Power transmission device and method

Abstract

To provide a highly convenient wireless power transmission system in which a plurality of communication methods can be used for control communication.SOLUTION: A power transmission device has a first communication function for communicating with a power reception device and a second communication function for communicating with the power reception device at a radio frequency different from that of the first communication function, and determines whether to use the first communication function or the second communication function for communication to control wireless power transmission, based on apparatus information obtained from the power reception device through communication using the first communication function.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a wireless power transmission system. [Background technology]

[0002] In recent years, devices having wireless communication functions and wireless power transmission functions have been studied. Patent Document 1 describes a power transmission device that performs control communication when transmitting power from a power transmission coil via the power transmission coil at the same frequency as the transmitted power. Hereinafter, communication performed at the same frequency as the transmitted power will be referred to as "in-band communication." Patent Document 2 describes a power transmission device that performs control communication at a different frequency from the transmitted power via an antenna different from the power transmission coil. Hereinafter, communication performed at a different frequency from the transmitted power will be referred to as "out-band communication." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-075857 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-198562 Summary of the Invention [Problem to be solved by the invention]

[0004] Whether to use one of a plurality of communication methods, such as in-band communication or out-band communication, for control communication may differ for each device. In contrast, conventionally, a separate power transmission device has been required for each communication method used by a device, resulting in a problem of low convenience.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a highly convenient wireless power transmission system in which a plurality of communication methods can be used for control communication. [Means for solving the problem]

[0006] A power transmission device according to one aspect of the present invention includes: Wirelessly transmits power to a powered device power transmitting means and the power receiving device; At the first frequency Communicate R a first means of communication; A second frequency higher than the first frequency communicate with the power receiving device on the R A second communication means; the first communication means receives identification information of the power receiving device at the first frequency after starting power transmission to the power receiving device at the first frequency, and receives a power transmission stop request from the power receiving device at the first frequency after receiving the identification information; the power transmitting means starts power transmission at the second frequency after receiving the power transmission stop request by the first communication means; and the second communication means receives the identification information of the power receiving device at the second frequency after starting power transmission at the second frequency. . [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a highly convenient wireless power transmission system in which a plurality of communication methods can be used for control communication. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a block diagram illustrating a configuration example of a power transmission device. [Figure 2] FIG. 2 is a block diagram illustrating a configuration example of a power receiving device. [Figure 3] FIG. 1 illustrates an example of a system configuration. [Figure 4] 1 is a time chart showing communication within the system. [Figure 5] 10 is a flowchart illustrating an example of the flow of processing executed by the power transmitting device. [Figure 6] 10 is a flowchart illustrating an example of the flow of processing executed by a power receiving device. [Figure 7] FIG. 10 is a diagram illustrating an example of the configuration of identification information. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples for the purpose of explanation, and at least some of the configurations according to the following embodiments may be omitted, or additional elements may be added. Furthermore, the order of the methods of the following embodiments may be changed, some steps may be omitted, or additional steps may be used.

[0010] In a wireless power transmission system, a power transmitting device and a power receiving device may perform control communication using either in-band communication, which performs communication using the same radio frequency band as the wireless power transmission, or out-band communication, which performs communication using a different radio frequency band. In this case, the power transmitting device according to the present embodiment determines whether to perform control communication using in-band communication or out-band communication based on information acquired from the power receiving device via in-band communication. The acquired information may include, for example, device information indicating whether the power receiving device supports high-power wireless power transmission, whether out-band communication is possible, or other functions possessed by the power receiving device. However, this information is not limited to this, and various other information, such as the status of the power receiving device, may also be acquired. This allows the power transmitting device to perform control communication in an appropriate manner depending on, for example, the capabilities and status of the power receiving device. Note that in-band communication and out-band communication are merely examples. For example, the power transmitting device may have a first communication function and a second communication function using a different radio frequency than the first communication function, and may determine which communication function to use based on information acquired via the first communication function. In this case, the first communication function may use the same radio frequency as that for wireless power transmission, or may use a different radio frequency. That is, in the following, in-band communication is used as an example of the first communication function, and out-band communication is used as an example of the second communication function, but the following technology can be applied in various ways.

[0011] (Device configuration) First, the configuration of the device according to this embodiment will be described. Fig. 1 is a block diagram showing an example of the configuration of a power transmitting device 100 according to this embodiment. The power transmitting device 100 includes, for example, a control unit 101, a power source 102, a power transmitting unit 103, a communication unit 104, a power transmitting coil 105, an RFID (Radio Frequency IDentifier) ​​reader 106, and a memory 107.

[0012] The control unit 101 controls the entire device by executing a control program stored in, for example, memory 107. The control unit 101 may be, for example, one or more processors such as a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor). The control unit 101 may also use the memory 107 to store values ​​of variables acquired during the execution of the control program. The memory 107 stores the control program executed by the control unit 101 and other information.

[0013] The power source 102 supplies power to the power transmitting unit 103 when the power transmitting device 100 performs wireless power transmission. The power source 102 is, for example, a commercial power source or a battery. The power transmitting unit 103 converts DC power or AC power input from the power source 102 into AC power in a frequency band used for wireless power transmission, and generates electromagnetic waves to be transmitted via the power transmitting coil 105. The power transmitting unit 103 according to this embodiment operates in accordance with, for example, a standard established by the Wireless Power Consortium (WPC), a standardization organization for contactless charging standards, and the AC power uses a frequency in the 100 kHz band. However, this is not necessarily limited thereto, and the power transmitting unit 103 may also comply with a standard other than the WPC standard, or a frequency other than the 100 kHz band may be used as the AC power. Based on an instruction from the control unit 101, the power transmitting unit 103 outputs electromagnetic waves from the power transmitting coil 105 to transmit power to a partner device of the wireless power transmission (for example, the power receiving device 200). Furthermore, the power transmitting unit 103 can control the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmission voltage) or current (power transmission current) input to the power transmitting coil 105. Increasing the power transmission voltage or power transmission current increases the intensity of the electromagnetic waves transmitted accordingly. Furthermore, the power transmitting unit 103 can perform control to stop power transmission from the power transmitting coil 105 based on an instruction from the control unit 101.

[0014] The communication unit 104 performs control communication related to wireless power transmission based on the WPC standard with the communication unit 204 of the power receiving device 200. The communication unit 104 performs control communication through in-band communication using the same frequency as the wireless power transmission. The communication unit 104 may transmit information by modulating the electromagnetic waves output from the power transmitting unit 105. The communication unit 104 may also acquire information through load modulation performed by the power receiving device that receives the electromagnetic waves output from the power transmitting unit 105. The communication unit 104 may also perform communication other than control communication as necessary. The reader 106 is, for example, an interrogator that complies with the ISO / IEC 18000-63 standard, which is an RFID standard for the UHF band (900 MHz band). The reader 106 supplies power for operating the RFID tag by continuously transmitting a carrier wave, and can also read and write information stored in the memory of the RFID tag. The reader 106 performs control communication when the power transmitting unit 103 transmits power to the power receiving unit 205 of the power receiving device 200 by out-of-band communication, which uses a frequency different from that of wireless power transmission.

[0015] 2 is a diagram showing an example of the configuration of a power receiving device 200 according to this embodiment. The power receiving device 200 includes, for example, a control unit 201, an RFID tag 202, a power receiving coil 203, a communication unit 204, a power receiving unit 205, a charging unit 206, and a battery 207.

[0016] In one example, the control unit 201 is connected to the tag 202, the communication unit 204, and the power receiving unit 205, and controls the entire power receiving device 200 by executing a control program stored in a memory (not shown), for example. The control unit 201 can be one or more processors, such as a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor).

[0017] The tag 202 is a UHF band (900 MHz band) RFID tag that operates in compliance with the same standards as the reader 106 of the power transmitting device 100. The tag 202 operates using the carrier wave transmitted by the reader 106 as activation power, and performs control communication with the reader 106 via out-of-band communication when the power receiving unit 205 receives power from the power transmitting unit 103 of the power transmitting device 100.

[0018] The memory in the tag 202 consists of four banks (UII memory or EPC memory, TID memory, USER memory, and RESERVED memory). Here, UII is an acronym for Unique Item Identifier, EPC is an acronym for Electrical Product Code, and TID is an acronym for Tag Identifier. The UII memory or EPC memory stores the UII or EPC, which is the identification information of the product in which the tag is mounted. The TID memory stores the identification code of the tag manufacturer, etc. The USER memory stores information that can be freely used by the tag user. The RESERVED memory may store passwords for accessing each memory bank and for disabling the chip. With RFID, a reader can read and write to the memory in the tag in three stages: Select, Inventory, and Access. Of these stages, the reader can obtain some of the information, such as the UII or EPC, stored in the memory area in the tag during the inventory stage.

[0019] The communication unit 204 performs control communication for wireless power transmission based on the WPC standard with the communication unit 104 of the power transmitting device 100 via in-band communication. The communication unit 204 may acquire information by demodulating modulated electromagnetic waves from the power transmitting device 100. The communication unit 204 may also vary the load of the power receiving unit 205 and transmit information through load modulation. The communication unit 204 may also perform communication other than control communication as necessary. The power receiving unit 205 receives power transmitted by the power transmitting unit 103 of the power transmitting device 100 via the power receiving coil 203, converts it into a DC voltage, and supplies it to the charging unit 206. The power receiving coil 203 and the power receiving unit 205 are configured to extract power from electromagnetic waves transmitted by a device operating in accordance with the WPC standard, such as the power transmitting device 100. The charging unit 206 controls charging of the battery 207 using the DC voltage supplied from the power receiving unit 205.

[0020] The power transmitting device 100 and the power receiving device 200 may be devices dedicated to wireless power transmission, or may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, and projectors. The power transmitting device 100 and the power receiving device 200 may be storage devices such as hard disk drives or memory devices, or information processing devices such as personal computers (PCs) or smartphones. That is, the power transmitting device 100 and the power receiving device 200 may be any electronic device having a function of wireless power transmission. In this case, for example, the destination of the power received by the power receiving unit 205 does not have to be the charging unit 206. For example, the power receiving unit 205 may be directly connected to a predetermined circuit in the electronic device including the power receiving device 200, and the received power may be supplied to the circuit.

[0021] (Processing flow) The processing flow in the system state shown in FIG. 3A will be described below with reference to FIGS. 4 to 6. FIG. 3A shows a state in which the power receiving device 200 is placed on the power transmitting device 100. A dashed line 300 exemplarily indicates the power transmission range of the power transmitting unit 103 and the range in which in-band communication by the communication unit 104 can be performed. A dashed-dotted line 301 exemplarily indicates the range in which out-band communication by the reader 106 can be performed. As shown in FIG. 3A, the range in which out-band communication can be performed is wider than the range in which in-band communication can be performed. FIG. 4 is a time chart showing an outline of the processing flow executed by the power transmitting unit 103 and the reader 106 of the power transmitting device 100 and the tag 202 and the power receiving unit 205 of the power receiving device 200 according to this embodiment. In FIG. 4, the horizontal axis represents time, and the vertical axis represents power in the power transmitting unit 103, the reader 106, the tag 202, and the power receiving unit 205, respectively. 5 is a flowchart showing an example of the flow of processing executed by the power transmitting device 100, and FIG. 6 is a flowchart showing an example of the flow of processing executed by the power receiving device 200. In FIG. 6, the processing indicated by dotted lines is optional and does not necessarily need to be executed. That is, for example, if the determination in S602 in FIG. 6 is NO, the processing indicated by dotted lines may be omitted and the processing in S603 may be executed. Below, first, a case where such optional processing is not executed will be described, and these optional processing will be described afterwards.

[0022] Below, (1) the case where out-of-band communication is used will be explained, followed by (2) the case where out-of-band communication is not used, according to the time chart of FIG.

[0023] (1) When out-of-band communication is used <Time t1-t2> The power transmitting unit 103 performs an operation defined in the Selection phase of the WPC standard from time t1 to time t2. The Selection phase is a phase in which the power transmitting device 100 performs object detection. During this phase, the power transmitting unit 103 periodically transmits Analog Ping 400, which is a small amount of power for detecting an object placed within the power transmitting device 100. When an object is present within the power transmitting range indicated by the dashed line 300, the voltage of the power transmitting coil 105 when transmitting the Analog Ping is smaller than when an object is not present within the range. Therefore, the power transmitting unit 103 can detect the presence of an object within the power transmitting range by monitoring the voltage of the power transmitting coil 105. In this example, it is assumed that the power receiving device 200 is placed on the power transmitting device 100, and the power transmitting unit 103 detects the object at time t2 and notifies the control unit 101. In response to this, the power transmitting device 100 transitions from the Selection phase to the Ping phase and starts the processing of FIG. 5. 5 may be started by, for example, the control unit 101 executing a program stored in the memory 107. Meanwhile, the power receiving device 200 may start the process of FIG. 6 when the power receiving unit 205 is powered on. For example, the power receiving device 200 may start the process of FIG. 6 when the power is turned on or when the wireless power transmission function is turned on. Also, the control unit 201 and the power receiving unit 205 of the power receiving device 200 may be activated in response to receiving a Digital Ping in S601 of FIG. 6 and then execute the subsequent process. Note that during the period from time t1 to t2, the reader 106 of the power transmitting device 100 does not transmit a carrier wave.

[0024] <Time t2-t3> Between time t2 and t3, the Ping phase, Identification & Configuration (I&C) phase, and Negotiation phase in the WPC standard are executed. Here, the state transitions defined in the WPC standard will be described.

[0025] In the Ping phase, the power transmitting unit 103 transmits a Digital Ping. The Digital Ping is power used to supply power to the power receiving unit 205 to activate it and perform in-band communication, and has a higher power level than the Analog Ping. In the Ping phase, the power receiving device 200 transmits a Signal Strength (SS) Packet, which is a packet that stores the voltage value of the received Digital Ping. Then, when the power transmitting device 100 receives this packet, the process transitions to the I&C phase.

[0026] In the I&C phase, the power receiving unit 205 transmits identification information to the power transmitting unit 103 as an Identification (ID) Packet. Thereafter, the power receiving unit 205 transmits a Configuration Packet that stores information including the maximum amount of power to be supplied to the load (in this case, the charging unit 206). Thereafter, the power receiving unit 205 transmits a Negotiation Request Packet to transition to the Negotiation phase. When the power transmitting unit 103 transmits an ACK indicating acceptance in response to the Negotiation Request Packet, the processing transitions to the Negotiation phase. Note that if the power transmitting unit 103 transmits a NAK indicating rejection in response to the Negotiation Request Packet, the power transmitting unit 103 stops transmitting Digital Ping power, and the processing returns to the Selection phase.

[0027] The identification information transmitted by the power receiving unit 205 in the I&C phase has a configuration, for example, as shown in FIG. 7 . In FIG. 7 , Major Version 701 and Minor Version 702 indicate the versions of the WPC standard. For example, for WPC standard version 1.2, Major Version 701 is set to “1” and Minor Version 702 is set to “2.” WPC standard version 1.2 is a standard for transmitting low power (maximum 15 watts), and in this embodiment, in-band communication is used for control communication related to power transmission in this standard. Also, in this embodiment, when a standard for transmitting high power, such as maximum 50 watts (hereinafter referred to as a high-power standard), is used, out-band communication is used for control communication related to power transmission. Manufacture ID 703 indicates an identification number indicating the manufacturer of the power receiving unit 205 or the power receiving device 200, and Device ID 704 indicates an individual identification number of the power receiving unit 205 or the power receiving device 200. The combination of Manufacture ID 703 and Device ID 704 of one device will not overlap with the combination of Manufacture ID 703 and Device ID 704 of another device. Hereinafter, the combination of Manufacture ID 703 and Device ID 704 will be referred to as individual identification information. In this embodiment, the memory area of ​​the tag 202 is assumed to include identification information such as that shown in FIG. 7 as a UII or EPC.

[0028] In the Negotiation phase, negotiations regarding the power to be transmitted and received are carried out between the power transmitting unit 103 and the power receiving unit 205. When this negotiation is successful, the process transitions to the Calibration phase. The Calibration phase is not relevant to the following explanation and will not be described here, but the process here is one that is typically performed by devices that perform wireless power transmission using WPC. When the Calibration phase ends, the process transitions to the Power Transfer (PT) phase, in which the power receiving unit 205 supplies power to the load. If the power transmitting unit 103 transmits an ACK to the power receiving unit 205 in the Calibration phase, the process transitions to the PT phase, but if a NAK is transmitted, the process remains in the Calibration phase.

[0029] Note that arrow 401 in FIG. 4 indicates that in-band communication is being performed between power transmitting unit 103 and power receiving unit 205 from the Ping phase to the Negotiation phase.

[0030] In this period, as described above, at time T2, the control unit 101 and the power transmitting unit 103 of the power transmitting device 100 detect an object (power receiving device 200) and therefore transmit a Digital Ping (S501).

[0031] When the control unit 201 of the power receiving device 200 receives a Digital Ping (S601), it is activated by the power supply and determines whether or not charging of the battery 207 is necessary. For example, this determination can be made depending on whether or not the remaining charge of the battery 207 is equal to or greater than a predetermined value. If the power receiving unit 205 determines that charging is not necessary, it transmits an End Power Transfer (EPT), which is a message indicating that power transmission will be stopped, to the power transmitting unit 103 via in-band communication. It is assumed here that the power receiving unit 205 determines that charging is necessary and does not transmit an EPT. Then, the control unit of the power receiving device transmits an SS Packet, an ID Packet, and a Configuration Packet to the power transmitting device 100.

[0032] Next, the control unit 201 of the power receiving device 200 determines whether control communication can be performed via RFID (S602). For example, the control unit 201 accesses the memory in the tag 202 via wired communication such as I2C (Inter-Integrated Circuit). If the control unit 201 can access the memory, it determines that the tag is activated and control communication via RFID can be performed. If the control unit 201 cannot access the memory, it determines that control communication via RFID cannot be performed. According to FIG. 4, during the period from time t2 to t3, the reader 106 does not transmit a carrier wave and the tag 202 is not activated. Therefore, the control unit 201 determines that control communication cannot be performed via RFID because it cannot access the tag 202 (NO in S602), and determines that control communication should be performed via in-band communication rather than via RFID (S603).

[0033] In the power transmitting device 100, the power transmitting unit 103 does not receive the EPT (NO in S502) but receives the SS Packet and the ID Packet (and the Configuration Packet) (S503, S504). Then, the control unit 101 stores the information elements stored in the ID Packet in the memory 107 (S505). Then, the control unit 101 determines whether or not control communication via RFID is executable (S506). Note that the determination of whether control communication via RFID is executable may be a determination of whether high power can be transmitted. For example, the control unit 101 may check whether the power receiving device 200 supports control communication using RFID based on the identification information stored in the ID Packet as shown in FIG. 7. Here, it is assumed that the power receiving device 200 supports the high power standard and is capable of control communication using RFID. In this case, the communication unit 204 of the power receiving device 200 stores information indicating the high power standard in the Major Version and Minor Version of the ID Packet and transmits it. The control unit 101 of the power transmitting device 100 determines from this ID packet that control communication with the power receiving device 200 can be performed using RFID (YES in S506), and determines to perform control communication using RFID rather than in-band communication (S507). In this case, the power transmitting device 100 performs processing to switch the control communication from in-band communication to out-band communication. In this embodiment, the power transmitting unit 103 of the power transmitting device 100 stops Digital Ping, thereby ending the control sequence using in-band communication. For example, when the power transmitting device 100 receives a Negotiation Request packet transmitted by the power receiving device 200 (S508), it transmits a NAK in response (S509). After transmitting the NAK, the power transmitting device 100 terminates Digital Ping at time t3 (S510). In this case, when the power transmitting device 100 transmits Digital Ping again, it will perform the control using out-band communication, as will be described later.

[0034] <Time t3-t4> During this period, the power transmitting unit 103 of the power transmitting device 100 stops transmitting Digital Ping power, and therefore the control unit 201 and the power receiving unit 205 of the power receiving device 200 cannot receive drive power and are in a power-off state.

[0035] <Time t4-t5> During the period from time t4 to t5, the reader 106 of the power transmitting device 100 detects the tag 202 of the power receiving device 200, and the reader 106 is ready to read and write data from and to the memory in the tag 202. Specifically, the control unit 101 of the power transmitting device 100 causes the reader 106 to transmit a carrier wave to start supplying drive power to the tag 202 of the power receiving device 200 (S511), and the tag 202 receives the carrier wave and starts up. Then, the reader 106 executes inventory processing (S512). In the inventory processing, the reader 106 first transmits a Query command to the tag 202. In response to this command, the tag 202 transmits RN16, which is a 16-bit random bit string, to the reader 106. The reader 106 transmits an ACK(RN16) containing RN16 to the tag 202. Upon receiving the ACK(RN16), the tag 202 transmits the UII or EPC, which is identification information of the product (i.e., the power receiving device 200) in which the tag 202 is implemented, to the reader 106. The reader 106 transmits to the tag 202 a Req_RN command requesting a "Handle," which is a 16-bit authentication number used when reading from or writing to the memory in the tag 202. The tag 202 then transmits the Handle to the reader 106. Through these processes, the reader 106 becomes able to read from or write to the memory in the tag 202.

[0036] 4 indicates out-of-band communication between the tag 202 and the reader 106. During the time period from t4 to t5, the power transmitting unit 103 does not transmit a Digital Ping, and the control unit 201 and the power receiving unit 205 of the power receiving device 200 remain powered off.

[0037] When the control unit 101 of the power transmitting device 100 acquires the identification information (UII or EPC) from the tag 202, the control unit 101 compares the acquired identification information with the identification information of the power receiving device 200 stored in the memory 107 in S505 (S513). Here, since the same identification information as that included in the ID Packet is included in the memory area (UII or EPC) of the tag, the identification information included in the UII or EPC matches the identification information included in the ID Packet (YES in S514). Therefore, the control unit 101 of the power transmitting device 100 can determine that the power receiving device 200 equipped with the tag 202 that performed outband communication during the period from time t4 to t5 is the same as the power receiving device 200 that performed inband communication during the period from time t2 to t3. Therefore, the control unit 101 of the power transmitting device 100 determines that the tag 202 from which the identification information was acquired is the counterpart of control communication using the reader 106 (S515).

[0038] In the determination of S514, it is not necessary that the identification information included in the ID packet and the identification information stored in the memory 107 exactly match, but it is sufficient that these pieces of identification information have a predetermined correspondence relationship, that is, that they relate to the same power receiving device 200. For example, if the value resulting from calculation of a predetermined function that uses the identification information included in the ID packet as an argument and returns different results for different arguments is the same as the value of the identification information stored in the memory 107, it can be determined that these pieces of information have the predetermined correspondence relationship.

[0039] <Time t5-t6> The control unit 101 of the power transmitting device 100 executes the WPC sequence via out-of-band communication. Arrow 403 in FIG. 4 indicates control communication according to the WPC standard, which is performed using communication between the reader 106 and the tag 202 enabled by arrow 402, and corresponds to control from the Ping phase to just before the PT phase. In this control, first, the control unit 101 of the power transmitting device 100 causes the power transmitting unit 103 to transmit a Digital Ping (S516). Upon receiving this Digital Ping (S601), the control unit 201 of the power receiving device 200 determines whether control communication can be performed via RFID (S602), as in the above-described case. In this case, because the tag 202 has received a carrier wave from the reader 106 and is activated, the control unit 201 can access the memory in the tag 202 via wired communication, such as I2C. Therefore, the control unit 201 determines that control communication via RFID is executable (YES in S602), and determines that control communication will be executed via RFID (S604).

[0040] The control unit 101 of the power transmitting device 100 executes the above-described processes of the I&C phase, the Negotiation phase, and the Calibration phase through out-band communication between the reader 106 and the tag 202 (S517). Note that, unlike S509, the control unit 101 of the power transmitting device 100 here transmits an ACK in response to the Negotiation Request transmitted by the power receiving device 200. This is because, at the time when the Negotiation Request is received, the control communication is being performed through out-band communication, and therefore there is no need to switch from in-band communication to out-band communication.

[0041] <Time t6-t7> During this period, the process shifts to the PT phase, and the control unit 101 of the power transmitting device 100 controls the power transmitting unit 103 to transmit power to the power receiving unit 205 (S518). During this period, the reader 106 transmits a carrier wave to the tag 202, and in parallel with the supply of power related to wireless power transmission by the power transmitting unit 103, the reader 106 supplies driving power to the tag 202 for control communication using RFID.

[0042] The control communication at t5-t7 uses the USER memory in the memory area of ​​the RFID tag.

[0043] <Time t7-t8> When charging of the battery 207 is completed at time t7, the power receiving device 200 transmits an EPT. When the control unit 101 of the power transmitting device 100 receives the EPT (S519), it stops power transmission from the power transmitting unit 103 (S520) and controls the reader 106 to stop transmitting the carrier wave (S521). That is, the control unit 101 stops the supply of drive power from the reader 106 to the tag 202 in response to the stop of power transmission from the power transmitting unit 103. When the control unit 101 of the power transmitting device 100 stops power transmission from the power transmitting unit 103, it executes the operation of the Selection phase described above. That is, the power transmitting unit 103 periodically transmits an Analog Ping. In this case, because the power receiving device 200 remains placed on the power transmitting device 100, the control unit 101 of the power transmitting device 100 transmits a Digital Ping at time t8. However, in this case, the control unit 201 of the power receiving device 200 transmits the EPT to the power transmitting device 100 (arrow 404 in FIG. 4) because charging of the battery 207 has finished. Note that, at this time t7, the reader 106 has stopped transmitting the carrier wave, so this control communication is performed by in-band communication, not by RFID.

[0044] In this way, the power transmitting device can determine whether the power receiving device is capable of out-of-band communication based on device information received from the power receiving device, such as an ID packet, and accordingly, the power transmitting device can appropriately perform wireless power transmission (e.g., at high power) with the power receiving device capable of out-of-band communication.

[0045] (2) When out-of-band communication is not used The control unit 101 of the power transmitting device 100 receives an ID packet from the power receiving device 200 via in-band communication from time t2 to t3 (S504). In this case, if the information in the ID packet indicates WPC1.2 compatibility, for example, the control unit 101 determines that control communication via RFID cannot be performed (NO in S506) and determines to continue control communication via in-band communication (S522). Thereafter, the control communication described as being performed via out-band communication from time t5 to t8 above is performed via in-band communication.

[0046] In this way, the power transmitting device can determine whether the power receiving device should use in-band communication based on device information received from the power receiving device, such as an ID packet, and can appropriately transmit wireless power to and from the power receiving device that should use in-band communication.

[0047] Furthermore, when the power transmitting device 100 is performing in-band communication, the power receiving device 200 of this embodiment performs in-band communication accordingly (time t2-t3), and when the power transmitting device 100 is performing out-band communication, the power receiving device 200 performs out-band communication accordingly (time t4-t7). In this way, the power receiving device 200 selects a control communication method in accordance with the operation of the power transmitting device 100. Therefore, even if the power transmitting device 100 supports only in-band communication, the power receiving device 200 will not be unable to perform control communication with the power transmitting device 100.

[0048] As described above, the power transmitting device 100 according to this embodiment can perform control communication regardless of whether the power receiving device 200 supports out-band communication or in-band communication, thereby improving the convenience of the wireless power transmission system.

[0049] Furthermore, the reader 106 of the power transmitting device 100 according to this embodiment transmits a carrier wave during a period (e.g., time t4-t7) when an RFID-compatible power receiving device is present within the power transmission range and charging is required. This reduces the power consumption of the power transmitting device 100 and reduces radio wave interference with surrounding wireless systems compared to when the reader 106 continues to transmit the carrier wave during time t1-t8. Note that the reader 106 may continue to transmit the carrier wave constantly.

[0050] Furthermore, from the viewpoint of power saving and reduction of radio wave interference, the time during which the reader transmits the carrier wave can be shortened as much as possible. That is, power transmission may be started after it is confirmed that the RFID is usable, and power transmission may be stopped immediately when it is determined that control communication using the RFID is not necessary. In this embodiment, the reader 106 starts transmitting the carrier wave after the power receiving device 200 determines that control communication using the RFID is possible, and the reader 106 quickly stops transmitting the carrier wave when it receives the EPT at t7. This allows the time during which the reader 106 transmits the carrier wave to be minimized.

[0051] Furthermore, the control unit 101 of the power transmitting device 100 transmits a Digital Ping at t5 after the reader 106 has become capable of reading and writing to the tag 202 from t4 to t5, i.e., after control communication has become possible. This enables stable power transmission control using RFID. For example, if the power transmitting unit transmits a Digital Ping at time t4, the reader 106 is not yet capable of reading and writing to the tag 202, and therefore power transmission control may be impossible from t4 to t5. However, according to this embodiment, it is possible to avoid such a state.

[0052] It has also been described that the control unit 101 of the power transmitting device 100 selects a tag to be read from or written to based on the identification information of the power receiving device received through in-band communication and the identification information received through out-band communication (period t3-t4, NO in S514). This enables the power transmitting device 100 to appropriately select and communicate with a partner device (power receiving device 200) of wireless power transmission. For example, as shown in FIG. 3B, a tag 202 (tag of the power receiving device 200) that complies with the WPC standard and a tag 302 that does not comply with the WPC standard are present around the power transmitting device 100. In this case, the power transmitting device 100 acquires the identification information of both the tag 202 and the tag 302 of the power receiving device 200 in S513. At this time, the power transmitting device 100 compares the acquired identification information with the identification information acquired through in-band communication in S505, and therefore does not select the tag 302 as an RFID access target (NO in S514). Even if the tag 302 is provided in another power receiving device that complies with the high-power standard, the power transmitting device 100 does not select the tag 302 as an RFID access target because the power transmitting device 100 does not acquire identification information of the other power receiving device through in-band communication. The individual identification information of the tag 302, including at least the Manufacture ID and Device ID, is different from the individual identification information of the power receiving device 200 acquired through in-band communication, so the power transmitting device 100 can distinguish the tag 302 from the tag 202.

[0053] Furthermore, the control unit 101 of the power transmitting device 100 selects a tag to connect to based on the individual identification information, thereby making it possible to appropriately select a tag to be accessed even when wireless power transmission systems are adjacent to each other as shown in FIG. 3C. In FIG. 3C, the power transmitting device 304 and the power receiving device 303 are adjacent to the system shown in FIG. 3A, and the range in which the power transmitting device 304 can perform out-band communication is indicated by a two-dot chain line 305. According to FIG. 3C, the reader 106 of the power transmitting device 100 and the reader of the power transmitting device 304 can communicate with tags of both the power receiving device 200 and the power receiving device 303. However, the communication ranges of the power transmitting device 100 and the power transmitting device 304 for in-band communication do not overlap. Therefore, based on the individual identification information acquired by each in-band communication, the power transmitting device 100 can perform out-band communication using RFID with the power receiving device 200, and the power transmitting device 304 can perform out-band communication with the power receiving device 303.

[0054] In this embodiment, it is assumed that no reception errors occur in the RFID control communication (403, S517). For example, an error may occur due to the influence of the radio wave environment. In such a case, the power transmitting device 100 may switch the control communication to in-band communication. In this case, the power that can be transmitted by wireless power transmission may be limited to, for example, 15 watts based on the WPC1.2 standard using in-band communication, rather than 50 watts based on the high-power standard using out-band communication.

[0055] In an example of in-band communication, control data is superimposed by applying load modulation to the transmitted power waveform to minutely change the voltage amplitude. Because the voltage amplitude generated in the transmitting and receiving coils varies more significantly with high power than with low power, it is difficult to detect minute changes in voltage amplitude due to load modulation during high-power transmission. As a result, using in-band communication during high-power transmission may prevent the transmission and reception of control data, potentially causing the wireless power transmission system to become unstable. In contrast, as described above, when out-band communication is not possible, switching to in-band communication and adjusting the transmitted power value to the upper limit for in-band communication enables stable power transmission and control communication.

[0056] Furthermore, although the identification information of the power receiving device in this embodiment (FIG. 7) is stored in the UII or EPC memory in the memory area of ​​the tag 202, it may also be stored in the TID memory or the USER memory. Here, when storing the identification information in the UII memory, EPC memory, or USER memory, it may be set so that it cannot be written to by the reader 106. This makes it possible to prevent the identification information from being intentionally rewritten by a malicious reader.

[0057] In the present embodiment, an example has been described in which the power transmitting device 100 determines to switch from in-band communication to out-band communication based on the identification information of the power receiving device 200. However, the present invention is not limited to this, and the power receiving device 200 may determine to switch from in-band communication to out-band communication based on the identification information of the power transmitting device 100. This can be performed, for example, based on S605 to S607 shown as options in FIG. 6.

[0058] When this optional process is executed, the power receiving device 200 transmits a Negotiation Request between time t2 and t3. The power transmitting device 100 then transmits an ACK in response to this, and the process transitions to the Negotiation phase. In the Negotiation phase, the power receiving device 200 transmits a message to the power transmitting device 100 requesting the identification information (ID) of the power transmitting device 100 (S605). In the Negotiation phase, the power receiving device can transmit a General Request Packet to make various requests to the power transmitting device. The General Request Packet can specify the content of the request in the packet header. For example, the power receiving device can transmit a Power Transmitter Identification transmission request by specifying a header value of 0x30. This request allows the power receiving device to obtain information related to the power transmitting device similar to that shown in FIG. 7. Based on the identification information of the power transmitting device obtained in S605, the power receiving device determines whether an RFID tag is implemented, i.e., whether the power transmitting device complies with a high-power standard, for example (S606). If the power receiving device determines that the power transmitting device is capable of control communication via RFID (YES in S606), it determines to perform control communication via RFID (S604). In this case, the power receiving device may transmit an EPT (S607) and return the wireless power transmission process to the Selection phase. Even with this process, control communication related to wireless power transmission can be performed between the power transmitting device and the power receiving device using an appropriate communication method.

[0059] The power transmission method used in the wireless power transmission system is not particularly limited. For example, a magnetic resonance method may be used, in which power is transmitted by coupling due to magnetic resonance between a resonator (resonant element) of a power transmitting device and a resonator (resonant element) of a power receiving device. Alternatively, an electromagnetic induction method, an electric field resonance method, a microwave method, a laser method, or the like may also be used.

[0060] In the above embodiment, an example has been described in which an RFID interface in the UHF band is used as an interface for performing out-of-band communication, but this is not limiting. For example, an interface conforming to the Bluetooth (registered trademark) Low Energy (BLE) standard or the Wireless Fidelity (Wi-Fi (registered trademark)) standard may be used as the interface for performing out-of-band communication.

[0061] When the BLE standard is used, the reader 106 of the power transmitting device 100 can communicate as a central (control station) of the BLE standard. Furthermore, the tag 202 of the power receiving device 200 can communicate as a peripheral (child station) of the BLE standard. Then, when the power receiving device 200 recognizes in S606 that the power transmitting device supports control communication using the BLE standard, it can transmit an Advertise packet including the information elements of FIG. 7 to the power transmitting device in S607. The Advertise packet is a packet used by a peripheral to convey information about itself. Then, by the above-described processes of S513 and S514, the power transmitting device 100 determines the power receiving device 200 present within the power transmission range as a communication partner for control communication, and transmits a Connect packet to the power receiving device 200. Here, the Connect packet is a packet for establishing a wireless connection with the peripheral that transmitted the Advertise packet, and is defined in the BLE standard. By doing so, it is possible to obtain the same effect as the above-described process.

[0062] In addition, in the case of the Wi-Fi (registered trademark) standard, the power transmitting device 100 can be an access point, and the power receiving device 200 can be a station. In this case, the power receiving device 200 may store the information elements in Fig. 7 as information about itself in a Probe Request packet and transmit the packet.

[0063] 5 and 6 may be implemented by, for example, a CPU executing a program, but at least a portion of the process may be implemented by hardware. For example, a specific compiler may be used to automatically generate a dedicated circuit on an FPGA from a program for implementing each step, thereby implementing some of the operations by hardware. A gate array circuit other than an FPGA may also be used, or some of the operations may be performed by non-programmable hardware such as an ASIC, unlike circuits such as an FPGA.

[0064] <<Other embodiments>> The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0065] 100: power transmitting device, 101: control unit, 103: power transmitting unit, 104: communication unit, 106: reader, 200: power receiving device, 201: control unit, 202: tag, 204: communication unit, 205: power receiving unit

Claims

1. A power transmission means for wirelessly transmitting power to a power receiving device; a first communication means for communicating with the power receiving device at a first frequency; second communication means for communicating with the power receiving device at a second frequency higher than the first frequency; and The first communication means is receiving identification information of the power receiving device at the first frequency after starting power transmission to the power receiving device at the first frequency; receiving a power transmission stop request at the first frequency from the power receiving device after receiving the identification information; the power transmitting means starts transmitting power at the second frequency after receiving the power transmission stop request by the first communication means; The power transmitting device, wherein the second communication means receives identification information of the power receiving device at the second frequency after starting power transmission at the second frequency.

2. The power transmission device described in Claim 1, characterized in that the first communication means receives the power transmission stop request after sending a specific packet to the power receiving device.

3. A power transmission device as described in claim 1 or 2, characterized in that the second communication means negotiates power with the power receiving device.

4. A method performed by a power transmission device, a first power transmitting step of transmitting power at a first frequency to a power receiving device; a first receiving step of receiving identification information of the power receiving device at the first frequency after starting power transmission at the first frequency; a second receiving step of receiving a power transmission stop request at the first frequency from the power receiving device after the first receiving step; a second power transmitting step of transmitting power to the power receiving device at a second frequency higher than the first frequency after the second receiving step; a third receiving step of receiving identification information of the power receiving device at the second frequency after starting power transmission at the second frequency.

5. The method described in claim 4, characterized in that the second receiving step is performed after transmitting a specific packet to the receiving device.

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