Patent ID: 8711068
Filing Date: 2014-04-29
Classification: G09G

Abstract:
1. A liquid crystal display device comprising: a frame counter operable to count a number of an input frame; a controller operable to judge a scan line system of an image signal displayed on a liquid crystal display panel via a frame number counted by the frame counter during a designated unit time to selectively control a supply of a first common voltage and a second common voltage based on the judged scan line system, wherein the controller includes a first control output port for outputting a first enable/disable signal and a second control output port for outputting a second enable/disable signal; a first common voltage generator operable to supply the first common voltage directly to a common electrode of liquid crystal cells based on a control of the controller wherein the first common voltage generator is configured to be enabled and disabled via the first enable/disable signal communicated from the first control output port; and a second common voltage generator operable to supply the second common voltage directly to a common electrode of liquid crystal cells based on a control signal of the controller wherein the second common voltage generator is configured to be enabled and disabled via the second enable/disable signal communicated from the second control output port, wherein the frame counter counts a number of a rising edge of the input vertical synchronizing signal to thereby count a frame number, wherein if the counted frame number is the same as a predetermined first reference frame number to be judged as a phase-alternating line (PAL) system, the controller communicates the first enable/disable signal comprising an enable signal via the first control output port to the first common voltage generator and simultaneously communicates the second enable/disable signal comprising a disable signal via the second control output port to the second common voltage generator at the same time, wherein if the counted frame number is the same as a predetermined second reference frame number to be judged as a National Television Systems Committee (NTSC) system, the controller communicates the second enable/disable signal comprising an enable signal via the second control output port to the second common voltage generator and simultaneously communicates the first enable/disable signal comprising a disable signal via the first control output port to the first common voltage generator at the same time, and wherein the first and second common voltage generators are separate and independently controlled by the controller.