Liquid crystal display driver and method thereof
AssigneeIBM Corporation
InventorsYoshitami Sakaguchi, Katsuyuki Sakuma
Life of this patent
Estimating the term…
Abstract
JP920010105US125 A liquid crystal display driver for applying a voltage to liquid crystal cells forming an image display area includes a pulse generation circuit for generating a plurality of reference pulses in which pulse generation densities are weighted, a pulse select/synthesis circuit for generating a pulse string by selecting and synthesizing necessary reference pulses on the basis of digital input data and the reference pulses and an integration circuit (low pass filter) for integrating the pulse string generated by the pulse select/synthesis circuit to output an analog voltage for gamma correction.
Claims18
A liquid crystal display, comprising:
- liquid crystal cells forming an image display area on a substrate;
- and
- a driver for applying a voltage to said liquid crystal cells based on a reference voltage for gamma correction corresponding to digital input data, wherein said driver keeps a number of switching times for pulse strings per time unit constant for a predetermined range of said digital input data when generating the pulse strings with pulse densities corresponding to said digital input data.
A liquid crystal display, comprising:
- liquid crystal cells forming an image display area on a substrate;
- and
- a driver for applying a voltage to said liquid crystal cells based on a reference voltage for gamma correction corresponding to digital input data, wherein said driver has no local peak in a number of switching times for pulse strings per time unit when generating the pulse strings with pulse densities corresponding to said digital input data.
A liquid crystal display, comprising:
- liquid crystal cells forming an image display area on a substrate;
- and
- a driver for applying a voltage to said liquid crystal cells based on a reference voltage for gamma correction corresponding to digital input data, wherein said driver obtains an output voltage using pulse density modulation (PDM) as well as obtains an output voltage using pulse width modulation (PWM) for a predetermined range of said digital input data around a medium value when generating pulse strings corresponding to said digital input data.
A liquid crystal display driver for applying a voltage to liquid crystal cells forming an image display area, comprising:
- a pulse generation circuit for generating a plurality of reference pulses in which pulse generation densities are weighted;
- and
- a pulse select/synthesis circuit for generating a pulse string by selecting and synthesizing necessary reference pulses on the basis of digital input data and said reference pulses, wherein said pulse generation circuit generates said reference pulses without changing a number of switching times per time unit for a predetermined range of said digital input data around a medium value.
A reference pulse generation circuit for generating reference pulses corresponding to n-bit digital input data, comprising:
- an n-bit binary counter for counting up in synchronization with an input clock;
- an n−1 bit latch for generating signals by delaying high order n−1 bits output B (n−1) through B(1) from said binary counter by one input clock period;
- and
- n−1 logical circuits for performing logical operations with receiving as inputs said high order n−1 bits output B(n−1) through B(1) from said binary counter and the delayed signals corresponding to the high order n−1 bits output B(n−1) through B(1) from said n−1 bit latch and obtaining outputs X(0) through X(n−2) with lower reference pulse densities, whereas output X(n−1) is obtained bypassing the logical circuit.
A reference pulse generation circuit for digital-analog conversion employing a pulse density modulation scheme, comprising:
- means for generating reference pulses that are exclusively in a high state corresponding to digital input data;
- and
- means for generating the reference pulses such that a number of switching times for pulse strings per time unit is constant for a predetermined range of said digital input data around a medium value.
A method for generating reference pulses in a digital-analog converter, comprising the steps of:
- generating pulse strings with pulse densities corresponding to digital input data that is input to said digital-analog converter;
- and
- keeping a number of switching times for said pulse strings per time unit constant for a predetermined range of said digital input data around a medium value.
A method for providing an analog voltage output corresponding to digital input data, comprising the steps of:
- for a range of said digital input data excluding a predetermined range around a medium value, integrating a pulse string, whose number of pulses is adjusted depending on said digital input data, to output an analog voltage;
- and
- for the predetermined range of said digital input data around said medium value, integrating a pulse string, whose duty is adjusted depending on said digital input data, to output an analog voltage.
Dependencies are inferred from the claim text.