Patent ID: 6462728
Filing Date: 2002-10-08
Classification: G09G

Abstract:
An apparatus for applying various levels of voltage to individual pixels in a display device having a matrix of pixels arranged vertically in columns and horizontally in rows, said apparatus comprising:(a) a digital signal source for producing a plurality of digital signals which change monotonically in value in successive steps during a frame cycle, and repeat such changes during a plurality of successive cycles; (b) a digital-to-analog converter (DAC), connected to said digital signal source, for producing a voltage signal having a value corresponding to that of said digital signal; (c) a plurality of column drivers, each column driver being associated with a column of the display device and including a track and hold circuit, coupled to the pixels in the respective column of said display device, for storing said voltage signal when it reaches a prescribed value, said prescribed value corresponding to a particular brightness level of a pixel in the respective column and in a particular row during a given cycle; (d) a column control circuit, coupled to said column drivers, for causing respective ones of said track and hold circuits to store said voltage signal when it reaches said prescribed value for each respective column; and; (f) a row control circuit for repeatedly selecting one or more pixel rows which receive the voltage signals stored in said track and hold circuits of said column drivers; the improvement wherein said column control circuit comprises: (1) a plurality of column registers, each column register being associated with a column of said display device, for storing a digital number corresponding to the desired brightness level of a pixel in the respective column; (2) a control circuit coupled to the column registers for causing each column driver associated with a respective column to hold the voltage signal when it reaches a value corresponding to a digital number stored the column register associated with that column; and (3) an input circuit, coupled to said plurality of column registers, for supplying digital numbers to said column registers, said input circuit causing said digital numbers to alternate during a plurality of frame cycles between a number representing a value above, and a number representing a value below the desired brightness level of a pixel in each respective column when the desired brightness level falls between such two values.