Abstract:
The invention discloses a driving apparatus for driving a back light module, and the driving apparatus comprises a driving unit and a deviation detecting unit. The driving unit is used for driving a plurality of lighting units to emit light. The deviation detecting unit is used for calculating for a current deviation of each of the lighting emitting units. Wherein, when the deviation overtakes a first threshold, the deviation detecting unit controls the driving unit to stop driving the lighting emitting units to light.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a driving apparatus and method, and more particularly, to a driving apparatus and method for driving a backlight module of a LCD. 
         [0003]    2. Description of the Prior Art 
         [0004]    Nowadays, along with the advance of Internet and wireless communication techniques, various kinds of portable computer products, such as a notebook, a mobile phone, a Personal Digital Assistant (PDA), etc., have been rapidly developed and launched. However, because of large volume, heavy weight, and high requirement of power, Cathode Ray Tube (CRT) display is not suitable for those portable computer products. Therefore, LCDs, with the advantages of thin thickness, light weight, and lower power consumption, become the main stream of displays corresponding to the trend of the development of the portable computer products. 
         [0005]    At present, the LCD widely used on business situations is Thin-Film LCD (TFT-LCD). The panel itself is not able to light but it can present various gray scales according the light emitted from the backlight module through crystal molecules. The light source of the backlight module includes Cold Cathode Fluorescent Lamp (CCFL), Hot Cathode Fluorescent Lamp (HCLP), Light Emitting Diode (LED), and Electro-Luminscence (EL), wherein CCFL with the advantages of having high luminance, high efficiency, long lifetime, and various appearances, becomes a mainstream light source of the present backlight modules. 
         [0006]    Since the backlight area of large-size LCDs is large, the number of the required CCFLs is then increased. Therefore, keeping the brightness difference of the CCFLs in an acceptable range is a critical issue of the backlight module. The brightness of a CCFL is determined according to the current flowing through the CCFL. Therefore, the driving apparatus has a current balancing mechanism, enabling the currents flowing through each of the CCFLs to be substantially similar, for keeping uniform brightness. However, because each of the CCFLs has parasitic capacitances and parametric variations, the current balancing mechanism can not ensure all currents flowing through the CCFLs are totally similar, so that the differences of brightness still exist. When the difference of brightness is overly large, the brightness of the frame of the panel is not uniform and the presenting image is changed, and furthermore, it may cause the user uncomfortable and even damage their vision. 
       SUMMARY OF THE INVENTION 
       [0007]    Therefore, a scope of the invention is to provide a driving apparatus for driving a backlight module of a LCD. Particularly, the driving apparatus of the invention can control the on/off status of the backlight module according to a current difference to improve the shortcomings of the prior art. 
         [0008]    According to an embodiment, the invention discloses a driving apparatus for driving a backlight module of a LCD. The driving apparatus comprises a driving unit and a deviation detecting unit. The driving apparatus is used for driving a plurality of light emitting units of the backlight module lighting. The deviation detecting unit is used for calculating a current deviation of each of the light emitting units. When the calculated current deviation overtakes a first threshold, the deviation detecting unit controls the driving unit to stop driving the light emitting units lighting. 
         [0009]    According to another embodiment, the deviation detecting unit of the invention further includes a subtracter, a comparator, and a sender. The operation of the deviation detecting unit includes the following steps: firstly, the subtracter measuring a current difference between each of the light emitting units respectively; afterwards, the comparator calculating the current deviation of each of the light emitting units respectively according to the current difference and the current of each light emitting units; and finally, the sender sending a first controlling signal to control the driving unit to stop driving the light emitting units lighting when the current deviation overtaking the first threshold. 
         [0010]    According to another embodiment, the driving apparatus further includes a protecting unit. The protecting unit sends a second controlling signal to control the driving unit to stop driving the light emitting units lighting when the voltage of any of the light emitting units in open circuit overtakes a second threshold. Furthermore, the sender sends a first controlling signal to the protecting unit when the current deviation overtakes the first threshold, so that the protecting unit further sends the second controlling signal to control the driving unit to stop driving the light emitting units lighting. 
         [0011]    Another scope of the invention is to provide a backlight module regarded as a light source of a LCD. 
         [0012]    According to an embodiment, the backlight module of the invention includes a plurality of light emitting units and a driving apparatus. The apparatus is used for driving the light emitting units lighting. Furthermore, the driving apparatus can calculate a current deviation of each of the light emitting units respectively. When the current deviation overtakes a first threshold, the driving apparatus will stop driving the light emitting units lighting. Besides, the driving apparatus of the backlight module of the invention further includes a driving unit and a deviation detecting unit. The driving unit is used for driving the plurality of light emitting units lighting, and the deviation detecting unit is used for calculating the current deviation of each of the light emitting units. 
         [0013]    Another scope of the invention is to provide a driving method for driving a backlight module of a LCD. 
         [0014]    According to an embodiment, the driving method of the invention includes the following steps: firstly, driving a plurality of light emitting units of the backlight module lighting; afterwards, calculating a current deviation of each of the light emitting units; and finally, stopping driving the light emitting units lighting when the current deviation overtaking a first threshold. 
         [0015]    The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         [0016]      FIG. 1A  is a schematic diagram illustrating a driving apparatus and a plurality of light emitting units according to an embodiment of the invention. 
           [0017]      FIG. 1B  is a schematic diagram illustrating the internal structure of the deviation detecting unit in  FIG. 1A . 
           [0018]      FIG. 1C  is a schematic diagram illustrating that the driving apparatus connects to the light emitting units according to another embodiment of the invention. 
           [0019]      FIG. 1D  is a schematic diagram illustrating that the driving apparatus connects to the light emitting units according to another embodiment of the invention. 
           [0020]      FIG. 2A  is a schematic diagram illustrating a backlight module according to an embodiment of the invention. 
           [0021]      FIG. 2B  is a schematic diagram illustrating a backlight module according to another embodiment of the invention. 
           [0022]      FIG. 3A  is a flow chart illustrating the driving method according to an embodiment of the invention. 
           [0023]      FIG. 3B  is a flow chart illustrating the driving method according to another embodiment of the invention. 
           [0024]      FIG. 3C  is a flow chart illustrating the driving method according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Please refer to  FIG. 1A .  FIG. 1A  is a schematic diagram illustrating a driving apparatus  1  and a plurality of light emitting units  2  according to an embodiment of the invention. The driving apparatus  1  is used for driving the plurality of light emitting units  2  of a backlight module of a LCD to light. In practice, the LCD can be, but not limited to, a Thin-Film Transistor LCD (TFT-LCD). The light emitting units  2  can be, but not limited to, CCFLs. 
         [0026]    In the embodiment, the backlight module includes three light emitting units  24 ,  26 , and  28 . As shown in  FIG. 1A , the driving apparatus  1  includes a driving unit  10  and deviation detecting unit  12 . The driving unit  10  is used for driving the light emitting units  2  lighting, and the driving unit  10  has a current balancing mechanism for stabilizing the voltage and the current of the light emitting units  24 ,  26 , and  28  to make the brightness of the light emitted from the light emitting units  24 ,  26 , and  28  substantially similar. The deviation detecting unit  12  can calculate a current deviation of each of the light emitting units  24 ,  26 , and  28  respectively to reach secondary current balancing, and when the current deviation overtakes a first threshold, the deviation detecting unit  12  sends a first controlling signal to control the driving unit  10  to stop driving the light emitting units  2  lighting. 
         [0027]    In practice, the first threshold can be set as a deviation range of 5%, and in the present driving circuit of LCD, the deviation range of 5% is about 1 mA. For example, when the deviation detecting unit  12  detects that the current deviations of the light emitting units  24 ,  26 , and  28  are 3%, 2%, and 2% respectively, and no current deviation overtakes the first threshold, the light emitting units  2  will keep lighting. On the other hand, when the deviation detecting unit  12  detects that the current deviations of the light emitting units  24 ,  26 , and  28  are 3%, 7%, and 2% respectively, and the current deviation of the light unit  26  overtakes the first threshold, the deviation detecting unit  12  will send a first controlling signal to control the driving unit  10  to stop driving the light emitting unit  26  or all the light emitting units  2  lighting. It should be noticed that the first threshold can be set as other values but not limited to 5% according to different situations. 
         [0028]    Please refer to  FIG. 1B .  FIG. 1B  is a schematic diagram illustrating the internal structure of the deviation detecting unit  12  in  FIG. 1A . As shown in  FIG. 1B , the detecting unit  12  includes a subtracter  120 , a comparator  122 , and a sender  124  according to another embodiment of the invention. The subtracter  120  is used for measuring a current difference between each of the light emitting units  2  respectively. In practice, the subtracter  120  can be formed of an operational amplifier and a subtracting circuit. The comparator  122  is used for calculating a current deviation of each of the light emitting units  2  respectively according to the current difference and the current of each of the light emitting units  2 . The sender  124  is used for sending a first controlling signal to control the driving unit  10  to stop driving the light emitting units  2  lighting when the current deviation overtakes the first threshold. 
         [0029]    Please refer to  FIG. 1C .  FIG. 1C  is a schematic diagram illustrating that the driving apparatus  1  connects to the light emitting units  2  according to another embodiment of the invention. As shown in  FIG. 1C , besides the elements of the above-mentioned embodiments, the driving apparatus  1  further includes protecting unit  14 . When the voltage of any of the light emitting units  2  in open circuit overtakes a second threshold, the protecting unit  14  will send a second controlling signal to control the driving unit  10  to stop driving the light emitting units  2  lighting. In practice, the second threshold is higher than the normal voltage of the light emitting units in open circuit, i.e., 650V. Certainly, in practice, the second threshold can be set as other values but not limited to 650V. 
         [0030]    Furthermore, please refer to  FIG. 1D .  FIG. 1D  is a schematic diagram illustrating that the driving apparatus  1  connects to the light emitting units  2  according to another embodiment of the invention. As shown in  FIG. 1D , in the embodiment, when the current deviation overtakes the first threshold, the deviation detecting unit  12  will send a first controlling signal to the protecting unit  14 , so that the protecting unit  14  further sends the second controlling signal to control the driving unit  10  to stop driving the light emitting units  2  lighting. 
         [0031]    In practice, the structure of the driving unit  10  can includes a current-fed parallel resonance circuit, a half-bridge series resonance inverter, a full-bridge phase shift inverter, a push-pull inverter, or other suitable driving device circuits. 
         [0032]    Please refer to  FIG. 2A .  FIG. 2A  is a schematic diagram illustrating a backlight module  3  according to an embodiment of the invention. As shown in  FIG. 2A , the backlight module  3  includes a light emitting unit  30  and a driving apparatus  32 . It should be noticed that the light emitting unit  30  includes the plurality of light emitting units in  FIG. 1A , and for the succinct figure, the light emitting unit  30  in  FIG. 2A  presents all the light emitting units. The driving apparatus  32  is used for driving the light emitting unit  30  lighting, and the driving apparatus  32  has a current balancing mechanism for stabilizing the voltage and current of each of the light emitting units  30  to make the brightness of the light emitted from each of the light emitting units  30  substantially similar. Besides, the driving apparatus  32  can calculate a current deviation of each of the light emitting units  30  and stop driving the light emitting unit  30  lighting when the current deviation overtakes a first threshold. 
         [0033]    In the embodiment, the driving apparatus  32  can further include a driving unit  320  and a deviation detecting unit  322 . The driving unit  320  is used for driving the light emitting unit  30  lighting. The deviation detecting unit  322  is used for calculating the current deviation of each of the light emitting units  30 . 
         [0034]    Please refer to  FIG. 2B .  FIG. 2B  is a schematic diagram illustrating a backlight module  3  according to another embodiment of the invention. As shown in  FIG. 2B , the driving apparatus  32  further includes a protecting unit  324 . The protecting unit  324  will send a second controlling signal to control the driving unit  320  to stop driving the light emitting unit  30  lighting when the voltage of any of the light emitting units  30  in open circuit overtakes a second threshold. Besides, in the embodiment, the deviation detecting unit  322  will send a first controlling signal to the protecting unit  324  when the current deviation overtaking the first threshold, so that the protecting unit  324  further sends the second controlling signal to control the driving unit  320  to stop driving the light emitting unit  30  lighting. 
         [0035]    In another embodiment, the protecting unit  324  can be independent from the driving apparatus  32 , however, the operation of the protecting unit  324  is the same with that in the above-mentioned embodiment, so those are not described here. 
         [0036]    Please refer to  FIG. 3A .  FIG. 3A  is a flow chart illustrating the driving method, for driving a backlight module of a LCD, according to an embodiment of the invention. In the embodiment, the driving method of the invention includes the following steps: firstly, in step S 10 , driving a plurality of light emitting units of the backlight module lighting; afterwards, in step S 12 , calculating a current deviation of each of the light emitting units; and finally, in step S 14 , judging if the current deviation overtakes a first threshold, and if yes, stopping driving the light emitting units lighting. 
         [0037]    Please refer to  FIG. 3B .  FIG. 3B  is a flow chart illustrating the driving method according to another embodiment of the invention. AS shown in  FIG. 3B , the difference of the driving method of the embodiment from that of the last embodiment is that the step  12  further includes the following steps: in step S 120 , measuring a current difference between each of the light emitting units; and in step S 122 , calculating the current deviation of each of the light emitting units respectively according to the current difference and the current of each of the light emitting units. The other steps of the embodiment are the same with the corresponding steps of the last embodiment, and those are not described here. 
         [0038]    Please refer to  FIG. 3C .  FIG. 3C  is a flow chart illustrating the driving method according to another embodiment of the invention. As shown in  FIG. 3C , the driving method of the invention further includes the following step: in step S 16 , stopping driving the light emitting units lighting when the voltage of any of the light emitting units in open circuit overtakes a second threshold. The other steps of the embodiment are the same with the corresponding steps of the above-mentioned embodiments, and those are not described here. 
         [0039]    Compared to the prior art, the driving apparatus and method of the invention can measure and calculate the current deviation of each of the light emitting units, and the backlight module will stop lighting when the current deviation is overly large. Accordingly, it can be prevent from the condition that the brightness of the panel of LCD is not uniform to cause users uncomfortable and even to damage their vision. 
         [0040]    While the invention has been described in some preferred embodiments, it is understood that the words which have been used are words of description rather than words of limitation and that changes within the purview of the appended claims may be made without departing from the scope and spirit of the invention in its broader aspect.