Power transmission device, transmission method, and program

Abstract

To reduce transmission of a large power in the case where an inadequacy object is mounted onto a power transmission device when transmitting the large power.SOLUTION: A power transmission device includes: power transmission means for performing power transmission in radio to a power reception device; transmission means for transmitting a signal; and acquisition means for acquiring a value related to a Q factor. The transmission means transmits a first signal. The transmission means transmits a second signal activating the power reception device in the case where the value acquired by the acquirement means after the transmission of the first signal exceeds a threshold. The transmission means transmits a third signal, and the transmission means transmits the first signal in the case where the presence / absence of an object satisfies a predetermined condition after the transmission of the third signal.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a power transmission device, a transmission method, and a program of a wireless power transmission system.

Background Art

[0002] In recent years, the technological development of wireless power transmission systems has been widely carried out. In Patent Document 1, a power transmission device and a power reception device compliant with the standards established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards, are disclosed. Further, Patent Document 2 discloses a power transmission device that intermittently and repeatedly outputs detection power and outputs authentication power transmission when the presence of an object to be powered is detected in a plurality of consecutive outputs. In the WPC standard, the power transmission device first transmits a signal of detection power (Analog Ping) of power weak enough not to activate the power reception device to detect an object placed within the power transmission range. Subsequently, when it is detected that an object is placed on the power transmission device, a signal of communication power (Digital Ping) for wireless communication with the power reception device, which has power sufficient to activate the power reception device, is transmitted to perform communication.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, for example, there may be a case where a power receiving device having a small power receiving coil on which power transmission by the power transmission device is not assumed is placed on a large power transmission coil of the power transmission device. In such a case, since the coupling coefficient between the power transmission coil and the power receiving coil is low, the transmission efficiency decreases, which may cause heat generation in the power receiving device. Therefore, in Digital Ping that transmits a larger amount of power compared to Analog Ping, the heat generation in the power receiving device also increases, which may cause damage or malfunction of the electronic components included in the power receiving device.

[0005] In view of such problems, an object of the present invention is to reduce the transmission of a large amount of power when an inappropriate object is placed on the power transmission device during the transmission of a large amount of power.

Means for Solving the Problems

[0006] In order to solve the above-described problems, a power transmission device according to the present invention includes a power transmission means for wirelessly transmitting power to a power receiving device, a transmission means for transmitting a signal, and an acquisition means for acquiring a value related to the Q factor. Receiving means for receiving identification information from the power receiving device, The transmission means transmits a first signal. After transmitting the first signal, when the value acquired by the acquisition means exceeds a threshold value, the transmission means transmits a second signal for activating the power receiving device. The transmission means transmits a third signal. After transmitting the third signal, when the presence or absence of an object satisfies a predetermined condition, the transmission means transmits the first signal.

Effects of the Invention

[0007] According to the present invention, it is possible to reduce the transmission of a large amount of power when an inappropriate object is placed on the power transmission device during the transmission of a large amount of power.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention according to the claims, and not all combinations of the features described in the present embodiments are essential for the solution means of the present invention. The same components are denoted by the same reference numerals, and the description thereof is omitted.

[0010] <Embodiment 1> Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following embodiments are merely examples for explaining the technical idea of the present invention, and it is not intended to limit the present invention to the configurations and methods described in the embodiments.

[0011] (Configuration of the system) Fig. 1 shows a configuration example of a wireless power transmission system (wireless charging system) according to this embodiment. This system is configured to include a power receiving device 101 and a power transmitting device 102 in one example. Hereinafter, the power receiving device 101 may be referred to as RX, and the power transmitting device 102 may be referred to as TX. RX is an electronic device that receives wireless power from TX and charges a built-in battery. TX is an electronic device that wirelessly transmits power to RX placed on a charging stand 103 which is a part of TX. Hereinafter, since the charging stand 103 is a part of TX, "placed on the charging stand 103" may be referred to as "placed on the power transmitting device" in some cases. 104 is a range (power transmission range) in which RX can receive power from TX. Note that RX and TX may have functions to execute applications other than wireless charging.

[0012] This system is assumed to perform wireless power transmission using an electromagnetic induction method for wireless charging based on the WPC (Wireless Power Consortium) standard. That is, RX and TX perform wireless power transmission for wireless charging based on the WPC standard between a power receiving coil (power receiving antenna) of RX and a power transmitting coil (power transmitting antenna) of TX. Note that the wireless power transmission method is not limited to the method defined by the WPC standard, and other electromagnetic induction methods, magnetic field resonance methods, electric field resonance methods, microwave methods, methods using lasers, etc. may be used. Also, in this embodiment, it is assumed that wireless power transmission is used for wireless charging, but wireless power transmission may be performed for applications other than wireless charging.

[0013] In the WPC standard, the magnitude of power guaranteed when RX receives power from TX is defined by a value called Guaranteed Power (GP). GP indicates a power value that is guaranteed to be output to a load of RX such as a charging circuit even if, for example, the positional relationship between RX and TX changes and the power transmission efficiency between the power receiving coil and the power transmitting coil decreases. For example, when GP is 5 watts, even if the positional relationship between the power receiving coil and the power transmitting coil changes and the power transmission efficiency decreases, TX controls power transmission so that 5 watts can be output to the load in RX.

[0014] In addition, the RX and TX according to this embodiment can perform communication for power transmission and reception control based on the WPC standard.

[0015] First, the processing (phases) based on the WPC standard will be described. The WPC standard defines a plurality of phases, including the Power Transfer phase in which power transmission is executed and the phases before the actual power transmission, and communication for power transmission control required in each phase is performed. The phases before power transmission include the Selection phase, the Ping phase, the Identification and Configuration phase, the Negotiation phase, and the Calibration phase. Hereinafter, the Identification and Configuration phase will be referred to as the I&C phase.

[0016] In the Selection phase, the TX intermittently transmits an Analog Ping to detect the presence of an object within the power transmission range 104 (for example, the receiving device 101, a conductor piece, etc. being placed on the charging stand 103). In the Ping phase, the TX transmits a Digital Ping and recognizes that the detected object is the RX by receiving a response from the RX that has received the Digital Ping. In the I&C phase, the RX notifies the TX of the identification information and the capability information. In the Negotiation phase, the value of the GP is determined based on the value of the GP required by the RX, the power transmission capability of the TX, etc. In the Calibration phase, based on the WPC standard, the RX notifies the TX of the received power value, and the TX performs adjustments for efficient power transmission. In the Power Transfer phase, control is performed for the continuation of power transmission, and for stopping power transmission due to errors, full charge, etc. The TX and the RX perform communication for these power transmission and reception controls by means of a first communication in which signals are superimposed using the same coil (antenna) as that for wireless power transmission based on the WPC standard. Note that the range within which the first communication based on the WPC standard is possible between the TX and the RX is almost the same as the power transmission possible range. In FIG. 1, the range 104 represents the range within which wireless power transmission and the first communication are possible by the power transmission and reception coils of the TX and the RX. Note that in the following description, for the RX to be "placed" means that the RX has entered the inside of the range 104, and actually includes a state where the RX is not placed on the charging stand 103.

[0017] (Device Configuration) Subsequently, the configurations of the receiving device 101 (RX) and the power transmission device 102 (TX) according to the present embodiment will be described. Note that the configurations described below are merely examples, and a part (in some cases, all) of the described configurations may be replaced with other configurations that perform the same functions or omitted, and further configurations may be added to the described configurations. Furthermore, one block shown in the following description may be divided into a plurality of blocks, or a plurality of blocks may be integrated into one block.

[0018] FIG. 2 is a diagram showing a configuration example of the RX according to the present embodiment. It is assumed that the RX complies with the standards established by the Wireless Power Consortium (WPC), a standardization organization for wireless charging standards.

[0019] In one example, the RX includes a control unit 201, a battery 202, a power receiving unit 203, a power receiving coil 204, a charging unit 205, a communication unit 206, a display unit 207, an operation unit 208, a memory 209, and a timer 210.

[0020] The control unit 201 controls the operation of the entire RX by executing, for example, a control program stored in the memory 210. In one example, the control unit 201 performs control necessary for power reception in the RX. The control unit 201 may perform control for executing applications other than wireless power transmission. 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 dedicated hardware for specific processing such as an application-specific integrated circuit (ASIC) or an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 201 stores information to be stored during the execution of various processes in the memory 210. Also, the control unit 201 can measure time using the timer 211.

[0021] The battery 202 supplies power necessary for control, power reception, and communication to the entire RX. Also, the battery 202 can store the power received via the power reception coil 204. The power reception coil 204 receives the electromagnetic wave energy radiated from the transmission coil 304 of the TX, and the power reception unit 203 acquires the AC power generated via the power reception coil 204. Then, the power reception unit 203 converts the AC power into DC or AC power of a predetermined frequency, and outputs the power to a charging unit 205 that performs a process for charging the battery 202. That is, the power reception unit 203 supplies power to the load in the RX. The above-mentioned GP is the amount of power guaranteed to be output from the power reception unit 203. The communication unit 206 performs control communication based on the WPC standard as described above with the TX by the first communication. The communication unit 206 performs control communication for wireless charging based on the WPC standard with the communication unit of the transmission device. The control communication is a so-called first communication that load-modulates the electromagnetic wave received by the power reception coil 204. However, this may be a second communication that uses a frequency different from the frequency of the transmission unit 303, rather than the first communication. The second communication may be NFC or RFID or Wi-Fi (registered trademark) or Bluetooth (registered trademark). The display unit 207 presents information to the user by any method such as visual, auditory, or tactile. The display unit 207 notifies the user of, for example, the state of the RX or the state of the wireless power transmission system including the TX and the RX as shown in FIG. 1. The display unit 207 is configured to include, for example, a liquid crystal display, an LED, a speaker, a vibration generation circuit, and other notification devices. The operation unit 208 has a reception function for receiving an operation on the RX from the user. The operation unit 208 is configured to include, for example, a button, a keyboard, a voice input device such as a microphone, a motion detection device such as an acceleration sensor or a gyro sensor, or other input devices. Note that a device in which the display unit 207 and the operation unit 208 are integrated, such as a touch panel, may be used. The memory 209 stores various information as described above. Note that the memory 209 may store information obtained by a functional unit different from the control unit 201.The timer 210 measures time, for example, by an up-counter timer that measures the elapsed time since the start time, a down-counter timer that counts down from a set time, or the like.

[0022] FIG. 3 is a diagram showing a configuration example of the TX according to the present embodiment. In one example, the TX includes a control unit 301, a power supply unit 302, a power transmission unit 303, a power transmission coil 304, a communication unit 305, a detection unit 306, a determination unit 307, a display unit 308, an operation unit 309, a memory 310, and a timer 311.

[0023] The control unit 301 controls the overall operation of the TX by executing, for example, a control program stored in the memory 310. In one example, the control unit 301 performs control necessary for power transmission in the TX. The control unit 301 may perform control for executing applications other than wireless power transmission. The control unit 301 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 301 may include dedicated hardware for specific processing such as an application-specific integrated circuit (ASIC) or an array circuit such as an FPGA (Field Programmable Gate Array) compiled to execute predetermined processing. The control unit 301 stores information to be stored during the execution of various processes in the memory 310. Also, the control unit 301 can measure time using the timer 311.

[0024] The power supply unit 302 supplies power necessary for control, power transmission, and communication to the entire TX. The power supply unit 302 is, for example, a commercial power supply or a battery.

[0025] The power transmission unit 303 converts the DC or AC power input from the power supply unit 302 into AC frequency power in the frequency band used for wireless power transmission, and generates an electromagnetic wave for causing power reception at the RX by inputting the AC frequency power to the power transmission coil 304. Note that the frequency of the AC power generated by the power transmission unit 303 is about several hundred kHz (for example, 87 kHz to 205 kHz). The power transmission unit 303 inputs the AC frequency power to the power transmission coil 304 so as to output an electromagnetic wave for power transmission to the RX from the power transmission coil 304 based on an instruction from the control unit 301. Further, the power transmission unit 303 controls the intensity of the output electromagnetic wave by adjusting the voltage (transmission voltage) or current (transmission current) input to the power transmission coil 304. When the transmission voltage or transmission current is increased, the intensity of the electromagnetic wave becomes stronger, and when the transmission voltage or transmission current is decreased, the intensity of the electromagnetic wave becomes weaker. Also, the power transmission unit 303 performs output control of the AC frequency power so that power transmission from the power transmission coil 304 is started or stopped based on an instruction from the control unit 301. Note that in the present embodiment, the power transmission unit 303 and the power transmission coil 304 are collectively referred to as a power transmission circuit.

[0026] The detection unit 306 detects whether an object is placed within the power transmission range (range 104) based on the WPC standard. The detection unit 306 detects, for example, the voltage value or current value of the power transmission coil 304 when the power transmission unit 303 transmits an Analog Ping of the WPC standard via the power transmission coil 304. Then, the detection unit 306 can determine that an object exists in the range 104 when the voltage falls below a predetermined voltage value or the current value exceeds a predetermined current value. Whether this object is the RX or another foreign object is determined to be the RX when a predetermined response is received for the Digital Ping transmitted in the first communication by the communication unit 305 subsequently.

[0027] The communication unit 305 performs control communication based on the WPC standard as described above with the RX by means of the first communication. In this embodiment, the communication performed by the communication unit 305 is the so-called first communication that modulates the electromagnetic wave output from the power transmission coil 304 and superimposes communication on the wireless power. However, this may be the second communication that uses a frequency different from the frequency of the power transmission unit instead of the first communication. The second communication may be NFC or RFID or Wi-Fi (registered trademark) or Bluetooth (registered trademark). The communication unit 305 modulates the electromagnetic wave output from the power transmission coil 304 to transmit information to the RX. Also, the communication unit 305 demodulates the electromagnetic wave output from the power transmission coil 304 and modulated at the RX to obtain the information transmitted by the RX. That is, the communication performed by the communication unit 305 is performed superimposed on the power transmission from the power transmission coil 304.

[0028] The display unit 308 presents information to the user by any method such as vision, audition, touch, etc. The display unit 308 notifies the user, for example, of the state of the TX or information indicating the state of the wireless power transmission system including the TX and the RX as shown in FIG. 1. The display unit 308 is configured to include, for example, a liquid crystal display, an LED, a speaker, a vibration generation circuit, and other notification devices. The operation unit 309 has a reception function of receiving an operation on the TX from the user. The operation unit 309 is configured to include, for example, a button, a keyboard, a voice input device such as a microphone, a motion detection device such as an acceleration sensor and a gyro sensor, or other input devices. Note that a device in which the display unit 308 and the operation unit 309 are integrated, such as a touch panel, may be used. The memory 310 stores various information as described above. Note that the memory 310 may store information obtained by a functional unit different from the control unit 301. The timer 311 measures time, for example, by an up-counter that measures the elapsed time from the start time or a down-counter that counts down from the set time.

[0029] The above is the system configuration and device configuration of the WPC (Wireless Power Consortium) standard defined by the WPC. In one example, one or more components including the control unit 201 of the power receiving device 101, or one or more components including the control unit 301 of the power transmitting device 102 may be implemented by a computer.

[0030] As described above, in the Selection phase, the TX intermittently transmits an Analog Ping. After detecting the presence of an object within the power transmission range, it transitions to the Ping phase, and the TX transmits a Digital Ping. The presence of an object within the power transmission range includes, for example, the power receiving device 101 being placed on the charging stand 103 or a conductor piece being placed.

[0031] In the WPC standard, the Analog Ping transmitted by the above TX is a signal with a weak power that does not activate the power receiving device. On the other hand, the Digital Ping is a signal with sufficient power to activate the power receiving device and has a stronger power than the Analog Ping.

[0032] Here, as shown in FIG. 4, consider the case where a small power receiving device 404 having a power receiving coil 405 for receiving small power is placed inside a large power transmitting coil 403 of a power transmitting device 401 that transmits large power. In this case, the power transmitting device 401 detects the placement of the power receiving device 404 on the power transmitting device 401 with an Analog Ping and transmits a Digital Ping to the small power receiving device 404. As described above, the Digital Ping also transmits power sufficient to activate the power receiving device to the power receiving device. For this reason, the power receiving device 404 will be exposed to electromagnetic energy in parts other than the power receiving coil 405, which may cause, for example, an increase in the temperature of the housing of the power receiving device 404 or damage to electronic components within the power receiving device 404. Also, a large amount of the power of the Digital Ping transmitted from the power transmitting device 401 that is not consumed by the power receiving device 404 will be radiated as noise to the surroundings, which is a problem.

[0033] To solve the above problems, when the power transmission device 401 detects that an object is placed on the power transmission device 401 by Analog Ping, it transmits a signal with a power (judgment power) as weak as that of Analog Ping without transmitting Digital Ping. Then, based on the electrical response to the judgment power, it is determined whether the object placed on the power transmission device 401 is an inappropriate object for power transmission. And when it is determined that the object placed on the power transmission device 401 does not satisfy a predetermined condition, it is prevented from proceeding to the Ping phase. That is, a signal stronger than Analog Ping (Digital Ping) is not transmitted to the object. In addition, to realize the above, the power transmission device 102 includes a determination unit (307 in FIG. 3) for determining whether the object placed on the power transmission device 102 satisfies a predetermined condition.

[0034] The processing flow of the power transmission device 102 and the details of the configuration of the power transmission device 102 for solving the above problems will be described below. FIG. 5 shows the processing flow of the power transmission device 102. After the power transmission device 102 is started (S501), it shifts to the Selection phase and transmits an Analog Ping (S502) to detect whether an object is placed on the power transmission device 102 (S503). If the placement of the object is not detected, after waiting for a predetermined time with a timer (S504), the Analog Ping is transmitted again. That is, the power transmission device periodically transmits the Analog Ping to detect whether an object is placed on the power transmission device 102. When the Analog Ping is transmitted and it is detected that an object is placed on the power transmission device, the power transmission device transmits a signal of determination power as weak as the Analog Ping (S505). Subsequently, it is determined whether the object placed on the power transmission device 102 satisfies a predetermined condition as a power transmission target (S506). If it is determined that the predetermined condition is satisfied, it shifts to the Ping phase and transmits a Digital Ping to the object (S507). Then, it shifts to the Identification and Configuration phase (S508) and the Negotiation phase (S509) to perform predetermined operations. Subsequently, it shifts to the Calibration phase (S510) and the Power Transfer phase (S511) to perform power transmission processing. If it is determined that the object does not satisfy the predetermined condition as a power transmission target, it does not shift to the Ping phase and ends without transmitting the Digital Ping. At this time, in order to let the user recognize that an inappropriate object that does not satisfy the predetermined condition is placed on the power transmission device, for example, information indicating that an inappropriate object is placed may be displayed on the display unit 308 of the power transmission device (S512). In the present embodiment, the determination power may be any power smaller than the Digital Ping. In one example, it is the same power as the Analog Ping.

[0035] The following describes a method for determining whether an object placed on a power transmission device meets a predetermined condition, that is, whether the object is an inappropriate object for power transmission or whether the placement is inappropriate. FIG. 6 is a schematic circuit diagram for explaining the measurement for performing the determination. 601 is the AC power generated by the power transmission unit 303. 602 is the power transmission coil 304. 603 is a resonant capacitor and is included in the power transmission unit 303. The voltage value V1 is the voltage value of a predetermined frequency for operating the wireless power transmission system, which is applied to the power transmission unit of the power transmission device, and the voltage value V2 is the voltage value applied to the power transmission coil. Here, the power transmission device can change the frequency of the voltage value. Also, the voltage values V1 and V2 are weak powers to the extent that the power receiving device is not activated even if the power receiving device is placed on the power transmission device. Since the voltage values V1 and V2 are AC, the effective value (RMS) may be used.

[0036] The fact that an object is placed on the power transmission device means that the object is placed near the power transmission coil 602. Here, it is assumed that the power transmission coil 602 of the power transmission device is a single large coil. Consider the voltage ratio V2 / V1 of V1 and V2 shown in FIG. 6. Since the voltage ratio V2 / V1 is the Q factor of the power transmission coil 602, when an object is placed near the power transmission coil 602, this Q factor also changes. An example of the relationship between the voltage ratio V2 / V1, which is the Q factor, and the frequency of the transmitted power is shown in FIG. 7. The change in the Q factor varies depending on the size of the object, the material of the object, the arrangement relationship between the power transmission coil and the object, and the like.

[0037] Therefore, for example, by creating a table that holds correlation information associating V2 / V1 measured at a predetermined frequency with the size of the object, and making a determination based on this, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as the power transmission target. As a result, even if a small power receiving device is placed inside a large power transmission coil, the power transmission device will not transmit a Digital Ping to the power receiving device. Note that the "predetermined frequency" may be, for example, the resonance frequency of the wireless power transmission system. In this embodiment, an example of controlling so as not to transmit a Digital Ping to a small power receiving device will be used for explanation, but it is similarly applicable to a large power receiving device. For example, when a large power receiving device different from the power receiving device assumed by the wireless power transmission system is arranged, by controlling so as not to transmit a Digital Ping from the power transmission device, power transmission can be performed only to the power receiving device that is the power transmission target.

[0038] Further, the power transmission device 102 may hold a table showing the association between the voltage ratio V2 / V1 measured at a predetermined frequency and information regarding the material of the object, and based on this, determine whether the object placed on the power transmission device is an inappropriate object as the power transmission target. Also, the power transmission device 102 may hold a table showing the association between the voltage ratio V2 / V1 and information indicating the arrangement of the power transmission coil and the object, and based on the measured voltage ratio and this table, determine whether the placed object is in an appropriate arrangement (state) as the power transmission target. Alternatively, a predetermined threshold value for determining whether the object is appropriate as the power transmission target may be provided by comprehensively considering the size of the object, the material of the object, and the arrangement relationship between the power transmission coil and the object described above. In this case, by determining whether the voltage ratio V2 / V1 exceeds the threshold value, it is possible to determine whether the object placed on the power transmission device is an inappropriate object or arrangement (state) as the power transmission target.

[0039] As another method, for example, there is also a method of using the voltage ratio V2 / V1 measured at a plurality of frequencies. Here, the plurality of frequencies are, for example, arbitrary frequencies near the resonance frequency of the wireless power transmission system. For example, by holding a table showing the association between the voltage ratio V2 / V1 measured at a plurality of frequencies and the information indicating the size of the object, and making a determination based on it, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target. Also, for example, by holding a table showing the association between the voltage ratio V2 / V1 measured at a plurality of frequencies and the information indicating the material of the object, and making a determination based on it, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target.

[0040] Also, the power transmission device 102 may hold a table showing the association between the voltage ratio V2 / V1 measured at a plurality of frequencies and the information indicating the arrangement relationship of the object, and based on this, determine whether the object placed within the power transmission range is in an inappropriate arrangement (state) as a power transmission target. Alternatively, considering the size of the object, the material of the object, the arrangement relationship between the power transmission coil and the object, etc., a predetermined threshold for determining whether the object is appropriate as a power transmission target may be provided for each of the voltage ratios V2 / V1 measured at a plurality of frequencies. In this case, by making a determination based on the information on whether the voltage ratio V2 / V1 measured at each frequency exceeds or is below the threshold, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target, or whether it is in an inappropriate arrangement (state). In one example, a curve of the voltage ratio V2 / V1 for each measured frequency is correlated with a curve of the voltage ratio measured when an appropriate object as a power transmission target is arranged, and when the correlation value is equal to or greater than the threshold, it may be determined that the object placed on the power transmission device is appropriate as a power transmission target.

[0041] As another method, for example, there is also a method of utilizing the resonance frequency of the power transmission unit including the power transmission coil or the resonance frequency of the wireless power transmission system. When an object is placed near the power transmission coil 602, the resonance frequency of the power transmission unit including this power transmission coil or the resonance frequency of the wireless power transmission system also changes. As an example of a method for measuring the resonance frequency, the voltage ratio V2 / V1 is measured at a plurality of frequencies within a predetermined frequency range and calculated from the measurement results. For example, if measurement results as shown in FIG. 7 are obtained, the resonance frequency ω0 is 100 kHz.

[0042] For example, by holding a table (correlation information) showing the association between the resonance frequency of the power transmission unit including the power transmission coil and the size of the object and making a determination based on it, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target.

[0043] Also, for example, by creating a table that holds information showing the relationship between the resonance frequency of the power transmission unit including the power transmission coil and the material of the object and making a determination based on it, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target.

[0044] In addition, create a table showing the association between the resonance frequency of the power transmission unit including the power transmission coil and the information indicating the arrangement relationship of the object with respect to the power transmission coil, and based on this, it is possible to determine whether the object placed on the power transmission device is in an inappropriate arrangement (state) as a power transmission target. Alternatively, a predetermined threshold value for determining whether the object is appropriate as a power transmission target may be set by comprehensively considering the size of the object, the material of the object, and the arrangement relationship between the power transmission coil and the object, etc. In this case, based on whether the measured resonance frequency of the power transmission unit including the power transmission coil exceeds the threshold value, it is possible to determine whether the object placed on the power transmission device is an inappropriate object or arrangement (state) as a power transmission target.

[0045] As another method, for example, there is also a method that utilizes the sharpness of a resonance curve, which is obtained from a curve (resonance curve) showing the relationship between V2 / V1 measured at a plurality of frequencies within a predetermined frequency range, such as that shown in FIG. 7. When an object is placed near the power transmission coil 602, the sharpness of this resonance curve also changes.

[0046] As can be seen from the schematic circuit diagram of FIG. 6, since it becomes a series resonance circuit, the sharpness of the resonance curve of the series resonance circuit may also be utilized. As an example, the sharpness of the resonance curve is determined using the width (half-value width Δω) of the frequencies (ω1 and ω2) at which the magnitude of V2 / V1 indicated by the arrow in FIG. 7 becomes 1 / √2 of V2 / V1 at the resonance frequency ω0. ω0 / (ω2 - ω1) and can be calculated as such.

[0047] Alternatively, similarly, the voltage or current applied to the power transmission coil 602 or the resonance capacitor 603 in FIG. 6 may be measured, and the sharpness of the resonance curve may be calculated therefrom.

[0048] For example, by holding a table (associated information) that holds information indicating the sharpness of the resonance curve of the resonance circuit constituted by the power transmission unit and the size of the object, and making a determination based thereon, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target. Also, for example, by storing a table showing the association between the sharpness of the resonance curve of the resonance circuit constituted by the power transmission unit and information indicating the material of the object, it is possible to determine whether the object placed on the power transmission device is an inappropriate object as a power transmission target based on the table.

[0049] Also, for example, it holds a table showing the association between the sharpness of the resonance curve of the resonance circuit constituted by the power transmission circuit and the information indicating the positional relationship between the power transmission coil and the object. Based on this, it is possible to determine whether the object placed thereon is in an inappropriate position (state) as a power transmission target. Alternatively, a predetermined threshold value may be provided to determine whether the object is appropriate as a power transmission target by comprehensively considering the size of the object, the material of the object, the positional relationship between the power transmission coil and the object, and the like. Then, by determining based on the information on whether the sharpness of the resonance curve of the measured power transmission unit or the resonance circuit constituting the wireless power transmission system exceeds or falls below the threshold value, it is possible to determine whether the object within the power transmission range is an inappropriate object or in an inappropriate position (state) as a power transmission target.

[0050] The case has been described where it is determined whether the object placed on the power transmission device is an inappropriate object as a power transmission target or is in an inappropriate position (state) by using the electrical characteristics (Q factor, resonance frequency, sharpness of the resonance curve) of the power transmission unit of the power transmission device. However, those used for the determination may be the electrical characteristics of the power transmission unit including the power transmission coil of the power transmission device other than the above. Also, for example, electrical characteristics such as the inductance value of the coil, the impedance value, and the coupling coefficient between the power transmission coil and the object may be used, or a combination of these and the electrical characteristics of the power transmission unit including the power transmission coil of the power transmission device may be used to create the above-mentioned predetermined threshold value or table.

[0051] Further, they may be created based on the electrical characteristics at one frequency or based on the electrical characteristics at multiple frequencies. As a method for measuring the electrical characteristics at multiple frequencies, it is possible to achieve by transmitting signals (e.g., sine waves, rectangular waves, etc.) at each frequency for which the electrical characteristics are to be measured multiple times and measuring the electrical characteristics in the signals at each frequency. This method has the effect of enabling measurement with relatively less arithmetic processing in the power transmission device. Alternatively, by transmitting a signal having all the frequency components at multiple frequencies for which the electrical characteristics are to be measured (e.g., a pulse wave) once and performing arithmetic processing (e.g., Fourier transform) on the measurement result, the electrical characteristics at multiple frequencies can be calculated. Alternatively, by transmitting signals having some of the frequency components at multiple frequencies for which the electrical characteristics are to be measured multiple times and performing arithmetic processing (e.g., Fourier transform) on the measurement result, the electrical characteristics at multiple frequencies can be calculated. This method has the effect of enabling measurement in a relatively short time because the number of times of transmitting the signal for measurement can be reduced.

[0052] Also, the above assumes the case where the power transmission coil mounted on the power transmission device is a single large coil for transmitting large power. However, the power transmission coil is composed of a plurality of small power transmission coils, and even for a power transmission device that transmits large power by transmitting power from the plurality of power transmission coils to the power receiving device, the above-described method is applicable. That is, the above-described method may be executed not for one coil but for the plurality of power transmission coils mounted on the power transmission device. In this case, based on the measurement results of the electrical characteristics such as the inductor value of the coil, the impedance value, the coupling coefficient between the power transmission coil and the object, etc., and the electrical characteristics of the power transmission unit including each power transmission coil of the power transmission device, the above-described predetermined threshold values and tables may be created. Further, they may be created based on the electrical characteristics at one frequency or based on the electrical characteristics at multiple frequencies.

[0053] As described above, by determining whether the object placed on the power transmission device is an inappropriate object or arrangement (state) for the power transmission target, it is possible not to transmit a signal with a power greater than the power transmission for determination to the object. As a result, even if the object is a small power receiving device, the power receiving device will not be exposed to large electromagnetic energy, the temperature of the housing of the power receiving device will not rise, the electronic components in the power receiving device will not be damaged, and radiation of noise to the surroundings can be prevented.

[0054] Also, the above-mentioned "table" or "threshold value" may be determined based on the electrical characteristics of the power transmission unit, including the inductor value, impedance value of the power transmission coil, and the coupling coefficient between the power transmission coil and the power receiving device, when the power receiving device to be powered is placed on the power transmission device. Further, they may be created based on the electrical characteristics at one frequency, or may be created based on the electrical characteristics at a plurality of frequencies. For example, when the power transmission device is a power transmission device for charging and supplying power to a Note PC, the power transmission device holds a "table" or "threshold value" based on the electrical characteristics of the power transmission unit when the Note PC, which is the power receiving device, is placed in advance. When an object is placed on the power transmission device, the electrical characteristics are measured, and by determining whether the object placed on the power transmission device is a Note PC by referring to the table or the threshold value, the same effect can be obtained.

[0055] In this embodiment, after transmitting an Analog Ping and detecting that an object is placed on the power transmission device, the power transmission device is configured to transmit a signal of determination power that is as weak as the Analog Ping. However, it is also possible to determine whether an object is placed by using the signal of determination power for determining whether the object is an inappropriate object as a power transmission target. That is, it is also possible to transmit once a signal that can perform both detection of the placement of the object and determination of whether the placed object is an inappropriate object or an inappropriate arrangement (state) as a power transmission target. As a result, it is not necessary to separately transmit the Analog Ping and the signal of determination power twice, and the time for determining whether the object is an appropriate power transmission target can be shortened.

[0056] <Embodiment 2> In Embodiment 1, a configuration was described in which when measuring the electrical characteristics of the power transmission circuit of the power transmission device and determining that the placed object is an inappropriate object or arrangement (state) as a power transmission target, a signal with a power greater than the detection power transmission is not transmitted to the object.

[0057] In this embodiment, a case where a sensor installed in the power transmission device is used to determine that an object placed on the power transmission device is an inappropriate object as a Digital Ping transmission target or an inappropriate arrangement (state) will be described.

[0058] FIG. 8 is a diagram showing a power transmission device equipped with a sensor. As the sensor 804 to be mounted, it is sufficient if at least any one of the parameters of the size, weight, and position of the object can be acquired. For example, a photoelectric sensor, an eddy current displacement sensor, a contact displacement sensor, an ultrasonic sensor, or an image discrimination sensor can be used. Also, a weight sensor 805 may be used.

[0059] The photoelectric sensor emits visible light or infrared rays from the light projecting unit, and detects the change in the amount of light reflected by the object placed on the power transmission device or the blocked light by the light receiving unit, thereby making it possible to detect the arrangement state such as the position from the sensor to the object.

[0060] The eddy current displacement sensor passes a high-frequency current through the coil of the sensor head to generate a high-frequency magnetic field, and detects the distance to the object based on the change amount of the oscillation state due to the change in the impedance of the coil, thereby making it possible to detect the state of the object.

[0061] The contact type displacement sensor can detect the state of the object by detecting the position of the object when the contact touches the object directly.

[0062] The ultrasonic sensor transmits ultrasonic waves from the sensor head, receives the ultrasonic waves reflected from the object by the sensor head, and detects the distance to the object, thereby making it possible to detect the state of the object.

[0063] The image discrimination sensor can detect the state such as the position and type of the object by applying known image processing techniques to the image taken by the camera.

[0064] The weight sensor can detect the state of the object by detecting the weight of the object placed on the power transmission device.

[0065] By using these sensors, it is possible to determine whether the object placed on the power transmission device is appropriate. Also, by combining these sensors as needed, it becomes possible to detect the state of the object with higher accuracy.

[0066] When it is determined, using the above-mentioned flat sensor, that an object placed on the power transmission device is an inappropriate object or arrangement (state) as a power transmission target, a signal with a power greater than that of the detection power transmission is not transmitted to the object. As a result, even if a small power receiving device is placed on the power transmission device, the power receiving device can be prevented from being exposed to a large amount of electromagnetic energy such as Digital Ping. As a result, it is possible to prevent the temperature rise of the housing of the power receiving device, the destruction of electronic components inside the power receiving device, or the radiation of noise to the surroundings.

[0067] <Other Embodiments> Embodiment 1 and Embodiment 2 can be arbitrarily combined. For example, when the power transmission device has a plurality of power transmission coils, the position where the object is placed is specified by a contact displacement sensor, and only the power transmission coil corresponding to the specified position is used to determine whether the object is a power transmission target object. The processing of Embodiment 1 or 2 may be performed.

[0068] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0069] 101: Power receiving device, 102: Power transmission device, 103: Charging stand, 104: Power transmission range

Claims

1. Power transmission means for wirelessly transmitting power to a power receiving device, Transmission means for transmitting a signal, Acquisition means for acquiring a value related to the Q factor, Receiving means for receiving identification information from the power receiving device, having, The transmission means transmits a first signal, After transmitting the first signal, the transmission means transmits a second signal for starting the power receiving device when the value acquired by the acquisition means exceeds a threshold value, The transmission means transmits a third signal, After transmitting the third signal, the transmission means transmits the first signal when the presence or absence of an object satisfies a predetermined condition. A power transmission device characterized by this.

2. The power transmission device according to claim 1, wherein the transmission means does not transmit the second signal when the value acquired by the acquisition means does not exceed the threshold value.

3. The power transmission device according to claim 1 or 2, wherein the second signal is a Digital Ping defined by the Wireless Power Consortium standard.

4. The power transmission device according to any one of claims 1 to 3, wherein the power receiving device is not activated by the first signal.

5. The power transmission device according to any one of claims 1 to 4, wherein the first signal is a signal for determining whether the object is a power transmission target.

6. The power transmission device according to any one of claims 1 to 5, wherein the transmission means transmits the first signal when the object is present.

7. The power transmission device according to any one of claims 1 to 6, wherein the power receiving device is not activated by the third signal.

8. The power transmission device according to claim 7, wherein the third signal is a signal that does not activate the power receiving device and is a signal for detecting the presence of an object.

9. The power transmission device according to claim 7 or 8, wherein the third signal is an Analog Ping defined by the Wireless Power Consortium standard.

10. The power transmission device according to any one of claims 1 to 9, wherein the transmission means does not transmit the second signal even when the object is a power receiving device and the value acquired by the acquisition means does not exceed the threshold value.

11. A method for transmitting a signal of a power transmission device, A first transmission step of transmitting a first signal, An acquisition step of acquiring a value related to the Q factor, A reception step of receiving identification information from a power receiving device, A second transmission step of transmitting a second signal for starting the power receiving device when the value acquired in the acquisition step exceeds a threshold after the transmission of the first signal, A third transmission step of transmitting a third signal, comprising: The first transmission step is performed after the third transmission step when the presence or absence of an object satisfies a predetermined condition. A transmission method characterized by this.

12. The transmission method according to claim 11, characterized in that the second signal is not transmitted when the value acquired by the acquisition step does not exceed the threshold.

13. The third signal is a signal that does not start the power receiving device and is a signal for detecting the presence of an object. The transmission method according to claim 11 or 12, characterized by this.

14. A program for operating a computer as the power transmission device according to any one of claims 1 to 10.

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