TFT LCD with experience

First of all, we understand the structure of a number of TFT LCD, as shown below, mainly by the polarizer, consider color base plate, LCD, TFT substrates, chip-chip oscillator, backlight components. Consider color in the base plate and the TFT substrate enclosed in twisted nematic liquid crystal (TN), constitute the liquid crystal cell, taking into account color devices are fabricated on a transparent substrate a common electrode, TFT substrate produced a matrix of thin-mode transistor, for the opening pixel electrode voltage signal, in order to maintain a certain thickness of the liquid crystal layer, placed between two pieces of glass with transparent septum (polyester film or glass ball mode).

     TFT LCD signal components: the main circuit from the backlight and display circuit.
     Backlight circuit: 3.5-inch TFT LCD backlight, mostly using white LED as backlight source, usually by 6 white LED serial composition (as shown), probably drive voltage of about 20V, 20mA current around a lot of parts consumption . For battery-powered systems, most of the boost DC / DC to drive, many manufacturers have introduced specifically for white LED drive thread.
     Display circuit: the display circuit generally Timing Controller, Source LCD Driver, Gate Driver composition. Some IC Timing Controller and Source Driver to integrate together, and some IC are integrated into three parts. This three-part integrated circuits are generally inside the TFT LCM, and some TFT LCD Timing Controller IC to put out a (such as SHARP some of the LCD).
     SAMSUNG LTV350QV LCD Block Diagram Analysis (as shown): LTV350QV the DRIVER IC is S6F2002,
S6F2002 Integrated Timing Controller, Source Driver, Gate Driver section and power management components, 164RGB X 240 driving ability, so for 320 X 240 QVGA resolution, you need two S6F2002. Two S6F2002, one as the main controller, one as a slave controller, it is precisely because there are two LVT350QV DRIVER IC driver's sake, if the timing with the bad power, it is prone to show abnormal (half of the display is not normal, half of the show normal).
     A block diagram of the Taiwan TFT LCD (below): it is driven IC has two pieces, one integrates the Timing Controller and Source Driver, another one is the Gate Driver.

     TFT LCD common signal interpretation:
     LED_Cathode / LED_Anode: LCD backlight power supply
     M / POL: LCD driver polarity model, used to generate VCOM signal
     RESET: Global reset signal
     CS / SCL / SDI: LCD TCON IC configuration port
     DATA [0:23]: LCD RGB24BIT data signal, generally we use 16BIT, as observed by the human eye color and 24BIT 16BIT color is not much different, but 16BIT 24BIT required data to be processed is much smaller than the general the status of the remaining cases we have data cable to connect to high.
     HSYNC: Horizontal sync clock signal
     VSYNC: Vertical sync clock signal
     DOTCLK: pixel clock signal
     VDD: digital power supply, usually 3.3V
     AVDD: Analog power supply, usually 5V
     VGL: GATE OFF control voltage
     VGH: GATE ON control voltage
     VCOM: LCD common drive electrode
     ENABLE: data enable signal
     TFT circuit driving principle: sent by the CPU through the LCD interface, the video signal and the timing clock after TCON converter, RGB data through the D / A converter to the SOURCE side, while the shift clock signal driving TCON GATE side strobe line open the line all the transistors, SOURCE capacitor to the LCD, grayscale LCD produce and maintain, through the GATE shift, continue to write the following line of the LCD image, when the whole line of finish, starting from the first line again.
     If you always show a static image, the LCD voltage on the electrode would have been the same, when the revocation of voltage, the LCD is difficult to be reinstated, and likely to cause liquid damage. To solve this problem is to change the polarity of the LCD control voltage, that even the static images, the voltage on the liquid crystal electrodes have also been overturned. LCD are used generally in the form of flip line, by changing the voltage polarity of VCOM the public to achieve the purpose of flipping. TCON IC will normally send a signal M or POL, and we use this signal generator VCOM, the general conversion circuit using a non-party circuit have or shipped. VCOM by adjusting the DC side, we can change the color LCD, adjust AC side, you can change the LCD contrast. Perhaps the reason is because the line flip, and some level of LCD will produce stripes (Flicker phenomenon), LTV350QV not very clear, generally more obvious in Taiwan LCD.

     Point-screen experience:
     Common point screen steps:
1, ensure that the data, clock, power and other connections to normal.
2, to ensure that the work of several groups of LCD power supply VDD / AVDD / VGL / VGH normal.
3, LCD Configuration: Some LCD's TCON IC need to use the SPI interface configuration.
a) configuration is mainly the polarity of the clock signal, scanning direction, and some support CCIR601/656/OSD TCON IC function, according to the actual situation of the main configuration.
b) GAMMA correction: the general parameters provided by the manufacturer under the LCD correction, before the transfer is because the manufacturers give LTV350QV GAMMA parameter is incorrect, resulting in the color display is not normal.
c) SPI time series: general different LCD screen SPI timing and registers, there will be some differences, I usually operate under the register timing diagram (below), by writing to registers, as long as the LCD has responded, that there is little SPI communication problem.
4, the clock setting:
a) general LCD SPEC will be given in the parameters on the timing and sequence diagram, we follow the figure set on it. The following figure: we can know that the clock frequency, pulse width, the first sweep, retrace and so on.
         As shown by the picture we can know the HSYNC and VSYNC clock polarity is negative.
     Through the following figure we can know is latched data, falling edge of the data
     Through the above steps should appear above the LCD screen is beautiful, the image position may also have some bias, but that's okay, look at the screen before scanning the image adjustment, left and right back to sweep up or down to OK.
     Image exception handling:
     Image color is not normal: it is possible clock polarity model, there may VCOM adjustment is not normal.
     Water ripples appear: Make sure the power VDD / AVDD / VGL / VGH ripple is small enough to ensure that the correct waveform VCOM, VCOM circuit side of the power supply stability.
     Black and white on the CLP: General TFT LCD on power requirements are more stringent, the timing required in accordance with the Power LCD SPEC