JP2014212660A - Power transmission apparatus, power reception apparatus, method and program therefor, and power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transmission efficiency by appropriately detecting foreign matter between a power transmission apparatus and a power reception apparatus and performing power transmission when a positional relationship between the power transmission apparatus and the power transmission apparatus is appropriate.SOLUTION: The power transmission apparatus for transmitting electric power to the power reception apparatus intermittently performs transmission of electric power by radio, detects a load-modulated signal from the power reception apparatus relative to transmitted electric power and, when the load-modulated signal is detected, extends a transmission period. The power transmission apparatus starts normal power transmission on the basis of received electric power of the power reception apparatus when an acquired ID is appropriate.

Description

  The present invention relates to a power transmission device, a power reception device, a method thereof, a program, and a power transmission system.

  Since MIT (Massachusetts Institute of Technology) conducted a field experiment of wireless power transmission by magnetic resonance in 2007, wireless power transmission technology has been widely researched and developed. In addition, wireless power transmission is used in combination with wireless communication, and has attracted attention as a technology aiming for complete wireless transmission (Non-Patent Document 1). Further, in recent years, wireless power transmission technology is spreading in various fields such as charging / transmission of electric vehicles and hybrid vehicles, and charging of small devices such as smartphones. For example, Patent Document 1 describes a power transmission management device that transmits power to a vehicle.

JP 2013-38924

"Developed technology to transmit power wirelessly, lighting 60W light bulb in experiment", Nikkei Electronics, No. 966, December 3, 2007

  When considering the safe operation of a wireless power transmission system, especially in systems that can transmit power even when the distance between the power transmitting device and the power receiving device is long, such as the magnetic resonance method, objects that can exist in the transmittable range Consideration is necessary. That is, it is necessary to prevent power transmission to a foreign object other than the power transmission target and other unauthenticated devices as much as possible within the power transmission range of the power transmission device. In addition, it is necessary to suppress heat generation or the like due to a reduction in efficiency because the power receiving device is arranged at an appropriate position as a relative positional relationship for the power transmitting device and the power transmitting device transmits power only when the power receiving device is in an appropriate positional relationship.

  Patent Document 1 discloses a method in which authentication between a power transmission device and a power reception device is performed before power transmission by the power transmission device, and the power transmission supplied by the power transmission device is confirmed to match the power received by the vehicle to continue power transmission. Have been described. However, when this method is used, high power is transmitted and received immediately after the authentication between the power transmitting apparatus and the power receiving apparatus is completed. Therefore, even when the positional relationship between the power transmission device and the power reception device is not appropriate, there is a problem in that the power transmission device starts power transmission and transmission efficiency decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to enable wireless power transmission based on the positional relationship between a power transmission device and a power reception device.

  As a means for achieving the above object, a power transmission device of the present invention has the following configuration. That is, a power transmission device that transmits power to a power receiving device detects intermittently transmitting power that intermittently performs wireless power transmission, and a load-modulated signal from the power receiving device for power transmitted by the intermittent power transmitting device And a means for extending the power transmission period of the intermittent power transmission means when the load-modulated signal is detected by the detection means.

  ADVANTAGE OF THE INVENTION According to this invention, it can detect efficiently that the positional relationship of a power transmission apparatus and a power receiving apparatus is appropriate.

1 is a diagram illustrating a wireless power transmission system according to an embodiment. The figure which shows the power transmission part structure of the power transmission apparatus by embodiment. The figure which shows the power receiving part structure of the power receiving apparatus by embodiment. The timing chart of the wireless power transmission system in an embodiment. The flowchart which shows operation | movement of the power transmission apparatus by embodiment. The flowchart which shows operation | movement of the power receiving apparatus by embodiment. The figure which shows the appropriate positional relationship of the power transmission apparatus and power receiving apparatus in embodiment.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings. The configurations shown in the following embodiments are merely examples, and the present invention is not limited to the illustrated configurations.

[First Embodiment]
The present embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a wireless power transmission system according to the present embodiment. The wireless power system according to the present embodiment includes a power transmission device 20 and a power reception device 30. The power transmission device 20 and the power reception device 30 respectively include a communication unit 22 and a communication unit 32 that perform wireless communication using, for example, Bluetooth (registered trademark). The communication unit 22 and the communication unit 32 convert digital signals transmitted through the communication line 26 and the communication line 36, respectively, and perform wireless communication through the antenna 24 and the antenna 34, respectively. The power transmission unit 21 in the power transmission device 20 converts direct current or alternating current power input from the transmission line 25 into alternating current frequency power in the transmission band, and transmits the power via the antenna 23. The power receiving unit 31 in the power receiving device 30 converts AC power received via the antenna 33 into DC power or AC power having a desired frequency, and outputs the AC power to the power transmission line 35.

  When using power transmission using resonance or microwaves, the power transmission distance is long, so pairing the power transmission device and power reception device to transmit power to the desired device, and power transmission to other devices and objects It is necessary to prevent. In the present embodiment, the power receiving device 30 first searches for the power transmitting device 20 via the communication unit 32, and performs authentication between the communication unit 32 and the communication unit 22. Specifically, an ID is exchanged between the communication unit 32 of the power receiving device 30 and the communication unit 22 of the power transmission device 20 at the time of authentication.

  FIG. 2 is a block diagram illustrating an example of details of the internal configuration of the power transmission unit 21 of the power transmission device 20. The CPU 212 includes an initial power transmission unit 2121, a power transmission period extension unit 2122, a detection mode signal detection unit 2123, an ID match determination unit 2124, a power reception efficiency calculation unit 2125, a normal power transmission unit 2126, and a foreign object detection unit 2127. The description of the function of each part of the CPU 212 will be described later. The display unit 27 displays information input from each unit of the CPU 212. The constant power transmission unit 214 is a constant voltage source or the like, and the initial power transmission unit 2121 of the CPU 212 sets power necessary for power reception and power necessary for a power transmission initial sequence (hereinafter referred to as “initial sequence”). The initial power transmission unit 2121 may further transmit initial power by periodic intermittent power transmission. The switch 215 is used when the initial power is periodically intermittently transmitted during the initial sequence. The switch 215 may be used for transmitting simple data to the power receiving device 30 by ON / OFF. In FIG. 2, the switch 215 is disposed between the constant power transmission unit 214 and the AC conversion unit 216. However, since the output power only needs to be ON / OFF, the switch 215 is provided in front of the constant power transmission unit 214 or the AC conversion unit 216. May be placed after. Further, the output of AC power may be turned on / off by turning on / off a drive signal of a switching element (not shown) inside the AC converter 216 instead of the switch 215. The AC conversion unit 216 converts direct current or alternating current such as commercial power into a frequency for power transmission.

  The power reception impedance detection unit 213 detects load modulation performed by the power reception device 30 and impedance changes of the antenna 33 and other power reception units 31. The power reception impedance detection unit 213 generally detects power reception impedance by detecting reflection due to mismatch between the power transmission device 20 side impedance including the power transmission antenna 23 and the power reception device 30 side impedance. Generally, since the coupling efficiency between power transmission and reception changes when the positional relationship between the power transmission and reception devices changes, reflection due to mismatching changes even if the power reception impedance of the power reception device 30 does not change. However, when the load modulation in the power receiving device 30 is performed with a predetermined value such as a unique word, the power receiving impedance detection unit 213 can distinguish whether the power receiving impedance is changed or the position is changed. In addition, the power reception impedance detection unit 213 can detect that an object is placed in a predetermined range from the power transmission device 20 based on a change in impedance on the power transmission device 20 side including the power transmission antenna 23.

  The initial impedance storage unit 217 stores the initial impedance when there is nothing around the power transmission device 20. When the power receiving impedance detection unit 213 detects an impedance different from the initial impedance without receiving the load modulation from the power receiving device 30 during initial power transmission, the foreign object detection unit 2127 controls the switch 215 to stop the initial power transmission. To do. Then, the foreign object detection unit 2127 displays the foreign object detection on the display unit 27. The ID storage memory 211 stores an ID determined by device authentication by the communication unit 22. Also, the ID match determination unit 2124 checks whether the ID included in the detection mode signal detected by the detection mode signal detection unit 2123 matches the ID stored in the ID storage memory 211, and if it matches, the ID match notification I do.

  After transmitting the ID match notification, the power transmission device 20 performs intermittent power transmission for power reception efficiency calculation. When receiving the intermittent power transmission for calculating the power receiving efficiency, the power receiving apparatus 30 transmits the received power amount to the power transmitting apparatus 20 via load modulation or the communication unit 32. When the power reception efficiency calculation unit 2124 of the CPU 212 detects the power reception power amount of the power reception device 30 from the impedance detection unit 213 or the communication unit 22, the power reception efficiency is calculated by comparing with the transmission power. The power reception efficiency calculation unit 2124 determines that the power reception efficiency is lower than a predetermined threshold value. The display unit 27 displays that the power receiving efficiency is poor, and prompts the user to move the power receiving device 30 to an appropriate position. On the other hand, when the power reception efficiency exceeds the threshold, the normal power transmission unit 2125 starts normal power transmission.

  Even if the initial sequence power transmission is intermittent power transmission and power is transmitted to a foreign object, it is desirable to secure a heat dissipation period for the foreign object and suppress a steady temperature rise due to continuous power transmission. However, when the transmission power in the initial sequence is sufficiently small and the foreign object detection time in the initial sequence is sufficiently short, the power transmission in the initial sequence can be performed by continuous power transmission.

  FIG. 3 is a block diagram showing an example of the details of the internal configuration of the power receiving unit 31 of the power receiving device 30 of FIG. The CPU 312 includes a detection mode signal generation unit 3121, a power calculation unit 3122, and an ID match notification reception unit 3123. The description of the function of each part of the CPU 312 will be described later. The display unit 37 displays information input from each unit of the CPU 312. 314 in the power reception unit 31 is an AC power conversion unit, which includes a rectifier circuit, a constant voltage source, and the like. The impedance changing unit 313 adjusts the matching of the power receiving antenna 33 and further performs load modulation with the detection mode signal. The impedance changing unit 313 sets the impedance when the circuit side is viewed from the power receiving antenna 33 to a high impedance unless the authentication by the communication unit 32 is finished. The detection mode signal generation unit 3121 of the CPU 312 reads the ID from the ID storage memory 311 that stores the ID determined by the authentication by the communication unit 32, and generates a detection mode signal. The impedance changing unit 313 performs load modulation with the generated detection mode signal.

  Next, operations in the initial sequence of the power transmission device 20 and the power reception device 30 will be described with reference to FIG. FIG. 4 shows a timing chart of the power transmission device 20 and the power reception device 30. In FIG. 4, the vertical axis of the power transmission device 20 schematically shows the amount of power transmission, and the vertical axis of the power reception device 30 schematically shows the power reception impedance. In the following description, as shown in FIG. 7, it is assumed that the power receiving device 30 is approaching the power transmitting device 20 to receive power. FIG. 7 shows a communication range 701, a power transmission range 702, and a range 703 in which power transmission is possible with appropriate efficiency when the power receiving device 30 approaches the power transmission device 20.

  When the power receiving device 30 enters the communication range 701 of the power transmitting device 20 illustrated in FIG. 7, the power receiving device 30 enters device authentication with the power transmitting device 20. In the device authentication, an ID is exchanged between the power transmission device 20 and the power reception device 30. When the device authentication 400 is completed, the power transmission device 20 starts initial power transmission for ID detection at a constant period. In this embodiment, initial power is intermittently transmitted (T401 to T405). At this time, the initial power transmission unit 2121 of the CPU 212 supplies the minimum power value necessary for the initial sequence until normal power transmission (until ID detection within the band with the power receiving device and confirmation of power reception efficiency is completed) at constant power transmission. Set in section 214. Specifically, the initial power transmission unit 2121 sets the load modulation of the power receiving device 30 to power that can be detected by the power transmission device 20 within a range including the range 703 in which power can be transmitted with appropriate efficiency.

  The power receiving apparatus 30 repeatedly performs load modulation with the detection mode signal including the ID exchanged at the time of device authentication 400, which is “1,0,1,0,0,1,0,1” in the example of FIG. 4 (R401 to R406). ). When the power receiving device 30 is separated from the power receiving device 20 and is not within the power receivable range, even if the power receiving device 30 performs load modulation, the transmitted power is not consumed, and almost all the intermittent power transmission from T401 to T404 is performed. reflect. When the power receiving device 30 enters the power transmission range 702 shown in FIG. 7 as the power receiving device 30 approaches the power transmitting device 20, the power modulated by the load modulation of the power receiving device 30 starts to be transmitted like the intermittent power transmission T405. .

  When the power transmission device 20 performs intermittent power transmission when transmission power starts to be modulated by the ID, the power transmission period of the intermittent power transmission is extended to the start point of the next detection mode signal, which is the ID start point in FIG. In FIG. 4, the detection mode signal is composed of only the ID, but may include a start bit sequence, a stop bit sequence, and other information. In addition, in the figure, for the sake of simplicity, the detection mode signal is only ID, and the power transmission period is extended based on partial detection of the ID, but the power transmission period is extended based on partial detection of the detection mode signal. May be. After extending the power transmission period of intermittent power transmission to the start point of the next detection mode signal, the power transmission device 20 continues power transmission to the end point of the detection mode signal in order to acquire an ID. In FIG. 4, the power transmission device 20 continues to transmit power until it detects the ID of the next detection mode signal. Thereafter, the power transmission device 20 checks a match between the detected ID and the ID determined by the device authentication. If they match, the power transmission device 20 transmits an ID match notification T406. The ID match notification T406 may be transmitted from the communication unit 22 of the power transmission device 20 to the communication unit 32 of the power reception device 30, or by controlling the constant power transmission unit 214 and the switch 215, the transmitted power is transmitted as an ID match notification signal. You may modulate and transmit. After transmitting the ID match notification, the power transmission device 20 starts intermittent reception for detecting power reception efficiency (T407 to 409).

  The power receiving device 30 detects the ID match notification after the power from the power transmitting device 20 exceeds the predetermined value, and then receives the intermittent power, measures the received power every time the intermittent power is received, and modulates the load with that value. (R407-409). The power transmission device 20 detects the received power value from the load-modulated value, and compares the power transmitted by the own device with the received power to calculate the power reception efficiency. In the example of FIG. 4, it is determined that the power reception efficiency exceeds a predetermined threshold at the time of the third intermittent transmission T409, and the power reception device 30 enters the appropriate efficiency transmission range 703 shown in FIG. Switching. In FIG. 4, the power receiving device 30 performs load modulation with the amount of received power and transmits it, but it may transmit from the communication unit 32 to the communication unit 22 of the power transmission device 20.

  In FIG. 4, the power transmission device 20 starts intermittent power transmission for power reception efficiency measurement after the ID match notification T406, but the power reception efficiency measurement method is not limited to this. That is, the power receiving device 30 detects the amount of received power at the time of low impedance at the time of load modulation by the detection mode signal, that is, at the time of transmitting “0” of R406, and the amount of received power at the time of receiving the ID match notification T406. May be notified. As this notification, there can be considered a method of the received power amount notification by load modulation during the ID match notification and out-of-band communication using the communication unit 32. Further, another power transmission period may be provided after the ID match notification, and may be performed during that period. It is clear that intermittent power transmission for detecting power reception efficiency is not necessary if the received power at the time of modulation by the detection mode signal or at the time of ID coincidence notification exceeds a predetermined threshold.

  Next, the operation of the power transmission device 20 will be described with reference to FIGS. 2 and 5. FIG. 5 is an example of a flowchart from device authentication of the power transmission device 20 to normal power transmission. When power transmission / reception device authentication is completed (S501), the initial power transmission unit 2121 sets the transmission power of the constant power setting unit 214 to initial setting power (S502), and starts ID detection initial power transmission (S503). . In the case of intermittent power transmission, the initial power is intermittently transmitted using the switch 215. The power receiving impedance detection unit 213 constantly monitors the impedance during the power transmission period of intermittent power transmission, and detects a device whose load is modulated by the detection mode signal including the ID determined in the device authentication S501. Here, the initial impedance storage unit 217 stores in advance an initial impedance in a state where there is no foreign object such as a device or metal that can receive power of a frequency transmitted to the periphery by the power transmission device 20.

  When the power reception impedance detection unit 213 detects an impedance different from the initial impedance (Yes in S504), the foreign object detection unit 2127 determines the presence of the foreign object. Specifically, the foreign object detection unit 2127 determines that a foreign object has been detected when it detects an impedance that is modulated by the ID and has no possibility of load modulation (Yes in S505). Then, the power reception impedance detection unit 213 controls the switch 215 via the CPU 212 to stop power transmission (S516), and performs an error display indicating foreign object detection via the display unit 27 (S517). For example, if the power reception impedance detection unit 213 detects an impedance that is constant different from the initial impedance, there is a possibility that a metal or the like is in proximity, so the display unit 27 displays that there is a metal object and moves to the user Prompt. Similarly, when the power receiving impedance detection unit 213 detects a load modulated signal in a format different from that of the power receiving device 30, there is a power receiving device of a different model or a device communicating in the same band in the vicinity. This is displayed on the display unit 27 to prompt the user to move. Here, since the power transmission device 20 has stopped power transmission, after the user removes the foreign matter, an operation such as pressing a button (not shown) indicating the completion of the foreign matter removal work is detected (S518), and ID detection initial power is detected. Return to power transmission (S503). If the transmission power of the ID detection initial power transmission is sufficiently small or the foreign object detection time is sufficiently small and the possibility of failure due to heat generation or power reception of the foreign object is sufficiently small (No in S504, No in S505), You may return to the ID detection initial power transmission (S503) without the user's return operation.

  When the impedance detected by the power reception impedance detection unit 213 is the same as the initial impedance, and when the detection mode signal detection unit 2123 partially detects the detection mode signal (Yes in S504), when initial power is intermittently transmitted The process proceeds to S506. Then, the power transmission period extending unit 2122 extends the power transmission period of intermittent power transmission until the head portion of the next detection mode signal is detected (S506). When the initial power is continuously transmitted, the process of S506 is not necessary. Here, if the detection mode signal detection unit 2123 does not detect the head portion of the next detection mode signal during a certain period, it has detected load modulation of a power receiving device of another standard or the desired power receiving device 30 It may have gone away. In this case, the detection mode signal detection unit 2123 displays an error on the display unit 27 and prompts the user to respond (S519). Then, by returning to the initial power transmission for ID detection, it is confirmed that other standard devices are excluded or the desired power receiving device 30 is detected. When the detection mode signal detection unit 2123 detects the start of the detection mode signal (Yes in S507), when the initial power is intermittently controlled, the power transmission period extension unit 2122 further extends the power transmission period until the detection mode signal completion time (S508). Here, even when the head of the detection mode signal is detected from the beginning in S504, the power transmission period until the detection mode signal is completed can be extended because the head portion of the detection mode signal in S507 has already been detected.

  The ID match determination unit 2124 checks for a match between the ID determined by the device authentication and the ID detected by the detection mode signal (S509). If the ID is different (No in S509), there is a possibility that another power receiving device of the same standard that has been authenticated with another power transmitting device exists in the vicinity, so that is displayed on the display unit 27 and moved to the user (S519). Then, by returning to the initial power transmission for ID detection, the exclusion of another power receiving device of the same standard can be confirmed. If it is determined that the IDs match (Yes in S509), the ID match determination unit 2124 transmits an ID match notification (S510). The ID match determination unit 2124 may transmit this ID match notification from the communication unit 22 to the communication unit 32 of the power receiving device 30, or control the constant power transmission unit 214 and the switch 215 to match the transmitted power with the ID match. You may transmit by modulating with a notification signal. After transmitting the ID match notification, the initial power transmission unit 2121 starts intermittent power reception efficiency detection transmission (S511). When the power receiving device 30 receives intermittent power, the power receiving device 30 measures the received power each time and performs load modulation with the measured value. The power reception efficiency calculation unit 2125 detects the power reception power value from the load-modulated value (S512), and compares the power transmitted by the own device with the power reception power to calculate the power reception efficiency (S513). When the power reception efficiency is equal to or less than a predetermined threshold, the power reception efficiency calculation unit 2125 determines that the power reception device 30 is not in the appropriate efficiency transmission range 703 shown in FIG. Display a recommendation to move to a location (520). When the efficiency exceeds the threshold value, the power reception efficiency calculation unit 2125 determines that the efficiency is within the appropriate efficiency transmission range 703, and switches the process to normal power transmission by the normal power transmission unit 2126 (S515).

  Next, the operation of the power receiving device 30 will be described with reference to FIGS. 3 and 6. FIG. 6 is an example of a flowchart from device authentication of the power receiving device 30 to normal power transmission. The impedance changing unit 313 sets the impedance of the antenna 33 or a load (not shown) (power reception impedance) high until the device authentication (S602) with the power transmission device 20 is finished, and transmits the power transmission device of another standard or the same standard. The power from the unauthorized power transmission device is not received (S601). This avoids heat generation and failure of the power receiving device. After the device authentication (S602), the power receiving apparatus 30 performs load modulation with the detection mode signal including the ID exchanged by the device authentication (S603). This detection mode signal is generated by a detection mode signal generation unit 3121. Further, this load modulation may be performed by the impedance changing unit 313 in FIG. 3 or by changing the load of the AC power converting unit 314. Further, ON / OFF of an antenna switch (not shown) may be used.

  When the power receiving device 30 is far from the power transmitting device 20, the power receiving device 30 receives little power (No in S604), but when the power receiving device 30 approaches the power transmitting device 20 and enters the power transmission range 702 in FIG. The electric power transmitted by the device 20 is modulated by the load modulation of the own device and received (Yes in S604). That is, it becomes a power detection state. If the power transmitting device is a device that has been authenticated by device authentication (S602), an ID match notification is transmitted from the power transmitting device 20 following the completion of load modulation of the detection mode signal by the power receiving device 30 (S603, S604). Yes). For this reason, the impedance changing unit 313 sets the power receiving impedance to such an extent that the ID match notification can be received after the completion of the next detection mode signal modulation after the power detection (S605). However, the ID match notification may be performed via the communication units 22 and 23. In FIG. 6, the modulation by the detection mode signal is stopped after the power detection, but the detection mode signal modulation may be continued until the ID match notification is received. Further, when the ID match notification is transmitted / received via the communication units 22 and 32, the impedance changing unit 313 may set the power receiving impedance high after the detection mode signal modulation is completed.

  If the ID match notification is not received even if power is detected (No in S606), there is a possibility of power transmission from another standard power transmission device or power reception from another power transmission device of the same model. An error is displayed in 37 (S611), and the user is prompted to move the position. When the power receiving device 30 receives the ID match notification (Yes in S606), the impedance changing unit 313 sets the power receiving impedance low (S607), and receives the intermittent power transmission for calculating the power receiving efficiency. Each time the power receiving device 30 receives power, the power receiving device 30 returns the received power by load modulation, or returns information on the received power via the communication units 32 and 22 (S608). However, each time the power receiving device 30 receives power, it simply returns the received power by load modulation or via the communication units 32 and 22 (S611), and this process is continued until it is determined that the power is continuously received (No in S609). ). If it is determined that power is continuously received (Yes in S609), it is determined that power is normally received (S610).

  As described above, the power transmission device 20 according to the present embodiment does not start power transmission unless the desired power transmission target for which authentication has been performed enters a range in which the desired power can be supplied and the power transmission target does not match the desired power transmission target. Thereby, although it is not a power transmission object, the heat_generation | fever and the failure by electric power transmission can be prevented. In addition, the power receiving device 30 according to the present embodiment reduces the power receiving impedance only when power from the authenticated power transmitting device is supplied, thereby preventing unnecessary power reception from an unauthenticated device and damaging the device. The possibility of this can be reduced.

  In the present embodiment, the power transmission device 20 starts normal power transmission when the power receiving efficiency is equal to or higher than the threshold after determining the ID match, but may start normal power transmission after determining the ID match. . In addition, the power transmission device 20 determines an appropriate positional relationship with the power receiving device 30 from the power receiving efficiency that can be calculated from the power received by the power receiving device 30, but the power received by the power receiving device 30 is not limited to the power receiving efficiency. Any relevant value is acceptable. In this embodiment, in order to calculate the power reception efficiency, the power reception efficiency is calculated by intermittent power transmission from the power transmission device. However, the power reception efficiency may be calculated by continuous power transmission.

[Other Embodiments]
The present invention can also be realized by executing the following processing. That is, software (program) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (21)

A power transmission device for transmitting power to a power receiving device,
Intermittent power transmission means for performing wireless power transmission intermittently;
Detecting means for detecting a load-modulated signal from the power receiving apparatus for the power transmitted by the intermittent power transmitting means;
A power transmission apparatus comprising: an extension unit that extends a power transmission period of the intermittent power transmission unit when the load-modulated signal is detected by the detection unit.   The power transmission device according to claim 1, further comprising a determination unit that determines whether or not a predetermined ID matches between the ID acquired from the load-modulated signal and the power receiving device.   The power transmission device according to claim 2, further comprising notification means for notifying the power receiving device of an ID match notification when the determination means determines that the IDs match.   The power transmission device according to claim 2 or 3, wherein normal power transmission is started when the determination unit determines that the IDs match.   The power transmission device according to claim 4, wherein the normal power transmission is started when a value related to the received power of the power receiving device is equal to or greater than a threshold before the normal power transmission is started.   The power transmission device according to claim 4 or 5, wherein the power transmitted by the intermittent power transmission means is lower than the power transmitted by the normal power transmission. A foreign matter detection means for detecting foreign matter between the storage means for storing the initial impedance and the power receiving device;
When the impedance when the load-modulated signal is not detected by the detection means is different from the initial impedance stored in the storage means, the foreign object detection means determines that a foreign object has been detected. The power transmission device according to any one of claims 1 to 6.   The power transmission device according to claim 7, further comprising a display unit configured to display an error when a foreign object is detected by the foreign object detection unit.   The power transmission device according to any one of claims 2 to 6, further comprising a display unit that displays an error when the determination unit determines that the IDs do not match.   The power transmission device according to claim 5 or 6, further comprising a display unit that performs a display for prompting movement when a value obtained from the received power of the power reception device is lower than a threshold value.   The power transmission apparatus according to claim 2, wherein the predetermined ID is determined in device authentication performed between the power transmission apparatus and the power reception apparatus. A power receiving device that receives power from a power transmitting device,
A modulation means for repeating load modulation with a signal including a predetermined ID is provided.
A power receiving device that repeats load modulation by the modulation means until electric power intermittently transmitted from the power transmitting device becomes larger than a predetermined value. A power receiving device that receives power from a power transmitting device,
A notification means for notifying the power transmission device of a predetermined ID by load modulation,
The power receiving device, wherein the notification by the notification unit is repeated until a notification indicating that the ID is received from the power transmitting device is received. It further includes a changing unit that changes the value of the power receiving impedance,
14. The power receiving device according to claim 12, wherein the changing unit sets the power receiving impedance to a low value when receiving the power intermittently transmitted from the power transmitting device after setting the power receiving impedance to be high. .   The power receiving device according to claim 14, wherein the power receiving impedance is further set lower when an ID match notification is notified from the power transmitting device after the changing unit sets the power receiving impedance low.   The power receiving device according to claim 12, further comprising a display unit that displays an error when an ID match notification is not notified from the power transmitting device. A power transmission system having a power transmitting device and a power receiving device,
The power transmission device is:
Intermittent power transmission means for performing wireless power transmission intermittently;
Detecting means for detecting a load-modulated signal from the power receiving apparatus for the power transmitted by the intermittent power transmitting means;
When the load-modulated signal is detected by the detection unit, the extension unit extends a power transmission period by the intermittent power transmission unit,
The power receiving device is:
A modulation means for repeating load modulation with a signal including a predetermined ID is provided.
The power transmission system, wherein load modulation by the modulation means is repeated until the power transmitted intermittently from the power transmission device becomes larger than a predetermined value. A method of controlling a power transmission device that transmits power to a power receiving device,
An intermittent power transmission process for intermittently transmitting power by wireless;
A detection step of detecting a load-modulated signal from the power receiving device for the electric power transmitted in the intermittent power transmission step;
A control method for a power transmission device comprising: an extension step of extending a power transmission period in the intermittent power transmission step when the load-modulated signal is detected in the detection step. A method of controlling a power receiving device that receives power from a power transmitting device,
A modulation process that repeats load modulation with a signal including a predetermined ID;
A method for controlling a power receiving apparatus, wherein load modulation is repeated in the modulation step until electric power transmitted intermittently from the power transmitting apparatus becomes larger than a predetermined value.   The program for making a computer perform each process of the control method of the power transmission apparatus described in Claim 18.   A program for causing a computer to execute the steps of the power receiving apparatus control method according to claim 19.

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