Sanyo TI5110LCD Training Manual

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-19-Training Manual Principle of LCDSystem of LCD DisplayY 0 Y 1 Y 2 Y 3X0X1X2X3Liquid CrystalCOMMON ElectrodeTFT (Switch)Fig. 18 Structure of TFT MatrixThe LCD shutter is operated byTFT at the address (X1, Y0).The amplification operation of a transistor is used for the TFT switch in the active matrix system. In thissystem, switching speed is unified over the whole display, increasing drive response speed as comparedwith the passive matrix system. Therefore, TFT LCD display (active matrix system) is adopted for thehighly efficient display, which can provide the response speed required for big screens or quickly movingpictures. However, further response speed is needed for high definition LCD television. This will bedescribed later.5-6 Drive of Active Matrix SystemThe TFT LCD display consists of a matrix of n lines of X direction (X0 - Xn-1) and of n rows of Y direction(Y0 - Yn-1). The line of X direction is called the “gate line” and the line (row) of Y direction is called the“data line.”First, the scan is started from the pixel address(X0, Y0), and when the address (X0, Yn-1) isselected the scan of X0 line is completed. Next, allthe pixels from X1 line to Xn-1 line are scanned insequence, and the final address is (Xn-1, Yn-1).The operation of selected pixel address (X1, Y2)is explained below.First, (signal) voltage is supplied to X1 line (gateof TFT), next voltage is supplied to Y2 row (sourceof TFT), and the address of the intersection of X1line and Y2 row is selected and its TFT is turnedOn or Off. However, just switching the TFT on andoff will not change the brightness of the screen.The brightness of a screen is changed by control-ling the voltage of a data line (Y row). Fig. 19shows the voltage characteristic of the matrix sys-tem.TimeActive Matrix SystemVoltage to liquid crystalPassive Matrix SystemFig. 19 Voltage Characteristic of Matrix SystemSince the time for the drive voltage to reach itsrequired value is shorter in the active matrix system,the response time of the display becomes quicker.