OLED Pixel Circuit Layout for Leakage and Kickback Control
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Solution Overview
Problem
Organic light emitting display devices face display quality degradation due to leakage currents in switching transistors, which are exacerbated at low frequencies.
Innovation Solution
The implementation of a pixel structure with a p-channel MOS driving transistor and n-channel MOS switching transistors, along with a first capacitor to reduce the kickback effect, enhances reliability and prevents display quality degradation by using a specific configuration of transistors and capacitors to manage scan signals and power voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching transistors are used to drive OLEDs, then pixel operation control is achieved, but leakage current occurs causing display quality degradation
Solution Approach 1:
The patent introduces a compensation transistor as an intermediary element that mediates between the switching transistor and the OLED. This compensation transistor actively compensates for the leakage current generated by the switching transistor, thereby maintaining display quality without requiring a complete redesign of the pixel structure.
Solution Approach 2:
The patent changes the operational parameters of the transistors by applying different voltages to their gate electrodes. By dynamically adjusting the gate voltages of the switching and compensation transistors, the system optimizes current control and minimizes leakage effects while maintaining proper pixel operation.
2Reliability
If more transistors and capacitors are added to compensate for leakage, then display quality improves, but device complexity increases
Solution Approach 1:
The patent segments the pixel circuit into distinct functional modules: switching transistor, compensation transistor, storage capacitor, and emission control transistor. Each segment performs a specific function, allowing for targeted optimization and easier manufacturing while achieving overall improved display quality through coordinated operation of these segmented components.
Data Source
AI summary
An organic light emitting display device includes a plurality of pixels. Each of the pixels includes an organic light emitting diode, first to third transistors, a storage capacitor, and a first capacitor. The second transistor includes a gate electrode receiving a first scan signal, a first electrode receiving a data signal, and a second electrode connected to a first electrode of the first transistor. The third transistor includes a gate electrode receiving a second scan signal, a first electrode connected to a second electrode of the first transistor, and a second electrode connected to a gate electrode of the first transistor. The storage capacitor includes a first electrode receiving a power voltage and a second electrode connected to the gate electrode of the first transistor. The first capacitor includes a first electrode connected to the gate electrode of the third transistor and a second electrode receiving the power voltage.