Patent Publication Number: US-2011074836-A1

Title: Display driver capable of selectively providing gamma correction and display apparatus using same

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure relates to flat panel display (FPD) technology, and more particularly, to a display driver capable of selectively providing gamma correction, and a display apparatus using the display driver. 
     2. Description of Related Art 
     FPDs are widely used in various portable information products, such as notebooks, personal digital assistants, video cameras, and the like. 
     A typical FPD includes a display panel activated by a driver application. Due to photoelectric characteristics of a display panel, color temperature of the display panel may deviate from a desired value, which may impair display quality of the FPD. 
     Gamma correction is one technique that can be utilized to adjust the color temperature of the FPD. Often, a gamma correction function module can be integrated in the driver of the FPD, for example, a gamma correction table is pre-configured in the driver. When an RGB signal is provided to the driver, the driver reads a corresponding gamma correction value from the gamma correction table, and then performs a gamma correction operation on the RGB signal. Moreover, the gamma-corrected RGB signal is further converted to a data voltage, and output to the display panel to drive a pixel unit to display a corresponding picture element. 
     Some types of FPD, however, may not require this gamma correction capability, and may, for example, utilize other techniques for color temperature adjustment. Because the existing gamma correction function module is integrated in the driver, the driver is incompatible with FPDs without gamma correction capability. Therefore, to a display apparatus manufacturer, different drivers must be prepared to meet different requirements of gamma correction capability of FPDs. This complicates manufacture and management thereof. 
     What is needed, therefore, is an LCD that can overcome the described limitations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead placed upon clearly illustrating the principles of at least one embodiment. In the drawings, like reference numerals designate corresponding parts throughout the various views. 
         FIG. 1  is a block diagram of a display apparatus according to an embodiment of the present disclosure, the display apparatus including a display driver. 
         FIG. 2  illustrates one embodiment of operation of the display driver and the display apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings to describe certain exemplary embodiments of the present disclosure in detail. 
       FIG. 1  is a block diagram of a display apparatus  100  according to an embodiment of the present disclosure. The display apparatus  100  may include a scaler  3 , a display driver  4 , a memory  10 , and a display panel  5 . The display driver  4  is electrically coupled between the scaler  3  and the display panel  5 , and the display driver  4  is also electrically coupled to the memory  10 . 
     The display panel  5  may be a flat display panel such as a liquid crystal panel, which is adapted to display pictures according to data signals output by the display driver  4 . 
     The memory  10  may include a gamma correction table  11 . The gamma correction table  11  includes a plurality of entries, each corresponding to a respective gray level of the display panel  5 . The gamma correction table  11  is used to indicate mapping relations between the gray levels and corresponding gamma correction values. The gamma correction table  11  can be read by the display driver  4 , such that the display driver  4  can perform gamma correction operations on received RGB signals according to gray levels of the RGB signals. In the illustrated embodiment, the memory  10  is an element independent from the display driver  4 , it is noted, however, that in an alternative embodiment, the memory may also be integrated inside the display driver, that is, be configured as an internal element of the display driver  4 . 
     The scaler  3  is adapted to provide scaled RGB signals to the display driver  4 . The scaler  3  may also provide a control signal to the display driver  4 , and the control signal is used to notify the display driver  4  of whether to perform the gamma correction operation on the received RGB signals. In one embodiment, the control signal may have a constant value, which can be preset. In an alternative embodiment, the control signal may be variable, generated by the scaler  3  according to the RGB signals output to the display driver  4 . 
     The display driver  4  is adapted to provide data signals to the display panel  5  in accordance with a predetermined timing, and drive the display panel  5  to display pictures by use of the data signals. The data signals may be generated by the display driver  4  based on the RGB signals output from the scaler  3 . Moreover, before the RGB signals are converted to the data signals, the display driver  4  may selectively perform the gamma correction operations on the RGB signals, for example, in an exemplary embodiment, the gamma correction operations can be activated or deactivated by a control signal output from the scaler  3 . In addition, the display driver  4  may be a timing controller or a data driver, in the illustrated embodiment, the timing controller is used as an example. 
     To implement the selective performance of the gamma correction operations, in one embodiment, as shown in  FIG. 1 , the display driver  4  includes a data selector  14 , a data processor  16 , and a storage unit  12 . The storage unit  12  may pre-store information about nonperformance of gamma correction, for example, a preset digital code, which may have a format similar to that of the gamma correction values of the gamma correction table  11  in the memory  10 . The data selector  14  is electrically coupled to the memory  10  and the storage unit  12 , and includes a control terminal  140  for receiving the control signal. The data selector  14  can receive the preset digital code from the storage unit  12  and a corresponding gamma correction value from the gamma correction table  11 , and selectively output the preset digital code or the corresponding gamma correction value under the control of the control signal. The data processor  16  is adapted to selectively perform the gamma correction operation on the RGB signals according to the information output by the data selector  14 , and convert the RGB signals to the data signals. 
     Referring to  FIG. 2 , in operation, firstly, the data selector  14  receives a control signal from the scaler  3  (step S 102 ). The control signal can be a one-bit digital signal, which can be a high level voltage (represented as “1”) or a low level voltage (represented as “0”). Secondly, the data selector  14  determines an electrical level of the control signal, and selectively read information from a corresponding one of the memory  10  and the storage unit  12  (step S 104 ). Thirdly, the data processor  16  processes the RGB signals according the information read by the data selector  14  (step S 106 ). 
     In detail, when the control signal is the high level voltage (i.e., the control signal has a first value of “1”), the display driver  4  is activated to perform gamma correction. Accordingly, the data selector  14  reads a corresponding gamma correction value from the gamma correction table  11 , and then outputs the gamma correction value to the data processor  16 . The data processor  16  further performs a gamma correction operation on the RGB signal based on the gamma correction value, and then converts the RGB signal to a corresponding data signal, and output the data signal to the display panel  5 , so as to enable the display panel to display a picture. 
     When the control signal is the low level voltage (i.e., the control signal has a second value of “0”), the display driver  4  is deactivated to perform the gamma correction operation. Accordingly, the data selector  14  reads the preset digital code from the storage unit  12 , and then outputs the preset digital code to the data processor  16 . Upon obtaining the preset digital code, the data processor  16  is directed to not perform the gamma correction operation on the RGB signal, and thus the data processor  16  directly converts the RGB signal to the data signal and outputs the data signal to the display panel  5 . 
     In the display apparatus  100  as described, as can be seen, the memory  10 , the storage unit  12 , and the data selector  14  cooperatively serve as a gamma correction control module directing the data processor  16  to selectively perform the gamma correction operation on the RGB signals, in response to a control signal. In the illustrated embodiment, as above, the control signal is provided by the scaler  3 , however, the control signal may alternatively be provided by other components in the display apparatus  100 , such as a microprocessor unit. 
     It is noted that when the control signal is preset as a constant, for example, constant “1”, the display driver  4  is controlled to continue the gamma correction operation on the RGB signals once the display apparatus  100  is powered on. Similarly, when the control signal is preset as constant “0”, the display driver  4  is directed to bypass any gamma correction operation on the RGB signal. 
     Furthermore, in an alternative embodiment, the gamma correction table  11  may include a plurality of sub-tables. The, for example, three sub-tables may be respectively named as a first sub-table, a second sub-table, and a third sub-table. Correspondingly, the control signal output by the scaler  3  may be a 2-bit digital signal, which can be represented as (0, 0), (0, 1), (1, 0), or (1, 1). In particular, a (0, 0) control signal indicates no gamma correction operation is to be performed, accordingly, the data selector  14  reads the preset digital code from storage unit  12 , and the data processor  16  directly converts the RGB signal to the data signal upon receiving the preset digital code. 
     A control signal of (1, 1) indicates a gamma correction value in the first sub-table is to be selected for gamma correction. Accordingly, the data selector  14  reads a gamma correction value from the first sub-table, and the data processor  16  converts the RGB signal to the data signal based on the gamma correction value selected by the data selector  14  from the first sub-table. A control signal value of (1, 0) indicates a gamma correction value in the second sub-table is to be selected for gamma correction, and a value of (0, 1) indicates a gamma correction value in the third sub-table is to be selected for gamma correction. 
     According to the disclosure, it can be seen that because the data processor  16  of the display driver  4  can selectively perform the gamma correction operation on the RGB signals according to the control signal, the display driver  4  can be used in a variety of display apparatuses, irrespective of whether gamma correction operation is to be performed, simplifying management of components manufacture. 
     It is to be further understood that even though numerous characteristics and advantages of a preferred embodiment have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.