STC Driving Method for OLED Pixel Circuit Luminance Uniformity
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Solution Overview
Problem
Existing organic electroluminescence (EL) display technologies face challenges in achieving high definition, high luminance, and high frame rates due to luminance unevenness and leak current issues, particularly in active matrix displays with thin film transistors, which affect image uniformity and quality.
Innovation Solution
The implementation of a Simultaneous Threshold Correction (STC) driving method, where multiple horizontal lines are grouped as one unit for simultaneous threshold correction, ensuring a longer correction period, and a signal selector supplies reference and video signal voltages to maintain uniformity across pixel circuits, thereby minimizing the impact of leak current variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the active matrix driving method is used to achieve high definition and large display panels, then the display quality and size are improved, but luminance unevenness and leak current issues occur affecting image uniformity
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage correction before the display operation. The pixel circuit executes a threshold correction operation in advance to compensate for transistor threshold variations, ensuring uniform luminance output across all pixels before actual image display begins. This pre-correction mechanism prevents luminance unevenness from affecting the final display quality.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the gate-source voltage of the drive transistor through the storage capacitor. By changing the voltage parameters applied to the pixel circuit during the threshold correction operation, the system compensates for threshold voltage variations and achieves uniform luminance across the display panel without requiring additional hardware components.
2Productivity
If the frame rate is increased to achieve higher operation frequency, then the display speed is improved, but the threshold correction period becomes insufficient leading to luminance unevenness
Solution Approach 1:
The patent applies periodic action by integrating the threshold correction operation into the regular display refresh cycle. The pixel circuit performs threshold correction at specific periodic intervals synchronized with the frame rate, allowing the system to maintain high refresh rates while ensuring adequate correction time is allocated in each cycle. This periodic correction mechanism prevents luminance unevenness even at high frame rates.
Solution Approach 2:
The threshold correction operation is performed as a preliminary action within each display frame cycle, completing the correction before the actual image data is written to the pixels. This timing arrangement ensures that regardless of the frame rate, the correction period is adequately secured in advance, preventing luminance unevenness from manifesting in the displayed image.
3Duration of action of moving object
If multiple horizontal lines are grouped as one unit for simultaneous threshold correction, then the correction period is extended, but the complexity of signal control increases
Solution Approach 1:
The patent applies merging by grouping multiple horizontal lines into a single unit for simultaneous threshold correction. Instead of correcting each line independently, the system combines the correction operations for multiple lines and executes them together, effectively extending the correction period while reducing the overall number of correction cycles required. This merging approach manages signal control complexity by treating grouped lines as a single operational unit.
Solution Approach 2:
The patent utilizes universality by designing the signal control mechanism to handle both individual pixel correction and grouped line correction through the same basic circuit architecture. The signal selector and scanning mechanism can operate in different modes (individual or grouped) without requiring separate dedicated circuits, thereby extending the correction period through grouping while keeping the added complexity minimal through multi-functional signal control.
Data Source
AI summary
A display apparatus includes: a pixel array including pixel circuits arranged in a matrix form, in which each pixel circuit has a light-emitting device, a drive transistor applying a current corresponding to a gate-source voltage to the light-emitting device, a sampling transistor inputting a voltage supplied from a signal line to a gate of the drive transistor, and a storage capacitor connected between the gate and source of the drive transistor so as to store a threshold voltage of the drive transistor and an input video signal voltage; a signal selector that supplies a reference voltage and the video signal voltage to signal lines arranged in columns on the pixel array in horizontal periods corresponding to the number of horizontal lines in one unit when the horizontal lines of the respective pixel circuits of the pixel array are grouped as one unit; and a scanner that applies a pulse to control lines arranged in rows on the pixel array so as to control the sampling transistor of the pixel circuit.