Abstract:
An organic light emitting display capable of reducing power consumption in a standby mode to increase the use time of a battery and a method of driving the same. The organic light emitting display includes a pixel unit for displaying an image by utilizing a plurality of frames and in accordance with data signals and scan signals; a data driver for outputting the data signals; a scan driver for outputting the scan signals; and a controller for controlling the data driver and the scan driver so that, in at least one frame of the plurality of frames, the scan signals are not transmitted to the pixel unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0071274, filed on Aug. 3, 2009, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    An embodiment of the present invention relates to an organic light emitting display and a method of driving the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Various flat panel displays (FPD) that are lighter in weight and smaller in volume than comparable cathode ray tube (CRT) displays are being developed. Non-limiting examples of these FPDs include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting display. 
         [0006]    Among the FPDs, the organic light emitting display displays an image using organic light emitting diodes (OLED) that generate light by re-combination of electrons and holes generated to correspond to the flow of current. 
         [0007]    The organic light emitting display is widely utilized in a personal digital assistant (PDA), an MP3 player, and/or a mobile telephone due to its excellent color reproducibility and small thickness. 
         [0008]      FIG. 1  is a block diagram illustrating the structure of an organic light emitting display according to an embodiment of the present invention. Referring to  FIG. 1 , the organic light emitting display includes a pixel unit (a display region)  10 , a data driver  20 , a scan driver  30 , and a controller  40 . 
         [0009]    A plurality of pixels  11  are arranged in the pixel unit  10  and each of the pixels  11  includes an organic light emitting diode (OLED) that emits light to correspond to the flow of current therein. The pixel unit  10  includes n scan lines S 1 , S 2 , . . . , Sn−1, and Sn formed to extend in a first direction (a row direction) and to transmit scan signals, and m data lines D 1 , D 2 , . . . , Dm−1, and Dm formed to extend in a second direction (a column direction) crossing the first direction and to transmit data signals. 
         [0010]    In addition, the pixel unit  10  receives a first power of a first power source and a second power of a second power source having a lower voltage level than that of the first power source to be driven. Therefore, in the pixel unit  10 , current flows to the OLED by utilizing the scan signals, the data signals, the first power source, and the second power source to emit light and to display an image. 
         [0011]    The data driver  20  receives data driver control signals DCS and image signals R, G, B data from the controller  40  to generate the data signals. The data driver  20  is coupled to the data lines D 1 , D 2 , . . . , Dm−1, and Dm of the pixel unit  10  to apply the generated data signals to the pixel unit  10 . 
         [0012]    The scan driver  30  receives scan driver control signals SCS from the controller  40  to generate the scan signals. The scan driver  30  is coupled to the scan lines S 1 , S 2 , . . . , Sn−1, and Sn to transmit the scan signals to specific rows of the pixel unit  10 . The data signal output from the data driver  20  is transmitted to the pixel  11  where the scan signal is transmitted so that the voltage corresponding to the data signal is transmitted to the pixel  11 . 
         [0013]    The controller  40  controls the data driver  20  and the scan driver  30  so that the pixel unit  10  can display an image. 
         [0014]    When the above structured organic light emitting display is used for a mobile telephone, in a standby mode, an image representing date and hour is displayed only on a partial region of the pixel unit and the image is not displayed on the remaining region. 
         [0015]    The image is displayed only on the partial region (a partial screen) in order to reduce power consumption and to increase the use time of a battery of the organic light emitting display. 
         [0016]    However, in the standby mode, the data driver  20  and the scan driver  30  are driven in the same way. That is, the power consumptions of the data driver  20  and the scan driver  30  do not change in the standby mode. Therefore, in order to reduce power consumption, an improved method of reducing power consumption in the data driver  20  and the scan driver  30  in the standby mode is needed. 
       SUMMARY OF THE INVENTION 
       [0017]    Aspects of embodiments of the present invention are directed toward an organic light emitting display with a relatively small power consumption and a method of using the same. 
         [0018]    Aspects of embodiments of the present invention are directed toward an organic light emitting display capable of reducing power consumption in a standby mode to increase the use time of a battery of the display and a method of using the same. 
         [0019]    An embodiment of the present invention provides an organic light emitting display, including a pixel unit (display region) for displaying an image by utilizing a plurality of frames and in accordance with data signals and scan signals; a data driver for outputting the data signals; a scan driver for outputting the scan signals; and a controller for controlling the data driver and the scan driver so that, in at least one frame of the plurality of frames, the scan signals are not transmitted to the pixel unit. 
         [0020]    In one embodiment, the scan driver is stopped from being driven by the controller during a frame period of the at least one frame when the scan signals are not transmitted. 
         [0021]    In one embodiment, the organic light emitting display further includes a demultiplexer between the data driver and the pixel unit to distribute a plurality of data signals output from one output end of the data driver during a frame period of at least an other frame of the plurality of frames. Here, an operation of the demultiplexer may stop in the at least one frame when the scan signals are not transmitted to the pixel unit. 
         [0022]    In one embodiment, the image is displayed only in a partial region of the pixel unit. 
         [0023]    In one embodiment, the image is a standby image. 
         [0024]    Another embodiment of the present invention provides a method of driving an organic light emitting display for displaying an image by utilizing a plurality of frames and in accordance with data signals and scan signals. The method includes: transmitting the data signals to pixels of a pixel unit of the organic light emitting display by the scan signals to display a first image of a first frame of the plurality of frames; and maintaining the data signals transmitted in the first frame in the pixels to display a second image of a second frame of the plurality of frames. 
         [0025]    In one embodiment, the scan signals are not transmitted in the second frame. 
         [0026]    In one embodiment, the first and second images are displayed only on a part of the pixel unit. The first and second images may be a standby image. 
         [0027]    In one embodiment, the second frame is an adjacent frame following the first frame. 
         [0028]    In the organic light emitting display and the method of driving the same according to embodiments of the present invention, the scan driver is driven to output the scan signals only in a part of the time where the image is displayed so that power consumption in accordance with the driving of the scan signals can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
           [0030]      FIG. 1  is a block diagram illustrating the structure of an organic light emitting display; 
           [0031]      FIG. 2  is a block diagram illustrating the structure of an organic light emitting display according to an embodiment of the present invention; 
           [0032]      FIG. 3  is a view illustrating an image displayed on the pixel unit of the organic light emitting display of  FIG. 2  in a standby mode; 
           [0033]      FIG. 4  is a circuit diagram illustrating a pixel adopted by the organic light emitting display of  FIG. 2 ; and 
           [0034]      FIG. 5  is a waveform diagram illustrating scan signals and demultiplexer control signals input to the organic light emitting display of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Hereinafter, certain exemplary embodiments according to the present invention will be described with reference to the accompanying drawings. Here, when a first element is described as being coupled to a second element, the first element may be not only directly coupled to the second element but may also be indirectly coupled to the second element via one or more third elements. Further, some of the elements that are not essential to the complete understanding of the invention are omitted for clarity. Also, like reference numerals refer to like elements throughout. 
         [0036]    Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
         [0037]      FIG. 2  is a block diagram illustrating the structure of an organic light emitting display according to the present invention. Referring to  FIG. 2 , the organic light emitting display includes a pixel unit (display region)  100 , a data driver  200 , a scan driver  300 , a demultiplexer  400 , and a controller  500 . 
         [0038]    A plurality of pixels  101  are arranged in the pixel unit  100 , and each of the pixels  101  includes an organic light emitting diode (OLED) that emits light to correspond to the flow of current. The pixel unit  100  includes n scan lines S 1 , S 2 , . . . , Sn−1, and Sn formed to extend in a first direction (a row direction) and to transmit scan signals, and m data lines D 1 , D 2 , . . . , Dm−1, and Dm formed to extend in a second direction (a column direction) crossing the first direction and to transmit data signals. 
         [0039]    In addition, the pixel unit  100  receives a first power of a first power source ELVDD and a second power of a second power source ELVSS having a lower voltage level than the first power source ELVDD to be driven. Therefore, in the pixel unit  100 , current flows to the OLED by utilizing the scan signals, the data signals, the first power source ELVDD, and the second power source ELVSS to emit light and to display an image. 
         [0040]    The data driver  200  receives data driver control signals DCS and image signals R, G, B data from the controller  500  to generate the data signals. The data driver  200  is coupled to the data lines D 1 , D 2 , . . . , Dm−1, and Dm of the pixel unit  100  through the demultiplexer  400  to apply the generated data signals to the pixel unit  100 . 
         [0041]    The scan driver  300  receives scan driver control signals SCS from the controller  500  to generate the scan signals. The scan driver  300  is coupled to the scan lines S 1 , S 2 , . . . , Sn−1, and Sn to transmit the scan signals to specific rows of the pixel unit  100 . The data signal output from the data driver  200  is transmitted to the pixel  101  where the scan signal is transmitted so that the voltage corresponding to the data signal is transmitted to the pixel  101 . 
         [0042]    The demultiplexer  400  transmits the data signals transmitted through the output terminals O 1  . . . Ok of the data driver  200  to the data lines D 1 , D 2 , . . . , Dm−1, and Dm. In particular, one output terminal is coupled to three data lines through the demultiplexer. One output terminal of the data driver  200  sequentially outputs red, green, and blue data signals. The demultiplexer  400  has the red, green, and blue data signals transmitted to the three data lines by demultiplexer control signals CLA, CLB, and CLC. Therefore, the number of output terminals O 1  . . . Ok of the data driver  200  can be reduced by the demultiplexer  400 . 
         [0043]    The controller  500  transmits the image signals R, G, B data and the data driver control signals DCS to the data driver  200 , transmits the scan driver control signals SCS to the scan driver  300 , transmits demultiplexer control signals CLA, CLB, and CLC to the demultiplexer  400 , and has the data driver  200  select transmitted data signals so that the pixel unit  100  can display an image. 
         [0044]      FIG. 3  is a view illustrating an image displayed on the pixel unit of the organic light emitting display of  FIG. 2  in a standby mode. Referring to  FIG. 3 , the organic light emitting display is driven in a display mode where images such as a moving picture and a photograph are displayed and in a standby mode where only date and hour are displayed. 
         [0045]    In order to reduce power consumption in the standby mode, the pixel unit is divided into a non-display region  110  and a display region  120 . In the display region  120 , icons such as date and hour are displayed. The non-display region  110  does not emit light so that the non-display region  110  is displayed black (displays no emitting light). 
         [0046]    Since the organic light emitting display displays an image corresponding to the current that flows to each pixel, current flows to the pixels positioned in the display region  120  in the standby mode and current does not flow to the pixels positioned in the non-display region  110 . That is, the amount of the current that flows to the pixel unit  100  in the standby mode is smaller than the amount of the current that flows to the pixel unit in the display mode. Therefore, power consumption is reduced. 
         [0047]    However, in the case where the image is displayed only in the display region  120  that is not the entire region of the pixel unit  100  but is a part of the pixel unit  100 , the scan driver  300  performs the same operation as when the scan driver  300  operates in the display mode. Therefore, in order to effectively reduce power consumption, the scan signals input to the pixel unit  100  are to be differently transmitted in the display mode and in the standby mode. 
         [0048]      FIG. 4  is a circuit diagram illustrating a pixel adopted by the organic light emitting display of  FIG. 2 . Referring to  FIG. 4 , the pixel  101  includes a first transistor M 1 , a second transistor M 2 , a capacitor Cst, and an organic light emitting diode (OLED) and receives a data signal and a scan signal through the data line Dm and the scan line Sn. 
         [0049]    The source of the first transistor M 1  is coupled to the first power source ELVDD. The drain of the first transistor M 1  is coupled to the anode electrode of the OLED. The gate of the first transistor M 1  is coupled to a first node N 1 . Therefore, the amount of the current that flows from the source to the drain is determined to correspond to the voltage of the first node N 1 . 
         [0050]    The source of the second transistor M 2  is coupled to the data line Dm. The drain of the second transistor M 2  is coupled to the first node N 1 . The gate of the second transistor M 2  is coupled to the scan line Sn. Therefore, the data signal transmitted through the data line Dm to correspond to the scan signal transmitted through the scan line Sn can be transmitted to the first node N 1 . 
         [0051]    The first electrode of the capacitor Cst is coupled to the first power source ELVDD and the second electrode of the capacitor Cst is coupled to the first node N 1 . Therefore, the voltage of the first node N 1  can be maintained. 
         [0052]    The anode electrode of the OLED is coupled to the drain of the first transistor M 1 . The cathode electrode of the OLED is coupled to the second power source ELVSS. A light emitting layer is formed between the anode electrode and the cathode electrode. Light is emitted to correspond to the current that flows from the anode electrode to the cathode electrode. Therefore, light is emitted to correspond to the amount of current that flows from the source of the first transistor M 1  to the drain of the first transistor M 1 . 
         [0053]      FIG. 5  is a waveform diagram illustrating scan signals and demultiplexer control signals input to the organic light emitting display of  FIG. 2 . Referring to  FIG. 5 , the image displayed by the pixel unit  100  of the organic light emitting display is displayed by utilizing a plurality of frames. 
         [0054]    First, in a first frame period, the scan signal Sn and demultiplexer control signals are transmitted. Therefore, the data signals output from the data driver  200  by the demultiplexer control signals CLA, CLB, and CLC are sequentially distributed to the data lines. Then, the data signal is transmitted to a specific pixel  101  by the scan signal Sn and the pixel  101  emits light to correspond to the data signal. Therefore, an image (a standby image) is displayed on the display region  120  of the pixel unit  100 . 
         [0055]    The scan signal Sn and the demultiplexer control signals CLA, CLB, and CLC are not transmitted in a second frame period (e.g., an adjacent frame following the first frame). Therefore, the data signals corresponding to the second frame are not transmitted to the pixel  101 . However, since the data signals transmitted in the first frame period are previously stored in the capacitor Cst in the pixel  101 , the same image as the image of the first frame is displayed in the second frame. 
         [0056]    Then, in a third frame period (e.g., an adjacent frame following the second frame), the scan signal Sn and the demultiplexer control signals CLA, CLB, and CLC are transmitted. At this time, light is emitted from the pixel  101  in accordance with (to correspond to) the transmitted data signals. 
         [0057]    Therefore, the scan signal Sn is not transmitted in the second frame period since the scan driver  300  is not driven. Therefore, power consumption utilized by the scan driver  300  can be reduced by the stopping of driving of the scan driver  300 . In addition, since the icons displayed in the standby mode are images that do not frequently change, although the data signals are not received during all of the frames, it is still possible to reduce or prevent the images from being distorted or wrongly transmitted. 
         [0058]    While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.