OLED Pixel Pre-Charge Period Adjustment for Luminance Consistency
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Solution Overview
Problem
Display devices, such as OLED displays, face challenges in maintaining consistent pixel luminance due to process variations in manufacturing, leading to degraded driving characteristics over time. This results in increased luminance during sensing operations in blank periods, causing issues like horizontal bright lines.
Innovation Solution
A display device and method that involve a panel driver applying initialization voltages and data voltages to pixels during specific pre-charge periods within frame periods. The lengths of these pre-charge periods are adjusted based on the frame rate using look-up tables, ensuring that the gate-source voltage of driving transistors remains consistent across active and blank periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing operation is performed in blank period, then pixel characteristics can be measured, but pixel luminance increases causing horizontal bright lines
Solution Approach 1:
The patent applies preliminary anti-action by performing an initialization operation before the sensing operation in the blank period. The panel driver applies an initialization voltage to the pixel through the sensing transistor, which resets the pixel state and prevents luminance increase during subsequent sensing operations. This preliminary action counteracts the potential harmful effect of luminance increase before it occurs.
Solution Approach 2:
The patent uses preliminary action by adjusting the pre-charge period duration based on frame rate. The panel driver dynamically modifies the pre-charge period length to ensure proper pixel initialization before sensing operations, maintaining consistent gate-source voltages and preventing luminance artifacts while enabling accurate pixel characteristic measurement.
2Reliability
If pre-charge period is extended to initialize pixel, then pixel initialization is improved, but frame rate decreases
Solution Approach 1:
The patent applies dynamics by making the pre-charge period duration variable rather than fixed. The panel driver dynamically adjusts the pre-charge period length based on the current frame rate, allowing the system to optimize between initialization quality and frame rate performance. When frame rate decreases, the pre-charge period is extended; when frame rate is high, the pre-charge period is shortened.
Solution Approach 2:
The patent uses parameter changes by modifying the time duration parameter of the pre-charge period. The panel driver changes this temporal parameter dynamically based on operating conditions (frame rate), enabling the system to adapt the initialization time to match performance requirements and maintain both reliability and productivity.
Data Source
AI summary
A display device includes a display panel including a pixel and panel driver configured to apply an initialization voltage to the pixel in a first pre-charge period included in an active period of a frame period, to apply a data voltage to the pixel, to perform a sensing operation to the pixel in a sensing period included in a blank period of the frame period, to apply the initialization voltage to the pixel in a second pre-charge period included in the blank period and to apply a previous data voltage to the pixel in a previous frame writing period included in the blank period. The panel driver may change one of a length of the first pre-charge period and a length of the second pre-charge period based on a frame rate.