Power receiving device, control method, and computer-readable storage medium

Abstract

The power receiving device wirelessly receives power from the power transmitting device, measures a value corresponding to the received power during a first time period in which the power transmission by the power transmitting device is restricted, measures a value corresponding to the received power for detecting an object different from the power transmitting device and the power receiving device during a second time period based on the relationship between the value corresponding to the transmitted power in the power transmitting device and the value corresponding to the received power in the power receiving device, and controls the timing of the second time period so that the first time period and the second time period do not overlap.

Description

Technical Field

[0001] The present invention relates to object detection technology in wireless power transmission. Background Art

[0002] Technological development of wireless power transmission systems has been widely carried out, and as a wireless charging standard, the standard (WPC standard) established by the standardization organization Wireless Power Consortium (WPC) is well-known. In such wireless power transmission, if there is a foreign object within the range where the power transmission device can transmit power, it is important to detect the foreign object and control power transmission / reception. A foreign object is an object different from the power reception device. Patent Document 1 describes the following method: if there is a foreign object near a power transmission / reception device conforming to the WPC standard, the foreign object is detected and power transmission / reception is restricted. Patent Document 2 describes a technique for detecting a foreign object by short-circuiting a coil in a wireless power transmission system. Patent Document 3 describes a technique for detecting a foreign object based on a change in the Q factor (Quality factor) of a power transmission coil in a wireless power transmission system, and this change in the Q factor is measured by applying a high-frequency signal to the coil and continuing for a predetermined period of time.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-070074

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-034972

[0007] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2013-132133 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The present invention provides a technique for accurately performing detection of an object different from a power reception device.

[0010] Solutions to the Problems

[0011] According to one aspect of the present invention, there is provided a power receiving device including: a power receiving component for wirelessly receiving power from a power transmitting device; a first measuring component for measuring a value corresponding to the received power during a first time period in which the power transmitting device restricts power transmission; a second measuring component for measuring a value corresponding to the received power for detecting an object different from the power transmitting device and the power receiving device during a second time period based on the relationship between the value corresponding to the transmitted power in the power transmitting device and the value corresponding to the received power in the power receiving device; and a control component for controlling the timing of the second time period such that the first time period and the second time period do not overlap.

[0012] Effects of the Invention

[0013] According to the present invention, the detection of an object different from the power receiving device can be accurately performed.

[0014] Other features and advantages of the present invention will be apparent from the following description in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals denote the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings included in and constituting a part of the specification illustrate embodiments of the present invention and, together with the specification, are used to explain the principles of the present invention.

[0016] Figure 1 is a diagram showing an example of the structure of a wireless power transmission system;

[0017] Figure 2 is a block diagram showing an example of the structure of a power receiving device;

[0018] Figure 3 is a block diagram showing an example of the structure of a power transmitting device;

[0019] Figure 4 is a block diagram showing an example of the functional structure of the control unit of a power receiving device;

[0020] Figure 5A is a sequence diagram showing an example of the process of processing performed by a conventional power transmitting device and a conventional power receiving device;

[0021] Figure 5B is a sequence diagram showing an example of the process of processing performed by the power transmitting device and the power receiving device according to the present embodiment;

[0022] Figure 5C is a sequence diagram showing an example of the process of processing performed by the power transmitting device and the power receiving device according to the present embodiment;

[0023] Figure 6AIt is a diagram for explaining the relationship between the measurement time period for second foreign object detection, the measurement result notification time period, and the power transmission power limit time period for third foreign object detection;

[0024] Figure 6B It is a diagram for explaining the relationship between the measurement time period for second foreign object detection, the measurement result notification time period, and the power transmission power limit time period for third foreign object detection;

[0025] Figure 6C It is a diagram for explaining the relationship between the measurement time period for second foreign object detection, the measurement result notification time period, and the power transmission power limit time period for third foreign object detection;

[0026] Figure 7 It is a flowchart showing an example of the process of processing performed by the power receiving device;

[0027] Figure 8A It is a diagram for explaining the time relationship between the report of received power and the request for third foreign object detection;

[0028] Figure 8B It is a diagram for explaining the time relationship between the report of received power and the request for third foreign object detection;

[0029] Figure 9A It is a flowchart showing an example of the process of processing performed by the power receiving device;

[0030] Figure 9B It is a flowchart showing an example of the process of processing performed by the power receiving device;

[0031] Figure 10 It is a flowchart showing an example of the process of processing performed by the power transmission device;

[0032] Figure 11A It is a conceptual diagram for explaining the Q-factor measurement method in the time domain;

[0033] Figure 11B It is a conceptual diagram for explaining the Q-factor measurement method in the time domain; and

[0034] Figure 12 It is a conceptual diagram of foreign object detection by the power loss method. Detailed Description of the Invention

[0035] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. In the embodiments, multiple features are described, but the invention is not limited to requiring all of these features, and multiple of these features can be appropriately combined. Further, in the drawings, the same reference numerals are assigned to the same or similar structures, and redundant descriptions thereof are omitted.

[0036] (System Structure)

[0037] Figure 1 An example of the structure of a wireless power transmission system according to the present embodiment is shown. In the example, the wireless power transmission system is configured to include a power transmission device 100 and a power reception device 102. It is assumed that the power transmission device 100 and the power reception device 102 comply with the WPC (Wireless Power Consortium) standard. The power transmission device 100 is an electronic device that wirelessly transmits power to the power reception device 102 placed on its own device, for example. The power transmission device 100 wirelessly transmits power to the power reception device 102 via a power transmission coil 101. The power reception device 102 is an electronic device that receives power from the power transmission device 100 and charges an internal battery, for example. The power reception device 102 may be configured to be built into other devices (camera, smartphone, tablet PC, laptop computer, automobile, robot, medical device, or printer) and supply power to these devices. The power transmission device 100 may be a smartphone or the like. In this case, for example, the power reception device 102 may be another smartphone or wireless earphones. The power reception device 102 may be a transport vehicle or a vehicle such as an automobile, and the power transmission device 100 may be a charger installed in the console of the transport vehicle or a vehicle such as an automobile. Note that the arrow 104 indicates that the power reception device 102 moves on the power transmission device 100, and indicates that the positional relationship between the power transmission coil 101 and the power reception coil of the power reception device 102 changes before and after this movement.

[0038] Figure 1 A case where a conductive foreign object 103 exists in a range (power transmission range, operating volume) affected by the wireless power output from the power transmission coil 101 is shown. If the foreign object 103 exists in the operating volume, the power transmission / reception efficiency decreases, and problems such as heat generation may occur in some cases. Therefore, it is important for the power transmission device 100 and the power reception device 102 to detect the foreign object 103 and perform power transmission / reception control. In the present embodiment, the power transmission device 100 and the power reception device 102 measure the Q factor (quality factor) based on the time change of the voltage in the power transmission coil within the range of control compliant with the WPC standard, detect the foreign object 103, and control the power transmission / reception. Examples of the structure of the device and the process of the process for performing this process will be described in detail below. Note that the foreign object 103 is an object different from the power reception device. The foreign object 103 is, for example, a conductive object such as a metal sheet or an IC card.

[0039] (Structure of the Device)

[0040] Figure 2An example of the structure of the power receiving device 102 is shown. The power receiving device 102 is configured to include, for example, a control unit 200, a power receiving coil 201, a rectifying unit 202, a voltage control unit 203, a communication unit 204, a charging unit 205, a battery 206, a resonance capacitor 207, a switch 208, and a UI unit 209. The control unit 200 controls the entire power receiving device 102. The control unit 200 is configured to include, for example, one or more processors such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). Note that the control unit 200 may include, for example, one or more storage devices such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The control unit 200 may be configured to execute, for example, a program stored in the storage device by the processor, thereby performing various processes to be described later. The power receiving coil 201 is a coil for receiving power from the power transmitting coil 101 of the power transmitting device 100. The rectifying unit 202 converts the received AC voltage and AC current via the power receiving coil 201 into a DC voltage and a DC current. The voltage control unit 203 converts the level of the DC voltage input from the rectifying unit 202 into a level of a DC voltage (neither too high nor too low) suitable for the operations of the control unit 200 and the charging unit 205, etc. The voltage control unit 203 also supplies the voltage of the converted level to the charging unit 205. The charging unit 205 charges the battery 206 using the voltage supplied from the voltage control unit 203. The communication unit 204 performs control communication for wireless charging based on the WPC standard with respect to the power transmitting device 100. This control communication is performed by load modulation of the AC voltage and AC current received by the power receiving coil 201.

[0041] In addition, the power receiving coil 201 is connected to the resonance capacitor 207 and is configured to resonate at a specific frequency F2. The switch 208 is a switch configured to short-circuit the power receiving coil 201 and the resonance capacitor 207, and is controlled by the control unit 200. If the switch 208 is turned on, the power receiving coil 201 and the resonance capacitor 207 form a series resonance circuit. At this time, current only flows through the closed circuit of the power receiving coil 201, the resonance capacitor 207, and the switch 208, and no current flows through the rectifying unit 202 and the voltage control unit 203. On the other hand, if the switch 208 is turned off, current flows through the rectifying unit 202 and the voltage control unit 203 via the power receiving coil 201 and the resonance capacitor 207.

[0042] The UI unit 209 is a user interface (UI) that outputs various types of information to the user. The UI unit 209 outputs information through operations such as, for example, screen display, blinking or color change of an LED, voice output from a speaker, and vibration of the main body of the power receiving device 102. The UI unit 209 is configured to include, for example, a liquid crystal panel, a speaker, and a vibration motor. Note that the UI unit 209 may have a function of accepting information input by the user and may be configured to include, for example, buttons and a touch panel.

[0043] The output capacitor 210 is connected between the voltage control unit 203 and the charging unit 205 and stabilizes the output voltage, for example, when the load in the charging unit 205 increases sharply in a short period of time. Even when the power that can be supplied by the voltage control unit 203 decreases sharply in a short period of time, the output capacitor 210 enables a stable voltage to be supplied to the charging unit 205 and continues for a predetermined period. Note that the power transmission device 100 sometimes stops power transmission for a short period of time (for example, from time T0 to time T5 in the third foreign object detection process to be described in association with Figure 11A and Figure 11B ). In this case, it is assumed that one of the input power, input voltage, and input current of the rectification unit 202 stops or decreases sharply for a short period of time. The output capacitor 210 is configured to supply a voltage, current, and power sufficient to operate the power receiving device 102 and the charging unit 205 serving as a load even in such a case.

[0044] Figure 3 An example of the structure of the power transmission device 100 is shown. The power transmission device 100 is configured to include, for example, a control unit 300, a power supply unit 301, a power transmission unit 302, a power transmission coil 303, a communication unit 304, a memory 305, a resonance capacitor 306, and a switch 307. The control unit 300 controls the entire power transmission device 100. The control unit 300 is configured to include, for example, one or more processors such as a CPU and an MPU. Note that the control unit 300 may be configured to execute programs stored in the memory 305 to be described later or a storage device built into the control unit 300 by the processor, thereby executing the various processes to be described later. The power supply unit 301 supplies power to each functional block. The power supply unit 301 is, for example, a commercial power supply or a battery. The battery can store power supplied from, for example, a commercial power supply.

[0045] The power transmission unit 302 converts the DC or AC power input from the power supply unit 301 into AC power in the frequency band used for wireless power transmission, and inputs this AC power to the power transmission coil 303, thereby enabling the power transmission coil 303 to generate electromagnetic waves to be received by the power receiving device 102. For example, the power transmission unit 302 uses a switching circuit having a half-bridge or full-bridge configuration using FETs (field effect transistors) to convert the DC voltage supplied from the power supply unit 301 into an AC voltage. In this case, the power transmission unit 302 includes a gate driver that controls the ON / OFF of the FETs. In addition, the power transmission unit 302 adjusts at least one of the voltage (transmission voltage) and current (transmission current) input to the power transmission coil 303, or the frequency, thereby controlling the intensity or frequency of the electromagnetic waves to be output. For example, the power transmission unit 302 increases the intensity of the electromagnetic waves by increasing the transmission voltage or transmission current, and decreases the intensity of the electromagnetic waves by decreasing the transmission voltage or transmission current. Here, it is assumed that the power transmission unit 302 has the ability to supply power to output at least 15 watts (W) of power to the charging unit 205 of the power receiving device 102 corresponding to the WPC standard. In addition, the power transmission unit 302 controls the output of the AC power based on an instruction from the control unit 300, so as to start or stop the output of the electromagnetic waves from the power transmission coil 303.

[0046] The communication unit 304 communicates with the power receiving device 102 for power transmission control based on the WPC standard via the power transmission coil 303. The communication unit 304 uses frequency modulation (FSK (Frequency Shift Keying)) to modulate the AC voltage and AC current output from the power transmission unit 302 and transmits this information to the power receiving device 102. In addition, the communication unit 304 demodulates the AC voltage and AC current modulated by the load modulation of the communication unit 204 of the power receiving device 102, thereby obtaining the information transmitted from the power receiving device 102. That is, the communication unit 304 superimposes the information to be transmitted to the power receiving device 102 on the electromagnetic wave transmitted from the power transmission unit 302 and detects the power receiving signal superimposed on the electromagnetic wave by the power receiving device 102, thereby communicating with the power receiving device 102. In addition, the communication unit 304 can communicate with the power receiving device 102 according to a standard different from the WPC standard using a coil (or antenna) different from the power transmission coil 303. In addition, the communication unit 304 can communicate with the power receiving device 102 by selectively using multiple communication functions. The memory 305 stores, for example, the control program to be executed by the control unit 300 and information such as the states of the power transmission device 100 and the power receiving device 102. For example, the state of the power transmission device 100 is obtained by the control unit 300. The state of the power receiving device 102 is obtained by the control unit 200 of the power receiving device 102 and transmitted from the communication unit 204. The power transmission device 100 obtains the information indicating this state via the communication unit 304.

[0047] The power transmission coil 303 is connected to the resonance capacitor 306 and is configured to resonate at a specific frequency F1. The switch 307 is a switch configured to short-circuit the power transmission coil 303 and the resonance capacitor 306 and is controlled by the control unit 300. If the switch 307 is turned on, the power transmission coil 303 and the resonance capacitor 306 form a series resonance circuit. At this time, current only flows through the closed circuit of the power transmission coil 303, the resonance capacitor 306, and the switch 307. If the switch 307 is turned off, power is supplied from the power transmission unit 302 to the power transmission coil 303 and the resonance capacitor 306.

[0048] Figure 4An example of the functional configuration of the control unit 200 of the power receiving device 102 is shown. The control unit 200 includes, for example, a second Q-factor measurement unit 401, a calibration processing unit 402, a second foreign object detection processing unit 403, and a third foreign object detection processing unit 404. As will be described later, the second Q-factor measurement unit 401 measures the Q factor in the time domain (second Q-factor measurement). As will be described later, the calibration processing unit 402 notifies the power transmission device 100 of the acquisition of calibration data points and the received power required for the calibration curve creation process. The second foreign object detection processing unit 403 performs foreign object detection processing (second foreign object detection processing) based on the power loss method to be described later. The third foreign object detection processing unit 404 performs foreign object detection processing (third foreign object detection processing) based on the Q factor measured by the second Q-factor measurement unit 401. Figure 4 The processing units shown are configured as, for example, multiple independent programs and can operate concurrently while establishing synchronization between the multiple programs through event processing or the like.

[0049] (Foreign object detection method in the WPC standard)

[0050] Next, a foreign object detection method defined by the WPC (Wireless Power Consortium) standard will be described using the power transmission device 100 and the power receiving device 102 as examples. Here, a foreign object detection method based on the Q factor measured in the frequency domain (first foreign object detection method) and a foreign object detection method based on the power loss method (second foreign object detection method) will be described.

[0051] (1) Foreign object detection method based on the Q factor measured in the frequency domain (first foreign object detection method)

[0052] In the first foreign object detection method, first, the power transmission device 100 measures the Q factor changed due to the influence of a foreign object in the frequency domain (first Q-factor measurement). This measurement is performed after the power transmission device 100 sends an Analog Ping until it sends a Digital Ping (see Figure 5A F501). For example, to measure the Q factor, the power transmission unit 302 scans the frequency of the wireless power output from the power transmission coil 303, and the power transmission device 100 measures the voltage value at the terminal portion of the resonant capacitor 306 connected in series (or in parallel) with the power transmission coil. The power transmission device 100 searches for the resonant frequency at which the voltage value exhibits a peak, and calculates the Q factor of the power transmission coil 303 based on this resonant frequency and the frequency representing the voltage value 3 dB lower than the peak voltage value measured at the resonant frequency.

[0053] The Q factor can be measured by another method. For example, the power transmission unit 302 scans the frequency of the wireless power output from the power transmission coil 303, and the power transmission device 100 measures the voltage value at the terminal portion of the resonance capacitor 306 connected in series with the power transmission coil 303, and searches for the resonance frequency at which the voltage value exhibits a peak. Then, the power transmission device 100 measures the voltage values at the two terminals of the resonance capacitor 306 at this resonance frequency, and calculates the Q factor of the power transmission coil 303 based on the ratio of the voltage values at these two terminals.

[0054] After calculating the Q factor of the power transmission coil 303, the control unit 300 of the power transmission device 100 obtains, via the communication unit 304, the Q factor used as a criterion for foreign object detection from the power receiving device 102. For example, the control unit 300 receives, from the power receiving device 102, the Q factor (the first characteristic value) of the power transmission coil when the power receiving device is placed on the power transmission coil defined by the WPC standard. The Q factor is stored in the FOD (Foreign Object Detection) status packet sent from the power receiving device 102, and the power transmission device 100 receives this FOD status packet, thereby obtaining the Q factor. The control unit 300 estimates the Q factor of the power transmission coil 303 when the power receiving device 102 is placed on the power transmission device 100 based on the obtained Q factor. In this embodiment, the estimated Q factor will be referred to as the first reference Q factor. Note that the Q factor stored in the FOD status packet may be pre-stored in a non-volatile memory (not shown) of the power receiving device 102. That is, the power receiving device 102 can notify the power transmission device 100 of the pre-stored Q factor. Note that the Q factor corresponds to Q1 to be described later.

[0055] The control unit 300 of the power transmission device 100 compares the first reference Q factor with the Q factor measured by the power transmission device 100, and determines the presence / absence of a foreign object based on the comparison result. For example, using a Q factor that is a% (the first ratio) lower than the first reference Q factor as a threshold, if the measured Q factor is lower than the threshold, the control unit 300 determines that there is a high possibility of the presence of a foreign object, otherwise, it determines that there is a high possibility of the absence of a foreign object.

[0056] (2) Foreign object detection method based on the power loss method (second foreign object detection method)

[0057] Next, reference will be made to Figure 12 describe the foreign object detection method based on the power loss method defined by the WPC standard. Figure 12 is a conceptual diagram of foreign object detection by the power loss method. The horizontal axis represents the power transmitted by the power transmission device 100, and the vertical axis represents the power received by the power receiving device 102.

[0058] First, the power transmission unit 302 of the power transmission device 100 sends a digital Ping to the power reception device 102. The calibration processing unit 402 of the power transmission device 100 notifies the power transmission device 100 of the received power value Pr1 (referred to as Light Load) in the power reception device 102 when the digital Ping is received. The received power value includes at least the power to be input to the charging unit 205. Note that this notification is made using a received power packet (mode1). The received power packet (mode1) will be referred to as "RP1" hereinafter. At this time, the power reception device 102 does not supply the received power to the load (charging unit 205 and battery 206). The control unit 300 of the power transmission device 100 stores the relationship between the received power Pr1 represented by the received RP1 and the transmitted power value Pt1 when Pr1 is obtained ( Figure 12 the point 1200 shown) in the memory 305. Therefore, the power transmission device 100 can recognize that the power loss amount between the power transmission device 100 and the power reception device 102 when Pt1 is transmitted as the transmitted power is Pt1 - Pr1 (Ploss1).

[0059] Next, the calibration processing unit 402 of the power reception device 102 notifies the power transmission device 100 of the value of the received power value Pr2 (referred to as Connected Load) in the power reception device 102. This notification is made using a received power packet (mode2). Note that the received power packet (mode2) will be referred to as "RP2" hereinafter. At this time, the power reception device 102 supplies the received power to the load. The control unit 300 of the power transmission device 100 stores the relationship between the received power Pr2 represented by the received RP2 and the transmitted power value Pt2 when Pr2 is obtained ( Figure 12 the point 1201 shown) in the memory 305. Therefore, the power transmission device 100 can recognize that the power loss amount between the power transmission device 100 and the power reception device 102 when Pt2 is transmitted as the transmitted power is Pt2 - Pr2 (Ploss2). Note that the transmitted power value is a value that includes at least the power output from the power transmission unit 302 to the power transmission coil 303.

[0060] The control unit 300 of the power transmission device 100 performs linear interpolation on points 1200 and 1201, thereby generating line 1202. Line 1202 corresponds to the relationship between the transmitted power and the received power in a state where there are no foreign objects around the power transmission device 100 and the power reception device 102. Therefore, the power transmission device 100 can predict the received power in a state where the possibility of no foreign objects is high based on the transmitted power value and line 1202. For example, for the case where the transmitted power value is Pt3, the power transmission device 100 can predict the received power value Pr3 from point 1203 on line 1202 corresponding to the case where the transmitted power value is Pt3.

[0061] Here, it is assumed that if the power transmission unit 302 of the power transmission device 100 transmits power to the power reception device 102 with the transmitted power Pt3, the communication unit 304 receives the received power value Pr3' from the power reception device 102. The control unit 300 of the power transmission device 100 calculates Pr3 - Pr3' (= Ploss_FO), which is a value obtained by subtracting the actually received received power value Pr3' from the received power value Pr3 in a state where no foreign object exists. Ploss_FO can be regarded as the power loss consumed by the foreign object when a foreign object exists between the power transmission device 100 and the power reception device 102. Therefore, if the power Ploss_FO consumed by the foreign object exceeds a predetermined threshold, the control unit 300 of the power transmission device 100 can determine that a foreign object exists. This threshold is derived based on the relationship between, for example, point 1200 and point 1201. Note that even if the foreign object does not exist between the TX and the RX but exists within the power transmission range, the foreign object receives power and generates heat.

[0062] In addition, the control unit 300 of the power transmission device 100 previously obtains the power loss amount Pt3 - Pr3 (Ploss3) between the power transmission device 100 and the power reception device 102 from the received power value Pr3 in a state where no foreign object exists. The control unit 300 of the power transmission device 100 calculates the power loss amount Pt3 - Pr3' (Ploss3') between the power transmission device 100 and the power reception device 102 in a state where a foreign object exists based on the received power value Pr3' received from the power reception device 102 in a state where it is not clear whether a foreign object exists. Then, the control unit 300 of the power transmission device 100 calculates Ploss3' - Ploss3. If this value exceeds a predetermined threshold, it can be determined that a foreign object exists. Note that Ploss3' - Ploss3 = Pt3 - Pr3' - Pt3 + Pr3 = Pr3 - Pr3'. Therefore, it is possible to estimate the power Ploss_FO that will be consumed by the foreign object by comparing the power loss amounts.

[0063] As described above, the power Ploss_FO consumed by the foreign object can be calculated as the difference Pr3 - Pr3' of the received power, or can be calculated as Ploss3' - Ploss3 (= Ploss_FO) which is the difference of the power losses.

[0064] After obtaining the line 1202, the control unit 300 of the power transmission device 100 periodically receives the current received power value (e.g., the above-mentioned Pr3') from the power reception device 102 via the communication unit 304. The current received power value periodically transmitted from the calibration processing unit 402 of the power reception device 102 is transmitted to the power transmission device 100 as a received power packet (mode0). The control unit 300 of the power transmission device 100 performs foreign object detection based on the received power value stored in the line 1202 and the received power packet (mode0). Note that the received power packet (mode0) will be referred to as (RP0) hereinafter.

[0065] Note that in the present embodiment, the points 1200 and 1201 of the line 1202 for obtaining the relationship between the transmitted power and the received power in a state where there are no foreign objects around the power transmission device 100 and the power reception device 102 will be referred to as "calibration data points". In addition, the line segment (line 1202) obtained by interpolating at least two calibration data points will be referred to as a "calibration curve". The calibration data points and the calibration curve (second reference) are used for the foreign object detection process of the control unit 300 of the power transmission device 100.

[0066] (Q-factor measurement method in the time domain)

[0067] Reference will be made to Figure 11A and Figure 11B to describe the Q-factor measurement method in the time domain. Figure 11A and Figure 11B are conceptual diagrams for explaining the method of measuring the Q-factor in the time domain (second Q-factor measurement). In the present embodiment, the foreign object detection method based on the second Q-factor will be referred to as the third foreign object detection method. In the power reception device 102, the second Q-factor measurement is performed by the second Q-factor measurement unit 401. In the second Q-factor measurement, the power transmission device 100 and the power reception device 102 turn on the switch in the same time period to instantaneously cut off the power transmission, so no received power is supplied to the load. Accordingly, for example, the voltage applied to the coil gradually decreases. The second Q-factor is calculated based on how the voltage decreases.

[0068] Figure 11A The waveform 1100 shown represents the elapsed time of the voltage value of the power transmission coil or the power reception coil. Note that the voltage value of the power transmission coil or the power reception coil can be the value of the high-frequency voltage applied to the terminal portion of the power transmission coil 303 of the power transmission device 100 or the power reception coil 201 of the power reception device 102. Alternatively, the voltage value of the power transmission coil or the power reception coil here can be the value of the high-frequency voltage applied to the terminal portion of the resonant capacitor 306 of the power transmission device 100 or the resonant capacitor 207 of the power reception device 102. Note that in Figure 11A and Figure 11BIn this figure, the horizontal axis represents time, and the vertical axis represents voltage values. At time T0, the power transmission device 100 stops applying a high-frequency voltage (power transmission) to the power transmission coil 303 or the resonance capacitor 306. Accordingly, the voltage value in the power transmission coil 303 or the resonance capacitor 306 of the power transmission device 100 gradually decreases, and the voltage value in the power reception coil 201 or the resonance capacitor 207 of the power reception device 102 gradually decreases. Point 1101 is a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T1. In Figure 11A this figure, (T1, A1) indicates that the voltage value at time T1 is A1. Similarly, point 1102 is a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T2. In Figure 11A this figure, (T2, A2) indicates that the voltage value at time T2 is A2.

[0069] The Q factor measurement is performed based on the time variation of the voltage value starting from time T0. For example, based on the time and voltage values of points 1101 and 1102, which are the envelopes of the voltage values, and the frequency f of the high-frequency voltage (f will be hereinafter referred to as the operating frequency), the Q factor is calculated as follows:

[0070]

[0071] That is to say, the Q factor here is an electrical characteristic determined by the relationship between the elapsed time of the power transmission coil 303 after power transmission is restricted (stopped) and the voltage drop amount during this time.

[0072] Next, reference will be made to Figure 11BTo describe the process of the power receiving device 102 in this embodiment for measuring the Q factor in the time domain. The waveform 1103 represents the value of the high-frequency voltage applied to the power receiving coil 201, and its frequency falls within the range of 110 kHz to 148.5 kHz used in the Qi standard. In addition, the points 1104 and 1105 are each part of the envelope of the voltage value. As described above, the power transmitting device 100 stops power transmission in the period from time T0 to T5. The control unit 300 of the power transmitting device 100 turns on the switch 307, thereby forming a resonant circuit including the power transmitting coil 303 and the resonant capacitor 306. In addition, when the power transmission stop of the power transmitting device 100 is detected by observing the voltage value of the power receiving coil 201, the control unit 200 of the power receiving device 102 turns on the switch 208, thereby forming a resonant circuit including the power receiving coil 201 and the resonant capacitor 207. The second Q factor measurement unit 401 of the power receiving device 102 measures the Q factor based on the voltage value A3 (point 1104) at time T3, the voltage value A4 (point 1105) at time T4, and the operating frequency of the high-frequency voltage (Equation (1)). Note that the power transmitting device 100 resumes power transmission at time T5. When the resumption of power transmission at time T5 is detected by observing the voltage value of the power receiving coil 201, the control unit 200 of the power receiving device 102 turns off the switch 208, thereby opening the resonant circuit including the power receiving coil 201 and the resonant capacitor 207. As described above, in the second Q factor measurement, during the momentary disconnection of the power transmission by the power transmitting device 100, the second Q factor measurement unit 401 of the power receiving device 102 measures the Q factor based on the elapsed time, the voltage value, and the operating frequency.

[0073] In foreign object detection (the first foreign object detection method) based on the Q factor (the first Q factor) measured in the frequency domain, the frequency is scanned to search for the resonant frequency each time the measurement is performed. If such a scan is performed while the power transmitting device 100 is transmitting relatively large power for digital Ping or the power transmission stage, the switching noise in the power transmission unit 302 may increase. On the other hand, foreign object detection (the third foreign object detection method) based on the Q factor (the second Q factor) measured in the time domain can be performed using a single frequency and does not require frequency scanning. For this reason, this method can be performed at the operating frequency during power transmission in the digital Ping or power transmission stage, and has little impact on the switching noise. Therefore, compared with the first foreign object detection method, the third foreign object detection method can be performed at the operating frequency during power transmission in the digital Ping or power transmission stage, and can reduce the switching noise even during power transmission of large power.

[0074] (Operations of Conventional Power Transmitting and Receiving Devices)

[0075] For reference Figure 5ATo describe the operations of the conventional power transmission device 100 and the conventional power reception device 102. In Figure 5A the description, it is assumed that the power transmission device 100 and the power reception device 102 are power transmission and reception devices compliant with the WPC standard v1.2.3.

[0076] The power transmission device 100 transmits an analog Ping to detect an object (F500) present near the power transmission coil 303. The analog Ping is pulsed power and is power used to detect an object. Even if the power reception device 102 receives the analog Ping, the power is too small to activate the control unit 200. Through the analog Ping, the power transmission device 100 detects an object based on the shift in the resonance frequency of the voltage value in the power transmission coil 303 caused by an object present near the power transmission coil 303, or the change in the voltage value / current value flowing through the power transmission coil 303. When an object is detected through the analog Ping, the power transmission device 100 measures the Q factor of the power transmission coil 303 (F501) through the above-described first Q factor measurement. If the first Q factor measurement is completed, the power transmission device 100 starts transmitting a digital Ping (F502). The digital Ping is power used to activate the control unit 200 of the power reception device 102 and is power greater than the analog Ping. The digital Ping is continuously transmitted from this point on. That is, the power transmission device 100 continuously transmits power equal to or greater than the digital Ping from the start of the transmission of the digital Ping (F502) until it receives EPT (End Power Transfer) data (F524) from the power reception device 102.

[0077] When the power reception device 102 is activated by receiving the digital Ping, it stores the voltage value of the received digital Ping in the Signal Strength data and sends the signal strength data to the power transmission device 100 (F503). Next, the power reception device 102 sends ID data (F504) to the power transmission device 100. The ID data stores an ID including version information of the WPC standard that the power reception device 102 complies with and device identification information. In addition, the power reception device 102 sends Configuration data (F505) to the power transmission device 100. The configuration data includes information such as the maximum value of the power to be supplied from the voltage control unit 203 to the load (charging unit 205). The power transmission device 100 receives the ID data and the configuration data. When it is determined based on these data that the power reception device 102 supports the extended protocol (including Negotiation to be described later) of the WPC standard v1.2, the power transmission device 100 responds with an ACK (positive response) (F506).

[0078] The power receiving device 102 receives the ACK and transitions to the negotiation phase to negotiate the power to be transmitted / received. First, the power receiving device 102 transmits FOD status data (F507) to the power transmitting device 100. In this embodiment, the FOD status data will be referred to as "FOD(Q1)". The power transmitting device 100 performs foreign object detection by the first foreign object detection method based on the Q factor (Q factor measured in the frequency domain) stored in the received FOD(Q1) and the Q factor measured by the first Q factor measurement. When it is determined that the possibility of the presence of a foreign object is low, the power transmitting device 100 transmits an ACK indicating the determination result to the power receiving device 102 (F508).

[0079] Upon receiving the ACK, the power receiving device 102 transmits a general request (Capability) which is data for inquiring about capabilities and is one of the general requests defined by the WPC standard to the power transmitting device 100 (F509). This data is referred to as GRQ(CAP). Upon receiving the GRQ(CAP), the power transmitting device 100 transmits capability data (referred to as CAP) storing the capability information supported by its own device (F510).

[0080] Next, the power receiving device 102 negotiates the guaranteed power (GP) which is the maximum value of the power value requested to be received by the power receiving device 102. The guaranteed power is the maximum value of the load power (power to be consumed by the battery 206) of the power receiving device 102 agreed upon between the power transmitting device 100 and the power receiving device 102. This negotiation is achieved by transmitting data storing the value of the guaranteed power requested by the power receiving device 102 in the specific request data defined by the WPC standard to the power transmitting device 100 (F511). In this embodiment, this data will be referred to as "SRQ(GP)". The power transmitting device 100 responds to the SRQ(GP) considering its own power transmission capability and the like. When it is determined that the guaranteed power is acceptable, the power transmitting device 100 transmits an ACK indicating that the request is accepted (F512). In this embodiment, it is assumed that the power receiving device 102 requests 15W as the guaranteed power through the SRQ(GP). If the negotiation of multiple parameters including the guaranteed power is completed, the power receiving device 102 transmits "SRQ(EN)" which is the end of the request negotiation (end negotiation) in the specific request to the power transmitting device (F513). The power transmitting device 100 transmits an ACK for the SRQ(EN), ends the negotiation, and transitions to the power transmission phase for transmitting / receiving the power defined by the guaranteed power.

[0081] Next, the power transmission device 100 performs foreign object detection (second foreign object detection method) based on the above power loss method. First, the power transmission device 100 receives RP1 (F515) from the power reception device 102. The power transmission device 100 accepts the received power value stored in RP1 and the power transmission value of the power transmission device 100 when obtaining the received power value as calibration data points (corresponding to the point 1200 in Figure 12 ). The power transmission device 100 sends an ACK (F516) indicating acceptance of the calibration data points to the power reception device 102.

[0082] After receiving the ACK, the power reception device 102 sends a control error (Control Error) (hereinafter referred to as CE) that requests the power transmission device 100 to increase / decrease the received voltage (or received current or received power) to the power transmission device 100. CE stores a sign and a value. If the sign is positive, it means a request to increase the received voltage. If the sign is negative, it means a request to decrease the received voltage. If the value is zero, it means a request to maintain the received voltage. Here, the power reception device 102 sends CE(+) indicating an increase in the received voltage to the power transmission device 100 (F517).

[0083] When receiving CE(+), the power transmission device 100 changes the setting value of the power transmission unit 302 to increase the power transmission voltage (F518). When the received power increases in response to CE(+), the power reception device 102 supplies the received power to the load (charging unit 205 and battery 206) and sends RP2 to the power transmission device 100 (F519). The power transmission device 100 accepts the received power value stored in RP2 and the power transmission value of the power transmission device 100 at this time as calibration data points (corresponding to the point 1201 in Figure 12 ). The power transmission device 100 sends an ACK (F520) indicating acceptance of the calibration data points to the power reception device 102. Since the power transmission device 100 obtains two calibration data points (the points 1200 and 1201 in Figure 12 ) at this time point, a calibration curve (the line 1202 in Figure 12 ) can be derived.

[0084] The power transmission device 100 and the power reception device 102 have transitioned to the power transmission phase at this time point, and the power transmission device 100 is transmitting power that enables the power reception device 102 to receive the maximum power of 15W negotiated in the negotiation phase. The power reception device 102 periodically sends to the power transmission device 100 a CE for requesting the power transmission device 100 to maintain the transmitted power and an RP0 (F521 and F522) for storing the current received power value. When receiving the RP0 from the power reception device 102, the power transmission device 100 performs foreign object detection based on the above-described second foreign object detection method. When it is determined as highly likely that there is no foreign object as a result of the foreign object detection, the power transmission device 100 sends an ACK (F523) to the power reception device 102. Note that when it is determined as highly likely that there is a foreign object, the power transmission device 100 sends a NAK to the power reception device 102. After that, if the charging of the battery 206 is completed, the power reception device 102 sends EPT (End Power Transmission) data (F524) for requesting the stop of power transmission to the power transmission device 100.

[0085] In the above-described manner, wireless power transmission is performed between the power transmission device 100 and the power reception device 102 that conform to the WPC standard V1.2.3.

[0086] In the first foreign object detection method, foreign objects are detected in the above-described manner at the timing when the power transmission device 100 measures the first Q factor in F501. On the other hand, even if a foreign object 103 is placed in the operating volume after the measurement of the first Q factor until a calibration data point is obtained (for example, until an ACK is sent in F516), the foreign object 103 is not detected. This is because in the first foreign object detection method, the power transmission device 100 determines the presence / absence of a foreign object when measuring the first Q factor in F501 only when receiving FOD (Q1).

[0087] In addition, in the second foreign object detection method, foreign object detection cannot be performed during the period when a calibration curve (line 1202) is not generated. That is, foreign object detection cannot be performed at the stage when the power reception device 102 obtains RP1 and the first calibration data point (point 1200) in F515. After that, when the power transmission device 100 sends an ACK in F520, obtains the next calibration data point (point 1201), and generates a calibration curve (line 1202), the foreign object 103 can be detected. For example, if the foreign object 103 is placed in the operating volume immediately after the power reception device 102 sends CE(+) in F517, since the calibration curve has not been generated at this time point, the foreign object 103 is not detected. In addition, at this time point, of course, the first foreign object detection process is not performed.

[0088] In addition, for example, if a foreign object 103 is placed immediately after the CE(+) is transmitted in F517, the power transmission device 100 obtains calibration data points in a state where the foreign object 103 is present. In this case, the power transmission device 100 cannot perform an accurate second foreign object detection process thereafter. For example, if a foreign object 103 is present in the operating volume, the power transmitted by the power transmission device 100 is consumed by the foreign object 103. As a result, as Figure 12 shown, when the power transmission device 100 transmits power and the power receiving device 102 obtains the received power Pr2, the transmitted power of the power transmission device 100 is Pt2'(≠Pt2), which is a value obtained by adding the power consumed by the foreign object to the power (Pt2) provided to the power receiving device 102. Therefore, the power transmission device 100 obtains point 1204 as a calibration data point, and as a result, line 1205 is created as a calibration curve. The second foreign object detection method is a method of creating a calibration curve in a state where no foreign object is placed as described above, and detecting the presence of a foreign object by checking the deviation between the curve and the combination of the actually measured transmitted power and received power. On the other hand, since line 1205 is a calibration curve created under the influence of a foreign object, accurate foreign object detection cannot be performed. In addition, even when the foreign object 103 is placed in the operating volume after the power transmission device 100 measures the first Q factor in F501 until the power receiving device 102 transmits RP1 in F515, the accuracy of foreign object detection by the second foreign object detection method is also reduced. This is because the calibration data points obtained when the power receiving device 102 transmits ACK (F516) are created in a state where the foreign object 103 is present in the operating volume.

[0089] As described above, when a foreign object 103 is placed after the measurement of the first Q factor until the generation of the calibration curve, the foreign object 103 cannot be detected, and it may be difficult to use the second foreign object detection method thereafter.

[0090] In the present embodiment, in consideration of this situation, a third foreign object detection method is applied to the WPC standard. For example, the power transmission device 100 and the power receiving device 102 are highly likely to be confirmed as having no foreign object by the third foreign object detection method, and then calibration data points are created. Reference will be made to Figure 5B and Figure 5C to describe this process.

[0091] First, in F500 to F503, the power transmission device 100 and the power receiving device 102 perform the same processing as in Figure 5A . In F503, the power transmission device 100 receives the signal strength from the power receiving device 102, and stops power transmission for the third foreign object detection as described in reference Figure 11B . When the stop of power transmission is detected, the power receiving device 102 is as described in reference Figure 11BPerform the operation to execute the second Q-factor measurement (F551). The power receiving device 102 receives an ACK (F508) for FOD (Q1) in F507, and if it is highly likely that no foreign object is detected by the first foreign object detection, the power receiving device 102 transmits the Q-factor measured by the second Q-factor measurement in F551 to the power transmitting device 100. Note that, as will be described later, the power receiving device 102 may transmit GRQ (CAP) in F508 and determine whether the power transmitting device 100 supports the second Q-factor measurement (the third foreign object detection method) based on the CAP received in F509. As Figure 5B shown, if the power transmitting device 100 supports the second Q-factor measurement, the power receiving device 102 may notify the power transmitting device 100 of the Q-factor measured in F551. If the Q-factor is correctly received, the power transmitting device 100 transmits an ACK (F553) to the power receiving device 102. Since the power transmitting device 100 determines that no foreign object exists in the operating volume in the first Q-factor measurement when transmitting the ACK for FOD (Q1), the possibility of a foreign object existing is low even during the second Q-factor measurement performed by the power receiving device 102 immediately after the first Q-factor measurement. For this reason, the power transmitting device 100 may store the Q-factor received in F552 in the memory 305 as a reference value (the second reference Q-factor) for determining the presence / absence of a foreign object in the third foreign object detection process.

[0092] After that, before sending RP1 in F515, the power receiving device 102 requests the power transmitting device 100 to perform a third foreign object detection process (F554). When receiving an ACK indicating that the power transmitting device 100 has accepted this request (F555), the power receiving device 102 performs a second Q factor measurement (F556). The power receiving device 102 sends the Q factor measured by the second Q factor measurement to the power transmitting device 100 (F557). The power transmitting device 100 compares the Q factor received in F557 with a threshold value of a second reference Q factor received in F552 and stored in the memory 305, thereby determining whether the possibility of the presence of a foreign object is high. When it is determined as a result of the comparison that the possibility of the presence of a foreign object is not high, the power transmitting device 100 sends an ACK to the power receiving device 102 (F558). The power receiving device 102 recognizes through the received ACK that the possibility of the presence of a foreign object is not high, and sends RP1 to the power transmitting device 100 to create a calibration data point (F515). As described above, by applying the third foreign object detection method to the WPC standard, it is possible to confirm the presence / absence of a foreign object immediately before creating a calibration data point. The states of the power transmitting device 100 and the power receiving device 102 from when the power receiving device 102 receives an ACK for the third foreign object detection request (F554) (F555) until it sends the Q factor to the power transmitting device 100 (F557) and receives a response (F558) are referred to as the third foreign object detection processing state. Note that the power receiving device 102 may shift to the third foreign object detection processing state not when receiving an ACK in F555 but when detecting the stop of power transmission.

[0093] Here, if the power receiving device 102 performs the third foreign object detection method immediately before creating calibration data points (sending RP1 and RP2 to the power transmitting device 100), it may not be possible to correctly measure the received power values to be stored in RP1 and RP2. This will be described with reference to Figure 6A explanation.

[0094] F515 is the RP1 data sent by the power receiving device 102. Note that the RP1 data can be RP2 data. The time period 601 is called Twindow and is defined as the window size in the WPC standard v1.2.3. In the time period 601, the power receiving device 102 measures the value associated with the received power value and notifies the power transmitting device 100 of the measured value stored in the RP1 (or RP2) data. The time period 602 is an offset time period. The time period 602 is called Toffset and is defined as the window offset in the WPC standard v1.2.3. The time period 602 is the time period between the end of the time period 601 and the start of the RP1 (or RP2) data. The power receiving device 102 measures the value associated with the received power value in the time period 601, waits only for the time period 602, and sends the RP1 (RP2) data. The length of the time period 601 (window size) and the length of the time period 602 (window offset) are sent from the power receiving device 102 to the power transmitting device 100 as information elements of the configuration packet. Note that the power transmitting device 100 measures the transmitted power at the same time as the time period 601 and creates a calibration data point based on the measured value and the received power value included in the RP1 (or RP2) data.

[0095] Note that the waveform 600 schematically shows the output of the power transmission unit 302 of the power transmitting device 100. The waveform 600 indicates that the power transmitting device 100 stops power transmission from the power transmission unit 302 at time T0 and resumes power transmission at time T5. Note that Figures 6A to 6C the time T0 and time T5 in Figure 11B correspond to the time T0 and time T5 in

[0096] Here, as Figure 6A shown, the time period 601 may overlap with the power transmission stop time period (T0 to T5). If the power transmission stop time period is short, the voltage control unit 203 of the power receiving device 102 can supply sufficient power for the operation of the charging unit 205. Therefore, the received power value is the same as in the case where there is no power transmission stop time period (i.e., Figure 12 Pr2 in Figure 6A ). On the other hand, in the case as Figure 6A shown, since power transmission is not performed during the relatively long power transmission stop time period with respect to the transmitted power value, the received power value can be a value smaller than Pt2. That is, if the power transmission stop time period (T0 to T5) overlaps with the time period 601, the calibration data point is a point different from the point 1201. Therefore, the foreign object detection accuracy by the power loss method deteriorates.

[0097] On the other hand, as Figure 6BAs shown, the power receiving device 102 according to the present embodiment transmits the RP1 or RP2 data in F515 to the power transmitting device 100 after at least the time periods 601 and 602 have elapsed since the power transmission of the power transmitting device 100 resumed at time T5. For example, the power receiving device 102 may start measuring the power receiving period 601 of the received power at time T7 after the power transmission of the power transmitting device 100 resumes at time T5. If the period 601 for measuring the received power overlaps with the power transmission stop period (T0 to T5), the power receiving device 102 may delay the transmission of the RP1 or RP2 data in F515 to the power transmitting device 100. Accordingly, as Figure 6B shown, the power transmission stop period (T0 to T5) does not overlap with the period 601. Therefore, the power transmitting device 100 can accurately create calibration data points based on the received power value in F515.

[0098] In addition, the power transmitting device 100 may measure the transmitted power at each predetermined time so that the transmitted power can be measured at the same time as the period during which the power receiving device 102 measures the received power. This predetermined time is referred to as Tslice. If the time when the power transmitting device 100 measures the transmitted power overlaps with the power transmission stop period (T0 to T5), correct foreign object detection cannot be performed using the power loss method. On the other hand, as Figure 6B shown in the example, Tslice is set as the difference between time T6 and time T8. The power transmitting device 100 measures the transmitted power during the period 603 of Twindow starting from time T6. Similarly, the power transmitting device 100 also measures the transmitted power during the period 604 of Twindow starting from time T8, which is after time Tslice has elapsed since time T6. That is, the power transmitting device 100 measures the transmitted power during the period of Twindow while offsetting the starting point for each Tslice used for measurement. At the time point when the start of the RP1 or RP2 data in F515 is received, the power transmitting device 100 selects the transmitted power measured during the period corresponding to the period 601 during which the power receiving device 102 measures the received power. For example, as Figure 6B shown, if the time interval between T6 and T7 is less than Tslice / 2, the power transmitting device 100 selects the transmitted power value measured during the period 603. If the time interval between T6 and T7 is greater than Tslice / 2, the power transmitting device 100 selects the transmitted power value measured during the period 604.

[0099] After at least Tslice / 2, time period 601, and time period 602 have elapsed since the resumption of power transmission of the power transmission device 100 at time T5, the power receiving device 102 transmits the RP1 or RP2 data in F515 to the power transmission device 100. Accordingly, the time selected for transmitting the power transmission power by the power transmission device 100 as described above does not overlap with the power transmission stop time period (T0 to T5). In addition, the power receiving device 102 may start measuring the power receiving power in time period 601 at time T7 after at least time Tslice / 2 has elapsed after the resumption of power transmission of the power transmission device 100 at time T5.

[0100] In addition, unless the power transmission stop time period (T0 to T5) overlaps with time period 601, another configuration may be used. This will be described with reference to, for example Figure 6C as follows. According to Figure 6C , the power transmission stop time period (T0 to T5) overlaps with time period 602 but does not overlap with time period 601. That is, if the power transmission stop time period (T0 to T5) is completely included in time period 602, the power receiving device 102 may perform subsequent transmission of the RP1 or RP2 data in time period 602. That is, if the power transmission stop timing (time T0) is after time period 601 (after the start of time period 602) and the power transmission resumption timing (time T5) is before the end of time period 602, the power receiving device 102 may perform subsequent transmission of the RP1 or RP2 data in time period 602.

[0101] In addition, in the above example, the power receiving device 102 transmits the RP1 or RP2 data to the power transmission device 100 after at least a time period of Tslice / 2, time period 601, and time period 602 have elapsed since the resumption of power transmission at time T5. However, this is merely an example, and another configuration may be used. For example, the RP1 or RP2 data may be transmitted to the power transmission device 100 after at least a predetermined time (which is referred to as Tstable) has elapsed since the resumption of power transmission at time T5 and after at least a time period of Tslice / 2, time period 601, and time period 602 have elapsed.

[0102] (Operations of the power transmission device and the power receiving device)

[0103] This will be described with reference to Figure 5B and Figure 5CTo describe the operations of the power transmission device 100 and the power reception device 102 according to this embodiment. Note that the same step numbers as those already described above represent the same configurations, and their descriptions will be omitted. When receiving the signal strength (F503), the power transmission device 100 only stops power transmission for a predetermined time so that the power reception device 102 measures the Q factor within a predetermined time from the end of the time interval of the transmitted signal strength (F503). The predetermined time here is set to a maximum of the time from the end of the time interval of the previous data (in this case, the signal strength in F503) until the start of the time interval of the subsequent data (in this case, the ID in F504). For example, the predetermined time is set by the power transmission device 100 such that its maximum does not exceed the minimum value of Tstart (11.5 ms) defined by the WPC standard. Here, Tstart is the time interval defined by the WPC standard and is the time from the end of the previous data until the start of the transmission of the subsequent data. In addition, the power transmission device 100 stops power transmission and then resumes power transmission before the elapsed time from the end of the time interval of the previous data (in this case, the signal strength in F503) exceeds the minimum value of the above-mentioned Tstart.

[0104] When detecting the stop of power transmission, the power reception device 102 performs a second Q factor measurement (F551) between, for example, Figure 11B times T3 and T4 in. When receiving the CAP from the power transmission device 100 in F510 and determining that the power transmission device 100 supports the second Q factor measurement (the third foreign object detection method), the power reception device 102 notifies the power transmission device 100 of the Q factor measured in F551 (F552). If the Q factor is normally received in F552, the power transmission device 100 sends an ACK (F553) to the power reception device 102. The power transmission device 100 stores the Q factor received in F552 in the memory 305 as a reference value for determining the presence / absence of a foreign object in the third foreign object detection process.

[0105] Before sending RP1 in F515, the power receiving device 102 sends a request for the third foreign object detection process (F554) to the power transmitting device 100. When an ACK is received (F555), the power receiving device 102 transitions to the above-described third foreign object detection process state. The power receiving device 102 performs the second Q factor measurement (F556), and sends the measured Q factor to the power transmitting device 100 (F557). The power transmitting device 100 compares the Q factor received in F557 with a threshold value of the Q factor received in F552 and stored in the memory 305. If it is determined as a result of the comparison that the possibility of no foreign object is high, the power transmitting device 100 sends an ACK to the power receiving device 102 (F558). When the ACK is received and it is recognized that the possibility of no foreign object is high, the power receiving device 102 ends the above-described third foreign object detection process state, and sends RP1 to the power transmitting device 100 to create a calibration data point (F515).

[0106] Similarly, before sending RP2 in F519, the power receiving device 102 requests the power transmitting device 100 to perform the third foreign object detection process (F559). If an ACK is received from the power transmitting device 100 (F560), the power receiving device 102 performs the second Q factor measurement (F561). The power receiving device 102 sends the measured Q factor to the power transmitting device 100 (F562). The power transmitting device 100 compares the Q factor received in F562 with a threshold value of the Q factor received in F552 and stored in the memory 305. If it is determined as a result of the comparison that the possibility of no foreign object is high, the power transmitting device 100 sends an ACK to the power receiving device 102 (F563). When the ACK is received and it is recognized that the possibility of no foreign object is high, the power receiving device 102 sends RP2 to the power transmitting device 100 to create a calibration data point (F519).

[0107] Here, it is assumed that the power receiving device 102 is as Figure 1moves as indicated by the arrow 104 in [the figure], and the positional relationship with the power transmission device 100 changes. In this case, it may be difficult to detect the movement by the first foreign object detection method. Therefore, if the power transmission device 100 supports the third foreign object detection process, the power receiving device 102 can request the third foreign object detection at the timing of transmitting RP0. That is, after transmitting RP0 (F522) and receiving ACK (F523), the power receiving device 102 sends a third foreign object detection request (F564) to the power transmission device 100. When receiving ACK for the third foreign object detection request (F565), the power receiving device 102 transitions to the above-mentioned third foreign object detection processing state. Then, the power receiving device 102 performs the second Q factor measurement (F566). The power receiving device 102 sends the measured Q factor to the power transmission device 100 (F567). The power transmission device 100 compares the Q factor received in F567 with the threshold based on the Q factor received in F552. When it is determined that the Q factor exceeds the threshold, the power transmission device 100 sends NAK to the power receiving device 102 (F568).

[0108] Note that since the power receiving device 102 periodically transmits RP0, RP0 can be transmitted even in the third foreign object detection processing state. That is, the power receiving device 102 can transition to the third foreign object detection processing state according to the ACK received in F565, and thereafter, before the end of the third foreign object detection processing state, RP0 can be sent to the power transmission device 100 (F522) and ACK can be received from the power transmission device 100 (F523). When ACK is received for the RP0 transmitted in F522 in F523, the power receiving device 102 ends the third foreign object detection processing state. If ACK for RP0 is received during the operation in the third foreign object detection processing state and NAK for the Q factor transmitted in F567 is received in F568, the power receiving device 102 determines that the possibility that the power receiving device 102 has moved is high. Then, the power receiving device 102 can determine that it is necessary to recreate the created calibration curve. For this purpose, the power receiving device 102 sends a recalibration request (F569) to the power transmission device 100, and performs calibration again based on the processing of F554 to F520 above (F571).

[0109] In the above-described embodiment, the power transmission device 100 stops power transmission between the previous data (signal strength in F503) and the subsequent data (ID in F504), and the power reception device 102 performs the second Q factor measurement during the stop of power transmission. Here, the previous data is not limited to the signal strength (F503), and the subsequent data is not limited to the ID (F504). For example, the previous data may be the ID in F504, and the subsequent data may be the configuration in F505. In this case, the power transmission device 100 may stop power transmission and then resume power transmission before the elapsed time from the end of the time period of the ID in F504 exceeds the minimum value of the above Tstart. Alternatively, the previous data may be the ID in F504, and the subsequent data may be data storing additional identification information related to the power reception device 102. The subsequent data may be an extended ID defined by the WPC standard. The previous data may be the extended ID, and the subsequent data may be data for notifying the delay time from the end of the time period of the CE data until the power transmission device 100 starts to control the power transmission voltage based on the CE data. This data may be the Power Control Hold Off defined by the WPC standard.

[0110] In addition, as described above, after at least the time periods 601 and 602 have elapsed since the power transmission device 100 resumes power transmission at time T5, the power reception device 102 transmits the RP1 or RP2 data to the power transmission device 100 in F515. However, the present invention is not limited thereto. For example, after resuming power transmission at time T5, the power reception device 102 first waits for at least the following time (Tstable), which is the time until the received voltage of the power reception device 102 (i.e., the input voltage and output voltage of the rectifying unit 202) stabilizes. After that, after at least the time periods 601 and 602 have elapsed, the power reception device 102 may transmit the RP1 or RP2 to the power transmission device 100 in F515.

[0111] In the above-described embodiment, the power transmission device 100 stops power transmission and then resumes power transmission before the elapsed time from the end of the time interval corresponding to the previous data exceeds the minimum value of the above Tstart. It may also be performed such that the received voltage of the power receiving device 102 (i.e., the input voltage and output voltage of the power receiving coil 201 and the rectifying unit 202) is sufficiently stable before the elapsed time from the end of the time interval corresponding to the previous data exceeds the minimum value of Tstart. For example, power transmission may be resumed at a time calculated by subtracting Tstable from the end of the following predetermined time period, which is defined as the time period from the timing at the end of the time interval corresponding to the previous data until the timing obtained by adding the minimum value of the above Tstart to the end. That is, the timing at which the input voltage and output voltage of the power receiving coil 201 and the rectifying unit 202 are sufficiently stable after the start of power transmission is set before the timing at which the elapsed time from the end of the time interval corresponding to the previous data exceeds the minimum value of the above Tstart. This enables the power receiving device 102 to perform a more accurate second Q factor measurement.

[0112] In addition, in the WPC standard, during the time defined by Tsilent from the end of the time interval corresponding to the data transmitted by the power receiving device 102, the transmission of the next data is not permitted. This means that the change in the voltage value of the power transmission coil 303 or the power receiving coil 201 caused by data modulation performed by the power transmission device 100 or the power receiving device 102 stabilizes within the time period Tsilent at the latest. For this reason, the power transmission device 100 can stop power transmission and then resume power transmission within the minimum value of the above Tstart after Tsilent has elapsed from the end of the time interval corresponding to the previous data. That is, it is possible to prohibit the stop / resumption of the power transmission device before the change in the voltage value of the power transmission coil 303 or the power receiving coil 201 caused by data modulation stabilizes. This enables the power receiving device 102 to perform a more accurate second Q factor measurement. Also in this case, the power transmission device 100 can operate to resume power transmission before the time calculated by subtracting Tstable from the minimum value of the above Tstart has elapsed from the end of the time interval corresponding to the previous data.

[0113] In addition, the power transmission device 100 may stop / resume power transmission during the time period from the end of the time period corresponding to the previous data until the start of the time period for transmitting a response to the data. For example, the power transmission device 100 may stop and resume power transmission during the time period from the end of the time period corresponding to the configuration data transmitted from the power receiving device 102 in F505 until the start of the time period corresponding to the ACK transmitted by its own device in F506. The WPC standard defines that the power transmission device 100 starts transmitting response data for the data before a time Tresponse has elapsed since the end of the time period corresponding to the data transmitted by the power receiving device 102. Therefore, the power transmission device 100 can perform stop and resume of power transmission, for example, before the minimum value of Tresponse has elapsed since the end of the time period corresponding to the configuration data in F505. In addition, the power transmission device 100 may perform stop / resume of power transmission from after Tsilent has elapsed since the end of the time period corresponding to the previous data until the timing obtained by adding the minimum value of Tresponse to the end. Also in this case, the power transmission device 100 can operate to resume power transmission before a time calculated by subtracting Tstable from the above Tresponse has elapsed since the end of the time period corresponding to the previous data. Note that the previous data is not limited to the configuration data in F505, and the subsequent data is not limited to the ACK in F506. For example, the previous data may be the ACK in F506, and the subsequent data may be the FOD (Q1) in F507.

[0114] In addition, as the time ( Figure 11B T0 to T5 in) when the power transmission device 100 stops power transmission, a predetermined time defined by the WPC standard may be used until the second reference Q factor is stored in the memory 305. When power transmission is stopped in response to a third foreign object detection request transmitted from the power receiving device 102, the power transmission device 100 may stop power transmission based on the time requested by the power receiving device 102. At the time point when the third foreign object detection request is transmitted, the power receiving device 102 is supplying power to the load, and the power consumption of the load changes each time. However, if the above configuration is adopted, the power receiving device 102 can change the request time according to the change in power consumption. For example, if the power consumption is large, the request time can be made shorter. If the power consumption is small, the request time can be made longer.

[0115] If a third foreign object detection request is sent to the power transmission device 100 and ND (undefined) is received as a response, the power receiving device 102 may determine that the power transmission device 100 does not support the third foreign object detection process, and from then on, prohibit the sending of the third foreign object detection request. ND is a response defined by the WPC standard and sent by the power transmission device 100 that is neither an ACK (positive response) nor a NAK (negative response), and indicates that the power transmission device 100 does not support the requested data.

[0116] In Figure 5B it is described the case of sending RP1 or RP2 data in F515. However, the present invention is not limited thereto, and another data for notifying the received power value may be sent in F515. For example, RP0 data may be sent in F515.

[0117] Note that in the above embodiment, if an ACK (positive response) to the RP0 in F522 for Figure 5C is received in F523, the power receiving device 102 sends a third foreign object detection request to the power transmission device 100 in F564. According to the ACK received in F565, the power receiving device 102 transitions to the third foreign object detection processing state. As described above, the power receiving device 102 sometimes sends RP0 (F522) after transitioning to the third foreign object detection processing state. In this case, the power receiving device 102 may send the third foreign object detection request again even after sending the third foreign object detection request in the immediately preceding F564. Therefore, the second foreign object detection unit 403 of the power receiving device 102 can be used to prevent the repeated sending of the third foreign object detection request. An example of the process of this processing will be described with reference to Figure 7

[0118] ​The power receiving device 102 transmits the beginning part of RP0 (step S701), and resets the timer for defining the transmission interval of RP0 (step S702). When timeout is detected (Yes in step S703), the power receiving device 102 determines whether its own device is currently in the third foreign object detection processing state (step S704). If the operation is being performed in the third foreign object detection processing state (Yes in step S704), the power receiving device 102 prohibits the transmission of the next RP0 (step S705). This makes it possible to suppress the power receiving device 102 from transmitting RP0 in the third foreign object detection processing state, and prevent the third foreign object detection request from being repeatedly transmitted to the power transmission device 100. Note that if the power receiving device 102 is not in the third foreign object detection processing state at the time of timeout (No in step S704), the next RP0 is transmitted to the power transmission device 100 (step S706). Note that the power transmission device 100 can shift to the third foreign object detection processing state according to the transmission of ACK for the third foreign object detection request. When receiving RP0 in the third foreign object detection processing state, the power transmission device 100 can stop power transmission, output an error, and end the processing associated with wireless power transmission.

[0119] Reference will be made Figure 8A to describe the outline of the operation of the power receiving device 102 when the transmission of RP0 is prohibited in the third foreign object detection processing state. The time length 800 is the time length from the beginning of RP0 (F522) until the transmission of the next RP0, and it is the time length defined as Treceived in the WPC standard. The power receiving device 102 transmits RP0 to the power transmission device 100 at a cycle of the time length 800. The time length 800 can correspond to the time length of timeout in step S703. Here, in Figure 8A the time when the beginning of the next RP0 should be transmitted is defined as T6. The time length 801 is the time from the end of ACK (F523) as a response to RP0 until the end of ACK (F568) as a response to the Q factor (F567). T7 is the end of ACK (F568), and represents the timing when the power transmission device 100 and the power receiving device 102 end the operation in the third foreign object detection processing state. The power receiving device 102 does not transmit RP0 during the operation in the third foreign object detection processing state. Therefore, if T7 is later than T6 in terms of time, the power receiving device 102 does not transmit the next RP0 at T6.

[0120] On the other hand, in Figure 8BAt the timing shown, the power receiving device 102 operates so that the time length 801 becomes shorter than the time length 800. That is, if the time interval corresponding to the time length 801 starts after the start of the time interval corresponding to the time length 800, the transmission of the Q factor in F567 is executed in advance. Therefore, the power receiving device 102 operates so that the time T7 until the end of the response (ACK in F568) to the Q factor (F567) arrives before the time T6 at the start of the transmission of the next RP0. This enables the power receiving device 102 to transmit RP0 for each Treceived.

[0121] In addition, the time length 800 can be used as a timeout time in which, if the power supply device 100 does not receive the start of the next RP0 within the time length 800 after transmitting the start of RP0 in F522, the power supply is stopped. Note that the timeout time is defined as Tpower by the WPC standard.

[0122] In the above example, in order to prohibit the transmission of RP0 during the operation in the third foreign object detection processing state, the power receiving device 102 controls the timing of Q factor transmission and the like. On the other hand, the power receiving device 102 can transmit RP0 regardless of whether the power receiving device 102 is operating in the third foreign object detection processing state without controlling the timing of Q factor transmission. For example, the power receiving device 102 can be configured to transmit a third foreign object detection request only when transmitting RP0 in the third foreign object detection processing state and obtaining a NAK as a response. The process of the processing in this case will be described with reference to Figure 9A The power receiving device 102 transmits RP0 (step S901) and receives a response (step S902). If the response is NAK (Yes in step S903), the power receiving device 102 determines whether it is in the third foreign object detection processing state. If it is operating in the third foreign object detection processing state (Yes in step S904), the power receiving device 102 does not transmit a third foreign object detection request (step S906). On the other hand, if it is not operating in the third foreign object detection processing state (No in step S904), the power receiving device 102 transmits a third foreign object detection request to the power supply device 100 (step S905). In addition, if the response is not NAK (No in step S903), the power receiving device 102 ends the processing. Accordingly, the power receiving device 102 can continuously transmit RP0 without adjusting the timing of Q factor reporting and the like.

[0123] In addition, the power supply device 100 can operate to change the response to RP0 according to whether it is in the third foreign object detection processing state. The process will be described with reference to Figure 10To describe the process of the processing performed by the power transmission device 100 in this case. The power transmission device 100 receives RP0 (step S1001), and determines whether its own device is operating in the third foreign object detection processing state. If it is operating in the third foreign object detection processing state (Yes in step S1002), the power transmission device 100 sends ND (undefined) to the power reception device 102 (step S1003). Note that if it is not operating in the third foreign object detection processing state (No in step S1002), the power transmission device 100 selects ACK / NAK based on the second foreign object detection method and sends it to the received RP0 (step S1004).

[0124] will refer to Figure 9B To describe the process of the processing performed by the power reception device 102 in this case. The power reception device 102 sends RP0 (step S911), receives a response (step S912), and determines whether its own device is operating in the third foreign object detection processing state (step S913). If its own device is operating in the third foreign object detection processing state (Yes in step S913) and the response is ND (Yes in step S916), the power reception device 102 ends the processing without performing any operations. On the other hand, if its own device is operating in the third foreign object detection processing state (Yes in step S913) and the response is not ND (No in step S916), the power reception device 102 determines based on Figure 10 the processing shown that the power transmission device 100 is not operating, and the power transmission device 100 has a fault or is an unauthorized device. Therefore, the power reception device 102 sends EPT (step S915) and ends the wireless power transmission. If it is not operating in the third foreign object detection processing state (No in step S913) and the response is not ND (No in step S914), the power reception device 102 directly ends the processing. This is because in this case, the response is ACK or NAK, and the power reception device 102 can determine that the power transmission device 100 is operating based on the second foreign object detection method. If its own device is not operating in the third foreign object detection processing state (No in step S913) and the response is ND (Yes in step S914), the power reception device 102 determines based on Figure 10 the processing shown that the power transmission device 100 is not operating, and the power transmission device 100 has a fault or is an unauthorized device. Therefore, the power reception device 102 sends EPT (step S915) and ends the wireless power transmission. Similarly, based on this, the power reception device 102 can continuously send RP0 without adjusting the timing of the Q factor report, etc.

[0125] In the above embodiments, in the second Q factor measurement, the power receiving device 102 measures the Q factor based on the high-frequency voltage of the power receiving coil 201. Here, the high-frequency voltage may include three frequencies, namely, the power transmission frequency of the power transmission coil 303, the resonance frequency F1 of the power transmission coil 303 and the resonance capacitor 306, and the resonance frequency F2 of the power receiving coil 201 and the resonance capacitor 207. For this reason, the power receiving device 102 can measure the Q factor at any one of the three frequencies.

[0126] In addition, in the above embodiments, an example in which the power receiving device 102 measures the Q factor has been described. However, the present invention is not limited thereto, and the power transmission device 100 can measure the Q factor. In addition, the power transmission device 100 can measure the Q factor at one of the above three frequencies. When performing the second Q factor measurement, the power transmission device 100 can not only stop / resume power transmission at the timing described above, but also stop / resume power transmission during the period from when an analog Ping is sent in F500 and an object is detected until the start of the digital Ping transmission in F502. For example, after the user places the power receiving device 102 in the operating volume, the power transmission device 100 can transmit a predetermined power for a predetermined period of time and stop and resume power transmission. The predetermined period of time is a period determined by, for example, Tdetect defined by the WPC standard, which represents the time from when the power receiving device 102 is placed in the operating volume until the start of the digital Ping transmission.

[0127] In addition, the second Q factor measurement can be performed after the power transmission device 100 sends an analog Ping and detects an object in F500 and before performing the first Q factor measurement in F501. The second Q factor measurement can be performed during the time from the end of the first Q factor measurement in F501 until the start of the digital Ping transmission in F502. The second Q factor measurement can be performed after the start of the digital Ping transmission in F502 and before the signal strength is transmitted / received in F503. For example, the second Q factor measurement can be performed during a period equal to or shorter than Twake in the WPC standard, where Twake represents the time from when the power transmission device 100 starts transmitting the digital Ping in F502 until the power receiving device 102 transmits the signal strength.

[0128] In the description related to the CAP in F510, when it is recognized that the power transmission device 100 supports the second Q factor measurement (the third foreign object detection method), the power receiving device 102 notifies the power transmission device 100 of the measurement result of the Q factor in F552. However, the present invention is not limited thereto. When it is recognized through the CAP in F510 that the power transmission device 100 does not support the second Q factor measurement, the power receiving device 102 may not measure the second Q factor. Alternatively, if ND or NAK is received after sending the Q factor to the power transmission device 100, then the power receiving device 102 may not send the third foreign object detection request thereafter.

[0129] If the Q factor is correctly received, the power transmission device 100 sends an ACK to the power receiving device 102. If it is determined through the third foreign object detection that the possibility of the presence of a foreign object is high, the power transmission device 100 may send a NAK for the Q factor in F552. When receiving the NAK, the power receiving device 102 may send an EPT to cause the power transmission device 100 to stop power transmission.

[0130] In addition, in the above-described embodiment, the power receiving device 102 observes the voltage value of the power receiving coil 201, thereby detecting the stop and resumption of power transmission. However, the present invention is not limited thereto. For example, the power transmission device 100 and the power receiving device 102 may pre-share the timing of the stop / resumption of power transmission, and the power receiving device 102 may use a timer and the shared timing to detect the stop and resumption.

[0131] Note that instead of the above-described second Q factor measurement, measurement of another physical quantity that changes according to the presence of a foreign object may be performed. For example, the change in the voltage value or current value over time, or the attenuation rate of the voltage value or current value, may be measured, or the coupling coefficient between the coils may be measured. Therefore, foreign object detection by the above-described third foreign object detection method may be performed based on an electrical characteristic (such as the second Q factor or another value) related to at least one of the power transmission coil and the power receiving coil. Note that foreign object detection does not need to be performed based on both the electrical characteristics of the power transmission coil and the electrical characteristics of the power receiving coil, and foreign object detection may be performed based only on the electrical characteristics of the power transmission coil or only on the electrical characteristics of the power receiving coil.

[0132] In addition, Figure 7 , Figure 9A , Figure 9B and Figure 10The processing shown can be implemented by, for example, a control unit 200 of the power receiving device 102 or a control unit 300 of the power transmitting device 100 reading and executing a program stored in advance and controlling a functional unit. However, the present invention is not limited thereto, and at least a part of the processing can be implemented by hardware. When the processing is implemented by hardware, for example, a dedicated circuit can be automatically generated on an FPGA according to a program configured to implement processing steps using a predetermined compiler. Here, FPGA is an abbreviation for Field Programmable Gate Array. In addition, similar to the FPGA, a gate array circuit can be formed to implement the hardware configured to execute at least a part of the above-described processing.

[0133] The present invention can be implemented by the following processing: supplying a program for implementing one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. The present invention can also be implemented by a circuit (e.g., ASIC) for implementing one or more functions.

[0134] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, in order to inform the public of the scope of the present invention, the appended claims are added.

[0135] This application claims priority to Japanese Patent Application No. 2020-080694, filed on Apr. 30, 2020, which is incorporated herein by reference.

Claims

1. A power receiving device, comprising: A power receiving component for wirelessly receiving power from a power transmitting device; A communication component for transmitting information related to the received power; A first measurement component for measuring a quality factor based on an envelope of a waveform after the power receiving component receives power for waking up the power receiving device during a first time period when the power transmission of the power transmitting device is restricted; A second measurement component for measuring a value corresponding to the received power for detecting a foreign object during a second time period based on a relationship between a value corresponding to the transmitted power in the power transmitting device and a value corresponding to the received power in the power receiving device; And A control component for controlling the timing of the second time period such that the first time period and the second time period do not overlap, wherein the communication component receives, from the power transmitting device, a result of a process for detecting a foreign object based on the measured quality factor, and wherein, in a case where no foreign object is detected based on the quality factor, the communication component transmits information related to the received power measured by the second measurement component and being a calibration data point for a process for detecting a foreign object based on power loss.

2. The power receiving device according to claim 1, further comprising a detection component configured to detect a restriction and resumption of power transmission in the power transmission device based on a measurement of a value corresponding to the received power.

3. The power receiving device according to claim 1, further comprising a component configured to share the timing of the first time period with the power transmission device in advance.

4. The power receiving device according to claim 1, wherein, The control component controls to start the second time period after the power transmission is continued again.

5. The power receiving device according to claim 4, wherein, After the power transmission is continued again, the control component controls to start the second time period after a time until a value corresponding to the received power in the power receiving device becomes stable has elapsed.

6. The power receiving device according to claim 1, wherein, The control component controls to end the second time period before the power transmission is restricted.

7. The power receiving device according to claim 6, wherein, The control component controls the timing of the second time period such that the power transmission is restricted and continued again during an offset time period after the second time period ends until a value corresponding to the received power measured during the second time period is transmitted to the power transmitting device.

8. A computer-readable storage medium storing a program configured to cause a computer to function as the power receiving device according to any one of claims 1 to 7.

9. A control method executed by a power receiving device configured to wirelessly receive power from a power transmission device, the control method comprising: During a first time period when the power transmitting device restricts power transmission, after receiving power for waking up the power receiving device, measure a quality factor based on an envelope of a waveform; Measure a value corresponding to the received power for detecting a foreign object during a second time period based on a relationship between a value corresponding to the transmitted power in the power transmitting device and a value corresponding to the received power in the power receiving device; And Control the timing of the second time period such that the first time period and the second time period do not overlap, Receive, from the power transmitting device, a result of a process for detecting a foreign object based on the measured quality factor, and In a case where no foreign object is detected based on the quality factor, transmit information related to the measured received power and being a calibration data point for a process for detecting a foreign object based on power loss.

10. A computer program product comprising a program configured to cause a computer to function as the power receiving device according to any one of claims 1 to 7.

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