OLED Driving Scheme Compensating for Transistor Variations
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Solution Overview
Problem
Organic light emitting devices (OLEDs) in display panels age differently, leading to non-uniformities and degradation, causing visible differences and luminance issues due to varying current requirements over time.
Innovation Solution
A method and system that detect deviations in device current from a reference current by processing voltage differences through readout systems, using current comparators and integrators to generate quantized output signals, which are then used to adjust programming values for pixel circuits, thereby compensating for non-uniformities and degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLEDs are driven with different currents in different pixel areas, then luminance uniformity is improved, but device complexity increases due to need for compensation circuits
Solution Approach 1:
The patent implements feedback by measuring the actual current through each OLED and using this measurement to adjust the programming voltage. The readout circuit measures device current, compares it to reference current, and feeds back compensation information to adjust the programming value, creating a closed-loop system that maintains luminance uniformity across the display panel.
Solution Approach 2:
The pixel circuit performs self-compensation by including measurement and adjustment functions within each pixel. The circuit measures its own device current, generates compensation values, and adjusts its programming voltage autonomously without requiring external intervention, enabling each pixel to self-correct for aging and manufacturing variations.
2Illumination intensity
If compensation operations are performed frequently, then display uniformity is improved, but loss of time increases due to additional processing steps
Solution Approach 1:
The patent performs preliminary compensation by measuring device currents and adjusting programming values before the display is fully operated. The compensation operation is executed in advance during initialization or calibration phases, so that subsequent display operation can proceed without repeated compensation interruptions, reducing time loss during normal operation.
Solution Approach 2:
The compensation operation is performed periodically rather than continuously, with measurements and adjustments made at scheduled intervals. This periodic approach maintains display uniformity while minimizing the time spent on compensation processing, as the system can operate normally between compensation cycles.
3Manufacturing precision
If precise current measurement is performed, then manufacturing precision is improved, but device complexity increases due to additional measurement circuits
Solution Approach 1:
The readout circuit serves multiple functions: it measures device current for compensation, reads pixel data during normal operation, and provides feedback for uniformity correction. By making the readout circuit multi-functional, the patent achieves precise current measurement without adding dedicated measurement circuits, thereby avoiding increased device complexity.
Solution Approach 2:
The patent merges the current measurement function with the existing readout circuitry. Instead of adding separate measurement circuits, the measurement capability is integrated into the readout system that already exists for displaying pixel data, combining multiple functions into a single circuit structure.
Data Source
AI summary
Systems and methods detect and compensate for process or performance-related non-uniformities and/or degradation in displays. The systems and methods can compare a device current with one or more reference currents to generate an output signal indicative of the difference between the device and reference currents. This output voltage can be amplified, and quantized and then be used to determine how the device current differs from the reference current and to adjust the programming voltage for the device of interest accordingly.