Pixel Sensing During Frame Blanking for Uniform Display Luminance
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Solution Overview
Problem
Display devices, such as OLEDs, experience non-uniform luminance due to process variations and degradation of driving transistors, leading to increased luminance during sensing operations in blank periods.
Innovation Solution
A display device and method that applies a pre-charge data voltage followed by a previous data voltage after a sensing operation in a blank period to maintain the gate-source voltage of driving transistors, preventing luminance increase by ensuring the same voltage levels as in active periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing operation is performed on at least one pixel in a blank period of a frame period, then the driving characteristics of the driving transistor can be sensed in real-time, but the luminance of the pixel may be increased causing horizontal bright lines
Solution Approach 1:
A pre-charge data voltage is applied to the pixel before the sensing operation to charge the parasitic capacitor of the light emitting element. This preliminary action ensures that when the sensing operation is performed, the pixel luminance remains consistent with other pixels, preventing horizontal bright lines while still enabling accurate sensing of the driving transistor characteristics.
2Productivity
If the parasitic capacitor of the light emitting element is not charged during the sensing operation, then the sensing operation can be performed quickly, but the pixel luminance becomes inconsistent causing display defects
Solution Approach 1:
The pre-charge data voltage is applied before the sensing operation to charge the parasitic capacitor in advance. This allows the sensing operation to proceed without delay while ensuring proper luminance, as the capacitor is already charged when sensing begins.
Solution Approach 2:
The data voltage applied to the pixel is changed from a normal data voltage to a pre-charge data voltage that is higher than the maximum gray data voltage. This parameter change ensures sufficient charging of the parasitic capacitor while maintaining pixel luminance consistency during the sensing operation.
3Illumination intensity
If a pre-charge data voltage is applied to charge the parasitic capacitor, then the pixel luminance becomes consistent, but additional voltage application time is required
Solution Approach 1:
The blank period is divided into distinct phases: a pre-charge data application period for charging the parasitic capacitor, followed by a sensing period for performing the sensing operation. This periodic structure ensures luminance uniformity while efficiently utilizing the available blank period time.
Data Source
AI summary
A display device includes a display panel including pixels, and a panel driver configured to sequentially apply data voltages to the pixels on a row basis in an active period of a frame period, and to perform a sensing operation on at least one pixel of the pixels in a blank period of the frame period. Within the blank period, the panel driver applies a pre-charge data voltage to the at least one pixel after the sensing operation, and applies a previous data voltage to the at least one pixel after a predetermined time from a time point at which the pre-charge data voltage is applied.