Patent Publication Number: US-11024222-B2

Title: Display device and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2019-0025097, filed on Mar. 5, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The disclosure relates to a display device and control method thereof, which controls forward and backward voltages applied across a light emitting diode device. 
     2. Description of Related Art 
     Display devices are used as output devices for visually presenting image data, and are used in various areas such as homes and businesses. 
     Display devices may be implemented in various manners. For example, some displays control transmission of light emitted by a backlight unit through a panel, and other displays directly emit light. The displays that directly emit light may include an organic light emitting diode display that uses organic materials based on an electroluminiscence effect by which a fluorescent organic compound emits light when a current is applied to the fluorescent organic compound, and an inorganic light emitting diode display using inorganic compounds. 
     The inorganic light emitting diode display has light emitting diodes (LEDs) directly display image data based on a voltage applied across terminals of each LED. When a difference in voltage between both terminals of the LED is greater than a reference voltage, the LED emits light. 
     An LED display may steadily perform a discharging operation to control a voltage at an anode of the LED terminals by discharging a capacitor connected in parallel with the LED terminals and a pre-charging operation to control a voltage at a cathode of the LED terminals by charging the capacitor at all light emitting levels. 
     In this case, when input image data is a low grayscale image value, such as a black image, a voltage may be applied across the LED terminals according to the steady discharging and charging operations. When such a voltage is continuously applied, the LED may be stressed and thus the lifespan of the LED may be shortened. 
     SUMMARY 
     Provided are a display device and control method thereof, which controls the magnitude of a voltage applied to an LED based on an input signal, thereby reducing the stress on the LED and increasing the lifespan of the LED. 
     In accordance with an aspect of the disclosure, a display device includes a light emitting diode (LED) module including a plurality of LEDs; a plurality of driving integrated chips (ICs), each of the plurality of driving ICs being configured to apply voltages to a corresponding group of the plurality of LEDs; and a controller. The controller is configured to identify a first voltage corresponding to a first LED from among the plurality of LEDs based on image data, identify a first LED driving voltage as the first voltage or a second voltage based on the first voltage and a reference value, and control a first driving IC, from among the plurality of driving ICs, that corresponds to the first LED based on the first LED driving voltage-. 
     The controller may be further configured to identify the first LED driving voltage based on whether the first voltage is equal to or less than the reference value. 
     The second voltage may correspond to a preset voltage. 
     The controller may be further configured to identify, based on the image data, a second LED, from among the plurality of LEDs, to be driven at the second voltage. 
     Each of the plurality of driving ICs may be further configured to control a cathode voltage of the corresponding group of the plurality of LEDs, and the controller may be further configured to control an anode voltage of the plurality of LEDs and control the plurality of driving ICs. 
     The controller may be further configured to control the anode voltage of the plurality of LEDs based on the second voltage. 
     The controller may be further configured to identify a driving IC to control the cathode voltage of the first LED, from among the plurality of driving ICs, based on the image data, and cease control of the anode voltage of the first LED while controlling the cathode voltage of the first LED using the driving IC. 
     The controller may be further configured to identify the first LED driving voltage as the second voltage based on a screen off signal. 
     The LED module may be one from among a plurality of LED modules provided in an LED module array, and the controller may be further configured to identify a black LED module, from among the plurality of LED modules, based on the image data indicating driving voltages of each LED of the black LED module as being below the reference value, and apply the second voltage to LEDs of the black LED module. 
     The controller may be further configured to generate a control signal to drive the first driving IC. 
     According to an aspect of the disclosure, a method of driving a display device including light emitting diodes (LEDs) and a driving integrated circuit (IC) configured to apply a voltage to a group of the LEDs, includes: receiving image data; identifying a first LED driving voltage to be applied to a first LED from among the LEDs based on analysis of the image data and a reference value; and controlling the driving IC based on the first LED driving voltage. 
     The identifying may include: identifying a first voltage corresponding to the first LED based on the image data; identifying the first voltage as the first driving voltage based on the first voltage being greater than the reference value; and identifying a second voltage as the first LED driving voltage based on the first voltage being equal to or less than the reference value. 
     The second voltage may correspond to a preset voltage. 
     The identifying may include identifying, based on the image data, a second LED, from among the plurality of LEDs, to be driven at the second voltage. 
     The controlling may include: controlling an anode voltage of the first LED; and controlling the driving IC to control a cathode voltage of the LED. 
     The controlling of the anode voltage may include controlling the anode voltage to a preset voltage. 
     The controlling may include: identifying to control the cathode voltage of the first LED based on the image data; and ceasing control of the anode voltage of the first LED while controlling the driving IC. 
     The identifying may include identifying a second voltage as the first LED driving voltage to be applied to the first LED based on a screen off signal. 
     The LEDs may be included in an LED module that is one from among a plurality of LED modules provided in an LED module array, and the controlling may include: identifying a black LED module, from among the plurality of LED modules, based on the image data indicating driving voltages of each LED of the black LED module as being below the reference value; and applying a second voltage to LEDs of the black LED module. 
     The controlling may include generating a control signal to drive the driving IC based on the first LED driving voltage. 
     According to an aspect of the disclosure, a display device includes: a plurality of light emitting diodes (LEDs); a driving integrated circuit; and a timing controller configured to. The timing controller is configured to: identify a first voltage based on image data corresponding to a first LED from among the plurality of LEDs; compare the first voltage with a reference voltage; identify the first voltage as a first LED driving voltage based on the first voltage exceeding the reference voltage; identify a preset voltage as the first LED driving voltage based on the first voltage being less than or equal to the reference voltage; and control the first LED and the driving integrated circuit based on the first LED driving voltage. 
     The timing controller may be further configured to identify a driving voltage for each of the plurality of LEDs based on a comparison of the reference voltage and a corresponding voltage, from among a plurality of voltages, identified based on the image data. 
     The timing controller may be further connected to an anode of the first LED and the driving integrated circuit is connected to a cathode of the first LED. 
     According to an aspect of the disclosure, a non-transitory computer readable recording medium having embodied thereon a program, which when executed by a processor of a display device, causes the display device to execute a method, the method including: identifying a first voltage based on image data corresponding to a first LED from among a plurality of LEDs; comparing the first voltage with a reference voltage; identifying the first voltage as a first LED driving voltage based on the first voltage exceeding the reference voltage; identifying a preset voltage as the first LED driving voltage based on the first voltage being less than or equal to the reference voltage; and controlling the first LED based on the first LED driving voltage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exterior view of a display system, according to an embodiment; 
         FIG. 2  shows a schematic arrangement and signal flows in a display system, according to an embodiment; 
         FIG. 3  is a front view of a light emitting diode (LED) module array, according to an embodiment; 
         FIG. 4  is a rear view of an LED module array, according to an embodiment; 
         FIG. 5  is an exploded view of an LED module array, according to an embodiment; 
         FIG. 6  is a control block diagram of a display device, according to an embodiment; 
         FIG. 7  is a schematic diagram of a rear surface of an LED module, according to an embodiment; 
         FIG. 8  is a block diagram of an LED module, according to an embodiment; 
         FIG. 9  is a depiction for explaining a possible problem occurring in a display device; 
         FIG. 10  is a flowchart illustrating a control method of a display device, according to an embodiment; 
         FIG. 11  is a flowchart illustrating a control method of a display device, according to another embodiment; and 
         FIGS. 12 and 13  are flowcharts illustrating control methods of a display device, embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be described with reference to accompanying drawings. 
     The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be suggested to those of ordinary skill in the art. The progression of processing operations described is an example; however, the sequence of and/or operations is not limited to that set forth herein and may be changed as is known in the art, with the exception of operations necessarily occurring in a particular order. In addition, respective descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness. 
     Additionally, embodiments will now be described more fully hereinafter with reference to the accompanying drawings. The embodiments may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the exemplary embodiments to those of ordinary skill in the art. Like numerals denote like elements throughout. 
     It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     The expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. 
       FIG. 1  is an exterior view of a display system, according to an embodiment.  FIG. 2  shows a schematic arrangement and signal flows in a display system, according to an embodiment. 
     Referring to  FIGS. 1 and 2 , a display system  1  may include a display device  10  that visually presents an image and an image reproducing device  20  that provides image data to the display device  10 . 
     The display system  1  may be used as a big screen in theaters, as a general display device, such as in televisions (TVs) and monitors, or for a large billboard. The display system  1  may installed outdoors, e.g., on the rooftop of a building or at a bus stop. However, the display system  1  may be installed indoors, e.g., at subway stations, shopping malls, theaters, offices, stores, etc. 
     The display device  10  may include a plurality of light emitting diode (LED) module arrays  100 . Each LED module array  100  may include LEDs to provide a particular resolution. When a relatively large pitch size is provided between the LEDs, the display device  10  may be used for an information transferring device, such as a large billboard. On the contrary, when a relatively small pitch size, such as on the scale of micrometers (m), is provided between the LEDs, the display device  10  may be used for a high resolution screen in a theater as well as TVs. 
     The plurality of LED module arrays  100  may be arranged in rows and columns. In other words, the LED module arrays  100  may be arranged in the form of a matrix, for example, in a 16×6 matrix with 16 columns and six rows. 
     The plurality of LED module arrays  100  arranged in a matrix may be integrated into a single screen S. The integrated LED module arrays  100  may be controlled to display an image. 
     Each LED in the plurality of LED module arrays  100  may correspond to a unit pixel P, and an image may be formed by a combination of light emitted from the plurality of pixels P. For example, the plurality of pixels P may emit light with various brightnesses and colors, and the light emitted by the plurality of pixels P may be combined into an image that may be perceived by a viewer. 
     The screen S may include a variable number of LEDs corresponding to various resolutions. For example, to have 4K resolution according to Digital Cinema Initiatives (DCI), the screen S may include 4096×2160 LEDs. In another example, to have 4K ultra high definition (UHD) resolution according to the International Telecommunication Union (ITU), the screen S may include 3840×2160 LEDs. Specifically, when each unit pixel P of the screen S having the 4K resolution includes a red LED, a blue LED, and a green LED, the number of LEDs corresponding to the 4K resolution may be 4096×2160×3 or 3840×2160×3. When each LED corresponding to the unit pixel P is a single LED chip, which is an encapsulation of red, blue, and green LEDs, the number of LEDs corresponding to the 4K resolution may be 4096×2160 or 3840×2160. 
     The image reproducing device  20  may store content, such as a video, or may receive the content from an external content source (e.g., a video streaming service server). For example, the image reproducing device  20  may store a file of content data in a storage, or receive content data from the external content source in real time. 
     The image reproducing device  20  may decode the stored or received content data into image frame data (hereinafter, image data). For example, a broadcast signal or content data may be compressed according to various video compression standards, such as Moving Picture Experts Group (MPEG), High Efficiency Video Coding (HEVC), etc. The image reproducing device  20  may restore the image data representing each image frame from the compressed content data. 
     The image reproducing device  20  may send the restored image data to the display device  10 . 
     Referring to  FIG. 2 , there may be image data lines, such as image data line L 1 , between the image reproducing device  20  and the plurality of LED module arrays  100 ,  100   a ,  100   b , and the image reproducing device  20  may send the image frame data to the plurality of LED module arrays  100 ,  100   a ,  100   b  through the image data lines.  FIG. 2  illustrates a single image data line L 1 . However, embodiments are not limited thereto, and one or more embodiments may include additional image data lines to connect LED module arrays to the image reproducing device  20 . 
     The plurality of LED module arrays  100 ,  100   a ,  100   b  may also receive image frame data from the image reproducing device  20  through the image data lines, and display an image corresponding to the received image data. 
     Upon reception of the image data, the plurality of LED module arrays  100 ,  100   a ,  100   b  may each display a portion of an image to be displayed on the entire screen S. Specifically, each of the plurality of LED module arrays  100 ,  100   a ,  100   b  may occupy a certain area on the screen S and output a portion of the entire image corresponding to where the LED module array is arranged. 
     For example, the image reproducing device  20  may send image data of the entire image to each of the plurality of LED module arrays  100 ,  100   a ,  100   b , which may in turn extract portions of the image data of the entire image corresponding to the location of the particular LED module array, and display images corresponding to the image data that is extracted according to the locations of the LED module arrays  100 ,  100   a ,  100   b . In another example, the image reproducing device  20  may divide the image data into a plurality of sub image frame data and send the plurality of sub image frame data to corresponding LED module arrays  100 ,  100   a ,  100   b , each of which may, in turn, display an image corresponding to the sub image frame data. 
       FIG. 3  is a front view of an LED module array, according to an embodiment.  FIG. 4  is a rear view of an LED module array, according to an embodiment.  FIG. 5  is an exploded view of an LED module array, according to an embodiment. 
     Referring to  FIGS. 3, 4, and 5 , a cabinet  101  of the LED module array  100  may include constituent parts to display an image I on the screen S. 
     The LED module array  100  may include LED modules  104  to emit light in the forward direction to generate an image, a control assembly  106  to control the LED modules  104 , a power assembly  107  to supply power to the LED modules  104  and the control assembly  106 , and a chassis  105  to support/fix LED modules  104 , the control assembly  106  and the power assembly  107 . 
     There may be a plurality of LED modules  104  in the LED module array  100 . In an embodiment, the LED module array  100  may include multiple LED modules  104  arranged in a 4×6 matrix. The LED module array  100  is not, however, limited thereto, and the number and arrangement of the LED modules may be variously modified. 
     The LED module  104  may include a plurality of LEDs  200  mounted on a module substrate  104   c , and for example, the plurality of LEDs  200  may be arranged in the form of a matrix. 
     The LED  200  is a semiconductor device that emits light with preset wavelength when power is supplied thereto. Similar to the normal diode, the LED  200  has also polarities, the anode and the cathode, and emits light when a voltage across the anode and the cathode is equal to or greater than a preset level. 
     The plurality of LEDs  200  may emit light with different colors and different brightnesses. In an embodiment, the LED  200  may emit light with different wavelengths (different colors) depending on the constituent material. For example, when the LED  200  includes aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), gallium phosphide (GaP), etc., the LED  200  may emit red light of about 620 nm to about 750 nm; when the LED  200  includes indium gallium nitride (InGaN), the LED  200  may emit green light of about 495 nm to about 570 nm; when the LED  200  includes gallium nitride (GaN), the LED  200  may emit blue light ray about 450 nm to about 495 nm. The LED  200  may emit various wavelengths of light such as white light other than the aforementioned wavelengths. 
     The plurality of LEDs  200  may include red LEDs that embody red sub pixels (PRs), green LEDs that embody green sub pixels (PGs), and blue LEDs that embody blue sub pixels (PBs). A red LED, a green LED, and a blue LED may be integrated into the single pixel P, and may be repeatedly arranged. 
     Furthermore, the plurality of LEDs  200  may emit light with different intensities depending on the magnitude of a current applied. For example, as the current applied increases, the plurality of LEDs  200  may emit light with higher intensities. 
     An image may be formed by a combination of light emitted from the plurality of LEDs  200 . For example, an image may be formed by a combination of red light emitted from red LEDs, green light emitted from green LEDs, and blue light emitted from blue LEDs. 
     The control assembly  106  may include a timing controller (TCON) and other various control circuits for controlling operation of the LED module  104 . 
     The timing controller (see  FIG. 8 ) may process an image signal into image data, and control a plurality of driving integrated chips (ICs) (see  FIG. 8 ) and LEDs mounted on the module substrate  104   c . The driving IC is a semiconductor that converts control image data into an analog value to directly drive an LED. The control image data may be based on a digital signal. The timing controller and driving ICs will be described later in more detail in connection with other drawings. 
     The power assembly  107  supplies stable power to the LED modules  104  in order for the plurality of LEDs  200  to emit light with different colors and different brightnesses. For example, the power assembly  107  may include a switching mode power supply (SMPS) for supplying power to the control assembly  107  and driving ICs by switching operations. 
     The control assembly  106  and the power assembly  107  may be implemented with printed circuit boards (PCBs) and various circuits mounted on the PCBs. For example, a power circuit may include a power circuit board, and a capacitor, a coil, a resistor, a microprocessor, etc., which are mounted on the power circuit board. The timing controller may also include a control circuit board, and a memory and a microprocessor mounted on the control circuit board. 
     The cabinet  101  may include a front bracket  101   a , a frame bracket  102 , and a rear cover  103 , and the front bracket  101   a , the frame bracket  102 , and the rear cover  103  may support and accommodate the LED modules  104 , the control assembly  106 , and the power assembly  107 . 
     The front bracket  101   a  may support the LED modules  104 . The frame bracket  102  may be located on the rear surface of the front bracket  101   a  to accommodate the control assembly  106  and the power assembly  107 . The rear cover  103  may be detachably connected to the frame bracket  102  to provide access to the cabinet  101 . 
     The chassis  105  may support the control assembly  106  and the power assembly  107 . For example, the control assembly  106  and the power assembly  107  may be fixed to the chassis  105 , and the chassis  105  may be fixed to the rear surface of the front bracket  101   a.    
     The mechanical structure of the LED module array  100  is not, however, limited to the aforementioned descriptions and drawings. For example, it is enough for the LED module array  100  to include the plurality of LED modules  104 , the control assembly  106  for controlling the LED modules  104 , and the power assembly  107 , and other components may be optionally included in the LED module array  100 . 
       FIG. 6  is a control block diagram of a display device, according to an embodiment.  FIG. 7  schematically shows a rear surface of an LED module, according to an embodiment.  FIG. 8  represents an area of an LED module according to an embodiment. As shown, the LED module includes control blocks. The embodiment will be described in connection with  FIGS. 6 to 8  together to avoid overlapping explanation. 
     Referring to  FIG. 6 , the display device  10  may include a user input device  110  for receiving a user input from the user, a content receiver  120  for receiving a video signal and/or an audio signal (or collectively, an image signal) from content sources, an image display  130  for displaying an image, a communicator  140  for communicating with external devices, a sound output device  150  for outputting sound, a data storage  160  for storing various programs and data, and a controller  170  for controlling operations of the display device  10 . 
     The user input device  110  may include an input button  111  for receiving a user input, and a signal receiver  112  for receiving a remote control signal from a remote controller. For example, the user input device  110  may include a power button for soft turn-on (operation start) or soft turn-off (operation stop) of the display device  10 , a sound control button to control sound volume output by the display device  10 , a source selection button to select a content source, etc. 
     The input button  111  may receive a user input, generate an electric signal corresponding to the user input, and send the electric signal to the controller  170 . The input button  111  may be implemented with various input devices such as a push switch, a touch switch, a dial, a slide switch, a toggle switch, etc. 
     The remote controller may be provided separately from the display device  100 , and may receive a user input and send a radio signal corresponding to the user input to the display device  10 . The signal receiver  112  may receive a radio signal corresponding to a user input from the remote controller, generate an electric signal corresponding to the user input, and send the electric signal to the controller  170 . 
     The content receiver  120  may include receiving terminal  121  and a tuner  122  for receiving an image signal including a video signal and/or an audio signal from the content sources. According to one or more embodiments, the content receiver  120  may include a plurality of receiving terminals  121 . 
     The receiving terminals  121  may receive a video signal and an audio signal from the content sources through a cable. For example, the receiving terminals  121  may include a component (YPbPr/RGB) terminal, a composite video blacking and sync (CVBS) terminal, an audio terminal, a high definition multimedia interface (HDMI) terminal, a universal serial bus (USB) terminal, etc. 
     The tuner  122  may receive broadcast signals through an antenna or a cable, and extract a broadcast signal corresponding to a channel selected by the user among the received broadcast signals. For example, the tuner  122  may pass a broadcast signal having a frequency corresponding to a channel selected by the user among the plurality of broadcast signals received through the antenna or the cable, and block other broadcast signals having different frequencies. 
     As such, the content receiver  120  may receive an image signal from the content sources through the receiving terminal  121  and/or the tuner  122 , and send the image signal to the controller  170 . The controller  170  may analyze/process the image signal and then convert the image signal to image data, as will be described later. 
     The image display  130  may include driving ICs  131  for converting image data to an analog signal, and the plurality of LEDs  200  driven by the driving ICs  131 . 
     In an embodiment, the LED module  104  may include 10×4 driving ICs  131 . Referring to  FIG. 7 , first to 40th driving ICs  131 - 1  to  131 - 40  may be mounted on the PCB provided on the rear surface of the LED module  104 . 
     Referring to  FIG. 8 , the first driving IC  131 - 1  of a first column may control a first line of LEDs  200  including 16×30 LEDs  200 . Specifically, the first driving IC  131 - 1  may apply a voltage to the cathode of LEDs  200  included in the first line through output lines RO to R 15 . The second driving IC  131 - 2  may apply a voltage to the cathode of LEDs  200  included in the second line through output lines R 16  to R 31 . The tenth driving IC  131 - 10  may apply a voltage to the cathode of LEDs  200  included in the tenth line through output lines R 144  to R 159 . 
     The timing controller  173  may apply a voltage to anodes of the LEDs  200  through output lines C 0  through C 29 . A voltage applied to the anode of the LEDs  200  included in each line may be determined by the timing controller  173  arranged in the control assembly  106 . The anode of the LEDs  200  may be connected to the timing controller  173 , and the cathode of the LEDs  200  may be connected to the driving ICs  131 . 
     The timing controller  173  may determine a voltage to be applied to the anode of the LEDs  200  included in each line while controlling the driving ICs  131  based on the analyzed image data. When a difference in voltage between the anode of the LED  200  and the cathode of the LED  200  applied by the driving IC  131  is equal to or greater than a preset voltage, the LED  200  emits light. 
     The function of the driving IC  131  controlling the voltage applied to the cathode of the LEDs  200  included in each line is a charging operation, and the function of the timing controller  173  controlling the voltage applied to the anode of the LEDs  200  included in the LED module  104  is a discharging operation. The display device  10  may attain enhanced image quality by controlling the voltage at the cathode using the driving ICs  131 . 
     A criterion for controlling voltages at both terminals of the LED  200  may take diode and circuit characteristics into account. Specifically, when the charging and discharging operations are performed by taking into account the circuit characteristics, a reverse voltage may occur across the LED  200  when image data including a black image or low gray scale image value is input. Hence, after analyzing the image data, the display device  10  may apply a new voltage that may reduce stress to some LEDs  200  across which the reverse voltage is likely to occur. This will be described later in more detail with reference to other drawings. 
     The aforementioned operations of the driving IC  131  and the timing controller  173  correspond to a passive matrix (PM) driving method for controlling the LEDs  200  line by line. However, embodiments are not limited to the PM driving method, and an active matrix (AM) driving method may be used by the display device  10  for controlling the LEDs  200  individually. Specifically, when employing the AM driving method, the display device  10  may include driving ICs for driving LEDs individually, the number of LEDs being preset according to a resolution, and a controller for analyzing received image data to determine a first voltage for the LED to emit light, determining a second voltage applied to the LED based on the first voltage and a reference value, and controlling the driving IC based on the second voltage. 
     The communicator  140  may exchange data with external devices other than the display device  10 . For example, the communicator  140  may exchange data with a user equipment or other electronic devices. 
     The wired communication interface  141  may access a wired communication network and communicate with an external device over the wired communication network. For example, the wired communication interface  141  may access a wired communication network through Ethernet, the IEEE 802.3 technology standard, and receive data from external devices over the wired communication network. 
     The wireless communication interface  142  may communicate wirelessly with a base station or an access point (AP), and access the wired communication network via the base station or the AP. The wireless communication interface  142  may communicate with external devices connected to the wired communication network via the base station or the AP. For example, the wireless communication interface  142  may use WiFi™, the IEEE 802.11 technology standard, to communicate with an AP, or use code divisional multiple access (CDMA), wideband code division multiple access (WCDMA), Global Systems for Mobile communications (GSM), Long Term Evolution (LTE), WiBro, etc., to communicate with a base station. The wireless communication interface  142  may receive data from the external devices via the base station or the AP. 
     In addition, the wireless communication interface  142  may communicate directly with the external device, such as a UE. For example, the wireless communication interface  142  may use Wireless Fidelity (Wi-Fi), Bluetooth™, which is the IEEE 802.15.1 technology standard, ZigBee™, which is the IEEE 802.15.4 technology standard, etc., to wirelessly receive data directly from the external device. 
     The sound output device  150  may include a speaker  151  for outputting sound in an audible signal or sound waves. 
     The speaker  151  may convert an analog sound signal amplified by an amplifier to a sound or sound waves. For example, the speaker  151  may include a thin film that vibrates according to an electric sound signal, and the vibration of the thin film may generate sound waves. 
     The data storage  160  may include a storage medium for storing a program and data for controlling the operation of the display device  10 . The program may include a plurality of instructions containing a code made by a compiler or a code executable by an interpreter, which when executed by a processor of the display device, control the display to device to perform a particular function, and the data may be processed according to the plurality of instructions included in the program. 
     The storage medium  161  may store content data in a file format. For example, the storage medium  161  may store the content data in the form of “*.mpg”, “*.avi”, “*.asf”, or “*.mp4” file, and provide the content data to the controller  170  in response to a readout instruction from the controller  170 . 
     For example, the storage medium  161  may store an image signal input from the content receiver  120  and/or the communicator  140 , and provide the stored image signal for the controller  170  to process image data. In another example, the storage medium  161  may receive and store the image data processed by the controller  170 . 
     The storage medium  161  may store the program and/or data electrically, magnetically, or optically. For example, the storage medium  161  may include a solid state drive (SSD), a hard disc drive (HDD), an optical disc drive (ODD), or the like. 
     The controller  170  may include one or more memories  172  for memorizing/storing a program/data, and one or more processors  171  for processing the data according to the program. The controller  170  may include hardware, such as the memory  172  and the processor  160 , and software, such as the program and/or data memorized/stored in the memory  171  and/or the data storage  160 . 
     The memory  172  may store a program and data for controlling the components included in the display device  10 . For example, the memory  172  may store instructions that contain a code made by a compiler or a code executable by an interpreter to be executed by processor  171 . 
     The memory  172  may temporarily store data provided from the components of the display device  10 . For example, the memory  172  may store a user input received through the user input device  110 , image data received through the content receiver  120 , communication data received through the communicator  140 , data stored in the data storage  160 , etc. 
     The memory  172  may include a non-volatile memory, such as a Read Only Memory (ROM), a flash memory, and/or the like, which may store data for a long period, and a volatile memory, such as a static random access memory (SRAM), a dynamic RAM (DRAM), or the like, which may temporarily store data. 
     The processor  171  processes the data stored in the memory  172  according to the program (or a series of programs) stored in the memory  172 . For example, the processor  171  may process the user input, the image data, the communication data, the stored data, etc., according to the program stored in the memory  172 . Furthermore, the processor  171  may generate a control signal to control at least one of the image display  130 , the communicator  140 , or the data storage  160  based on a result of processing the data. 
     The processor  171  may include an operation circuit for performing a logic operation and an arithmetic operation, and a memory circuit for storing the data resulting from the operation. 
     As such, the controller  170  may process the data obtained from the components included in the display device  10  and control the components. 
     Specifically, the controller  190  may control operations of the display device  10  based on user inputs received through the user input device  110 . For example, the controller  170  may supply power to the image display  130  and send the processed image data to the image display  130 , in response to a user input to initiate operation (turn-on operation). Furthermore, the controller  170  may stop sending the image data to the image display  130  and block the power to the image display  130 , in response to a user input to stop operation (turn-off operation). 
     The controller  170  may analyze an image signal (a TV broadcast signal, streaming data, etc.) received through the content receiver  120  or stored in the data storage  160  and convert the image signal to image frame data (hereinafter, image data). For example, the controller  190  may obtain a compressed/encoded image signal from the content receiver  120  and/or the data storage  160 , and decode the compressed/encoded image signal to image data. 
     The controller  170  may analyze the image data, and then determine an LED  200  to emit light and a particular voltage value for the LED  200  to emit light based on the image data. The controller  170  may determine a voltage (hereinafter, a first voltage) for the LED  200  based on the particular voltage value, and then output a control signal corresponding to the first voltage to the driving IC  131 . The image display  130  may apply a voltage to the LED  200  to control light emission according to the control signal from the controller  170 . 
     The controller  170  may compare the first voltage determined by analyzing the image data with a preset reference value to determine whether to control the image display  130  at the first voltage. When the image data is a black image or includes a low grayscale that is less than a reference value, the controller  170  may control the display  130  at a preset voltage (hereinafter, a second voltage) instead of the first voltage. This enables the controller  170  to reduce the stress on some of the LEDs  200  displaying image data in the LED module  104  or in the LED module array  100  and prevent LED damage and line defect, which will be described later. 
     The processor  171  and the memory  172  may be implemented separately with a plurality of semiconductor devices or integrated in a single semiconductor device. 
     The timing controller  173  as described above in connection with  FIGS. 3 to 5  may be an example of the controller  170 . In another embodiment, the timing controller  173  may be provided in each LED module  104  included in the display device  10 . In this case where the timing controller  173  is provided in the plural, a separate processor may be provided to analyze image data and collectively control the respective timing controllers  173 . 
     The display device  1  may further include a component for performing an additional function in addition to the aforementioned components as shown in  FIG. 6 , or may leave out one or more of the aforementioned components, as needed. 
       FIG. 9  is a depiction for explaining a possible problem occurring in a display device. 
     In the display device  10 , the controller  170  analyzes an image signal and controls the LED  200  emit light based on the analyzed image data. The display device  10  may control the voltage across both terminals of the LED  200  by the aforementioned discharging and charging operations. Such voltage control may be determined by taking into account characteristics of the LED  200  and associated circuits. 
     However, image data in some areas of the image I displayed on the display device  10  may have a voltage that is less than a certain level. Specifically, when the display device  10  includes the plurality of LED module arrays  100 , some LED module arrays  100  located at either edge of the image I may output the black image. Furthermore, some of the continuously displayed images I may include black content on the entire screen. 
     Even when displaying the image data that is a black image, a related device performs steady discharging and charging operations, which may lead to a reverse voltage across the LED  200 . The reverse voltage applied across the LED  200  causes stress. When the reverse voltage is continuously applied, the LED  200  has a continuous stress. Continuous stress may damage the LED  200 , causing a vertical line corresponding to the damaged LEDs  200 , for example line defect (I−1) as shown in  FIG. 9 , to appear on the display device  10 . The line defect causes the LEDs to emit a large amount of light, and is noticeably visible in the black image or a low grayscale image. For example, the line defect occur in sub pixels of a certain color, and the line defect may appear in a corresponding color. 
     In order to reduce the stress on the LED  200  and prevent the line defect, the display device  10  identifies image data that has a grayscale lower than a preset reference value and applies the preset second voltage to the LED  200  driven to emit light for the identified image data. 
       FIG. 10  is a flowchart illustrating a control method of a display device, according to an embodiment. 
     For example, the controller  170  may control the display device  10  to perform the control method illustrated in  FIG. 10 . 
     Referring to  FIG. 10 , the controller  170  receives an image signal, in operation  300 . Specifically, the image signal received by the display device  10  may have various types, and for example, the image signal may be movie streaming data. 
     The controller  170  analyzes the image signal to determine a first voltage corresponding to the LED  200  in operation  310 . 
     Specifically, the controller  170  may determine LEDs  200  included in the LED module  104  or the LED module array  100  in each frame of the image data, and determine an emission level of an LED  200  to emit light. As described above, the emission level of the LED  200  may be determined based on the voltage, and the voltage may be determined from the image data. 
     The controller  170  determines whether the image data includes a black image, in operation  320 . 
     Of multiple frames corresponding to the image data, some frames may include the black image. 
     When the image data is the black image, the controller  170  changes the voltage applied to all the LEDs  200  included in the LED module  104  or the LED module array  100  to the second voltage, in operation  340 . The controller  170  generates a control signal based on the second voltage, and controls the driving IC  131 , in operation  341 . 
     The second voltage may be preset, and may correspond to a forward voltage of the LED  200 . By applying the second voltage, stress that may be imposed on the LED  200  due to a reverse voltage across the LED  200  may be reduced. The value of the second voltage is not changed depending on the image data. For example, the second voltage may have a value set by the manufacturer of the display device  10  in a manufacturing stage. 
     Alternatively, the value of the second voltage may be changed by the user input device  110 . 
     When the image data is not the black image, the controller  170  compares the value of the first voltage and a preset reference value, in operation  330 . 
     Specifically, the value of the first voltage is determined by analyzing the image data. The first voltage may be different for each LED  200  included in the LED module  104  or the LED module array  100 . For example, even for one frame, the plurality of LEDs  200  may be divided into LEDs that display an image with content and LEDs that display a low grayscale image with no content. The LEDs that display a low grayscale image with no content may be usually located at edges of the screen S. 
     When the LEDs  200  emit light at a particular grayscale or less at the first voltage, the controller  170  changes the voltage to be applied to the LEDs  200  from the first voltage to the second voltage, in  340 . The controller  170  generates a control signal based on the second voltage, and controls the driving IC  131 , in operation  341 . 
     On the other hand, when it is determined that the LED  200  does not display the black image and emits light at the first voltage that exceeds the preset reference value, the controller  170  controls the driving IC  131  based on the first voltage, in operation  350 . 
     When the controller  170  controls the driving IC  131 , a control signal may drive multiple LEDs  200  on each line, which may correspond to the charging operation. On the other hand, the controller  170  may control emission of the LED  200  not only through the driving IC  131  but directly control the LED  200  based on the second voltage by performing the discharging operation. This will be described later in more detail with reference to  FIGS. 12 and 13 . 
       FIG. 11  is a flowchart illustrating a control method of a display device, according to another embodiment. 
     Referring to  FIG. 11 , the controller  170  receives a screen off signal in operation  400 . 
     The screen off signal is a signal to prevent the LED  200  from emitting light, and may be used in a standby mode, a suspend mode, an off mode, etc., to minimize power consumption of the display device  10 . The screen off signal may be received through the user input device  110  or generated by the controller  170  when a certain condition is met. 
     The LED  200  does not emit light in response to the screen off signal. However, a reverse voltage may be applied across the LED  200  due to the aforementioned charging and discharging operations. 
     Accordingly, in the disclosure, the controller  170  controls the driving IC  131  at the second voltage according to the screen off signal, for example when the screen off signal is received through the user input device  110  or generated by the controller  170  when the condition is met, in operation  410 . 
     The display device  10  may apply the second voltage to the LED  200  based on various external signals other than the result of analysis of the image data, thereby reducing the stress and preventing damage to the LED  200 . 
       FIGS. 12 and 13  are flowcharts illustrating control methods of a display device, according to embodiments. 
     Referring to  FIG. 12 , the controller  170  determines to drive the LED  200  at the second voltage, in operation  500 . 
     As described above in connection with  FIGS. 10 and 11 , the controller  170  may determine to drive the LED  200  at the second voltage based on different reasons such as a result of analysis of the image data or the screen off signal. In this case, the controller  170  may control the LED  200  at the second voltage in the following two examples. 
     First, the controller  170  applies the second voltage to the LED  200  by controlling a voltage at the anode of the LED  200 , in operation  510 . 
     As described above in connection with  FIG. 8 , when the timing controller  173  controls the voltage applied to the anode of the LED  200 , the controller  170  applies the second voltage to the LED  200  by directly performing the discharging operation. 
     Alternatively, the controller  170  may apply the second voltage to the LED  200  by controlling a voltage at the cathode of the LED  200  through the driving IC  131 . Referring to  FIG. 13 , the controller  170  determines to drive the LED  200  at the second voltage, in operation  600 . 
     As described above in connection with  FIG. 8 , the driving IC  200  may control the voltage at the cathode of the LED  200 . Accordingly, the controller  170  may apply the second voltage to the LED  200  by performing the charging operation through the driving IC  131 , in operation  620 . 
     Furthermore, the controller  170  stops controlling the voltage at the anode of the LED  200 , in operation  630 . For example, when the charging operation is used, the controller  170  may not perform the discharging operation that controls the voltage at the anode of the LED  200 . 
     However, it is also possible for the controller  170  to apply the second voltage to the LED  200  while performing the charging operation and discharging operation together without the need to separate the charging operation from the discharging operation all the time. 
     According to the embodiments, a display device and control method thereof can control the magnitude of a voltage applied to an LED based on an input signal, thereby reducing the stress on the LED and increasing the lifespan of the LED. 
     In addition, the display device and control method thereof can prevent a line defect from occurring due to steady stress on the LED. 
     Embodiments have been described above. In the embodiments, some components may be implemented as a “module”. Here, the term ‘module’ indicates, but is not limited to, a software and/or hardware component, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks. A module may be configured to reside on the addressable storage medium and configured to execute on one or more processors. 
     Thus, a module may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The operations provided for in the components and modules may be combined into fewer components and modules or further separated into additional components and modules. In addition, the components and modules may be implemented such that they execute one or more CPUs in a device. 
     Additionally, embodiments can also be implemented through computer readable code or instructions that are stored in or on a medium, e.g., a computer readable medium, to control at least one processing element to implement any above described exemplary embodiment. The medium can correspond to any medium/media permitting the storing and/or transmission of the computer readable code. 
     The computer-readable code can be recorded on a medium or transmitted through the Internet. The medium may include Read Only Memory (ROM), Random Access Memory (RAM), Compact Disk-Read Only Memories (CD-ROMs), magnetic tapes, floppy disks, and optical recording medium. Also, the medium may be a non-transitory computer-readable medium. The media may also be a distributed network, so that the computer readable code is stored or transferred and executed in a distributed fashion. Still further, as only an example, the processing element could include at least one processor or at least one computer processor, and processing elements may be distributed and/or included in a single device. 
     While embodiments have been shown and described above, it will be apparent to those skilled in the art that many variations and modifications may be made to the embodiments without departing from the principles of the present disclose as defined by the attached claims.