OLED Pixel 2T2C Circuit Anode Discharge for Black Level Control
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Solution Overview
Problem
The existing pixel structures in organic light emitting diode (OLED) display devices are limited in size reduction and resolution increase due to the presence of multiple transistors and wirings required for data writing, OLED driving, and emission control, which can lead to undesired light emission during black data voltage application.
Innovation Solution
A pixel structure with a two-transistor-two-capacitor (2T2C) configuration that includes a switching transistor, a storage capacitor, a driving transistor, an organic light emitting diode, and an anode discharging capacitor, where the anode discharging capacitor is connected between the scan line and the anode of the OLED, allowing the anode voltage to be decreased below the threshold voltage at the start of the emission period, preventing undesired light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple transistors and wirings are used for data writing, OLED driving, and emission control, then the display device can achieve proper control functions, but the pixel size cannot be reduced and resolution cannot be increased
Solution Approach 1:
The patent combines the anode discharging function with the existing scan line structure by connecting an anode discharging capacitor between the scan line and the OLED anode. This integration allows the scan line to serve dual purposes: scanning control and anode voltage discharge, thereby reducing the need for separate dedicated discharge transistors and minimizing pixel area while maintaining control functionality.
2Area of moving object
If a simple pixel structure is used, then the pixel area can be reduced, but undesired light emission occurs during black data voltage application
Solution Approach 1:
The patent applies preliminary anti-action by proactively discharging the OLED anode voltage to below the threshold voltage at the start of the emission period through the anode discharging capacitor connected to the scan line. This preemptive voltage reduction prevents undesired light emission during black data voltage application before the harmful effect can occur, while using a minimal pixel structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents undesired light emission by ensuring the anode voltage is lowered below the OLED's threshold voltage at the start of the emission period, even when a black data voltage is applied, thereby enhancing the pixel's ability to control light emission and improve display performance.
Implementation Method 1
an anode discharging capacitor connected between the scan line and an anode of the organic light emitting diode
Data Source
AI summary
A pixel of an organic light emitting diode display device includes a switching transistor which transfers a data voltage in response to a scan voltage applied thereto through a scan line, a storage capacitor which stores the data voltage transferred by the switching transistor, a driving transistor which generates a driving current based on the data voltage stored in the storage capacitor, an organic light emitting diode which emits light based on the driving current, and an anode discharging capacitor connected between the scan line and an anode of the organic light emitting diode.