How The TFT Module Works

- Jul 04, 2018 -


TFT LCD working principle

        In a TFT-LCD, the function of the TFT is a switching transistor. A commonly used TFT is a three-terminal device. The current applied between the source and drain electrodes is controlled by the voltage applied to the gate. For the display screen, each pixel can be seen as a layer of liquid crystal between the pixel electrode and the common electrode. More importantly, it can be considered as a capacitor from an electrical point of view. The equivalent circuit is shown in Figure 1. To charge the pixel P(i,j) of the j-row i column, the switch T(i,j) is turned on, and the target voltage is applied to the signal line D(i). When the pixel electrode is sufficiently charged, even if the switch is turned off, the charge in the capacitor is preserved, and the liquid crystal molecules between the electrodes continue to have an electric field. The role of the data (column) driver is to apply the target voltage to the signal line, and the gate (row) driver functions to turn the switch on and off. The key to displaying an image is also the molecular orientation of the liquid crystal under the action of an electric field. Different display modes are generally achieved by orientation treatment of the inside of the substrate to cause a desired deformation of the alignment of the liquid crystal molecules. Under the action of the electric field, the liquid crystal molecules undergo an orientation change, and by the cooperation with the polarizing plate, the intensity of the incident light changes after passing through the liquid crystal layer. Thereby achieving image display. TFT-LCD colorization is typically achieved by adding a layer of color filter to the front panel of the display. It requires red, green, and blue colors and a black matrix for shading on each pixel.

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