Gamma Curve ADC Interpolation for Lower LCD Circuit Area

Solution Overview

Problem

Conventional analog to digital converters for liquid crystal displays require large circuit areas and high costs due to increased bit numbers and non-linear pixel voltage relationships, resulting in higher errors and poorer display quality.

Innovation Solution

An analog to digital converter design utilizing a decoding device with multiple decoding circuits and an operational amplifier to generate pixel voltages through interpolation, allowing flexible selection of linear and non-linear segments of the Gamma curve, reducing circuit area and cost while minimizing pixel voltage errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the bit number of grey level and the grade of Gamma voltage resistor string are increased to improve display quality, then the display quality is improved, but the circuit area and cost increase dramatically

Engineering Contradiction:

Improvedisplay qualityVSAvoidcircuit area

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

The patent divides the k-bit grey level into multiple segments: w most significant bits (MSBs), x MSBs next to the w MSBs, y MSBs next to the x MSBs, and z LSBs. This segmentation allows different decoding circuits to handle different bit segments independently, reducing the overall circuit complexity and area while maintaining display quality through selective interpolation in specific segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying interpolation to all digital codes, the patent selectively applies interpolation only to certain segments (specifically when w MSBs correspond to different logic values). This partial action approach reduces computational overhead and circuit area while maintaining adequate display quality by focusing interpolation resources where they are most needed.

Inventive Principle:

Principle #16Partial or excessive action

2Manufacturing precision

If the bit number of grey level and the grade of Gamma voltage resistor string are increased to improve display quality, then the display quality is improved, but the cost increases accordingly

Engineering Contradiction:

Improvedisplay qualityVSAvoidcost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent divides the k-bit grey level into multiple segments: w most significant bits (MSBs), x MSBs next to the w MSBs, y MSBs next to the x MSBs, and z LSBs. This segmentation allows different decoding circuits to handle different bit segments independently, reducing the overall circuit complexity and area while maintaining display quality through selective interpolation in specific segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying interpolation to all digital codes, the patent selectively applies interpolation only to certain segments (specifically when w MSBs correspond to different logic values). This partial action approach reduces computational overhead and circuit area while maintaining adequate display quality by focusing interpolation resources where they are most needed.

Inventive Principle:

Principle #16Partial or excessive action

3Area of stationary object

If interpolation is applied to each digital code to down-size the analog to digital converter, then the circuit area is reduced, but the pixel voltage has larger error and the liquid crystal display has poorer display quality

Engineering Contradiction:

Improvecircuit areaVSAvoidpixel voltage error

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies different processing strategies to different segments of the grey level code. Specifically, it performs interpolation only when w MSBs correspond to different logic values, while using direct conversion for other cases. This local differentiation ensures that interpolation is applied where it most improves accuracy (reducing pixel voltage error) while avoiding it where it would unnecessarily increase circuit complexity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of applying interpolation to all digital codes, the patent selectively applies interpolation only to certain segments (specifically when w MSBs correspond to different logic values). This partial action approach reduces computational overhead and circuit area while maintaining adequate display quality by focusing interpolation resources where they are most needed.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS8742967B2Analog to digital converter

Publication Date: 2014.06.03 RAYDIUM SEMICON

AI summary

An analog to digital converter generating a number of corresponding voltages in response to a number of values of a grey level is provided. The analog to digital converter includes a decoder and an operational amplifier. The decoder provides first to third output voltages having the same level when w most significant bits (MSBs) of the grey level correspond to the same value, provides first and second intermediate voltages in response to the x MSBs next to the w MSBs when the w MSBs correspond to different values, and selectively has the first to the third output voltages equal to one of the first and the second intermediate voltages. The operational amplifier obtains a pixel voltage by interpolating the first to the third output voltages, wherein the sum of w and x is smaller than or equal to the bit number of the gray level.