OLED Driver Transistor Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In OLED display devices, discrepancies in threshold voltage among semiconductors lead to variations in driving current, causing mura (brightness inconsistencies) in images, which current solutions attempt to address with additional circuitry that reduces pixel opening ratio.
Innovation Solution
A four-terminal driver transistor adjusts its threshold voltage using an offset voltage to control the driving current, allowing for brightness uniformity without adding new circuit structures to each pixel, by selectively writing gray scale and offset voltages into capacitors and adjusting the voltage difference between the gate and source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional circuitry is added to each pixel to compensate for driving current differences, then brightness uniformity is improved, but pixel opening ratio is reduced
Solution Approach 1:
The patent merges the compensation function into the existing driver transistor by adding a second gate terminal, eliminating the need for separate compensation circuitry in each pixel. This combines the driving and compensation functions into a single component, maintaining pixel area while achieving brightness uniformity.
Solution Approach 2:
The driver transistor is designed to perform multiple functions: it acts as both the driving transistor for the light emitting diode and the compensation transistor for threshold voltage discrepancies. The dual-gate structure enables the same component to handle both driving current control and compensation, reducing overall circuit complexity.
2Manufacturing precision
If a four-terminal driver transistor is used to adjust threshold voltage, then brightness uniformity is improved without adding circuit structure, but device complexity increases
Solution Approach 1:
The patent changes the electrical parameters of the driver transistor by introducing a second gate terminal that controls threshold voltage. By adjusting the voltage applied to the second gate, the threshold voltage can be dynamically modified to compensate for manufacturing variations, achieving brightness uniformity through parameter control rather than structural multiplication.
Data Source
AI summary
The present disclosure provides a display device including a light emitting diode and a driving module. The driving module drives the light emitting diode. The driving module includes a first switch circuit, a second switch circuit, and a driver transistor. The first switch circuit selectively writes a gray scale voltage in a first capacitor. The second switch circuit selectively writes an offset voltage in a second capacitor. The driver transistor is coupled to the light emitting diode, the first capacitor, and the second capacitor. The driver transistor adjusts a driving current being outputted to the light emitting diode according to the gray scale voltage and the offset voltage. The gray scale voltage adjusts the voltage difference between the gate and the source of the driver transistor, while the offset voltage adjusts a threshold voltage of the driver transistor.