Patent Publication Number: US-8525773-B2

Title: Apparatus for control liquid crystal timing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Taiwan application serial no. 91112175, filed on Jun. 6, 2002. 
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to an apparatus for controlling a liquid crystal timing. More particularly, the present invention relates to an apparatus for controlling a liquid crystal timing, in which a back light driving device is built-in. 
     2. Description of Related Art 
     The liquid crystal display (LCD) has had applications on the calculator and the electronic watches since 1970. After then, many properties of photoelectric effect have been discovered, and the driving technologies have been greatly improved. Now, the LCD has several advantages, such as high quality of image displaying, low power consumption, thin and in massive production, low driving voltage, and small volume. The current applications have been applied to the portable TV, image phone, video device, notebook computer, desk displaying terminal, or the projection color TV. It have been one of the promising part for a product. 
     In general, the LCD includes a large number of image pixels. When an image is to be displayed on the LCD, a graphic controller of the LCD will export the vertical synchronizing signal, horizontal synchronizing signal, and color signal to the liquid crystal timing controller. The liquid crystal timing controller the exports a control signal, according to the above signals, to the gate driver and exports the color signal to the data driver. As a result, the pixels are controlled in action. 
     Since the liquid crystal by itself cannot emit the light, it is necessary to include a back light source or an external light source to serve as the light source for displaying the image on the screen. In the case of using a light emitted diode (LED) to serve as a back light source, it usually needs a constant current to supply to each LED by a constant current source. Otherwise, it would easily occur that the LED is burnt down or the brightness is not uniform. The current conventional method is basically categorized into two manners. One is that each of the LED of the back light source is driven by coupling with a resistor in cascade. However, this manner does not improve efficiency or even reduce the efficiency. Another conventional method is directly using a constant current chip to provide a constant current to each LED. However, this constant current chip has to be designed externally. This would increase the use of space for the LCD driving circuit. Also and the fabrication cost is also increased. 
     SUMMARY OF INVENTION 
     One of the objectives of the invention is to provide an apparatus for controlling a liquid crystal timing, which can combine with a back light driving device having a constant current source, so that the efficiency can be improved. Also and, the cost and space can be saved. 
     Another one of the objectives of the invention is to provide an apparatus for controlling a liquid crystal timing, which includes a back light driving device. The apparatus for controlling a liquid crystal timing has the function to have a constant current, and can be used provide the constant current to the back light source, such as the light emitted diode. The apparatus for controlling a liquid crystal timing controls the liquid crystal display at the specific timing period. 
     Another one yet of the objectives of the invention is to provide an apparatus for controlling a liquid crystal timing, which can combine a back light driving device having a constant current source, but it is not necessary to use the resistors coupled in cascade for driving the back light source, so as to improve the efficiency and save the cost and space. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is an apparatus for controlling a liquid crystal timing, wherein the back light source is a light emitted diode, according to one preferred embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , it is a drawing, schematically illustrating an apparatus for controlling a liquid crystal timing  10 , with a back light source  20 , according to one preferred embodiment of this invention. The back light source  20  can be a light emitted diode or any type being used for operation as the back light source. The invention does not limit the type of back light source. For the preferred embodiment of the invention, the back light source  20  is composed of a number of light emitted diodes  22 ,  24 , â . The apparatus for controlling a liquid crystal timing  10  for the embodiment includes a timing control circuit  14  and a back light driving device  12 , such as a light emitted diode (LED) driving device. In order to assure that the back light source  20  can be operated in stable, the back light driving device  12  is built in the apparatus for controlling a liquid crystal timing  10  in the embodiment and exports a constant current I to the back light source  20 . Since the back light driving device  12  includes the function for constant current, it can be used as a current source generator. The function of constant current of the back light driving device  12  can be achieved by using an integrated circuit for constant current. Since the liquid crystal molecules in the liquid crystal display cannot emit light by itself, it needs the light from the back light source  20  to achieve the image displaying effect, so as to display image on the LCD. The timing control circuit  14  in the apparatus for controlling a liquid crystal timing  10  then exports the timing control signals to the driving device on the LED panel, such as the data driving device, the gate driving device, and all of the needed timing control for controlling the LED. 
     The back light driving device  12  includes the function to have a constant current, so as to provide a constant current to the back light source  20 , such as the LED&#39;s  22 ,  24 . The timing control circuit  14  controls the LCD panel  30  at the specific timing period. For example, when an image is to be displayed on the LCD panel  30 , under the specific timing period, such as three clock cycles, the timing control circuit  14  will receive the vertical signals, the parallel signals, and the color signals from the graphic controller (not shown). Then, the timing control circuit  14  would export the control signal and the color signal to the gate driving device (not shown), according to the vertical signals, the parallel signals, and the color signals, so as to control the degree of twist angle on the liquid crystal molecules for each pixel. Since the liquid crystal in each pixel cannot emit light by itself, the invention use the back light driving device  12  to drive the LED&#39;s  22 ,  24  to serve as the back light source  20 . Further, the apparatus for controlling a liquid crystal timing  10 , according to the foregoing signals, then exports the control signal to the gate driving device and exports the color signal to the data driving device, so that each pixel can display the desired effect. 
     As known by the skilled artisans, the apparatus for controlling a liquid crystal timing of the invention can be applied to LCD of the computer system, the LCD of the portable electronic device, and the usual LCD. The apparatus for controlling the liquid crystal timing used in the foregoing devices has the same function of the timing control circuit and the back light driving device. 
     The advantages of the invention includes that the back light driving device with a constant current source is combined with the apparatus for controlling the liquid crystal timing. As a result, when the apparatus for controlling the liquid crystal timing is in operation, a constant current can also be supplied at the same time without the need of the cascade resistors coupled with the light emitted diode. The efficiency can be improved, and the fabrication cost and space can be saved. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.