Patent Publication Number: US-11380248-B2

Title: Driving method and driving device for driving a scan-type display

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application Nos. 109110131 and 109144111, respectively filed on Mar. 26, 2020 and Dec. 14, 2020. 
     FIELD 
     The disclosure relates to display driving techniques, and more particularly to a driving method and a driving device for driving a scan-type display. 
     BACKGROUND 
     A conventional driving device for driving a scan-type display to show images includes a control module and a driver module. The driver module receives a synchronization control signal and an image stream from the control module. The image stream contains multiple pieces of image data that respectively correspond to multiple images or image frames to be shown by the scan-type display. The driver module drives the scan-type display based on the synchronization control signal and the image stream such that switching of a backlight module, which includes a light emitting diode (LED) array, of the scan-type display between a state where all LEDs are lit and a state where no LEDs are lit is related to the synchronization control signal, such that light emitted by the backlight module is modulated by a display module of the scan-type display to show the images or image frames represented by the image stream, and such that refreshing of images on the scan-type display is synchronous to the synchronization control signal. The synchronization control signal is a vertical synchronization signal, is periodic, and has a frequency of, for example, 60 Hz. Therefore, the scan-type display refreshes periodically, and a frame rate thereof is equal to the frequency of the synchronization control signal. 
     However, under a circumstance where the synchronization control signal is non-periodic and where the backlight module is a scanning backlight module that is triggered by the synchronization control signal and that emits light in a line scan manner, driving the display module in the aforesaid manner will result in image tearing or image interruption. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a driving method and a driving device for driving a scan-type display. The driving method and the driving device can alleviate the drawback of the prior art. 
     According to an aspect of the disclosure, the driving method is to be implemented by a driver module, and is adapted to drive a scan-type display. The driving method includes steps of: (A) receiving an image stream from a control module; (B) receiving a synchronization control signal from the control module; (C) generating a drive output based on the synchronization control signal, the image stream and a clock signal and outputting the drive output to the scan-type display, such that the scan-type display emits light in a line scan manner; and (D) generating an image refresh signal based on the synchronization control signal and the drive output. The image refresh signal is related to refreshing of images on the scan-type display. 
     According to another aspect of the disclosure, the driving device is adapted to drive a scan-type display that includes a backlight module and a display module. The driving device includes a control module and a driver module. The control module generates an image stream and a synchronization control signal. The driver module is adapted to be coupled to the backlight module and the display module, and is further coupled to the control module to receive the image stream and the synchronization control signal therefrom. The driver module generates a drive output based on the synchronization control signal, the image stream and a clock signal and outputs the drive output to the backlight module, such that the backlight module emits light in a line scan manner. The driver module generates an image refresh signal based on the synchronization control signal and the drive output. The image refresh signal is related to refreshing of images on the scan-type display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a circuit block diagram illustrating an embodiment of a driving device according to the disclosure in use with a scan-type display; 
         FIG. 2  is a flowchart illustrating a driving method performed by the embodiment; and 
         FIG. 3  is a timing diagram illustrating an image stream, a synchronization control signal, an image refresh signal and multiple switching signals of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 to 3 , an embodiment of a driving device  2  according to the disclosure is adapted to drive a scan-type display  1  to show images. The scan-type display  1  (e.g., a liquid crystal display (LCD)) supports dynamic frame rate technologies, and includes a backlight module  11  and a display module  12  (e.g., an LCD panel). The backlight module  11  includes a plurality of scan switches and a light emitting diode (LED) array  115 . For illustration purposes, the backlight module  11  exemplarily includes four scan switches  111 - 114 . Each of the scan switches  111 - 114  (e.g., a P-type metal oxide semiconductor field effect transistor (pMOSFET)) has a first terminal (e.g., a source terminal) that is to receive an input voltage (V LED ), a second terminal (e.g., a drain terminal) that is coupled to first terminals (e.g., anodes) of LEDs  116  in a respective row of the LED array  115 , and a control terminal (e.g., a gate terminal). It should be noted that while the scan switches  111 - 114  are included in the backlight module  11  in this embodiment, they may be included in the driving device  2  or be independent of the scan-type display  1  and the driving device  2  in other embodiments. 
     The driving device  2  includes a control module  21  and a driver module  22 . 
     The control module  21  generates a synchronization control signal (Vsync), and includes a graphic processing unit (GPU) (not shown) that generates an image stream (Dr). The image stream (Dr) contains multiple pieces of image data (Draw) that respectively correspond to multiple images or image frames to be shown by the scan-type display  1 . In this embodiment, the control module  21  sequentially outputs the pieces of image data (Draw) to serve as the image stream (Dr). The driver module  22  is adapted to be coupled to the backlight module  11  and the display module  12 , is further coupled to the control module  21  to receive the synchronization control signal (Vsync) and the image stream (Dr) therefrom, and drives the backlight module and the display module  12  based on the synchronization control signal (Vsync) and the image stream (Dr). In this embodiment, the driver module  22  includes a register  221 , a first signal generator  222  and a second signal generator  223 . The register  221  is coupled to the control module  21 . The first signal generator  222  is adapted to be coupled to the control terminals of the scan switches  111 - 114  and second terminals (e.g., cathodes) of the LEDs  116  of the LED array  115 , is further coupled to the control module  21  and the register  221 , and includes a phase-locked loop (PLL)  224 . The second signal generator  223  is adapted to be coupled to the display module  12 , and is further coupled to the register  221  and the first signal generator  222 . It should be noted that the second signal generator  223  includes a source driver and a gate driver, and is well known in the art, and therefore details thereof are omitted herein for the sake brevity. It should also be noted that the first and second signal generators  222 ,  223  may be fabricated on a single chip or on two separate chips. 
     In this embodiment, a driving method performed by the driver module  22  to drive the scan-type display  1  to show images includes the following steps  31 - 36 . 
     In step  31 , the PLL  224  generates a clock signal. 
     In step  32 , the register  221  receives the image stream (Dr) from the control module  21 , and stores the image stream (Dr). 
     In step  33 , the first signal generator  222  receives the synchronization control signal (Vsync) and the image stream (Dr) respectively from the control module  21  and the register  221 . 
     In step  34 , the first signal generator  222  generates a first drive output based on the synchronization control signal (Vsync), the image stream (Dr) and the clock signal and outputs the first drive output to the backlight module  11 , such that the backlight module  11  emits light in a line scan manner (i.e., light emitted in lines). In this embodiment, the first drive output includes a plurality of switching signals (e.g., four switching signals (SW 1 -SW 4 )) and a plurality of driving signals (D 1 -Dn), and step  34  includes the following sub-steps  341 - 343 . 
     In sub-step  341 , the first signal generator  222  generates the switching signals (SW 1 -SW 4 ) based on the synchronization control signal (Vsync) and the clock signal. In this embodiment, each of the switching signals (SW 1 -SW 4 ) is a pulse signal, and has a pulse width that is a multiple of a period of the clock signal; and in each line scan cycle of the backlight module  11 , the pulses of the switching signals (SW 1 -SW 4 ) are staggered and non-overlapping in time (i.e., the pulse of the switching signal (SW 1 ), the pulse of the switching signal (SW 2 ), the pulse of the switching signal (SW 3 ) and the pulse of the switching signal (SW 4 ) occur one by one without overlapping one another in time). In addition, transition of the switching signals (SW 1 -SW 4 ) is triggered by the first pulse of the synchronization control signal. 
     In sub-step  342 , the first signal generator  222  generates the driving signals (D 1 -Dn) based on the image stream (Dr) and the clock signal. In this embodiment, each of the driving signals (D 1 -Dn) is a pulse signal, and has a pulse width that is a multiple of the period of the clock signal, and the multiple varies according to the image stream (Dr). 
     In sub-step  343 , the first signal generator  222  outputs the switching signals (SW 1 -SW 4 ) and the driving signals (D 1 -Dn) to the backlight module  11 . Each of the switching signals (SW 1 -SW 4 ) is for receipt by the control terminal of a respective one of the scan switches  111 - 114 . Each of the driving signals (D 1 -Dn) is for receipt by the second terminals of the LEDs  116  in a respective column of the LED array  115 . Therefore, the scan switches  111 - 114  conduct one by one, and the LEDs  116  of the LED array  115  emit light row by row (i.e., the backlight module  11  emits light in the line scan manner). It should be noted that each row of the LED array  115  corresponds to a respective line of the line scan of the backlight module  11  (namely, a respective line of the backlight module  11  that emits light in each line scan cycle). 
     In step  35 , the first signal generator  222  generates an image refresh signal (Vr) based on the synchronization control signal (Vsync) and the first drive output. The image refresh signal (Vr) is related to refreshing of images on the scan-type display  1  (i.e., an act of the scan-type display  1  switching from displaying a current image or image frame to displaying a next image or image frame). 
     In this embodiment, the first signal generator  222  generates the image refresh signal (Vr) based on the synchronization control signal (Vsync) and one of the switching signals (SW 1 -SW 4 ) that corresponds to a last line of the line scan in each line scan cycle (i.e., the switching signal (SW 4 )). Each of the synchronization control signal (Vsync) and the image refresh signal (Vr) is a pulse signal. Each pulse of the image refresh signal (Vr), except the first pulse, lags a respective pulse of the synchronization control signal (Vsync), and a starting point thereof is concurrent with an end point of a pulse of said one of the switching signals (SW 1 -SW 4 ) (i.e., the switching signal (SW 4 )) that occurs immediately after a starting point of the respective pulse of the synchronization control signal (Vsync). 
     In step  36 , the second signal generator  223  receives the image stream (Dr) and the image refresh signal (Vr) respectively from the register  221  and the first signal generator  222 , and generates a second drive output (Do) based on the image stream (Dr) and the image refresh signal (Vr) and outputs the second drive output (Do) to the display module  12 , such that the scan-type display  1  shows images or image frames represented by the image stream (Dr) and that the refreshing of images on the scan-type display  1  is synchronous to the line scan. In this embodiment, light transmittance of the display module  12  varies according to the image stream (Dr), and light emitted by the backlight module  11  is modulated by the display module  12  to produce the images or image frames represented by the image stream (Dr). 
     It should be noted that, in this embodiment, step  31  is executed before execution of step  32 . However, in other embodiments, step  31  may be executed after execution of step  32  and before execution of step  33 , or may be executed after execution of step  33  and before execution of step  34 . In other words, step  31  is executed before execution of step  34  regardless. 
     In view of the above, in this embodiment, by virtue of the second signal generator  223  generating the second drive output (Do) based on the image refresh signal (Vr), the refreshing of images on the scan-type display  1  can occur when the line scan cycle of the backlight module ends, thereby preventing image tearing or image interruption and attaining better display quality. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that the disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.