Power receiving device and method

Abstract

To suppress unnecessary stoppage of power transmission that may occur when calculating a power loss reference value used for detecting an object different from a power receiving device and a power transmitting device.SOLUTION: When a power receiving device satisfies a predetermined condition, a timeout period for processing related to the calculation of the power loss reference value is set to be longer than a timeout period when the predetermined condition is not satisfied.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to a power transmission device, a power receiving device, a wireless power transmission system, a control method for a power transmission device, a control method for a power receiving device, and a program. [Background technology]

[0002] In recent years, technological development of wireless power transmission systems has been widespread, and standards (WPC standards) have been established by the Wireless Power Consortium (WPC), a standardization body for wireless charging standards. Patent document 1 discloses a power transmission device and a power receiving device that conform to the WPC standards.

[0003] Furthermore, in wireless power transmission systems, it is crucial to detect foreign objects (hereinafter referred to as "foreign objects") that are different from the power receiving device and the power transmission device within the range to which the power transmission device can transmit power, and to control power transmission and reception accordingly. Patent Document 2 discloses a method for detecting foreign objects and restricting power transmission and reception when they are present near the power transmission and reception devices. Furthermore, Patent Document 3 discloses a technique for detecting foreign objects by applying a high-frequency signal to the power transmission coil of a wireless power transmission system for a certain period of time, measuring the Q value (Quality factor) from the time change of voltage inside the power transmission coil, and detecting foreign objects based on the change in the Q value. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-56959 [Patent Document 2] Japanese Patent Publication No. 2017-70074 [Patent Document 3] Japanese Patent Publication No. 2018-45845 [Overview of the project] [Problems that the invention aims to solve]

[0005] One method for detecting foreign objects is to use power loss. First, a baseline value for power loss without foreign objects between the power transmission equipment and the power reception equipment is calculated in advance from the difference between the power transmitted at the power transmission equipment and the power received at the power reception equipment. Then, during subsequent power transmission, it is determined whether or not foreign objects are present based on the power loss between the power transmission equipment and the power reception equipment calculated. Here, when calculating the baseline value for power loss in the absence of foreign objects in advance, it is desirable to perform foreign object detection using another method, for example, after each power loss calculation, in order to avoid calculations with foreign objects present. Also, in order to improve the accuracy of calculating the baseline value for power loss, it is conceivable to perform power loss calculation and foreign object detection for each calculation multiple times. However, a predetermined timeout period is set for the process related to calculating the baseline value for power loss. Therefore, if the calculation of the baseline value for power loss and foreign object detection for each calculation are performed multiple times, it may not be possible to complete the process within the timeout period, which could result in an unintended power outage.

[0006] In light of the aforementioned problems, this disclosure aims to suppress unnecessary power outages that may occur when calculating the reference value for power loss used to detect objects other than power receiving and power transmitting equipment. [Means for solving the problem]

[0007] The power transmission device according to this disclosure is a power transmission device that wirelessly transmits power to a power receiving device, and comprises: a first detection means for detecting whether or not an object other than the power transmission device and the power receiving device exists based on the power loss between the power transmission device and the power receiving device; an acquisition means for acquiring capability information relating to the power receiving device from the power receiving device; a second detection means for detecting whether or not an object other than the power transmission device and the power receiving device exists based on the attenuation state of the voltage or current waveform relating to the power transmission; a calculation means for calculating a reference value of power loss when no object other than the power transmission device and the power receiving device used for detection by the first detection means exists, based on the detection result by the second detection means; and a specification means for specifying a timeout time for the calculation of the reference value by the calculation means based on the capability information relating to the power receiving device acquired by the acquisition means, wherein the specification means selects a first value as the timeout time if the power receiving device does not meet predetermined conditions, and specifies a second value that is greater than the first value as the timeout time if the power receiving device meets the predetermined conditions. [Effects of the Invention]

[0008] According to this disclosure, it is possible to suppress unnecessary power outages that may occur when calculating the reference value of power loss used for detecting objects other than power receiving equipment and power transmitting equipment. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an example configuration of a wireless power transmission system according to an embodiment. [Figure 2] This is a block diagram showing an example of the internal configuration of a power receiving device according to an embodiment. [Figure 3] This is a block diagram showing an example of the internal configuration of a power transmission device according to an embodiment. [Figure 4] This is a block diagram showing an example of the functional configuration of a power transmission device according to an embodiment. [Figure 5] This flowchart shows an example of the basic processing procedure performed by the power transmission device in the first embodiment. [Figure 6] In the first embodiment, it is a flowchart showing an example of a selection processing procedure of a timeout time by a power transmission device. [Figure 7] It is a diagram for explaining an operation sequence by a power transmission device and a power reception device in the first embodiment. [Figure 8] In the second embodiment, it is a flowchart showing an example of a basic processing procedure executed by a power reception device. [Figure 9] In the second embodiment, it is a flowchart showing an example of a selection processing procedure of a maximum transmission time interval of an RP packet by a power reception device. [Figure 10] It is a diagram for explaining an operation sequence by a power transmission device and a power reception device in the second embodiment. [Figure 11] It is a diagram for explaining a foreign object detection method based on a power loss method. [Figure 12] It is a diagram for explaining a foreign object detection method based on a Q value measurement method in the time domain.

Embodiments for Carrying Out the Invention

[0010] (First Embodiment) Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present disclosure. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the present disclosure, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and duplicate explanations are omitted.

[0011] (Configuration of the System) Figure 1 shows an example configuration of the contactless charging system (wireless power transmission system) 100 according to this embodiment. As shown in Figure 1, the contactless charging system according to this embodiment is composed of a power receiving device 101 and a power transmitting device 102. Here, the power receiving device 101 and the power transmitting device 102 are assumed to conform to the WPC (Wireless Power Consortium) standard.

[0012] The power receiving device 101 is an electronic device that receives power from the power transmitting device 102 and charges its built-in battery. The power transmitting device 102 is an electronic device that wirelessly transmits power to the power receiving device 101, which is placed on the charging base 103. Hereinafter, being placed on the charging base 103 will be simply referred to as being placed on the power transmitting device 102. Range 104 indicates the range within which the power receiving device 101 can receive power transmitted from the power transmitting device 102. Note that the power receiving device 101 and the power transmitting device 102 have functions to perform applications other than contactless charging. Furthermore, in the following description, objects other than the power transmitting device 102 and the power receiving device 101 that are included in the power transmission range of the power transmitting device 102 will be referred to as foreign objects. Foreign objects are, for example, paper clips or IC cards. Foreign objects are not considered foreign objects if they are parts of the power receiving device 101, the power transmitting device 102, or other essential parts of the product into which they are incorporated, and which may unintentionally generate heat when exposed to the wireless power transmitted by the power transmitting antenna.

[0013] Furthermore, in the following explanation, "the power receiving device 101 is placed on the power transmitting device 102" means "the power receiving device 101 is included in the power transmission range of the power transmitting device 102." The power transmission range of the power transmitting device 102 is the range in which power can be transmitted to the power receiving device 101 using the power transmission coil. Also, the state in which the power receiving device 101 is placed on the power transmitting device 102 does not mean that the power receiving device 101 and the power transmitting device 102 are in contact. For example, the state in which the power receiving device 101 is included in the power transmission range without contact with the power transmitting device 102 shall also be considered as "the power receiving device 101 is placed on the power transmitting device 102." In addition, the power receiving device 101 may be configured to be placed on the side of the power transmitting device 102, for example, instead of being placed on top of the power transmitting device 102.

[0014] (Device configuration) Next, the configurations of the power receiving device 101 and the power transmitting device 102 according to this embodiment will be described. Note that the configuration described below is merely an example, and some (or in some cases all) of the described configuration may be replaced or omitted by other configurations that perform similar functions, and further configurations may be added to the described configuration. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0015] Figure 2 is a block diagram showing an example of the internal configuration of the power receiving device 101 according to this embodiment. Figure 3 is a block diagram showing an example of the internal configuration of the power transmitting device 102 according to this embodiment. The power receiving device 101 includes 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 resonant capacitor 207, a switch 208, a memory 209, and a timer 210.

[0016] The control unit 200 controls the entire power receiving device 101 by executing a control program stored in, for example, memory 209. The control unit 200 may also perform control for executing applications other than wireless power transmission. The control unit 200 is configured to include one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 200 may also be configured to include hardware dedicated to specific processing, such as an Application Specific Integrated Circuit (ASIC). Furthermore, the control unit 200 may be configured to include an array circuit, such as an FPGA (Field Programmable Gate Array), compiled to execute predetermined processing. The control unit 200 stores information that should be stored while various processing is being executed in memory 209. The control unit 200 also measures time using a timer 210.

[0017] The receiving coil 201 receives power from the transmitting coil 303 of the power transmission device 102. The receiving coil 201 is also connected to a resonant capacitor 207 and resonates at a specific frequency F2. The rectifier 202 converts the AC voltage and AC current received from the transmitting coil 303 via the receiving coil 201 into DC voltage and DC current. The voltage control unit 203 converts the level of the DC voltage input from the rectifier unit 202 into a DC voltage level at which the control unit 200 and the charging unit 205 operate.

[0018] The communication unit 204 performs control communication with the power transmission device 102 using in-band communication, based on the WPC standard. The communication unit 204 demodulates the electromagnetic waves input from the receiving coil 201 to acquire information transmitted from the power transmission device 102, and then modulates these electromagnetic waves with the load to superimpose the information to be transmitted to the power transmission device 102 onto the electromagnetic waves, thereby communicating with the power transmission device 102. In other words, the communication performed by the communication unit 204 is superimposed on the power transmission from the power transmission coil 303 of the power transmission device 102.

[0019] Battery 206 supplies the power necessary for control, power reception, and communication to the entire power receiving device 101. Battery 206 also stores the power received via the power receiving coil 201. Switch 208 is a switch for short-circuiting the power receiving coil 201 and the resonant capacitor 207, and is controlled by the control unit 200. When switch 208 is turned on, the power receiving coil 201 and the resonant capacitor 207 form a series resonant circuit. At this time, current flows only in the closed circuit between the power receiving coil 201, the resonant capacitor 207, and switch 208, and no current flows to the rectifier unit 202 and the voltage control unit 203. When switch 208 is turned off, current flows to the rectifier unit 202 and the voltage control unit 203 via the power receiving coil 201 and the resonant capacitor 207.

[0020] As described above, memory 209 stores various types of information. Note that memory 209 may also store information obtained by a different functional unit than the control unit 200. Timer 210 performs timing using, for example, a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

[0021] Next, an example of the internal configuration of the power transmission device 102 according to this embodiment will be described with reference to Figure 3. The power transmission device 102 includes a control unit 300, a power supply unit 301, a power transmission unit 302, a power transmission coil 303, a communication unit 304, a resonant capacitor 305, a switch 306, a memory 307, and a timer 308.

[0022] The control unit 300 controls the entire power transmission device 102 by executing a control program stored in, for example, the memory 307. The control unit 300 may also perform control for executing applications other than wireless power transmission. The control unit 300 is configured to include one or more processors, such as a CPU or MPU. The control unit 300 may also be configured to include hardware dedicated to specific processing, such as an application-specific integrated circuit (ASIC), or array circuits such as an FPGA compiled to execute predetermined processing. The control unit 300 stores information that should be stored while various processes are being executed in the memory 307. The control unit 300 also measures time using a timer 308.

[0023] The power supply unit 301 supplies the power necessary for control, power transmission, and communication to the entire power transmission device 102. The power supply unit 301 is, for example, a commercial power source or a battery.

[0024] The power transmission unit 302 converts the DC or AC power input from the power supply unit 301 into AC frequency power in the frequency band used for wireless power transmission, and outputs this AC frequency power to the power transmission coil 303, thereby generating electromagnetic waves for the power receiving device 101 to receive power. The frequency of the AC power generated by the power transmission unit 302 is several hundred kHz (for example, 110 kHz to 205 kHz). Based on instructions from the control unit 300, the power transmission unit 302 outputs AC frequency power to the power transmission coil 303 so that electromagnetic waves for transmitting power to the power receiving device 101 are output from the power transmission coil 303. The power transmission unit 302 also controls the intensity of the output electromagnetic waves by adjusting the voltage (transmission voltage) or current (transmission current) input to the power transmission coil 303. Increasing the transmission voltage or transmission current increases the intensity of the electromagnetic waves, and decreasing the transmission voltage or transmission current decreases the intensity of the electromagnetic waves. Furthermore, the power transmission unit 302 controls the output of AC frequency power so that power transmission from the power transmission coil 303 is started or stopped based on instructions from the control unit 300. The power transmission coil 303 is connected to a resonant capacitor 305 and resonates at a specific frequency F1.

[0025] The communication unit 304 performs control communication with the power receiving device 101 via in-band communication, based on the WPC standard. The communication unit 304 modulates the electromagnetic waves output from the power transmission coil 303 and transmits information to the power receiving device 101. The communication unit 304 also demodulates the electromagnetic waves output from the power transmission coil 303 and modulated at the power receiving device 101 to obtain the information transmitted by the power receiving device 101. In other words, the communication performed by the communication unit 304 is superimposed on the power transmission from the power transmission coil 303.

[0026] Switch 306 is a switch for short-circuiting the power transmission coil 303 and the resonant capacitor 305, and is controlled by the control unit 300. When switch 306 is turned on, the power transmission coil 303 and the resonant capacitor 305 form a series resonant circuit. At this time, current flows only in the closed circuit between the power transmission coil 303, the resonant capacitor 305 and switch 306. When switch 306 is turned off, power is supplied to the power transmission coil 303 and the resonant capacitor 305 from the power transmission unit 302. Memory 307 stores various information as described above. Note that memory 307 may store information obtained by a functional unit other than the control unit 300. Timer 308 performs timing, for example, by a count-up timer that measures the elapsed time from the time of activation, or a count-down timer that counts down from a set time.

[0027] Next, the functions of the control unit 300 of the power transmission device 102 will be described with reference to Figure 4. Figure 4 is a block diagram showing an example of the functional configuration of the control unit 300 of the power transmission device 102. The power transmission device 102 has a communication processing unit 401, a power transmission processing unit 402, a foreign object detection processing unit 403, and a time selection processing unit 404. The functions of each of these processing units are realized as programs that operate in the control unit 300. Furthermore, each of these processing units is configured as an independent program and operates in parallel while synchronizing the programs through event processing, etc.

[0028] The communication processing unit 401 controls communication with the power receiving device 101 based on the WPC standard via the communication unit 304. The power transmission processing unit 402 controls the power transmission unit 302 and controls the power transmission to the power receiving device 101.

[0029] The foreign object detection processing unit 403 detects foreign objects by measuring power loss between the power transmission device and the power receiving device, and the Q value in the power transmission coil 303. The foreign object detection processing unit 403 performs foreign object detection using the power loss method expected by the WPC standard, and foreign object detection using the Q value. In addition, the foreign object detection processing unit 403 may perform foreign object detection processing using other methods. For example, in a power transmission device 102 equipped with NFC (Near Field Communication) communication functionality, foreign object detection processing may be performed using the opposing device detection function according to the NFC standard. Furthermore, in addition to the two foreign object detection methods described above, the foreign object detection processing unit 403 can also perform foreign object detection based on the time-domain Q value measurement method described later. Moreover, in addition to detecting foreign objects, the foreign object detection processing unit 403 can also detect changes in the state on the power transmission device 102. For example, it can also detect increases or decreases in the number of power receiving devices on the power transmission device 102.

[0030] The time selection processing unit 404 selects a timeout period for the Calibration phase, which will be described later. In this embodiment, the timeout period is selected based on information such as whether the power receiving device 101 is capable of performing foreign object detection based on the Q-value measurement method in the time domain, and the number of attempts to perform foreign object detection based on the Q-value measurement method in the time domain. Details of the process for selecting the timeout period will be described later.

[0031] In this system, wireless power transmission is performed using an electromagnetic induction method for contactless charging, based on the WPC standard. Specifically, the power receiving device 101 and the power transmitting device 102 perform wireless power transmission for contactless charging based on the WPC standard between the power receiving coil 201 of the power receiving device 101 and the power transmitting coil 303 of the power transmitting device 102. In this embodiment, the wireless power transmission method (contactless power transmission method) is not limited to the method specified in the WPC standard, but may also be a method utilizing other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, lasers, etc. Furthermore, in this embodiment, wireless power transmission is used for contactless charging, but wireless power transmission may also be used for purposes other than contactless charging.

[0032] The WPC standard specifies that the amount of power guaranteed when the receiving device 101 receives power from the transmitting device 102 is defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value that is guaranteed to be output to the load of the receiving device 101, such as a charging circuit, even if the relative positions of the receiving device 101 and the transmitting device 102 change and the power transmission efficiency between the receiving coil 201 and the transmitting coil 303 decreases. For example, if the GP is 15 watts, even if the relative positions of the receiving coil 201 and the transmitting coil 303 change and the power transmission efficiency decreases, the transmitting device 102 will be controlled to output 15 watts of power to the load inside the receiving device 101 and will transmit power accordingly.

[0033] Furthermore, the WPC standard specifies a method for the power transmission device 102 to detect the presence of an object other than a power receiving device (foreign object) around the power transmission device 102 (near the power receiving antenna). More specifically, it first specifies a method for detecting foreign objects by changing the quality coefficient (Q value) of the power transmission antenna (power transmission coil) 303 in the power transmission device 102 (foreign object detection method using Q value). The WPC standard also specifies a power loss method for detecting foreign objects by the difference between the power transmitted by the power transmission device 102 and the power received by the power receiving device 101. The foreign object detection process using Q value is performed before power transmission. In addition, the foreign object detection process using the power loss method is performed during power transmission (power transmission) based on the data obtained from the calibration process described later. Details will be described later.

[0034] Here, there are essential metal parts that constitute the power receiving device 101 (and the product incorporating the power receiving device 101) or the power transmitting device 102 (and the product incorporating the power transmitting device 102). Among these essential metal parts, there are some that may unintentionally generate heat when exposed to the wireless power transmitted by the power transmitting coil 303. Metal parts that may generate heat include, for example, the metal frame around the power transmitting coil 303 or the power receiving coil 201. In this embodiment, foreign matter refers to objects other than such metal parts that may generate heat when exposed to the wireless power transmitted by the power transmitting coil. For example, paper clips, IC cards, etc., fall into this category.

[0035] Furthermore, the power receiving device 101 and the power transmitting device 102 in this embodiment perform communication for power transmission and reception control based on the WPC standard and communication for equipment authentication before performing power transmission. Here, the communication for power transmission and reception control based on the WPC standard will be described.

[0036] The WPC standard defines multiple phases, including the Power Transfer phase in which power transmission takes place and the phases preceding the actual power transmission. Communication for necessary power transmission and reception control takes place in each phase. The phases preceding power transmission include the Selection phase, Ping phase, Identification and Configuration phase, Negotiation phase, and Calibration phase. In the following, the Identification and Configuration phase will be referred to as the I&C phase.

[0037] During the Selection phase, the power transmission device 102 intermittently transmits Analog Pings to detect the presence of an object within the power transmission range (for example, when a power receiving device 101 or a conductive piece is placed on the charging base 103).

[0038] In the Ping phase, the power transmitter 102 transmits a Digital Ping with higher power than the Analog Ping. The power of the Digital Ping is sufficient to activate the control unit 200 of the power receiver 101, which is mounted on top of the power transmitter 102. The power receiver 101 notifies the power transmitter 102 of the magnitude of the received voltage using a Signal Strength Packet. In this way, the power transmitter 102 recognizes that the object detected in the Selection phase is the power receiver 101 by receiving the response from the power receiver 101 that received the Digital Ping. Upon receiving notification of the received voltage, the power transmitter 102 transitions to the I&C phase. Also, before transmitting the Digital Ping, the power transmitter 102 measures the Q-Factor of the power transmitting antenna (power transmitting coil). This measurement result is used when performing foreign object detection processing using the Q value before transmitting the Digital Ping.

[0039] In the I&C phase, the power transmission device 102 identifies the power receiving device 101 and obtains equipment configuration information (capacity information) from the power receiving device 101. To this end, the power receiving device 101 sends an ID Packet and a Configuration Packet. The ID Packet contains identifier information as identification information for the power receiving device 101, and the Configuration Packet contains equipment configuration information (capacity information) for the power receiving device 101. Upon receiving the ID Packet and Configuration Packet, the power transmission device 102 responds with an acknowledgment (ACK). The I&C phase then ends, and the system moves on to the next Negotiation phase.

[0040] In the Negotiation phase, the GP value is determined based on the GP value requested by the power receiving device 101 and the power transmission capacity of the power transmission device 102. The foreign object detection processing unit 403 of the power transmission device 102 performs foreign object detection processing using the Q value in accordance with the request from the power receiving device 101. Furthermore, the WPC standard specifies a method in which, after transitioning to the Power Transfer phase (described later), the same processing as the Negotiation phase is performed again at the request of the power receiving device 101. Hereinafter, the phase in which these processes are performed after transitioning from the Power Transfer phase will be referred to as the Renegotiation phase.

[0041] In the Calibration phase, the power receiving device 101 notifies the power transmission device 102 of a predetermined power received value (power received value under light load conditions / power received value under maximum load conditions) based on the WPC standard, and the power transmission device 102 makes adjustments to efficiently transmit power. The power received value notified to the power transmission device 102 is used for foreign object detection processing using a power loss method.

[0042] During the Power Transfer phase, control is performed to ensure continued power transmission and to stop power transmission due to errors or full charge. The power transmission device 102 and the power receiving device 101 communicate for these power transmission and reception control purposes using in-band communication, which superimposes signals using the same antenna (coil) as wireless power transmission, based on the WPC standard. The range in which in-band communication based on the WPC standard is possible between the power transmission device 102 and the power receiving device 101 is approximately the same as the power transmission range. In other words, in Figure 1, range 104 represents the range in which wireless power transmission and in-band communication are possible using the power transmission and reception coils of the power transmission device 102 and the power receiving device 101.

[0043] (Foreign object detection method) Next, the foreign object detection method in this embodiment will be described in detail. In addition to the foreign object detection methods (1) and (2) below, a foreign object detection process using the Q value specified in the WPC standard is performed in the Ping phase and the Negotiation phase.

[0044] (1) Foreign object detection method based on power loss technique A foreign object detection method based on the power loss method specified in the WPC standard will be explained using Figure 11. In Figure 11, the horizontal axis represents the power transmitted by the power transmission device 102, and the vertical axis represents the power received by the power receiving device 101. First, the power transmission device 102 sends a Digital Ping to the power receiving device 101. Then, the power transmission device 102 receives the power received value Pr1 in the light load state when the power receiving device 101 receives power from the power receiving device 101 as a Received Power Packet (mode1) (hereinafter, RP packet (mode1)). At this time, the power receiving device 101 does not supply the received power to the load (charging circuit and battery, etc.). Then, the power transmission device 102 stores the power received value Pr1 at point 1100 in Figure 11 and the power transmitted value Pt1 at that time. At this time, the power transmission device 102 determines that the power loss between the power transmission device 102 and the power receiving device 101 when transmitting power at the transmission power value Pt1 is Pt1-Pr1(P loss1 ) is recognized as such.

[0045] Next, the power transmission device 102 receives the power received by the power receiving device 101 at the maximum load state, Pr2, as a Received Power Packet (mode2) (hereinafter, RP packet (mode2)) from the power receiving device 101. At this time, the power receiving device 101 supplies the received power to the load. The power transmission device 102 then stores the power received power value Pr2 and the power transmitted power value Pt2 at point 1101 in Figure 11. At this time, the power transmission device 102 calculates that the power loss between the power transmission device 102 and the power receiving device 101 when transmitting power at the power transmitted power value Pt2 is Pt2 - Pr2(P loss2 ) is recognized as such.

[0046] Then, through the calibration process, the power transmission device 102 linearly interpolates between point 1100 and point 1101 to create a straight line 1102. The straight line 1102 shows the relationship between the transmitted power and the received power when there is no foreign object around the power transmission device 102 and the power reception device 101. Therefore, the power transmission device 102 can predict the received power in a state where there is a high possibility of no foreign object from the transmitted power value and the straight line 1102. For example, when the transmitted power value is Pt3, from point 1103 on the straight line 1102 indicating the transmitted power value Pt3, it can be predicted that the received power value is Pr3. Note that the process of creating this straight line is performed in the Calibration phase.

[0047] Here, assume that when the power transmission device 102 transmits power to the power reception device 101 at the transmitted power value Pt3, the power transmission device 102 receives the received power value Pr3' from the power reception device 101. The power transmission device 102 calculates the value Pr3 - Pr3' (= P loss _FO) by subtracting the actually received power value Pr3' from the power reception device 101 from the received power value Pr3 in a state where there is no foreign object. This power value P loss _FO can be considered as the power loss consumed by the foreign object when there is a foreign object between the power transmission device 102 and the power reception device 101. Therefore, when the power value P loss _FO estimated to be consumed by the foreign object exceeds a predetermined threshold value, it is determined that there is a foreign object.

[0048] Alternatively, the power transmission device 102 previously obtains the power loss Pt3 - Pr3 (P loss3 ) between the power transmission device 102 and the power reception device 101 from the received power value Pr3 in a state where there is no foreign object. Then, the power transmission device 102 obtains the power loss Pt3 - Pr3' (P loss3 ') between the power transmission device 102 and the power reception device 101 in a state where there is a foreign object from the received power value Pr3' received from the power reception device in a state where there is a foreign object. Then, using P loss3 '-P loss3 (=P loss _FO), the power value P lossYou may also calculate _FO. As described above, the estimated power value P consumed by the foreign object loss The way to find _FO is Pr3-Pr3'(=P loss You can also obtain it as _FO) or P loss3 '-P loss3 (=P loss You can also obtain it as _FO).

[0049] After acquiring a straight line 1102 representing a reference value through a calibration process, the power transmission device 102 periodically receives the current received power value (Pr3') from the power receiving device 101 during the Power Transfer phase. The current received power value transmitted periodically by the power receiving device 101 is sent to the power transmission device 102 as a Received Power Packet (mode0) (hereinafter, RP packet (mode0)). The power transmission device 102 performs foreign object detection based on the received power value stored in the RP packet (mode0) and the straight line 1102. In this embodiment, points 1100 and 1101, which are used to acquire the straight line 1102 representing the relationship between transmitted power and received power when no foreign objects are present around the power transmission device 102 and the power receiving device 101, are referred to as calibration data points. Furthermore, the line segment (straight line 1102) obtained by interpolating at least two calibration data points is referred to as the Calibration curve.

[0050] If foreign matter is present when deriving the calibration curve, for example, the straight line 1106 connecting point 1100 and point 1104 may be derived as the calibration curve 1105. The same applies to the straight line 1108 connecting point 1107 and point 1104. Therefore, in this embodiment, foreign matter detection based on the Q-value measurement method in the time domain, as described below, is performed to detect the absence of foreign matter and to derive the correct calibration curve.

[0051] (2) Foreign object detection method based on Q-value measurement method in the time domain The following describes a foreign object detection method based on the Q-value measurement method in the time domain, with reference to Figure 12. In Figure 12(a), waveform 1200 shows the time course of the high-frequency voltage applied to the end of the power transmission coil 303 or resonant capacitor 305 of the power transmission device 102 (hereinafter simply referred to as the voltage value of the power transmission coil), with the horizontal axis representing time and the vertical axis representing voltage. In the example in Figure 12(a), it is shown that the application of high-frequency voltage (power transmission) was stopped at time T0. Point 1201 is a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T1. (T1, A1) at point 1201 indicates that the voltage value at time T1 is A1. Similarly, point 1202 is also a point on the envelope of the high-frequency voltage and represents the high-frequency voltage at time T2. (T2, A2) at point 1202 indicates that the voltage value at time T2 is A2. The quality factor (Q value) of the transmission coil 303 is measured based on the time variation of the voltage value after time T0. Specifically, the Q value is calculated using Equation 1 below, based on the time, voltage value, and frequency f of the high-frequency voltage (hereinafter referred to as the operating frequency) at points 1201 and 1202, which are the envelope of the voltage value. Q=πf(T2-T1) / ln(A1 / A2) (Formula 1)

[0052] Next, the process by which the power transmission device 102 measures the Q value in the time domain in this embodiment will be described with reference to Figure 12(b). Waveform 1203 shows the value of the high-frequency voltage applied to the power transmission coil 303, and its frequency is between 120 kHz and 148.5 kHz, as used in the Qi standard. Points 1204 and 1205 are part of the envelope of the voltage value.

[0053] For example, the power transmission processing unit 402 of the power transmission device 102 shall stop power transmission for a period of time T0 to T5. The foreign object detection processing unit 403 of the power transmission device 102 measures the Q value based on Equation 1 above, using the voltage value A3 (point 1204) at time T3, the voltage value A4 (point 1205) at time T4, and the operating frequency of the high-frequency voltage. The power transmission processing unit 402 of the power transmission device 102 shall resume power transmission at time T5. In this way, the Q value is measured based on the elapsed time, voltage value, and operating frequency when the power transmission device 102 momentarily interrupts power transmission. Hereafter, the period of time T0 to T5 during which power transmission is stopped will be referred to as the stop time.

[0054] If foreign matter is present near the power transmission device 102 and the power receiving device 101, the Q value decreases. This is because energy loss occurs due to the presence of foreign matter. Therefore, focusing on the slope of voltage attenuation, the slope of the line connecting point 1204 and point 1205 becomes steeper when foreign matter is present than when it is absent, as more energy is lost due to the foreign matter. This results in a higher attenuation rate of the waveform amplitude. In other words, the foreign matter detection method based on the Q value measurement method in the time domain determines the presence or absence of foreign matter based on the voltage attenuation state between point 1204 and point 1205. Furthermore, in actually determining the presence or absence of foreign matter, it is possible to make a determination by comparing some numerical value that represents this attenuation state. For example, the above-mentioned Q value can be used for the determination. Alternatively, the waveform attenuation of the current value may be used instead of the voltage value.

[0055] The downtime must be determined before measuring the Q value, taking into account the characteristics of the power transmission device 102 and the power receiving device 101. For example, the shortest possible downtime differs depending on the capabilities of the switches 306 and control unit 300 of the power transmission device 102, so the downtime must be longer than the shortest possible downtime. Also, the accuracy of foreign object detection differs even with the same downtime depending on the operating frequency and the amount of voltage drop, so it is necessary to select a downtime that can maintain a predetermined level of accuracy. Furthermore, depending on the type of power receiving device 101, it may not function properly if the received power drops for more than a certain period of time. Therefore, the downtime must be longer than the longest possible downtime that the power receiving device 101 can tolerate.

[0056] (Basic processing flow by power transmission device 102) Next, an example of the basic processing flow performed by the power transmission device 102 will be described. Figure 5 is a flowchart showing an example of the basic processing procedure performed by the power transmission device 102 in this embodiment. This process is realized, for example, by the control unit 300 of the power transmission device 102 executing a program read from the memory 307. This process is performed in response to the power of the power transmission device 102 being turned on, in response to the user of the power transmission device 102 inputting a command to start a contactless charging application, or in response to the power transmission device 102 being connected to a commercial power source and receiving power. This process may also be started by other triggers.

[0057] First, in S501, the control unit 300 of the power transmission device 102 executes the processes specified as the Selection phase and Ping phase of the WPC standard, and waits for the object to be placed on the power transmission device 102.

[0058] Here, referring to Figure 7, the processes defined as the Selection phase and Ping phase performed in S501 will be explained. In the Selection phase, the communication processing unit 401 of the power transmission device 102 repeatedly and intermittently transmits Analog Ping according to the WPC standard (F701). The control unit 300 of the power transmission device 102 detects that an object has been placed on it (F704) when the power receiving device 101 is placed on it (F702), causing a change in Analog Ping (F703). Then, when it is detected that an object is within the power transmission range, it moves to the Ping phase, and the communication processing unit 401 of the power transmission device 102 transmits Digital Ping according to the WPC standard (F705). The power receiving device 101 detects that it has been placed on the power transmission device 102 by the Digital Ping (F706). When the control unit 300 of the power transmission device 102 receives a predetermined response to its Digital Ping, it determines that the detected object is the power receiving device 101 and that the power receiving device 101 has been placed on the charging stand 103.

[0059] When the power receiving device 101 is detected to have been placed in S501, the communication processing unit 401 of the power transmitting device 102 then obtains identification information and capability information from the power receiving device 101 via I&C phase communication as defined in the WPC standard in S502. Here, the identification information received from the power receiving device 101 via ID Packet includes the Manufacturer Code and Basic Device ID as identifier information. The capability information received from the power receiving device 101 via Configuration Packet includes information elements that can identify the version of the WPC standard it supports. Furthermore, the capability information includes the Maximum Power Value, which is a value that identifies the maximum power that the power receiving device 101 can supply to the load, and information indicating whether or not it has the Negotiation function of the WPC standard.

[0060] The information described above is merely an example of the information to be acquired in S502. The identification information and capability information of the power receiving device 101 may be replaced by other information, or other information may be included in addition to the information described above. For example, the identification information may be any other identification information that can identify an individual power receiving device 101, such as a Wireless Power ID. Furthermore, the power transmitting device 102 may acquire the identification information and capability information of the power receiving device 101 by a method other than communication in the I&C phase of the WPC standard.

[0061] Next, in S503, the control unit 300 of the power transmission device 102 performs negotiation processing with the power receiving device 101 through communication in the negotiation phase as defined in the WPC standard, and determines the value of GP. Note that in S503, other procedures for determining GP may be performed in addition to the communication in the negotiation phase as defined in the WPC standard. Furthermore, the power transmission device 102 may, for example, obtain information in S502 indicating that the power receiving device 101 does not support the negotiation phase. In such cases, the power transmission device 102 may not perform communication in the negotiation phase and may set the value of GP to a small value (for example, one predetermined in the WPC standard). In addition, in the negotiation phase, in addition to the procedure for determining GP, information regarding foreign object detection based on the Q-value measurement method in the time domain is exchanged with the power receiving device 101. For example, the power receiving device 101 may notify the power receiving device 101 of supplementary information regarding whether or not it is capable of performing foreign object detection based on the Q-value measurement method in the time domain, or the power transmitting device 102 may notify the power receiving device 101 of the number of attempts to perform foreign object detection based on the Q-value measurement method in the time domain.

[0062] Next, in S504, the power transmission device 102 executes a process to select the calibration timeout period. The detailed procedure for selecting the calibration timeout period will be described later.

[0063] Next, in S505, the foreign object detection processing unit 403 of the power transmission device 102 executes the Calibration phase based on the selected timeout period. In the Calibration phase, as described above, the foreign object detection processing unit 403 of the power transmission device 102 derives the relationship between transmitted power and received power in the absence of foreign objects. Specifically, the foreign object detection processing unit 403 of the power transmission device 102 derives a Calibration curve using predetermined received power values ​​(including received power values ​​in light load conditions and received power values ​​in maximum load conditions) obtained from the power receiving device 101. When deriving the Calibration curve, the foreign object detection processing unit 403 of the power transmission device 102 performs foreign object detection based on the Q-value measurement method in the time domain for each predetermined received power value obtained. Furthermore, if it is decided in the Negotiation phase to perform multiple trials of foreign object detection based on the Q-value measurement method in the time domain, the foreign object detection processing unit 403 acquires the received power values ​​and performs foreign object detection for each predetermined received power value for the number of trials. This avoids deriving a calibration curve in the presence of foreign objects and suppresses undetected or falsely detected foreign objects.

[0064] Next, in S506, the power transmission processing unit 402 of the power transmission device 102 starts transmitting power to the power receiving device 101 in the Power Transfer phase. Although power transmission is performed by the processing of the Power Transfer phase, it is not limited to this, and power transmission may be performed by methods other than those specified in the WPC standard.

[0065] Here, if the control unit 300 of the power transmission device 102 determines that the power receiving device 101 is not mounted on the power transmission device 102, it returns the process to the Selection phase of S501. Furthermore, if the power transmission device 102 receives an End Power Transfer according to the WPC standard from the power receiving device 101, it forcibly terminates the process in any processing phase according to the WPC standard, stops power transmission, and returns to the Selection phase of S501. Also, if the device is fully charged, an End Power Transfer is sent from the power receiving device 101, so the process returns to the Selection phase of S501.

[0066] Next, with reference to Figure 6, an example of the flow of the selection process for the calibration timeout period performed by the power transmission device 102 in S504 will be described. The following explanation will use the case where selection is made as an example, but the timeout period may be selected from a predetermined list of candidates, or it may be calculated and determined according to a specific rule. First, in S601, the time selection processing unit 404 determines whether the power receiving device 101 is of a predetermined version or higher of the Qi standard. Here, whether or not it is of a predetermined version or higher can be determined from the version information in the capability information contained in the Configuration Packet received from the power receiving device 101 in the I&C phase. Alternatively, it may be determined from information contained in another packet, or based on information obtained using out-of-band communication such as Bluetooth® or NFC.

[0067] If the determination in S601 indicates that the power receiving device 101 is of a predetermined version or higher, the process proceeds to S602. On the other hand, if it is determined that the power receiving device 101 is not of a predetermined version or higher, the process proceeds to S605. In S605, the time selection processing unit 404 of the power transmission device 102 selects a predetermined value as the timeout period for the Calibration phase processing and terminates the process. This predetermined value is the default reference value.

[0068] On the other hand, in S602, the control unit 300 of the power transmission device 102 determines whether or not to perform foreign object detection based on the Q-value measurement method in the time domain. Here, in the Negotiation phase of S503, as shown in Figure 7, supplementary information is notified from the power receiving device 101 regarding whether or not foreign object detection based on the Q-value measurement method in the time domain is possible (F709). Based on this supplementary information, the control unit 300 determines whether or not to perform foreign object detection based on the Q-value measurement method in the time domain. Alternatively, the determination may be made based on whether or not supplementary information has been received from the power receiving device 101 regarding whether or not it is possible to perform the foreign object detection method based on the Q-value measurement method in the time domain. In this case, it may be determined by default that it is possible if no information is received from the power receiving device 101, or it may be determined that the power receiving device 101 is not compatible with the foreign object detection method based on the Q-value measurement method in the time domain and therefore it may be determined not to perform the detection. If, as a result of the determination in S602, foreign object detection based on the Q-value measurement method in the time domain is possible, the process proceeds to S603. On the other hand, if foreign object detection based on the Q-value measurement method in the time domain is not feasible, the process proceeds to S605.

[0069] In S603, the control unit 300 of the power transmission device 102 determines whether to attempt foreign object detection based on the time-domain Q-value measurement method a predetermined number of times or more. In this process, it is determined whether the number of attempts determined in the Negotiation phase of S503 through information exchange with the power receiving device 101 is greater than or equal to a predetermined number. Alternatively, the determination may be made based on, for example, a default number of attempts defined within the power transmission device 102. If the determination in S603 results in attempts being made a predetermined number of times or more, the process proceeds to S604. On the other hand, if attempts are not made a predetermined number of times or more, the process proceeds to S605.

[0070] In S604, the time selection processing unit 404 of the power transmission device 102 selects a value greater than the predetermined value defined in S605 as the timeout time for processing in the Calibration phase, and terminates the processing. The value greater than the predetermined value is a fixed value predetermined as a Qi standard, but it may also be a variable value that increases in proportion to the number of trials, for example. The timeout time is determined according to the processing time required to perform foreign object detection based on the Q value measurement method in the time domain, and the processing time required until the power receiving device 101 notifies a predetermined power received value in an RP packet, etc.

[0071] (The flow of processes executed by the system) Next, the operation sequence when the power transmission device 102 performs the above-described process will be explained with reference to Figure 7. Initially, the power receiving device 101 is not mounted on the power transmission device 102, and the power transmission device 102 is assumed to have sufficient power transmission capacity to perform GP transmission as requested by the power receiving device 101. Also, in the example shown in Figure 7, the predetermined number of times used as the judgment criterion in S603 is assumed to be 5, but this is merely an example, and other values ​​may be used. Furthermore, F701 to F706 are the procedures described in S501 above.

[0072] In the I&C phase, identification information and capability information are exchanged between the power transmission device 102 and the power receiving device 101 (F707). The processing performed by the power transmission device 102 in F707 is the processing shown in S502 of Figure 5. In the example shown in Figure 7, it is assumed that the power receiving device 101 is of a specified version or higher based on the capability information contained in the Configuration Packet.

[0073] Next, the power transmission device 102 and the power receiving device 101 perform communication in the negotiation phase (F708). In this negotiation process, it is assumed that GP = 15 watts is determined. Once GP is determined, the power transmission device 102 receives supplementary information from the power receiving device 101 indicating that foreign object detection based on the Q-value measurement method in the time domain can be performed (F709), and responds with an ACK (F710).

[0074] Next, the power transmission device 102 notifies the power receiving device 101 of 7 attempts as information regarding the number of attempts to detect foreign objects based on the Q-value measurement method in the time domain (F711), starts the process shown in Figure 6, and selects a timeout period (F712). In this embodiment, the information regarding the number of attempts to detect foreign objects based on the Q-value measurement method in the time domain is included in the response to the Generic Request packet sent from the power receiving device 101, but it may also be notified at a different time or in a different packet.

[0075] Subsequently, the system moves to the Calibration phase, where the power transmission unit 102 receives a Control Error packet (CE packet) from the power receiving unit 101 with a positive Control Error Value (F713). The power transmission unit 102 then changes the power transmission output based on the Control Error Value. Next, when the power transmission unit 102 receives an RP packet (mode1) from the power receiving unit 101 indicating the power received under light load conditions (F714), it performs foreign object detection processing based on the Q-value measurement method in the time domain (F715). As this is the first trial out of seven trials, the power transmission unit 102 responds that it does not make a judgment (F716). After completing the response, the power transmission unit 102 determines whether or not a timeout has occurred in the Calibration phase processing. In the example in Figure 7, it is assumed that the selected timeout period has not elapsed (no timeout has occurred) (F717). Subsequently, the processing from F714 to F717 is repeated five more times between the power transmission unit 102 and the power receiving unit 101.

[0076] Next, when the power transmission device 102 receives an RP packet (mode1) from the power receiving device 101 (F718), it performs foreign object detection processing based on the Q-value measurement method in the time domain (F719). Since this is the 7th trial out of 7 trials, the power transmission device 102 determines that there is no foreign object based on the results of the foreign object detection processing from the 1st to the 7th trials. The power transmission device 102 then responds with an ACK indicating that it accepts the received power value Pr1 under light load conditions to be used to derive the calibration curve (F720). If the detection results of the foreign object detection processing based on the Q-value measurement method in the time domain for 7 trials determine that a foreign object is present, the calibration curve cannot be derived. In such a case, the power transmission device 102 responds with a NAK (negative response) indicating that it cannot accept the received power value under light load conditions.

[0077] Once the power transmission device 102 has completed its response, it determines whether or not a timeout has occurred in the Calibration phase processing. In the example in Figure 7, it is determined that the selected timeout period has not elapsed (no timeout has occurred) (F721).

[0078] Next, the same processing as in F713-F717 is performed between the power transmission device 102 and the power receiving device 101 regarding the RP packet (mode2) indicating the received power value under maximum load conditions (F722-F726). Subsequently, when the power transmission device 102 receives the RP packet (mode2) from the power receiving device 101 (F727), it performs foreign object detection processing based on the Q-value measurement method in the time domain (F728). Since this is the 7th trial out of 7 trials, the power transmission device 102 determines that there are no foreign objects based on the results of the foreign object detection processing in the 1st to 7th trials. The power transmission device 102 then responds with an ACK indicating that it accepts the received power value Pr2 under maximum load conditions to be used to derive the Calibration curve (F729). Once the power transmission device 102 has completed its response, it determines whether or not a timeout has occurred in the Calibration phase processing. In the example in Figure 7, if a timeout period is selected in S605, it is assumed that the timeout period has already elapsed. In the example shown in Figure 7, the power transmission device 102 determines that no timeout has occurred because, although the predetermined timeout period has elapsed, the selected timeout period has not elapsed (F730). It then terminates the Calibration phase. Subsequently, it moves to the Power Transfer phase and performs power transmission and reception processing between the power transmission device 102 and the power receiving device 101 (F731).

[0079] As described above, according to this embodiment, the power transmission device 102 is configured to select a timeout period that is necessary and sufficient to perform the calibration process, depending on the trial content of the foreign object detection process. This makes it possible to derive a calibration curve with high accuracy, and to realize a safer and more efficient wireless power transmission system.

[0080] (Second embodiment) In the first embodiment, the power transmission device, which is the main component that derives the calibration curve, changes the timeout time for the calibration phase processing to a larger value as needed, based on the results of the foreign object detection trial. On the other hand, when the timeout time is set to a value larger than a predetermined value, there is a problem that the time until power transmission and reception start becomes longer. Therefore, if it is possible to control the system so that the desired calibration phase processing can be performed without changing the timeout time, it is desirable to perform such control. In this embodiment, as an example, a method is described in which the power receiving device selects and controls the maximum transmission time interval of RP packets according to the results of the foreign object detection processing trial. Note that the internal configuration of the power transmission device and power receiving device is the same as in the first embodiment, so the explanation is omitted. The differences from the first embodiment will be described below. In this embodiment, the power transmission device 102 does not perform a timeout time selection process, and is fixed to the value set in S605.

[0081] (Processing flow by the power receiving device) Figure 8 is a flowchart showing an example of a basic processing procedure performed by the power receiving device 101 in this embodiment. This process is implemented, for example, by the control unit 200 of the power receiving device 101 executing a program read from the memory 209. Alternatively, this process may be executed when the power receiving device 101 is turned on and the power receiving device 101 is started up by power supplied from the battery 206 or the power transmitting device 102. Or, it may be executed when the user of the power receiving device 101 inputs a command to start a contactless charging application. Furthermore, this process may be started by other triggers.

[0082] In S801, the control unit 200 of the power receiving device 101 executes the processes defined as the Selection phase and Ping phase of the WPC standard and waits for its device to be placed on the power transmitting device 102 (S801). The control unit 200 of the power receiving device 101 detects that it has been placed on the power transmitting device 102, for example, by detecting a Digital Ping from the power transmitting device 102.

[0083] When the device detects in S501 that it has been placed on the power transmission device 102, the control unit 200 of the power receiving device 101 then transmits identification information and capability information to the power transmission device 102 in S802 via I&C phase communication as defined by the WPC standard. At this time, the power receiving device 101 stores the identification information in an ID Packet and transmits it, and stores the capability information in a Configuration Packet and transmits it.

[0084] Next, in S803, the control unit 200 of the power receiving device 101 exchanges information with the power transmitting device 102 through communication in the Negotiation phase as defined in the WPC standard, and determines the GP (Power Point). Furthermore, in S803, in addition to the procedure for determining the GP, information regarding foreign object detection based on the Q-value measurement method in the time domain is exchanged with the power transmitting device 102. For example, this includes information such as the processing time required to perform foreign object detection based on the Q-value measurement method in the time domain, and the processing time required to reach a predetermined power receiving value.

[0085] Then, in S804, the control unit 200 of the power receiving device 101 performs a selection process for the maximum transmission time interval of RP packets. Details of the selection process for the maximum transmission time interval of RP packets will be described later.

[0086] Next, in S805, the control unit 200 of the power receiving device 101 performs communication for the Calibration phase of the WPC standard. In this process, as described above, it transmits information such as predetermined power values ​​necessary for deriving the Calibration curve to the power transmitting device 102. Then, in S806, the control unit 200 of the power receiving device 101 starts receiving power through communication for the Power Transfer phase as defined in the WPC standard. Subsequently, if an error occurs or when full charge is reached, the power receiving device 101 transmits an End Power Transfer according to the WPC standard to the power transmitting device 102. This stops power transmission from the power transmitting device 102, and the series of processes for contactless charging are completed.

[0087] Next, with reference to Figure 9, an example of the flow of the selection process for the maximum transmission time interval of RP packets, which is performed by the power receiving device 101 in S804, will be described. First, in S901, the control unit 200 of the power receiving device 101 determines whether the power transmitting device 102 is of a predetermined version or higher of the Qi standard. In this process, first, a Generic Request packet is sent to the power transmitting device 102, and the determination of whether it is of a predetermined version or higher is made from the version information contained in the response. Alternatively, the determination may be made based on version information notified by the power transmitting device 102 using another packet, or based on information obtained using out-of-band communication such as Bluetooth or NFC. Furthermore, version information may be obtained from the power transmitting device 102 as capability information during the I&C phase, and the determination may be made based on that information.

[0088] If the result of the S901 check indicates that the version is above the specified version, the process proceeds to S902. On the other hand, if the version is not above the specified version, the process proceeds to S905. In S905, the control unit 200 of the power receiving device 101 selects a predetermined value as the maximum transmission time interval for RP packets and terminates the process. This predetermined value is the default reference value.

[0089] On the other hand, in S902, the control unit 200 of the power receiving device 101 determines whether or not to perform foreign object detection based on the Q-value measurement method in the time domain. Here, the determination of whether or not to perform foreign object detection is made based on whether or not it is capable of performing foreign object detection based on the Q-value measurement method in the time domain. Alternatively, the determination may be made based on whether or not it has received notification from the power transmission device 102 regarding the number of attempts for foreign object detection based on the Q-value measurement method in the time domain. In this case, it may be determined that it is possible to perform the detection if no notification is received from the power transmission device 102, or it may be determined that it is not possible to perform the detection because the power transmission device 102 is not compatible with the foreign object detection method based on the Q-value measurement method in the time domain. If, as a result of the determination in S902, foreign object detection based on the Q-value measurement method in the time domain is possible, the process proceeds to S903. On the other hand, if foreign object detection based on the Q-value measurement method in the time domain is not possible, the process proceeds to S905.

[0090] In S903, the control unit 200 of the power receiving device 101 determines whether to attempt foreign object detection based on the time-domain Q-value measurement method a predetermined number of times or more. In this process, it is determined whether the number of attempts notified by the power transmission device 102 in the Negotiation phase is the predetermined number or more. Alternatively, the determination may be made based on whether or not a notification regarding the number of attempts for foreign object detection based on the time-domain Q-value measurement method has been received from the power transmission device 102. In this case, it may be determined that the number of attempts will be the predetermined number or more if no notification is received from the power transmission device 102, or it may be determined that the number of attempts is less than the predetermined number if no notification is received. If the determination in S903 is to attempt the predetermined number of times or more, the process proceeds to S904. On the other hand, if the number of attempts is not the predetermined number or more, the process proceeds to S905.

[0091] In S904, the control unit 200 of the power receiving device selects a value smaller than the predetermined value defined in S905 as the maximum transmission time interval for RP packets, and terminates processing. The value smaller than the predetermined value may be a variable value that decreases in proportion to the number of trials, for example. The maximum transmission time interval is determined according to the processing time required to perform foreign object detection based on the Q value measurement method in the time domain, the processing time required to reach a predetermined power receiving value, etc.

[0092] (The flow of processes executed by the system) Next, the operation sequence when the power receiving device 101 performs the above-described process will be explained with reference to Figure 10. F1001 to F1006 are the same as F701 to F706 in Figure 7. In this embodiment, for example, in the I&C phase of F1007, in addition to the process of F707, version information including a value of a predetermined version or higher is received from the power transmitting device 102. After that, the processes of F1008 to F1010 are performed, and notification of the number of attempts for foreign object detection based on the Q value measurement method in the time domain is received from the power transmitting device 102 (F1011). The processes of F1008 to F1010 are the same as F708 to F710 in Figure 7.

[0093] Upon receiving notification of the number of attempts from the power transmission device 102, the power receiving device 101 begins the process of selecting the maximum transmission time interval for RP packets (F1012). The power receiving device 101 determines that the version of the power transmission device 102 is above a predetermined value, that foreign object detection based on the Q-value measurement method in the time domain is possible, and that the number of attempts is above a predetermined number (= 5 times), and therefore selects a value smaller than the predetermined value as the maximum transmission time interval for RP packets. Subsequently, the Calibration phase process is initiated between the power transmission device 102 and the power receiving device 101, and the power receiving device 101 sends a CE packet with a positive Control Error Value to the power transmission device 102 (F1013).

[0094] Next, the receiving device 101 sends an RP packet (mode1) to the transmitting device 102 indicating the received power value under light load conditions (F1014), and the transmitting device 102 performs foreign object detection processing based on the Q-value measurement method in the time domain (F1015). Here, since it is the first trial out of seven trials, the receiving device 101 receives a response from the transmitting device 102 indicating that no judgment is being made (F1016). After completing the response, in the example in Figure 10, the transmitting device 102 is assumed to have determined that no timeout has occurred in the Calibration phase processing (F1017). Subsequently, the transmitting device 102 and the receiving device 101 repeat the process from F1014 to F1017 five more times. At this time, the receiving device 101 sends the next RP packet so as not to exceed the maximum transmission time interval selected in F1012 after receiving the response indicating that no judgment was being made regarding the previous RP packet transmission.

[0095] Next, the receiving device 101 sends an RP packet (mode1) to the transmitting device 102 (F1018), and the transmitting device 102 performs foreign object detection processing based on the Q-value measurement method in the time domain (F1019). Since this is the 7th trial out of 7 trials, the transmitting device 102 determines that there is no foreign object based on the results of the foreign object detection processing from the 1st to the 7th trials. The transmitting device 102 then responds with an ACK indicating that it accepts this as the received power value Pr1 under light load conditions to be used to derive the calibration curve (F1020). Once the transmitting device 102 has completed its response, it determines whether or not a timeout has occurred in the processing of the calibration phase. In the example in Figure 10, it is assumed that it has determined that the predetermined timeout period has not elapsed (F1021).

[0096] Next, the power receiving device 101 sends a CE packet with a positive Control Error Value to the power transmitting device 102 (F1022) in order to set the power received value to the maximum load state. At this time, the power receiving device 101 specifies a larger value for the Control Error Value compared to when multiple attempts are not made to detect foreign objects based on the Q-value measurement method in the time domain. In addition, the number of CE packet transmissions is increased compared to when multiple attempts are not made to detect foreign objects based on the Q-value measurement method in the time domain. This makes it possible to reach the desired power received value in a shorter time than when multiple attempts are not made to detect foreign objects based on the Q-value measurement method in the time domain. In other words, RP packets (mode2) indicating the power received value to the maximum load state can be transmitted at shorter time intervals. For this reason, even if a value smaller than a predetermined value is selected as the maximum transmission time interval for RP packets, the Calibration process can continue while maintaining the interval. The processing from F1023 to F1031 is the same as F723 to F731 in Figure 7, so the explanation is omitted.

[0097] As described above, according to this embodiment, the power receiving device 101 selects the maximum transmission time interval of RP packets according to the trial content of the foreign object detection process. This makes it possible to derive a calibration curve while improving the foreign object detection accuracy within a predetermined timeout period related to the calibration process, thereby realizing a safer and more efficient wireless power transmission system.

[0098] (Other embodiments) In the first embodiment, the power transmission device 102 immediately starts the calibration process after selecting a timeout period through a timeout period selection process. However, the selected timeout period may be notified to the power receiving device 101. For example, the power transmission device 102 may notify the power receiving device 101 of the number of attempts to detect foreign objects based on the Q-value measurement method in the time domain, and then notify the timeout period by including it in the response to the Generic Request packet sent from the power receiving device 101. Alternatively, notification may be given at a different timing or using a different packet. This allows the power receiving device 101 to efficiently control the value of the Control Error Value included in the CE packet, the number of transmissions, and the transmission time interval of the RP packet in accordance with the timeout period notified by the power transmission device 102, while suppressing the processing load. This enables the realization of a safer and more efficient wireless power transmission system.

[0099] In the second embodiment, the power receiving device 101 selects the maximum transmission time interval through a selection process for the maximum transmission time interval of RP packets and immediately starts the Calibration process. However, the selected maximum transmission time interval may be notified to the power transmitting device 102. For example, one method is to include the information of the maximum transmission time interval in a Specific Request packet and send it before sending the RP packet, but notification may also be done at a different timing or using a different packet. This allows the power transmitting device 102 to use the notified maximum transmission time interval as the timeout period until the RP packet is received. Therefore, it is possible to determine whether a timeout occurs in the Calibration phase process at an earlier timing than when a timeout determination is made using a predetermined timeout period until the RP packet is received.

[0100] In the first and second embodiments, the power transmission device 102 notifies the power receiving device 101 of the number of attempts for foreign object detection based on the Q-value measurement method in the time domain, and the power receiving device 101 unconditionally accepts this number of attempts. However, the power receiving device 101 may refuse to accept the notified number of attempts. For example, if the number of attempts notified by the power transmission device 102 is executed, it may not be possible to complete the Calibration phase processing within the timeout period. In other words, it may not be possible to shorten the transmission interval of RP packets. In this case, the power receiving device 101 may request the power transmission device 102 to re-notify information regarding the number of attempts using a Generic Request packet or the like in order to redetermine the number of attempts. Alternatively, the power receiving device 101 may send an End Power Transfer to stop processing and restart from the Selection phase processing. Furthermore, if it is expected that the processing will be completed within the timeout period for the Calibration phase processing, the number of attempts may be redetermined with the aim of increasing the number of attempts in order to improve the accuracy of foreign object detection.

[0101] In the first and second embodiments, the case in which processing is completed within the timeout period for the Calibration phase processing was described. On the other hand, if a timeout occurs, the power transmission device 102 stops power transmission, but it may suppress the power transmission output without stopping power transmission, or it may restart the Selection phase processing after stopping power transmission. When restarting the Selection phase processing, the Calibration phase processing is performed by setting the timeout period to a value even larger than the value selected last time, or by reducing the number of attempts for foreign object detection based on the Q value measurement method in the time domain. This makes it possible to more reliably complete the Calibration phase processing within the timeout period, that is, to derive the Calibration curve, and realize a safer and more efficient wireless power transmission system. Furthermore, the processing of the power transmission device 102 according to the first embodiment and the processing of the power receiving device 101 according to the second embodiment may be combined.

[0102] In the first and second embodiments, the power transmission device 102 determined whether a timeout had occurred each time it received an RP packet, but this could also be done after multiple receptions or at predetermined intervals. This would suppress the execution of unnecessary processing and enable a highly efficient wireless power transmission system.

[0103] The power receiving device 101 and the power transmitting device 102 may have functions to execute applications other than wireless charging. An example of the power receiving device 101 is an information processing terminal such as a smartphone, and an example of the power transmitting device 102 is an accessory device for charging that information processing terminal. For example, an information terminal device has a display unit that displays information to the user, and is supplied with power received from a power receiving coil (antenna). The power received from the power receiving coil is stored in a power storage unit (battery), and power is supplied to the display unit from the battery. In this case, the power receiving device 101 may have a communication unit that communicates with other devices different from the power transmitting device 102. The communication unit may support communication standards such as NFC communication or fifth-generation mobile communication systems (5G). In this case, the communication unit may perform communication by being powered from the battery. Furthermore, the power receiving device 101 may be a tablet terminal, a storage device such as a hard disk drive and memory device, or an information processing device such as a personal computer (PC). Furthermore, the power receiving device 101 may be, for example, an imaging device (such as a camera or video camera). The power receiving device 101 may also be an image input device such as a scanner, or an image output device such as a printer, copier, or projector. The power receiving device 101 may also be a robot, medical equipment, etc. The power transmitting device 102 may be a device for charging the aforementioned equipment.

[0104] Alternatively, the power transmission device 102 may be a smartphone. In this case, the power receiving device 101 may be another smartphone or a wireless earphone.

[0105] Furthermore, the power receiving device 101 in this embodiment may be a vehicle such as an automobile. For example, the automobile, which is the power receiving device 101, may receive power from a charger (power transmission device 102) via a power transmission antenna installed in a parking lot. Alternatively, the automobile, which is the power receiving device 101, may receive power from a charger (power transmission device 102) via a power transmission coil (antenna) embedded in the road. In such an automobile, the received power is supplied to a battery. The power from the battery may be supplied to a drive unit (motor, electric unit) that drives the wheels, or it may be used to drive sensors used for driving assistance or a communication unit that communicates with external devices. In other words, in this case, the power receiving device 101 may have a battery, motors and sensors that are driven using the received power, and a communication unit that communicates with devices other than the power transmission device 102, in addition to the wheels. Furthermore, the power receiving device 101 may have a dwelling unit for accommodating people. For example, sensors may be used to measure the distance between vehicles or the distance to other obstacles. The communication unit may, for example, be compatible with the Global Positioning System (Global Positioning Satellite, GPS). The communication unit may also be compatible with communication standards such as 5G. The vehicle may be a bicycle or a motorcycle. Furthermore, the power receiving device 101 is not limited to a vehicle, but may be a mobile or flying object having an activation unit that uses power stored in a battery for propulsion.

[0106] Furthermore, the power receiving device 101 in this embodiment may be a power tool, a home appliance, or the like. These devices, which are the power receiving device 101, may have a battery, as well as a motor driven by the power received from the battery. These devices may also have a notification means for notifying the remaining battery level, etc. Furthermore, these devices may have a communication unit that communicates with other devices different from the power transmitting device 102. The communication unit may support communication standards such as NFC or fifth-generation mobile communication systems (5G).

[0107] Furthermore, the power transmission device 102 in this embodiment may be an in-vehicle charger that transmits power to portable information terminal devices such as smartphones and tablets that support wireless power transmission within the vehicle. Such an in-vehicle charger may be installed anywhere in the vehicle. For example, the in-vehicle charger may be installed on the vehicle's console, on the instrument panel (dashboard), between passenger seats, on the ceiling, or on the doors. However, it is preferable not to install it in a location that would interfere with driving. In addition, although the power transmission device 102 has been described using the example of an in-vehicle charger, such chargers are not limited to those installed in vehicles, but may also be installed in transport vehicles such as trains, aircraft, and ships. In this case, the charger may also be installed between passenger seats, on the ceiling, or on the doors.

[0108] Alternatively, the power transmission device 102 may be a vehicle such as an automobile equipped with an on-board charger. In this case, the power transmission device 102 has wheels and a battery, and uses the power from the battery to supply power to the power receiving device 101 via a power transmission circuit and a power transmission coil (antenna).

[0109] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of symbols]

[0110] 401 Communication processing unit, 403 Foreign object detection processing unit, 404 Time selection processing unit

Claims

1. A power receiving device, A power receiving means for wirelessly receiving power from a power transmitting device; a transmitting means for transmitting identification information of the power receiving device and a packet including information on the received power at time intervals; and a control means for switching between a first mode in which the packets are transmitted at a first time interval and a second mode in which the packets are transmitted at a second time interval that is shorter than the first time interval.

2. A power supply device comprising: a receiving means for receiving information from the power transmitting device; The power receiving device according to claim 1 , wherein the control means switches between a first mode and a second mode based on the information.

3. A power receiving device as described in claim 2, wherein the information is included in a response from the power transmitting device to a packet other than a packet containing information about the received power from the power receiving device.

4. A power receiving device as described in claim 2 or 3, wherein the information is version information indicating the version of the power transmitting device.

5. A power receiving device as described in claim 2 or 3, wherein the information is information indicating whether the power transmitting device performs foreign object detection based on a Q value.

6. A power receiving device as described in claim 2 or 3, wherein the information is information indicating whether the power transmitting device performs foreign object detection based on a Q value a predetermined number of times or more.

7. A method performed by a power receiving device, comprising: Transmitting identification information of the power receiving device; switching between a first mode in which a packet including information on the received power is transmitted at a first time interval and a second mode in which the packet is transmitted at a second time interval shorter than the first time interval; The method of claim 1, wherein if in the first mode, the packets are transmitted at the first time interval, and if in the second mode, the packets are transmitted at the second time interval.

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