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LCD module with checkered common voltage swing Disclosure Number: IPCOM000015437D
Original Publication Date: 2001-Nov-17
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 79K

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LCD module with checkered common voltage swing


  Described in this paper is a method to reduce the voltage rating of the source drivers used in TFT-LCD modules.

    To pattern the VCOM lines into checkered two channels and swinging each VCOM electrode opposite to the source electrode, make it possible to provide higher voltage than conventional method using conventional dot inversion source drivers without losing the advantages of the dot inversion drive method.

    In other words, makes it possible to use lower rating source drivers, which cost lower than the higher rating ones.

    The screen quality is the same level of the traditional ~ Dot inversion drive~ method, and the cost capability will close to the traditional ~Line inversion drive~ method.


  The major driving method of TFT-LCD modules is called ~ Dot inversion~ . This method provide the opposite polarity of the voltage vertically and horizontally side by side to each pixels, to reduce clustered DC voltage in the screen which may result in ~ image sticking~ and to reduce the screen flickering.

  However because of the polarity is opposite side by side, and the VCOM voltage is just a single channel, the source driver has to have the capability to provide two times voltage of the amplitude to be supplied to the each pixel. This disadvantage makes it difficult to increase the amplitude to be supplied to each pixel, nor to reduce the rating of the source drivers.

Output of the source driver (to be provided to each pixel)

Supply voltage to the source driver (AVDD)


Pixel voltage(Vamp)

The outline of newly proposed idea

  Divide the VCOM channel in two channels, then swing each channel opposite to the polarity provided to each pixel.

VCOM channel-A

VCOM channel-B


GND level

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Vpix-positive = Vsource-positive - VCOMpositive

               = Vsource-positive - VCOMtraditional + Vswing Vpix-negative = VCOMnegative - Vsource-negative

= VCOMtraditional - Vsource-negative + Vswing

  Because the VCOM is divided into checkered two channels, the source lines across Ch-A and Ch-B alternately, so the action of inverting the VCOM occurs just one time per a frame.

The traditio...