Patent Publication Number: US-7911443-B2

Title: Driving-control device and method of backlight module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 095132244 filed in Taiwan, Republic of China on Aug. 31, 2006, and 096130724 filed in Taiwan, Republic of China on Aug. 20, 2007, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a driving-control device and a driving-control method of a backlight module, and, in particular, to a driving-control device and a driving-control method of a backlight module having a sequential flashing function. 
     2. Related Art 
     Nowadays, liquid crystal displays (LCD) are being used widely. They can be found on computer monitors, touch-screens for man-machine interface and home televisions. As popularity grows, its technical performance becomes more demanding in parameters such as viewing angle, contrast ratio, color saturation, and response time. 
     Among all the performance parameters, quick response time has always been one of the most sought-after items in improving motion picture quality. Low quality LCD with slow response time often causes picture blurring while viewing moving objects. This may not be a major issue if the LCD is just for a desktop computer monitor on which most of the pictures are still all the time. However, if the LCD is for home televisions, quicker response time is a must. 
     Besides the response time, there is a fundamental technical issue, the display type (or mode), that limits the LCD motion picture quality. The CRT display device, the predecessor of LCD, displays pictures by tracing out the images on a glass screen with a single scanning electron beam. Therefore, at any given moment, only a small fraction of the glass screen will be lightened while being scanned across by the electron beam. CRT display device cannot hold still the complete picture to be displayed on the glass screen. Actually, it displays pictures dot-by-dot and line-by-line. This is referred to as impulse-type display. LCD displays pictures in a different way. The LCD screen is composed of numerous pixels arrayed in rows and columns. Each pixel stores a graphic data. To display a picture, the LCD screen loads pixel data of a complete frame in parallel. Each pixel keeps its graphic data until being reloaded. At any given time, every pixel of the entire screen is lightened. Hence, LCD can hold still the complete picture to be displayed, so it displays pictures frame-by-frame. This is referred to as holding-type display. 
     A major drawback of holding-type display is the picture blurring caused by frame switching when displaying moving objects. Because the previous frame will never completely disappear from the screen before the next frame comes in. The most straightforward way to solve this problem is to make the previous frame disappear completely by inserting an extra dark frame before the next frame comes in. This will require some efforts on graphic processor. Another simpler solution is to shut off the backlight module of the LCD device for a specific period of time to create a momentary dark image. This dark image neutralizes human eyes from the previous frame and makes them ready to accept the next one. This is referred to as flashing backlight technology. To further eliminate blurring of holding-type display and mimic impulse-type display, an LCD backlight module is divided into several light zones. Each zone can be turned on and off sequentially. A specific control timing sequence is used to turn on and off each light zone. This timing sequence is synchronized to the frame data reload timing to optimize the motion picture quality. This is referred to as sequential flashing backlight technology. Since this sequential flashing backlight technique turns on and off a number of individual light zones, this can also be applied to power-saving and brightness-dimming control. 
     In some related arts, analog phase delay array is adopted to do the backlight on/off control. However, the timing sequence is adjusted by altering resistance or capacitance value of the control circuit. Therefore, it is an important subject to provide a digital programmable control for making the timing adjusting easier. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, the invention is to provide a digital programmable control for making the timing adjusting easier 
     To achieve the above, this invention discloses a driving-control device of a backlight module. The backlight module firstly receives a first digital burst signal. The driving-control device includes a start signal generating unit, a counter unit, a memory unit, a comparator unit and a driving unit. The start signal generating unit generates a digital start signal on receiving the first digital burst signal. The counter unit is electrically connected to the start signal generating unit and starts counting to generate a counting value whenever the start signal is generated. The memory unit stores at least one target counting value. The comparator unit is electrically connected to the counter unit and the memory unit and generates triggering signals whenever the counter value matches the target counting value. The driving unit is electrically connected to the comparator unit and outputs sequentially delayed driving signals on receiving the triggering signal. 
     To achieve the above, this invention also discloses a backlight driving-control method that includes the following steps of: generating a digital start signal on receiving a first digital burst signal, activating a counter unit to count so as to generate a counting value on receiving the digital start signal, comparing the counter value with at least one target counting value to generate at least one triggering signal, and outputting sequentially delayed driving signals on receiving the triggering signal. 
     As mentioned above, the driving-control device and the method of the backlight module of the invention have the following advantages. The comparator unit is utilized to compare the counting values generated by the counter unit with the target counting value stored in the memory unit to generate the sequentially delayed driving signals. Thus, when the light emitting units of the backlight module are driven by the sequentially delayed driving signals, the light emitting units can be sequentially lighted so that the light emitting units alternately light on and off. In other words, the impulse-type display may be simulated using the simple digital circuit design in accordance with the driving-control device and the method of the backlight module of the invention, and the blurring phenomenon may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a schematic view showing a driving control device of a backlight module according to a preferred embodiment of this invention; 
         FIG. 2  is a timing diagram for the driving control device in  FIG. 1 ; 
         FIG. 3  is a block diagram showing a driving unit of the driving control device according to the preferred embodiment of the invention; 
         FIG. 4  is a schematic view showing a logic gate array of the driving unit in  FIG. 3 ; 
         FIG. 5  is a schematic view showing another driving-control device according to another preferred embodiment of the invention; 
         FIG. 6  is a timing diagram for the driving-control device in  FIG. 5 ; and 
         FIG. 7  is a flow chart showing a driving-control method according to the preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
     Referring to  FIGS. 1 and 2 , a driving-control device  2  of a backlight module according to a preferred embodiment of this invention includes a start signal generating unit  21 , a counter unit  22 , a memory unit  23 , a comparator unit  24  and a driving unit  25 . The driving-control device  2  receives a first digital burst signal Bs 1  and outputs a series of sequentially delayed driving signals Ps to a plurality of light emitting units  3 , wherein the light emitting unit  3  may be a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL) or a light emitting diode (LED). In this embodiment, the driving-control device  2  drives six light emitting units  3 , for example. 
     In this embodiment, the start signal generating unit  21  generates the digital start signal Ss 1  on receiving a start triggering edge Ed 1  of the first digital burst signal Bs 1  (see  FIG. 2 ). In addition, the start signal generating unit  21  may further generate a digital end signal Ss 2  on receiving an end triggering edge Ed 2  of the first digital burst signal Bs 1 . 
     The counter unit  22  is electrically connected to the start signal generating unit  21 , and starts to count on receiving the digital start signal Ss 1  for generating counting values Cv. If the counter unit  22  is a 4-bit counter, it may count from 0000 to 1111. If the counter unit  22  is a 2-bit counter, it may count from 00 to 11. In this embodiment, the 2-bit counter is illustrated as an example. In addition, the counting unit  22  also starts to count after receiving the digital end signal Ss 2 . Herein, it is to be noted that the counting unit  22  may also be implemented by a timer. 
     The memory unit  23  stores at least one target counting value TCv. If the counter unit  22  is a 4-bit counter, the target counting value TCv may range from 0000 to 1111. If the counter unit  22  is a 2-bit counter, the target counting value TCv may range from 00 to 11. 
     The comparator unit  24  is electrically connected to the counter unit  22  and the memory unit  23 . Whenever the counting value Cv matches the target counting value TCv, the comparator unit  24  generates a triggering signal Tr. In this embodiment, the counter unit  22  will be reset after the triggering signal Tr is generated. That is, after the counter unit  22  receives the triggering signal Tr outputted from the comparator unit  24 , it starts to count again from 00. In this embodiment, six light emitting units  3  are illustrated. Hence, there are six activating triggering signals Tr 1  to Tr 6  and six de-activating triggering signals Tr 7  to Tr 12 . 
     The driving unit  25  is electrically connected to the comparator unit  24  and outputs the sequentially delayed driving signals Ps on receiving the triggering signals Tr. Herein, a time delay exists between subsequent two sequentially delayed driving signals. The driving unit  25  sequentially outputs six delayed driving signals Ps 1  to Ps 6  for respectively driving those six light emitting units  3  so that the light emitting units  3  turn on and off alternately. 
     The driving unit  25  activates the delayed driving signal Ps 1  on receiving the activating triggering signal Tr 1 . Similarly, on receiving the activating triggering signals Tr 2  to Tr 6 , it activates delayed driving signals Ps 2  to Ps 6 . Then, the driving unit  25  de-activates the delayed driving signal Ps 1  on receiving the de-activating triggering signal Tr 7 . Similarly, on receiving the de-activating triggering signals Tr 8  to Tr 12  it de-activates the delayed driving signals Ps 2  to Ps 6 . 
     Referring again to  FIG. 3 , the driving unit  25  of the driving-control device  2  further includes a register set  251  and a logic gate array  252 . The register set  251  is electrically connected to the logic gate array  252 . The register set  251  sequentially outputs second digital burst signals Bs 2  on receiving the triggering signals Tr, and the logic gate array  252  generates the sequentially delayed driving signals Ps on receiving the second digital burst signals Bs 2  and a digital pulse width modulation (PWM) signal S PWM . The frequency of the second digital burst signal Bs 2  is lower than that of the digital pulse width modulation signal S PWM . For example, the frequency of the second digital burst signal Bs 2  is 120 Hz, and the frequency of the digital pulse width modulation signal S PWM  is 50 KHz. 
     As shown in  FIG. 4 , the logic gate array  252  of this embodiment includes six AND gates G 1  to G 6 , the second digital burst signals Bs 2  outputted from the register set  251  are inputted to the AND gates G 1  to G 6 , respectively, and the digital pulse width modulation signal S PWM  is also inputted to the AND gates G 1  to G 6 , respectively. The AND gates G 1  to G 6  may output the sequentially delayed driving signals Ps on receiving the second digital burst signal Bs 2  and the digital pulse width modulation signal S PWM . 
     As shown in  FIGS. 5 and 6 , a driving-control device according to another preferred embodiment of the invention includes the start signal generating unit  21 , the counter unit  22 , the memory unit  23 , the comparator unit  24  and the driving unit  25 . The driving unit  25  receives the first digital burst signal Bs 1 , and only the triggering signals Tr 1  to Tr 6  are outputted from the comparator unit  24  as shown in  FIG. 5 . After sequentially receiving the start triggering signals Tr 1  to Tr 6  and the first digital burst signal Bs 1 , the driving unit  25  sequentially outputs the second digital burst signals Bs 2 . The second digital burst signals Bs 2  are just delayed versions of the first digital burst signals Bs 1 . 
     Referring to  FIG. 7 , a driving-control method of a backlight module according to the preferred embodiment includes the following steps. 
     In step S 01 , a digital start signal is generated on receiving a first digital burst signal. Step S 02  is to start counting to generate a counting value on receiving the digital start signal. In step S 03 , the counting value is compared with at least one target counting value TCv to generate a triggering signal. In step S 04 , sequentially delayed driving signals are outputted on receiving the triggering signal. 
     The detailed driving-control method and variations thereof have been described in the above-mentioned embodiments, so detailed descriptions thereof will be omitted. 
     Hereinafter, a summary of this work is given. To improve LCD picture quality, a sequential flashing driving control and method is developed in this invention. It includes a counter unit, a comparator unit, a memory unit and a driving unit. The counter unit receives a triggering signal and starts counting. The memory unit stores at least one target counting value. The comparator unit compares the counting value of the counter unit with the target counting value stored in the memory unit. Once these two values matching each other, a sequentially delayed driving signal will be generated. The counter unit can be reset and re-triggered multiple times to generate a group of sequentially delayed driving signals. These sequentially delayed driving signals drive the light emitting units of the backlight module. Therefore, the light emitting units can be sequentially turned on. In this way, LCD motion picture quality can be improved by turning its holding-type display characteristic into CRT-like impulse-type display. Still in this way, since the light emitting units are turned on alternately, a power-saving scheme can be designed using the sequential flashing technique disclosed in this invention. 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.