acquired transmitted power, and stores it in association with the received power. In this way, pairs of received power and power loss for at least two states of the RX101 are stored in the TX102. In the subsequent power transfer phase (described later), the TX102 performs foreign object detection processing using the pair of received power and power loss stored as described above as parameters.

[0022] Here, a method for performing foreign object detection processing using two sets of received power and power loss as parameters in TX102 will be described. For example, TX102 stores pairs of two sets of received power and power loss through communication in the Calibration phase. Let these be (received power = RP1, power loss = PL1) and (received power = RP2, power loss = PL2). When TX102 performs foreign object detection processing in the Power Transfer phase, first, it obtains the current received power = P received from RX101. Subsequently, TX102 calculates the expected value PL cal of the power loss at this time by linear interpolation between the two points (RP1, PL1) and (RP2, PL2). Assume that RP1 < RP2. For example, the expected value PL cal of the power loss can be obtained by the following Equation 1. [Equation 1] PL cal = (PL2 - PL1) / (RP2 - RP1)·(P received - RP1) + PL1

[0023] The current power loss PL can be obtained by the following Equation 2 from the current transmission power P transmitted in TX102 and the received power = P received notified from RX101. When the current power loss PL of TX102 exceeds the expected value PL cal by a predetermined value or more, it is determined that power is consumed due to 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

[0024] In the above-described method, the expected value of the current power loss is calculated by linear interpolation using the previously acquired power loss value as a parameter. This is referred to as calibrating the power loss. Note that the calibration target may be the received power of the RX101 or the transmitted power of the TX102 instead of the power loss of the RX101. The method for calculating the expected value of the power loss, i.e., the calibration method, is not limited to linear interpolation, but may be nonlinear interpolation using, for example, a power series. Three or more sets of information (for example, a set of received power and transmitted power) may also be used as parameters. An example of using three or more sets of information as parameters is a broken line linear interpolation connecting (RP1, PL1) and (RP2, PL2), and (RP2, PL2) and (RP3, PL3). Here, (RP3, PL3) is the third set of information of received power and power loss, and RP2 <RP3であるとする。

[0025] 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. In this embodiment, in the power transfer phase, processing is also performed to change GP to a larger value, change the output voltage to the load of the power receiving device, and request reacquisition or addition of foreign object detection parameters. Details of these processing will be described later.

[0026] The TX102 and the RX101 perform communication based on the WPC standard for controlling power transmission and reception by superimposing a signal on the transmitted power using the same antenna (coil) as that used for wireless power transmission. Note that the TX102 and the RX101 may perform communication for controlling power transmission and reception using an antenna (coil) different from that used for wireless power transmission. An example of communication using an antenna (coil) different from that used for wireless power transmission is a communication method conforming to the Bluetooth (registered trademark) Low Energy standard. Alternatively, communication may be performed using other communication methods such as wireless LAN (e.g., Wi-Fi (registered trademark)) of the IEEE802.11 standard series, ZigBee, or NFC (Near Field Communication). Communication using an antenna (coil) different from that used for wireless power transmission may be performed at a frequency different from that used for wireless power transmission.

[0027] (Device configuration) Next, the configurations of the power receiving device 101 (RX101) and the power transmitting device 102 (TX102) according to this embodiment will be described. Note that the configurations described below are merely examples, and part (or in some cases the entirety) 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 configurations described below. Furthermore, one hardware block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0028] 2 is a diagram showing an example of the configuration of the RX101 according to this embodiment. The RX101 includes a control unit 201, a battery 202, a power receiving unit 203, a placement detection unit 204, a power receiving coil 205, a communication unit 206, a notification unit 207, an operation unit 208, a memory 209, and a timer 210. The RX101 also includes a charging unit 211, a variable voltage circuit 212, a voltage acquisition unit 213, a voltage determination unit 214, a parameter reacquisition request unit 215, and a parameter addition request unit 216.

[0029] The control unit 201 controls the entire RX101 by executing a control program stored in, for example, the memory 209. That is, the control unit 201 controls each functional unit shown in FIG. 2. The control unit 201 also performs control related to power reception control in the RX101. The control unit 201 may also perform control for executing applications other than wireless power transmission. The control unit 201 is configured to include one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 201 may also be configured with hardware dedicated to specific processing, such as an Application Specific Integrated Circuit (ASIC). The control unit 201 may also be configured with an array circuit, such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 201 stores information to be stored during execution of various processes in the memory 209. The control unit 201 may also measure time using a timer 210.

[0030] The battery 202 supplies the entire RX 101 with power required for the control of each part of the RX 101 by the control unit 201 and for power reception and communication. The battery 202 also stores the power received via the power receiving coil 205.

[0031] In the power receiving coil 205, an induced electromotive force is generated by electromagnetic waves radiated from the power transmitting coil of the TX102. The power receiving unit 203 acquires the power generated in the power receiving coil 205. The power receiving unit 203 acquires AC power generated by electromagnetic induction in the power receiving coil 205, converts the AC power into DC power or AC power of a predetermined frequency, and outputs the power to the charging unit 211, which performs processing to charge the battery 202. In other words, the power receiving unit 203 supplies power to a load in the RX101, and the charging unit 211 and the battery 202 are examples of such loads. The above-mentioned GP is power guaranteed to be output from the power receiving unit 203. Furthermore, the power receiving unit 203 notifies the control unit 201 of the current received power. This allows the control unit 201 to know the received power at any timing. Note that the measurement of the received power and the notification of the received power to the control unit 201 may be performed by a unit other than the power receiving unit 203.

[0032] The placement detection unit 204 detects that the RX101 is placed on the charging stand 103 based on the WPC standard. The placement detection unit 204 detects, for example, at least one of the voltage value and the current value of the power receiving coil 205 when the power receiving unit 203 receives a Digital Ping of the WPC standard via the power receiving coil 205. The placement detection unit 204 determines that the RX101 is placed on the charging stand 103 when, for example, the voltage value is below a predetermined voltage threshold or the current value exceeds a predetermined current threshold.

[0033] The communication unit 206 performs control communication based on the WPC standard as described above with the TX 102. The communication unit 206 demodulates the electromagnetic waves input from the power receiving coil 205 to acquire information transmitted from the TX 102, and performs load modulation on the electromagnetic waves to superimpose information to be transmitted to the TX 102 onto the electromagnetic waves, thereby performing communication with the TX 102. That is, the communication performed by the communication unit 206 is superimposed on the electromagnetic waves transmitted from the power transmitting coil of the TX 102.

[0034] The notification unit 207 notifies the user of information by any method, such as visually, audibly, or tactilely. The notification unit 207 notifies the user of, for example, the charging status of the RX101 and the status of power transmission in the wireless power transmission system including the TX102 and the RX101 as shown in FIG. 1 . The notification unit 207 includes, for example, an LCD display, an LED, a speaker, a vibration generating circuit, or other notification devices. The operation unit 208 has a function of accepting operations on the RX101 from the user. The operation unit 208 includes, 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. A device in which the notification unit 207 and the operation unit 208 are integrated, such as a touch panel, may also be used. The memory 209 stores various information, such as identification information and device configuration information, as well as control programs, as described above. The memory 209 may also store information obtained by a functional unit other than the control unit 201. The timer 210 measures time by, for example, a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

[0035] The charging unit 211 charges the battery 202 with power supplied from the power receiving unit 203. The charging unit 211 also starts or stops charging the battery 202 based on the control of the control unit 201, and further adjusts the power used to charge the battery 202 based on the charging state of the battery 202. When the power used by the charging unit 211 changes, the power supplied from the power receiving unit 203, i.e., the received power at the RX101, also changes accordingly. As described above, the charging unit 211 is a load on the RX101. Note that the charging unit 211 and the battery 202 may exist as separate devices outside the RX101. This device may be, for example, a device that operates on power supplied in accordance with the USB PD standard. In this case, the control unit 201 may acquire information on the amount of power required by the charging unit 211 from the charging unit 211 via communication in accordance with the USB PD standard.

[0036] Variable voltage circuit 212 sets an output voltage for supplying power from power receiving unit 203 to charging unit 211, i.e., a load, under the control of control unit 201. Voltage acquisition unit 213 acquires the voltage output to charging unit 211. This voltage value can be read by control unit 201 at any timing. Voltage determination unit 214 determines the voltage to be set in variable voltage circuit 212.

[0037] The parameter reacquisition request unit 215 uses the communication unit 206 to request the TX 102 to reacquire foreign object detection processing parameters. The foreign object detection processing parameters are the pair of received power and power loss, as described in the calibration phase above. The parameter addition request unit 216 uses the communication unit 206 to request the TX 102 to add foreign object detection processing parameters. This is a request to add and save a third pair of parameters when, for example, two pairs of parameters are already stored in the TX 102. Note that the voltage determination unit 214, the parameter reacquisition request unit 215, and the parameter addition request unit 216 may all or partly be configured to operate on a processor separate from the control unit 201, or may be executed by a program running on the control unit 201. The voltage determination unit 214, the parameter reacquisition request unit 215, and the parameter addition request unit 216 may be realized, for example, by the control unit 201 executing a program stored in the memory 209.

[0038] 3 is a diagram showing an example of the configuration of the TX 102 according to this embodiment. In one example, the TX 102 includes a control unit 301, a power supply unit 302, a power transmission unit 303, a placement detection unit 304, a power transmission coil 305, a communication unit 306, a notification unit 307, an operation unit 308, a memory 309, a timer 310, and a variable voltage circuit 311.

[0039] The control unit 301 controls the entire TX 102 by executing a control program stored in the memory 309, for example. That is, the control unit 301 controls each functional unit shown in FIG. 3. The control unit 301 also controls power transmission control in the TX 102. The control unit 301 may also control the execution of applications other than wireless power transmission. The control unit 301 is configured to include one or more processors, such as a CPU or MPU. The control unit 301 may also be configured to include hardware dedicated to 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 301 stores information to be stored while various processes are being executed in the memory 309. The control unit 301 may also measure time using a timer 310.

[0040] The power supply unit 302 supplies the entire TX 102 with power required for the control of the TX 102 by the control unit 301 and for power transmission and communication. The power supply unit 302 is, for example, a commercial power supply or a battery. The battery stores power supplied from the commercial power supply.

[0041] The power transmitting unit 303 converts DC or AC power input from the power supply unit 302 into AC frequency power in a frequency band used for wireless power transmission, and inputs the AC frequency power to the power transmitting coil 305 to generate electromagnetic waves for transmitting power to the RX101. The frequency of the AC power generated by the power transmitting unit 303 is, for example, several hundred kHz (e.g., 110 kHz to 205 kHz). Based on an instruction from the control unit 301, the power transmitting unit 303 inputs the AC frequency power to the power transmitting coil 305 so that the power transmitting coil 305 outputs electromagnetic waves for transmitting power to the RX101. The power transmitting unit 303 also controls the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmitting voltage) or current (power transmitting current), or both, input to the power transmitting coil 305. Increasing the power transmitting voltage or power transmitting current increases the intensity of the electromagnetic waves, and decreasing the power transmitting voltage or power transmitting current decreases the intensity of the electromagnetic waves. Furthermore, the power transmitting unit 303 controls the output of AC frequency power so as to start or stop power transmission from the power transmitting coil 305 based on instructions from the control unit 301. Furthermore, the power transmitting unit 303 notifies the control unit 301 of the current transmitted power. This allows the control unit 301 to know the transmitted power at any timing. Note that the measurement of the transmitted power and the notification to the control unit 301 may be performed by a device other than the power transmitting unit 303.

[0042] The placement detection unit 304 detects whether an object is placed on the charging stand 103 based on the WPC standard. Specifically, the placement detection unit 304 detects whether an object is placed on the interface surface of the charging stand 103. For example, the placement detection unit 304 detects at least one of the voltage value and the current value of the power transmitting coil 305 when the power transmitting unit 303 transmits an Analog Ping of the WPC standard via the power transmitting coil 305. The placement detection unit 304 may also detect a change in impedance. Then, the placement detection unit 304 can determine that an object is placed on the charging stand 103 when the voltage value is below a predetermined voltage value or the current value is above a predetermined current value. Whether the object is a power receiving device or another foreign object is determined based on whether or not a predetermined response is received to the Digital Ping subsequently transmitted by the communication unit 306. That is, if the TX102 receives a predetermined response, it determines that the object is the power receiving device (RX101), and if not, it determines that the object is an object different from the power receiving device.

[0043] The communication unit 306 performs control communication with the RX101 based on the WPC standard as described above. The communication unit 306 modulates the electromagnetic waves output from the power transmitting coil 305 and transmits information to the RX101 to perform communication. The communication unit 306 also demodulates the electromagnetic waves output from the power transmitting coil 305 and modulated by the RX101 to acquire information transmitted by the RX101. That is, the communication performed by the communication unit 306 is superimposed on the electromagnetic waves transmitted from the power transmitting coil 305.

[0044] The notification unit 307 notifies the user of information by any method, such as visually, audibly, or tactilely. The notification unit 307 notifies the user of, for example, the charging state of the TX102 or the state of power transmission in a wireless power transmission system including the TX102 and the RX101 as shown in FIG. 1. The notification unit 307 includes, for example, an LCD display, an LED, a speaker, a vibration generating circuit, or other notification devices. The operation unit 308 has a reception function for receiving operations on the TX102 from the user. The operation unit 308 includes, for example, a voice input device such as a button, a keyboard, or a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, or other input device. Note that a device in which the notification unit 307 and the operation unit 308 are integrated, such as a touch panel, may be used.

[0045] Memory 309 stores various types of information such as identification information and capability information, control programs, etc. Note that memory 309 may store information obtained by a functional unit other than control unit 301. Timer 310 measures time using, for example, a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

[0046] Variable voltage circuit 311 sets the input voltage for supplying power from power supply unit 302 to power transmission unit 303 under the control of control unit 301. Note that power supply unit 302 and variable voltage circuit 311 may exist as separate devices outside TX102. This device may be a power adapter that supplies power in accordance with the USB PD standard. In this case, control of variable voltage circuit 311 by control unit 301 may be performed via communication in accordance with the USB PD standard.

[0047] (Processing flow) Next, an example of the flow of processing executed by the RX 101 and the TX 102 will be described.

[0048] [Processing in the power receiving device] 4A and 4B are flowcharts showing an example of processing executed by the RX101. This processing can be realized, for example, by the control unit 201 of the RX101 executing a program read from the memory 209. This processing also includes processing in the voltage determination unit 214, the parameter reacquisition request unit 215, and the parameter addition request unit 216. At least a part of the procedure of this processing described below can be realized by hardware. In this case, the hardware can be realized, for example, by using a predetermined compiler to automatically generate a dedicated circuit using a gate array circuit such as an FPGA from a program for implementing each processing step. This processing can also be started when the power supply of the RX101 is turned on, when the RX101 is started up by power supply from the battery 202 or the TX102, or when the user of the RX101 inputs a command to start a wireless charging application. This processing can also be started by other triggers.

[0049] After starting processing related to power transmission and reception, RX101 executes processing defined as the Selection phase and Ping phase of the WPC standard, and waits for its own device to be placed on TX102 (S401). Then, RX101 detects that TX102 has been placed on the charging stand 103 by detecting, for example, a Digital Ping from TX102. When RX101 detects the Digital Ping, it transmits an SS packet including a received power voltage value to TX102. When RX101 detects that its own device has been placed on the charging stand 103 of TX102, it executes processing defined as the I&C phase of the WPC standard by the communication unit 206, and transmits identification information and device configuration information (capability information) to TX102 (S402).

[0050] Figure 7(A) shows the flow of communication in the I&C phase. In the I&C phase, the RX101 transmits an Identification Packet (ID Packet) to the TX102 (F701). The ID Packet stores the Manufacturer Code and Basic Device ID, which are identification information for the RX101, as well as information elements that can identify the version of the WPC standard supported by the RX101 as capability information. The RX101 also transmits a Configuration Packet to the TX102 (F702). The Configuration Packet contains the following information as capability information for the RX101: the Maximum Power Value, which is a value that specifies the maximum power that the RX101 can supply to a load, and information indicating whether or not the RX101 has a negotiation function of the WPC standard.

[0051] Upon receiving these packets, TX102 transmits an ACK (F703), and the I&C phase ends. Note that RX101 may notify TX102 of its identification information and device configuration information (capability information) by a method other than the I&C phase communication of the WPC standard. Furthermore, the identification information of RX101 may be a Wireless Power ID of the WPC standard, or any other identification information capable of identifying an individual RX101. The capability information may include information other than the above.

[0052] Returning to FIG. 4A, the RX101 negotiates with the TX102 through communication in the negotiation phase to determine the GP (S403). FIG. 7(B) shows an example of the flow of the negotiation phase. The GP is determined based on a Specific Request Packet from the RX101 and a response from the TX102 to that packet. First, the RX101 notifies the TX102 of the requested GP value by sending a Specific Request Packet to the TX102 (F711). The RX101 determines the requested GP value based on the power required by its own device. It is assumed that this value is stored in advance in the memory 209. An example of the GP value is 5 watts.

[0053] The TX102 determines whether to accept the request from the RX101 based on the power transmission capacity of its own device, and transmits an ACK (acknowledgement) if it accepts, or a NAK (negative acknowledgement) if it does not accept to the RX101. Note that FIG. 7B shows an example in which the TX102 transmits an ACK (F712). When the TX102 transmits an ACK, the GP value is determined to be the same as the value requested by the RX101, and this value is stored in the memories of both the RX101 and the TX102. On the other hand, when the TX102 transmits a NAK, the GP value is set to a small default value, for example, a value of 5 watts or less. In one example, the default value is stored in advance in the memories of both the RX101 and the TX102. Note that the method of determining the GP described above is just an example, and the GP may be determined by other methods.

[0054] Returning to FIG. 4A, the RX101 determines the output voltage for supplying power from the power receiving unit 203 to the charging unit 211 based on the GP determined in S403 (S404). If an output voltage has already been stored in S404, the stored output voltage is adopted as the output voltage for supplying power from the power receiving unit 203 to the charging unit 211, regardless of the determined GP. An example of an output voltage determined based on the GP is shown in table 1001 in FIG. 10(A). By referring to table 1001, it is possible to determine, for example, an output voltage of 5 volts when the GP is 5 watts, and an output voltage of 9 volts when the GP is 15 watts. Here, each value in table 1001 is a value determined in advance based on the electrical characteristics of the charging unit 211 of the RX101 in order to efficiently charge the battery 202. Table 1001 is stored in, for example, the memory 209. In addition, if the charging unit 211 is an external device that operates based on the USB PD standard, the power receiving unit 203 may acquire the output voltage from the charging unit 211 via communication, or the output voltage may be stored in the memory 209 as a table defined by the USB PD standard.

[0055] Returning to FIG. 4A, the RX101 sets the output voltage determined in S404 in the variable voltage circuit 212 and waits until the actual output voltage stabilizes (S405). Next, the RX101 requests the TX102 to acquire parameters for foreign object detection processing, thereby requesting the TX102 to perform the above-mentioned calibration phase (S406). Note that by waiting until the output voltage stabilizes in S405, the calibration phase processing can be performed in S406 with the output voltage stabilized. As a result, the obtained parameters for foreign object detection processing are not affected by temporal fluctuations in the output voltage, allowing for more accurate foreign object detection.

[0056] 7(C) shows the processing flow of the calibration phase. The RX101 transmits a Received Power Packet via the communication unit 206 (F721). The Received Power Packet includes a Received Power Value, which is the current received power. It also includes information Mode=1, which indicates the start of the calibration phase. The TX102 stores the received power information included in the Received Power Packet as a foreign object detection processing parameter, and then returns an ACK (F722). The TX102 also detects the start of the calibration phase by detecting Mode=1, and discards any foreign object detection processing parameters that have already been stored up to that point. Other processing by the TX102 will be described in detail later.

[0057] In the calibration phase, the RX101 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 power close to GP is received. That is, the communication of the Received Power Packet and ACK shown in FIG. 7C occurs at least twice, and the TX102 stores information on two received powers. Furthermore, when the GP value exceeds 5 watts, the RX101 notifies the received power at voltage value intervals of approximately 5 watts. For example, when the GP value is 15 watts, the RX101 notifies the received power in states where approximately 0 watts, approximately 5 watts, approximately 10 watts, and approximately 15 watts are received. Note that the voltage value intervals for notifying the received power by the RX101 do not have to be 5 watts, and they do not have to be constant. The TX102 stores all received powers notified by the RX101 as parameters for foreign object detection processing.

[0058] Returning to FIG. 4A, the RX101 connects the charging unit 211, which is a load, to the power receiving unit 203 and starts power reception in the Power Transfer phase (S407). After starting power reception, the RX101 acquires the power required by the charging unit 211 (S408). This value may be stored in advance in the memory 209, or, if the charging unit 211 is an external device, may be acquired from the external device via communication. If the power required by the charging unit 211 is within the range of the current GP, the RX101 determines that there is no need to change the GP (NO in S409) and continues power reception for a predetermined time (S419 in FIG. 4B). The predetermined time is, for example, one second. Thereafter, if charging of the battery 202 by the charging unit 211 is completed (YES in S420), the RX101 disconnects the load and stops power reception. If charging is not completed (NO in S420), the process returns to S408 to continue charging.

[0059] Here, while continuing power reception in S419, the RX101 repeatedly and periodically notifies the TX102 of the current received power. The TX102 performs foreign object detection based on the received power notified by the RX101. The Received Power Packet is used to notify the current received power. As described above, the Received Power Packet is also used to notify parameters for foreign object detection processing. For this reason, the RX101 adds information to distinguish whether the notification is of parameters for foreign object detection processing, i.e., a notification requesting the TX102 to save them, or a notification of the current received power for performing foreign object detection processing in the TX102. This information is stored, for example, in the Mode value of the Received Power Packet. In this embodiment, Mode = 0 means that the notification is of received power for foreign object detection processing. If the TX102 is requested to save the received power as a parameter, the Mode value should be a value other than 0. For example, in the calibration phase described above, the Mode value of the Received Power Packet is set to 1.

[0060] If the RX101 needs to change the GP (YES in S409) as a result of obtaining the power required by the charging unit 211 (S408), it negotiates with the TX102 and changes the GP (S410). If the GP is to be changed to a value greater than a predetermined value, the RX101 may perform device authentication of the TX102 through communication. By performing device authentication, it is possible to receive power at a predetermined level or greater only from a TX102 that is guaranteed to meet the conditions of the WPC standard, etc. One example of device authentication is challenge-response communication using a digital certificate.

[0061] Next, the RX101 determines the output voltage to be supplied to the charging unit 211 based on the updated GP (S411 in FIG. 4B). The output voltage to the charging unit 211 is determined based on Table 1001 in FIG. 10(A). After that, the RX101 compares the output voltage determined in S411 with the current output voltage (S412). If the result of the comparison shows that the determined output voltage is the same as the current output voltage (NO in S412), the RX101 requests the TX102 to add parameters for foreign object detection processing (S418). This request is made by setting the received power to a value close to the updated GP and then transmitting a Received Power Packet. Here, it is assumed that Mode=2 is used as a Mode value other than 0. For example, when the GP is changed from 5 watts to 10 watts, the RX101 sets the received power to approximately 10 watts and then transmits a Received Power Packet (Mode=2). Note that if the GP is to be reduced, it is not necessary to transmit an additional request. Furthermore, if the updated GP becomes very large (if the difference from the current GP becomes larger than a predetermined value), the Received Power Packet may be transmitted multiple times in multiple received power states, for example, in increments of approximately 5 watts.

[0062] The TX 102 adds the information about the received power notified in S418 to the memory 309 as a foreign object detection processing parameter and stores it there. To distinguish this from the start of the calibration phase or the notification of the received power, the value of Mode in the Received Power Packet requesting the addition of parameters for foreign object detection processing is set to a value other than 0 or 1. As described above, in this embodiment, Mode=2 is used. Thereafter, the process proceeds to S419. The process from S419 onwards is as described above.

[0063] On the other hand, if the output voltage determined in S411 differs from the current output voltage (YES in S412), the communication unit 206 is used to request the TX 102 to reacquire the foreign object detection processing parameters (S413), and a response from the TX 102 is awaited. This reacquisition request differs from the request for adding foreign object detection processing parameters in S418 described above. In other words, the reacquisition request requests the TX 102 to discard the foreign object detection processing parameters held in the memory 309 and to save the foreign object detection processing parameters newly notified by the RX 101.

[0064] This reacquisition request may be made by transmitting a packet conforming to the WPC standard, or by transmitting another packet that the TX102 can recognize. In the WPC standard, the TX102 responds with one of three types: ACK (Acknowledge), ND (Not Defined), or NAK (Not-Acknowledge). ACK is a positive response indicating that the TX102 has accepted the reacquisition request. ND is a response indicating that the packet is undefined, i.e., that the TX102 does not have the functionality to accept a reacquisition request. NAK is a negative response indicating that the reacquisition request is rejected. If the response from the TX102 is a positive response (ACK) (ACK in S414), the RX101 disconnects the load, stops power reception, and returns to S405 (S415). At S405, the RX101 sets the output voltage determined in S411 in the variable voltage circuit 212. Then, in S406, the RX101 performs the calibration phase processing with the set output voltage. The processing from S406 onward is as described above. Note that in S412, the determination of whether the determined output voltage is the same as or different from the current output voltage may be replaced by whether the difference between the determined output voltage and the current output voltage is greater than or equal to a predetermined threshold. Here, the threshold is 0 or greater. Furthermore, the threshold may be determined based on the magnitude of the output voltage determined in S411. For example, the threshold may be a value that increases as the output voltage determined in S411 increases. Also, for example, the threshold may be set to 10% of the magnitude of the output voltage determined in S411.

[0065] On the other hand, if the response from the TX102 indicates that it is undefined (ND) (ND in S414), the RX101 stores the GP value updated in S410 in the memory 209 (S416) and then requests the TX102 to stop power transmission (S417). Thereafter, the process returns to S401, and the RX101 waits for a Digital Ping. The request to stop power transmission is made, for example, by the RX101 transmitting an End Power Transfer Packet of the WPC standard to the TX102. Note that instead of a request to stop power transmission, a request to limit the transmission power to a small value equal to or less than a predetermined value may be used. When the process returns to S401, S401 to S402 are immediately executed because the mounted state continues, and in S403 the RX101 negotiates with the TX102 to set the GP updated in S410. As a result, the output voltage from the variable voltage circuit 212 becomes the output voltage determined in S411 (S404), and once that output voltage is stable (S405), the calibration phase processing is performed (S406). As described above, in the calibration phase, the foreign object detection processing parameters already stored in the TX102 are discarded, and a Received Power Packet (Mode=1) is issued with the received power in increments of 5 watts from 0 watts. The TX102 stores the received power notified by these Received Power Packets as new foreign object detection processing parameters. The subsequent processing is as described above.

[0066] In this way, even if the response from TX 102 to the parameter re-acquisition request from RX 101 is ND, foreign object detection processing parameters are re-acquired by RX 101 and TX 102. Therefore, even if TX 102 does not respond to the request to re-acquire the foreign object detection processing parameters and the response in S414 is ND, foreign object detection processing parameters can be re-acquired in the output voltage state determined in S411.

[0067] If the response from the TX102 is NAK in S414 (NAK in S414), the RX101 requests the addition of parameters for foreign object detection processing based on the GP updated in S410 (S418). In this case, the output voltage remains unchanged. This makes it possible to prevent the output voltage from being changed if the TX102 refuses to change the output voltage.

[0068] [Processing in power transmission device 102] Next, an example of the flow of processing executed by the TX102 will be described with reference to FIGS. 5A and 5B. This processing can be implemented, for example, by the control unit 301 of the TX102 executing a program read from the memory 309. At least a part of the following procedure can be implemented by hardware. In this case, the hardware can be implemented, for example, by using a predetermined compiler to automatically generate a dedicated circuit using a gate array circuit such as an FPGA from a program for implementing each processing step. This processing can also be executed when the TX102 is powered on, when the user of the TX102 inputs an instruction to start a wireless charging application, or when the TX102 is connected to a commercial power source and receives power. This processing can also be started by some other trigger.

[0069] First, the TX102 executes the processes defined as the Selection phase and Ping phase of the WPC standard, and waits for the RX101 to be placed on it (S501). Specifically, the TX102 repeatedly and intermittently transmits an Analog Ping of the WPC standard to detect the presence or absence of an object placed on the charging stand 103. Then, when the TX102 detects that an object has been placed on the charging stand 103, it transmits a Digital Ping. When a predetermined response (Signal Strength Packet) is received in response to the Digital Ping, the TX102 determines that the detected object is the RX101 and that the RX101 has been placed on the charging stand 103.

[0070] When the TX102 detects that the RX101 has been placed, the TX102 executes communication in the I&C phase described above using the communication unit 306, and acquires identification information and device configuration information (capability information) from the RX101 (S502). Then, the TX102 executes communication in the Negotiation phase with the RX101, and determines the GP based on the request of the RX101 (S503). Specifically, as explained in the processing of the power receiving device, this is done using the Specific Request Packet shown in Fig. 7(B) and the response thereto.

[0071] Returning to FIG. 5A, the TX102 determines the input voltage for supplying power from the power supply unit 302 to the power transmitting unit 303 based on the GP determined in S503 and sets the input voltage in the variable voltage circuit 311 (S504). An example of the input voltage to the power transmitting unit 303 determined based on the GP is shown in table 1002 in FIG. 10B. By referring to table 1002, the TX102 can determine, for example, an input voltage of 5 volts when the GP is 5 watts, and an input voltage of 9 volts when the GP is 15 watts. The values ​​in table 1002 are predetermined values ​​for efficient power transmission based on the electrical characteristics of the power transmitting unit 303 of the TX102, and are stored in memory 309. Note that the power supply unit 302 and variable voltage circuit 311 may be external devices that operate in accordance with the USB PD standard. In this case, the input voltage to the power transmitting unit 303 may be acquired from the external device (power supply unit 302) via communication, or may be stored in memory 309 as a table defined by the USB PD standard. The table 1002 held by the TX 102 and the table 1001 held by the RX 101 may be the same or different.

[0072] Returning to FIG. 5A, after setting the input voltage, the TX102 acquires foreign object detection processing parameters through calibration phase processing (S505). Calibration phase processing begins by receiving a Received Power Packet including Mode=1 from the RX101. Upon receiving this packet, the TX102 discards any foreign object detection processing parameters that have already been stored. The TX102 associates the received power included in the Received Power Packet (Mode=1) received from the RX101 with the power loss, which is the difference between the received power and the transmitted power in the power transmitting unit 303 at that time, and stores these in the memory 309. Note that the transmitted power may be stored in association with the received power instead of the power loss, or both the power loss and the transmitted power may be stored in association with the received power.

[0073] Table 800 in Fig. 8 shows an example of the contents of foreign object detection processing parameters stored in memory 309. For example, the information in row 801 indicates that the power loss is 0.6 watts when the received power notified from RX101 is 0.1 watts. Thereafter, each time TX102 receives a Received Power Packet (Mode = 2) from RX101, it adds a row to table 800. However, as described above, if Mode = 0, TX102 does not add a row. Furthermore, if Mode = 1, TX102 clears the contents of table 800 up to that point.

[0074] Returning to FIG. 5A, the TX102 starts foreign object detection processing and power transmission (S506, S507). The foreign object detection processing in the TX102 is processing that is executed periodically while wireless power transmission is being performed, and is performed, for example, as follows. First, the TX102 periodically acquires information about the current received power from the RX101. Note that, as described above, the RX101 periodically transmits information about the received power in a Received Power Packet that includes Mode=0 (S419), and the TX102 acquires this information. The TX102 then calculates the expected value of the power loss for the acquired received power by linear interpolation of each point using the foreign object detection processing parameters in Table 800 of FIG. 8. For example, Equation 1 above can be used for the linear interpolation. The TX102 calculates the power loss from the difference between the measured transmitted power and the acquired received power. If the difference between the calculated power loss and the calculated expected value exceeds a predetermined threshold, the TX102 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 within the power transmission range. If it is determined that there is a foreign object within the power transmission range, the control unit 201 of the TX102 limits power transmission to the RX101. Specifically, the control unit 201 controls the power transmitting unit 303 to stop power transmission or reduce the transmitted power. The control unit 201 may also notify the RX101 of the presence of a foreign object via the communication unit 306. Furthermore, the control unit 201 may notify that the transmitted power will be limited.

[0075] Here, the foreign object detection process will be described in more detail using an example in which the foreign object detection process parameters are those shown in rows 801 and 802 of table 800 in Fig. 8. When rows 801 and 802 are plotted on a graph with received power and power loss as axes, they become points A and B in Fig. 9(A), respectively. The TX 102 calculates the expected value of power loss for the current received power by linear interpolation using a line connecting points A and B. For example, if the current received power (RP) is 2.5 watts, the values ​​in row 801 (RP1 = 0.1 watts, PL1 = 0.6 watts) and row 802 (RP1 = 4.9 watts, PL2 = 1.6 watts) are substituted into Equation 1 above. In this case, the expected value of power loss, PL, is calculated as follows: PL=(1.6-0.6) / (4.9-0.1)*(2.5-0.1)+0.6=1.1 Then, the TX 102 calculates the power loss from the difference between the current transmitted power and the current received power (RP = 2.5 watts). If the difference between the calculated power loss value and the expected value (PL = 1.1 watts) is equal to or greater than a threshold, the TX 102 determines that power is being lost in the foreign object and that the foreign object is within the power transmission range. The threshold may be an absolute value such as 1 watt, or a relative value such as 50 percent of the expected value. Information regarding this threshold is stored in the memory 309. The threshold may also change in stages depending on the received power and the expected value of power loss.

[0076] Returning to FIG. 5A, the TX102 accepts GP negotiation from the RX101 even during power transmission. When GP negotiation is accepted from the RX101, the GP is updated (S508). If there is no GP negotiation, S508 is simply skipped. Also, as described above, there are cases where a request to reacquire parameters for foreign object detection processing is received from the RX101. When a request to reacquire parameters for foreign object detection processing is received (YES in S509), the TX102 returns an ACK (S510), and the processing returns to S504. In this way, in response to the reacquisition request from the RX101, the TX102 resets the input voltage to the variable voltage circuit 311 and reacquires parameters for object detection processing in the calibration phase.

[0077] On the other hand, if a request to reacquire foreign object detection processing parameters has not been received (NO in S509), the process proceeds to S511 in FIG. 5B. When a request to add foreign object detection processing parameters is received from RX101, TX102 adds foreign object detection processing parameters (S511). In the process of adding foreign object detection processing parameters, TX102 receives from RX101 a received power value greater than the previous GP value, calculates the difference between this and the transmitted power at that time as the power loss, associates the received power with the calculated power loss, and adds and stores this in table 800. For example, if the transmitted power when receiving a received power of 9.9 watts from RX101 is 13.4 watts, TX102 obtains the difference between the two, 3.5 watts, as the power loss. TX102 associates the received power of 3.5 watts with the power loss of 9.9 watts and stores this as an additional foreign object detection processing parameter. This state is shown in row 803 of table 800 in Figure 8. Row 803 corresponds to point C in Figure 9(B). This allows the TX102 to more accurately calculate the expected value of power loss when the received power becomes greater than the value of the conventional GP, enabling more accurate foreign object detection. Note that if there is no request from the RX101 for additional parameters for foreign object detection processing, S511 is skipped.

[0078] Returning to FIG. 5B, the TX102 determines whether a power transmission stop request has been received from the RX101 or whether a foreign object has been detected (S512). If a power transmission stop request has not been received or a foreign object has been detected (NO in S512), the process returns to S508 in FIG. 5A, and the TX102 continues power transmission by repeating the above-described process. If a power transmission stop request has been received or a foreign object has been detected (YES in S512), the TX102 stops power transmission (S513). Thereafter, the TX102 determines whether to end the process (S514), and if it is determined that the process should be ended (YES in S514), the process ends. On the other hand, if the process should not be ended (NO in S514), the process returns to S501, and the above-described process is repeated. Whether to end the process is determined based on, for example, the operation content of the user on the operation unit 308.

[0079] [System Operation] The operation sequences of the RX101 and TX102 explained using FIGS. 4A to 4B and 5A to 5B will now be explained using FIGS. 6A to 6B. In FIGS. 6A to 6B, time flows from top to bottom. In the initial state, the RX101 is not placed on the TX102, and the load (charging unit 211) of the RX101 is not connected to the power receiving unit 203. Furthermore, the power required by the charging unit 211 of the RX101 is initially 5 watts, which then increases to 10 watts and 15 watts after the start of the Power Transfer phase.

[0080] First, TX102 transmits an Analog Ping and waits for an object to be placed on the charging stand 103 (F601, S501). When RX101 is placed (F602), a change occurs in the voltage or current of the Analog Ping (F603). This change causes TX102 to detect the placement of an object (F604). When the placement of an object is detected, TX102 transmits a Digital Ping (F605). By receiving this Digital Ping, RX101 detects that its own device has been placed on TX102 (F606). Furthermore, TX102 detects from the response to the Digital Ping that the object placed on the charging stand 103 is RX101. Next, through communication in the I&C phase, RX101 transmits identification information and device configuration information (capability information) to TX102 (F607, S402, S502).

[0081] Next, GP is determined between RX101 and TX102 (F608, S403, S503). RX101 initially requests the necessary power of 5 watts, so GP here is 5 watts. Because GP is 5 watts, RX101 references Table 1001 and sets the output voltage to 5 volts (F609, S404, S405). Similarly, TX102 references Table 1002 and sets the input voltage to 5 volts (F610, S504). Next, through processing in the calibration phase, foreign object detection processing parameters for GP = 0 watts to 5 watts are acquired and stored in TX102 (F611, S406, S505). At this stage, the foreign object detection processing parameters stored by TX102 correspond to those shown in Figure 9(A). Next, the RX 101 starts receiving power (F612, S407), and the TX 102 starts foreign object detection processing and power transmission (F613, S506, S507).

[0082] After that, power transmission / reception and foreign object detection processing continue for a while with GP = 5 watts (F614, loop of NO in S408 → S409 → NO in S419 → S420 → S408, and NO in S508 → S509 → S511 → S512 → NO → S508). When 10 watts is required by the charging unit 211 (YES in F615, S408, S409), GP is updated to 10 watts between RX101 and TX102 (F616, S410, S508). When GP is updated to 10 watts, RX101 refers to table 1001 and determines to maintain the output voltage at 5 volts (F617, S411). Because the current output voltage will continue, RX101 requests the addition of foreign object detection processing parameters in the range of 5 to 10 watts (F618, NO in S412, S418). As a result, point C in Fig. 9B is added to the foreign object detection processing parameters held by the TX 102. Note that, because the calibration processing for points A and B has already been performed in F611, the results are maintained.

[0083] After that, power transmission and reception and foreign object detection processing continue for a while with GP = 10 watts (F619, a loop of NO in S408 → S409 → NO in S419 → S420 → S408, and a loop of NO in S508 → S509 → NO in S511 → S512 → S508). When 15 watts is required by the charging unit 211 (YES in F620, S408, S409), GP is updated to 15 watts between RX101 and TX102 (F621, S410, S508). When GP is updated to 15 watts, RX101 refers to table 1001 and determines to change the output voltage to 9 volts (F622, S411). Because the output voltage has changed, RX101 requests TX102 to reacquire the foreign object detection processing parameters (YES in F623, S412). When an ACK is returned in response to this (F624, YES in S414, YES in S509, S510), the RX101 disconnects the load and stops receiving power (F625, S415).

[0084] Next, the RX101 sets the determined output voltage = 9 volts in the variable voltage circuit 212 and waits for the output voltage to stabilize (F626, S405). Meanwhile, after sending the ACK, the TX102 changes the input voltage to the power transmitting unit 303 to 9 volts by referring to table 1002 based on GP = 15 watts (F627, S504). Then, the calibration phase processing for GP = 0 to 15 watts is performed (F628, S406, S505). At the beginning of the calibration phase, the TX102 clears the foreign object detection processing parameters that it had held up to that point. Then, when the output voltage to the load of the RX101 is 9 volts, the TX102 again acquires information for each of 0 watts, 5 watts, 10 watts, and 15 watts as parameters for foreign object detection processing. Furthermore, at this time, the variable voltage circuit 212 of RX101 and the variable voltage circuit 311 of TX102 are each set to a voltage of 9 volts based on the GP. In other words, the electrical state is different from when the foreign object detection processing parameters were updated in F611 or F618. Therefore, as a result of the calibration processing in F628, points A', B', C', and D' in Figure 9(C) are obtained, which are different from points A, B, and C in Figure 9(B).

[0085] After that, the RX101 connects the load and starts receiving power (F629, S407), and thereafter power transmission and reception and foreign object detection processing continue at GP = 15 watts (F630).

[0086] In the operation described above, the RX101 changes the GP to 5 watts, 10 watts, and 15 watts based on the power required by the charging unit 211, which is the load. When increasing the GP from 5 watts to 10 watts, the RX101 leaves the output voltage unchanged at 5 volts and requests additional foreign object detection processing parameters (F618). Furthermore, when increasing the GP from 10 watts to 15 watts, the RX101 changes the output voltage to 9 volts and requests reacquisition of foreign object detection processing parameters (F623). In other words, the RX101 selects an appropriate output voltage based on the power required by the load, and when the output voltage changes, it controls the RX101 so that foreign object detection parameters are reacquired with the changed output voltage. This allows for more accurate foreign object detection, even if the electrical state of the RX101 changes due to a change in output voltage, by using parameters updated to match that state. Furthermore, when the output voltage remains unchanged but the GP increases, the RX101 performs additional calibration processing in the increased GP range. This allows for more accurate foreign object detection when the received power and power loss change nonlinearly.

[0087] Note that the RX101 may add information about the output voltage determined in S411 to a request for reacquisition of foreign object detection processing parameters, and the TX102 may associate this output voltage information with table 800 of FIG. 8 and store it in memory 309. That is, the TX102 stores table 800 for each output voltage included in the reacquisition request in memory 309. Then, when a reacquisition request is received from the RX101, if there is a table 800 that matches the output voltage included in the request, the TX102 may use the information in table 800 corresponding to the output voltage stored in memory 309 as a parameter. This prevents the repeated reacquisition of foreign object detection processing parameters corresponding to previously acquired output voltages, allowing foreign object detection processing parameters to be set efficiently. As a result, the efficiency of charging the battery 202 is improved.

[0088] Furthermore, the RX 101 may add information indicating the reason for re-acquisition to the request to re-acquire the foreign object detection processing parameters. This allows the TX 102 to notify the user of the reason for re-acquisition via the notification unit 307. Furthermore, this notification allows the user to know that power transmission has been temporarily stopped due to a change in output voltage.

[0089] Second Embodiment In the first embodiment, the RX101 determined the output voltage based on the GP (S411 in FIG. 4B). In the second embodiment, the RX101 determines the output voltage based on the current power consumption of the charging unit 211, which is the load, instead of the GP. FIG. 11 shows the processing by the RX101 in the second embodiment. Note that the processing shown in FIG. 11 replaces part of the processing in the first embodiment (the processing shown in FIG. 4B). That is, the difference from the first embodiment is that S411 in FIG. 4B is replaced by S1101, and that the processing proceeds to S1101 if the answer is NO in S409 (if there is no need to change the GP). Furthermore, in the RX101 of the second embodiment, the voltage acquisition unit 213 can also acquire the amount of power supplied to and consumed by the charging unit 211.

[0090] 11, the RX101 starts the power transfer phase by processing similar to that of the first embodiment (S401 to S408). Next, the RX101 determines the GP based on the power required by the charging unit 211 (S408, S409, S410). After that, regardless of whether the GP has been changed, the RX101 acquires the current power consumption of the charging unit 211 and determines the output voltage to the charging unit 211 based on that value (S1101). Here, the RX101 determines the output voltage by referring to table 1201 of FIG. 12(A). Table 1201 lists the power consumption of the charging unit 211 and the output voltage to the charging unit 211 that is efficient for that power consumption. It is also assumed that table 1201 is stored in advance in the memory 209. According to the configuration of the second embodiment, the output voltage can be determined based on the current power consumption of the charging unit 211. Therefore, for example, even if the charging unit 211 and the battery 202 are external devices and the information on the required power cannot be frequently obtained from the charging unit 211 in S408, an appropriate output voltage can be quickly determined.

[0091] If the output voltage determined in S1101 is different from the current output voltage (YES in S412), the process proceeds to S413. The process from S413 onwards is the same as in the first embodiment. However, if S405 is executed because it is determined in S414 that an ACK response has been received, the output voltage determined in S1101 is set in the variable voltage circuit 212. Also, if S416 is executed because it is determined in S414 that an ND response has been received, the output voltage set in S404 is the output voltage determined in S1101. On the other hand, if it is determined that the output voltage determined in S1101 is the same as the current output voltage, the process proceeds to S418. If the GP has been changed in S410, the RX101 requests the TX102 to add parameters for foreign object detection processing, as in the first embodiment. However, if the GP has not been changed, the process of S418 is skipped. The process from S419 onwards is the same as in the first embodiment.

[0092] Note that the RX101 may determine the output voltage to the charging unit 211 based on table 1202 shown in FIG. 12(B) instead of table 1201. In table 1202, different power consumption thresholds are used for increasing and decreasing the output voltage. This makes it possible to prevent frequent changes in the output voltage and the associated process of re-acquiring parameters for foreign object detection processing when the power consumption in the charging unit 211 tends to fluctuate in a short period of time. Furthermore, as another method for solving the same problem, the RX101 may use the timer 210 to prevent the output voltage from being changed for a predetermined period of time after the output voltage has been changed.

[0093] <Other embodiments> 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.

[0094] At least some of the processes shown in the flowcharts of Figures 4A to 4B, 5A to 5B, 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 process. Alternatively, a gate array circuit may be formed in the same way as an FPGA and implemented as hardware.

[0095] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention. [Explanation of symbols]

[0096] 101: power receiving device, 203: power receiving unit, 213: voltage determination unit, 215: parameter reacquisition request unit

Claims

[Claim 1] A power receiving device, power receiving means for receiving power wirelessly transmitted from a power transmitting device; a communication means for communicating with the power transmitting device; a change unit for changing an output voltage to be output to a load of the power receiving device; and 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 Guaranteed Power and changes the output voltage after the first received power packet is transmitted and after authentication of the power transmitting device is performed; the communication means transmits, after the first received power packet has been transmitted and after the output voltage has been changed, a second received power packet including information indicating a value of a second received power to the power transmitting device; The power receiving device is characterized in that the communication means transmits identification information to the power transmitting device.

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