Brightness Compensation Circuitry for AMOLED Displays

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Solution Overview

Problem

Conventional AMOLED displays using TFTs in the saturation region face issues with high current requirements, power consumption, and brightness uniformity due to threshold voltage drift and degradation, which are exacerbated by high aspect ratio and high definition displays.

Innovation Solution

A brightness compensation circuitry with a data-setting switch unit, pixel units, and a compensation circuit that operates in the subthreshold region, allowing precise control of driving current to meet target brightness and reduce power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If TFTs operate in saturation region to drive OLEDs, then sufficient driving current is provided, but power consumption increases and current requirements become too high for small size and high resolution displays

Engineering Contradiction:

Improvedriving currentVSAvoidpower consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent changes the operational parameter of TFTs from saturation region to subthreshold region, fundamentally altering the current-voltage characteristics to achieve lower power consumption while maintaining adequate driving current through compensation mechanisms

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback mechanism where the compensation circuit monitors the actual brightness output and adjusts the driving current accordingly, allowing the system to operate in subthreshold region while maintaining sufficient OLED drive current through real-time compensation

Inventive Principle:

Principle #23Feedback

2Quantity of substance

If TFTs operate in saturation region, then high current is generated, but this exacerbates power consumption issues in high aspect ratio and high definition displays

Engineering Contradiction:

Improvecurrent magnitudeVSAvoidpower consumption

Core Design Contradiction:

Quantity of substanceVSUse of energy by stationary object

Solution Approach 1:

The patent transforms the operational mode from saturation to subthreshold region, changing the fundamental parameter regime to achieve lower current magnitudes and reduced power consumption suitable for high definition displays

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If no current compensation is provided, then circuit complexity is reduced, but brightness uniformity deteriorates due to threshold voltage drift and degradation

Engineering Contradiction:

Improvecircuit structureVSAvoidbrightness uniformity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The compensation circuit implements a feedback loop that detects threshold voltage drift and degradation in real-time, adjusting the driving signal to compensate for these changes and maintain uniform brightness across the display

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The compensation circuit proactively addresses threshold voltage drift before it significantly impacts brightness uniformity, continuously monitoring and adjusting parameters to prevent degradation effects

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10339895B2Brightness compensation circuitry, and display device including the same

Publication Date: 2019.07.02 ANDRITZ INC

AI summary

A brightness compensation circuitry includes a data-setting switch unit receiving a data-setting signal, a pixel unit including a pixel driving circuit that receives the data-setting signal during a data-input period to generate a driving current, and a compensation circuit receiving the driving current generated by the pixel driving circuit. The compensation circuit controls the data-setting switch unit to conduct or not conduct by determining whether or not a magnitude of the driving current conforms with a criterion that is associated with target brightness of the pixel unit.