Power transmission device, method, and program

Abstract

To more accurately execute detection of an object different from a power reception device in a power transmission device and the power reception device conforming to the standard of the WPC.SOLUTION: A power transmission device wirelessly transmits power to a power reception device. The power transmission device receives a Specific Request including information about a period during which transmission of power from the power transmission device is restricted from the power reception device, and after the power transmission is started in a Power Transfer phase, executes object detection in a period during which the power transmission is restricted.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Technological development of wireless power transmission systems has been widely conducted, and the standard (WPC standard) established by the standardization organization Wireless Power Consortium (WPC) as a wireless charging standard is widely known. In such wireless power transmission, it is essential to detect a foreign object present within a range where a power transmitting device can transmit power and control power transmission and reception. A foreign object is an object different from a power receiving device. Patent Document 1 describes a method for detecting a foreign object and restricting power transmission and reception when the foreign object is present near a power transmitting and receiving device conforming to the WPC standard. Patent Document 2 discloses a technology for detecting a foreign object by short-circuiting a coil in a wireless power transmission system. Furthermore, Patent Document 3 describes a technology for detecting a foreign object by measuring a change in the quality factor (Q factor) of a power transmitting coil of a wireless power transmission system by applying a high-frequency signal to the coil for a certain period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-070074 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-034972 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-132133 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a technology that enables a power transmitting device and a power receiving device that comply with the WPC standard to detect an object different from the power receiving device with higher accuracy. [Means for solving the problem]

[0005] A power transmission device according to one aspect of the present invention includes a power transmission means for wirelessly transmitting power to a power receiving device, a communication means for receiving a Specific Request from the power receiving device including information regarding a period during which power transmission from the power transmitting device is restricted, and a detection means for detecting an object during the period during which power transmission is restricted after power transmission has begun in the Power Transfer phase. [Effects of the Invention]

[0006] According to the present invention, in a power transmitting device and a power receiving device that comply with the WPC standard, it is possible to more accurately detect an object that is different from the power receiving device. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a wireless power transmission system. [Figure 2] FIG. 2 illustrates an example of the configuration of a power receiving device. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of a power transmitting device. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of a control unit of the power transmitting device. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a control unit of a power receiving device. [Figure 6A] FIG. 10 is a diagram illustrating an example of a flow of processing executed by a conventional power transmitting device and a power receiving device. [Figure 6B] FIG. 2 is a diagram illustrating an example of a flow of processing executed by a power transmitting device and a power receiving device according to an embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of the flow of a third foreign object detection process performed by the power transmitting device. [Figure 8] FIG. 10 is a diagram illustrating an example of the flow of a third foreign object detection process performed by the power receiving device. [Figure 9] FIG. 10 is a diagram illustrating an example of the flow of a measurement process of a second Q value performed by a power transmitting device. [Figure 10]FIG. 10 is a diagram illustrating an example of the flow of a measurement process of a second Q value by a power receiving device. [Figure 11] FIG. 10 is a diagram illustrating foreign object detection using a power loss method. [Figure 12] FIG. 1 is a diagram illustrating a method for measuring a Q value in the time domain. [Figure 13] FIG. 10 is a diagram illustrating the frame format of a Configuration Packet. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0009] (System Configuration) FIG. 1 shows an example of the configuration of a wireless power transmission system according to this embodiment. In one example, the wireless power transmission system includes a power transmission device 100 and a power receiving device 102. The power transmission device 100 and the power receiving device 102 comply with the Wireless Power Consortium (WPC) standard. The power transmission device 100 is, for example, an electronic device that wirelessly transmits power to a power receiving device 102 placed thereon. The power transmission device 100 wirelessly transmits power to the power receiving device 102 via a power transmission coil 101. The power receiving device 102 is, for example, an electronic device that receives power from the power transmission device 100 and charges an internal battery. The power receiving device 102 may also be built into other devices (such as a camera, a smartphone, a tablet PC, a laptop, an automobile, a robot, a medical device, or a printer) and supplies power to those devices. The power transmission device 100 may be a smartphone, for example. In this case, the power receiving device 102 may be, for example, another smartphone or a wireless earphone. The power receiving device 102 may be a vehicle such as an automobile or a transport device, and the power transmitting device 100 may be a charger installed in the console of a vehicle such as an automobile or a transport device.

[0010] FIG. 1 also illustrates a situation in which a conductive foreign object 103 is present within the operating volume affected by the wireless power output from the power transmitting coil 101. The presence of such a foreign object 103 within the operating volume can degrade the efficiency of power transmission and reception and, in some cases, cause problems such as heat generation. Therefore, it is important for the power transmitting device 100 and the power receiving device 102 to detect such a foreign object 103 and perform power transmission and reception control. In this embodiment, the power transmitting device 100 and the power receiving device 102 measure a quality factor (Q factor) based on the time change in the voltage inside the power transmitting coil within a control range compliant with the WPC standard, detect such a foreign object 103, and perform power transmission and reception control. The following describes in detail an example of the configuration of a device that executes such a procedure and a processing flow. The foreign object 103 is a different object from the power receiving device. The foreign object 103 is, for example, a conductive object such as a metal piece or an IC card.

[0011] (Device configuration) 2 shows a configuration example of the power receiving device 102. The power receiving device 102 includes, for example, a control unit 200, a power receiving coil 201, a rectifier unit 202, a voltage control unit 203, a communication unit 204, a charging unit 205, a battery 206, a resonance capacitor 207, and a switch 208. The control unit 200 controls the entire power receiving device 102. The control unit 200 includes, for example, one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 200 may include, for example, one or more storage devices such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The control unit 200 can be configured to perform each process described below by, for example, executing a program stored in the storage device using the processor. The power receiving coil 201 is a coil used when receiving power from the power transmitting coil 101 of the power transmitting device 100. Rectification unit 202 converts the AC voltage and AC current received via power receiving coil 201 into DC voltage and DC current. Voltage control unit 203 converts the level of the DC voltage input from rectification unit 202 into a DC voltage level suitable for operation of control unit 200, charging unit 205, etc. (neither too high nor too low). Voltage control unit 203 also supplies the converted voltage to charging unit 205. Charging unit 205 charges battery 206 with the voltage supplied from voltage control unit 203. Communication unit 204 performs control communication for wireless charging based on the WPC standard with power transmitting device 100. This control communication is performed by load modulating the AC voltage and AC current received by power receiving coil 201.

[0012] Furthermore, receiving coil 201 is connected to resonant capacitor 207 and is configured to resonate at a specific frequency F2. Switch 208 is a switch for shorting receiving coil 201 and resonant capacitor 207, and is controlled by control unit 200. When switch 208 is turned on, receiving coil 201 and resonant capacitor 207 form a series resonant circuit. At this time, current flows only through the closed circuit of receiving coil 201, resonant capacitor 207, and switch 208, and no current flows through rectifier unit 202 or voltage control unit 203. On the other hand, when switch 208 is turned off, current flows through rectifier unit 202 and voltage control unit 203 via receiving coil 201 and resonant capacitor 207.

[0013] FIG. 3 shows a configuration example of the power transmitting device 100. The power transmitting device 100 includes, for example, a control unit 300, a power supply unit 301, a power transmitting unit 302, a power transmitting coil 303, a communication unit 304, a memory 305, a resonant capacitor 306, and a switch 307. The control unit 300 controls the entire power transmitting device 100. The control unit 300 includes, for example, one or more processors such as a CPU or an MPU. The control unit 300 can be configured to perform each process described below by, for example, executing a program stored in a memory 305 (described below) or a storage device built into the control unit 300 using the processor. 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 the commercial power supply, for example.

[0014] The power transmitting unit 302 converts DC or AC power input from the power supply unit 301 into AC power in a frequency band used for wireless power transmission, inputs the AC power to the power transmitting coil 303, and thereby generates electromagnetic waves from the power transmitting coil 303 for receiving power at the power receiving device 102. For example, the power transmitting unit 302 converts the DC voltage supplied from the power supply unit 301 into an AC voltage using a half-bridge or full-bridge switching circuit using field effect transistors (FETs). In this case, the power transmitting unit 302 includes a gate driver that controls the ON / OFF of the FETs. The power transmitting unit 302 also controls the intensity and frequency of the electromagnetic waves to be output by adjusting at least one of the voltage (transmission voltage) and current (transmission current) input to the power transmitting coil 303, or the frequency. For example, the power transmitting 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 transmitting unit 302 has the capacity to supply 15 watts (W) of power to the charging unit 205 of the power receiving device 102, which complies with the WPC standard. Furthermore, the power transmitting unit 302 controls the output of AC power based on instructions from the control unit 300, so that the output of electromagnetic waves from the power transmitting coil 303 is started or stopped.

[0015] The communication unit 304 communicates with the power receiving device 102 via the power transmitting coil 303 for power transmission control based on the WPC standard. The communication unit 304 modulates the AC voltage and AC current output from the power transmitting unit 302 using frequency modulation (FSK (Frequency Shift Keying)) and transmits information to the power receiving device 102. The communication unit 304 also demodulates the AC voltage and AC current modulated by load modulation by the communication unit 204 of the power receiving device 102 to acquire information transmitted by the power receiving device 102. That is, the communication unit 304 superimposes information to be transmitted to the power receiving device 102 on electromagnetic waves transmitted from the power transmitting unit 302 and detects a received signal superimposed by the power receiving device 102 on the electromagnetic waves, thereby communicating with the power receiving device 102. The communication unit 304 may also communicate with the power receiving device 102 using a coil (or an antenna) different from the power transmitting coil 303 and in accordance with a standard different from the WPC standard. Furthermore, the communication unit 304 may selectively use a plurality of communication functions to communicate with the power receiving device 102. The memory 305 stores, for example, a control program executed by the control unit 300 and information such as the states of the power transmitting device 100 and the power receiving device 102. For example, the state of the power transmitting device 100 is acquired by the control unit 300. Furthermore, the state of the power receiving device 102 is acquired by the control unit 200 of the power receiving device 102 and transmitted from the communication unit 204, and the power transmitting device 100 acquires information indicating this state via the communication unit 304.

[0016] Furthermore, the transmitting coil 303 is connected to a resonant capacitor 306 and configured to resonate at a specific frequency F1. The switch 307 is a switch for shorting the transmitting coil 303 and the resonant capacitor 306, and is controlled by the control unit 300. When the switch 307 is turned on, the transmitting coil 303 and the resonant capacitor 306 form a series resonant circuit. At this time, current flows only through the closed circuit of the transmitting coil 303, the resonant capacitor 306, and the switch 307. When the switch 308 is turned off, power is supplied from the power transmitting unit 302 to the transmitting coil 303 and the resonant capacitor 306.

[0017] FIG. 4 shows an example of a functional configuration realized by the control unit 300 of the power transmitting device 100. The control unit 300 can operate as, for example, each of the functional units: a first Q-value measurement unit 400, a second Q-value measurement unit 401, a calibration processing unit 402, a first foreign object detection processing unit 403, a second foreign object detection processing unit 404, a third foreign object detection processing unit 405, and a power transmission processing unit 406. The first Q-value measurement unit 400 measures the Q-value in the frequency domain (first Q-value measurement) as described below. The second Q-value measurement unit 401 measures the Q-value in the time domain (second Q-value measurement) as described below. The calibration processing unit 402 acquires calibration data points and creates a calibration curve as described below. The first foreign object detection processing unit 403 executes foreign object detection processing (first foreign object detection processing) based on the first Q-value measured by the first Q-value measurement unit 400. The second foreign object detection processing unit 404 executes foreign object detection processing (second foreign object detection processing) based on a power loss method described below. The third foreign object detection processing unit 405 executes foreign object detection processing (third foreign object detection processing) based on the second Q value measured by the second Q value measurement unit 401. The power transmission processing unit 406 performs processing related to the start and stop of power transmission by the power transmission unit 302, and the increase and decrease of the transmitted power. Each processing unit shown in FIG. 4 may be configured as a plurality of independent programs, and these programs may operate in parallel while being synchronized by event processing or the like.

[0018] 5 shows an example of a functional configuration realized by the control unit 200 of the power receiving device 102. The control unit 200 can operate as, for example, functional units of a second Q-value measurement unit 500 and a power receiving processing unit 501. The second Q-value measurement unit 500 measures the Q-value in the time domain (second Q-value measurement) as described below. The power receiving processing unit 501 performs processing related to the start and stop of power reception by the power receiving device 102 and the increase and decrease of power requested from the power transmitting device 100. Each processing unit shown in FIG. 5 is configured as an independent program and can operate in parallel while maintaining synchronization between the programs by event processing or the like.

[0019] (WPC standard foreign body detection method) Next, foreign object detection methods defined in the WPC (Wireless Power Consortium) standard will be described using the power transmitting device 100 and the power receiving device 102 as examples. Here, a foreign object detection method based on a Q value measured in the frequency domain (first foreign object detection method) and a foreign object detection method based on a power loss technique (second foreign object detection method) will be described.

[0020] (1) Foreign object detection method based on Q value measured in the frequency domain (first foreign object detection method) In the first foreign object detection method, first, the power transmitting device 100 performs a measurement (first Q-factor measurement) in the frequency domain of the Q-factor, which changes due to the influence of a foreign object. This measurement is performed between the time when the power transmitting device 100 transmits an Analog Ping and the time when it transmits a Digital Ping (see F601 in FIG. 6A). For example, to measure the Q-factor, the power transmitting unit 302 sweeps the frequency of the wireless power output by the power transmitting coil 303, and the first Q-factor measuring unit 400 measures the voltage value at the end of the resonant capacitor 306 connected in series (or parallel) with the power transmitting coil. Then, the first Q-factor measuring unit 400 searches for the resonant frequency at which the voltage value peaks, and calculates the Q-factor of the power transmitting coil 303 from the resonant frequency and the frequency indicating a voltage value 3 dB lower than the peak voltage value measured at the resonant frequency.

[0021] Alternatively, the Q value may be measured by another method. For example, the power transmitting unit 302 sweeps the frequency of the wireless power output by the power transmitting coil 303, and the first Q value measuring unit 400 measures the voltage value at the ends of the resonant capacitor 306 connected in series with the power transmitting coil 303, and searches for the resonant frequency at which the voltage value reaches a peak. The first Q value measuring unit 400 then measures the voltage value at both ends of the resonant capacitor 306 at the resonant frequency, and calculates the Q value of the power transmitting coil 303 from the ratio of the voltage values ​​at both ends.

[0022] After calculating the Q value of the power transmitting coil 303, the first foreign object detection processing unit 403 of the power transmitting device 100 acquires the Q value, which is a criterion for determining foreign object detection, from the power receiving device 102 via the communication unit 304. For example, the first foreign object detection processing unit 403 receives from the power receiving device 102 the Q value (first characteristic value) of the power transmitting coil defined by the WPC standard when the power receiving device is placed on the power transmitting coil. This Q value is stored in an FOD (Foreign Object Detection) Status packet transmitted by the power receiving device 102, and the power transmitting device 100 acquires this Q value by receiving this FOD Status packet. From the acquired Q value, the first foreign object detection processing unit 403 estimates the Q value of the power transmitting coil 303 when the power receiving device 102 is placed on the power transmitting device 100. In this embodiment, the estimated Q value is referred to as a first reference Q value. The Q value stored in the FOD Status packet may be stored in advance in a non-volatile memory (not shown) of the power receiving device 102. That is, the power receiving device 102 may notify the power transmitting device 100 of the Q value stored in advance. This Q value corresponds to Q1, which will be described later.

[0023] The first foreign object detection processing unit 403 of the power transmitting device 100 compares the first reference Q value with the Q value measured by the first Q value measurement unit 400, and determines whether or not a foreign object is present based on the comparison result. For example, the first foreign object detection processing unit 403 sets a Q value that is lower by a % (first percentage) than the first reference Q value as a threshold value, and determines that there is a high possibility that a foreign object is present if the measured Q value is lower than the threshold value, and otherwise determines that there is a high possibility that there is no foreign object.

[0024] (2) Foreign object detection method based on power loss technique (second foreign object detection method) Next, a foreign object detection method based on the power loss method defined in the WPC standard will be described with reference to Fig. 11. Fig. 11 is a conceptual diagram of foreign object detection using the power loss method, where the horizontal axis indicates the transmitted power of the power transmitting device 100 and the vertical axis indicates the received power of the power receiving device 102. Note that the transmitted power by the power transmitting unit 302 of the power transmitting device 100 can be controlled by the power transmission processing unit 406.

[0025] First, the power transmitting unit 302 of the power transmitting device 100 transmits a Digital Ping to the power receiving device 102. Then, the communication unit 304 of the power transmitting device 100 receives the received power value Pr1 (referred to as Light Load) of the power receiving device 102 by a Received Power Packet (mode 1). Note that Received Power Packet (mode 1) will be referred to as "RP1" below. Pr1 is the received power value when the power receiving device 102 is not supplying received power to a load (such as the charging unit 205 and battery 206). The control unit 300 of the power transmitting device 100 stores in the memory 305 the relationship between the received Pr1 and the transmitted power value Pt1 when Pr1 was obtained (point 1100 in FIG. 11 ). This allows the power transmitting device 100 to recognize that the amount of power loss between the power transmitting device 100 and the power receiving device 102 when transmitting Pt1 as the transmission power is Pt1-Pr1 (Ploss1).

[0026] Next, the communication unit 304 of the power transmitting device 100 receives the value of the received power value Pr2 (referred to as Connected Load) of the power receiving device 102 from the power receiving device 102 in a Received Power Packet (mode 2). Note that Received Power Packet (mode 2) will be referred to as "RP2" hereinafter. Pr2 is the received power value when the power receiving device 102 is supplying the received power to a load. The control unit 300 of the power transmitting device 100 then stores in the memory 305 the relationship between the received Pr2 and the transmitted power value Pt2 when Pr2 was obtained (point 1101 in FIG. 11 ). This allows the power transmitting device 100 to recognize that the amount of power loss between the power transmitting device 100 and the power receiving device 102 when Pt2 is transmitted as the transmitted power is Pt2-Pr2 (Ploss2).

[0027] Then, the calibration processing unit 402 of the power transmitting device 100 linearly interpolates between point 1100 and point 1101 to create a straight line 1102. The straight line 1102 corresponds to the relationship between the transmitted power and the received power in a state where no foreign object is present around the power transmitting device 100 and the power receiving device 102. Therefore, the power transmitting device 100 can predict the received power in a state where there is a high possibility that no foreign object is present, from the transmitted power value and the straight line 1102. For example, when the transmitted power value is Pt3, the power transmitting device 100 can predict that the received power value will be Pr3 from point 1103 on the straight line 1102, which corresponds to the case where the transmitted power value is Pt3.

[0028] Here, assume that when the power transmitting unit 302 of the power transmitting device 100 transmits power to the power receiving device 102 at a transmission power of Pt3, the communication unit 304 receives a received power value Pr3' from the power receiving device 102. The second foreign object detection processing unit 404 of the power transmitting device 100 calculates a value Pr3-Pr3' (=Ploss_F0) by subtracting the received power value Pr3' actually received from the power receiving device 102 from the received power value Pr3 in a state where no foreign object is present. This Ploss_F0 can be considered to be the power loss consumed by a foreign object if the foreign object is present between the power transmitting device 100 and the power receiving device 102. Therefore, the second foreign object detection processing unit 404 can determine that a foreign object is present when the power Ploss_F0 that would have been consumed by the foreign object exceeds a predetermined threshold. This threshold is derived, for example, based on the relationship between point 1100 and point 1101.

[0029] Furthermore, the second foreign object detection processing unit 404 of the power transmitting device 100 previously calculates the amount of power loss Pt3-Pr3 (Ploss3) between the power transmitting device 100 and the power receiving device 102 from the received power value Pr3 when no foreign object is present. The second foreign object detection processing unit 404 then calculates the amount of power loss Pt3-Pr3' (Ploss3') between the power transmitting device 100 and the power receiving device 102 when a foreign object is present from the received power value Pr3' received from the power receiving device 102 when it is unclear whether a foreign object is present. The second foreign object detection processing unit 404 then calculates Ploss3'-Ploss3, and can determine that a foreign object is present if this value exceeds a predetermined threshold. Note that Ploss3'-Ploss3=Pt3-Pr3'-Pt3+Pr3=Pr3-Pr3'. Therefore, by comparing the amounts of power loss, it is also possible to estimate the power Ploss_FO predicted to be consumed by the foreign object.

[0030] As described above, the power Ploss_FO that would have been consumed by the foreign object may be calculated as the difference in received power Pr3-Pr3', or may be calculated as the difference in power loss Ploss3'-Ploss3 (=Ploss_FO).

[0031] After the calibration processing unit 402 acquires the line 1102, the second foreign object detection processing unit 404 of the power transmitting device 100 periodically receives the current received power value (for example, the above-mentioned Pr3') from the power receiving device 102 via the communication unit 304. The current received power value periodically transmitted by the power receiving device 102 is transmitted to the power transmitting device 100 as a Received Power Packet (mode 0). The second foreign object detection processing unit 404 of the power transmitting device 100 performs foreign object detection based on the received power value stored in the Received Power Packet (mode 0) and the line 1102. Note that Received Power Packet (mode 0) will be referred to as "RP0" below.

[0032] In this embodiment, points 1100 and 1101 for obtaining a line 1102 representing the relationship between transmitted power and received power when no foreign object is present around the power transmitting device 100 and the power receiving device 102 are called "calibration data points." Also, a line segment (straight line 1102) obtained by interpolating at least two calibration data points is called a "calibration curve." The calibration data points and the calibration curve (second standard) are used for foreign object detection processing by the second foreign object detection processing unit 404.

[0033] (Method for measuring Q-factor in the time domain) A method for measuring a Q value in the time domain will be described with reference to FIGS. 12(A) and 12(B). FIGS. 12(A) and 12(B) are conceptual diagrams for explaining a method for measuring a Q value in the time domain (second Q value measurement). In this embodiment, the foreign object detection method based on the second Q value is referred to as a third foreign object detection method. The second Q value measurement is performed by the second Q value measurement unit 401. Furthermore, control of the transmitted power by the power transmission unit 302 of the power transmitting device 100 is performed by the power transmission processing unit 406. In the second Q value measurement, the power transmitting device 100 and the power receiving device 102 turn on their switches for the same period, causing a momentary interruption in power transmission and preventing the received power from being delivered to the load. This causes, for example, a gradual decrease in the voltage applied to the coil. The second Q value is then calculated based on the manner in which this decrease occurs.

[0034] Waveform 1200 in FIG. 12(A) shows the time course of the value of the high-frequency voltage applied to the end of the power transmitting coil 303 or the resonant capacitor 306 of the power transmitting device 100 (hereinafter simply referred to as the "voltage value of the power transmitting coil"). Note that in FIGS. 12(A) and 12(B), the horizontal axis represents time, and the vertical axis represents the voltage value. At time T0, the application of the high-frequency voltage (power transmission) is stopped. Point 1201 is a point on the envelope of the high-frequency voltage, and is the high-frequency voltage at time T1. (T1, A1) in FIG. 12(A) indicates that the voltage value at time T1 is A1. Similarly, point 1202 is a point on the envelope of the high-frequency voltage, and is the high-frequency voltage at time T2. (T2, A2) in FIG. 12(A) indicates that the voltage value at time T2 is A2.

[0035] The Q value is measured based on the change in the voltage value over time after time T0. For example, the Q value is calculated using Equation 1 based on the time, voltage value, and angular velocity ω (ω=2πf, f is the operating frequency of the high-frequency voltage) of points 1201 and 1202 on the voltage value envelope. TIFF2025188143000002.tif2579 (Formula 1) Next, the process for measuring the Q-factor in the time domain by the power transmitting device 100 in this embodiment will be described with reference to FIG. 12(B). Waveform 1203 shows the value of the high-frequency voltage applied to the power transmitting coil 303, and its frequency is between 110 kHz and 148.5 kHz, which is used in the Qi standard. Points 1204 and 1205 are part of the envelope of the voltage value. The power transmitting unit 302 of the power transmitting device 100 stops power transmission from time T0 to T5. The second Q-factor measuring unit 401 of the power transmitting device 100 measures the Q-factor based on the voltage value A3 (point 1204) at time T3, the voltage value A4 (point 1205) at time T4, the operating frequency of the high-frequency voltage, and (Equation 1). The power transmitting unit 302 of the power transmitting device 100 resumes power transmission at time T5. In this way, the second Q value measurement is performed by the power transmitting device 100 momentarily interrupting power transmission and measuring the Q value based on the elapsed time, the voltage value, and the operating frequency.

[0036] In the third foreign matter detection method, it is sufficient to measure (T3, A3) and (T4, A4), and it is not necessary to measure the second Q value. That is, as shown in (Equation 1), the presence or absence of a foreign matter may be detected by using an index based on the value of T4-T3 and the ratio of A4 to A3 (A4 / A3) or the ratio of A3 to A4 (A3 / A4). Specifically, the presence or absence of a foreign matter may be detected by comparing the index with a threshold value.

[0037] In the third foreign object detection method, the current value may be measured instead of the voltage value, and the presence or absence of a foreign object may be detected using an index based on the ratio of the current values. That is, the current value at time T3 and the current value at time T4 may be measured. The second Q value may also be obtained based on the current values.

[0038] (Operation of conventional power transmitting device and power receiving device) The operations of the conventional power transmitting device 100 and power receiving device 102 will be described with reference to Fig. 6A. In the description of Fig. 6A, it is assumed that the power transmitting device 100 and power receiving device 102 are, respectively, power transmitting device and power receiving device compliant with WPC standard v1.2.3.

[0039] The power transmitting device 100 transmits an Analog Ping to detect an object present near the power transmitting coil 303 (F600). The Analog Ping is a pulsed power used to detect an object. The Analog Ping is a very small power that cannot activate the control unit 200 even if the power receiving device 102 receives it. The power transmitting device 100 detects an object by detecting a shift in the resonant frequency of the voltage value inside the power transmitting coil 303 or a change in the voltage and current values ​​flowing through the power transmitting coil 303 due to an object present near the power transmitting coil 303 using the Analog Ping. When the power transmitting device 100 detects an object using the Analog Ping, it measures the Q value of the power transmitting coil 303 using the first Q value measurement described above (F601). Then, following the first Q value measurement, the power transmitting device 100 starts transmitting a Digital Ping (F602). The Digital Ping is power for starting the control unit 200 of the power receiving device 102, and is greater than the Analog Ping. The Digital Ping is then transmitted continuously. That is, the power transmitting device 100 continues to transmit power equal to or greater than the Digital Ping from the time when the power transmitting device 100 starts transmitting the Digital Ping (F602) until it receives an EPT (End Power Transfer) packet (described later) from the power receiving device 102 (F622).

[0040] When the power receiving device 102 receives a Digital Ping and starts up, it stores the voltage value of the received Digital Ping in a Signal Strength packet and transmits the Signal Strength packet to the power transmitting device 100 (F603). Next, the power receiving device 102 transmits to the power transmitting device 100 an ID packet storing an ID including version information of the WPC standard to which the power receiving device 102 conforms and device identification information (F604). Furthermore, the power receiving device 102 transmits to the power transmitting device 100 a Configuration packet including information such as the maximum value of power that the voltage control unit 203 supplies to the load (charging unit 205) (F605). The power transmitting device 100 receives the ID packet and the Configuration packet. Then, when the power transmitting device 100 determines from these packets that the power receiving device 102 supports an extended protocol of the WPC standard v1.2 or later (including Negotiation, which will be described later), it responds with an ACK (F606).

[0041] Upon receiving the ACK, the power receiving device 102 transitions to a negotiation phase in which negotiations are conducted regarding the power to be transmitted and received. First, the power receiving device 102 transmits an FOD Status packet to the power transmitting device 100 (F607). In this embodiment, this FOD Status packet is referred to as "FOD(Q1)." The power transmitting device 100 performs foreign object detection using the first foreign object detection method based on the Q value (Q value measured in the frequency domain) stored in the received FOD(Q1) and the Q value measured in the first Q value measurement. Then, if the power transmitting device 100 determines that there is a high possibility that a foreign object is not present, it transmits an ACK indicating the determination result to the power receiving device 102 (F608).

[0042] Upon receiving the ACK, the power receiving apparatus 102 negotiates Guaranteed Power (GP), which is the maximum value of the power value that the power receiving apparatus 102 requests to receive. The Guaranteed Power indicates the load power of the power receiving apparatus 102 (the power consumed by the battery 206) agreed upon with the power transmitting apparatus 100. This negotiation is realized by the power receiving apparatus 102 transmitting to the power transmitting apparatus 100 a packet that stores the value of the requested Guaranteed Power, which is one of the Specific Requests defined in the WPC standard (F609). In this embodiment, this packet is called an "SRQ(GP)." The power transmitting apparatus 100 responds to the SRQ(GP) taking into consideration the power transmission capability of the power transmitting apparatus 100 and the like. If the power transmitting apparatus 100 determines that the Guaranteed Power is acceptable, it transmits an ACK indicating that the request has been accepted (F610). In this embodiment, it is assumed that the power receiving apparatus 102 requests 15 watts as Guaranteed Power in the SRQ(GP). When the negotiation of multiple parameters including the Guaranteed Power is completed, the power receiving device 102 transmits an "SRQ (EN)" of the Specific Requests requesting the end of the negotiation (End Negotiation) to the power transmitting device (F611). Then, the power transmitting device 100 transmits an ACK in response to the SRQ (EN) (F612), ends the negotiation, and transitions to the Power Transfer phase in which the power determined by the Guaranteed Power is transmitted and received.

[0043] Next, the power transmitting device 100 performs foreign object detection based on the above-described power loss technique (second foreign object detection method). First, the power transmitting device 100 receives RP1 from the power receiving device 102 (F613). The power transmitting device 100 accepts the received power value stored in RP1 and the transmitted power value of the power transmitting device 100 when the received power was obtained as a calibration data point (corresponding to point 1100 in FIG. 11). Then, the power transmitting device 100 transmits an ACK indicating acceptance of the calibration data point to the power receiving device 102 (F614).

[0044] After receiving the ACK, the power receiving device 102 transmits a Control Error (hereinafter referred to as CE) to the power transmitting device 100, requesting that the power transmitting device 100 increase or decrease the receiving voltage (or receiving current, receiving power). A sign and a numerical value are stored in the CE, and a positive sign indicates a request to increase power, a negative sign indicates a request to decrease power, and a zero numerical value indicates a request to maintain power. Here, the power receiving device 102 transmits a CE(+), which indicates an increase in power, to the power transmitting device 100 (F615).

[0045] Upon receiving CE(+), the power transmitting device 100 changes the setting value of the power transmitting unit 302 to increase the transmitted power (F616). When the received power increases in response to CE(+), the power receiving device 102 supplies the received power to the load (the charging unit 205 or the battery 206) and transmits RP2 to the power transmitting device 100 (F617). The power transmitting device 100 accepts the received power value stored in RP2 and the transmitted power value of the power transmitting device 100 at that time as a calibration data point (corresponding to point 1101 in FIG. 11). Then, the power transmitting device 100 transmits an ACK indicating acceptance of the calibration data point to the power receiving device 102 (F618). At this point, the power transmitting device 100 has acquired two calibration data points (points 1100 and 1101 in FIG. 11), and therefore can derive a calibration curve (straight line 1102 in FIG. 11).

[0046] At this point, the power transmitting device 100 and the power receiving device 102 have transitioned to the Power Transfer phase, and the power transmitting device 100 is transmitting power that the power receiving device 102 can receive, up to 15 watts, negotiated in the Negotiation phase. The power receiving device 102 periodically transmits to the power transmitting device 100 a CE requesting the power transmitting device 100 to maintain the transmitted power and an RP0 storing the current received power value (F619, F620). Upon receiving RP0 from the power receiving device 102, the power transmitting device 100 performs foreign object detection based on the second foreign object detection method described above. If the power transmitting device 100 determines, as a result of the foreign object detection, that there is a high possibility that no foreign object is present, it transmits an ACK to the power receiving device 102 (F621). Thereafter, when charging of the battery 206 is completed, the power receiving device 102 transmits an EPT (End Power Transfer) packet to the power transmitting device 100 requesting that power transmitting device 100 stop transmitting power (F622).

[0047] In this manner, wireless power transmission is performed between the power transmitting device 100 and the power receiving device 102 that comply with the WPC standard v1.2.3.

[0048] As shown in the processing example of FIG. 6A , foreign object detection is performed using the power loss method during the power transfer phase. However, using only one foreign object detection method leaves a certain degree of possibility for erroneous detection of a foreign object when one is not present, or conversely, for erroneous determination of the absence of a foreign object when one is present. In contrast, combining multiple foreign object detection methods can be expected to improve the accuracy of foreign object detection. In particular, the power transfer phase is the phase in which the TX transmits power, and if a foreign object is present between the TX and RX during power transmission, heat generation from the foreign object increases. Note that even if a foreign object is not between the TX and RX, it can receive power and generate heat if it is present within the power transmission range. Therefore, performing multiple foreign object detections during this phase offers significant benefits for improving foreign object detection accuracy. Therefore, in this embodiment, a foreign object detection method other than the power loss method is introduced into the power transfer phase.

[0049] Here, foreign object detection based on a Q value (first Q value) measured in the frequency domain (first foreign object detection method) sweeps the frequency to search for the resonant frequency for each measurement. If such a sweep is performed while the power transmitting device 100 is transmitting relatively large power, such as during the Digital Ping or Power Transfer phase, it may cause an increase in switching noise in the power transmitting unit 302. On the other hand, foreign object detection based on a Q value (second Q value) measured in the time domain (third foreign object detection method) can be performed at a single frequency and does not require frequency sweeping. Therefore, it can be performed at the operating frequency during power transmission during the Digital Ping or Power Transfer phase, and has little effect on switching noise. In this embodiment, in the second Q value measurement, when the power transmitting device stops transmitting power, the switch 208 is turned on to configure a closed circuit including the power receiving coil 201 and the resonant capacitor 207. This allows the second Q value to be measured while eliminating the effects of load fluctuations in the power receiving device 102.

[0050] When applying the third foreign object detection method to the WPC standard, various configurations of the power receiving device 102 are assumed, and therefore, the power transmitting device 100 needs to appropriately control the processing performed according to the capabilities of the power receiving device 102. For example, if the power transmitting device 100 performs the second Q-value measurement on a power receiving device 102 that cannot be controlled to form a closed circuit, the measurement will be affected by fluctuations in the load of the power receiving device 102 and the Q-value will not be measured correctly. Furthermore, although the second Q-value measurement may be performed on the power receiving device 102 side, the power transmitting device 100 cannot determine whether to perform the second Q-value measurement itself unless it knows the capabilities of the power receiving device 102. For example, if the power receiving device 102 can form a closed circuit but cannot perform the second Q-value measurement, the power transmitting device 100 will not be able to determine the presence or absence of a foreign object unless it measures the second Q-value. Similarly, if the capability of the power receiving device 102 is unknown, the power transmitting device 100 cannot determine whether to receive the measurement result of the second Q value from the power receiving device 102. For example, if the power transmitting device 100 attempts to receive the measurement result from the power receiving device 102 even though the power receiving device 102 is unable to measure the second Q value, unnecessary waiting time will occur. On the other hand, if the power transmitting device 100 does not receive the measurement result from the power receiving device 102 even though the power receiving device 102 is able to measure the second Q value, a state mismatch will occur between the power transmitting device 100 and the power receiving device 102. For this reason, in this embodiment, a control method is used to appropriately apply the third foreign object detection method based on measurement of the second Q value to the WPC standard. This control method will be described below.

[0051] (Explanation of operation when the third foreign object detection method is applied to the WPC standard) FIG. 6B shows an example of the flow of processing executed by the power transmitting device 100 and the power receiving device 102 according to this embodiment. Note that the same processes as those in FIG. 6A are denoted by the same reference numerals, and description thereof will be omitted. After executing the processes of F600 to F604, the power receiving device 102 transmits a Configuration packet to the power transmitting device 100 (F623). In this embodiment, the Configuration Packet notifies the power transmitting device 100 of capability information about the power receiving device 102. In this embodiment, the Configuration Packet defines a Short Ability bit and a Measure Ability bit as the capability information to be notified. The Short Ability bit is information indicating whether the power receiving device 102 is capable of controlling the configuration of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for the second Q-value measurement. For example, if the power receiving device 102 has the capability of controlling the configuration of a closed circuit for the second Q-value measurement, the power receiving device 102 stores "1" in the Short Ability bit, and if not, stores "0". The Measure Ability bit is information indicating whether the power receiving device 102 is capable of measuring the second Q value of the power receiving circuit. For example, if the power receiving device 102 has the ability to measure the second Q value of the power receiving circuit, the power receiving device 102 stores "1" in the Measure Ability bit; otherwise, the power receiving device 102 stores "0." Note that this information may be information indicating whether the power receiving device 102 is capable of performing a predetermined process associated with foreign object determination based on the measurement of the second Q value performed by the power transmitting device 100. In other words, whether a closed circuit can be configured or whether the power receiving device 102 is capable of measuring the second Q value of the power receiving circuit is merely one type of this predetermined process, and information bits regarding other processes may also be transmitted from the power receiving device 102 to the power transmitting device 100.

[0052] FIG. 13 shows the configuration of a Configuration Packet of the WPC Standard v1.2.3. Note that portions unrelated to the present embodiment will not be described here. The Configuration Packet of the WPC Standard v1.2.3 includes multiple Reserved areas. Specifically, an area 1300 from bit 0 to bit 7 of Bank 1, an area 1301 from bit 4 to bit 6 of Bank 2, and an area 1302 from bit 0 to bit 2 of Bank 4 are all Reserved areas. In the present embodiment, as an example, the Short Ability bit is allocated to bit 2 of Bank 4, and the Measure Ability bit is allocated to bit 1 of Bank 4. These bits may also be allocated to other Reserved areas. Alternatively, information indicating the version of the WPC Standard may be allocated to the Reserved area instead of these bits. In this case, the version may indicate whether the power receiving device 102 is capable of controlling the power receiving device 102 to configure a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for second Q-value measurement, and whether the power receiving device 102 is capable of measuring the second Q-value of the power receiving circuit. For example, a future version of the WPC standard may stipulate that a power receiving device 102 compliant with that version must have these functions. In this case, the version information of the power receiving device 102 is notified in the configuration packet, allowing the power transmitting device 100 to determine whether the power receiving device 102 has these functions. Note that in the WPC standard v1.2.3, all of the bits in the above-mentioned reserved areas are 0. Also, a power transmitting device 100 that cannot use the third foreign object detection method ignores the values ​​stored in these reserved areas.

[0053] Note that, here, a case will be described in which the Short Ability bit and the Measure Ability bit are set in a Configuration Packet and transmitted from the power receiving device 102 to the power transmitting device 100, but this is not limiting. For example, this information may be included in a new packet that is not defined in the WPC standard and transmitted / received. Also, this information may be included in another packet defined in the WPC standard and transmitted / received.

[0054] In this embodiment, it is assumed that the power receiving device 102 is capable of controlling the configuration of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for measuring the second Q value, and is also capable of measuring the second Q value of the power receiving circuit. For this reason, the power receiving device 102 sets the Short Ability bit to "1" and transmits a Configuration Packet in which the Measure Ability bit is also set to "1" in F623. The power transmitting device 100 refers to the Short Ability bit and the Measure Ability bit included in the received Configuration Packet, and stores these values ​​in the memory 305.

[0055] After receiving the Configuration Packet, the power transmitting device 100 responds with an ACK (F606). Then, when the power receiving device 102 receives the ACK for the Configuration Packet, it transitions to the Negotiation phase. Then, in the Negotiation phase, the power transmitting device 100 and the power receiving device 102 negotiate regarding the third foreign object detection. In the second Q-value measurement, the power receiving device 102 negotiates the measurement start time, which is the time until the power transmitting unit 302 of the power transmitting device 100 stops transmitting power. This negotiation is performed by the power receiving device 102 transmitting to the power transmitting device 100 a packet that stores the value of the requested measurement start time, which is one of the Specific Requests defined in the WPC standard (F631). The power receiving device 102 determines the value of the requested measurement start time based on its own processing capability, etc., and transmits a packet that stores the value of the measurement start time to the power transmitting device 100. Here, this packet is called an "SRQ(M1)". The power transmitting device 100 responds to the SRQ(M1) taking into consideration the processing capability of the power transmitting device 100, etc. If the power transmitting device 100 determines that the measurement start time indicated in the SRQ(M1) is acceptable, it transmits an ACK, and if it determines that the measurement start time is unacceptable, it transmits a NAK. Here, it is assumed that the power transmitting device 100 has determined that the measurement start time is acceptable and transmitted an ACK (F632). Note that, as an example, it is assumed that the power receiving device 102 has requested 50 ms as the measurement start time of the Q value in the SRQ(M1).

[0056] The power receiving device 102 negotiates a window length, which is the length of a period during which the power transmitting unit 302 of the power transmitting device 100 stops power transmission (the period from time T0 to time T5) in the second Q-value measurement. This negotiation is performed by the power receiving device 102 transmitting to the power transmitting device 100 a packet containing a requested window length value, which is one of the Specific Requests defined in the WPC standard (F633). Here, this packet is referred to as an "SRQ(M2)." The power receiving device 102 determines the window length value based on the processing capability of the power receiving device 102 and transmits a packet containing the determined window length value to the power transmitting device 100. The power transmitting device 100 responds to the SRQ(M2) taking into consideration the processing capability of the power transmitting device 100. The power transmitting device 100 transmits an ACK if it determines that the window length indicated in the SRQ(M2) is acceptable, and transmits a NAK if it determines that the window length is unacceptable. Here, it is assumed that the power transmitting apparatus 100 determines that the window length is acceptable and transmits an ACK (F634). Note that, as an example, it is assumed here that the power receiving apparatus 102 requests a window length of 100 ms in the SRQ(M2).

[0057] Furthermore, the power receiving device 102 negotiates a timeout length, which is the time for the power transmitting device 100 to accept the Q-value measured by the power receiving device 102 in the second Q-value measurement from the power receiving device 102. This negotiation is performed by the power receiving device 102 transmitting to the power transmitting device 100 a packet that stores the value of the requested timeout length, which is one of the Specific Requests defined in the WPC standard (F635). Here, this packet is referred to as an "SRQ(M3)." The power receiving device 102 determines the value of the timeout length based on the processing capability of the power receiving device 102 and transmits a packet that stores the value of the timeout length to the power transmitting device 100. The power transmitting device 100 responds to the SRQ(M3) taking into consideration the processing capability of the power receiving device 102. The power transmitting device 100 transmits an ACK if it determines that the timeout length is acceptable, and transmits a NAK if it determines that the timeout length is unacceptable. Here, the power transmitting device 100 determines that the timeout length is acceptable and transmits an ACK (F636). In this embodiment, it is assumed that the power receiving apparatus 102 requests a timeout length of 500 ms in the SRQ (M3).

[0058] Here, in one example, a Type of Specific Request that is not defined in v1.2.3 may be assigned to each negotiation of the measurement start time, window length, and timeout length. Measure Delay Req is a packet that requests the power transmitting device 100 to change the measurement start time. Window Length Req is a packet that requests the power transmitting device 100 to change the window length. Timeout Req is a packet that requests the power transmitting device 100 to change the timeout length. These three packets are Reserved Packets whose packet type is not specified in WPC Standard v1.2.3. In this embodiment, of these Reserved Packets, a packet with a packet header of 0x40 is defined as a Measure Delay Req packet. Similarly, a packet with a packet header of 0x41 is defined as a Window Length Req packet, and a packet with a packet header of 0x42 is defined as a Timeout Req packet.

[0059] Furthermore, among the packets defined in the WPC standard v1.2.3, packets whose type is not defined, rather than Specific Request or General Request, may be defined as the above three packets. For example, instead of Specific Request or General Request, Reserved Packet or Proprietary Packet packets whose packet type is not defined may be defined as the above three packets. Furthermore, among General Request or Specific Request defined in the WPC standard v1.2.3, packets whose packet type is not defined may be defined as the above three packets. In other words, among General Request or Specific Request, Reserved Packet or Proprietary Packet whose packet type is not defined may be defined as the above three packets.

[0060] 6B, when the processes from F607 to F612 are executed in the Negotiation phase, the Negotiation phase ends and the system transitions to the Power Transfer phase. In the Power Transfer phase, the processes from F613 to F617 described above are executed. Here, it is assumed that a foreign object is placed in the Operating Volume immediately after the power receiving device 102 receives an ACK in F618. The power receiving device 102 transmits to the power transmitting device 100 a CE requesting the power transmitting device 100 to maintain the transmitted power and an RP0 storing the current received power value (F619, F620).

[0061] When the power transmitting device 100 receives RP0 from the power receiving device 102, it performs foreign object detection based on the second foreign object detection method described above. As a result of the foreign object detection, the power transmitting device 100 determines that there is a high possibility that a foreign object is present, and transmits a NAK to the power receiving device 102 (F624). When the power receiving device 102 receives the NAK from the power transmitting device 100, it transmits a Q2R packet to the power transmitting device 100, which is a packet requesting the start of third foreign object detection, in order to measure the presence or absence of a foreign object in more detail (F625). The Q2R packet is, for example, a packet in which the Reserved bit of a Received Power packet in the WPC standard is set to a value indicating that it is a Q2R packet, but is not limited to this. For example, the power receiving device 102 may request the start of third foreign object detection using an undefined Received Power packet mode, or may define a new packet to request the start of third foreign object detection. In addition, in this embodiment, a case is described in which the power receiving device 102 requests the start of third foreign object detection using a Q2R packet, but third foreign object detection may also be started in response to a NAK response to RP2 without using a Q2R packet.

[0062] When the power transmitting device 100 receives Q2R, it determines whether to perform third foreign object detection, and transmits an ACK to the power receiving device 102 if it determines to perform the third foreign object detection, or a NAK to the power receiving device 102 if it determines not to perform the third foreign object detection. Here, it is assumed that the power transmitting device 100 has determined to perform third foreign object detection. In this case, the power transmitting device 100 transmits an ACK to the power receiving device 102 (F626). After completing the transmission of the ACK, the power transmitting device 100 and the power receiving device 102 start third foreign object detection. In the third foreign object detection, the power transmitting device 100 and the power receiving device 102 measure a second Q value (F629, F630). After measuring the second Q value, the power receiving device 102 stores the second Q value measured by itself in a packet (QRS) and transmits this QRS to the power transmitting device 100 (F627). The QRS is a packet including at least the second Q value measured by the power receiving device 102, but may also include other information such as the current received power value. When the power transmitting device 100 receives the QRS from the power receiving device 102, the power transmitting device 100 determines the presence or absence of a foreign object based on the received second Q value of the power receiving device 102 and the second Q value measured by the power receiving device 102 itself. By determining the presence or absence of a foreign object by adding the second Q value measured by the power receiving device 102 to the second Q value measured by the power transmitting device 100, the presence or absence of a foreign object can be determined with higher accuracy. If the power transmitting device 100 determines that a foreign object is present, it transmits a NAK to the power receiving device 102, and if it determines that no foreign object is present, it transmits an ACK to the power receiving device 102. Here, it is assumed that the power transmitting device 100 determines that a foreign object is present. In this case, the power transmitting device 100 transmits a NAK to the power receiving device 102 (F628). Thereafter, the power transmitting device 100 stops power transmission.

[0063] (Flow of Third Foreign Object Detection Process in Power Transmitting Device 100) Next, an example of the flow of the third foreign object detection process in the power transmitting device 100 will be described with reference to Fig. 7. After receiving a third foreign object detection request, the power transmitting device 100 determines whether the power receiving device 102 can execute control to configure a closed circuit including the power receiving coil 201 and the resonant capacitor 207 for measuring the second Q value (S701). The power transmitting device 100 refers to the Short Ability bit stored in memory in the Configuration phase, for example, and if the value is 1, determines that such control is possible (YES in S701) and proceeds to S702. On the other hand, if the value of the Short Ability bit is 0, the power transmitting device 100 determines that such control is not possible (NO in S701), transmits a NAK (S708), and ends the process.

[0064] In S702, the power transmitting device 100 determines whether the power receiving device 102 is capable of measuring the second Q value of the power receiving circuit. For example, the power transmitting device 100 refers to the Measure Ability bit stored in memory in the Configuration phase, and if the value is 0, determines that measurement of the second Q value is not possible (NO in S702), and proceeds to S709. The power transmitting device 100 then measures the second Q value in its own device (S709), and proceeds to S706. On the other hand, if the value of the Measure Ability bit is 1, the power transmitting device 100 determines that measurement of the second Q value is possible (YES in S702), and proceeds to S703.

[0065] In S703, the power transmitting device 100 determines whether or not to measure the second Q value of the power transmitting circuit. If the power transmitting device 100 determines to measure the second Q value (YES in S703), it measures the second Q value (S704) and proceeds to S705. On the other hand, if the power transmitting device 100 determines not to measure the second Q value (NO in S703), it does not measure the second Q value and proceeds to S705. In S705, the power transmitting device 100 receives the second Q value from the power receiving device and proceeds to S706. At this time, if the power transmitting device 100 does not receive the second Q value from the power receiving device within the long timeout period after transmitting the ACK in F626, it ends the process and stops power transmission. By setting the timeout period, it is possible to appropriately proceed or stop the process when the second Q value is not transmitted from the power receiving device 102. In addition, at this time, an appropriate timeout length is determined and set through negotiation as described above according to the processing capability of the power receiving device 102, so that even a power receiving device 102 with low processing capability can complete transmission of the second Q value before the timeout.

[0066] In S706, the power transmitting device 100 determines whether or not a foreign object is present by using at least one of the second Q value measured in S704 and the second Q value received in S705. If the power transmitting device 100 determines that a foreign object is present (YES in S706), it transmits a NAK to the power receiving device 102 (S708), and on the other hand, if it determines that no foreign object is present (NO in S706), it transmits an ACK to the power receiving device 102 (S707), and ends the process.

[0067] 6B , the power transmitting device 100 confirms in S701 that the value of the Short Ability bit is 1, determines that the power receiving device 102 is capable of executing control to configure a closed circuit, and proceeds to S702. Then, in S702, the power transmitting device 100 confirms that the value of the Measure Ability bit is 1, determines that the power receiving device 102 is capable of measuring the second Q value, and proceeds to S703. Then, in S703, the power transmitting device 100 decides to measure the second Q value itself, and proceeds to S704. The power transmitting device 100 measures the second Q value itself in S704, and receives the second Q value measured by the power receiving device 102 in S705, and proceeds to S706. Next, in S706, the power transmitting device 100 determines that there is a foreign object using the second Q value received from the power receiving device 102 and the second Q value measured by the power transmitting device 100 itself, and in S708, sends a NAK to the power receiving device 102 and terminates the processing.

[0068] 7, in S701, the power transmitting device 100 determines whether the power receiving device 102 can execute control to configure a closed circuit, thereby preventing the power transmitting device 100 from measuring the second Q value for a power receiving device 102 that cannot execute such control. As a result, the power transmitting device 100 can prevent erroneous control from being executed due to measuring the Q value under inappropriate conditions.

[0069] In the present embodiment, when it is determined in step S701 that the power receiving device 102 is unable to execute control to configure a closed circuit, the power transmitting device 100 transmits a NAK and terminates the process. However, this is not limited to this. For example, the power transmitting device 100 may measure the second Q value when the power receiving device 102 does not configure a closed circuit and determine the presence or absence of a foreign object based on the measured second Q value. However, when the second Q value is measured when a closed circuit is not configured, it is expected that the measured value will be affected by fluctuations in the load of the power receiving device. For this reason, when such a measurement of the second Q value is used, the presence or absence of a foreign object is determined using a criterion different from the criterion for determining the presence or absence of a foreign object based on the measurement result of the second Q value when a closed circuit can be configured.

[0070] Furthermore, in S702, the power transmitting device 100 determines whether the power receiving device 102 has the ability to measure the second Q value of the power transmitting circuit. This prevents the power transmitting device 100 from measuring the second Q value even though the power receiving device 102 is unable to measure the second Q value, thereby preventing the foreign object detection flow from failing. Furthermore, the power transmitting device 100 can prevent the power receiving device 102 from unnecessarily waiting for the measurement result of the second Q value to be transmitted from the power receiving device 102 even though the power receiving device 102 is unable to measure the second Q value. Furthermore, when the power receiving device 102 is able to measure the second Q value, the power transmitting device 100 can prevent a state deviation from occurring due to not receiving the second Q value transmitted from the power receiving device 102.

[0071] Furthermore, in S704, the power transmitting device 100 measures the second Q value not only in the power receiving device 102 but also in its own device, thereby enabling highly accurate foreign object detection with reduced influence of noise, etc. Also, by determining in S703 that its own device will not measure the second Q value, the power transmitting device 100 can omit measuring the second Q value in its own device and determine the presence of a foreign object using the second Q value received from the power receiving device 102. This makes it possible to prevent unnecessary measurements from being made by simultaneously measuring the Q value in the power transmitting device 100 and the power receiving device 102.

[0072] (Flow of Third Foreign Object Detection Process in Power Receiving Device 102) Next, an example of the flow of the third foreign object detection process in the power receiving device 102 will be described with reference to FIG. 8. The power receiving device 102 determines whether or not the power receiving device 102 is capable of controlling the configuration of a closed circuit including the power receiving coil 201 and the resonant capacitor 207 to measure the second Q value (S801). If the power receiving device 102 determines that the power receiving device 102 is capable of controlling the configuration of a closed circuit (YES in S801), the process proceeds to S802. If the power receiving device 102 determines that the power receiving device 102 is not capable of controlling the configuration of a closed circuit (NO in S801), the process proceeds to S805. In S802, the power receiving device 102 determines whether or not the power receiving device 102 is capable of measuring the second Q value of the power receiving circuit. If the power receiving device 102 is capable of measuring the second Q value (YES in S802), the process proceeds to S803. If the power receiving device 102 is not capable of measuring the second Q value (NO in S802), the process proceeds to S805. The power receiving device 102 measures the second Q value in S803, and then transmits the Q value measured in S803 to the power transmitting device 100 in S804, and the process proceeds to S805. Then, in S805, the power receiving device 102 receives the result of foreign object detection from the power transmitting device 100 and ends the process.

[0073] 6B, the power receiving device 102 determines in S801 that it is possible to perform control to configure a closed circuit including the power receiving coil 201 and the resonant capacitor 207 to measure the second Q value. Also, the power receiving device 102 determines in S802 that it is possible to measure the second Q value of the power receiving circuit. Then, the power receiving device 102 executes the processes from S803 to S805 and ends the process in FIG. 8.

[0074] (Flow of Second Q-Value Measurement Process in Power Transmitting Device 100) An example of the flow of the measurement process of the second Q value of the power transmitting device 100, which is executed in S704 or S709 described above, will be described with reference to FIG. 9. The power transmitting device 100 stops power transmission within 50 ms, which is the value negotiated in the negotiation of the measurement start time, after completing the transmission of the ACK at F626 (after completing the transmission of the rear end of the ACK time domain) (S901). The power transmitting device 100 measures a voltage value A3 of the power transmitting coil at time T3 (S902) and also measures a voltage value A4 of the power transmitting coil at time T4 (S903). The power transmitting device 100 calculates the Q value as described above from the operating frequency, the time when the measurement was performed, and the voltage value (S904). Then, the power transmitting device 100 resumes power transmission after a time of 100 ms or more, which is the value negotiated in the negotiation of the window length, has elapsed since the power transmission was stopped in S901 (S905), and ends the process.

[0075] (Flow of Second Q-Value Measurement Process in Power Receiving Apparatus 102) An example of the flow of the measurement process of the second Q value of the power receiving device 102 executed in S803 will be described with reference to FIG. 10. The power receiving device 102 detects that power transmission has stopped within 50 ms, which is the value negotiated in the measurement start time negotiation, after completing reception of the ACK at F626 (receiving the rear end of the ACK time domain). Then, the power receiving device 102 executes control to configure a closed circuit including the power receiving coil 201 and the resonant capacitor 207 (S1001). The power receiving device 102 measures a voltage value A3 of the power receiving coil at time T3 (S1002), and also measures a voltage value A4 of the power receiving coil at time T4 (S1003). Then, the power receiving device 102 calculates a Q value from the operating frequency, the measurement time, and the voltage value (S1004). Thereafter, the power receiving device 102 reconnects the load before 100 ms, which is the value negotiated in the window length negotiation, elapses from the power transmission stop detected in S1001 (S1005), and ends the process. Note that the reconnection of the load is performed by turning off the switch 208.

[0076] The processes of FIGS. 7 to 10 can be realized, for example, by the control unit 300 of the power transmitting device 100 or the control unit 200 of the power receiving device 102 reading and executing a pre-stored program. However, this is not limiting, and at least a part of these processes may be realized by hardware. When realized by hardware, for example, by using a predetermined compiler, a dedicated circuit can be automatically generated on an FPGA from a program for realizing each processing step. Here, FPGA is an acronym for Field Programmable Gate Array. Furthermore, a gate array circuit may be formed in a manner similar to that of an FPGA, and hardware that executes at least a part of the above-described processes may be realized.

[0077] In this embodiment, the measurement start time is negotiated in advance, allowing the power receiving device 102 to recognize the timing when the power transmitting device 100 will stop power transmission and appropriately start measuring the second Q value. At this time, the negotiation of the measurement start time allows an appropriate measurement start time to be set depending on the process executed by the power receiving device 102 and its processing capacity, so that the power receiving device 102 can start measuring the second Q value at a timing appropriate for the power receiving device 102. For example, if the power receiving device 102 needs to transmit another packet around the time it measures the second Q value, the measurement start time can be negotiated so that the second Q value measurement can be completed before the packet transmission begins. This prevents a momentary interruption in power transmission for measuring the second Q value while the power receiving device 102 is transmitting another packet, thereby preventing a deterioration in power transmission efficiency. Furthermore, if it takes the power receiving device 102 a long time to start measuring the second Q value due to the hardware configuration or processing capacity of the power receiving device 102, the measurement start time is determined to be later depending on the capacity of the power receiving device 102. This allows the power transmitting device 100 to stop power transmission at the timing when the power receiving device 102 completes the configuration of a closed circuit and is ready to start the measurement process of the second Q value, for example.

[0078] Furthermore, in this embodiment, the window length is negotiated in advance, which allows the power receiving device 102 to reconnect the power receiving coil 201 to the load at an appropriate timing. That is, if power transmission is resumed while a closed circuit is formed in the power receiving device 102, an excessive current may flow through the power receiving coil 201 and the resonant capacitor 207. In contrast, in this embodiment, the window length is determined in advance through negotiation, which prevents such a situation from occurring. Furthermore, the time required to measure the second Q value may vary depending on the performance of the power receiving device 102 and the required measurement accuracy. In contrast, the power receiving device 102 of this embodiment negotiates the window length in accordance with its own performance and the required measurement accuracy, thereby ensuring a sufficient measurement period and preventing measurement failures and degradation of measurement accuracy.

[0079] In the above description, the timing to start measurement, the length of the measurement period, and the period until the measurement report of the second Q value in the power receiving device (timeout period) are all determined by negotiation, but at least one of these may be negotiated. That is, for example, negotiation of only one of these may be performed, or negotiation of only two of these may be performed. That is, these elements may be used independently, and it is not necessary that all of them be used at all times.

[0080] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0081] 300: Control unit, 303: Power transmission coil, 304: Communication unit, 401: Second Q value measurement unit, 403: Calibration processing unit, 405: Third foreign object detection processing unit

Claims

1. A power transmission device a power transmitting means for wirelessly transmitting power to a power receiving device; a communication means for receiving a specific request from the power receiving device, the specific request including information regarding a period during which power transmission from the power transmitting device is restricted; a detection means for detecting an object during a period in which power transfer is restricted after power transfer is started in the power transfer phase; A power transmission device comprising:

2. The power transmitting device according to claim 1 , wherein the object detection is a process for detecting a foreign object.

3. 3. The power transmitting device according to claim 1, wherein the communication unit receives information for limiting power transmission by the power transmitting device from the power receiving device in a negotiation phase.

4. A method performed by a power transmitting device, receiving a specific request from a power receiving device, the specific request including information regarding a period during which power transmission from the power transmitting device is restricted; After power transfer is started in the power transfer phase, object detection is performed during a period in which the power transfer is limited; A method comprising:

5. The method according to claim 4 , wherein, in the negotiation phase, information for limiting power transmission by the power transmitting device is received from the power receiving device.

6. A program for causing a computer to execute the method according to claim 4 or 5.

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