Power transmission equipment, methods used by power transmission equipment, and programs

Abstract

When foreign object detection is performed based on voltage or current measurement results during periods when power transmission is interrupted, the decrease in detection accuracy is suppressed. [Solution] The power transmission device 101 includes a communication unit 206 that communicates wirelessly with the power receiving device using an antenna, a power transmission unit 203 that wirelessly transmits power to the power receiving device using an antenna, a detection unit 204 that measures at least one of the voltage and current output from the antenna during periods when power transmission is stopped and communication by the communication unit 206 is not performed, and determines, based on the measurement results, that an object other than the power receiving device exists, and a control unit 201 that restricts power transmission if it is determined that an object other than the power receiving device exists.

Description

Technical Field

[0001] The present invention relates to a power transmission device.

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. Patent Document 1 discloses a power transmission device and a power reception device compliant with the standard (hereinafter referred to as the WPC standard) formulated by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards. Communication between the power transmission device and the power reception device is realized by superimposing a signal on the transmitted power using an antenna used during wireless power transmission.

[0003] Patent Document 1 discloses a method of identifying the presence of a foreign object when a foreign object (hereinafter referred to as a foreign object), different from the power reception device, exists within the range where the power transmission device can transmit power, and restricting the power transmission based on the identification result.

[0004] Further, Patent Document 2 discloses a method of determining whether an object exists near a power transmitter based on the attenuation amount of the voltage value of the power transmitter during a period when the voltage of the power transmitter gradually decreases after the power transmission is stopped.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When using an antenna used for wireless power transmission for communication between a power transmission device and a power reception device, the method disclosed in Patent Document 2 presents the following problems. Specifically, when measuring voltage during a period when power transmission is stopped, if communication using the antenna used for wireless power transmission is taking place, the amplitude change of that signal is reflected in the power, i.e., the measured voltage. Therefore, the measured voltage is affected not only by the object but also by the communication. Furthermore, if the presence of an object is determined based on this measured voltage, there is a problem in that the accuracy of object detection is reduced, such as failing to detect an object when it is present or falsely detecting an object when it is not present. Moreover, if this method is applied to the detection of foreign objects, the accuracy of foreign object detection may be reduced. The same problem arises even when the object to be measured is electric current.

[0007] The present invention has been made in view of the above-mentioned problems. Its purpose 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. [Means for solving the problem]

[0008] One embodiment of a power transmission device according to the present invention includes: receiving means for receiving identification information of a power receiving device; negotiating means for negotiating with the power receiving device in a negotiation phase; power transmission means for wirelessly transmitting power to the power receiving device in a power transfer phase after the negotiation phase; restricting means for restricting the power transmission when predetermined information is received from the power receiving device in the power transfer phase; and detection means for detecting an object during the period in which the power transmission is restricted, wherein the power transmission means resumes power transmission in the power transfer phase without going through the negotiation phase again after the end of the period in which the power transmission is restricted, and the receiving means receives information on the power received in the power transfer phase. [Effects 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, a decrease in detection accuracy can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing an example configuration of a wireless power transmission system. [Figure 2] This figure shows an example of the configuration of a power transmission device. [Figure 3] This figure shows an example of the configuration of a power receiving device. [Figure 4] This is a flowchart illustrating the process performed by the power transmission device in the first embodiment. [Figure 5] This is a flowchart illustrating the process performed by the power receiving device in the first embodiment. [Figure 6] This is a sequence diagram illustrating the operation of the power transmission device and power receiving device in the first embodiment. [Figure 7] This is a diagram illustrating the method for measuring the Q-value. [Figure 8] This is a flowchart illustrating the process performed by the power transmission device in the second embodiment. [Figure 9] This is a flowchart illustrating the process performed by the power receiving device in the second embodiment. [Figure 10] This is a sequence diagram illustrating the operation of the power transmission device and power receiving device in the second embodiment. [Figure 11] This figure shows an example of information transmitted by the power transmission device in the second embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. The components described in the following embodiments are merely examples of embodiments of the present invention and do not limit the present invention to them.

[0012] (First Embodiment) Figure 1 shows an example of the configuration of a wireless charging system (wireless power transmission system) according to this embodiment. In one example, this system is configured to include a power transmission device 101 and a power receiving device 102. Hereinafter, the power receiving device may be referred to as RX and the power transmission device as TX. RX102 is an electronic device that receives power from TX101 and charges its built-in battery. TX101 is an electronic device that wirelessly transmits power to RX102 placed on a charging base 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 that smartphone. Note that RX102 and TX101 may be storage devices such as hard disk drives or memory devices, or information processing devices such as personal computers (PCs). Also, RX102 and TX101 may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, or projectors. Furthermore, RX102 and TX101 may have the ability to run applications other than wireless charging. Also, TX101 may be a smartphone. In this case, RX102 may be another smartphone or wireless earphones. Also, RX102 may be an automobile. Also, TX101 may be a charger installed in the console or elsewhere inside an automobile.

[0013] Furthermore, although one TX101 and RX102 are shown in this embodiment, the configuration can also be applied to multiple RX102s that are powered by one TX101 or each of separate TX101s.

[0014] This system shall perform wireless power transmission using the electromagnetic induction method for wireless charging based on the standard for wireless charging (WPC standard) defined by the Wireless Power Consortium (WPC). That is, RX102 and TX101 shall perform wireless power transmission for wireless charging based on the WPC standard between the power receiving coil (power receiving antenna) of RX102 and the power 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 other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, methods using lasers, etc. may also be used. Also, in this embodiment, it is assumed that wireless power transmission is used for wireless charging, but wireless power transmission may be performed for applications other than wireless charging.

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

[0016] RX102 and TX101 according to this embodiment perform communication for power transmission and reception control based on the WPC standard. Here, the communication for power transmission and reception control will be described. In the WPC standard, a plurality of phases are defined, including the Power Transfer phase in which power transmission is executed and the phases before power transmission. The phases before power transmission include (1) Selection phase, (2) Ping phase, (3) Identification&Configuration phase, (4) Negotiation phase, and (5) Calibration phase. Hereinafter, the Identification and Configuration phase will be referred to as the I&C phase.

[0017] (1) In the Selection phase, TX101 intermittently transmits an Analog Ping to detect the presence of an object within the power transmission range (for example, the presence of the power receiving device 102, a conductor piece, etc. placed on the charging stand 103). That is, the Analog Ping is a detection signal for detecting the presence of an object. TX101 transmits the Analog Ping by applying a voltage or current to the power transmission coil. Then, when an object is placed on the charging stand 103 and when no object is placed, a change occurs in the voltage or current applied to the power transmission coil. Therefore, TX101 detects at least one of the voltage value and the current value of the power transmission coil when transmitting the Analog Ping, and determines that an object is present when the voltage value is below a certain threshold or the current value exceeds a certain threshold, and transitions to the Ping phase.

[0018] (2) In the Ping phase, TX101 transmits a Digital Ping with a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start the control unit of RX102101 which is placed on the charging base 103. RX102 notifies TX101 of the magnitude of the received voltage. That is, RX102 transmits a Signal Strength packet (hereinafter referred to as "SS packet") to TX101. In this way, TX101 recognizes that the object detected in the Selection phase is RX102 by receiving the response from RX102 which received the Digital Ping. Upon receiving notification of the received voltage value, TX101 transitions to the I&C phase.

[0019] (3) In the I&C phase, TX101 identifies RX102 and obtains equipment configuration information (capability information) from RX102. To this end, RX102 sends an ID packet and a Configuration packet to TX101. The ID packet contains the identification information of RX102, and the Configuration packet contains the equipment configuration information (capability information) of RX102. Upon receiving the ID packet and Configuration packet, TX101 responds with an acknowledgment (ACK). The I&C phase then ends.

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

[0021] (5) In the Calibration phase, based on the WPC standard, RX102 notifies TX101 of the received power value using a Received Power packet. 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 sets of received and transmitted power. In this embodiment, parameters for foreign object detection processing are also calculated and stored in the Power Transfer phase, which will be described later. Foreign object detection is the process of determining whether an object different from RX102 (hereinafter referred to as a foreign object) exists within the power transmission range of TX101, or whether there is a possibility that a foreign object exists.

[0022] During the Power Transfer phase, control is performed for starting and continuing power transmission, as well as for detecting foreign objects and stopping power transmission due to full charge.

[0023] TX101 and RX102 superimpose the signals related to communication for power transmission and reception control onto the power using the same antenna (coil) as wireless power transmission, in accordance with the WPC standard. This allows TX101 and RX102 to communicate for power transmission and reception control using the same antenna (coil) as wireless power transmission. The range in which communication based on the WPC standard is possible between TX101 and RX102 is approximately the same as the range in which power can be transmitted. That is, in Figure 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 transmission 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 some (or in some cases all) of the described configuration may be replaced or omitted by other configurations that perform similar functions, and further configurations may be added to the described configuration. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0025] Figure 2 shows an example of the configuration of the power transmission device 101 (TX101) according to this embodiment. The TX101 includes a control unit 201, a power supply unit 202, a power transmission unit 203, a detection unit 204, a power transmission 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 TX101 by executing a control program stored in, for example, memory 209. That is, the control unit 201 controls each functional unit shown in Figure 2. The control unit 201 also performs control related to power reception control in the TX101. In one example, the control unit 201 performs equipment authentication and the control necessary for power transmission in the TX101. The control unit 201 may also perform control for executing applications other than wireless power transmission. The control unit 201 is configured to include one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 201 may also be configured to include hardware dedicated to specific processing, such as an Application Specific Integrated Circuit (ASIC). Furthermore, the control unit 201 may be configured to include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 201 stores information that should be stored while various processing is being executed in memory 209. The control unit 201 can also measure time or time using the timer 210. Furthermore, when the detection unit 204 (described later) detects a foreign object, the control unit 201 restricts the transmission of power by the power transmission unit 203 (described later) based on the detection of the foreign object.

[0027] The power supply unit 202 transmits the power necessary for control, power transmission, and communication to the entire TX101. 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 transmission unit 203 converts the DC or AC power input from the power supply unit 202 into AC frequency power in the frequency band used for wireless power transmission. Furthermore, by inputting this AC frequency power to the power transmission coil 205, it generates electromagnetic waves for the RX102 to receive power. The frequency of the AC power generated by the power transmission unit 203 is several hundred kHz (for example, 110 kHz to 205 kHz).

[0029] Based on instructions from the control unit 201, the power transmission unit 203 inputs AC frequency power to the power transmission coil 205 so that it outputs electromagnetic waves from the power transmission coil 205 for power transmission to the RX102. The power transmission unit 203 also controls the intensity of the output electromagnetic waves by adjusting the voltage (transmission voltage) or current (transmission current) input to the power transmission coil 205. Increasing the transmission voltage or transmission current increases the intensity of the electromagnetic waves, and decreasing the transmission voltage or transmission current decreases the intensity of the electromagnetic waves. Furthermore, based on instructions from the control unit 201, the power transmission unit 203 controls the output of AC frequency power so that power transmission from the power transmission coil 205 is started or stopped. In this embodiment, the power transmission unit 203 of the RX102 has a switch on the circuit connected to the power transmission coil 205. When measuring the Q value (Quality factor), which will be described later, the power transmission unit 203 switches a switch inside the power transmission unit 203, disconnecting the connection to the power transmission coil 205 and stopping the application of voltage to the power transmission coil 205. Note that the switch may be located outside the power transmission unit 203. For example, the switch may be provided between the power transmission unit 203 and the detection unit 204, or between the detection unit 204 and the power transmission coil 205, as shown in Figure 2.

[0030] The detection unit 204 detects whether an object is present in range 104 by measuring the voltage or current of the transmission coil 205. For example, the detection unit 204 detects the voltage or current of the transmission coil 205 when the transmission unit 203 transmits an Analog Ping according to the WPC standard via the transmission coil 205. The detection unit 204 can then determine that an object is present in range 104 if the voltage falls below a predetermined voltage value or the current value exceeds a predetermined current value. Furthermore, whether this object is RX102 or another foreign object is determined when a predetermined response is received to the Digital Ping subsequently transmitted by the communication unit 206, and the object is determined to be RX102. In addition, the detection unit 204 measures the voltage of the transmission coil 205 when acquiring the Q value, as described later, and uses the Q value acquired based on the measurement result to detect foreign objects. Details will be described later.

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

[0032] The output unit 207 provides information to the user by any means, such as visual, auditory, or tactile. For example, the output unit 207 notifies the user of information indicating the status of TX101 or the status of the wireless power transmission system including TX101 and RX102 as shown in Figure 1. The output unit 207 is composed of, 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 that receives operations from the user to the TX101. The operation unit 208 is composed of, for example, buttons, a keyboard, an audio input device such as a microphone, a motion detection device such as an accelerometer or gyroscope, or other input devices. Alternatively, a device in which the output unit 207 and the operation unit 208 are integrated, such as a touch panel, may be used.

[0034] Memory 209 stores various information. Note that memory 209 may also store information obtained by a different functional unit than the control unit 201. Timer 210 performs timing using, for example, a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

[0035] Figure 3 shows 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, for example, memory 309. In one example, the control unit 301 performs the necessary controls for device authentication and power reception in the RX102. The control unit 301 may also perform controls for executing applications other than wireless power transmission. The control unit 301 is configured to include one or more processors, such as a CPU or MPU. The control unit 201 may be configured to include hardware dedicated to specific processing, such as an ASIC, or array circuits such as an FPGA compiled to execute predetermined processing. The control unit 301 stores information that should be stored while various processes are being executed in memory 309. The control unit 301 can also measure time using a timer 310.

[0037] Battery 302 transmits the power necessary for control, power reception, and communication to the entire RX102. Battery 302 also stores the power received via the power receiving coil 305. An induced electromotive force is generated in the power receiving coil 305 by electromagnetic waves radiated from the power transmitting coil 205 of TX101, and the power receiving unit 303 acquires the power generated in the power receiving coil 305.

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

[0039] The detection unit 304 detects whether or not RX102 is placed within the range 104 from which it can receive power from TX101. For example, the detection unit 304 detects the voltage or current of the receiving coil 305 when the power receiving unit 303 receives a Digital Ping in accordance with the WPC standard via the receiving coil 305. The detection unit 304 can then determine, for example, that RX102 is placed within the range 104 if the detected voltage falls below a predetermined voltage threshold, or if 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 superimposing signals using the same antenna (coil) as 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 receiving coil 305. The communication unit 306 further modulates the electromagnetic waves with a load to superimpose the information to be transmitted to the TX101 onto the electromagnetic waves, thereby communicating with the TX101. In other words, communication by the communication unit 306 can be performed by superimposing it onto the power transmission from the transmitting coil 205 (Figure 2) of the TX101.

[0041] The output unit 307 provides information to the user by any means, such as visual, auditory, or tactile. For example, the output unit 307 notifies the user of the status of RX102 and the status of the wireless power transmission system including TX101 and RX102 as shown in Figure 1. The output unit 307 is composed of, for example, a liquid crystal display, LEDs, a speaker, a vibration generating circuit, and other notification devices.

[0042] The operation unit 308 has a reception function that accepts user input to the RX102. The operation unit 308 is composed of, for example, buttons, a keyboard, an audio input device such as a microphone, a motion detection device such as an accelerometer or gyroscope, or other input devices. Alternatively, a device in which the output unit 307 and the operation unit 308 are integrated, such as a touch panel, may be used.

[0043] Memory 309 stores various information. Note that memory 309 may also store information obtained by a different functional unit than the control unit 301. Timer 310 performs timing using, for example, a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

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

[0045] <Processing in power transmission equipment> Figure 4 is a flowchart showing the processes performed by the power transmission device 101 (TX101) in this embodiment. The flowchart shown in Figure 4 can be realized when the control unit 201 of TX101 executes a control program stored in the memory 209, performing calculations of information, processing of information, and control of various hardware components.

[0046] In F401, the control unit 201 performs the processes defined as the Selection phase and Ping phase of the WPC standard. Then, RX102 detects that it has been placed on the charging base 103 of TX101, for example by detecting a Digital Ping from TX101. Upon detecting the Digital Ping, RX102 sends an SS packet containing the received voltage value to TX101. RX102 detects that it has been placed within the power transmission range of TX101.

[0047] In F402, the control unit 201 obtains identification information and capability information from RX102 by communicating in the I&C phase via the communication unit 206. The identification information of RX102 may include the Manufacturer Code and Basic Device ID. The capability information of RX102 may include information that can identify the version of the WPC standard it supports, the Maximum Power Value indicating the maximum power that RX102 can receive, and information indicating whether or not it has the Negotiation function of the WPC standard. Note that TX101 may obtain the identification information and capability information of RX102 by means other than communication in the I&C phase. Furthermore, the identification information may include information that can identify an individual RX102, such as the Wireless Power ID. Thus, the identification information may include information other than that described above, and similarly, the capability information may also include information other than that described above.

[0048] In F403, the control unit 201 determines the value of GP based on the GP value requested by RX102 by communicating in the Negotiation phase via the communication unit 206.

[0049] In F404, the control unit 201 starts the processing in the Calibration phase (hereinafter referred to as the calibration process). Here, the calibration process is a process that calibrates the correlation between the value measured internally of TX101 (transmitted power) and the value measured internally of RX102 (received power) for the power transmitted by TX101 to RX102. In the Calibration phase, TX101 transmits power to communicate information for the calibration process and to acquire the power correlation described above.

[0050] Processes F404 to F407 are performed in the Calibration phase. Here, the Q value is measured to confirm that no foreign matter is present within the power transmission range. The method for measuring the Q value in the time domain is explained using Figure 7(a). The waveform shown in Figure 7(a) shows the change over time of the measured voltage inside the power transmission coil 205 of TX101 (hereinafter referred to as the voltage value), with the horizontal axis representing time and the vertical axis representing the voltage value. Waveform 700 is the voltage value of the high-frequency voltage applied to the power transmission coil 205. Time T0 indicates the time when the application of the high-frequency voltage to the power transmission coil 205 is stopped. Point 701 is part of the envelope of the voltage value shown by waveform 700. (T1, A1) corresponding to point 701 indicates that the voltage value at time T1 is A1. Similarly, point 702 is part of the envelope of the voltage value shown 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 after the application of high-frequency voltage to the transmission coil 205 is stopped. In the example shown in Figure 7(a), the Q value is obtained by measuring the change in voltage after time T0. In Figure 7(a), for example, the voltage values ​​A1 and A2 at times T1 and T2, respectively, which are times in the period after time T0 when the application of high-frequency voltage is stopped, are measured. 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) Thus, 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. Here, ω represents the angular velocity of the high-frequency voltage 700 (frequency multiplied by 2π).

[0053] Next, the process by which TX101 measures the Q value in this embodiment will be explained using Figure 7(b). Waveform 703 is the high-frequency voltage applied to the transmission coil 205 by the transmission unit 203, and its frequency is between 110 kHz and 148.5 kHz, as used in the WPC standard. During the period from time T0 to time T5, the transmission unit 203 switches a switch and disconnects the connection with the transmission coil 205, thereby stopping the application of the high-frequency voltage. Note that the period from T0 to time T5 is a very short period compared to the period during which TX101 transmits power to RX102.

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

[0055] In this embodiment, TX101 acquires a Q value using the method described above. TX101 also performs foreign object detection based on the acquired Q value and confirms that no foreign objects are present within the power transmission range. At this time, TX101 stores the Q value measured when no foreign objects are present within the power transmission range as a reference value. If power transmission is performed while foreign objects such as conductive fragments are present within the power transmission range, not only RX102 but also the foreign objects consume power. As a result, when foreign objects are present, the voltage value when TX101 stops transmitting power is expected to be significantly attenuated compared to when no foreign objects are present. Therefore, the Q value based on Equation 1 when foreign objects are present is expected to be smaller than the Q value when no foreign objects are present. Accordingly, TX101 determines that foreign objects are present (detects foreign objects) based on the acquired Q value being smaller than the reference value. At this time, TX101 calculates the difference between the acquired Q value and the reference value, and if the difference is greater than a predetermined threshold, it determines that foreign objects are present. Furthermore, if the difference between the acquired Q value and the reference value is smaller than a predetermined threshold, TX101 can confirm that no foreign objects are present within the power transmission range.

[0056] In this embodiment, the communication unit 206 of TX101 communicates information with RX102 by modulating or demodulating the electromagnetic waves generated by the voltage applied by the power transmission unit 203 to the power transmission coil 205. Similarly, the communication unit 306 of RX102 communicates information with TX101 by load modulating the electromagnetic waves received by the power receiving coil 305. Therefore, even if the voltage value is measured while communication is taking place between the communication units 206 and 306, a 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 TX101 stops applying voltage in Figure 7(b), the voltage value may change compared to the case where load modulation is not performed. As a result, the voltage values ​​A3 and A4 at times T3 and T4 when load modulation is performed may be larger or smaller than the voltage values ​​when load modulation is not performed. If the Q value obtained based on this voltage value is used for foreign object detection, it may result in the foreign object not being detected when it is present, or in false detection when it is not present.

[0057] For the reasons stated above, it is desirable that TX101 and RX102 do not communicate information while the power transmission device is measuring the Q value. During the calibration process, RX102 transmits power information to TX101 to notify it of the received power, and information to request an increase or decrease in the received power. In this embodiment, RX102 does not communicate during specific periods specified in the WPC standard that the power receiving device must not transmit signals. The period during which RX102 does not communicate is, for example, the period specified in the WPC standard that the power receiving device must not transmit the preamble for the next packet from the trailing end of the packet it has transmitted. That is, the period during which RX102 does not communicate is the period from when the power receiving device transmits a signal until a predetermined time has elapsed that the power receiving device must not transmit the next signal. Alternatively, for example, the period during which RX102 does not communicate is the period specified in the WPC standard that the power transmission device must not transmit the preamble for the next packet from the trailing end of the packet it has transmitted. In other words, the period during which RX102 does not communicate is the 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 is prohibited from transmitting the next signal. Therefore, in this embodiment, TX101 measures the Q value by utilizing the period during which RX102 does not communicate, as described above. At this time, TX101 also refrains from transmitting a signal to RX102. In this embodiment, TX101 waits until information is transmitted from RX102 (F405), and after receiving the information transmitted from RX102, measures the voltage value of the power transmitting coil 205 during the period when 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 will be simply referred to as measuring the Q value, but the process of calculating the Q value based on Equation 1 may be performed during the period when communication is taking place. In this embodiment, TX101 will measure the voltage value at least during the period when communication is not taking place.

[0058] Furthermore, foreign object detection based on Q-value measurement results can be used in conjunction with foreign object detection based on power loss. However, foreign object detection based on power loss cannot be performed until the Calibration phase, which calculates 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 foreign objects are present within the power transmission range during the Calibration phase, inappropriate parameters may be obtained, potentially reducing the accuracy of foreign object detection based on power loss in subsequent Power Transfer phases. In contrast, foreign object detection based on Q-value measurement results can be performed during the Calibration phase, allowing for a determination of whether or not foreign objects are present during the Calibration phase. This enables the TX101 to determine the presence of foreign objects during the Calibration phase and restrict power transmission.

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

[0060] In F409, TX101 transitions to the Power Transfer phase and begins transmitting power to RX102 for wireless charging. Even after starting to transmit power for charging, TX101 periodically receives power information from RX102. Therefore, in F410, TX101 monitors whether or not predetermined information has been transmitted from RX102. This predetermined information includes power information to notify the power level as described above, and information to request an increase or decrease in power.

[0061] In F410, when predetermined information is received, TX101 measures the Q value (F411) during periods when RX102 is not transmitting information. In F411, foreign object detection is performed based on the Q value measurement result and foreign object detection is performed based on the loss of transmitted power. Foreign object detection based on power loss is a process that determines the presence of a foreign object if the value of the power transmitted by TX101 is lost by a predetermined amount. Foreign object detection based on power loss is performed by RX102 notifying TX101 of the power it has received. By performing foreign object detection in F411, it is possible to detect if a foreign object has been placed within the power transmission range during charging. Note that the foreign object detection performed here may be either foreign object detection based on the Q value measurement result or foreign object detection based on the loss of transmitted power. In addition, in F411, it is sufficient that the voltage value of the power transmission coil 205 is measured during periods when no communication is taking place. In other words, the calculation of the Q value based on the measured voltage value of the power transmission coil 205, and the foreign object detection process based on the Q value, can be performed even while communication is taking place, and may be performed, for example, after F411. Also, foreign object detection based on power loss can be performed while communication is taking place, and may be performed in a process other than F411 after RX102 has notified TX101 of the power it has received.

[0062] Here, we will explain the combined use of foreign object detection based on Q-value measurement results and foreign object detection based on power loss. If both the foreign object detection result based on Q-value measurement results and the foreign object detection result based on power loss result indicate "no foreign object present," TX101 will determine that no foreign object is present. On the other hand, if at least one of the foreign object detection results based on Q-value measurement results and the foreign object detection result based on power loss result indicates "foreign object present," TX101 will determine that a foreign object is present (or highly likely to be present). This allows TX101 to suppress the transmission of power by incorrectly determining that no foreign object is present when one is actually present.

[0063] Furthermore, if the TX101 receives different foreign object detection results based on Q-value measurement and power loss, it may prioritize one of the foreign object detection results. For example, if the foreign object detection result based on power loss is prioritized, and the foreign object detection based on Q-value measurement determines that "no foreign object exists," but the foreign object detection based on power loss determines that "a foreign object exists," then the TX101 will prioritize the result based on power loss and determine that "a foreign object exists." Similarly, the foreign object detection result based on Q-value measurement may also be prioritized. In the above-mentioned method where the TX101 determines that "a foreign object exists" if at least one of the multiple foreign object detection methods determines that "a foreign object exists," power transmission despite the presence of a foreign object is suppressed. However, this method may frequently restrict power transmission. Therefore, when using multiple foreign object detection methods, it can be expected that frequent restrictions on power transmission will be avoided by pre-determining which foreign object detection result to prioritize.

[0064] If a foreign object is detected at F412, TX101 stops the charging process (Yes at F414). The process from F410 to F412 is repeated until a charging completion notification is received from RX102. If TX101 does not receive the required information at F410 (No at F410) and receives a charging completion notification from RX102 (Yes at F413), it stops supplying power for charging (F414).

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

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

[0067] In F504, the communication unit 306 performs a calibration process to establish a correlation between the transmitted power and the received power with respect to the TX101. Once the calibration process is complete, in F505, the power receiving process for charging the RX102 is started. During the calibration and power receiving processes, the RX102 transmits received power information to the TX101, notifying it of the received power, and information to request an increase or decrease in the received power. When charging is complete, the RX102 sends a notification to the TX101 indicating that charging is complete (F506).

[0068] <Operating sequence of power transmission and receiving equipment> Figure 6 shows the operation sequence of the power transmission device 101 (TX101) and the power receiving device 102 (RX102). TX101 intermittently transmits WPC-compliant Analog Pings to detect objects within its transmission range (S601). RX102 is placed within the transmission range of TX101 by a user or other party (S602). TX101 detects when the voltage of the transmission coil 205 falls below a predetermined value, or when the current of the transmission coil 205 exceeds a predetermined value, upon transmitting the Analog Ping. This allows TX101 to detect the presence of an object within its transmission range (S603, S604). After detecting the presence of an object within its transmission range, TX101 transmits a WPC-compliant Digital Ping (S605). RX102 receives the Digital Ping and recognizes that it was detected by TX101 (S606). When TX101 receives a predetermined response to Digital Ping, it detects that the detected object is RX102 and that RX102 has been placed on the charging base 103.

[0069] When TX101 detects that RX102 has been installed, it obtains identification and capability information from RX102 by communicating in the I&C phase of the WPC standard (S607). TX101 then determines the GP value with RX102 through communication in the Negotiation phase of the WPC standard (S608). Note that in S608, other procedures for determining GP, different from the Negotiation phase of the WPC standard, may be performed. Furthermore, if RX102 does not support the Negotiation phase of the WPC standard, it transmits information indicating this to TX101 at a timing such as S607. In this case, if TX101 receives information indicating that RX102 does not support the Negotiation phase of the WPC standard, it may determine GP without performing the Negotiation phase communication. The GP value determined in this case may be, for example, a value specified in the WPC standard. In the example in Figure 6, GP = 5W (watts) is determined in S608.

[0070] Next, the calibration process is performed. First, RX102 transmits the 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 refrains from communicating (transmitting information) until a predetermined time has elapsed, in accordance with the WPC standard (S610). When TX101 receives the reference power information transmitted from RX102, it uses the period during which RX102 does not communicate to perform a Q value measurement (S611). Based on the Q value measurement result, TX101 checks whether or not there is any foreign matter within the power transmission range. If foreign matter is detected, TX101 terminates the power transmission process to RX102.

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

[0072] Here, we will discuss the timing of S611 (Q value measurement) and S612 (ACK transmission). If S611 and S612 overlap, for the reasons mentioned above, it may not be possible to measure a voltage value suitable for obtaining the Q value used for foreign object detection. Also, if TX101 stops applying voltage while transmitting the ACK, the ACK data may be corrupted. Therefore, it is best to perform S611 and S612 so as not to overlap. Furthermore, since the period during which RX102 does not communicate is a period of waiting for a response from TX101, RX102 resumes communication when it receives an ACK or NAK transmitted from TX101. Therefore, TX101 measures the Q value before transmitting the ACK. Note that the process of determining whether or not a foreign object is present based on the Q value measurement result may be performed either before or after transmitting the ACK.

[0073] After receiving an ACK from TX101, RX102 processes a request to TX101 to transmit power equal to the value of GP. In the example in Figure 6, since GP = 5W, RX102 transmits instruction information (S613) indicating that TX101 should change its transmission output to increase the transmitted power to 5W. This instruction information may include a value (positive value) indicating the amount by which the power should be increased. After transmitting the instruction information, RX102 does not communicate until a predetermined time has elapsed, in accordance with the WPC standard. TX101 uses the period during which RX102 does not communicate to measure the Q value and perform foreign object detection based on the Q value (S615). After measuring the Q value, TX101 sends an ACK to RX102 as a response indicating that it is able to respond to the instruction to increase the power indicated by the instruction information, and also changes the transmission output based on the instruction information (S616, S617).

[0074] In S618, RX102 transmits information indicating that it will receive 5W of power as second reference power information. The second reference power information is information indicating the power received by the receiving coil 305, measured when the receiving unit 303 and the charging unit 311 are connected. TX101 uses the period of no communication after RX102 transmits the second reference power information to measure the Q value and perform foreign object detection (S619, S620). TX101 also calculates an estimated value of the power loss to be transmitted based on at least one of the voltage and current values ​​of the transmitting coil 205 when the device transmits power, and the first and second reference power information. Based on the calculated estimated power loss, TX101 performs foreign object detection (S621). TX101 also sends an ACK to RX102 as a response indicating acceptance of the second reference power information transmitted from RX102 (S622). Note that the processing in S621 and S622 may be reversed. After processing up to S622, TX101 determines that it has completed the calibration process and is ready to start the charging process, so it starts supplying power to RX102, and charging of RX102 begins.

[0075] Here, referring to S623 onwards in Figure 6, the operation sequence when the GP, once determined, is changed (re-determined) will be explained. For example, TX101 and RX102 perform an authentication process to authenticate each other's devices (S623), and based on the authentication result, they determine whether their respective devices can handle a GP larger than the current GP (5W). If it is determined that they can handle a larger GP, they re-determine the GP to, for example, 15W (S624). Note that the determination of whether they can handle a larger GP may be based on a method other than the authentication process. RX102 transmits instruction information to increase the power transmission output of TX101 to 15W. TX101 transmits an ACK or NAK to RX102 in response to the instruction information. If TX101 transmits an ACK, it increases the power transmission output based on the instruction information. In this process as well, TX101 measures the Q value and detects foreign objects during the period when there is no communication after RX102 has transmitted information. In addition, foreign object detection based on estimated power loss is performed, similar to S621 (S625-S630).

[0076] TX101 and RX102 perform calibration processing again. RX102 transmits information to TX101 indicating that it has received the re-determined GP=15W as the third reference power information (S631). TX101 uses the period of no communication after RX102 transmits the third reference power information to measure the Q value and perform foreign object detection (S633). TX101 also performs foreign object detection by calculating an estimated power loss based on at least one of the voltage and current values ​​of the transmission coil 205 when the device transmits power, and the first, second, and third reference power information (S634). TX101 also sends an ACK to the third reference power information transmitted from RX102 (S635) and starts the power transmission process. Regarding S631, if TX101 is unable to respond to the third reference power information within a predetermined time, it may either continue transmitting power at 15W while suspending the transmission of ACK, or continue transmitting power at up to 5W. In this case, TX101 and RX102 may display a screen on their respective output units 207 and 307 to allow the user to select whether to charge at 15W or 5W. The user may also specify their choice by operating the operation unit 208 or 308, or by operating the operation screen displayed on the output unit 207 or 307.

[0077] As explained above, TX101 measures the voltage of the transmission coil 205 when it stops applying voltage to the transmission coil 205 during a period when no communication is taking place after RX102 has transmitted information, and calculates the Q value. TX101 also performs foreign object detection based on the calculated Q value, and stops power transmission if a foreign object is detected. This prevents power transmission from continuing even if a conductive foreign object is present within the transmission range. Furthermore, by combining the above method with foreign object detection based on power loss, TX101 can perform more reliable foreign object detection. Regarding TX101's actions when a foreign object is detected, it may restrict power transmission to stop as described above, or it may restrict the transmitted power to be lower than when no foreign object is detected.

[0078] Furthermore, as a process for handling the detection of foreign matter, the GP may be re-determined between TX101 and RX102. If TX101 determines that RX102 is capable of re-negotiating the GP, it sends a signal to RX102 instructing it to re-negotiate the GP. At this time, TX101 may notify the power receiving device of the maximum value of the negotiable GP. Alternatively, the maximum value of the negotiable GP may be limited to 5W. If TX101 determines that RX102 is not capable of re-negotiating the GP, it performs processing such as limiting the transmitted power to be less than when no foreign matter is detected, changing the value of the transmitted power to a predetermined value (e.g., 5W), or stopping the transmission.

[0079] (Second embodiment) In the following explanation, we will focus on the differences from the first embodiment. The configurations of the power transmission device 101 (TX101) and the power receiving device 102 (RX102) are the same as in the first embodiment, so we will omit their explanation.

[0080] <Processing in power transmission equipment> Figure 8 is a flowchart showing the processes performed by the power transmission device 101 (TX101) in the second embodiment. The flowchart shown in Figure 8 can be realized by the control unit 201 of TX101 executing a control program stored in memory 209, performing information calculations, information processing, and control of each hardware component. Note that the processes from F801 to F804 are the same as the processes from F401 to F404 in Figure 4, so their explanation is omitted.

[0081] When calibration processing begins in F804, RX102 transmits power information to TX101 to notify it of the received power, as well as information to request an increase or decrease in power (F405). TX101 responds to the received information with an ACK or similar. At this time, TX101 adds information to the ACK data that allows it to specify the timing for measuring the Q value (F806). For example, TX101 adds time information indicating the time to measure the Q value using a data format as shown in Figure 11. The time information may be, for example, a value based on the elapsed time relative to the time TX101 was started, or a value indicating an offset time from the time the ACK was sent. If a value based on elapsed time is applied, TX101 and RX102 are configured to process based on the same time. For example, TX101 and RX102 are configured to synchronize their processing times by sharing the time TX101 was started and the time elapsed since TX101 was started during the I&C phase, etc. Then, RX102 receives an ACK from TX101 and refrains from communicating at the time indicated by the time information. Also, if an offset time value is applied, RX102 receives an ACK from TX101 and refrains from communicating until the offset time indicated by the time information has elapsed.

[0082] TX101 transmits the time information described above along with the ACK, and measures the Q value during periods when RX102 is not communicating based on the time information. The processes from F808 to F810 are the same as those from F407 to F409, so the explanation is omitted. In F811, TX101 monitors whether predetermined information (such as power information to notify power, and information to request an increase or decrease in power) has been transmitted from RX102. In F811, if predetermined information is received, TX101 sends an ACK as a response to the predetermined information. At this time, TX101 transmits the time information described above along with the ACK (F812). In F813, TX101 measures the Q value based on the timing indicated by the transmitted time information and performs foreign object detection (F813). At this time, TX101 may also perform foreign object detection based on power loss. Foreign object detection based on power loss may be performed in a process other than F813, or it may not be performed at all during the entire process. The method for measuring the Q value and the method for detecting foreign objects are the same as in the first embodiment. Processes F814 to F816 are the same as processes F412 to F414, so the explanation is omitted.

[0083] As explained above, TX101 transmits information to RX102 that allows it to specify the timing for measuring the Q value, thereby preventing communication from occurring during the measurement of the Q value. The information attached to the ACK does not need to be limited to the above, as long as it allows TX101 to specify the timing for measuring the Q value. For example, instruction information may be sent to RX102 to stop communication, and RX102 may refrain from communicating until a predetermined time has elapsed after receiving the instruction information. This predetermined time may be set in advance based on the time required to measure the Q value and the delay time related to communication between RX102 and TX101, or it may be included in the instruction information. Alternatively, the predetermined time may be determined by communication in the Negotiation phase of F803. Furthermore, TX101 may transmit time information and instruction information separately without attaching information to the ACK. Alternatively, as in the first embodiment, this may be combined with a method of measuring the Q value during a period when no communication occurs after predetermined information is transmitted from RX102. For example, TX101 may be configured to use the method described in this embodiment for steps F805 to F807, and the method described in the first embodiment for steps F810 and later. These modifications are also applicable in subsequent descriptions.

[0084] <Processing in the power receiving device> Figure 9 is a flowchart showing the processes performed by the power receiving device 102 (RX102) in the second embodiment. The flowchart shown in Figure 9 can be realized by the control unit 301 of RX102 executing a control program stored in memory 309, performing calculations on information, processing of information, and control of each hardware. The processes from F901 to F905 are the same as those from F501 to F505 in Figure 5, so their explanation is omitted. When the power receiving process starts, RX102 transmits power information that notifies the received power, and data requesting an increase or decrease in power (F906). RX102 receives an ACK from TX101 as a response to the transmitted information (F907). At this time, the ACK includes time information that allows TX101 to specify the timing for measuring the Q value, so RX102 extracts the time information (F908). Based on the time information, RX102 restricts communication (F909). From this point onward, RX102 repeatedly performs processes F906 through F909 until charging is complete. When charging is complete (F910), RX102 sends a notification to TX101 indicating that charging is complete (F911).

[0085] <Operating sequence of power transmission and receiving equipment> Figure 10 shows the operation sequence of the power transmission device 101 (TX101) and the power receiving device 102 (RX102) in the second processing example. Since the processing from S1001 to S1008 is the same as S601 to S608 in Figure 6, these processing steps will not be explained.

[0086] Once TX101 determines the GP value with RX102, it starts the calibration process. First, RX102 transmits to TX101 information indicating the power received by the receiving coil 305 when the receiving unit 303 and the charging unit 311 are connected, as first reference power information (S1009). In the example in Figure 10, the first reference power information is 500mW. Based on the power transmission status of its own device, TX101 determines whether or not to accept the first reference power information. If it determines to accept it, it sends an ACK to RX102; if it determines not to accept it, it sends a NAK. In the example in Figure 10, TX101 determines that it can stably transmit the power indicated by the first reference power information and sends an ACK to RX102.

[0087] TX101 sets the timing for measuring the Q value and transmits the ACK with time information attached as information that can identify that timing (S1010, S1011). Upon receiving the ACK, RX102 extracts the time information attached to the ACK and restricts communication based on this time information (S1012). Based on the timing indicated by the time information, TX101 measures the Q value and performs foreign object detection (S1013).

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

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

[0090] Subsequently, RX102 transmits a second reference power information (5W) to TX101 (S1020). TX101 calculates an estimated power loss based on the received power included in the first and second reference power information and performs foreign object detection (S1021). TX101 also sends an ACK to RX102 for the second reference power information. In this case, TX101 also performs Q-value measurement, but the method is the same as in S1010 to S1013, so the explanation is omitted (S1022~S1025). With the above processing, TX101 and RX102 complete the calibration process and begin charging RX102.

[0091] Here, the process in this embodiment when the GP, once determined, is changed (re-determined) will be explained with reference to Figure 10. TX101 and RX102 perform, for example, device authentication processing (S1026), and if they determine that the devices can handle a larger GP, they re-determine the GP to 15W (S1027). Subsequently, RX102 and TX101 perform recalibration processing to increase the power transmission of TX101 to 15W in the same manner as the processing in S1014 to S1017 (S1028-S1031). Also, RX102 transmits a value of 15W as third reference power information. TX101 transmits a response to the third reference power information to RX102. During this time, TX101 also transmits time information attached to the ACK, measures the Q value based on the timing indicated by the time information, and performs foreign object detection (S1033-S1038). TX101 confirms the absence of foreign objects and begins power transmission for charging. Regarding S1033, if TX101 is unable to respond to the third reference power information within a predetermined time, it may continue power transmission at 15W while withholding the transmission of ACK, or it may continue power transmission at a power of up to 5W. At this time, TX101 and RX102 may display a screen on their respective output units 207 and 307 to allow the user to select whether to perform 15W charging or 5W charging. The user may also specify their selection by operating the operation unit 208 or 308, or by operating the operation screen displayed on the output unit 207 or 307.

[0092] As explained above, TX101 can prevent communication from occurring during Q-value measurement by transmitting, for example, time information as a signal to specify the timing for measuring the Q-value. Note that TX101 may also notify RX102 of the timing for measuring the Q-value using other configurations. For example, TX101 stores information that makes the timing for measuring the Q-value specific in a Power Transmitter Capability packet, which is defined in the WPC standard as a packet that notifies the receiving device of information regarding the capabilities of the power transmission device. TX101 can notify RX102 of the timing for measuring the Q-value by transmitting a packet containing instruction information and time information to RX102. Alternatively, for example, in the Negotiation phase, RX102 may request TX101 to transmit information that makes the timing for measuring the Q-value specific in order to determine the timing for measuring the Q-value. In this case, TX101 sends an acknowledgment (ACK) and time information to RX102, or a negative acknowledgment (NAK) to RX102. Alternatively, for example, RX102 may send time information or other data to TX101 to specify the timing for measuring the Q value.

[0093] (Third embodiment) In this embodiment, a configuration is described in which the power receiving device 102 (RX102) restricts communication by detecting the measurement of the Q value performed by the power transmitting device 101 (TX101). The detection unit 304 of RX102 detects that TX101 has stopped applying voltage in order to measure the Q value by measuring at least one of the voltage or current of the power receiving coil 305. For example, if RX102 measures the voltage of the power receiving coil 305 and detects a drop in voltage, RX102 determines that 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, RX102 can prevent communication while TX101 is measuring the Q value.

[0094] Furthermore, the situations in which RX102 detects a drop in the voltage of the receiving coil 305 include when TX101 is measuring the Q value, and when power transmission stops due to an error such as a malfunction of TX101. Therefore, when RX102 detects a drop in the voltage of the receiving coil 305, it may wait without communicating for a predetermined time required for measuring the Q value, and if power transmission does not resume after the predetermined time has elapsed, it may send a signal to request power transmission. In this way, RX102 can also respond to power transmission interruptions in the event of a malfunction.

[0095] (Other embodiments) In the embodiment described above, TX101 measures the Q value based on the time course of the voltage inside the transmission coil 205, but is not limited to this method. It is also possible to measure the Q value based on the time course of the current inside the transmission coil 205. In this case, 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 value and the frequency of the high-frequency current.

[0096] Furthermore, TX101 may perform foreign object detection without calculating the Q value. In the case of Figure 7(b), for example, TX101 measures the voltage values ​​A1 and A2 at times T3 and T4 during the period when the voltage application to the power transmission coil 205 is stopped. Based on the measurement results, TX101 determines whether or not a foreign object is present based on the difference (slope) of the voltage values ​​during the period from time T3 to time T4. If a foreign object is present within the power transmission range, the voltage value of the power transmission coil 205 is expected to be attenuated more significantly than when no foreign object is present. Therefore, TX101 determines that a foreign object is present if the measured voltage difference (slope) is greater than a certain threshold value (the difference in voltage at two times) obtained when no foreign object is present. In addition, TX101 can also perform foreign object detection by determining the ratio of voltage value A1 to voltage value A2. For example, if the ratio of voltage A1 at time T1 to voltage A2 at time T2 is a certain value greater than the reference value (the ratio of voltages at the two times) obtained when no foreign object is present, TX101 will determine that a foreign object is present.

[0097] Furthermore, as mentioned above, when foreign object detection is performed without calculating the Q value, the difference and percentage of voltage to be calculated may vary depending on the magnitude of the voltage applied to the transmission coil 205 and the timing of the voltage measurement. Therefore, by matching the magnitude of the voltage and the timing of the voltage measurement with the conditions under which the reference value was obtained, it becomes possible to detect foreign objects more reliably.

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

[0099] Furthermore, in the above-described embodiment, TX101 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 connection with the power transmission coil 205 when measuring the Q value, but it is not limited to this. For example, the power transmission unit 203 may stop the application of voltage by setting the transmission voltage to 0 when measuring the Q value. Alternatively, the transmission voltage may not be set to 0 when measuring the Q value, but switched to a lower voltage value. However, since the Q value measurement method in this embodiment calculates the Q value based on the degree of voltage decay, the Q value can be measured without completely stopping the application of voltage by lowering the voltage value to at least a voltage value where the voltage decay can be observed. In this case, if the period of voltage reduction exceeds a certain time, RX102 may determine that an error has occurred in TX101. Therefore, it is desirable to set the voltage reduction amount such that the voltage decay can be measured during a period in which RX102 does not determine that TX101 is abnormal.

[0100] Furthermore, in the embodiments described above, TX101 detects foreign objects by stopping the voltage and measuring the Q value. However, in all embodiments, it is possible that RX102 may determine that an error has occurred in TX101 due to the voltage being stopped. Therefore, a method to solve the above problem will be described, in which RX102 acquires information about TX101 when RX102 is placed within the power transmission range of TX101.

[0101] RX102, for example during the Negotiation phase of communication, sends a signal to TX101 instructing it to transmit information about TX101. This information includes the version information of TX101, information about the standards that TX101 conforms to, and information about the foreign object detection method used by TX101. TX101 transmits this information to RX102, and based on the acquired information, RX102 recognizes that TX101 will stop the voltage for a predetermined period to measure the Q value. This prevents RX102 from mistakenly determining that an error has occurred in TX101 when TX101 stops applying voltage for Q value measurement, allowing the charging process to continue stably. Furthermore, if information is transmitted to allow TX101 to specify the timing of Q value measurement, as in the second embodiment, RX102 can appropriately restrict communication by sharing the information format.

[0102] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of Symbols]

[0103] 102 Power transmission equipment 201 Control Unit 203 Power Transmission Section 204 Detection Unit 205 Power transmission coil 206 Communications Department

Claims

1. A receiving means for receiving identification information of a power receiving device, Negotiation methods for negotiating with the power receiving equipment in the Negotiation phase, After the Negotiation phase, the Power Transfer phase includes a power transmission means that wirelessly transmits power to the power receiving device, In the Power Transfer phase, when predetermined information is received from the power receiving device, a limiting means is provided to limit the power transmission. The system includes a detection means for detecting objects during the period when power transmission is restricted, The power transmission means restarts power transmission in the Power Transfer phase after the end of the period during which power transmission is restricted, without going through the Negotiation phase again, and the receiving means receives information on the received power in the Power Transfer phase.

2. The power transmission device according to 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 according to claim 2, wherein the detection means detects the object according to the timing based on the time information.

4. The power transmission device according to any one of claims 1 to 3, wherein the detection means detects the object based on a Quality factor.

5. A method used by power transmission equipment, Receive identification information of the power receiving device, Negotiations were conducted with the power receiving equipment during the negotiation phase. After the Negotiation phase, the Power Transfer phase wirelessly transmits power to the power receiving device. When predetermined information is received from the power receiving device during the Power Transfer phase, the power transmission is restricted. During the period when power transmission was restricted, object detection was performed. A method for restarting power transmission in the Power Transfer phase and receiving information on received power in the Power Transfer phase, without going through the Negotiation phase again, after the end of the period during which power transmission was restricted.

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