Abstract:
An organic light emitting display capable of reducing power consumption in a standby mode and a method of driving the same. The organic light emitting display includes a pixel unit having a first emission region and a second emission region, wherein the pixel unit is configured to generate a driving current in accordance with data signals and scan signals to emit light so that light is emitted by the pixel unit only in the first emission region in a standby mode, a data driver for transmitting the data signals only to the first emission region in the standby mode, a scan driver for outputting the scan signals, and a power source supplier for generating and outputting voltages of an initialization power source and for blocking the driving current from flowing to the second emission region by utilizing a voltage of the initialization power source in the standby mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0071276, 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]    One or more embodiments of the present invention relate 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 the 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, that is, the remaining region is displayed black (displays no emitting light). 
         [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 where there are many regions displayed black, the data driver  20  is driven in the same way. Therefore, the power consumptions of the data driver  20  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  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 and a method of using the same. 
         [0019]    An embodiment of the present invention provides an organic light emitting display, including a pixel unit having a first emission region and a second emission region, wherein the pixel unit is configured to generate a driving current in accordance with data signals and scan signals to emit light so that light is emitted by the pixel unit only in the first emission region in a standby mode; a data driver for transmitting the data signals only to the first emission region in the standby mode; a scan driver for outputting the scan signals; and a power source supplier for generating and outputting voltages of an initialization power source and for blocking the driving current from flowing to the second emission region by utilizing a voltage of the initialization power source in the standby mode. 
         [0020]    In one embodiment, the pixel unit includes a plurality of pixels, and each of the pixels includes: an organic light emitting diode (OLED); a first transistor including a first electrode coupled to a first node, a second electrode coupled to a second node, and a gate coupled to a third node so that driving current flows from the first node to the second node in accordance with a voltage of the gate; a second transistor including a first electrode coupled to a data line, a second electrode coupled to the first node, and a gate coupled to a first scan line; a third transistor including a first electrode coupled to the second node, a second electrode coupled to the third node, and a gate coupled to the first scan line; a fourth transistor including a first electrode coupled to the initialization power source, a second electrode coupled to the third node, and a gate coupled to a second scan line; a fifth transistor including a first electrode coupled to a first power source, a second electrode coupled to the first node, and a gate coupled to an emission control line; a sixth transistor including a first electrode coupled to the second node, a second electrode coupled to the organic light emitting diode (OLED), and a gate coupled to the emission control line; and a capacitor including a first electrode coupled to the first power source and a second electrode coupled to the third node. 
         [0021]    In one embodiment, the data driver is configured to be driven only in a period where data signals are transmitted to the first emission region in the standby mode. 
         [0022]    In one embodiment, the power source supplier is configured to output a first voltage when the initialization power source is set to have the first voltage and a second voltage differing form the first voltage and when the data driver stops driving in the standby mode, and is configured to output the second voltage when the data driver is driven. 
         [0023]    In one embodiment, the first voltage is a voltage, at which the driving current is not generated by the first transistor. 
         [0024]    Another embodiment of the present invention provides a method of driving an organic light emitting display having a pixel unit having a first emission region and a second emission region, wherein the pixel unit is configured to generate a driving current in accordance with data signals and scan signals to emit light. The method includes: transmitting a voltage of an initialization power source set to have a first voltage or a second voltage differing from the first voltage to the pixel unit and setting the transmitted voltage of the initialization power source as the first voltage in a standby mode to output the first voltage; and converting the transmitted voltage of the initialization power source from the first voltage into the second voltage when data signals are transmitted to the first emission region in the standby mode. 
         [0025]    In one embodiment, the pixel unit includes a plurality of pixels, and each of the pixels includes: an organic light emitting diode (OLED); a first transistor including a first electrode coupled to a first node, a second electrode coupled to a second node, and a gate coupled to a third node so that driving current flows from the first node to the second node in accordance with a voltage of the gate; a second transistor including a first electrode coupled to a data line, a second electrode coupled to the first node, and a gate coupled to a first scan line; a third transistor including a first electrode coupled to the second node, a second electrode coupled to the third node, and a gate coupled to the first scan line; a fourth transistor including a first electrode coupled to the initialization power source, a second electrode coupled to the third node, and a gate coupled to a second scan line; a fifth transistor including a first electrode coupled to a first power source, a second electrode coupled to the first node, and a gate coupled to an emission control line; a sixth transistor including a first electrode coupled to the second node, a second electrode coupled to the organic light emitting diode (OLED), and a gate coupled to the emission control line; and a capacitor including a first electrode coupled to the first power source and a second electrode coupled to the third node. 
         [0026]    In one embodiment, when the initialization power source has the first voltage, the pixel unit display is displayed black. 
         [0027]    In one embodiment, when the initialization power source has the first voltage, an operation of a data driver for transmitting the data signals is stopped. 
         [0028]    In the organic light emitting display and the method of driving the same according to embodiments of the present invention, the driving time of the data driver is reduced so that the power consumption of the data driver is 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 timing diagram illustrating a voltage change in the scan signals, the emission control signals, and the initialization power source input to the organic light emitting display of  FIG. 2  in the standby mode. 
       
    
    
     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 controller  400 , and a power source supplier  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 a plurality of 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, a plurality of emission control lines E 1 , . . . , and En−1 formed to extend in the first direction (the row direction) and to transmit emission control signals, and a plurality of 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. Also, the pixel unit  100  receives an initialization power source Vinit for initializing a voltage stored in the pixel  101 . 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. The voltage stored in the pixel  101  is initialized by the initialization power source Vinit. 
         [0040]    Here, the pixel unit  100  can be operated to display an image in a standby mode and an image in a display mode. In the standby mode, an image is displayed only in a part of the pixel unit  100  and the remaining part is displayed black (displays no emitting light). Current does not flow to the part displayed black so that the amount of power consumed by the pixel unit  100  is reduced. The shape of the pixel unit  100  in the standby mode will be described in more detail in  FIG. 3 . 
         [0041]    The data driver  200  receives data driver control signals DCS and image signals R, G, B data from the controller  400  to generate the data signals. The data driver  200  is continuously driven in the display mode, however, a period where operation is stopped is generated in a period in one frame in the standby mode. Therefore, the operation of the data driver  200  is stopped so that the amount of power consumed by the data driver  200  is reduced. 
         [0042]    The scan driver  300  receives scan driver control signals SCS from the controller  400  to generate the scan signals and the emission control signals. The scan driver  300  is coupled to the plurality of scan lines S 1 , S 2 , . . . , Sn−1, and Sn and the plurality of emission control lines E 1 , . . . , and En−1 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 . 
         [0043]    The controller  400  transmits the image signals R, G, B data and the data driver control signals DSC to the data driver  200  and transmits the scan driver control signals SCS to the scan driver  300  to control the operations of the data driver  200  and the scan driver  300 . 
         [0044]    The power source supplier  500  generates the first power of the first power source ELVDD, the second power of the second power source ELVSS, and the initialization power of the initialization power source Vinit to transmit the generated first power of the power source ELVDD, the second power of the second power source ELVSS, and the initialization power of the initialization power source Vinit to the pixel unit  100 . Here, the initialization power source Vinit has a first voltage, a second voltage, a third voltage between the first voltage and the second voltage to correspond to the driving of the data driver  200 . 
         [0045]      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. The pixel unit is divided into a first emission region  120  and a second emission region  110 . The first emission region  120  emits light in the standby mode and the display mode. The second emission region  110  emits light only in the display mode. 
         [0046]    The second emission region  110  emits light only in the display mode in order to reduce power consumption in the standby mode. In the standby mode, the icons such as date and hour are displayed on the first emission region  120  and the second emission region  110  does not emit light but is displayed black. 
         [0047]    Since the organic light emitting display displays an image to correspond to the current that flows to each pixel, current flows to the pixel positioned in the first emission region  120  in the standby mode and current does not flow to the pixel positioned in the second emission region  110 . That is, since the area where light is emitted in the pixel unit  100  in the standby mode is smaller than in the display mode, 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  100  in the display mode. Therefore, the power consumption of the pixel unit  100  is reduced. 
         [0048]    However, when the data driver  200  performs the same operation as when the data driver  200  operates in the display mode in the case where an image is displayed only in the first emission region  120  that is not the entire region of the pixel unit  100  but is only a part of the pixel unit  100  in the standby mode, in this standby mode, the data driver  200  has the same power consumption as in the display mode. Therefore, in order to effectively reduce power consumption and in one embodiment of the present invention, the data driver  200  stops operating at the point of time where the pixel positioned in the second emission region  110  is selected by the scan signal in the standby mode and the data driver  200  operates at the point of time where the pixel positioned in the first emission region  120  is selected. That is, in order to effectively reduce power consumption, it is necessary that the data signals input to the pixel unit  100  are differently transmitted in the display mode and in the standby mode. 
         [0049]      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 third transistor M 3 , a fourth transistor M 4 , a fifth transistor M 5 , a sixth transistor M 6 , a capacitor Cst, and an organic light emitting diode (OLED). 
         [0050]    The source of the first transistor M 1  is coupled to a first node N 1 . The drain of the first transistor M 1  is coupled to a second node N 2 . The gate of the first transistor M 1  is coupled to a third node N 3 . Therefore, the amount of the driving current that flows from the source to the drain of the first transistor corresponds to the voltage of the third node N 3 . 
         [0051]    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 can be selectively transmitted with the second transistor M 2  to the first node N 1  in accordance with the scan signal transmitted through the scan line Sn. 
         [0052]    The source of the third transistor M 3  is coupled to the second node N 2 . The drain of the third transistor M 3  is transmitted to the third node N 3 . The gate of the third transistor M 3  is coupled to the first scan line Sn. Therefore, the second node N 2  and the third node N 3  are electrically coupled to each other to correspond to the scan signal transmitted through the first scan line Sn so that the voltage of the second node N 2  is equal to the voltage of the third node N 3  and that the first transistor M 1  is diode coupled (connected as a diode by the transistor M 3 ). 
         [0053]    The source of the fourth transistor M 4  is coupled to the initialization power source Vinit. The drain of the fourth transistor M 4  is coupled to the third node N 3 . The gate of the fourth transistor M 4  is coupled to the second scan line Sn−1. Therefore, the initialization power source Vinit is transmitted to the third node N 3  to correspond to the scan signal transmitted through the second scan line Sn−1. 
         [0054]    The source of the fifth transistor M 5  is coupled to the first power source ELVDD. The drain of the fifth transistor M 5  is coupled to the first node. The gate of the fifth transistor M 5  is coupled to the emission control line En−1. Therefore, the first power of the power source ELVDD can be selectively transmitted with the fifth transistor M 5  to the first node N 1  in accordance with the emission control signal transmitted through the emission control line En−1. 
         [0055]    The source of the sixth transistor M 6  is coupled to the second node N 2 . The drain of the sixth transistor M 6  is coupled to the OLED. The gate of the sixth transistor M 6  is coupled to the emission control line En−1. Therefore, the transmission of the driving current generated by the first transistor M 1  to the OLED is controlled (with the sixth transistor M 6 ) in accordance with the emission control signal transmitted through the emission control line En−1. 
         [0056]    The first electrode of the capacitor Cst is coupled to the first power source ELVDD. The second electrode of the capacitor Cst is coupled to the third node N 3 . Therefore, the voltage of the third node N 3  is maintained. 
         [0057]    The anode electrode of the OLED is coupled to the first power source ELVDD. 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 through the source of the first transistor M 1  and the drain of the first transistor M 1 . 
         [0058]      FIG. 5  is a timing diagram illustrating a voltage change in the scan signals, the emission control signals, and the initialization power source input to the organic light emitting display of  FIG. 2  in a standby mode. For convenience sake, in the standby mode, it is assumed that the row of pixels, to which a data signal is transmitted by utilizing an (a+1)th scan signal SSa+1, to the row of pixels, to which a data signal is transmitted by utilizing an (a+4)th scan signal SSa+4, are the pixels positioned in the first emission region  120 , in which an image is displayed in the standby mode. Referring to  FIG. 5 , in the operation of the pixel, initially, the fourth transistor M 4  is turned on to correspond to the scan signal transmitted through the second scan line Sn−1. When the fourth transistor M 4  is turned on, the initialization power source is transmitted to the third node N 3  so that the third node N 3  has the voltage of the initialization power source Vinit. The scan signal transmitted through the first scan line Sn is transmitted. The fourth transistor M 4  is turned off. The second transistor M 2  and the third transistor M 3  are turned on. When the second transistor M 2  and the third transistor M 3  are turned on, the data signal that flows to the data line Dm is transmitted to the first node N 1 . Then, the second node N 2  and the third node N 3  are electrically coupled to each other by the third transistor M 3  so that the second node N 2  and the third node N 3  have equal potential. Therefore, the first transistor M 1  is diode coupled. At this time, since the fifth transistor M 5  and the sixth transistor M 6  are turned off by the emission control signal transmitted through the emission control line En−1, current does not flow to the OLED. Here, the third node N 3  stores the voltage corresponding to the data signal. Then, when the fifth transistor M 5  and the sixth transistor M 6  are turned on by the emission control signal transmitted through the emission control line En−1, the third node N 3  still stores the voltage corresponding to the data signal. Therefore, since driving current flows from the first node N 1  to the second node N 2  by the first transistor M 1  and the driving current is transmitted to the OLED, the OLED emits light. 
         [0059]    In the pixels that operate as described above, in the pixels that receive the data signals by utilizing the first scan signal to the ath scan signal SSa, the initialization power source Vinit has the first voltage. At this time, the first voltage has the same voltage (for example, 4.2V) as the first power of the first power source ELVDD. Therefore, since the initialization power source Vinit having the first voltage is transmitted to the third node N 3 , the voltage of the third node N 3  has the first voltage. When the data signal is transmitted to the first node N 1  and the first transistor M 1  is diode coupled by the third transistor M 3  in the state where the third node N 3  has the first voltage, since the third node N 3  has a high voltage, the voltage of the third node N 3  maintains the first voltage. That is, the voltage of the third node N 3  maintains the first voltage regardless of the voltage of the data signal. When the third node N 3  has the first voltage, current does not flow from the source of the first transistor M 1  to the drain of the first transistor M 1  so that the OLED does not emit light. Therefore, the OLED is displayed black. Due to the above, although the data driver  200  does not output the data signal, the OLED is displayed black by the initialization power source. 
         [0060]    The pixels that received the data signals by utilizing the (a+1)th scan signal SSa+1 to the (a+4)th scan signal SSa+4 receive the second voltage as the voltage of the initialization power source Vinit. At this time, the second voltage is in a low level (for example, −2V). 
         [0061]    Then, when the fourth transistor M 4  is turned on, the second voltage is transmitted to the third node N 3  by the initialization power source Vinit and the second voltage is maintained in the third node N 3  by the capacitor Cst. When the first transistor M 1  is diode coupled in a state where the third node N 3  has the second voltage, current flows to the third node N 3  and the third node N 3  has the voltage corresponding to the voltage of the data signal. Then, when the fifth transistor M 5  and the sixth transistor M 6  are turned on by the emission control signal, since the driving current flows from the source of the first transistor M 1  to the drain of the first transistor M 1  by the voltage of the third node N 3 , the driving current corresponding to the data signal flows to the OLED so that the OLED emits light. 
         [0062]    Therefore, the data driver  200  can be stopped from being driven for a period of time excluding the period of time where the data signals are received by the pixels positioned in the first emission region  120  by utilizing the (a+1)th scan signal SSa+1 to the (a+4)th scan signal SSa+4. As such, the amount of power consumed by the data driver  200  can be reduced. 
         [0063]    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.