Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display (LCD) module and a method for adjusting a response time period thereof. 
     2. Description of Prior Art 
     An advanced monitor with multiple functions is an important feature for use in current consumer electronic products. Liquid crystal display (LCD) devices which are colorful monitors with high resolution are widely used in various electronic products such as monitors for mobile phones, personal digital assistants (PDAs), digital cameras, laptop computers, and notebook computers. 
     A conventional LCD module comprises an LCD panel, a gate driver, and a source driver. The LCD panel comprises a plurality of pixel units. The gate driver supplies the plurality of pixel units with a scan signal. The source driver outputs a data signal to the plurality of pixel units to display images. Generally speaking, when the temperature of an LCD panel varies, values of viscosity coefficients of liquid crystals and equivalent capacitances change. This may result in variations of the response time period of the liquid crystals as well. How to adjust the response time period of the liquid crystals according to variations in temperature of an LCD panel is a technical problem for LCD module manufacturers. 
     SUMMARY OF THE INVENTION 
     To solve the technical problem that the response time period of the conventional LCD module changes with the temperature of the LCD panel, the present invention provides an LCD module capable of adjusting the response time period of liquid crystals according to temperature variations of an LCD panel and a method for adjusting the response time period thereof. 
     According to the present invention, a liquid crystal display module comprises a gate driver and a liquid crystal display panel having a plurality of pixel units, a transistor mounted on the LCD panel, a first error amplifier, an analog to digital converter, and a voltage regulator. A voltage difference between a gate and a source of the transistor varies with temperature. The first error amplifier having two input terminal electrically connected to the gate and the source of the transistor respectively, is used for outputting an amplified value of the voltage difference between the gate and the source of the transistor. The analog to digital converter is used for receiving the amplified value of the voltage difference and for outputting a corresponding binary signal, the corresponding binary signal being the temperature sensing signal; the voltage regulator is used for adjusting scan voltage according to the temperature sensing signal. The gate driver outputs a scan signal with the adjusted scan voltage to the plurality of pixel units. 
     In one aspect of the present invention, the liquid crystal display module further comprises a constant current generator electrically connects to the gate and the drain of the transistor to feed a predetermined voltage, the source of the transistor receives a reference voltage, a relation between the predetermined voltage and the reference voltage complying with a conducting criterion of the transistor. 
     In one aspect of the present invention, the voltage regulator comprises a digital to analog converter having an input terminal coupling to an output terminal of the analog to digital converter, for outputting an analog voltage, a feedback circuit for generating a feedback voltage upon receiving the scan voltage, a second error amplifier for outputting an amplified value of a voltage difference between the analog voltage and the feedback voltage; and a scan voltage generator for adjusting the scan voltage according to the amplified value of the voltage difference from the second error amplifier. 
     In one aspect of the present invention, the transistor is a thin film transistor. 
     In one aspect of the present invention, the transistor is mounted on a position of the LCD panel where a mean temperature of the LCD panel is capable of being sensed. 
     According to the present invention, a method of adjusting a response time period of an LCD module comprises following steps: using a temperature sensor to sense a temperature of a LCD panel and to generate a temperature sensing signal; using a voltage regulator to adjust scan voltage according to the temperature sensing signal; and using a gate driver to output a scan signal having the adjusted scan voltage to a plurality of pixel units of the LCD panel. 
     In one aspect of the present invention, the steps of using the temperature sensor to sense the temperature of the LCD panel and to generate the temperature sensing signal comprises: mounting a transistor on a position where the temperature of the LCD panel is capable of being sensed, the voltage difference between the gate and the source of the transistor changing with temperature; using a first error amplifier to calculate the voltage difference between the gate and the source and to output an amplified value of the voltage difference; and using an analog to digital converter (ADC) to receive the amplified value of the voltage difference and to output a corresponding binary signal, the corresponding binary signal being the temperature sensing signal. 
     In one aspect of the present invention, the step of using the temperature sensor to sense the temperature of the LCD panel and to generate the temperature sensing signal further comprises: using a constant current generator to provide a predetermined voltage to a drain of the transistor, and providing a reference voltage to a source and a gate of the transistor, a relation between the predetermined voltage and the reference voltage complying with a conducting criterion of the transistor. 
     In one aspect of the present invention, the reference voltage is a common voltage applied on the LCD panel from a driving chip of the LCD module. 
     In one aspect of the present invention, the step of using the temperature sensor to sense the temperature of the LCD panel and to generate the temperature sensing signal comprises: mounting a transistor on a position where the temperature of the LCD panel is capable of being sensed, the voltage difference between the gate and the source of the transistor changing with temperature; using a first error calculator to calculate the voltage difference between the gate and the source; and using an analog to digital converter to receive the voltage difference and to output a corresponding binary signal, the corresponding binary signal being the temperature sensing signal. 
     In one aspect of the present invention, the step of using a voltage regulator to adjust the scan voltage according to the temperature sensing signal comprises: using a digital to analog converter (DAC) to transform the temperature sensing signal into an analog voltage; using a second error amplifier to compare the analog voltage with a feedback voltage when the scan voltage is feed-backed by a feedback circuit and to output an amplified value of a voltage difference between the analog voltage and the feedback voltage; and using a scan voltage generator to adjust the scan voltage according to the amplified value of the voltage difference. 
     In one aspect of the present invention, the step of using a voltage regulator to adjust the scan voltage according to the temperature sensing signal comprises: using a digital to analog converter (DAC) to transform the temperature sensing signal into an analog voltage; using a second error amplifier to compare the analog voltage with a feedback voltage when the scan voltage is feed-backed by a feedback circuit and to output a voltage difference between the analog voltage and the feedback voltage; and using a scan voltage generator to adjust the scan voltage according to the voltage difference. 
     According to the present invention, a liquid crystal display module comprises a gate driver and a liquid crystal display panel having a plurality of pixel units, a temperature sensor for generating a temperature sensing signal based on a temperature of the liquid crystal display panel, and a voltage regulator for adjusting scan voltage according to the temperature sensing signal, the gate driver outputs a scan signal with the adjusted scan voltage to the plurality of pixel units. 
     In one aspect of the present invention, the temperature sensor comprises a transistor mounted on the LCD panel, a voltage difference between a gate and a source of the transistor changing with temperature, a first error amplifier having two input terminal electrically connected to the gate and the source of the transistor respectively, for outputting the voltage difference between the gate and the source of the transistor, and an analog to digital converter for receiving the voltage difference and for outputting a corresponding binary signal, the corresponding binary signal being the temperature sensing signal. 
     In one aspect of the present invention, the voltage regulator comprises a digital to analog converter having an input terminal coupling to an output terminal of the analog to digital converter, for outputting an analog voltage, a feedback circuit for generating a feedback voltage upon receiving the scan voltage, a second error amplifier for outputting a voltage difference between the analog voltage and the feedback voltage, and a scan voltage generator for adjusting the scan voltage according to the voltage difference from the second error amplifier. 
     The present invention has an advantage that the LCD module of the present invention comprises a temperature sensor and a voltage regulator. The temperature sensor outputs a temperature sensing signal according to the temperature of the LCD panel. The voltage regulator adjusts scan voltage according to the temperature sensing signal. A scan driving circuit outputs scan signal having the scan voltage to a plurality of pixel units to regulate the charging current to charge the pixel units, shortening the response time period of the LCD module. 
     These and other features, aspects and advantages of the present disclosure will become understood with reference to the following description, appended claims and accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram showing an LCD module according to a preferred embodiment of the present invention. 
         FIG. 2  is a circuit diagram showing the temperature sensor and the voltage regulator of the LCD module. 
         FIG. 3  is a flow chart of showing an adjustment method for the response time period of the LCD module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of a liquid crystal module and a method thereof according to the present invention are described as follow with accompanying figures. 
       FIG. 1  is a structural diagram showing an LCD module  10  according to a preferred embodiment of the present invention. The LCD module  10  comprises an LCD panel  20 , a temperature sensor  22 , a voltage regulator  24 , a source driver  26 , and a gate driver  28 . The LCD panel  20  comprises a plurality of pixel units (unlabeled). The gate driver  28  generates scan signals and outputs them to the plurality of pixel units. Meanwhile, the source driver  26  transmits data signals to the plurality of pixel units to display images. The temperature sensor  22  which is mounted on the LCD panel  20  generates a temperature sensing signal V sense  according to the temperature of the LCD panel  20 . The voltage regulator  24  adjusts scan voltage V GH  according to the temperature sensing signal V sense  to regulate the charging current of the plurality of pixel units. 
     Refer to  FIG. 2 , which is a circuit diagram showing the temperature sensor  22  and the voltage regulator  24  of the LCD module  10 . The temperature sensor  22  comprises a thin film transistor (TFT)  11 , a first error amplifier  12 , an analog to digital converter (ADC)  19 , and a constant current generator  14 . A source S of the TFT  11  is electrically connected to a first voltage input terminal (unlabeled) of the first error amplifier  12 . A gate G and a drain D of the TFT  11  are electrically connected together and further electrically connected to a second voltage input terminal (unlabeled) of the first error amplifier  12 . The drain. D of the TFT  11  is fed a predetermined voltage V 1  from driving chips of the LCD module  10  via the constant current generator  14 . The source S is fed a reference voltage V 2  from the driving chips of the LCD module  10 . Preferably, the reference voltage V 2  can be the common voltage applied on the LCD panel  20 . A voltage output terminal (unlabeled) of the first error amplifier  12  is electrically connected to an analog voltage input terminal (unlabeled) of the ADC  19 . The TFT  11  is mounted on the LCD panel  20 . 
     The voltage regulator  24  comprises a digital to analog converter (DAC)  13 , a second error amplifier  17 , a feedback circuit  21 , and a scan voltage generator  16 . A plurality of binary signal input terminals (unlabeled) of the DAC  13  is electrically connected to a plurality of binary signal output terminals (unlabeled) of the ADC  19 . A first voltage input terminal of the second error amplifier  17  receives the analog voltage output by the DAC  13 . A second voltage input terminal of the second error amplifier  17  receives the feedback voltage V FB  of the scan voltage V GH  output by the feedback circuit  21 . The scan voltage generator  16  which is electrically connected to a voltage output terminal of the second error amplifier  17  generates corresponding scan voltage V GH  according to the voltage output by the second error amplifier  17 . The scan voltage generator  16  is integrated in the DC/DC converter (not shown) of the LCD module  10 . 
       FIG. 3  is a flow chart of showing an adjustment method for the response time period of the LCD module  10 . The adjustment method comprises the following steps: Step S 31 : The temperature sensor  22  senses the temperature of the LCD panel  20  and generates a temperature sensing signal V sense . Step S 32 : The voltage regulator  24  adjusts the scan voltage V GH  according to the temperature sensing signal V sense . Step S 33 : The gate driver  28  outputs a scan signal having the scan voltage V GH  to regulate the charging current of the pixel units. 
     Refer to  FIGS. 1 ,  2 , and  3 . The adjustment method for the response time period of the LCD module  10  is elaborated as follows: 
     Step S 31 : The TFT  11  is mounted on the LCD panel  20 . If the temperature of the LCD panel  20  is evenly distributed, the TFT  11  can be mounted on any position of the LCD panel  20 . If the temperature of the LCD panel  20  is unevenly distributed, the TFT  11  can be mounted on a position which reflects the mean temperature of the LCD panel  20  based on demand. The drain D of the TFT  11  receives the predetermined voltage V 1  through the constant current generator  14 . The source S receives the reference voltage V 2 . The gate G is electrically connected to the drain D. The relation between the predetermined voltage V 1  and the reference voltage V 2  complies with conducting conditions of the TFT  11 . 
     In the TFT  11 , the voltage Vgs between the source S and the gate G is a function of temperature. The function can be simplified as V gs =V gs0 +aT where V gs0  is the voltage corresponding to the voltage between the source S and the gate G at room temperature, and a is the temperature coefficient of the voltage. According to ΔVgs=a·ΔT, the temperature variation ΔT of the LCD panel  20  sensed by the TFT  11  causes variations ΔVgs in the voltage difference between the source S and the gate G. In other words, the voltage difference between the source S and the gate G of the TFT  11  changes correspondingly with the temperature of the LCD panel  20 . The first voltage input terminal and the second voltage input terminal of the first error amplifier  12  are fed the voltage from the source S of the TFT  11  and from the gate G of the TFT  11 , respectively, and output an amplified value of the voltage difference between the voltage of the gate G and the voltage of the source S. 
     The ADC  19  receives the amplified value of the voltage difference output by the first error amplifier  12  and outputs a corresponding binary signal according to the amplified value of the voltage difference at different temperatures. The binary signal can be regarded as the temperature sensing signal V sense . 
     Step S 32 : The DAC  13  transforms the temperature sensing signal V sense  output by the temperature sensor  22  into an analog voltage V REF . The first voltage input terminal of the second error amplifier  17  receives the analog voltage V REF . The second voltage input terminal of the second error amplifier  17  receives the feedback voltage V FB  output by the feedback circuit  21 . The second error amplifier  17  compares the analog voltage V REF  with the feedback voltage V FB  generated when the scan voltage V GH  is feed-backed by the feedback circuit, and transmits the amplified error voltage to the scan voltage generator  16 . The variation in temperature produces different temperature sensing signals V sense , so the analog voltage V REF  changes at different temperatures. Accordingly, the difference in voltage output by the second error amplifier  17  differs at different temperatures. The scan voltage generator  16  adjusts the scan voltage V GH  according to the difference in voltage output by the second error amplifier  17 . The feedback voltage V FB  varies whenever the scan voltage V GH  varies. The scan voltage V GH  and the feedback voltage V FB  change by loop until the scan voltage V GH  becomes stable at the current temperature. 
     Step  33 : The gate driver  28  outputs a scan signal having the scan voltage V GH  to regulate the charging current I CH  of the plurality of pixel units. 
     
       
         
           
             
               
                 I 
                 CH 
               
               = 
               
                 
                   
                     μ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       C 
                       ox 
                     
                     ⁢ 
                     W 
                   
                   L 
                 
                 × 
                 
                   ( 
                   
                     
                       V 
                       GH 
                     
                     - 
                     
                       V 
                       TH 
                     
                   
                   ) 
                 
                 × 
                 
                   V 
                   DS 
                 
               
             
             , 
           
         
       
     
     where C OX  is an oxide capacitance; μ is an electron mobility; W and L are the channel width and the channel length of the TFT of the pixel units, respectively; V TH  is the threshold voltage of the TFT; V DS  is the voltage difference between the drain D and the source S of the TFT. As the equation shows, the charging current I CH  of the pixel units varies with the scan voltage V GH . 
     In conclusion, the LCD module  10  comprises the temperature sensor  22  and the voltage regulator  24 . The temperature sensor  22  outputs a temperature sensing signal according to the temperature of the LCD panel  20 . The voltage regulator  24  adjusts the scan voltage V GH  according to the temperature sensing signal. The gate driver  28  outputs a scan signal having the scan voltage V GH  to the plurality of pixel units to regulate the charging current I CH  of the pixel units to improve the response time period of the LCD module  10 . 
     In addition, the LCD module  10  uses the voltage difference between the gate G and the source S of the TFT  11  to reflect variations in the temperature of the LCD panel  20  to implement temperature sensing and further, to achieve low cost of manufacturing process, simple manufacturing, and small volume. 
     The described embodiment is a preferred one of the present invention. In other words, the LCD module of the present invention is not limited to this preferred embodiment. For example, the first error amplifier  12  can be replaced by an error calculator as long as the accuracy of the ADC  19  is fulfilled and the ADC  19  can output a corresponding binary signal according to the voltage difference between the gate G and the source S of the TFT  11  at different temperatures. The second error amplifier  17  can be replaced by an error calculator as long as the scan voltage generator  16  generates different scan voltages V GH  according to the difference in voltage output by the error calculator. The TFT  11  can be replaced by any other transistor, such as a triode. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.

Technology Category: g