Power transmission device, method that is performed by power transmission device, and program

Abstract

This power transmission device has a plurality of coils including a first coil and a second coil disposed inside the first coil. The power transmission device applies, from each of the plurality of coils, a power signal for detecting the presence of an object, and selects, from among the plurality of coils, one coil to which a power signal for starting a power reception device is to be applied, on the basis of the electrical characteristics exhibited when the power signal for detecting the presence of the object has been applied from at least the first coil.

Description

Power transmission device, method performed by the power transmission device, and program

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

[0002] In recent years, technological development of wireless power transmission systems has been widely conducted. Patent Document 1 discloses a power transmitting device and a power receiving device that comply with the standards established by the Wireless Power Consortium (WPC), a standardization organization for contactless charging standards. Furthermore, Patent Document 2 discloses a technology for wireless power transmission using a power transmitting device having multiple power transmitting coils, selecting a power transmitting coil to be used depending on the transmission distance from the power receiving coil.

[0003] In the WPC standard, a power transmitting device transmits detection power (Analog Ping) to detect an object placed on the power transmitting device, the detection power being weak enough not to activate a power receiving device, and detects that an object has been placed on the power transmitting device.

[0004] JP 2015-56959 A JP 2017-93174 A

[0005] The present disclosure provides a technique that enables appropriate wireless power transmission.

[0006] A power transmission device according to one embodiment of the present disclosure includes a plurality of coils including a first coil and a second coil arranged inside the first coil, a power transmission means for applying a power signal for detecting the presence of an object from each of the plurality of coils, and a selection means for selecting one of the plurality of coils to which a power signal for activating a power receiving device is applied based on electrical characteristics when a power signal for detecting the presence of an object is applied from at least the first coil.

[0007] According to the present disclosure, appropriate wireless power transmission can be performed.

[0008] 1A is a diagram showing an example of the configuration of a plurality of power transmission coils of a power transmission device in one embodiment, and FIG. 1B is a diagram showing an example of the configuration of a wireless power transmission system in one embodiment. FIG. 1B is a functional block diagram showing an example of the configuration of a power transmission device in one embodiment. FIG. 1A and FIG. 1B are both block diagrams showing an example of the configuration of a power receiving device. FIG. 1B is a flowchart showing the processing of a power transmission device in a first embodiment. FIG. 1C is a flowchart showing the processing of a power transmission device in a second embodiment. FIG. 1D is a flowchart showing the processing of a power transmission device in a third embodiment. FIG. 1E is a sequence diagram showing the control of a power transmission device and a power receiving device in accordance with the WPC standard.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Not all of the features in the embodiments of the present disclosure are essential, and multiple features may be combined as desired. Furthermore, the configurations shown in the following embodiments are merely examples, and the present disclosure is not limited to the illustrated configurations. In the drawings, the same reference symbols are used to designate the same or similar configurations, and redundant explanations will be omitted.

[0010] In the WPC standard, a power transmitting device transmits detection power (Analog Ping) that is weak enough to detect an object placed on the power transmitting device, thereby detecting that an object is placed on the power transmitting device. For example, if a power receiving device having a small coil that is not suitable for receiving power from a large power transmitting coil of the power transmitting device is placed on the power transmitting device, the power transmitting device may not be able to detect that the power receiving device has been placed on the power transmitting device using Analog Ping. This may result in inappropriate wireless power transmission. In contrast, the wireless power transmission technology disclosed herein enables appropriate wireless power transmission.

[0011] First Embodiment In the following embodiment, a wireless charging system to which a wireless power transmission system is applied will be described. As an example, wireless power transmission based on a standard established by the Wireless Power Consortium (WPC) (hereinafter referred to as the "WPC standard") will be described.

[0012] [System Configuration] The configuration of a system according to an embodiment will be described with reference to Figures 1A and 1B. Figure 1A is a diagram showing an example configuration of multiple power transmission coils 101 of a power transmission device 103 (Figure 2). The multiple power transmission coils 101 include, for example, a first power transmission coil 101a and a second power transmission coil 101b. The first power transmission coil 101a and the second power transmission coil 101b differ in size. Here, the coil size corresponds to the winding radius of the coil or the size of the coil in a planar view in Figure 1A (outer diameter of the coil). If the coil is not circular, the coil size is based on the maximum length from the center to the outer peripheral edge of the coil in a planar view.

[0013] In this embodiment, as shown in Fig. 1A, the first power transmitting coil 101a is larger than the second power transmitting coil 101b. The larger first power transmitting coil 101a is arranged on the outer periphery of the smaller second power transmitting coil 101b. In other words, the second power transmitting coil 101b is arranged inside the first power transmitting coil 101a. This allows space saving.

[0014] 1A, the centers of the first power transmitting coil 101a and the second power transmitting coil 101b are substantially at the same position, but they do not necessarily have to be at the same position. Furthermore, the first power transmitting coil 101a and the second power transmitting coil 101b may have different shapes. Alternatively, the shape of at least one of the first power transmitting coil 101a and the second power transmitting coil 101b is not limited to a curve and may be a straight line.

[0015] Hereinafter, when referring to a "power transmitting coil 101," it basically refers to either the first power transmitting coil 101 a or the second power transmitting coil 101 b. However, when referring to multiple power transmitting coils (for example, the first power transmitting coil 101 a and the second power transmitting coil 101 b), it will be referred to as "multiple power transmitting coils 101," "two power transmitting coils 101," or "those power transmitting coils 101."

[0016] 1B is a diagram showing an example of the configuration of a wireless power transmission system. The wireless power transmission system includes a power transmitting device 103 and a power receiving device 104. Hereinafter, the power transmitting device 103 may be referred to as a TX, and the power receiving device 104 may be referred to as an RX. The TX is, for example, an electronic device that wirelessly transmits power to an RX placed on the TX via a power transmitting coil 101. The RX is, for example, an electronic device that receives power from the TX and charges an internal battery.

[0017] Note that the charging mode is not limited to the case where the RX is placed on the TX. For example, the TX and RX may be in contact or close proximity to each other through mechanical engagement, or the RX may be in contact with the TX through magnetic force.

[0018] The TX may be a device that primarily has a power transmission function, or may be a device that primarily has a function other than power transmission. Similarly, the RX may be a device that primarily has a power receiving function, or may be a device that primarily has a function other than power receiving. Examples of devices that primarily have a function other than power transmission or a function other than power receiving include imaging devices, smartphones, tablet PCs, laptop PCs, automobiles, robots, medical equipment, printers, smartwatches, etc.

[0019] [Power Transmitting Device] Fig. 2 is a functional block diagram showing an example configuration of a TX. The TX has a control unit 201, a power supply unit 202, a power transmitting unit 203, a measurement unit 204, a communication unit 205, multiple power transmitting coils 101, a timer 206, a memory 207, an operation unit 208, and a notification unit 209. Note that although each functional block element is depicted as a separate entity in Fig. 2, any multiple functional block elements may be implemented on the same chip. Furthermore, the TX may have multiple control units 201, power supply units 202, and memories 207.

[0020] In this embodiment, for ease of explanation, the TX is described as having two power transmitting coils 101, but is not limited to this. For example, the TX may have three or more power transmitting coils.

[0021] The control unit 201 controls the entire TX by executing a control program stored in the memory 207. This realizes, for example, the processes shown in Figures 4 to 7 described below. The control unit 201 may also be configured to perform power transmission control, including communication for device authentication in the TX. Furthermore, the control unit 201 can perform control for executing applications other than wireless power transmission.

[0022] The control unit 201 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (Microprocessor Unit). Alternatively, the control unit 201 may be configured with hardware, such as an application-specific integrated circuit (ASIC). The control unit 201 may also include an array circuit, such as an FPGA (Field Programmable Gate Array), compiled to execute predetermined processes. The control unit 201 can store information to be stored during execution of various processes in a memory 207 and can perform timing processing using a timer 206.

[0023] The power supply unit 202 supplies power for operation of at least the control unit 201 and the power transmitting coil 101. The power supply unit 202 may be, for example, a wired power receiving circuit that receives power from a commercial power source, a battery, etc. The battery stores the power supplied from the commercial power source.

[0024] The power transmitting unit 203 converts the DC power or AC power input from the power supply unit 202 into AC power in a frequency band used for wireless power transmission, and inputs the AC power to the power transmitting coil 101, thereby generating electromagnetic waves for receiving power at the RX. For example, the power transmitting unit 203 includes an inverter, and converts the DC voltage supplied by the power supply unit 202 into an AC voltage using a switching circuit with a half-bridge or full-bridge configuration. The power transmitting unit 203 includes a plurality of FETs (Field Effect Transistors) that form a bridge, and a gate driver that controls the ON / OFF of the plurality of FETs.

[0025] The power transmitting unit 203 controls the intensity of the electromagnetic waves (transmission power) to be output by adjusting the voltage (transmission voltage) or current (transmission current), or both, input to the power transmitting coil 101. The strength of the electromagnetic waves (corresponding to the magnitude of the transmission power, hereinafter also referred to as intensity) is controlled by the magnitude of the transmission voltage or transmission current. For example, if the power transmitting unit 203 has an inverter, the intensity of the output electromagnetic waves is controlled by adjusting the voltage or current, or both, input to the inverter. Alternatively, the intensity of the output electromagnetic waves is controlled by adjusting the voltage or current, or both, output from the inverter included in the power transmitting unit 203. The control unit 201 controls the start and stop of power transmission by issuing instructions to the power transmitting unit 203, and also controls the intensity of the output electromagnetic waves. The power transmitting unit 203 performs output control related to the power of AC frequency electromagnetic waves based on instruction signals from the control unit 201, so as to start or stop power transmission by the power transmitting coil 101 or control the intensity of the output electromagnetic waves. Furthermore, the power transmitting unit 203 has a power supply capacity sufficient to output, for example, 15 watts (W) of power to the charging unit of the RX that complies with the WPC standard. In other words, the potential load power of the power transmitting unit 203 is 15 W. Note that while one block element is shown as the power transmitting unit 203 in FIG. 2 , the power transmitting unit 203 has the above-described configuration and functions for each power transmitting coil 101. As described below, the power transmitting unit 203 is an example of a power transmitting means that applies a power signal to detect the presence of an object. The power signal is, for example, a voltage signal or a current signal.

[0026] The measurement unit 204 is connected between the control unit 201 and the two power transmitting coils 101, and is configured to measure (acquire) the electrical characteristics of each of the two power transmitting coils 101, for example. Specifically, the measurement unit 204 measures the electrical characteristics of at least one of the multiple power transmitting coils 101 when a power signal for detecting the presence of an object is applied from the at least one coil. The object refers to an RX or a foreign object other than an RX. The control unit 201 detects an object (e.g., an RX) placed on the TX based on the amount of change in the electrical characteristics measured by the measurement unit 204. Part or all of the measurement unit 204 may be configured by hardware. The control unit 201 may have part or all of the functions of the measurement unit 204.

[0027] The electrical characteristics include a Q value, impedance, voltage, current, and / or resonant frequency (resonant frequency of a voltage signal or a current signal). When viewed from above in FIG. 1B (here, viewed from the top or bottom along the plane of FIG. 1B ), the electrical characteristics of the power transmitting coil 101 are determined by how much an object overlaps with the magnetic flux penetrating the power transmitting coil 101. The extent to which an object overlaps with the magnetic flux penetrating the power transmitting coil 101 can be considered as the area of ​​overlap between the object and the region enclosed by the outline of the power transmitting coil 101. For example, the electrical characteristics of the power transmitting coil 101 change between when there is no object on the power transmitting coil 101 and when at least a portion of the object overlaps the power transmitting coil 101. The electrical characteristics of the power transmitting coil 101 when there is no object on the power transmitting coil 101 may be stored in advance in the memory 207. The TX detects an object placed on the TX based on the amount of change. Details of the object detection process will be described later.

[0028] The control unit 201 and the measurement unit 204, or the control unit 201, are an example of a selection unit. The selection unit selects one of the multiple power transmitting coils to which a power signal for activating the power receiving device is applied, based on, for example, electrical characteristics when a power signal for detecting the presence of an object is applied from at least the first power transmitting coil. Note that the term "selection" refers to the selection of the coil to which a power signal for activating the power receiving device is applied.

[0029] The communication unit 205 is connected to the control unit 201 and the power transmitting unit 203, and performs communication with the RX for power transmission control based on the WPC standard. The communication unit 205 performs frequency shift keying of the electromagnetic waves output from the power transmitting coil 101, and transmits information to the RX to perform communication. The communication unit 205 also acquires information transmitted by the RX by demodulating the electromagnetic waves output from the power transmitting coil 101 and modulated by the RX. Communication by the communication unit 205 is performed by superimposing a communication signal on the electromagnetic waves transmitted from the power transmitting coil 101.

[0030] The memory 207 can store information about the TX and RX states in addition to the control program. The information about the TX and RX states includes the transmitted power value, the received power value, etc. The information about the TX state is acquired by the control unit 201 and received by the communication unit 205.

[0031] The notification unit 209 is connected to the control unit 201 and performs various outputs to the user. The notification unit 209 performs various operations such as screen display, blinking or color changing of an LED (Light Emitting Diode), audio output from a speaker, and vibration of the TX main body. The notification unit 209 is realized by a liquid crystal panel, a speaker, a vibration motor, etc.

[0032] The operation unit 208 is connected to the control unit 201 and has a function of receiving operations for the RX from the user. The operation unit 210 includes, for example, a voice input device such as a button, a keyboard, or a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, and other input devices. Note that a device in which the notification unit 209 and the operation unit 208 are integrated, such as a touch panel, may also be used.

[0033] [Power Receiving Device] Figures 3A and 3B are block diagrams showing configuration examples of the power receiving device 104. These power receiving devices 104 differ in that they have a power receiving coil 310a and a power receiving coil 310b of different sizes, but the other components are the same. The power receiving coil 310a of the power receiving device 104a shown in Figure 3A is larger than the power receiving coil 310b of the power receiving device 104b shown in Figure 3B. The meaning of the "size" of the coil is as described above. Note that, hereinafter, when the power receiving device 104a and the power receiving device 104b are to be distinguished from each other, they will be referred to as RX 104a and RX 104b, respectively. When there is no need to distinguish between them, they will be referred to as RX.

[0034] As shown in Fig. 3A, RX 104a has a control unit 301, a power receiving unit 302, a charging unit 303, a battery 304, a communication unit 305, a timer 306, a memory 307, an operation unit 308, a notification unit 309, and a power receiving coil 310a. RX 104a may have a plurality of control units 301, power receiving units 302, batteries 304, and / or memories 307. As shown in Fig. 3B, RX 104b has the same configuration as RX 104a except that, as described above, RX 104b has a power receiving coil 310b that is smaller than power receiving coil 310a. Typical examples include, but are not limited to, a smartphone as RX 104a and a smartwatch as RX 104b.

[0035] The control unit 301 controls each functional block element of the RX by executing a control program stored in the memory 307. The control unit 301 can perform control for executing applications other than wireless power transmission. The control unit 301 includes one or more processors such as a CPU or an MPU. The control unit 301 can also control the entire RX (e.g., the entire smartphone) in cooperation with an operating system (OS) running on the control unit 301. Alternatively, the control unit 301 can be configured with hardware such as an ASIC, or can include an array circuit such as an FPGA compiled to execute predetermined processes. The control unit 301 stores information to be stored during execution of various processes in the memory 307 and can also perform timing processing using a timer 306.

[0036] The notification unit 309 is connected to the control unit 301 and performs various outputs to the user. The specific configuration and functions of the notification unit 309 are similar to those of the notification unit 209 of the TX described above.

[0037] The operation unit 308 is connected to the control unit 301 and has a reception function for receiving operations for the RX from the user. The specific configuration and functions of the operation unit 308 are similar to those of the operation unit 208 for the TX described above.

[0038] The power receiving unit 302 receives, via the power receiving coil 310a (or 310b), AC power (AC voltage and AC current) generated by electromagnetic induction based on electromagnetic waves radiated from the power transmitting coil 101 of the TX. The power receiving unit 302 then converts the AC power into DC or AC power of a predetermined frequency and outputs the power to the charging unit 303. The charging unit 303 charges the battery 304. The power receiving unit 302 includes a rectifier (rectifier, rectifier circuit) and a voltage control unit required for supplying power to the load (charging unit 303) in the RX. The rectifier converts the AC voltage and AC current received from the power transmitting coil 101 via the power receiving coil 310 into DC voltage and DC current. The voltage control unit converts the level of the DC voltage input from the rectifier to a predetermined level. The predetermined level is a DC voltage level at which the control unit 301, the charging unit 303, and the like can operate. The power receiving unit 302 supplies power for charging the battery 304 via the charging unit 303. The power receiving unit 302 has a power supply capacity sufficient to output, for example, 15 W of power to the charging unit 303.

[0039] The communication unit 305 communicates with the communication unit 205 of the TX for power reception control based on the WPC standard. The communication unit 305 is connected to the power receiving coil 310a (or 310b) and the control unit 301. The communication unit 305 demodulates the electromagnetic waves input from the power receiving coil 310a (or 310b) to acquire information transmitted from the TX. The communication unit 305 performs load modulation or amplitude modulation on the input electromagnetic waves and superimposes a signal related to information to be transmitted to the TX on the electromagnetic waves, thereby communicating with the TX.

[0040] The memory 307 can store information about the states of the TX and RX in addition to the control program. Information about the state of the RX is acquired by the control unit 301. Information about the state of the TX is acquired by the control unit 201 of the TX and received by the communication unit 305.

[0041] [Processing Sequence of Power Transmitting Device and Power Receiving Device in WPC Standard] Fig. 7 is a sequence diagram showing the control of the TX and RX in accordance with the WPC standard. The TX applies an Analog Ping (hereinafter referred to as A-Ping) to detect an object present near the power transmitting coil 101 (F700). Here, the A-Ping is a pulsed power signal, and as described above, is a power signal for detecting the presence of an object. The power is so small that even if the RX receives the A-Ping, it cannot start up the RX. The A-Ping is applied, for example, at a constant cycle.

[0042] When the TX detects an object by A-Ping, it measures the Q value (quality factor) of the transmitting coil 101 (F701). After completing the Q value measurement, the TX starts applying a Digital Ping (hereinafter referred to as a D-Ping) from one selected from the multiple transmitting coils 101 (F702). The D-Ping is a power signal for activating the RX, and its power is greater than that of the A-Ping. The D-Ping is transmitted continuously thereafter. That is, the TX continues to apply power equal to or greater than that of the D-Ping from the time it starts applying the D-Ping (F702) until it receives EPT (End Power Transfer) data from the RX requesting that power transmission be stopped (F716).

[0043] When the RX receives a D-Ping and starts up, it transmits to the TX a Signal Strength, which is data storing the voltage value of the received D-Ping (F703). The RX then transmits data storing an ID, including version information of the WPC standard to which the power receiving device conforms and device identification information (F704). The RX then transmits Configuration data, including information such as the maximum value of power that the power receiving unit 302 supplies to a load (e.g., the charging unit 303) (F705). Upon receiving the ID and Configuration data, the TX determines that the RX supports the extended protocol (including the negotiation protocol described later) of the WPC standard v1.2 or later, and responds with an acknowledgement (ACK) (F706).

[0044] When the RX receives the ACK, it transitions to the Negotiation phase, where it negotiates the power to be transmitted and received. First, the RX transmits FOD (Foreign Object Detection) Status data to the TX (F707). In this embodiment, the FOD Status data is expressed as FOD(Q). The TX performs foreign object detection based on the Q value stored in the received FOD(Q) and the Q value measured in F701, and transmits an ACK to the RX indicating that it has determined that there is a high possibility that a foreign object is not present (F708).

[0045] When the RX receives the ACK, it transmits a packet inquiring about the capabilities of the TX (F717). Specifically, this is a packet of General Request (Capability) (represented as GRQ (CAP)), which is one of the General Requests defined in the WPC standard. When the TX receives the GRQ (CAP), it transmits Capability data (referred to as CAP) that stores the capability information supported by the TX itself (F718).

[0046] Next, the RX transmits a packet requesting the TX to transmit its identification information (F719). Specifically, this is a packet of General Request (ID) (referred to as GRQ(ID)), which is one of the General Requests defined in the WPC standard. When the TX receives the GRQ(ID), it transmits Identification data (referred to as ID) that stores its own identification information (F720). This ID includes the supported standard version, etc.

[0047] Next, the RX negotiates the Guaranteed Load Power (referred to as GP), which is the maximum power value that the RX requests to receive. Specifically, the GP is the power agreed upon in the negotiation with the TX. This negotiation is performed, for example, by transmitting Specific Request data defined in the WPC standard to the TX (F709). Specifically, the value of Requested Load Power, which is the power requested by the RX, is stored in the Specific Request data. In this embodiment, this data is represented as SRQ (GP). The TX responds to the SRQ (GP) taking into account its own power transmission capability, etc. If the TX can accept the power requested by the RX, it transmits an ACK (F710). The RX can request, for example, 5W as the Requested Load Power in the SRQ (GP), but it goes without saying that the power is not limited to 5W and may be 10W or 15W.

[0048] When the negotiation of multiple parameters including GP is completed, the RX transmits an SRQ (EN) of the Specific Request, which requests the end of the negotiation (End Negotiation), to the TX (F711). The TX transmits an ACK in response to the SRQ (EN) (F712) and ends the negotiation. Subsequently, the processing transitions to the Calibration phase and the Power Transfer phase.

[0049] In the Power Transfer phase, the RX transmits a Control Error (hereinafter referred to as CE) to the TX, requesting the TX to increase or decrease the receiving voltage (or receiving current, receiving power). CE stores a code and a value; if the code of the value stored in CE is positive, it requests that the receiving voltage be increased; if the code is negative, it requests that the receiving voltage be decreased; and if the value is zero, it requests that the receiving voltage be maintained. Here, the RX transmits a CE(+) to the TX, indicating that the receiving voltage should be increased (F713).

[0050] When the TX receives CE(+), it changes the setting value of the power transmission circuit to increase the transmission voltage. When the received power increases in response to CE(+), the RX supplies the received power to the charging unit 303, which is the load, and transmits a Received Power Packet (hereinafter referred to as RPP) to the TX (F714). Here, the RPP stores the received power value when the RX supplies the output of the power receiving unit 302 to the load (e.g., the charging unit 303).

[0051] When the TX receives the RPP, it performs foreign object detection. If the difference between the transmitted power value and the received power value when the RPP is received is equal to or greater than a threshold, it determines that a foreign object may be present. Note that, in this disclosure, a foreign object refers to an object that is not the RX or part of a product incorporating the RX, or the TX or part of a product incorporating the TX, but that may generate heat when exposed to a power signal. Examples of foreign objects include a paper clip or an IC card. Among the RX and a product incorporating the RX, or the TX and an object that is an integral part of a product incorporating the TX, an object that may unintentionally generate heat when exposed to wireless power transmitted by the transmitting coil 101 is not considered a foreign object.

[0052] If the TX determines that there is a high possibility that there is no foreign object as a result of foreign object detection, it transmits an ACK to the RX (F715). If it determines that there is a high possibility that there is a foreign object, the TX transmits a negative acknowledgement (NAK) to the RX. An authentication phase for authenticating the TX and the RX may also be inserted here (F721).

[0053] When charging of the battery 304 is completed, the RX transmits EPT (End Power Transfer) data requesting the TX to stop power transmission (F716). The above is the control sequence of the TX and RX in accordance with the WPC standard.

[0054] [Processing of Power Transmitting Device] The following describes a process in which the TX shown in Fig. 2 selects one of the multiple power transmitting coils 101 to be used for power transmission by the placed RX. In this embodiment, the selection of the power transmitting coil 101 is performed automatically, which can improve user convenience.

[0055] 4 is a flowchart showing the processing of the TX. When the TX starts the processing, it applies a power signal from the first power transmitting coil 101a at frequency x and from the second power transmitting coil 101b at frequency y (S401). This processing is for detecting (capturing) an object near the power transmitting coil 101 by A-Ping. Here, the frequencies x and y are assumed to be different values. This makes it possible to simultaneously detect an object from multiple power transmitting coils 101, thereby reducing the time required for RX detection.

[0056] It is determined whether the amount of change in the electrical characteristics of the first power transmitting coil 101a is equal to or greater than a threshold T1 (S402), and the result is stored in the memory 207. If the amount of change is equal to or greater than the threshold T1, the TX determines that an object has been detected near the first power transmitting coil 101a, and proceeds to S403.

[0057] The TX checks the amount of change in the electrical characteristics of the second power transmitting coil 101b and stores the amount of change in the memory 207. If the amount of change is equal to or greater than a threshold value T2 (Yes in S403), the TX determines that an object has been detected near the second power transmitting coil 101b. Here, the threshold value T1 is set to a value greater than the threshold value T2.

[0058] When the first power transmitting coil 101a and the second power transmitting coil 101b each detect an object near the power transmitting coil, the TX determines that it has detected the RX 104a having the large power receiving coil 310a. The TX then selects to use the first power transmitting coil 101a for the power transmitting process (S404). The power transmitting process here refers to, for example, the process from applying the D-Ping signal at F702 to receiving the EPT signal at F716.

[0059] If the change in the electrical characteristics does not exceed the threshold T2 (No in S403), the TX determines that no object has been detected near the second power transmitting coil 101b. In this case, the TX determines that there is a possibility that the RX is misaligned or that a foreign object other than the RX is present, because the TX has detected the first power transmitting coil 101a but has not detected an object near the second power transmitting coil 101b. If the result in S403 is No, the TX starts the process again from S401.

[0060] If the answer is No in S403, the TX may end the processing, or may change the thresholds T1 and T2 and start over. When ending the processing, the TX may loop S401 to S403 a predetermined number of times and then end the processing. Alternatively, the TX may store the transmission power value in memory 207 in order to limit and control the transmission power (for example, by setting GP to 5 W or less) in a subsequent charging (power transmission) sequence. Alternatively, the TX may issue a predetermined notification, such as a warning, via the notification unit 209.

[0061] If the amount of change as a result of applying A-Ping from the first power transmitting coil 101a in S402 is less than threshold T1, the TX checks the amount of change in the electrical characteristics of the second power transmitting coil 101b (S405). If the amount of change is greater than or equal to threshold T2, the TX determines that an object has been detected near the second power transmitting coil 101b. In other words, the TX was unable to detect an object with the first power transmitting coil 101a, but was able to detect an object with the second power transmitting coil 101b, and therefore determines that the RX 104b, which has a small power receiving coil 310b, has been detected. In this case, the TX selects to use the second power transmitting coil 101b for power transmission processing (S406).

[0062] If the amount of change is less than the threshold value T2 in S405, the TX determines that no object has been detected near the second power transmitting coil 101b. In this case, the TX has not detected any objects near both the first power transmitting coil 101a and the second power transmitting coil 101b, and therefore determines that no RX has been detected, and starts the process again from S401. Alternatively, if the answer is No in S405, the TX may end the process. When ending the process, the TX may end the process after looping S401, S402, and S405 a predetermined number of times.

[0063] After determining the power transmitting coil 101 to be used for power transmission processing, the TX executes the charging sequence (F700 to F716) of the WPC standard shown in FIG. 7 (S407) to perform charging. As described above, the process of S403 may be able to detect the presence of a foreign object. Therefore, if the determination in S403 is No, it may be determined that a foreign object has been detected in F700 of FIG. 7. Alternatively, in F700, the TX may perform foreign object detection using yet another threshold value based on the amount of change in the electrical characteristics of the power transmitting coil 101.

[0064] As described above, in this embodiment, the TX selects one power transmitting coil to which a power signal for activating the RX is applied based on the electrical characteristics when power signals for detecting the presence of an object are applied from the multiple power transmitting coils 101. This allows the TX to automatically select a power transmitting coil 101 that is suited to the size of the power receiving coil possessed by the RX, regardless of the user's selection. In other words, it is possible to perform appropriate power transmission processing according to the size of the power receiving coil possessed by the power receiving device. Furthermore, automatic selection of the power transmitting coil 101 improves user convenience.

[0065] After a coil to which a power signal to activate the power receiving device is applied is selected, if there is no response to the power signal, the TX determines that the detected object is a foreign object and stops applying the power signal from the selected coil. On the other hand, after a coil to which a power signal to activate the power receiving device is applied is selected, if there is a response to the power signal, the TX determines that the detected object is an RX and continues applying the power signal from the selected coil.

[0066] Second Embodiment Next, a second embodiment will be described. In the second embodiment, an example of a wireless charging system will be described, similar to the first embodiment. In the second embodiment, the system configuration, the TX configuration, the RX configuration, and the processing sequence of the power transmitting device and the power receiving device in accordance with the WPC standard are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0067] 5 is a flowchart showing the processing of the TX. When the TX starts the processing, it applies an A-Ping from the second power transmitting coil 101b in order to detect an object near the power transmitting coil 101 (S501).

[0068] The TX determines whether the amount of change in the electrical characteristics of the second power transmitting coil 101b is equal to or greater than a threshold T2 (S502), and stores the result in the memory 207. If the amount of change is less than the threshold T2, the TX determines that an object has not been detected near the second power transmitting coil 101b, and starts the process again. The process may end here.

[0069] If the amount of change is equal to or greater than the threshold value T2 in S502, the TX applies an A-Ping from the first power transmitting coil 101a (S503). The frequency of the A-Ping applied from the first power transmitting coil 101a may be the same as or different from the frequency of the A-Ping applied from the second power transmitting coil 101b in S501.

[0070] The TX determines whether the amount of change in the electrical characteristics of the first power transmitting coil 101a is equal to or greater than a threshold T1 (S504), and stores the result in the memory 207. If the amount of change is equal to or greater than the threshold T1, the TX determines that an object has been detected near the first power transmitting coil 101a, and stores the result in the memory 207.

[0071] When the TX detects an object near the first power transmitting coil 101a, it determines that it has detected the RX 104a having the large power receiving coil 310a. In this case, the TX selects to use the first power transmitting coil 101a for the power transmission process (S505).

[0072] If the amount of change is less than the threshold T1 in S504, the TX did not detect an object using the first power transmitting coil 101a, but because the amount of change in S502 was equal to or greater than the threshold T2, the TX determines that an object was detected using the second power transmitting coil 101b. In other words, the TX determines that it has detected the RX 104b having the small power receiving coil 310b. The TX then stores the result in the memory 207. In this case, the TX selects to use the second power transmitting coil 101b for power transmission processing (S506).

[0073] After determining the power transmitting coil 101 to be used for the power transmission process, the TX executes the charging sequence (F700 to F716) of the WPC standard shown in FIG. 7 (S507) to perform charging.

[0074] As described above, according to this embodiment, it is possible to obtain the same effects as those of the first embodiment. Furthermore, in this embodiment, if an object cannot be detected by the second power transmitting coil 101b, which consumes less power (No in S502), the process returns to S501 or ends. In other words, A-Ping is not applied from the first power transmitting coil 101a. As a result, this embodiment can achieve more power saving in TX than the first embodiment. Furthermore, since A-Ping is not applied from the first power transmitting coil 101a, it is possible to suppress the generation of noise.

[0075] Third Embodiment Next, a third embodiment will be described. In the third embodiment, an example of a wireless charging system will be described, similar to the first and second embodiments. In the third embodiment, the system configuration, the TX configuration, the RX configuration, and the processing sequences of the power transmitting device and the power receiving device in the WPC standard are the same as those in the first and second embodiments, and therefore description thereof will be omitted.

[0076] 6 is a flowchart showing the processing of the TX. When the TX starts the processing, it applies an A-Ping from the first power transmitting coil 101a in order to detect an object near the power transmitting coil 101 (S601).

[0077] The TX determines whether the amount of change in the electrical characteristics of the second power transmitting coil 101b is equal to or greater than a threshold T1 (S602) and stores the result in the memory 207. If the amount of change is equal to or greater than the threshold T1, the TX determines that an object has been detected near the first power transmitting coil 101a. In this case, the TX determines that it has detected the RX 104a having the large power receiving coil 310a, and selects to use the first power transmitting coil 101a for power transmission processing (S603).

[0078] If the amount of change is less than the threshold value T1 in S602, the TX applies an A-Ping from the second power transmitting coil 101b (S604). The frequency of the A-Ping applied from the second power transmitting coil 101b may be the same as or different from the frequency of the A-Ping applied from the first power transmitting coil 101a in S601.

[0079] The TX determines whether the amount of change in the electrical characteristics of the second power transmitting coil 101b is equal to or greater than a threshold T2 (S605) and stores the result in the memory 207. If the amount of change is equal to or greater than the threshold T2, the TX determines that an object was not detected by the first power transmitting coil 101a, but that an object was detected by the second power transmitting coil 101b because the amount of change was equal to or greater than the threshold T2 in S605. In other words, the TX determines that it has detected the RX 104b having the small power receiving coil 310b. The TX then stores the result in the memory 207. In this case, the TX selects to use the second power transmitting coil 101b for power transmission processing (S606).

[0080] After determining the power transmitting coil 101 to be used for the power transmission process, the TX executes the charging sequence (F700 to F716) of the WPC standard shown in FIG. 7 (S607) to perform charging.

[0081] As described above, according to this embodiment, it is possible to obtain the same effects as those of the first embodiment. Furthermore, in this embodiment, if an object is detected by the first power transmitting coil 101a (Yes in S602), A-Ping is not applied from the second power transmitting coil 101b. Therefore, power saving of the TX can be achieved. Furthermore, since A-Ping is not applied from the second power transmitting coil 101b, it is possible to suppress the generation of noise.

[0082] In the above embodiment, A-Ping is used as the power signal for detecting the presence of an object. However, the power signal for detecting the presence of an object may be other than A-Ping, for example, a power signal with a power different from that of A-Ping.

[0083] In the above embodiment, as shown in FIG. 1A , a configuration in which the second power transmitting coil 101b is arranged on the same plane inside the first power transmitting coil 101a has been exemplified. However, the two coils do not have to be arranged on the same plane. For example, the multiple power transmitting coils may be arranged so that they are offset in the vertical direction (perpendicular to the plane) when viewed in cross section. Furthermore, for example, the multiple power transmitting coils may be arranged so that at least a portion of them overlap each other in a planar view, but they may also be arranged so that they are offset in the vertical direction (perpendicular to the plane) when viewed in cross section. Even with such a configuration, the same embodiment as described above can be realized by appropriately setting the threshold value for the amount of change in the electrical characteristics.

[0084] In an embodiment of the present disclosure, at least a portion of the processes shown in the flowcharts of Figures 4, 5, and 6 may be implemented by hardware. For example, by using a predetermined compiler, a dedicated circuit can be automatically generated on an FPGA from a program for implementing each step. Alternatively, a gate array circuit may be formed in the same manner as an FPGA and implemented as hardware.

[0085] The power transmitting device and the power receiving device may be, for example, an image input device such as an imaging device (such as a camera or a video camera) or a scanner, or an image output device such as a printer, a copier, a projector, etc. Furthermore, they may be storage devices such as a hard disk drive or a memory device, or information processing devices such as a personal computer (PC) or a smartphone.

[0086] The power receiving device of the present disclosure may also be an information terminal device. For example, the information terminal device has a display unit (display) that receives power from a power receiving antenna and displays information to a user. The power received from the power receiving antenna is stored in a power storage unit (battery), and power is supplied from the battery to the display unit. In this case, the power receiving device may have a communication unit that communicates with another device different from the power transmitting device. The communication unit may be compatible with communication standards such as NFC communication and the fifth generation mobile communication system (5G).

[0087] The power receiving device of the present disclosure may also be a vehicle such as an automobile. For example, the automobile serving as the power receiving device may receive power from a charger (power transmitting device) via a power transmitting antenna installed in a parking lot. The automobile serving as the power receiving device may also receive power from the charger (power transmitting device) via a power transmitting antenna embedded in the road. In such an automobile, the received power is supplied to a battery. The battery power may be supplied to a driving unit (motor, electric unit) that drives the wheels, or may be used to drive a sensor used for driving assistance or a communication unit that communicates with an external device. In other words, in this case, the power receiving device may include, in addition to the wheels, a battery, a motor or sensor that is driven using the received power, and even a communication unit that communicates with devices other than the power transmitting device. Furthermore, the power receiving device may have a storage unit for accommodating a person. For example, the sensor may be a sensor used to measure the distance between vehicles or the distance to other obstacles. The communication unit may be compatible with, for example, the Global Positioning System (GPS), or may be compatible with a communication standard such as the fifth generation mobile communication system (5G). The vehicle may be a bicycle or a motorcycle.

[0088] The power receiving device of the present disclosure may also be an electric tool, a home appliance, or the like. These devices, which are power receiving devices, may have a battery and a motor that is driven by the received power stored in the battery. These devices may also have a notification means for notifying the remaining battery charge, etc. These devices may also have a communication unit that communicates with other devices different from the power transmitting device. The communication unit may be compatible with communication standards such as NFC and the fifth generation mobile communication system (5G).

[0089] The power transmission device of the present disclosure may also be an on-board charger that transmits power to a mobile information terminal device, such as a smartphone or tablet, that supports wireless power transmission within the vehicle. Such an on-board charger may be installed anywhere within the vehicle. For example, the on-board charger may be installed in the console of the vehicle, on the instrument panel (instrument panel, dashboard), between passenger seats, on the ceiling, or in the door. However, it is preferable that the on-board charger is not installed in a location that interferes with driving. Furthermore, although the power transmission device has been described using the example of an on-board charger, such a charger is not limited to being installed in a vehicle, but may also be installed in transportation such as a train, airplane, or ship. In this case, the charger may also be installed between passenger seats, on the ceiling, or in the door.

[0090] The power transmitting device may also be a vehicle such as an automobile equipped with an on-board charger. In this case, the power transmitting device has wheels and a battery, and supplies power to the power receiving device via a power transmitting circuit unit and a power transmitting antenna using power from the battery.

[0091] The present disclosure has been described in detail above based on preferred embodiments thereof, but the present disclosure is not limited to the above embodiments, and various modifications are possible based on the gist of the present disclosure, and these modifications are not excluded from the scope of the present disclosure.

[0092] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Japanese Patent Application No. 2024-070264, filed on April 24, 2024. The contents of the above Japanese patent application are incorporated herein by reference in their entirety.

Claims

1. A power transmission device comprising: a plurality of coils including a first coil and a second coil placed inside the first coil; power transmission means for applying a power signal for detecting the presence of an object from each of the plurality of coils; and selection means for selecting one of the plurality of coils to which a power signal for starting a power receiving device is applied, based on electrical characteristics when a power signal for detecting the presence of an object is applied from at least the first coil.

2. The power transmitting device according to claim 1, wherein the selection means selects the one coil based on the result of comparing the amount of change in the electrical characteristic with different threshold values.

3. The power transmission device according to claim 1 or 2, characterized in that the power transmission means simultaneously applies a plurality of power signals with different frequencies from the plurality of coils, and the selection means selects one coil from the plurality of coils to which a power signal that activates the power receiving device is applied based on electrical characteristics when a plurality of power signals with different frequencies are simultaneously applied from the plurality of coils.

4. The power transmitting device according to claim 1, characterized in that the selection means acquires the electrical characteristics of the first coil after acquiring the electrical characteristics of the second coil.

5. The power transmitting device according to claim 1, wherein the selection means acquires the electrical characteristics of the first coil and then acquires the electrical characteristics of the second coil.

6. The power transmitting device according to any one of claims 1 to 5, wherein the power signal for detecting the presence of an object is an Analog Ping standard of the Wireless Power Consortium (WPC).

7. The power transmitting device according to any one of claims 1 to 6, wherein the power signal that activates the power receiving device is a Digital Ping signal conforming to the Wireless Power Consortium (WPC) standard.

8. A method performed by a power transmission device having multiple coils including a first coil and a second coil placed inside the first coil, the method comprising: an application step of applying a power signal for detecting the presence of an object from at least the first coil; and a selection step of selecting one coil from the multiple coils to which a power signal for starting up a power receiving device is applied based on electrical characteristics when the power signal for detecting the presence of an object is applied from at least the first coil.

9. A program for causing a computer to execute the method according to claim 8.

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