OLED Driving Transistor Kickback Mitigation via Segmented Initialization
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Solution Overview
Problem
In organic light emitting diode (OLED) display devices with a 4T1C compensating unit, the kickback of low-level voltage during the initialization period leads to deterioration such as horizontal crosstalk due to changes in the source electrode voltage of the driving transistor.
Innovation Solution
The OLED display device incorporates a method where two transistors are sequentially switched and connected to the source electrode of the driving transistor, changing the voltage from a start value to a final value through a median value, using an initial voltage applied to the gate electrode as a median value of the source electrode voltage, and driving the device with the same kind of gate signal for both transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a 4T1C compensating unit is used to compensate threshold voltage, then display quality is improved, but kickback of low level voltage occurs during initialization causing horizontal crosstalk
Solution Approach 1:
The patent divides the single initialization operation into two sequential transistor operations. The first transistor initializes the source electrode to a first initial voltage, and the second transistor initializes it to a second initial voltage. This segmentation allows the source electrode voltage to change gradually through intermediate values rather than directly, reducing kickback effects and preventing horizontal crosstalk while maintaining threshold voltage compensation capability.
2Productivity
If the source electrode voltage is changed directly from start value to final value, then initialization is completed quickly, but kickback amount increases causing display deterioration
Solution Approach 1:
The patent introduces intermediate voltage values as mediators in the initialization process. The source electrode voltage transitions through these intermediate values (first initial voltage and second initial voltage) rather than changing directly from start to final value. This intermediary approach reduces the kickback amount during voltage transitions while still completing initialization within the same time period, preventing display deterioration.
Data Source
AI summary
An organic light emitting diode display device includes: a driving transistor; a first transistor switched according to an nth gate voltage and connected to a data voltage and the driving transistor; a second transistor switched according to an nth initialization voltage and connected to an initial voltage and the driving transistor; a third transistor switched according to an nth sensing voltage and connected to a reference voltage and the driving transistor; a fourth transistor switched according to an (n−2)th sensing voltage and connected to the initial voltage and the driving transistor; a storage capacitor connected to the driving transistor and the first transistor; and a light emitting diode connected to a low level voltage and the driving transistor.