LCD Driving Apparatus Precharge Compensation Fields
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Solution Overview
Problem
Liquid crystal displays (LCDs) suffer from slow response times and image residue due to their hold-type frame display method, which affects displaying quality compared to traditional CRT monitors.
Innovation Solution
The method involves dividing a frame period into a precharge field and a compensation field, determining precharge and compensation pixel values, and applying corresponding driving voltages to improve response speed and reduce image residue, mimicking the impulse-type display of CRTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LCD uses hold-type frame display method, then each pixel emits constant light during frame period, but response time is slow and image residue occurs
Solution Approach 1:
The frame period is divided into multiple sub-fields (first sub-field and second sub-field), each with different driving voltages. This segmentation allows the liquid crystal molecules to undergo multiple switching cycles within one frame period, effectively reducing the overall response time while maintaining stable light emission through cumulative hold effect.
Solution Approach 2:
The patent applies periodic voltage switching within the frame period by dividing it into multiple sub-fields with alternating high and low driving voltages. This periodic action accelerates liquid crystal molecule response by creating multiple transition cycles, thereby reducing response time while the cumulative hold effect across sub-fields ensures stable illumination.
2Illumination intensity
If LCD uses hold-type frame display method, then each pixel maintains constant light output, but image residue overlaps with next frame image
Solution Approach 1:
By segmenting the frame period into multiple sub-fields with alternating voltage levels, the patent creates distinct switching phases that prevent image residue accumulation. Each sub-field contributes to the overall image while the alternating voltage pattern ensures complete molecular response before the next frame begins, eliminating overlap and residue effects.
Solution Approach 2:
The periodic alternation between high and low driving voltages across multiple sub-fields creates a rhythm of molecular switching that completes full response cycles within each frame period. This periodic action ensures that liquid crystal molecules fully respond to each voltage change before the next frame starts, preventing image residue while maintaining consistent light output.
3Loss of time
If over-driving method is used to improve response speed, then response time decreases, but display quality is still not satisfying due to hold-type display
Solution Approach 1:
The patent segments the frame period into multiple sub-fields, each applying different driving voltages. This segmentation enables over-driving in specific sub-fields to accelerate response while other sub-fields maintain proper voltage levels to ensure accurate light output, thus improving both response time and display quality simultaneously.
Solution Approach 2:
By implementing periodic voltage switching across multiple sub-fields with alternating high and low driving voltages, the patent achieves over-driving effects that accelerate liquid crystal response. The periodic pattern ensures that accelerated response in high-voltage sub-fields is balanced by proper voltage application in low-voltage sub-fields, maintaining display quality while reducing overall response time.
Data Source
AI summary
A pixel of the LCD is driven according to a precharge pixel value and a compensation pixel value both being generated from a pixel value during a precharge field and a compensation field respectively. A precharge driving voltage corresponding to the precharge pixel value, and a compensation driving voltage corresponding to the compensation pixel value is then determined and used to drive the pixel. The lightness of the pixel driven according to the precharge pixel value and the compensation pixel value is substantially the same as the lightness of the pixel if driven according to the pixel value. The precharge field comes before the compensation field when the precharge pixel value is larger than the compensation pixel value, and the compensation field comes before the precharge field when the compensation pixel value is larger than the precharge pixel value.