Patent Publication Number: US-10789889-B2

Title: Source driver module, display device and method for driving a display panel

Description:
FIELD OF THE INVENTION 
     The present invention relates to a source driver module, a display device, and a method for driving a display panel. Specifically, the present invention relates to a source driver module, a display device, and a method for driving a display panel that increases the image uniformity of the display panel. 
     BACKGROUND OF THE INVENTION 
     Conventional source driver can be divided into two types according to the design of the trace thereof. One type of source driver is disposed on the upper end or the lower end of the display panel, and coupled to each data line through switch units. The source driver outputs pixel data to each data line according to a source signal generator. 
     Another type of source driver has traces connected to every two data lines through the upper end and the lower end of the display panel via switch units. Taking two adjacent data lines for example, one of the two data lines receives pixel data from the upper end of the display panel through a switch unit, and the other data line receives pixel data from the lower end of the display panel through another switch. 
     However, since the traces possess certain resistance, the pixel voltage signal transmitted through the traces to the data lines will not be the same as originally generated by the source signal generator. For instance, with respect to the first type of source driver mentioned above, when the source drivers are all disposed on the lower end of the display panel and output the same pixel voltage to all the pixels of the display panel, then the pixels closer to the lower end of the display panel will receive a pixel voltage higher than that received by the pixels closer to the upper end of the display panel. This is due to the larger resistance exhibited by the longer traces that the pixel voltage signals encounter when transmitted to the pixels closer to the upper end of the display panel. 
     On the other hand, when in the aforementioned second type of source driver, two pixels on the same horizontal level and respectively on two adjacent data lines receive the same pixel voltage signal, then the pixel receiving pixel voltages from the upper end of the display panel will receive a pixel voltage higher than the pixel receiving pixel voltages from the lower end of the display panel. This is because the pixel voltage transmitted through the lower end of the display panel goes through a relatively long data line, and therefore more voltage is consumed during the process, resulting in nonuniformity of brightness in the horizontal direction. 
     The aforementioned issues cause image nonuniformity; hence, conventional source drivers still have room for improvement. 
     SUMMARY OF THE INVENTION 
     In light of the above, one of the objectives of the present invention is to provide a source driver module, a display device, and a method for driving a display panel that reduce image nonuniformity by way of evening out voltage. 
     One embodiment of the present invention provides a source driver module used for driving a display panel. The source driver module comprises a source driver circuit, a first switch, and a second switch. The first switch is coupled between the source driver circuit and a first end of a first data line of the display panel. The second switch is coupled between the source driver circuit and a second end of the first data line of the display panel. The source driver circuit is used for outputting a first voltage signal to the first end of the first data line through the first switch when the display panel displays a first image, and outputting a second voltage signal to the second end of the first data line through the second switch when the display panel displays a second image after displaying the first image. 
     Another embodiment of the present invention provides a display device. The display device comprises a display panel and a source driver module coupled to the display panel. The source driver module comprises a source driver circuit, a first switch, and a second switch. The first switch is coupled between the source driver circuit and a first end of a first data line of the display panel. The second switch is coupled between the source driver circuit and a second end of the first data line of the display panel. The source driver circuit is used for outputting a first voltage signal to the first end of the first data line through the first switch when the display panel displays a first image, and outputting a second voltage signal to the second end of the first data line through the second switch when the display panel displays a second image after displaying the first image. 
     Another embodiment of the present invention provides a method for driving the above-mentioned display panel. The method includes: when the display panel displays the first image, the source driver circuit outputs the first voltage signal to the first end of the first data line through the first switch; and when the display panel displays the second image after displaying the first image, the source driver circuit outputs the second voltage signal to the second end of the first data line through the second switch. 
     To further understand the features and technical content of the present invention, please refer to the following detailed descriptions and drawings related to the present invention. However, the provided drawings are used only for providing reference and descriptions, and are not intended to limit the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the schematic view of a display device according to a first embodiment of the present invention. 
         FIG. 2  shows a flow chart illustrating a method for driving a display panel according to the first embodiment of the first invention. 
         FIG. 3A  shows a schematic view illustrating step S 100  of  FIG. 2  being performed. 
         FIG. 3B  shows a schematic view illustrating step S 102  of  FIG. 2  being performed. 
         FIG. 4  shows a voltage-time diagram of the pixel voltage received by the pixel unit P 11 . 
         FIG. 5  shows a display device according to a second embodiment of the present invention. 
         FIG. 6  shows a flow chart illustrating a method for driving a display panel according to the second embodiment of the present invention. 
         FIG. 7A  shows a schematic view illustrating step S 200  of  FIG. 6  being performed. 
         FIG. 7B  shows a schematic view illustrating step S 202  of  FIG. 6  being performed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention are described below with reference to  FIG. 1  to  FIG. 7B . A person skilled in the art can understand the advantages and effects of the present invention from the description disclosed below. However, the content disclosed below is not intended to limit the protection scope of the present invention. The present invention can be implemented by a person skilled in the art based on different perspectives and applications without departing from the concept and spirit of the present invention. In addition, it should be stated in advance that the accompanying drawings of the present invention are merely used for illustration, and are not drawn according to actual dimensions for sake of clear illustration. Moreover, the same reference number corresponds to the same component. It should also be understood that expressions such as one component is “connected to” or “disposed on” another may mean that the former is either directly or indirectly connected to or disposed on the latter, wherein “connected” may refer to either physical or electrical connection. 
     First Embodiment 
     The first embodiment of the present invention is described below with reference to  FIG. 1  to  FIG. 4 . The device of the present invention will be first explained, and then the description for the method applicable to the device follows. First of all, referring to  FIG. 1 , the first embodiment of the present invention provides a display device D having a source driver module Z and a display panel A. In the present embodiment, the display panel A can be an organic light-emitting panel, and the source driver module Z can be a ramp source driver. Moreover, the display device D can be made a silicon-based, that is, the display device D can be a Si-OLED. However, the present invention is not limited thereto. For example, in other embodiments, the display panel A can also be a thin film transistor display panel. 
     As shown in  FIG. 1 , the display panel A of the present invention includes a plurality of pixel units (P 11 , P 22 , . . . Pnm) arranged in an n by m matrix, in which each column of pixel units are connected in series by each being connected to a data line via a transistor. The source driver module Z further includes a source driver circuit C, a first switch S 1  and a second switch S 2 . The first switch S 1  is coupled between the source driver circuit C and the first end E 1  of the first data line D 1  of the display panel A. The second switch S 2  is coupled between the source driver circuit C and the second end E 2  of the first data line D 1 . The source driver circuit C is used for generating pixel voltage signals required for each pixel units (P 11 , P 22 , . . . Pnm), and outputting the pixel voltage signals to the first data line D 1  through the first switch S 1  or the second switch S 2 . The first switch S 1  and the second switch S 2  turn off to form a conductive path for the current to go through when the source driver circuit C outputs pixel voltages to the first data line D 1 . In practice, line buffers or buffers can be provided between the source driver circuit C and the first switch S 1  and the second switch S 2  so as to store and output voltage signals respectively. That is to say, the structure of the source driver module Z is not limited to the present embodiment. 
     Please refer to  FIG. 2 ,  FIG. 3A , and  FIG. 3B , wherein  FIG. 3A  and  FIG. 3B  illustrate the partial schematic view of the portion of  FIG. 2 . The present embodiment provides a method for driving a display panel including at least step S 100 : when the display panel A displays the first image, the source driver circuit C outputs the first voltage signal V 1  to the first end E 1  of the first data line D 1  through the first switch S 1 ; and step S 102 : when the display panel A displays the second image after displaying the first image, the source driver circuit C outputs the second voltage signal V 2  to the second end E 2  of the first data line D 1  through the second switch S 2 . 
       FIG. 3A  corresponds to step S 100 , in which the display panel A displays the first image wherein the first switch S 1  forms a conductive path so that the first voltage signal V 1  is outputted to the first end E 1  of the first data line D 1 .  FIG. 3B  corresponds to step S 102 , in which the display panel A displays the second image wherein the first switch S 1  is opened and the second switch S 2  is closed to form a conductive path so that the second voltage signal V 2  is outputted the second end E 2  of the first data line D 1 . For instance, the first voltage signal V 1  and the second voltage signal V 2  in  FIG. 3A  and  FIG. 3B  are generated by the source driver circuit C to be outputted to the pixel unit P 11 . After the first voltage signal V 1  is outputted into the first data line D 1 , the voltage signal goes through the trace resistance r between the first end E 1  and the pixel unit P 11  before being received by the pixel unit P 11 . After the second voltage signal V 2  is outputted into the first data line D 1 , the voltage signal goes through the n units of trace resistance r between the second end E 2  and the pixel unit P 11  before being received by the pixel unit P 11 . 
     Please refer to  FIG. 4 , which shows a voltage-time diagram of the pixel unit P 11  of  FIG. 3A  and  FIG. 3B . Specifically, when the first image is shown and the first voltage signal V 1  is received by the pixel unit P 11 , the actual voltage value received by the pixel unit P 11  is (V 1 −Vr) since the voltage signal goes through one unit of trace resistance r to get to the pixel unit P 11 , wherein Vr represents the voltage value consumed by one unit of trace resistance. When the second image is shown and the second voltage signal V 2  is received by the pixel unit P 11 , the actual voltage value received by the pixel unit P 11  is (V 2 −Vnr) since the voltage signal goes through n units of trace resistance r, wherein Vnr represents the voltage value consumed by n units of trace resistance. When performing step S 100  and step S 102  repeatedly and alternately for a period of time, the waveform of the voltage signal received by the pixel unit P 11  can be shown as  FIG. 4 . Through the technical solution mentioned above, the pixel unit P 11  displays the grey scale controlled by the average voltage V′ of the highest voltage (V 1 −Vr) and the lowest voltage (V 2 −Vnr), thereby achieving evened out pixel voltage. 
     In the present embodiment, the problem of image non-uniformity of conventional display panels can be solved. More specifically, a pixel unit in a conventional display panel constantly receives pixel voltage from a certain end of each data line. For example, if a pixel unit is closer to the upper end of the display panel and all the pixel units in the display panel receive pixel voltages from the bottom of the display panel, then the pixel unit closer to the upper end of the display panel will receive a voltage smaller than those closer to the bottom of the display panel. Consequently, from a macro perspective, if all the pixel units on the same data line receive the same voltage, the displayed image will have a brighter upper part and a dimmer lower part along the direction of the data line. In the present embodiment, by providing a switch (S 1 , S 2 ) to both ends (E 1 , E 2 ) of the first data line D 1  and outputting the pixel voltage signals to the pixel units (P 11 , P 21  . . . Pn 1 ) on the first data line D 1  through the first end E 1  and the second end E 2  alternately, an evened out pixel voltage can be achieved, thereby alleviating the problem of brightness non-uniformity along the data line so that the pixel units (P 11 , P 21  . . . Pn 1 ) on the first data line D 1  can output light of uniform brightness. 
     It should be understood that in the previous embodiment, only the first data line D 1  is used to describe the technical solution of the present embodiment; however, the present invention is not limited thereto. In other embodiment, the aforementioned technical solution can be applied to all the data line (D 1 , D 2  . . . Dm) of the display panel A, thereby enhancing the image uniformity of the display panel A. 
     Second Embodiment 
     The second embodiment of the present invention will be described below with reference to  FIG. 5  to  FIG. 7B . The main difference between the first embodiment and the second embodiment lies in: in the first embodiment, the pixel voltage is alternately outputted into the first end E 1  and the second end E 2  of a data line so as to alleviate the problem of bright non-uniformity along the data line; in the second embodiment, the pixel voltage is outputted to the data lines alternately through the first end E 1  and the second end E 2  along a direction perpendicular to the data lines so as to further reduce bright non-uniformity along the direction. 
     Specifically, referring to  FIG. 5 , the source driver module Z of the display device D of the present embodiment further includes a third switch S 3  and a fourth switch S 4 . The third switch S 3  is coupled between the first end E 1  of the second data line D 2  and the source driver circuit C, and the fourth switch S 4  is coupled between the second end E 2  of the second data line D 2  and the source driver circuit C. As shown in the drawing, the first end E 1  of the second data line D 2  is on the first side L 1  of the display panel A with the first end E 1  of the first data line D 1 , and the second end E 2  of the second data line D 2  is on the second side L 2  of the display panel A with the second end E 2  of the first data line D 1 . The second side L 2  is opposite the first side L 1 . In the present embodiment, the third switch S 3  and the fourth switch S 4  are used for a similar purpose as that of the first switch S 1  and the second switch S 2 , in which the third switch S 3  and the fourth switch S 4  close whenever the source driver circuit C outputs pixel voltage to the second data line D 2 . 
     The method provided by the present embodiment is applicable to the display device D of  FIG. 5 , which will be described below with reference to  FIG. 6 ,  FIG. 7A  and  FIG. 7B .  FIG. 7A  and  FIG. 7B  respectively show the portion VIIA/VIIB of  FIG. 5  at difference time points. The method for driving a display panel according to the second embodiment of the present invention includes at least step S 200 : when the display panel A displays a first image, the source driver circuit C outputs a first voltage signal V 1  to the first end E 1  of the first data line D 1  through the first switch S 1 , and outputs a third voltage signal V 3  to the second end E 2  of the second data line D 2  through the fourth switch S 4 ; and step S 202 : when the display panel A displays a second image after displaying the first image, the source driver circuit C outputs a second voltage signal V 2  to the second end E 2  of the first data line D 1  through the second switch S 2 , and outputs a fourth voltage signal V 4  to the first end E 1  of the second data line D 2  through the third switch S 3 . 
     Specifically,  FIG. 7A  corresponds to step S 200 , wherein the display panel A displays the first image wherein the source driver circuit C outputs the first voltage signal V 1  to the first data line D 1  through the first switch S 1  and outputs the third voltage signal V 3  to the second data line D 2  through the fourth switch S 4 .  FIG. 7B  corresponds to step S 202 , wherein the display panel A displays the second image wherein the source driver circuit C outputs the second voltage signal V 2  to the first data line D 1  through the second switch S 2  and outputs the fourth voltage signal V 4  to the second data line D 2  through the third switch S 3 . 
     Through the technical solution mentioned above, the method of the present embodiment achieves at least the following effects. On the one hand, the first data line D 1  and the second data line D 2  display images with enhanced uniformity along the data line. Taking pixel unit P 11  for example, when performing step S 200  and step S 202  repeatedly and alternately on the first data line D 1 , the pixel unit P 11  will display the grey scale controlled by the average voltage of the highest voltage (V 1 −Vr) and the lowest voltage (V 2 −Vnr). Taking the pixel unit P 12  for example, when performing step S 200  and step S 202  repeatedly and alternately, the pixel unit P 12  will display the grey scale controlled by the average voltage of the highest voltage (V 4 -Vr) and the lowest voltage (V 3 −Vnr). 
     On the other hand, the present embodiment enhances the image uniformity along the direction perpendicular to eh data lines. For instance, if the source driver circuit C outputs the same voltage signal to the pixel unit P 11  and the pixel unit P 12  when displaying the first image and the second image, i.e. the first voltage signal V 1 , the second voltage signal V 2 , the third voltage signal V 3  and the fourth voltage signal V 4  are the same, although the pixel unit P 11  and the pixel unit P 12  displays light with brightness difference in the first image (the pixel unit P 11  receives a voltage (V 1 −Vr) greater than the voltage (V 3 −Vnr) received by the pixel unit P 12 ), the pixel unit P 11  and the pixel unit P 12  will display light of similar brightness since when displaying the second image, the brightness difference between the pixel unit P 11  and the pixel unit P 12  is compensated, in which the pixel unit P 12  receives a voltage value (V 4 -V 4 ) greater than the voltage value (V 2 −Vnr) received by the pixel unit P 11 . Therefore, when repeatedly performing step S 200  and step S 202 , the pixel unit P 11  and the pixel unit P 12  will display light of similar brightness. 
     It is worth noting that the present invention is applicable to ramp source drivers. In general, in a display panel that uses a ramp source driver, the pixel voltages are inputted through the upper end and lower end of the display panel alternately so as to have a thinner bezel. For example, a first data line receives pixel voltage through the upper end, the second data line receives pixel voltage through the lower end, the third data line receives pixel voltage through the upper end . . . and so on. Based on the above-mentioned problem caused by trace resistance, image uniformity exists along the data line. Through the technical solution of the present embodiment, brightness difference between the pixel unit P 11  and the pixel unit P 12  within a frame of image is compensated after performing step S 200  and step S 202 . This way, the problem of brightness non-uniformity along the data lines in conventional ramp source drivers can be solved. 
     In addition, in the present embodiment, the first switch S 1  and the second switch S 2  form the first multiplexer M 1 , and the second switch S 2  and the fourth switch S 4  form the second multiplexer M 2 . It should be understood that, although only the first data line D 1  and the second data line D 2  are used to describe the technical solution of the present invention, in other embodiments, multiplexers can also be provided at the first end E 1  and the second end E 2  of two adjacent data lines among other data lines (D 3 , D 4  . . . Dm). In this way, the display panel A of the present embodiment can provide images of enhanced uniformity along the data lines and perpendicular to the data lines. 
     In summary, the source driver module Z, the display device D, and the method for driving a display panel provided by the embodiments of the present invention achieve enhanced image uniformity in the display panel A by the technical solutions of “when the display panel A displays the first image, the source driver circuit C outputs the first voltage signal V 1  to the first end E 1  of the first data line D 1  through the first switch S 1 ” and “when the display panel A displays the second image after displaying the first image, the source driver circuit C outputs the second voltage signal V 2  to the second end E 2  of the first data line D 1  through the second switch S 2 ”. 
     The present invention has been described with reference to the above embodiments, but the above embodiments are merely examples for implementing the present invention. It should be noted that the disclosed embodiments are not intended to limit the scope of the present invention. On the contrary, any modification and equivalent configuration within the spirit and scope of the appended claims shall fall within the scope of the present invention.