Patent Publication Number: US-7714822-B2

Title: Liquid crystal display device capable of switching scanning frequencies

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a liquid crystal display device capable of switching scanning frequencies and the driving method thereof, and more particularly, to a liquid crystal display device capable of switching scanning frequencies according to received noise signals and the driving method thereof. 
   2. Description of the Prior Art 
   The progress of science and technology has led to small, effective, and portable intelligent information products becoming a part of our lives. Display devices play an important role because all intelligent information products, such as mobile phones, personal digital assistants (PDAs), or notebooks, require display devices to function as a communication interface. The advantages of an LCD device include portability, low power consumption, and low radiation. Therefore, the LCD device is widely used in, for example, various portable products, such as notebooks and personal data assistants (PDA). Moreover, the LCD device is gradually replacing the CRT monitor for use with desktop computers. Nevertheless, liquid crystal molecules under different arrangements have different polarity against light therefore the liquid crystal molecules in different arrangements can control penetration of light to generate different intensity of outputted light, and the LCD device displays different color levels of red, blue and green by way of changing an arrangement of the liquid crystal molecules so as to display picture images. 
   A glittering frequency of a fluorescent lamp is due to an electric power frequency of a power supply. There are two different electric power frequencies (50 Hz, 60 Hz) applied in different regions all over the world. When a scanning frequency of a liquid crystal display device can not match the electric power frequency of the fluorescent lamp, users feel glittery and uncomfortable, especially for a monochrome LCD monitor with a reflective or semi-reflective backlight module, causing of that the fluorescent lamp provides light to the reflective or semi-reflective backlight module. Traditionally the solution is utilizing an interlaced scan technique or increasing the scanning frequency of the LCD monitor. However, first, the interlaced scan technique can not solve this problem entirely; second, users feel glittery and uncomfortable when the LCD monitor is shaken upward and downward; and third, increasing the scanning frequency of the LCD monitor causes disadvantages of power consumption and delay of liquid crystal molecules. There is a need to solve the problem mentioned above. 
   SUMMARY OF THE INVENTION 
   It is therefore a primary objective of the claimed invention to provide a liquid crystal display device capable of switching scanning frequencies and the driving method thereof for solving the above-mentioned problem. 
   According to the claimed invention, a liquid crystal display device includes a noise-receiving module for receiving external noise signals, a liquid crystal display module, and a frequency-switching means for switching scanning frequencies of the liquid crystal display module according to frequencies of the noise signals received by the noise-receiving module. 
   According to the claimed invention, a liquid crystal display drive IC for switching scanning frequencies of a liquid crystal display module is disclosed. The liquid crystal display drive IC includes a noise-receiving module for receiving external noise signals, and a frequency-switching means for switching scanning frequencies of the liquid crystal display module according to frequencies of the noise signals received by the noise-receiving module. 
   According to the claimed invention, a method for driving a liquid crystal display module includes: (a) receiving external noise signals; and (b) driving the liquid crystal display module according to frequencies of the noise signals received in step (a). 
   These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a functional block diagram of a liquid crystal display device according to the present invention. 
       FIG. 2  is a flowchart of driving a liquid crystal display module according to the present invention. 
       FIG. 3  is a time response diagram of the noise signals received by a noise-receiving module according to the present invention. 
       FIG. 4  is a frequency response diagram of the noise signals analyzed by a frequency analysis circuit according to the present invention. 
   

   DETAILED DESCRIPTION 
   Please refer to  FIG. 1 .  FIG. 1  is a functional block diagram of a liquid crystal display device  10  according to the present invention. The liquid crystal display device  10  includes a liquid crystal display module  12  including a liquid crystal display panel  14  and a drive circuit  16  for driving the liquid crystal display panel  14  at different scanning frequencies. The drive circuit  16  can include a COM drive circuit and a SEG drive circuit. The liquid crystal display device  10  further includes a noise-receiving module  18  for receiving external noise signals. The noise-receiving module  18  can be a conducting wire of Indium Tin Oxide glass (ITO glass), an antenna module, and so on. The liquid crystal display device  10  further includes a frequency-switching means  20  coupled to the liquid crystal display module  12  for switching scanning frequencies of the liquid crystal display module  12  according to frequencies of the noise signals received by the noise-receiving module. The frequency-switching means  20  includes a signal amplifier  22  coupled to the noise-receiving module  18  for amplifying the noise signals received by the noise-receiving module  18 , a frequency analysis circuit  24  coupled to the signal amplifier  22  for analyzing frequencies of the amplified noise signals, and a frequency discrimination circuit  26  coupled to the frequency analysis circuit  24  for discriminating a frequency of the noise signal with the largest signal energy according to an analysis result of the frequency analysis circuit  24 . The frequency discrimination circuit  26  includes at least one band-pass filter  28  for filtering signals analyzed by the frequency analysis circuit  24 . The amount of the band-pass filters  28  depends on the amount of the scanning frequencies to be switched. The frequency-switching means  20  further includes a multiplexer  30  coupled to the frequency discrimination circuit  26  for outputting a signal corresponding to the specific scanning frequency (such as 50 Hz or 60 Hz) generated by the drive circuit  16  to the liquid crystal display panel  14  according to a discrimination result of the frequency discrimination circuit  26 . The drive circuit  16 , the noise-receiving module  18 , and the frequency-switching means  20  can be integrated in a liquid crystal display drive IC. 
   Please refer to  FIG. 2 .  FIG. 2  is a flowchart of driving the liquid crystal display module  12  according to the present invention. The method includes following steps: 
   Step  100 : The noise-receiving module  18  receives external noise signals. 
   Step  102 : The signal amplifier  22  amplifies the noise signals received by the noise-receiving module  18 . 
   Step  104 : The frequency analysis circuit  24  analyzes frequencies of the amplified noise signals. 
   Step  106 : The frequency discrimination circuit  26  discriminates a frequency of the noise signal with the largest signal energy according to an analysis result of the frequency analysis circuit  24 . 
   Step  108 : The multiplexer  30  outputs a signal corresponding to the specific scanning frequency generated by the drive circuit  16  to the liquid crystal display panel  14  according to a discrimination result of the frequency discrimination circuit  26 . 
   Step  110 : The liquid crystal display panel  14  displays images at the specific scanning frequency. 
   Step  112 : End. 
   First the noise-receiving module  18  receives external noise signals. For example, the electromagnetic field intensity of the noise signal at a frequency 50 Hz is greater than the electromagnetic field intensity of the noise signal at other frequency when locating in a region wherein the frequency of the power supply is 50 Hz, such as the region applying Phase Alternation Line (PAL) standard. The electromagnetic field intensity of the noise signal at a frequency 60 Hz is greater than the electromagnetic field intensity of the noise signal at other frequency when locating in a region wherein the frequency of the power supply is 60 Hz, such as the region applying National Television Standards Committee (NTSC) standard. The frequency of the fluorescent lamp can be obtained by utilizing the noise-receiving module  18  to detect the frequency of electromagnetic interference. The noise-receiving module  18  can be a conducting wire of Indium Tin Oxide glass of the liquid crystal display panel  14  for receiving noise signals. When the liquid crystal display device  10  is applied in portable communication devices, such as mobile phones and personal data assistants (PDA), the noise-receiving module  18  can be an antenna module for receiving noise signals as the wireless communication module of the portable communication devices. The noise signals received by the noise-receiving module  18  are transmitted to the signal amplifier  22  of the frequency-switching means  20 , and the signal amplifier  22  amplifies the noise signals. Then the frequency analysis circuit  24  analyzes frequencies of the amplified noise signals. The frequency discrimination circuit  26  discriminates the frequency of the noise signal with the largest signal energy according to the analysis result of the frequency analysis circuit  24 . For example, the band-pass filters  28  filter the noise signals at the frequencies 50 HZ and 60 Hz, and then the frequency discrimination circuit  26  discriminates which output peak value is greater with the band-pass filters  28  so as to discriminate that the frequency of the noise signal with the largest signal energy is 50 Hz or 60 Hz. Please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  is a time response diagram of the noise signals received by the noise-receiving module  18  according to the present invention.  FIG. 4  is a frequency response diagram of the noise signals analyzed by the frequency analysis circuit  24  according to the present invention. The frequency analysis circuit  24  can process spectrum analysis with the noise signals in time domain as shown in  FIG. 3  to transform the noise signals in time domain into frequency domain. Then the frequency discrimination circuit  26  discriminates the frequency of the noise signal with the largest signal energy is 60 Hz so as to discriminate that the frequency of the power source is 60 Hz in that region. 
   Then the multiplexer  30  outputs the signal corresponding to the specific scanning frequency generated by the drive circuit  16  to the liquid crystal display panel  14  according to the discrimination result of the frequency discrimination circuit  26 . For example, when the frequency discrimination circuit  26  discriminates the frequency of the noise signal with the largest signal energy is 50 Hz, the frequency discrimination circuit  26  outputs a corresponding selecting signal to the multiplexer  30 . After the multiplexer  30  receives the corresponding selecting signal, the multiplexer  30  outputs a driving signal corresponding to the scanning frequency 50 Hz transmitted from the drive circuit  16  selectively to the liquid crystal display panel  14  so as to drive the liquid crystal display panel  14  to display images at the scanning frequency matching 50 Hz. Similarly when the frequency discrimination circuit  26  discriminates the frequency of the noise signal with the largest signal energy is 60 Hz, the frequency discrimination circuit  26  outputs a corresponding selecting signal to the multiplexer  30 . After the multiplexer  30  receives the corresponding selecting signal, the multiplexer  30  outputs a driving signal corresponding to the scanning frequency 60 Hz transmitted from the drive circuit  16  selectively to the liquid crystal display panel  14  so as to drive the liquid crystal display panel  14  to display images at the scanning frequency matching 60 Hz. 
   In contrast to the conventional liquid crystal display device and the driving method thereof, the liquid crystal display device and the driving method thereof according to the present invention discriminate the frequency of the external noise signal with the largest signal energy for discriminating the frequency of the fluorescent lamp. The scanning frequency of the liquid crystal display device can be adjusted according to the discrimination result so as to match the scanning frequency of the liquid crystal display device with the frequency of the fluorescent lamp. The present invention solves the problem that users feel glittery and uncomfortable when the scanning frequency of the liquid crystal display device can not match the electric power frequency of the fluorescent lamp. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.