OLED Display Degradation Compensation via Sensing Feedback
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) in displays degrade quickly under regulated voltage drive, leading to reduced luminance and inability to display desired images due to increased resistance, which reduces the electric current flowing through them.
Innovation Solution
An organic light emitting display with a sensing unit that supplies a first current to OLEDs during a sensing period to convert voltage to a digital value and sinks a compensation current during a sampling period, using a current source unit, current DAC, switching unit, ADC, memory, and controller to adjust the current and compensate for OLED degradation, thereby maintaining desired luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If regulated voltage drive is applied to OLEDs, then luminance control is achieved, but OLED degradation accelerates and resistance increases
Solution Approach 1:
The patent implements a feedback mechanism where the sensing unit measures the voltage across each OLED and converts it to a digital value. This measured value is fed back to the controller, which then adjusts the compensation current accordingly. The feedback loop continuously monitors OLED voltage and dynamically adjusts the current to compensate for degradation, resolving the contradiction between maintaining luminance control and preventing OLED degradation.
Solution Approach 2:
The patent changes the driving parameter from regulated voltage to compensated current. By measuring the actual voltage across each OLED and converting it to a digital value, the system determines the appropriate compensation current level. This parameter change allows the system to maintain desired luminance while compensating for OLED degradation, as the current is adjusted based on the measured voltage rather than applying fixed regulated voltage.
2Illumination intensity
If compensation current is increased to maintain luminance, then OLED degradation is compensated, but device complexity increases
Solution Approach 1:
The patent merges the sensing function and the current control function into an integrated compensation system. The sensing unit that measures OLED voltage is directly coupled to the current DAC that generates compensation current, eliminating the need for separate complex control circuits. This merging reduces overall device complexity while maintaining luminance consistency through degradation compensation.
Solution Approach 2:
The system performs self-diagnosis and self-compensation by measuring its own OLED voltage and automatically adjusting the compensation current. The sensing unit monitors the actual voltage across each OLED and the controller automatically determines the required compensation current without external intervention. This self-service mechanism simplifies the device architecture compared to systems requiring external calibration and adjustment circuits.
3Reliability
If sensing and compensation operations are performed continuously, then OLED degradation is compensated in real-time, but power consumption increases
Solution Approach 1:
The patent implements periodic sensing and compensation operations rather than continuous operation. The sensing unit measures OLED voltage at specific intervals (at the beginning of each frame period or sub-frame period), and the compensation current is adjusted periodically based on these measurements. This periodic action maintains real-time degradation compensation while significantly reducing power consumption compared to continuous monitoring and adjustment.
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
The solution effectively compensates for OLED degradation by adjusting the electric current, ensuring consistent luminance and improved gradation expression performance, even as OLEDs age.
Implementation Method 1
the organic light emitting display makes use of organic light emitting diodes that emit light by re-combination of electrons and holes
Data Source
AI summary
An organic light emitting display including pixels, each including an organic light emitting diode and a pixel circuit for controlling a supply of an electric current to the organic light emitting diode; and a sensing unit for converting a voltage applied to the organic light emitting diode to a digital value during a sensing period during a sampling period, and for sinking a second current from the pixel corresponding to the digital value to compensate a degradation of the organic light emitting diode during a sampling period.