Patent Publication Number: US-11381116-B2

Title: Display system for wirelessly supplying power

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Entry of PCT International Application No. PCT/KR2019/002942, filed on Mar. 14, 2019, which claims priority to Korean Patent Application No. 10-2018-0045218 filed on Apr. 18, 2018, the contents of all of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     Embodiments disclosed in the disclosure relate to a technique for transmitting wireless power. 
     BACKGROUND ART 
     Recently, wireless power transmission technology that may supply power without using wires has been attracting attention. As wireless power transmission technology advances, it is easier to supply energy to the display. 
     In the wireless power transmission using magnetic resonance, power is supplied from an AC source to generate an AC current in a transmission coil, and a resonant coil is coupled to the transmission coil to transmit power by the resonant coil. The wireless power transmission by the magnetic resonance may transmit power farther than an electromagnetic induction method, but its transmittable distance is still short, so many improvements are necessary. 
     DISCLOSURE 
     Technical Problem 
     In a display system, as the distance from a wireless power transmitter to a component (e.g., speaker, or display) for outputting content increases, since the power transmission (or reception) efficiency is significantly reduced, the component may be difficult to place beyond a specified distance from the wireless power transmitter. When a coil is wound around a thick magnetic material to improve power reception efficiency, the thickness of the display itself may be thickened. In addition, when the display system further includes a separate repeater to increase the distance between the wireless power transmitter and the component, not only does the production cost increase, but also the volume of the display system may increase. 
     Meanwhile, when a sound bar separated from the display is used as a repeater, due to a load of the component for outputting sound, it is difficult to generate a power signal having a sufficient magnitude for transferring power, or as a resonance point for receiving the generated signal is changed, a transfer efficiency may be significantly reduced. 
     According to various embodiments of the disclosure, a display system may increase power transmission and reception efficiency by generating a power signal having a sufficient magnitude to transfer power at a uniform resonance point while using a speaker as a repeater. 
     Technical Solution 
     A display system according to an embodiment disclosed in the disclosure includes a wireless power transmitter that converts power supplied from a power source unit into a first magnetic field and to transmit a first power signal to a speaker; the speaker including a wireless power transmission/reception circuit that converts the first power signal received from the wireless power transmitter into a first current, and to generate a second magnetic field by the first current to transmit a second power signal to a display, a distribution circuit that distributes power received through the first power signal to a sound output unit by distributing the first current and outputting a second current, and the sound output unit that outputs sound using power supplied from the distribution circuit; and the display including a wireless power reception circuit that converts the second power signal received from the speaker into a third current, and an image output unit that outputs an image by using power transferred through the third current. 
     In addition, a display system according to an embodiment disclosed in the disclosure includes a wireless power transmitter that converts power supplied from a power source unit into a first magnetic field and to transmit a first power signal to a speaker; the speaker including a first wireless power reception circuit that converts the first power signal received from the wireless power transmitter into a first current, a distribution circuit that distributes power received through the first power signal to a sound output unit and a first wireless power transmission circuit by distributing the first current and outputting a second current, the sound output unit that outputs sound using a first power distributed by the distribution circuit, and the first wireless power transmission circuit that converts a second power distributed by the distribution circuit into a second magnetic field to transmit a second power signal to a display; and the display including a second wireless power reception circuit that converts the second power signal received from the speaker into a third current, and an image output unit that outputs an image by using power transferred through the third current. 
     In addition, a wireless power repeating apparatus according to an embodiment disclosed in the disclosure includes a wireless power transmission/reception circuit that converts a first power signal received from a first external device through a first magnetic field into a first current, to generate a second magnetic field by the first current to transmit a second power signal to a second external device, a distribution circuit that distributes power received through the first power signal to a load unit by distributing the first current and outputting a second current, and the load unit that performs a function by using the power supplied from the distribution circuit. 
     In addition, a wireless power repeating apparatus according to an embodiment disclosed in the disclosure includes a wireless power reception circuit that converts a first power signal received from a first external device through a first magnetic field into a first current, a distribution circuit that distributes power received through the first power signal to a load unit and a wireless power transmission circuit by distributing the first current and outputting a second current, the load unit that performs a function by using a first power distributed by the distribution circuit, and the wireless power transmission circuit that converts a second power distributed by the distribution circuit into a second magnetic field to transmit a second power signal to a display. 
     Advantageous Effects 
     According to an exemplary embodiment of the disclosure, a display system may improve the appearance of the display system by allowing the display that receives power wirelessly to be spaced over a specified distance from the power transmitter, using a speaker placed close to the display as a wireless power repeater. 
     In addition, by placing a circuit that transmits power for performing an operation of outputting sound to a speaker used as a repeater, the speaker may smoothly repeat power to the display while supplying power for internal operation. 
     In addition, various effects may be provided that are directly or indirectly identified through this document. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a display system according to various embodiments. 
         FIG. 2  is a block diagram illustrating a configuration of a display system according to an embodiment. 
         FIG. 3  is a circuit diagram of a display system according to an exemplary embodiment. 
         FIG. 4  is a graph illustrating power received by a speaker and a display according to an embodiment of the disclosure. 
         FIG. 5  is a diagram illustrating adding a coil for retransmitting power in a speaker of a display system according to an embodiment. 
         FIG. 6  is a block diagram illustrating a configuration of a display system in which a retransmission coil of a speaker is added, according to an embodiment. 
     
    
    
     In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar components. 
     MODE FOR INVENTION 
     Hereinafter, various embodiments of the disclosure will be described with reference to the accompanying drawings. However, this is not intended to limit the disclosure to specific embodiments, and it should be understood that the disclosure includes various modifications, equivalents, and/or alternatives. In connection with the description of the drawings, similar reference numerals may be used for similar components. 
       FIG. 1  is a diagram illustrating a display system according to various embodiments. 
     Referring to  FIG. 1 , a display system  100  may include a wireless power transmitter  110 , a speaker  120 , and a display  130 . The display system  100  may output content by transmitting and receiving wireless power in each component included in the display system  100 . The content may be stored, for example, in the display system  100 , or may be received from an external device (e.g., a set-top box, a DVD player, etc.). The content may include image information and sound information. 
     According to one embodiment, the display system  100  may transmit power wirelessly to each component for displaying the content. 
     According to one embodiment, the wireless power transmitter  110  may be connected to an external power source  10  to receive power. The external power source  10  may supply, for example, an AC voltage within a specified range (e.g., 85 V to 256 V) as a wall power (or commercial power) to the display system  100 . 
     According to an embodiment, the wireless power transmitter  110  may transmit power supplied from the external power source  10  to an external device. For example, the wireless power transmitter  110  may transmit a first power signal  20  to the external device (e.g., the speaker  120 ) using the input power (or supplied power). The first power signal  20  may be, for example, a signal for wirelessly transmitting power generated by the input power (e.g., the external power source  10 ). According to an embodiment, the wireless power transmitter  110  may generate the first power signal  20  by generating a magnetic field through a first coil  110 ′. Accordingly, the wireless power transmitter  110  may convert power supplied from the external power source  10  into the magnetic field (or a first magnetic field) and may transmit the converted power to the speaker  120  through the first power signal  20 . 
     According to one embodiment, the wireless power transmitter  110  may supply power to the external device through a wire as well as wirelessly. For example, the wireless power transmitter  110  may supply power to the external device connected wiredly. The external device may be, for example, a device for performing an additional function (e.g., a camera function). 
     According to an embodiment, the speaker  120  may repeat power transmitted from the wireless power transmitter  110  and may transfer the power to the external device. For example, the speaker  120  may receive the first power signal  20  from the wireless power transmitter  110  and may transmit a second power signal  30  to an external device, using the received first power signal  20 . The second power signal  30  may be generated by using, for example, a part of power received through the first power signal  20 . According to an embodiment, an induced electromotive force may be generated due to the magnetic field generated by the wireless power transmitter  110  in a second coil  120 ′ of the speaker  120 , and the magnetic field may be generated from the generated induced electromotive force to repeat the power. 
     According to one embodiment, the speaker  120  may output a specified sound. For example, the speaker  120  may output sound included in the content using a part of the first power signal  20  received from the wireless power transmitter  110 . Accordingly, the speaker  120  may output the specified sound while repeating the power to the external device. 
     According to one embodiment, the speaker  120  is a wireless power repeating apparatus that repeats the power signal (e.g., the first power signal  20 ) transmitted from the wireless power transmitter  110  and may transmit the power signal to the display  130 . In addition, the wireless power repeating apparatus may output the sound included in the content. 
     According to one embodiment, the display  130  may receive power from the speaker  120 . The display  130  may receive power transferred (or repeated) through the speaker  120 . For example, the display  130  may receive the second power signal  30 . According to an embodiment, the display  130  may receive the second power signal  30  by generating the induced electromotive force in a third coil  130 ′ that resonates with the magnetic field generated by the speaker  120 . 
     According to one embodiment, the display  130  may output a specified image using the received power signal (e.g., the second power signal  30 ). The specified image may be an image included in the content. 
     As a distance from the wireless power transmitter  110  to a component (e.g., the speaker  120  or the display  130 ) for outputting the content increases, a power transmission (or reception) efficiency of the display system  100  may be significantly decreased. Accordingly, the component may be difficult to be placed beyond a specified distance from the wireless power transmitter  110 . When a coil is wound around a thick magnetic material to improve the power reception efficiency, the thickness of the display  130  itself may be thickened. In addition, when the display system  100  further includes a separate repeater to increase the distance between the wireless power transmitter  110  and the component, not only does the production cost increase, but also the volume of the display system  100  may increase. When the speaker  120  of the display system  100  is separated from the display  130  and disposed in the form of a sound bar, and the speaker  120  is used as a repeater, it is difficult to generate a power signal having a sufficient magnitude for transmitting power due to the load on the component for outputting the sound, or since a resonance point for receiving the generated signal is changed, the transfer efficiency may be significantly reduced. However, the display system  100  according to various embodiments of the disclosure may generate the power signal having the sufficient magnitude to transmit power at a uniform resonance point, and may increase the transmission/reception efficiency of power, while using the speaker  120  as the repeater. 
       FIG. 2  is a block diagram illustrating a configuration of a display system according to an embodiment. 
     Referring to  FIG. 2 , the wireless power transmitter  110  of the display system  100  may include a power factor regulator  111 , an inverter  112 , and a first resonant circuit  113  (or wireless power transmission circuit). The wireless power transmitter  110  may transmit power supplied from the external power source  10  to the speaker  120  through the power factor regulator  111 , the inverter  112 , and the first resonant circuit  113 . In the wireless power transmitter  110 , an additional configuration for wirelessly transmitting power may be included, or some configurations may be omitted. 
     According to an embodiment, the power factor regulator  111  may output a specified voltage by adjusting a power factor of power supplied from the external power source  10 . For example, the power factor regulator  111  may change the power factor to close to 1 by matching a phase of a voltage and a phase of a current of a rectified AC voltage, and may output a DC voltage through a capacitor connected to an output end. 
     According to an embodiment, the inverter  112  may change the DC voltage input from the power factor regulator  111  to the AC voltage. The inverter  112  may include a PWM circuit for a pulse width modulation (PWM). According to an embodiment, a controller (not illustrated) of the wireless power transmitter  110  may control the inverter  112  to determine a frequency of an output voltage. For example, the controller may determine the frequency (or switching frequency) of the output voltage by changing a duty ratio of a control signal input to a switch of the PWM circuit. The controller may control an on-off period of the switch of the PWM circuit to determine the frequency of the output voltage. 
     According to an embodiment, the first resonant circuit  113  may transmit the first power signal  20  of a specified frequency (or operating frequency) to the speaker  120 , using a voltage applied from the inverter  112 . The specified frequency may be, for example, a frequency (or switching frequency) of the voltage output from the inverter  112 . 
     According to an embodiment, the speaker  120  may include a second resonant circuit  121  (or wireless power transmission/reception circuit), a distribution circuit  122 , a first impedance conversion circuit  123 , a first rectifier  124 , a first converter  125 , and a first load unit  126 . The speaker  120  may repeat a part of the power transferred from the wireless power transmitter  110  to the display  130  through the second resonant circuit  121 , the distribution circuit  122 , the impedance conversion circuit  123 , the first rectifier  124 , the first converter  125 , and the first load unit  126 , and may output the specified sound by using the remaining power. An additional configuration for repeating a power signal or outputting the sound may be included to the speaker  120 , or some configuration may be omitted. 
     According to an embodiment, the second resonant circuit  121  may receive the first power signal  20  from the first resonant circuit  113 . For example, the second resonant circuit  121  may receive the first power signal  20  by resonating at a frequency of the first power signal  20 . The second resonant circuit  121  may resonate at the frequency of the first power signal  20  by adjusting values of an inductor and of a capacitor. 
     According to one embodiment, the second resonant circuit  121  may transmit a part of the received power to the display  130 . The second resonant circuit  121  may repeat (or transfer) power received from the wireless power transmitter  110  to the display  130 . For example, the second resonant circuit  121  may transmit the second power signal  30  of a specified frequency using a part of the first power signal  20  received from the wireless power transmitter  110 . The specified frequency may be, for example, the frequency of the received first power signal  20 . 
     According to an embodiment, the second resonant circuit  121  may supply a part (e.g., the remaining part) of the received power to the first load unit  126 . The second resonant circuit  121  may supply a portion of the received power into the speaker  120  to output a specified sound. 
     According to an embodiment, the distribution circuit  122  may be connected to the second resonant circuit  121  to transfer the supplied power to the first load unit  126 . According to an embodiment, the distribution circuit  122  may prevent the resonance frequency of the second resonant circuit  121  from being changed by an operation of outputting the sound of the first load unit  126 , and may allow a repeat operation for transmitting and receiving wireless power to be stably performed. The distribution circuit  122  may electrically separate the second resonant circuit  121  from the first load unit  126 . 
     According to one embodiment, the first impedance conversion circuit  123  may be connected to the distribution circuit  122 , may change an impedance of the distribution circuit  122  such that an amount of change in the current supplied to the first load unit  126  by the part of the received power signal becomes a minimum. For example, the first impedance conversion circuit  123  may change the impedance of the distribution circuit  122  such that a current flowing through the second resonant circuit  121 , which may be changed by the operation of the first load unit  126  and the amount of change in the distribution circuit of the current supplied to the first load unit  126  become the minimum. The first impedance conversion circuit  123  is connected to an output end of the distribution circuit  122  to convert (transduce) the impedance of the distribution circuit  122 . According to an embodiment, the first impedance conversion circuit  123  may change the impedance of the distribution circuit  122  depending on the first load unit  126 . For example, the first impedance conversion circuit  123  may change the impedance of the distribution circuit  122  depending on an output capacity of the first load unit  126 . 
     According to one embodiment, the first rectifier  124  may rectify the AC voltage input from the distribution circuit  122  and the impedance conversion circuit  123  to generate a DC voltage. According to an embodiment, a capacitor for generating the DC voltage may be connected to an output end of the first rectifier  124 . 
     According to one embodiment, the first converter  125  may adjust the DC voltage input from the first rectifier  124  to match the capacity of the first load unit  126 . For example, the first converter  125  may adjust the level of the DC voltage and may supply the DC voltage having the adjusted level to the first load unit  126 . According to an embodiment, the first converter  125  may be a DC/DC converter. According to an embodiment, the first converter  125  may output a specified DC voltage. 
     According to an embodiment, the first load unit  126  (or sound output unit) may output a specified sound using the voltage input from the first converter  125 . The first load unit  126  may receive a part of the power received from the second resonant circuit  121  through the distribution circuit  122  and may output the specified sound. 
     According to one embodiment, the display  130  may further include a third resonant circuit  131  (or wireless power receiving circuit), a second impedance conversion circuit  132 , a second rectifier  133 , a second converter  134 , and a second load unit  135 . The display  130  may output the specified image by using the power transferred from the speaker  120  through the third resonant circuit  131 , the second impedance conversion circuit  132 , the second rectifier  133 , the second converter  134 , and the second load unit  135 . An additional configuration for wirelessly receiving power or outputting the image may be included in the display  130 , or some configuration may be omitted. 
     According to an embodiment, the third resonant circuit  131  may receive the second power signal  30  from the second resonant circuit  121 . For example, the third resonant circuit  131  may receive the second power signal  30  by resonating at a frequency of the second power signal  30 . The third resonant circuit  131  may resonate at the frequency of the second power signal  30  by adjusting values of an inductor and a capacitor. 
     According to one embodiment, the second impedance conversion circuit  132  may change the impedance of the third resonant circuit  131  such that the second power signal  30  received through the third resonant circuit  131  becomes a maximum. The second impedance conversion circuit  132  is connected to an output end of the third resonant circuit  131  to change the impedance of the third resonant circuit  131 . 
     According to one embodiment, the second rectifier  133  may rectify the AC voltage input from the impedance conversion circuit  132  to generate the DC voltage. According to an embodiment, a capacitor for generating the DC voltage may be connected to the output end of the second rectifier  133 . 
     According to one embodiment, the second converter  134  may adjust the DC voltage input from the second rectifier  133  to match the capacity of the second load unit  135 . For example, the second converter  134  may adjust the level of the DC voltage and may supply the DC voltage having the adjusted level to the second load unit  135 . According to an embodiment, the second converter  134  may be a DC/DC converter. According to an embodiment, the second converter  134  may output a specified DC voltage. 
     According to an embodiment, the second load unit  135  (or the image output unit) may output a specified image using the voltage input from the second converter  134 . In other words, the second load unit  135  may output the specified image using the power repeated (or relayed) through the speaker  120 . 
       FIG. 3  is a diagram illustrating a circuit diagram of a display system according to an exemplary embodiment of the disclosure. 
     Referring to  FIG. 3 , the display system  100  may wirelessly supply power from the wireless power transmitter  110  to the display  130  using the speaker  120  as a repeater. 
     According to an embodiment, a specified current Is may be input to the first resonant circuit  113  of the wireless power transmitter  110 . The wireless power transmitter  110  may additionally include a resonant circuit (not illustrated) for supplying the specified current Is. The resonant circuit for supplying the specified current may be connected to an input end of the first resonant circuit  113  to supply the specified current Is to the first resonant circuit  113 . According to an embodiment, the first resonant circuit  113  may flow the first current i 1  by the input current Is. 
     According to an embodiment, the first resonant circuit  113  may include a first capacitor C 1  and a first inductor L 1 . The first capacitor C 1  and the first inductor L 1  may be connected, for example, in series with each other. According to an embodiment, the first resonant circuit  113  may generate a magnetic field forming the resonance point at a specified frequency through the first inductor L 1  through which the first current i 1  flows. Accordingly, the first resonant circuit  113  may transmit the first power signal for transmitting power to the speaker  120 . 
     According to one embodiment, the second resonant circuit  121  of the speaker  120  may include a second capacitor C 2  and a second inductor L 2 . The second capacitor C 2  and the second inductor L 2  may be connected, for example, in series with each other. According to an embodiment, the induced electromotive force may be generated by the magnetic field generated by the first resonant circuit  113  in the second inductor L 2  of the second resonant circuit  121 . The second inductor L 2  of the second resonant circuit  121  may generate the induced electromotive force by inductively coupling (inductive coupling constant=K12) with the first inductor L 1  of the first resonant circuit  113 . The induced electromotive force may be generated, for example, by the second resonant circuit  121  resonating with the magnetic field generated by the first resonant circuit  113 . Accordingly, a second current i 2  may flow through the second resonant circuit  121  by the induced electromotive force of the second inductor L 2 . 
     According to an embodiment, the second resonant circuit  121  may output the second current i 2  to the distribution circuit  122  to supply power required for the first load unit  126 . Accordingly, the second resonant circuit  121  may supply a part of the power received from the wireless power transmitter  110  to a configuration (e.g., a sound output unit) inside the speaker  120 . 
     According to one embodiment, the second resonant circuit  121  may repeat the magnetic field generated by the first resonant circuit  113 . The second resonant circuit  121  may expand a range of the magnetic field generated by the first resonant circuit  113 . For example, the second inductor L 2  of the second resonant circuit  121  may generate a magnetic field forming the resonance point at a specified frequency by using the generated induced electromotive force. The second resonant circuit  121  may convert the received first power signal into the second current i 2 , and may generate the magnetic field (or the second magnetic field) by the second current i 2  to transmit the second power signal of the specified frequency to the display  130 . The specified frequency may be, for example, a frequency of the second current i 2 . Accordingly, the second resonant circuit  121  may transmit a part of the power received from the wireless power transmitter  110  to the display  130 . 
     According to one embodiment, the distribution circuit  122  may include a resonant circuit. For example, the distribution circuit  122  may include a fourth inductor L 4  and a fourth capacitor C 4  that are connected in series with each other. According to an embodiment, the distribution circuit  122  may be connected to an output end of the second resonant circuit  121 . The fourth inductor L 4  may be connected to the second resonant circuit  121  in series, and the fourth capacitor C 4  may be connected to the second resonant circuit  121  in parallel. The fourth inductor L 4  may be connected to one end of the output of the second resonant circuit  121 , and the fourth capacitor C 4  may be connected to both ends of the output of the second resonant circuit  121 . According to an embodiment, the distribution circuit  122  may output a second′ current i 2 ′ using the input second current i 2 . In other words, the distribution circuit  122  may distribute the second current i 2  output from the second resonant circuit  121  to output the second′ current i 2 ′. Accordingly, the distribution circuit  122  may output the power received through the first power signal of the wireless power transmitter  110  to the first load unit  126 . 
     According to an embodiment, values of the fourth inductor L 4  and the fourth capacitor C 4  of the distribution circuit  122  may be determined according to Equation 1 below. 
     
       
         
           
             
               
                 
                   
                     [ 
                     63 
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                             L 
                             4 
                           
                           * 
                           
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                             4 
                           
                         
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                   [ 
                   
                     Equation 
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                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     The Ws may be a switching frequency, or an operating frequency of the wireless power transmitter  110 . According to an embodiment, when the values of the fourth inductor L 4  and the fourth capacitor C 4  are determined to completely resonate with the frequency of the received first power signal, power reception efficiency and power transfer efficiency may be increased. 
     According to one embodiment, the value of the second capacitor C 2  of the second resonant circuit  121  is determined depending on Equation 2 below when the value of the fourth inductor L 4  is determined depending on Equation 1 above. 
     
       
         
           
             
               
                 
                   
                     [ 
                     66 
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                     1 
                     
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                         ( 
                         
                           
                             ( 
                             
                               
                                 L 
                                 2 
                               
                               - 
                               
                                 L 
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                   [ 
                   
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     The Ws may be the switching frequency or the operating frequency of the wireless power transmitter  110  in the same manner as in Equation 1. A value of the second inductor L 2  may be predetermined for the resonance. According to an embodiment, when the value of the second inductor L 2  is determined as described above, the power reception efficiency and the power repeating efficiency may be increased. 
     According to an embodiment, the power distributed to the first load unit  126  (e.g., the sound output unit) through the distribution circuit  122  may vary depending on an operation of the first load unit  126  and the second load unit  135  (e.g., the image output unit) of the display  130 . For example, when the first load unit consumes higher power than the second load unit  135  (e.g., outputting a loud sound), the power distributed to the first load unit  126  through the distribution circuit  122  may be increased. Accordingly, the power distributed to the display  130  (e.g., the image output unit  135 ) may be lowered. For another example, when the first load unit  126  (e.g., the sound output unit) consumes lower power than the second load unit  135  (e.g., outputting a small sound), the power distributed to the first load unit  126  through the distribution circuit  122  may be lowered. Accordingly, the power distributed to the display  130  may be increased. According to one embodiment, the second current i 2  related to the second power signal transmitting power to the display  130  and the second′ current i 2 ′ related to the operation of the first load unit  126  may be changed, based on the change. Accordingly, the first impedance conversion circuit  123 , which will be described below, may adjust the impedance of the distribution circuit  122  to minimize the amount of change in the second current i 2  and the second′ current i 2 ′. 
     According to an embodiment, the first impedance conversion circuit  123  may include a fifth capacitor CP 1 . The fifth capacitor CP 1  may be connected to both ends of an output of the distribution circuit  122 . Accordingly, the first impedance conversion circuit  123  may convert the impedance of the distribution circuit  122 , and may minimize the amount of change in the second current i 2  and the second′ current i 2 ′ that may be changed by the operation of the first load unit  126 . According to one embodiment, a value of the fifth capacitor CP 1  may be determined such that the amount of change of the second current i 2  and the second′ current i 2 ′ that may be changed by the operation of the first load unit  126  is minimized. According to an embodiment, the capacitance of the fifth capacitor CP 1  may be determined based on the output capacity of the first load unit  126 . For example, the value of the fifth capacitor CP 1  may be determined in proportion to the output capacity of the first load unit  126 . When the output capacity of the first load unit  126  is high, the fifth capacitor CP 1  having a high capacitance may be installed. In addition, when the output capacity of the first load unit  126  is low, the fifth capacitor CP 1  having a low capacitance may be installed. 
     According to an embodiment, the first rectifier  124  and the first converter  125  may supply power to the first load unit  126  (or the sound output unit) by using the input second′ current i 2 ′. According to an embodiment, the first load unit  126  may output the specified sound by using the supplied power. 
     According to an embodiment, the third resonant circuit  131  of the display  130  may include a third capacitor C 3  and a third inductor L 3 . The third capacitor C 3  and the third inductor L 3  may be connected, for example, in series with each other. According to an embodiment, the induced electromotive force may be generated in the third inductor L 3  of the third resonant circuit  131  by the magnetic field generated by the second resonant circuit  121 . The third inductor L 3  of the third resonant circuit  131  may generate the induced electromotive force by inductively coupling (inductive coupling constant=K23) with the second inductor L 2  of the second resonant circuit  121 . The induced electromotive force may be generated based on, for example, the third resonant circuit  131  resonating with the magnetic field generated by the second resonant circuit  121 . According to an embodiment, a third current i 3  may flow through the third resonant circuit  131  by the induced electromotive force of the third inductor L 3 . Accordingly, the third resonant circuit  131  may convert the second power signal received from the speaker  120  into the third current i 3 . 
     According to an embodiment, the second impedance conversion circuit  132  may include a sixth capacitor CP 2 . The sixth capacitor CP 2  may be connected to both ends of the output of the third resonant circuit  131 . Accordingly, the second impedance conversion circuit  132  may change the third current i 3  by converting the impedance of the third resonant circuit  131 . According to an embodiment, a value of the sixth capacitor CP 2  may be determined such that the value of the third current i 3  is a maximum. 
     According to an embodiment, the second rectifier  133  and the second converter  134  may supply power to the second load unit  135  (or the image output unit) using the input third current i 3 . According to an embodiment, the second load unit  135  may output a specified image by using the supplied power. 
       FIG. 4  is a graph illustrating power received by a speaker and a display according to an embodiment of the disclosure. 
     Referring to  FIG. 4 , in a state in which the wireless power transmitter  110 , the speaker  120 , and the display  130  of the display system  100  are sequentially disposed, power for performing a specified operation may be transmitted and received. 
     According to an embodiment, the speaker  120  and the display  130  may transmit and receive power equal to or greater than a specified magnitude for performing a specified operation in a state that is disposed to be spaced apart by a specified length from a device that receives power (e.g., the wireless power transmitter  110  or speaker  120 ). The speaker  120  may require, for example, power of 20 W or more to output a specified sound. The display  130  may require power of 300 W or more to output a specified image. 
     According to an embodiment, the speaker  120  may be disposed 50 cm apart from the wireless power transmitter  110 , and the display  130  may be disposed 20 cm apart from the speaker  120 . According to an embodiment, the wireless power transmitter  110  may receive the AC voltage within a specified range (e.g., 85 to 256 V) from wall power (or commercial power). According to an embodiment, the wireless power transmitter  110  may operate at an operating frequency of 85 kHz. Referring to (a), when the speaker  120  is disposed as above, 21.7 W (P1) of the power received from the wireless power transmitter  110  at a frequency near the frequency (e.g., 85 kHz) of the transmitted power may be transferred to the sound output unit. 20 W or more of power required to output the specified sound of the speaker  120  may be transferred to the load. Referring to (b), when the display  130  is disposed as above, 369 W (P2) transferred through the speaker  120  at a frequency near the frequency (e.g., 85 kHz) of the transmitted power may be transferred to the image output unit. 300 W or more of power required to output a specified image of the display  130  may be transferred to the load. 
     Accordingly, when the wireless power transmitter  110 , the speaker  120 , and the display  130  of the display system  100  are disposed as described above, power may be smoothly transmitted and received with high efficiency. 
     The display system  100  according to various embodiments of the disclosure described with reference to  FIGS. 1 to 4  may take advantage of design (or aesthetics), by separating the display  130  that receives power wirelessly from the wireless power transmitter  110  by a specified distance or more, using the speaker  120  disposed close to the display  130  as a wireless power repeater. 
     In addition, the speaker  120  may smoothly repeat power to the display  130  by disposing a circuit that transfers power to perform an operation of outputting sound to the speaker  120  used as the repeater, while the speaker  120  supplies power for an internal operation. 
       FIG. 5  is a diagram illustrating adding a coil for retransmitting power in a speaker of a display system according to an embodiment. 
     Referring to  FIG. 5 , a display system  500  may repeat power transmitted from a wireless power transmitter  510  through coils  520 - 3  and  520 - 5  that retransmit the received power included in a speaker  520 . 
     According to an embodiment, the wireless power transmitter  510  may transmit power supplied from the external power source  10  to the speaker  520 . For example, the wireless power transmitter  510  may transmit the first power signal to the speaker  520 . According to an embodiment, the wireless power transmitter  510  may generate the magnetic field through a first coil  510 - 1 . Accordingly, the wireless power transmitter  510  may convert the supplied power into the magnetic field (or a first magnetic field) and may transmit the first power signal to the speaker  520 . 
     According to an embodiment, the speaker  520  may repeat power transmitted from the wireless power transmitter  510  and transmit the power to a display  530 . 
     According to an embodiment, the speaker  520  may receive power from the wireless power transmitter  510 . For example, the speaker  520  may receive the first power signal from the wireless power transmitter  510 . According to one embodiment, the induced electromotive force may be generated by the magnetic field generated by the wireless power transmitter  510  in a second coil  520 - 1  of the speaker  520 , and power may be supplied to an internal configuration of the speaker  520  depending on the generated induced electromotive force. 
     According to an embodiment, the speaker  520  may retransmit a part of the power received from the wireless power transmitter  510  to the display  530 . For example, the speaker  520  may transmit a second power signal and a third power signal through a plurality of transmitters. According to an embodiment, the speaker  520  may form the magnetic field through the 3-1 coil  520 - 3  and the 3-2 coil  520 - 5 . According to an embodiment, the speaker  520  may output a specified sound by using a part (e.g., a remaining part) of power received from the wireless power transmitter  510 . 
     According to an embodiment, the speaker  520  may be the wireless power repeating apparatus that repeats the power signal (e.g., the first power signal) transmitted from the wireless power transmitter  510  and transmits the power signal to the display  530 . In addition, the wireless power repeating apparatus may output sound included in the content. According to an embodiment, the display  530  may receive power from the speaker  520 . For example, the speaker  520  may receive the second power signal and the third power signal through a plurality of receivers. According to an embodiment, the induced electromotive force may be generated by the magnetic field generated by the speaker  520  in a 4-1 coil  530 - 1  and a 4-2 coil  530 - 3  of the display  530 , and power may be supplied to an internal configuration of the display  530  depending on the generated induced electromotive force. According to an embodiment, the display  530  may output a specified image by using power received from the speaker  520 . 
     According to an embodiment, when power among the wireless power transmitter  510 , the speaker  520 , and the display  530  of the display system  500  is transmitted, electromagnetic interference (EMI) signals may be generated by a leakage magnetic field generated in coils. An efficiency of wireless power transmission/reception may be reduced by the EMI signals. 
     According to an embodiment, a first EMI signal may be generated by the first leakage magnetic field  40  of the first coil  510 - 1  of the wireless power transmitter  510 . According to an embodiment, a second EMI signal may be generated by a second leakage magnetic field  50  of the second coil  520 - 1  of the speaker  520 . In addition, a third EMI signal and a fourth EMI signal may be generated by a third leakage magnetic field  60  of the 3-1 coil  520 - 3  of the speaker  520  and a fourth leakage magnetic field  70  of the 3-2 coil  520 - 5  of the speaker  520 . According to one embodiment, a fifth EMI signal and a sixth EMI signal may be generated by a fifth leakage magnetic field  80  of the 4-1 coil  530 - 1  of the display  530  and a sixth leakage magnetic field  90  of the 4-2 coil  530 - 3  of the display  530 . 
     According to an embodiment, since a phase difference between a signal generated by the first coil  510 - 1  of the wireless power transmitter  510  and a signal generated by the second coil  520 - 1  of the speaker  520  is 90 degrees, there may be no interference with each other. Since a phase difference between a signal generated by the 3-1 coil  520 - 3  of the speaker  520  and a signal generated by the 4-1 coil  530 - 1  of the display  530 , and a phase difference between a signal generated by the 3-2 coil  520 - 5  of the speaker  520  and a signal generated by the 4-2 coil  530 - 3  of the display  530  are 90 degrees, respectively, there may be no interference with each other. In addition, when the phase difference between the signal generated by the second coil  520 - 1  of the speaker  520  and the signals generated by the 3-1 coil  520 - 3  and the 3-2 coil  520 - 5  of the speaker  520  is set to 90 degrees, there may be no interference with each other. 
     According to an embodiment, since the first EMI signal generated from the first coil  510 - 1  of the wireless power transmitter  510  has a phase difference of 180 degrees compared to the third EMI signal and the fourth EMI signal generated from each of the 3-1 coil  520 - 3  and the 3-2 coil  520 - 5  of the speaker  520 , the first EMI signal may be canceled out with each other. In addition, since the second EMI signal generated from the second coil  520 - 1  of the speaker  520  has a phase difference of 180 degrees compared to the fifth EMI signal of the 4-1 coil  530 - 1  and the sixth EMI signal of the 4-2 coil  530 - 3  of the display  530 , the second EMI signal may be canceled out with each other. 
     Accordingly, the interference caused by the EMI signal that may occur in transmitting wireless power of the display system  500  may be canceled. In addition, a resonator having a small size may be included in the display  530  by dividing the coils  520 - 3  and  520 - 5  for a retransmission of the speaker  520  into a plurality of coils. 
       FIG. 6  is a block diagram illustrating a configuration of a display system in which a retransmission coil of a speaker is added, according to an embodiment. 
     Referring to  FIG. 6 , the speaker  520  of the display system  500  may retransmit a part of the received power to the display  530 . 
     According to an embodiment, as in the above description of the wireless power transmitter  110  of  FIG. 2 , the wireless power transmitter  510  may transmit the first power signal for power transmission to the speaker  520 . According to one embodiment, the first EMI signal may be generated due to the first leakage magnetic field generated through the first resonant circuit (or the first wireless power transmission circuit) of the wireless power transmitter  510 . 
     According to one embodiment, as in the above description of the speaker  120  of  FIG. 2 , the speaker  520  may receive the first power signal through a second resonant circuit  521  (or the first wireless power receiving circuit). The second resonant circuit  521  may convert the first power signal received from the wireless power transmitter  510  into the first current. According to an embodiment, the second EMI signal may be generated by the second leakage magnetic field generated through the second resonant circuit  521 . 
     According to an embodiment, the speaker  520  may supply the first power signal received through a distribution circuit  522  to a first load unit  526 , and a 3-1st resonant circuit  529 - 1  (or a second wireless power transmission circuit) and a 3-2nd resonant circuit  529 - 3  (or the third wireless power transmission circuit), which retransmit the power signal. For example, the speaker  520  may supply a part of the first power signal received through the distribution circuit  522  to the first load unit  526 , and may supply a part of the received first power signal to the 3-1st resonant circuit  529 - 1  and the 3-2nd resonant circuit  529 - 3 . In other words, the distribution circuit  522  may output the first′ current by distributing the first current generated by the second resonant circuit  521 . Accordingly, the distribution circuit  522  may distribute the first′ current to the first load unit  526 , the 3-1st resonant circuit  529 - 1 , and the 3-2nd resonant circuit  529 - 3 . According to one embodiment, a first impedance conversion circuit  523  is connected to the distribution circuit  522  and may convert an impedance of the distribution circuit  522  such that an amount of change in the current supplied to the first load unit  526  by the first power signal becomes a minimum. For example, the first impedance conversion circuit  523  may convert the impedance of the distribution circuit  522  such that the amount of change of the current flowing through the second resonant circuit  521  that may be changed depending on the operation of the first load unit  526 , and the amount of change of the current that is transferred to the first load unit  526 , the 3-1st resonant circuit  529 - 1 , and the 3-2nd resonant circuit  529 - 3  become the minimum. According to an embodiment, the speaker  520  may output a specified sound through a first rectifier  524 , a first converter  525 , and the first load unit  526 , as in the above description of the speaker  120  of  FIG. 2 . 
     According to an embodiment, unlike the speaker  120  of  FIG. 2 , the speaker  520  may include a second rectifier  527 , an inverter  528 , the 3-1st resonant circuit  529 - 1 , and the 3-2nd resonant circuit  529 - 3  for retransmission. According to an embodiment, the second rectifier  527  and the inverter  528  may change the current transferred through the distribution circuit  522  into the AC current having a specified magnitude. According to an embodiment, the speaker  520  may transmit the second power signal and the third power signal through the 3-1st resonant circuit  529 - 1  and the 3-2nd resonant circuit  529 - 3 , respectively. In other words, the speaker  520  may transmit power by dividing power through the 3-1st resonant circuit  529 - 1  and the 3-2nd resonant circuit  529 - 3 . The 3-1st resonant circuit  529 - 1  and the 3-2nd resonant circuit  529 - 3  may be, for example, electrically connected to each other. According to one embodiment, the power distributed by the distribution circuit  522  may be converted into a third magnetic field and a fourth magnetic field and may be transmitted to the display  530 . According to an embodiment, the third EMI signal may be generated by the third leakage magnetic field generated through the 3-1st resonant circuit  529 - 1 , and the fourth EMI signal may be generated by the fourth leakage magnetic field generated through the 3-2nd resonant circuit  529 - 3 . The third EMI signal and the fourth EMI signal, for example, may have a phase difference of 180 degrees compared to the first EMI signal generated by the first resonant circuit of the wireless power transmitter  510 . Accordingly, the third EMI signal and the fourth EMI signal may be canceled out with the first EMI signal. 
     According to an embodiment, unlike the display  130  of  FIG. 2 , the display  530  may receive the second power signal and the third power signal through a 4-1st resonant circuit  531 - 1  and a 4-2nd resonant circuit  531 - 3 . In other words, the display  530  may divide and receive power through the 4-1st resonant circuit  531 - 1  (or the second wireless power reception circuit) and the 4-2nd resonant circuit  531 - 3  (or the third wireless power reception circuit). The 4-1st resonant circuit  531 - 1  and the 4-2nd resonant circuit  531 - 3  may be, for example, electrically connected to each other. According to an embodiment, the 4-1st resonant circuit  531 - 1  and the 4-2nd resonant circuit  531 - 3  may convert the second power signal and the third power signal received from the speaker  520  into the third current. According to one embodiment, a fifth EMI signal may be generated by the fifth leakage magnetic field generated through the 4-1st resonant circuit  531 - 1 , and a sixth EMI signal may be generated by the sixth leakage magnetic field generated through the 4-2nd resonant circuit  531 - 3 . The fifth EMI signal and the sixth EMI signal, for example, may have a phase difference of 180 degrees compared to the second EMI signal generated by the second resonant circuit  521  of the speaker  520 . Accordingly, the fifth EMI signal and the sixth EMI signal may be canceled with the second EMI signal. 
     According to an embodiment, a second impedance conversion circuit  532  may change the impedances of the 4-1st resonant circuit  531 - 1  and the 4-2nd resonant circuit  531 - 3  such that the second power signal and the third power signal received through the 4-1st resonant circuit  531 - 1  and the 4-2nd resonant circuit  531 - 3  become the maximum. According to an embodiment, the display  530  may output a specified image through a second rectifier  533 , a second converter  534 , and a second load unit  535 . 
     Accordingly, the display system  500  may transmit and receive power without interference by an EMI signal. In addition, the display system  500  may reduce the size of the resonator included in the display  530  by dividing the resonator for retransmission into a plurality of resonators. 
     At least a portion of an apparatus (e.g., modules or functions thereof) or a method (e.g., operations) according to various embodiments of the disclosure may be implemented by instructions stored in a computer-readable storage medium in the form of a program module. When the instruction is executed by the processor, the processor may perform a function corresponding to the instruction. Computer-readable recording media include hard disks, floppy disks, magnetic media (e.g., magnetic tape), optical recording media (e.g., CD-ROM, DVD), magnetic-optical media (e.g., a floptical disc), internal memory, etc. Instructions may include code generated by a compiler or code that may be executed by an interpreter. 
     The embodiments disclosed herein are presented for the purpose of explanation and understanding of the disclosure, and are not intended to limit the scope of the disclosure. Accordingly, the scope of the disclosure should be construed as including all changes or various other embodiments based on the technical spirit of the disclosure.