Display Compensation Circuitry for IR Drop and Uniformity
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Solution Overview
Problem
Electronic displays face issues with uniformity due to temperature fluctuations, threshold voltage variations, and voltage drops caused by electrical resistance (IR drop), leading to brightness errors and display artifacts, especially as more pixels share a current or voltage supply.
Innovation Solution
The implementation of row and column drivers, microdrivers, and compensation circuitry to generate and distribute reference currents or voltages, reducing the impact of IR drop by local current generation and compensation for threshold voltage variations, thereby maintaining display uniformity and reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If more pixels share a current or voltage supply, then the display can be driven with fewer drivers, but IR drop increases causing non-uniformity and artifacts
Solution Approach 1:
The display is divided into multiple segments, each with its own current source. Instead of using a single current source for the entire display, the current supply is segmented into multiple independent sources distributed across different regions of the display, reducing the total resistance in any single current path and thereby reducing IR drop.
Solution Approach 2:
Different regions of the display are provided with locally generated currents rather than relying on a distant central current source. Each local current source is positioned near the pixels it serves, ensuring that the current path length and resistance are minimized for each pixel, thereby maintaining uniformity across the display.
2Device complexity
If more pixels share a current or voltage supply, then the driver circuitry can be simplified, but voltage drop due to electrical resistance increases
Solution Approach 1:
The voltage supply network is segmented into multiple independent voltage lines, each serving a specific region of the display. This segmentation reduces the current load on each individual voltage line and shortens the effective length of each voltage path, thereby reducing the voltage drop due to electrical resistance in each segment.
Solution Approach 2:
Intermediate voltage regulation circuitry is introduced at strategic points within the display to maintain stable voltage levels. These intermediary elements act as local voltage sources that compensate for voltage drops occurring in the distribution network, ensuring that pixels throughout the display receive adequate voltage despite the resistance in the supply lines.
3Area of stationary object
If more pixels share a current or voltage supply, then the overall system can be more compact, but display artifacts increase
Solution Approach 1:
The display area is segmented into multiple zones, each with its own dedicated current source. This segmentation allows each zone to be independently optimized, and the reduced current path length in each segment minimizes the voltage drop and associated display artifacts such as brightness non-uniformity and Mura effects.
Solution Approach 2:
Each local current source is specifically positioned and sized to serve its local region optimally. The local current sources ensure that each pixel receives the appropriate current regardless of its distance from the display edges, thereby eliminating the brightness gradients and artifacts that would otherwise occur in a uniformly designed display.
Data Source
AI summary
An electronic display row drivers or column drivers that send reference currents or voltages to microdrivers to be used to drive micropixels to particular levels. The microdrivers, in turn, ship current to micropixels that display images based at least in part on the shipped current.