Display Device Efficiency Residual Ratio Correction Circuit
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Solution Overview
Problem
In light-emitting elements like organic electroluminescent (EL) elements, the initial stage of deterioration, characterized by a loss of carrier balance between hole injection and electron injection characteristics, leads to insufficient correction accuracy of display unevenness, resulting in residual images, color drift, and luminance deterioration, which conventional techniques fail to adequately address.
Innovation Solution
A display device with a correction circuit that converts input gradation values into target luminance values using an efficiency residual ratio, calculates corrected luminance values by accounting for current stress and carrier balance stress, and updates the efficiency residual ratio to accurately predict and correct for deterioration, thereby reducing display unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional video signal correction techniques are used, then display unevenness can be corrected to some extent, but correction accuracy is insufficient during the initial stage of deterioration due to loss of carrier balance
Solution Approach 1:
The patent introduces a new parameter called 'efficiency residual ratio' to characterize the deterioration state of light-emitting elements. By monitoring this parameter and adjusting correction values based on its changes, the system achieves accurate correction even during the initial stage of deterioration when carrier balance is lost. This parameter change enables the correction system to adapt to the deteriorating state of the elements.
Solution Approach 2:
The patent implements a feedback mechanism where the efficiency residual ratio is continuously monitored and used to adjust the correction values in real-time. The correction values are dynamically updated based on the measured efficiency residual ratio, allowing the system to compensate for carrier balance loss and maintain high correction accuracy throughout the initial deterioration period.
2Duration of action of stationary object
If the light-emitting element operates for extended periods, then luminance deterioration occurs, but conventional correction methods fail to predict and correct this deterioration accurately
Solution Approach 1:
The patent performs preliminary measurement of the efficiency residual ratio at regular intervals during operation. By measuring this parameter before significant luminance deterioration occurs, the system can predict future luminance changes and adjust correction values in advance, maintaining accurate correction throughout the extended operational lifetime.
Solution Approach 2:
The system continuously monitors the efficiency residual ratio and uses this feedback to dynamically update correction values. This feedback mechanism enables the system to track luminance deterioration over time and maintain prediction accuracy throughout the operational lifetime, allowing for continuous adaptation to changing element characteristics.
3Measurement precision
If correction values are adjusted frequently to account for deterioration, then correction accuracy improves, but the complexity of the correction circuit increases
Solution Approach 1:
The patent employs a lookup table that is pre-calculated and stored in the correction circuit. The correction values are automatically retrieved from this table based on the efficiency residual ratio, eliminating the need for complex real-time calculations. This self-service approach using pre-computed data reduces the computational burden and circuit complexity while maintaining high correction accuracy.
Solution Approach 2:
The patent uses a pre-stored lookup table that contains correction values for various efficiency residual ratio levels. Instead of calculating correction values in real-time, the system copies pre-computed values from the table, significantly reducing the complexity of the correction circuit while maintaining accurate correction performance.
Data Source
AI summary
A display device includes: a luminance converter which converts input gradation value into a corresponding target luminance value; a luminance correction calculator which calculates output gradation value from the target luminance value using efficiency residual ratio representing a deterioration degree of a light-emitting element, and calculates a corrected luminance value therefrom; a current stress calculator which converts current stress amount on a light-emitting element calculated from the corrected luminance value into current stress amount when first reference current flows through the light-emitting element, and accumulates this to calculate an accumulated first stress amount; a CB stress calculator which converts CB stress amount on the light-emitting element into current stress amount when second reference current flows through the light-emitting element, and accumulates this to calculate an accumulated second stress amount; and an efficiency residual ratio calculator which updates the efficiency residual ratio, using the accumulated first and second stress amounts calculated.