Abstract:
A display device and a driving method thereof where different sounds are output depending upon characteristics of display images. The display device includes a display unit having a plurality of pixels, a signal controller, and a sound controller. The display unit displays images by selectively activating pixels from among the plurality of pixels in accordance with input video signals and input image control signals. The signal controller reads the input video signals to generate on-pixel signals having information about a ratio of a number of the activated pixels compared to a total number of pixels in the plurality of pixels per each frame and generating a sound output start signal. The sound controller determines a range from among predetermined ratio ranges corresponding to the ratio of the number of active pixels to define a plurality of volume levels, and determining the volume level corresponding to the on-pixel signal so as to generate a sound output instruction signal corresponding to the determined volume level.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0050484, filed Jun. 8, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Aspects of the present invention relate generally to a display device and a driving method thereof, and more particularly, to an organic light emitting diode (OLED) display and a method of driving the same. 
     2. Description of the Related Art 
     A display device has a display area including a plurality of pixels arranged on a substrate in the form of a matrix and scan and data lines connected to the respective pixels. Data signals are selectively applied to the pixels to display desired images. The display devices are classified into passive and active matrix types, depending upon the method of driving the pixels. With consideration to resolution, contrast, and response time, the trend is towards using the active matrix type display device where the respective unit pixels are selectively turned on or off. 
     The display device is used as a display unit for a personal computer, a portable phone, a PDA, and other mobile information devices, or as a monitor for various kinds of information systems or other similar devices. A liquid crystal panel-based LCD, an organic light emitting diode (OLED) display, a plasma panel-based PDP, or other similar displays, are well known. 
     Various kinds of emissive display devices, which are smaller and weigh less than CRTs, have been recently developed, and particularly, the organic light emitting diode display has come to the forefront because it provides improved in emissive efficiency, luminance, and viewing angle, and has a short response time. 
     However, a problem with such display devices is that when still images such as photographs are displayed without any sound or audio information, they user experience in viewing such photographs may be diminished. 
     The above information disclosed in this Background section is only for enhancement of invention understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     Aspects of the present invention provide a display device and a driving method thereof having advantages of outputting different sounds depending upon characteristics of display images. 
     Aspects of the present invention provide a display device including a display unit having a plurality of pixels, a signal controller, and a sound controller. The display unit displays images by selectively activating pixels from among the plurality of pixels in accordance with input video signals and input image control signals. The signal controller reads the input video signals to generate on-pixel signals having information about a ratio of a number of the active pixels compared to a total number of pixels in the plurality of pixels per each frame and generating a sound output start signal. The sound controller determines a range from among predetermined ratio ranges corresponding to the ratio of the number of active pixels to define a plurality of volume levels, and determining the volume level corresponding to the on-pixel signal to generate a sound output instruction signal corresponding to the determined volume level. The input image control signals include a vertical synchronization signal, and the signal controller generates the sound output start signal in synchronization with the vertical synchronization signal. A sound output unit outputs the sound corresponding to the sound output instruction signal in accordance with the sound output start signal. The sound controller generates a plurality of sound output instruction signals to output different sounds corresponding to the plurality of steps, respectively. One of the plurality of sound output instruction signals is a signal instructing to output no sound. 
     Aspects of the present invention provide a method of driving a display device such that a plurality of pixels are selectively activated in accordance with input video signals and input image control signals to display images. The input video signals are read so as to generate on-pixel signals having information about a ratio of the number of active pixels to a total number of pixels in the plurality of pixels per each frame. A range from among predetermined ratio ranges is determined to correspond to the ratio of the number of activate pixels to define a plurality of volume levels. The volume level corresponding to the on-pixel signal is determined, and a sound output instruction signal corresponding to the determined volume level is generated. The input image control signals include a vertical synchronization signal and a sound output start signal is generated in synchronization with the vertical synchronization signal. A sound corresponding to the sound output instruction signal is output in accordance with the sound output start signal. 
     According to aspects of the present invention, different sounds may be output depending upon the characteristics of the display images. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a block diagram of a display device according to an exemplary embodiment; 
         FIG. 2  is an equivalent circuit diagram of the pixel PX shown in  FIG. 1 ; and 
         FIG. 3  is a flowchart illustrating a method of driving a display device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
     Herein, when a first element is described as being connected to a second element, the first element may be directly connected to the second element or may be electrically connected or indirectly connected to the second element via a third element. 
       FIG. 1  is a block diagram of a display device according to an exemplary embodiment, and  FIG. 2  is an equivalent circuit diagram of the pixel PX shown in  FIG. 1 . 
     Referring to  FIG. 1 , a display device according to an exemplary embodiment includes a display unit  100 , a scan driver  200 , a data driver  300 , a signal controller  400 , a sound controller  500 , and a sound output unit  600 . From the viewpoint of an equivalent circuit, the display unit  100  includes a plurality of signal lines S 1  to Sn and D 1  to Dm, and a plurality of pixels PX connected to those signal lines and arranged roughly in the form of a matrix. The signal lines S 1  to Sn and D 1  to Dm include a plurality of scan lines S 1  to Sn for transmitting scan signals, and a plurality of data lines D 1  to Dm for transmitting data voltages. The scan lines S 1  to Sn extend roughly in the pixel row direction while standing substantially parallel to each other, and the data lines D 1  to Dm extend roughly in the pixel column direction while standing substantially parallel to each other. 
     Referring to  FIG. 2 , each pixel PX, for example the pixel PXij connected to the i-th (i=1, 2, . . . , n) scan line Si and the j-th (j=1, 2, . . . , m) data line Dj, includes an organic light emitting element OLED, a driving transistor M 1 , a capacitor Cst, and a switching transistor M 2 . 
     The driving transistor M 1  has a control terminal, an input terminal, and an output terminal. The control terminal of the driving transistor M 1  is connected to the switching transistor M 2 , while the input terminal of the driving transistor M 1  is connected to a driving voltage VDD and the output terminal of the driving transistor M 1  is connected to the organic light emitting element OLED. The driving transistor M 1  outflows an electric current IOLED of varying amplitude according to the voltages held between the control and output terminals. 
     The switching transistor M 2  has a control terminal, an input terminal, and an output terminal. The control terminal of the switching transistor M 2  is connected to the scan line Si, while the input terminal the switching transistor M 2  is connected to the data line Dj and the output terminal the switching transistor M 2  is connected to the driving transistor M 1 . The switching transistor M 2  transmits a data signal, that is, a data voltage, from the data line Dj in response to the scan signal applied to the scan line Si. 
     The capacitor Cst is connected between the control and input terminals of the driving transistor M 1 . The capacitor Cst is charged by and stores the data voltage applied to the control terminal of the driving transistor M 1 . 
     The organic light emitting element OLED, which may be an organic light emitting diode (OLED), has an anode connected to the output terminal of the driving transistor M 1  and a cathode connected to a common voltage VSS. The organic light emitting element OLED emits light of varying intensity according to the electric current IOLED supplied from the driving transistor M 1  so as to display an image. 
     The organic light emitting element OLED may emit light of one of the primary colors red, green, and blue, and the desired color may be expressed by a spatial or temporal sum of the three primary colors. Some of the organic light emitting element OLED may emit light of a white color so as to heighten the luminance. Alternatively, the organic light emitting elements OLED of each of the respective pixels PX may emit light of a white color, and in this case, some of the pixels PX of the display unit  100  may further include a color filter (not shown) for converting the white-colored light from the organic light emitting elements OLED into any one of the primary colors. 
     The driving transistor M 1  and the switching transistor M 2  are p-channel field effect transistors (FET). In this case, the control terminal, the input terminal, and the output terminal correspond to the gate, the source, and the drain, respectively. However, at least one of the switching transistor M 2  and the driving transistor M 1  may be an n-channel field effect transistor. Furthermore, the transistors M 1  and M 2 , the capacitor Cst, and the organic light emitting element OLED may be changed in interconnection. The pixel PXij shown in  FIG. 2  illustrates a pixel of a display device, and another pixel having a different structure with at least two transistors or at least one capacitor may be used instead. 
     Referring to  FIG. 1  again, the scan driver  200  is connected to the scan lines S 1  to Sn of the display unit  100 , and sequentially applies scan signals to the scan lines S 1  to Sn in accordance with the scan control signals CONT 1 . The scan signals include a gate-on voltage Von (not shown) for turning on the switching transistor M 2 , and a gate-off voltage Voff (not shown) for turning off the switching transistor M 2 . When the switching transistor M 2  is a p-channel field effect transistor, the gate-on voltage Von and the gate-off voltage Voff are low and high voltages, respectively. 
     The data driver  300  is connected to the data lines D 1  to Dm of the display unit  100  and converts the data signals DR, DG, and DB input from the signal controller  400  into data voltages in accordance with the data control signals CONT 2  so as to apply them to the data lines D 1  to Dm. 
     The signal controller  400  receives input signals IS, horizontal synchronization signals Hsync, vertical synchronization signals Vsync, and main clock signals MCLK from the outside, and generates image data signals DR, DG, and DB, scan control signals CONT 1 , data control signals CONT 2 , and sound control signals CONT 3 . The scan control signals CONT 1  include a scan start signal STV, and at least one clock signal for controlling the output cycle of the gate on voltage Von. The scan control signals CONT 1  may further include an output enable signal OE for defining the duration time of the gate on voltage Von. The data control signals CONT 2  include horizontal synchronization start signals STH for starting the transmission of image data signals DR, DG, and DB with respect to a row of pixels PX to the data driver  300 , and load signals LOAD for applying data voltages to the data lines D 1  to Dm. The sound control signals CONT 3 , according to an exemplary embodiment, include sound output start signals (SOUT) for instructing to output the sound in synchronization with the vertical synchronization signals Vsync, and on-pixel signals (OPS) containing information about the number of turned-on pixels within one frame. The on-pixel signal (OPS) represents a percent ratio of the number of turned-on pixels compared to the total number of pixels PX in the display unit  100 . For example, when the total number of pixels in the display unit  100  is 100, the on-pixel signal (OPS) represents a percent ratio of 10% when the number of turned-on pixels within one frame is 10. 
     The sound controller  500  defines a plurality of ranges for the ratio of the number of turned-on pixels PX compared to the total number of the pixels level by level, and detects the level corresponding to the ratio of on-pixel signals (OPS). The sound controller  500  generates a plurality of sound output instruction signals SS 1  to SS 10  such that they correspond to the detected levels. In the present exemplary embodiment, the sound controller  500  defines the levels corresponding to the ratios of the turned-on pixels PX to all of the pixels PX by the unit of 10%. That is, a first level is made when the ratio of the turned-on pixels PX to all of the pixels PX ranges from 0% to less than 10%, and a second step is made when the ratio of the turned-on pixels PX to all of the pixels PX ranges from 10% to less than 20%. Similarly, a tenth step is made when the ratio of the turned-on pixels PX to all of the pixels PX ranges from 90% to 100%. In this way, the ratio of the turned-on pixels PX to all of the pixels PX is demarcated in range step by step. The embodiment is not limited thereto, and the ratio range of the turned-on pixels may increase or decrease per the respective steps. For example, when the ratio of the turned-on pixels PX to all of the pixels PX is defined by the unit of 20%, five steps are made. The plurality of sound output instruction signals SS 1  to SS 10  are signals that correspond to the first to tenth steps, respectively, and make different sounds including no sound output. 
     The sound output unit  600  outputs a sound corresponding to the sound output instruction signal selected from the plurality of sound output instruction signals SS 1  to SS 10  in accordance with the sound output start signal (SOUT). 
       FIG. 3  is a flowchart illustrating a method of driving a display device according to an exemplary embodiment. 
     Referring to  FIG. 3 , the signal controller  400  detects the number of turned-on pixels PX from the input signals IS per each frame, and computes the ratio of the turned-on pixels PX to all of the pixels PX, with a first step S 11 . The computed ratio is output by the on-pixel signal (OPS). Thereafter, the sound controller  500  detects the step coinciding with the ratio computed at the first step S 11 . Specifically, the sound controller  500  judges whether the ratio computed at the first step S 11  is in the range of 0% to less than 10%, with a second step S 12 . When it is judged that the ratio computed at the first step S 11  is in that range, the sound controller  500  generates a first sound output instruction signal SS 1 , with a third step S 13 . When the ratio computed at the first step S 11  is not in that range, a fourth step S 14  is made. The sound controller  500  judges with the fourth step S 14  whether the ratio computed at the first step S 11  is in the range of 10% to less than 20%. When it is judged that the ratio computed at the first step S 11  is in that range, the sound controller  500  generates a second sound output instruction signal SS 2 , with a fifth step S 15 . When the ratio computed at the first step S 11  is not in that range, a sixth step S 16  is made. This process is conducted repeatedly. Finally, the sound controller  500  judges with a twentieth step S 30  whether the ratio computed at the first step S 11  is in the range of 90% to 100%. When it is judged that the ratio computed at the first step S 11  is in that range, the sound controller  500  generates a tenth sound output instruction signal SS 10 , with a twenty-first step S 31 . 
     As described above, with a display device and a driving method thereof according to an exemplary embodiment, different sounds are output in accordance with the ratio of the turned-on pixels computed from the video signals per each frame so that the sounds corresponding to the characteristics of the display images can be heard. Furthermore, the sounds may be diversified in kind by controlling the range of demarcating the ratio of turned-on pixels. 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.