Power transmission device and method

Abstract

To detect removal of a power receiving apparatus even during a period in which power transmission is stopped on a power transmitting device that has received an EPT packet specifying a period in which power transmission is stopped.SOLUTION: A power transmission device 100 controls a power transmission coil 105 based on reception of an EPT packet including information on a period in which power transmission is stopped from a power reception device 200 via a communication unit 104, transmits a verification signal for verifying the presence of the power reception device 200 in the period in which the power transmission is stopped, detects via a detection unit 108 at least one of a voltage and a current that is applied to the power transmission coil 105 in transmission of the verification signal, and determines whether or not a RX 200 that has transmitted the EPT packet exists based on the result of detection.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power transmission device, a control method executed by the power transmission device, and a program. [Background technology]

[0002] In recent years, technological development of wireless power transmission systems such as contactless charging systems has been widespread. Patent Document 1 discloses a power transmitting device and a power receiving device that comply with the standard (hereinafter referred to as the "WPC standard") established by the Wireless Power Consortium (WPC), a standardization organization for contactless charging. Patent Document 1 also discloses that when the power receiving device detects an abnormality, it transmits a signal indicating that power transmission should be stopped. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-165761 Summary of the Invention [Problem to be solved by the invention]

[0004] It is conceivable to designate a power transmission suspension period using this signal indicating a power transmission suspension. Specifically, it is conceivable to include information designating the power transmission suspension period in the signal indicating a power transmission suspension. When the power transmission device receives a signal indicating a power transmission suspension including information designating the power transmission suspension period, the power transmission device will suspend power transmission during the power transmission suspension period. As a result, it is conceivable that the power transmission device will also no longer transmit a signal for detecting an object. In this case, even if the power receiving device on the power transmission device is removed during the power transmission suspension period, it is conceivable that the removal of the power receiving device cannot be detected until the period has elapsed, and it is conceivable that it will take time to detect the removal.

[0005] In view of the above problems, the present invention aims to detect the removal of a power receiving device even during the period when power transmission is stopped in a power transmitting device that has received a signal indicating the stop of power transmission, which specifies the period when power transmission is stopped. [Means for solving the problem]

[0006] One aspect of the present invention is a power transmission device that includes an antenna that wirelessly transmits power to a power receiving device, a receiving means that receives a signal from the power receiving device, a detection means that detects at least one of the voltage and current of the antenna, and a control means that controls the antenna, wherein the control means, based on receiving a signal from the power receiving device indicating a stop of power transmission that includes information on the period for which power transmission will be stopped, controls the antenna to transmit a confirmation signal to confirm the presence of the power receiving device that transmitted the signal indicating the stop of power transmission, the detection means detects at least one of the voltage and current of the antenna when the confirmation signal is transmitted, and the control means, based on the detection result by the detection means, determines whether the power receiving device that transmitted the signal indicating the stop of power transmission is present. [Effects of the Invention]

[0007] In the present invention, the power transmitting device that receives a signal indicating power transmission stop that specifies the period for stopping power transmission can detect removal of the power receiving device even during the period for stopping power transmission. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a power transmission device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a power receiving device according to an embodiment of the present invention; [Figure 3] FIG. 1 is a diagram illustrating an example of a wireless power transmission system according to an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram illustrating an example of a sequence when the power receiving device is not removed according to the present embodiment. [Figure 5] FIG. 10 is a diagram illustrating an example of a sequence when a power receiving device is removed and a new power receiving device is placed in the present embodiment. [Figure 6] FIG. 1 is a diagram showing an example of a flowchart of processing by a power transmission device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples for explaining the technical concept of the present invention, and are not intended to limit the present invention to the configurations and methods described in the embodiments.

[0010] FIG. 3 shows an example of the configuration of a contactless charging system (wireless power transmission system) according to this embodiment. This system includes a power transmitting device and a power receiving device. Hereinafter, the power transmitting device may be referred to as TX, and the power receiving device may be referred to as RX. The TX100 is an electronic device that wirelessly transmits power to the RX200 placed on its charging stand. The RX200 is an electronic device that receives power wirelessly from the TX100 and charges its built-in battery. The following description will be given taking as an example a case where the RX200 is placed on the charging stand. However, for the TX100 to transmit power to the RX200, the RX200 does not need to be placed on the charging stand as long as it is within the power transmission range of the TX100.

[0011] The TX100 receives power from a commercial power source via an AC connector 301, and supplies the power to a power supply unit 102. The RX200 receives power from a power transmitting coil 105 of the TX100 via a power receiving coil 205 of the RX200 itself. The power received by the RX200 is charged into a battery (not shown). The power transmitting coil 105 and the power receiving coil 205 are a type of antenna. In the following description, a coil is used as an example, but an antenna having a shape other than a coil may be used instead of the power transmitting coil 105 and the power receiving coil 205.

[0012] The TX100 and the RX200 may have a function to execute applications other than contactless charging. An example of the RX200 is a smartphone, and an example of the TX100 is an accessory device for charging the smartphone. The TX100 and the RX200 may be storage devices such as hard disk drives or memory devices, or information processing devices such as personal computers (PCs). The TX100 and the RX200 may be image input devices such as imaging devices (cameras, video cameras, etc.) or scanners, or image output devices such as printers, copiers, and projectors. The TX100 may be a smartphone. In this case, the RX200 may be another smartphone or wireless earphones. The RX200 may be an automobile. The TX100 may be a charger installed in a console or the like inside the automobile.

[0013] Furthermore, in this embodiment, one RX200 and one TX100 are shown, but the present invention can also be applied to a configuration in which a plurality of RX200 receive power from one TX100 or from separate TX100s.

[0014] This system performs wireless power transmission using an electromagnetic induction method for contactless charging based on the WPC standard. That is, the RX200 and the TX100 perform wireless power transmission for contactless charging based on the WPC standard between the receiving coil 205 of the RX200 and the transmitting coil 105 of the TX100. Note that the wireless power transmission method (contactless power transmission method) applied to this system is not limited to the method specified by the WPC standard, and may be other methods such as electromagnetic induction, magnetic field resonance, electric field resonance, microwave, or laser. Furthermore, in this embodiment, wireless power transmission is used for contactless charging, but wireless power transmission may also be performed for purposes other than contactless charging.

[0015] In the WPC standard, the amount of power guaranteed when the RX200 receives power from the TX100 is defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value that is guaranteed to be output to the load (e.g., a charging circuit) of the RX200, even if the positional relationship between the RX200 and the TX100 fluctuates and the power transmission efficiency between the receiving coil 205 and the transmitting coil 105 decreases. For example, if the GP is 5 watts, the TX100 transmits power by controlling so that it can output 5 watts to the load in the RX200, even if the positional relationship between the receiving coil and the transmitting coil fluctuates and the power transmission efficiency decreases.

[0016] The RX200 and TX100 according to this embodiment communicate for power transmission and reception control based on the WPC standard. The WPC standard defines multiple phases, including a power transfer phase in which power transmission is performed and a phase before the actual power transmission, and communication for the necessary power transmission and reception control is performed in each phase. Phases before power transmission include a selection phase, a ping phase, an identification and configuration phase, a negotiation phase, and a calibration phase. Note that the identification and configuration phase will be referred to as the I&C phase below.

[0017] In the Selection phase, the TX100 intermittently transmits Analog Pings to detect that an object has been placed on the charging base (for example, that the RX200 or a conductor piece has been placed on the charging base). In other words, the Analog Ping is a detection signal for detecting the presence of an object. The TX100 transmits Analog Pings by applying a voltage or current to the transmitting coil 105. The voltage and current applied to the transmitting coil 105 change when an object is placed on the charging base and when no object is placed on the charging base. Therefore, the TX100 detects at least one of the voltage value and current value applied to the transmitting coil 105 when transmitting Analog Pings. If the detected voltage value is below a threshold value or the detected current value exceeds a threshold value, the TX100 determines that an object is present and transitions to the Ping phase.

[0018] In the Ping phase, the TX100 transmits a Digital Ping, which has a higher power than the Analog Ping. The power of the Digital Ping is sufficient to start up the control unit of the RX200 placed on the charging stand. The RX200 notifies the TX100 of the magnitude of the received power voltage. That is, the RX200 transmits a Signal Strength packet (hereinafter referred to as an "SS packet") to the TX100. In this way, the TX100 recognizes that the object detected in the Selection phase is the RX200 by receiving a response from the RX200 that received the Digital Ping. When the TX100 is notified of the received power voltage value, it transitions to the I&C phase.

[0019] In the I&C phase, the TX100 identifies the RX200 and obtains device configuration information (capability information) from the RX200. To do this, the RX200 transmits an ID packet and a configuration packet to the TX100. The ID packet contains the identification information of the RX200, and the configuration packet contains the device configuration information (capability information) of the RX200. Upon receiving the ID packet and configuration packet, the TX100 responds with an acknowledgement (ACK). Then the I&C phase ends.

[0020] In the negotiation phase, the GP value is determined based on the GP value requested by the RX200 and the power transmission capability of the TX100.

[0021] In the calibration phase, the RX200 notifies the TX100 of the received power value based on the WPC standard, and the TX100 makes adjustments to transmit power efficiently.

[0022] In the power transfer phase, control is performed to start and continue power transmission, as well as to stop power transmission due to an error or full charge.

[0023] The TX100 and RX200 communicate for these power transmission and reception control by superimposing a signal on the transmitted power using the same antenna (or coil) as for wireless power transmission based on the WPC standard (hereinafter referred to as "first communication"). Note that the range in which the first communication based on the WPC standard is possible between the TX100 and RX200 is approximately the same as the power transmission range of the TX100.

[0024] The RX200 according to this embodiment may perform challenge-response communication using a digital certificate with the TX100 to perform device authentication of the TX100. In other words, the TX100 and RX200 perform communication for device authentication. Device authentication may be performed before the above-mentioned negotiation phase. In this case, the results of device authentication can be reflected in the negotiation phase. Specifically, this is as follows:

[0025] The RX200 requests that the TX100 for which device authentication is successful set the GP to 15 watts, and requests that the TX100 for which device authentication is unsuccessful set the GP to 5 watts. Note that the GP combination is not limited to 15 watts and 5 watts, and any combination of values is acceptable as long as the GP with the TX100 for which device authentication is successful is greater than the GP when device authentication is unsuccessful. In other words, the RX200 requests that power transmission and reception be performed at a higher GP only with TX100s for which device authentication is successful. In this way, by determining the GP based on the results of device authentication, it is possible to receive power at a higher GP only from TX100s that have passed a specified test defined in the WPC standard or the like and are recognized as being capable of transmitting power at a higher GP. Note that unsuccessful device authentication includes cases where the TX100 does not have the function to perform this device authentication, or cases where the TX100 has the function but the authentication fails.

[0026] However, device authentication may be performed after the Negotiation phase. For example, device authentication may be performed during the Power Transfer phase. In this case, in order to reflect the results of device authentication in the GP, the system may transition to the ReNegotiation phase, re-determine the GP, and then transition again to the Power Transfer phase. Device authentication may also be performed in parallel with a phase before the Power Transfer phase, such as the Selection phase.

[0027] Furthermore, the communication for device authentication may be performed as a first communication using the same antenna (or coil) as that used for wireless power transmission, or may be performed as a communication (hereinafter referred to as "second communication") using an antenna (or coil) and frequency different from those used for wireless power transmission. Here, the second communication is capable of faster communication than the first communication. Specifically, the electromagnetic waves used for the second communication are in a higher frequency band than those used for the first communication.

[0028] In this embodiment, the second communication is performed using a communication method conforming to the Bluetooth (registered trademark) Low Energy (hereinafter referred to as "BLE") standard, as an example. The TX100 operates as a BLE peripheral and the RX200 operates as a BLE central, but these BLE roles may be reversed. The second communication may also be performed using other communication methods, such as wireless LAN (e.g., Wi-Fi (registered trademark)) of the IEEE802.11 standard series, ZigBee, or NFC (Near Field Communication).

[0029] (Device configuration) Next, the configurations of the power transmitting device (TX100) and the power receiving device (RX200) according to this embodiment will be described. Note that the configurations described below are merely examples, and part (or in some cases the entirety) of the described configurations may be replaced with other configurations that perform similar functions or may be omitted, or additional configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into multiple blocks, or multiple blocks may be integrated into one block.

[0030] 1 is a diagram showing an example of the configuration of a TX 100 according to this embodiment. The TX 100 includes a control unit 101, a power supply unit 102, a power transmission unit 103, a communication unit 104, a power transmission coil 105, a notification unit 106, a memory 107, a detection unit 108, a timer 109, and a temperature sensor 110. In addition to these, the TX 100 may also include an authentication unit that performs device authentication.

[0031] In the following, an example will be shown in which the communication unit 104 performs the first communication using the power transmitting coil 105, but this is not limiting. That is, the TX 100 may have a communication antenna used when performing the second communication described above, and perform the second communication. Furthermore, the communication performed by the communication unit 104 includes communication for power transmission and reception control, and may further include communication for device authentication.

[0032] The control unit 101 controls the entire TX by executing a control program stored in, for example, the memory 107. That is, the control unit 101 controls each unit shown in FIG. 1 . The control unit 101 may also perform control for executing applications other than wireless power transmission. The control unit 101 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 101 may also be configured with hardware dedicated to a specific process, such as an Application Specific Integrated Circuit (ASIC). The control unit 101 may also be configured with an array circuit, such as a Field Programmable Gate Array, compiled to execute a predetermined process. The control unit 101 stores information to be stored during execution of various processes in the memory 107. The control unit 101 may also measure time using a timer 109.

[0033] The power supply unit 102 supplies the entire TX 100 with power required for the control of the TX 100 by the control unit 101 and for power transmission and communication. The power supply unit 102 converts power supplied from an external source, such as a commercial power source, to the required voltage and supplies power to the entire TX 100. The power supply unit 102 may also be a battery. The battery stores power supplied from the commercial power source.

[0034] The power transmitting unit 103 converts DC or AC power input from the power supply unit 102 into AC frequency power in a frequency band used for wireless power transmission, and inputs the AC frequency power to the power transmitting coil 105 to generate electromagnetic waves for the RX200 to receive power. The frequency of the AC power generated by the power transmitting unit 103 is, for example, about several hundred kHz (for example, 110 kHz to 205 kHz). This frequency is different from, for example, the BLE communication frequency (2.4 GHz) used in the second communication. Based on an instruction from the control unit 101, the power transmitting unit 103 inputs the AC frequency power to the power transmitting coil 105 so that the power transmitting coil 105 outputs electromagnetic waves for transmitting power to the RX200. The power transmitting unit 103 also controls the intensity of the electromagnetic waves to be output by adjusting the voltage (power transmitting voltage) or current (power transmitting current) input to the power transmitting coil 105, or both. Increasing the transmission voltage or transmission current increases the intensity of the electromagnetic waves, and decreasing the transmission voltage or transmission current decreases the intensity of the electromagnetic waves. Furthermore, based on instructions from the control unit 101, the power transmitting unit 103 controls the output of AC frequency power so that power transmission from the power transmitting coil 105 starts or stops.

[0035] Specifically, the power transmitting unit 103 converts the voltage supplied by the power supply unit 102 into an AC voltage using a switching circuit with a half-bridge or full-bridge configuration using FETs. The power transmitting unit 103 also includes a gate driver that controls the ON / OFF of the FETs.

[0036] The communication unit 104 performs control communication based on the WPC standard as described above with the RX200. The communication unit 104 modulates the electromagnetic waves output from the power transmitting coil 105 and transmits information to the RX200 to perform the first communication. The communication unit 104 also demodulates the electromagnetic waves output from the power transmitting coil 105 and modulated by the RX200 to acquire information transmitted by the RX200. That is, the first communication performed by the communication unit 104 is superimposed on the electromagnetic waves transmitted from the power transmitting coil 105.

[0037] The communication unit 104 may also perform the second communication using a communication antenna (not shown). As described above, the second communication is faster than the first communication. Specifically, the electromagnetic waves used in the second communication are in a higher frequency band than the electromagnetic waves used in the first communication. The communication unit 104 may have a modulation / demodulation circuit and a communication protocol processing function required for performing communication conforming to the BLE standard, for example.

[0038] The communication unit 104 may perform communication for device authentication with the RX 200. The communication for device authentication may be second communication, which is communication faster than the first communication.

[0039] The communication unit 104 receives a signal indicating the stop of power transmission (End Power transfer packet, hereinafter referred to as "EPT packet") from the RX200. This EPT packet may include information indicating the reason for requesting the stop of power transmission, or may include information indicating the power transmission stop period and the power transmission start time. Reasons for requesting the stop of power transmission include when the temperature of the RX200 exceeds an upper limit, when charging is completed, when negotiation fails, or when a request is made to detect an object other than the power receiving device (hereinafter referred to as "foreign object").

[0040] The notification unit 106 notifies the user of information by any method, such as visually, audibly, or tactilely. The notification unit 106 notifies the user of, for example, information indicating the charging state of the TX100 or the state of power transmission in the wireless power transmission system. The notification unit 106 may include, for example, a display, an LED, a speaker, a vibration generating circuit, or other notification devices. The notification unit 106 may have any configuration as long as it allows the user to know whether or not power is being transmitted. For example, the notification unit 106 may be an LED that lights up green when power is not being transmitted and lights up red when power is being transmitted. Alternatively, the notification unit 106 may be an LED that lights up when power is being transmitted and flashes when power is not being transmitted. Alternatively, the notification unit 106 may notify the user by emitting light when power is being transmitted and by making a sound when power is not being transmitted.

[0041] The memory 107 stores various information such as information indicating the state of each unit or the overall state of the wireless power transmission system, control programs, etc. The memory 107 may store information obtained by a functional unit other than the control unit 101.

[0042] The detection unit 108 detects at least one of the voltage value and the current value of the power transmitting coil 105. Specifically, the detection unit 108 detects the voltage value and / or the current value of the power transmitting coil 105 when an Analog Ping is transmitted in the Selection phase. The detection unit 108 also detects the voltage value and / or the current value of the power transmitting coil 105 when a signal for confirming the presence of the RX200, which will be described later, is transmitted. Based on the detection result by the detection unit 108, i.e., the detection value, the control unit 101 can detect that an object has been placed on or removed from the charging stand.

[0043] The timer 109 measures time using, for example, a count-up timer that measures the elapsed time from the time it is activated, a count-down timer that counts down from a set time, etc. After the communication unit 104 receives an EPT packet indicating a power transmission stop from the RX200, if the EPT packet contains information indicating a power transmission stop period, the timer 109 sets the period and starts counting down.

[0044] The temperature sensor 110 measures the temperature of the TX 100. Based on the temperature measured by the temperature sensor 110, the control unit 101 determines whether or not to transmit power. For example, the control unit 101 compares the temperature measured by the temperature sensor 110 with an upper limit value of the temperature stored in the memory 107, and if the temperature measured by the temperature sensor 110 exceeds the upper limit value, the control unit 101 controls the power transmitting unit 103 to stop power transmission. Note that the temperature of the TX 100 may rise when transmitting large amounts of power continuously for a long period of time or when transmitting power in a high-temperature environment such as the inside of a car under the blazing sun in the daytime.

[0045] In FIG. 1, the control unit 101, power supply unit 102, power transmission unit 103, communication unit 104, memory 107, and timer 109 are shown as separate units, but any multiple of these units may be implemented within the same chip.

[0046] 2 is a diagram showing an example of the configuration of the RX 200 in this embodiment. The RX 200 has a control unit 201, a charging unit 202, a battery 203, a power receiving unit 204, a power receiving coil 205, a communication unit 206, a memory 207, a notification unit 208, and a temperature sensor 209. In addition to these, the RX 200 may have an authentication unit that performs device authentication.

[0047] The control unit 201 controls the entire RX200 by executing a control program stored in the memory 207, for example. That is, the control unit 201 controls each unit shown in FIG. 2. The control unit 201 may also perform control related to power reception control, including communication for device authentication in the RX200. Furthermore, the control unit 201 may perform control for executing applications other than wireless power transmission. The control unit 201 is configured to include one or more processors, such as a CPU or MPU. The control unit 201 may also be configured with hardware dedicated to specific processing, such as an application-specific integrated circuit (ASIC). The control unit 201 may also be configured to include an array circuit, such as an FPGA, compiled to execute predetermined processing. The control unit 201 stores information to be stored during execution of various processes in the memory 207.

[0048] The charging unit 202 charges the battery 203 using power supplied from the power receiving unit 204, which will be described later.

[0049] The battery 203 supplies power required for control of each part of the RX 200 by the control unit 201, and for power reception and communication. The battery 203 also stores power received by the charging unit 202 via the power receiving coil 205.

[0050] In the power receiving coil 205, an induced electromotive force is generated by the electromagnetic waves radiated from the power transmitting coil 105 of the TX100, and the power receiving unit 204 acquires the power generated in the power receiving coil 205. The power receiving unit 204 acquires AC power generated by electromagnetic induction in the power receiving coil 205. The power receiving unit 204 then converts the AC power into DC power or AC power of a predetermined frequency, and outputs the power to the charging unit 202, which performs processing to charge the battery 203. The above-mentioned GP is power that is guaranteed to be output from the power receiving unit 204.

[0051] The communication unit 206 performs control communication based on the WPC standard as described above with the TX100. The communication unit 206 demodulates the electromagnetic waves input from the power receiving coil 205 to acquire information transmitted from the TX100, and performs first communication with the TX100 by load modulating the electromagnetic waves to superimpose information to be transmitted to the TX100 onto the electromagnetic waves. That is, the first communication performed by the communication unit 206 is performed by superimposing the information on the electromagnetic waves transmitted from the power transmitting coil 105 of the TX100.

[0052] Furthermore, the communication unit 206 may perform the second communication using a communication antenna (not shown). As described above, the second communication is faster than the first communication. Specifically, the electromagnetic waves used in the second communication are in a higher frequency band than the electromagnetic waves used in the first communication. The communication unit 206 may have a modulation / demodulation circuit and a communication protocol processing function required for performing communication conforming to the BLE standard, for example.

[0053] The communication unit 206 may perform communication for device authentication with the TX 100. The communication for device authentication may be second communication, which is communication faster than the first communication.

[0054] The communication unit 206 transmits an EPT packet indicating a power transmission stop to the TX100. This EPT packet may include information indicating the reason for requesting a power transmission stop, or may include information indicating the power transmission stop period. Reasons for requesting a power transmission stop include when the temperature of the RX200 exceeds an upper limit, when charging is completed, when negotiation fails, or when a request is made to detect an object other than the power receiving device (hereinafter referred to as a "foreign object").

[0055] As described above, the memory 207 stores various information such as identification information and device configuration information, control programs, etc. The memory 207 may store information obtained by a functional unit other than the control unit 101.

[0056] The notification unit 208 notifies the user of information by any method, such as visually, audibly, or tactilely. The notification unit 208 notifies the user of, for example, the charging status of the RX200 or the status of power transmission in the wireless power transmission system. The notification unit 208 includes, for example, a display, an LED, a speaker, a vibration generating circuit, or other notification devices. The notification unit 106 may have any configuration as long as it allows the user to know whether or not power is being transmitted. For example, the notification unit 208 may be an LED that lights up green when power is not being received and lights up red when power is being received. Alternatively, the notification unit 208 may be an LED that lights up when power is being received and flashes when power is not being received. Alternatively, the notification unit 208 may notify the user by emitting light when power is being received and by making a sound when power is not being received.

[0057] The temperature sensor 209 measures the temperature of the RX200. Based on the temperature measured by the temperature sensor 209, the control unit 201 determines whether to transmit an EPT packet. For example, the control unit 201 compares the upper limit of the temperature stored in the memory 207 with the temperature measured by the temperature sensor 209, and if the temperature measured by the temperature sensor 209 exceeds the upper limit, controls the communication unit 206 to transmit the EPT packet. Note that the temperature of the RX200 may rise if it receives large amounts of power continuously for a long period of time, or if it receives power in a high-temperature environment such as the inside of a car under the blazing sun in the daytime.

[0058] In FIG. 2, the control unit 201, charging unit 202, power receiving unit 204, communication unit 206, and memory 207 are shown as separate units, but any two or more of these may be implemented on the same chip.

[0059] (Processing flow) In this embodiment, when the TX100 receives an EPT packet including information specifying a power transmission suspension period, the TX100 sends a signal (hereinafter referred to as a "confirmation signal") to confirm the presence of the RX200. This allows the TX100 to detect early removal of the RX200. Then, the TX100 can quickly return to the selection phase.

[0060] Here, an example of the flow of processing executed by the TX100 and the RX200 will be described with reference to Figures 4 and 5. Figure 4 shows the sequence of processing between the power transmitting device and the power receiving device when power transmission is stopped, in the case where the power receiving device has not been removed. On the other hand, Figure 5 shows the sequence of processing between the power transmitting device and the power receiving device when power transmission is stopped, in the case where the power receiving device is removed and a new power receiving device is installed.

[0061] First, the processing between the power transmitting device (TX) and the power receiving device (RX) when power transmission is stopped and when there is no replacement of the power receiving device will be described with reference to Fig. 4. The sequence in Fig. 4 starts from a state in which the power transmitting device (TX) and the power receiving device (RX) are in the Power Transfer phase. In other words, the power transmitting device (TX) and the power receiving device (RX) have already gone through the Selection phase, Ping phase, I&C phase, Negotiation phase, and Calibration phase.

[0062] In S401, the RX200 transmits an EPT packet including information specifying a period for which power transmission is stopped. Here, the specified period is 10 seconds, but is not limited to this. Furthermore, as described above, the EPT packet is transmitted when the temperature of the RX200 exceeds an upper limit. However, the RX200 can also transmit an EPT packet when it detects an abnormality other than temperature. For example, the RX200 may transmit an EPT packet when it determines that a foreign object such as an NFC tag may be placed on the charging stand. Furthermore, when the TX100 detects an abnormality in the TX100, the TX100 may transmit a signal to the RX200 to transmit an EPT packet. Based on receiving this signal, the RX200 may transmit an EPT packet. An example of a case in which an abnormality in the TX100 is detected is when the temperature measured by the temperature sensor 110 exceeds an upper limit.

[0063] When the communication unit 104 of the TX 100 receives the above-mentioned EPT packet, the TX 100 stops power transmission from the power transmission unit 103, sets the timer 109 to 10 seconds, and starts counting down.

[0064] In S402, one second after the start of the countdown, the control unit 101 of the TX 100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal. Here, the power of the confirmation signal is the same as the power of the Analog Ping transmitted in the above-mentioned Selection phase.

[0065] The TX100 detects at least one of the voltage value and current value applied to the power transmitting coil 105 when transmitting the confirmation signal. This is because the removal of the RX200 is detected by utilizing the fact that a change occurs in the voltage or current applied to the power transmitting coil 105 when the RX200 is placed on the charging base and when the RX200 is removed. The TX100 determines that the RX200 is placed on the charging base because the difference between the detected value and the detected value when an object, i.e., the RX200, is detected in the Selection phase (hereinafter referred to as the "reference detection value") is within a predetermined range. This is because the power of the confirmation signal is equivalent to that of the Analog Ping. Note that the reference detection value is stored in the memory 107. The Analog Ping does not have to be sent one second after the start of the countdown. For example, the timing at which the Analog Ping is sent may be set by the user.

[0066] Although details will not be given here, for example, if the EPT packet contains information indicating a request for foreign object detection, the TX 100 will perform foreign object detection using a known method.

[0067] In S403, two seconds after the countdown starts, the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal. The TX100 detects at least one of the voltage value and the current value applied to the power transmitting coil 105 when transmitting the confirmation signal. Then, the TX100 determines that the RX200 is placed on the charging stand because the difference between the detected value and the reference detected value is within a predetermined range.

[0068] Thereafter, a confirmation signal is transmitted in the same manner every second. The transmission interval of the confirmation signal may be shorter or longer than one second. The transmission interval of the confirmation signal may be set by the user. The confirmation signal may be transmitted periodically or non-periodically.

[0069] In S404, 10 seconds after the start of the countdown, the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal. The TX100 detects at least one of the voltage value and current value applied to the power transmitting coil 105 when transmitting the confirmation signal. Then, the TX100 determines that the RX200 is placed on the charging stand because the difference between the detected value and the reference detected value is within a predetermined range.

[0070] In S405, after it is determined that the RX200 is placed on the charging stand, the control unit 101 of the TX100 controls the power transmission unit 103 to transmit a Digital Ping.

[0071] In S406, the RX200 transmits an SS packet in response to the Digital Ping. After that, the TX100 and the RX200 go through the Ping phase, I&C phase, Negotiation phase, and Calibration phase again, and then transition to the Power Transfer phase.

[0072] In S406, the RX200 can also transmit an EPT packet instead of an SS packet. If the EPT packet contains information specifying the period for which power transmission is to be stopped, the process returns to S402. If the EPT packet does not contain information specifying the period for which power transmission is to be stopped, the process proceeds to the Selection phase.

[0073] 5 illustrates processing between a power transmitting device (TX) and a power receiving device (RX) during power transmission stop when a power receiving device is removed and a new power receiving device is placed. Specifically, this refers to the case where the RX500 is placed on the charging stand of the TX100 after the RX200 is removed. The RX500 is a power receiving device having the same configuration as the RX200 described above. Note that detailed description of the same points as in FIG. 4 will be omitted. Also, the sequence in FIG. 5 starts with the power transmitting device (TX) and the power receiving device (RX) in the Power Transfer phase, as in FIG. 4.

[0074] In S501, similarly to S401, the RX200 transmits an EPT packet including information specifying the period for which power transmission is to be stopped. When the TX100 receives the above-mentioned EPT packet at the communication unit 104, it stops power transmission from the power transmitting unit 103, sets the timer 109 to 10 seconds, and starts counting down.

[0075] In S502, similar to S402, the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal one second after the countdown starts. The TX100 detects at least one of the voltage value and current value of the power transmitting coil 105 applied when transmitting the confirmation signal. Then, the TX100 determines that the RX200 is placed on the charging stand because the difference between the detected value and the reference detected value is within a predetermined range.

[0076] A case will be described where the RX200 is removed after S502 and before the next confirmation signal is transmitted.

[0077] In S503, two seconds after the countdown starts, the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal. The TX100 detects at least one of the voltage value and current value applied to the power transmitting coil 105 when transmitting the confirmation signal. However, because the RX200 has been removed, the detected value detected by the TX100 changes. Specifically, the difference between this detected value and the reference detected value exceeds a predetermined range. As a result, the TX100 determines that the RX200 is not placed on the charging base, forcibly stops the timer 109, and ends the countdown operation. Then, transmission of the confirmation signal is stopped.

[0078] In S504, the TX100 returns to the Selection phase, and the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit an Analog Ping. The TX100 then detects at least one of the voltage value and the current value applied to the power transmitting coil 105 when transmitting the Analog Ping. The TX100 determines that no object is placed on the charging stand because the difference between the detected value and the detected value when no object is placed on the charging stand is within a predetermined range.

[0079] The following describes the case where the RX500 is placed on the charging base of the TX100 after S504 and before the next Analog Ping is sent.

[0080] In S505, the control unit 101 of the TX100 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit an Analog Ping. Then, the TX100 detects at least one of the voltage value and the current value applied to the power transmitting coil 105 when transmitting the Analog Ping. The TX100 determines that an object has been placed on the charging stand because the difference between the detected value and the detected value when no object is placed on the charging stand exceeds a predetermined range.

[0081] Next, in S506, the TX 100 transmits a Digital Ping.

[0082] In S507, the RX500 transmits an SS packet in response to the Digital Ping. After that, the TX100 and the RX500 go through the Ping phase, I&C phase, Negotiation phase, and Calibration phase again, and then transition to the Power Transfer phase.

[0083] In this way, when the TX100 receives an EPT packet specifying the period for which power transmission is to be stopped, it operates the timer and transmits a confirmation signal to confirm the presence of the RX200. This makes it possible to quickly detect when the presence of the RX200 can no longer be confirmed, that is, when the RX200 has been removed.

[0084] Furthermore, even if the timer is running, if the TX100 no longer detects an object, the timer is forcibly terminated and the system transitions to the normal Selection phase. This allows the control sequence for power transmission to be started quickly for the newly placed power receiving device (RX500) on the charging stand, shortening the time until power transmission starts, if the power receiving device is replaced during the power transmission stop period specified in the EPT packet.

[0085] (Flowchart showing processing of power transmitting device) The following describes the process that the TX 100 executes upon receiving an EPT packet. Figure 6 is a flowchart of this process.

[0086] In S600, the control unit 101 of the TX 100 determines whether or not an EPT packet has been received by the communication unit 104. If the communication unit 104 has received an EPT packet (Yes in S600), the process proceeds to S601. If the communication unit 104 has not received an EPT packet, the process remains in the Power Transfer phase and the determination in S600 is performed.

[0087] In S601, when the control unit 101 of the TX 100 determines that the communication unit 104 has received an EPT packet, it controls the power transmitting unit 103 and the power transmitting coil 105 to stop power transmission.

[0088] In S602, the control unit 101 sets the timer 109 based on the power transmission suspension period specified in the EPT packet, and starts the operation of the timer 109, that is, starts counting down.

[0089] In S603, the control unit 101 controls the power transmitting unit 103 and the power transmitting coil 105 to transmit a confirmation signal at predetermined intervals.

[0090] In S604, the control unit 101 determines whether an object is placed on the charging stand for the TX100. Specifically, the control unit 101 performs the following steps. First, the control unit 101 detects at least one of the voltage value and the current value of the power transmitting coil 105. Next, the control unit 101 compares this detected value with a reference detected value stored in the memory 107. If the difference is within a predetermined range (Yes in S604), it is determined that the RX200 is still placed there, and the process proceeds to S605. On the other hand, if the difference between the detected value and the reference detected value exceeds the predetermined range (No in S604), it is determined that the RX200 has been removed, and the process proceeds to S607.

[0091] In S605, the control unit 101 determines whether the power transmission stop period has elapsed using the timer 109. If the power transmission stop period has not elapsed (No in S605), the process returns to S603. On the other hand, if the power transmission stop period has elapsed (Yes in S605), the process proceeds to S606.

[0092] In S607, the control unit 101 forcibly ends the operation of the timer 109 that is counting down.

[0093] In S608, the control unit 101 controls the power transmitting unit 103 to transmit Analog Pings at predetermined transmission intervals.

[0094] In S609, the control unit 101 determines whether an object has been placed on the charging stand of the TX100. Specifically, this is done as follows: First, the control unit 101 detects at least one of the voltage value and the current value of the power transmitting coil 105. Next, the control unit 101 compares this detected value with the detected value stored in the memory 107 when no object is placed, and if the difference exceeds a predetermined range (Yes in S609), it determines that an object has been placed, and the process proceeds to S606. On the other hand, if the difference is within the predetermined range (No in S609), it determines that no object has been placed, and the process returns to S608.

[0095] In S606, the control unit 101 controls the power transmitting unit 103 to transmit a Digital Ping. After that, when an SS packet transmitted from RX200 or RX500 is received, the process proceeds to the I&C phase in S610.

[0096] Thereafter, the process proceeds to the I&C phase of S610, the Negotiation phase of S611, the Calibration phase of S612, and the Power Transfer phase of S613. Thereafter, the Power Transfer phase ends, for example, when charging of the battery of the RX200 or RX500 is completed. Note that the I&C phase, Negotiation phase, Calibration phase, and Power Transfer phase only need to perform the processes described above, and therefore further description will be omitted here.

[0097] <Other embodiments> (Regarding confirmation signals) Although the above-mentioned example has been described in which the power of the confirmation signal is the same as the power of the Analog Ping, this is not limiting. The power of the confirmation signal may be smaller than the power of the Analog Ping, or may be larger than the power of the Analog Ping. Furthermore, the power of the confirmation signal may be equal to the power of the Digital Ping. Note that the power of the confirmation signal is smaller than the power in the Power Transfer phase. In other words, the power of the confirmation signal is smaller than the power transmitted from the TX100 to charge the battery 203 based on the power received by the RX200.

[0098] If the power of the confirmation transmission is the same as that of Analog Ping or Digital Ping, the power setting can be simplified.

[0099] In the above-described embodiment, the transmission interval of the confirmation signal may be the same as or different from the transmission interval of the Analog Ping in the Selection phase. For example, the time interval between S502 and S503 in Fig. 5 may be the same as or different from the time interval between S503 and S504 or between S504 and S505.

[0100] If the transmission interval of the Analog Ping in the Selection phase is made shorter than the transmission interval of the confirmation signal, when the power receiving device is replaced as shown in FIG. 5, the new power receiving device (RX500) can be detected quickly.

[0101] If the transmission interval of the confirmation signal is made shorter than the transmission interval of the Analog Ping in the Selection phase, the removal of the power receiving device can be detected earlier, and the transition to the Selection phase can be made earlier.

[0102] (Determining whether a power receiving device has been removed) When the power of the confirmation signal is different from the power of the Analog Ping, the following configuration may be adopted to detect the removal of the RX200. That is, first, when the TX100 transmits the first confirmation signal (S402, S502), it detects at least one of the voltage value and the current value of the power transmitting coil 105 and stores the detected value in the memory 107 as a reference detection value. Then, it detects at least one of the voltage value and the current value of the power transmitting coil 105 when it transmits the second or subsequent confirmation signal. Then, it compares this detected value with the reference detection value, and if the difference exceeds a predetermined range, it is determined that the RX200 has been removed. On the other hand, if the difference is within a predetermined range, it is determined that the RX200 is placed on the charging base.

[0103] The reference detection value that serves as the basis for determining whether the power receiving device has been removed may be either the voltage value or the current value of the power transmitting coil 105 detected when no object is placed on it. The detection value when the confirmation signal is transmitted is compared with this reference detection value, and if the difference exceeds a predetermined range, it is determined that the RX200 is placed on the charging base, and if the difference is within the predetermined range, it is determined that the RX200 has been removed. In this case, the processing is the same as object detection using normal Analog Ping, and the processing content can be simplified.

[0104] (Detection of powered device replacement) In the above-described embodiment, an example has been described in which it is determined that the RX200 has been removed, and then it is determined that the RX500 has been placed. However, if the replacement of the power receiving device is performed in a time shorter than the transmission interval of the confirmation signal, there is a possibility that the replacement cannot be detected. To this end, the TX100 first detects at least one of the voltage value and the current value of the power transmitting coil 105 when transmitting the first confirmation signal (S402, S502) and stores the detected value in the memory 107 as a reference detection value. Then, it detects at least one of the voltage value and the current value of the power transmitting coil 105 when transmitting the second or subsequent confirmation signal. Then, it compares this detected value with the reference detection value, and if the difference exceeds a predetermined range, it is determined that the RX200 has been replaced with the RX500. That is, in this case, it is possible to simultaneously determine that the RX200 has been removed and that the RX500 has been placed.

[0105] Alternatively, the present invention can be realized by supplying a program for realizing one or more of the above-described functions 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. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more of the functions.

[0106] At least a part of the processing shown in the flowchart of Fig. 6 may be implemented by hardware. In this case, for example, a specific compiler may be used to automatically generate a dedicated circuit on an FPGA (Field Programmable Gate Array) from a program for implementing each process. Alternatively, a gate array circuit may be formed in the same way as an FPGA and implemented as hardware. [Explanation of symbols]

[0107] 100 Power transmission device 101 Control section 105 Transmission coil 104 Communications Department 108 Detector 200 Powered Device

Claims

1. an antenna that wirelessly transmits power to a power receiving device; receiving means for receiving a signal from the power receiving device; a detection means for detecting at least one of a voltage and a current applied to the antenna, and a control means for controlling the antenna; the control means controls the antenna to transmit a confirmation signal for confirming the presence of the power receiving device that transmitted the signal indicating the power transmission stop, based on receiving, from the power receiving device, a signal indicating the power transmission stop including information on a period for which the power transmission is to be stopped; the detection means detects at least one of a voltage and a current applied to the antenna when the confirmation signal is transmitted; The power transmitting device is characterized in that the control means determines whether or not there is a power receiving device that has transmitted the signal indicating the power transmission stop based on the detection result by the detection means.

2. The power transmission device according to claim 1, characterized in that the control means controls the antenna to stop transmitting the confirmation signal based on determining that there is no power receiving device that has transmitted the signal indicating the power transmission stop.

3. 3. The power transmitting device according to claim 2, wherein the control means controls the antenna to transmit a detection signal for detecting the presence of an object after stopping transmission of the confirmation signal.

4. the transmission of the confirmation signal and the transmission of the detection signal are performed intermittently, The power transmitting device according to claim 3 , wherein the interval at which the confirmation signal is transmitted is different from the interval at which the detection signal is transmitted.

5. The power transmitting device according to claim 4 , wherein an interval between transmissions of the detection signal is shorter than an interval between transmissions of the confirmation signal.

6. The power transmitting device according to claim 4 , wherein the intervals at which the confirmation signals are transmitted are shorter than the intervals at which the detection signals are transmitted.

7. 7. The power transmitting device according to claim 3, wherein the detection signal is an Analog Ping signal based on the Wireless Power Consortium standard.

8. The power transmission device according to any one of claims 1 to 7, characterized in that when the control means determines that there is a power receiving device that has transmitted a signal indicating the power transmission stop, it determines whether the period for stopping the power transmission has elapsed.

9. 9. The power transmitting device according to claim 8, wherein the control means controls the antenna to transmit a Digital Ping based on a Wireless Power Consortium standard based on determining that the period for stopping the power transmission has elapsed.

10. The power transmitting device according to any one of claims 1 to 9, characterized in that the transmitted confirmation signal is smaller than the power transmitted by the antenna to charge the battery of the power receiving device based on the power received by the power receiving device.

11. 11. The power transmitting device according to claim 1, wherein the confirmation signal is transmitted intermittently.

12. 12. The power transmitting device according to claim 1, wherein the power of the confirmation signal is the same as that of an Analog Ping based on the Wireless Power Consortium standard.

13. A control method executed by a power transmitting device having an antenna for wirelessly transmitting power to a power receiving device, the control method comprising: a receiving step of receiving, from the power receiving device, a signal indicating a power transmission stop, the signal including information about a period for stopping power transmission; a transmitting step of transmitting a confirmation signal for confirming the presence of a power receiving device that transmitted the signal indicating the power transmission stop during the period in which the power transmission is stopped, based on the reception of the signal indicating the power transmission stop in the receiving step; a detection step of detecting at least one of a voltage and a current applied to the antenna when the confirmation signal is transmitted in the transmission step; and a determining step of determining whether or not there is a power receiving device that has transmitted the signal indicating that power transmission has been stopped, based on a detection result by the detecting means.

14. The control method according to claim 13, further comprising a stop step of stopping transmission of the confirmation signal based on the determination step that there is no power receiving device that has transmitted the signal indicating the power transmission stop.

15. 15. The control method according to claim 14, wherein after the transmission of the confirmation signal is stopped by the stopping step, a detection signal for detecting the presence of an object is transmitted.

16. A program for causing a computer to function as the power receiving device according to any one of claims 1 to 12.

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