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

Abstract

To suppress the reduction in detection accuracy in a case where foreign object detection is performed on the basis of a measurement result of a voltage or a current during a period in which power transmission is suspended.SOLUTION: A power transmission device 101 has a communication unit 206 that communicates with a power receiving device wirelessly using an antenna, a power transmission unit 203 that uses the antenna to transmit power wirelessly to the power receiving device, a detection unit 204 that measures at least one of a voltage and a current output from the antenna during a period when power transmission is stopped and communication by the communication unit 206 is not performed, and determines, on the basis of the measurement results, that an object different from the power receiving device is present, and a control unit 201 that restricts the power transmission when it is determined that the object different from the power receiving device is present.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a power transmitting device. [Background technology]

[0002] In recent years, technological development of wireless power transmission systems has been widely carried out. Patent Document 1 discloses 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 standards. Communication between the power transmitting device and the power receiving device is realized by superimposing a signal on the transmitted power using an antenna used for wireless power transmission.

[0003] Patent document 1 discloses a method for identifying the presence of an object (hereinafter referred to as a foreign object) other than a power receiving device within a range to which a power transmitting device can transmit power, and for restricting the transmission of power based on the identification result.

[0004] Patent document 2 also discloses a method for determining whether or not an object is present near a power transmitter based on the amount of attenuation in the voltage value of the power transmitter during the period in which the voltage of the power transmitter gradually decreases after power transmission is stopped. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-70074 A [Patent Document 2] Special Publication No. 2018-512036 Summary of the Invention [Problem to be solved by the invention]

[0006] When an antenna used for wireless power transmission is used for communication between a power transmitting device and a power receiving device, the method disclosed in Patent Document 2 has the following problems. That is, when communication is performed using an antenna used for wireless power transmission when measuring the voltage during a period when power transmission is stopped, the amplitude change of the signal is reflected in the power, that is, the measured voltage. Therefore, the measured voltage is affected not only by the object but also by the communication. If the presence of an object is determined based on this measured voltage, there is a problem that the accuracy of object detection is reduced, such as the object not being detected when it exists or being erroneously detected even when the object does not exist. And when this method is applied to the detection of a foreign object, the accuracy of foreign object detection may be reduced. The same problem occurs even if the measurement target is a current.

[0007] The present invention has been made in view of the above problems, and has an object to suppress a decrease in detection accuracy when foreign object detection is performed based on voltage or current measurement results during a period when power transmission is stopped. [Means for solving the problem]

[0008] One aspect of the power transmission device according to the present invention is During the Negotiation Phase Power receiving device and negotiation Do negotiation Means and the said After the Negotiation phase, in the Power Transfer phase The power receiving device No By line Power Transmission A power transmission means for performing the above. A limiting step for limiting the power transmission when predetermined information is received from the power receiving device in the power transfer phase. Means and the said During the period when power transmission was restricted, body Detecting the detection Means and ,of Yes After the end of the period during which the power transmission is restricted, the power transmitting means resumes the power transmission in the power transfer phase without going through the negotiation phase. The present invention is characterized by the above. Effect of the Invention

[0009] According to the present invention, when foreign object detection is performed based on the measurement results of voltage or current during a period when power transmission is stopped, it is possible to suppress a decrease in detection accuracy. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a wireless power transmission system. [Diagram 2] FIG. 2 is a diagram illustrating a configuration example of a power transmitting device. [Diagram 3] FIG. 2 illustrates an example of the configuration of a power receiving device. [Figure 4] 4 is a flowchart for explaining a process executed by a power transmitting device in the first embodiment. [Diagram 5] 4 is a flowchart for explaining a process executed by a power receiving device in the first embodiment. [Figure 6] 4 is a sequence diagram for explaining the operations of a power transmitting device and a power receiving device in the first embodiment. FIG. [Figure 7] FIG. 1 is a diagram for explaining a method for measuring a Q value. [Figure 8] 10 is a flowchart illustrating a process executed by a power transmitting device according to a second embodiment. [Figure 9] 10 is a flowchart illustrating a process executed by a power receiving device according to a second embodiment. [Figure 10] FIG. 11 is a sequence diagram for explaining the operations of a power transmitting device and a power receiving device in the second embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of information transmitted by a power transmitting device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the components described in the following embodiment are examples of the embodiment of the present invention, and the present invention is not limited to them.

[0012] (First embodiment) FIG. 1 shows a configuration example of a wireless charging system (wireless power transmission system) according to the present embodiment. In one example, this system includes a power transmitting device 101 and a power receiving device 102. Hereinafter, the power receiving device may be called RX, and the power transmitting device may be called TX. RX102 is an electronic device that receives power from TX101 and charges a built-in battery. TX101 is an electronic device that wirelessly transmits power to RX102 placed on a charging stand 103. RX102 can receive power from TX101 within a range 104. An example of RX102 is a smartphone, and an example of TX101 is an accessory device for charging the smartphone. Note that RX102 and TX101 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). In addition, RX102 and TX101 may be image input devices such as an imaging device (camera, video camera, etc.) or a scanner, or may be image output devices such as a printer, a copier, or a projector. Furthermore, RX102 and TX101 may have a function of executing an application other than wireless charging. Furthermore, TX101 may be a smartphone. In this case, RX102 may be another smartphone or a wireless earphone. Furthermore, RX102 may be an automobile. Furthermore, TX101 may be a charger installed in a console or the like in the automobile.

[0013] Furthermore, in this embodiment, one TX 101 and one RX 102 are shown, but the present invention can also be applied to a configuration in which a plurality of RX 102 transmit power from one TX 101 or from separate TX 101s.

[0014] This system performs wireless power transmission using an electromagnetic induction method for wireless charging based on the standard for wireless charging (WPC standard) defined by WPC (Wireless Power Consortium). That is, RX102 and TX101 perform wireless power transmission for wireless charging based on the WPC standard between the receiving coil (power receiving antenna) of RX102 and the transmitting coil (power transmitting antenna) of TX101. Note that the wireless power transmission method is not limited to the method defined by the WPC standard, and may be a method using other electromagnetic induction method, magnetic field resonance method, electric field resonance method, microwave method, laser method, etc. Also, in this embodiment, wireless power transmission is used for wireless charging, but wireless power transmission may be performed for purposes other than wireless charging.

[0015] In the WPC standard, the amount of power guaranteed when the RX102 receives power from the TX101 is stipulated by a value called Guaranteed Power (hereafter referred to as "GP"). GP indicates the power value that is guaranteed to be output to a load (such as a charging circuit) in the RX102, even if the positional relationship between the RX102 and TX101 fluctuates and the power transmission efficiency between the receiving coil and the transmitting coil decreases. For example, if the GP is 5 watts, the TX101 controls and transmits power so that it can output 5 watts to the load in the RX102, even if the positional relationship between the receiving coil and the transmitting coil fluctuates and the power transmission efficiency decreases.

[0016] The RX102 and the TX101 according to this embodiment communicate for power transmission and reception control based on the WPC standard. Here, the communication for power transmission and reception control will be described. The WPC standard specifies a number of phases including a power transfer phase in which power transmission is performed and a phase before power transmission is performed. The phase before power transmission includes (1) a selection phase, (2) a ping phase, (3) an identification and configuration phase, (4) a negotiation phase, and (5) a calibration phase. In the following, the identification and configuration phase is referred to as an I&C phase.

[0017] (1) In the Selection phase, the TX101 intermittently transmits Analog Pings to detect the presence of an object within the power transmission range (for example, the power receiving device 102 or a conductor piece is placed on the charging stand 103). In other words, the Analog Ping is a detection signal for detecting the presence of an object. The TX101 transmits Analog Pings by applying a voltage or current to the power transmitting coil. The voltage or current applied to the power transmitting coil changes depending on whether an object is placed on the charging stand 103 or not. Therefore, the TX101 detects at least one of the voltage value and current value of the power transmitting coil when the Analog Ping is transmitted, and determines that an object is present when the voltage value is below a certain threshold value or the current value exceeds a certain threshold value, and transitions to the Ping phase.

[0018] (2) In the Ping phase, the TX101 transmits a Digital Ping with a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start up the control unit of the RX102 101 placed on the charging stand 103. The RX102 notifies the TX101 of the magnitude of the received voltage. That is, the RX102 transmits a Signal Strength packet (hereinafter referred to as an "SS packet") to the TX101. In this way, the TX101 recognizes that the object detected in the Selection phase is the RX102 by receiving a response from the RX102 that received the Digital Ping. When the TX101 is notified of the received voltage value, it transitions to the I&C phase.

[0019] (3) In the I&C phase, TX101 identifies RX102 and acquires device configuration information (capability information) from RX102. To this end, RX102 transmits an 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. Having received the ID packet and the configuration packet, TX101 responds with an acknowledgement (ACK). Then, the I&C phase ends.

[0020] (4) In the negotiation phase, the GP value is determined based on the GP value requested by the RX102, the power transmission capability of the TX101, and the like.

[0021] (5) In the calibration phase, RX102 notifies TX101 of the received power value using a Received Power packet based on the WPC standard. Accordingly, TX101 acquires the transmitted power corresponding to the received power and stores it in association with the received power. Then, TX101 calculates and stores parameters for foreign object detection processing based on power loss based on at least two pairs of received power and transmitted power. In this embodiment, parameters for foreign object detection processing are also calculated and stored in the power transfer phase described later. Foreign object detection is processing to determine whether or not an object other than RX102 (hereinafter referred to as a foreign object) exists within the power transmission range of TX101, or whether or not there is a possibility that a foreign object exists.

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

[0023] Based on the WPC standard, TX101 and RX102 superimpose signals related to communication for power transmission and reception control on power using the same antenna (coil) as for wireless power transmission. This allows TX101 and RX102 to perform communication for power transmission and reception control using the same antenna (coil) as for wireless power transmission. Note that the range in which communication based on the WPC standard is possible between TX101 and RX102 is almost the same as the range in which power transmission is possible. That is, in FIG. 1, range 104 represents the range in which wireless power transmission and communication are possible using the power transmission and reception coils of TX101 and RX102.

[0024] <Device configuration> Next, the configuration of the power transmitting device 101 (TX101) and the power receiving device 102 (RX102) according to this embodiment will be described. Note that the configuration described below is merely an example, and a part (or in some cases, the whole) of the configuration described may be replaced with another configuration performing a similar function or may be omitted, and further configuration may be added to the configuration described. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0025] 2 is a diagram showing an example of the configuration of a power transmitting device 101 (TX101) according to this embodiment. The TX101 includes a control unit 201, a power supply unit 202, a power transmitting unit 203, a detection unit 204, a power transmitting coil 205, a communication unit 206, an output unit 207, an operation unit 208, a memory 209, and a timer 210.

[0026] The control unit 201 controls the entire TX 101 by executing a control program stored in the memory 209, for example. 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 TX 101. In one example, the control unit 201 performs device authentication in the TX 101 and control required for power transmission. The control unit 201 may perform control for executing applications other than wireless power transmission. The control unit 201 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 201 may be configured with hardware dedicated to a specific process, such as an application specific integrated circuit (ASIC). The control unit 201 may also be configured with an array circuit, such as a field programmable gate array (FPGA) compiled to execute a specific process. The control unit 201 stores information to be stored during execution of various processes in the memory 209. Furthermore, control unit 201 may measure time or hour using timer 210. Furthermore, when detection unit 204 described later detects a foreign object, control unit 201 limits the transmission of power performed by power transmission unit 203 described later based on the detection of a foreign object.

[0027] The power supply unit 202 transmits power required for control, power transmission, and communication to the entire TX 101. The power supply unit 202 is, for example, a commercial power supply or a battery. The battery stores power transmitted from the commercial power supply.

[0028] The power transmitting unit 203 converts the DC or AC power input from the power supply unit 202 into AC frequency power in a frequency band used for wireless power transmission. The AC frequency power is further input to the power transmitting coil 205 to generate electromagnetic waves for receiving power in the RX 102. The frequency of the AC power generated by the power transmitting unit 203 is about several hundred kHz (for example, 110 kHz to 205 kHz).

[0029] The power transmitting unit 203 inputs AC frequency power to the power transmitting coil 205 so that the power transmitting coil 205 outputs electromagnetic waves for transmitting power to the RX102 based on an instruction from the control unit 201. The power transmitting unit 203 also controls the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmitting voltage) or current (power transmitting current) input to the power transmitting coil 205. 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. Based on an instruction from the control unit 201, the power transmitting unit 203 also performs output control of AC frequency power so that power transmission from the power transmitting coil 205 is started or stopped. The power transmitting unit 203 of the RX102 in this embodiment has a switch on a circuit connected to the power transmitting coil 205. When measuring a Q value (Quality factor) described later, power transmitting unit 203 switches a switch inside power transmitting unit 203 to disconnect power transmitting coil 205, thereby stopping application of a voltage to power transmitting coil 205. The switch may be located at a position other than inside power transmitting unit 203. For example, a switch may be provided between power transmitting unit 203 and detection unit 204, or between detection unit 204 and power transmitting coil 205 in FIG. 2.

[0030] The detection unit 204 detects whether an object exists in the range 104 by measuring the voltage or current of the power transmission coil 205. For example, the detection unit 204 detects the voltage or current of the power transmission coil 205 when the power transmission unit 203 transmits an Analog Ping of the WPC standard through the power transmission coil 205. Then, the detection unit 204 can determine that an object exists in the range 104 when the voltage is below a predetermined voltage value or the current value exceeds a predetermined current value. Furthermore, whether this object is the RX102 or another foreign object is determined to be the RX102 when a predetermined response is received in response to the Digital Ping transmitted by the communication unit 206. Furthermore, the detection unit 204 measures the voltage of the power transmission coil 205 when acquiring a Q value to be described later, and detects a foreign object using a Q value acquired based on the measurement result. Details will be described later.

[0031] The communication unit 206 performs control communication based on the WPC standard as described above with the RX102. The communication unit 206 modulates the electromagnetic waves output from the power transmitting coil 205 and transmits information to the RX102. The communication unit 206 also demodulates the electromagnetic waves output from the power transmitting coil 205 and modulated in the RX102 to acquire information transmitted by the RX102. That is, the communication performed by the communication unit 206 is superimposed on the power transmission from the power transmitting coil 205.

[0032] The output unit 207 provides information to the user by any method such as visual, auditory, or tactile. The output unit 207 notifies the user of, for example, information indicating the state of the TX101 or the state of the wireless power transmission system including the TX101 and the RX102 as shown in Fig. 1. The output unit 207 includes, for example, a liquid crystal display, an LED (Light Emitting Diode), a speaker, a vibration generating circuit, and other notification devices.

[0033] The operation unit 208 has a reception function for receiving operations from a user on the TX 101. The operation unit 208 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 output unit 207 and the operation unit 208 are integrated, such as a touch panel, may be used.

[0034] The memory 209 stores various information. Note that the memory 209 may store information obtained by a functional unit other than the control unit 201. The timer 210 measures time, for example, by 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] 3 is a diagram showing an example of the configuration of the power receiving device 102 (RX102) according to this embodiment. The RX102 includes a control unit 301, a battery 302, a power receiving unit 303, a detection unit 304, a power receiving coil 305, a communication unit 306, an output unit 307, an operation unit 308, a memory 309, a timer 310, and a charging unit 311.

[0036] The control unit 301 controls the entire RX102 by executing a control program stored in the memory 309, for example. In one example, the control unit 301 performs control necessary for device authentication and power reception in the RX102. The control unit 301 may perform control for executing applications other than wireless power transmission. The control unit 301 includes one or more processors, such as a CPU or an MPU. The control unit 201 may include hardware dedicated to a specific process, such as an ASIC, or an array circuit, such as an FPGA, compiled to execute a predetermined process. The control unit 301 stores information to be stored during the execution of various processes in the memory 309. The control unit 301 may also measure time using a timer 310.

[0037] The battery 302 transmits power required for control, power reception, and communication to the entire RX 102. The battery 302 also stores the power received via the power receiving coil 305. In the power receiving coil 305, an induced electromotive force is generated by an electromagnetic wave radiated from the power transmitting coil 205 of the TX 101, and the power receiving unit 303 acquires the power generated in the power receiving coil 305.

[0038] The power receiving unit 303 obtains AC power generated by electromagnetic induction in the power receiving coil 305. Then, the power receiving unit 303 converts the AC power into DC or AC power of a predetermined frequency, and outputs the power to the charging unit 311 that performs processing to charge the battery 302. That is, the power receiving unit 303 transmits power to the load in the RX102. The above-mentioned GP is the amount of power guaranteed to be output from the power receiving unit 303.

[0039] The detection unit 304 detects whether the RX102 is placed in the range 104 where it can receive power from the TX 101. The detection unit 304 detects, for example, the voltage or current of the power receiving coil 305 when the power receiving unit 303 receives a Digital Ping conforming to the WPC standard via the power receiving coil 305. Then, the detection unit 304 can determine that the RX102 is placed in the range 104 when, for example, the detected voltage is below a predetermined voltage threshold or the detected current value exceeds a predetermined current threshold.

[0040] The communication unit 306 performs control communication based on the WPC standard with the TX101 by communication in which signals are superimposed using the same antenna (coil) as in wireless power transmission based on the WPC standard. The communication unit 306 acquires information transmitted from the TX101 by demodulating the electromagnetic waves input from the power receiving coil 305. The communication unit 306 further performs load modulation on the electromagnetic waves to superimpose information to be transmitted to the TX101 on the electromagnetic waves, thereby performing communication with the TX101. That is, communication by the communication unit 306 can be performed by being superimposed on power transmission from the power transmitting coil 205 (FIG. 2) of the TX101.

[0041] The output unit 307 provides information to the user by any method such as visual, auditory, tactile, etc. The output unit 307 notifies the user of, for example, the state of RX102 and the state of the wireless power transmission system including TX101 and RX102 as shown in Fig. 1. The output unit 307 includes, for example, a liquid crystal display, an LED, a speaker, a vibration generating circuit, and other notification devices.

[0042] The operation unit 308 has a reception function for receiving operations from the user on the RX 102. 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 output unit 307 and the operation unit 308 are integrated, such as a touch panel, may be used.

[0043] The memory 309 stores various information. Note that the memory 309 may store information obtained by a functional unit other than the control unit 301. The timer 310 measures time, for example, by 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.

[0044] Next, the processes performed by the power transmitting device 101 (TX101) and the power receiving device 102 (RX102) according to this embodiment will be described with reference to the drawings.

[0045] <Processing in power transmission device> Fig. 4 is a flowchart showing the process executed by the power transmitting device 101 (TX101) in this embodiment. The flowchart shown in Fig. 4 can be realized by the control unit 201 of the TX101 executing a control program stored in the memory 209, and performing calculations of information, processing of information, control of each hardware, and the like.

[0046] In F401, the control unit 201 executes processes defined as the Selection phase and Ping phase of the WPC standard. Then, the RX102 detects that the TX101 has been placed on the charging stand 103 by, for example, detecting a Digital Ping from the TX101. Then, when the RX102 detects the Digital Ping, it transmits an SS packet including the received voltage value to the TX101. It is detected that the RX102 has been placed within the power transmission range of the TX101.

[0047] In F402, the control unit 201 acquires the identification information and capability information from the RX102 by performing communication in the I&C phase via the communication unit 206. The identification information of the RX102 may include a manufacturer code and a basic device ID. The capability information of the RX102 may include information capable of identifying the version of the WPC standard supported, a maximum power value indicating the maximum power that the RX102 can receive, and information indicating whether or not the RX102 has a negotiation function of the WPC standard. The TX101 may acquire the identification information and capability information of the RX102 by a method other than the communication in the I&C phase. The identification information may include information capable of identifying an individual unit of the RX102, such as a wireless power ID. In this way, the identification information may include information other than the above, and similarly, the capability information may include information other than the above.

[0048] In F403, the control unit 201 performs communication in the negotiation phase via the communication unit 206 to determine the GP value based on the GP value requested by the RX 102 and the like.

[0049] In F404, the control unit 201 starts processing in the calibration phase (hereinafter, referred to as calibration processing). Here, the calibration processing is processing for calibrating the correlation between a value (transmitted power) measured inside the TX101 and a value (received power) measured inside the RX102 for the power transmitted by the TX101 to the RX102. In the calibration phase, the TX101 communicates information in the calibration processing and transmits power to obtain the above-mentioned power correlation.

[0050] Steps F404 to F407 are processes performed in the calibration phase. Here, the Q value is measured to confirm that no foreign object is present within the power transmission range. A method for measuring the Q value in the time domain will be described with reference to FIG. 7(a). The waveform shown in FIG. 7(a) shows the change over time of the measured voltage (hereinafter referred to as the voltage value) inside the power transmission coil 205 of the TX101, with the horizontal axis showing the time and the vertical axis showing the voltage value. A waveform 700 is the voltage value of the high-frequency voltage applied to the power transmission coil 205. Time T0 shows the time when the application of the high-frequency voltage to the power transmission coil 205 is stopped. A point 701 is a part of the envelope of the voltage value shown by the waveform 700. (T1, A1) corresponding to the point 701 shows that the voltage value at time T1 is A1. Similarly, point 702 is part of the envelope of voltage values ​​represented by waveform 700, and (T2, A2) corresponding to point 702 indicates that the voltage value at time T2 is A2.

[0051] The Q value is measured based on the change in voltage value after application of the high frequency voltage to the power transmitting coil 205 is stopped. In the example shown in Fig. 7(a), the Q value is acquired by measuring the amount of change in the voltage value after time T0. In the case of Fig. 7(a), for example, voltage values ​​A1 and A2 are measured at times T1 and T2, which are times in the period after time T0 when application of the high frequency voltage is stopped. Based on these times and the measured voltages, the Q value is calculated using Equation 1.

[0052] Q=ω(T2-T1) / 2ln(A1 / A2) (Equation 1) In this way, the Q value is calculated based on the time length from time T1 to time jT2 and the ratio of the voltage value A1 corresponding to time T1 to the voltage value A2 corresponding to time T2, where ω represents the angular velocity of the high-frequency voltage 700 (the frequency multiplied by 2π).

[0053] Next, the process for the TX101 to measure the Q value in this embodiment will be described with reference to Fig. 7(b). A waveform 703 is a high-frequency voltage applied to the power transmitting coil 205 by the power transmitting unit 203, and the frequency is between 110 kHz and 148.5 kHz used in the WPC standard. During the period from time T0 to time T5, the power transmitting unit 203 switches and disconnects the connection with the power transmitting coil 205, thereby stopping the application of the high-frequency voltage. Note that the period from T0 to time T5 is very short compared to the period during which the TX101 transmits power to the RX102.

[0054] Points 704 and 705 are part of the envelope of the voltage value indicated by the waveform 703. The power transmitting unit 203 stops power transmission during the period from time T0 to time T5, and the detection unit 204 measures the voltage value at time T3 during this period and at time T4 after a predetermined time has elapsed since time T3. In the example shown in FIG. 7(b), the voltage value at time T3 and the voltage value at time T4 are A3 and A4, respectively. The TX101 calculates the Q value by Equation 1 using time T3, time T4, the voltage value A3, the voltage value A4, and the angular velocity of the high-frequency voltage. In this way, the detection unit 204 in the TX101 measures the voltage value and calculates the Q value in a state in which the power transmitting unit 203 stops power transmission to the RX102. The TX101 switches the switch in the power transmitting unit 203 at time T5 to resume power transmission.

[0055] According to the above-described method, the TX101 in this embodiment acquires the Q value. The TX101 also performs foreign object detection based on the acquired Q value, and confirms that no foreign object exists within the power transmission range. At this time, the TX101 prestores the Q value measured when no foreign object exists within the power transmission range as a reference value. When power transmission is performed when a foreign object such as a conductor piece exists within the power transmission range, not only the RX102 but also the foreign object consumes power. As a result, when a foreign object exists, it is assumed that the voltage value when the TX101 stops transmitting power is attenuated more than when the foreign object does not exist. As a result, it is assumed that the value of the Q value based on the formula 1 when a foreign object exists is smaller than the Q value when the foreign object does not exist. Therefore, the TX101 determines that a foreign object exists (detects a foreign object) based on the fact that the acquired Q value is smaller than the reference value. At this time, the TX101 calculates the difference between the acquired Q value and the reference value, and determines that a foreign object exists when the difference is larger than a predetermined threshold value. Furthermore, if the difference between the acquired Q value and the reference value is smaller than a predetermined threshold, the TX 101 can confirm that no foreign object is present within the power transmission range.

[0056] Here, the communication unit 206 of the TX101 in this embodiment communicates information with the RX102 by modulating or demodulating the electromagnetic waves generated by the voltage applied by the power transmitting unit 203 to the power transmitting coil 205. Also, the communication unit 306 of the RX102 communicates information with the TX101 by load modulating the electromagnetic waves received by the power receiving coil 305. Therefore, even if the voltage value is measured while the communication unit 206 and the communication unit 306 are communicating, the voltage value suitable for obtaining the Q value used for foreign object detection may not be measured. For example, if load modulation is performed during the period T0 to T5 when the TX101 stops applying the voltage in FIG. 7(b), the voltage value may change compared to when the load modulation is not performed. As a result, the values ​​of the voltages A3 and A4 at the times T3 and T4 when the load modulation is performed may be larger or smaller than the voltage values ​​when the load modulation is not performed. If the Q value obtained based on this voltage value is used for foreign object detection, there is a possibility that a foreign object will not be detected when it is present, or that a foreign object will be erroneously detected when it is not present.

[0057] For the above reasons, while the power transmitting device is measuring the Q value, it is desirable that the TX101 and the RX102 are not communicating information. During the calibration process, the RX102 transmits to the TX101 received power information for notifying the received power and information for requesting an increase or decrease in the received power. The RX102 in this embodiment does not communicate during a specific period specified in the WPC standard that the power receiving device should not transmit a signal. The period during which the RX102 does not communicate is, for example, a period specified in the WPC standard that the power receiving device should not transmit a preamble of the next packet from the rear end of the packet transmitted by the power receiving device. That is, the period during which the RX102 does not communicate is a period from the power receiving device transmitting a signal until a predetermined time has elapsed that is specified that the power receiving device should not transmit the next signal. Also, for example, the period during which the RX102 does not communicate is a period specified in the WPC standard that the power transmitting device should not transmit a preamble of the next packet from the rear end of the packet transmitted by the power transmitting device. That is, the period during which the RX102 does not communicate is a period from when the power receiving device receives a signal from the power transmitting device until a predetermined time has elapsed during which the power receiving device must not transmit the next signal. Therefore, the TX101 in this embodiment measures the Q value by utilizing the period during which the RX102 does not communicate as described above. At this time, the TX101 also does not transmit a signal to the RX102. The TX101 in this embodiment waits until information is transmitted from the RX102 (F405), and after receiving the information transmitted from the RX102, measures the voltage value of the power transmitting coil 205 during the period during which the RX102 does not transmit information (F406). In the following description, measuring the voltage value of the power transmitting coil 205 to calculate the Q value used for foreign object detection is simply expressed as measuring the Q value, but the process of calculating the Q value based on Equation 1 may be performed during the period during which communication is performed. The TX101 in this embodiment measures at least the voltage value during the period during which communication is not performed.

[0058] It should be noted that foreign object detection based on the measurement result of the Q value can be used in combination with foreign object detection based on power loss. However, foreign object detection based on power loss cannot be performed until the processing of the calibration phase for calculating the parameters used for foreign object detection is completed. In other words, foreign object detection based on power loss cannot be used in the calibration phase. If a foreign object is present within the power transmission range in the calibration phase, inappropriate parameters may be acquired, and the accuracy of foreign object detection based on power loss in the subsequent power transfer phase may decrease. In contrast, foreign object detection based on the measurement result of the Q value can be performed in the calibration phase, so it is possible to determine whether or not a foreign object is present in the calibration phase. This allows the TX101 to determine the presence of a foreign object in the calibration phase and limit the transmission of power.

[0059] In F407, the TX101 performs foreign object detection by comparing the Q value measured in F406 with a reference value stored in advance. If a foreign object is detected (Yes in F407), the TX101 stops power transmission (F414). If no foreign object is detected (No in F407), the calibration process ends (F408).

[0060] In F409, the TX101 transitions to the Power Transfer phase and starts transmitting power to the RX102 for wireless charging. Even after starting the power transmission for charging, the TX101 periodically receives received power information from the RX102. Therefore, in F410, the TX101 monitors whether or not predetermined information has been transmitted from the RX102. The predetermined information is the received power information for notifying the above-mentioned power, information for requesting an increase or decrease in the received power, and the like.

[0061] When predetermined information is received in F410, the TX101 measures the Q value by utilizing a period during which the RX102 does not transmit information (F411). In F411, foreign object detection based on the measurement result of the Q value and foreign object detection based on the loss of transmitted power are performed. Foreign object detection based on the loss of power is a process of determining that a foreign object exists when the value of the power transmitted by the TX101 is lost more than a predetermined amount. Foreign object detection based on the loss of power is performed by the RX102 notifying the TX101 of the power received. By performing foreign object detection in F411, it is possible to detect that a foreign object has been placed within the range in which power can be transmitted during charging. Note that the foreign object detection performed here may be either the foreign object detection based on the measurement result of the Q value or the foreign object detection based on the loss of transmitted power. In addition, in F411, at least a process of measuring the voltage value of the power transmitting coil 205 may be performed during a period during which communication is not performed. That is, since calculation of the Q value based on the measured voltage value of the power transmitting coil 205 and processing of foreign object detection based on the Q value can be performed even while communication is being performed, they may be performed after F411, for example. Furthermore, since foreign object detection based on power loss can also be performed while communication is being performed, they may be performed in a step other than F411 as long as it is after RX102 notifies TX101 of the received power.

[0062] Here, a description will be given of the combined use of foreign object detection based on the Q-value measurement result and foreign object detection based on the power loss. If the result of foreign object detection based on the Q-value measurement result and the result of foreign object detection based on the power loss are both "no foreign object is present", the TX101 determines that no foreign object is present. On the other hand, if at least one of the result of foreign object detection based on the Q-value measurement result and the result of foreign object detection based on the power loss is "a foreign object is present", the TX101 determines that a foreign object is present (highly likely to be present). This allows the TX101 to erroneously determine that a foreign object is not present when a foreign object is present, and to suppress the transmission of power.

[0063] In addition, when the result of the foreign object detection based on the Q value measurement result differs from the result of the foreign object detection based on the power loss, the TX101 may prioritize one of the results of the foreign object detection. For example, when the result of the foreign object detection based on the power loss is prioritized, it is assumed that the foreign object detection based on the Q value measurement result determines that "no foreign object exists" and the foreign object detection based on the power loss determines that "a foreign object exists". In this case, the TX101 prioritizes the result of the foreign object detection based on the power loss and determines that "a foreign object exists". Similarly, the result of the foreign object detection based on the Q value measurement result may be prioritized. In the above-mentioned method in which the TX101 determines that "a foreign object exists" when at least one of the multiple foreign object detections determines that "a foreign object exists", the transmission of power despite the presence of a foreign object is suppressed. However, this method may frequently restrict the transmission of power. Therefore, when multiple foreign object detection methods are used, it is expected that the transmission of power will not be frequently restricted by determining in advance which foreign object detection result to prioritize.

[0064] If a foreign object is detected in F412, the TX101 stops the charging process (Yes in F414). The processes from F410 to F412 are repeatedly executed until a charging completion notification is received from the RX102. If the TX101 does not receive predetermined information in F410 (No in F410) and receives a notification indicating charging completion sent from the RX102 (Yes in F413), the TX101 stops transmitting power for charging (F414).

[0065] <Processing in the power receiving device> Fig. 5 is a flowchart showing the process executed by the power receiving device 102 (RX102) in this embodiment. The flowchart shown in Fig. 5 can be realized by the control unit 301 of the RX102 executing a control program stored in the memory 309, and executing information calculations, information processing, and control of each piece of hardware.

[0066] In F501, the RX102 is loaded within the power transmission range of the TX101 by a user or the like. In F502, the communication unit 306 transmits identification information and capability information to the TX101 through communication in the I&C phase. In F503, the control unit 301 determines the value of the GP with the TX101 through communication in the negotiation phase via the communication unit 306. Note that in F503, another procedure for determining the GP, different from the communication in the negotiation phase, may be executed.

[0067] In F504, the communication unit 306 executes a calibration process for configuring a correlation between the transmission power and the received power between the TX101 and the communication unit 306. When the calibration process is completed, in F505, a power receiving process for charging the RX102 is started. Note that in the calibration process and the power receiving process, the RX102 transmits to the TX101 received power information notifying the TX101 of the received power, and information for requesting an increase or decrease in the received power. When the charging is completed, the RX102 transmits a notification indicating that the charging is completed to the TX101 (F506).

[0068] <Operation sequence of power transmitting device and power receiving device> FIG. 6 shows an operation sequence of the power transmitting device 101 (TX101) and the power receiving device 102 (RX102). The TX101 intermittently transmits Analog Ping of the WPC standard to detect an object present within the power transmitting range (S601). The RX102 is placed within the power transmitting range of the TX101 by a user or the like (S602). The TX101 detects that the voltage of the power transmitting coil 205 is lower than a predetermined value or the current of the power transmitting coil 205 is higher than a predetermined value when the Analog Ping is transmitted. This allows the TX101 to detect that an object exists within the power transmitting range (S603, S604). After detecting that an object exists within the power transmitting range, the TX101 transmits Digital Ping of the WPC standard (S605). The RX102 receives the Digital Ping and recognizes that it has been detected by the TX101 (S606). When there is a predetermined response to the Digital Ping, the TX 101 detects that the detected object is the RX 102 and that the RX 102 has been placed on the charging stand 103 .

[0069] When the TX101 detects that the RX102 is placed, the TX101 acquires identification information and capability information from the RX102 by performing communication in the I&C phase of the WPC standard (S607). The TX101 determines a GP value between the TX101 and the RX102 by communication in the negotiation phase of the WPC standard (S608). Note that in S608, other procedures for determining the GP may be executed, which are different from the communication in the negotiation phase of the WPC standard. In addition, when the RX102 does not support the negotiation phase of the WPC standard, the TX101 transmits information indicating that the RX102 does not support the negotiation phase to the TX101 at the timing of S607 or the like. At this time, when the TX101 acquires information indicating that the RX102 does not support the negotiation phase of the WPC standard, the TX101 may determine the GP without performing communication in the negotiation phase. The GP value determined at this time may be, for example, a value specified in the WPC standard. In the example of FIG. 6, the GP=5W (watts) is determined in S608.

[0070] Next, a calibration process is performed. First, RX102 transmits first reference power information to TX101 (S609). Here, the reference power information is information indicating the power received by RX102. After transmitting the reference power information, RX102 does not communicate (transmit information) until a predetermined time has elapsed based on the WPC standard (S610). When TX101 receives the reference power information transmitted from RX102, it performs a Q-value measurement using the period during which RX102 does not communicate (S611). Based on the measurement result of the Q-value, TX101 checks whether or not a foreign object is present within the power transmission range. If a foreign object is detected, TX101 ends the power transmission process to RX102.

[0071] In S609, RX102 transmits information indicating that 500 mW (milliwatts) of power is received as the first reference power information. The first reference power information is information indicating the power received by the power transmitting coil 305, measured when the power receiving unit 303 and the charging unit 311 are not connected. TX101 judges whether to accept the first reference power information based on the power transmission state of its own device. If the TX101 accepts the first reference power information, it transmits an affirmative response (ACK), and if the TX101 does not accept the first reference power information, it transmits a negative response (NAK) to RX102. At this time, TX101 can accept the first reference power information if it is judged that the power indicated by the first reference power information can be stably transmitted, and not accept the first reference power information if it is judged that the power cannot be stably transmitted. In the example of FIG. 6, TX101 judges that the power transmission state is stable, and transmits an ACK to RX102 (S612). If the TX101 transmits a NAK, the RX102 measures the received voltage value again and transmits new first reference power information to the TX101.

[0072] Here, the timing of S611 (measurement of Q value) and S612 (transmission of ACK) will be mentioned. If the processes of S611 and S612 overlap, there is a possibility that a voltage value suitable for acquiring the Q value used for foreign object detection cannot be measured due to the above-mentioned reasons. In addition, if the TX101 stops applying voltage while transmitting the ACK, the ACK data may be corrupted. Therefore, it is preferable to perform the processes of S611 and S612 so as not to overlap. In addition, since the period during which the RX102 does not communicate is a period during which the RX102 waits for a response from the TX101, when the RX102 receives an ACK or NAK transmitted from the TX101, the RX102 resumes communication. Therefore, the TX101 measures the Q value before transmitting the ACK. The process of determining whether or not a foreign object exists based on the measurement result of the Q value may be performed before or after the transmission of the ACK.

[0073] After receiving the ACK from the TX101, the RX102 performs a process for requesting the TX101 to transmit power of the value of GP. In the example of FIG. 6, since GP=5W, the RX102 transmits instruction information indicating an instruction to change the transmission power output in order to increase the transmission power by the TX101 to 5W (S613). This instruction information may include a value (positive value) indicating the amount of power increase. Even after transmitting the instruction information, the RX102 does not perform communication until a predetermined time has elapsed based on the WPC standard. The TX101 measures the Q value by utilizing the period during which the RX102 does not perform communication, and performs foreign object detection based on the Q value (S615). After measuring the Q value, the TX101 transmits an ACK to the RX102 as a response indicating that it is capable of responding to the instruction to increase the power indicated by the instruction information, and changes the transmission power output based on the instruction information (S616, S617).

[0074] In S618, RX102 transmits information indicating that 5 W of power is received as second reference power information. The second reference power information is information indicating the power received by the power receiving coil 305, measured when the power receiving unit 303 and the charging unit 311 are connected. TX101 performs measurement of the Q value and foreign object detection by utilizing a period during which RX102 does not perform communication after transmitting the second reference power information (S619, S620). Furthermore, TX101 calculates an estimate of the loss of the power to be transmitted based on at least one of the voltage value and the current value of the power transmitting coil 205 when the device transmits power, and the first and second reference power information. TX101 performs foreign object detection based on the calculated estimate of the power loss (S621). Furthermore, TX101 transmits an ACK to RX102 as a response indicating that the second reference power information transmitted from RX102 is accepted (S622). By the processes up to S622, the TX101 completes the calibration process, determines that the charging process can be started, starts the power transmission process to the RX102, and starts charging the RX102.

[0075] Here, with reference to S623 and subsequent steps in FIG. 6, an operation sequence when a GP once determined is changed (re-determined) will be described. For example, TX101 and RX102 perform authentication processing to authenticate each other's devices (S623), and determine whether or not the devices can support a GP larger than the current GP (5W) based on the authentication result. If it is determined that the larger GP is supported, the GP is re-determined to, for example, 15W (S624). Note that when determining whether or not the larger GP is supported, the determination may be made based on a method other than the authentication processing. RX102 transmits instruction information for increasing the transmission output in order to increase the transmission output of TX101 to 15W. TX101 transmits ACK or NAK to RX102 as a response to the instruction information. When TX101 transmits ACK, it increases the transmission output based on the instruction information. In this process as well, TX101 measures the Q value and performs foreign object detection by utilizing a period in which RX102 does not communicate after transmitting information. Also, similar to S621, foreign object detection based on an estimated value of power loss is performed (S625 to S630).

[0076] The TX101 and the RX102 perform the calibration process again. The RX102 transmits information indicating that the re-determined GP=15W will be received as the third reference power information to the TX101 (S631). The TX101 measures the Q value and performs foreign object detection by utilizing a period in which the RX102 does not perform communication after transmitting the third reference power information (S633). The TX101 also performs foreign object detection by calculating an estimated value of power loss based on at least one of the voltage value and the current value of the power transmitting coil 205 when the own device transmits power and the first, second, and third reference power information (S634). The TX101 also transmits an ACK in response to the third reference power information transmitted from the RX102 (S635) and starts the power transmission process. Regarding S631, if the TX101 cannot respond to the third reference power information within a predetermined time, the TX101 may transmit power at 15 W while suspending the transmission of ACK, or may continue transmitting power at up to 5 W. At this time, the TX101 and the RX102 may display a screen on the output unit 207 and the output unit 307 that they respectively have, to allow the user to select whether to charge at 15 W or 5 W. The user may specify which to select by operating the operation unit 208 or the operation unit 308, or may specify by operating an operation screen displayed on the output unit 207 or the output unit 307.

[0077] As described above, the TX101 measures the voltage value of the power transmitting coil 205 when the application of the voltage to the power transmitting coil 205 is stopped during the period in which communication is not performed after the RX102 transmits information, and calculates the Q value. In addition, the TX101 performs foreign object detection based on the calculated Q value, and stops power transmission when a foreign object is detected. This prevents power transmission from continuing even when a conductive foreign object is present within the power transmission range. In addition, by combining the above method with foreign object detection based on power loss, the TX101 can perform more reliable foreign object detection. Note that, as a process of the TX101 when a foreign object is detected, the power transmission may be restricted to be stopped as described above, or the transmission power may be restricted to be smaller than the power transmission power when no foreign object is detected.

[0078] Furthermore, as a process for when a foreign object is detected, a GP may be re-determined between the TX101 and the RX102. When the TX101 determines that the RX102 is capable of renegotiating the GP, the TX101 transmits a signal instructing the RX102 to re-negotiate the GP. At this time, the TX101 may notify the power receiving device of the maximum negotiable GP. The maximum negotiable GP may be limited to 5W. When the TX101 determines that the RX102 is not capable of renegotiating the GP, the TX101 may perform a process such as limiting the transmission power to be smaller than when a foreign object is not detected, changing the value of the transmission power to a predetermined value (for example, 5W), or stopping the transmission power.

[0079] Second Embodiment In the following description, differences from the first embodiment will be mainly described. The configurations of the power transmitting device 101 (TX101) and the power receiving device 102 (RX102) are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0080] <Processing in power transmission device> Fig. 8 is a flowchart showing the process executed by the power transmitting device 101 (TX101) in the second embodiment. The flowchart shown in Fig. 8 can be realized by the control unit 201 of the TX101 executing a control program stored in the memory 209, and executing calculation of information, processing of information, and control of each hardware. Note that the process from F801 to F804 is similar to the process from F401 to F404 in Fig. 4, and therefore the description will be omitted.

[0081] When the calibration process is started in F804, the RX102 transmits to the TX101 received power information for notifying the received power and information for requesting an increase or decrease in the received power (F405). The TX101 responds to the received information with an ACK or the like. At this time, the TX101 adds information that enables identification of the timing of the measurement of the Q value to the ACK data and transmits it (F806). The TX101 adds time information indicating the time to measure the Q value using a data format as shown in FIG. 11 as an example. The time information may be, for example, a value based on the elapsed time based on the time when the TX101 was started, or may be a value indicating an offset time from the time when the ACK was transmitted. When a value based on the elapsed time is applied, the TX101 and the RX102 are set to perform processing based on the same time. For example, the TX101 and the RX102 are set to match the processing time by sharing the time when the TX101 was started and the time that has elapsed since the TX101 was started in the I&C phase or the like. Then, the RX 102 receives an ACK from the TX 101 and does not perform communication at the time indicated by the time information. When a value indicating an offset time is applied, the RX 102 receives an ACK from the TX 101 and does not perform communication until the offset time indicated by the time information has elapsed.

[0082] The TX101 adds the time information as described above to the ACK and transmits it, and measures the Q value based on the time information during a period when the RX102 does not communicate. The processes from F808 to F810 are the same as the processes from F407 to F409, and therefore the description will be omitted. In F811, the TX101 monitors whether or not predetermined information (received power information for notifying the power, information for requesting an increase or decrease in the received power, etc.) has been transmitted from the RX102. In the case where the predetermined information has been received in F811, the TX101 transmits an ACK as a response to the predetermined information. At this time, the TX101 transmits, for example, the time information as described above by adding it to the ACK (F812). In F813, the TX101 measures the Q value based on the timing indicated by the transmitted time information, and performs foreign object detection wp (F813). At this time, the TX101 may perform foreign object detection based on power loss. Foreign object detection based on power loss may be performed in a step other than F813, or may not be performed as part of the entire process. The method of measuring the Q value and the method of detecting foreign objects are the same as those in the first embodiment. The process from F814 to F816 is the same as that from F412 to F414, so a description thereof will be omitted.

[0083] As described above, the TX101 transmits information to the RX102 that enables the timing of the Q-factor measurement to be specified, thereby making it possible to prevent communication from being performed when the Q-factor is measured. The information added to the ACK is not limited to the above, as long as it is information that enables the TX101 to specify the timing of the Q-factor measurement. For example, instruction information for instructing the RX102 to stop communication may be transmitted, and the RX102 may not perform communication until a predetermined time has elapsed since acquiring the instruction information. The predetermined time may be set in advance based on the time required for the Q-factor measurement and the delay time related to the communication between the RX102 and the TX101, or may be included in the instruction information. The predetermined time may be determined by the communication in the negotiation phase in F803. The TX101 may transmit time information, instruction information, and the like, individually, without adding information to the ACK. As in the first embodiment, the method may be combined with a method of measuring the Q-factor during a period in which no communication is performed after the predetermined information is transmitted from the RX102. For example, the TX101 may be configured to use the method described in this embodiment from F805 to F807, and to use the method described in the first embodiment from F810 onward. These modified examples are similarly applicable to the following description.

[0084] <Processing in the power receiving device> FIG. 9 is a flowchart showing the process executed by the power receiving device 102 (RX102) in the second embodiment. The flowchart shown in FIG. 9 can be realized by the control unit 301 of the RX102 executing a control program stored in the memory 309, and executing calculation of information, processing of information, and control of each hardware. The process from F901 to F905 is the same as F501 to F505 in FIG. 5, and therefore the description is omitted. When the power receiving process is started, the RX102 transmits received power information notifying the received power and data requesting an increase or decrease in the received power (F906). The RX102 receives an ACK or the like from the TX101 as a response to the transmitted information (F907). At this time, the ACK includes time information for enabling the TX101 to specify the timing for measuring the Q value, so the RX102 extracts the time information (F908). The RX102 restricts communication based on the time information (F909). After that, the RX102 repeats the processes from F906 to F909 until charging is completed. When charging is completed (F910), the RX102 transmits a notification indicating that charging is completed to the TX101 (F911).

[0085] <Operation sequence of power transmitting device and power receiving device> Fig. 10 shows an operation sequence of the power transmitting device 101 (TX101) and the power receiving device 102 (RX102) in the second processing example. The processes of S1001 to S1008 are similar to S601 to S608 in Fig. 6, and therefore the description of these processes will be omitted.

[0086] When the TX101 determines the value of the GP with the RX102, the calibration process is started. First, the RX102 transmits information indicating the power received by the power receiving coil 305 in a state in which the power receiving unit 303 and the charging unit 311 are connected to the TX101 as the first reference power information (S1009). In the example of FIG. 10, the first reference power information is 500 mW. The TX101 judges whether or not to accept the first reference power information based on the power transmission state of the own device. If it is judged to be accepted, the TX101 transmits an ACK to the RX102, and if it is judged not to be accepted, the TX101 transmits a NAK to the RX102. In the example of FIG. 10, the TX101 judges that the power indicated by the first reference power information can be stably transmitted, and transmits an ACK to the RX102.

[0087] The TX101 sets the timing for measuring the Q-factor, and transmits the ACK with time information added thereto as information that can identify the timing (S1010, S1011). The RX102 that receives the ACK extracts the time information added to the ACK, and restricts communication based on the time information (S1012). The TX101 measures the Q-factor and performs foreign object detection based on the timing indicated by the time information (S1013).

[0088] After limiting communication to a predetermined period based on the time information, RX102 transmits to TX101, as second reference power information, information indicating the power received by the power receiving coil 305 in a state in which the power receiving unit 303 and the charging unit 311 are connected. In the example of FIG. 10, since GP=5 W, the second reference power information is set to 5 W. RX102 transmits instruction information instructing a change in the power transmission output in order to increase the power transmitted by TX101 to 5 W (S1014). TX101 receives the instruction information transmitted from RX102, and if the TX101 can handle the increase in the power transmitted, increases the power transmitted (S1015).

[0089] Even when responding to the instruction information, the TX101 adds time information to the ACK to identify the timing for measuring the Q value and transmits it (1016, S1017). The RX102 that receives the ACK extracts the time information added to the ACK and restricts communication based on this time information (S1018). The TX101 measures the Q value and performs foreign object detection based on the timing indicated by the time information (S1019).

[0090] After that, RX102 transmits second reference power information (5 W) to TX101 (S1020). TX101 calculates an estimated value of power loss based on the received power included in the first and second reference power information, and performs foreign object detection (S1021). Furthermore, TX101 transmits an ACK in response to the second reference power information from RX102. In this case as well, TX101 performs Q-factor measurement, but the method is the same as in S1010 to S1013, so the description will be omitted (S1022 to S1025). Through the above processing, TX101 and RX102 complete the calibration processing, and start charging RX102.

[0091] Here, a process when a GP once determined in this embodiment is changed (re-determined) will be described with reference to FIG. 10. For example, TX101 and RX102 perform device authentication processing (S1026), and if it is determined that the devices can support a larger GP, the GP is re-determined to 15 W (S1027). Thereafter, RX102 and TX101 perform recalibration processing to increase the transmission power of TX101 to 15 W in the same manner as the processing from S1014 to S1017 (S1028 to S1031). Furthermore, RX102 transmits a value of 15 W as third reference power information. TX101 transmits a response to the third reference power information to RX102. During this time, TX101 transmits time information by adding it to an ACK, measures the Q value based on the timing indicated by the time information, and performs foreign object detection (S1033 to S1038). The TX101 confirms that no foreign object is present and starts power transmission for charging. Regarding S1033, if the TX101 cannot respond to the third reference power information within a predetermined time, the TX101 may transmit power at 15 W while suspending the transmission of ACK, or may continue transmitting power at up to 5 W. At this time, the TX101 and the RX102 may display a screen on the output unit 207 and the output unit 307 that they respectively have, to allow the user to select whether to charge at 15 W or 5 W. The user may specify which to select by operating the operation unit 208 or the operation unit 308, or may specify by operating the operation screen displayed on the output unit 207 or the output unit 307.

[0092] As described above, the TX101 can prevent communication from being performed when the Q value is measured by transmitting, for example, time information as a signal for making it possible to specify the timing for measuring the Q value. The TX101 may notify the RX102 of the timing for measuring the Q value using another configuration. For example, the TX101 stores information for making it possible to specify the timing for measuring the Q value in a Power Transmitter Capability packet, which is defined in the WPC standard as a packet for notifying the power receiving device of information related to the capabilities of the power transmitting device. The TX101 can notify the RX102 of the timing for measuring the Q value by transmitting a packet in which instruction information and time information are stored to the RX102. Also, for example, in the negotiation phase, the TX101 may request the TX101 to transmit information for making it possible to specify the timing for measuring the Q value in order to specify the timing for measuring the Q value. In this case, the TX101 transmits an acknowledgment (ACK) and time information, etc. to the RX102 in response to the request, or transmits a negative acknowledgment (NAK) to the RX102. Also, for example, the RX 102 may transmit time information or the like to the TX 101 in order to specify the timing for measuring the Q value to the TX 101.

[0093] (Third embodiment) In this embodiment, a configuration will be described in which the power receiving device 102 (RX102) detects the measurement of the Q value performed by the power transmitting device 101 (TX101) and restricts communication. The detection unit 304 of the RX102 detects that the TX101 has stopped applying voltage to measure the Q value by measuring at least one of the voltage and current of the power receiving coil 305. For example, when the RX102 measures the voltage of the power receiving coil 305 and detects a drop in the voltage, the RX102 determines that the TX101 is measuring the Q value and restricts communication until a predetermined time has elapsed. The predetermined time can be set in advance based on the length of time required to measure the Q value, etc. With this configuration, the RX102 can prevent communication while the TX101 is measuring the Q value.

[0094] The RX102 may detect a voltage drop in the power receiving coil 305 when the TX101 is measuring the Q value and when the TX101 has stopped transmitting power due to an error such as a breakdown. Therefore, when the RX102 detects a voltage drop in the power receiving coil 305, the RX102 may wait without communicating for a predetermined time required to measure the Q value, and if power transmission is not resumed even after the predetermined time has elapsed, transmit a signal to request power transmission. In this way, the RX102 can also handle the stop of power transmission in the event of a breakdown.

[0095] (Other embodiments) In the above-described embodiment, the TX101 measures the Q value based on the time lapse of the voltage inside the power transmitting coil 205, but is not limited to this method, and it is also possible to measure the Q value based on the time lapse of the current inside the power transmitting coil 205. In this case, the TX101 measures the current value A3 at time T3 and the current value A4 at time T4, and calculates the Q value based on Equation 1 using the measured current values ​​and the frequency of the high-frequency current.

[0096] Also, the TX101 may perform foreign object detection without calculating the Q value. In the case of FIG. 7(b), for example, the TX101 measures the voltage values ​​A1 and A2 at time T3 and time T4 during the period when the application of the voltage to the power transmitting coil 205 is stopped. The TX101 determines whether or not a foreign object is present based on the measurement result and the difference (slope) of the voltage value during the period from time T3 to time T4. When a foreign object is present within the power transmitting range, it is assumed that the voltage value of the power transmitting coil 205 attenuates more than when the foreign object is not present. Therefore, the TX101 determines that a foreign object is present when the difference (slope) of the measured voltage is greater than a reference value (difference between the voltages at two times) obtained when the foreign object is not present by a certain amount or more. The TX101 can also perform foreign object detection by calculating the ratio between the voltage value A1 and the voltage value A2. For example, if the ratio of voltage A1 at time T1 to voltage A2 at time T2 is greater than a certain value (the ratio of voltages at the two times) obtained when no foreign object is present, the TX101 determines that a foreign object is present.

[0097] When foreign object detection is performed without calculating the Q value as described above, the calculated voltage difference and ratio may differ depending on the magnitude of the voltage applied to the power transmitting coil 205 and the timing of measuring the voltage. Therefore, by aligning the voltage magnitude and the timing of measuring the voltage with the conditions when the reference value was obtained, foreign object detection can be performed more reliably.

[0098] Furthermore, the TX101 in the above-described embodiment measures at least one of the voltage or current output by the power transmitting coil 205, and performs foreign object detection based on the measurement results, but is not limited to this. For example, a configuration may be adopted in which another device connected to the outside of the TX101 measures and calculates the voltage, current, and power output by the power transmitting coil 205, and the energy stored in a capacitor in the TX101, and provides the obtained values ​​to the TX101. The TX101 can perform foreign object detection based on the values ​​provided by the other device.

[0099] In addition, the TX101 in the above-described embodiment is configured to stop the application of voltage to the power transmission coil 205 by switching a switch in the power transmission unit 203 to disconnect the power transmission coil 205 when measuring the Q value, but is not limited thereto. For example, the power transmission unit 203 may stop the application of voltage by setting the power transmission voltage to 0 when measuring the Q value. Also, the power transmission voltage may be switched to a lower voltage value without being completely set to 0 when measuring the Q value. However, since the method of measuring the Q value in this embodiment calculates the Q value based on the degree of attenuation of the voltage value, the Q value can be measured without completely stopping the application of the voltage by lowering the voltage value to at least a voltage value at which the attenuation of the voltage value can be observed. At this time, if the period during which the voltage is lowered exceeds a certain time, the RX102 side may determine that an error has occurred in the TX101. Therefore, it is desirable to set a voltage value reduction range that allows the voltage attenuation to be measured during a period during which the RX102 does not determine that the TX101 is abnormal.

[0100] In addition, the TX101 in the above-mentioned embodiments detects foreign objects by stopping the voltage and measuring the Q value, but in any embodiment, it is possible that stopping the voltage may cause the RX102 to determine that an error has occurred in the TX101. Therefore, a method for solving the above problem by having the RX102 acquire information about the TX101 when the RX102 is placed within the power transmission range of the TX101 will be described.

[0101] The RX102 transmits a signal to the TX101 to instruct the TX102 to transmit information about the TX101, for example, by communication in the negotiation phase. The information about the TX101 includes information such as version information about the TX101, information about the standard to which the TX101 conforms, and a method of detecting foreign objects used by the TX101. The TX101 transmits information about the TX101 to the RX102, and the RX102 recognizes that the TX101 stops applying voltage for a predetermined period for Q-value measurement based on the acquired information. This prevents the RX102 from erroneously determining that an error has occurred in the TX101 when the TX101 stops applying voltage for Q-value measurement, and allows the charging process to be continued stably. In addition, when transmitting information for enabling the TX101 to specify the timing of Q-value measurement as in the second embodiment, the RX102 can appropriately restrict communication by sharing the format of the information.

[0102] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0103] 102 Power transmission equipment 201 Control section 203 Power Transmission Division 204 Detection unit 205 Transmission coil 206 Communications Department

Claims

1. A negotiation means for negotiating with the power receiving device in a negotiation phase; a power transmitting means for wirelessly transmitting power to the power receiving device in a power transfer phase after the negotiation phase; a limiting means for limiting the power transmission when predetermined information is received from the power receiving device in the Power Transfer phase; A detection unit that detects an object during the period in which the power transmission is restricted, The power transmitting device, wherein after the period during which the power transmission is restricted ends, the power transmitting means resumes the power transmission in the Power Transfer phase without going through the Negotiation phase.

2. The power transmitting device as described in claim 1, wherein the detection means detects the object based on time information determined by the negotiation with the power receiving device.

3. The power transmission device as described in Claim 2, wherein the detection means detects the object according to timing based on the time information.

4. The power transmitting device according to claim 1 , wherein the detection means detects the object based on a quality factor.

5. The power transmitting device according to claim 4 , further comprising a measuring means for measuring the Quality factor based on an envelope of a waveform attenuation.

6. The power transmitting device according to claim 1 , wherein the predetermined information is information indicating received power.

7. A method performed by a power transmitting device, comprising: In the Negotiation phase, negotiations are performed with the power receiving device. After the Negotiation phase, power is wirelessly transmitted to the power receiving device in a Power Transfer phase; When predetermined information is received from the power receiving device in the Power Transfer phase, the power transmission is limited; During the period in which power transmission is restricted, an object is detected; After the period during which the power transmission is restricted ends, the power transmission in the Power Transfer phase is resumed without going through the Negotiation phase.

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