LCD Screen Drive And Features

- Jul 19, 2018-

     

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A driving voltage is applied between the segment electrode of the LCD and the common electrode. In order to extend the life of the liquid crystal, an alternating current voltage (AC) is used instead of a direct current voltage (DC).

    The LCD screen can be static or dynamic. The static drive features high contrast, uniform display, fast response and easy control. However, since each segment is driven separately, the number of electrodes is large. Therefore, dynamic driving is usually adopted.

    LCD drive waveforms can be described in three ways;

    LCD drive voltage (VLCD)

    The driving voltage of the LCD is the difference between the segment voltage applied to the lighting portion and the common voltage (peak-to-peak).

    Duty cycle

    In order to reduce the number of electrodes on the LCD, multi-channel driving is adopted, and the voltage of the LCD is an alternating current waveform, and the duty ratio Duty of the LCD is a ratio of a portion of the threshold voltage higher than the threshold voltage in one cycle.

    Bias ratio (Bias)

    The driving waveform of the LCD is composed of several levels. In order to prevent the contrast from being uneven, a certain voltage is added to the electrode corresponding to the non-lighting pixel, which reduces the cross interference caused by the lighting pixel and prevents the contrast from being uneven. important.

    The ratio of the voltage effective value of the non-lighting pixel (non-selected point) in the LCD to the effective value of the lighting pixel (selection point) voltage (1/n) is called the bias ratio. When ordering a liquid crystal display, the selected drive voltage, duty cycle, and bias ratio should match the driver.

    LCD characteristics

    Depending on the application and performance requirements of the customer's product, the appropriate level of reliability should be chosen and there are three types of reliability levels. They are standard reliability level (STD), high reliability level (HQ) and ultra high reliability level (SHQ). Generally speaking, the higher the reliability level, the better the display performance.