POWER TRANSMISSION DEVICE, CONTROL METHOD FOR POWER TRANSMISSION DEVICE, AND PROGRAM

Abstract

To perform appropriate control over wireless power transmission in a power transmission device including a plurality of power transmission coils.SOLUTION: A power transmission device 100 comprises: a power transmission coil group 210 for wirelessly transmitting power to a power receiving device, the power transmission coil group 210 including a first power transmission coil 209, and a second power transmission coil 209 arranged at a position closer than a position separated by a prescribed distance from the first coil; and a control unit 201 that implements detection for detecting an object by having a signal for detecting the object be output from some of the power transmission coils within the power transmission coil group 210, and that, on the basis of the detected object being a power receiving device, wirelessly transmits power to the power receiving device using at least one power transmission coil 209 and performs a control such that signals for detecting the object are not simultaneously output from the first power transmission coil 209 and the second power transmission coil 209.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to control of wireless power transmission.

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. And there are provided a power transmission device and a power reception device compliant with the standard (hereinafter referred to as the WPC standard) established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards.

[0003] Further, Patent Document 1 discloses a power transmission device having a plurality of power transmission coils.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 discloses the arrangement of a plurality of power transmission coils, but does not consider a method for controlling wireless power transmission of a power transmission device having a plurality of power transmission coils.

[0006] An object of the present disclosure is to provide a technology capable of performing appropriate control related to wireless power transmission in a power transmission device having a plurality of power transmission coils.

Means for Solving the Problems

[0007] The power transmission device according to the present disclosure is a plurality of coils used for wirelessly transmitting power to a power reception device, a first coil, and a second coil disposed at a position closer than a position at a predetermined distance from the first coil. and a third coil disposed at a position farther than a position at a predetermined distance from the first coilA plurality of coils, detection means for detecting an object by outputting a signal for detecting the object from some of the plurality of coils, and based on the object detected by the detection means being a power receiving device, power transmission means for wirelessly transmitting power to the power receiving device using at least one of the plurality of coils, and control means for controlling so that signals for detecting an object are not simultaneously output from the first coil and the second coil. wherein when there are a plurality of power receiving devices, the power transmission means wirelessly transmits power to the first power receiving device via the coil corresponding to the first power receiving device included in the plurality of power receiving devices, and wirelessly transmits power to the second power receiving device via the coil corresponding to the second power receiving device included in the plurality of power receiving devices, and the control means controls so that a signal for detecting an object is not output via the second coil during the wireless power transmission to the power receiving device via the first coil It is characterized by doing so.

Effect of the Invention

[0008] According to the present disclosure, in a power transmission device having a plurality of power transmission coils, appropriate control regarding wireless power transmission can be performed.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the components described in the following embodiments are examples of the embodiments of the present disclosure, and the present disclosure is not limited thereto.

[0011] (Embodiment 1) [Configuration of the System] FIG. 1 shows an example of a wireless power transmission system according to the present embodiment. The wireless power transmission system in the present embodiment includes a power transmission device 100 and power reception devices (a first power reception device 101a and a second power reception device 101b). The power transmission device 100 in the present embodiment has a function of simultaneously charging the first power reception device 101a and the second power reception device 101b placed within its power transmission range. Note that in FIG. 1, an example where two power reception devices exist on the power transmission device is shown, but it is not limited thereto. For example, the power transmission device 100 may charge one device. Further, the power transmission device 100 may be configured to be able to simultaneously charge three or more power reception devices.

[0012] In the present embodiment, the term "the power reception device is placed" includes the following states. The state where the power reception device is placed includes, for example, the case where the power reception device is placed (installed) on the surface within the power transmission range of the power transmission device. However, the method described in the present embodiment is applicable at least in a state where the power reception device is included within the power transmission range of the power transmission device, and for example, the power reception device and the power transmission device may be in a non-contact state. Further, the surface on which the power reception device can be placed may be not only a horizontal plane but also a vertical plane or an inclined plane.

[0013] [Device Configuration] FIG. 2 is a block diagram for explaining the functional configuration of the power transmission device 100. The power transmission device 100 includes a control unit 201, a power supply unit 202, a first power transmission circuit 203, a first communication unit 204, a second power transmission circuit 205, a second communication unit 206, a memory 207, a selection unit 208, and a power transmission coil group 210. The power transmission coil group 210 includes a plurality of power transmission coils 209a to 209n. Note that the number of the power transmission coils 209a to 209b can be two or more. In the following description, when there is no particular need for distinction, they are simply referred to as the power transmission coil 209. Each processing unit will be described below.

[0014] The control unit 201 controls the entire power transmission device 100. The control unit 201 includes, for example, one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Note that the control unit 201 may include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like configured to execute the processes described later.

[0015] The power supply unit 202 is a power supply that supplies power for the control unit 201, the first power transmission circuit 203, and the second power transmission circuit 205 to operate. The power supply unit 202 can be, for example, a wired power reception circuit that receives power from a commercial power supply, a battery, or the like.

[0016] The first power transmission circuit 203 and the second power transmission circuit 205 generate an alternating voltage and an alternating current in any power transmission coil 209 included in the power transmission coil group 210 described later. The first power transmission circuit 203 and the second power transmission circuit 205 convert, for example, the direct current voltage supplied by the power supply unit 202 into an alternating voltage using a switching circuit having a half-bridge or full-bridge configuration using FETs (Field Effect Transistors). In this case, the power transmission circuit 203 includes a gate driver that controls the ON / OFF of the FET.

[0017] The first communication unit 204 performs control communication for wireless power transmission based on the standard established by the Wireless Power Consortium (WPC) (hereinafter referred to as the WPC standard) with the communication unit of the power receiving device described later. In the present embodiment, the first communication unit 204 load-modulates the AC voltage or AC current generated by the first power transmission circuit 203, and superimposes communication data on the power to be transmitted, thereby transmitting the communication data to the power receiving device. Further, the first communication unit 204 demodulates the AC voltage or AC current modulated by the communication unit of the power receiving device described later, thereby receiving the communication data transmitted from the power receiving device. By this process, control communication is realized. Similar to the first communication unit 204, the second communication unit 206 realizes control communication by load-modulating or demodulating the AC voltage or AC current generated by the second power transmission circuit 205 and performing transmission and reception of communication data.

[0018] The memory 207 stores the power transmission device 100, and the states of each element and the whole of the wireless power transmission system.

[0019] The power transmission coil group 210 has a plurality of power transmission coils 209. Any one or more of the plurality of power transmission coils 209 are connected to the first power transmission circuit 203 or the second power transmission circuit 205. The selection unit 208 connects any one or more of the power transmission coils 209 included in the power transmission coil group 210 to the first power transmission circuit 203 or the second power transmission circuit 205. The selection unit 208 connects the first power transmission circuit 203 to any one or more of the power transmission coils 209, and connects the second power transmission circuit 205 to the other one or more of the power transmission coils 209. Which of the first power transmission circuit 203 and the second power transmission circuit 205 is connected to which power transmission coil 209 is determined by the control unit 201 controlling the selection unit 208. The selection unit 208 switches the connection between the first power transmission circuit 203 and the second power transmission circuit 205 and the power transmission coil according to the control by the control unit 201. The control of the connection between the first power transmission circuit 203 and the second power transmission circuit 205 and the power transmission coil will be described later.

[0020] In this embodiment, the first power transmission circuit 203 and the second power transmission circuit 205 can operate independently, and each can transmit power for charging to a maximum of one power receiving device at the same time. That is, the power transmission device 100 can charge a maximum of two power receiving devices simultaneously.

[0021] In FIG. 2, the control unit 201, the power supply unit 202, the first power transmission circuit 203, the first communication unit 204, the second power transmission circuit 205, the second communication unit 206, the memory 207, the selection unit 208, and the power transmission coil group 210 are described as separate blocks, but are not limited thereto. Two or more of the above blocks may be combined by one chip or the like. Also, one block may be divided into a plurality of blocks.

[0022] FIG. 3 is a block diagram for explaining the functional configurations of the first power receiving device 101a and the second power receiving device 101b. The first power receiving device 101a and the second power receiving device 101b in this embodiment are assumed to have the same functional configuration, and when there is no particular need to distinguish them, they are simply denoted as the power receiving device 101. However, the first power receiving device 101a and the second power receiving device 101b may be different types of devices. The power receiving device 101 includes a control unit 301, a power receiving unit 302, a communication unit 303, a memory 304, a power receiving coil 305, a charging unit 306, and a battery 307. Each processing unit will be described below.

[0023] The control unit 301 controls the entire power receiving device 101. The control unit 301 is configured to include one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Note that the control unit 201 may include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like configured to execute the processes described later. The control unit 301 is activated by receiving predetermined power from the power transmission device 100.

[0024] The power receiving unit 302 acquires the AC voltage and AC current generated in the power receiving coil 305 by power transmission from any one or more power transmission coils 209 included in the power transmission coil group 210. Further, the power receiving unit 302 converts the acquired AC voltage and AC current into a DC voltage and DC current for the operation of the control unit 301, the charging unit 306, and the like.

[0025] The communication unit 303 performs control communication for wireless power transmission based on the WPC standard with the first communication unit 204 or the second communication unit 206 of the power transmission device 100. The communication unit 303 transmits communication data to the power transmission device 100 by load modulating the AC voltage and AC current received by the power receiving coil 305. Further, the communication unit 303 receives communication data transmitted from the power transmission device 100 by demodulating the AC voltage and AC current modulated by the power transmission device 100.

[0026] The charging unit 306 charges the battery 307 using the DC voltage and DC current supplied from the power receiving unit 302. The memory 304 stores the states of each element and the whole of the power receiving device 101 and the wireless power transmission system.

[0027] In FIG. 3, the control unit 301, the power receiving unit 302, the communication unit 303, the memory 304, and the charging unit 306 are each described as separate blocks, but it is not limited thereto. Two or more of the above blocks may be combined by one chip or the like. Also, one block may be divided into a plurality of blocks.

[0028] Note that the power receiving device 101 and the power transmitting device 100 may have functions to execute applications other than wireless charging. An example of the power receiving device 101 is a smartphone, and an example of the power transmitting device 100 is an accessory device for charging the smartphone. The power receiving device 101 and the power transmitting device 100 may be storage devices such as hard disk devices and memory devices, or may be information processing devices such as personal computers (PCs). Further, the power receiving device 101 and the power transmitting device 100 may be, for example, image input devices such as imaging devices (cameras, video cameras, etc.) and scanners, or may be image output devices such as printers, copiers, projectors, etc. Further, the power transmitting device 100 may be a smartphone. In this case, the power receiving device 101 may be another smartphone or a wireless earphone. Further, the power transmitting device 100 may be a charger installed in a console or the like inside an automobile.

[0029] Next, the configuration of the power transmission coil group 210 included in the power transmission device 100 in the present embodiment will be described with reference to FIG. 4. FIG. 4 shows a top view of the power transmission coil group 210. That is, FIG. 4 shows the arrangement of a plurality of power transmission coils 209 on the xy plane which is a two-dimensional plane. However, the actual plurality of power transmission coils 209 can be arranged in a three-dimensional space including the height direction. Note that the arrangement of the plurality of power transmission coils shown in FIG. 4 is an example and is not limited thereto. Further, the power transmission coils 400 to 411 in the following description correspond to the plurality of power transmission coils 209 constituting the power transmission coil 210.

[0030] FIGS. 4(a) and (b) are top views of a part of the power transmission coil group 210. FIG. 4(a) shows the arrangement of six circular coils of power transmission coils 400 to 405. The power transmission coil 400, the power transmission coil 401, and the power transmission coil 402 are arranged such that the circumferences of the power transmission coils are in contact with the other two coils, respectively. Similarly, the power transmission coil 403, the power transmission coil 404, and the power transmission coil 405 are arranged such that the circumferences of the power transmission coils are in contact with the other two coils, respectively. Similarly, the power transmission coil 402, the power transmission coil 403, and the power transmission coil 404 are arranged such that the circumferences of the power transmission coils are in contact with the other two coils, respectively.

[0031] Figure 4(b) shows the arrangement of the six circular coils of the power transmission coils 406 to 411. The arrangement of the power transmission coils 406 to 411 shown in Figure 4(a) corresponds to the arrangement obtained by horizontally inverting the arrangement of the power transmission coils 400 to 405 shown in Figure 4(b). The power transmission coil 409, the power transmission coil 410, and the power transmission coil 411 are each arranged such that the circumference of the power transmission coil is in contact with the other two coils. Similarly, the power transmission coil 406, the power transmission coil 407, and the power transmission coil 408 are each arranged such that the circumference of the power transmission coil is in contact with the other two coils. Similarly, the power transmission coil 408, the power transmission coil 409, and the power transmission coil 411 are each arranged such that the circumference of the power transmission coil is in contact with the other two coils.

[0032] Figure 4(c) is a top view of the entire power transmission coil group 210. The power transmission coil group 210 is configured by arranging the power transmission coils 400 to 405 shown in Figure 4(a) on top of the power transmission coils 406 to 411 shown in Figure 4(b).

[0033] FIG. 4(d) is a diagram for explaining the positional relationship between the power transmission coils. In FIG. 4(d), among the power transmission coil groups 210 shown in FIG. 4(c), the power transmission coils 400, 401, 410, and 411 are shown. The power transmission coil 400 and the power transmission coil 410 overlap when viewed from above. Power transmission coils having such a positional relationship are expressed as "overlapping". Similarly, the power transmission coil 401 and the power transmission coil 410 overlap. On the other hand, the power transmission coil 400 and the power transmission coil 411 do not overlap when viewed from above. Power transmission coils having such a positional relationship are expressed as "not overlapping". Also, the distance 412 is the distance between the tangent of the circumference of the power transmission coil 400 and the tangent of the circumference of the power transmission coil 411. Each tangent passes through the intersection of the straight line connecting the centers of the circles of the power transmission coil 400 and the power transmission coil 411 and the circumferences of the respective power transmission coils. That is, the distance 412 is the shortest distance between the power transmission coil 400 and the power transmission coil 411, indicating that the power transmission coil 400 and the power transmission coil 411 are separated by the distance 412. In the present embodiment, as the definition of the distance between the power transmission coils, it is assumed to be the distance between the positions on the power transmission coils when a plurality of power transmission coils are viewed from above, but the definition of the distance is not limited to this. For example, using the center of gravity of the power transmission coil or the like as a reference point, the distance between the reference points of the power transmission coils may be used as the distance between the power transmission coils. Also, although the distance 412 in FIG. 4(d) is the distance in the xy plane, the plurality of coils can be arranged at arbitrary positions in a three-dimensional space including the z-axis direction. Similarly in this case, the distance between the power transmission coils may be the shortest distance between the power transmission coils in the xyz space, or the distance between the reference points of the power transmission coils.

[0034] Also, although the power transmission coil has been described as a circular coil, the shape is not limited to this. The power transmission coil may be, for example, a coil having a rectangular shape of a quadrilateral.

[0035] FIG. 4(e) is a diagram for explaining the power transmission range of the first power transmission circuit 203 and the second power transmission circuit 205. The first power transmission circuit 203 in the present embodiment is assumed to be connectable to power transmission coils 400, 401, 402, 403, 405, 408, 409, 410, 411. Thereby, the first power transmission circuit 203 can perform power transmission to the power receiving device 101 placed in the region 413 indicated by the dotted line. Further, the second power transmission circuit 205 in the present embodiment is assumed to be connectable to power transmission coils 402, 403, 404, 405, 406, 407, 408, 409, 411. Thereby, the second power transmission circuit 205 can perform power transmission to the power receiving device 101 placed in the region 414 indicated by the dashed-dotted line.

[0036] The region 415 is a common region where the region 413 and the region 414 overlap. The region 415 is a power transmission range by the power transmission coils 402, 403, 405, 408, and these power transmission coils are connectable to both the first power transmission circuit 203 and the second power transmission circuit 205. That is, the power receiving device 101 placed in the region 415 is powered from either the first power transmission circuit 203 or the second power transmission circuit 205. In the following description, the region 415 is expressed as the shared region 415. Further, the region of the region 413 excluding the shared region 415 is expressed as the dedicated region 416 of the first power transmission circuit 203. The power receiving device 101 placed in the dedicated region 416 can be charged only from the first power transmission circuit 203. Further, the region of the region 414 excluding the shared region 415 is expressed as the dedicated region 417 of the second power transmission circuit 205. The power receiving device 101 placed in the region 417 can be charged only from the second power transmission circuit 205.

[0037] Next, the control flow between the power transmission device 100 and the power reception device 101 in this embodiment will be described. First, the control of wireless power transmission compliant with the WPC standard will be explained. FIG. 5 is a sequence diagram showing the control flow of a power transmission device and a power reception device compliant with the WPC standard v1.2.3. The sequence shown in FIG. 5 is not limited to the power transmission device 100 having a plurality of power transmission coils and a plurality of power transmission circuits as in this embodiment, but is control executed by a power transmission device having a configuration compliant with the WPC standard. In the following description, it will be described assuming that the power transmission device 100 performs power transmission to the power reception device 101 using an arbitrary power transmission coil 209. Note that, in the following, the case where the power transmission device and the power reception device comply with the WPC standard v1.2.3 will be described, but it is not limited thereto. That is, the power transmission device and the power reception device of the present disclosure may comply with a version of the WPC standard after v1.2.3 of the WPC standard, or may comply with a version before v1.2.3 of the WPC standard.

[0038] In the WPC standard, a plurality of phases are defined, including a Power Transfer phase in which power transmission for charging is executed and a phase before the power transmission for charging is performed. The phases before power transmission are (1) Selection phase, (2) Ping phase, (3) Identification&Configuration phase, (4) Negotiation phase, and (5) Calibration phase. Note that, in the following, the Identification and Configuration phase will be referred to as the I&C phase.

[0039] In the Selection phase, the power transmission device 100 transmits an Analog Ping (hereinafter referred to as A-Ping) (F500) to detect an object existing in the vicinity of the power transmission coil 209. The control method of A-Ping in this embodiment will be described later. A-Ping is pulsed power and is the power for detecting an object. Also, even if the power receiving device receives A-Ping, the power is so minute that the control unit 301 of the power receiving device 101 cannot be activated. The power transmission device 100 intermittently transmits A-Ping. Here, when an object is placed within the power transmission range of the power transmission device 100 and when no object is placed, a change occurs in the voltage and current applied to the power transmission coil 209. Therefore, the control unit 201 of the power transmission device 100 detects at least one of the voltage value and the current value of the power transmission coil 209 when transmitting A-Ping. When the detected voltage value is lower than a certain threshold value or the current value exceeds a certain threshold value, the control unit 201 determines that an object exists and transitions to the Ping phase.

[0040] In the Ping phase, when the power transmission device 100 detects that an object is placed by A-Ping, it measures the Q value (Quality Factor) of the power transmission coil 209 (F501). When the Q value measurement is completed, the power transmission device 100 starts the power transmission of Digital Ping (hereinafter referred to as D-Ping) (F502). D-Ping is the power for activating the control unit 301 of the power receiving device 101 and is greater than the power of A-Ping. Thereafter, after starting the power transmission of D-Ping (F502), the power transmission device 100 continues to transmit power equal to or greater than D-Ping until it receives an EPT (End Power Transfer) packet requesting power transmission stop from the power receiving device 101 (F522). When the control unit 301 of the power receiving device 101 is activated by receiving D-Ping, it transmits a Signal Strength packet, which is data storing the voltage value of the received D-Ping, to the power transmission device 100 (F503). By receiving the Signal Strength packet from the power receiving device 101 that has received D-Ping, the power transmission device 100 recognizes that the object detected in the Selection phase is a power receiving device. When the power transmission device 100 receives the Signal Strength packet, it transitions to the I&C phase.

[0041] In the I&C phase, the power receiving device 101 transmits data storing an ID including the version information of the WPC standard and device identification information to which the power receiving device 101 conforms (F504). Also, the power receiving device 101 transmits a Configuration packet including information indicating the maximum value of the power supplied by the power receiving unit 302 to the load (charging unit 306) to the power transmitting device 100 (F505). The power transmitting device 100 determines whether the power receiving device 101 corresponds to the version of the WPC standard to which it conforms by receiving the ID and the Configuration packet, and transmits an ACK. Specifically, when the power transmitting device 100 determines that the power receiving device 101 corresponds to an extended protocol after WPC standard v1.2 (including the processing in the Negotiation phase described later), it responds with an ACK (F506). When the power receiving device 101 receives the ACK, it transitions to the Negotiation phase for negotiating the power to be transmitted and received.

[0042] In the Negotiation phase, the power receiving device 101 transmits FOD Status data to the power transmitting device 100 (F507). In this embodiment, the FOD Status data is expressed as FOD(Q). The power transmitting device 100 performs foreign object detection based on the Q value stored in the received FOD(Q) and the Q value measured by Q value measurement, and transmits an ACK indicating that it is determined that there is a high possibility that there is no foreign object to the power receiving device (F508).

[0043] When the power receiving device receives the ACK, it transmits a General Request (Capability) packet, which is data for inquiring about the capabilities of the power transmitting device 100 and is one of the General Requests defined in the WPC standard (F535). Hereinafter, the General Request (Capability) packet is expressed as a GRQ(CAP) packet. When the power transmitting device 100 receives the GRQ(CAP) packet, it transmits a Capability packet (hereinafter referred to as CAP) storing the capability information to which it corresponds (F536).

[0044] The power receiving device 101 negotiates Guaranteed Power (hereinafter referred to as GP), which is the maximum value of the power value required for power reception. Specifically, Guaranteed Power represents the amount of power available for the power receiving device 101 agreed upon in the negotiation with the power transmission device 100. That is, GP is the maximum value of the power (the power consumed by the charging unit 306) that can be used to supply the load of the power receiving device 101. The negotiation is realized by transmitting a packet storing the value of Guaranteed Power requested by the power receiving device among the Specific Request packets defined in the WPC standard to the power transmission device 100 (F509). In this embodiment, this data is expressed as an SRQ(GP) packet.

[0045] The power transmission device 100 responds to the SRQ(GP) packet in consideration of its own power transmission capacity and the like. When the power transmission device 100 determines that Guaranteed Power can be accepted, it transmits an ACK indicating that the request has been accepted (F510). When the negotiation of a plurality of parameters including Guaranteed Power is completed, the power receiving device 101 transmits an SRQ(EN) requesting the end of the negotiation (End Negotiation) among the Specific Requests to the power transmission device (F511). The power transmission device 100 transmits an ACK to the SRQ(EN) packet (F512), ends the Negotiation, and transitions to the Calibration phase for creating a criterion for performing foreign object detection based on the power loss method. Note that foreign object detection is a process for determining whether an object different from the power receiving device (hereinafter referred to as a foreign object) exists or may exist within the power transmission range of the power transmission device 100.

[0046] In the calibration phase, without connecting the power receiving device 101 to the power receiving unit 302 and the load (battery 307), the power receiving device 101 notifies the power transmitting device 100 of the received power value R1 when the power receiving device 101 receives a D-Ping. At this time, the power receiving device 100 transmits a Received Power packet (mode1) (hereinafter referred to as PR1) storing the received power value R1 to the power transmitting device 100. When receiving the RP1, the power transmitting device 100 transmits an ACK to the power receiving device 101 (F514). At this time, the power transmitting device 100 measures its own transmitted power value T1 and calculates the difference Δ1 between T1 and R1, which is the power loss. After receiving the ACK, the power receiving device 101 transmits a Control Error packet (hereinafter expressed as CE), which requests the power transmitting device 100 to increase or decrease the received voltage, to the power transmitting device 100 with the power receiving unit 302 and the load connected. The CE stores a sign and a numerical value. If the sign of the numerical value stored in the CE is positive, it means requesting to increase the received voltage; if negative, it means requesting to decrease the received voltage; and if the numerical value is zero, it means requesting to maintain the received voltage. Here, the power receiving device transmits a CE(+) indicating an increase in the received voltage to the power transmitting device 100 (F515).

[0047] When receiving the CE(+), the power transmitting device 100 changes the set value of the power transmission circuit and increases the transmitted voltage (F516). When the received power increases in response to the CE(+), the power receiving device 100 supplies the received power to the charging unit 306, which is the load, and transmits an RP2 (Received Power packet (mode2) (hereinafter referred to as RP2)) to the power transmitting device 100 (F517). Here, the RP2 stores the received power value R2 in the state where the power receiving device 101 supplies the output of the power receiving unit 302 to the load (battery 307).

[0048] When the power transmission device 100 receives RP2, it transmits ACK to the power receiving device (F514). At this time, the power transmission device 100 measures its own power transmission value T2 and calculates the difference Δ2 between T2, which is the power loss, and R2. When the power receiving unit 302 is not connected to the load and the power consumption of the load is 0, the power loss Δ1, and when the power receiving unit 302 is connected to the load and the power consumption of the load is not 0, the power loss Δ2 are used as references to perform foreign object detection based on the power loss. Specifically, the power transmission device 100 can predict the power loss in the state without foreign objects at an arbitrary power reception value from Δ1 and Δ2, and perform foreign object detection based on the actually received power reception value and the power transmission value. When the power transmission device 100 transmits ACK to RP2, it transitions to the Power Transfer phase.

[0049] In the Power Transfer phase, the power transmission device 100 transmits power that the power receiving device can receive up to a maximum of 15 watts negotiated in the Negotiation phase. The power receiving device 101 periodically transmits RP0 (Received Power packet (mode0) (hereinafter referred to as RP0) storing CE and the current power reception value to the power transmission device 100 (F519, F520). When the power transmission device 100 receives RP0 from the power receiving device, it predicts the power loss at an arbitrary power reception from the above Δ1 and Δ2 and performs foreign object detection. If the power transmission device 100 determines, as a result of foreign object detection, that there is a high possibility that there is no foreign object, it transmits ACK to the power receiving device (F521). Here, if it is determined that there is a high possibility that there is a foreign object, the power transmission device 100 transmits NAK to the power receiving device.

[0050] When the charging of the battery 307 in the power receiving device 101 is completed, it transmits an EPT (End Power Transfer) packet requesting the power transmission device 100 to stop power transmission (F522). The above is the control flow of the power transmission device 100 and the power receiving device compliant with the WPC standard v1.2.3.

[0051] Next, an example of control when the power transmission device 100 having a plurality of power transmission coils 209 performs power transmission based on the WPC standard will be described with reference to FIG. 6. The first power transmission circuit 203 and the second power transmission circuit 205 included in the power transmission device 100 in the present embodiment can each perform the processing shown in FIG. 5. Although descriptions of some processing are omitted in FIG. 6 for simplicity of explanation, it is assumed that the same processing as that shown in FIG. 5 is actually executed.

[0052] First, the first power transmission circuit 203 and the second power transmission circuit 205 each intermittently transmit an A-Ping for detecting a power receiving device placed within the power transmission range of the power transmission device 100 using the power transmission coil 209 to which it is connected (F541). The control method of the A-Ping in the present embodiment will be described later. Here, when the first power receiving device 101a is placed near the power transmission coil 209 to which the first power transmission circuit 203 is connected, the first power receiving device 203 transmits a D-Ping to the first power receiving device 101a (F542, 543). Further, the first power transmission circuit 203 performs the above-described control communication, transitions to the Power Transfer phase, and performs power transmission for charging to the first power receiving device 101a (F544). At this time, it is assumed that the second power transmission circuit 205 continues to transmit the A-Ping (F545).

[0053] Then, when the second power receiving device 101b is placed near the power transmission coil 209 to which the second power transmission circuit 205 is connected, the second power receiving device 205 transmits a D-Ping to the second power receiving device 101b (546). Further, the second power transmission circuit 205 performs the above-described control communication, transitions to the Power Transfer phase, and performs power transmission for charging to the second power receiving device 101b (F547). By the processing described above, the power transmission device 100 can simultaneously charge a plurality of power receiving devices.

[0054] [Processing in the Power Transmission Device] Problems to be solved in this embodiment will be described. When the first power transmission circuit 203 and the second power transmission circuit 205 perform control communication and power transmission respectively, the power transmitted by the power transmission coil connected to one power transmission circuit may be superimposed on the power of the power transmission coil connected to the other power transmission circuit. This phenomenon is referred to as interference in this embodiment. Definitions of interference and non-interference will be described. The two power transmission coils are "non-interfering" as follows. That is, when the voltage, current amplitude fluctuation, or frequency fluctuation amount of the modulation signal transmitted and received by one of the two power transmission coils is not observed by the other power transmission coil, or when the observed level is below a predetermined value and does not affect the demodulation performance when the communication unit demodulates the other modulation signal. Also, the two power transmission coils are "interfering" as follows. That is, when the voltage, current amplitude fluctuation, or frequency fluctuation of the modulation signal transmitted and received by one of the two power transmission coils is observed by the other power transmission coil, or when the observed level is greater than a predetermined value and affects the demodulation performance when the communication unit demodulates the other modulation signal.

[0055] Further, the presence or absence of interference may be expressed based on the high-frequency voltage or high-frequency current applied to one of the two magnetically coupled (i.e., the coupling coefficient is not zero) power transmission coils. That is, when the fluctuation of the high-frequency voltage or high-frequency current applied to one power transmission coil is not induced in the other power transmission coil, or when the induced level is below a predetermined value, it may be regarded as "non-interfering", and otherwise as "interfering".

[0056] The above-described interference may occur, for example, when the first power transmission circuit 203 and the second power transmission circuit 205 perform control communication or power transmission simultaneously. To prevent interference, for example, a method of shifting the timing at which the first power transmission circuit 203 and the second power transmission circuit 205 perform control communication or power transmission may be used. Hereinafter, a method of outputting A-Ping using a plurality of power transmission coils to perform object detection without causing interference will be described. According to this method, since A-Ping is output simultaneously from power transmission coils at different positions, an object can be efficiently detected in a short time.

[0057] The degree of interference varies depending on the positional relationship between the two power transmission coils. In the present embodiment, it is assumed that the two power transmission coils do not interfere with each other if they are separated by a predetermined distance D or more. Now, it is assumed that the distance 412 between the power transmission coil 400 and the power transmission coil 411 shown in FIG. 4(d) is D. In this case, it can be said that the power transmission coil 400 and the power transmission coil 411 are non-interfering power transmission coils. Also, the power transmission coil 400 and the power transmission coil 410, and the power transmission coil 401 and the power transmission coil 410 overlap each other and are not separated by a distance D or more, so it can be said that they are power transmission coils that interfere with each other.

[0058] Note that the predetermined distance D is set in advance, for example, by measuring the distance between non-interfering power transmission coils. For example, a voltage or current is applied to a predetermined power transmission coil among a plurality of power transmission coils, and the voltage or current fluctuations in other power transmission coils at this time are measured. By this measurement, power transmission coils in which no fluctuation occurs or the fluctuation is below a predetermined amount are identified, and if the distance from the predetermined power transmission coil is measured, the non-interfering distance D can be obtained. Also, for example, the amplitude or frequency of the voltage or current applied to a predetermined power transmission coil among a plurality of power transmission coils is varied, and the amplitude or frequency fluctuations of the voltage or current in other power transmission coils at this time are measured. By this measurement, power transmission coils in which no fluctuation occurs or the fluctuation is below a predetermined amount are identified, and if the distance from the predetermined power transmission coil is measured, the non-interfering distance D can be obtained. The predetermined value used for determining the presence or absence of interference and the predetermined distance D may be defined in the WPC standard.

[0059] Note that the predetermined distance D at which no interference occurs can be a different value depending on the definition of the distance between the power transmission coils. For example, the distance between the power transmission coils can be different when it is the distance between the reference points (e.g., the center of gravity, etc.) of the power transmission coils and when it is the shortest distance between the power transmission coils. Also, not only can they be arranged on a two-dimensional plane as shown in FIG. 4, but they can also be arranged in a three-dimensional space (e.g., in the height direction). In this embodiment, under any conditions, a predetermined distance D at which no interference occurs can be obtained by the same method, and the control described later can be implemented.

[0060] As described above, when power is simultaneously transmitted from power transmission coils in a predetermined positional relationship, the power transmission coils may interfere with each other, affecting the power transmission and control communication of each power transmission coil. Therefore, when selecting the power transmission coils connected to the first power transmission circuit 203 and the second power transmission circuit 205, the power transmission device 100 in this embodiment operates to select power transmission coils that are at a predetermined distance D or more apart so as not to interfere with each other. Thereby, appropriate power transmission can be performed even in power transmission using a plurality of power transmission coils.

[0061] Note that in the present disclosure, it is also possible to use a method of not determining a specific predetermined distance D. Specifically, it is only necessary to identify other power transmission coils that are interfered with by the power transmission to a certain power transmission coil. That is, when power is transmitted to a certain power transmission coil, other power transmission coils that interfere or do not interfere may be identified in advance, and the identified results may be retained. Based on this specific result, when selecting a certain power transmission coil, select the power transmission coil that is identified as not interfering. Then, it can be operated using the selected power transmission coils.

[0062] FIG. 7 is a flowchart for explaining the processing executed by the power transmission device 100 in the present embodiment. FIG. 8 is a sequence diagram showing the processing executed by the power transmission device 100 in the present embodiment. The flowchart shown in FIG. 7 and the sequence diagram shown in FIG. 8 can be realized by the control unit 201 of the power transmission device 100 executing a control program stored in the memory 207 and performing calculation and processing of information and control of each hardware.

[0063] When the power of the power transmission device 100 is turned on (S601), the control unit 201 performs a process of selecting a power transmission coil to be connected to the first power transmission circuit 203 and the second power transmission circuit 205 from among the power transmission coil groups 210. At this time, the process changes depending on whether the power transmission device 100 is already performing power transmission processing for charging (S602). Here, since the power transmission device 100 is immediately after being powered on, it is assumed that the power transmission process has not been performed, and the process proceeds to S603. The control unit 201 selects a coil that does not cause interference even when the first power transmission circuit 203 and the second power transmission circuit 205 are used simultaneously.

[0064] Here, a method for selecting a coil that does not cause interference will be described. As described with reference to FIG. 4(d), if two power transmission coils are separated by a distance D or more, interference between the coils does not occur. The control unit 201 determines a combination of power transmission coils that are separated from each other by a distance D or more, such as the power transmission coil 400 and the power transmission coil 411 shown in FIG. 4(d). As an example, the control unit 201 sets the combinations of power transmission coils that do not cause interference in the power transmission coil group 210 shown in FIG. 4(c) to (400, 411), (401, 409), (402, 404), (403, 407), (405, 406), (408, 410). Note that this combination example is only an example, and other combinations may be determined. The selection unit 208 connects two power transmission coils in a non-interfering positional relationship to the first power transmission circuit 203 and the second power transmission circuit 205, respectively, according to the combination determined by the control unit 201 (S603).

[0065] The power transmission device 100 waits for the power receiving device to be placed on the power transmission device 100 (S605). With reference to FIG. 8, the control of A-Ping will be described in detail. The selection unit 208 first connects the first power transmission circuit 203 and the coil 400, and the second power transmission circuit 205 and the coil 411 based on the determined combination of power transmission coils. Further, the control unit 201 performs object detection processing (F701) by simultaneously outputting A-Ping from the coil 400 and the coil 411. Since the power transmission coil 400 and the power transmission coil 411 are in a positional relationship where they do not interfere with each other, even if the first power transmission circuit 203 and the second power transmission circuit 205 are controlled to transmit A-Ping simultaneously, interference between the power transmission coils does not occur. Note that the timings and periods at which A-Ping is output from each of the two power transmission coils may or may not match. It is sufficient that the periods during which A-Ping is output from each of the two power transmission coils overlap at least partially. Note that, in order not to cause interference, a method may be used in which the periods during which A-Ping is output from each of the plurality of power transmission coils do not overlap.

[0066] If the power receiving device is not detected here, the selection unit 208 then connects the first power transmission circuit 203 and the coil 401, and the second power transmission circuit 205 and the coil 409 to perform detection processing of the power receiving device. In this way, until the power receiving device is detected, the power transmission device 100 connects the first power transmission circuit 203 and the second power transmission circuit 205 respectively to the power transmission coils based on the determined coil combination, and performs object detection processing.

[0067] In F702, when the power receiving device is placed on the power transmission device 100, a change in voltage or current in the coil 400 of the power transmission device 100 that is transmitting A-Ping at that time is detected. Then, the power transmission device 100 transmits D-Ping in the Ping phase described above. And through communication in the Ping phase, the power transmission device 100 identifies that the object is the power receiving device 101. In this way, the power receiving device 101 is detected (F703).

[0068] Returning to FIG. 7, when the control unit 201 of the power transmission device 100 detects that the power receiving device has been placed (Yes in S506), the first power transmission circuit 203 performs a power transmission process through a plurality of phases defined by the WPC standard (S606). Here, it is assumed that the power transmission device 100 detects the placement of the power receiving device 101 via the power transmission coil 400 connected to the first power transmission circuit 203. The power transmission device 100 performs power transmission for charging using the power transmission coil 400 that detected the power receiving device. The control unit 201 prohibits the use of coils that interfere with the power transmission coil (here, the power transmission coil 400) used for the power transmission process in the power transmission coil group 210. Specifically, in FIG. 4(c), the power transmission coils that are not more than a distance D away from the power transmission coil 400 are (401, 402, 409, 410). Therefore, these coils are prohibited from being used while the power transmission coil 400 is in use (S607).

[0069] On the other hand, since the second power transmission circuit 205 has not detected the placement of the power receiving device (No in S608), by performing the processes after S602 again, a power transmission coil is selected from the coil group 210 to detect the placement of the power receiving device. Since the first power transmission circuit 203 is already performing a power transmission process (Yes in S602), the second power transmission circuit 205 selects a power transmission coil other than the power transmission coils prohibited from being used from the coil group 210 and performs a detection process until the placement of the power receiving device is detected (S610). That is, the second power transmission circuit 205 uses a power transmission coil having a positional relationship that does not interfere with the power transmission coil 400 used by the first power transmission circuit 203 for power transmission for charging to detect a newly placed power receiving device.

[0070] This will be described in detail with reference to FIG. 8. When the power transmission device 100 detects that the power receiving device has been placed on the power transmission coil 400, (F703), it starts power transmission for charging using the power transmission coil 400 (F704). Also, the power transmission device 100 prohibits the use of power transmission coils that interfere with the power transmission coil 400 (F705). The power transmission device 100 sequentially connects a power transmission coil other than the power transmission coils prohibited from being used and the second power transmission circuit 205, and executes A-Ping power transmission for detecting the power receiving device (F706).

[0071] Returning to FIG. 7, when the second power transmission circuit 205 detects a power receiving device, power transmission processing is performed through a plurality of phases defined by the above-described WPC standard (S606). When all the power transmission circuits of the power transmission device 100 are performing power transmission for charging (Yes in S608), the control processing for power transmission ends. Note that a power transmission circuit that has ended power transmission processing by receiving an EPT packet from a power receiving device or the like executes the processing from S602 and subsequent steps again to detect a new power receiving device and perform power transmission. The processing shown in FIG. 7 is assumed to be repeatedly performed until the power of the power transmission device 100 is turned off.

[0072] As described above, the power transmission device 100 in the present embodiment controls so that A-Ping is not simultaneously output from two power transmission coils arranged closer to each other than a predetermined distance among the plurality of power transmission coils. According to the present embodiment, even in a configuration where a plurality of power transmission coils are laid out without gaps, it is possible to efficiently control power transmission while preventing interference between the power transmission coils. Thereby, the power transmission device 100 can appropriately detect and perform power transmission even when a plurality of power receiving devices are placed at arbitrary locations on the power transmission device 100.

[0073] Note that, although an example in which power transmission for charging is performed using the power transmission coil that has detected an object (power receiving device) has been described, the present disclosure is not limited to this. In order to perform efficient power transmission, power transmission for charging may be performed using a coil different from the power transmission coil that has detected an object (power receiving device). In that case, a power transmission circuit different from the power transmission circuit used for charging performs A-Ping transmission using a power transmission coil that does not interfere with the power transmission coil used for charging. That is, a power transmission coil that does not interfere with the power transmission coil used for charging may be specified, and A-Ping may be transmitted using that power transmission coil.

[0074] Also, in this embodiment, an example in which there are two power transmission circuits has been described. However, the method described in this embodiment is applicable even when there are three or more power transmission circuits. For example, when the power transmission device 100 has three power transmission circuits including a first power transmission circuit 203 and a second power transmission circuit 205 and a third power transmission circuit (not shown), the power transmission device 100 performs the following processing. That is, when the control unit 201 of the power transmission device 100 outputs a signal for object detection using each power transmission circuit, the three power transmission coils 209 connected to each power transmission circuit are arranged at positions separated from each other by a predetermined distance D or more. In the example of the power transmission coil group 210 shown in FIG. 4(c), for example, the power transmission coils 400, 403, and 411 are selected as the three power transmission coils. Since these three power transmission coils are separated from each other by a distance D or more, no interference occurs even when A-Ping is transmitted simultaneously. By selecting the power transmission coils 209 connected to each power transmission circuit in this way, the power transmission device 100 can prevent interference from occurring between the three power transmission coils 209 even when A-Ping is output from them. The same applies when there are four or more power transmission circuits.

[0075] (Embodiment 2) In the above-described Embodiment 1, the power transmission capabilities of the first power transmission circuit 203 and the second power transmission circuit 205 may be the same or different. In this embodiment, control in the case where the power transmission capabilities of a plurality of power transmission circuits included in the power transmission device are different will be described. When power transmission is performed on the power reception device using a power transmission device having a plurality of power transmission circuits with different power transmission capabilities, the following problems may occur. For example, when the power reception device is placed on the power transmission device, power transmission processing may be performed by a power transmission circuit that cannot sufficiently transmit the power that the power reception device can receive (low power transmission capability). As a result, there is a problem that the charging of the power reception device is not performed efficiently. Thus, when power transmission is performed on the power reception device using a power transmission device having power transmission circuits with different power transmission capabilities, appropriate power transmission may not be performed.

[0076] In this embodiment, a method for supplying sufficient power to a power receiving device by determining which power transmission circuit to use for power transmission based on the power transmission capacity of the power transmission circuit and the power reception capacity of the power receiving device will be described. In this embodiment, the same components as those in Embodiment 1 are denoted by the same names and reference numerals.

[0077] [Processing in the Power Transmission Device] Hereinafter, the processing executed by the power transmission device 100 will be described with reference to FIGS. 9 and 10. The processing in FIG. 9(a) is obtained by adding the power transmission circuit switching processing described in this embodiment to the processing shown in FIG. 5. In F505, when the power transmission device 100 acquires a Configuration packet from the power receiving device 101, it acquires the power reception capacity of the power receiving device 101 from the acquired packet. The power reception capacity referred to here is the power that the power receiving device 101 can receive, based on the maximum value of the power supplied by the power reception unit 302 of the power receiving device 101 to the load (charging unit 306), and specifically corresponds to the power corresponding to the Maximum Power in the WPC standard. The power transmission device 100 executes a switching process (F826) based on the maximum power (power transmission capacity) that it can transmit itself to charge the power receiving device and the power reception capacity of the acquired power receiving device 101. This switching process may be executed before transitioning to the Power Transfer phase.

[0078] Figure 10 shows the processing flow of the power transmission circuit switching process according to the present embodiment. The process shown in Figure 10 is performed at F826 in Figure 9. Now, assume that the power transmission device 100 has detected the power receiving device 101 by the first power transmission circuit 203 and acquired the Configuration packet from the power receiving device 101. First, the power transmission device 100 determines whether another power transmission circuit with a higher power transmission capacity than the first power transmission circuit 203 that is performing control communication with the power receiving device can be used for power transmission (S901). That is, the power transmission device 100 determines whether there is a power transmission circuit that has a higher power transmission capacity than the first power transmission circuit 203 and has not yet performed power transmission to other power receiving devices. Here, assume that the second power transmission circuit 205 has a higher power transmission capacity than the first power transmission circuit 203 and has not performed power transmission. Note that if the power transmission circuit performing control communication with the power receiving device is the second power transmission circuit, there is no power transmission circuit with a higher power transmission capacity than the second power transmission circuit in the first place, so the determination in S901 is No.

[0079] If the corresponding power transmission circuit can be used for power transmission (Yes in S901), the power transmission device 100 determines whether the power transmission capacity of the power transmission circuit currently performing control communication with the power receiving device is lower than the power receiving capacity of the power receiving device (S902). Here, if the power transmission device 100 cannot perform power transmission that satisfies the Maximus Power included in the Configuration packet, it is considered that the power transmission capacity is lower than the power receiving capacity. If the power transmission capacity is lower than the power receiving capacity (Yes in S902), the power transmission device 100 switches the first power transmission circuit 203 that is performing control communication with the power receiving device 101 to another power transmission circuit with a higher power transmission capacity (S903). Here, the power transmission device 100 uses the selection unit 208 to switch the connection of the power transmission coil performing control communication with the power receiving device 101 from the first power transmission circuit 203 to the second power transmission circuit 205. On the other hand, if the power transmission capacity is higher than the power receiving capacity (No in S902), the process ends.

[0080] Also, the case where there is no other power transmission circuit corresponding in S901 (No in S901) will be described. In the case of No in S901, the power transmission device 100 has another power transmission circuit with a lower power transmission capacity, and determines whether or not the other power transmission circuit is available (S906). If the other power transmission circuit with a lower power transmission capacity is available (Yes in S906), the process proceeds to S904. On the other hand, if the other power transmission circuit with a lower power transmission capacity is not available, the process ends without switching the power transmission circuit. The power transmission device 100 determines whether or not the power transmission capacity of the other power transmission circuit with a lower power transmission capacity is equal to or greater than the power reception capacity of the power reception device (S904). That is, the power transmission device 100 determines whether or not the maximum power that can be transmitted by the other power transmission circuit is equal to or greater than the power that can be received by the power reception device. If the power transmission capacity of the other power transmission circuit is equal to or greater than the power reception capacity, the first power transmission device 100 switches the connection of the power transmission coil that is performing control communication with the power reception device to the other power transmission circuit with a lower power transmission capacity (S905). If it is lower than the power reception capacity, the process ends. By performing the process described here, when a second power reception device as described later is placed, sufficient power can be transmitted to the second power reception device, and there is an effect that the power transmission capacity of the power transmission device 100 can be effectively utilized.

[0081] Here, the processing of the power transmission device according to this embodiment will be described using a specific example. Now, when a first power receiving device 101a with a power receiving capacity of 60 W is placed on a power transmission device 100 where the power transmission capacity of the first power transmission circuit is 15 W and the power transmission capacity of the second power transmission circuit is 60 W, a method for supplying sufficient power to the power receiving device will be described. The power transmission device 100 sends A-Ping via the first power transmission circuit 203 at F500 in FIG. 9(a). When the first power receiving device 101a is placed, the first power transmission device 100 and the first power receiving device 101a execute the sequence from F509 to F506. Here, at F505, the power transmission device 100 can know that the power receiving capacity of the first power receiving device 101a is 60 W based on the value of the maximum power receiving capacity included in the Configuration packet. Since the power transmission device 100 is performing power transmission via the first power transmission circuit 203, it cannot supply sufficient power to the first power receiving device 101a. Therefore, the first power transmission device 100 performs power transmission circuit switching processing F826. At S901 in FIG. 10, since there is a second power transmission circuit 205 with a power transmission capacity of 60 W, the power transmission device 100 proceeds to S902. Subsequently, at S902, since the power transmission capacity of the first power transmission circuit 203 currently performing power transmission is 60 W or less, which is the power receiving capacity of the power receiving device, the power transmission device 100 proceeds to S903. At S903, the power transmission device 100 stops power transmission and switches the power transmission circuit that performs power transmission to the first power receiving device 101a to the second power transmission circuit 205. The power transmission device 100 performs the processing after F507 using the second power transmission circuit 205. Also, since the first power transmission circuit 203 is not communicating with the power receiving device, it sends A-Ping for detecting a new power receiving device. In this way, in a power transmission device having a plurality of power transmission circuits with different capabilities, by switching the power transmission circuit that performs power transmission to the power receiving device based on the power receiving capacity of the power receiving device and the power transmission capacity of the power transmission circuit, it becomes possible to supply sufficient power to the power receiving device.

[0082] FIG. 9(b) is a sequence diagram for explaining the operation of each power transmission circuit and the processing when the second power receiving device is placed. In the processing shown in FIG. 9, the same processes as those shown in FIGS. 5 and 9(a) are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 9(b), when the first power transmission circuit 203 detects the placement of the power receiving device 101a (F542), the first power transmission circuit 203 transmits D-Ping to the power receiving device 101a and performs control communication (F543). When the first power transmission circuit 203 acquires a Configuration packet from the first power receiving device 101a (F505), the first power transmission circuit 203 transmits an ACK to the first power receiving device 101a (F506) and performs the power transmission circuit switching process shown in FIG. 10 (F826). Thereby, the subsequent processing is performed by the second power transmission circuit 205.

[0083] The second power transmission circuit 205 performs the processing after F507 in FIG. 9(a) and performs power transmission for charging to the first power receiving device 101a (F827). Since the power transmission device 100 has already acquired information regarding the first power receiving device 101a via the first power transmission circuit 203, the second power transmission circuit 205 can perform the power transmission process without acquiring information such as a Configuration packet again. On the other hand, the first power transmission circuit 203 performs A-Ping transmission in order to detect the placement of a new power receiving device (F828). Here, when the first power transmission circuit 203 detects that the second power receiving device 101b is newly placed, the first power transmission circuit 203 transmits D-Ping to the second power receiving device 101b to perform control communication (F829) and starts power transmission for charging (F830).

[0084] Here, a specific example of the process in Fig. 9(b) will be described. Now, assume that in a power transmission device 100 with a power transmission capacity of 15w for the first power transmission circuit and 5w for the second power transmission circuit, a first power receiving device 101a with a power receiving capacity of 5w is placed, and then a power receiving device with a power receiving capacity of 15w is placed. The first power transmission device 100 sends A-Ping via the first power transmission circuit 203 at F541. When the first power receiving device 101a is placed, the first power transmission device 100 acquires a Configuration packet from the first power receiving device 101a at F506 and can know that the power receiving capacity of the first power receiving device 101a is 5w. The first power transmission device 100 performs the power transmission circuit switching process shown in Fig. 10 (F826). At S901, since there is no other power transmission circuit with a higher power transmission capacity for the power transmission circuit performing control communication, the power transmission device proceeds to S906. At S906, since another power transmission circuit (the second power transmission circuit 205) with a lower power transmission capacity than the power transmission circuit performing control communication is available, the process proceeds to S904. Subsequently, at S904, since the power transmission capacity of the other power transmission circuit is equal to or greater than the power receiving capacity of the power receiving device, the power transmission device proceeds to S905. At S905, the power transmission device switches the power transmission circuit for transmitting power to the first power receiving device 101a to the second power transmission circuit 205.

[0085] The first power transmission device 100 sends A-Ping via the first power transmission circuit 203 at F828. After that, when a second power receiving device 101b with a power receiving capacity of 15w is placed, D-Ping is transmitted to the second power receiving device 101b (F829), and power transmission for charging is started (F830). Here, although the second power transmission circuit 205 is not shown in Fig. 9(b), it is assumed that after F828, it acquires a Configuration packet from the second power receiving device 101b and performs the switching process in the same way. However, since the power transmission device 100 already knows that power transmission by the first power transmission circuit 203 is being performed and there is no other available power transmission circuit other than the second power transmission circuit 205, the switching process may be omitted.

[0086] Through the above-described processing, the power transmission device 100 can supply sufficient power to the newly placed second power receiving device 101b. Thus, in a power transmission device having a plurality of power transmission circuits with different capabilities, it becomes possible to supply sufficient power by switching the power transmission circuit that performs power transmission to the power receiving device based on the power receiving capability of the power receiving device and the power transmission capability of the power transmission circuit. In the present embodiment, the power transmission circuit is switched using the selection unit 208 so that power transmission does not stop, but other methods may also be used. For example, the power transmission device 100 transmits an EPT to the first power receiving device 101a, stops power transmission, then switches the power transmission circuit using the selection unit 208, and resumes processing from A-Ping. As a result, even in a power transmission device that cannot instantaneously switch the power transmission circuit, it becomes possible to supply sufficient power to the power receiving device. Further, the power transmission device 100 may perform a switching process before responding with an ACK when receiving a Configuration packet from the power receiving device.

[0087] Note that in the present embodiment, it is assumed that the determination of switching the power transmission circuit is made based on the information included in the Configuration packet acquired by the power transmission device 100 in the I&C phase, but it is not limited to this. The power transmission device 100 may be configured to determine the switching of the power transmission circuit based on, for example, the information of the GP acquired from the power receiving device 101 in the Negotiation phase. The power transmission device 100 compares the power that the power transmission circuit can transmit with the power represented by the GP included in the SRQ(GP) packet acquired from the power receiving device 101, and determines the switching of the power transmission circuit. When the power transmission device 100 cannot transmit the power corresponding to the GP, it switches to a power transmission circuit with a higher power transmission capability (Yes in S902 and S903 in FIG. 10). Also, when the power that another power transmission circuit with a lower power transmission capability can transmit is greater than the GP, the power transmission circuit 100 switches to another power transmission circuit with a lower power transmission capability (Yes in S904 and S905 in FIG. 10). In this case, in the sequence of FIG. 9(a), the power transmission device 100 performs a switching process after acquiring the SRQ(GP) packet at F511 or after transmitting an ACK as a response to the SRQ(GP) packet at F512.

[0088] Further, when the GP is changed during power transmission, the power transmission device 100 may perform power transmission circuit switching processing based on the changed GP. The power transmission device 100 and the power reception device 101 can be configured to be able to change the GP by performing renegotiation. In this case, when the power corresponding to the GP determined by renegotiation cannot be transmitted by the power transmission device 100, it switches to a power transmission circuit having a higher power transmission capacity. Thereby, when sufficient power cannot be supplied by the power transmission circuit during power transmission, sufficient power can be supplied by switching the power transmission circuit. Further, when the power that can be transmitted by another power transmission circuit with a low power transmission capacity is greater than the power corresponding to the GP determined by renegotiation, the power transmission device 100 switches to another power transmission circuit with a lower power transmission capacity. Thereby, when a new power reception device is placed, power transmission using a power transmission circuit with a high power transmission capacity can be performed for the new power reception device. As a result, the power transmission device 100 can effectively utilize the power transmission capacity of the power transmission circuit.

[0089] Further, after determining the power transmission circuit to be used for power transmission in the I&C phase, the power transmission device 100 may further switch the power transmission circuit based on the information included in the SRQ packet obtained in the Negotiation phase. Further, the power transmission device 100 may further switch the power transmission circuit based on the information obtained in the renegotiation.

[0090] Also, the power reception capacity of the power reception device is not limited to the maximum power reception value or GP. For example, based on the identification number of the power reception device, information capable of specifying the type of the power reception device, information on the version of WPC, etc., the power reception capacity of the power reception device may be obtained and power transmission circuit switching processing may be performed. For example, the power transmission device can specify that the power reception device is one that has been powered transmitted in the past based on the identification number of the power reception device, and determine the power transmission circuit to be used according to the past power transmission record. Also, for example, the power transmission device can specify the type of the power reception device and switch the power transmission device depending on whether the power reception device is a smartphone or a PC. Note that the type of the power reception device described here is just an example, and the power reception device may be of a type other than the above. Also, the switching process may be performed based on any number of the above-described information obtained from the power reception device.

[0091] Also, the method described in this embodiment is applicable even to a power transmission device having a plurality of power transmission coils as shown in FIGS. 2 and 4. That is, this embodiment is applicable to a power transmission device having a plurality of power transmission circuits with different power transmission capabilities. For example, it may be a power transmission device capable of connecting a plurality of power transmission circuits with different power transmission capabilities to one power transmission coil. Also, the method of this embodiment is applicable to a power transmission device having a plurality of power transmission circuits including at least two power transmission circuits with different power transmission capabilities. For example, even in a power transmission device having two or more power transmission circuits, by applying the processing shown in FIG. 10, power transmission using an appropriate power transmission circuit can be performed.

[0092] (Embodiment 3) In this embodiment, consider a case where a power transmission device having a plurality of power transmission circuits detects another power receiving device while transmitting power to one or more power receiving devices. At this time, if an A-Ping is constantly transmitted from each power transmission coil to detect another power receiving device while transmitting power to the power receiving device, there is a problem that the radiated noise increases and adversely affects peripheral devices (existing power transmission). In addition, since the A-Ping is continuously transmitted from a plurality of power transmission coils, there is a problem that the power transmission device consumes unnecessary power while another power receiving device is not placed. Thus, when a power transmission device having a plurality of power transmission coils detects a power receiving device, there is a risk of adverse effects between the power transmission coils.

[0093] To solve this problem, the power transmission device in this embodiment determines whether power is being transmitted to the power receiving device. If power is being transmitted, the transmission of the A-Ping in the power transmission coil is stopped, and an object is detected based on a change in a physical quantity (physical parameter) in the object detection coil. Then, the A-Ping is transmitted from each power transmission coil only when an object is detected by the object detection coil. Thereby, by suppressing the transmission of unnecessary A-Pings, it is possible to detect the placement of a new power receiving device while reducing the adverse effect on the existing power transmission due to the generation of radiated noise. In addition, unnecessary power consumption can be suppressed.

[0094] Hereinafter, the embodiment will be described in detail with reference to the accompanying drawings. Note that the same names and reference numerals are used for configurations similar to those in the above-described embodiment.

[0095] [Configuration of the device] FIG. 11 is a diagram for explaining the configuration of the power transmission device 200 in the present embodiment. As shown in FIG. 11(a), the power transmission device 200 is further assumed to have an object detection coil 211 configured to encompass the entire power transmission range of the power transmission coil group 210. A configuration example of the object detection coil is shown in FIG. 11(b). The object detection coil 211 is, for example, a coil configured to surround the transmission coil group 210 shown in FIG. 4(c). That is, the area where the object exposure coil 211 can transmit power encompasses the area where the power transmission coil group 210 can transmit power. Note that the shape of the object detection coil 211 is not limited to that shown in FIG. 11(b).

[0096] [Processing in the Power Transmission Device] Subsequently, the flow of the process executed by the power transmission device 200 will be described. FIG. 12 shows a flowchart of the process executed by the power transmission device 200. This process can be realized, for example, by the control unit 201 of the power transmission device executing a program read from the memory 207. Note that at least a part of the following steps 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. Also, this process can be executed in response to the power of the power transmission device 200 being turned on, in response to the user of the power transmission device 200 inputting an instruction to start the non-contact charging application, or in response to the power transmission device 200 being connected to a commercial power supply and receiving power supply. Also, this process may be started by other triggers. Note that the power transmission device 200 executes this process using a plurality of power transmission coils 209, and one of them may be sequentially selected and used for execution, or it may be executed in parallel in a plurality or all of the power transmission coils.

[0097] In the following description, it is assumed that one or more power receiving devices are placed on the power transmission device 200 (for example, on a charging stand (mounting surface) configured to be close to a plurality of power transmission coils in the power transmission device 200), but it is not limited thereto. It may be assumed that one or more power receiving devices are present, for example, within the power transmission range of the power transmission device 200.

[0098] First, the power transmission device 200 determines whether it is currently transmitting power to a power receiving device (S1001). If it is transmitting power to the power receiving device (Yes in S1001), the process proceeds to S1002. If it is not transmitting power to the power receiving device (No in S1001), the process proceeds to S1005. Next, in S1002, the power transmission device 200 transmits an object detection signal from the object detection coil 211, and the process proceeds to S1003. At this time, in order to detect an object within a predetermined time length, such as one second, the power transmission device 200 transmits A-Ping as an object detection signal once per second from the object detection coil 211.

[0099] Here, the object detection signal may be A-Ping of the WPC standard, or it may be another signal. In S1003, the power transmission device 200 calculates the change amount of the physical quantity in the object detection coil 211, and the process proceeds to S1004. Here, the change amount of the physical quantity can be calculated by measuring the current value of the object detection coil 211 generated by the change in the state of the object detection coil 211 and obtaining the difference from the previously measured value, but it is not limited thereto. For example, it may be the difference in the voltage value applied to the object detection coil 211, the shift amount of the resonance frequency of the object detection coil 211, or the difference in the characteristic impedance of the object detection coil 211. In this way, when there is a change in the state within the object detection coil 211 due to the transmission of the object detection signal, at least one of the current, voltage, resonance frequency, etc. generated in the coil changes. The control unit 201 of the power transmission device 200 can detect that there is a possibility that a new power receiving device has been placed based on this change. The reason why the current, voltage, resonance frequency, etc. in the coil change is that the magnetic flux in the coil changes or the characteristic impedance changes due to the change in the state within the object detection coil 211.

[0100] In S1004, the power transmission device 200 determines whether the change amount of the physical quantity calculated by the object detection coil 211 is equal to or greater than a threshold value, that is, whether there is a possibility that a new power reception device has been placed. When the change amount of the physical quantity is equal to or greater than the threshold value (Yes in S1004), the process proceeds to S1005. When the change amount of the physical quantity is less than the threshold value (No in S1004), the process returns to S1001. The case where the change amount of the physical quantity is equal to or greater than the threshold value means that a new object has been placed on the power transmission device 200.

[0101] Next, in S1005, the power transmission device 200 starts the process defined as the Selection phase of the above-mentioned WPC standard. The power transmission device 200 sequentially transmits A-Pings from the power transmission coil 209 to detect the position of an object existing within the power transmission range. At this time, in order for the power transmission device 200 to detect the position of the object during a predetermined time length such as 1 second, it is necessary to transmit A-Pings from each of the plurality of power transmission coils 209 within 1 second. Therefore, in this case, the power transmission device 200 sequentially transmits A-Pings from the plurality of power transmission coils 209, for example, every (1 / N) seconds (N is the number of power transmission coils 209).

[0102] When the power transmission device 200 detects an object within the power transmission range, it shifts to the Ping phase of the WPC standard and transmits D-Ping using the power transmission coil 209 that detected the object. When there is a predetermined response to the D-Ping, the power transmission device 200 determines and stores that the detected object is a power receiving device and the power receiving device is placed on the target power transmission coil (S1006). When the power transmission device 200 detects that the power receiving device is placed, it shifts to the I&C phase of the above-described WPC standard and acquires the identifier information and capability information of the power receiving device (S1007). Subsequently, the power transmission device 200 shifts to the Negotiation phase of the above-described WPC standard and determines the value of GP with the power receiving device (S1008). After determining the GP, the power transmission device 200 shifts to the Calibration phase of the above-described WPC standard. Here, the power receiving device notifies the power transmission device 200 of a predetermined power reception value (received power value in the light load state / received power value in the maximum load state), and the power transmission device 200 performs adjustments for efficient power transmission.

[0103] Next, the power transmission device 200 shifts to the Power Transfer phase of the above-described WPC standard, controls for continuing power transmission and stopping power transmission due to errors or full charge, etc. (S1010), and the process returns to S1001. If the power supply to the power transmission device 200 is stopped, the power transmission device 100 ends the process.

[0104] As described above, when the power transmission device of the present embodiment is transmitting power to the power receiving device and has not detected the placement of an object, it does not start the process for detecting an object in the power transmission coil, that is, the process defined as the Selection phase of the above-described WPC standard. Thereby, the adverse effect on the existing power transmission due to the generation of radiated noise can be reduced. Also, unnecessary power consumption can be suppressed.

[0105] [Processing of the entire system] Next, the operation sequence of the power transmission device 200 will be described with reference to FIGS. 13 and 14. Here, for simplicity of explanation, it is assumed that the power transmission device 200 has three power transmission coils 209a to 209c and an object detection coil 211 as shown in FIG. 14(a). As an initial state, it is assumed that the power reception device is not placed on the power transmission device 200, and the power transmission device 200 has sufficient power transmission capacity to execute power transmission at the GP required by the power reception device. Also, it is assumed that the threshold value for the change amount of the physical quantity calculated by the object detection coil is set in advance in the power transmission device 200 as a predetermined value. Note that the threshold value may be set by an input operation by the user or the like. Also, the expression that the power reception device is placed on the power transmission coil 209 of the power transmission device 200 in the following description includes the following cases. That is, the power reception device is placed means that the power reception device is placed on a charging stand (placement surface) configured close to the power transmission coil 209, or is synonymous with the power reception device being arranged in the vicinity (power transmission possible range) of the power transmission coil 209.

[0106] In this embodiment, the power transmission device 200 detects the placement of the first power reception device 101a and starts power transmission. At this time, when the power transmission device 200 starts power transmission to the first power reception device 101a, it stops transmitting A-Ping in the power transmission coil 209 and starts object detection by transmitting an object detection signal in the object detection coil 211. Then, when the second power reception device 101b is placed, the state of the object detection coil 211 changes, causing a change in the physical quantity, and the difference becomes equal to or greater than the threshold value. Therefore, the power transmission device 200 determines that an object is placed. The power transmission device 200 resumes transmitting A-Ping in the power transmission coil 209 to detect the placement of the second power reception device 101b and starts power transmission. After that, the power transmission device 200 stops transmitting A-Ping in the power transmission coil 209 again and resumes object detection by transmitting an object detection signal in the object detection coil 211.

[0107] In FIG. 13, since the power transmission device 200 is not transmitting power to the power receiving device, in the power transmission coils 209a to 209c, it waits for an object to be placed by sequentially transmitting A-Pings (No in S1001, F1101). When the first power receiving device 300 is placed, the power transmission coil 209a detects a change in the A-Ping transmitted from it, thereby detecting that an object has been placed (F1102, F1103, F1104). The first power receiving device 300 detects that it has been placed on the power transmission device 200 (near the power transmission coil 209a) by the subsequent D-Ping (F1105, F1106). Also, the power transmission device 200 detects that the placed object is the power receiving device (the first power receiving device 300) based on the response to the D-Ping, and stores that it has been placed on the power transmission coil 209a (S1005, S1006).

[0108] Subsequently, through communication in the I&C phase, the power transmission device 200 acquires identification information and capability information from the first power receiving device 300 (S1007, F1107). Next, the power transmission device 200 and the first power receiving device 300 execute communication in the Negotiation phase and determine that GP = 15W (S1008, F1108). Subsequently, the power transmission device 200 and the first power receiving device 300 derive Calibration data through communication in the Calibration phase (S1009, F1109). After that, the power transmission device 200 executes power transmission to the first power receiving device 101a (S1010, F1110).

[0109] Subsequently, since the power transmission device is transmitting power to the first power receiving device 300, it stops transmitting A-Ping in the power transmission coil 209, transmits an object detection signal from the object detection coil 211, and calculates the change amount of the physical quantity (S1001 to 1003, F1111 to 1113). At this time, no new power receiving device is placed, and since the calculated change amount of the physical quantity is less than the threshold value, it is determined that no new object is detected. Also, the power transmission device 200 repeatedly executes the transmission of the object detection signal and the calculation of the change amount of the physical quantity at a predetermined interval (No in S1004, S1001 to 1003, F1112 to 1113). After that, when the second power receiving device 310 is placed, since the change amount of the physical quantity calculated by the power transmission device 200 is equal to or greater than the threshold value, it is determined that a new object has been detected. The power transmission device 200 resumes transmitting A-Ping in 209b to 209c excluding the power transmission coil 209a that is transmitting power (Yes in S1004, F1114 to 1116). When the second power receiving device 101b is placed, the power transmission device 200 detects a change in the A-Ping transmitted from the power transmission coil 209c, thereby detecting that an object has been placed on the power transmission coil 209c (F1117, F1118). Thereafter, since the processing of F1119 to F1124 is the same as that of F1105 to F1110, the description is omitted. When power transmission to the second power receiving device 310 is executed via the power transmission coil 209c, since the power transmission device 200 is transmitting power to the first power receiving device 101a and the second power receiving device 101b, it stops object detection by A-Ping in the power transmission coil 209 again. Also, the power transmission device 200 transmits an object detection signal from the object detection coil 211 and calculates the change amount of the physical quantity (Yes in S1001, S1002 to 1003, F1125 to 1127).

[0110] According to the operations described above, after starting power transmission to the power receiving device, the power transmission device 200 stops transmitting A-Ping from each power transmission coil 209 and starts detecting an object using the object detection coil. Then, based on detecting an object using the object detection coil, the power transmission device 200 detects the power receiving device by transmitting an object detection signal (A-Ping) from each power transmission coil 209. At this time, the object detection coil is configured to encompass the entire power transmission range of the power transmission coil group. For this reason, the number of times of transmitting the object detection signal from the object detection coil within a predetermined time duration is less than the total number of times of transmitting A-Ping from each power transmission coil within the same predetermined time duration. Thereby, it becomes possible to relatively suppress the generation of radiation noise and the like, and to detect the placement of a new power receiving device while reducing the adverse effect on power transmission to an existing power receiving device. Also, by transmitting A-Ping only from the object detection coil, the power consumption can be relatively reduced compared to transmitting A-Ping from each power transmission coil.

[0111] In the above-described embodiment, when the power transmission device starts power transmission to the power receiving device, it stops transmitting A-Ping from each power transmission coil and transmits an object detection signal from the object detection coil to calculate the change amount of the physical quantity. However, it is not necessary to transmit the object detection signal. At this time, the power transmission device can calculate the change amount of the physical quantity caused by the change in the state within the object detection coil caused by the power transmitted from the power transmission coil during power transmission. Thereby, compared with the case where the object detection signal is transmitted, it is possible to further suppress the generation of radiation noise and the like and the suppression of unnecessary power consumption.

[0112] Note that in the above-described embodiment, when the power transmission device is not performing power transmission to the power receiving device, it is configured to sequentially transmit A-Ping from each power transmission coil, but it is not limited to this. That is, even when the power transmission device 200 is not performing power transmission to the power receiving device (no power receiving device is placed), it may perform object detection by transmitting an object detection signal from the object detection coil 211 and calculating the change amount of the physical quantity. Thereby, even when not performing power transmission to the power receiving device, unnecessary power consumption can be suppressed.

[0113] Also, in the above-described embodiment, the power transmission device is assumed to have an object detection coil configured to encompass the entire power transmission range of the power transmission coil group, but it is not limited thereto. For example, the power transmission device 200 may select a specific power transmission coil 209 other than the power transmission coil 209 during power transmission, and transmit A-Ping from the determined specific power transmission coil 209. Thereby, compared with the case of sequentially transmitting A-Ping from a plurality of power transmission coils, it is possible to suppress the generation of radiation noise and the like, and suppress unnecessary power consumption. Further, in the case of this configuration, the power transmission device 200 does not necessarily have the object detection coil 211 that surrounds the power transmission coil group 210.

[0114] Also, in the above-described embodiment, the power transmission device is assumed to have one object detection coil configured to encompass the entire power transmission range of the power transmission coil group, but it is not limited thereto. The power transmission device 200 may have a plurality of object detection coils. For example, a case where a plurality of object detection coils that respectively encompass areas where each power transmission circuit can transmit power (for example, dedicated areas 416 and 417 in FIG. 4) will be described. In this case, the power transmission device 200 starts object detection only with an object detection coil that encompasses the area where the power transmission circuit that is not in power transmission can transmit power, and when an object is detected, it can transmit A-Ping only with the power transmission coil in the area encompassed by the object detection coil. In this way, by transmitting A-Ping only in the area determined to have detected an object, the number of signal transmissions is reduced compared with the case of sequentially transmitting A-Ping over the entire power transmission range. Thereby, it becomes possible to relatively suppress the generation of radiation noise and the like, and while further reducing the adverse effect on power transmission to an existing power receiving device, it is possible to detect the placement of a new power receiving device.

[0115] (Embodiment 4) As described in the above Embodiment 1, when power transmission is performed simultaneously from a plurality of power transmission coils, if the power transmission coils are not appropriately selected, there is a problem that the power transmitted from each power transmission coil interferes with each other. In Embodiment 1, a method of suppressing interference by performing power transmission using power transmission coils having a positional relationship without interference (separated by a predetermined distance D or more) was described. In this embodiment, another method for suppressing interference between power transmission coils will be described. In this embodiment, in particular, a method for suppressing the influence (interference) between power transmission coils when another power transmission coil transmits A-Ping for object detection while power transmission for charging is being performed by a power transmission coil will be described. Note that the same names and reference numerals are used for the same configurations as those in the above-described embodiment.

[0116] [Processing in Power Transmission Device] FIG. 15 is a flowchart showing the processing executed by the power transmission device 100. The flowchart shown in FIG. 15 can be realized by the control unit 201 of the power transmission device 100 executing a control program stored in the memory 207 and performing calculation and processing of information and control of each hardware.

[0117] First, when the power supply of the power transmission device is turned on, the processing is started (S1301). The power transmission device 100 selects, via the control unit 201, a first power transmission coil used for power transmission by the first power transmission circuit 203 and a second power transmission coil used for power transmission by the second power transmission circuit 205 from among the power transmission coil group 210, and connects each power transmission circuit and each power transmission coil (S1302). Here, the power transmission device 100 selects power transmission coils that do not interfere with each other even when A-Ping is transmitted simultaneously from the first power transmission circuit and the second power transmission circuit. As the selection method at this time, for example, the method described in Embodiment 1 may be used.

[0118] Next, the power transmission device 100 determines whether the power transmission circuit is in the process of power transmission (S1303). Here, since it is immediately after the power is turned on, it is assumed that power transmission is not being performed in any of the power transmission circuits (No in S1303). Next, the power transmission device 100 transmits (powers) the above-described A-Ping from each power transmission coil connected to each power transmission circuit (S1304). The power of the A-Ping is a small power compared to the power transmission power during power transmission.

[0119] Next, the power transmission device 100 determines whether a power receiving device is placed on the coil of the power transmission device (S1305). Here, when the power transmission device 100 detects that an object is placed on the power transmission device by A-Ping, it detects the placement of the power receiving device through the above-described Selection phase, Ping phase, and I&C phase.

[0120] Next, the power transmission device performs a power transmission process on the power receiving device detected in S1305 through a plurality of phases defined by the above-described WPC standard and starts power transmission (S1306).

[0121] Next, the power transmission device 100 determines whether all the power transmission circuits of the power transmission device are in use (S1307). If all are in use, the power transmission device 100 ends the control for power transmission. Although not shown in FIG. 15, the power transmission device 100 performs power transmission for charging until, for example, the battery of the power receiving device is fully charged and it receives a power transmission stop command (EPT) from the power receiving device. Also, when the power transmission device 100 ends the power transmission for charging, in order to detect a new power receiving device, it executes the processes after S1303 again. The processes after S1303 are assumed to be repeatedly executed until the power of the power transmission device 100 is turned off. Also, if no power receiving device is detected in S1305 before a predetermined time has elapsed, after the predetermined time has passed, it returns to S1303.

[0122] Next, the case where it is determined in S1303 that the power transmission device is in the power transmission state will be described. Here, it is assumed that the first power transmission circuit 203 and the second power transmission circuit 205 are configured to be capable of power transmission using the first power transmission coil and the second power transmission coil, respectively. The reason for performing the control described here is as follows. That is, if the power transmission from the first power transmission coil and the transmission of A-Ping, which is a signal for object detection, from the second power transmission coil are performed simultaneously, the small A-Ping as power may be disturbed by the power of the large-power power transmission. For this reason, the A-Ping transmitted from the second power transmission coil may not function correctly as a detection signal, leading to the possibility of misdetection of an object. The power transmission device 100 in the present embodiment suppresses the problem that A-Ping is disturbed by performing the following processing.

[0123] In S1303, when it is determined that the power transmission device is in the process of power transmission (Yes in S1303), the power transmission device 100 temporarily interrupts the power transmission from the first power transmission circuit 203 and stops the power transmission. Then, during the period (instant) when the power transmission device 100 has stopped power transmission, a detection signal is transmitted from another power transmission coil that is not being used for power transmission. Here, it is assumed that the second power transmission coil is not being used for power transmission and the detection signal is transmitted from the second power transmission coil. The power transmission device 100 stops (interrupts) the power transmission from the first power transmission coil that is performing power transmission for a predetermined period (S1308). Then, during the period when the power transmission from the first power transmission coil has been stopped, a detection signal is transmitted from the second power transmission coil that is not performing power transmission (S1309). That is, during the period when the power transmission from the first power transmission circuit 203 that performs power transmission is stopped, an A-Ping is transmitted using the second power transmission circuit 205 that is not performing power transmission. Then, after the power transmission device 100 has stopped power transmission for a predetermined period, it resumes power transmission (S1310). At this time, it is necessary to ensure that the A-Ping output by the second power transmission circuit 205 for object detection does not overlap with the power transmission performed by the first power transmission circuit 203. That is, the period when the power transmission from the first power transmission coil is stopped is controlled to be longer than the period when the detection signal is being transmitted from the second power transmission coil. For this reason, the predetermined period during which the power transmission is stopped is longer than the period during which the second power transmission circuit 205 performs object detection. By this process, it is possible to transmit the detection signal transmitted from the second power transmission coil without the charging power transmitted from the first power transmission coil overlapping with it.

[0124] Using FIG. 16, the timing of stopping power transmission for charging and the timing of detecting signal transmission by the power transmission device 100 will be described. In the above-described embodiment, the case where the power transmission device 100 performs power transmission processing using two power transmission circuits and two power transmission coils connected to each of them has been described. However, the present invention is not limited to this, and the present embodiment is applicable even in power transmission processing using more power transmission circuits and power transmission coils. Now, assume that the first power transmission circuit 203 is performing power transmission for charging using the first power transmission coil. Also, assume that the second power transmission circuit 205 is sequentially connected to the second power transmission coil, the third power transmission coil, and the fourth power transmission coil, and transmits A-Ping from each power transmission coil.

[0125] In FIG. 16, the first power transmission coil is used for power transmission and performs power transmission to the power receiving device. After a predetermined time has elapsed, the first power transmission circuit 203 stops (interrupts) power transmission from the first power transmission coil for a predetermined period at the first timing (S1308). Then, during the period when power transmission is stopped, the second power transmission circuit 205 transmits A-Ping using the second power transmission coil (S1309). The first power transmission circuit connected to the first power transmission coil resumes power transmission after interrupting power transmission for a predetermined period (S1310). If the power receiving device is not detected by the second power transmission circuit 205 (S1305), after a predetermined time has elapsed, the first power transmission circuit 203 stops (interrupts) power transmission from the first power transmission coil for a predetermined period at the second timing (S1308). Then, during the period when power transmission is stopped, the second power transmission circuit 205 transmits A-Ping using the third power transmission coil (S1309). Then, the first power transmission circuit 203 resumes power transmission after stopping power transmission for a predetermined period (S1310). If the power receiving device is not detected by the second power transmission circuit 205 (S1305), after a predetermined time has elapsed, the first power transmission circuit 203 stops (interrupts) power transmission from the first power transmission coil for a predetermined period at the third timing (S1308). Then, during the period when power transmission is stopped, the second power transmission circuit 205 transmits A-Ping using the third power transmission coil (S1309). Then, the first power transmission circuit 203 resumes power transmission after stopping power transmission for a predetermined period (S1310).

[0126] The above-mentioned flat processing is repeatedly performed until the second power transmission circuit 205 detects the power receiving device. When the second power transmission circuit 205 detects an object placed on the power transmission device with A-Ping and detects the power receiving device after passing through a plurality of predetermined phases (S1305), the power transmission device starts power transmission to the power receiving device detected in S1305 by the second power transmission circuit 205 (S1306).

[0127] In this way, the power transmission device 100 can periodically check whether there is a power receiving device near each power transmission coil by stopping the power transmission for charging and sequentially transmitting detection signals from other power transmission coils. Note that the timing at which the power transmission device 100 stops the power transmission for charging may be set in advance in the power transmission device 100. Also, the predetermined period during which the power transmission device 100 stops the power transmission may be set to a length that does not affect the power receiving process of the power receiving device. Alternatively, the power transmission device 100 may be configured to perform the above processing after determining whether it is okay to momentarily interrupt the power transmission based on the version of the power receiving device for which the power transmission for charging is being performed. Further, the power transmission device 100 may share the timing of momentarily interrupting the power transmission with each other by, for example, transmitting information indicating the timing of momentarily interrupting the power transmission to the power receiving device in the Negotiation phase or acquiring the information from the power receiving device.

[0128] Also, the configuration of the power transmission circuit and the power transmission coil is not limited to the above-mentioned one. For example, a configuration may be adopted in which four power transmission circuits are used, the first power transmission coil is connected to the first power transmission circuit, the second power transmission coil is connected to the second power transmission circuit, the third power transmission coil is connected to the third power transmission circuit, and the fourth power transmission coil is connected to the fourth power transmission circuit. Also, the number of power transmission coils may be any number.

[0129] Also, in the above-described embodiment, the power transmission device 100 was configured to sequentially transmit detection signals from power transmission coils not in use for power transmission. However, the A-Ping, which is a detection signal, may be transmitted simultaneously from a plurality of coils. That is, the power transmission device may temporarily stop (interrupt) power transmission from the first power transmission coil, and during the period when the power transmission is stopped, transmit A-Ping simultaneously from the second power transmission coil, the third power transmission coil, and the fourth power transmission coil. Alternatively, the first power transmission circuit may be connectable to the first power transmission coil and the second power transmission coil, the second power transmission circuit may be connected to the third power transmission coil, and the third power transmission circuit may be connected to the fourth power transmission coil. In such a configuration, the power transmission device 100 may temporarily stop (interrupt) power transmission from the first power transmission coil, the first power transmission circuit may be connected to the second power transmission coil, and A-Ping may be transmitted simultaneously from the second power transmission coil, the third power transmission coil, and the fourth power transmission coil. At this time, the combination of power transmission coils that transmit A-Ping simultaneously may be determined using, for example, the method of Embodiment 1 described above.

[0130] Also, in the above-described embodiment, the detection signal transmitted from the power transmission device was described as a signal for detecting the power reception device. However, the detection signal may be used to detect a foreign object (object) different from the power reception device. For example, if there is a foreign object such as a conductor on the power transmission device, when the power transmission device performs power transmission, power may be consumed by the foreign object and the foreign object may generate heat. Therefore, when the power transmission device 100 detects the presence of an object with A-Ping transmitted in S1304 or S1309 and determines that "there is a foreign object" or "there may be a foreign object", it may be controlled to stop power transmission. The determination of the presence or absence of a foreign object can be made by going through the above-described Ping phase, Selection phase, Ping phase, Identification and Configuration phase, and Negotiation phase. As a result, the power transmission device shown in FIG. 14 can periodically check whether there is a foreign object in the vicinity of each power transmission coil by sequentially transmitting a detection signal from the power transmission coil not in use for power transmission. Therefore, the power transmission device can detect foreign objects on the power transmission device with high accuracy.

[0131] Alternatively, foreign objects may be detected based on the transient response of the voltage or current in the power transmission coil when power transmission is interrupted momentarily.

[0132] In addition, in the above-described embodiment, a configuration has been described in which power can be simultaneously transmitted to the power receiving device from both the first power transmission circuit and the second power transmission circuit. However, instead of simultaneously transmitting power from each power transmission circuit, a configuration may be adopted in which power is transmitted only from one of the power transmission circuits. That is, when it is detected that the first power receiving device exists by the first power transmission coil and it is also detected that the second power receiving device exists near the second power transmission coil (S1305), after S1305, one of the power receiving devices is selected based on a predetermined condition. Here, as a predetermined condition for selecting the power receiving device, for example, it may be selected based on the priority (priority order) to be the power transmission target. The priority is information for the power transmission device to communicate with the first power receiving device and the second power receiving device and determine the priority. The reason for the power transmission device to select one of the power receiving devices as the power transmission target is as follows. For example, when the power transmitted from the first power transmission circuit and the second power transmission circuit is very large, even if the selection of the power transmission coil used for power transmission is appropriately performed, interference may occur between the power transmitted from the first power transmission circuit and the power transmitted from the second power transmission circuit. This is because there is a risk of communication errors and the like occurring between the power transmission device and the power receiving device. In addition, the noise generated by power transmission from a plurality of power transmission circuits may be greater than the reference value. Therefore, by performing "selection of the power receiving device" and transmitting power to the selected power receiving device, power interference is suppressed.

[0133] Also, even when power transmission from a plurality of power transmission circuits exceeds the power supply capacity of the hardware of the power transmission device, it is possible to appropriately perform power transmission by performing "selection of the power receiving device". Also, when such "selection of the power receiving device" is performed, the method of this embodiment is used to periodically check whether a new power receiving device is placed on the power transmission device. For example, even when a power receiving device with a high priority is newly placed, it is possible to detect and start power transmission at an early stage.

[0134] (Embodiment 5) In this embodiment, the operation of the power transmission device 100 when the first power reception device 101a and the second power reception device 101b are placed on the power transmission coil group 210 will be described. With reference to FIG. 17, the problems to be solved in this embodiment will be described. FIG. 17 is an arrangement configuration diagram of the power transmission coil group 210 and the power reception devices. Note that the configuration of the power transmission device in this embodiment is the same as that in Embodiment 1, and it is assumed that the first power transmission circuit 203 and the second power transmission circuit 205 included in the power transmission device 100 can each transmit power to a maximum of one power reception device.

[0135] In FIG. 17(a), the first power reception device 101a is placed in the shared area 415, and no power reception device is placed in the dedicated area 416 of the first power transmission circuit 203 and the dedicated area 417 of the second power transmission circuit 205. FIG. 17(b) shows that, from the state of FIG. 17(a), the second power reception device 101b is further placed in the dedicated area 416 of the first power transmission circuit 203. Here, it is assumed that the first power transmission circuit 203 is transmitting power to the first power reception device 101a placed in the shared area 415 in FIG. 17(a). In this case, when the second power reception device 101b is newly placed in the dedicated area of the first power transmission circuit 203 as shown in FIG. 17(b), the first power transmission circuit 203 cannot transmit power to the second power reception device 101b. This is because the maximum number of power reception devices that the first power transmission circuit 203 can transmit power to simultaneously is 1. Thus, even though the power transmission device 100 itself has two power transmission circuits and is configured to be able to transmit power to two power reception devices simultaneously, there is a problem that power can be transmitted to only one power reception device depending on the order of placement and the position where the power reception devices are placed.

[0136] Hereinafter, an embodiment for appropriately controlling power transmission regardless of the placement conditions of the power reception devices in a power transmission device capable of transmitting power to a plurality of power reception devices will be described. Note that the same names and reference numerals are used for the same configurations as those in the other embodiments described above.

[0137] [Processing in the Power Transmission Device] The processing performed by the power transmission device in this embodiment will be described with reference to FIGS. 17 and 18. Note that this processing can be started in response to the power transmission circuit 203 being powered on and activated, for example, by receiving power supply from the power supply unit 202. Also, this processing can be realized by the control unit 201 executing a program stored in the memory 207. However, it is not limited to these. For example, this processing may be executed in response to the power transmission function being activated by an operation such as a user pressing a predetermined button. Also, at least a part of the processing shown in FIG. 18 may be realized by hardware. When at least a part of the processing is realized by hardware, for example, a dedicated circuit automatically generated on an FPGA using a predetermined compiler from a program for realizing the processing step can be used. Also, similar to an FPGA, hardware for executing a predetermined processing step may be realized by a Gate Array circuit.

[0138] In FIG. 18, when the power transmission device 100 is powered on, the processing starts. The power transmission device 100 transmits an A-Ping and determines whether a power receiving device is placed thereon (S1600). Here, as shown in FIG. 17(a), assume that the first power receiving device 101a is placed in the shared area 415. When the power transmission device 100 detects the placement of the power receiving device (Yes in S1600), the process proceeds to S1602.

[0139] When the power transmission device 100 transmits a D-Ping and receives a Signal Strength packet, it determines that the first power receiving device 101a has been detected. Here, it is assumed that the D-Ping is transmitted by the first power transmission circuit 203. Here, the power transmission device 100 compares the number of power receiving devices currently being powered (in the Power Transfer phase) with the upper limit value of the number of power receiving devices that the power transmission circuit can power (S1602). In the example of Fig. 17(a), although the first power transmission circuit 203 transmits a D-Ping to the first power receiving device 101a, since there is no power receiving device being powered in the Power Transfer phase, the number of power receiving devices is 0. Also, as described above, the upper limit value of the first power transmission circuit 203 is 1. Since the upper limit value is greater than the number of power receiving devices (Yes in S1602), the power transmission device 100 proceeds to process S1611. The power transmission device 100 compares the number of power receiving devices being powered in the area where the power receiving device is detected with the upper limit value of the number of power receiving devices that can be powered in the area where the power receiving device is detected (S1611). Here, the number of power receiving devices in the shared area 415 is compared with the upper limit value representing the number of power receiving devices that the first power transmission circuit 203 can power in the shared area 415. Now, since there is no power receiving device being powered in the shared area 415, the number of power receiving devices is 0. Also, the upper limit value of the number of power receiving devices that the first power transmission circuit 203 can power in the shared area 415 is 1. Since the number of power receiving devices is smaller than the upper limit value of the area (Yes in S1611), the power transmission device 100 determines that the first power transmission circuit 203 that detected the first power receiving device 101a will perform power transmission to the first power receiving device 101a (S1607) and ends the process. Since the power transmission circuit for powering the power receiving device has been determined, the power transmission device 100 performs power transmission to the first power receiving device 101a based on the flow of Fig. 5.

[0140] Subsequently, as shown in FIG. 17(b), assume that the second power receiving device 101b is further placed in the dedicated area 416 of the first power transmission circuit 203. The power transmission device 100 detects the second power receiving device 101b using A-Ping (Yes in S1600). Although the power transmission device 100 is transmitting power to the first power receiving device 101a, it may also detect the second power receiving device 101b using the object detection coil shown in Embodiment 3. Further, as shown in Embodiment 4, the power transmission device 100 may detect the second power receiving device 101b while interrupting the power transmission that the first power transmission circuit is performing on the first power receiving device 101a in the shared area 416. Specifically, the power transmission device 100 may detect the second power receiving device 101b placed in the dedicated area 416 using the power transmission coil included in the dedicated area 416 during the interruption.

[0141] When the power transmission device 100 detects the second power receiving device 101b, it compares the number of power receiving devices with the upper limit value (S1602). Since the first power transmission circuit 203 is transmitting power to the first power receiving device 101a, the number of power receiving devices is 1. Since the upper limit value of the first power transmission circuit 203 is 1, it is determined that the upper limit value is not greater than the number of power receiving devices (No in S1602). Then, the power transmission device 100 acquires the placement area of the detected power receiving devices including the power receiving device during power transmission (S1601). Whether the power receiving device is placed in which area can be determined by which power transmission coil in FIG. 4(e) received the Signal Strength Packet.

[0142] Now, since the first power transmission circuit 203 is performing power transmission in the shared area 415 to the first power receiving device 101a (Yes in S1603), the power transmission device 100 selects another power transmission circuit that can perform power transmission in the shared area 415 (S1604). Here, since the second power transmission circuit 205 can perform power transmission in the shared area 415, the power transmission device 100 selects the second power transmission circuit 205 (S1604), and the second power transmission circuit 205 compares the number of power receiving devices receiving power with the upper limit value of the number of power receiving devices capable of power reception (S1605). At this point, since the second power transmission circuit 205 is not transmitting power to any power receiving device, the upper limit value (=1) is greater than the number of power receiving devices (=0) (Yes in S1605). Next, the power transmission device compares the number of power receiving devices receiving power in the current shared area with the upper limit value of the number of power receiving devices capable of power transmission in the shared area. Since power is being transmitted to the first power receiving device 101a in the shared area 415, the number of power receiving devices is 1. Also, the upper limit value of the number of power receiving devices to which the selected second power transmission circuit 205 can perform power transmission in the shared area 415 is 1. Therefore, since the number of power receiving devices is less than or equal to the upper limit value of the area (Yes in S1610), the power transmission device 100 determines that the first power receiving device 101a placed in the shared area 415 will be powered by the currently selected second power transmission circuit 205 (S1606).

[0143] The power transmission device 100 stops the power transmission of the first power transmission circuit 203 that is currently performing power transmission in the shared area 415 (S1609). Also, the second power transmission circuit 205 performs power transmission to the first power receiving device 101a in the shared area 415 based on the flow shown in FIG. 5. Here, the first power transmission circuit 203 is in a state where it is not transmitting power to any power receiving device. The power transmission device 100 detects the second power receiving device 101b placed in the dedicated area 416 using the first power transmission circuit 203 (S1600), and compares the number of power receiving devices during power transmission with the upper limit value of the number of power receivable devices (S1602). As a result of the comparison, it is determined that the upper limit value (=1) of the first power transmission circuit 203 is larger than the number of power receiving devices during power transmission (=0), and the process proceeds to S1611. Since the power transmission device 100 has already detected the second power receiving device 101b, the detection process here may be omitted. The power transmission device 100 compares the number of power receiving devices during power transmission (=0) with the upper limit value of the number of power receivable devices in the dedicated area 416 (=0) (S1611), and performs power transmission to the second power receiving device 101b (S1607).

[0144] The above is the power transmission control process performed by the power transmission device 100 in this embodiment. By performing the above-described control, it becomes possible to efficiently perform power transmission to a plurality of power receiving devices using a plurality of power transmission circuits.

[0145] Next, another example of power transmission control will be described. Here, in Fig. 17(b), first, it is assumed that the second power receiving device 101b is placed in the dedicated area 416 of the first power transmission circuit 203, and then the first power receiving device 101a is placed in the shared area 415. In this case, the power transmission device 100 first performs power transmission to the second power receiving device 101b using the first power transmission circuit 203. Subsequently, when the first power receiving device 101a is placed in the shared area 415, the power transmission device 100 detects the first power receiving device 101a using the first power transmission circuit 203 or the second power transmission circuit 205. When the first power transmission circuit 203 detects the first power receiving device 101a, since it is No in S1602, the power transmission device 100 selects the second power transmission circuit 205 at S1604 and performs power transmission to the first power receiving device 101a using the second power transmission circuit 205. Also, when the second power transmission circuit 205 detects the first power receiving device 101a, since it is Yes in S1602, the second power transmission circuit 205 performs power transmission to the first power receiving device 101a at S1607.

[0146] Also, although not shown in the figure, it is assumed that a third power receiving device is placed in the dedicated area 417 of the second power transmission circuit 205 from the state of Fig. 17(b). In this case, the upper limit value (=1) of the number of power receiving devices to which the second power transmission circuit 205 can perform power transmission is not greater than the number of power receiving devices during power transmission (=1) (No in S1605). Therefore, the power transmission device 100 determines that it does not perform power transmission to the third power receiving device using any power transmission circuit (S1608). Note that when detecting the third power receiving device, the power transmission device 100 may also detect the second power receiving device 101b using the object detection coil shown in Embodiment 3. Also, as described in Embodiment 4, the power transmission performed by the first power transmission circuit 203 in the dedicated area 416 and the second power transmission circuit 205 in the shared area 416 may be interrupted momentarily, and the operation may be based on the flow of Fig. 15. Specifically, the first power transmission circuit 203 periodically performs A-Ping power transmission using the power transmission coils included in the dedicated area 416 and the shared area 416 while the above-mentioned momentary interruption is occurring. The second power transmission circuit 205 may periodically perform A-Ping power transmission using the power transmission coils included in the dedicated area 417 and the shared area 416 while the above-mentioned momentary interruption is occurring to detect the third power receiving device.

[0147] Also, as shown in FIG. 15(c), when the first power receiving device 101a and the second power receiving device 101b are placed in the respective dedicated areas of the first power transmission circuit 203 and the second power transmission circuit 205, the following operation occurs. That is, the first power transmission circuit 203 and the second power transmission circuit 205 transmit power to the first power receiving device 101a and the second power receiving device 101b according to the processes of S1602, S1611, and S1607, respectively.

[0148] Also, as shown in FIG. 15(d), consider the case where the first power receiving device 101a is first placed in the dedicated area 416 of the first power transmission circuit 203 and the second power receiving device 101b is placed in the dedicated area 416 of the first power transmission circuit 203 while the first power transmission circuit 203 is transmitting power to the first power receiving device 101a. In this case, the power transmission device 100 detects the second power receiving device 101b in accordance with the method described in the above-described Embodiment 3 or Embodiment 4. In this case, since power cannot be transmitted to any more power receiving devices in the dedicated area 416 when the second power receiving device 101b is placed (No in S1610), the power transmission device 100 determines not to transmit power from any power transmission circuit to the detected second power receiving device 101b (S1608).

[0149] [Processing of the entire system] Using FIGS. 17(a), (b), and 19, the processing of the entire system will be described. The power transmission device 100 transmits A-Ping using the first power transmission circuit 203 and the second power transmission circuit 205 (F1701), and performs detection processing of the power reception device. Here, it is assumed that the first power reception device 101a is placed in the shared area 415 and is detected by the A-Ping transmitted by the first power transmission circuit 203. The first power transmission circuit 203 transmits D-Ping to the first power reception device 101a (F1701), and performs power transmission for charging according to the flow shown in FIG. 5 (F1702). Here, it is assumed that the second power reception device 101b is further placed in the dedicated area 416 of the first power transmission circuit 203 and is detected by the A-Ping transmitted by the first power transmission circuit 203 (F1703). The first power transmission circuit 203 transmits D-Ping (F1711) and performs the processing of S1602 in FIG. 18. Since the first power transmission circuit 203 is already transmitting power to the first power reception device 101a (No in S1602), the power transmission device 100 selects the second power transmission circuit 205 at S1604 and controls to perform power transmission to the first power reception device 101a using the second power transmission circuit 205 (S1609). Also, the power transmission device 100 stops the power transmission to the first power reception device 101a by the first power transmission circuit 203 (S1609, F1704). Note that in FIG. 19, it is assumed that D-Ping is transmitted at F1711, but a configuration in which power transmission is stopped at F1704 without transmitting D-Ping may also be used.

[0150] The second power transmission circuit 205 transmits A-Ping (S1705) and D-Ping (F1706), and performs power transmission to the first power reception device 101a (F1707). The first power transmission circuit 203 transmits A-Ping (S1708) and D-Ping (F1709), and performs power transmission to the second power reception device 101b (F1710).

[0151] As described above, in the power transmission device according to the present embodiment, when a power reception device is placed, a power transmission circuit that transmits power to the placed power reception device is determined based on the upper limit value of the number of power reception devices to which the power transmission circuit can transmit power and the placed area. Thereby, for example, even when a power reception device is placed as shown in FIG. 17(b), it becomes possible to simultaneously transmit power to a plurality of power reception devices.

[0152] According to the method described above, the power transmission device 100 determines a power transmission circuit that transmits power to the placed power receiving devices based on the upper limit value of the number of power receiving devices to which the power transmission circuit can transmit power and the placed area. However, it is not limited to this. The power transmission device 100 may determine a power transmission circuit that transmits power to the power receiving device based on the fact that the power transmission circuit is performing a predetermined process on the power receiving device. For example, when the number of power receiving devices that the power transmission circuit can transmit power to simultaneously is 1, the power transmission device 100 determines whether the power transmission circuit is performing the following process. That is, the power transmission device 100 determines whether the power transmission circuit is transmitting A-Ping (it is the Selection phase) or transmitting D-Ping (it is the Negotiation phase, Power Transfer phase). In the processes of S1602 and S1605 shown in FIG. 18, the power transmission device 100 determines No when the power transmission circuit is transmitting A-Ping or D-Ping, and Yes when it is not transmitting. As a result, it is determined that the power transmission circuit 100 cannot transmit power to any new power receiving devices for the power transmission circuits that have already transmitted A-Ping or D-Ping.

[0153] In addition, when the power transmission device 100 of the present embodiment receives a Signal Strength Packet for the transmitted D-Ping, it determines that the first power receiving device 101a has been detected. However, this may also be determined as the presence of an object in the vicinity with A-Ping.

[0154] In addition, as shown in Fig. 15(d), when the number of power receiving devices mounted in the power transmission circuit's upper limit value for power transmission or in the same area exceeds the upper limit value of the power receiving devices that can be powered in that area, the following processing may be performed. For example, the power transmission device 100 may use the communication unit to transmit a message regarding the "number of power receiving devices" to the second power receiving device 101b mounted later. Specifically, it may be a message indicating that "the number of power receiving devices that the power transmission device or the power transmission circuit can simultaneously power exceeds the upper limit value" or that "the number of power receiving devices that the power transmission device or the power transmission circuit can power in the same area exceeds the upper limit value". Or it may simply be a message such as "many" or "too much". Also, the message may be related to the "distance between multiple power receiving devices". Specifically, it may be a message indicating that "the distance between the mounted multiple power receiving devices is short" or simply "close" or "too close". By doing so, the power transmission device 100 can notify the reason for not performing power transmission to the power receiving device. Also, the power receiving device can recognize the reason why the power transmission device 100 does not perform power transmission.

[0155] Furthermore, the power receiving device that has received the message may display on the UI of the power receiving device a prompt to place the power receiving device at a different position in the power transmission coil group 210 so that power transmission to the power receiving device becomes possible. For example, displays such as "Please place the charging device in another location", "The distance to other charging devices (power receiving devices) is too close to perform wireless charging", or "Please place the wireless charging device at a distance from other charging devices (power receiving devices)" may be shown.

[0156] Also, the attributes of the charging device (power receiving device) may be detected using the Identification Packet, Extended Identification Packet, and Configuration Packet defined in the WPC standard, and the attributes may be displayed on the UI. For example, if the first power receiving device 101a is a smartphone and the second power receiving device 101b is a smartwatch, the following display may be shown on the UI of the smartwatch. For example, messages such as "Please place the smartwatch in a location different from the smartphone to perform wireless charging", "The distance to the smartphone is too close to perform wireless charging", "Please move the smartwatch away from the smartphone to perform wireless charging" may be displayed.

[0157] If a user who has confirmed a message as described above moves the second power receiving device 101b in the shared area 415 in FIG. 15(d), for example, the power transmission device 100 can transmit power to the second power receiving device 101b. In this way, the power transmission device notifies the power receiving device of the reason why power cannot be transmitted, and the notified power receiving device displays the attributes of the device on the UI in addition to the reason why power cannot be transmitted or the method to enable power transmission. By doing so, power can be transmitted to the power receiving device. Similar messages can obtain similar effects in cases not shown in the figure, for example, when both the first power receiving device 101a and the second power receiving device 101b are placed in the shared area 416 and no other power receiving devices are placed.

[0158] Also, in FIG. 15(b), the power transmission device 100 switched the power transmission circuit for transmitting power to the first power reception device 101a from the first power transmission circuit 203 to the second power transmission circuit 205. Then, the second power transmission circuit 205 started power transmission to A-Ping according to the flow of FIG. 5 (S500, F1705), that is, starting from the Selection phase. However, although the power transmission circuit switches from the first power transmission circuit 203 to the second power transmission circuit 205, since the power transmission device 100 already grasps the information of the first power reception device 101a, the second power transmission circuit 205 may start from the middle of the flow of FIG. 5. Specifically, the Negotiation process and the Calibration process may be omitted, and the power transmission in the Power Transfer phase may be started. By doing so, the power transmission to the first power reception device 101a can be started earlier.

[0159] Also, when the first power reception device 101a is a device having a display unit such as a smartphone and the second power reception device 101b is a device that cannot display such as a wireless earphone, the power transmission device may cause the charging smartphone to display the following information. The information that the power transmission device causes the smartphone to display is, for example, the upper limit value of the number of power reception devices to which the power transmission device can transmit power, a message indicating that the upper limit value that can be transmitted in the same area is exceeded, and information on devices that cannot be charged. Then, the power transmission device may display information regarding the wireless earphone on the display unit of the charging smartphone. For example, a display such as "Please place the wireless earphone in a different location from the smartphone to wirelessly charge it" or "The distance from the smartphone is too close to wirelessly charge the wireless earphone" may be displayed. Also, for example, a display such as "Please place the wireless earphone at a distance from the smartphone to wirelessly charge it" may be displayed. This enables the user to also confirm information on devices without a display unit (such as wireless earphones).

[0160] Further, the power transmission device 100 may transmit a message to the second power reception device 101b placed later, indicating that the upper limit value that the communication unit can transmit power or the upper limit value that can transmit power in the same area is exceeded. Then, when the upper limit value that the power transmission circuit can transmit power or the upper limit value that can transmit power in the same area is exceeded, the power transmission device may display the reason why power cannot be transmitted on the display unit of the device that cannot transmit power. For example, the power transmission device may display "The number of devices that can be wirelessly charged simultaneously has been exceeded" and "To perform wireless charging, please end the wireless charging of other devices."

[0161] Also, the power transmission coils 402, 403, 405, 408, 409, 411 existing in the shared area 416 are made to be exclusively connectable to either the first power transmission circuit 203 or the second power transmission circuit 205. However, this is because if either the first power transmission circuit 203 or the second power transmission circuit 205 can transmit power to the power reception device placed in the shared area 416, each power transmission circuit does not have to be connected to all of the above power transmission coils. For example, the first power transmission circuit 203 may be configured to be connectable to the power transmission coils 402, 403, 405, and the second power transmission circuit 205 may be configured to be connectable to the power transmission coils 408, 409, 411.

[0162] Also, although the power reception device performs UI display based on the message transmitted by the communication unit of the power transmission device, the message may be transmitted by a communication unit other than the communication unit and compliant with a communication standard outside the WPC standard. The communication unit may be a communication unit compliant with the Bluetooth Low Energy standard, the Wi-Fi standard, or the NFC standard.

[0163] Also, in the present embodiment, the power transmission circuit has two, the first power transmission circuit 203 and the second power reception device 101b, and the shared area 415 has been described by taking one power transmission device 100 as an example. However, it is obvious that this is applicable even if there are an arbitrary number of power transmission circuits and an arbitrary number of shared areas 415 and dedicated areas.

[0164] (Other embodiments) The above-described Embodiments 1 to 5 can be implemented in any combination of embodiments.

[0165] The present disclosure can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Explanation of Reference Numerals

[0166] 100 Power transmission device 201 Control unit 203 First power transmission circuit 205 Second power transmission circuit 209 Power transmission coil 210 Power transmission coil group

Claims

1. a plurality of coils used for wirelessly transmitting power to a power receiving device, the plurality of coils including a first coil, a second coil arranged at a position closer than a predetermined distance from the first coil, and a third coil arranged at a position farther than the predetermined distance from the first coil; a detection unit that detects an object by outputting a signal for detecting the object from a part of the plurality of coils; a power transmitting unit that transmits power wirelessly to the power receiving unit using at least one of the plurality of coils based on the fact that the object detected by the detecting unit is a power receiving unit; a control means for controlling the first coil and the second coil so that signals for detecting an object are not output simultaneously; having When there are a plurality of power receiving devices, the power transmitting means wirelessly transmits power to a first power receiving device through a coil corresponding to the first power receiving device included in the plurality of power receiving devices, and wirelessly transmits power to a second power receiving device through a coil corresponding to the second power receiving device included in the plurality of power receiving devices; The power transmitting device is characterized in that the control means controls the power transmitting device so that a signal for detecting an object is not output via the second coil during wireless power transmission to the power receiving device via the first coil.

2. The power transmission device according to claim 1, characterized in that the specified distance is a distance at which the voltage or current in the second coil does not fluctuate due to the voltage or current in the first coil when a signal for detecting an object is output from the first coil.

3. The power transmission device according to claim 1, characterized in that the specified distance is a distance at which a fluctuation in voltage or current in the second coil caused by the voltage or current in the first coil when a signal for detecting an object is output from the first coil is less than a specified value.

4. 4. The power transmitting device according to claim 1, wherein the detection means causes the first coil and the third coil to simultaneously output signals for detecting an object.

5. The power transmission means has a first power transmission circuit that wirelessly transmits power through some of the plurality of coils, and a second power transmission circuit that wirelessly transmits power through some of the plurality of coils, the first power transmitting circuit and the second power transmitting circuit are capable of wirelessly transmitting power via the second coil; The power transmitting device according to any one of claims 1 to 4, characterized in that the control means controls the second power transmitting circuit so that a signal for detecting an object is not output via the second coil while wirelessly transmitting power to the power receiving device via the first coil using the first power transmitting circuit.

6. The power transmission device described in Claim 5, characterized in that the detection means detects an object other than the power receiving device by outputting a signal for detecting an object through the third coil using the second power transmission circuit.

7. The power transmission device according to any one of claims 1 to 6, characterized in that when the power transmission means is transmitting power to the power receiving device via the first coil, the detection means detects an object other than the power receiving device by outputting a signal for detecting an object from the third coil.

8. 8. The power transmitting device according to claim 1, wherein the signal is an Analog Ping defined by a Wireless Power Consortium (WPC) standard.

9. The power transmitting device according to claim 1 , wherein the simultaneous output means that periods in which signals for detecting an object are output from the two coils overlap at least partially with each other.

10. A method for controlling a power transmitting device having a plurality of coils used for wirelessly transmitting power to a power receiving device, the plurality of coils including a first coil, a second coil arranged at a position closer than a predetermined distance from the first coil, and a third coil arranged at a position farther than a predetermined distance from the first coil, the method comprising: a detection step of detecting an object by outputting a signal for detecting the object from a part of the plurality of coils; a power transmitting step of wirelessly transmitting power to a first power receiving device through a coil corresponding to a first power receiving device included in the plurality of power receiving devices, and wirelessly transmitting power to a second power receiving device through a coil corresponding to a second power receiving device included in the plurality of power receiving devices, based on the fact that the objects detected in the detection step are a plurality of power receiving devices; a first control step of controlling the first coil and the second coil so that signals for detecting an object are not output simultaneously; a second control step of controlling the second coil so that a signal for detecting an object is not outputted during wireless power transmission to the power receiving device via the first coil; A control method comprising the steps of:

11. A program for causing a computer to function as the power transmitting device according to claim 1 .

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