Power transmission device and method performed by power transmission device

Abstract

To appropriately transmit electric power from a power transmission device to a plurality of power reception devices.SOLUTION: A power transmission device 100 that wirelessly transmits electric power to a plurality of power reception devices 200 in a time sharing scheme derives a plurality of power loss data between the power transmission device 00 and the plurality of power reception devices 200 on the basis of a plurality of received powers received from the plurality of power reception devices 200, and detects an abnormality in a power transmission available range of the power transmission device 100 on the basis of the plurality of power loss data.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. Patent Document 1 discloses a power transmission device and a power reception device compliant with the standard (WPC standard) established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards. Further, Patent Document 2 discloses a method for foreign object detection in the WPC standard. Here, a foreign object is a conductive object such as a metal piece. In the WPC standard, first, the power loss in a state where there is no foreign object between the power transmission device and the power reception device is calculated in advance from the difference between the power transmitted by the power transmission device and the power received by the power reception device, and the calculated value is regarded as the power loss in the normal state (state without foreign objects) during power transmission. Moreover, when the power loss between the power transmission device and the power reception device calculated during subsequent power transmission deviates from the power loss in the normal state serving as a reference by a threshold value or more, it is determined that there is a foreign object or there may be a foreign object.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a power transmission device capable of charging a plurality of power receiving devices, since the power loss between the power transmission device and the first power receiving device is different from the power loss between the power transmission device and the second power receiving device, there is a problem that the foreign object detection accuracy decreases when using the same power loss as the reference normal state power loss. In addition, when the first power receiving device and the second power receiving device are placed on the power transmission device, the power loss between the power transmission device and the first power receiving device may be affected by the second power receiving device. Similarly, the power loss between the power transmission device and the second power receiving device may be affected by the first power receiving device. Therefore, when there is a change in the state (number of units, etc.) of the power receiving devices placed on the power transmission device, the power loss between the power transmission and power receiving devices in the normal state calculated in advance also changes, resulting in a problem that the foreign object detection accuracy decreases.

[0005] The present invention has been made in view of the above problems, and an object thereof is to appropriately transmit power from a power transmission device to a plurality of power receiving devices.

Means for Solving the Problems

[0006] As one means for solving the above problems, the power transmission device of the present invention has the following configuration. That is, A power transmission device, Power transmission means for wirelessly transmitting power to a plurality of power receiving devices in a time-division manner, Communication means for communicating with the plurality of power receiving devices, Derivation means for deriving data on a plurality of power losses between the power transmission device and the plurality of power receiving devices based on a plurality of received power values received from the plurality of power receiving devices via the communication means, Detection means for detecting an object different from the power receiving device that performs the communication within the power transmission range of the power transmission device based on the data on the plurality of power losses.

Effects of the Invention

[0007] It becomes possible to appropriately transmit power from the power transmission device to a plurality of power receiving devices.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 5

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Figure 10

Figure 11

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and redundant explanations are omitted.

[0010] [Embodiment 1] <Foreign Object Detection Method Based on Power Loss Method> First, a foreign object detection method based on the power loss method defined in the WPC (Wireless Power Consortium) standard will be described with reference to FIG. 10. FIG. 10 is a diagram for explaining the foreign object detection method based on the power loss method. In FIG. 10, the horizontal axis represents the power transmitted by the power transmission device, and the vertical axis represents the power received by the power reception device. A foreign object is a conductive object such as a metal piece, which is an object different from the power reception device. That is, when multiple power reception devices are the power transmission targets, the other power reception devices become foreign objects. A power reception device during power transmission or a power reception device that performs communication for power transmission may be the power transmission target.

[0011] First, the power transmission device transmits power to the power reception device, and the power transmission device receives the received power value Pr1 received by the power reception device from the power reception device. Then, the power transmission device stores the transmission power value Pt1 at that time (point 1000). Here, the transmission power value Pt1 or the received power value Pr1 is a predetermined minimum transmission power or received power. At this time, the power reception device controls the load so that the received power becomes the minimum power. For example, the power reception device can disconnect the load from the power reception antenna so that the received power is not supplied to the load (such as a charging circuit and a battery). Note that this state can be called a Light Load state (light load state). At this time, the power transmission device can recognize that the power loss between the power transmission device and the power reception device when transmitting Pt1 as the transmission power is Pt1 - Pr1 (Ploss1). Next, the power transmission device receives the value of the received power value Pr2 received by the power reception device from the power reception device. At this time, the power reception device supplies the received power to the load. Then, the power transmission device stores the transmission power value Pt2 at that time (point 1001). Here, the transmission power value Pt2 or the received power value Pr2 is a predetermined maximum transmission power or received power. At this time, the power reception device controls the load so that the received power becomes the maximum power. For example, the power reception device connects the power reception antenna and the load so that the received power is supplied to the load. Note that this state can be called a Connected Load state (load connection state). At this time, the power transmission device can recognize that the power loss between the power transmission device and the power reception device when transmitting Pt2 as the transmission power is Pt2 - Pr2 (Ploss2). Then, the power transmission device linearly interpolates between point 1000 and point 1001 to create a straight line 1002. The straight line 1002 shows the relationship between the transmission power and the received power in a state where there is no foreign object around the power transmission device and the power reception device. Therefore, the power transmission device can predict the received power in a state without foreign objects from the transmission power value and the straight line 1002. For example, when the transmission power value is Pt3, it can be predicted that the received power value is Pr3 from point 1003 on the straight line 1002 indicating Pt3 for the transmission power value.

[0012] Here, assume that when the power transmission device transmits power to the power reception device at the transmission power of Pt3, the power transmission device receives a power reception value Pr3' from the power reception device. The power transmission device calculates a value Pr3 - Pr3' (= Ploss_FO), which is the value obtained by subtracting the actually received power reception value Pr3' from the power reception device from the power reception value Pr3 in the state where the foreign object does not exist. This Ploss_FO can be considered as the power loss consumed by the foreign object when a foreign object exists between the power transmission device and the power reception device. Therefore, when the power Ploss_FO that would have been consumed by the foreign object is equal to or greater than a predetermined threshold value, it is determined that "there is a foreign object" or "there may be a foreign object".

[0013] Alternatively, the power transmission device may previously obtain the power loss Pt3 - Pr3 (Ploss3) between the power transmission device and the power reception device from the power reception value Pr3 in the state where the foreign object does not exist. Then, next, from the power reception value Pr3' received from the power reception device in the state where the foreign object exists, the power loss Pt3 - Pr3' (Ploss3') between the power transmission device and the power reception device in the state where the foreign object exists is obtained. And the power Ploss_FO that would have been consumed by the foreign object may be obtained by Ploss3' - Ploss3 (= Ploss_FO).

[0014] As described above, as a method for obtaining the power Ploss_FO that would have been consumed by the foreign object, it may be obtained as Pr3 - Pr3' (= Ploss_FO), or it may be obtained as Ploss3' - Ploss3 (= Ploss_FO). In the following description of this specification, basically, the method of obtaining it as Ploss3' - Ploss3 (= Ploss_FO) will be described, but it is also applicable to the method of obtaining it as Pr3 - Pr3' (= Ploss_FO). The above is the explanation of foreign object detection based on the power loss method.

[0015] <Outline of the foreign object detection method according to this embodiment> Next, a foreign object detection method in a power transmission device capable of transmitting power to a plurality of power reception devices will be described. FIG. 11 shows a configuration example of a wireless power transmission system according to the present embodiment. Hereinafter, the power transmission device may be referred to as TX, and the power reception device may be referred to as RX. The configurations of TX100 and RX200 to 220 are shown in FIGS. 1 and 2, respectively, and details will be described later.

[0016] TX100 transmits power to RX200, 210, and 220 placed on TX100 (for example, on a charging stand (placement surface) disposed in proximity to power transmission antennas 105a, 105b, and 105c) via power transmission antennas 105a, 105b, and 105c. RX200, 210, and 220 each receive power transmitted from TX100 via a power reception antenna 205. Note that communication between TX and each RX is also performed via the power transmission antenna and the power reception antenna.

[0017] TX100 shown in FIG. 11(a) has power transmission antennas 105a to 105b and transmits power to RX200 and RX210, for example, as shown in FIG. 11(b). Also, TX100 shown in FIG. 11(c) has power transmission antennas 105a to 105c and transmits power to RX200 to 220, for example, as shown in FIGS. 11(d) to (f).

[0018] Here, consider the power loss between each TX-RX pair between TX and multiple RXs. In a TX capable of transmitting power (charging) to multiple RXs (for example, the first RX and the second RX), the power loss between TX and the first RX is different from the power loss between TX and the second RX. For example, the TX100 shown in FIG. 11(c) transmits power to the RX200 via the power transmission antenna 105a and the power reception antenna 205 of the RX200. Further, the TX100 shown in FIG. 11(c) transmits power to the RX210 via the power transmission antenna 105b and the power reception antenna 205 of the RX210. At this time, the power loss between TX100-RX200 is different from the power loss between TX100-RX210. The reasons include the characteristics of the power transmission antenna, the characteristics of the power reception antenna, the positional relationship between the TX (power transmission antenna) and the RX, the influence of the RX200 on the electrical characteristics of the power transmission antenna 105b, the influence of the RX210 on the electrical characteristics of the power transmission antenna 105a, the state of the circuit in the RX (for example, the connection state between the power reception antenna and the load (charging circuit, battery, etc.)), and so on. Therefore, if the power loss between TX and RX when there is no foreign object between them, or the straight line showing the relationship between the transmitted power and the received power as shown in FIG. 10, is used to be the same between TX and the first RX and between TX and the second RX, there will be a problem that the foreign object detection accuracy decreases.

[0019] Also, when the first RX and the second RX are placed on the TX, the power loss between TX and the first RX may be affected by the second RX. Similarly, the power loss between TX and the second RX may be affected by the first RX. Therefore, when there is a change in the state (number, placement position, etc.) of the RXs placed on the TX, there will also be a change in the power loss between TX and RX when there is no foreign object between them calculated in advance, or the straight line showing the relationship between the transmitted power and the received power as shown in FIG. 10, and there will be a problem that the foreign object detection accuracy decreases.

[0020] To solve such problems, TX calculates separately the "power loss between TX and the first RX in the absence of foreign objects" and the "power loss between TX and the second RX in the absence of foreign objects" as the power loss between TX and RX in the state where no foreign objects are calculated in advance. Then, when transmitting power to the first RX, TX uses the "power loss between TX and the first RX in the absence of foreign objects" as a reference, and when the power loss between TX and the first RX calculated during power transmission exceeds the threshold from the "power loss between TX and the first RX in the absence of foreign objects", it determines that "there is a foreign object" or "there may be a foreign object". Similarly, when transmitting power to the second RX, TX uses the "power loss between TX and the second RX in the absence of foreign objects" as a reference, and when the power loss between TX and the second RX calculated during power transmission exceeds the threshold from the "power loss between TX and the second RX in the absence of foreign objects", it determines that "there is a foreign object" or "there may be a foreign object".

[0021] In this way, TX calculates the power loss in the state without foreign objects in advance for each RX, calculates the power loss during power transmission for each RX, performs a comparison, and determines the presence or absence of foreign objects. As a result, even in a wireless power transmission system where TX transmits power to a plurality of RXs, it becomes possible to appropriately detect foreign objects.

[0022] As described above with reference to FIG. 10, TX calculates a value Pr3 - Pr3' (= Ploss_FO) obtained by subtracting the received power value Pr3' actually received from RX from the received power value Pr3 in a state where no foreign object is present, and can also determine the presence of a foreign object based on whether it is equal to or greater than a predetermined threshold value. That is, TX separately obtains in advance, in a state where there is no foreign object, "the received power value from the first RX in a state where there is no foreign object" and "the received power value from the second RX in a state where there is no foreign object". Then, when transmitting power to the first TX, TX determines that "there is a foreign object" or "there may be a foreign object" if the difference between "the received power value from the first RX in a state where there is no foreign object" and the received power value from RX obtained during power transmission is equal to or greater than the threshold value. Similarly, when transmitting power to the second RX, TX determines that "there is a foreign object" or "there may be a foreign object" if the difference between "the received power value from the second RX in a state where there is no foreign object" and the received power value from RX obtained during power transmission is equal to or greater than the threshold value. By determining the presence or absence of a foreign object in this way, it becomes possible to appropriately detect a foreign object even in a wireless power transmission system in which TX transmits power to a plurality of RXs.

[0023] Also, when calculating in advance the power loss between TX and RX in a state where there is no foreign object (or when receiving the received power value from RX), and when calculating the power loss between TX and RX during power transmission (or when receiving the received power value from RX), the power transmission and reception states need to be the same. The power transmission and reception state is, for example, the characteristics of the power transmission antenna, the characteristics of the power reception antenna, the positional relationship between TX (power transmission antenna) and RX, the influence of RX200 on the electrical characteristics of the power transmission antenna 105b, the influence of RX210 on the electrical characteristics of the power transmission antenna 105a, and the state of the circuit in RX (for example, the connection state between the power reception antenna and the load (charging circuit, battery, etc.)).

[0024] To achieve this, for example, first, when calculating the power loss between the TX and RX in the state where there is no foreign object in advance (or when receiving the received power value from the RX), the TX selects one RX (target RX) to be targeted from a plurality of RXs. The TX controls the non-target RXs so that the power transmitted from the TX is not charged or supplied. The state where the transmitted power is not charged or supplied is, for example, a state where the connection to the load (such as a charging circuit or a battery) is disconnected. Then, the TX calculates the power loss between the TX and the target RX using a transmission antenna capable of transmitting power to the target RX. When calculating the power loss between the TX and the RX during power transmission (or when receiving the received power value from the RX), in the same state, the TX calculates the power loss between the TX and the target RX using a transmission antenna capable of transmitting power to the target RX. After that, the TX compares the power loss between the TX and the target RX calculated during power transmission with the power loss between the TX and the target RX in the state where there is no foreign object calculated in advance, and determines whether there is a foreign object between the TX and the target RX. Alternatively, the TX determines whether there is a foreign object between the TX and the target RX from the difference between the received power value of the target RX received during power transmission and the received power value of the target RX in the state where there is no foreign object.

[0025] In this way, by matching the state when calculating the power loss between the TX and the RX in the state where there is no foreign object in advance and the power transmission and reception state when calculating the power loss between the TX and the RX during power transmission (as described above, the characteristics of the transmission antenna, etc.), it becomes possible to appropriately detect foreign objects even in a wireless power transmission system where the TX transmits power to a plurality of RXs. Also, when the TX detects a change in the power transmission and reception state, the TX recalculates the "power loss between the TX and the RX" described above.

[0026] By doing so, when calculating the power loss between TX and RX in the absence of foreign objects in advance and when calculating the power loss between TX and RX during power transmission, the power transmission and reception states (characteristics of the power transmission antenna, characteristics of the power reception antenna, positional relationship between TX (power transmission antenna) and RX, influence of RX200 on the electrical characteristics of the power transmission antenna 105b, influence of RX210 on the electrical characteristics of the power transmission antenna 105a, state of the circuit in RX (for example, connection state between the power reception antenna and the load (charging circuit, battery, etc.)) and other states) can be made the same. Therefore, in a wireless power transmission system where TX transmits power to a plurality of RXs, it becomes possible to appropriately detect foreign objects.

[0027] [System Configuration] The wireless power transmission system according to the present embodiment shown in FIG. 11 will be described in more detail. TX100 and RX200, 210, 220 comply with the WPC standard. RX200, 210, 220 receive power from TX100 and enable charging of the battery. TX100 is an electronic device that wirelessly transmits power to RX200, 210, 220 placed on TX100. Hereinafter, the case where RX200, 210, 220 are placed on TX100 will be described as an example. However, as long as RX200, 210, 220 are within the power transmission range of TX100 when TX100 transmits power to them, they do not have to be placed on TX100.

[0028] In addition, RX200, 210, 220 and TX100 may have functions to execute applications other than non-contact charging. An example of RX200, 210, 220 is a smartphone, and an example of TX100 is an accessory device for charging the smartphone. RX200, 210, 220 and TX100 may be a tablet, a storage device such as a hard disk device or a memory device, or an information processing device such as a personal computer (PC). Further, RX200, 210, 220 and TX100 may be, for example, an image input device such as an imaging device (camera, video camera, etc.) or a scanner, or an image output device such as a printer, a copier, or a projector. Also, TX100 may be a smartphone. In this case, RX200, 210, 220 may be another smartphone or a wireless earphone. Further, TX100 may be a charger installed in a console or the like inside an automobile.

[0029] This system performs wireless power transmission using an electromagnetic induction method for non-contact charging based on the WPC standard. That is, RX200, 210, 220 and TX100 perform wireless power transmission for non-contact charging based on the WPC standard between the power receiving antenna 205 of RX200, 210, 220 and the power transmitting antennas (power transmitting coils) 105a to 105c of TX100. Note that the wireless power transmission method (non-contact power transmission method) applied to this system is not limited to the method defined by the WPC standard, and may be other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, methods using lasers, etc. Also, in this embodiment, it is assumed that wireless power transmission is used for non-contact charging, but wireless power transmission may be performed for uses other than non-contact charging.

[0030] Here, taking TX100 as TX, and RX200, 210, and 220 as RX, the power transmission control according to the WPC standard will be described. In the WPC standard, the magnitude of the power guaranteed when RX200, 210, and 220 receive power from TX100 is defined by a value called Guaranteed Power (hereinafter referred to as "GP"). GP indicates the power value that guarantees the output to the loads (such as charging circuits, batteries, etc.) of RX200, 210, and 220 even if, for example, the positional relationship between RX200, 210, 220 and TX100 changes and the power transmission efficiency between the power receiving antenna and the power transmitting antenna decreases. For example, when GP is 5 watts, even if the positional relationship between the power receiving antenna and the power transmitting antenna changes and the power transmission efficiency decreases, TX100 controls the power transmission so that it can output 5 watts to the loads within RX200, 210, and 220.

[0031] Also, in the WPC standard, a method for TX100 to detect the presence of an object (foreign object) other than RX around TX100 (near the power receiving antenna) is defined. More specifically, a power loss method for detecting foreign objects based on the difference between the transmitted power at TX100 and the received power at RX200, 210, and 220, and a Q value measurement method for detecting foreign objects based on the change in the quality factor (Q value) of the power transmitting antenna (power transmitting coil) at TX100 are defined. The detection of foreign objects by the power loss method is performed during power transmission (the Power Transfer phase described later). Also, the detection of foreign objects by the Q value measurement method is performed before power transmission (the Negotiation phase or the Renegotiation phase described later).

[0032] RX200, 210, 220 and TX100 according to this embodiment perform communication for power transmission and reception control based on the WPC standard. In the WPC standard, a plurality of phases are defined, including a Power Transfer phase in which power transmission is executed and one or more phases before actual power transmission. Communication for power transmission and reception control required in each phase is performed. The phases before power transmission may include a Selection phase, a Ping phase, an Identification and Configuration phase, a Negotiation phase, and a Calibration phase. Hereinafter, the Identification and Configuration phase is referred to as the I&C phase.

[0033] In the Selection phase, TX100 intermittently transmits an Analog Ping to detect that an object is placed on TX100 (for example, RX200, 210, 220 or a conductor piece is placed on the charging stand of TX100). TX100 detects at least one of the voltage value and the current value of the power transmission antenna when transmitting the Analog Ping, and determines that an object exists when the voltage value is below a certain threshold or the current value exceeds a certain threshold, and then transitions to the Ping phase.

[0034] In the Ping phase, TX100 transmits a Digital Ping with higher power than the Analog Ping. The magnitude of the Digital Ping is sufficient power for the control unit 201 (FIG. 2) of RX200, 210, 220 placed on TX100 to start. RX200, 210, 220 notify TX100 of the magnitude of the received power voltage. In this way, TX100 recognizes that the object detected in the Selection phase is RX200, 210, 220 by receiving the response from RX200, 210, 220 that has received its Digital Ping. When receiving the notification of the received power voltage value, TX100 transitions to the I&C phase.

[0035] In the I&C phase, TX100 identifies RX200, 210, and 220 and obtains device configuration information (capability information) from RX200, 210, and 220. Therefore, RX200, 210, and 220 send an ID Packet and a Configuration Packet to TX100. The ID Packet contains the identification information of RX200, 210, and 220, and the Configuration Packet contains the device configuration information (capability information) of RX200, 210, and 220. TX100 that has received the ID Packet and the Configuration Packet responds with an acknowledge (ACK, positive response). Then, the I&C phase ends.

[0036] In the Negotiation phase, the value of GP is determined based on the value of GP requested by RX200, 210, 220 and the power transmission capability of TX100, etc. Also, TX100 executes foreign object detection processing using the Q-value measurement method in accordance with the requests from RX200, 210, 220. Further, in the WPC standard, once the Power Transfer phase has been entered, a method of performing the same processing as in the Negotiation phase again in response to a request from the RX is defined. The phase of performing these processes after transitioning from the Power Transfer phase is called the Renegotiation phase.

[0037] In the Calibration phase, based on the WPC standard, RX200, 210, and 220 notify TX100 of a predetermined received power value (received power value in the light load state / received power value in the maximum load state), and TX100 performs adjustments for efficient power transmission. The received power value notified to TX100 can be used for foreign object detection processing by the power loss method.

[0038] In the power transfer phase, control is performed for starting power transmission, continuing power transmission, and stopping power transmission due to errors or full charge. TX100 and RX200, 210, 220 perform communication that superimposes a signal on the electromagnetic wave transmitted from the power transmission antenna or the power reception antenna, using the same power transmission antenna (power transmission coil) and power reception antenna (power reception coil) as those used when performing wireless power transmission based on the WPC standard for these power transmission and reception controls. Note that the range within which communication based on the WPC standard is possible between TX100 and RX200, 210, 220 is almost the same as the power transmission range of TX100.

[0039] [Configuration of Power Transmission Device and Power Reception Device] Subsequently, the configurations of the power transmission device and the power reception device according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration example of TX (power transmission device) 100 according to the present embodiment. FIG. 2 is a block diagram showing a configuration example of RX (power reception device) 200 according to the present embodiment. Note that RX210 and RX220 have the same configuration as RX200. The configurations described below are merely examples, and a part (in some cases, all) of the described configurations may be replaced with other configurations that perform the same functions or omitted, and additional configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into a plurality of blocks, or a plurality of blocks may be integrated into one block. In addition, each of the functional blocks shown below is assumed to have its functions implemented as a software program, but a part or all of the functions included in this functional block may be implemented in hardware.

[0040] First, TX100 (FIG. 1) will be described. As shown in FIG. 1, TX100 includes a control unit 101, a power supply unit 102, a power transmission unit 103, a communication unit 104, power transmission antennas 105a to 105c, a memory 106, and an antenna switching unit 107. In FIG. 1, the control unit 101, the power supply unit 102, the power transmission unit 103, the communication unit 104, the memory 106, and the antenna switching unit 107 are shown as separate entities, but any plurality of these functional blocks may be implemented on the same chip.

[0041] The control unit 101 controls the entire TX100 by executing, for example, a control program stored in the memory 106. The control unit 101 also performs control related to power transmission control including communication for device authentication in the TX100. Further, the control unit 101 may perform control for executing applications other than wireless power transmission. The control unit 101 includes, for example, one or more processors such as a CPU (Central Processing Unit) or an MPU (MicroProcessor Unit). Note that the control unit 101 may be configured by hardware dedicated to specific processing such as an ASIC (Application Specific Integrated Circuit). Also, the control unit 101 may include an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 101 stores in the memory 106 information to be stored during the execution of various processes. Also, the control unit 101 can measure time using a timer (not shown).

[0042] The power supply unit 102 supplies power to each functional block. The power supply unit 102 is, for example, a commercial power supply or a battery. Electric power supplied from the commercial power supply is stored in the battery.

[0043] The power transmission unit 103 converts the 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 generates an electromagnetic wave for causing power reception at the RX by inputting the AC frequency power to the power transmission antennas 105a to 105c. For example, the power transmission unit 103 converts the DC voltage supplied by the power supply unit 102 into an AC voltage using a switching circuit having a half-bridge or full-bridge configuration using FETs (Field Effect Transisters). In this case, the power transmission unit 103 includes a gate driver that controls the ON / OFF of the FETs.

[0044] The power transmission unit 103 controls the intensity of the electromagnetic wave to be output by adjusting the voltage (transmission voltage) or current (transmission current), or both, input to the power transmission antennas 105a to 105c under the control of the control unit 101. When the transmission voltage or transmission current is increased, the intensity of the electromagnetic wave becomes stronger, and when the transmission voltage or transmission current is decreased, the intensity of the electromagnetic wave becomes weaker. Also, the power transmission unit 103 performs output control of AC frequency power so that power transmission from the power transmission antennas 105a to 105c is started or stopped based on an instruction from the control unit 101. Further, it is assumed that the power transmission unit 103 has the ability to supply power sufficient to output 15 watts (W) of power to the charging unit of the RX (in the case of RX200 to 220, the charging unit 206 (Fig. 2)) corresponding to the WPC standard.

[0045] The communication unit 104 performs communication for power transmission control based on the WPC standard as described above with the RX under the control of the control unit 101. The communication unit 104 modulates the electromagnetic wave output from the power transmission antennas 105a to 105c, transmits information to the RX, and performs communication. Also, the communication unit 104 demodulates the electromagnetic wave output from the power transmission antennas 105a to 105c and modulated at the RX to acquire the information transmitted by the RX. That is, the communication performed by the communication unit 104 is performed with a signal superimposed on the electromagnetic wave transmitted from the power transmission antennas 105a to 105c. Further, the communication unit 104 may communicate with the RX by a standard different from the WPC standard using an antenna different from the power transmission antennas 105a to 105c, or may communicate with the RX by selectively using a plurality of communications.

[0046] In addition to storing the control program, the memory 106 can also store the states of the TX100 and the RX (such as the received power value). For example, the state of the TX100 is acquired by the control unit 101, and the state of the RX is acquired by the RX control unit (in the case of RX200 to 220, the control unit 201 (Fig. 2)) and can be received via the communication unit 104.

[0047] A plurality of power transmission antennas (coils) 105a to 105c are connected to the antenna switching unit 107. The antenna switching unit 107 selects and switches one or more of the plurality of antennas (coils). In FIG. 1, three power transmission antennas 105a to 105c are shown, but the number of power transmission coils is not limited to this number. Also, in the following description, the power transmission antennas 105a to 105c may be collectively referred to as the power transmission antenna 105.

[0048] Next, RX200 (FIG. 2) will be described. As described above, RX210 and RX220 have the same configuration as RX200. As shown in FIG. 2, RX200 includes a control unit 201, a UI (User Interface) unit 202, a power receiving unit 203, a communication unit 204, a power receiving antenna 205, a charging unit 206, a battery 207, a memory 208, and a switch unit 209. Note that the plurality of functional blocks shown in FIG. 2 may be realized as one hardware module.

[0049] The control unit 201 controls the entire RX200 by executing, for example, a control program stored in the memory 208. That is, the control unit 201 controls each functional unit shown in FIG. 2. Further, the control unit 201 may perform control for executing applications other than wireless power transmission. An example of the control unit 201 includes one or more processors such as a CPU or an MPU. Note that the control unit 201 may control the entire RX200 (the entire smartphone when RX200 is a smartphone) in cooperation with the OS (Operating System) being executed.

[0050] Also, the control unit 201 may be configured by dedicated hardware such as an ASIC. Also, the control unit 201 may include an array circuit such as an FPGA compiled to execute a predetermined process. The control unit 201 stores information to be stored during the execution of various processes in the memory 208. Also, the control unit 201 can measure time using a timer (not shown).

[0051] The UI unit 202 performs various outputs to the user. The various outputs here refer to operations such as screen display, blinking or color change of the LED, voice output by the speaker, vibration of the RX200 main body, etc. The UI unit 202 is realized by a liquid crystal panel, a speaker, a vibration motor, etc.

[0052] The power receiving unit 203 obtains AC power (AC voltage and AC current) generated by electromagnetic induction caused by the electromagnetic wave radiated from the power transmission antenna 105 of TX100 at the power receiving antenna 205. Then, the power receiving unit 203 converts the AC power into DC power or AC power of a predetermined frequency, and outputs the power to the charging unit 206 that performs a process of charging the battery 207. That is, the power receiving unit 203 supplies power to the load in RX200. The above-mentioned GP is the amount of power that is guaranteed to be output from the power receiving unit 203. It is assumed that the power receiving unit 203 has the ability to supply the power required for the charging unit 206 to charge the battery 207 and supply 15 watts of power to the charging unit 206. The switch unit 209 is for controlling whether to supply the received power to the battery (load) or not. If the switch unit 209 connects the charging unit 206 and the battery 207, the received power is supplied to the battery 207. If the switch unit 209 disconnects the charging unit 206 and the battery 207 with a switch, the received power is not supplied to the battery 207. Note that in FIG. 2, the switch unit 209 is arranged between the charging unit 206 and the battery 207, but it may also be arranged between the power receiving unit 203 and the charging unit 206. Alternatively, in FIG. 2, the switch unit 209 is shown as a single block, but it is also possible to implement the switch unit as part of the charging unit 206. The communication unit 204 performs communication for power receiving control based on the WPC standard as described above with the communication unit 104 of TX100. The communication unit 204 demodulates the electromagnetic wave input from the power receiving antenna 205 to obtain the information transmitted from TX100. Then, the communication unit 204 performs communication with TX100 by superimposing a signal related to the information to be transmitted to TX100 on the electromagnetic wave by load-modulating the input electromagnetic wave. Note that the communication unit 204 may communicate with TX100 by a standard different from the WPC standard using an antenna different from the power receiving antenna 205, or may communicate with TX100 by selectively using a plurality of communications.

[0053] In addition to storing the control program, the memory 208 also stores the states of the TX100 and RX200, etc. For example, the state of the RX200 is acquired by the control unit 201, and the state of the TX100 is acquired by the control unit 101 of the TX100 and can be received via the communication unit 204.

[0054] [Functional Configuration of Control Unit of Power Transmission Device] Next, the functional configuration of the control unit 101 of the TX (power transmission device) 100 according to the present embodiment will be described with reference to FIG. 3. FIG. 3 is a block diagram showing an example of the functional configuration of the control unit 101. The control unit 101 includes a communication control unit 301, a power transmission control unit 302, a foreign object detection unit 303, and a calculation unit 304.

[0055] The communication control unit 301 is a processing unit that performs control communication with an RX based on the WPC standard via the communication unit 104. The power transmission control unit 302 is a processing unit that controls the power transmission unit 103 and controls power transmission to the RX. The foreign object detection unit 303 is a processing unit that measures the power transmitted in the power transmission unit 103 and the Q value in the power transmission antenna 105 to detect foreign objects. The foreign object detection unit 303 can implement a foreign object detection function based on the power loss method and a foreign object detection function based on the Q value measurement method. Also, the foreign object detection unit 303 may perform foreign object detection processing using other methods. For example, in a TX equipped with an NFC (Near Feald Communication) communication function, foreign object detection processing may be performed using the opposing device detection function according to the NFC standard. Further, the foreign object detection unit 303 can also detect that the state on the TX100 has changed as a function other than detecting foreign objects. For example, it is possible to detect an increase or decrease in the number of RXs on the TX100. The calculation unit 304 measures the power output to the RX via the power transmission unit 103 and calculates the average output power value for each unit time. The foreign object detection unit 303 performs foreign object detection processing based on the power loss method using the calculation result by the calculation unit 304 and the received power information received from the RX via the communication control unit 301.

[0056] The functions of the communication control unit 301, the power transmission control unit 302, the foreign object detection unit 303, and the calculation unit 304 are realized as programs operating in the control unit 101. Each processing unit is configured as an independent program and can operate in parallel while synchronizing between programs through event processing or the like.

[0057] [Flow of Processing by Power Transmission Device] Subsequently, the flow of processing executed by TX100 will be described. FIG. 4 shows a flowchart of the processing executed by TX100 in the present embodiment. This processing can be realized, for example, by the control unit 101 of TX100 executing a program read from the memory 106. Note that at least a part of the following procedures may be realized by hardware. In this case, the hardware can be realized, for example, by automatically generating a dedicated circuit using a gate array circuit such as an FPGA from a program for realizing each processing step using a predetermined compiler.

[0058] When TX100 is activated, this process starts (S401). Alternatively, this process can be started in response to the user of TX100 inputting a start instruction for the contactless charging application via an input unit (not shown), or in response to TX100 being connected to a commercial power supply and receiving power supply. Also, this process may be started by other triggers. When this process starts, the antenna switching unit 107 of TX100 selects one power transmission antenna from a plurality of power transmission antennas (power transmission coils) under the control of the control unit 101 (S402). Next, TX100 shifts to the Selection phase, and the communication control unit 301 transmits an Analog Ping (S403) to determine whether an object is detected (S404). If no object is detected, the communication control unit 301 continues to transmit the Analog Ping periodically. If an object is detected in S404 (Yes in S404), TX100 shifts to the Ping phase, and the communication control unit 301 transmits a Digital Ping (S405). Then, the foreign object detection unit 303 recognizes that the detected object is an RX. Next, TX100 shifts to the Identification & Configuration phase, and the communication control unit 301 acquires information of the RX (device configuration information (capability information) and identification information of the RX) from the RX (S406). Next, in S407, the control unit 101 stores in the memory 106 the information of the RX obtained in S406 and the information associating the power transmission antenna that detected the RX.

[0059] Next, in S408, the control unit 101 determines whether the selection and switching of all the power transmission antennas are completed. Here, if the switching of all the antennas is not completed, the process shifts to S402, and the control unit 101 controls the antenna switching unit 107 to select another power transmission antenna. If it is determined in S408 that the selection and switching of all the power transmission antennas are completed, the process proceeds to S409.

[0060] By performing the processes from S401 to S408, TX100 can associate each power transmission antenna (power transmission coil) that TX100 has with an RX recognizable by each power transmission antenna. Also, TX100 can recognize information on all RXs present on TX100.

[0061] Next, in S409, control unit 101 determines whether there are multiple RXs placed on TX100 based on the results from S401 to S408. If it is determined in S409 that there are multiple RXs placed on TX100 (Yes in S409), the process proceeds to S410. If it is determined that there is one RX placed on TX100 (No in S409), the process proceeds to S413. In S410, control unit 101 selects one RX from the multiple RXs. Hereinafter, in the description of FIG. 4, the one RX selected in S410 is referred to as the target RX. Then, in S411, communication control unit 301 transmits a message for making non-target RXs (RXs other than the target RX) recognize that they were not selected.

[0062] This message may be a message for notifying all RXs of the information of the target RX (the selected RX), or may be a message for notifying all RXs of the information of non-target RXs (RXs not selected). Since these messages need to be notified to all the multiple RXs on TX100, they are transmitted from all the multiple power transmission antennas 105 that TX100 has. Alternatively, it may be a message for notifying information indicating that it was not selected with non-target RXs as the destination. This message is transmitted from a power transmission antenna 105 capable of communicating at least with non-target RXs. Alternatively, it may be a message for notifying information indicating that it was selected with the target RX as the destination. In this case, non-target RXs recognize that they were not selected when a message notifying information indicating that it was selected does not reach within a predetermined time. Also, this message is transmitted from a power transmission coil capable of communicating at least with the target RX.

[0063] When a non-target RX receives the message, it controls to enter a state where charging or power supply from TX100 does not occur (for example, disconnecting the connection to a load (such as a charging circuit and a battery)). That is, the RX controls to disconnect the load (such as a charging circuit and a battery) in the switch unit 209 (Fig. 2) and does not supply the received power to the load (such as a charging circuit and a battery).

[0064] Next, in S412, the control unit 101 of TX100 selects a power transmission antenna (power transmission coil) capable of transmitting power to the target RX (corresponding to the target RX), and makes it possible to communicate and transmit power to the target RX with the antenna. Next, TX100 shifts to the Negotiation phase (S413) and then shifts to the Calibration phase (S414). In the Calibration phase, based on the WPC standard, the target RX notifies TX100 of a predetermined received power value (received power value in the light load state / received power value in the maximum load state), and TX100 performs adjustments for efficient power transmission. The received power value notified to TX100 can be used for foreign object detection processing by the power loss method.

[0065] In the calibration phase, as described above with reference to FIG. 10, TX100 derives the relationship between the received power and the transmitted power in the state without foreign objects. Specifically, the foreign object detection unit 303 of TX100 uses a predetermined received power value (including the received power value in the light load state and the received power value in the connected load state) acquired from the RX based on the WPC standard to derive data indicating the power loss between TX and RX in the state without foreign objects (power loss data) (corresponding to the straight line 1002 in FIG. 10). Hereinafter, the power loss data is referred to as calibration data. The calibration data can be used for foreign object detection processing by the power loss method. The explanation of foreign object detection based on the power loss method is as described above. That is, when the power loss between TX and RX during power transmission, calculated based on the calibration data obtained in the calibration phase and the received power value at the RX received during power transmission, is equal to or greater than a predetermined threshold value, TX determines that "there is a foreign object" or "there may be a foreign object".

[0066] In S415, the control unit 101 stores the calibration data obtained in the calibration phase and the information of the target RX (S407) in the memory 106 in association with each other. Then, in S416, the control unit 101 determines whether the calibration data of all the RXs placed on TX100 has been acquired. Since TX100 has obtained the information of all the RXs on TX100 from S401 to S408, this determination can be made by checking whether all the information of the RXs and the calibration data obtained in S415 are associated with each other.

[0067] Through the processing from S409 to S416 above, TX100 can individually acquire (derive) the calibration data for each RX of all the RXs placed on TX100 in a time-division manner. Next, in S417, TX100 shifts to the power transfer phase. Then, the process ends in S418.

[0068] In the Power Transfer phase (S417), TX100 controls power transmission to a plurality of RXs placed on TX100 in a time-division manner. Hereinafter, the detailed operations in the Power Transfer phase will be described with reference to FIG. 5. FIG. 5 is a flowchart of the process in the Power Transfer phase of the present embodiment. In the time-division method, different power transmission periods are assigned to each of the plurality of power receiving devices, and power transmission is performed on one power receiving device within the assigned power transmission period.

[0069] When TX100 starts the Power Transfer phase (S501), the control unit 101 selects one RX to be the power transmission target from among the plurality of RXs placed on TX100 (S502). Hereinafter, in the description of FIG. 5, the one RX selected in S502 will be referred to as the target RX. Then, in S503, the communication control unit 301 transmits a message to the RXs other than the target RX (non-target RXs) to make them recognize that they have not been selected. Since this message is the same as the message used in the notification of S411 in FIG. 4, the description thereof will be omitted.

[0070] Upon receiving the message, the non-target RXs control themselves to be in a state where no charging or power supply is received from TX100 (for example, disconnecting the connection to the load (such as the charging circuit and the battery)). That is, the non-target RXs control the switch unit 209 (FIG. 2) to disconnect the load (such as the charging circuit and the battery), and do not supply the received power to the load (such as the charging circuit and the battery). Next, in S504, the control unit 101 of TX100 selects a power transmission antenna (power transmission coil) capable of power transmission to the target RX (corresponding to the target RX), and makes the antenna in a state where communication and power transmission to the target RX are possible. Subsequently, in S505, the power transmission control unit 302 performs power transmission to the target RX.

[0071] During power transmission, the foreign object detection unit 303 detects changes in the power transmission and reception state within the power transmission range of TX100 (for example, state changes on TX100) (S506). For example, the foreign object detection unit 303 uses the Calibration data of the target RX obtained in the Calibration phase (S414 in FIG. 4) to detect foreign objects by the aforementioned power loss method. If a foreign object is detected (Yes in S506), the process returns to the process of S402 in FIG. 4 (the process after TX startup). On the other hand, it is also possible that the change in the power transmission and reception state is not due to a foreign object but due to an increase or decrease in the number of RXs placed on TX100. Even when the number of RXs on TX100 increases or decreases, since the above-described power loss changes, the foreign object detection unit 303 can use the power loss method to detect an increase or decrease in the number of RXs on TX100.

[0072] When a change in the power transmission and reception state is detected in S506, by returning to after TX startup in the processing flow of FIG. 4, for example, even when there is an increase or decrease in the number of RXs placed on TX100, power transmission to all RXs can be appropriately performed. During power transmission by the power transmission control unit 302, the foreign object detection unit 303 of TX100 periodically monitors changes in the power transmission and reception state until power transmission ends (No in S506, No in S507). When TX100 ends power transmission without detecting a change in the power transmission and reception state (Yes in S507), it stores the information of the target RX (the RX for which power transmission has been completed) in the memory 106. Then the process proceeds to S508, and the control unit 101 determines whether power transmission has been completed for all RXs by comparing with the RX information already stored. When power transmission has been completed for all RXs, it ends at S509, and when power transmission has not been completed for all RXs, the process returns to S502 (after the start of the Power Transfer phase). Note that the completion of power transmission can be confirmed when the communication control unit 301 of TX100 receives End Power Transfer of the WPC standard from the RX to which power is to be transmitted (the same applies in the following description).

[0073] Through the processes from S501 to S509 above, TX100 can appropriately complete power transmission to all RXs by performing time-division power transmission to a plurality of RXs placed on TX100.

[0074] Thus, in this embodiment, first, TX100 sets a specific RX among the plurality of RXs placed on TX100 as the target RX, controls so that charging or power supply from TX100 is not performed to non-target RXs, and then derives (acquires) the Calibration data of the target RX (Fig. 4). Then, TX100 acquires the Calibration data for all RXs. After that, in the Power Transfer phase, TX100 sets a specific RX among the plurality of RXs placed on TX100 as the target RX, controls so that charging or power supply from TX100 is not performed to non-target RXs, and then performs power transmission to the target RX using the already-derived Calibration data (Fig. 5). Thereby, by making the state of each RX at the time of Calibration data derivation match the state of each RX at the time of power transmission, TX100 can appropriately complete power transmission to all RXs.

[0075] [Embodiment 2] In Embodiment 1, a control method for appropriately performing power transmission to a plurality of RXs was described. In this embodiment, another control method for appropriately performing power transmission to a plurality of RXs will be described. Hereinafter, differences from Embodiment 1 will be described, and descriptions of common parts will be omitted.

[0076] [Flow of Processing by Power Transmission Device] FIG. 6 shows a flowchart of the process executed by TX100 in the present embodiment. This process can be realized, for example, by the control unit 101 of TX100 executing a program read from the memory 106. Note that at least a part of the following procedures may be realized by hardware. In this case, the hardware can be realized, for example, by automatically generating a dedicated circuit using a gate array circuit such as an FPGA from a program for realizing each processing step using a predetermined compiler.

[0077] Since the processes of S601 to S606 are the same as those of S401 to S406 in FIG. 4 described in Embodiment 1, the description thereof is omitted. In S607, the control unit 101 selects one RX. The RX can be the RX detected using the power transmission antenna selected in S602. Hereinafter, in the description of FIG. 6, the one RX selected in S607 is referred to as the target RX. Then, in S608, the communication control unit 301 transmits a message for causing the RXs other than the target RX (non-target RXs) to recognize that they have not been selected. Since the message is the same as the message used in the notification of S411 in FIG. 4, the description thereof is omitted.

[0078] Upon receiving the message, the non-target RXs are controlled to be in a state where charging or power supply is not performed from TX100 (for example, disconnecting the connection to a load (such as a charging circuit and a battery)). That is, the non-target RXs are controlled to disconnect the load (such as a charging circuit and a battery) in the switch unit 209 (FIG. 2) and not supply the received power to the load (such as a charging circuit and a battery).

[0079] Next, TX100 transitions to the Negotiation phase (S609) and then to the Calibration phase (S610). In the Calibration phase, based on the WPC standard, the target RX notifies TX100 of a predetermined received power value (the received power value in the light load state / the received power value in the maximum load state), and the power transmission control unit 302 of TX100 performs adjustments for efficient power transmission. The received power value notified to TX100 can be used for foreign object detection processing by the power loss method. Since the processing in the Calibration phase is the same as the processing of S414 in FIG. 4, the description is omitted.

[0080] In S611, the control unit 101 associates the Calibration data obtained in the Calibration phase with the information of the target RX (device configuration information (capability information) and RX identification information) obtained in S606 and stores them in the memory 106. Then, in S612, the control unit 101 determines whether the selection and switching of all power transmission antennas are completed.

[0081] Through the processing from S602 to S612 above, TX100 can individually acquire (derive) the Calibration data for each RX for all RXs placed on TX100 in a time-division manner. Next, in S613, TX100 transitions to the Power Transfer phase. And in S614, the processing ends.

[0082] In the Power Transfer phase (S613), TX100 controls to perform power transmission to a plurality of RXs placed on TX100 in a time-division manner. Hereinafter, the detailed operation in the Power Transfer phase will be described with reference to FIG. 7. FIG. 7 is a flowchart of the processing in the Power Transfer phase in this embodiment. Since the processing of S701 to S704 is the same as that of S501 to S504 in FIG. 5, the description is omitted. After the processing of S704, in S705, the power transmission control unit 302 performs power transmission to the target RX.

[0083] During power transmission, the foreign object detection unit 303 detects changes in the power transmission and reception state within the power transmission range of TX100 (for example, state changes on TX100) (S706). For example, the foreign object detection unit 303 uses the Calibration data of the target RX obtained in the Calibration phase (S610 in FIG. 6) to detect foreign objects by the aforementioned power loss method. If a foreign object is detected, the process returns to the process of S602 in FIG. 6 (the process after TX startup). On the other hand, it is also possible that the change in the power transmission and reception state is not due to a foreign object but due to an increase or decrease in the number of RXs placed on TX100. Even when the number of RXs on TX100 increases or decreases, since the above-described power loss changes, the foreign object detection unit 303 can use the power loss method to detect an increase or decrease in the number of RXs on TX100.

[0084] If a change in the power transmission and reception state is detected in S706, by returning after TX startup in the flow of FIG. 6, for example, even when there is an increase or decrease in the number of RXs placed on TX100, power transmission to all RXs can be appropriately performed. If a change in the power transmission and reception state is not detected, the process proceeds to S707, and the control unit 101 determines whether a predetermined counter (a period specified by the predetermined counter) has ended. This counter is, for example, a counter that counts time, the number of power transmission times of intermittently performed power transmission, or the number of communication packets or frames. If the counter ends in S707 (for example, when a predetermined condition / number is satisfied) (Yes in S707), the process returns to S702, and TX100 selects another RX and performs power transmission.

[0085] If the predetermined counter has not ended in S707 (No in S707), the process proceeds to S708, and the control unit 101 determines whether the power transmission to the target RX has been completed. As a result of the determination, for example, if it is not yet fully charged and the power transmission has not been completed, the process returns to S705, and the power transmission control unit 302 continues the power transmission. If it is determined in S708 that the power transmission to the target RX has been completed, the process proceeds to S709, and the control unit 101 determines whether the power transmission to all the RXs has been completed. If the power transmission to all the RXs has not been completed, the process returns to S702, the control unit 101 selects another RX for which the power transmission has not been completed, and the power transmission control unit 302 performs power transmission to the selected RX (target RX). When the power transmission to all the RXs placed on the TX100 has been completed, the process proceeds to S710 and ends.

[0086] As described above, in this embodiment, first, the TX100 sets a specific RX as the target RX among the plurality of RXs placed on the TX100, controls so that charging or power supply is not performed from the TX100 to the non-target RXs, and then derives (acquires) the Calibration data of the target RX (FIG. 6). Then, the TX100 acquires the Calibration data for all the RXs. After that, in the Power Transfer phase, the TX100 sets a specific RX as the target RX among the plurality of RXs placed on the TX100, controls so that charging or power supply is not performed from the TX100 to the non-target RXs, and then uses the already derived Calibration data to perform power transmission to the target RX (FIG. 7). As a result, by matching the state of each RX at the time of Calibration data derivation with the state of each RX at the time of power transmission, the TX100 can appropriately complete the power transmission to all the RXs.

[0087] In addition, in Embodiment 1, the description was based on the flows of FIGS. 4 and 5, and in Embodiment 2, the description was based on the flows of FIGS. 6 and 7. However, this combination can be changed, and it is also possible to realize a process that combines the flows of FIGS. 4 and 6, and FIGS. 5 and 7.

[0088] [Embodiment 3] In Embodiment 1 and Embodiment 2, a control method for appropriately performing power transmission to a plurality of RXs was described. In this embodiment, another control method for appropriately performing power transmission to a plurality of RXs will be described. Hereinafter, differences from Embodiment 1 and 2 will be described, and common parts will be omitted from the description.

[0089] [Flow of Processing by Power Transmission Device] FIG. 8 shows a flowchart of the processing executed by TX100 in this embodiment. This processing can be realized, for example, by the control unit 101 of TX100 executing a program read from the memory 106. Note that at least a part of the following procedures may be realized by hardware. In this case, the hardware can be realized, for example, by automatically generating a dedicated circuit using a gate array circuit such as an FPGA from a program for realizing each processing step using a predetermined compiler.

[0090] The processing of S801 to S806 is the same as that of S401 to S406 in FIG. 4 described in Embodiment 1, and thus the description thereof will be omitted. In S807, the control unit 101 selects one RX. The RX can be the RX detected using the power transmission antenna selected in S802. Hereinafter, in the description of FIG. 8, the one RX selected in S807 will be referred to as the target RX. Then, in S808, the communication control unit 301 transmits a message for causing the RXs other than the target RX (non-target RXs) to recognize that they have not been selected. Since the message is the same as the message used in the notification of S411 in FIG. 4, the description thereof will be omitted.

[0091] Upon receiving the message, the non-target RXs are controlled to be in a state where charging or power supply is not performed from TX100 (for example, disconnecting the connection to a load (such as a charging circuit and a battery)). That is, the non-target RXs control the switch unit 209 (FIG. 2) to disconnect the load (such as a charging circuit and a battery), and do not supply the received power to the load (such as a charging circuit and a battery).

[0092] Next, TX100 transitions to the Negotiation phase (S809) and then to the Calibration phase (S810). In the Calibration phase, based on the WPC standard, the target RX notifies TX100 of a predetermined received power value (the received power value in the light load state / the received power value in the maximum load state), and the power transmission control unit 302 of TX100 performs adjustments for efficient power transmission. The received power value notified to TX100 can be used for foreign object detection processing by the power loss method. Since the processing in the Calibration phase is the same as the processing of S414 in FIG. 4, the description is omitted.

[0093] In S811, the control unit 101 associates the Calibration data obtained in the Calibration phase with the information of the target RX (device configuration information (capability information) and RX identification information) obtained in S806 and stores them in the memory 106.

[0094] Next, in S812, TX100 transitions to the Power Transfer phase. Then, in S813, the control unit 101 determines whether the selection and switching of all power transmission antennas are completed. If the switching of all antennas is not completed, the process returns to S802, and the control unit 101 selects another unselected antenna. If the switching of all antennas is completed, the process proceeds to S814 and ends.

[0095] In the Power Transfer phase (S812), TX100 controls to perform power transmission to a plurality of RXs placed on TX100 in a time-division manner. Hereinafter, the detailed operation in the Power Transfer phase will be described with reference to FIG. 9. FIG. 9 is a flowchart of the processing in the Power Transfer phase in the present embodiment.

[0096] When TX100 starts the Power Transfer phase (S901), the power transmission control unit 302 performs power transmission to the target RX (S902). During power transmission, the foreign object detection unit 303 detects changes in the power transmission and reception state within the power transmission range of TX100 (for example, state changes on TX100) (S706). For example, the foreign object detection unit 303 uses the Calibration data of the target RX obtained in the Calibration phase (S810 in FIG. 8) to detect foreign objects by the aforementioned power loss method. If a foreign object is detected, the process returns to the process of S802 in FIG. 8 (the process after TX startup). On the other hand, it is also possible that the change in the power transmission and reception state is not due to a foreign object but due to an increase or decrease in the number of RXs placed on TX100. Since the above-described power loss also changes due to an increase or decrease in the number of RXs on TX100, the foreign object detection unit 303 can detect an increase or decrease in the number of RXs on TX100 using the power loss method.

[0097] When a change in the power transmission and reception state is detected in S903, by returning after TX startup in the flow of FIG. 8, appropriate power transmission to all RXs can be performed even when there is an increase or decrease in the number of RXs placed on TX100, for example. When a change in the power reception state is not detected, the process proceeds to S904, and the control unit 101 determines whether the power transmission to the target RX has been completed. For example, if it is determined that the power transmission has been completed because the RX is fully charged, etc., the process proceeds to S905 and ends. If it is determined that the power transmission has not been completed, the process proceeds to S902, and the power transmission control unit 302 continues the power transmission.

[0098] Thus, in this embodiment, first, TX100 sets a specific RX as the target RX among the plurality of RXs placed on TX100, and controls the non-target RXs so that they are not charged or powered from TX100. Then, TX100 derives (acquires) the Calibration data of the target RX (Fig. 8). And TX100 acquires the Calibration data for all RXs. After that, in the Power Transfer phase, TX100 sets a specific RX as the target RX among the plurality of RXs placed on TX100, controls the non-target RXs so that they are not charged or powered from TX100, and then performs power transmission to the target RX using the already-derived Calibration data (Fig. 9). By making the states of each RX at the time of Calibration data derivation match the states of each RX at the time of power transmission, TX100 can appropriately complete power transmission to all RXs.

[0099] As described above, three embodiments have been given to explain the control method for appropriately performing power transmission to a plurality of RXs. In the above embodiments, as a foreign object detection function, a method of detecting a state change on the power transmission device by the power loss method has been described. However, since the Q value changes depending on the increase or decrease in the number of RXs on the TX, it is also possible to detect the increase or decrease in the number of RXs on the TX by the Q value measurement method. Therefore, in the Q value measurement method performed in the Negotiation phase, when the TX detects a change in the power transmission and reception state (for example, a state change on the TX), it may be controlled to return to the operation after TX startup. That is, in Embodiment 1, the process returns from S506 in Fig. 5 to S402 in Fig. 4, in Embodiment 2, the process returns from S706 in Fig. 7 to S602 in Fig. 6, and in Embodiment 3, the process returns from S903 in Fig. 9 to S802 in Fig. 8.

[0100] Alternatively, instead of the Q-value measurement method, based on the measurement results of the resonance frequency of the power transmission antenna, the sharpness of the resonance curve, the inductance value of the power transmission antenna, the coupling coefficient between the power transmission antenna and the object placed on the TX, the electrical characteristics of the power transmission unit including the power transmission antenna of the TX, etc., or based on the measurement results of sensors such as a photoelectric sensor, an eddy current displacement sensor, a contact displacement sensor, an ultrasonic sensor, an image discrimination sensor, a weight sensor, etc. mounted on the TX, when a change in the power transmission and reception state at the TX is detected, it may be controlled to return to the operation after the TX is activated. Also, the TX may periodically transmit an Analog Ping from a power transmission antenna other than the power transmission antenna that performs communication and power transmission to the RX, and when it is detected that an object is placed, it may be controlled to return to the operation after the TX is activated. This is because there is a possibility that a new RX or a foreign object may exist in the vicinity of the power transmission antenna in these cases.

[0101] In this way, the TX can improve the foreign object detection accuracy during power transmission by measuring the power loss in the state without foreign objects between the TX and RX for each individual RX in a time-division manner for a plurality of RXs existing within the power transmission range of the TX, and also performing power transmission for each individual RX in a time-division manner.

[0102] [Other Embodiments] In Embodiments 1 to 3, the power transmission device has been described for the case where one power transmission antenna selected from a plurality of power transmission antennas is connected to one power transmission unit. However, a configuration in which a plurality of power transmission units are connected to one power transmission antenna may also be used. That is, the power transmission device has a first power transmission unit (power transmission circuit) and a second power transmission unit (power transmission circuit), and when it has a first power transmission antenna and a second power transmission antenna, either the first power transmission unit or the second power transmission unit may be connectable to the first power transmission antenna. Here, consider the case where the first power transmission unit (power transmission circuit) is connected to the first power transmission antenna and power transmission is being performed to the power reception device, and then the power transmission unit (power transmission circuit) connected to the first power transmission antenna is switched from the first power transmission unit (power transmission circuit) to the second power transmission unit (power transmission circuit). When the electrical characteristics of the first power transmission unit and the second power transmission unit are the same, the above-described Calibration data does not change, so it is possible to perform power transmission from the second power transmission unit (power transmission circuit) to the power reception device using the already acquired Calibration data and by the method described in Embodiments 1 to 3. On the other hand, when the electrical characteristics of the first power transmission unit and the second power transmission unit are different, the above-described Calibration data also changes, so power transmission cannot be performed using the already acquired Calibration data. Therefore, it becomes possible to derive (acquire) Calibration data again by the method described in Embodiments 1 to 3 and perform power transmission from the second power transmission unit (power transmission circuit) to the power reception device using the Calibration data. At this time, the power transmission device stores in the memory information in which the information of the RX to be powered, the information of the power transmission antenna used for power transmission, and the information of the power transmission unit (power transmission circuit) used for power transmission are associated with each other.

[0103] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium and causing one or more processors in the computer of the system or device to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0104] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the claims are appended to disclose the scope of the invention.

Description of Reference Numerals

[0105] 100 Transmission device (TX), 200 - 220 Receiving device (RX)

Claims

[Claim 1] A power transmission device, A power transmitting means for wirelessly transmitting power to a plurality of power receiving devices in a time division manner; A communication means for communicating with the plurality of power receiving devices; a derivation means for deriving a plurality of pieces of data on power losses between the power transmitting device and the plurality of power receiving devices based on a plurality of values ​​of received power received from the plurality of power receiving devices via the communication means; a detection unit configured to detect a foreign object different from the plurality of power receiving devices within a power transmission range of the power transmitting device based on the plurality of power loss data.

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