OLED Display Driving Circuit Discharge Control
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Solution Overview
Problem
Existing organic light emitting display devices face non-uniform image quality due to deviations in threshold voltage and mobility of driving TFTs, leading to reduced accuracy in external compensation and increased discharging time when switching from driving to sensing mode.
Innovation Solution
An organic light emitting display device and method that employs an external compensation scheme, where the reference power lines are completely discharged to ground at the start of the sensing mode, allowing precise sensing of pixels independent of image patterns and reducing discharging time to a few microseconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the reference power lines are not completely discharged when switching from driving mode to sensing mode, then the discharging time is reduced, but the sensing accuracy deteriorates and non-uniform image quality occurs
Solution Approach 1:
The patent applies preliminary action by completely discharging the reference power lines to ground voltage before initiating pixel sensing in the sensing mode. This pre-discharge operation ensures that the reference power lines start from a known zero-voltage state, eliminating residual voltage effects from the driving mode and enabling accurate pixel current sensing without requiring extended discharge time during the sensing phase.
2Device complexity
If the threshold voltage and mobility of driving TFTs vary due to manufacturing non-uniformity, then device complexity is reduced, but manufacturing precision of display uniformity deteriorates
Solution Approach 1:
The patent implements feedback by measuring the actual pixel currents through the sensing mode and using these measurements to calculate compensation values. These compensation values are then applied to adjust the data voltages for subsequent frame periods, creating a closed-loop system that compensates for TFT parameter variations and achieves uniform display output despite manufacturing non-uniformity.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the data voltage parameters based on measured pixel characteristics. The compensation circuit modifies the voltage levels applied to pixels with degraded TFT performance, changing the electrical parameters to compensate for threshold voltage shifts and mobility variations, thereby maintaining consistent luminance across the display.
3Productivity
If external compensation is performed without complete discharge of reference power lines, then productivity is improved, but reliability of compensation accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by completely discharging the reference power lines to ground voltage before initiating pixel sensing in the sensing mode. This pre-discharge operation ensures that the reference power lines start from a known zero-voltage state, eliminating residual voltage effects from the driving mode and enabling accurate pixel current sensing without requiring extended discharge time during the sensing phase.
Data Source
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AI summary
An organic light emitting display device includes a display panel (100) including a plurality of pixels (P) having an organic light emitting diode (OLED) and a pixel circuit (PC); a gate driver (300) to supply the plurality of pixels (P) with a scan signal (scan), a sensing signal (sense), and a driving voltage; a data driver (200) to supply data voltages to the data lines (DL) and a reference voltage (Vpre_r) to the sensing lines (RL) in a driving mode, to supply a reference voltage (Vpre_s) to the sensing lines (RL) during parts of the sensing mode, and sense voltages charged into the plurality of pixels (P) in a sensing mode; a discharging driving unit (250) to initialize voltages of a plurality of sensing power lines (RL) when the display device switches from the driving mode to the sensing mode; a timing controller (400) to control the gate driver (300), the data driver (200), and the discharging driving unit (250) to operate in and switch between the driving mode and the sensing mode; and a memory (500) to store compensation data for the plurality of pixels (P).