JP2019097389A - Power transmission device, power transmission method, power reception device, and power reception method - Google Patents

Abstract

To efficiently perform wireless power supply.SOLUTION: There is provided a power transmission device provided with: a resonance circuit including a coil; a detection part which detects presence/absence of a foreign matter affecting wireless power supply using the resonance circuit; and a control part which controls transmission of power by the wireless power supply according to a detection result of the foreign matter, in which the detection part detects the foreign matter by determining the presence/absence of the foreign matter by a first detection method which is the one for determining the presence/absence of the foreign matter by using a Q value of the coil on the basis of first determination information including information regarding the Q value of the coil to be transmitted from a power reception device in a first period which is temporally before a second period which is the one for supplying power to the power reception device by the wireless power supply, and determining the presence/absence of the foreign matter by a second detection method different from the first detection method in the second period. This technology can be applied to, for example, the case of performing the wireless power supply.SELECTED DRAWING: Figure 1

Description

  The present technology relates to a power transmission device, a power transmission method, a power reception device, and a power reception method, and more particularly to a power transmission device, a power transmission method, a power reception device, and a power reception method that enables wireless power feeding to be efficiently performed.

  In recent years, wireless power supply that supplies power wirelessly has been actively studied. As a method of wireless power supply, there is a method using a magnetic field. There are two types of systems that use a magnetic field: an electromagnetic induction system and a magnetic field resonance system.

  The electromagnetic induction method is a method that is already widely known, and the degree of coupling between a power transmission device that transmits power and a power reception device that receives power is very high, and power can be fed with high efficiency.

  The magnetic field resonance method is a method of actively utilizing a resonance (resonance) phenomenon, and is characterized in that the magnetic flux shared between the power transmission device and the power reception device may be small.

  Since the electromagnetic induction method and the magnetic field resonance method are both methods of supplying power using a magnetic field, the power transmission device has a power transmission coil which is a coil for transmitting power using a magnetic field. The power receiving device has a power receiving coil which is a coil for receiving power using a magnetic field.

  Then, by magnetically coupling the power transmission coil and the power reception coil, power feeding from the power transmission device to the power reception device is performed.

  By the way, when a foreign substance capable of receiving energy from a magnetic field such as metal mixes in between the magnetically coupled (magnetically coupled) power transmission coil and the power receiving coil, an eddy current flows in the foreign substance to generate heat, etc. , Energy is consumed, and the efficiency of the power supply is reduced.

  Therefore, various methods have been proposed for detecting foreign matter between the power transmission device and the power reception device.

  For example, Patent Document 1 describes that the current on the power transmission device side is monitored, and if the current is an overcurrent, the transmission of power from the power transmission device is stopped on the assumption that foreign matter is detected.

JP 2001-275280 A

  The power receiving device may be a portable portable terminal, a home appliance such as a fixedly installed television receiver or a refrigerator, an electric car, or any other device using a power.

  Furthermore, since the power receiving device is not particularly manufactured considering wireless power feeding, metal used as foreign matter for wireless power feeding is used in considerable amount in the housing of the power receiving device and inside the housing. There is.

  Then, for example, when (a part of) the housing of the power receiving device uses metal that is a foreign object for wireless power feeding, the power transmitting device is used to determine whether the current on the power transmitting device side is an overcurrent. Even if there is no foreign object between the power source and the power receiving device, metal as a housing of the power receiving device may be detected as the foreign object and transmission of power from the power transmission device may be stopped.

  However, if no foreign matter is present between the power transmission device and the power reception device, the transmission of power from the power transmission device may be stopped, which reduces the efficiency of power feeding.

  The present technology has been made in view of such a situation, and enables wireless power feeding to be efficiently performed.

  A power transmission device according to one aspect of the present technology includes a resonant circuit including a coil, a detection unit that detects the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit, and the wireless power feeding according to a detection result of the foreign substance. And a control unit configured to control transmission of power by the control unit, wherein the detection unit is a first period that is temporally earlier than a second period which is a period in which the power is supplied to the power receiving device by the wireless power supply. A first detection method is a method of determining the presence or absence of the foreign object using a Q value of a coil based on first determination information including information on a Q value of a coil transmitted from the power receiving device during a period. A power transmission device that determines the presence or absence of the foreign matter and determines the presence or absence of the foreign matter by the second detection method different from the first detection method in the second period; .

  A power transmission method according to one aspect of the present technology includes a resonant circuit including a coil, a detection unit that detects the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit, and the wireless power feeding according to the detection result of the foreign substance. And a control unit configured to control transmission of power by the transmission unit, wherein the detection unit is more timely than the second period in which the power is supplied to the power receiving device by the wireless power feeding. A method of determining the presence or absence of the foreign object using a Q value of a coil based on first determination information including information on a Q value of a coil transmitted from the power receiving device in a first period which is a previous period In the first detection method, the presence or absence of the foreign matter is determined, and during the second period, the presence or absence of the foreign matter is determined by the second detection method different from the first detection method. Power transmission to detect foreign matter It is the law.

  In the power transmission device and the power transmission method according to one aspect of the present technology, in the first period, which is a period earlier than the second period in which power is supplied to the power receiving device by wireless power feeding, The presence / absence of foreign matter is determined by a first detection method that is a method of determining the presence / absence of foreign matter using the Q value of the coil based on first determination information including information on the Q value of the coil to be transmitted. During the second period, the presence or absence of foreign matter is determined by the second detection method different from the first detection method, and the foreign matter is detected.

  A power receiving device according to one aspect of the present technology includes a resonant circuit including a coil, a processing unit that performs processing for detecting the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit, and a detection result of the foreign object. And a control unit that controls the supply of power by the wireless power supply, and the processing unit is earlier than the second period in which the power from the power transmission device is supplied by the wireless power supply. Coil Q value used when determining the presence or absence of foreign matter by the first detection method, which is a method of determining the presence or absence of the foreign material using the Q value of the coil in the first period which is the period of Used to determine the presence or absence of the foreign matter in the second period by the second detection method different from the first detection method, and transmits the first determination information including the information related to The first judgment information to be The second determination information comprising a power receiving apparatus which performs a process for detecting the foreign substance by transmitting to the power transmission device.

  A power receiving method according to one aspect of the present technology includes a resonant circuit including a coil, a processing unit that performs processing for detecting the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit, and a detection result of the foreign object. A control unit configured to control supply of power by the wireless power supply, wherein the processing unit is a period during which the power from the power transmission device is supplied by the wireless power supply; During the first detection method, which is a method of determining the presence or absence of the foreign object using the Q value of the coil in the first period which is a period temporally earlier than the period of Transmitting, to the power transmission apparatus, first determination information including information on a Q value of a coil used for the second foreign object detection method according to a second detection method different from the first detection method during the second period Used to determine the presence or absence of The second determination information different from the first determination information, a power receiving method for performing processing for detecting the foreign substance by transmitting to the power transmission device.

  In the power reception device and the power reception method according to one aspect of the present technology, the coil is performed in the first period which is a period earlier than the second period which is a period in which power from the power transmission device is supplied by wireless power supply. The first determination information including information on the Q value of the coil used when determining the presence or absence of a foreign object by the first detection method, which is a method of determining the presence or absence of a foreign object using the Q value of And second determination information different from the first determination information used when determining the presence or absence of a foreign object by the second detection method different from the first detection method during the second period. It is sent to the device and processing for detecting foreign matter is performed.

  Note that the power transmission device and the power reception device may be independent devices, or may be an internal block constituting one device.

  According to the present technology, wireless power feeding can be performed efficiently.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram illustrating a configuration example of an embodiment of a wireless power supply system to which the present technology is applied. It is a figure explaining the foreign material detection method by efficiency. It is a figure which shows the relationship between the positional relationship (position shift of a receiving coil) of a power transmission coil and a receiving coil, and electric power efficiency (efficiency between coils). It is a figure explaining the foreign material detection method by Q value. FIG. 2 is a block diagram showing a configuration example of a power transmission device 11. FIG. 2 is a circuit diagram showing a configuration example of a driver circuit 22. FIG. 2 is a block diagram showing an example of the configuration of a power reception device 12; It is a flowchart explaining the process of the wireless electric power feeding of a wireless electric power feeding system. FIG. 6 is a block diagram showing an example of the configuration of a foreign matter detection unit 46. It is a flowchart explaining the process of the wireless electric power feeding of a wireless electric power feeding system. It is a figure explaining calculation of an appropriate threshold. It is a flow chart explaining processing of a wireless electric supply system in a case of performing charge by wireless electric supply. FIG. 18 is a block diagram showing another configuration example of the foreign matter detection unit 46. It is a flowchart explaining the process of the wireless electric power feeding of a wireless electric power feeding system. FIG. 8 is a block diagram illustrating another configuration example of the power receiving device 12; Fig. 21 is a block diagram illustrating a configuration example of an embodiment of a computer to which the present technology is applied.

  [One embodiment of a wireless power supply system to which the present technology is applied]

  FIG. 1 is a block diagram showing a configuration example of an embodiment of a wireless power supply system to which the present technology is applied.

  In FIG. 1, the wireless power supply system includes a power transmission device 11 and a power reception device 12 and performs wireless power supply, for example, by a method using a magnetic field, that is, an electromagnetic induction method, a magnetic resonance method, or the like.

  The power transmission device 11 has a power transmission coil which is a coil for transmitting power using a magnetic field, and transmits power.

  The power receiving device 12 has a power receiving coil, which is a coil for receiving power using a magnetic field, and receives power transmitted from the power transmitting device 11 when placed near the power transmitting device 11. .

  Further, the power transmission device 11 and the power reception device 12 have a foreign matter detection function of detecting foreign matter that affects wireless power feeding.

  As for the foreign matter detection function, only one of the power transmission device 11 and the power reception device 12 has all of the foreign matter detection function, and both the power transmission device 11 and the power reception device 12 There are cases in which the foreign matter detection function is shared.

  Here, as a system to which the wireless power supply system of FIG. 1 is applied, for example, a set of a cradle as the power transmission device 11 and a portable terminal such as a mobile telephone as the power reception device 12 or the power transmission device 11 For example, as a charging stand, for example, as a set with an electric car as a power receiving device 12, as a power transmission device 11, for example as a set with a television rack and a TV (television receiver) as the power receiving device 12. Etc.

  Further, although only one power receiving device 12 is illustrated as a power receiving device that receives power from one power transmitting device 11 by wireless power feeding in FIG. 1, a plurality of power receiving devices that receive power by wireless power feeding are illustrated. It may be.

  According to the wireless power supply system having a plurality of power reception devices, for example, by placing a plurality of portable terminals as a plurality of power reception devices in a tray (charge tray) as the power transmission device 11, for example The terminal can be charged at the same time.

  [Method of detecting foreign matter detection]

  FIGS. 2 to 4 are diagrams for explaining a foreign matter detection detection method which can be adopted as the foreign matter detection function of wireless power feeding.

  As a foreign matter detection detection method that can be adopted as the foreign matter detection function of wireless power feeding, for example, there are the following methods.

  That is, as a foreign matter detection detection method, as described in the above-mentioned patent document 1, depending on whether the current on the power transmission device side is an overcurrent, besides the method of detecting foreign matter, for example, power transmission device 11 There is a method of determining the presence or absence of foreign matter by threshold processing of the temperature with the power receiving device 12 (hereinafter, also referred to as a foreign matter detection method based on temperature).

  In addition, as a method of detecting foreign matter detection, for example, a method of determining the presence or absence of foreign matter by threshold processing of change in load when looking at the power receiving device 12 from the power transmission device 11 (hereinafter, also referred to as foreign matter detection method by load) There is.

  Furthermore, as a method of detecting foreign matter detection, for example, there is a method of determining the presence or absence of foreign matter depending on whether optical communication is possible between the power transmission device 11 and the power reception device 12 (hereinafter also referred to as foreign matter detection method by light). is there.

  Further, as a method of detecting foreign matter detection, for example, there is a method of determining the presence or absence of foreign matter using an image obtained by photographing between the power transmission device 11 and the power reception device 12 (hereinafter also referred to as foreign matter detection method by image) .

  Furthermore, as a method of detecting foreign matter detection, for example, a method of determining the presence or absence of foreign matter by threshold processing of power efficiency indicating the ratio of the power received by the power receiving device 12 to the power transmitted from the power transmitting device 11 And foreign matter detection methods by efficiency).

  Further, as a method of detecting foreign matter detection, for example, there is a method of determining the presence or absence of foreign matter using the Q value (Quality factor) of the power receiving coil of the power receiving device 12 (hereinafter also referred to as foreign matter detection method by Q value) .

  Furthermore, as a method of detecting foreign matter detection, there is a method of determining the presence or absence of foreign matter using the effective resistance value of the power receiving coil of the power receiving device 12 (hereinafter, also referred to as foreign matter detection method based on effective resistance value).

  In the temperature-based foreign matter detection method, a temperature sensor such as a thermistor is provided in the wireless power supply system, and when the temperature sensor detects a temperature equal to or higher than a predetermined value, it is determined that foreign matter is present.

  The foreign matter detection method based on temperature is described, for example, in Japanese Patent Application Laid-Open No. 2001-258182.

  In the foreign object detection method based on load, load modulation is performed by the power receiving device 12, and a change in load when the power receiving device 12 is viewed from the power transmitting device 11 based on a modulation signal of load modulation by the power receiving device 12. Is recognized. Then, it is determined that there is a foreign object when it is considered that there is no change in load by the threshold processing of the change in load (processing of comparing the change in load with the threshold) when the power transmission device 11 looks at the power receiving device 12 .

  The foreign object detection method based on the load is described in, for example, Japanese Patent Application Laid-Open No. 2008-206231.

  In the foreign matter detection method using light, optical communication is performed between the power transmission device 11 and the power reception device 12, and it is determined that foreign matter is present when the optical communication can not be performed.

  The foreign substance detection method using light is described in, for example, Japanese Patent Application Laid-Open No. 2001-112190.

  In the foreign matter detection method using an image, for example, the space between the power transmission device 11 and the power reception device 12 is photographed, and the image obtained as a result thereof is compared with an image photographed in advance and an image in a state without foreign matter. The presence or absence is determined.

  In the efficiency-based foreign matter detection method, the voltage and current of each of the power transmission device 11 and the power reception device 12, and hence the power is measured, and the power efficiency representing the ratio of the power of the power reception device 12 to the power of the power transmission device 11 is predetermined. When it is not larger than the threshold (or equal to or larger than a predetermined threshold), it is determined that there is a foreign substance.

  Here, for example, in the foreign matter detection method based on temperature or the foreign matter detection method based on light, a sensor that senses temperature or light may need to be attached so as to be exposed to the outside in the power transmission device 11 or the power reception device 12 In this case, restrictions may be imposed on the design of the power transmission device 11 and the power reception device 12.

  Furthermore, when wireless power feeding is performed by the magnetic field resonance method, the range in which wireless power feeding can be performed is wide (the degree of freedom of the positional relationship between the power transmitting device 11 and the power receiving device 12 is high). In the apparatus 12, when employing the temperature-based foreign matter detection method or the light-based foreign matter detection method, a large number of sensors may be required, which may increase the cost.

  On the other hand, for example, in the foreign object detection method based on efficiency, it is sufficient for the power transmission device 11 and the power reception device 12 to be able to measure voltage and current, requiring a large number of sensors and imposing restrictions on design. It is advantageous because there is not.

  In the foreign matter detection method based on the Q value, the Q value of the power receiving coil of the power receiving device 12 (Q value when the power receiving coil is viewed from inside the power receiving device 12) is measured, and the Q value is not larger than a predetermined threshold. It is determined that there is a foreign substance.

Here, the Q value (hereinafter also referred to as the Q value of the coil L) of the (series) resonant circuit composed of the coil L (a coil having an inductance of L) and the capacitor C (a capacitor having a capacitance of C) Is expressed as f _r = 1 / (2π√ (LC)), and the effective resistance value of the resonant circuit is expressed as r, it is expressed by equation (1).

Q = 2πf _r L / _r
... (1)

  As the metal approaches the coil L, the effective resistance value r becomes large, so the Q value of the equation (1) becomes small.

  Now, when the coil L is adopted as the power receiving coil of the power receiving device 12, the Q value of the coil L as the power receiving coil indicates that the metal approaches, and in addition, the fr, L, r on the right side of the equation (1) fluctuates As long as there are no factors causing it, it will be constant.

  That is, in the power receiving device 12, there are cases where metal is contained in the housing or the inside, but the positional relationship between the metal and the power receiving coil does not change. Therefore, the Q value of the coil L as the power receiving coil is smaller than that in the absence of the metal due to the influence of the housing of the power receiving device 12 and the metal in the inside, but does not change.

  On the other hand, it is difficult to use no metal in the housing because the power receiving device 12 may be a product of various applications such as a portable terminal and an electric car, but the power transmission device 11 performs wireless power feeding. In the case of the above device, it is possible to adopt a configuration in which metal is not used in the housing (in particular, the portion to which the power receiving device 12 can be approached).

  In this case, even if the power receiving device 12 is brought close to the power transmitting device 11, the Q value of the coil L as the power receiving coil of the power receiving device 12 does not change (almost), but changes only when the metal as the foreign object approaches.

  That is, the coil L as the power receiving coil of the power receiving device 12 has a unique Q value due to the influence of the metal or the like included in the housing of the power receiving device 12, and the Q value is that metal can be brought close to the coil L It will be a fixed value (does not change) unless there is an equality.

  Therefore, based on the unique Q value (hereinafter also referred to as a standard Q value) of the coil L in a state where the metal is not brought close to the coil L as the power receiving coil of the power receiving device 12, for example, the standard Q value Of α (0 <α <1) is determined as a threshold of unique Q value (hereinafter also referred to as threshold Q value), and threshold processing of Q value of coil L using threshold Q value is performed Thus, the metal as the foreign matter can be detected with high accuracy.

  As described above, it is difficult to use no metal in the case of the power receiving device 12, and the power receiving devices 12 of various cases including metal can be brought close to the power transmission device 11. Therefore, the Q value of the power transmission coil of the power transmission device 11 changes (decreases) not only when there is metal as a foreign object but also when the power receiving device 12 of a housing containing metal approaches. Therefore, in the Q value of the power transmission coil of the power transmission device 11, it is difficult to distinguish between the case where there is metal as a foreign object and the case where the power receiving device 12 of the housing containing the metal approaches.

  In the foreign matter detection method based on the effective resistance value, the effective resistance value r of the power receiving coil of the power receiving device 12 (the effective resistance value r when the power receiving coil is viewed from the inside of the power receiving device 12) is measured. If it is not smaller than the threshold of (or less than a predetermined threshold), it is determined that there is a foreign substance.

Here, from the equation (1) and the equation f _r = 1 / (2π√ (LC)) representing the resonance frequency f _r , the effective resistance value in the case where the coil L is adopted as the power receiving coil of the power receiving device 12 r is expressed by equation (2).

_{r = 2πf r L / Q =} 1 / (2πf r CQ)
... (2)

  Therefore, the effective resistance value r can be obtained, for example, from the inductance L and the Q value.

  As in the case of the Q value, the coil L as the power receiving coil of the power receiving device 12 is unique due to the influence of the metal or the like contained in the housing of the power receiving device 12 as long as metal does not approach the coil L or the like. It has an effective resistance value r, and the effective resistance value r is increased by bringing the metal closer to the coil L.

  Therefore, based on the effective resistance value r of the coil L in a state where the metal is not brought close to the coil L as the power receiving coil of the power reception device 12, for example, β times the effective resistance value r (2> β> By determining 1) as a specific threshold value and performing threshold processing using the threshold value of the effective resistance value r of the coil L, it is possible to detect metal as a foreign substance with high accuracy.

  FIG. 2 is a diagram for explaining the foreign matter detection method based on efficiency.

  That is, FIG. 2 schematically shows the positional relationship between the power transmission coil of the power transmission device 11 and the power reception coil of the power reception device 12.

  Now, in FIG. 2, in the three-dimensional coordinate system in which the left to right direction is the x axis, the direction from the near side is the y axis, and the top to bottom direction is the z axis, It is assumed that it is located at 0).

  Further, the fact that the power receiving coil is located at a point (0, 0, Z) on the z-axis means that the power receiving coil faces the power transmitting coil or is in the facing state.

  Furthermore, in the present embodiment, the z-coordinate of the power receiving coil is fixed to a predetermined value Z in order to simplify the description.

  When the power receiving coil is in the facing state as shown on the left side of FIG. 2, the ratio of the power received by the power receiving device 12 to the power efficiency, ie, the power transmitted by the power transmitting device 11, is highest. . In FIG. 2, the power efficiency when the power receiving coil is in the facing state is 90%.

  When the power receiving coil deviates from the position directly facing the power transmitting coil, as shown in the center of FIG. 2, the power efficiency decreases. In particular, the electromagnetic induction system has a large change (decrease) in power efficiency due to misalignment.

  On the other hand, even when the power receiving coil is in the directly-facing state, as shown on the right side of FIG. 2, if metal or the like as a foreign object is present between the power transmitting coil and the power receiving coil, the power efficiency decreases.

  In the foreign matter detection method based on the efficiency, it is difficult to determine which of the positional deviation and the presence of the foreign matter is the cause of the decrease in the power efficiency.

  In FIG. 2, the power efficiency in the case where the positional deviation occurs is 60%, and the power efficiency in the presence of foreign matter is 70%.

  As described above, when positional deviation occurs, the power efficiency may be lower than when foreign matter is present.

  FIG. 3 shows the relationship between the positional relationship between the power transmission coil and the power reception coil (displacement of the power reception coil) and the power efficiency (inter-coil efficiency).

  In FIG. 3, a 40 mm square coil is used as a power transmission coil, and a 30 mm square coil is used as a power reception coil, and the distance between the power transmission coil and the power reception coil (4 mm as the z coordinate Z of the power reception coil) Adopted.

  In FIG. 3, X and Y respectively represent the z coordinate and y coordinate of the power receiving coil.

  L1 represents the inductance (L2_open) of the power transmission coil when the power reception coil is opened and the inductance (L2_short) of the power transmission coil when the power reception coil is shorted.

  k represents a coupling coefficient between the power transmission coil and the power reception coil, and Q1 and Q2 represent Q values of the power transmission coil and the power reception coil, respectively.

  Further, in FIG. 3, S is represented by the equation S = k × √ (Q1 × Q2), and hereinafter also referred to as an S value.

The inter-coil efficiency is a type of power efficiency and represents the ratio of the power obtained by the power receiving coil to the power supplied to the power transmitting coil. The theoretical maximum value η _max of the inter-coil efficiency is expressed by the equation _{max max} = S2 / (1 + √ (1 + S2)) 2.

  Here, the power efficiency includes, for example, DC-DC efficiency in addition to inter-coil efficiency.

  The DC-DC efficiency is derived from the power received by the power receiving coil in the power receiving device for the power determined from the direct current (DC) voltage and current used when transmitting power from the power transmitting coil in the power transmitting device It represents the proportion of power determined from direct current (DC) voltage and current.

  Now, in the power transmission device, transmission efficiency when power is transmitted from the position where direct current voltage and current are given to transmit power from the power transmission coil to the power transmission coil, and power reception in the power receiving device. Assuming that the transmission efficiency when power is transmitted is referred to as circuit efficiency from the coil to the position where DC voltage and current are taken out, the DC-DC efficiency multiplies the coil efficiency by the circuit efficiency. You can ask for it by doing.

  For example, when degrees of freedom of about 10 mm are taken respectively in the x and y directions as the degree of freedom (permissible range) of positional displacement of the power receiving coil, the power efficiency (inter-coil efficiency) is as shown in FIG. In the foreign matter detection method based on efficiency, the threshold value of the power efficiency used for foreign matter detection is set to, for example, 85% of a value smaller than 85.5%.

  In this case, when the power efficiency does not exceed 85%, which is the threshold value, it is determined that there is a foreign matter.

  Also, for example, when the degrees of freedom of positional displacement of the power receiving coil are about 15 mm in the x and y directions, respectively, the power efficiency (inter-coil efficiency) is the worst, as shown in FIG. Since the efficiency is 62.7%, in the foreign matter detection method based on efficiency, the power efficiency threshold value used for foreign matter detection is set to, for example, 62% of a value smaller than 62.7%.

  In this case, when the power efficiency is not larger than the threshold 62%, it is determined that there is a foreign matter.

  Therefore, assuming that the power receiving coil is in the directly-paired state and the power efficiency when foreign matter is present is, for example, about 70% as shown in FIG. If the threshold is set to 62%, taking the degree only about 15 mm, the power efficiency will be 70%, which is larger than the threshold 62%, even if there is a foreign object in the facing state. It is not determined that there is a foreign object, and the foreign object can not be detected.

  As described above, it is difficult to say that the foreign substance detection accuracy of the foreign substance detection method based on efficiency is high.

  Furthermore, in consideration of manufacturing variations of the power receiving coil of the power receiving device and other circuits, the power efficiency threshold has a smaller value (a value that makes it difficult to detect foreign matter) in order to secure a predetermined degree of freedom in positional deviation. In this case, the detection accuracy of the foreign matter in the foreign matter detection method by the efficiency is further lowered.

  As a method of improving the detection accuracy of the foreign substance detection method based on efficiency, there is a method of eliminating the degree of freedom of positional deviation or limiting to a small value, but in that case, the usability of wireless power feeding is impaired.

  As described above, in the foreign substance detection method based on efficiency, the foreign substance detection accuracy and the usability are in a trade-off relationship.

  In the present embodiment, as described above, when power receiving device 12 is brought closer to the casing (in particular, a portion to which power receiving device 12 can be brought into), power transmitting device 11 does not use metal. It is assumed that the configuration in which the Q value of the power receiving coil of the power receiving device is not varied is adopted.

  In this case, the positional relationship between the power transmission device 11 and the power reception device 12 does not affect the Q value (Q2) of the power receiving coil. Therefore, in FIG. 3, the Q value (Q2) of the power receiving coil, that is, the Q value when the power receiving coil is viewed from the inside of the power receiving device 12, is constant regardless of the position (X, Y) of the power receiving device 12. It has become.

  FIG. 4 is a diagram for explaining the foreign matter detection method based on the Q value.

  As described above, in the foreign matter detection method based on the Q value, the threshold value is determined based on the Q value (standard Q value) of the coil L in a state in which metal is not brought close to the coil L as the power receiving coil of the power receiving device 12. (Threshold value Q value) is determined, and by performing threshold processing using the threshold value Q value of the Q value of the power receiving coil, metal as foreign matter is detected.

  As described above, the power reception coil of the power reception device 12 has a unique Q value due to the influence of the metal or the like included in the housing of the power reception device 12. Then, the Q value of the power receiving coil changes as the metal approaches the coil L, and is not affected by the positional deviation with the power transmission device 11, so in the foreign matter detection method based on the Q value, the electromagnetic induction method and the magnetic field With any of the resonance methods, foreign objects can be detected with high accuracy while ensuring usability.

  The foreign substance detection method based on the Q value is described in Japanese Patent Application No. 2011-149465 filed by the present applicant.

  By the way, in order to obtain the Q value of the power receiving coil, it is necessary for the power receiving device 12 to apply a voltage to a series resonant circuit having the power receiving coil as a component and to measure a necessary voltage or current.

Assuming that the voltage applied to the series resonant circuit and the voltage applied to the power receiving coil are represented by V ₁ and V ₂ , respectively, the Q value of the power receiving coil (series resonant circuit having the component) is Is represented by

Q = (V ₂ -V ₁ ) / V ₁
... (3)

Here, the inductance of the power receiving coil that constitutes the series resonance circuit, the capacitance of the capacitor, and the resistance value (effective resistance value) of the effective resistance are denoted as L, C, and r, respectively, and , when the voltage of the resonance frequency f _r is applied, the formula _{j2πf r L = 1 / (j2πfrC} ) is established (j = √ (-1)) , i.e., the impedance j2πf _r L of the power receiving coil, Since the capacitor impedance 1 / (j2πfLC) is canceled out, the voltage V ₁ applied to the series resonant circuit is equal to the voltage v _r applied to the effective resistance.

Further, the voltage V ₂ applied to the power receiving coil, a voltage drop v _L with no effective resistance (ideal) power receiving coil is equal to the addition value v _L + v _r of the voltage drop v _r of the effective resistance.

On the other hand, since the currents flowing through the power receiving coil forming the series resonant circuit and the effective resistance are equal, the equation v _r / r = v _L / (2πf _r L) holds.

Therefore, the equation (1) can be obtained by substituting the equation v _r / r = v _L / (2πfr _L ), using the voltage drop v _L of the power receiving coil and the voltage drop v _r of the effective resistance. It is represented by 4).

_{Q = 2πf r L / r =} v L / v r
... (4)

The voltage V ₁ applied to the series resonant circuit is equal to the voltage v _r applied to the effective resistance, and the voltage V ₂ applied to the power receiving coil is the sum v of the voltage drop v _L of the power receiving coil and the voltage drop v _r of the effective resistance. Since it is equal to _L + v _r , the voltage v _r applied to the effective resistance is represented by voltage V ₁ (= v _r ), and the voltage drop v _L of the receiving coil is voltage V _{2 −} V ₁ (= v _L + v _r It is represented by -v _r ).

Therefore, the Q value of equation (4) is expressed by equation (3) (Q = (V ₂ −V ₁ ) / V ₁ ) using voltages V ₁ and V ₂ .

Here, when the voltage applied to the series resonant circuit is a voltage of the resonance frequency f _r , generally, the voltage drop v _L of the power receiving coil is sufficiently larger than the voltage v _r applied to the effective resistance. Therefore, the voltage V ₂ = v _L + v _r is sufficiently larger than the voltage V ₁ = v _r . Therefore, the Q value of equation (3) can be approximated by equation (5).

Q = V ₂ / V ₁
... (5)

  In addition, the Q value of the power receiving coil (a series resonant circuit having a component) is obtained by, for example, measuring a voltage V applied to the series resonant circuit and a current I flowing through the series resonant circuit by the half width method. It can be determined using the obtained impedance Z = V / I.

In other words, the frequency of the voltage applied to the series resonant circuit, resonating with the frequency f impedance when it is _r Z, when become √2 times the impedance, the lower frequency f _L and higher than the resonance frequency f _r The frequency f _H can be determined, and the Q value can be determined according to the equation Q = f _r / (f _H −f _L ).

  In the foreign matter detection method based on the Q value, as shown in FIG. 4, processing of the first Q measurement is performed, and thereafter, the power transmission device 11 supplies power to the power reception device 12 by wireless power feeding.

  Then, thereafter, the processing of the second Q value measurement, the processing of the third Q value measurement,... Are performed periodically or irregularly.

  In the process of the first Q measurement, first, in consideration of the case where the power receiving device 12 does not have a power source, the power receiving device 12 obtains power necessary to perform the first Q measurement process. Charging takes place.

  That is, the power transmission device 11 transmits power, and the power reception device 12 receives the power from the power transmission device 11 and charges it.

For example, the power reception device 12 stops charging and operates using the power obtained by the charging when the charging of the electric power more than the power necessary for one measurement of the Q value is completed. Then, the power receiving apparatus 12, a predetermined voltage frequency f _1, is applied to the power receiving coil (series resonant circuits as components), determine the Q value (measured).

Thereafter, the power receiving device 12 starts charging again, and stops charging when the charging above the power necessary for one Q value measurement is completed, and operates using the power obtained by the charging. Then, the power receiving apparatus 12 applies, to the power receiving coil, a voltage of a frequency f _n higher than the frequency f _n−1 used for the previous measurement of the Q value to measure the Q value.

Likewise, the power receiving apparatus 12 repeats charging and measuring the Q value to obtain Q values for each of a plurality of N frequencies f ₁ , f ₂ ,..., F _N determined in advance.

Here, as the N frequencies f ₁ , f ₂ ,..., F _N , for example, the inductance of the power receiving coil of the series resonant circuit having the power receiving coil of the power receiving device 12 as a component and the capacitance C of the capacitor It is possible to use a frequency within a predetermined frequency band centered on the theoretical resonance frequency f _r = 1 / (2π√ (LC)) obtained from

When the power reception device 12 obtains the Q value for each of the _N frequencies f ₁ to f _N , the power reception device 12 performs charging for performing the subsequent processing.

Then, the power receiving apparatus 12 obtains the maximum value among the N Q values as the Q value of the power receiving coil, and obtains the frequency f ₀ when the Q value is obtained as the resonance frequency.

Furthermore, the power reception device 12 stores the resonance frequency f ₀ and transmits the Q value of the power reception coil to the power transmission device 11 together with the threshold Q value, for example, by load modulation, to process the first Q measurement. Ends.

  Here, in the power receiving device 12, based on the Q value (standard Q value) of the coil L in a state where the metal as the foreign object is not brought close to the power receiving coil of the power receiving device 12, the threshold (threshold Q value) ) Are determined in advance and stored.

  When the process of the first Q measurement is completed, the power transmission device 11 supplies (transmits) power (power for the power reception device 12 to perform the original operation) by wireless power feeding to the power reception device 12.

  In the subsequent processing of the m-th Q measurement, the power receiving device 12 charges more than the power necessary for one measurement of the Q value, and stops the charging when the charging is completed.

Then, the power receiving device 12 applies a voltage of the resonance frequency f _{0 to} the power receiving coil to measure the Q value of the power receiving coil.

  Furthermore, the power reception device 12 performs charging for transmitting the Q value of the power reception coil to the power transmission device 11, and transmits the Q value of the power reception coil to the power transmission device 11 together with the threshold Q value, for example, by load modulation. Then, the processing of the m th Q measurement is ended.

  On the other hand, the power transmission device 11 intermittently transmits power to the power reception device 12 as described above, and the Q value of the power receiving coil transmitted in the process of the mth Q measurement, and Receive threshold Q value.

  Then, the power transmission device 11 performs threshold processing to compare the Q value of the power reception coil with the threshold Q value, and when the Q value of the power reception coil is not larger than the threshold Q value, the power transmission device 11 determines that foreign matter is present. And stop transmitting power.

  Here, the threshold processing for comparing the Q value of the power receiving coil with the threshold Q value can be performed not by the power transmission device 11 but by the power reception device 12. In this case, when the Q value of the power receiving coil is not larger than the threshold Q value, the power receiving device 12 determines that there is a foreign object, and transmits the determination result to the power transmission device 11.

  When the power transmission device 11 receives from the power receiving device 12 the determination result that there is a foreign object, the power transmission device 11 stops the transmission of the power.

  In addition, although the power transmission device 11 transmits power to the power receiving device 12 as described above, while the power receiving device 12 is measuring the Q value in the process of the mth Q measurement, The transmission of power is suspended to measure the Q value.

  That is, in the process of the mth Q measurement, the power transmission device 11 intermittently stops the transmission of power, and the power reception device 12 outputs the Q value while the transmission of power of the power transmission device 11 is stopped. taking measurement. When an electromotive force is generated by the power from the power transmission device 11 in the power reception coil of the power reception device 12, it is difficult to correctly measure the Q value of the power reception coil.

  Therefore, with regard to the foreign matter detection method based on the Q value, although the detection accuracy of the foreign matter is high, since the power transmission device 11 has to intermittently stop the transmission of power, it is difficult to say that the time efficiency of wireless power feeding is good. .

  As described above, in the foreign matter detection method based on the Q value, although the detection accuracy of the foreign matter is high, there is a problem in the time efficiency of the wireless power feeding.

  On the other hand, with regard to the foreign matter detection method by efficiency, there is a problem in the detection precision of foreign matter, but it is not necessary to intermittently stop transmission of power as in the foreign matter detection method by Q value. There is no problem of time efficiency of

  Therefore, in the wireless power feeding system shown in FIG. 1, for example, foreign matter detection can be enhanced without impairing the usability by a new detection method using two foreign matter detection methods of the foreign matter detection method by Q value and the foreign matter detection method by efficiency. Accurately and wirelessly feed efficiently.

  [Configuration Example of Power Transmission Device 11]

  FIG. 5 is a block diagram showing a configuration example of the power transmission device 11 of FIG.

  In FIG. 5, the power transmission device 11 includes a resonance circuit 20, a DC power supply 21, a driver circuit 22, a waveform detection unit 23, and a control unit 24.

Resonant circuit 20, the power transmission coil L ₁ and a series resonant circuit composed of the capacitor C _1, is driven by the driver circuit 22. By the resonance circuit 20 is driven, magnetic flux (magnetic field) to the power transmission coil L ₁ is generated by the magnetic flux, an electromagnetic induction method or a magnetic field resonance method, the power is transmitted to the power receiving device 12.

  The DC power supply 21 supplies a predetermined DC voltage (current) to the driver circuit 22.

The driver circuit 22 uses the DC voltage from DC power source 21, drives the resonant circuit 20, by generating a magnetic flux in the power transmission coil L ₁ constituting the resonance circuit 29, an electromagnetic induction method or a magnetic resonance method , Send power.

  The waveform detection unit 23 detects (detects) information transmitted from the power reception device 12 by load modulation from the current or voltage flowing to the resonance circuit 20, and supplies the information to the control unit 24.

  The control unit 24 controls the driver circuit 22 and other blocks that constitute the power transmission device 11 based on the information and the like supplied from the waveform detection unit 23.

  FIG. 6 is a circuit diagram showing a configuration example of the driver circuit 22 of FIG.

  In FIG. 6, the driver circuit 22 is configured by a full bridge circuit.

  That is, the driver circuit 22 includes a gate drive circuit 31 and FET (Field Effect Transistors) 32, 33, 34, and 35 of an NMOS (Negative Channel Metal Oxide Semiconductor).

  The gate drive circuit 31 applies a predetermined voltage to the gates of the FETs 32 to 35 under the control of the control unit 24 to turn on or off the FETs 32 to 35, respectively.

  The drain of the FET 32 is connected to the DC power supply 21. Therefore, a predetermined DC voltage output from the DC power supply 21 is applied to the drain of the FET 32.

  The source of the FET 32 is connected to the drain of the FET 33, and the source of the FET 33 is grounded (connected to the ground).

  The FETs 34 and 35 are connected in the same manner as the FETs 32 and 33.

  That is, the drain of the FET 34 is connected to the DC power supply 21, and the source of the FET 34 is connected to the drain of the FET 35. The source of the FET 35 is grounded.

  Furthermore, one end of the resonant circuit 20 is connected to a connection point P1 of the source of the FET 32 and the drain of the FET 33, and the other end of the resonant circuit 20 is connected to a connection point P2 of the source of the FET 34 and the drain of the FET 35. ing.

Here, in FIG. 6, the resonant circuit 20, one end each other of the power transmission coil L ₁ and the capacitor C ₁ is connected. The other end of the capacitor C ₁ is connected to the connection point P1 between the source and the drain of FET33 the FET 32, the other end of the power transmission coil L ₁ is connected to a connection point P2 between the drain of the source and FET35 of FET34 ing.

  In the driver circuit 22 configured as described above, the gate drive circuit 31 controls the FETs 32 to 35 to be turned on or off by applying a predetermined voltage to the gates of the FETs 32 to 35.

  As a result, the FETs 32 and 33 are periodically turned on and off, respectively, in a complementary manner.

  That is, the FETs 32 are alternately turned on and off periodically.

  Then, when the FET 32 is turned on, the FET 33 is turned off, and when the FET 32 is turned off, the FET 33 is turned on.

  Also, the set of FETs 34 and 35 are periodically turned on and off complementarily to the set of FETs 32 and 33.

  That is, when the FET 32 is turned on and the FET 33 is turned off, the FET 34 is turned off and the FET 35 is turned on.

  Furthermore, when the FET 32 is turned off and the FET 33 is turned on, the FET 34 is turned on and the FET 35 is turned off.

  For example, focusing on the FET 32, when the FET 32 is in the on state, the FET 33 is in the off state, the FET 34 is in the off state, and the FET 35 is in the on state.

  As a result, the connection point P1 between the source of the FET 32 and the drain of the FET 33 is a predetermined DC voltage output from the DC power supply 21, for example, H (High) level. The source of the FET 34 and the drain of the FET 35 The connection point P2 is at the ground level, for example, L (Low) level.

Accordingly, the resonant circuit 20, from the connection point P1, through a capacitor C ₁ and the power transmission coil L _1, toward the connecting point P2, a current flows.

  On the other hand, when the FET 32 is in the off state, the FET 33 is in the on state, the FET 34 is in the on state, and the FET 35 is in the off state.

  As a result, the connection point P2 between the source of the FET 34 and the drain of the FET 35 becomes H level which is a predetermined DC voltage output from the DC power supply 21. The connection point P1 between the source of the FET 32 and the drain of the FET 33 is ground It becomes L level which is the level of

Accordingly, the resonant circuit 20, from the connection point P2, through the power transmission coil L ₁ and a capacitor C _1, in the direction towards the connection point P1, current flows.

  As described above, an alternating voltage having a cycle in which the FETs 32 to 35 are turned on (or off) is applied to the resonance circuit 20, and an alternating current having the same cycle flows in response to the application of the alternating voltage.

The resonant circuit 20, while the AC voltage is applied, the power transmission coil L _1, continuously, a magnetic flux is generated by the magnetic flux, power is transmitted.

The period in which the FETs 32 to 35 are turned on (or off) is, for example, based on the resonant frequency 1 / (2π√ (L ₁ C ₁ )) of the resonant circuit 20. It is set to the reciprocal of L ₁ C ₁ )).

  Further, in FIG. 6, a full bridge circuit is adopted as the driver circuit 22. However, for example, a half bridge circuit or a class E amplifier circuit can be adopted as the driver circuit 22.

  [Configuration Example of Power Receiving Device 12]

  FIG. 7 is a block diagram showing a configuration example of the power receiving device 12 of FIG.

  In FIG. 7, the power receiving device 12 includes a resonant circuit 40, a rectifying unit 41, a communication unit 42, a regulator 43, a load 44, a control unit 45, and a foreign matter detecting unit 46.

Resonant circuit 40, the receiving coil L ₂ and a series resonant circuit composed of the capacitor C _2, connected to the rectifier 41.

At the resonant circuit 40, by the magnetic flux power transmission coils L1 (FIG. 5) is generated in the power transmission apparatus 11 passes through the receiving coil L _2, the receiving coil L _2, and thus, a current flows through the resonant circuit 40, from the power transmission device 11 The transmitted power is received.

  The rectifying unit 41 is configured of, for example, a bridge rectifier circuit or the like. The rectifying unit 41 rectifies the current (voltage) flowing to the resonant circuit 40 and supplies the rectified voltage to the regulator 43 via the communication unit 42.

  The communication unit 42 has, for example, an FET and a resistor, and the FET is turned on or off according to the control of the control unit 45, whereby the resistor is connected to the resonant circuit via the rectifying unit 41. Connect to 40 or disconnect from the resonant circuit 40.

  The resistance is connected to the resonance circuit 40 or disconnected from the resonance circuit 40, so that the impedance of the resonance circuit 40 as a load as viewed from the (external) power transmission device 11 changes, and the resonance circuit of the power transmission device 11 The current flowing to 20 (FIG. 5) is load modulated.

  The regulator 43 stabilizes the current (voltage) supplied from the rectifying unit 41 via the communication unit 42, and supplies the stabilized current (voltage) to the load 44.

  The load 44 is, for example, a battery or other circuit that utilizes the power transmitted by wireless power supply.

  The control unit 45 controls the supply of the power (voltage, current) to the load 44 by the regulator 43 based on the detection (determination) result of the foreign matter from the foreign matter detection unit 46.

  That is, the control unit 45 basically causes the load 44 to supply power by controlling the regulator 43.

  However, when the foreign matter detection unit 46 supplies the detection result that there is a foreign matter, the control unit 45 supplies power to the load 44 (power supply) by controlling the regulator 43 when necessary. Stop.

  In addition, the control unit 45 causes the power transmission device 11 to transmit necessary information by load modulation by turning on or off the FET of the communication unit 42.

  The foreign matter detection unit 46 detects foreign matter by the new detection method, and supplies the detection result to the control unit 45.

  That is, before the start of power feeding to the load 44 of the power by wireless feeding, the foreign substance detection unit 46 determines the presence or absence of the foreign substance affecting the wireless feeding by the first detection method.

  In the first detection method, when it is determined that there is no foreign matter, the power transmitted by wireless power feeding is supplied to the load 44 via the resonant circuit 40, the rectifying unit 41, the communication unit 42, and the regulator 43. (Powered).

  Then, while power is supplied to the load 44, the foreign matter detection unit 46 determines the presence or absence of foreign matter by a second detection method different from the first detection method.

  When the foreign matter detection unit 46 determines that there is a foreign matter, the foreign matter detection unit 46 supplies the control unit 45 with a detection result indicating the presence of the foreign matter.

  Note that, in the power receiving device 12, the control unit 45 and the foreign matter detection unit 46 constitute a processing device (foreign matter processing device) that performs a process related to the foreign matter.

  FIG. 8 is a flowchart illustrating processing of wireless power feeding of the wireless power feeding system of FIG. 1 in which detection of foreign matter is performed by the new detection method.

  In step S11, the power transmission device 11 starts transmission (power transmission) of power, and the process proceeds to step S12.

  Here, when the power transmission device 11 recognizes that the power reception device 12 has approached, for example, the power transmission device 11 starts transmission of power.

  In the power transmission device 11, the proximity of the power reception device 12 can be recognized, for example, by the power transmission device 11 polling and the power reception device 12 responding to the polling.

  In the power transmission device 11, the fact that the power reception device 12 is close means that the mechanical switch provided in the power transmission device 11 is pressed by the power reception device 12 being placed on the power transmission device 11, or by a load sensor. It can be recognized by detecting the load of the power receiving device 12 or the like.

  Furthermore, in the power transmission device 11, transmission of power can be initiated by, for example, operation of the switch by the user or any other trigger.

  Immediately after the power transmission device 11 starts transmission of power, for example, the control unit 45 (FIG. 7) of the power reception device 12 controls the regulator 43 to supply (feed) power to the load 44. Stop it.

  In step S12, the foreign matter detection unit 46 (FIG. 7) of the power reception device 12 detects foreign matter by determining the presence or absence of foreign matter by the first detection method before the start of power feeding to the load 44 by wireless feeding. And the process proceeds to step S13.

  In step S13, the foreign matter detection unit 46 determines whether a foreign matter has been detected by the first detection method.

  If it is determined in step S13 that a foreign object is detected, the process proceeds to step S18, and control section 45 (FIG. 7) of power reception device 12 controls communication unit 42 to detect the foreign object. Is sent to the power transmission device 11.

  Furthermore, in step S18, the power transmission device 11 receives the detection message from the power reception device 12, and ends (stops) the transmission of power according to the detection message. That is, in the power transmission device 11, the control unit 24 stops the transmission of the power by the resonance circuit 20 by controlling the driver circuit 22.

  Thereafter, the process proceeds from step S18 to step S19, at least one of the power transmission device 11 and the power reception device 12 notifies the user that there is a foreign matter, and further, removes the foreign matter as necessary. Abnormal processing (for example, display of a message indicating the presence of a foreign object, lighting of a lamp indicating the presence of a foreign object, etc.) is performed to urge the wireless power supply, and the processing of the wireless power supply ends.

  On the other hand, in step S13, when it is determined by the first detection method that no foreign object is detected, the process proceeds to step S14, and control unit 45 (FIG. 7) of power reception device 12 controls regulator 43. Thus, the power supply to the load 44 is started, and the process proceeds to step S15.

  In step S15, the foreign matter detection unit 46 (FIG. 7) of the power receiving device 12 detects foreign matter by determining presence or absence of the foreign matter by the second detection method, and the process proceeds to step S16.

  In step S16, the foreign matter detection unit 46 determines whether a foreign matter is detected by the second detection method.

  If it is determined in step S16 that no foreign matter has been detected, the process returns to step S15, and the same process is repeated thereafter.

  Therefore, according to the first detection method, after it is determined that there is no foreign substance and power feeding to the load 44 is started, the foreign substance detection unit 46 performs the first detection while the power feeding to the load 44 is being performed. The foreign substance is detected by a second detection method different from the detection method.

  On the other hand, when it is determined in step S16 that the foreign matter is detected by the second detection method, the process proceeds to step S17, and control unit 45 (FIG. 7) of power reception device 12 controls regulator 43. Thus, the power supply to the load 44 is stopped.

  And a process returns from step S17 to step S12, and the same process is repeated hereafter.

  Therefore, when the foreign matter is detected by the second detection method, the foreign matter is detected again by the first detection method.

  Then, when no foreign matter is detected by the first detection method, power supply to the load 44 is started again (step S14).

  On the other hand, when foreign matter is also detected by the first detection method, the transmission of power by the power transmission device 11 is ended (step S18), and an abnormality process is performed (step S19).

  Here, as the first detection method, it is possible to adopt a detection method in which the detection accuracy of foreign matter is higher than that of the second detection method.

  On the other hand, as the second detection method, it is possible to adopt a detection method capable of detecting foreign matter even if power supply to the load 44, and hence transmission of power by the power transmission device 11, is performed. Furthermore, the second detection method may be a detection method in which the detection accuracy of the foreign matter is lower than that of the first detection method.

  As the first detection method as described above, for example, there is a foreign matter detection method based on Q value, and as a second detection method, for example, there is a foreign matter detection method based on efficiency.

  FIG. 9 is a block diagram showing a configuration example of the foreign object detection unit 46 of FIG.

  That is, FIG. 9 shows a configuration example of the foreign matter detection unit 46 in the case where the foreign matter detection method based on Q value and the foreign matter detection method based on efficiency are adopted as the first and second detection methods, respectively.

  In FIG. 9, the foreign matter detection unit 46 includes a Q value measurement unit 51, an efficiency measurement unit 52, and a determination unit 53.

Q value measuring unit 51 applies a predetermined voltage to the resonant circuit composed of 40 at the receiving coil L ₂ and capacitor C _2.

Furthermore, Q value measuring unit 51, voltages V ₁ across the resonant circuit 40, i.e., the voltage drop of the power reception coil L ₂ and capacitor C ₂ connected in series, the voltage V ₂ applied to the power receiving coil L _2, i.e., measuring the voltage drop of the power reception coil L _2.

Then, the Q-factor measurement unit 51 uses the voltages V ₁ and V ₂ to determine the Q factor of the power receiving coil L ₂ (resonant circuit 40 having the constituent element) according to equation (3) or equation (5) (measurement ), And supplies the judgment unit 53.

  The efficiency measuring unit 52 measures the current and voltage at the output side (the side from which the current and voltage after rectification are output) of the rectifying unit 41, and can be obtained by wireless power feeding in the power receiving device 12 using the current and voltage. DC power (hereinafter, also referred to as received DC power) is determined.

  Furthermore, the efficiency measurement unit 52 acquires direct-current power (hereinafter, transmission direct-current power) used by the power transmission device 11 for wireless power feeding.

  Here, the efficiency measurement unit 52 requests the control unit 45 to transmit DC power via the determination unit 53, and the control unit 45 controls the communication unit 42 in response to the request from the efficiency measurement unit 52. Thus, a request message requesting transmission DC power is transmitted to the power transmission device 11 by load modulation.

  In the power transmission device 11, the control unit 24 (FIG. 5) receives the request message from the power receiving device 12 via the waveform detection unit 23, and according to the request message, the voltage and current of the DC power supply 21 Are transmitted to the power receiving apparatus 12 as (the value of) transmission DC power.

  Transmission of (the value of) transmission DC power from the power transmission device 11 to the power reception device 12 is performed, for example, by amplitude-modulating the current flowing in the resonant circuit 20 by controlling the driver circuit 22 by the control unit 24. be able to.

  The efficiency measurement unit 52 obtains the ratio of the received DC power to the transmission DC power as the power efficiency (DC-DC efficiency), and supplies the power efficiency (DC-DC efficiency) to the determination unit 53.

Determination unit 53, using the Q-value of the receiving coil L ₂ from the Q value measurement unit 51, at the foreign matter detection method Q value, by determining the presence or absence of foreign matter, to detect the foreign matter, the result of detection, The control unit 45 is supplied.

That is, determination unit 53 stores a threshold Q value specific to power reception device 12 in a built-in memory (not shown), and determines the Q value of power reception coil L ₂ from Q value measurement unit 51 as the threshold Q value. Perform threshold processing to compare.

Then, the determination unit 53, if the Q value of the receiving coil L ₂ is greater than the threshold Q value, determines that there is no foreign matter, if the Q value of the receiving coil L ₂ is not greater than the threshold Q value, there is a foreign object It is determined that

  Further, the determination unit 53 detects foreign particles by determining the presence or absence of foreign particles by the efficiency-based foreign particle detection method using the power efficiency from the efficiency measurement unit 52 (hereinafter, also referred to as measured power efficiency). The detection result is supplied to the control unit 45.

  That is, the determination unit 53 performs threshold processing to compare the measured power efficiency from the efficiency measurement unit 52 with a predetermined threshold of the power efficiency.

  Then, the determination unit 53 determines that there is no foreign substance when the measured power efficiency is larger than a predetermined threshold, and determines that there is a foreign substance when the measured power efficiency is not larger than the predetermined threshold.

  The predetermined threshold used for the threshold processing of the measured power efficiency is, for example, the worst threshold and the appropriate threshold.

The worst threshold is predetermined, for example, assuming a predetermined case. For example, in the worst case of the positional deviation tolerance range of the power receiving device 12 (of the power receiving coil L ₂ ) (the case where the positional deviation is the largest), the measured power efficiency does not fall below that value unless foreign matter is present If there is, that value is used for the worst threshold, which is assumed to be below the measured power efficiency.

  If the measured power efficiency is not greater than the worst threshold, then either the misalignment is out of tolerance or foreign objects will be (almost) reliably present.

  The appropriate threshold is a threshold of power efficiency appropriate for foreign matter detection in the state of the wireless power feeding system when it is determined that there is no foreign matter (hereinafter also referred to as a system state) by the first detection method, and the Q value It is calculated using the power efficiency measured immediately after it is determined that there is no foreign matter, according to the foreign matter detection method according to the above.

  Here, the foreign matter detection method based on the Q value has high detection accuracy. Therefore, according to the foreign matter detection method based on the Q value, immediately after it is determined that there is no foreign matter, the absence of the foreign matter is securely ensured (almost). Ru.

  Therefore, with the foreign matter detection method based on the Q value, the power efficiency measured immediately after it is determined that there is no foreign matter (hereinafter, also referred to as immediate efficiency) is the power obtained when there is no foreign matter in the current positional deviation state. It can be said that efficiency is maintained, and if the current positional deviation is maintained, the measured power efficiency measured after that will not (mostly) be significantly less than the efficiency immediately thereafter, unless foreign matter is inserted. .

  Therefore, in the present embodiment, the immediately after efficiency is used, and for example, a value somewhat lower than the immediately after efficiency is calculated as the appropriate threshold.

  For example, a value obtained by multiplying the immediately subsequent efficiency by a predetermined value close to 1 less than 1 (for example, 0.9 or the like), or from the immediately subsequent efficiency, the fluctuation of the power efficiency predicted to occur regardless of the presence or absence of foreign matter. A value or the like obtained by subtracting a predetermined value (for example, 10% or the like) in consideration of the predetermined margin is calculated as the appropriate threshold.

  For the foreign matter detection method based on efficiency as the second detection method, the determination unit 53 performs threshold processing (first threshold processing) using the worst threshold as described above and threshold processing (second Threshold processing).

  When the worst threshold is used as the worst threshold and the appropriate threshold, if foreign matter is detected, a value by which the foreign matter is detected is always used even when the appropriate threshold is used. .

  That is, for example, for the foreign matter detection method based on efficiency, the worst threshold is used, and as the appropriate threshold, a value for which the appropriate threshold is equal to or greater than the worst threshold is used. Therefore, if the appropriate threshold calculated based on the immediate efficiency is less than the worst threshold, the appropriate threshold is set to the same value as the worst threshold.

  FIG. 10 is a flow chart for explaining the processing of the wireless power feeding of the wireless power feeding system of FIG. 1 when the foreign matter detector 46 is configured as shown in FIG.

  That is, FIG. 10 is a flowchart for explaining processing of wireless power feeding in the case of adopting the foreign matter detection method based on Q value and the foreign matter detection method based on efficiency as the first and second detection methods, respectively.

  When the power receiving device 12 approaches the power transmission device 11, the power transmission device 11 starts power transmission (power transmission) in step S21 as in step S11 of FIG. 8, and the process proceeds to step S22.

In step S22, before the start of power feeding to the load 44 by wireless power feeding, the Q factor measurement unit 51 of the power receiving device 12 (the foreign substance detection method using the Q factor as the first detection method) 9) measures the Q value of the receiving coil L _2.

Here, (while measuring the voltage V ₁ and V ₂ necessary for obtaining a Q value) Q value measuring unit 51, while measuring the Q-value of the receiving coil L _2, as described in FIG. 4, The power transmission device 11 suspends transmission of power.

The measurement of Q-value of the receiving coil L ₂ in step S22, the processing by returning from step S34 to be described later to step S22, there can occur multiple times, the m-th step S22, for example, FIG. The process of the m-th Q measurement described in 4 is performed.

  In addition, in step S22, the process of the first Q measurement described in FIG. 4 can be performed, for example, regardless of the number of times of step S22.

In step S22, the Q-value measuring section 51, when measuring the Q-value of the receiving coil L _2, Q value obtained by the measurement (hereinafter, measured Q value also referred to), and is supplied to the determining unit 53, the process , And proceeds to step S23.

  In step S23, the determination unit 53 uses the measurement Q value from the Q value measurement unit 51 to determine whether a foreign object is detected by the foreign matter detection method using the Q value as the first detection method.

  That is, in step S23, the determination unit 53 performs threshold processing to compare the measured Q value from the Q value measurement unit 51 with the threshold Q value, and determines whether the measured Q value is larger than the threshold Q value. Do.

  In step S23, when it is determined that the measured Q value is not larger than the threshold Q value, the determination unit 53 determines that there is a foreign object, and the control unit 45 detects that the foreign object is detected. , And the process proceeds to step S24.

  In step S24, the power transmission device 11 stops (ends) the transmission of power, as in step S18 of FIG.

  That is, in step S24, the control unit 45 of the power receiving device 12 controls the communication unit 42 to transmit, to the power transmission device 11, a detection message indicating that a foreign object has been detected. Furthermore, in step S24, the power transmission device 11 receives the detection message from the power reception device 12, and ends the transmission of power according to the detection message.

  Thereafter, the process proceeds from step S24 to step S25, in which abnormality processing is performed as in step S19 of FIG. 8, and the process of the wireless power supply ends.

  Here, when the power receiving device 12 approaches the power transmitting device 11, there is a high possibility that foreign matter such as metal is mixed between the power transmitting device 11 and the power receiving device 12. Further, the threshold used in the foreign substance detection method based on efficiency as the second detection method is calculated from the power efficiency in the state where there is no foreign substance. Therefore, in the new detection method, immediately after the power receiving device 12 approaches the power transmission device 11, before power feeding to the load 44 is started, the foreign matter detection method by the Q value as the first detection method with high detection accuracy is Detection of foreign matter is performed.

  If it is determined in step S23 that the measured Q value is larger than the threshold Q value, the determination unit 53 determines that there is no foreign substance, and the process proceeds to step S26.

  In step S26, the control unit 45 (FIG. 9) of the power receiving device 12 controls the regulator 43 to start power supply to the load 44.

  That is, when it is ensured that there is no foreign object (with high possibility) by the foreign object detection method based on the Q value with high detection accuracy, the power supply to the load 44 is started.

  In step S26, when power feeding to the load 44 is started, the process proceeds to step S27, and the efficiency of the power receiving device 12 is detected in order to detect foreign particles by the efficiency-based foreign particle detection method as the second detection method. The measurement unit 52 (FIG. 9) measures the power efficiency.

  In step S27, when the power efficiency is measured, the efficiency measurement unit 52 supplies the power efficiency (measured power efficiency) obtained by the measurement to the determination unit 53, and the process proceeds to step S28.

  Here, when the power efficiency is measured in step S27, it is ensured that no foreign matter is present by the foreign matter detection method using the Q value with high detection accuracy.

Therefore, (a small value) power inefficient measured in step S27 in the case, the power transmission device 11 (power transmission coils L ₁₎ power receiving device 12 (power receiving coil L ₂₎ misalignment is presumed large for Be done. In addition, when the power efficiency measured in step S27 is high (the value is large), it is estimated that the positional deviation of the power reception device 12 with respect to the power transmission device 11 is small.

  In step S28, the determination unit 53 determines, using the measured power efficiency from the efficiency measurement unit 52, whether or not a foreign matter is detected by the foreign matter detection method based on the efficiency as the second detection method.

  That is, in step S28, determination unit 53 performs a first threshold process that compares the measured power efficiency from efficiency measurement unit 52 with the worst threshold, and determines whether the measured power efficiency is greater than the worst threshold. Do.

  If it is determined in step S28 that the measured power efficiency is not greater than the worst threshold, the determination unit 53 determines that the positional deviation exceeds the allowable range or the positional deviation is within the allowable range. It is determined that an abnormality has occurred such that the power efficiency is unexpectedly low while displacement is occurring, and a detection result indicating that a foreign object is detected as in the case where it is determined that a foreign object is present Are supplied to the control unit 45 (FIG. 9).

  Then, the process proceeds from step S28 to step S24, and the same process as described above is performed.

  On the other hand, if it is determined in step S28 that the measured power efficiency is greater than the worst threshold, the process proceeds to step S29, and the determining unit 53 determines the power efficiency measured in the immediately preceding step S27 (measured power efficiency ) Using the measured power efficiency (immediately after efficiency) multiplied by a predetermined value, or a value obtained by subtracting a predetermined value from the measured power efficiency, etc., as the appropriate threshold of the power efficiency, Go to S30.

  Here, the threshold of the power efficiency used for the threshold processing of the foreign object detection method by efficiency generally takes into consideration, for example, manufacturing variations of the power transmitting device 11 and the power receiving device 12 and allowable positional deviation. It is determined such that foreign matter can be detected as accurately as possible while allowing positional deviation.

  However, when foreign matter detection is performed using only the foreign matter detection method based on efficiency, the positional deviation to be considered when determining the threshold of the power efficiency and the actual positional deviation coincide in many cases. Furthermore, manufacturing variations to be considered when determining the power efficiency threshold often do not coincide with actual manufacturing variations.

  Therefore, when foreign matter detection is performed using only the foreign matter detection method based on efficiency, it is difficult to determine the threshold value capable of detecting foreign matter with high accuracy.

  On the other hand, in the new detection method, the appropriate threshold is calculated using the power efficiency (immediate efficiency) measured immediately after it is determined that there is no foreign substance by the foreign substance detection method based on the Q value.

  Since the efficiency immediately after is the actual power efficiency obtained in the state of the current positional deviation and in the state without foreign matter, the power efficiency in which the actual positional deviation and the actual manufacturing variation are considered (reflected) By calculating an appropriate threshold value using such an immediately after efficiency, the appropriate threshold value becomes a value in which the actual positional deviation and the actual manufacturing variation are considered.

  As a result, according to the appropriate threshold value, foreign matter can be detected with high accuracy in the state of misalignment when the appropriate threshold value is obtained.

  In step S30, a waiting time of X seconds which is a predetermined time is set, and then the process proceeds to step S31.

  In step S31, the efficiency measurement unit 52 of the power receiving device 12 measures the power efficiency as in step S27, supplies the power efficiency (measured power efficiency) obtained by the measurement to the determination unit 53, and the process , And proceeds to step S32.

  In step S <b> 32, the determination unit 53 uses the measured power efficiency from the efficiency measurement unit 52 to determine whether a foreign object has been detected by the efficiency-based foreign matter detection method as the second detection method.

  That is, in step S32, determination unit 53 performs a first threshold process that compares the measured power efficiency from efficiency measurement unit 52 with the worst threshold, and determines whether the measured power efficiency is greater than the worst threshold. Do.

  If it is determined in step S32 that the measured power efficiency is not greater than the worst threshold value, the determination unit 53 supplies the control unit 45 with a detection result indicating that a foreign object has been detected.

  Then, the process proceeds from step S32 to step S24, and thereafter, the same process as described above is performed.

  On the other hand, when it is determined in step S32 that the measured power efficiency is greater than the worst threshold, the process proceeds to step S33, and the measured power efficiency from the efficiency measuring unit 52 is used as a second detection method. It is determined again whether foreign matter has been detected by the efficiency-based foreign matter detection method.

  That is, in step S33, determination unit 53 performs a second threshold process that compares the measured power efficiency from efficiency measurement unit 52 with the appropriate threshold, and determines whether the measured power efficiency is greater than the appropriate threshold. Do.

  If it is determined in step S32 that the measured power efficiency is higher than the appropriate threshold, that is, the power efficiency of the appropriate value is obtained as the power efficiency of the position state when the efficiency is measured immediately after. Therefore, if it can be determined that there is no foreign substance, the process returns to step S30, and the same process is repeated thereafter.

  In addition, when it is determined in step S32 that the measured power efficiency is not larger than the appropriate threshold, that is, a small power efficiency is obtained as the power efficiency in the position state when the efficiency immediately after is measured, Therefore, when foreign matter is mixed or the positional deviation changes (increases), the process proceeds to step S34, and the control unit 45 of the power receiving device 12 controls the regulator 43 to load the load 44. Turn off the power supply.

  Then, the process returns from step S34 to step S22, and thereafter, the same process as described above is repeated.

  Therefore, in the new detection method, after the calculation of the appropriate threshold, the power efficiency is monitored periodically while supplying power to the load 44, and the first threshold process using the worst threshold and the appropriate threshold are used. Foreign substance detection is performed by the foreign substance detection method based on efficiency by the second threshold processing described above.

  Note that the appropriate threshold is a threshold based on the power efficiency of the position shift state when the efficiency is measured immediately after, so to speak, when the positional deviation becomes larger than the position shift when the efficiency is measured immediately, The power efficiency may be below the appropriate threshold due to the large misalignment.

  When the power efficiency falls below the appropriate threshold due to the large positional deviation, the large positional deviation is within the allowable range and there is no foreign matter, the power supply from the transmitting device 11 is If it ends, usability will be impaired.

  Therefore, in FIG. 10, when the power efficiency falls below the appropriate threshold, the process proceeds from step S33 to step S34 and returns to step S22, and the foreign matter is detected by the foreign matter detection method using the Q value with high detection accuracy. Detection is performed.

  Then, when no foreign matter is detected by the foreign matter detection method based on the Q value with high detection accuracy, the power feeding from the transmission device 11 is continued without being ended (the process from step S26 is performed).

  On the other hand, when a foreign substance is detected by the foreign substance detection method based on the Q value with high detection accuracy, the power feeding from the transmission device 11 is ended (the processing after step S24 is performed).

  As described above, in the new detection method, before the start of power feeding to the load 44, the first detection method determines the presence or absence of foreign matter, and while the power feeding to the load 44 is being performed, the first detection method The foreign matter is detected by determining the presence or absence of the foreign matter by a second detection method different from the above.

  Furthermore, in the new detection method, as a first detection method, a foreign matter detection method with a Q value higher in detection accuracy than the foreign matter detection method with efficiency as a second detection method is adopted, and a foreign matter detection method with the Q value An appropriate threshold is calculated using the measured power efficiency (immediate efficiency) measured immediately after it is determined that there is no foreign matter.

  Therefore, before the start of power feeding to the load 44, foreign substances can be detected with high precision by the foreign substance detection method using Q value with high detection precision, and an appropriate threshold is used during power feeding to the load 44. Foreign matter detection can be performed with relatively high accuracy by the foreign matter detection method based on efficiency (second threshold processing).

  Then, in the foreign matter detection method based on efficiency (using the appropriate threshold), even if power is supplied to the load 44, detection of the presence or absence of foreign matter is possible, and transmission of power by the power transmission device 11 when measuring the Q value. The time efficiency of the wireless power feeding can be improved as compared with the case of using only the foreign matter detection method based on the Q value which must stop the power supply to the load 44.

  Furthermore, in the foreign matter detection method based on the efficiency using the appropriate threshold, if it is determined that there is a foreign matter, that is, if the measured power efficiency decreases and falls below the appropriate threshold, the positional deviation may become large. Therefore, the foreign matter is detected again by the foreign matter detection method based on the Q value, and when the foreign matter is not detected by the foreign matter detection method based on the Q value, the power feeding from the transmission device 11 is not terminated. As it continues, within the allowable range, due to the positional deviation becoming large, the power supply from the transmitting device 11 is terminated and the usability is impaired only when the power efficiency falls below the appropriate threshold. It can be prevented.

  As described above, according to the new detection method, foreign matter detection can be performed with high accuracy and wireless power feeding can be efficiently performed without impairing the usability.

The determination unit 53 in FIG. 9 can be provided in the power transmission device 11 instead of the power reception device 12. In this case, the power receiving device 12 transmits to the power transmitting device 11 the Q value and the threshold Q value of the power receiving coil L ₂ and the received DC power necessary for obtaining the power efficiency, and the determination provided in the power transmitting device 11 In the unit 53, the presence or absence of foreign matter is determined using the Q value from the power receiving device 12 and the power efficiency obtained from the received DC power.

  Then, the determination result of the presence or absence of the foreign object is transmitted from the power transmission device 11 to the power receiving device 12, and in the power reception device 12, according to the determination result of the presence or absence of the foreign particle from the power transmission device 11, It is controlled.

  As described above, how to share the foreign matter detection function in the power transmission device 11 and the power reception device 12 is arbitrary.

  However, when the power receiving device 12 operates with power supplied by wireless power feeding from the power transmitting device 11 or power such as a battery charged with the power, the power consumed by the foreign object detection function in the power receiving device 12 Is desirable, and from such a viewpoint, the burden on the foreign object detection function of the power receiving device 12 is preferably small.

Therefore, in the power receiving device 12, processing that can be performed only on the power receiving device 12 side, that is, for example, measurement of the voltages V ₁ and V ₂ required to obtain the Q value of the power receiving coil L ₂ and power efficiency Calculation of Q value from voltages V ₁ and V ₂ , calculation of power efficiency using received DC power, and other foreign matter detection functions, bearing only the measurement of received DC power necessary to obtain The power transmission device 11 can bear the processing.

  [Calculation of appropriate threshold]

  FIG. 11 is a diagram for explaining the calculation of the appropriate threshold.

  That is, FIG. 11 shows an example of calculation of the threshold in the case of using the foreign substance detection method by efficiency alone and the appropriate threshold used in the new detection method (the foreign substance detection method by efficiency performed).

  In FIG. 11, the maximum value (maximum efficiency value) of the power efficiency is 90%, and the maximum variation (the positional relationship variation width) of the power efficiency generated according to the positional deviation within the allowable range is 30%. .

  Furthermore, in FIG. 11, the maximum variation in power efficiency (production variation range) caused by manufacturing variation is 15%, and the maximum variation in power efficiency (measurement variation range) caused by an error in power efficiency measurement is 5%. It is supposed to be there.

  Therefore, in FIG. 11, the power efficiency fluctuates up to 50% (= 30% + 15% + 5%) due to misalignment, manufacturing variation, and measurement error, so in FIG. It is 50% of the maximum efficiency value (maximum efficiency value x 0.5 = 45%).

  When the foreign matter detection method based on the efficiency is used alone, as the power efficiency actually measured (the efficiency value in the actual use state), values reflecting positional deviation, manufacturing variations, and measurement errors can be obtained.

  However, in the case of using the efficiency-based foreign matter detection method alone, is it possible that the low power efficiency is attributable to misregistration or the presence of foreign matter when the actually measured power efficiency is small? Is unknown.

  Here, when the foreign matter detection method based on efficiency is used alone, when priority is given to usability, for example, a worst threshold can be adopted as a threshold to be compared with the power efficiency.

  In this case, unless the power efficiency falls below the worst threshold value, that is, the highest efficiency value × 0.5 = 45%, it is not determined that there is a foreign object. Therefore, in the case of using the foreign matter detection method based on efficiency alone, even if foreign matter is mixed, there is almost no positional deviation, so that foreign matter will be missed when the power efficiency does not fall below the worst threshold.

  On the other hand, in the new detection method, the power efficiency actually measured (the efficiency value in the actual use state) is the power efficiency (immediate efficiency) immediately after it is determined that there is no foreign substance by the foreign substance detection method based on Q value. .

  Immediately after, the efficiency reflects the positional deviation, manufacturing variation, and measurement error, and it is ensured that there is no foreign matter, so if the positional deviation is maintained as it is, then as long as the foreign matter is not inserted, The power efficiency measured by the power supply does not fall far below the efficiency immediately after.

  Therefore, in the new detection method, using the immediately after efficiency, for example, a value obtained by multiplying the efficiency by a predetermined value is calculated as an appropriate threshold value.

  In FIG. 11, for example, 80% is obtained as the immediate efficiency, and 72% is obtained as the appropriate threshold value by multiplying 80% thereof by, for example, 0.9 as a predetermined value.

  According to the new detection method, when the power efficiency falls below the worst threshold of 45%, it is determined that foreign matter is present, and power feeding is stopped.

  Also, the power efficiency is not less than 45% which is the worst threshold, but if it falls below 72% which is an appropriate threshold, there is a possibility that foreign matter may be mixed in, and there may be a large positional deviation. The presence or absence of foreign matter is determined by the foreign matter detection method based on the Q value, which has a detection accuracy higher than that of the foreign matter detection method based on efficiency.

  Therefore, according to the new detection method, the power feeding can not be stopped only by the power efficiency falling below the appropriate threshold because the positional deviation becomes large, so that the wireless power feeding can be efficiently performed while securing the usability. it can.

  In the new detection method, when the power efficiency falls below the appropriate threshold due to the inclusion of foreign matter, the foreign matter is detected by the foreign matter detection method using a Q value with high detection accuracy, and power feeding is stopped.

  Here, as a second detection method among the first and second detection methods used in combination in the new detection method, a predetermined physical quantity is measured as in the foreign substance detection method by efficiency, and the measured value of the physical quantity is measured By performing threshold processing to compare with a predetermined threshold, it is possible to adopt a detection method for determining the presence or absence of foreign matter.

  Then, in the new detection method, the second detection method uses a measurement value of the second detection method (hereinafter, also referred to as an immediately after measurement value) measured immediately after it is determined that there is no foreign substance by the first detection method. An appropriate threshold used for thresholding of the detection method can be calculated (decided).

  The calculation of the appropriate threshold value using the immediately after measurement value can be performed by manipulating the immediately after measurement value, for example, by multiplying or adding (subtracting) a predetermined value to the immediately after measurement value, but the degree of the operation is It can determine based on the largest variation (measurement variation width) of the measurement value which arises by the error (error of measurement) when measuring a measurement value by 2 detection methods.

  That is, the degree of operation of the immediately after measurement value, specifically, a predetermined value by which multiplication or addition is performed on the immediately after measurement value is, for example, a value that shows a margin about twice the measurement variation width at an appropriate threshold. And the immediately after measurement value can be determined to match.

  [Charging by wireless power supply]

  FIG. 12 is a flowchart illustrating processing of the wireless power supply system of FIG. 1 when charging is performed by wireless power supply.

  Here, in the wireless power feeding system, when charging by wireless power feeding is performed, the load 44 (FIG. 9) of the power receiving device 12 has a battery, and charging of the battery is performed.

  In FIG. 12, in steps S41 to S54, processing similar to that of steps S21 to S34 in FIG. 10 is performed.

  Then, in step S49, as described in step S29 of FIG. 10, after determination unit 53 calculates the appropriate threshold using the efficiency immediately after, the process proceeds to step S61, and control unit 45 of power reception device 12 is performed. (FIG. 9) determines whether the battery of the load 44 is fully charged.

  If it is determined in step S61 that the battery possessed by load 44 is not yet fully charged, the process proceeds to step S50, and in steps S50 to S54, steps S30 to S34 in FIG. Processing is performed.

  When it is determined in step S61 that the battery included in the load 44 is fully charged, the process proceeds to step S62, and the control unit 45 of the power receiving device 12 controls the communication unit 42 to charge the battery. Transmits a completion message to the power transmission apparatus 11 to the effect that the transmission has been completed.

  Furthermore, in step S62, the power transmission device 11 receives the completion message from the power reception device 12, and ends (stops) the transmission of power according to the completion message.

  Thereafter, the process proceeds from step S62 to step S63, and at least one of the power transmission device 11 and the power reception device 12 performs a charge completion process (for example, charge completion) for notifying the user that the charge is completed. Is turned on, and the processing is completed.

  [Another Configuration Example of Foreign Object Detection Unit 46]

  FIG. 13 is a block diagram showing another configuration example of the foreign matter detection unit 46 of FIG.

  In the figure, the portions corresponding to the case of FIG. 9 are denoted with the same reference numerals, and the description thereof will be appropriately omitted below.

  In FIG. 13, the foreign matter detection unit 46 has the Q value measurement unit 51 and the determination unit 53 in common with the case of FIG. 9.

  However, the foreign matter detection unit 46 of FIG. 13 is different from the case of FIG. 9 in that a temperature measurement unit 62 is provided instead of the efficiency measurement unit 52.

  In the foreign substance detection unit 46 of FIG. 13, as the first detection method, the foreign substance detection method by the Q value is adopted as in the case of FIG. 9, but as the second detection method, the case of FIG. A foreign substance detection method based on temperature, which is a detection method different from the above, is adopted.

  Therefore, the foreign matter detection unit 46 of FIG. 13 is provided with a temperature measurement unit 62 instead of the efficiency measurement unit 52 of FIG. 9.

The temperature measurement unit 62 has a temperature sensor such as a thermistor (not shown), for example, measures the temperature in the vicinity of the power receiving coil L ₂ and supplies the temperature to the determination unit 53.

  The determination unit 53 performs the same process as in FIG. 9 except that the temperature from the temperature measurement unit 62 is used instead of the power efficiency.

  FIG. 14 is a flow chart for explaining the process of wireless power feeding of the wireless power feeding system of FIG. 1 when the foreign matter detector 46 is configured as shown in FIG.

  That is, FIG. 14 is a flow chart for explaining processing of wireless power feeding in the case of adopting the foreign matter detection method based on Q value and the foreign matter detection method based on temperature as the first and second detection methods, respectively.

  When the power receiving device 12 approaches the power transmission device 11, the power transmission device 11 starts power transmission (power transmission) in step S71 as in step S21 of FIG. 10, and the process proceeds to step S72.

In step S72, the Q-value measuring section 51 of the power receiving device 12 (FIG. 13), similarly to step S22 in FIG. 10, for measuring the Q-value of the receiving coil L _2.

In step S72, the Q-value measuring section 51, when measuring the Q-value of the receiving coil L _2, Q value obtained by the measurement (measurement Q value), and supplies the determining unit 53, the process in step S73 move on.

  In step S73, the determination unit 53 performs threshold processing to compare the measured Q value from the Q value measurement unit 51 with the threshold Q value as in step S23 of FIG. 10, and the measured Q value is greater than the threshold Q value. Determine if it is large.

  If it is determined in step S73 that the measured Q value is not larger than the threshold Q value, the determination unit 53 determines that there is a foreign object, and the control unit 45 determines that the foreign object is detected (see FIG. 13). ) And the process proceeds to step S74.

  In step S74, as in step S24 of FIG. 10, the power transmission device 11 stops (ends) transmission of power.

  Thereafter, the process proceeds from step S74 to step S75, in which abnormality processing is performed as in step S25 of FIG. 10, and the process of the wireless power supply ends.

  On the other hand, when it is determined in step S73 that the measured Q value is larger than the threshold Q value, the determination unit 53 determines that there is no foreign substance, and the process proceeds to step S76.

  In step S76, the control unit 45 (FIG. 13) of the power receiving device 12 controls the regulator 43 to start power supply to the load 44.

  In step S76, when power feeding to the load 44 is started, the process proceeds to step S77, and the temperature of the power receiving device 12 is detected to detect foreign matter by the temperature-based foreign matter detection method as the second detection method. The measurement unit 62 (FIG. 13) measures the temperature.

  In step S77, when the temperature is measured, the temperature measurement unit 62 supplies the temperature obtained by the measurement (hereinafter, also referred to as measurement temperature) to the determination unit 53, and the process proceeds to step S78.

  In step S78, the determination unit 53 determines, using the temperature measured by the temperature measurement unit 62, whether a foreign object has been detected by the temperature-based foreign matter detection method as the second detection method.

  That is, in step S78, the determination unit 53 performs a first threshold process that compares the measured temperature from the temperature measurement unit 62 with the worst threshold, and determines whether the measured temperature is smaller than the worst threshold.

  Here, as the worst threshold value of the foreign matter detection method based on temperature, a (nearly) minimum value (e.g., 60 degrees or the like) of a temperature at which the foreign matter is present is set.

  In step S78, when it is determined that the measured temperature is not smaller than the worst threshold, the determination unit 53 determines that an abnormal situation has occurred in which the temperature is unexpectedly high, and determines that there is a foreign matter As in the case, the detection result to the effect that the foreign matter is detected is supplied to the control unit 45 (FIG. 13).

  Then, the process proceeds from step S78 to step S74, and the same process as described above is performed.

  On the other hand, if it is determined in step S78 that the measured temperature is lower than the worst threshold value, the process proceeds to step S79, and the determination unit 53 determines the foreign matter detection method by the Q value measured in the previous step S77. A value obtained by multiplying or adding a predetermined value determined based on the measurement variation width to the temperature immediately thereafter using the measured temperature (hereinafter also referred to as the immediately subsequent temperature) by which the absence of foreign matter is ensured , The temperature obtained by adding 10 degrees, etc. as an appropriate threshold value, and the process proceeds to step S80.

  In step S80, a waiting time of X seconds which is a predetermined time is set, and then the process proceeds to step S81.

  In step S81, as in step S77, the temperature measurement unit 62 of the power receiving device 12 measures the temperature, supplies the temperature (measurement temperature) obtained by the measurement to the determination unit 53, and the process proceeds to step S82. Go to

  In step S82, the determination unit 53 uses the temperature measured by the temperature measurement unit 62 to determine whether a foreign object is detected by the temperature-based foreign object detection method as the second detection method.

  That is, in step S82, the determination unit 53 performs a first threshold process that compares the measured temperature from the temperature measurement unit 62 with the worst threshold, and determines whether the measured temperature is smaller than the worst threshold.

  If it is determined in step S82 that the measured temperature is not smaller than the worst threshold value, the determination unit 53 supplies the control unit 45 with a detection result indicating that a foreign object has been detected.

  Then, the process proceeds from step S82 to step S74, and thereafter, the same process as described above is performed.

  On the other hand, if it is determined in step S82 that the measured temperature is lower than the worst threshold value, the process proceeds to step S83, and using the measured temperature from the temperature measuring unit 62, the temperature is determined as a second detection method. It is determined again by the foreign matter detection method whether or not the foreign matter is detected.

  That is, in step S83, the determination unit 53 performs a second threshold process that compares the measured temperature from the temperature measurement unit 62 with the appropriate threshold, and determines whether the measured temperature is smaller than the appropriate threshold.

  If it is determined in step S82 that the measured temperature is lower than the appropriate threshold, that is, the temperature is measured to the same extent as when the temperature immediately after it was measured, and therefore it is determined that there is no foreign matter If yes, the process returns to step S80, and the same process is repeated thereafter.

  In addition, if it is determined in step S82 that the measured temperature is not smaller than the appropriate threshold, that is, a somewhat higher temperature is measured as compared to when the temperature immediately after it is measured, and foreign matter may be mixed. If there is, the process proceeds to step S 84, and the control unit 45 of the power receiving device 12 stops the power supply to the load 44 by controlling the regulator 43.

  Then, the process returns from step S84 to step S72, and thereafter, the same process as described above is repeated.

  As described above, in the new detection method adopting the foreign matter detection method based on Q value and the foreign matter detection method based on temperature as the first and second detection methods, respectively, to the load 44 after calculation of the appropriate threshold value The temperature is monitored periodically while feeding power, and the foreign substance detection by the foreign substance detection method based on temperature is performed by the first threshold processing using the worst threshold and the second threshold processing using the appropriate threshold. To be done.

  The measured temperature may be the arrangement of the temperature sensor as the temperature measuring unit 62 or the state of contact with other devices, the condition of the room in which the wireless power supply system is placed (such as the room temperature around the wireless power supply system) It changes with the situation of the wireless feeding system.

  Therefore, when a low temperature is set as the worst threshold, the measured temperature may exceed the worst threshold because the room temperature is high even in the absence of foreign matter. In this case, it is determined that there is a foreign object (misjudgment), power feeding is stopped, and usability is impaired.

  Therefore, in order to ensure usability, the worst threshold is a value such that the measured temperature does not rise even if the room temperature is high, etc., and if there is a foreign substance, the measured temperature will be exceeded. A relatively high value (for example, 60 degrees).

  However, if only threshold processing using such a worst threshold is performed, a foreign substance is present, but, for example, when the measured temperature does not exceed the worst threshold because the room temperature is low, the foreign substance may be detected. It can not be done, and the detection accuracy of foreign matter is lowered.

  In the new detection method that employs the foreign matter detection method based on the Q value and the foreign matter detection method based on the temperature as the first and second detection methods, the measurement that ensures that no foreign matter is ensured by the foreign matter detection method based on the Q value An appropriate threshold is set from the temperature (immediately after temperature), and when the measured temperature exceeds the appropriate threshold, foreign matter is detected by the foreign matter detection method using Q value with high detection accuracy, so usability is not impaired. The detection of foreign matter can be performed with high accuracy, and wireless power feeding can be performed efficiently.

  In the new detection method, it is desirable that the first detection method is a detection method with as high detection accuracy as possible.

  Furthermore, in the new detection method, before the start of power feeding to the load 44, the first detection method determines the presence or absence of foreign matter, so that the first detection method is to feed power to the load 44 and hence the power transmission device 11 When the transmission of the electric power is not performed, a detection method capable of detecting a foreign object can be adopted.

  Further, in the new detection method, while power supply to the load 44 is being performed, the second detection method is used to determine the presence or absence of foreign matter. It is necessary to adopt a detection method capable of detecting foreign matter even when power is transmitted by the device 11.

  Therefore, as the first detection method, in addition to the foreign matter detection method based on the Q value, for example, the aforementioned foreign matter detection method using light, foreign matter detection method using an image, foreign matter detection method using an effective resistance value, etc. can be adopted. .

  Light foreign particle detection methods and image foreign particle detection methods have disadvantages in terms of cost, mounting area, etc. compared to foreign particle detection methods using Q values, but detection accuracy is relatively high, and power transmission Similar to the foreign matter detection method based on the Q value in that transmission of power by the magnetic field of the device 11 (wireless power supply) is affected as noise, and it is desirable to avoid performing constantly as much as possible from the viewpoint of power consumption. There is a nature.

  Further, as the second detection method, in addition to the foreign matter detection method by efficiency and the foreign matter detection method by temperature, for example, the foreign matter detection method by load described above can be adopted.

  Furthermore, in FIG. 7, in the communication unit 42 of the power receiving device 12, load modulation is performed by turning on and off the connection of the resistance, and the information is transmitted from the power receiving device 12 to the power transmission device 11. The communication method for communicating between the power transmission device 11 and the power reception device 12 is not limited to this.

  [Another Configuration Example of Power Receiving Device 12]

  FIG. 15 is a block diagram showing another configuration example of the power receiving device 12 of FIG.

  In the figure, the portions corresponding to the case of FIG. 7 are denoted with the same reference numerals, and the description thereof will be appropriately omitted below.

  The power receiving device 12 of FIG. 15A is common to the case of FIG. 7 in that it includes a resonant circuit 40, a rectifying unit 41, a regulator 43, a load 44, a control unit 45, and a foreign matter detecting unit 46.

  However, the power receiving device 12 of FIG. 15A is different from the case of FIG. 7 in that a communication unit 71 is provided instead of the communication unit 42.

  In FIG. 15A, the communication unit 71 is provided between the resonant circuit 40 and the rectifying unit 41.

  The communication unit 42 in FIG. 7 has an FET and a resistor, but the communication unit 71 has, for example, an FET and a capacitor, and the FET is turned on or under the control of the control unit 45. The capacitor is connected to the resonance circuit 40 or disconnected from the resonance circuit 40 by being turned off.

  The capacitor is connected to the resonance circuit 40 or disconnected from the resonance circuit 40, so that the impedance of the resonance circuit 40 as a load as viewed from the (external) power transmission device 11 changes, and the resonance circuit of the power transmission device 11 The current (voltage) flowing to 20 (FIG. 5) is load-modulated.

  The power receiving device 12 of FIG. 15B is common to the case of FIG. 7 in that it includes a resonant circuit 40, a rectifying unit 41, a regulator 43, a load 44, a control unit 45, and a foreign matter detecting unit 46.

  However, the power receiving device 12 of FIG. 15B is different from the case of FIG. 7 in that a communication unit 81 and a communication antenna 82 are provided instead of the communication unit 42.

  The communication unit 81 performs wireless communication in accordance with, for example, ZIGBEE (registered trademark), Bluetooth (registered trademark), a wireless LAN, or another communication method by transmitting and receiving radio waves using the communication antenna 82.

  When the power receiving device 12 includes the communication unit 81, the power transmission device 11 also needs to include a block capable of communicating with the communication unit 81.

  [Description of computer to which the present technology is applied]

  Next, at least a part of the processing performed by the control unit 24 of the power transmission device 11, the control unit 45 of the power reception device 12, and the determination unit 53 among the processing as the foreign matter detection function can be performed by hardware. It can also be done by software. When the processing is performed by software, a program that configures the software is installed on a computer (processor).

  FIG. 16 shows a configuration example of an embodiment of a computer in which a program for executing processing is installed.

  The program can be recorded in advance in a hard disk 105 or a ROM 103 as a recording medium built in the computer.

  Alternatively, the program can be stored (recorded) in the removable recording medium 111. Such removable recording medium 111 can be provided as so-called package software. Here, examples of the removable recording medium 111 include a flexible disc, a compact disc read only memory (CD-ROM), a magneto optical disc (MO), a digital versatile disc (DVD), a magnetic disc, a semiconductor memory, and the like.

  The program may be installed on the computer from the removable recording medium 111 as described above, or may be downloaded to the computer via a communication network or a broadcast network and installed on the built-in hard disk 105. That is, for example, the program is wirelessly transferred from the download site to the computer via an artificial satellite for digital satellite broadcasting, or transferred to the computer via a network such as a LAN (Local Area Network) or the Internet. be able to.

  The computer incorporates a CPU (Central Processing Unit) 102, and an input / output interface 110 is connected to the CPU 102 via a bus 101.

  When an instruction is input by the user operating the input unit 107 via the input / output interface 110, the CPU 102 executes a program stored in a ROM (Read Only Memory) 103 accordingly. . Alternatively, the CPU 102 loads a program stored in the hard disk 105 into a random access memory (RAM) 104 and executes the program.

  Thus, the CPU 102 performs the processing according to the above-described flowchart or the processing performed by the configuration of the above-described block diagram. Then, the CPU 102 outputs the processing result from the output unit 106, transmits the processing result from the communication unit 108, or records the processing result on the hard disk 105, for example, through the input / output interface 110, as necessary.

  The input unit 107 is configured of a keyboard, a mouse, a microphone, and the like. Further, the output unit 106 is configured of an LCD (Liquid Crystal Display), a speaker, and the like.

  Here, in the present specification, the processing performed by the computer according to the program does not necessarily have to be performed chronologically in the order described as the flowchart. That is, the processing performed by the computer according to the program includes processing executed in parallel or separately (for example, parallel processing or processing by an object).

  The program may be processed by one computer (processor) or may be distributed and processed by a plurality of computers. Furthermore, the program may be transferred to a remote computer for execution.

  Furthermore, in the present specification, the system means a set of a plurality of components (apparatus, modules (parts), etc.), and it does not matter whether all the components are in the same housing or not. Therefore, a plurality of devices housed in separate housings and connected via a network, and one device housing a plurality of modules in one housing are all systems. .

  Note that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present technology.

  For example, the present technology can have a cloud computing configuration in which one function is shared and processed by a plurality of devices via a network.

  Further, each step described in the above-described flowchart can be executed by one device or in a shared manner by a plurality of devices.

  Furthermore, in the case where a plurality of processes are included in one step, the plurality of processes included in one step can be executed by being shared by a plurality of devices in addition to being executed by one device.

  DESCRIPTION OF SYMBOLS 11 Power transmission apparatus, 12 power receiving apparatus, 20 resonance circuit, 21 DC power supply, 22 driver circuit, 23 waveform detection part, 24 control part, 31 gate drive circuit, 32 to 25 FET, 40 resonance circuit, 41 rectification part, 42 communication part , 43 regulator, 44 load, 45 control unit, 46 foreign substance detection unit, 51 Q value measurement unit, 52 efficiency measurement unit, 53 determination unit, 62 temperature measurement unit, 71, 81 communication unit, 82 communication antenna, 101 bus, 102 CPU, 103 ROM, 104 RAM, 105 Hard Disk, 106 Output Unit, 107 Input Unit, 108 Communication Unit, 109 Drive, 110 I / O Interface, 111 Removable Storage Medium

Claims (20)

A resonant circuit including a coil;
A detection unit that detects the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit;
A control unit configured to control transmission of power by the wireless power supply according to the detection result of the foreign matter;
The detection unit is
The information on the Q value of the coil transmitted from the power receiving device is included in the first period which is a period earlier than the second period which is a period of supplying the power to the power receiving device by the wireless power feeding. The presence / absence of the foreign matter is determined by a first detection method which is a method of determining the presence / absence of the foreign matter using the Q value of the coil based on the first determination information,
A power transmission device that detects the foreign matter by determining the presence or absence of the foreign matter by a second detection method different from the first detection method during the second period. The second detection method includes a method of determining the presence or absence of the foreign matter based on power efficiency representing a ratio of received power to transmission power in the wireless power supply or temperature with the power receiving device,
The detection unit determines the presence or absence of the foreign matter by the second detection method based on second determination information including information on the power efficiency or the temperature transmitted from the power reception device. Power transmission device as described. The control unit intermittently stops transmission of the power;
The power transmission device according to claim 1, wherein the first determination information includes information on a Q value obtained by the power receiving device while stopping transmission of the power. The power transmission device according to claim 2, wherein the control unit controls transmission of the power according to the temperature. It further comprises a housing that houses each part,
The housing uses a material other than metal in a portion to which the power receiving device can be approached,
The power transmission device according to claim 1, wherein the foreign matter includes a housing of the power receiving device or a metal used inside a housing of the power receiving device. The control unit
When a completion message indicating that charging has been completed is received from the power receiving device, transmission of the power is stopped,
The power transmission device according to claim 1, which notifies a user that the charging has been completed. A power supply supplying a predetermined voltage;
The power transmission device according to claim 1, further comprising: a driver circuit that drives the resonant circuit using a voltage from the power supply and transmits the power. It is configured as a cradle for portable terminals, a rack for home appliances, or a charging stand for electric vehicles,
The power transmission device according to claim 1, which is a set with one or more of the power receiving devices configured as a portable terminal, a home appliance, or an electric vehicle. It further comprises a communication antenna and a communication unit,
The power transmission device according to claim 1, wherein the communication unit performs wireless communication with the power reception device in accordance with a predetermined communication scheme. A resonant circuit including a coil;
A detection unit that detects the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit;
And a control unit configured to control transmission of power by the wireless power supply according to the detection result of the foreign matter.
The detection unit
The information on the Q value of the coil transmitted from the power receiving device is included in the first period which is a period earlier than the second period which is a period of supplying the power to the power receiving device by the wireless power feeding. The presence / absence of the foreign matter is determined by a first detection method which is a method of determining the presence / absence of the foreign matter using the Q value of the coil based on the first determination information,
In the second period, the foreign matter is detected by determining the presence or absence of the foreign matter by a second detection method different from the first detection method. A resonant circuit including a coil;
A processing unit that performs processing for detecting the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit;
A controller configured to control supply of power by the wireless power supply according to the detection result of the foreign matter;
The processing unit is
During the first period, which is a period earlier than the second period in which the power from the power transmission apparatus is supplied by the wireless power supply, the presence or absence of the foreign matter is determined using the Q value of the coil Transmitting, to the power transmission device, first determination information including information on a Q value of a coil, which is used when determining the presence or absence of the foreign matter by a first detection method which is a method of
In the second period, second determination information different from the first determination information used when determining the presence or absence of the foreign matter by the second detection method different from the first detection method, A power receiving device that performs processing for detecting the foreign matter by transmitting to a power transmission device. The second detection method includes a method of determining the presence or absence of the foreign matter based on power efficiency representing a ratio of received power to transmission power in the wireless power supply or temperature with the power transmission device.
The power receiving device according to claim 11, wherein the second determination information includes information related to the power efficiency or the temperature. The processing unit is
The frequency at which the Q value of the coil is obtained is detected as a resonant frequency,
The power reception device according to claim 11, wherein the detected resonant frequency is transmitted to the power transmission device. It further comprises a housing that houses each part,
The power receiving device according to claim 11, wherein the foreign matter includes the housing or a metal used inside the housing. The power receiving device according to claim 11, wherein the control unit, when charging is completed, notifies a user that the charging is completed. A rectifying unit that rectifies a current flowing through the resonant circuit;
A regulator that stabilizes the current rectified by the rectifying unit;
The power receiving device according to claim 11, further comprising: a load in which the power transmitted by the wireless power supply is supplied via the resonance circuit, the rectifying unit, and the regulator. The power receiving device according to claim 12, further comprising a temperature measurement unit configured to measure the temperature in the vicinity of the coil. Configured as a mobile terminal, a home appliance, or an electric car,
The power reception device according to claim 11, which is a set with the power transmission device configured as a cradle for a portable terminal, a rack for a home appliance, or a charging stand for an electric vehicle. It further comprises a communication antenna and a communication unit,
The power receiving device according to claim 11, wherein the communication unit performs wireless communication with the power transmission device according to a predetermined communication scheme. A resonant circuit including a coil;
A processing unit that performs processing for detecting the presence or absence of a foreign object that affects wireless power feeding using the resonant circuit;
And a control unit configured to control supply of power by the wireless power supply according to the detection result of the foreign matter.
The processing unit
During the first period, which is a period earlier than the second period in which the power from the power transmission apparatus is supplied by the wireless power supply, the presence or absence of the foreign matter is determined using the Q value of the coil Transmitting, to the power transmission device, first determination information including information on a Q value of a coil, which is used when determining the presence or absence of the foreign matter by a first detection method which is a method of
In the second period, second determination information different from the first determination information used when determining the presence or absence of the foreign matter by the second detection method different from the first detection method, A power receiving method for performing processing for detecting the foreign matter by transmitting to a power transmission device.

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