Power transmitting device, power receiving device, and wireless power transmission system

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] The present disclosure relates to a power transmitting device, a power receiving device, a wireless power transmission system, a control method for a power transmitting 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 widely carried out, and standards (WPC standards) have been established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards. Patent Document 1 discloses a power transmitting device and a power receiving device that comply with the WPC standards.

[0003] Furthermore, in a wireless power transmission system, when an object other than the power receiving device and the power transmitting device (hereinafter referred to as a foreign object) is present within a range to which the power transmitting device can transmit power, it is essential to detect the foreign object and control power transmission and reception. Patent Document 2 discloses a method for detecting a foreign object near a power transmitting and receiving device and restricting power transmission and reception. Furthermore, Patent Document 3 discloses a technology in which a high-frequency signal is applied to a power transmitting coil of a wireless power transmission system for a certain period of time, a Q factor (Quality Factor) is measured from the time change in the voltage inside the power transmitting coil, and a foreign object is detected based on the change in the Q factor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-56959 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-70074 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-45845 Summary of the Invention [Problem to be solved by the invention]

[0005] One method for detecting foreign objects is to use power loss. First, a reference value for power loss between the power transmitting device and the power receiving device when there is no foreign object is calculated in advance from the difference between the transmitted power at the power transmitting device and the received power at the power receiving device. Then, the presence or absence of a foreign object is determined based on the power loss between the power transmitting device and the power receiving device calculated during subsequent power transmission. Here, when calculating the reference value for power loss in a foreign object-free state in advance, it is desirable to perform foreign object detection, for example, by a different method, for each power loss calculation to avoid calculations that are performed when a foreign object is present. Furthermore, to improve the accuracy of the calculation of the reference value for power loss, it is possible to perform multiple attempts to calculate the power loss and detect a foreign object for each calculation. However, a predetermined timeout period is set for the process related to the calculation of the reference value for power loss. Therefore, if multiple attempts are made to calculate the reference value for power loss and detect a foreign object for each calculation, the process may not be completed within the timeout period, which may result in an unintended power transmission stop.

[0006] In view of the above-mentioned problems, the present disclosure aims to suppress unnecessary power transmission interruptions that may occur when calculating a reference value for power loss used to detect objects other than a power receiving device and a power transmitting device. [Means for solving the problem]

[0007] The power transmission device of the present disclosure is a power transmission device that transmits power wirelessly to a power receiving device, and includes: a first detection means that detects whether an object other than the power transmission device and the power receiving device is present based on power loss between the power transmission device and the power receiving device; an acquisition means that acquires performance information related to the power receiving device from the power receiving device; a second detection means that detects whether an object other than the power transmission device and the power receiving device is present based on the attenuation state of the voltage or current waveform related to the power transmission; a calculation means that calculates a reference value for power loss to be used for detection by the first detection means when an object other than the power transmission device and the power receiving device is not present based on the detection result by the second detection means; and a determination means that determines a timeout period for processing related to calculation of the reference value by the calculation means based on the performance information related to the power receiving device acquired by the acquisition means, wherein the determination means selects a first value as the timeout period if the power receiving device does not satisfy a specified condition, and determines a second value greater than the first value as the timeout period if the power receiving device satisfies the specified condition. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to suppress unnecessary power transmission interruptions that may occur when calculating a reference value of power loss used for detecting an object other than a power receiving device and a power transmitting device. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless power transmission system according to an embodiment. [Figure 2] 2 is a block diagram illustrating an example of an internal configuration of a power receiving device according to an embodiment. FIG. [Figure 3] 1 is a block diagram illustrating an example of an internal configuration of a power transmitting device according to an embodiment. [Figure 4] 2 is a block diagram illustrating an example of a functional configuration of a power transmission device according to an embodiment. FIG. [Figure 5] 5 is a flowchart illustrating an example of a basic processing procedure executed by the power transmitting device according to the first embodiment. [Figure 6] 5 is a flowchart illustrating an example of a selection process for a timeout period performed by a power transmitting device in the first embodiment. [Figure 7] 4 is a diagram for explaining an operation sequence of the power transmitting device and the power receiving device in the first embodiment. FIG. [Figure 8] 10 is a flowchart illustrating an example of a basic processing procedure executed by a power receiving device according to the second embodiment. [Figure 9] 10 is a flowchart illustrating an example of a procedure for a process of selecting a maximum transmission time interval of an RP packet by a power receiving device in the second embodiment. [Figure 10] FIG. 10 is a diagram illustrating an operation sequence of a power transmitting device and a power receiving device according to the second embodiment. [Figure 11] FIG. 10 is a diagram for explaining a foreign object detection method based on a power loss technique. [Figure 12] 10A and 10B are diagrams for explaining a foreign object detection method based on a Q-value measurement method in the time domain. DETAILED DESCRIPTION OF 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 multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the present disclosure, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] (System configuration) Fig. 1 is a diagram showing an example of the configuration of a contactless charging system (wireless power transmission system) 100 according to this embodiment. As shown in Fig. 1, the contactless charging system according to this embodiment includes a power receiving device 101 and a power transmitting device 102. Here, it is assumed that the power receiving device 101 and the power transmitting device 102 comply with 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 placed on it via a charging stand 103. Hereinafter, placing the device on the charging stand 103 will simply be referred to as being placed on the power transmitting device 102. A range 104 indicates a 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 a function to execute applications other than contactless charging. In the following description, an object that is included in the power transmission range of the power transmitting device 102 and is different from the power transmitting device 102 and the power receiving device 101 will be referred to as a foreign object. The foreign object is, for example, a paper clip or an IC card. Foreign objects do not include objects that are integral parts of the power receiving device 101, the power transmitting device 102, or the product in which they are incorporated, and that may unintentionally generate heat when exposed to wireless power transmitted by the power transmitting antenna.

[0013] In the following description, "the power receiving device 101 is placed on the power transmitting device 102" refers to "a state in which 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 a range in which power can be transmitted to the power receiving device 101 using a power transmitting coil. In addition, the state in which the power receiving device 101 is placed on the power transmitting device 102 does not necessarily mean that the power receiving device 101 and the power transmitting device 102 are not in contact with each other. For example, a state in which the power receiving device 101 is included in the power transmission range without being in contact with the power transmitting device 102 is also considered to be the state in which "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 disposed, for example, on a side of the power transmitting device 102 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 configurations described below are merely examples, and part (or in some cases the entirety) of the described configurations may be replaced with other configurations that perform similar functions or may be omitted, or additional configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0015] Fig. 2 is a block diagram showing an example of the internal configuration of the power receiving device 101 according to this embodiment. Fig. 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 has a control unit 200, a power receiving coil 201, a rectifying unit 202, a voltage control unit 203, a communication unit 204, a charging unit 205, a battery 206, a 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 the memory 209, for example. The control unit 200 may also perform control for executing applications other than wireless power transmission. The control unit 200 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 200 may also include hardware dedicated to a specific process, such as an Application Specific Integrated Circuit (ASIC). The control unit 200 may also include an array circuit, such as an FPGA (Field Programmable Gate Array) compiled to execute a predetermined process. The control unit 200 stores information to be stored during execution of various processes in the memory 209. The control unit 200 also measures time using a timer 210.

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

[0018] The communication unit 204 performs control communication based on the WPC standard through in-band communication with the power transmitting device 102. The communication unit 204 demodulates the electromagnetic waves input from the power receiving coil 201 to acquire information transmitted from the power transmitting device 102, and performs load modulation of the electromagnetic waves to superimpose information to be transmitted to the power transmitting device 102 on the electromagnetic waves, thereby performing communication with the power transmitting device 102. That is, the communication performed by the communication unit 204 is superimposed on power transmitted from the power transmitting coil 303 of the power transmitting device 102.

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

[0020] As described above, the memory 209 stores various types of information. Note that the memory 209 may store information obtained by a functional unit other than the control unit 200. The timer 210 measures time 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 transmitting device 102 according to this embodiment will be described with reference to Fig. 3. The power transmitting device 102 includes a control unit 300, a power supply unit 301, a power transmitting unit 302, a power transmitting coil 303, a communication unit 304, a resonance capacitor 305, a switch 306, a memory 307, and a timer 308.

[0022] The control unit 300 controls the entire power transmitting 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 includes one or more processors, such as a CPU or an MPU. The control unit 300 may also include hardware dedicated to a specific process, such as an application specific integrated circuit (ASIC), or an array circuit, such as an FPGA, compiled to execute a predetermined process. The control unit 300 stores information to be stored while executing various processes in the memory 307. The control unit 300 also measures time using a timer 308.

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

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

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

[0026] Switch 306 is a switch for shorting power transmitting coil 303 and resonant capacitor 305, and is controlled by control unit 300. When switch 306 is turned on, power transmitting coil 303 and resonant capacitor 305 form a series resonant circuit. At this time, current flows only through the closed circuit between power transmitting coil 303, resonant capacitor 305, and switch 306. When switch 306 is turned off, power is supplied from power transmitting unit 302 to power transmitting coil 303 and resonant capacitor 305. Memory 307 stores various information as described above. Note that memory 307 may store information obtained by a functional unit other than control unit 300. Timer 308 measures time, for example, using 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 function of the control unit 300 of the power transmitting device 102 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing an example of the functional configuration of the control unit 300 of the power transmitting device 102. The power transmitting 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 run in the control unit 300. Furthermore, each of these processing units is configured as an independent program, and operates in parallel while maintaining synchronization between the programs through event processing or the like.

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

[0029] The foreign object detection processor 403 detects foreign objects by measuring the power loss between the power transmitting device and the power receiving device and the Q-factor of the power transmitting coil 303. The foreign object detection processor 403 performs a foreign object detection method using a power loss method as expected by the WPC standard and a foreign object detection method using a Q-factor. The foreign object detection processor 403 may also perform foreign object detection using other methods. For example, in a power transmitting device 102 equipped with an NFC (Near Field Communication) communication function, the foreign object detection processor 403 may perform foreign object detection using an opposite device detection function according to the NFC standard. In addition to the two foreign object detection methods described above, the foreign object detection processor 403 can also perform foreign object detection based on a Q-factor measurement method in the time domain, which will be described later. In addition to detecting foreign objects, the foreign object detection processor 403 can also detect changes in the state of the power transmitting device 102. For example, it can detect an increase or decrease in the number of power receiving devices on the power transmitting device 102.

[0030] The time selection processing unit 404 selects a timeout time related to processing in the calibration phase, which will be described later. In this embodiment, the timeout time is selected based on information on whether the power receiving device 101 is capable of performing foreign object detection based on the Q-value measurement method in the time domain, the number of attempts to detect foreign objects based on the Q-value measurement method in the time domain, etc. The process of selecting the timeout time will be described in detail 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. Note that in this embodiment, the wireless power transmission method (contactless power transmission method) is not limited to the method specified in the WPC standard, and may be other methods such as an electromagnetic induction method, a magnetic field resonance method, an electric field resonance method, a microwave method, or a method using a laser. Also, in this embodiment, wireless power transmission is used for contactless charging, but wireless power transmission may also be performed for purposes other than contactless charging.

[0032] In the WPC standard, the amount of power guaranteed when the power receiving device 101 receives power from the power transmitting device 102 is defined by a value called guaranteed power (hereinafter referred to as "GP"). GP indicates a power value that is guaranteed to be output to a load of the power receiving device 101, such as a charging circuit, even if, for example, the positional relationship between the power receiving device 101 and the power transmitting device 102 changes and the power transmission efficiency between the power receiving coil 201 and the power transmitting coil 303 decreases. For example, if the GP is 15 watts, the power transmitting device 102 transmits power by controlling the power so that 15 watts of power can be output to the load in the power receiving device 101, even if the positional relationship between the power receiving coil 201 and the power transmitting coil 303 changes and the power transmission efficiency decreases.

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

[0034] Here, there are essential metal parts that constitute the power receiving device 101 (and a product incorporating the power receiving device 101) or the power transmitting device 102 (and a product incorporating the power transmitting device 102). Among these essential metal parts, there are metal parts that may unintentionally generate heat when exposed to wireless power transmitted by the power transmitting coil 303. Examples of metal parts that may generate heat include a metal frame around the power transmitting coil 303 or the power receiving coil 201. In this embodiment, a foreign object refers to any metal object that may generate heat when exposed to wireless power transmitted by the power transmitting coil, excluding such metal parts. Examples of foreign objects include clips, IC cards, etc.

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

[0036] The WPC standard specifies multiple phases, including a power transfer phase in which power transfer is performed and a phase prior to the actual power transfer, during which communication is performed to control power transmission and reception. Phases prior to power transfer include the selection phase, ping phase, identification and configuration phase, negotiation phase, and calibration phase. Note that the identification and configuration phase will be referred to as the I&C phase below.

[0037] In the selection phase, the power transmitting device 102 intermittently transmits Analog Pings to detect the presence of an object within the power transmitting range (for example, the power receiving device 101, a conductor piece, etc., being placed on the charging stand 103).

[0038] In the Ping phase, the power transmitting device 102 transmits a Digital Ping with a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start up the control unit 200 of the power receiving device 101 placed on the power transmitting device 102. The power receiving device 101 notifies the power transmitting device 102 of the magnitude of the received voltage using a Signal Strength Packet. In this way, the power transmitting device 102 receives a response from the power receiving device 101 that has received the Digital Ping, thereby recognizing that the object detected in the Selection phase is the power receiving device 101. Upon receiving the notification of the received voltage, the power transmitting device 102 transitions to the I&C phase. Furthermore, before transmitting the Digital Ping, the power transmitting device 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-factor before transmitting the Digital Ping.

[0039] In the I&C phase, the power transmitting apparatus 102 identifies the power receiving apparatus 101 and acquires device configuration information (capability information) from the power receiving apparatus 101. To this end, the power receiving apparatus 101 transmits an ID packet and a configuration packet. The ID packet contains identifier information as identification information for the power receiving apparatus 101, and the configuration packet contains device configuration information (capability information) of the power receiving apparatus 101. Upon receiving the ID packet and the configuration packet, the power transmitting apparatus 102 responds with an acknowledgement (ACK, positive response). Then, the I&C phase ends, and the apparatus moves 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, the power transmission capability of the power transmitting device 102, and the like. Furthermore, the foreign object detection processing unit 403 of the power transmitting device 102 executes foreign object detection processing using a Q value in accordance with a request from the power receiving device 101. Furthermore, the WPC standard specifies a method of transitioning to a power transfer phase (described later) once, and then performing processing similar to that of the negotiation phase again at the request of the power receiving device 101. Hereinafter, the phase transitioning from the power transfer phase and performing these processing will be referred to as the renegotiation phase.

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

[0042] In the power transfer phase, control is performed to continue power transmission and to stop power transmission due to an error or full charge. The power transmitting device 102 and the power receiving device 101 communicate for this power transmission and reception control through in-band communication in which signals are superimposed using the same antenna (coil) as for wireless power transmission based on the WPC standard. Note that the range in which in-band communication based on the WPC standard is possible between the power transmitting device 102 and the power receiving device 101 is almost the same as the power transmission range. That is, in FIG. 1 , range 104 represents the range in which wireless power transmission and in-band communication are possible using the power transmitting and receiving coils of the power transmitting 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, foreign object detection processing using the Q value defined in the WPC standard is performed in the Ping phase and Negotiation phase.

[0044] (1) Foreign object detection method based on power loss technique A foreign object detection method based on the power loss technique defined in the WPC standard will be described with reference to FIG. 11. The horizontal axis of FIG. 11 represents the transmitted power of the power transmitting device 102, and the vertical axis represents the received power of the power receiving device 101. First, the power transmitting device 102 transmits a Digital Ping to the power receiving device 101. Then, the power transmitting device 102 receives from the power receiving device 101 a received power value Pr1 in a light load state in which the power receiving device 101 has received power, as a Received Power Packet (mode 1) (hereinafter, RP packet (mode 1)). At this time, the power receiving device 101 does not supply the received power to a load (such as a charging circuit or a battery). Then, the power transmitting device 102 stores the received power value Pr1 at point 1100 in FIG. 11 and the transmitted power value Pt1 at that time. At this time, when the power transmitting device 102 transmits power at a transmission power value Pt1, the power loss between the power transmitting device 102 and the power receiving device 101 is Pt1-Pr1 (P loss1 ) is recognized as such.

[0045] Next, the power transmitting device 102 receives from the power receiving device 101 a received power value Pr2 in the maximum load state when the power receiving device 101 receives power as a Received Power Packet (mode 2) (hereinafter referred to as an RP packet (mode 2)). At this time, the power receiving device 101 supplies the received power to the load. Then, the power transmitting device 102 stores the received power value Pr2 at point 1101 in FIG. 11 and the transmitted power value Pt2 at that time. At this time, the power transmitting device 102 calculates that the power loss between the power transmitting device 102 and the power receiving device 101 when transmitting power at the transmitted power value Pt2 is Pt2-Pr2(P loss2 ) is recognized as such.

[0046] Then, through calibration processing, the power transmitting device 102 linearly interpolates between points 1100 and 1101 to create a straight line 1102. The straight line 1102 represents the relationship between transmitted power and received power in a state where no foreign object is present around the power transmitting device 102 and the power receiving device 101. Therefore, the power transmitting device 102 can predict the received power in a state where there is a high possibility that no foreign object is present, based on the transmitted power value and the straight line 1102. For example, if the transmitted power value is Pt3, it can be predicted that the received power value is Pr3 from point 1103 on the straight line 1102, which indicates the transmitted power value Pt3. Note that the processing to create this straight line is performed in the calibration phase.

[0047] Here, it is assumed that when the power transmitting device 102 transmits power to the power receiving device 101 at a transmission power value Pt3, the power transmitting device 102 receives a received power value Pr3' from the power receiving device 101. The power transmitting device 102 subtracts the received power value Pr3' actually received from the power receiving device 101 from the received power value Pr3 in a state where no foreign object is present, to obtain a value Pr3-Pr3' (=P loss _FO) is calculated. loss _FO can be considered as the power loss consumed by a foreign object when the foreign object exists between the power transmitting apparatus 102 and the power receiving apparatus 101. Therefore, the power value P loss If _FO exceeds a predetermined threshold, it is determined that a foreign object is present.

[0048] Alternatively, the power transmitting device 102 may calculate in advance the power loss Pt3-Pr3 (Pt3) between the power transmitting device 102 and the power receiving device 101 from the received power value Pr3 in a state where no foreign object is present. loss3 ) is calculated from the received power value Pr3' of the power received from the power receiving device in the presence of the foreign object. loss3 ') and P loss3 -P loss3 (=P loss _FO) to calculate the power consumption P lossAs described above, the estimated power consumption P loss To calculate _FO, use Pr3-Pr3' (=P loss _FO) or P loss3 -P loss3 (=P loss _FO).

[0049] After acquiring a straight line 1102 representing a reference value through calibration processing, the power transmitting device 102 periodically receives a current received power value (Pr3') from the power receiving device 101 in the power transfer phase. The current received power value periodically transmitted by the power receiving device 101 is transmitted to the power transmitting device 102 as a Received Power Packet (mode 0) (hereinafter, referred to as an RP packet (mode 0)). The power transmitting device 102 performs foreign object detection based on the received power value stored in the RP packet (mode 0) and the straight line 1102. Note that in this embodiment, points 1100 and 1101 used to acquire the straight line 1102, which represents the relationship between transmitted power and received power when no foreign object is present around the power transmitting device 102 and the power receiving device 101, are referred to as calibration data points. Furthermore, a line segment (straight line 1102) acquired by interpolating at least two calibration data points is referred to as a calibration curve.

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

[0051] (2) Foreign object detection method based on Q-factor measurement in the time domain A foreign object detection method based on the Q-factor measurement method in the time domain will be described below with reference to FIG. 12. Waveform 1200 in FIG. 12(a) shows the value of the high-frequency voltage applied to the end of the power transmitting coil 303 or the resonance capacitor 305 of the power transmitting device 102 (hereinafter simply referred to as the voltage value of the power transmitting coil) over time, with the horizontal axis representing time and the vertical axis representing the voltage value. The example in FIG. 12(a) shows that the application of the 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, which represents the high-frequency voltage, 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 indicates that the voltage value at time T2 is A2. The quality factor (Q value) of the transmitting coil 303 is measured based on the change in the voltage value over time 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 performed by the power transmitting device 102 in this embodiment to measure the Q-factor in the time domain will be described with reference to Fig. 12(b). Waveform 1203 shows the value of the high-frequency voltage applied to the power transmitting coil 303, and its frequency is between 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, it is assumed that the power transmission processing unit 402 of the power transmitting device 102 stops power transmission during the period from time T0 to T5. The foreign object detection processing unit 403 of the power transmitting device 102 measures the Q value based on 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, based on the above-mentioned formula 1. Note that the power transmission processing unit 402 of the power transmitting device 102 resumes power transmission at time T5. In this way, the Q value is measured based on the elapsed time, the voltage value, and the operating frequency after the power transmitting device 102 momentarily interrupts power transmission. Hereinafter, the period from time T0 to T5 during which power transmission is stopped will be referred to as the stop time.

[0054] If a foreign object is present near the power transmitting device 102 and the power receiving device 101, the Q value decreases. This is because the presence of a foreign object causes energy loss due to the foreign object. Therefore, when focusing on the slope of the voltage attenuation, the slope of the line connecting points 1204 and 1205 becomes steeper and the attenuation rate of the waveform amplitude becomes higher when a foreign object is present than when no foreign object is present, because more energy is lost due to the foreign object. In other words, a foreign object detection method based on the Q value measurement method in the time domain determines the presence or absence of a foreign object based on the attenuation state of the voltage value between points 1204 and 1205. Furthermore, the actual presence or absence of a foreign object can be determined by comparing some numerical value representing this attenuation state. For example, the above-mentioned Q value can be used for the determination. Note that the waveform attenuation of the current value may be used instead of the voltage value.

[0055] The downtime must be determined based on the characteristics of the power transmitting device 102 and the power receiving device 101 before measuring the Q value. For example, the shortest possible downtime differs depending on the capabilities of the switch 306 and the control unit 300 of the power transmitting device 102, so the downtime must be longer than the shortest possible downtime. Also, since the accuracy of foreign object detection varies depending on the operating frequency and the amount of drop in voltage value even for the same downtime, it is necessary to select a downtime that can maintain a predetermined 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 the power transmitting device 102) Next, an example of the flow of basic processing executed by the power transmitting device 102 will be described. Fig. 5 is a flowchart showing an example of a basic processing procedure executed by the power transmitting device 102 in this embodiment. This processing is realized, for example, by the control unit 300 of the power transmitting device 102 executing a program read from the memory 307. This processing is also executed in response to the power being turned on of the power transmitting device 102, in response to the user of the power transmitting device 102 inputting an instruction to start a contactless charging application, or in response to the power transmitting device 102 being connected to a commercial power source and receiving power supply. This processing may also be started in response to some other trigger.

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

[0058] 7, the processes defined as the Selection phase and Ping phase performed in S501 will be described. In the Selection phase, the communication processing unit 401 of the power transmitting device 102 repeatedly and intermittently transmits an Analog Ping conforming to the WPC standard (F701). When the power receiving device 101 is placed (F702), the control unit 300 of the power transmitting device 102 detects that an object has been placed (F704), which causes a change in the Analog Ping (F703). When the control unit 300 detects that an object exists within the power transmission range, the process proceeds to the Ping phase, and the communication processing unit 401 of the power transmitting device 102 transmits a Digital Ping conforming to the WPC standard (F705). The power receiving device 101 detects that it has been placed on the power transmitting device 102 by the Digital Ping (F706). When a predetermined response to the Digital Ping is received, the control unit 300 of the power transmitting device 102 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 it is detected in S501 that the power receiving device 101 has been placed, the communication processing unit 401 of the power transmitting device 102 then acquires identification information and capability information from the power receiving device 101 through communication in the I&C phase defined by the WPC standard in S502. Here, the identification information received from the power receiving device 101 by the ID packet includes a manufacturer code and a basic device ID as identifier information. Furthermore, the capability information received from the power receiving device 101 by the configuration packet includes an information element that can identify the version of the WPC standard that the power receiving device 101 supports. Furthermore, the capability information includes a maximum power value that is a value that specifies the maximum power that the power receiving device 101 can supply to a load, and information indicating whether the power receiving device 101 has a negotiation function of the WPC standard.

[0060] Note that the above-described information acquired in S502 is an example, and the identification information and capability information of the power receiving device 101 may be replaced by other information, or may include other information in addition to the above-described information. For example, the identification information may be any other identification information capable of identifying 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 transmitting device 102 executes a negotiation process with the power receiving device 101 through communication in the negotiation phase defined in the WPC standard, and determines the value of the GP. Note that in S503, other procedures for determining the GP may be executed, not limited to communication in the negotiation phase defined in the WPC standard. Furthermore, for example, the power transmitting device 102 may acquire information indicating that the power receiving device 101 does not support the negotiation phase in S502. In such a case, the power transmitting device 102 may not execute communication in the negotiation phase, and may set the GP to a small value (predefined in advance in the WPC standard, for example). Furthermore, in the negotiation phase, in addition to the procedure for determining the GP, information regarding foreign object detection based on a Q-factor measurement method in the time domain is exchanged with the power receiving device 101. For example, the power receiving device 101 may notify supplementary information as to whether foreign object detection based on the Q-value measurement method in the time domain is possible, or the power transmitting 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.

[0062] Next, in S504, the power transmitting apparatus 102 executes a process of selecting a timeout period for calibration. Note that the detailed process of selecting a timeout period for calibration will be described later.

[0063] Next, in S505, the foreign object detection processing unit 403 of the power transmitting device 102 executes a 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 transmitting device 102 derives the relationship between transmitted power and received power in a state where no foreign object is present. Specifically, the foreign object detection processing unit 403 of the power transmitting device 102 derives a calibration curve using predetermined received power values ​​(including received power values ​​in a light load state and received power values ​​in a maximum load state) acquired from the power receiving device 101. Note that when deriving the calibration curve, the foreign object detection processing unit 403 of the power transmitting device 102 performs foreign object detection based on a Q-factor measurement method in the time domain each time each predetermined received power value is acquired. Furthermore, if it is decided in the negotiation phase to perform multiple attempts at foreign object detection based on the time-domain Q-factor measurement method, the foreign object detection processing unit 403 acquires the received power value and performs foreign object detection for each predetermined received power value for the number of attempts. This prevents the derivation of a calibration curve when a foreign object is present, and reduces the chance of foreign object detection or false detection.

[0064] Next, in S506, the power transmission processing unit 402 of the power transmitting apparatus 102 starts transmitting power to the power receiving apparatus 101 in the Power Transfer phase. Note that power transmission is performed by processing in the Power Transfer phase, but is not limited to this, and power transmission may be performed by a method other than the WPC standard.

[0065] If the control unit 300 of the power transmitting device 102 determines that the power receiving device 101 is not placed on the power transmitting device 102, the control unit 300 returns the process to the selection phase of S501. When the power transmitting device 102 receives an End Power Transfer of the WPC standard from the power receiving device 101, the power transmitting device 102 forcibly terminates the process in any processing phase in accordance with the WPC standard, stops power transmission, and returns to the selection phase of S501. When the power receiving device 101 is fully charged, the End Power Transfer is also transmitted from the power receiving device 101, and the process returns to the selection phase of S501.

[0066] Next, an example of the flow of a process for selecting a timeout period for calibration executed by the power transmitting device 102 in S504 will be described with reference to Fig. 6. Although the following describes an example of a selection process, the timeout period may be selected from predetermined candidates or 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 the version is of a predetermined version or higher can be determined from version information in capability information included in a configuration packet received from the power receiving device 101 in the I&C phase. Alternatively, for example, the determination may be made from information included in another packet, or based on information acquired using out-of-band communication such as Bluetooth (registered trademark) or NFC.

[0067] If it is determined in S601 that the version of the power receiving device 101 is equal to or higher than the predetermined version, the process proceeds to S602. On the other hand, if it is determined that the version of the power receiving device 101 is not equal to or higher than the predetermined version, the process proceeds to S605. In S605, the time selection processing unit 404 of the power transmitting device 102 selects a predetermined value as the timeout time related to the processing of the calibration phase, and ends the process. Note that this predetermined value is a reference value set by default.

[0068] Meanwhile, in S602, the control unit 300 of the power transmitting device 102 determines whether to perform foreign object detection based on the Q-factor measurement method in the time domain. Here, in the negotiation phase of S503, as shown in FIG. 7, supplemental information indicating whether foreign object detection based on the Q-factor measurement method in the time domain is possible is notified from the power receiving device 101 (F709). Then, the control unit 300 determines whether to perform foreign object detection based on the Q-factor measurement method in the time domain based on this supplemental information. Note that, for example, the determination may be made based on whether supplemental information indicating whether foreign object detection based on the Q-factor measurement method in the time domain is possible is received from the power receiving device 101. In this case, it may be determined that foreign object detection is possible by default if supplemental information is not received from the power receiving device 101, or it may be determined that the power receiving device 101 is not compatible with foreign object detection based on the Q-factor measurement method in the time domain based on the non-reception of supplemental information and therefore not to perform foreign object detection. If it is determined in S602 that foreign object detection based on the Q-factor 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-factor measurement method in the time domain is not possible, the process proceeds to S605.

[0069] In S603, the control unit 300 of the power transmitting device 102 determines whether or not to attempt foreign object detection based on the Q-value measurement method in the time domain a predetermined number of times or more. In this process, it determines whether or not the number of attempts determined by information exchange with the power receiving device 101 in the negotiation phase of S503 is a predetermined number of times or more. Alternatively, it may determine whether or not the number of attempts is a predetermined number of times or more based on, for example, a default number of attempts defined in the power transmitting device 102. If the determination in S603 indicates that the number of attempts is to be made a predetermined number of times or more, the process proceeds to S604. On the other hand, if the number of attempts is not to be 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 transmitting device 102 selects a value greater than the predetermined value determined in S605 as the timeout time for the processing of the calibration phase, and ends the processing. Note that the value greater than the predetermined value is a fixed value determined in advance as part of the Qi standard, but it may also be a variable value that increases in proportion to the number of attempts, for example. The timeout time is determined depending on the processing time required to perform foreign object detection based on the Q-factor measurement method in the time domain, the processing time required for the power receiving device 101 to notify the predetermined received power value by an RP packet, and the like.

[0071] (Processing flow executed by the system) Next, an operation sequence when the power transmitting device 102 executes the above-mentioned process will be described with reference to Fig. 7. Note that, in an initial state, the power receiving device 101 is not placed on the power transmitting device 102, and the power transmitting device 102 has a sufficient power transmission capability to be able to transmit power at the GP requested by the power receiving device 101. In the example shown in Fig. 7, the predetermined number of times that serves as the determination criterion in S603 is five times, but this is merely an example and another value may be used. Furthermore, F701 to F706 are the procedure described in S501 above.

[0072] In the I&C phase, identification information and capability information are exchanged between the power transmitting apparatus 102 and the power receiving apparatus 101 (F707). The processing of the power transmitting apparatus 102 in F707 is the processing of S502 in Fig. 5. In the example shown in Fig. 7, it is assumed that the power receiving apparatus 101 is a predetermined version or higher based on the capability information included in the configuration packet.

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

[0074] Next, the power transmitting device 102 notifies the power receiving device 101 of 7 times as information regarding the number of attempts to detect a foreign object based on the Q-value measurement method in the time domain (F711), starts the processing in Fig. 6, and selects a timeout period (F712). Note that in this embodiment, the information regarding the number of attempts to detect a foreign object based on the Q-value measurement method in the time domain is notified by being included in a response to the Generic Request packet transmitted from the power receiving device 101, but may be notified at another timing or in another packet.

[0075] Thereafter, the process shifts to the calibration phase, and the power transmitting device 102 receives a control error packet (CE packet) with a positive control error value from the power receiving device 101 (F713). The power transmitting device 102 then changes the transmission power output based on the control error value. Subsequently, when the power transmitting device 102 receives an RP packet (mode 1) indicating the received power value in a light load state from the power receiving device 101 (F714), the power transmitting device 102 performs foreign object detection processing based on the Q-factor measurement method in the time domain (F715). Because this is the first attempt out of seven attempts, the power transmitting device 102 responds that no determination will be made (F716). After completing the response, the power transmitting device 102 determines whether a timeout related to the processing in the calibration phase has occurred. In the example of FIG. 7, it is assumed that the selected timeout period has not elapsed (a timeout has not occurred) (F717). Thereafter, the processing of F714 to F717 is repeated five more times between the power transmitting device 102 and the power receiving device 101.

[0076] Next, when the power transmitting device 102 receives an RP packet (mode 1) from the power receiving device 101 (F718), it performs foreign object detection processing based on the Q-factor measurement method in the time domain (F719). Because this is the seventh attempt out of seven attempts, the power transmitting device 102 determines that no foreign object is present based on the results of the first to seventh foreign object determination processing. The power transmitting device 102 then responds with an ACK to the effect that it accepts the received power value Pr1 in the light load state to be used to derive a calibration curve (F720). Note that if it is determined that a foreign object is present based on the detection results of the seven foreign object detection processings based on the Q-factor measurement method in the time domain, it is not possible to derive a calibration curve. Therefore, in such a case, the power transmitting device 102 responds with a NAK (negative acknowledgement) to the effect that it cannot accept the received power value in the light load state.

[0077] When the power transmitting device 102 completes the response, it determines whether a timeout related to the processing of the calibration phase has occurred. In the example of Fig. 7, it is assumed that it has determined that the selected timeout period has not elapsed (a timeout has not occurred) (F721).

[0078] Next, the same processes as those in F713 to F717 are performed between the power transmitting device 102 and the power receiving device 101 for an RP packet (mode 2) indicating the received power value in the maximum load state (F722 to F726). Next, when the power transmitting device 102 receives the RP packet (mode 2) from the power receiving device 101 (F727), it performs foreign object detection processing based on the Q-factor measurement method in the time domain (F728). Because this is the seventh attempt out of seven attempts, the power transmitting device 102 determines that no foreign object is present based on the results of the first to seventh foreign object determination processing. Then, the power transmitting device 102 responds with an ACK indicating that it accepts the received power value Pr2 in the maximum load state to be used to derive the calibration curve (F729). After completing the response, the power transmitting device 102 determines whether a timeout related to the processing in the calibration phase has occurred. Note that in the example of FIG. 7, if a timeout time was selected in S605, it is assumed that the timeout time has already elapsed. 7, the power transmitting device 102 determines that a timeout has not occurred because the predetermined timeout period has elapsed but the selected timeout period has not elapsed (F730). Then, the calibration phase ends. After that, the power transmitting device 102 transitions to the power transfer phase, and processes related to power transmission and reception are performed between the power transmitting device 102 and the power receiving device 101 (F731).

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

[0080] (Second embodiment) In the first embodiment, the power transmitting device, which is responsible for deriving the calibration curve, changes the timeout period for the calibration phase processing to a larger value as needed based on the details of the foreign object detection attempt. However, setting the timeout period to a value greater than a predetermined value presents a problem in that it takes longer to start power transmission and reception. Therefore, if control is possible so that the desired calibration phase processing can be performed without changing the timeout period, such control is desirable. As an example, this embodiment describes a method in which the power receiving device selects and controls the maximum transmission time interval for RP packets based on the details of the foreign object detection attempt. The internal configurations of the power transmitting device and the power receiving device are the same as those of the first embodiment, and therefore a description thereof will be omitted. Below, differences from the first embodiment will be described. In this embodiment, the power transmitting device 102 does not select the timeout period, but instead fixes it to the value set in S605.

[0081] (Processing flow by the power receiving device) 8 is a flowchart showing an example of a basic processing procedure executed by the power receiving device 101 in this embodiment. This processing is realized, for example, by the control unit 200 of the power receiving device 101 executing a program read from the memory 209. This processing may also be executed in response to the power receiving device 101 being powered on and starting up as a result of power transmission from the battery 206 or the power transmitting device 102. Alternatively, this processing may also be executed in response to the user of the power receiving device 101 inputting an instruction to start a contactless charging application. This processing may also be started by some other trigger.

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

[0083] When it is detected in S501 that the power receiving device 101 has been placed on the power transmitting device 102, the control unit 200 of the power receiving device 101 then transmits identification information and capability information to the power transmitting device 102 by communication in the I&C phase defined in the WPC standard in S802. 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 defined in the WPC standard to determine the GP. 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, the information includes 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 received power value.

[0085] Then, in S804, the control unit 200 of the power receiving apparatus 101 executes a process of selecting the maximum transmission time interval of an RP packet. Details of the process of selecting the maximum transmission time interval of an RP packet will be described later.

[0086] Next, in S805, the control unit 200 of the power receiving device 101 performs communication in the calibration phase of the WPC standard. In this process, as described above, information on a predetermined received power value required to derive a calibration curve is transmitted to the power transmitting device 102. Then, in S806, the control unit 200 of the power receiving device 101 starts receiving power through communication in the power transfer phase defined in the WPC standard. Thereafter, if an error occurs or if the power receiving device 101 reaches full charge, the power receiving device 101 transmits an end power transfer command in 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 ends.

[0087] Next, an example of the flow of the process of selecting the maximum transmission time interval of an RP packet executed by the power receiving apparatus 101 in S804 will be described with reference to FIG. 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 transmitted to the power transmitting device 102, and whether the version is of the predetermined version or higher is determined based on version information included in the response. Alternatively, for example, the determination may be made based on version information notified from the power transmitting device 102 using a separate packet, or based on information obtained using out-of-band communication such as Bluetooth or NFC. Alternatively, the determination may be made based on version information obtained as capability information from the power transmitting device 102 in the I&C phase.

[0088] If the result of the determination in S901 is that the version is equal to or higher than the predetermined version, the process proceeds to S902. On the other hand, if the version is not equal to or higher than the predetermined 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 of RP packets, and ends the process. Note that this predetermined value is a reference value set by default.

[0089] Meanwhile, in S902, the control unit 200 of the power receiving device 101 determines whether to perform foreign object detection based on the Q-value measurement method in the time domain. Here, the determination of whether to perform foreign object detection is made based on whether the power receiving device 101 itself is capable of foreign object detection based on the Q-value measurement method in the time domain. On the other hand, for example, the determination may be made based on whether a notification regarding the number of attempts to perform foreign object detection based on the Q-value measurement method in the time domain has been received from the power transmitting device 102. At this time, it may be determined that foreign object detection is possible if no notification has been received from the power transmitting device 102, or that the power transmitting device 102 does not support foreign object detection based on the Q-value measurement method in the time domain and therefore is not capable of performing foreign object detection if no notification has been received from the power transmitting device 102. If the determination in S902 indicates that 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 Q-value measurement method in the time domain a predetermined number of times or more. In this process, it determines whether the number of attempts notified from the power transmitting device 102 in the negotiation phase is a predetermined number or more. Alternatively, for example, it may be determined based on whether a notification regarding the number of attempts to detect foreign objects based on the Q-value measurement method in the time domain has been received from the power transmitting device 102. At this time, it may be determined that attempts will be made a predetermined number of times or more if no notification is received from the power transmitting 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 indicates that attempts will be made a predetermined number of times or more, the process proceeds to S904. On the other hand, if attempts are not made a predetermined number of times 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 determined in S905 as the maximum transmission time interval of the RP packet, and ends the process. Note that the value smaller than the predetermined value may be, for example, a variable value that decreases in proportion to the number of attempts. In addition, the maximum transmission time interval is determined depending on the processing time required to perform foreign object detection based on the Q-factor measurement method in the time domain, the processing time required to reach a predetermined received power value, etc.

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

[0093] Upon receiving notification of the number of attempts from the power transmitting device 102, the power receiving device 101 starts processing to select the maximum transmission time interval for RP packets (F1012). Because the version of the power transmitting device 102 is equal to or greater than a predetermined value, foreign object detection based on the Q-factor measurement method in the time domain is possible, and the number of attempts is equal to or greater than a predetermined number (=5), the power receiving device 101 selects a value smaller than a predetermined value as the maximum transmission time interval for RP packets. Thereafter, processing of the calibration phase is started between the power transmitting device 102 and the power receiving device 101, and the power receiving device 101 transmits a CE packet with a positive Control Error Value to the power transmitting device 102 (F1013).

[0094] Next, the power receiving device 101 transmits an RP packet (mode 1) indicating the received power value in a light load state to the power transmitting device 102 (F1014), and the power transmitting device 102 performs foreign object detection processing based on the Q-factor measurement method in the time domain (F1015). In this case, since this is the first attempt out of seven attempts, the power receiving device 101 receives a response from the power transmitting device 102 indicating that no determination has been made (F1016). After completing the response, in the example of FIG. 10, it is assumed that the power transmitting device 102 determines that no timeout has occurred in the processing of the calibration phase (F1017). Thereafter, the power transmitting device 102 and the power receiving device 101 repeat the processing of F1014 to F1017 five more times. At this time, after receiving the response indicating that no determination has been made in response to the transmission of the previous RP packet, the power receiving device 101 transmits the next RP packet so as not to exceed the maximum transmission time interval selected in F1012.

[0095] Next, when the power receiving device 101 transmits an RP packet (mode 1) to the power transmitting device 102 (F1018), the power transmitting device 102 performs foreign object detection processing based on the Q-factor measurement method in the time domain (F1019). Because this is the seventh attempt out of seven attempts, the power transmitting device 102 determines that no foreign object is present based on the results of the first to seventh foreign object determination processes. The power transmitting device 102 then responds with an ACK indicating that it accepts the received power value Pr1 in a light load state to be used to derive a calibration curve (F1020). After completing the response, the power transmitting device 102 determines whether a timeout has occurred related to the processing of the calibration phase. In the example of FIG. 10, it is determined that a predetermined timeout period has not elapsed (F1021).

[0096] Next, the power receiving apparatus 101 transmits a CE packet with a positive Control Error Value to the power transmitting apparatus 102 to set the received power value at the maximum load state (F1022). At this time, the power receiving apparatus 101 specifies a larger positive value for the Control Error Value compared to when foreign object detection based on the Q-factor measurement method in the time domain is not attempted multiple times. The number of CE packet transmissions is also increased compared to when foreign object detection based on the Q-factor measurement method in the time domain is not attempted multiple times. This makes it possible to reach the desired received power value in a shorter time than when foreign object detection based on the Q-factor measurement method in the time domain is not attempted multiple times. In other words, RP packets (mode 2) indicating the received power value at the maximum load state can be transmitted at shorter time intervals. Therefore, even if a value smaller than a predetermined value is selected as the maximum transmission time interval for RP packets, the calibration process can be continued while maintaining the interval. The subsequent processes from F1023 to F1031 are the same as F723 to F731 in FIG. 7, and therefore description thereof will be omitted.

[0097] As described above, according to this embodiment, the power receiving device 101 selects the maximum transmission time interval for RP packets depending on the content of the foreign object detection process attempt. 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 transmitting device 102 immediately starts the calibration process after selecting a timeout time through the timeout time selection process. However, the selected timeout time may be notified to the power receiving device 101. For example, the power transmitting device 102 may notify the power receiving device 101 of the number of attempts to detect a foreign object based on the Q-value measurement method in the time domain, and then notify the power receiving device 101 of the timeout time by including the timeout time in a response to a Generic Request packet transmitted from the power receiving device 101. Note that notification may also be made 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, according to the timeout time notified from the power transmitting device 102, while reducing the processing load. This makes it possible to realize 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 the process of selecting the maximum transmission time interval of the RP packet and then immediately starts the calibration process. However, the selected maximum transmission time interval may be notified to the power transmitting device 102. For example, a method is conceivable in which information about the maximum transmission time interval is included in a Specific Request packet and transmitted before transmitting the RP packet, or notification may be made at another timing or using another packet. This enables 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 related to the process of the calibration phase will occur at an earlier timing than when a timeout determination is made using the timeout period until the specified RP packet is received.

[0100] In the first and second embodiments, the power transmitting device 102 notifies the power receiving device 101 of the number of attempts to detect a foreign object 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 transmitting device 102 is performed, 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 the RP packet. In this case, the power receiving device 101 may request the power transmitting device 102 to notify information about the number of attempts again, using a generic request packet or the like, in order to re-determine the number of attempts. Alternatively, the power receiving device 101 may send an End Power Transfer to stop the processing and restart from the selection phase processing. Alternatively, if the processing of the calibration phase is expected to be sufficiently completed within the timeout period for the processing of the calibration phase, the power receiving device 101 may re-determine the number of attempts to increase the number of attempts in order to improve the accuracy of foreign object detection.

[0101] In the first and second embodiments, the case where the processing of the calibration phase is completed within the timeout period has been described. On the other hand, when a timeout period occurs, the power transmitting device 102 stops power transmission. However, the power transmitting output may be reduced without stopping power transmission, or the processing of the selection phase may be restarted after power transmission is stopped. When the processing of the selection phase is restarted, the timeout period may be set to a value greater than the previously selected value, or the number of attempts to detect a foreign object based on the Q-factor measurement method in the time domain may be reduced, and the processing of the calibration phase may be executed. This makes it possible to more reliably complete the processing of the calibration phase within the timeout period, i.e., to derive a calibration curve, thereby realizing a safer and more efficient wireless power transmission system. Furthermore, the processing of the power transmitting 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 transmitting device 102 determines whether a timeout has occurred each time it receives an RP packet, but it may also determine whether a timeout has occurred after multiple receptions or after a predetermined period of time. This makes it possible to suppress the execution of unnecessary processes and realize a highly efficient wireless power transmission system.

[0103] The power receiving device 101 and the power transmitting device 102 may have a function 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 the information processing terminal. For example, the information terminal device has a display unit (display) that displays information to a 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 from the battery to the display unit. In this case, the power receiving device 101 may have a communication unit that communicates with another device different from the power transmitting device 102. The communication unit may be compatible with communication standards such as NFC communication or the fifth generation mobile communication system (5G). In this case, the communication unit may perform communication by receiving power from the battery. The power receiving device 101 may be a tablet terminal, a storage device such as a hard disk device and a memory device, or an information processing device such as a personal computer (PC). The power receiving device 101 may also be, for example, an imaging device (such as a camera or a 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, a copier, or a projector. The power receiving device 101 may also be a robot, a medical device, or the like. The power transmitting device 102 may be a device for charging the above-mentioned devices.

[0104] The power transmitting 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 the present embodiment may be a vehicle such as an automobile. For example, the automobile serving as the power receiving device 101 may receive power from a charger (power transmitting device 102) via a power transmitting antenna installed in a parking lot. Alternatively, the automobile serving as the power receiving device 101 may receive power from the charger (power transmitting device 102) via a power transmitting 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 driving unit (motor, electric unit) that drives the wheels, or may be used to drive a sensor used for driving assistance or a communication unit that communicates with an external device. In other words, in this case, the power receiving device 101 may include, in addition to the wheels, a battery, a motor or sensor that is driven using the received power, and a communication unit that communicates with devices other than the power transmitting device 102. Furthermore, the power receiving device 101 may have a storage unit for accommodating a person. For example, the sensor may be a sensor used to measure the distance between vehicles or the distance to other obstacles. The communication unit may be compatible with, for example, a Global Positioning System (Global Positioning Satellite, GPS). The communication unit may also be compatible with communication standards such as a fifth-generation mobile communication system (5G). The vehicle may also be a bicycle or a motorcycle. The power receiving device 101 is not limited to a vehicle, and may also be a moving object, an aircraft, or the like having a power generating unit that is driven using power stored in a battery.

[0106] Furthermore, the power receiving device 101 in this embodiment may be an electric tool, a home appliance, or the like. These devices, which are the power receiving device 101, may have a battery and a motor that is driven by received power stored in the battery. These devices may also have a notification means that notifies the user of the remaining battery charge, etc. These devices may also have a communication unit that communicates with other devices different from the power transmitting device 102. The communication unit may be compatible with communication standards such as NFC and the fifth generation mobile communication system (5G).

[0107] Furthermore, the power transmitting device 102 in this embodiment may be an in-vehicle charger that transmits power to a mobile information terminal device, such as a smartphone or tablet, that supports wireless power transmission within the vehicle. Such an in-vehicle charger may be installed anywhere within the vehicle. For example, the in-vehicle charger may be installed in the console of the vehicle, on the instrument panel (instrument panel, dashboard), between passenger seats, on the ceiling, or in the door. However, it is preferable that the charger not be installed in a location that interferes with driving. Furthermore, although the power transmitting device 102 has been described as an example of an in-vehicle charger, such a charger is not limited to being installed in a vehicle, but may also be installed in transportation vehicles such as trains, airplanes, and ships. In this case, the charger may also be installed between passenger seats, on the ceiling, or in the door.

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

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

[0110] 401 communication processing unit, 403 foreign object detection processing unit, 404 time selection processing unit

Claims

[Claim 1] A power transmitting device that wirelessly transmits power to a power receiving device, a first detection means for detecting whether or not an object other than the power transmitting device and the power receiving device is present based on a power loss between the power transmitting 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 transmitting device and the power receiving device is present based on an attenuation state of a waveform of a voltage or a current related to the power transmission; a calculation means for calculating a reference value of power loss when there is no object different from the power transmitting device and the power receiving device used for detection by the first detection means, based on a detection result by the second detection means; a determination unit that determines a timeout period for a process related to calculation of the reference value by the calculation unit based on the capability information related to the power receiving device acquired by the acquisition unit; and The power transmitting device is characterized in that the determination means selects a first value as the timeout time if the power receiving device does not satisfy a specified condition, and determines a second value greater than the first value as the timeout time if the power receiving device satisfies the specified condition.

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