OLED Pixel Current Sensing Circuit for Luminance Compensation
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Solution Overview
Problem
Organic light emitting displays face luminance variations due to changes in driving TFT characteristics over time, leading to inconsistencies and reduced lifespan, and existing compensation methods require additional gate drivers and multiplexers, increasing bezel area and causing image distortion.
Innovation Solution
An organic light emitting display that senses pixel current within a display period and updates offset compensation values during a vertical blank period, eliminating the need for separate gate drivers and multiplexers by integrating sensing and display operations within a single horizontal display period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate gate drivers and multiplexers are added to compensate for luminance variations, then luminance consistency is improved, but device complexity and bezel area increase
Solution Approach 1:
The patent combines the sensing gate driver and display gate driver into a single integrated gate driver unit. The same gate driver sequentially performs both sensing operations (to detect pixel current and calculate compensation values) and display operations (to drive the OLED), eliminating the need for separate gate drivers and multiplexers. This merging approach reduces device complexity and bezel area while maintaining luminance consistency through compensation.
Solution Approach 2:
The gate driver is designed to perform multiple functions: it acts as both a sensing gate driver (measuring pixel current, calculating offset compensation values) and a display gate driver (driving the OLED display). This multi-functional design eliminates the need for dedicated separate circuits for sensing and display operations, reducing overall system complexity while achieving luminance compensation.
2Reliability
If sensing operations are performed during vertical blank period, then luminance compensation is achieved, but display period is reduced and image distortion occurs
Solution Approach 1:
The patent implements periodic sensing operations during the display period itself, rather than during the vertical blank period. The gate driver sequentially selects different pixels or pixel groups to perform sensing operations interspersed with display operations, creating a periodic pattern of sense-display-sense-display. This approach ensures continuous display period without reduction while achieving luminance compensation through periodic offset value updates.
3Measurement precision
If pixel current is sensed through reference line, then measurement precision is improved, but device complexity increases due to additional circuitry
Solution Approach 1:
The reference line is designed to serve dual purposes: it functions as a sensing path for measuring pixel current during compensation operations, and simultaneously serves as a display signal line during normal operation. This multi-functional use of the reference line improves measurement precision for pixel current sensing without requiring completely separate dedicated sensing circuitry, thereby limiting the increase in device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces bezel area, prevents image distortion, and compensates for luminance variations, thereby enhancing display consistency and lifespan by directly addressing changes in driving TFT characteristics.
Implementation Method 1
an organic light emitting layer emits light by recombination of electrons and holes
Data Source
AI summary
Provided are an organic light emitting display and a method of manufacturing the same. The organic light emitting display includes: a display panel including a plurality of pixels, each pixel including: a light emitting element, and a driving element to drive the light emitting element, a data driving circuit to, within one horizontal display period: write sensing data to a pixel on a horizontal display line through a data line, sense the pixel current of the pixel through a reference line, and then write display data compensated by a first offset compensation value to the pixel, an offset calculator to calculate a second offset compensation value for compensating changes in the driving element over time based on the sensed value of the pixel current, and an offset memory to update the pre-stored first offset compensation value with the second offset compensation value when display data writing is stopped.