OLED Display Bias Signal Initialization for Threshold Voltage Stability
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Solution Overview
Problem
Display devices with organic light emitting diodes (OLEDs) face issues with luminance uniformity due to shifted threshold voltages of driving transistors, resulting in inadequate light generation during grayscale transitions, which degrades image quality.
Innovation Solution
A display device and driving method that involve a timing controller to supply bias signals during vertical blank periods, adjusting the voltage for specific pixel rows to initialize and reset the threshold voltage of driving transistors, ensuring accurate grayscale representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a white grayscale is expressed after a black grayscale is expressed, then the display device can show grayscale transitions, but light with luminance lower than desired is generated during about two frame periods, degrading image quality
Solution Approach 1:
The patent applies preliminary action by initializing the threshold voltage of driving transistors during a bias period before the display period. Specifically, a bias signal is supplied to pixels during the vertical blank period (bias period) to reset the threshold voltage of driving transistors to a reference value, ensuring that when the display period begins, the transistors are ready to accurately generate the required luminance without degradation from previous frame effects.
2Device complexity
If the threshold voltage of driving transistors is not initialized, then the device structure remains simple, but the threshold voltage shifts corresponding to voltage applied during previous frame periods, preventing accurate light generation
Solution Approach 1:
The patent implements periodic action by establishing a repeating cycle of bias period followed by display period. During each bias period (vertical blank period), the threshold voltage of driving transistors is initialized through bias signals. This periodic initialization ensures that before each display period, the transistors are reset to their reference threshold voltage, maintaining consistent and accurate luminance generation across all frames without requiring complex additional circuitry.
Data Source
AI summary
A display device may include pixels coupled to scan lines and data lines, at least one scan driver for supplying a scan signal to the pixels through the scan lines, and a data driver for supplying a data signal and a bias signal to the pixels through the data lines. The pixels are supplied with the data signal when the scan signal is supplied during display periods, and are supplied with the bias signal when the scan signal is supplied during a bias period between the display periods. By the bias signal, a bias voltage is supplied to first group pixels that emit light with a preset grayscale during the display periods.