Patent Publication Number: US-9852691-B2

Title: Display device, system having the same, and pixel

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Applications No. 10-2015-0008469, filed on Jan. 19, 2015 in the Korean Intellectual Property Office (KIPO), the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     Field 
     The described technology generally relates to display devices, systems having the same, and pixels. 
     Description of the Related Technology 
     Display devices include a display panel having a plurality of pixels that are arranged in a matrix. The pixels are driven based on received driving voltages. For example, each of the pixels in an organic light-emitting diode (OLED) display includes an OLED. OLEDs generate light via the recombination of holes, which are provided from an anode to which a first power supply voltage (ELVDD) is applied, and electrons, which are provided from a cathode to which a second power supply voltage (ELVSS) is applied, in an organic material layer interposed between the anode and the cathode. 
     When supplying a power supply voltage across wires, such as power supply lines, a voltage drop (IR-drop) occurs along the wires. When pixels in the display panel receive a lower voltage due to such a voltage drop, it can degrade image quality. Further, the formation of power supply lines decreases the aperture ratio of the pixels. Especially, in medium and large size display panels, IR-drop data distortion along the power lines can have a negative effect on image quality, requiring the compensation of data voltages based on pixel location. As a result, display panel construction may be complicated to compensate the data voltages and the aperture ratio may be relatively low. In addition, data voltage compensation techniques do not perfectly compensate IR-drop data distortion. 
     SUMMARY OF CERTAIN INVENTIVE ASPECTS 
     One inventive aspect is a display device having a wireless power transmitter circuit and a wireless power receiver circuit. 
     Another aspect is a system including the display device. 
     Another aspect is a pixel that can wirelessly receive a power supply voltage. 
     Another aspect is a display device comprising a wireless power transmitter circuit configured to transmit a power to a plurality of wireless power receiver circuits wirelessly, a display panel including a plurality of pixels, and the plurality of wireless power receiver circuits configured to wirelessly receive the power from the wireless power transmitter circuit and to provide a first power supply voltage to the pixels based on the received power, a power supply configured to generate the first power supply voltage and to provide the first power supply voltage to the wireless power transmitter circuit, a display panel driver configured to drive the display panel, and a timing controller configured to control the display panel driver. 
     In exemplary embodiments, the wireless power receiver circuits can be formed in a thin film that is formed under the pixels. 
     In exemplary embodiments, each of the wireless power receiver circuits can be connected to at least two of the pixels. 
     In exemplary embodiments, each of the wireless power receiver circuits can be connected to N by N pixels that are arranged in a matrix form, where N is a positive integer. 
     In exemplary embodiments, the number of the wireless power receiver circuits can correspond to about 1/N 2 . 
     In exemplary embodiments, the power supply can further generate a second power supply voltage and provide the second power supply voltage to the pixels via a common power supply line. 
     In exemplary embodiments, the first power supply voltage can be greater than the second power supply voltage. 
     In exemplary embodiments, the wireless power receiver circuits can receive the power through a mutual resonance with the wireless power transmitter circuit based on a resonant frequency. 
     In exemplary embodiments, each of the wireless power receiver circuits can include a power receiver configured to receive an alternating current (AC) power through the mutual resonance with the wireless power transmitter circuit, a matcher configured to match an output impedance of the power receiver and an input impedance of a rectifier, and the rectifier configured to convert the AC power, received via the matcher, into the first power supply voltage, which is a direct current (DC) voltage. 
     In exemplary embodiments, the wireless power transmitter circuit can include an oscillator configured to oscillate the first power supply voltage provided from the power supply, and a power transmitter configured to transmit the AC power corresponding to the first power supply voltage to the wireless power receiver circuits through the mutual resonance with the wireless power receiver circuits based on an output of the oscillator and the resonant frequency. 
     In exemplary embodiments, the power transmitter can be included in a conductive film that is arranged on the display panel, and wherein the power transmitter includes a resonant coil. 
     In exemplary embodiments, the oscillator can be included in the power supply. 
     In exemplary embodiments, the wireless power receiver circuits can wirelessly receive the power from the wireless power transmitter circuit through electromagnetic induction. 
     Another aspect is a system comprising a storage device configured to store image data, a display device configured to display the image data, and a processor configured to control the storage device and the display device. The display device can include a wireless power transmitter circuit configured to transmit a power to a plurality of wireless power receiver circuits wirelessly, a display panel including the plurality of wireless power receiver circuits configured to receive the power from the wireless power transmitter circuit and to provide a first power supply voltage to a plurality of pixels based on the received power, a power supply configured to generate the first power supply voltage and to provide the first power supply voltage to the wireless power transmitter circuit, a display panel driver configured to drive the display panel, and a timing controller configured to control the display panel driver. 
     In exemplary embodiments, the wireless power receiver circuits can be formed in a thin film that is formed under the pixels. Each of the wireless power receiver circuits can be connected to N by N pixels that are arranged in a matrix form, where N is a positive integer. 
     Another aspect is a pixel comprising an OLED, a wireless power receiver circuit configured to receive a power from an external wireless power transmitter circuit wirelessly and to provide a power supply voltage to a driving transistor based on the received power, the driving transistor including a gate electrode connected to a second electrode of a switching transistor, a first electrode to which the power supply voltage is applied from the wireless power receiver circuit, and a second electrode connected to a cathode of the OLED, the switching transistor including a gate electrode to which a scan signal is applied, a first electrode to which a data signal is applied, and a second electrode connected to the gate electrode of the driving transistor, and a storage capacitor including a first electrode connected to the gate electrode of the driving transistor and a second electrode connected to the first electrode of the driving transistor. 
     In exemplary embodiments, the wireless power receiver circuit can be formed in a thin film that is formed under the driving transistor and the switching transistor. 
     In exemplary embodiments, the wireless power receiver circuit can receive the power through a mutual resonance with the wireless power transmitter circuit based on a resonant frequency. 
     In exemplary embodiments, the wireless power receiver circuit can include a power receiver configured to receive an alternating current (AC) power through the mutual resonance with the wireless power transmitter circuit, a matcher configured to match an output impedance of the power receiver and an input impedance of a rectifier, and the rectifier configured to convert the AC power, received via the matcher, into the first power supply voltage, which is a direct current (DC) voltage. 
     In exemplary embodiments, the wireless power receiver circuit can wirelessly receive the power from the wireless power transmitter circuit through electromagnetic induction. 
     Another aspect is a display device, comprising a display panel including a plurality of pixels and a plurality of wireless power receivers; a wireless power transmitter configured to: i) generate power based on an initial power supply voltage and ii) wirelessly transmit the generated power to the wireless power receivers, wherein each of the wireless power receivers is configured to: i) wirelessly receive the power from the wireless power transmitter, ii) convert the received power into a first power supply voltage, and iii) provide the first power supply voltage to the pixels; a power supply configured to: i) generate the initial power supply voltage and ii) provide the initial power supply voltage to the wireless power transmitter; a display panel driver configured to drive the display panel; and a timing controller configured to control the display panel driver. 
     In exemplary embodiments, the display panel further comprises a substrate on which the pixels are formed, wherein the wireless power receivers are formed in a thin film that is interposed between the pixels and the substrate. Each of the wireless power receivers can be connected to at least two of the pixels. Each of the wireless power receivers can be connected to a subset of the pixels that are arranged in an N by N matrix, where N is a positive integer. The number of the wireless power receivers can correspond to about 1/N 2 . The power supply can be further configured to generate a second power supply voltage and provide the second power supply voltage to the pixels via a common power supply line. 
     In exemplary embodiments, the first power supply voltage is greater than the second power supply voltage. Each of the wireless power receivers can be further configured to receive the power through a mutual resonance with the wireless power transmitter. Each of the wireless power receivers can include a power receiver configured to receive alternating current (AC) power from the wireless power transmitter; a rectifier configured to convert the AC power into the first power supply voltage, wherein the first power supply voltage is a direct current (DC) voltage; and an impedance matcher configured to match the output impedance of the power receiver and the input impedance of the rectifier. 
     In exemplary embodiments, the wireless power transmitter includes an oscillator configured to generate the AC power via oscillating the initial power supply voltage received from the power supply; and a power transmitter configured to transmit the AC power to the wireless power receivers. The power transmitter can be included in a conductive film that is arranged on the display panel, and wherein the power transmitter includes a resonant coil. The oscillator can be included in the power supply. Each of the wireless power receivers can be further configured to wirelessly receive the power from the wireless power transmitter through electromagnetic induction. 
     Another aspect is a system comprising a storage device configured to store image data; a display configured to display the image data; and a processor configured to control the storage device and the display, wherein the display includes: a display panel including a plurality of pixels and a plurality of wireless power receivers; a wireless power transmitter configured to: i) generate power based on an initial power supply voltage and ii) wirelessly transmit the generated power to the wireless power receivers, wherein each of the wireless power receivers is configured to: i) receive the power from the wireless power transmitter ii) convert the received power into a first power supply voltage, and iii) provide the first power supply voltage to the pixels; a power supply configured to: i) generate the initial power supply voltage and ii) provide the initial power supply voltage to the wireless power transmitter; a display panel driver configured to drive the display panel; and a timing controller configured to control the display panel driver. 
     In exemplary embodiments, the display panel further comprises a substrate on which the pixels are formed, wherein each of the wireless power receivers is formed in a thin film that is interposed between the pixels and the substrate, and wherein each of the wireless power receivers is connected a subset of the pixels that are arranged in an N by N matrix, where N is a positive integer. 
     Another aspect is a pixel, comprising an organic light-emitting diode (OLED); a switching transistor including: i) a gate electrode configured to receive a scan signal, ii) a first electrode configured to receive a data signal, and iii) a second electrode; a driving transistor configured to supply a driving current to the OLED, wherein the driving transistor includes: i) a gate electrode connected to the second electrode of the switching transistor, ii) a first electrode configured to receive a power supply voltage, and iii) a second electrode connected to the OLED; a wireless power receiver configured to: i) wirelessly receive power from an external wireless power transmitter, ii) convert the received power into the power supply voltage, and iii) provide the power supply voltage to the driving transistor; and a storage capacitor including: i) a first electrode connected to the gate electrode of the driving transistor and ii) a second electrode connected to the first electrode of the driving transistor. 
     In exemplary embodiments, the pixel is formed on a substrate and wherein the wireless power receiver is formed in a thin film that is interposed between: i) the substrate and ii) the driving transistor and the switching transistor. The wireless power receiver can be further configured to receive the power through a mutual resonance with the wireless power transmitter. The wireless power receiver can include a power receiver configured to receive alternating current (AC) power; a rectifier configured to convert the AC power into the power supply voltage, wherein the power supply voltage is a direct current (DC) voltage; and an impedance matcher configured to match an output impedance of the power receiver and the input impedance of a rectifier. The wireless power receiver can be further configured to wirelessly receive the power from the wireless power transmitter through electromagnetic induction. 
     Therefore, according to at least one embodiment, the pixel, the display device and the system include the plurality of wireless power receiver circuits connected to the pixels and the wireless power transmitter circuit configured to wirelessly transmit the power supply voltage (e.g., the first power supply voltage ELVDD and/or the second power supply voltage ELVSS) to the wireless power receiver circuits, so that the power supply lines for transmitting the power supply voltage can be omitted. Thus, the voltage drop (IR-drop) across the power supply lines does not occur, so that the display device can prevent a distortion of image quality in accordance with the IR-drop beforehand. Further, the power supply lines for transmitting the power supply voltage are omitted so that aperture ratio can increase. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments will be described in greater detail in the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a display device according to exemplary embodiments. 
         FIG. 2  is a block diagram illustrating an example of a wireless power receiver circuit that is connected to a plurality of pixels included in the display device of  FIG. 1 . 
         FIG. 3A  is a diagram illustrating an example of a portion of a display panel included in the display device of  FIG. 1 . 
         FIG. 3B  is a diagram illustrating another example of a portion of a display panel included in the display device of  FIG. 1 . 
         FIG. 4  is a block diagram illustrating an example of a wireless power transmitter circuit and a wireless power receiver circuit that are included in the display device of  FIG. 1 . 
         FIG. 5  is a diagram of a pixel according to exemplary embodiments. 
         FIG. 6  is a diagram illustrating an example of a wireless power receiver circuit included in the pixel of  FIG. 5 . 
         FIG. 7  is a block diagram of a system according to exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     Exemplary embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. 
       FIG. 1  is a block diagram of a display device according to exemplary embodiments. 
     Referring to  FIG. 1 , the display device  100  includes a wireless power transmitter circuit or wireless power transmitter  110 , a display panel  120 , a power supply  140 , a display panel driver  160 , and a timing controller  180 . The display device  100  can be implemented using one of various kinds of display panel in so far as the display panel  120  displays an image corresponding to a data signal. 
     The wireless power transmitter circuit  110  can wirelessly transmit a power to a plurality of wireless power receiver circuits or wireless power receivers  130 . The wireless power transmitter circuit  110  can receive the power from the power supply  140 . The received power may be an alternating current (AC) power or a direct current (DC) power. For example, the power may correspond to a first power supply voltage ELVDD that is supplied to the display panel  120 . The power can be the AC power corresponding to the first power supply voltage ELVDD. In some embodiments, the wireless power transmitter circuit  110  is included in a conductive film that is arranged on the display panel  120 . The wireless power transmitter circuit  110  can include a resonant coil. For example, the resonant coil can include conductive material arranged in a polarizer that is formed on the display panel  120 . 
     In some embodiments, the wireless power transmitter circuit  110  includes an oscillator configured to oscillate the first power supply voltage ELVDD provided from the power supply and a power transmitter configured to transmit an AC power corresponding to the first power supply voltage ELVDD to the wireless power receiver circuits  130  through mutual resonance with the wireless power receiver circuits  130  based on an output of the oscillator and a resonant frequency. The oscillator can be included in the power supply  140  and the power transmitter can be formed on the polarizer. 
     The display panel  120  includes a plurality of pixels  10 . The display panel  120  can include the wireless power receiver circuits  130  configured to receive the power from the wireless power transmitter circuit  110  and to provide the first power supply voltage ELVDD to the pixels  10  based on the received power. The pixels  10  are connected to a plurality of data lines DL 1  through DLm and a plurality of scan lines SL 1  through SLn. The pixels can receive data signals via the data lines DL 1  through DLm. The pixels can receive scan signals via the scan lines SL 1  through SLn. Each of the pixels may include an OLED. 
     The wireless power receiver circuits  130  can be formed under the pixels  10  in a manufacturing process of the display device  100 . For example, the wireless power receiver circuits  130  can be formed between a substrate on which a driving transistor (and a switching transistor) of the pixel  10  is formed and the driving transistor. In some embodiments, each of the wireless power receiver circuits  130  is connected to at least two of the pixels  10 . For example, as illustrated in  FIG. 1 , each of the wireless power receiver circuits  130  can be connected a pixel group that has at least two of the pixels  10  arranged in 2 by 2 matrix. Thus, each of the wireless power receiver circuits  130  can supply the first power supply voltage ELVDD to four pixels  10 . In some embodiments, the number of the wireless power receiver circuits  130  corresponds to about 1/N 2 , where N is a positive integer. For example, the total number of pixels  10  can be about quadruple the number of the wireless power receiver circuits  130  when each of the wireless power receiver circuits  130  is connected to a group of pixels  10  arranged in a 2 by 2 matrix. 
     In some embodiments, each of the wireless power receiver circuits  130  includes a power receiver configured to receive the AC power through the mutual resonance with the wireless power transmitter circuit  110 , a matcher or impedance matcher, and a rectifier configured to convert the AC power, received via the matcher, into the first power supply voltage ELVDD, that is a DC voltage. 
     Since this is an example, the power transmitted through the wireless power transmitter/receiver circuits  110  and  130  is not limited thereto. For example, the wireless power receiver circuits  130  can receive a power corresponding to the second power supply voltage ELVSS from the wireless power transmitter circuit  110 . 
     In one example embodiment, the wireless power receiver circuits  130  receive the power through a mutual resonance with the wireless power transmitter circuit  110  based on a resonant frequency. In another example embodiment, the wireless power receiver circuits  130  wirelessly receive the power from the wireless power transmitter circuit  110  through electromagnetic induction. Since these are examples, the methods for wirelessly receiving the power are not limited thereto. For example, the wireless power receiver circuits  130  can receive the power though a wireless power transfer method using microwaves. 
     The power supply  140  can generate the first and second power supply voltages ELVDD and ELVSS. The power supply  140  can provide the first power supply voltage ELVDD to the wireless power transmitter circuit  110 . The power supply  140  can provide the second power supply voltage ELVSS to the pixels  10 . The first power supply voltage ELVDD may be greater than the second power supply voltage ELVSS. For example, the first power supply voltage ELVDD may be a positive voltage and the second power supply voltage ELVSS may be a negative voltage or a ground voltage. Here, the first power supply voltage ELVDD is wirelessly supplied to the pixels  10  such that power supply lines for transmitting the first power supply voltage ELVDD to the pixels can be omitted. In some embodiments, the power supply  140  supplies the second power supply voltage ELVSS to the pixels  10  via a common power supply lines. 
     The display panel driver  160  can drive the display panel  120 . In the  FIG. 1  embodiment, the display panel driver  160  includes a scan driver  162  and a data driver  164 . 
     The scan driver  162  can respectively provide a plurality of scan signals to the display panel  120  via the scan lines SL 1  to SLn. The scan driver  162  can sequentially provide the scan signals to the scan lines SL 1  to SLn based on a first control signal CONT 1  received from the timing controller  180 . 
     The data driver  164  can provide a plurality of data signals to the display panel  120  via the data lines DL 1  to DLm. The data driver  164  can provide the data signals to the data lines DL 1  to DLm based on a second control signal CONT 2  and an output image signal DAT received from the timing controller  180 . 
     The timing controller  180  can control the display panel driver  160 . The timing controller  180  may receive a red, green, and blue (RGB) image signal, a vertical synchronization signal, a horizontal synchronization signal, a main clock signal, and a data enable signal from an external graphic controller (not illustrated), and can generate the output image signal DAT, the first control signal CON 1 , the second control signal CON 2 , and a third control signal CON 3 . The timing controller  180  can provide the first control signal CON 1  to the scan driver  162 , the second control signal CON 2  and the output image signal DAT to the data driver  164 , and the third control signal CON 3  to the power supply  140 . For example, the first control signal CON 1  may include a vertical synchronization start signal, which controls the start of outputting the scan signal, a scan clock signal, which controls the output timing of the scan signal, and an output enable signal, which controls the duration of the scan signal. The second control signal CON 2  may include a horizontal synchronization start signal, which controls the start of outputting the data signal, a data clock signal, which controls the output timing of the data signal, and a load signal. The third control signal CON 3  can control the start of driving the power supply  140 . 
     As described above, the display device according to exemplary embodiments includes the wireless power receiver circuits  130  connected to the pixels  10  and the wireless power transmitter circuit  110  configured to wirelessly transmit the power supply voltage to the wireless power receiver circuits  130 , so that power supply lines for transmitting the power supply voltage can be omitted. Thus, the voltage drop (IR-drop) across the power supply lines does not occur, so that the display device  100  can prevent image quality distortions that would otherwise occur due to an IR-drop. Further, by omitting the power supply lines for transmitting the power supply voltage the aperture ratio can be increased. 
       FIG. 2  is a block diagram illustrating an example of a wireless power receiver circuit that is connected to a plurality of pixels included in the display device of  FIG. 1 . 
     Referring to  FIG. 2 , the wireless power receiver circuit  130  includes the power receiver  132 , the matcher  134 , and the rectifier  136 . The wireless power receiver circuit  130  can be connected to N by N pixels  10  that are arranged in a matrix. For example, as illustrated in  FIG. 2 , the wireless power receiver circuit  130  can be connected to pixel  10  arranged in a 2 by 2 matrix. 
     In some embodiments, the power receiver  132  can wirelessly receive the power through a mutual resonance with the wireless power transmitter circuit  110  based on a resonant frequency. The power receiver  132  can include a resonator. When the resonant frequency of the power receiver  132  matches the resonant frequency of the power transmitter of the wireless power transmitter circuit  110 , the power can be transferred from the power transmitter to the power receiver  132  through the mutual resonance. In some embodiments, the power receiver  132  has a micro receiving antenna structure. The micro receiving antenna structure can correspond to micro strip lines. 
     The matcher  134  can connect a passive element (e.g., an inductor and/or a capacitor) to the rectifier  136  in series and/or in parallel in order to match the input impedance of the rectifier  136  to the output impedance of the power receiver  132 . The matcher  134  can be formed in a thin film. 
     The rectifier  136  can convert the AC power, received via the matcher  134 , into the first power supply voltage ELVDD, which is a direct current (DC) voltage. The first power supply voltage ELVDD can be applied to the pixels  10  that are connected to the wireless power receiver circuit  130 . In some embodiments, the rectifier  136  includes a bridge diode and a capacitor. The rectifier  136  can be formed in the thin film. In some embodiments, the wireless power receiver circuit  130  further includes a DC/DC converter to convert the DC voltage that is received from the rectifier  136  into a DC voltage (e.g., the first power supply voltage ELVDD) required for driving the pixels  10 . The DC/DC converter may step up or down the DC voltage that is received from the rectifier  136  to the DC voltage required for driving the pixels  10 . 
     In some embodiments, the wireless power receiver circuit  130  is formed in the thin film that is arranged under the pixels  10 . Thus, extra space is not required for wireless power transmission. 
     As described above, the display panel  120  can include the wireless power receiver circuit  130  so that the first power supply voltage ELVDD can be wirelessly supplied to the pixels  10 . 
       FIG. 3A  is a diagram illustrating an example of a portion of a display panel included in the display device of  FIG. 1 .  FIG. 3B  is a diagram illustrating another example of a portion of a display panel included in the display device of  FIG. 1 . 
     Referring to  FIGS. 3A and 3B , the wireless power receiver circuit  130 A and  130 B is connected to a plurality of pixels  10 . In some embodiments, the wireless power receiver circuit  130 A and  130 B is formed in a thin film that is arranged under the pixels  10 . For example, the wireless power receiver circuits  130 A and  130 B can be formed between a substrate on which a driving transistor (and a switching transistor) of the pixel  10  is formed and the driving transistor. In some embodiments, each wireless power receiver circuit  130 A and  130 B is connected to N by N pixels that are arranged in a matrix, where N is a positive integer. Thus, the number of the wireless power receiver circuits may correspond to about 1/N 2 . 
     For example, as illustrate in  FIG. 3A , the wireless power receiver circuit  130 A is connected to 4 by 4 pixels (i.e. 16 pixels). The wireless power receiver circuit  130 A supplies the first power supply voltage ELVDD to the 16 pixels. In some embodiments employing this configuration, the number of wireless power receiver circuits  130 A is 1920×1080/16 (=129600) when the total number of pixels in the display panel  120 A is 1920×1080. 
     In another example, as illustrate in  FIG. 3B , the wireless power receiver circuit  130 B is connected to 3 by 3 pixels (i.e. 9 pixels). The wireless power receiver circuit  130 B supplies the first power supply voltage ELVDD to the 9 pixels. In some embodiments employing this configuration, the number of wireless power receiver circuits  130 B is 1920×1080/9 (=230400) when total number of pixels in the display panel  120 A is 1920×1080. 
     As described above, the wireless power receiver circuit  130 A and  130 B is formed on (or under) the pixels  10  of the display panel  120 A and  120 B and can supply the power supply voltage (e.g., the first power supply voltage ELVDD) to the pixels. Thus, the wireless power receiver circuits can be efficiently arranged on the display panel. 
     In example embodiments, the power transmitter in the wireless power transmitter circuit  110  is formed on (or under) the display panel  120 A and  120 B. The power transmitter can be formed in a conductive film to have the resonant coil. 
       FIG. 4  is a block diagram illustrating an example of a wireless power transmitter circuit and a wireless power receiver circuit that are included in the display device of  FIG. 1 . 
     Referring to  FIG. 4 , the wireless power transmitter circuit  110  includes the oscillator  112  and the power transmitter  124 . The wireless power receiver circuit  130  includes the power receiver  132 , the matcher  134 , and the rectifier  136 . The wireless power receiver circuit  130  can wirelessly receive the AC voltage corresponding to the first power supply voltage ELVDD from the wireless power transmitter circuit  110 . 
     In some embodiments, the wireless power receiver circuit  130  receives the power (e.g., the first power supply voltage ELVDD) through a mutual resonance with the wireless power transmitter circuit  110  based on a resonant frequency. In another example embodiment, the wireless power receiver circuits  130  wirelessly receives the power from the wireless power transmitter circuit  110  through electromagnetic induction. Since these are examples, methods for wirelessly receiving the power are not limited thereto. For example, the wireless power receiver circuits  130  may receive the power though a wireless power transfer method using microwaves. 
     In some embodiments, the wireless power transmitter circuit  110  includes the oscillator  112  and the power transmitter  114 . 
     The oscillator  112  can oscillate the first power supply voltage ELVDD provided from the power supply  140 . In some embodiments, the oscillator  112  can generate power at a power transfer frequency (e.g., the resonant frequency) and amplify the AC voltage that is provided from the power supply  140 . The power transfer frequency may be generated by a frequency generator that is generally used in field of radio frequency (RF) communications. The oscillator  112  can amplify the amplitude of the AC power in consideration of energy transmission efficiency. In some embodiments, the oscillator  112  further includes an AC/DC converter configured to convert the AC voltage that is applied from the power supply  140  into a DC voltage. The AC/DC converter may operate as an analog to digital converter (ADC). 
     The power transmitter  114  can transmit the AC power corresponding to the first power supply voltage ELVDD to the wireless power receiver circuit  130  through the mutual resonance with the wireless power receiver circuit  130  based on an output of the oscillator  112  and the resonant frequency. The power transmitter  114  can include a resonator. 
     The wireless power receiver circuit  130  includes the power receiver  132 , the matcher  134 , and a rectifier  136 . 
     The power receiver  132  can wirelessly receive the power through the mutual resonance with the wireless power transmitter circuit  110  based on the resonant frequency. The power receiver  132  can include a resonator. When the resonant frequency of the power receiver  132  matches the resonant frequency of the power transmitter of the wireless power transmitter circuit  110 , the power can be transferred from the power transmitter to the power receiver  132  through the mutual resonance. The rectifier  136  can convert the AC power, received via the matcher  134 , into the first power supply voltage ELVDD, which is a DC voltage. 
     Since the wireless power receiver circuit  130  is described above referred to  FIGS. 1 through 3B , duplicate descriptions thereof will not be repeated. 
       FIG. 5  is a diagram of a pixel according to exemplary embodiments. 
     Referring to  FIG. 5 , the pixel  200  includes an OLED EL, a wireless power receiver circuit  230 , a driving transistor TD, a switching transistor TS, and a storage capacitor Cst. 
     The OLED EL includes a cathode to which a second power supply voltage ELVSS is applied and an anode connected to a second electrode of the driving transistor TD. In some embodiments, the second power supply voltage ELVSS is supplied to the OLED EL via a common power supply line. 
     The switching transistor TS includes a gate electrode to which a scan signal is applied, a first electrode to which a data signal DATA is applied, and a second electrode connected to a gate electrode of the driving transistor TD. The switching transistor TS can be turned on by the scan signal which is applied through a scan line such that the switching transistor TS can provide the data signal DATA to a first node N 1 . 
     The storage capacitor Cst includes a first electrode connected to the gate electrode of the driving transistor and a second electrode connected to the first electrode of the driving transistor. In some embodiments, the storage capacitor Cst stores a voltage corresponding to the data signal DATA. 
     The driving transistor TD includes the gate electrode connected to the second electrode of the switching transistor TS, the first electrode to which the first power supply voltage ELVDD is applied from the wireless power receiver circuit  230 , and the second electrode connected to a cathode of the OLED EL. The driving transistor TD can be turned on by a voltage from the storage capacitor Cst or the switching transistor TS such that a driving current corresponding to the data signal DATA flows into the OLED EL. The driving current can flow from a first power supply voltage terminal into a second power supply voltage terminal via the driving transistor TD and the OLED EL. The OLED EL can emit light according to the driving current. 
     The wireless power receiver circuit  230  can wirelessly receive power from an external wireless power transmitter circuit and provide the first power supply voltage ELVDD to the driving transistor TD based on the received power. In some embodiments, the wireless power receiver circuit  230  is formed in a thin film that is arranged under the driving transistor TD and the switching transistor TS. In some embodiments, the wireless power receiver circuit  230  receives the power through a mutual resonance with the wireless power transmitter circuit based on a resonant frequency. In some embodiments employing this configuration, the wireless power receiver circuit  230  includes a power receiver, a matcher, and a rectifier. In some embodiments, the wireless power receiver circuit  230  wirelessly receives the power from the wireless power transmitter circuit through electromagnetic induction. Since the operation and configuration of the wireless power receiver circuit  230  are described above referred to  FIGS. 1 through 3B , duplicate descriptions thereof will not be repeated. 
     As described above, the pixel  200  can include the wireless power receiver circuit  230  so that the first power supply voltage ELVDD can be applied to the pixel  200  wirelessly. However, the structure of the pixel  200  is not limited thereto. For example, the pixel  200  can further include a compensation circuit for compensating a gate voltage of the driving transistor TD, an initialization circuit for initializing the driving transistor TD (or the OLED EL), and/or a switching transistor for controlling emission of the pixel  200  based on an emission signal. 
       FIG. 6  is a diagram illustrating an example of a wireless power receiver circuit included in the pixel of  FIG. 5 . 
     Referring to  FIG. 6 , the wireless power receiver circuit  230  is connected to pixels  200 A,  200 B,  200 C, and  200 D arranged in an N by N matrix. For example, the wireless power receiver circuit  230  can be connected to 2 by 2 pixels  200 A,  200 B,  200 C, and  200 D. 
     In some embodiments, the wireless power receiver circuit  230  receives the power (e.g., the first power supply voltage ELVDD) through a mutual resonance with the wireless power transmitter circuit based on a resonant frequency. The wireless power receiver circuit  230  can convert the power into the first power supply voltage ELVDD that is a DC voltage and supply the first power supply voltage ELVDD to the pixels  200 A,  200 B,  200 C, and  200 D. The wireless power receiver circuit  230  can include the power receiver  232  configured to receive an AC power through the mutual resonance with the wireless power transmitter circuit, the matcher  234  configured to match an output impedance of the power receiver  232  and an input impedance of the rectifier  236 , and the rectifier  236  configured to convert the AC power, received via the matcher  134 , into the first power supply voltage ELVDD, which is the DC voltage. 
     As illustrated in the  FIG. 6  embodiment, the wireless power receiver circuit  230  is commonly connected to a plurality of pixels  200 A,  200 B,  200 C, and  200 D. Thus, the wireless power receiver circuit  230  can supply the first power supply voltage ELVDD to the pixels  200 A,  200 B,  200 C, and  200 D. 
       FIG. 7  is a block diagram of a system according to exemplary embodiments. 
     Referring to  FIG. 7 , the system  6000  includes the display device  1000 , a processor  2000 , and a storage device  3000 . The system  6000  further includes a memory device or memory  4000  and an input/output (I/O) device  5000 . The display device  1000  includes the display panel  120 , the power supply  140 , and the display panel driver  160 . 
     The display device  1000  can display the image data stored in the storage device  3000 . The display device  1000  includes a wireless power transmitter circuit  110 , a display panel  120  including a plurality of wireless power receiver circuits  130 , a power supply  140 , a display panel driver  160 , and a timing controller. The wireless power transmitter circuit  110  can transmit the power to the wireless power receiver circuits  130  wirelessly. The display panel  120  includes a plurality of pixels to which the first and second power supply voltages ELVDD and ELVSS and the data signal DATA are applied. The wireless power receiver circuits  130  can wirelessly receive the power and provide the first power supply voltage ELVDD based on the power to the pixels. The power supply  100  can generate the first and second power supply voltages ELVDD and ELVSS. The power supply  140  can provide the first power supply voltage ELVDD to the wireless power transmitter circuit  110  and provide the second power supply voltage ELVSS to the pixels. In some embodiments, the power supply  140  provides the second power supply voltage ELVSS to the pixels via a common power supply line. The display panel driver  160  can drive the display panel  120 . The display panel driver  160  can provide the data signal DATA to the display panel  120 . In some embodiments, the display panel driver  160  includes a data driver and a scan driver. The timing controller can control the display panel driver  160 . 
     In some embodiments, the wireless power receiver circuits  130  is formed in a thin film that is arranged under the pixels. Thus, extra space is not required for wireless power transmission. Each of the wireless power receiver circuits  130  can be connected to a plurality of pixels arranged in an N by N matrix, where N is a positive integer. 
     The display device  1000  can be implemented using various kinds of display panels in so far as the display panel  120  displays an image using first and second power supply voltages ELVDD and ELVSS received from the wireless power transmitter circuit  130  and the power supply  140 . For example, the display device  1000  cam be an OLED display. In this embodiment, each of the pixels included in the display panel  120  includes an OLED. 
     The display device  1000  can have the same structure as the display device  100  of  FIG. 1 . The structure and operation of the display device  1000  of  FIG. 7  are described above with reference to  FIGS. 1 to 6 . Thus, a detailed description of the display device  1000  included in the system  6000  will not be repeated. 
     The processor  2000  can control the storage device  3000  and the display device  1000 . The processor  2000  can perform specific calculations, computing functions for various tasks, etc. The processor  2000  can include, e.g., a microprocessor or central processing unit (CPU). The processor  2000  can be connected to the storage device  3000  and the display device  1000  via an address bus, a control bus, and/or a data bus. In addition, the processor  2000  can be connected to an extended bus such as a peripheral component interconnection (PCI) bus. 
     The storage device  3000  can store image data. The storage device  3000  can include a solid state drive (SSD), a hard disk drive (HDD), a CD-ROM, etc. 
     As discussed above, the system  6000  includes the memory device  4000  and the I/O device  5000 . In some embodiments, the system  6000  further includes a plurality of ports (not illustrated) that communicate with a video card, a sound card, a memory card, a universal serial bus (USB) device, other electric devices, etc. 
     The memory device  4000  can store data for operations of the system  6000 . For example, the memory device  4000  can include at least one volatile memory device such as a dynamic random access memory (DRAM) device, a static random access memory (SRAM) device, etc., and/or at least one non-volatile memory device such as an erasable programmable read-only memory (EPROM) device, an electrically erasable programmable read-only memory (EEPROM) device, a flash memory device, etc. 
     The I/O device  5000  can include one or more input devices (e.g., a keyboard, keypad, a mouse, a touch pad, a haptic device, etc.), and/or one or more output devices (e.g., a printer, a speaker, etc.). In some example embodiments, the display device  1000  can be included in the I/O device  5000 . 
     The system  6000  can include any of several types of electronic devices, such as a digital television, a cellular phone, a smart phone, a personal digital assistant (PDA), a personal media player (PMP), a portable game console, a computer monitor, a digital camera, a moving picture experts group (MPEG) audio layer III (MP3) player, etc. 
     As described above, the system  6000  including the display device  1000  can include the wireless power transmitter/receiver circuits  110  and  130  to wirelessly transmit the first power supply voltage ELVDD (or the second power supply voltage ELVSS) to the display panel  120 , so that the power supply lines for transmitting the first power supply voltage ELVDD (or the second power supply voltage ELVSS) to the pixels can be omitted. Thus, IR-drop across the power supply lines does not occur, so that the system  6000  and the display device  1000  can prevent image quality distortion that would otherwise occur due to IR-drop. 
     The present embodiments can be applied to any display device and any system including the display device. For example, the present embodiments may be applied to a television, a computer monitor, a laptop, a digital camera, a cellular phone, a smart phone, a smart pad, a PDA, a PMP, an MP3 player, a navigation system, a game console, a video phone, etc. 
     The foregoing is illustrative of exemplary embodiments, and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the exemplary embodiments. Accordingly, all such modifications are intended to be included within the scope of embodiments as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of exemplary embodiments and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.