AMOLED Pixel Calibration via Pre-Charge and Partial Action
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Solution Overview
Problem
Active matrix organic light-emitting diode (AMOLED) displays face challenges in achieving accurate and constant drive current due to parasitic line capacitances, leading to slow current programming and non-uniformity, especially with aging backplanes and OLEDs, which existing calibration methods fail to address effectively.
Innovation Solution
A method and system for real-time calibration that generates a priority list of pixels based on display and calibration data, monitors pixel currents, updates compensation memory, and adjusts programming data to ensure accurate and constant brightness across the display array, utilizing a calibration scheduler, monitor, and data process unit to manage pixel circuit aging and voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current programming is performed on AMOLED displays, then pixel current can be controlled, but the process becomes slow due to parasitic line capacitances
Solution Approach 1:
The patent applies preliminary action by performing pre-charge operations before current programming. The system pre-charges the parasitic line capacitances in advance, so that when actual current programming occurs, the capacitances are already charged and do not slow down the programming process. This separates the charging function from the programming function, enabling fast programming without sacrificing accuracy.
2Manufacturing precision
If calibration is performed on all pixels, then uniformity is improved, but the process becomes too slow for practical use
Solution Approach 1:
The patent implements partial action by calibrating only a subset of pixels (e.g., one pixel per column or selectively chosen pixels) rather than all pixels in the display. The calibration data from these selected pixels is then used to adjust the programming for other pixels. This approach achieves sufficient uniformity while dramatically reducing calibration time and computational burden.
Solution Approach 2:
The calibration process is segmented into multiple phases: first calibrating a representative subset of pixels, then using that calibration data to program the remaining pixels. This segmentation allows the system to achieve overall display uniformity without the prohibitive time cost of calibrating every single pixel individually.
3Productivity
If pre-charge is used to speed up programming, then programming speed improves, but current accuracy deteriorates
Solution Approach 1:
The pre-charge operation is performed as a separate preliminary step that only charges the parasitic capacitances without affecting the actual pixel current programming. By separating the pre-charge function from the programming function in time, the system achieves fast programming while maintaining current accuracy, as the programming phase occurs after capacitances are already charged.
4Measurement precision
If compensation memory is updated frequently, then calibration accuracy improves, but processing overhead increases
Solution Approach 1:
The compensation memory is updated selectively based on calibration needs rather than being updated for every pixel or operation. The system updates compensation data only when necessary (e.g., after calibrating a representative subset of pixels), reducing processing overhead while maintaining sufficient calibration accuracy through periodic updates.
Data Source
AI summary
A method and system for programming, calibrating and driving a light emitting device display is provided. The system may include extracting a time dependent parameter of a pixel for calibration.