Patent Publication Number: US-2012044360-A1

Title: Deterioration sensing apparatus for display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0080662 filed on Aug. 20, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a deterioration sensing apparatus for a display device, and more particularly, to a deterioration sensing apparatus for a display device capable of rapidly sensing deterioration by pre-charging a sensing voltage in an adjacent pixel while a deterioration of a single pixel is sensed in a display device having a plurality of pixels, in particular, an organic light emitting diode panel. 
     2. Description of the Related Art 
     Generally, a display device has been used for electronic devices in order to display images desired by a user, operational states of the electronic devices, and the like. 
     In the case of display devices, there exist a cathode ray tube (CRT) type display device that is a long-established device, a general display device such as a liquid crystal display (LCD) that has a smaller thickness than that of the PET type display device, and a display device adopting organic light emitting diodes (i.e., an OLED display). The OLED display is capable of achieving a reduction In thickness and weight of approximately ⅓, while remarkably increasing an image-quality reaction rate, as compared to those of the liquid crystal display, in order to adapt to the increased demand for large display devices having a small volume. 
     The OLED display is classified into a passive type and an active type according to a driving mode thereof. In particular, the active type OLED display, capable individually controlling pixels, the minimum units forming a screen, is in widespread use. 
     The OLED display exhibits excellent performance in terms of image quality, thickness, weight, brightness, power consumption, and the like, as compared to the existing liquid crystal display. 
     However, an OLED display as well as the liquid crystal display, needs Lo display an image desired by a user on a screen thereof; however, such a display may fail to display images having uniform luminance due to a deterioration phenomenon in which luminance of light is gradually lowered over time in response to the same data signal. 
     Therefore, there is a need to sense a deterioration in each pixel of the display device and appropriately compensate for each of the deteriorated pixels. However, sensing a deterioration in each pixel is a time-consuming operation. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a deterioration sensing apparatus for a display device capable of rapidly sensing deterioration by pre-charging a sensing voltage in an adjacent pixel while a deterioration of a single pixel is sensed in a display device having a plurality of pixels, in particular, an organic light emitting diode panel. 
     There is provided a deterioration sensing apparatus, including: a power supply unit transferring a preset current for deterioration sensing: a pixel unit including a plurality of pixel groups adjacent to each other, each of the plurality of pixel units receiving the current for deterioration sensing from the power supply unit; a transfer unit including a plurality of switch groups corresponding to each of the plurality of pixel groups, and transferring the current for deterioration sensing from the power supply unit to each pixel group of the plurality of pixel groups to sequentially sense a voltage, wherein, while transferring the current for deterioration sensing to a corresponding pixel group of the plurality of pixel groups to thereby sense a voltage, the transfer unit previously transfers the current for deterioration sensing to a next pixel group adjacent to the corresponding pixel group; and an analog-digital converter sequentially detecting the voltage of the pixel groups receiving the current for deterioration sensing among the plurality of pixel groups in the pixel unit and converting the voltage into a digital signal. 
     Each of the plurality of pixel groups may have a red pixel, a green pixel, and a blue pixel. 
     The transfer unit may previously transfer the current for deterioration sensing, being transferred to the corresponding pixel unit of the plurality of pixel groups, to a pixel of the red, green and blue pixels of the next pixel group having the same color as a pixel of the red, green and blue pixels of the corresponding pixel group being supplied with the current for deterioration sensing therefrom. 
     Each of the plurality of switch groups of the transfer unit may include a plurality of switches transferring the current for deterioration sensing from the power supply unit to a corresponding pixel of the red, green and blue pixels, and previously transferring the current for deterioration sensing to the pixel of the next pixel group having the same color as the the pixel of the corresponding pixel group. 
     The analog-digital converter may convert the voltage of a pixel group of the plurality of pixel groups, initially supplied with the current for deterioration sensing through the transfer unit, into a digital signal, and convert a voltage difference between the pixel unit, supplied with the current for deterioration sensing after the pixel unit initially supplied with the current for deterioration sensing among the plurality of pixel groups, and the previous pixel unit thereof into a digital signal. 
     The transfer unit may previously transfer the current for deterioration sensing to the adjacent pixel group to the corresponding pixel group being supplied with the current for deterioration sensing therethrough, and then, charge or discharge the current for deterioration sensing to the adjacent pixel group. 
     Each of the red, green and blue pixels may be configured of an organic light emitting diode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram schematically showing the configuration of a deterioration sensing apparatus according to an exemplary embodiment of the present invention; 
         FIGS. 2A to 2C  are diagrams showing operational examples of the deterioration sensing apparatus according to the exemplary embodiment of the present invention; 
         FIG. 3  is a diagram showing an example of voltage sensing of the deterioration sensing apparatus according to the exemplary embodiment of the present invention; and 
         FIG. 4A  is a table showing a sensing time of a deterioration sensing apparatus according to the related art, and  FIG. 4B  is a table showing a sensing time of the deterioration sensing apparatus according to the exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a diagram schematically showing the configuration of a deterioration sensing apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a deterioration sensing apparatus  100 , according to an exemplary embodiment of the present invention, maybe configured to include a power supply unit  110 , a transfer unit  120 , a pixel unit  130 , an analog-converting unit  140 , and a controller  150  controlling the transfer unit  120 . 
     The power supply unit  110  may supply a preset current for deterioration sensing (hereinafter, a sensing current). The power supply unit  110 , when transferring the sensing current to the pixel unit  130 , may charge or discharge extra sensing current due to voltage differences between a plurality of pixel groups  131 ,  132 , and  133  in the pixel unit  130 . To this end, the power supply unit  110  may be configured to include R current sources i 1 , i 2 , i 3 , and i 4  for charging and discharging, and switches Si 1 , Si 2 , Si 3 , and Si 4  for switching charging and discharging paths. 
     The transfer unit  120  may be configured to include a plurality of switch groups  121   a,    121   b,    121   c,    122   a,    122   b,    122   c,  and  123   a.  The plurality of switch groups  121   a,    121   b,    121   c,    122   a,    122   b,    122   c,  and  123   a  correspond to a corresponding one of the plurality of pixel groups  131 ,  132 , and  133 . In this case, the pixel groups  131 ,  132 , and  133  include respective sets of red, blue and green pixels R 1 , R 2 , R 3 , G 1 , G 2 , B 1  and B 2 . The plurality of switch groups  121   a,    121   b,    121   c,    122   a,    122   h,    122   c,  and  123   a  correspond to the red, green, blue, red, green blue and red pixels R 1 , G 1 , B 1 , R 2 , G 2 , B 2 , and R 3 , respectively. The above-mentioned red pixels R 1 , R 2 , and R 3 , the green pixels G 1  and G 2 , and the blue pixels B 1  and B 2  may he configured of organic light emitting diodes. 
     Each of the plurality of switch groups  121   a,    121   b,    121   c,    122   a,    122   b,    122   c,  and  123   a,  respectively corresponding to the the red, green, blue, red, green blue and red pixels R 1 , G 1 , B 1 , R 2 , G 2 , B 2 , and R 3 , transfers the sensing current to the corresponding pixel from the power supply unit  110 . In this case, the sensing current may be previously transferred to an adjacent pixel of the corresponding pixel. That is, according to the related art, the sensing current is sequentially transferred to corresponding pixels. On the other hand, the deterioration sensing apparatus  100  according to the exemplary embodiment of the present invention transfers the sensing current to a corresponding pixel while transferring the sensing current to the next pixel, which is to he sensed for deterioration, in advance, so that the time it takes to sense deterioration (hereinafter, sensing time) may be shortened. 
     Therefore, each of the plurality of switch groups  121   a,    121   b,    121   c,    122   a,    122   b,    122   c,  and  123   a  may include a plurality of switches S 1  and S 2  switching sensing-current transfer paths. In this case, the first switch S 1  and the plurality of second switches S 2  may be alternately switched in a single switch group. That is, in order to sense the deterioration of a corresponding pixel, the first switch Si may be turned on and the plurality of second switches S 2  may be opened. Also, in order to transfer the sensing current to an adjacent pixel thereto, the first switch S 1  may he opened and the plurality of second switches S 2  may be turned on. Since a level of the sensing current may be small, a buffer B may be provided to facilitate the inflow of the current. The parasitic resistance component and the parasitic capacitance component of the transfer line transferring the sensing current to the pixels are shown. In addition, a switch SD for driving may be provided in order to transfer driving signals driving the pixels after or before the operation of sensing the deterioration of the pixels. 
     The deterioration of the corresponding pixel is sensed as voltage, which is in turn transferred to the analog-digital converter  140 , and the analog-digital converter  140  converts it into a digital signal, which may be in turn transferred to the outside. 
     The controller  150  may provide a switch control signal, for sequentially operating the switches S 1  and S 2  of the switch groups  121   a,    121   b,    121   c,    122   a,    122   b,    122   c,  and  123   a , to the switches S 1  and S 2  of the switch groups  121   a,    121   b,    121   c,    122   a,    122   h,    122   c,  and  123   a.  In addition, the controller  150  receives the sensing signal from the analog-digital converter  140 , thereby determining the deterioration of pixels. 
       FIGS. 2A to 2C  are diagrams showing operational examples of the deterioration sensing apparatus according to the exemplary embodiment of the present invention. 
     Referring to  FIGS. 1 and 2A , the respective red pixels R 1 , R 2 , R 3 , and R 4  of the plurality of pixel groups  131 ,  132 , and  133  in the pixel unit  130  are illustrated as an example. Even in the case of the green pixel and the blue pixel, the operation is the same and there, the description of the operation of the green pixel and the blue pixel will be omitted. 
     First, the first switch Si of the switch group  121   a  for the first red pixel R 1  is turned on and the plurality of second switches S 2  are opened to sense the deterioration of the first red pixel R 1 . Thereafter, the first switch S 1  is opened and the plurality of second switches S 2  are turned on to previously charge the sensing current in the second red pixel R 2  adjacent to the first red pixel R 1 . To this end, the first switch S 1  of the switch group  122   a  for the second red pixel R 2  is turned on. 
     Thereafter, referring to  FIG. 2B , after the deterioration of the second red pixel R 2  is sensed, the first switch S 1  of the switch group  122   a  for the second red pixel R 2  is opened and the plurality of second switches S 2  are turned on, thereby previously charging the sensing current in the third red pixel R 3  adjacent to the second red pixel R 2 . To this end, the first switch S 1  of the switch group  123   a  for the third red pixel R 3  is turned on. 
     Similarly, referring to  FIG. 2C , after the deterioration of the third red pixel R 3  is sensed, the first switch S 1  of the switch group  123   a  for the third red pixel R 3  is opened and the plurality of second switches S 2  are turned on, thereby previously charging the sensing current in a fourth red pixel R 4  adjacent to the third red pixel R 3 . To this end, the first switch S 1  of the switch group  124   a  for the fourth red pixel R 4  is turned on. Even in the case of the green pixel and the blue pixel, the above-mentioned operation is operated in the same manner and the above-mentioned operation may be sequentially made according to the number of pixels. 
     Meanwhile, the deterioration sensing voltage of the first red pixel R 1  may be sensed as an absolute value, while the deterioration sensing voltages the second to fourth red pixels R 2 , R 3 , and R 4  may be sensed as the relative values to the deterioration sensing voltage of the previous red pixels. 
       FIG. 3  is a diagram showing an example of voltage sensing of the deterioration sensing apparatus according to the exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , when the deterioration voltage Vs 1  of a pixel into which the current for deterioration sensing is initially introduced is compared with with the deterioration voltages Vs 2 , Vs 3 , Vs 4 , Vs 5 , and Vs 6  of the adjacent pixels in sensing the deterioration voltages of the plurality of pixels, the deterioration voltage Vs 1  of the pixel into which the current for deterioration sensing is first introduced is sensed as an absolute value of, while the deterioration voltages Vs 2 , Vs 3 , Vs 4 , Vs 5 , and Vs 6  of the adjacent pixels may be sensed as relative values to the determination voltages of the corresponding previous pixels as the adjacent pixels previously receive the sensing current from the previous pixels. Therefore, the analog-digital converter  140  may vary resolution with respect to the sensed voltages of the pixel into which the sensing current is initially introduced and the sensed voltages of the adjacent pixels, and as a result, the sampling rate of the analog-digital converter  140  may be increased. 
       FIG. 4A  is a table showing a sensing time of a deterioration sensing apparatus according to the related art and  FIG. 4B  is a table showing a sensing time of the deterioration sensing apparatus according to the exemplary embodiment of the present invention. 
     Referring to  FIGS. 4A and 4B , the deterioration sensing apparatus according to the exemplary embodiment of the present invention previously transfers the sensing current to the next pixel of a corresponding pixel group and detects the relative deterioration voltage. Thus, it can be appreciated that the sensing time is reduced to approximately ½ or less and in particular, may be reduced to approximately ¼ or less when the voltage error of 1% is recognized, as compared with the related art in which the deterioration of pixels is sequentially sensed by transferring the sensing current to the pixels. 
     As set forth above, according to exemplary embodiments of the present invention, the determination of a single pixel as sensed for a display device having a plurality of pixels, in particular, an organic light emitting diode panel, while pre-charging a sensing current to an adjacent pixel thereto, such that the deterioration of the pixels can be rapidly sensed. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modification and variation can be made without departing from the spirit and scope of the invention as defined by the appended claims.