Patent Publication Number: US-2023146055-A1

Title: Electronic device wirelessly receiving power, and operating method therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/KR2021/006970 filed on 3 Jun. 2021, designating the United States, in the Korean Intellectual Property Receiving Office, and claiming priority to Korean Patent Application No. KR 10-2020-0083218, filed on Jul. 7, 2020, and to KR 10-2020-0110043, filed on Aug. 31, 2020, in the Korean Intellectual Property Office, the disclosures of which are all hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Field 
     Certain example embodiments relate to electronic devices wirelessly receiving power and/or methods for operating the same. 
     Description of Related Art 
     Portable digital communication devices have become a must-have item for everyone in modern era. Customers desire to receive various high-quality services anytime, anywhere. Internet of Thing (IoT) technology recently bundles various sensors, home appliances, and communication devices up into a single network. A diversity of sensors require a wireless power transmission system for seamless operations. Small Bluetooth headsets, wearing devices, smartphones, or robots, vacuums, or other large-scale electronic devices may be implemented to wirelessly receive power. 
     Wireless power transmission may be performed in a magnetic induction, magnetic resonance, and electromagnetic wave scheme. The magnetic induction or magnetic resonance scheme is advantageous in charging electronic devices positioned within a relatively short distance from the wireless power transmitter. The electromagnetic wave scheme is more advantageous for remote power transmission that reaches a few meters as compared with the magnetic induction or magnetic resonance scheme. Such electromagnetic wave scheme is primarily intended for remote power transmission and may exactly grasp the location of remote power receivers and deliver power in a most efficient way. 
     SUMMARY 
     As the distance between the electronic device and the wireless power transmitter decreases, high power may be wirelessly received from the wireless power transmitter. When the electronic device receives power from the wireless power transmitter by the magnetic resonance scheme, the power transferred to the load of the electronic device may vary depending on the configuration of the resonance circuit. For example, in a case where the electronic device includes a resonance circuit having a reception coil and a capacitor connected in series, when the distance between the electronic device and the wireless power transmitter is short (e.g., when receiving larger power from the wireless power transmitter), the power received from the wireless power transmitter may be transferred to the load of the electronic device at relatively high efficiency, as compared with when the electronic device includes a resonance circuit having a reception coil and a capacitor connected in parallel. In a case where the electronic device includes a resonance circuit having a reception coil and a capacitor connected in parallel, when the distance between the electronic device and the wireless power transmitter is far, the power received from the wireless power transmitter may be transferred to the load of the electronic device at relatively high efficiency, as compared with when the electronic device includes a resonance circuit having a reception coil and a capacitor connected in series. 
     Accordingly, to transfer the power received from the wireless power transmitter at high efficiency, the electronic device needs to connect the reception coil and the capacitor, included in the resonance circuit, in series or parallel based on the distance between the electronic device and the wireless power transmitter (or the magnitude of the power received from the wireless power transmitter). 
     According to various example embodiments, there may be provided an electronic device and its operation method for wirelessly receiving power, which may set different connection settings for the resonance circuit based on the distance between the electronic device and the wireless power transmitter. 
     According to various example embodiments, an electronic device may comprise a battery, a resonance circuit configured to wirelessly receive power and including a reception coil, at least one capacitor, and at least one switch, a rectification circuit configured to rectify AC power provided from the resonance circuit to DC power, a DC/DC converter configured to convert the DC power provided from the rectification circuit and output the converted DC power, and a charge control circuit configured to charge the battery with the converted power provided from the DC/DC converter, and a controller. The controller may be configured to identify a voltage output from the rectification circuit, if the voltage output from the rectification circuit is a threshold voltage or more, control the at least one switch to allow the reception coil and the at least one capacitor to configure a series resonance circuit, and if the voltage output from the rectification circuit is less than the threshold voltage, control the at least one switch to allow the reception coil and the at least one capacitor to configure a parallel resonance circuit. 
     According to various example embodiments, a method for wirelessly receiving power by an electronic device may comprise identifying a voltage output from a rectification circuit of the electronic device, if the voltage output from the rectification circuit is a threshold voltage or more, controlling at least one switch included in a resonance circuit of the electronic device to allow a reception coil and at least one capacitor included in the resonance circuit to configure a series resonance circuit, and if the voltage output from the rectification circuit is less than the threshold voltage, controlling the at least one switch to allow the reception coil and the at least one capacitor to configure a parallel resonance circuit. 
     According to various example embodiments, an electronic device may comprise a battery, a resonance circuit including a 1-1th capacitor and a 1-2th capacitor, a 1-1th switch and a 1-2th switch respectively connected in parallel with the 1-1th capacitor and the 1-2th capacitor, a 2-1th capacitor and a 2-2th capacitor, and a 2-1th switch and a 2-2th switch respectively connected in series with the 2-1th capacitor and the 2-2th capacitor, a rectification circuit rectifying AC power provided from the resonance circuit to DC power, a DC/DC converter converting the DC power provided from the rectification circuit and outputting the converted DC power, and a charge control circuit configured to charge the battery with the converted power provided from the DC/DC converter, and a controller. The controller may be configured to identify a voltage output from the rectification circuit, compare the voltage output from the rectification circuit with a first threshold voltage and a second threshold voltage, if the voltage output from the rectification circuit is the first threshold voltage or more, control the 1-1th switch, the 1-2th switch, the 2-1th switch, and the 2-2th switch to allow the resonance circuit to have a first connection setting in which the reception coil and the 1-1th capacitor are connected in series, if the voltage output from the rectification circuit is less than the second threshold voltage, control the 1-1th switch, the 1-2th switch, the 2-1th switch, and the 2-2th switch to allow the resonance circuit to have a second connection setting in which the reception coil and the 2-1th capacitor are connected in parallel, and if the voltage output from the rectification circuit is the second threshold voltage or more and less than the first threshold voltage, control the 1-1th switch, the 1-2th switch, the 2-1th switch, and the 2-2th switch to allow the resonance circuit to have a third connection setting in which the 1-1th capacitor and the 1-2th capacitor are connected in series with the reception coil, and the 2-1th capacitor and the 2-2th capacitor are connected in parallel with the reception coil. 
     According to various example embodiments, there may be provided an electronic device and its operation method for wirelessly receiving power, which may set different connection settings for the resonance circuit based on the distance between the electronic device and the wireless power transmitter. Thus, the electronic device may transfer the power received from the wireless power transmitter to the load at high efficiency. 
     Further, the electronic device may enhance power transfer efficiency by changing the connection settings of the resonance circuit based on the distance between the electronic device and the wireless power transmitter, thereby minimizing or reducing heat generation. 
     Further, the electronic device may determine the distance between the electronic device and the wireless power transmitter based on the output voltage of a rectification circuit of the electronic device even without communication with the wireless power transmitter. 
     Further, the electronic device may transfer the power received from the wireless power transmitter to the load at high efficiency regardless of whether the wireless power transmitter transmits power to an electronic device other than the electronic device. 
     Further, when the distance between the electronic device and the wireless power transmitter is short, the electronic device may prevent, or reduce the likelihood of, overvoltage from occurring in the electronic device at least by changing the connection settings of the resonance circuit to correspond to the distance between the electronic device and the wireless power transmitter. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and advantages of certain example embodiments will be more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a concept view illustrating the overall operation of a wireless charging system according to various example embodiments; 
         FIG.  2    is a block diagram illustrating an electronic device according to various example embodiments; 
         FIG.  3    is a view illustrating a resonance circuit according to various example embodiments; 
         FIG.  4    is a view illustrating a relationship between received power and impedance of a load according to various example embodiments; 
         FIG.  5    is a view illustrating the power received by a load depending on the connection settings of a resonance circuit according to various example embodiments; 
         FIG.  6    is a view illustrating a method for setting a threshold voltage compared with the output voltage V RECT  of a rectification circuit according to various example embodiments; 
         FIG.  7    is a view illustrating a resonance circuit according to various example embodiments; 
         FIG.  8    is a view illustrating a resonance circuit according to various example embodiments; 
         FIG.  9    is a view illustrating a method for setting a plurality of threshold voltages compared with the output voltage V RECT  of a rectification circuit according to various example embodiments; 
         FIG.  10    is a view illustrating a configuration of a switch according to various example embodiments; 
         FIG.  11    is a view illustrating a method for controlling a switch based on the output voltage V RECT  of a rectification circuit according to various example embodiments; 
         FIG.  12    is a view illustrating a method for controlling a switch based on the output voltage of a rectification circuit according to various example embodiments; and 
         FIG.  13    is a view illustrating a method for controlling a switch based on the output voltage V RECT  of a rectification circuit according to various example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, certain example embodiments are described in detail with reference to the accompanying drawings. It should be noted that the same element denotations are used to refer to the same elements throughout the specification. 
       FIG.  1    is a concept view illustrating the overall operation of a wireless charging system according to various embodiments. 
     Referring to  FIG.  1   , a wireless charging system may include a wireless power transmitter  102  (e.g., power transmitting unit (PTU)) and at least one wireless power receiver  101  (e.g., at least one power receiver  101 - 1 ,  101 - 2 , and  101 - n ) (e.g., power receiving unit (PRU)). 
     The wireless power transmitter  102  may wirelessly send power  1 - 1 ,  1 - 2 , and  1 - n  to the at least one wireless power receiver  101 - 1 ,  101 - 2 , and  101 - n , respectively. For example, the wireless power transmitter  102  may wirelessly transmit the power  1 - 1 ,  1 - 2 , and  1 - n  to a wireless power receiver authenticated by a predetermined authentication process. 
     The wireless power transmitter  102  may form electrical connections with the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n . For example, the wireless power transmitter  102  may electromagnetic fields or waves of wireless power to the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n.    
     The wireless power transmitter  102  may perform bi-lateral communication with the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n . Here, the wireless power transmitter  102  and the wireless power receiver  101 - 1 ,  101 - 2 , and  101 - n  may process or communicate packets  2 - 1 ,  202 , and  2 - n  including predetermined frames. In an embodiment, the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may be implemented as mobile communication terminals, PDAs, PMPs, smart phones, wearable devices, and the like. 
     The wireless power transmitter  102  may wirelessly provide power to a plurality of wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n . For example, the wireless power transmitter  102  may transmit power to the plurality of wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  through the resonant scheme. When the wireless power transmitter  102  adopts the resonant scheme, the distances between the wireless power transmitter  102  and the plurality of wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may be, e.g., 30 m or less, but are not limited thereto. When the wireless power transmitter  102  adopts the electromagnetic induction scheme, the distances between the wireless power transmitter  102  and the plurality of wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may be, e.g., 10 cm or less, but are not limited thereto. 
     The wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may receive the wireless power from the wireless power transmitter  102  to charge their respective batteries provided therein. Further, the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may transmit, to the wireless power transmitter  102 , a signal for requesting to transmit wireless power, information necessary to receive wireless power, state information about the wireless power receivers (e.g., information regarding the movement of the wireless power receivers) or control information about the wireless power transmitter  102 . 
     The wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may transmit to the wireless power transmitter  102  messages that indicate the respective states of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n.    
     Each of the wireless power transmitter  102  or the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  may include a display means, such as a display. For example, the wireless power transmitter  102  may display the state of each of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  based on the message received from each of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n . Further, the wireless power transmitter  102  may also display the time predicted to be taken until each of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  is completely charged. 
     The wireless power transmitter  102  may transmit a control signal to enable or disable the wireless charging function to each of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n . For example, when receiving the control signal to disable the wireless charging function from the wireless power transmitter  102 , the wireless power receiver  101  may disable the wireless charging function. 
       FIG.  2    is a block diagram illustrating an electronic device  100  according to various embodiments. 
       FIG.  3    is a view illustrating a resonance circuit  210  according to various embodiments. 
     Referring to  FIGS.  2  and  3   , in an embodiment, an electronic device  100  (e.g., at least one wireless power receiver  101 ) may include a resonance circuit  210 , a rectification circuit  220 , a DC/DC converter  230 , a charge control circuit  240  (e.g., power management integrated circuit (PMIC)), a battery  250 , a voltage detection circuit  260 , a communication circuit  270 , and a controller  280 . In an embodiment, the electronic device  100  may be one of the wireless power receivers  101 - 1 ,  101 - 2 , and  101 - n  of  FIG.  1   . 
     In an embodiment, an induced electromotive force may be generated in the resonance circuit  210  of the electronic device  100  based on a time-varying magnetic field output or formed by the wireless power transmitter  102 . This process may be expressed as receiving wireless power or wirelessly receiving power from the electronic device  100 . The power received through the resonance circuit  210  of the electronic device  100  may be AC power and may be transferred to the rectification circuit  220 . 
     In an embodiment, the resonance circuit  210  may include a reception coil  310 , first capacitors  321  and  323  connected, directly or indirectly, in series with the reception coil  310 , first switches  331  and  333  connected in parallel with the first capacitors  321  and  323 , a second capacitor  341  connected in parallel the reception coil  310 , and a second switch  351  connected, directly or indirectly, in series with the second capacitor  341 . 
     In an embodiment, when the first switches  331  and  333  connected in parallel with the first capacitors  321  and  323  are turned on (e.g., when the first switches  331  and  333  are short-circuited), no current flows through the first capacitors  321  and  323  from the induced electromotive force formed in the reception coil  310  (e.g., the first capacitors  321  and  323  may not be electrically connected to the reception coil  310 ), and current may flow through the first switches  331  and  333 . In an embodiment, when the first switches  331  and  333  connected in parallel with the first capacitors  321  and  323  are turned off (e.g., when the first switches  331  and  333  are opened), current may flow through the first capacitors  321  and  323  from the induced electromotive force formed in the reception coil  310  and no current may flow through the first switches  331  and  333 . 
     In an embodiment, the first capacitors  321  and  323  may include a plurality of capacitors having the same capacitance. For example, when the rectification circuit  220  connected, directly or indirectly, to the resonance circuit  210  includes a full-bridge circuit, the first capacitors  321  and  323  may include a capacitor  321  and a capacitor  323  having the same capacitance, respectively connected to the two input terminals of the rectification circuit  220  for the rectification circuit  220  to convert the input AC power into DC power and output the DC power. However, without limitations thereto, when the rectification circuit  220  connected to the resonance circuit  210  includes a half-bridge circuit, the first capacitors  321  and  323  may include only one capacitor connected, directly or indirectly, with the rectification circuit  220 . When the first capacitors  321  and  323  are implemented as one capacitor, the capacitance C1 of the capacitor may be identical to the equivalent capacitance of the capacitance C2 of the capacitor  321  and the capacitance C3 of the capacitor  323 . Specifically, it may be determined as 1/C1=1/C2+1/C3. When C2 and C3 are the same, it may be determined as C1=C2/2. 
     In an embodiment, when the first capacitors  321  and  323  include a plurality of capacitors, the first switches  331  and  333  may include a plurality of switches (e.g., the switch  331  and the switch  333 ) respectively connected in parallel with the plurality of capacitors. 
     In an embodiment, when the second switch  351  connected in series with the second capacitor  341  is turned on, the reception coil  310  is electrically connected to the second capacitor  341  so that current may flow to the second capacitor  341  by the induced electromotive force formed in the reception coil  310 . In an embodiment, when the second switch  351  connected in series with the second capacitor  341  is turned off, no current flows through the second capacitor  341  so that the second capacitor  341  may not be electrically connected with the reception coil  310 . 
     In an embodiment, the capacitances of the first capacitors  321  and  323  (e.g., the equivalent capacitance of the capacitor  321  and the capacitor  323 ) may be identical to the capacitance of the second capacitor  341 . 
     The first switch and the second switch may be operated based on the control signal received from the controller  280 . For example, the first switches  331  and  333  and the second switch  351  may perform a switching operation to make a connection setting in which the reception coil  310  and the first capacitors  321  and  323  in the resonance circuit  210  are electrically connected in series, and the reception coil  310  and the second capacitor  341  are not electrically connected based on the first control signal received from the controller  280  (hereinafter, denoted as a ‘first connection setting’). 
     Further, the first switches  331  and  333  and the second switch  351  may perform a switching operation to make a connection setting in which the reception coil  310  and the second capacitor  341  in the resonance circuit  210  are electrically connected in parallel, and the reception coil  310  and the first capacitors  321  and  323  are not electrically connected (e.g., the first switches  331  and  333  are short-circuited) based on the second control signal received from the controller  280  (hereinafter, denoted as a ‘second connection setting’). The first capacitors  321  and  323  and the second capacitor  341  may have the same capacitance so that the resonance circuit  210  forms resonance at the same frequency in the first connection setting and the second connection setting. In an embodiment, the inductance of the reception coil  310  may be 1.2 pH (henry), the first capacitor  321  and the first capacitor  323  each may be 940 pF (farad), and the second capacitor  341  may be 470 pF. In this case, the resonant frequency in the first connection setting of the resonance circuit  210  and the resonant frequency in the second connection setting of the resonance circuit  210  may be the same as 6.7 MHz. 
     In an embodiment, the impedance of the first connection setting of the resonance circuit  210  may be smaller than the impedance of the second connection setting of the resonance circuit  210 . For example, the impedance of the first connection setting of the resonance circuit  210  may be smaller than the impedance of the second connection setting in a designated frequency range (e.g., a frequency range between half-power frequencies (frequencies when ½ of the power in the resonance state is received)). The impedance of the first connection setting and the impedance of the second connection setting of the resonance circuit  210  may be impedances measured at the input terminal of the rectification circuit  220  (e.g., viewed from the input terminal of the rectification circuit  220  to the resonance circuit  210 ). 
     In an embodiment, the first connection setting of the resonance circuit  210  may be a connection setting in which the power received from the wireless power transmitter  102  may be transferred to a load (e.g., the battery  250 ) with high efficiency as compared with the second connection setting of the resonance circuit  210  when the power received from the wireless power transmitter  102  is a designated power or more (or when included in a power range of the designated power or more). For example, as the power received from the wireless power transmitter  102  increases, higher current may flow to the load. When a constant voltage (e.g., about 4.2V (volt)) is applied to both terminals of the battery  250  by the charge control circuit  240 , as the current to the load increases, the impedance of the load may reduce. A relationship between the reception power of the electronic device  100  and the load impedance is described below in detail with reference to  FIG.  4   . 
       FIG.  4    is a view illustrating a relationship between received power and impedance of a load according to various embodiments. 
     Referring to  FIG.  4   , in an embodiment, in the circuit  410 , V(s) (where s=w*j) may denote the voltage of the power received from the wireless power transmitter  102  by the reception coil  310  of the electronic device  100  (e.g., voltage induced in the reception coil  310  by the magnetic field radiated from the wireless power transmitter  102 ), and I(s) may denote the current flowing to the load (e.g., the battery  250 ). Zt may denote the impedance viewed from the load, and Z L  may denote the impedance of the load. V L  may denote the voltage of the load. In an embodiment, V L  is the output voltage of the charge control circuit  240  for charging the load, and may be a voltage having a constant (or fixed) magnitude (e.g., 4.2V) regardless of V(s). In an embodiment, as the power received by the reception coil  310  of the electronic device  100  from the wireless power transmitter  102  increases, the magnitude of V(s) may also increase. For example, as the power received by the reception coil  310  of the electronic device  100  from the wireless power transmitter  102  increases, the magnitude of V(s) as a voltage induced in the reception coil  301  may increase. 
     In an embodiment, the circuit  410  may be represented as Equation 1 and Equation 2 below. 
         V ( s )= I ( s )*( Z   t   +Z   L )  [Equation 1]
 
         V   L   =Z   L   /I ( s )  [Equation 2]
 
     Based on Equation 1 and Equation 2, Equation 3 below may be obtained. 
     
       
         
           
             
               
                 
                   
                     Z 
                     L 
                   
                   = 
                   
                     
                       
                         V 
                         L 
                         * 
                       
                       ⁢ 
                       
                         Z 
                         t 
                       
                     
                     
                       
                         V 
                         ⁡ 
                         ( 
                         s 
                         ) 
                       
                       - 
                       
                         V 
                         L 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     In an embodiment, the graph  420  may represent the relationship  400  between V(s) and Z L  according to Equation 3. In an embodiment, since the electronic device  100  may normally receive power from the wireless power transmitter  102  only when V(s) is higher than V L , the graph  420  may represent only the line  421  corresponding to when V(s) is higher than V L . In an embodiment, V L *Z t  in Equation 3 may be a constant value. Accordingly, as in line  421  of graph  420 , V(s) and Z L  may have an inverse relationship. For example, when V(s) increases, Z L  may decrease, and when V(s) decreases, Z L  may increase. 
     In an embodiment, as the power received by the reception coil  310  of the electronic device  100  from the wireless power transmitter  102  increases, the magnitude of V(s) as a voltage induced in the reception coil  301  may increase and, as the magnitude of V(s) increase, Z L  may decrease. Accordingly, as the power received by the reception coil  310  of the electronic device  100  from the wireless power transmitter  102  increases, Z L  as the impedance of the load may decrease. 
     In an embodiment, since the impedance in the first connection setting of the resonance circuit  210  is smaller than the impedance in the second connection setting of the resonance circuit  210 , the difference between the magnitude of the impedance in the first connection setting of the resonance circuit  210  and the reduced magnitude of the load impedance may be smaller than the difference between the magnitude of the impedance in the second connection setting and the reduced magnitude of the load impedance. Since the difference between the magnitude of the impedance in the first connection setting of the resonance circuit  210  and the reduced magnitude of the load impedance is smaller than the difference between the magnitude of the impedance in the second connection setting of the resonance circuit  210  and the reduced magnitude of the load impedance, the first connection setting of the resonance circuit  210  may be a connection setting in which when the power received from the wireless power transmitter  102  is a designated power or more, the power received from the wireless power transmitter  102  may be transferred to the load (e.g., the battery  250 ) with high efficiency as compared with the second connection setting of the resonance circuit  210 . In an embodiment, the first connection setting of the resonance circuit  210  may also be denoted as a ‘series connection setting of reception coil and capacitor.’ 
     In an embodiment, the second connection setting of the resonance circuit  210  may be a connection setting in which the power received from the wireless power transmitter  102  may be transferred to a load (e.g., the battery  250 ) with high efficiency as compared with the first connection setting of the resonance circuit  210  when the power received from the wireless power transmitter  102  is less than the designated power (or when included in a power range less than the designated power). In an embodiment, the second connection setting of the resonance circuit  210  may also be denoted as a ‘parallel connection setting of reception coil and capacitor.’ 
     In an embodiment, the first switches  331  and  333  and the second switch  351  may be bidirectional switches capable of performing an on/off operation for AC signals (e.g., AC voltage and AC current). The configuration and operation of the first switches  331  and  333  and the second switch  351  implemented as bidirectional switches are described below in detail with reference to  FIG.  10   . 
     In an embodiment, the rectification circuit  220  may rectify the AC current provided from the resonance circuit  210  into a DC current. The rectification circuit  220  may include a bridge circuit (e.g., a full-bridge circuit or a half-bridge circuit). The rectified power may be transferred to the DC/DC converter  230  according to the switching operation of the bridge circuit of the rectification circuit  220 . The output voltage V RECT  measured at the output terminal of the rectification circuit  220  may be sensed through the voltage detection circuit  260  for control of the controller  280  to be described below. 
     In an embodiment, the DC/DC converter  230  may convert and/or regulate the voltage of the rectified power transferred from the rectification circuit  220 . The DC/DC converter  230  may provide power having a substantially constant voltage. Meanwhile, the DC/DC converter  230  may be connected to at least one piece of hardware (or the charge control circuit  240  (e.g., PMIC) for providing power to the hardware). The at least one piece of hardware (or the charge control circuit  240 ) may be operate using the power from the DC/DC converter  230 . Here, a plurality of DC/DC converters  230  may be implemented. 
     In an embodiment, the charge control circuit  240  may receive the power output from the DC/DC converter  230  and charge the battery  250  connected to the charge control circuit  240  with the received power. The charge control circuit  240  may control the current and/or voltage applied to the battery  250  based on various charging modes (e.g., a constant current (CC) mode, a constant voltage (CV) mode, or a quick charging mode). For example, the charge control circuit  240  may control the current and/or voltage applied to the battery  250  based on the charge state of the battery  250 . Or, the charge control circuit  240  may control the current and/or voltage applied to the battery  250  based on a user input. The type of the battery  250  is not limited as long as it is a rechargeable secondary battery. 
     In an embodiment, the charge control circuit  240  may convert and/or regulate the current received from the DC/DC converter  230 . The charge control circuit  240  may transfer the converted and/or regulated current to the battery  250 . 
     In an embodiment, the voltage detection circuit  260  may detect (or measure) the voltage V RECT  of the output terminal of the rectification circuit  220 . The voltage detection circuit  260  may provide the voltage V RECT  of the output terminal of the rectification circuit  220  to the controller  280 . In  FIG.  2   , the voltage detection circuit  260  is exemplified as a component independent from the controller  280 , but is not limited thereto. For example, the voltage detection circuit  260  may be included in the controller  280 . 
     In an embodiment, the communication circuit  270  may enable the electronic device  100  to communicate with the wireless power transmitter  102 . In an embodiment, the communication circuit  270  may include an out-band communication circuit (e.g., a Bluetooth low energy (BLE) communication circuit). However, the communication circuit  270  may include an in-band communication circuit in place of or in addition to the out-band communication circuit. 
     In an embodiment, the controller  280  may perform an operation for charging the battery  250 . For example, when power is received from the wireless power transmitter  102  through the resonance circuit  210  ({circle around (1)}), the controller  280  may control the rectification circuit  220  to rectify the received AC power into DC power ({circle around (2)}). The controller  280  may control the DC/DC converter  230  to convert and output the DC current provided from the rectification circuit  220  ({circle around (3)}). The controller  280  may control the charge control circuit  240  to charge the battery  250  with the converted power provided from the DC/DC converter  230  ({circle around (4)}). 
     In an embodiment, the controller  280  may perform an operation (e.g., switching operations of the switches in the resonance circuit  210 ) to provide the power received from the wireless power transmitter  102  to the load (e.g., the battery  250 ) with maximum or high efficiency, using information related to the distance between the electronic device  100  (e.g., wireless power receiver) and the wireless power transmitter  102 . 
     In an embodiment, the controller  280  may receive information about the power transmitted from the wireless power transmitter  102  (hereinafter, denoted as ‘first power’), through the communication circuit  270  ({circle around (5)}). 
     In an embodiment, the first power may be the power output by the power amplifier (not shown) of the wireless power transmitter  102  (or the power input to the power transmission coil). For example, the wireless power transmitter  102  may detect the voltage and current output from the power amplifier (or power transmission coil) of the wireless power transmitter  102 . The wireless power transmitter  102  may determine (e.g., calculate) the first power based on the detected voltage and current. The wireless power transmitter  102  may transmit information about the first power to the electronic device  100  (e.g., the communication circuit  270 ) through the communication circuit of the wireless power transmitter  102 . Although the first power has been described above as having the [W] unit, it will be appreciated by one of ordinary skill in the art that the unit of the magnitude of the first power may be replaced with the unit of voltage or current in other various examples. 
     In an embodiment, the first power may be determined based on the power detected using a directional coupler of the wireless power transmitter  102 . For example, it is possible to separately detect the forwarded power output from the power amplifier of the wireless power transmitter  102  and the reflection power provided from the resonance circuit of the wireless power transmitter  102 , using the directional coupler of the wireless power transmitter  102 . The first power may be the forwarded power output from the power amplifier of the wireless power transmitter  102 , minus the reflection power provided from the resonance circuit of the wireless power transmitter  102 . 
     In an embodiment, the controller  280  may identify (e.g., measure) the output voltage V RECT  of the rectification circuit  220  detected ({circle around (6)}) by the voltage detection circuit  260 . 
     In an embodiment, the controller  280  may compare the output power V RECT  of the rectification circuit  220  with a threshold voltage (hereinafter referred to as a ‘threshold voltage’) ({circle around (7)}). For example, the controller  280  may identify whether the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more. 
     In an embodiment, the threshold voltage may be a voltage for the controller  280  to determine a connection setting (or a switching operation of a switch) of the resonance circuit  210 . For example, when the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more, the controller  280  may control the switch (e.g., the switches  331 ,  333 , and  351 ) so that the resonance circuit  210  has the first connection setting. As another example, when the output voltage V RECT  of the rectification circuit  220  is less than the threshold voltage, the controller  280  may control the switch (e.g., the switches  331 ,  333 , and  351 ) so that the resonance circuit  210  has the second connection setting. 
     In an embodiment, the threshold voltage may correspond to the first power (e.g., the magnitude of the first power) transmitted from the wireless power transmitter  102 . In a state in which the electronic device  100  is positioned at a predetermined distance from the wireless power transmitter  102 , as the wireless power transmitter  102  increases the first power (e.g., as the wireless power transmitter  102  increases the magnitude of the first power), the output voltage V RECT  of the rectification circuit  220  may increase. Since the threshold voltage is set for the electronic device  100  to determine (or predict) the distance from the wireless power transmitter  102 , as the first power increases, the threshold voltage may be set (or designated) to increase. 
     In an embodiment, when the memory (not shown) of the electronic device  100  stores information indicating that the wireless power transmitter  102  transmits a predetermined magnitude of first power when the electronic device  100  and the wireless power transmitter  102  are connected, the controller  280  may identify whether the output voltage V RECT  of the rectification circuit  220  is not less than the threshold voltage (or less than the threshold voltage) corresponding to the predetermined magnitude of first power stored in the memory of the electronic device  100 . For example, even before the electronic device  100  is connected to the wireless power transmitter  102  through the communication circuit  270 , the controller  280  may compare the output voltage V RECT  of the rectification circuit  220  with the threshold voltage set corresponding to the predetermined magnitude of first power. 
     In an embodiment, the controller  280  may determine (e.g., calculate) the distance between the electronic device  100  and the wireless power transmitter  102  based on the output voltage V RECT  of the rectification circuit  220  and the first power. For example, when the wireless power transmitter  102  transmits the first power having a constant magnitude regardless of the distance between the wireless power transmitter  102  and the electronic device  100 , the electronic device  100  may receive higher power from the wireless power transmitter  102  as the distance between the wireless power transmitter  102  and the electronic device  100  reduces. As the electronic device  100  receives higher power from the wireless power transmitter  102 , the output voltage V RECT  of the rectification circuit  220  may increase. A table in which the output voltage V RECT  of the rectification circuit  220  is set (e.g., mapped) to correspond to the distance between the wireless power transmitter  102  and the electronic device  100  according to the first power (e.g., the magnitude of the first power) (e.g., every designated magnitude interval of the first power) (hereinafter, denoted as a ‘first table’) may be stored in the memory. The controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  by identifying the output voltage V RECT  of the rectification circuit  220  and the first power based on the first table. The controller  280  may determine whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the connection setting (e.g., the first connection setting or second connection setting) of the resonance circuit  210 . 
     In an embodiment, the controller  280  may identify the current output from the rectification circuit  220  as information related to the distance between the wireless power transmitter  102  and the electronic device  100 . For example, although not shown in  FIG.  2   , the electronic device  100  may further include an over-voltage protection circuit connected between the rectification circuit  220  and the DC/DC converter  230 . Upon detecting a voltage V RECT  which is the designated voltage or more, in the rectification circuit  220  as the electronic device  100  approaches the wireless power transmitter  102  (e.g., upon identifying that the voltage V RECT  output from the rectification circuit  220  is the designated voltage or more), the controller  280  may provide a control signal to the switch included in the over-voltage protection circuit so that the switch included in the over-voltage protection circuit is turned on to perform an over-voltage protection operation to protect the components of the electronic device  100 . When the switch included in the over-voltage protection circuit is turned on, the current output from the rectification circuit  220  may flow to the over-voltage protection circuit. In an embodiment, the over-voltage protection circuit may include a transient voltage suppressor (TVS) diode. 
     The controller  280  may identify the output current of the rectification circuit  220  which flows to the over-voltage protection circuit. The controller  280  may determine whether the output current of the rectification circuit  220  is a threshold current or more (hereinafter, denoted as a ‘threshold current’). 
     In an embodiment, the threshold current may correspond to the first power transmitted by the wireless power transmitter  102 . In a state in which the electronic device  100  is positioned at a constant distance from the wireless power transmitter  102 , as the wireless power transmitter  102  increases the first power, the current flowing to the over-voltage protection circuit at the time of detection of the voltage V RECT  of the designated voltage or more in the rectification circuit  220  may increase. Since the threshold current is set for the electronic device  100  to determine (or predict) the distance from the wireless power transmitter  102 , as the first power increases, the threshold current may be set (or designated) to increase. 
     In an embodiment, the controller  280  may calculate the distance between the wireless power transmitter  102  and the electronic device  100  based on the current flowing to the over-voltage protection circuit and the first power. A table in which the current flowing to the over-voltage protection circuit at the time of detection of the voltage V RECT  of the designated voltage or more in the rectification circuit  220  is set to correspond to the distance between the wireless power transmitter  102  and the electronic device  100  according to the first power (e.g., the magnitude of the first power) (e.g., every designated magnitude interval of the first power) (hereinafter, denoted as a ‘second table’) may be stored in the memory. The controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  by identifying the current flowing to the over-voltage protection circuit and the first power based on the second table. The controller  280  may determine whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the connection setting (e.g., the first connection setting or second connection setting) of the resonance circuit  210 . 
     In an embodiment, the controller  280  may receive information about the voltage standing wave ratio (VSWR) as the information related to the distance between the wireless power transmitter  102  and the electronic device  100  from the wireless power transmitter  102  through the communication circuit  270 . In an embodiment, the wireless power transmitter  102  may detect the forwarded power output from the power amplifier of the wireless power transmitter  102  and the reflection power provided from the resonance circuit of the wireless power transmitter  102 , using the directional coupler of the wireless power transmitter  102 . The wireless power transmitter  102  may determine (e.g., calculate) the voltage standing wave ratio based on the detected forwarded power and reflection power. 
     In an embodiment, the controller  280  may determine whether the voltage standing wave ratio is equal to or larger than a threshold voltage standing wave ratio (hereinafter referred to as a ‘threshold voltage standing wave ratio’). 
     In an embodiment, as the distance between the electronic device  100  and the wireless power transmitter  102  decreases, the voltage standing wave ratio of the wireless power transmitter  102  may increase. 
     In an embodiment, the controller  280  may determine (e.g., calculate) the distance between the wireless power transmitter  102  and the electronic device  100  based on the voltage standing wave ratio. A table in which the voltage standing wave ratio is set to correspond to the distance between the wireless power transmitter  102  and the electronic device  100  (hereinafter, denoted as a ‘third table’) may be stored in the memory. The controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  by identifying the voltage standing wave ratio, based on the third table. The controller  280  may determine whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the connection setting (e.g., the first connection setting or second connection setting) of the resonance circuit  210 . In an embodiment, when using the voltage standing wave ratio as the information related to the distance between the wireless power transmitter  102  and the electronic device  100 , the controller  280  may not receive the information about the first power transmitted from the wireless power transmitter  102  through the communication circuit  270 . For example, since the voltage standing wave ratio of the wireless power transmitter  102  is determined regardless of the first power, the controller  280  may determine whether the voltage standing wave ratio is the threshold voltage standing wave ratio or calculate the distance between the wireless power transmitter  102  and the electronic device  100  based on the voltage standing wave ratio without using the first power. The controller  280  may determine whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the connection setting (e.g., the first connection setting or second connection setting) of the resonance circuit  210 . 
     In an embodiment, the controller  280  may receive information related to the impedance measured in the resonance circuit of the wireless power transmitter  102  (e.g., information about the phase of the impedance of the resonance circuit of the wireless power transmitter  102 ) as the information related to the distance between the wireless power transmitter  102  and the electronic device  100 , from the wireless power transmitter  102  through the communication circuit  270 . In an embodiment, the wireless power transmitter  102  may continuously detect the voltage input to the resonance circuit of the wireless power transmitter  102  (or output from the power amplifier of the wireless power transmitter  102 ), thereby detecting the waveform of the detected voltage. The wireless power transmitter  102  may continuously detect the current input to the resonance circuit of the wireless power transmitter  102  (or output from the power amplifier of the wireless power transmitter  102 ), thereby detecting the waveform of the detected current. The wireless power transmitter  102  may identify (e.g., calculate) the respective zero crossing points of the waveform of the voltage and the waveform of the current input to the resonance circuit from the waveform of the voltage and the waveform of the current input to the resonance circuit. The wireless power transmitter  102  may identify the phase of the impedance of the resonance circuit (e.g., the delayed phase of the waveform of the current input to the resonance circuit for the waveform of the voltage input to the resonance circuit) based on the identified zero crossing points. The phase of the impedance of the resonance circuit of the wireless power transmitter  102  may increase with a (−) sign (e.g., the capacitive component of the impedance of the resonance circuit of the wireless power transmitter  102  increases) as the distance between the wireless power transmitter  102  and the electronic device  100  decreases and may increase with a (+) sign (e.g., the inductive component of the impedance of the resonance circuit of the wireless power transmitter  102  increases) as the distance between the wireless power transmitter  102  and the electronic device  100  increases. 
     In an embodiment, the controller  280  may determine whether the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is a threshold phase or more (hereinafter, a ‘threshold phase’). 
     In an embodiment, the controller  280  may calculate the distance between the wireless power transmitter  102  and the electronic device  100  based on the phase of the impedance of the resonance circuit of the wireless power transmitter  102 . A table in which the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is set to correspond to the distance between the wireless power transmitter  102  and the electronic device  100  (hereinafter, denoted as a ‘fourth table’) may be stored in the memory. The controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  by identifying the phase of the impedance of the resonance circuit of the wireless power transmitter  102  based on the fourth table. In an embodiment, when using the phase of the impedance of the resonance circuit of the wireless power transmitter  102  as the information related to the distance between the wireless power transmitter  102  and the electronic device  100 , the controller  280  may not receive the information about the first power transmitted from the wireless power transmitter  102  through the communication circuit  270 . For example, since the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is determined regardless of the first power, the controller  280  may determine whether the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is the threshold phase or more or calculate the distance between the wireless power transmitter  102  and the electronic device  100  based on the phase of the impedance of the resonance circuit of the wireless power transmitter  102  without using the first power. The controller  280  may determine whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the connection setting (e.g., the first connection setting or second connection setting) of the resonance circuit  210 . 
     In an embodiment, the controller  280  may provide control signals for controlling the switches included in the resonance circuit  210  to the resonance circuit  210  based on whether the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more. For example, upon identifying that the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more, the controller  280  may provide a control signal for turning off the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the first connection setting in which the reception coil  310  is electrically connected in series with the first capacitors  321  and  323 , and the reception coil  310  is not electrically connected with the second capacitor  341 . As another example, upon identifying that the output voltage V RECT  of the rectification circuit  220  is less than the threshold voltage, the controller  280  may provide a control signal for turning on the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the second connection setting in which the reception coil  310  is electrically connected in series with the second capacitor  341 , and the reception coil  310  is not electrically connected with the first capacitors  321  and  323 . 
     In an embodiment, the controller  280  may provide control signals for controlling the switches included in the resonance circuit  210  to the resonance circuit  210  based on whether the current output from the rectification circuit  220  is the threshold current or more. For example, upon identifying that the current output from the rectification circuit  220  is the threshold current or more, the controller  280  may provide a control signal for turning off the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the first connection setting. As another example, upon identifying that the current output from the rectification circuit  220  is less than the threshold current, the controller  280  may provide a control signal for turning on the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, the controller  280  may provide a control signal for controlling the switches included in the resonance circuit  210  to the resonance circuit  210  based on whether the voltage standing wave ratio related to the first power transmitted from the wireless power transmitter  102 , received through the communication circuit  270 , is the threshold voltage standing wave ratio or more. For example, upon identifying that the voltage standing wave ratio related to the first power is the threshold voltage standing wave ratio or more, the controller  280  may provide a control signal for turning off the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the first connection setting. As another example, upon identifying that the voltage standing wave ratio related to the first power is less than the threshold voltage standing wave ratio, the controller  280  may provide a control signal for turning on the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, the controller  280  may provide a control signal for controlling the switches included in the resonance circuit  210  to the resonance circuit  210  based on whether the phase of the impedance of the resonance circuit of the wireless power transmitter  102  received through the communication circuit  270  is the threshold phase or more. For example, upon identifying that the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is the threshold phase or more, the controller  280  may provide a control signal for turning on the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the second connection setting. As another example, upon identifying that the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is less than the threshold phase, the controller  280  may provide a control signal for turning off the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the first connection setting. 
     In an embodiment, the controller  280  may control the switch included in the resonance circuit  210  using at least one method among a method for controlling the switch of the resonance circuit  210  based on whether the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more (hereinafter, denoted as a ‘first method’), a method for controlling the switch included in the resonance circuit  210  based on whether the current output from the rectification circuit  220  is the threshold current or more (hereinafter, denoted as a ‘second method’), a method for controlling the switch included in the resonance circuit  210  based on whether the voltage standing wave ratio related to the first power is the threshold voltage standing wave ratio or more (hereinafter, denoted as a ‘third method’), or a method for controlling the switch included in the resonance circuit  210  based on whether the phase of the impedance of the resonance circuit of the wireless power transmitter  102  is the threshold phase or more (hereinafter, denoted as a ‘fourth method’), as described above. 
     In an embodiment, the controller  280  may set priorities for the first method to the fourth method. For example, the controller  280  may set the highest priority for the first method, set the second highest priority for the second method, and set the same priority for the third method and the fourth method. However, the method for setting priorities for the first method to the fourth method is not limited to the above-described example. 
     In an embodiment, when the distance between the wireless power transmitter  102  and the electronic device  100  is determined, the controller  280  may provide a control signal for controlling the switches (e.g., the switches  331 ,  333 , and  351 ) included in the resonance circuit  210  to the resonance circuit  210  based on whether the determined distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more. For example, the controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  using at least one table among the first table to the fourth table. Upon identifying that the determined distance between the wireless power transmitter  102  and the electronic device  100  is the designated distance or more, the controller  280  may provide a control signal for turning on the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the second connection setting. Upon identifying that the determined distance between the wireless power transmitter  102  and the electronic device  100  is less than the designated distance, the controller  280  may provide a control signal for turning off the first switches  331  and  333  and the second switch  351  to the first switches  331  and  333  and the second switch  351  to allow the resonance circuit  210  to have the first connection setting. 
     In an embodiment, the threshold voltage, threshold current, threshold voltage standing wave ratio, or threshold phase may be changed considering the hysteresis characteristics depending on whether the resonance circuit  210  is in the first connection setting or the second connection setting. 
     In an embodiment, the controller  280  may be a component independent from the communication circuit  270  as shown in  FIG.  2   . However, without limitations thereto, in an embodiment, the controller  280  and the communication circuit  270  may be implemented as a single integrated component (e.g., one chip). 
     In an embodiment, the controller  280  may be replaced with a processor (e.g., an application processor) capable of performing the above-described operations of the controller  280 . Thus, it will be appreciated that the controller comprises processing circuitry. 
     In an embodiment, the controller  280 , the rectification circuit  220 , and the DC/DC converter  230  may be implemented as an integrated component (e.g., one chip) or may be implemented as one component further including the communication circuit  270 . 
       FIG.  5    is a view  500  illustrating the power received by a load depending on the connection settings of a resonance circuit  210  according to various embodiments. 
       FIG.  6    is a view  600  illustrating a method for setting a threshold voltage compared with the output voltage V RECT  of a rectification circuit  220  according to various embodiments. 
     Referring to  FIGS.  5  and  6   , in an embodiment, a first line  510  may denote the power (reception power W (Watt)) received by the load (e.g., the battery  250 ) depending on the distance d between the electronic device  100  and the wireless power transmitter  102  when the resonance circuit  210  is in the first connection setting (e.g., in the series connection state between the reception coil and the capacitor). For example, the first line  510  may denote the power received by the load (e.g., the battery  250 ) depending on the distance d between the electronic device  100  and the wireless power transmitter  102  when power is provided with the maximum efficiency to the load (e.g., the battery  250 ) when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1  (e.g., about 5 cm) (e.g., resonance is formed when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1 ) in the first connection setting of the resonance circuit  210 . As in the first line  410  of  FIG.  5   , the power received by the load when the distance d between the electronic device  100  and the wireless power transmitter  102  is shorter than d 1  (e.g., d 1  or less) may be substantially the same or smaller than the power received by the load when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1 . 
     In an embodiment, a second line  520  may denote the power (reception power W (Watt)) received by the load (e.g., the battery  250 ) depending on the distance d between the electronic device  100  and the wireless power transmitter  102  when the resonance circuit  210  is in the second connection setting (e.g., in the parallel connection state between the reception coil and the capacitor). For example, the second line  520  may denote the power received by the load (e.g., the battery  250 ) depending on the distance d between the electronic device  100  and the wireless power transmitter  102  when power is provided with the maximum or high efficiency to the load (e.g., the battery  250 ) when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 3  (e.g., about 30 cm) (e.g., resonance is formed when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 3 ) in the first connection setting of the resonance circuit  210 . 
     In an embodiment, as in the first and second lines  510  and  520 , as the distance between the wireless power transmitter  102  and the electronic device  100  increases, the power received by the load may decrease. 
     In an embodiment, as shown in  FIG.  5   , in a case where the distance d between the electronic device  100  and the wireless power transmitter  102  is less than d 2  (e.g., 10 cm), larger power may be transferred to the load (e.g., the battery  250 ) when the resonance circuit  210  is in the first connection setting than when the resonance circuit  210  is in the second connection setting. For example, when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1 , power W 3  (e.g., about 4 W) may be transferred to the load (e.g., the battery  250 ) in the second connection setting of the resonance circuit  210  and, in the first connection setting of the resonance circuit  210 , power W 1  (e.g., about 5 W) larger than power W 3  may be transferred to the load (e.g., the battery  250 ). In an embodiment, when the distance d between the electronic device  100  and the wireless power transmitter  102  is less than d 2 , the first connection setting of the resonance circuit  210  may be a connection setting in which the power received from the wireless power transmitter  102  may be transferred to the load (e.g., the battery  250 ) with high efficiency as compared with the second connection setting of the resonance circuit  210 . 
     In an embodiment, as shown in  FIG.  5   , in a case where the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2  or more, larger power may be transferred to the load (e.g., the battery  250 ) when the resonance circuit  210  is in the second connection setting than when the resonance circuit  210  is in the first connection setting. For example, when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 3 , power W 4  may be transferred to the load (e.g., the battery  250 ) in the first connection setting of the resonance circuit  210  and, in the second connection setting of the resonance circuit  210 , power W 2  (e.g., about 1 W) larger than power W 4  (e.g., about 0.5 W) may be transferred to the load (e.g., the battery  250 ). In an embodiment, when the distance d between the electronic device and the wireless power transmitter  102  is d 2  or more, the second connection setting of the resonance circuit  210  may be a connection setting in which the power received from the wireless power transmitter  102  may be transferred to the load (e.g., the battery  250 ) with high efficiency as compared with the first connection setting of the resonance circuit  210 . 
     In an embodiment, the first line  510  of  FIG.  5    may be related to Equation 4, and the second line  520  of  FIG.  5    may be related to Equation 5 below. 
     
       
         
           
             
               
                 
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     In Equation 4, P may denote the power received by the load when the resonance circuit  210  is in the first connection setting, V(s) (where s=j*w) may denote the voltage induced in the electronic device  100 , L 1  may denote the inductance of the reception coil  310 , Rs may denote the resistance viewed from the load, R L  may denote the resistance of the load, and Cs may denote the capacitance of the capacitor connected in series with the reception coil (e.g., the equivalent capacitance of the capacitor  321  and the capacitor  323 ). In Equation 4, when (L 1 *Cs*S 2 +1) is about 0, resonance may be formed. 
     As shown in Equation 4, the magnitude of the reception power P of the load may be proportional to the square of the voltage V(s) induced in the electronic device  100 . As the distance between the wireless power transmitter  102  and the electronic device  100  increases, the coupling coefficient k between the transmission coil (not shown) of the wireless power transmitter  102  and the reception coil  310  of the electronic device  100  may decrease. As the coupling coefficient k between the transmission coil (not shown) and the reception coil  310  of the electronic device  100  decreases, the voltage V(s) induced in the electronic device  100  may decrease. Accordingly, as the distance between the wireless power transmitter  102  and the electronic device  100  increases, the voltage V(s) induced in the electronic device  100  may decrease. 
     In Equation 5, P may denote the power received by the load when the resonance circuit  210  is in the first connection setting, V(s) may denote the voltage induced in the electronic device  100 , L 2  may denote the inductance of the reception coil  310 , Rs may denote the resistance viewed from the load, R L  may denote the resistance of the load, and Cp may denote the capacitance of the capacitor  341  connected in parallel with the reception coil. In Equation 5, when (1+S 2 *L 1 *Cp) is about 0, resonance may be formed. 
     As shown in Equation 5, the magnitude of the reception power P of the load may be proportional to the square of the voltage V(s) induced in the electronic device  100 . As the distance between the wireless power transmitter  102  and the electronic device  100  increases, the coupling coefficient k between the transmission coil (not shown) of the wireless power transmitter  102  and the reception coil  310  of the electronic device  100  may decrease. As the coupling coefficient k between the transmission coil (not shown) and the reception coil  310  of the electronic device  100  decreases, the voltage V(s) induced in the electronic device  100  may decrease. Accordingly, as the distance between the wireless power transmitter  102  and the electronic device  100  increases, the voltage V(s) induced in the electronic device  100  may decrease. 
     In an embodiment, as shown in  FIG.  5   , when the resonance circuit  210  is in the first connection setting (e.g., in the case of Equation 4) and the second connection setting (e.g., in the case of Equation 5), as the distance between the wireless power transmitter  102  and the electronic device  100  increases, the powers received by the load may be reduced differently (e.g., the degrees in which the powers received by the load are reduced may differ). 
     In a case where the wireless power transmitter  102  transmits a predetermined magnitude of power, as the distance d between the electronic device  100  and the wireless power transmitter  102  increases (e.g., as they get away from each other), the output voltage V RECT  of the rectification circuit  220  may reduce. In  FIG.  6   , as shown in the third line  610 , when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1 , the output voltage V RECT  of the rectification circuit  220  may be V 3 (V). V 3 (V) may be the output voltage V RECT  of the rectification circuit  220  to allow the load (e.g., the battery  250 ) to receive W 1 (W) (or W 3 (W)) in  FIG.  5   . When the distance d between the electronic device  100  and the wireless power transmitter  102  is d 3 , the output voltage V RECT  of the rectification circuit  220  may be V 1 (V). V 1 (V) may be the output voltage V RECT  of the rectification circuit  220  to allow the load (e.g., the battery  250 ) to receive W 2 (W) (or W 4 (W)). 
     In an embodiment, the controller  280  may set the threshold voltage to allow the resonance circuit  210  to have a connection setting (e.g., to switch to the connection setting) for transferring the power received from the wireless power transmitter  102  to the load (e.g., the battery  250 ) with high efficiency. For example, as shown in  FIG.  5   , when the distance d between the electronic device  100  and the wireless power transmitter  102  is less than d 2 , in the first connection setting of the resonance circuit  210 , the power received from the wireless power transmitter  102  may be transferred to the load with high efficiency. When the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2 , in the second connection setting of the resonance circuit  210 , the power received from the wireless power transmitter  102  may be transferred to the load with high efficiency. The controller  280  may set V 2 (V), as the output voltage V RECT  of the rectification circuit  220  corresponding to the distance d 2  between the electronic device  100  and the wireless power transmitter  102  where the first line  510  and second line  520  of  FIG.  5    cross each other (e.g., measured when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2 ), as the threshold voltage. V 2 (V) may be the output voltage V RECT  of the rectification circuit  220  to allow the load (e.g., the battery  250 ) to receive W 5 (W)(e.g., about 3.5 W) when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2  (e.g., about 10 cm) in  FIG.  5   . 
     In connection with  FIGS.  2  to  6   , examples in which one electronic device  100  receives wireless power from the wireless power transmitter  102  have been described. However, the electronic device  100  may perform the same or similar operations to those described above even when a plurality of electronic devices receive wireless power from the wireless power transmitter  102 . 
     For example, when the wireless power transmitter  102  simultaneously provides power to the electronic device  100  and at least one other electronic device, the wireless power transmitter  102  may receive information related to the power received by the electronic device  100  and the at least one other electronic device (e.g., the output voltage V RECT  of the rectification circuit  220 ) from each of the electronic device and the at least one other electronic device. The electronic device  100  may receive the information related to the power received by at least one other electronic device through the communication circuit  270  from the wireless power transmitter  102 . The electronic device  100  may adjust the threshold voltage to be compared with, e.g., the output voltage V RECT  of the rectification circuit  220  based on the received information related to the power received by the at least one other electronic device. For example, when the electronic device receives power from the wireless power transmitter  102  without at least one other electronic device (e.g., alone), the electronic device  100  may set (e.g., apply) a low threshold voltage based on the information related to the power received by the at least one other electronic device as compared with when the electronic device  100 , simultaneously with (or along with) the at least one other electronic device, receives power from the wireless power transmitter  102 . In the above-described example, the electronic device  100  is exemplified as receiving information about the power received by at least one other electronic device through the wireless power transmitter  102 . However, the electronic device  100  may receive the information about the power received by the at least one other electronic device directly from the at least one other electronic device through the communication circuit  270 . 
     As another example, in a case where the wireless power transmitter  102  simultaneously provides power to the electronic device  100  and at least one other electronic device using a resonance scheme through resonance, when a change in the distance between the wireless power transmitter  102  and the at least one other electronic device, and the number of the at least one other electronic device, is small, the wireless power transmitter  102  may transmit substantially constant power. In this case, the power received from the wireless power transmitter  102  by the electronic device  100  may be varied depending on the number of the at least one other electronic device and the distance between the at least one other electronic device and the wireless power transmitter  102 . The variation in the power received by the electronic device depending on the distance between the at least one other electronic device and the wireless power transmitter  102  and the number of the at least one other electronic device may be significantly small, and the variation in power may be disregarded when the electronic device  100  controls the switching operation of the switch (e.g., the switches  331 ,  333 , and  351 ). 
     Although not described through  FIGS.  2  to  6   , in an embodiment, when the electronic device  100  and the wireless power transmitter  102  are communicatively connected, the controller  280  may automatically (e.g., without user input) identify (e.g., measure) the power received by the load (e.g., the battery  250 ) in each of the first connection setting of the resonance circuit  210  and the second connection setting of the resonance circuit  210 . For example, when the electronic device  100  and the wireless power transmitter  102  are communicatively connected, the controller  280  may identify the power received by the load (e.g., the battery  250 ) in the first connection setting of the resonance circuit  210  and control the switch to allow the resonance circuit  210  to have the second connection setting based on the identified power. The controller  280  may identify the power received by the load (e.g., the battery  250 ) in the second connection setting. The controller  280  may identify the connection setting of the resonance circuit  210 , which makes the power received by the load (e.g., the battery  250 ) large, of the first connection setting and the second connection setting. The controller  280  may control the switch (e.g., the switches  331 ,  333 , and  351 ) to allow the resonance circuit  210  to have the identified connection setting, of the first connection setting and the second connection setting. 
       FIG.  7    is a view illustrating a resonance circuit according to various embodiments. 
     Referring to  FIG.  7   , in an embodiment, a resonance circuit  210  may include a reception coil  310 , a capacitor  363 , a first switch  361 , and a second switch  375 . 
     In an embodiment, the first switch  361  and the second switch  375  may perform a switching operation to become a state in which the reception coil  310  and the capacitor  363  are connected in series (hereinafter, denoted as a ‘first connection setting of the resonance circuit  210 ’). For example, when the first switch  361  is opened, and the second switch  375  are connected with the first node  371 , the reception coil  310  and the capacitor  363  may be connected in series. 
     In an embodiment, the first switch  361  and the second switch  375  may perform a switching operation to become a state in which the reception coil  310  and the capacitor  363  are connected in parallel (hereinafter, denoted as a ‘second connection setting of the resonance circuit  210 ’). For example, when the first switch  361  is closed, and the second switch  375  are connected with the second node  373 , the reception coil  310  and the capacitor  363  may be connected in parallel. 
     In an embodiment, comparison between  FIG.  7    and  FIG.  3    reveals that the resonance circuit  210  of  FIG.  7    may include fewer capacitors (e.g., one capacitor  363 ) and fewer switches  361  and  375  than the resonance circuit  210  of  FIG.  3   . In an embodiment, the controller  280  may perform the examples of the above-described operation of the controller  280  using the resonance circuit  210  of  FIG.  7    and, to avoid duplication, no description of the operations of the controller  280  related to  FIG.  7    is given. 
       FIG.  8    is a view illustrating a resonance circuit  210  according to various embodiments. 
     Referring to  FIG.  8   , in an embodiment, a resonance circuit  210  may include a reception coil  310 , a plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  connected in series with the reception coil  310 , a plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  respectively connected in parallel with the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2 , a plurality of second capacitors  341 - 1  and  341 - 2  connected in parallel with the reception coil  310 , and a plurality of second switches  351 - 1  and  351 - 2  respectively connected in series with the plurality of second capacitors  341 - 1  and  341 - 2 . 
     In an embodiment, when the rectification circuit  220  connected to the resonance circuit  210  includes a full-bridge circuit, the resonance circuit may include a plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and a plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  as shown in  FIG.  8   . In an embodiment, the equivalent capacitance of the capacitor  321 - 1  and the capacitor  321 - 2  may be the same as the equivalent capacitance of the capacitor  323 - 1  and the capacitor  323 - 2 . In an embodiment, when the rectification circuit  220  connected to the resonance circuit  210  includes a half-bridge circuit, the resonance circuit  210  may include two capacitors. For example, when the rectification circuit  220  connected to the resonance circuit  210  includes a half-bridge circuit, the capacitors  323 - 1  and  323 - 2  among the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the switches  333 - 1  and  333 - 2  connected in parallel with the capacitors  323 - 1  and  323 - 2  among the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  may be omitted, and the capacitors  321 - 1  and  321 - 2 , respectively, may be replaced with two capacitors whose capacitance is ½ (e.g., 1/(2*C1)) of the same capacitance (e.g., C1) of the capacitors  321 - 1  and  321 - 2 . However, without limitations thereto, the capacitors  321 - 1  and  321 - 2  among the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the switches  331 - 1  and  331 - 2  connected in parallel with the capacitors  321 - 1  and  321 - 2  among the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  may be omitted, and the capacitors  323 - 1  and  323 - 2 , respectively, may be replaced with two capacitors whose capacitance is ½ (e.g., 1/(2*C1)) of the same capacitance (e.g., C1) of the capacitors  323 - 1  and  323 - 2 . 
     In an embodiment, the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  may perform a switching operation to have a connection setting (hereinafter, denoted as a ‘first connection setting of the resonance circuit  210 ’) in which some  321 - 1  and  323 - 1  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  are electrically connected in series with the reception coil  310 , and others  321 - 2  and  323 - 2  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the plurality of second capacitors  341 - 1  and  341 - 2  are not electrically connected with the reception coil  310 . 
     In an embodiment, the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  may perform a switching operation to have a connection setting (hereinafter, denoted as a ‘second connection setting of the resonance circuit  210 ’) in which some  341 - 1  of the plurality of second capacitors  341 - 1  and  341 - 2  is electrically connected with the reception coil  310 , and some other  341 - 2  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the plurality of second capacitors  341 - 1  and  341 - 2  is not electrically connected with the reception coil  310 . 
     In an embodiment, the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  may perform a switching operation to have a connection setting (hereinafter, denoted as a ‘third connection setting of the resonance circuit  210 ’) in which the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  are electrically connected in series with the reception coil  310 , and the plurality of second capacitors  341 - 1  and  341 - 2  are electrically connected in parallel with the reception coil  310 . 
     In an embodiment, the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the plurality of second capacitors  341 - 1  and  341 - 2 , respectively, may have capacitances to form resonance at the same frequency in the first connection setting, the second connection setting, and the third connection setting of the resonance circuit  210 . 
     For example, the equivalent capacitance of some  321 - 1  and  323 - 1  among the plurality of first capacitors may be equal to the capacitances of the plurality of second capacitors  341 - 1  to form resonance at the same frequency in the first connection setting and second connection setting of the resonance circuit. For the third connection setting of the resonance circuit to form resonance at the same frequency as those of the first connection setting and second connection setting of the resonance circuit, the equivalent capacitance of the equivalent capacitance of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the equivalent capacitance of the plurality of second capacitors  341 - 1  and  341 - 2  (e.g., the sum of the equivalent capacitance of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the equivalent capacitance of the plurality of second capacitors  341 - 1  and  341 - 2 ) may be equal to the equivalent capacitance of some  321 - 1  and  323 - 1  of the plurality of first capacitors and the capacitance of the plurality of second capacitors  341 - 1 . 
     In an embodiment, the impedance of the first connection setting of the resonance circuit  210  may be smaller than the impedance of the third connection setting of the resonance circuit  210 . The impedance of the third connection setting of the resonance circuit  210  may be smaller than the impedance of the second connection setting of the resonance circuit  210 . 
     In an embodiment, the first connection setting of the resonance circuit  210  may be a connection setting in which when the power received from the wireless power transmitter  102  is a designated power (hereinafter, denoted as ‘first reception power’) or more, the power received from the wireless power transmitter  102  may be transferred to a load (e.g., the battery  250 ) with high efficiency as compared with the second connection setting and the third connection setting of the resonance circuit  210 . 
     In an embodiment, the third connection setting of the resonance circuit  210  may be a connection setting in which when the power received from the wireless power transmitter  102  is less than the first reception power and is not less than a designated power (hereinafter, denoted as ‘second reception power’), the power received from the wireless power transmitter  102  may be transferred to the load (e.g., the battery  250 ) with high efficiency as compared with the first connection setting and the second connection setting of the resonance circuit  210 . 
     In an embodiment, the second connection setting of the resonance circuit  210  may be a connection setting in which when the power received from the wireless power transmitter  102  is less than the second reception power, the power received from the wireless power transmitter  102  may be transferred to a load (e.g., the battery  250 ) with high efficiency as compared with the second connection setting and the third connection setting of the resonance circuit  210 . 
     In an embodiment, when additional capacitors (and corresponding switches) are included as compared with the resonance circuit  210  of  FIG.  3   , like the resonance circuit  210  of  FIG.  8   , the controller  280  may set a plurality of threshold values to be compared with the value measured in the electronic device  100  (e.g., the output voltage V RECT  of the rectification circuit  220 , the current output from the rectification circuit  220 , the voltage standing wave ratio related to the power transmitted by the wireless power transmitter  102 , or the phase of the impedance of the resonance circuit of the wireless power transmitter  102 ). 
       FIG.  9    is a view  900  illustrating a method for setting a plurality of threshold voltages compared with the output voltage V RECT  of a rectification circuit  220  according to various embodiments. 
     Referring to  FIG.  9   , in an embodiment, in a case where the wireless power transmitter  102  transmits a predetermined magnitude of power, as the distance d between the electronic device  100  and the wireless power transmitter  102  increases (e.g., as they get away from each other), the output voltage V RECT  of the rectification circuit  220  may reduce. In  FIG.  9   , when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 1  (e.g., about 5 cm), the output voltage V RECT  of the rectification circuit  220  may be V 3 (V) (e.g., about 15V). When the distance d between the electronic device  100  and the wireless power transmitter  102  is d 3  (e.g., about 30 cm), the output voltage V RECT  of the rectification circuit  220  may be V 1 (V) (e.g., about 5V). 
     In an embodiment, the controller  280  may set the plurality of threshold voltages to allow the resonance circuit  210  to have a connection setting (e.g., to switch to the state) for transferring the power received from the wireless power transmitter  102  to the load (e.g., the battery  250 ) with high efficiency. For example, as shown in  FIG.  9   , when the distance d between the electronic device  100  and the wireless power transmitter  102  is less than d 2-1  (e.g., about 8 cm), in the first connection setting of the resonance circuit  210 , the power received from the wireless power transmitter  102  may be transferred to the load with high efficiency, as compared with the second connection setting and the third connection setting. When the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2-1  or more and is less than d 2-2  (e.g., about 22 cm), in the third connection setting of the resonance circuit  210 , the power received from the wireless power transmitter  102  may be transferred to the load with high efficiency, as compared with the first connection setting and the second connection setting. When the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2-2  or more, in the second connection setting of the resonance circuit  210 , the power received from the wireless power transmitter  102  may be transferred to the load with high efficiency, as compared with the first connection setting and the third connection setting. 
     The controller  280  may set the output voltage V RECT  of the rectification circuit  220 , identified (e.g., measured) when the distance d between the electronic device  100  and the wireless power transmitter  102  is d 2-1  (e.g., about 8 cm) as a first threshold voltage (e.g., V 2-2 ) (e.g., about 12V). The controller  280  may set the output voltage V RECT  of the rectification circuit  220 , identified (e.g., measured) when the distance d between the electronic device and the wireless power transmitter  102  is d 2-2  (e.g., about 22 cm) as a second threshold voltage (e.g., V 2-1 ) (e.g., about 6V). 
     Although not shown in  FIGS.  8  and  9   , in an embodiment, the controller  280  may set a plurality of threshold values to be compared with the current output from the rectification circuit  220 , the voltage standing wave ratio of the wireless power transmitter  102 , or the phase of the impedance of the resonance circuit of the wireless power transmitter  102  in the same or similar manner as the method for setting a plurality of threshold voltages to be compared with the output voltage V RECT  of the rectification circuit  220  described in connection with  FIG.  9   . 
     In an embodiment, as compared with the resonance circuit  210  of  FIG.  3   , the resonance circuit  210  of  FIG.  8    may be implemented to have a third connection setting, in addition to the first connection setting and the second connection setting, by further including capacitors (e.g.,  321 - 2  and  323 - 2 ) (and corresponding switches  331 - 2  and  333 - 2 ) electrically connectable in series with the reception coil  310  and a capacitor (e.g.,  351 - 2 ) (and corresponding switch  341 - 2 ) electrically connectable in parallel with the reception coil  310 . 
     In an embodiment, when, as compared with the resonance circuit  210  of  FIG.  8   , the resonance circuit  210  further includes at least one capacitor (and at least one corresponding switch) electrically connectable in series with the reception coil  310  and at least one capacitor (and at least one corresponding switch) electrically connectable in parallel with the reception coil  310 , the resonance circuit  210  may be implemented to have at least one fourth connection setting having an impedance different from the impedance of each of the first connection setting, the second connection setting, and the third connection setting, in addition to the first connection setting, the second connection setting, and the third connection setting. 
     In an embodiment, when the resonance circuit  210  is implemented to have at least one fourth connection setting, the controller  280  may allow the power received from the wireless power transmitter  102  to be transferred to the load (e.g., the battery  250 ) with higher efficiency by controlling the switching operation of the switch depending on the distance between the wireless power transmitter  102  and the electronic device in the same or similar manner as those in the above-described examples. 
       FIG.  10    is a view  1000  illustrating a configuration of a switch according to various embodiments. 
     Referring to  FIG.  10   , in an embodiment, switches  1010  and  1020  may be switches constituting the first switches  331  and  333  and the second switch  351 , respectively. 
     In an embodiment, the switch  1010  and the switch  1020  may be implemented as N-channel MOSFETs whose respective sources are connected in series to have a common source voltage. The diode  1011  may be a body diode of the switch  1010 , and the diode  1021  may be a body diode of the switch  1020 . However, without limitations thereto, the switch  1010  and the switch  1020  may be implemented as P-channel MOSFETs whose respective drains are connected in series to have a common drain voltage. 
     In an embodiment, when the switch  1010  and the switch  1020  are in an on state, the AC current I 1  output from the reception coil  310  may flow from the drain of the switch  1010  to the source in the switch  1010  and then through the diode  1021 , and the AC current I 2  may flow from the drain of the switch  1020  to the source in the switch  1010  and then through the diode  1011 . In an embodiment, when the switch  1010  and the switch  1020  are in an off state, current may not flow through the switch  1010  and the switch  1020 . Further, since the diode  1011  and the diode  1021  have opposite directions, they are not simultaneously turned on, so that no current flows through the diode. 
       FIG.  11    is a view  1100  illustrating a method for controlling a switch based on the output voltage V RECT  of a rectification circuit according to various embodiments. 
     In an embodiment,  FIG.  11    may assume that the resonance circuit  210  is initially in the first connection setting. 
     Referring to  FIGS.  2 ,  3 ,  7 , and  11   , in operation  1101 , in an embodiment, the controller  280  may identify the voltage V RECT  output from the rectification circuit  220 . 
     In an embodiment, the controller  280  may identify the output V RECT  of the rectification circuit  220  detected through the voltage detection circuit  260  while performing the operation for charging the battery  250 . In an embodiment, the controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  based on the identified voltage V RECT  output from the rectification circuit  220 . 
     In an embodiment, the controller  280  may identify the current flowing through the over-voltage protection circuit. 
     In an embodiment, the controller  280  may receive information about the voltage standing wave ratio of the wireless power transmitter  102  through the communication circuit  270  from the wireless power transmitter  102  and identify the voltage standing wave ratio of the wireless power transmitter  102 . 
     In an embodiment, the controller  280  may receive information about the phase of the impedance of the resonance circuit of the wireless power transmitter  102  from the wireless power transmitter  102  through the communication circuit  270  and identify the phase of the impedance of the resonance circuit of the wireless power transmitter  102 . 
     In operation  1103 , in an embodiment, the controller  280  may identify whether the output voltage V RECT  of the rectification circuit  220  is less than a threshold voltage. 
     In an embodiment, the controller  280  may determine whether the distance between the wireless power transmitter  102  and the electronic device  100  is a designated distance or more to change (or maintain) the first connection setting of the resonance circuit  210 . 
     In an embodiment, the controller  280  may identify whether the identified current (e.g., the current flowing to the over-voltage protection circuit) is less than a threshold current. 
     In an embodiment, the controller  280  may determine whether the voltage standing wave ratio is less than a threshold voltage standing wave ratio. 
     In an embodiment, the controller  280  may determine whether the phase of impedance is a threshold phase or more. 
     In operation  1105 , upon identifying that the output voltage V RECT  of the rectification circuit  220  is not less than the threshold voltage, in operation  1107 , in an embodiment, the controller  280  may maintain the resonance circuit  210  in the first connection setting. 
     In an embodiment, when the distance between the wireless power transmitter  102  and the electronic device  100  is determined to be not the designated distance or more, the controller  280  may maintain the resonance circuit  210  in the first connection setting. 
     In an embodiment, upon identifying that the identified current is not less than the threshold current, the controller  280  may maintain the resonance circuit  210  in the first connection setting. 
     In an embodiment, upon identifying that the voltage standing wave ratio is not less than the threshold voltage standing wave ratio, the controller  280  may maintain the resonance circuit  210  in the first connection setting. 
     In an embodiment, upon identifying that the phase of impedance is not the threshold phase or more, the controller  280  may maintain the resonance circuit  210  in the first connection setting. 
     In an embodiment, the controller  280  may control the switches  331 ,  333 ,  351 ,  361 , and  375  to maintain the resonance circuit  210  in the first connection setting. In an embodiment, the controller  280  may transfer a first control signal to the switch to maintain the resonance circuit  210  in the first connection setting. 
     In operation  1105 , upon identifying that the output voltage V RECT  of the rectification circuit  220  is less than the threshold voltage, in operation  1109 , in an embodiment, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting 
     In an embodiment, when the distance between the wireless power transmitter  102  and the electronic device  100  is determined to be the designated distance or more, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     in an embodiment, upon identifying that the identified current is less than the threshold current, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, upon identifying that the voltage standing wave ratio is less than the threshold voltage standing wave ratio, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, upon identifying that the phase of impedance is the threshold phase or more, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, the controller  280  may transfer a second control signal to the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     Although  FIG.  11    exemplifies that the electronic device  100  receives power from the wireless power transmitter  102 , in an embodiment, the controller  280  may maintain the first connection setting of the resonance circuit  210  when power is not received by the electronic device  100  from the wireless power transmitter  102 . For example, the controller  280  may maintain the open state of the switches  331 ,  333 , and  351  so that the reception coil  310  and the capacitors  321  and  323  are connected in series. 
       FIG.  12    is a view  1200  illustrating a method for controlling a switch based on the output voltage of a rectification circuit according to various embodiments. 
     In an embodiment,  FIG.  12    may assume that the resonance circuit  210  is initially in the second connection setting. 
     Referring to  FIGS.  2 ,  3 ,  7 , and  11   , in operation  1201 , in an embodiment, the controller  280  may identify the voltage V RECT  output from the rectification circuit  220 . 
     In an embodiment, the controller  280  may identify the output V RECT  of the rectification circuit  220  detected through the voltage detection circuit  260  while performing the operation for charging the battery  250 . In an embodiment, the controller  280  may determine the distance between the wireless power transmitter  102  and the electronic device  100  based on the identified voltage VRECT output from the rectification circuit  220 . 
     In an embodiment, the controller  280  may identify the current flowing through the over-voltage protection circuit. 
     In an embodiment, the controller  280  may receive information about the voltage standing wave ratio of the wireless power transmitter  102  through the communication circuit  270  from the wireless power transmitter  102  and identify the voltage standing wave ratio of the wireless power transmitter  102 . 
     In an embodiment, the controller  280  may receive information about the phase of the impedance of the resonance circuit of the wireless power transmitter  102  from the wireless power transmitter  102  through the communication circuit  270  and identify the phase of the impedance of the resonance circuit of the wireless power transmitter  102 . 
     In operation  1203 , in an embodiment, the controller  280  may identify whether the output voltage V RECT  of the rectification circuit  220  is a threshold voltage or more. 
     In an embodiment, the controller  280  may determine whether the distance between the wireless power transmitter  102  and the electronic device  100  is less than the designated distance to change (or maintain) the second connection setting of the resonance circuit  210 . 
     In an embodiment, the controller  280  may identify whether the identified current (e.g., the current flowing to the over-voltage protection circuit) is a threshold current or more. 
     In an embodiment, the controller  280  may determine whether the voltage standing wave ratio is a threshold voltage standing wave ratio or more. 
     In an embodiment, the controller  280  may determine whether the phase of impedance is less than a threshold phase or more. 
     In operation  1205 , upon identifying that the output voltage V RECT  of the rectification circuit  220  is the threshold voltage or more, in operation  1207 , in an embodiment, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the first connection setting 
     In an embodiment, when the distance between the wireless power transmitter  102  and the electronic device  100  is determined to be less than the designated distance, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the first connection setting. 
     in an embodiment, upon identifying that the identified current is the threshold current or more, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the first connection setting. 
     In an embodiment, upon identifying that the voltage standing wave ratio is the threshold voltage standing wave ratio or more, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the first connection setting. 
     In an embodiment, upon identifying that the phase of impedance is less than the threshold phase, the controller  280  may control the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the first connection setting. 
     In an embodiment, the controller  280  may transfer a first control signal to the switch to allow the resonance circuit  210  to have the first connection setting. 
     In operation  1205 , upon identifying that the output voltage V RECT  of the rectification circuit  220  is not the threshold voltage or more, in operation  1209 , in an embodiment, the controller  280  may maintain the resonance circuit  210  in the second connection setting. 
     In an embodiment, when the distance between the wireless power transmitter  102  and the electronic device  100  is determined to be not less than the designated distance, the controller  280  may maintain the resonance circuit  210  in the second connection setting. 
     In an embodiment, upon identifying that the identified current is not the threshold current or more, the controller  280  may maintain the resonance circuit  210  in the second connection setting. 
     In an embodiment, upon identifying that the voltage standing wave ratio is not the threshold voltage standing wave ratio or more, the controller  280  may maintain the resonance circuit  210  in the second connection setting. 
     In an embodiment, upon identifying that the phase of impedance is not less than the threshold phase, the controller  280  may maintain the resonance circuit  210  in the second connection setting. 
     In an embodiment, the controller  280  may transfer a second control signal to the switch (e.g., the switches  331 ,  333 ,  351 ,  361 , and  375 ) to allow the resonance circuit  210  to have the second connection setting. 
     In an embodiment, the controller  280  may not transfer a control signal to the switch to maintain the resonance circuit  210  in the second connection setting. In an embodiment, the controller  280  may transfer a second control signal to the switch to maintain the resonance circuit  210  in the second connection setting. 
     Although  FIG.  12    exemplifies that the electronic device  100  receives power from the wireless power transmitter  102 , in an embodiment, the controller  280  may maintain the second connection setting of the resonance circuit  210  when power is not received by the electronic device  100  from the wireless power transmitter  102 . For example, the controller  280  may maintain the closed state of the switches  331 ,  333 , and  351  so that the reception coil  310  and the capacitor  341  are connected in parallel. 
       FIG.  13    is a view  1000  illustrating a method for controlling a switch (e.g., the switches  331 ,  333 , and  351 ) based on the output voltage V RECT  of a rectification circuit  220  according to various embodiments. 
     Referring to  FIGS.  2 ,  8 , and  13   , in operation  1001 , in an embodiment, the controller  280  may identify the voltage V RECT  output from the rectification circuit  220 . 
     Since operation  1301  is at least partially the same or similar to the operation  1101  of  FIG.  11   , no detailed description thereof is presented below. 
     In operation  1303 , the controller  280  may compare the voltage V RECT  output from the rectification circuit  220  with a first threshold voltage and a second threshold voltage. In an embodiment, the magnitude of the first threshold voltage may be larger than the magnitude of the second threshold voltage. 
     In operation  1305 , upon identifying that the output voltage V RECT  of the rectification circuit  220  is the first threshold voltage or more, in operation  1307 , in an embodiment, the controller  280  may control the switch to allow the resonance circuit  210  to have the first connection setting 
     In an embodiment, the first connection setting of the resonance circuit  210  may be when, in  FIG.  8   , the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  have a state in which some  321 - 1  and  323 - 1  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  are electrically connected in series with the reception coil  310 , and others  321 - 2  and  323 - 2  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the plurality of second capacitors  341 - 1  and  341 - 2  are not electrically connected with the reception coil  310 . 
     In operation  1309 , upon identifying that the voltage V RECT  output from the rectification circuit  220  is less than the first threshold voltage and not less than the second threshold voltage, in operation  1311 , the controller  280  may control the switch to allow the resonance circuit  210  to have the third connection setting. 
     In an embodiment, the third connection setting of the resonance circuit  210  may be when the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  have a connection setting in which the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  are electrically connected in series with the reception coil  310 , and the plurality of second capacitors  341 - 1  and  341 - 2  are electrically connected in parallel with the reception coil  310 . 
     In operation  1309 , upon identifying that the voltage V RECT  output from the rectification circuit  220  is less than the second threshold voltage, in operation  1313 , the controller  280  may control the switch to allow the resonance circuit  220  to have the second connection setting. 
     In an embodiment, the second connection setting of the resonance circuit  210  may be when the plurality of first switches  331 - 1 ,  331 - 2 ,  333 - 1 , and  333 - 2  and the plurality of second switches  351 - 1  and  351 - 2  have a connection setting in which some  341 - 1  of the plurality of second capacitors  341 - 1  and  341 - 2  are electrically connected with the reception coil  310 , and others  341 - 2  of the plurality of first capacitors  321 - 1 ,  321 - 2 ,  323 - 1 , and  323 - 2  and the plurality of second capacitors  341 - 1  and  341 - 2  are not electrically connected with the reception coil  310 . 
     In  FIG.  13   , upon identifying that the voltage V RECT  output from the rectification circuit  220  is the first threshold voltage or more in operation  1305 , in operation  1309 , it is identified whether the voltage V RECT  output from the rectification circuit is less than the first threshold voltage and not less than the second threshold voltage, but is not limited thereto. For example, in operation  1303 , the controller  280  may compare the voltage V RECT  output from the rectification circuit  220  with a first threshold voltage and a second threshold voltage. The controller may identify a range where the voltage VRECT output from the rectification circuit  220  belongs among a range not less than the first threshold voltage, a range not less than the second threshold voltage and less than the first threshold voltage, and a range less than the second threshold voltage. The controller  280  may control the switch to allow the resonance circuit  210  to have the connection setting corresponding to the range where the voltage V RECT  output from the rectification circuit  220  belongs. 
       FIG.  13    exemplifies a plurality of threshold voltages and the voltage V RECT  output from the rectification circuit  220 , but is not limited thereto. For example, in  FIG.  2   , the controller  280  may set a plurality of threshold values to be compared with the current output from the rectification circuit  220 , the voltage standing wave ratio of the wireless power transmitter  102 , or the phase of the impedance of the resonance circuit of the wireless power transmitter  102  in the same or similar manner as the method for setting a plurality of threshold voltages to be compared with the output voltage V RECT  of the rectification circuit  220  described in connection with  FIG.  13   . 
     It should be appreciated that various embodiments of the present disclosure and the terms used therein are not intended to limit the technological features set forth herein to particular embodiments and include various changes, equivalents, or replacements for a corresponding embodiment. With regard to the description of the drawings, similar reference numerals may be used to refer to similar or related elements. It is to be understood that a singular form of a noun corresponding to an item may include one or more of the things, unless the relevant context clearly indicates otherwise. As used herein, each of such phrases as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and “at least one of A, B, or C,” may include all possible combinations of the items enumerated together in a corresponding one of the phrases. As used herein, such terms as “1st” and “2nd,” or “first” and “second” may be used to simply distinguish a corresponding component from another, and does not limit the components in other aspect (e.g., importance or order). It is to be understood that if an element (e.g., a first element) is referred to, with or without the term “operatively” or “communicatively”, as “coupled with,” “coupled to,” “connected with,” or “connected to” another element (e.g., a second element), it means that the element may be coupled with the other element directly (e.g., wiredly), wirelessly, or via at least a third element. 
     As used herein, the term “module” may include a unit implemented in hardware, software, or firmware, and may interchangeably be used with other terms, for example, “logic,” “logic block,” “part,” or “circuitry”. A module may be a single integral component, or a minimum unit or part thereof, adapted to perform one or more functions. For example, according to an embodiment, the module may be implemented in a form of an application-specific integrated circuit (ASIC). Thus, each “module” herein may comprise circuitry. 
     Various embodiments as set forth herein may be implemented as software (e.g., the program) including one or more instructions that are stored in a storage medium (e.g., internal memory or external memory) that is readable by a machine (e.g., a master device or a device performing tasks). For example, a processor of the machine (e.g., a master device or a device performing tasks) may invoke at least one of the one or more instructions stored in the storage medium, and execute it, with or without using one or more other components under the control of the processor. This allows the machine to be operated to perform at least one function according to the at least one instruction invoked. The one or more instructions may include a code generated by a compiler or a code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Wherein, the term “non-transitory” simply means that the storage medium is a tangible device, and does not include a signal (e.g., an electromagnetic wave), but this term does not differentiate between where data is semi-permanently stored in the storage medium and where the data is temporarily stored in the storage medium. 
     According to an embodiment, a method according to various example embodiments may be included and provided in a computer program product. The computer program products may be traded as commodities between sellers and buyers. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or be distributed (e.g., downloaded or uploaded) online via an application store (e.g., Play Store™), or between two user devices (e.g., smart phones) directly. If distributed online, at least part of the computer program product may be temporarily generated or at least temporarily stored in the machine-readable storage medium, such as memory of the manufacturer&#39;s server, a server of the application store, or a relay server. 
     According to various embodiments, each component (e.g., a module or a program) of the above-described components may include a single entity or multiple entities. According to various embodiments, one or more of the above-described components may be omitted, or one or more other components may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, according to various embodiments, the integrated component may still perform one or more functions of each of the plurality of components in the same or similar manner as they are performed by a corresponding one of the plurality of components before the integration. According to various embodiments, operations performed by the module, the program, or another component may be carried out sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations may be executed in a different order or omitted, or one or more other operations may be added. 
     While the disclosure has been illustrated and described with reference to various embodiments, it will be understood that the various embodiments are intended to be illustrative, not limiting. It will further be understood by those skilled in the art that various changes in form and detail may be made without departing from the true spirit and full scope of the disclosure, including the appended claims and their equivalents. It will also be understood that any of the embodiment(s) described herein may be used in conjunction with any other embodiment(s) described herein.