Power transmission device and method performed by power transmission device

Abstract

To prevent a reduction in detection accuracy when foreign substance detection is performed on the basis of a result of measurement of voltage or current in a period during which transmission of power is stopped.SOLUTION: A power transmission device 101 has: a communication unit 206 that performs communication by radio using a power reception device and a power transmission coil 205; a power transmission unit 203 that transmits power by radio to the power reception device using the power transmission coil 205; a detection unit 204 that, in a period during which the transmission of power performed by the power transmission unit 203 is stopped, measures at least one of voltage and current output from the power transmission coil 205, and on the basis of a result of the measurement, performs determination processing of determining that an object different from the power reception device is present; and a control unit 201 that, when it is determined that the object different from the power reception device is present through the determination processing, restricts the transmission of power performed by the power transmission unit 203, and controls the detection unit 204 not to use, for the determination processing, a measurement result obtained by the detection unit 204 in a period during which communication is performed by the communication unit 206.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a power transmitting device, a control method for a power transmitting device, and a program. [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. Then, when 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 not detecting an object when it exists, or erroneously detecting an object even when it does not exist. Then, when this method is applied to the detection of a foreign object, the accuracy of foreign object detection may be reduced. Note that the same problem occurs even when 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 of the present invention is characterized in that it has a communication means for wirelessly communicating with a power receiving device using an antenna, a power transmission means for wirelessly transmitting power to the power receiving device using the antenna, a measurement means for measuring at least one of the voltage and current output from the antenna during a period when the transmission of power by the power transmission means is stopped, a judgment means for performing a judgment process to determine that an object other than the receiving device is present based on the measurement results obtained by the measurement means, a restriction means for restricting the transmission of power by the power transmission means if the judgment process performed by the judgment means determines that an object other than the power receiving device is present, and a control means for controlling the judgment means not to use the measurement results obtained by the measurement means during the period when communication by the communication means is performed in the judgment process. Effect of the Invention

[0009] According to the present invention, an object is to suppress a decrease in detection accuracy when foreign object detection is performed based on the measurement results of voltage or current during a period when power transmission is stopped. [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 illustrating a process executed by a power transmitting device according to the first embodiment. [Diagram 5] FIG. 1 is a diagram for explaining a method for measuring a Q value. [Figure 6] 5 is a flowchart illustrating a foreign object detection process in the first embodiment. [Figure 7] 10 is a flowchart illustrating a foreign object detection process in a modified example of the first embodiment. [Figure 8] 10 is a flowchart illustrating a foreign object detection process according to the second embodiment. [Figure 9] 10 is a flowchart illustrating a foreign object detection process in a modified example of the 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 performs a judgment process (foreign object detection) to judge whether a foreign object exists within the power transmission range using the 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] <Power transmission device flow chart> Next, the operation of the power transmitting device 101 (TX101) of this embodiment will be described with reference to Fig. 4. The process shown in Fig. 4 can be realized by the control unit 201 of the TX executing a control program stored in the memory 209, and performing calculations of information, processing of information, and control of each piece of hardware.

[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] The steps from F404 to F407 are processes performed in the calibration phase. Here, a Q value is calculated to confirm that no foreign object exists within the power transmission range, and a foreign object is detected based on the calculated Q value. The TX101 in this embodiment calculates the Q value as a parameter used for foreign object detection. A method for measuring the Q value in the time domain will be described with reference to FIG. 5(a). The waveform shown in FIG. 5(a) shows a change over time in 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 500 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 501 is a part of the envelope of the voltage value shown by the waveform 500. (T1, A1) corresponding to the point 501 shows that the voltage value at time T1 is A1. Similarly, point 502 is part of the envelope of voltage values ​​represented by waveform 500, and (T2, A2) corresponding to point 502 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. 5(a), the Q value is acquired by measuring the amount of change in the voltage value after time T0. In the case of Fig. 5(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. Q=ω(T2-T1) / 2ln(A1 / A2) (Equation 1)

[0052] In this way, the Q value is calculated based on the time length from time T1 to time T2 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 (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. 5(b). A waveform 503 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 504 and 505 are part of the envelope of the voltage value indicated by the waveform 503. 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. 5(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 Qx. 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 Qx. 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 Th. Furthermore, if the difference between the acquired Q value and the reference value is smaller than a predetermined threshold value Th, the TX 101 can confirm that no foreign object is present within the power transmission range.

[0056] That is, the TX 101 determines that a foreign object is present when the following formula 2 is satisfied for the measured Q value. Q≦Qx-Th (Formula 2)

[0057] 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. 5(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.

[0058] For the reasons described above, if foreign object detection is performed based on the Q value from a single measurement, for example, if this single measurement is performed during a period in which communication between the TX101 and the RX102 is being performed, there is a possibility that foreign object detection cannot be performed accurately. Therefore, the TX101 in this embodiment calculates the Q value for foreign object detection multiple times, and determines whether or not a foreign object is present based on each measurement result. In the following description, the measurement of the voltage value for calculating the Q value and the calculation of the Q value based on the measured voltage value may be collectively referred to as the measurement of the Q value.

[0059] The process of foreign object detection based on the measurement of the Q value in this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the operation of the foreign object detection process in the power transmitting device 101 (TX101), which corresponds to F406 and F412 in Fig. 4. Moreover, the TX101 in this embodiment measures the Q value a predetermined number of times that is set in advance. Here, the set predetermined number of times is five times (F601). Moreover, in the following description, the predetermined number of times that the Q value is measured will be referred to as the number of measurements.

[0060] In F602, the control unit 201 of the TX101 controls the power transmitting unit 203 to stop the application of voltage to the power transmitting coil 205. The detection unit 204 also measures the voltage value during the period when the application of voltage is stopped. The control unit 201 controls the communication unit 206 of the TX101 not to transmit a signal when measuring the voltage value. The detection unit 204 calculates the Q value based on the measured voltage value. Here, the TX101 stops the application of voltage, measures the voltage value, and then resumes the application of voltage. The TX101 stops the application of voltage, measures the voltage value at different timings (times T3 and T4 in FIG. 5(b)), and the measurement process until the application of voltage is resumed is regarded as one measurement of the Q value, and this measurement of the Q value is repeated the number of times of measurement. When repeatedly measuring the Q value, the TX101 waits for a random time within a predetermined time interval (for example, 10 msec to 50 msec) between the first measurement and the next measurement of the Q value (F603). The TX101 repeats the processes of F602 and F603 for the number of measurements. As a result, the measurements of the multiple Q values ​​are performed with a random time interval. Note that, in the example of FIG. 6, the Q value is calculated each time one measurement process is performed, but this is not limited to this. The TX101 can also stop the application of the voltage, measure the voltage value at different timings, and calculate the Q value based on each measurement value after performing the process five times until the application of the voltage is resumed. In other words, the calculation of the Q value may be performed after the application of the voltage is resumed. However, considering the possibility of the presence of a foreign object, if the Q value is calculated while the application of the voltage is stopped, the presence of the foreign object can be detected at an earlier stage, and the foreign object can be dealt with more quickly.

[0061] In F604, the detection unit 204 uses Equation 2 to determine whether or not the difference between the measurement value Q and the reference value Qx exceeds the threshold value Th for each of the Q values ​​obtained by measuring the Q value a predetermined number of times (here, five times). If the measurement value Q that exceeds the threshold value is equal to or greater than a certain number (Yes in F604), the detection unit 204 determines that a foreign object is present within the power transmission range of the TX101 (F605). If the measurement value Q that exceeds the threshold value is less than a certain number (No in F604), the detection unit 204 determines that a foreign object is not present within the power transmission range of the TX101 (F606). In the example of FIG. 6, the certain number is set to 4.

[0062] Through the above-described process, the TX 101 can detect a foreign object based on the measurement results of a plurality of Q values. As a result, even if any of the measurements of a plurality of Q values ​​is performed during a period in which the TX 101 and the RX 102 are communicating with each other, the other measurement results can be taken into consideration, and erroneous foreign object detection can be prevented.

[0063] 4, in F407, if a foreign object is detected in the foreign object detection process of F406 (Yes in F407), the TX 101 stops power transmission (F415). If a foreign object is not detected in the foreign object detection process of F406 (No in F407), the calibration process ends (F408).

[0064] In F409, the TX101 transitions to the power transfer phase and starts the process of transmitting charging power to the RX102. After starting the power transmission, the TX101 continues the power transmission until an End Power Transfer packet (hereinafter, referred to as EPT) is transmitted from the RX102 as a notification to stop the power transmission. When the TX101 receives the EPT (Yes in F410), it stops the power transmission (F415).

[0065] If the TX101 has not received an EPT (No in F410), it determines whether or not a predetermined time (hereinafter, referred to as the timeout time) has elapsed since the foreign object detection process was executed (F411). If the timeout time has elapsed since the previous foreign object detection process, the TX101 executes the foreign object detection process again, thereby periodically checking whether or not a new foreign object has been placed within the power transmission range. If the timeout time has not elapsed (No in F411), the TX101 executes the step of F410 again. If the timeout time has elapsed (Yes in F411), the TX101 executes the foreign object detection process based on the measurement of the Q value (F412). The foreign object detection process executed here is the same as that executed in F406.

[0066] In the power transfer phase, foreign object detection based on the Q value measurement and foreign object detection based on the power loss are performed (F413). Foreign object detection based on the power loss is a process of determining that a foreign object is present when the value of the power transmitted by the TX101 is lost by more than a predetermined amount. Foreign object detection based on the power loss is performed by the RX102 notifying the TX101 of the power received. Foreign object detection based on the power loss can be performed after the calibration phase is completed, and can be performed at any timing between F410 and F414. For example, it may be performed at the same timing as foreign object detection based on the Q value measurement, or at a different timing. Also, the order of F412 and F413 may be reversed.

[0067] 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.

[0068] 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. It is not necessary that both F412 and F413 are executed, and at least one of them may be executed.

[0069] In the above-described foreign object detection process, if no foreign object is detected (No in F414), the TX 101 executes the steps from F410 onwards again. If a foreign object is detected (Yes in F414), the TX 101 stops transmitting power (F415).

[0070] As described above, when performing foreign object detection based on the measurement of the Q value, the TX101 judges whether or not a foreign object exists based on the measurement of multiple Q values. As a result, even if any of the multiple Q value measurements is measured during the period when the TX101 and the RX102 are communicating with each other, it is possible to prevent erroneous foreign object detection by taking into consideration the other measurement results. Furthermore, by combining the foreign object detection based on the measurement of the Q value and the foreign object detection based on the loss of power, the TX101 can perform more reliable foreign object detection. Note that, as a process of the TX101 when a foreign object is detected, the TX101 may restrict the power transmission to be stopped as described above, or may restrict the power transmission to be smaller than when no foreign object is detected.

[0071] 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.

[0072] Here, the effect of foreign object detection based on Q-value measurement on foreign object detection based on power loss will be described. Foreign object detection based on power loss cannot be performed until the processing of the calibration phase for calculating 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.

[0073] (Modification of the first embodiment) A modified example of the first embodiment will be described. The configuration of the wireless charging system and the configuration of the devices in the wireless charging system are the same as those in the first embodiment, and therefore the description will be omitted. FIG. 7 is a flowchart for describing the foreign object detection process performed by the power transmitting device 101 (TX101) in the modified example of the first embodiment. The TX101 in this modified example executes the same process as that shown in FIG. 4, but executes the process shown in FIG. 7 in the foreign object detection of F406 and F412. The description of the same process content as that in FIG. 4 will be omitted.

[0074] As in the first embodiment, the TX101 is set to perform the measurement of the Q value a predetermined number of times (F701). Here, the number of measurements is assumed to be five. In F702, the TX101 measures the Q value. The method of measuring the Q value is the same as in the first embodiment, and therefore the description will be omitted. After measuring the Q value, the TX101 determines whether or not the difference between the measured value Q and the reference value Qx exceeds the threshold value Th. If the difference exceeds the threshold value Th (Yes in F703), in F704, the TX101 determines whether or not the Q values ​​acquired so far have exceeded the threshold value Th a predetermined number of times in succession while performing the Q value measurement a number of times (here, five times). The predetermined number at this time is referred to as the consecutive number in the following description. The consecutive number of times for the measurement results that exceed the threshold value Th is referred to as the first consecutive number, and the consecutive number of times for the measurement results that do not exceed the threshold value Th is referred to as the second consecutive number. In the example of FIG. 7, the first consecutive number and the second consecutive number are four and two, respectively.

[0075] When the Q value is measured at random time intervals, if multiple Q values ​​exceeding the threshold value Th are obtained consecutively, it is assumed that there is a high possibility that a foreign object exists. Therefore, if the Q value exceeds the threshold value Th consecutively for the first consecutive number of times (Yes in F704), the TX101 determines that a foreign object exists (F708). At this time, even if the number of times that the Q value has been measured is less than the number of measurements, it is determined that a foreign object exists. For example, if the number of times that the Q value has been measured is four and all of the Q values ​​obtained by each measurement exceed the threshold value Th, it is determined that a foreign object exists at this point. If the Q value exceeding the threshold value Th has not been obtained consecutively for the first consecutive number of times (No in F704) and if the number of times that the Q value has been measured is less than the first consecutive number of times, the TX101 waits for a random time to execute the next Q value measurement (F706). The TX101 repeats the Q value measurement until the Q value has been measured the number of measurements.

[0076] Furthermore, if the threshold value Th is not exceeded in F703 (No in F703), in F705, the TX101 determines whether or not the Q values ​​acquired so far have not exceeded the threshold value Th for the second consecutive number of times while performing the Q value measurement the number of times. When the Q value is measured at random time intervals, if multiple Q values ​​that do not exceed the threshold value Th are obtained consecutively, it is assumed that there is a high possibility that no foreign object is present. Therefore, if the threshold value Th is not exceeded for the second consecutive number of times (Yes in F705), the TX101 determines that no foreign object is present (F709). At this time, even if the number of times the Q value measurement is performed is less than the number of measurements, it is determined that no foreign object is present. If the Q value that does not exceed the threshold value Th is not obtained consecutively for the second consecutive number of times (No in F705) and if the number of times the Q value measurement is performed is less than the second consecutive number of times, the TX101 waits for a random time to execute the next Q value measurement (F706). The TX101 repeats the Q value measurement until the Q value measurement is performed the number of measurements.

[0077] If the results of F704 and F705 are not Yes and the Q value has been measured the number of times, the TX101 executes the process of F707. The processes of F707 to F709 are similar to the processes of F604 to F606 in the first embodiment, and therefore will not be described. For example, when the Q value is measured five times, if the determination results as to whether or not the threshold value Th has been exceeded are "exceeded," "exceeded," "not exceeded," "exceeded," "exceeded," in that order, the process of F707 is executed. In this example, the threshold value Th has been exceeded a certain number of times (here, four times) or more (Yes in F707), so it is determined that a foreign object is present (F708).

[0078] As described above, the TX101 in this modification judges whether the measured Q value exceeds the threshold value Th a predetermined number of times in succession. By performing the processes of F704 and F705, the TX101 can reduce the number of measurements of the Q value when the same measured value Q is obtained in succession. This makes it possible to reduce the processing load of the TX101 related to foreign object detection. In the above modification, the first consecutive number and the fixed number are equal to each other. Also, the second consecutive number is set to (the number of measurements-the first consecutive number+1). However, this is not limited to this, and the TX101 can set the first consecutive number and the second consecutive number to any value independently. For example, the TX101 may set both the first consecutive number and the second consecutive number to four times. That is, the first consecutive number and the second consecutive number can be set to any value as long as they are equal to or less than the number of measurements.

[0079] In the above-described first embodiment and its modified example, the TX101 is assumed to determine that a foreign object exists when there are a certain number or more of Q values ​​among the multiple measured values ​​Q whose difference from the reference value Qx exceeds the threshold value Th, but the present invention is not limited to this. For example, the TX101 may determine that a foreign object exists when the ratio of the number of Q values ​​whose difference from the reference value Qx exceeds the threshold value Th is a certain number or more with respect to the number of measurements set in advance. The TX101 may also determine that a foreign object does not exist when there are a certain number or more of Q values ​​whose difference from the reference value Qx does not exceed the threshold Th. The TX101 may also compare the number of Q values ​​whose difference from the reference value Qx exceeds the threshold Th with the number of Q values ​​whose difference does not exceed the threshold Th, and make a determination based on the result of the larger number. The TX101 is assumed to measure the Q value a certain number of times (measurement number), but may also repeatedly perform the measurement until, for example, a certain time has elapsed.

[0080] Second Embodiment In this embodiment, the TX101 is described which, when a Q value for foreign object detection is measured, determines whether or not to use the measured value Q for foreign object detection. The configuration of the wireless charging system and the configuration of the devices in the wireless charging system are similar to those in the first embodiment, and therefore description thereof will be omitted. FIG. 8 is a flowchart for describing the foreign object detection process performed by the power transmitting device 101 (TX101) in the second embodiment. The TX101 in this embodiment executes the same process as that shown in FIG. 4, but executes the process shown in FIG. 8 in foreign object detection of F406 and F412. Description of the same process content as that in FIG. 4 will be omitted.

[0081] In F801, the TX101 measures the Q value. The method of measuring the Q value is the same as that in the first embodiment, and therefore the description will be omitted. In F802, the TX101 judges whether or not communication has been performed at the timing when the voltage value of the power transmitting coil 205 is measured in order to calculate the Q value. The judgment of whether or not communication has been performed is performed by judging whether or not a signal transmitted from the RX102 has been superimposed on the voltage during the period from time T0 to time T5 in the example of FIG. 5(b). The communication unit 206 demodulates the electromagnetic wave generated from the power transmitting coil 205 during the period from time T0 to time T5, and judges that communication has been performed during the period when the application of the voltage is stopped if the signal transmitted from the RX102 has been superimposed. Therefore, the communication unit 206 can judge that communication has been performed at the timing when the voltage value of the power transmitting coil 205 is measured.

[0082] If the voltage value of the power transmission coil 205 is measured during communication, the voltage value measured may not be suitable for obtaining the Q value used in foreign object detection. Therefore, if the TX101 determines that communication has occurred during the measurement of the voltage value (Yes in F802), the measured voltage value may be inappropriate for calculating the Q value used in foreign object detection, so it measures the Q value again (F801). If the TX101 determines that communication has not occurred during the measurement of the voltage value (No in F802), it determines that the measured voltage value is suitable for calculating the Q value used in foreign object detection, and performs a process of determining foreign object detection (F803). In F803, the TX101 determines whether the difference between the measurement value Q and the reference value Qx has exceeded the threshold value Th. If it has exceeded the threshold value Th (Yes in F803), the TX101 determines that a foreign object is present (F804). If it has not exceeded the threshold value Th (No in F803), the TX101 determines that no foreign object is present (F805).

[0083] As described above, in the present embodiment, when communication is being performed at the timing when the voltage value of the power transmitting coil 205 is measured to calculate the Q value, the TX101 does not use the Q value based on this measurement value for foreign object detection, and measures the voltage value again. With this configuration, a voltage value that may not be suitable for the foreign object detection process is not used, so that a decrease in the accuracy of the foreign object detection process can be suppressed. Note that FIG. 8 shows an example of a process in which the measurement of the voltage value of the power transmitting coil 205 and the calculation of the Q value based on the voltage value are performed in F801, but the calculation of the Q value based on the voltage value may be performed after F802.

[0084] (Modification of the second embodiment) A modified example of the second embodiment will be described. The configuration of the wireless charging system and the configuration of the devices in the wireless charging system are the same as those in the first embodiment, and therefore the description will be omitted. FIG. 9 is a flowchart for describing the foreign object detection process performed by the power transmitting device 101 (TX101) in the modified example of the second embodiment. The TX101 in this modified example executes the same process as that shown in FIG. 4, but executes the process shown in FIG. 9 in the foreign object detection of F406 and F412. The description of the same process content as that in FIG. 4 will be omitted.

[0085] In F901, the TX101 measures the Q value. The method of measuring the Q value is the same as that in the first embodiment, and therefore the description will be omitted. In F902, the TX101 monitors whether or not a signal transmitted from the RX102 is received within a certain time from the timing of measuring the voltage value of the power transmitting coil 205 in order to calculate the Q value. The certain time is the time assumed to be required from the start of transmission of the signal transmitted from the RX102 to the TX101 to the completion of the transmission. When the RX102 transmits a data packet or the like including information indicating the power received by the RX102 as a signal, for example, a certain time is required from the start of transmission of the data packet to the completion of the transmission. In addition, the period during which the TX101 stops applying power to the power transmitting coil 205 in order to calculate the Q value may be shorter than the time required for the RX102 to transmit the data packet. Therefore, if the TX101 stops applying power to the power transmitting coil 205 and measures the voltage value during the period during which the RX102 is transmitting the data packet, the remaining data packet is transmitted even after the timing of measuring the voltage value. Therefore, TX101 can determine that communication is taking place because a data packet is received between the time when power application was stopped and the time assumed to be required for RX102 to transmit the data packet has elapsed.

[0086] If the TX101 receives a signal such as a data packet before the fixed time has elapsed, it determines that communication has taken place (Yes in F903), and since the measured voltage value may be unsuitable for calculating the Q value used in foreign object detection, it measures the Q value again (F901). If the TX101 does not receive a signal such as a data packet before the fixed time has elapsed, it determines that communication has not taken place (No in F903), and since the measured voltage value is suitable for calculating the Q value used in foreign object detection, it performs foreign object detection determination processing (F904). The processing from F904 to F906 is similar to the processing from F803 to F805 in FIG. 8, and therefore description thereof will be omitted.

[0087] As described above, the TX101 in this modification judges whether communication has been performed based on the fact that a signal has been received within a certain time from the timing of measuring the voltage value of the power transmission coil 205 for calculating the Q value. The TX101 in the second embodiment is configured to judge whether communication has been performed during the period when the voltage application is stopped. However, since the time when the voltage application is stopped is very short compared to the time required for communication, a certain level of detection accuracy is required to detect the communication status during the period when the voltage application is stopped. According to this modification, it is only necessary to be able to detect the communication status over a longer period of time, so that it is possible to analyze the communication status by, for example, a processing program or the like operating in the control unit 201.

[0088] Note that, while FIG. 9 illustrates an example of processing in which measurement of the voltage value of the transmitting coil 205 and calculation of the Q value based on the voltage value are performed in F901, calculation of the Q value based on the voltage value may be performed after F902.

[0089] In addition, in the above-described second embodiment and its modified example, when communication is being performed at the timing when the voltage value of the power transmission coil 205 is measured to calculate the Q value, the TX101 does not use the Q value based on this measurement value for foreign object detection, but this is not limited to the above. For example, the TX101 can use the Q value based on the voltage value measured during the period when communication is being performed with a lower priority than the Q value based on the voltage value measured during the period when communication is not being performed. For example, when the Q value is measured multiple times as in the first embodiment, the TX101 first performs a determination process of whether or not a foreign object exists based on the Q value based on the voltage value measured during the period when communication is not being performed. The TX101 then uses the measurement result of the Q value based on the voltage value measured during the period when communication is being performed, and can use it to confirm and correct the result of the determination process. In addition, the TX101 may estimate a voltage value that varies due to communication in advance, and correct the measurement result of the Q value based on the voltage value measured during the period when communication is being performed based on the estimated value.

[0090] (Other embodiments) Although the above-mentioned foreign object detection based on the measurement of the Q value is performed every time the timeout time elapses, the present invention is not limited to this. For example, the foreign object detection may be performed when a user operation is performed on the TX101 or the RX102, in addition to when the timeout time elapses. Also, for example, the TX101 may have a sensor for detecting vibration, temperature, weight of a placed object, etc. within the power transmission range, and may perform foreign object detection when vibration, a rise in temperature, a change in weight, etc. are detected.

[0091] In addition, the parameters used in the above-mentioned embodiment, such as the reference value Qx, the threshold value Th, the timeout period, the number of measurements, the fixed number, the predetermined time interval, the number of consecutive measurements, the predetermined time, and the fixed time, are assumed to be predetermined fixed values, but are not limited to this. These parameters may change dynamically depending on the state of the device, changes in the surrounding environment, and the execution status of the process. In addition, for example, these parameters may be determined by negotiation between the TX101 and the RX102 in the negotiation phase.

[0092] Furthermore, the TX101 in the above-described embodiment 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.

[0093] Also, the TX101 may perform foreign object detection without calculating the Q value. In the case of FIG. 5(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 is attenuated 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] For example, the RX102 transmits a signal to the TX101 to instruct the TX102 to transmit information about the TX101, 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 foreign object detection used by the TX101. The TX101 transmits the information about the TX101 to the RX102, and the RX102 recognizes that the TX101 will stop 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 continue stably.

[0099] 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]

[0100] 102 Power transmission equipment 201 Control section 203 Power Transmission Division 204 Detection unit 205 Transmission coil 206 Communications Department

Claims

1. A communication means for wirelessly communicating using a power receiving device and an antenna; a power transmitting unit that transmits power wirelessly to the power receiving device using the antenna; a measuring means for measuring at least one of a voltage and a current output from the antenna during a period in which the transmission of power by the power transmitting means is stopped; a determination means for performing a determination process for determining that an object different from the receiving device is present based on a measurement result obtained by the measurement means; a limiting means for limiting transmission of electric power by the power transmitting means when it is determined by the determination process performed by the determining means that an object other than the power receiving device is present; a control means for controlling the determination means not to use, in the determination process, a measurement result obtained by the measurement means during a period in which communication is performed by the communication means; A power transmitting device comprising:

2. A method for controlling a power transmitting device, comprising: a communication step of wirelessly communicating with the power receiving device using an antenna; a power transmitting step of wirelessly transmitting power to the power receiving device using the antenna; a measuring step of measuring at least one of a voltage and a current output from the antenna during a period in which the transmission of power in the power transmitting step is stopped; a determination step of performing a determination process for determining that an object different from the receiving device exists based on a measurement result obtained in the measurement step; a limiting step of limiting transmission of power in the power transmitting step when it is determined by the determination process in the determining step that an object other than the power receiving device is present; a control step of controlling so that a measurement result obtained by performing the measurement in the measuring step during a period in which the communication in the communication step is performed is not used in the determination process in the determination step; A control method comprising the steps of:

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

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