Patent ID: 7113161

Claim:
A horizontal shift clock pulse selecting circuit for driving a color LCD panel, comprising: a voltage controlled oscillator; an odd number line horizontal shift clock generator for generating an odd number line horizontal shift clock to select a pixel in an odd number line of the color LCD panel based on an output signal of said voltage controlled oscillator; an even number line horizontal shift clock generator for generating an even number line horizontal shift clock to select a pixel in an even number line of the color LCD panel based on an output signal of said voltage controlled oscillator; a horizontal shift clock switching device for selectively outputting said odd number line horizontal shift clock and said even number line horizontal shift clock to the color LCD panel; and a shift clock switch controller for providing a shift clock switching signal to said horizontal shift clock switching device, wherein: said shift clock switch controller receives controlling inputs including a PAL skip signal for skipping a horizontal scanning period at a ratio of m horizontal scanning periods per n horizontal scanning periods, wherein m and n are both arbitrary integers that satisfy the condition m<n, an H/2N pulse to be inverted in a cycle of one 2Nth of a horizontal scanning period H, wherein N is a positive integer, and a line selecting pulse for selecting either an odd number line or an even number line, said shift clock switch controller causes said horizontal shift clock switching device to select either an odd number line shift clock or an even number line shift clock according to said line selecting pulse in a normal period where said PAL skip signal is not at an effective level, and said shift clock switch controller inverts a selecting state of said horizontal shift clock by said horizontal shift clock switching device in a cycle of one 2Nth of a horizontal scanning period H in response to said H/2N pulse in a PAL skip period where said PAL skip signal is at an effective level.