The power transmission unit 203 converts direct-current or alternating-current power input from the power supply unit 202 into alternating-current frequency power in a frequency range used in the wireless power transmission and inputs the alternating-current frequency power to the power transmission coil 205, thereby generating an electromagnetic wave with which to cause the RX 102 to receive power. The frequency of the alternating-current power generated by the power transmission unit 203 is about several hundreds of kilohertz (e.g., 110 kHz to 205 kHz) and is different from the communication frequency (2.4 GHz) of BLE used in the out-of-band communication. Based on an instruction from the control unit 201, the power transmission unit 203 inputs alternating-current frequency power to the power transmission coil 205 to cause the power transmission coil 205 to output an electromagnetic wave with which to transmit power to the RX 102. The power transmission unit 203 also adjusts a voltage (a power transmission voltage) or a current (a power transmission current) to be input to the power transmission coil 205, thereby controlling the intensity of the electromagnetic wave to be output. If the power transmission voltage or the power transmission current is increased, the intensity of the electromagnetic wave strengthens. If the power transmission voltage or the power transmission current is decreased, the intensity of the electromagnetic wave weakens. Based on an instruction from the control unit 201, the power transmission unit 203 also controls the output of the alternating-current frequency power so that the transmission of power from the power transmission coil 205 is started or stopped.

Based on the WPC standard, the detection unit 204 detects whether an object is present in the power transmittable range 104. For example, the detection unit 204 detects the voltage value or the current value of the power transmission coil 205 when the power transmission unit 203 transmits an analog ping in the WPC standard via the power transmission coil 205. Then, if the voltage falls below a predetermined voltage value, or if the current value exceeds a predetermined current value, the detection unit 204 can determine that an object is present in the range 104. The determination of whether this object is the RX 102 or a foreign object other than the RX 102 is made in such a manner that if a predetermined response to a digital ping subsequently transmitted through the in-band communication from the first communication unit 206 is received, it is determined that this object is the RX 102.

The first communication unit 206 performs communication in each phase in the WPC standard as described above with the RX 102 through the in-band communication. The first communication unit 206 modulates an electromagnetic wave output from the power transmission coil 205 to transmit information to the RX 102. The first communication unit 206 also demodulates an electromagnetic wave output from the power transmission coil 205 and modulated by the RX 102, thereby acquiring information transmitted from the RX 102. That is, communication performed by the first communication unit 206 is performed by superimposing a signal on an electromagnetic wave corresponding to the transmission power from the power transmission coil 205.

The second communication unit 207 performs communication in each phase in the WPC standard as described above with the RX 102 through the out-of-band communication. For example, the second communication unit 207 includes a modulation/demodulation circuit and a communication protocol processing function that are required to perform the BLE communication.

The display unit 208 presents information to a user by an arbitrary technique such as a visual, auditory, or tactile technique. For example, the display unit 208 notifies the user of information indicating the state of the TX 101 or the state of the wireless power transmission system including the TX 101 and the RX 102 as illustrated in FIG. 1. For example, the display unit 208 includes a liquid crystal display, a light-emitting diode (LED) display, an organic electroluminescent (EL) display, a loudspeaker, a vibration generation circuit, and another notification device.

The operation unit 209 has a reception function for receiving an operation of the user on the TX 101. For example, the operation unit 209 includes a button, a keyboard, a sound input device such as a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, and another input device. Alternatively, a device obtained by integrating the display unit 208 and the operation unit 209 as in a touch panel may be used. As described above, the memory 210 stores various pieces of information. The memory 210 may store information obtained by a function unit different from the control unit 201. The timer 211 measures time using, for example, a count up timer that measures the time elapsed from the clock time when the count up timer is started, or a count down timer that counts down from a set time.

FIG. 3 is a diagram illustrating an example of the configuration of the RX 102 according to the present exemplary embodiment. As an example, the RX 102 includes a control unit 301, a battery 302, a power reception unit 303, a detection unit 304, a power reception coil 305, a first communication unit 306, a second communication unit 307, a display unit 308, an operation unit 309, a memory 310, a timer 311, and a charging unit 312.

For example, the control unit 301 executes a control program stored in the memory 310, thereby controlling the entirety of the RX 102. As an example, the control unit 301 performs control required for device authentication and the reception of power in the RX 102. The control unit 301 may perform control for executing an application other than a wireless power transmission application. The control unit 301 includes one or more processors such as a CPU and an MPU. The control unit 301 may include hardware dedicated to a specific process, such as an ASIC, or an array circuit such as an FPGA compiled to execute a predetermined process. The control unit 301 stores, in the memory 310, information that should be stored during the execution of various processes. The control unit 301 can also measure time using the timer 311.

The power reception unit 303 acquires alternating-current power generated by electromagnetic induction in the power reception coil 305. Specifically, an induced electromotive force is generated in the power reception coil 305 by an electromagnetic wave emitted from the power transmission coil 205 of the TX 101, and the power reception unit 303 acquires power generated in the power reception coil 305. Then, the power reception unit 303 converts alternating-current power into direct-current power or alternating-current power of a predetermined frequency and outputs the power to the charging unit 312 that performs a process for charging the battery 302. That is, the power reception unit 303 supplies the power to the load in the RX 102. The above GP is the power guaranteed to be output from the power reception unit 303. The battery 302 stores power received via the power reception coil 305.

Based on the WPC standard, the detection unit 304 detects that the RX 102 is placed in the range 104 where the RX 102 can receive power from the TX 101. For example, the detection unit 304 detects the voltage value or the current value of the power reception coil 305 when the power reception unit 303 receives power with a digital ping in the WPC standard via the power reception coil 305. For example, if the voltage falls below a predetermined voltage threshold, or if the current value exceeds a predetermined current threshold, the detection unit 304 can determine that the RX 102 is placed in the range 104.

The first communication unit 306 performs communication in each phase in the WPC standard as described above with the TX 101 through the in-band communication. The first communication unit 306 demodulates an electromagnetic wave input from the power reception coil 305, thereby acquiring information transmitted from the TX 101. Then, the first communication unit 306 performs load modulation on the electromagnetic wave, thereby superimposing information that should be transmitted to the TX 101 on the electromagnetic wave. Consequently, the first communication unit 306 communicates with the TX 101. That is, communication performed by the first communication unit 306 is performed by superimposing a signal on an electromagnetic wave corresponding to the transmission power from the power transmission coil 205 of the TX 101.

The second communication unit 307 performs communication in each phase in the WPC standard as described above with the TX 101 through the out-of-band communication. For example, the second communication unit 307 includes a modulation/demodulation circuit and a communication protocol processing function that are required to perform the BLE communication.

The display unit 308 presents information to the user by an arbitrary technique such as a visual, auditory, or tactile technique. For example, the display unit 308 notifies the user of the state of the RX 102 or the state of the wireless power transmission system including the TX 101 and the RX 102 as illustrated in FIG. 1. For example, the display unit 308 includes a liquid crystal display, an LED display, an organic EL display, a loudspeaker, a vibration generation circuit, and another notification device.

The operation unit 309 has a reception function for receiving an operation of the user on the RX 102. For example, the operation unit 309 includes a button, a keyboard, a sound input device such as a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, and another input device. Alternatively, a device obtained by integrating the display unit 308 and the operation unit 309 as in a touch panel may be used. As described above, the memory 310 stores various pieces of information. The memory 310 may store information obtained by a function unit different from the control unit 301. The timer 311 measures time using, for example, a count up timer that measures the time elapsed from the clock time when the count up timer is started, or a count down timer that counts down from a set time.

(Flow of Processing)

Next, an example of the flow of a power transmission/reception control process executed by the TX 101 and the RX 102 is described.

FIG. 4 is a flowchart illustrating an example of the flow of a power transmission control process executed by the TX 101. This processing can be achieved by, for example, the control unit 201 of the TX 101 executing a program read from the memory 210. At least a part of the following procedure may be achieved by hardware. The hardware in this case can be achieved by, for example, using a predetermined compiler to automatically generate a dedicated circuit that uses a gate array circuit such as an FPGA according to a program for achieving processing steps. This processing can be executed according to the fact that the TX 101 is powered on, or according to the fact that the user of the TX 101 inputs an instruction to start the wireless power transmission application, or according to the fact that the TX 101 is connected to commercial power supply and receives the supply of power. Alternatively, this processing may be started using another trigger.

First, the TX 101 executes a process defined as the selection phase and the ping phase in the WPC standard and waits for the RX 102 to be placed (step S401). The TX 101 repeatedly and intermittently transmits an analog ping in the WPC standard and detects an object present in the power transmittable range 104. Then, if the TX 101 detects that an object is present in the power transmittable range 104, the TX 101 transmits a digital ping. Then, if a predetermined response to the digital ping is received, the TX 101 determines that the detected object is the RX 102 and the RX 102 is placed on the charging stand 103.

If the TX 101 detects the placement of the RX 102, the TX 101 acquires identification information from the RX 102 through the in-band communication by performing communication in the I & C phase defined by the WPC standard (step S402). FIG. 10A illustrates the flow of the communication in the I & C phase. In the I & C phase, the RX 102 transmits an identification packet (an ID packet) to the TX 101 (step F1001). The ID packet stores a manufacturer code and basic device ID that are identification information regarding each individuality of the RX 102, and also an information element that allows specifying of a version of the WPC standard with which the RX 102 is compatible. Further, the RX 102 transmits a configuration packet to the TX 101 (step F1002). The configuration packet includes a maximum power value that is a value for specifying the maximum power that the RX 102 can supply to the load, and information indicating whether the RX 102 has the negotiation function in the WPC standard. When the TX 101 receives these packets, the TX 101 transmits ACK (step F1003), and the I & C phase ends. Alternatively, the TX 101 may acquire the identification information regarding the RX 102 using a method other than the communication in the I & C phase in the WPC standard. Further, the identification information regarding each individuality of the RX 102 may be wireless power ID. Further, the identification information regarding each individuality of the RX 102 may be any other identification information that allows the identification of the individuality of the RX 102, such as a Bluetooth address (hereinafter referred to as “BD_ADDR”) specific to the second communication unit 307 of the RX 102. BD_ADDR is an 8-byte address used in BLE. For example, BD_ADDR is a public address defined by the BLE standard and indicating the manufacturer of the RX 102 or individual identification information regarding a BLE communication function (the second communication unit 307). Alternatively, BD_ADDR may be a random address.

Next, the TX 101 determines whether the TX 101 can perform the out-of-band communication using BLE with the RX 102 (step S403). Specifically, the TX 101 waits for an advertising packet including the identification information regarding the RX 102 using BLE (using the second communication unit 207). For example, the TX 101 performs a BLE scan operation and waits for an advertising packet including information indicating that the identification information regarding the RX 102 is included and the identification information regarding the RX 102. For example, the AD type of an advertising packet in the BLE standard is set to a predetermined value, thereby indicating that the advertising packet includes the identification information regarding the RX 102. Further, it is defined in advance that if the AD type is the predetermined value, AD data includes the identification information regarding the RX 102. Then, by sharing this definition by the TX 101 and the RX 102, the TX 101 can wait for an advertising packet including the above information. The identification information regarding the RX 102 is information for identifying each individuality of the RX 102. For example, the identification information regarding the RX 102 is a manufacturer code and basic device ID defined by the WPC standard. Alternatively, the identification information regarding the RX 102 may be wireless power ID or BD_ADDR specific to the second communication unit 307 of the RX 102. In a case where BD_ADDR is used as the identification information regarding the RX 102, the identification information is included not in the AD data but in a header portion of an advertising packet. If the TX 101 receives an advertising packet including the identification information regarding the RX 102 within a predetermined time, the TX 101 determines that the TX 101 can perform the out-of-band communication using BLE with the RX 102. If not, the TX 101 determines that the TX 101 cannot perform the out-of-band communication using BLE with the RX 102. Alternatively, it may be determined whether the TX 101 can perform the out-of-band communication using BLE with the RX 102 using another method. For example, the configuration packet may store information regarding whether the RX 102 is compatible with the out-of-band communication, or whether the RX 102 is in the state where the RX 102 can perform communication. In this case, based on a corresponding information element in the configuration packet, the TX 101 may determine whether the TX 101 can perform the out-of-band communication using BLE with the RX 102. Consequently, if the TX 101 cannot perform the out-of-band communication using BLE with the RX 102, it is possible to eliminate the time to wait for an advertising packet. Thus, it is possible to hasten the start of the transmission of power to the power reception apparatus.

If it is determined that the TX 101 can perform the out-of-band communication (YES in step S403), the TX 101 establishes a BLE connection with the RX 102 that is the transmission source of the advertising packet (step S404). The TX 101 transmits CONNECT_REQ which is a connection request in the BLE standard in response to BD_ADDR included in a header portion of the advertising packet from the RX 102, thereby establishing a BLE connection with the RX 102. Next, based on a request from the RX 102, the TX 101 sets a connection interval which is the interval of intermittent communication in BLE (step S405). This setting is made by receiving LL_CONNECTION_PARAM_REQ in the BLE standard from the RX 102 and returning LL_CONNECTION_UPDATE_IND. The TX 101 performs subsequent communication with the RX 102 through the out-of-band communication using BLE. If it is determined that the TX 101 cannot perform the out-of-band communication with the RX 102 (NO in step S403), the processes of steps S404 and S405 are skipped, and the TX 101 performs subsequent communication with the RX 102 through the in-band communication.

Next, based on the result of device authentication, a request from the RX 102, and the power transmission capability of the TX 101, the TX 101 determines the GP by a negotiation with the RX 102 (step S406). In step S406, communication in the negotiation phase in the WPC standard as illustrated in FIG. 10B is performed. First, the RX 102 transmits a specific request to the TX 101, thereby notifying the TX 101 of the value of the GP requested by the RX 102 (step F1011). Based on the power transmission capability of the TX 101 and other conditions, the TX 101 determines whether the TX 101 accepts the request. If the TX 101 accepts the request, the TX 101 transmits ACK to the RX 102 (step F1012). If the TX 101 does not accept the request, the TX 101 transmits NACK to the RX 102. If the TX 101 accepts the request from the RX 102, the value of the GP to be determined is the value requested by the RX 102. If not, the value of the GP to be determined is a predetermined value (e.g., 5 watts) defined by the WPC standard.

Next, the TX 101 performs a process in the calibration phase in the WPC standard (step S407). The process in the calibration phase is advance measurement for detecting a foreign object between the TX 101 and the RX 102 with high accuracy, but is similar to that of the conventional art, and therefore is not described in detail here.

Then, the TX 101 transmits power until the RX 102 is fully charged (step $408). In step S408, communication in the power transfer phase in the WPC standard as illustrated in FIG. 10C is performed. The RX 102 repeatedly transmits a control error packet (hereinafter referred to as a “CE packet”) to the TX 101 at a time interval t_interval (step F1021). t_interval is a value defined by the WPC standard and is 250 milliseconds, for example. Each CE packet includes a request as to how much the transmission power is to be increased or decreased. The TX 101 controls the current of the power transmission coil 205 based on a received CE packet, thereby adjusting the transmission power. That is, the CE packet is a parameter for adjusting the transmission power. This process is repeated, whereby the transmission of power with appropriate power according to a request from the RX 102 is performed almost in real time.

If the RX 102 is fully charged, the RX 102 transmits an end power transfer packet (hereinafter referred to as an “EPT packet”), thereby ending the power transfer phase (step F1022). The RX 102 may transmit the EPT packet for a reason other than full charge. If the power transfer phase ends, the TX 101 stops the transmission of power for charging to the RX 102.

If the TX 101 does not receive a next CE packet even when t_timeout elapses since the TX 101 has received a CE packet last, the TX 101 determines that the RX 102 has been removed from the charging stand 103, and the power transfer phase ends. t_timeout is a value defined by the WPC standard and is 1500 milliseconds, for example.

During the power transfer phase, the RX 102 may transmit a packet other than a CE packet (step F1023). An example of a packet other than a CE packet is a charge status packet that notifies the TX 101 of the state of the battery 302 of the RX 102. The charge status packet stores a charge status value indicating to what percent the battery 302 is charged. If the TX 101 receives the charge status packet, for example, the TX 101 may display characters or a diagram on the display unit 208 based on the charge status value, thereby notifying the user of the charging state. The TX 101 may receive the charge status packet any time and notify the user of the charging state any time.

The processing of the real-time control of the transmission power performed between the TX 101 and the RX 102 is described with reference to FIG. 11C. After the TX 101 receives a CE packet 1103 and t_delay elapses, the TX 101 spends a time t_control to adjust the transmission power based on a control error value included in the CE packet 1103. t_delay and t_control are values determined in ranges defined by the WPC standard and are 5 milliseconds and 25 milliseconds, respectively, for example. After the transmission of the CE packet 1103, the RX 102 is prohibited from transmitting a Qi packet 1104 (a next CE packet in this case) until the TX 101 completes the adjustment of the transmission power based on the CE packet 1103.

That is, after the transmission of the CE packet 1103, the RX 102 can transmit the next CE packet (the Qi packet 1104) only after at least the total time of t_delay and t_control elapses. In the power transfer phase, the TX 101 and the RX 102 perform the real-time control of the transmission power under the above timing constraints represented by t_interval, t_timeout, t_delay, and t_control. Information regarding these timing constraints may be held in advance in the memory 210 of the TX 101 and the memory 310 of the RX 102, or the RX 102 may hold the information and notify the TX 101 of the information in the I & C phase. The TX 101 may hold the information and notify the RX 102 of the information, or the RX 102 or the TX 101 may notify the other of the information at a timing other than the I & C phase.

As described above, a CE packet is a packet for the real-time control (hereinafter referred to as “a real-time control packet”). In contrast, a notification to the user using a charge status packet does not have constraints regarding the timings of transmission, reception, and processing. That is, a charge status packet is not a real-time control packet. There may also be another packet not for the real-time control.

Referring back to FIG. 4, after the power transfer phase ends, and if the TX 101 had established a BLE connection with the RX 102 in step S403, the TX 101 disconnects this BLE connection, and the processing ends (YES in step S409, and step S410). After step S410, the TX 101 may further continue to communicate with the RX 102, however, in this case, the TX 101 communicates with the RX 102 through the in-band communication.

Next, an example of the flow of a power reception control process executed by the RX 102 is described with reference to FIG. 5. This processing can be achieved by, for example, the control unit 301 of the RX 102 executing a program read from the memory 310. At least a part of the following procedure may be achieved by hardware. The hardware in this case can be achieved by, for example, using a predetermined compiler to automatically generate a dedicated circuit that uses a gate array circuit such as an FPGA according to a program for achieving processing steps.

After the power reception control process is started, the RX 102 executes a process defined as the selection phase and the ping phase in the WPC standard and waits to be placed on the TX 101 (step S501). For example, the RX 102 detects a digital ping from the TX 101, thereby detecting that the RX 102 is placed on the TX 101.

If the RX 102 detects that the RX 102 is placed on the TX 101, the RX 102 transmits information including identification information regarding the RX 102 to the TX 101 through the in-band communication, using an ID packet and a configuration packet as described with reference to FIG. 10A (step S502). The identification information regarding the RX 102 may be transmitted using a method other than the communication in the I & C phase in the WPC standard. Alternatively, other identification information such as BD_ADDR may be used so long as the information allows the identification of each individuality of the RX 102. In step S502, the RX 102 may also transmit information other than the identification information to the TX 101.

Next, the RX 102 determines whether the RX 102 can perform the out-of-band communication using BLE with the TX 101 (step S503). Specifically, the RX 102 repeatedly transmits an advertising packet including the identification information regarding the RX 102 using BLE (using the second communication unit 307) and waits for CONNECT_REQ in BLE from the TX 101. For example, the RX 102 sets the AD type of an advertising packet in BLE to a predetermined value, thereby indicating that the advertising packet includes the identification information regarding the RX 102. For example, the identification information regarding the RX 102 is a manufacturer code and basic device ID defined by the WPC standard. Alternatively, the identification information regarding the RX 102 may be wireless power ID or BD_ADDR specific to the second communication unit 307 of the RX 102. If the RX 102 receives CONNECT_REQ from the TX 101 within a predetermined time, the RX 102 determines that the RX 102 can perform the out-of-band communication using BLE with the TX 101. If not, the RX 102 determines that the RX 102 cannot perform the out-of-band communication using BLE with the TX 101. Alternatively, it may be determined whether the RX 102 can perform the out-of-band communication using BLE with the TX 101 using another method. For example, the RX 102 may receive information or a signal indicating that the TX 101 is compatible with BLE from the TX 101, or may receive information or a signal indicating that the TX 101 can perform communication using BLE from the TX 101. In this case, based on the received information or signal, the RX 102 may determine whether the RX 102 cannot perform the out-of-band communication using BLE with the TX 101. Consequently, if the RX 102 cannot perform the out-of-band communication using BLE with the TX 101, it is possible to shorten the time to wait for the reception of CONNECT_REQ. Thus, it is possible to hasten the start of the transmission of power.

If it is determined that the RX 102 can perform the out-of-band communication (YES in step S503), the RX 102 establishes a BLE connection with the TX 101 that is the transmission source of CONNECT_REQ (step S504). The RX 102 receives CONNECT_REQ, thereby establishing a BLE connection. Next, the RX 102 requests the TX 101 to set a connection interval which is the interval of intermittent communication in BLE to the same time as the expected transmission interval of a real-time control packet (hereinafter referred to as a “Qi packet” to explicitly distinguish the packet from a packet in BLE) (step S505). An example of the Qi packet for the real-time control is a CE packet, and the expected transmission interval of the CE packet is t_interval. For example, the RX 102 makes the request to set the connection interval by transmitting LL_CONNECTION_PARAM_REQ in the BLE standard. Alternatively, the RX 102 may request the TX 101 to set the connection interval to a fraction of t_interval obtained by dividing by an integer instead of making the connection interval the same as t_interval. For example, if t_interval=250 milliseconds, the connection interval may be set to 125 milliseconds, which is one-half of 250 milliseconds.

The RX 102 performs subsequent communication with the TX 101 through the out-of-band communication using BLE. If it is determined that the RX 102 cannot perform the out-of-band communication with the TX 101 (NO in step S503), the processes of steps S504 and S505 are skipped, and the RX 102 performs subsequent communication with the TX 101 through the in-band communication.

Next, the RX 102 transmits the requested value of the GP to the TX 101, waits for a response from the TX 101, and determines the GP (step S506). In step S506, communication in the negotiation phase in the WPC standard as described with reference to FIG. 10B is performed.

Next, the RX 102 performs a process in the calibration phase in the WPC standard (step S507). The process in the calibration phase is advance measurement for detecting a foreign object between the TX 101 and the RX 102 with high accuracy, but is similar to that of the conventional art, and therefore is not described in detail here.

Then, the RX 102 receives power until the battery 302 is fully charged (step S508). In step S508, as described with reference to FIG. 10C, the RX 102 repeatedly transmits a CE packet at the interval t_interval, transmits an EPT packet last, and ends this phase.

Referring back to FIG. 5, after the power transfer phase ends, and if the RX 102 had established a BLE connection with the RX 102 in step S503, the RX 102 disconnects this BLE connection, and the processing ends (YES in step S509, and step S510). After step S510, the RX 102 may further continue to communicate with the TX 101. In this case, however, the RX 102 communicates with the TX 101 through the in-band communication.

As described above, if the TX 101 and the RX 102 can perform the out-of-band communication using BLE with each other (YES in steps S403 and S503), the TX 101 and the RX 102 perform communication in the following phases using BLE. Specifically, the phases are the negotiation phase, the calibration phase, and the power transfer phase. Even when the TX 101 and the RX 102 can perform the out-of-band communication using BLE with each other, the TX 101 and the RX 102 may not need to perform all the above communication using BLE. For example, the TX 101 and the RX 102 may perform only the communication in the power transfer phase using BLE.

A description is given of a method for transmitting a Qi packet defined by the WPC standard, using a communication signal used in the BLE communication (hereinafter referred to as a “BLE packet”). In the present exemplary embodiment, each of the second communication units 207 and 307 is configured so that after a BLE connection is established, the TX 101 operates as a Generic Attribute Profile (GATT) client in the BLE standard, and the RX 102 operates as a GATT server in the BLE standard. At this time, the TX 101 performs a write characteristic value process in the BLE standard, and the RX 102 performs a handle value notification process (hereinafter referred to as a “notify process”). Consequently, each of the TX 101 and the RX 102 can transmit an arbitrary byte string up to 20 bytes as an attribute value in the BLE standard. The upper limit up to 20 bytes can also be further extended by performing an exchange maximum transmission unit (MTU) process in the BLE standard. Alternatively, the TX 101 may be a GATT server, and the RX 102 may be a GATT client. Yet alternatively, each of the TX 101 and the RX 102 may be configured to transmit an arbitrary byte string using a profile in BLE other than GATT. That is, a plurality of Qi packets is stored in the attribute value of a BLE communication packet.

The size of a Qi packet in the WPC standard is smaller than the upper limit of the attribute value of a BLE packet. Thus, in the present exemplary embodiment, one or more Qi packets are collectively stored in one BLE packet and transmitted. FIG. 8 illustrates an example where three Qi packets are stored in one BLE packet. The same applies to a case where the number of Qi packets is other than three. First, the structure of a Qi packet is described. A Qi packet 800 includes a header 801 and a message 802. The header 801 has a 1-byte value indicating the type of the Qi packet such as a CE packet or an EPT packet. For example, in the case of a CE packet, the value of the header 801 is 03 in hexadecimal. The message 802 is a byte string defined with respect to each type of the Qi packet, and the number of bytes of the message 802 differs with respect to each type of the Qi packet. For example, if the type of the packet is a CE packet, the message 802 has a control error value with a length of 1 byte. A Qi packet in the WPC standard also includes preamble and checksum, but preamble and checksum are unnecessary if the Qi packet is transmitted using BLE, and therefore description thereof will be omitted. A byte string 820 in FIG. 8 is stored in an attribute value 811 of a BLE packet 810. In an area 821 at the beginning of the byte string 820, the number of Qi packets included in this attribute value is stored. In this example, the area 821 indicates 3. In a next area 822, the number of bytes of the first Qi packet is stored, and in an area 823, the contents, i.e., the header 801 and the message 802, of the first Qi packet are stored. Similarly, in areas 824 and 825, information regarding the second Qi packet is stored. In areas 826 and 827, information regarding the third Qi packet is stored. In this manner, a plurality of Qi packets is stored in one BLE packet. The above storage format is merely an example, and another storage format may be used.

Next, a transmission process performed by the power reception apparatus is described with reference to FIG. 6. If the BLE communication is not to be used (or if the BLE communication is not being used) (NO in step S601), the RX 102 provides a constraint specific to the in-band communication when the RX 102 performs communication (step S602). That is, if the RX 102 cannot perform the BLE communication with the TX 101 in FIG. 5 (NO in step S503), the RX 102 provides the constraint specific to the in-band communication. If the BLE communication is to be used (or if the BLE communication is being used) (YES in step S601), the RX 102 does not provide the constraint specific to the in-band communication when the RX 102 transmits a BLE packet (step S603). That is, if the RX 102 can perform the BLE communication with the TX 101 in FIG. 5 (YES in step S503), the RX 102 does not provide the constraint specific to the in-band communication when the RX 102 transmits a BLE packet.

The constraint specific to the in-band communication is described with reference to FIG. 11A. FIG. 11A illustrates the transmission timings of Qi packets defined by the WPC standard. Qi packets 1101 and 1102 are transmitted through the in-band communication from the RX 102. A time t_silent indicates the time required until the ripple of the current flowing through or the voltage applied to the power transmission coil 205 of the TX 101 due to modulation stabilizes after the packet 1101 is transmitted through the in-band communication. When the RX 102 transmits the Qi packet 1102, the RX 102 starts transmitting the preamble of the Qi packet 1102 in the time t_silent from the end of the immediately preceding Qi packet 1101. Or when the RX 102 transmits the Qi packet 1102, the RX 102 starts transmitting the preamble of the Qi packet 1102 at a time later than the time t_silent and earlier than a time t_start1 from the end of the immediately preceding Qi packet 1101. That is, during the time t_silent, the RX 102 does not start transmitting the preamble of any Qi packet. That is, the time t_silent is a period when the transmission of a signal is prohibited. The constraint specific to the in-band communication is the transmission timing of a Qi packet related to the time t_silent.

The provision of this constraint enables the RX 102 to start transmitting the preamble of the Qi packet 1102 after the current or the voltage of the power transmission coil 205 is stabilized. Thus, the RX 102 can perform stable in-band communication. The RX 102 may also provide a constraint where the transmission of the preamble of the next Qi packet is started in the time t_start1 (or before the time t_start1) from the end of the previous Qi packet.

FIG. 11B illustrates the timings when the RX 102 transmits packets through the BLE communication. In FIG. 11B, the time t_silent does not exist. The length of a time t_start2 may be the same as that of the time t_start1. From the end of a BLE packet 1111 including an immediately preceding Qi packet, the RX 102 starts transmitting the preamble of a BLE packet 1112 including another Qi packet. Or when the RX 102 transmits the BLE packet 1112, the RX 102 starts transmitting the preamble of the BLE packet 1112 including the Qi packet before the time t_start2 elapses from the end of the immediately preceding BLE packet 1111.

The reason why the time t_silent does not exist in FIG. 11B is that the time t_silent is provided to stabilize the ripple of the current flowing through or the voltage applied to the power transmission coil 205 due to the in-band communication. That is, if the BLE communication is used, the ripple of the current or the voltage of the power transmission coil 205 due to the in-band communication does not occur. In a case where the BLE communication is performed, it is possible to achieve high-speed control by not providing a constraint specific to the in-band communication.

That is, the BLE packet 1112 including the Qi packet can be transmitted within the period of the time t_silent illustrated in FIG. 11A, and therefore, it is possible to perform high-speed communication. For example, the transmission interval of a Qi packet for the real-time control can be shortened. Thus, the RX 102 can control power transmission more finely.

Next, a power level control process performed by the TX 101 is described with reference to FIG. 7. If the BLE communication is not to be used (or if the BLE communication is not being used) (NO in step S701), the TX 101 provides a constraint specific to the in-band communication when the TX 101 controls the power level (step S702). That is, if the TX 101 cannot perform the BLE communication with the RX 102 in FIG. 4 (NO in step S403), the TX 101 provides the constraint specific to the in-band communication. If the BLE communication is to be used (or if the BLE communication is being used) (YES in step S701), the TX 101 does not provide the constraint specific to the in-band communication when the TX 101 controls the power level (step S703). That is, if the TX 101 can perform the BLE communication with the RX 102 in FIG. 4 (YES in step S403), the TX 101 does not provide the constraint specific to the in-band communication.

The constraint specific to the in-band communication is described with reference to FIG. 11C. FIG. 11C illustrates the transmission timings of Qi packets defined by the WPC standard. A CE packet 1103 is one of the Qi packets. A time t_delay is the time required until the ripple of the current flowing through or the voltage applied to the power transmission coil 205 of the TX 101 due to modulation stabilizes after the CE packet 1103 is transmitted through the in-band communication. Further, during a time t_active, the TX 101 adjusts the power level based on a control error value included in the CE packet 1103. The time t_active is set to be later than the time t_delay that starts from the end of the CE packet 1103. That is, the TX 101 does not adjust any power level during the time t_delay. t_delay is a power control hold-off time defined by the WPC standard. The power control hold-off time is indicated by a power control hold-off value. The power control hold-off value is described in a power transfer contract in which parameters regarding the transmission and reception of power and communication shared by the TX 101 and the RX 102 are described. The constraint specific to the in-band communication in the TX 101 is the control timing of the power level related to the time t_delay. The provision of this constraint enables the TX 101 to control the power level in the state where the current or the voltage of the power transmission coil 205 is stabilized after the time t_delay. The vertical axis in FIG. 11C represents power. FIG. 11C illustrates a case where the TX 101 is requested to increase power by the RX 102, using the CE packet 1103.

When the RX 102 transmits a Qi packet 1104, the RX 102 starts transmitting the preamble of the Qi packet 1104 after a time t_delay+t_control elapses from the end of the immediately preceding CE packet 1103. In this case, the Qi packet 1104 is a Qi packet of a type different from that of the CE packet 1103. Or when the RX 102 transmits the Qi packet 1104, the RX 102 starts transmitting the preamble of the Qi packet 1104 later than the time t_delay+t_control from the end of the immediately preceding CE packet 1103. That is, during the time t_delay+t_control, the RX 102 does not start transmitting the preamble of any packet. In FIG. 11C, at least the time t_delay+t_control is a waiting period of waiting to transmit a signal. The constraint specific to the in-band communication in FIG. 11C is the transmission timing of a packet related to the time t_delay+t_control. t_control is a time obtained by adding to the time t_active the time required until the ripple of the current or the voltage of the power transmission coil 205 due to the adjustment of the power level in the time t_active stabilizes. The provision of this constraint enables the RX 102 to start transmitting the preamble of the Qi packet 1104 after the current of the power transmission coil 205 is stabilized. Thus, the RX 102 can perform stable in-band communication. The RX 102 may also provide a constraint where the transmission of the beginning of the next Qi packet 1104 is started within a time t_interval1 that starts from the beginning of the CE packet 1103.

FIG. 11D illustrates the timing when the TX 101 controls the power level of a BLE packet 1113 including a CE packet received through the BLE communication. In FIG. 11D, the time t_delay does not exist. The reason for this is that the time t_delay is provided to stabilize the ripple of the current or the voltage of the power transmission coil 205 due to the in-band communication. During the time t_active that starts from the end of the BLE packet 1113 including the CE packet, the TX 101 adjusts the power level based on a control error value included in the CE packet. As described above, if the BLE communication is used, the ripple of the current or the voltage of the power transmission coil 205 due to communication does not occur. Thus, in a case where the BLE communication is performed, a constraint specific to the in-band communication is not provided, whereby it is possible to achieve high-speed power control. The vertical axis in FIG. 11D represents power. FIG. 11D illustrates a case where the TX 101 is requested to increase power by the RX 102, using the BLE packet 1113 including the CE packet.

When the RX 102 transmits a BLE packet 1114 including a Qi packet, the RX 102 starts transmitting the preamble of the BLE packet 1114 including the Qi packet after a time t_control elapses from the end of the BLE packet 1113 including the immediately preceding CE packet. In this case, the BLE packet 1114 is a Qi packet of a type different from that of the CE packet. Alternatively, when the RX 102 transmits the BLE packet 1114 including the Qi packet, the RX 102 starts transmitting the preamble of the BLE packet 1114 including the Qi packet later than the time t_control from the end of the BLE packet 1113 including the immediately preceding CE packet. In FIG. 11D, at least the time t_control is a waiting period of waiting to transmit a signal. As described above, in a case where the BLE communication is performed, it is possible to achieve high-speed control by not providing a constraint specific to the in-band communication.

(Operation of System)

The operation of the system including the TX 101 and the RX 102 is described with reference to FIGS. 4, 5, and 9. On the assumption that the RX 102 is placed on the charging stand 103 of the TX 101, a subsequent operation is described. In the present exemplary embodiment, the timing constraints in the real-time control of the transmission power that should be followed by the TX 101 and the RX 102 are as follows. That is, based on the WPC standard, t_interval=250 milliseconds, t_delay=5 milliseconds, t_control=25 milliseconds, and t_timeout=1500 milliseconds.

First, the TX 101 and the RX 102 execute processes up to the I & C phase (steps F901, steps S401 and S402, and steps S501 and S502). The RX 102 transmits ADV_IND including identification information (step F902), And the TX 101 confirms that this ADV_IND includes identification information regarding the RX 102 acquired in the I & C phase (step F903). Next, the TX 101 transmits CONNECT_IND and establishes a BLE connection between the TX 101 and the RX 102 (step F904, step S404, and step S504). Next, the RX 102 requests the TX 101 to set t_interval=250 milliseconds, which is the interval at which a CE packet is to be transmitted by the real-time control to be performed after this, as the connection interval in BLE (step F906 and step S505). Then, the TX 101 sets t_interval=250 milliseconds (step F907 and step S405). Then, the TX 101 and the RX 102 perform processes in the negotiation phase and the calibration phase in the WPC standard (step F908, steps S406 and S407, and steps S506 and S507) and transition to the power transfer phase.

At the first connection interval of 250 milliseconds, the RX 102 generates one CE packet as a Qi packet for the real-time control and stores the one CE packet in a BLE packet (step F909). The RX 102 transmits the BLE packet including only the one CE packet (step F910). The transmission of the BLE packet is performed by a notify process as described above. Also at the next connection interval, similarly, the RX 102 generates a BLE packet including a CE packet (step F911) and transmits the BLE packet (step F912). At the next connection interval, first, the RX 102 generates a CE packet and stores the CE packet in a BLE packet (step F913).

Next, the RX 102 generates one charge status packet as a Qi packet not for the real-time control and adds the one charge status packet to the BLE packet (step F914). Since a further Qi packet not for the real-time control that should be generated is absent, the RX 102 transmits the BLE packet including the one CE packet and the one charge status packet (step F915).

At the subsequent connection interval, the RX 102 generates a BLE packet including only one CE packet (step F916) and transmits the BLE packet (step F917). At connection intervals after that, the RX 102 repeats a process similar to that at the connection interval in steps F916 and F917.

Then, at a certain connection interval, the RX 102 detects that the battery 302 reaches full charge (step F918). In this case, at the certain connection interval, the RX 102 generates one CE packet and stores the one CE packet in a BLE packet (step F919). Then, the RX 102 generates one EPT packet not for the real-time control and adds the one EPT packet to the BLE packet (step F920). The RX 102 transmits the BLE packet including the one CE packet and the one EPT packet (step F921). As described with reference to FIG. 10C, if the RX 102 transmits the EPT packet, the power transfer phase ends. Since the TX 101 and the RX 102 are performing the out-of-band communication using BLE, the out-of-band communication is disconnected to end the process (step F922, YES in step S409, step S410, YES in S509, and step S510).

If the battery 302 reaches full charge (step F918), the RX 102 may not generate a CE packet, and may not store a CE packet in a BLE packet. A Qi packet stored in the BLE packet is only an EPT packet. If the battery 302 reaches full charge (step F918), the RX 102 may not transmit a BLE packet. Even with these configurations, a next CE packet is not received by the TX 101, and therefore, a timeout occurs, and the transmission of power is stopped.

The processing by the TX 101 in the power transfer phase is described. First, a description is given of the processing by the TX 101 in a case where the TX 101 receives a BLE packet including a CE packet as in step F910 or F912. The TX 101 recognizes that the BLE packet received at the connection interval includes one Qi packet. Then, the TX 101 reads the one Qi packet, i.e., the CE packet, from the BLE packet and processes the one Qi packet without providing a constraint specific to the in-band communication. This process is the process of controlling the transmission power based on the control error value included in the CE packet. Then, since the reading of all the Qi packets is completed, the processing at the connection interval ends.

Next, a description is given of the processing of the TX 101 in a case where the TX 101 receives a BLE packet including one CE packet and a charge status packet as another Qi packet as in step F915. The TX 101 recognizes that the BLE packet received at the connection interval includes two Qi packets. Then, the TX 101 reads the one Qi packet at the beginning, i.e., the CE packet, from the BLE packet and processes the one Qi packet. This process is the process of controlling the transmission power based on the control error value included in the CE packet. Next, the TX 101 reads the charge status packet and processes the charge status packet. This process is the process of performing display on the display unit 208 based on the charge status value included in the charge status packet. Then, since the reading of all the Qi packets is completed, the processing at this connection interval ends.

In step F906, the RX 102 sets the connection interval to the same interval as t_interval, which is the expected transmission interval of the CE packet. That is, the TX 101 and the RX 102 repeat the real-time control of the transmission power described with reference to FIG. 11C at t_interval=250 milliseconds determined in advance by the RX 102, through the use of the out-of-band communication using BLE. Since a BLE packet including a CE packet arrives every 250 milliseconds, a timeout does not occur by the interval between CE packets becoming longer than t_timeout=1500 milliseconds. Further, a BLE packet transmitted in a cycle of 250 milliseconds from the RX 102 includes up to only one CE packet. During the period of step F930, the TX 101 can also perform the real-time control using a CE packet while receiving and processing a Qi packet not for the real-time control as a charge status packet.

Second Exemplary Embodiment

In the present exemplary embodiment, in a case where the out-of-band communication is performed, a timing related to the real-time control of the transmission power is changed to a value different from that in a case where the in-band communication is performed. The timing refers to, for example, t_interval or t_timeout described in the first exemplary embodiment. FIG. 12 is a diagram illustrating the flow of the processing of the TX 101 according to the second exemplary embodiment. The second exemplary embodiment is different from the first exemplary embodiment described with reference to FIG. 4 in the following respects. That is, the process of, in a case where the TX 101 can perform the BLE communication with the RX 102, changing the timing of the real-time control (step S1201), and the process of, after the BLE communication ends, changing the timing of the real-time control back to the state before the change (step S1202) are added. In the present exemplary embodiment, the TX 101 holds, in the memory 210, timing information in a case where the real-time control is performed through the in-band communication and timing information in a case where the real-time control is performed through the out-of-band communication. In a case where the out-of-band communication is performed, the real-time control is performed using the latter timing information.

The same applies to the RX 102. FIG. 13 is a diagram illustrating the flow of the processing of the RX 102 according to the second exemplary embodiment. The second exemplary embodiment is different from the first exemplary embodiment described with reference to FIG. 5 in the following respects. That is, the process of, in a case where the RX 102 can perform the BLE communication with the TX 101, changing the timing of the real-time control (step S1301), and the process of, after the BLE communication ends, changing the timing of the real-time control back to the state before the change (step S1302) are added. In the present exemplary embodiment, the RX 102 holds, in the memory 310, timing information in a case where the real-time control is performed through the in-band communication and timing information in a case where the real-time control is performed through the out-of-band communication. In a case where the out-of-band communication is performed, the real-time control is performed using the latter timing information.

After the process of step S404 illustrated in FIG. 4, the TX 101 according to the present exemplary embodiment changes the timing of the real-time control (step S1201). Specifically, the TX 101 changes the timing of the real-time control based on the timing information held in the memory 210 and regarding the real-time control in a case where the out-of-band communication is performed. The TX 101 and the RX 102 set the timing of the real-time control in a case where the out-of-band communication is performed to a value shorter than that in a case where the in-band communication is performed. For example, t_interval in a case where the in-band communication is performed is set to 250 milliseconds, and t_timeout in this case is set to 1500 milliseconds. On the other hand, t_interval in a case where the out-of-band communication is performed is set to 100 milliseconds, and t_timeout in this case is set to 500 milliseconds.

Then, after the process of step S410 illustrated in FIG. 4, the TX 101 changes the timing of the real-time control back to the previous value (step S1202). Specifically, the TX 101 changes the timing of the real-time control based on the timing information held in the memory 210 and regarding the real-time control in a case where the in-band communication is performed.

After the process of step S504 illustrated in FIG. 5, the RX 102 changes the timing of the real-time control (step S1301). Specifically, the RX 102 changes the timing of the real-time control based on the timing information held in the memory 310 and regarding the real-time control in a case where the out-of-band communication is performed. Then, after the process of step S510 illustrated in