Liquid Crystal Display Common Voltage Ripple Compensation

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Solution Overview

Problem

Liquid crystal display devices driven by inversion methods suffer from image quality deterioration due to common voltage ripples, which are not adequately addressed by existing compensation methods, particularly at gate voltage off timing.

Innovation Solution

A method that calculates the total sum of changed data voltages between row lines, generates common voltage data, and compensates it using a liquid crystal panel's characteristic parameter to output a common voltage that effectively eliminates ripples, synchronizing with data voltage output and adjusting voltage levels as needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If an inversion driving method is used to prevent DC stress in liquid crystal, then liquid crystal durability is improved, but common voltage ripples are generated causing image quality deterioration

Engineering Contradiction:

Improveliquid crystal durabilityVSAvoidcommon voltage ripples

Core Design Contradiction:

Duration of action of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the common voltage is monitored and the changed amounts of data voltages are calculated and fed back to adjust the common voltage. Specifically, the operation block calculates the total sum of changed amounts of data voltages between consecutive row lines and uses this information to compensate for common voltage ripples, creating a closed-loop control system that continuously optimizes common voltage stability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically changes the common voltage parameter based on calculated data voltage variations. The common voltage generator adjusts the common voltage level according to the compensated common voltage data, which is derived from the total sum of changed amounts of data voltages. This parameter adaptation allows the system to maintain optimal common voltage levels under different driving conditions.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If line inversion method is used to invert polarity in units of row line, then driving efficiency is improved, but common voltage ripples become significant

Engineering Contradiction:

Improvedriving efficiencyVSAvoidcommon voltage ripples

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary calculation of the total sum of changed amounts of data voltages before generating the common voltage. The operation block computes the voltage changes in advance for each row line transition, and the common voltage generator uses this pre-calculated information to proactively adjust the common voltage, preventing ripple formation rather than reacting after ripples occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces dynamic adjustment of common voltage based on real-time data voltage variations. Instead of using a fixed common voltage, the system continuously adapts the common voltage level according to the calculated changed amounts of data voltages between consecutive row lines, making the common voltage dynamic and responsive to driving conditions.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If inverting OP amplifier is used to output opposite voltage to common voltage ripple, then compensation is provided, but sufficient inverted voltage is not supplied at gate voltage off timing

Engineering Contradiction:

Improvecommon voltage ripple compensationVSAvoidcompensation precision at gate voltage off timing

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent segments the compensation process into discrete row line transitions. Instead of attempting to compensate for all common voltage variations continuously, the system calculates and compensates for voltage changes on a per-row-line basis, analyzing the transition from (n-1)-th row line to n-th row line individually. This segmentation allows precise targeting of compensation at critical moments including gate voltage off timing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the analog inverting OP amplifier approach with a digital calculation and generation system. Instead of using analog circuitry to generate inverted voltages, the system uses digital operations to calculate the total sum of changed amounts of data voltages and generates compensated common voltage data, which is then converted to analog voltage. This substitution provides better control precision and timing accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9324284B2Liquid crystal display device compensating for common voltage and method of driving the same

Publication Date: 2016.04.26 LG DISPLAY CO LTD

AI summary

There is provided a driving method of a liquid crystal display device that is driven by an inversion method, including: calculating a total sum of changed amounts of data voltages between an (n−1)-th row line and an n-th row line, using image data of the (n−1)-th row line and image data of the n-th row line; generating common voltage data according to the total sum of the changed amounts of the data voltages; compensating for the common voltage data using a characteristic parameter of a liquid crystal panel; and generating a common voltage according to the compensated common voltage data, and outputting the common voltage to the liquid crystal panel.