Patent Publication Number: US-2019197963-A1

Title: Display driving circuit and brightness control method applied to organic light-emitting diode panel

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a display apparatus; in particular, to a display driving circuit and a brightness control method applied to an organic light-emitting diode (OLED) panel. 
     2. Description of the Prior Art 
     As shown in  FIG. 1 , the organic light-emitting diode panel PL can include (M*N) pixels P 11 ˜PMN, and the display driving circuit of the organic light-emitting diode panel PL can include a data driver DD, a data writing scan line driver WSL and a light-emitting scan line driver LSL, and control the timing of data lines D 1 ˜DM, data writing scan lines W 1 ˜WN and light-emitting scan lines E 1 ˜EN of the organic light-emitting diode panel PL respectively according to the timing controlling signal emitted by the timing controller TCON. 
     As shown in  FIG. 2 , the light-emitting scan line driver LSL includes a brightness controller  10  and a light-emitting scan line generator  12 . The brightness controller  10  is coupled to the light-emitting scan line generator  12  and the light-emitting line generator  12  is coupled to the organic light-emitting diode panel PL. The light-emitting scan line driver LSL is used to control whether each line of the organic light-emitting diode panel PL emits light or not. 
     In fact, A lines of the organic light-emitting diode panel PL are generally selected as a basic unit of light-emitting scanning, where A is a positive integer. For example, a frame period FP in  FIG. 3  includes a single light-emitting period LEP. If the light-emitting period LEP in  FIG. 3  uses four lines as the basic unit of light-emitting scanning, then A=4. Wherein, “ON” represents the turn-on state; “OFF” represents the turn-off state; “W” represents the data writing state. 
     In order to improve the flicker phenomenon that may occur during light-emitting scanning, the frame period FP can include B light-emitting periods, where B is a positive integer. For example, each frame period FP in  FIG. 4  and  FIG. 5  includes four light-emitting periods LEP 1 ˜LEP 4 , namely B=4, and there is a non-light-emitting period NLEP between two adjacent light-emitting periods (e.g., light-emitting periods LEP 1 ˜LEP 2 ), whereby the light-emitting region and the non-light-emitting region of the organic light-emitting diode panel PL can be controlled by a light-emitting scan method having fixed period. 
     However, according to the above, since the width of the conventional light-emitting period LEP must be a multiple of the A lines and the B light-emitting periods included in each frame period FP must be fixed, resulting in that the fineness of fine-tuning a ratio of the light-emitting region to the overall display region is limited, as shown in Table 1. [Table 1 is based on the fineness of 10 bits (1024 levels), and one frame period includes 1920 lines], which needs to be improved. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Ratio of the 
                 Expected 
                 Conventional 
                 Conventional total width 
               
               
                 light-emitting 
                 average light- 
                 average light- 
                 of four light-emitting 
               
               
                 region to the 
                 emitting region 
                 emitting region 
                 regions in a frame period; 
               
               
                 overall  
                 in a frame 
                 in a frame 
                 Width of each of the four 
               
               
                 display 
                 period (Unit: 
                 period (Unit: 
                 light-emitting regions  
               
               
                 region 
                 line) 
                 line) 
                 (Unit: line) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 0/1024 
                 0 
                 0 
                  0; 0/0/0/0 
               
               
                 1/1024 
                 2 
                 0 
                  0; 0/0/0/0 
               
               
                 2/1024 
                 4 
                 0 
                  0; 0/0/0/0 
               
               
                 3/1024 
                 5 
                 0 
                  0; 0/0/0/0 
               
               
                 4/1024 
                 8 
                 0 
                  0; 0/0/0/0 
               
               
                 5/1024 
                 9 
                 16 
                 16; 4/4/4/4 
               
               
                 6/1024 
                 11 
                 16 
                 16; 4/4/4/4 
               
               
                 7/1024 
                 13 
                 16 
                 16; 4/4/4/4 
               
               
                 8/1024 
                 15 
                 16 
                 16; 4/4/4/4 
               
               
                 9/1024 
                 17 
                 16 
                 16; 4/4/4/4 
               
               
                 . . .  
                 . . .  
                 . . .  
                 . . . 
               
               
                   
               
            
           
         
       
     
     SUMMARY OF THE INVENTION 
     Therefore, the invention provides a display driving circuit and a brightness control method applied to an organic light-emitting diode (OLED) panel to solve the above-mentioned problems of the prior arts. 
     A preferred embodiment of the invention is a display driving circuit. In this embodiment, the display driving circuit is coupled to an OLED panel. The display driving circuit includes a brightness controller, a light-emitting scan line adjusting circuit and a light-emitting scan line generator. The brightness controller provides a brightness controlling signal. The light-emitting scan line adjusting circuit includes a first counting unit, a second counting unit and an arrangement unit. The first counting unit provides a frame period counting value. The second counting unit provides a light-emitting period counting value. The arrangement unit is coupled to the brightness controller, the first counting unit and the second counting unit and used to generate an adjusting signal according to the brightness controlling signal, the frame period counting value and the light-emitting period counting value. The light-emitting scan line generator is coupled to the light-emitting scan line adjusting circuit and the OLED panel and used to generate light-emitting scan lines to the OLED panel according to the adjusting signal. 
     In an embodiment, the display driving circuit is a light-emitting scan line driver. 
     In an embodiment, during a light-emitting period, A light-emitting scan lines emit lights, wherein A is a positive integer. 
     In an embodiment, a frame period includes B light-emitting periods, wherein B is a positive integer. 
     In an embodiment, a unit includes C frame periods and an expected total width is total light-emitting region of the C frame periods, wherein C is a positive integer. 
     In an embodiment, values of A, B and C can be adjusted according to different OLED panels or requirements. 
     Another preferred embodiment of the invention is a brightness control method. In this embodiment, the brightness control method is applied to a display driving circuit. The display driving circuit is coupled to an OLED panel. The brightness control method includes following steps of: providing a brightness controlling signal; providing a frame period counting value; providing a light-emitting period counting value; generating an adjusting signal according to the brightness controlling signal, the frame period counting value and the light-emitting period counting value; and generating light-emitting scan lines to the OLED panel according to the adjusting signal. 
     Compared to the prior art, the display driving circuit and the brightness control method according to the invention can adjust the number of light-emitting lines in each light-emitting period, the number of light-emitting periods in each frame period, and the number of frame periods per unit according to different organic light-emitting diode panels or requirements; therefore, the fineness of fine-tuning the light-emitting brightness of the organic light-emitting diode panel can be increased to effectively improve the shortcoming of the prior art cannot finely adjust the light-emitting brightness of the organic light-emitting diode panel, and the flexibility of fine-tuning the brightness of organic light-emitting diode panels can be significantly increased. 
     The advantage and spirit of the invention may be understood by the following detailed descriptions together with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1  illustrates a schematic diagram of the conventional organic light-emitting diode panel and its display driving circuit. 
         FIG. 2  illustrates a schematic diagram of the conventional light-emitting scan line driver coupled to the organic light-emitting diode panel. 
         FIG. 3  illustrates a schematic diagram of the frame period including a single light-emitting period. 
         FIG. 4  and  FIG. 5  illustrate schematic diagrams of the frame period including a plurality of periodic light-emitting periods. 
         FIG. 6  illustrates a schematic diagram of the display driving circuit applied to the organic light-emitting diode panel in a preferred embodiment of the invention. 
         FIG. 7  illustrates a flowchart of the brightness control method applied to the organic light-emitting diode panel in another preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the invention is a display driving circuit. In this embodiment, the display driving circuit is a light-emitting scan line driver, but not limited to this. 
     Please refer to  FIG. 6 .  FIG. 6  illustrates a schematic diagram of the display driving circuit applied to the organic light-emitting diode panel in this embodiment. 
     As shown in  FIG. 6 , the display driving circuit LSL is coupled to the organic light-emitting diode panel PL. The display driving circuit LSL includes a brightness controller  20 , a light-emitting scan line adjusting circuit  21  and a light-emitting scan line generator  22 . The brightness controller  20  is coupled to the light-emitting scan line adjusting circuit  21 ; the light-emitting scan line adjusting circuit  21  is coupled to the brightness controller  20  and the light-emitting scan line generator  22  respectively; the light-emitting scan line generator  22  is coupled to the light-emitting scan line adjusting circuit  21  and the organic light-emitting diode panel PL respectively. 
     The main function of the brightness controller  20  is to set and control the brightness of the display to provide a brightness controlling signal to the light-emitting scan line adjusting circuit  21 . 
     The light-emitting scan line adjusting circuit  21  includes an arrangement unit  210 , a first counting unit  212  and a second counting unit  214 . The arrangement unit  210  is coupled to the brightness controller  20 , the first counting unit  212 , the second counting unit  214  and the light-emitting scan line generator  22  respectively. The first counting unit  212  is coupled to the arrangement unit  210 . The second counting unit  214  is coupled to the arrangement unit  210 . 
     The first counting unit  212  is used to count frame periods to provide a frame period counting value to the arrangement unit  210 . The second counting unit  214  is used to count light-emitting periods to provide a light-emitting period counting value to the arrangement unit  210 . 
     When the arrangement unit  210  receives the brightness controlling signal, the frame period counting value and the light-emitting period counting value, the arrangement unit  210  will generate an adjusting signal to the light-emitting scan line generator  22  according to the brightness controlling signal, the frame period counting value and the light-emitting period counting value. Then, the light-emitting scan line generator  22  will generate light-emitting scan lines to the organic light-emitting diode panel PL according to the adjusting signal. 
     In practical applications, when the first counting unit  212  counts frame periods, if one unit includes C frame periods, then the expected total width is the total light-emitting region of the C frame periods, wherein C is a positive integer. When the second counting unit  214  counts light-emitting periods, if each frame period includes B light-emitting periods and during each light-emitting period, A light-emitting scan lines emit lights, wherein A and B are both positive integers. 
     It should be noted that, for the light-emitting scan line adjusting circuit  21  of the display driving circuit LSL of the invention, the light-emitting scan line adjusting circuit  21  can adjust values of the above-mentioned A, B, C according to different organic light-emitting diode panels or requirements respectively. That is to say, the number A of light-emitting scan lines in each light-emitting period, the number of light-emitting periods B in each frame period, and the number C of frame periods per unit can be adjusted according to different organic light-emitting diode panels or requirements. 
     For example, if every four frame periods (e.g., the first frame period˜the fourth frame period) is one unit (e.g., C=4), the expected total width will be the total light-emitting region of the four frame periods, and there are four light-emitting periods in each frame period (e.g., B=4). For different frame periods (e.g., the first frame period˜the fourth frame period), the number of light-emitting scan lines included in each light-emitting period (e.g., A) can be different. 
     If the fineness of 10 bits (1024 levels) is taken as an example, and a frame period is assumed to include 1920 lines, as shown in Table 2. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Total width 
                 Total width 
                 Total width 
                 Total width 
               
               
                   
                   
                   
                 of four light-emitting 
                 of four light-emitting 
                 of four light-emitting 
                 of four light-emitting 
               
               
                   
                   
                   
                 regions in a 
                 regions in a 
                 regions in a 
                 regions in a 
               
               
                   
                   
                 Average 
                 first frame period 
                 second frame period 
                 third frame period 
                 fourth frame period 
               
               
                 Ratio of the 
                 Expected average 
                 light-emitting 
                 in the invention; 
                 in the invention; 
                 in the invention; 
                 in the invention; 
               
               
                 light-emitting 
                 light-emitting 
                 region in a 
                 Width of each of the 
                 Width of each of the 
                 Width of each of the 
                 Width of each of the 
               
               
                 region to the 
                 region in a 
                 frame period 
                 four light-emitting 
                 four light-emitting 
                 four light-emitting 
                 four light-emitting 
               
               
                 overall 
                 frame period 
                 in the invention 
                 regions 
                 regions 
                 regions 
                 regions 
               
               
                 display region 
                 (Unit: line) 
                 (Unit: line) 
                 (Unit: line) 
                 (Unit: line) 
                 (Unit: line) 
                 (Unit: line) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 0/1024 
                 0 
                 0 
                  0; 0/0/0/0 
                 0; 0/0/0/0 
                 0; 0/0/0/0 
                 0; 0/0/0/0 
               
               
                 1/1024 
                 2 
                 2 
                  4; 4/0/0/0 
                 0; 0/0/0/0 
                 4; 4/0/0/0 
                 0; 0/0/0/0 
               
               
                 2/1024 
                 4 
                 4 
                  4; 4/0/0/0 
                 4; 4/0/0/0 
                 4; 4/0/0/0 
                 4; 4/0/0/0 
               
               
                 3/1024 
                 5 
                 5 
                  8; 4/0/4/0 
                 4; 4/0/0/0 
                 4; 4/0/0/0 
                 4; 4/0/0/0 
               
               
                 4/1024 
                 8 
                 8 
                  8; 4/0/4/0 
                 8; 4/0/4/0 
                 8; 4/0/4/0 
                 8; 4/0/4/0 
               
               
                 5/1024 
                 9 
                 9 
                 12; 4/4/4/0 
                 8; 4/0/4/0 
                 8; 4/0/4/0 
                 8; 4/0/4/0 
               
               
                 6/1024 
                 11 
                 11 
                 12; 4/4/4/0 
                 12; 4/4/4/0  
                 12; 4/4/4/0  
                 8; 4/0/4/0 
               
               
                 7/1024 
                 13 
                 13 
                 16; 4/4/4/4 
                 12; 4/4/4/0  
                 12; 4/4/4/0  
                 12; 4/4/4/0  
               
               
                 8/1024 
                 15 
                 15 
                 16; 4/4/4/4 
                 16; 4/4/4/4  
                 16; 4/4/4/4  
                 12; 4/4/4/0  
               
               
                 9/1024 
                 17 
                 17 
                 20; 8/4/4/4 
                 16; 4/4/4/4  
                 16; 4/4/4/4  
                 16; 4/4/4/4  
               
               
                 . . . 
                 . . . 
                 . . . 
                 . . . 
                 . . . 
                 . . . 
                 . . . 
               
               
                   
               
            
           
         
       
     
     As shown in Table 2, in the invention, the light-emitting period widths of different frame periods (e.g., the first frame period˜the fourth frame period) can be different, that is to say, the number of light-emitting scan lines included in the light-emitting period can be different. 
     It should be noted that the average number of lines included in a light-emitting region of one frame period can be consistent with the expected average number of lines included in a light-emitting region of one frame period; that is to say, the invention can adjust the brightness of the OLED panel more finely, so that the disadvantages of the prior art shown in Table 1 that the brightness of the OLED panel cannot be finely adjusted under some light-emitting region ratios can be effectively improved, thereby the flexibility of fine-tuning the brightness of organic light-emitting diode panels can be significantly increased. 
     Another embodiment of the invention is a brightness control method. In this embodiment, the brightness control method is applied to the display driving circuit, and the display driving circuit is a light-emitting scan line driver, but not limited to this. The display driving circuit is coupled to the organic light-emitting diode panel. 
     Please refer to  FIG. 7 .  FIG. 7  illustrates a flowchart of the brightness control method applied to the organic light-emitting diode panel in this embodiment. 
     As shown in  FIG. 7 , the brightness control method applied to the organic light-emitting diode panel includes the following steps: 
     Step S 10 : providing a brightness controlling signal; 
     Step S 12 : providing a frame period counting value; 
     Step S 14 : providing a light-emitting period counting value; 
     Step S 16 : generating an adjusting signal according to the brightness controlling signal, the frame period counting value and the light-emitting period counting value; and 
     Step S 18 : generating light-emitting scan lines to the OLED panel according to the adjusting signal. 
     Compared to the prior art, the display driving circuit and the brightness control method according to the invention can adjust the number of light-emitting lines in each light-emitting period, the number of light-emitting periods in each frame period, and the number of frame periods per unit according to different organic light-emitting diode panels or requirements; therefore, the fineness of fine-tuning the light-emitting brightness of the organic light-emitting diode panel can be increased to effectively improve the shortcoming of the prior art cannot finely adjust the light-emitting brightness of the organic light-emitting diode panel, and the flexibility of fine-tuning the brightness of organic light-emitting diode panels can be significantly increased. 
     With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.