Patent Publication Number: US-2021175756-A1

Title: Power receiving apparatus, power transmitting apparatus, method for controlling same, and computer-readable medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a power receiving apparatus, a power transmitting apparatus, a method for controlling the same, and a computer-readable medium. 
     Description of the Related Art 
     Development of technology relating to wireless power transmission systems such as wireless charging systems has been carried out extensively in recent years. In wireless power transmission systems, when a foreign object enters between a power transmitting apparatus and the power receiving apparatus, this incursion needs to be detected and power transmission needs to be restricted. As defined in the standard created by the Wireless Power Consortium (WPC), a standards development group for wireless charging, foreign object detection is performed on the basis of power loss, which is the difference between the transmission power and reception power, and the Quality-factor (hereinafter, referred to as Q-factor) of resonance in a power transmitting coil. Foreign object detection is performed by comparing the power loss or Q-factor to a threshold. 
     Japanese Patent Laid-Open No. 2015-164368 describes detecting a foreign object on the basis of the temperature between a power transmitting apparatus and a power receiving apparatus as per WPC standard and, in the case in which a foreign object is determined to exist, notify the user via audio or a display and restrict power transmission. 
     However, detecting the existence of a foreign object in a binary manner using exist and not exist may lead to certain issues. For example, in the case in which the power loss value is close to the threshold used to detect the existence of a foreign object, the existence of a foreign object may be falsely determined due to an error in measuring the power loss. This issue is also found in cases other than when using the power loss value, such as cases in which the existence of a foreign object is detected on the basis of a Q-factor or temperature. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides technology for implementing notifications appropriate to a user regarding presence or absence of a foreign object. 
     According to one aspect of the present disclosure, there is provided a power receiving apparatus, comprising: a power receiving unit configured to wirelessly receive power from a power transmitting apparatus; a communication unit configured to communicate with the power transmitting apparatus; a determination unit configured to determine, on the basis of foreign object existence information obtained from the power transmitting apparatus via the communication unit, one state from at least three states including a first state in which a foreign object exists in a power-transmittal range of the power transmitting apparatus, a second state in which a foreign object possibly exists in the power-transmittal range, and a third state in which a foreign object does not exist in the power-transmittal range; and a notification unit configured to perform a first notification when the first state is determined by the determination unit and perform a second notification, different from the first notification, when the second state is determined. 
     According to another aspect of the present disclosure, there is provided a power transmitting apparatus that wirelessly transmits power to a power receiving apparatus, comprising: a communication unit configured to communicate with the power receiving apparatus; and a transmission unit configured to transmit, to the power receiving apparatus via the communication unit, foreign object existence information that is information used by the power receiving apparatus to determine one state from at least three states including a first state in which a foreign object exists in a power-transmittal range of the power transmitting apparatus, a second state in which a foreign object possibly exists in the power-transmittal range, and a third state in which a foreign object does not exist in the power-transmittal range. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example configuration of a wireless charging system according to an embodiment. 
         FIG. 2  is a diagram illustrating an example configuration of a power receiving apparatus according to a first embodiment. 
         FIG. 3  is a diagram illustrating an example configuration of a power transmitting apparatus according to the first embodiment. 
         FIG. 4  is a flowchart illustrating an example of processing in the power receiving apparatus according to the first embodiment. 
         FIG. 5  is a flowchart illustrating an example of processing in the power transmitting apparatus according to the first embodiment. 
         FIGS. 6A to 6C  are diagrams illustrating examples of notifications for the user performed by the power receiving apparatus according to the first embodiment. 
         FIG. 7A  is a diagram for describing foreign object existence information generated by the power transmitting apparatus according to the first embodiment. 
         FIG. 7B  is a diagram for describing foreign object existence information generated by a power transmitting apparatus according to a second embodiment. 
         FIGS. 8A and 8B  are flowcharts for describing the operation of a power receiving apparatus of the second embodiment, 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted. 
     First Embodiment 
     1. System Configuration 
       FIG. 1  illustrates an example configuration of a wireless charging system (wireless power transmission system) according to the first embodiment. The system includes a power receiving apparatus  101  and a power transmitting apparatus  102 . Hereinafter, the power receiving apparatus may also be referred to as RX, and the power transmitting apparatus may also be referred to as TX. TX  102  is an electronic apparatus that wirelessly transmits power to the RX  101  placed in a charging stand  103 . The RX  101  is an electronic apparatus with a built-in battery that is charged by receiving power transmitted wirelessly from the TX  102 . In the example described below, the RX  101  is placed in the charging stand  103 . 
     Note that the RX  101  and the TX  102  may have a function of executing an application other than wireless charging. An example of the RX  101  is a smartphone, and an example of the TX  102  is an accessory device for charging the smartphone. The RX  101  and the TX  102  may be storage devices, such as a hard disk or a memory device, or may be information processing devices such as a personal computer (PC). Also, the RX  101  and the TX  102 , for example, may be image input devices, such as an image capture apparatus (a camera, a video camera, and the like) or a scanner, or may be an image output device, such as a printer, copying machine, or a projector. Also, the TX  102  may be a smartphone. In this case, the RX  101  may be another smartphone or a wireless earphone. Also, the RX  101  may be a vehicle. Also, the TX  102  may be a charger placed on the console or the like inside the vehicle. 
     Also, in the present embodiment, one RX  101  and one TX  102  are illustrated. However, other embodiments may have a configuration in which a plurality of RX  101  are charged by a single TX  102  or different individual TXs  102 . 
     In the present system, wireless power transmission is performed using an electromagnetic induction method for wireless charging on the basis of the WPC standard. In other words, for the RX  101  and the TX  102 , wireless power transmission is performed between a power receiving coil of the RX  101  and a power transmitting coil of the TX  102  to perform a wireless charge based on the WPC standard. Note that the wireless power transmission system (wireless power transmission method) used in the present system is not limited to that defined in the WPC standard, and other systems may be used, such as other electromagnetic induction systems, magnetic field resonance systems, electric field resonance systems, microwave systems, lasers, and the like. Also, in the present embodiment, the wireless charging uses wireless power transmission. However, wireless power transmission may be used for a different purpose other than for wireless charging. 
     The RX  101  and the TX  102  according to the present embodiment communicate to perform power transmission and reception control based on the WPC standard. The WPC standard defines a plurality of phases including a power transfer phase in which power is transmitted and phases before actual power transmission. In these phases, communication is executed to control the transmitting and receiving of power as necessary. Pre-power transmission phases include a selection phase, a ping phase, and an identification and configuration phase. Other phases may also be included. Note that hereinafter, the identification and configuration phase will be referred to as the I&amp;C phase. 
     In the selection phase, the TX  102  intermittently transmits an analog ping and detects if an object is placed on the charging stand  103  (for example, if the RX  101 , conductor piece, or the like is placed on the charging stand  103 ). The TX  102  detects at least a voltage value or a current value of a power transmitting coil when the analog ping was transmitted, determines that an object exists in the case in which the voltage value is less than a threshold or the current value is greater than a threshold, and transitions to the ping phase. 
     In the ping phase, the TX  102  transmits a digital ping with more power than the analog ping. The amount of power of the digital ping is sufficient enough to activate a control unit of the RX  101  placed on the charging stand  103 . The RX  101  notifies the TX  102  of the amount of the received voltage. In this way, by receiving a reply from the RX  101  that received the digital ping, the TX  102  recognizes that the object detected in the selection phase is the RX  101 . When the TX  102  receives a notification of the received voltage value, the process transitions to the I&amp;C phase. 
     In the I&amp;C phase, the TX  102  identifies the RX  101  and acquires device configuration information (capability information) from the RX  101 . The information includes a number indicating the model and the individual of the RX  101 , information indicating the maximum power required by the RX  101 , information indicating the operation mode that the RX  101  supports, and the like. An example of the operation mode information is whether Extended Power Profile (hereinafter, referred to as EPP) of the WPC standard is supported. By replying to the device configuration information (capability information) via an acknowledge (ACK), the TX  102  ends the I&amp;C phase and transitions to the power transfer phase. Note that in the case in which EPP is supported by the RX  101  and the TX  102  a different operation phase defined in the WPC standard may be transitioned to and additional communications and operations may be performed. 
     In the power transfer phase, control is performed to start power transmission, continue power transmission, and stop power transmission due to detection of a foreign object or a full charge. Note that hereinafter, “stop power transmission” includes in its meaning restricting power transmission to a small amount of power transmission without fully stopping power transmission. 
     The TX  102  and the RX  101  perform communication, for controlling the transmitting and receiving of power therebetween, that superimposes a signal on the transmission power using the same antenna (coil) as for the wireless power transmission on the basis of the WPC standard. Note that between the TX  102  and the RX  101 , the range in which communication that superimposes a signal on the transmission power can be performed is substantially similar to the power-transmittal range of the TX  102 . 
     Also, the TX  102  and the RX  101  may perform communication for power transmission and reception control using a different antenna (coil) to that used for wireless power transmission. An example of communication using a different antenna to that used for wireless power transmission is a communication system compliant with the Bluetooth (registered trademark) Low Energy standard. Other examples of communication using a different antenna to that used for wireless power transmission include IEEE  802 . 11  standard series wireless LAN (for example, Wi-Fi (registered trademark)) and ZigBee (registered trademark), Furthermore, communication using a different antenna (coil) to that used for wireless power transmission may be performed using another communication system, such as Near Field Communication (NFC), Radio Frequency Identifier (RFID), and the like. Communication using a different antenna (coil) to that used for wireless power transmission may be performed on a different frequency to that used for wireless power transmission. 
     2. Apparatus Configuration 
     Next, the configuration of the power receiving apparatus  101  (RX  101 ) and the power transmitting apparatus  102  (TX  102 ) according to the first embodiment will be described. Note that the configuration described below is simply one example, and a part (or all parts) of the configuration described below may be replaced by other configurations with similar functions, may be omitted, or other configurations may be added in addition to the configurations described below. Furthermore, one block described in the description below may be divided into a plurality of blocks or a plurality of blocks described in the description may be merged as a single block. 
     2.1 Power Receiving Apparatus Configuration 
       FIG. 2  is a diagram illustrating an example configuration of the RX  101  according to the first embodiment. The RX  101  includes a control unit  201 , a battery  202 , a power receiving unit  203 , a detecting unit  204 , a power receiving coil  205  a communication unit  206 , a notification unit  207 , an operation unit  208 , memory  209 , a tinier  210 , a charging unit  211 , and a foreign object existence information obtaining unit  212  (hereinafter, information obtaining unit  212 ). 
     The control unit  201 , for example, controls the entire RX  101  by executing a control program stored in the memory  209 . In other words, the control unit  201  controls the functional units illustrated in  FIG. 2 . Also, the control unit  201  executes control relating to power reception control of the RX  101 . Furthermore, the control unit  201  may execute control for executing an application other than wireless power transmission. The control unit  201 , for example, includes one or more processors, such as a central processing unit (CPU), a micro processing unit (MPU), or the like. Note that the control unit  201  may be constituted by hardware dedicated to specific processing, such as an application specific integrated circuit (ASIC), or the like. Also, the control unit  201  may include an array circuit such as a field programmable gate array (FPGA) compiled so as to execute predetermined processing. The control unit  201  causes information stored during the execution of various types of processing to be stored in the memory  209 . Also, the control unit  201  is capable of measuring time using the tinier  210 . 
     The battery  202  supplies the power to the entire RX  101  required for the control, power reception, and communication of the RX  101  by the control unit  201 . Also, the battery  202  stores the power received via the power receiving coil  205 . 
     The power receiving coil  205  generates power via electromagnetic induction utilizing electromagnetic waves radiated from the power transmitting coil of the TX  102 . The power receiving unit  203  obtains the power generated at the power receiving coil  205 . The power receiving unit  203  obtains alternating current power generated via electromagnetic induction at the power receiving coil  205 . Also, the power receiving unit  203  converts the alternating current power to direct current or alternating current power of a predetermined frequency and outputs the power to the charging unit  211  that executes processing to charge the battery  202 . In other words, the power receiving unit  203  supplies power to a load in the RX  101 . Furthermore, by the power receiving unit  203  notifying the control unit  201  of the current reception power value, the reception power value at any discretionary time can be known by the control unit  201 . Note that a configuration may be employed in which measuring the reception power and notifying the control unit  201  is performed by a unit other than the power receiving unit  203 . 
     The detecting unit  204  detects the RX  101  placed on the charging stand  103  on the basis of the WPC standard. The detecting unit  204 , for example, detects at least the voltage value or the current value of the power receiving coil  205  at the time when the power receiving unit  203  receives a digital ping according to the WPC standard via the power receiving coil  205 . The detecting unit  204 , for example, determines that the RX  101  is placed on the charging stand  103  in the case in which the voltage value is less than a predetermined voltage threshold or the current value is greater than a predetermined current threshold.  100361  The communication unit  206  performs control communication with the TX  102  based on the WPC standard such as that described above. The communication unit  206  performs communication with the TX  102  by acquiring information transmitted from the TX  102  by demodulating electromagnetic waves input from the power receiving coil  205 , and by superimposing, on electromagnetic waves, information to be transmitted to the TX  102  by performing load modulation on the electromagnetic waves. In other words, communication performed by the communication unit  206  is performed by superimposition of information on electromagnetic waves transmitted from the power transmitting coil of the TX  102 . Note that, as described above, the communication unit  206  may perform communication for power transmission and reception control using a different antenna to that used for wireless power transmission. 
     The notification unit  207  notifies the user of information via a discretionary method, such as a visual, auditory, or tactile method. The notification unit  207 , for example, notifies the user of the charge state of the RX  101  or the state of the power transmission of the wireless power transmission system including the TX  102  and the RN  101  as illustrated in  FIG. 1 . The notification unit  207 , for example, includes a liquid crystal display or LED, a speaker, a vibration generation circuit, or another type of notification device. 
     The operation unit  208  has a reception function of receiving operations for the RX  101  from the user. The operation unit  208 , for example, includes a button or keyboard, an audio input device such as a microphone, a motion detection device such as an acceleration sensor or gyro sensor, or another type of input device. Note that the notification unit  207  and the operation unit  208  may be formed integrally as a single device such as a touch panel. 
     As described above, the memory  209  stores various information, such as identification information and device configuration information, a control program, and the like. Also, the memory  209  functions as a work memory for storing information as necessary during the execution of various types of processing by the control unit  201 . Note that the memory  209  may store information obtained by a functional unit other than the control unit  201 . 
     The timer  210 , for example, measures time via a count up timer that measures the elapsed time from the time of activation or via a countdown timer that counts down from a set time. 
     The charging unit  211  charges the battery  202  via power supplied from the power receiving unit  203 . Also, the charging unit  211  starts or stops charging of the battery  202  on the basis of control from the control unit  201  and adjusts the power used to charge the battery  202  on the basis of the charge state of the battery  202 . When the power used by the charging unit  211  changes, the power supplied from the power receiving unit  203 , i.e., the reception power at the RX  101 , changes according to this change. The charging unit  211  is a load in the RX  101 . 
     The information obtaining unit  212  obtains foreign object existence information from the TX  102  using the communication unit  206 . The foreign object existence information can be represented in three levels: a foreign object exists, a foreign object possibly exists, and a foreign object does not exist. Note that the foreign object existence information may be represented in more than three levels. The information obtaining unit  212  is a program that operates on the control unit  201  that is stored in the memory  209 , for example, and read out by the control unit  201  when executed. Note that the information obtaining unit  212  may be configured to operate on a CPU other than the control unit  201 . 
     2.2 Power Transmitting Apparatus Configuration 
       FIG. 3  is a diagram illustrating the configuration of the TX  102  according to the present embodiment. The TX  102  includes, for example, a control unit  301 , power supply unit  302 , a power transmitting unit  303 , a detecting unit  304 , a power transmitting coil  305 , a communication unit  306 , a notification unit  307 , an operation unit  308 , memory  309 , a timer  310 , and a foreign object existence information transmitting unit  311  (hereinafter, information transmitting unit  311 ). 
     The control unit  301 , for example, controls the entire TX  102  by executing a control program stored in the memory  309 . In other words, the control unit  301  controls the functional units illustrated in  FIG. 3 . Also, the control unit  301  executes control relating to power transmission control of the TX  102 . Furthermore, the control unit  301  may execute control for executing an application other than wireless power transmission. The control unit  301 , for example, includes one or more processors, such as a CPU, an MPU, or the like. Note that the control unit  301  may include hardware dedicated to specific processing such as an application specific integrated circuit (ASIC) or an array circuit such as a FPGA compiled so as to execute predetermined processing. The control unit  301  causes information stored during the execution of various types of processing to be stored in the memory  309 . Also, the control unit  301  is capable of measuring time using the timer  310 . 
     The power supply unit  302  supplies the power to the entire TX  102  required for the control, power transmission, and communication of the TX  102  by the control unit  301 . The power supply unit  302 , for example, is a commercial power source or a battery. Power supplied from a commercial power source is stored in the battery. 
     The power transmitting unit  303  converts direct current or alternating current power input from the power supply unit  302  to AC power in a frequency band used for wireless power transmission and generates electromagnetic waves for reception by the RX  101  by inputting the AC power into the power transmitting coil  305 . Note that the frequency of the alternating current power generated by the power transmitting unit  303  is approximately in the hundreds of kHz range (for example, from 110 kHz to 205 kHz). The power transmitting unit  303  inputs the AC power to the power transmitting coil  305  to output, from the power transmitting coil  305 , electromagnetic waves for performing power transmission to the RX  101  on the basis of instructions from the control unit  301 . Also, the power transmitting unit  303  controls the intensity of the electromagnetic waves to be output by adjusting either one or both of the voltage (power transmission voltage) and the current (power transmission current) input to the power transmitting coil  305 . If power transmission voltage or power transmission current is increased, the intensity of electromagnetic waves is increased, and if power transmission voltage or power transmission current is decreased, the intensity of electromagnetic waves is decreased. In addition, on the basis of an instruction from the control unit  301 , the power transmitting unit  303  performs output control of the AC power to start or stop power transmission from the power transmitting coil  305 . Furthermore, by the power transmitting unit  303  notifying the control unit  301  of the current transmission power value, the transmission power value at any discretionary time can be known by the control unit  301 . Note that a configuration may be employed in which measuring the transmission power and notifying the control unit  301  is performed. by a unit other than the power transmitting unit  303 . 
     The detecting unit  304  detects whether an object is placed on the charging stand  103  on the basis of the WPC standard. Specifically, the detecting unit  304  detects whether or not an object is placed on an interface surface of the charging stand  103 . The detecting unit  304 , for example, detects at least the voltage value or the current value of the power transmitting coil  305  at the time when the power transmitting unit  303  transmits an analog ping according to the WPC standard via the power transmitting coil  305 . Note that the detecting unit  304  may detect a change in impedance. Also, the detecting unit  304 , for example, is capable of determining that an object is placed on the charging stand  103  in the case in which the voltage is less than a predetermined voltage value or the current value is greater than a predetermined current value. Note that next a digital ping is transmitted via communications by the communication unit  306  to determine whether the object is a power receiving apparatus or a different object on the basis of whether or not there is a predetermined reply to the digital ping. 
     In other words, in the case in which the TX  102  receives the predetermined reply, the object is determined to be a power receiving apparatus and, in the other case, the object is determined to be an object other than a power receiving apparatus. 
     The communication unit  306  performs control communication with the RX  101  based on the WPC standard such as that described above. The communication unit  306  performs communication including modulating the electromagnetic waves output from the power transmitting coil  305  and transmitting information to the RX  101 . Also, the communication unit  306  demodulates the electromagnetic waves modulated at the RX  101  outputs from the power transmitting coil  305  and obtained the information transmitted by the RX  101 . In other words, communication performed by the communication unit  306  is performed by superimposition of information on electromagnetic waves transmitted from the power transmitting coil  305 . Note that, as described above, the communication unit  306  may perform communication for power transmission and reception control using a different antenna to that used for wireless power transmission. 
     The notification unit  307  notifies the user of information via a discretionary method, such as a visual, auditory, or tactile method. The notification unit  307 , for example, notifies the user of information indicating the charge state of the TX  102  or the state of the power transmission of the wireless power transmission system including the TX  102  and the RX  101  as illustrated in  FIG. 1 . The notification unit  307 , for example, includes a liquid crystal display or LED, a speaker, a vibration generation circuit, or another type of notification device. 
     The operation unit  308  has a reception function of receiving operations for the TX  102  from the user. The operation unit  308 , for example, includes a button or keyboard, an audio input device such as a microphone, a motion detection device such as an acceleration sensor or gyro sensor, or another type of input device. Note that the notification unit  307  and the operation unit  308  may be formed integrally as a single device such as a touch panel. 
     The memory  309  stores various information, a control program, and the like. Also, the memory  309  functions as a work memory for storing information as necessary during the execution of various types of processing by the control unit  301 . Note that the memory  309  may store information obtained by a functional unit other than the control unit  301 . 
     The timer  310 , for example, measures time via a count up timer that measures the elapsed time from the time of activation or via a countdown timer that counts down from a set time. 
     The information transmitting unit  311  generates foreign object existence information and transmits the information to the RX  101  using the communication unit  306 . The method for generating foreign object existence information will be described below. The information transmitting unit  311  is a program that operates on the control unit  301  that is stored in the memory  309 , for example, and read out by the control unit  301  when executed. Note that the information transmitting unit  311  may be configured to operate on a CPU other than the control unit  301 . 
     Processing Flow 
     Next, an example of the flow of the processing executed by the RX  101  and the TX  102  will be described. 
     Processing in the Power Receiving Apparatus 
       FIG. 4  is a flowchart illustrating an example of the flow of the processing executed by the RX  101 . The present processing can be implemented by the control unit  201  of the RX  101  executing a program read out from the memory  209 , for example. The present processing also includes processing in the information obtaining unit  212 . Note that at least a part of the process of the present processing described below may be implemented by hardware. In the case of implementing processing by hardware, for example, the processing can be implemented by automatically generating, by using a predetermined compiler, a dedicated circuit that uses a gate array such as an FPGA from a program for implementing each type of processing. Also, the present processing may be executed in response to the power source of the RX  101  being turned on, in response to the RX  101  being activated by power being supplied from the battery  202  or the TX  102 , or in response to the user of the RX  101  inputting a wireless charging application start instruction. Also, the present processing may be started by another trigger. 
     After the processing relating to transmitting and receiving power is started, the RX  101  executes processing defined in the WPC standard as a selection phase and a ping phase and waits for the RX  101  to be placed on the TX  102  (step S 401 ). The RX  101 , for example, detects that the RX  101  is placed on the charging stand  103  of the TX  102  by detecting a digital ping from the TX  102 . Then, when the RX  101  detects a digital ping, a signal strength packet (received voltage value) is transmitted to the TX  102 . 
     When the RX  101  detects that the RX  101  is placed on the charging stand  103  of the TX  102 , the RX  101  executes processing defined in the WPC standard as the I&amp;C phase and transmits identification information and device configuration information (capability information) to the TX  102  via the communication unit  206  (step S 402 ). Note that the TX  102  may be notified of the identification information and the device configuration information (capability information) of the RX  101  by the RX  101  by a method other than communication in the I&amp;C phase according to the WPC standard. 
     Next, the RX  101  start receiving power for charging from the TX  102  and starts charging the battery  202  with the charging unit  211  (step S 403 ). After step S 403 , control to receive power is performed until full charge or a foreign object is detected according to the control in the power transfer phase defined in the WPC standards. In the present embodiment, the power transmission and reception control is performed based on detection of fully charging or a foreign object. However, control other than control described in the embodiments may be performed. Also, power transmission and reception control may be performed by a method other than a method according to the WPC standard. 
     After the RX  101  starts receiving power for charging in step S 403 , the RX  101  detects the current reception power value at the power receiving unit  203  and transmits reception power information to the TX  102  (step S 404 ). Then, the RX  101  obtains foreign object existence information from the TX  102  (step S 405 ). For example, the reception power information is transmitted as a received power packet according to the WPC standard, and the foreign object existence information is obtained by receiving the reply thereto. In this case, the foreign object existence information is included in the reply to the received power packet and transmitted by the TX  102 . 
     Here, the foreign object existence information is the value 1, 2, or 3, where 1 indicates that a foreign object does not exist, 2 indicates that a foreign object possibly exists, at 3 indicates that a foreign object exists. Note that as described above, the combination of the numbers 1 to 3 and their meaning is not limited to the above example. The branching described below is performed on the basis of the foreign object existence information (step S 406 ). 
     First, an example in which the foreign object existence information equals 1, i.e., a foreign object does not exist, in step S 406  will be described. In this case, the RX  101  continues charging (step S 407 ), and the RX  101  notifies the user via the notification unit  207  that the charging is in progress (step S 408 ). 
     As example of the notification performed via the notification unit  207  in step S 408  is illustrated in  FIG. 6A . As illustrated in  FIG. 6A , the electronic apparatus, which is the RX  101 , includes an LED  701  that indicates whether or not the apparatus is charging and a liquid crystal display  702  for various types of display. The LED  701  and the liquid crystal display  702  constitute the notification unit that notifies the user. The RX  101  indicates that it is charging by turning on the LED  701 . At this time, as illustrated in the drawing, nothing is displayed on the liquid crystal display  702 . Note that a percentage of the remaining power of the battery  202  may be displayed on the liquid crystal display as indicating of the charging progress or another type of display may be performed. Also, in addition to or instead of the LED  701  turning on and the display on the liquid crystal display  702 , audio or vibration may be used to perform a notification. Here, the length of continuous charging in step S 407  may be a predetermined amount of time measured by the timer  210  stored in advance in the memory  209  or may be until a predetermined packet is received from the TX  102 . 
     After charging and charging notification have been performed (step S 407 , step S 408 ), the RX  101  confirms whether the battery  202  is fully charged. If the battery  202  is not fully charged (NO in step S 409 ), the process returns to step S 404  and reception power information is transmitted. If the battery  202  is fully charged (YES in step S 409 ), charging is stopped (step S 412 ), a power transmission stop request is transmitted to the TX  102  (step S 413 ), the user is notified via the notification unit  207  that charging is stopped (step S 414 ), and the process ends. Note that after the processing of step S 414  ends, the RX  101  may return to step S 401  and wait until it is placed on the TX  102  again. 
     An example of the notification of step S 414  indicating that charging is stopped is illustrated in  FIG. 6C . The RX  101  turns off the LED  701  that indicates whether or not charging is in progress. At this time, as illustrated in the drawing, nothing is displayed on the liquid crystal display  702 . Note that characters informing that charging has stopped or another display may be displayed on the liquid crystal display  702 . Also, in addition to or instead of using the LEI)  701  and the liquid crystal display  702 , audio or vibration may be used to perform a notification. 
     Next, an example in which the foreign object existence information equals  2 , i.e., a foreign object possibly exists, in step S 406  will be described. In this case, the RX  101  notifies the user to confirm that there is no foreign object via the notification unit  207  (step S 410 ). After the notification, if the user, using the operation unit  208 , finishes a confirmation operation (an operation to confirm there is no foreign object) within a predetermined amount of time (YES in step S 411 ), the process proceeds to step S 408  and the RX  101  continues charging. If not (NO in step S 411 ), the process proceeds to step S 412  and the RX  101  stops charging. The process from step S 408  onward and the process from step S 412  onward are the same as described above. 
     An example of the notification unit  207  and the operation unit  208  in step S 410  and step S 411  is illustrated in  FIG. 6B . Because charging is still being continued in step S 410 , the LED  701  that indicates whether or not charging is in progress is turned on. Also, on the liquid crystal display  702 , a message prompting the user to confirm that there is no foreign object and a confirmation button  703  is displayed. The operation unit  208  is integrally formed with the liquid crystal display  702  as a touch panel and obtains operation information by detecting the confirmation button  703  being tapped and the user confirming that there is no foreign object. Note that, in the notification of  FIG. 6B , a message may be added to prompt the user to, if there is a foreign object, remove the foreign object and then push the confirmation button  703 . 
     Next, an example in which the foreign object existence information equals  3 , i.e., a foreign object exists, in step S 406  will be described. In this case, the RX  101  stops charging (step S 412 ), transmits a power transmission stop request to the TX  102  (step S 413 ), and notifies the user via the notification unit  207  that charging is stopped (step S 414 ,  FIG. 6C ), and the process ends. Note that the user may be notified that a foreign object exists via the notification unit  207  before the process proceeds from step S 406  to step S 412 . This notification differs from that of  FIGS. 6A, 6B, and 6C . For example, a message informing the user that charging will stop due to a foreign object existing is displayed on the liquid crystal display  702 . 
     To summarize the process from step S 404  to step S 414  described above, if the foreign object existence information obtained from the TX  102  indicates that a foreign object does not exist, charging is continued and the user is notified as illustrated in  FIG. 6A  (step S 407 , step S 408 ). If the foreign object existence information indicates that a foreign object possibly exists, the user is notified as illustrated in  FIG. 6B  and charging is continued or stopped on the basis of the result of a confirmation operation by the user (step S 410 , step S 411 , step S 407 , step S 412 ). If the foreign object existence information indicates that a foreign object exists, charging is stopped and the user is notified as illustrated in  FIG. 6C  (step S 412  to step S 414 ). If full charge is reached, charging is stopped (step S 412  to step S 414 ). 
     3.2 Processing in the Power Transmitting Apparatus 
     Next, an example of the flow of the processing executed by the TX  102  will be described using  FIG. 5 . The present processing can be implemented by the control unit  301  of the TX  102  executing a program read out from the memory  309 , for example. Note that at least a part of the process described below may be implemented by hardware. In the case of implementing processing by hardware, for example, the processing can be implemented by automatically generating, by using a predetermined compiler, a dedicated circuit that uses a gate array such as an FPGA from a program for implementing each type of processing. Also, the present processing can be executed in response to the power source of the TX  102  being turned on, in response to the user of the TX  102  inputting a wireless charging application start instruction, or in response to the TX  102  connecting to a commercial power source and receiving power supply. Also, the present processing may be started by another trigger. 
     As illustrated in  FIG. 5 , the TX  102  first executes processing defined in the WPC standard as a selection phase and a ping phase and waits for the RX  101  to be placed (step S 501 ). Specifically, the TX  102  repeats an analog ping according to the WPC standard, transmitting it intermittently, and detects whether or not an object is placed on the charging stand  103 . If the TX  102  detects an object placed on the charging stand  103 , the TX  102  transmits a digital ping. Also, if a predetermined reply (a signal strength packet) to the digital ping is received, then the detected object is determined to be the RX  101  and the RX  101  is determined to be placed on the charging stand  103 . 
     When the TX  102  detects the placement of the RX  101 , the TX  102  executes the I&amp;C phase communication described above via the communication unit  306  and obtains identification information and device configuration information (capability information) from the RX  101  (step S 502 ). Note that the TX  102  may obtain the identification information and the device configuration information (capability information) of the RX  101  from the RX  101  by a method other than I&amp;C phase communication according to the WPC standard. 
     Next, the TX  102  starts power transmission to charge the RX  101  (step S 503 ). After step S 503 , control to transmit power is performed until full charge or a foreign object is detected according to the control in the power transfer phase defined in the WPC standards. Note that control other than the control described in the present embodiment may be performed. Also, control may be performed by a method other than a method according to the WPC standard. 
     After power transmission for charging is started in step S 503 , the TX  102  receives the current reception power information from the RX  101  (step S 504 ). Furthermore, the current power loss is found from the difference between the current reception power value included in the reception power information and the current transmission power value of the TX  102  detected at the power transmitting unit  303  and the three level foreign object existence information is generated based on the power loss (step S 505 ). The TX  102  transmits the foreign object existence information generated as described above to the RX  101  (step S 506 ). Note that in step S 504 , for example, the reception power information can be obtained by receiving a received power packet according to the WPC standard. in step S 506 , for example, the TX  102  transmits a reply to the received power packet including the foreign object existence information. 
     A method for generating the foreign object existence information from the power loss will be described using  FIG. 7A . In the case in which a foreign object exists between the power transmitting coil  305  of the TX  102  and the power receiving coil  205  of the RX  101 , power is consumed and power loss is increased, in the case in which the power loss is a sufficiently large value, for example 750 mW or greater, the foreign object existence information is 3 (indicating a state (a first state) in which a foreign object exists in the power-transmittal range of the TX  102 ). In the case in which the power loss is a sufficiently small value, for example 250 mW or less, the foreign object existence information is 1 (indicating a state (a third state) in which a foreign object does not exist in the power-transmittal range). Also, in the case in which the power loss is between 250 mW and 750 mW, the foreign object existence information is 2 (indicating a state (a second state) in which a foreign object possibly exists in the power-transmittal range). This means that it is difficult to determine the foreign object&#39;s existence, i.e., whether or not a foreign object exists due to a measurement error of the power or the like. 
     Note that the values for the foreign object existence information indicating the existence state of the foreign object are set as 1, 2, and 3 according to the meaning. However, as long as the states can be allocated to at least three distinct levels, another allocation method may be used. Also, the thresholds of 250 mW and 750 mW for power illustrated in  FIG. 7A  are examples, and other thresholds may be used. These thresholds may be stored in advance in the memory  209  of the TX  102  or may be set dynamically according to the amount of transmission power. In the case in which the thresholds are set according to the amount of transmission power, the result of processing of a calibration phase defined in the WPC standard may be used. Also, the value of power loss as is may be used as the foreign object existence information. In this case, thresholds of 250 mW and 750 mW may be stored on the RX  101  and three distinct levels may be used. In this case, as with the processing in step S 505 , the RX  101  may determine the foreign object existence state from among the first state to the third. state described above on the basis of the foreign object existence information (power loss value). 
     Also, the foreign object existence information may be generated on the basis of a value other than the power loss, as long as this value changes depending on whether or not a foreign object exists. For example, the foreign object existence information may be generated on the basis of the Q-factor of resonance in the power transmitting coil  305 , defined in the WPC standard. Note that in the case in which the foreign object existence information is generated on the basis of the Q-factor, the RX  101  may obtain the foreign object existence information via a reply packet to a FOD status packet according to the WPC standard. Also, the foreign Object existence information may be generated on the basis of the temperature between the TX  102  and the RX  101 . Furthermore, a foreign object existence probability from 0 to 100% obtained from combining one or more values that change depending on whether or not a foreign object exists may be used as the foreign object existence information. In this case, the three levels can be defined as, for example, 80% or greater indicating that a foreign object exists, 20% or less indicating that a foreign object does not exist, and between 20% and 80% indicating that a foreign object possibly exists. Also, information including at least one from among: information for specifying the power loss, information for specifying the Q-factor, and information for specifying the temperature may be used as the foreign object existence information. In this case, for example, the foreign object existence information includes at least one of the value for power loss, the Q-factor, or the value for temperature described above. 
     Returning to  FIG. 5 , after the foreign object existence information generated as described above is transmitted to the RX  101  (step S 506 ), the TX  102  determines whether or not a power transmission stop request has been received from the RX  101  (step S 507 ). If a power transmission stop request has been received from the RX  101  (YES in step S 507 ), power transmission is stopped and the process is ended (step S 508 ). If this is not the case (NO in Step S 507 ), power transmission is continued and the process returns to step S 504 . Note that in the case in which the foreign object existence information is 3, i.e., a foreign object exists, in step S 505 , the TX  102  may perform control to voluntarily stop transmitting power without waiting to receive a power transmission stop request from the RX  101 . Also, after the processing of step S 508  ends, the TX  102  may return to step S 501  and wait until the RX  101  is placed again. 
     3.3 System Operation 
     The operation of the system including the RX  101  and the TX  102  described using  FIGS. 4 and 5  will be described using an example. 
     First, the case when no foreign object exists and the power loss detected by the TX  102  is 250 mW or less will be described. In this case, information that the foreign object existence information is 1, i.e., a foreign object does not exist, is generated and transmitted in step S 505  and step S 506  of the TX  102 . Then, at the branch at step S 406  of the RX  101 , the process proceeds to step S 407  and charging is performed and the notification unit  207  is put in the state illustrated in  FIG. 6A  indicating that charging is in progress. In other words, charging is automatically performed without user confirmation of a foreign object or user operation. 
     Next, the case when a foreign object exists partially on the charging stand  103  or the like and the power loss detected by the TX  102  is between 250 mW and 750 mW will be described. In this case, information that the foreign object existence information is 2, i.e., a foreign object possibly exists, is generated and transmitted in step S 505  and step S 506  of the TX  102 . Then, from the branch at step S 406  of the RX  101 , the process proceeds to step S 411  and the notification unit  207  performs a notification as illustrated in  FIG. 6B . The user receives the notification and continues or stops charging on the basis of the result of confirmation by the user. 
     Next, the case when a foreign object does not exist but the power loss detected by the TX  102  is between 250 mW and 750 mW due to circuit loss or error will be described. In this case, information that the foreign object existence information is 2, i.e., a foreign object possibly exists, is generated and transmitted in step S 505  and step S 506  of the TX  102 . Then, from the branch at step S 406  of the RX  101 , the process proceeds to step S 411  and the notification unit  207  performs a notification as illustrated in  FIG. 6B . The user receives the notification and continues or stops charging on the basis of the result of confirmation by the user. 
     Next, the case when a foreign object exists and the power loss detected by the TX  102  is 750 mW or greater will be described. In this case, information that the foreign object existence information is 3, i.e., a foreign object exist, is generated and transmitted in step S 505  and step S 506  of the TX  102 . Then, at the branch at step S 406  of the RX  101 , the process proceeds to step S 412  and charging is stopped and the notification unit  207  is put in the state illustrated in  FIG. 6C  indicating that charging is stopped. In other words, charging is automatically stopped without user confirmation of a foreign object or user operation. 
     As described above, according to the power receiving apparatus of the first embodiment, when it is difficult to determine the existence of a foreign object in a binary manner using exist and not exist, the user can be notified and made to confirm that there is no foreign object. In this way, uses operation can be more appropriately prompted. 
     Also, in the first embodiment, when a foreign object does not exist, the power receiving apparatus performs a notification informing of this. However, this notification can be omitted. In other words, when a foreign object does not exist, the user does not need to perform a task such as removing a foreign object. Thus, the notification can be omitted. This reduces power consumption and is effective in decreasing charge time. 
     Second Embodiment 
     The configuration of a wireless charging system (wireless power transmission system), the configuration of the RX  101 , and the configuration of the TX  102  according to the second embodiment are similar to that of the first embodiment ( FIGS. 1 to 3 ). The difference between the first embodiment and the second embodiment is that the processing in the RX  101  when the foreign object existence information is determined as “a foreign object possibly exists” is different. 
     In the first embodiment, in the case in which the foreign object existence information is 2, i.e., a foreign object possibly exists, the TX  102  continues power transmission, but stops power transmission on the basis of a request from the RX  101  if confirmation by the user has not been performed on the RX  101  for a predetermined amount of time. In other words, control is performed to continue power transmission while waiting for user confirmation. 
     In the second embodiment, in the case in which the foreign object existence information is  2 , i.e., a foreign object possibly exists, the TX  102  stops power transmission, but starts power transmission on the basis of a request from the RX  101  if confirmation by the user is performed on the RX  101  within a predetermined amount of time. In other words, control is performed to stop power transmission while waiting for user confirmation. In this way, when a foreign object actually exists, power transmission to the foreign object can be prevented while waiting for user confirmation. 
       FIG. 5A  is a flowchart for describing the operation of the RX  101  of the second embodiment.  FIG. 8A  illustrates a process that replaces steps S 410  to S 411  of  FIG. 4 . In the case in which the second state (a foreign object possibly exists) is determined in step S 406 , the RX  101  stops charging and power reception (step S 901 ). This process is similar to that of step S 412  and step S 413 . Then, the RX  101  instructs the user to confirm that there is no foreign object (step S 410 ). In the second embodiment, when charging is stopped, the display state is as in  FIG. 6B  with the LED  701  turned off A display informing that charging and power transmission are stopped may be displayed on the liquid crystal display  702 . Then, if confirmation from the user has not been obtained within a predetermined amount of time (NC) in step S 411 ), the process proceeds to step S 411 . If confirmation from the user is obtained within a predetermined amount of time (YES in step S 411 ), the RX  101  restarts receiving power from the TX  102  and charging the battery  202  (step S 902 ) and the process proceeds to step S 407 . 
     Also, the state of a foreign object possibly existing may be split into at least a first level and a second level in order of the highest possibility that a foreign object exists, and the process may be different for when the first level is determined and for when the second level is determined. 
     For example, the foreign object existence information generated in the TX  102  may have four levels as illustrated in  FIG. 7B , and, for the RX  101 , in the case in which a foreign object existing has a low possibility, power transmission may be continued and the RX  101  may wait for user confirmation and, in the case in which a foreign object existing has a high possibility, power transmission may be stopped and the RX  101  may wait for user confirmation. In this way, charging is given priority and finished quickly if a foreign object does not exist only when there is a low possibility for a foreign object existing. 
     The processing in this case is illustrated in  FIG. 8B .  FIG. 8B  illustrates a process that replaces steps S 410  to S 411  of  FIG. 4 . In the case in which the second state (a foreign object possibly exists) is determined in step S 406 , the RX  101  further determines whether the level of possibility is the first level (the foreign object existence information is 3) or the second level (the foreign object existence information is 2) (step S 911 ). In the case in which the first level is determined, the RX  101  stops charging and power reception (step S 912 ). This process is similar to that of step S 412  and step S 413 . In the case in which the second level is determined, the RX  101  skips step S 912  and continues receiving power. 
     Then, the RX  101  instructs the user to confirm that there is no foreign object (step S 410 ). In the case in which the first level is determined, as charging is stopped, the display state is as in  FIG. 6B  with the LED  701  turned off. Here, a display informing that charging and power transmission are stopped may be displayed on the liquid crystal display  702 . In the case in which the second level is determined, as charging is continued, the display state is as in  FIG. 6B . Then, if confirmation from the user has not been obtained within a predetermined amount of time (NO in step S 411 ), the process proceeds to step S 414 . If confirmation from the user is obtained within a predetermined amount of time (YES in step S 411 ), the RX  101  restarts receiving power from the TX  102  and charging the battery  202  (step S 913 ) and the process proceeds to step S 407 . Note that in the case in which the second level is determined, as power reception and charging is continued, step S 913  is a NOP. 
     As described above, the state of “a foreign object possibly exists” may be further split and power reception, charging, and notification may be controlled accordingly. This allows very detailed power reception control and user notification to be performed. 
     In other words, according to the embodiments described above, the user can be appropriately notified regarding the existence of a foreign object. 
     Other Embodiments 
     Embodiment(s) of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     Note that at least a part of the processing illustrated in the flowcharts of  FIGS. 4, 5, 5A, and 5B  may be implemented by hardware. In the case of implementing processing by hardware, for example, using a predetermined compiler, the processing can be implemented by automatically generating a dedicated circuit on an FPGA (Field Programmable Gate Array) from a program for implementing the processing. In addition, similarly to an FPGA, a gate array circuit may be formed and implemented as hardware. 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions, 
     This application claims the benefit of Japanese Patent Application No. 2019-223001, filed Dec. 10, 2019 which is hereby incorporated by reference herein in its entirely.