OLED Pixel Circuit Voltage Stabilization for Leakage Current Control
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Solution Overview
Problem
Organic light emitting display devices face display defects such as light spot defects due to leakage currents through transistors, which alter pixel luminance, leading to inconsistent display quality.
Innovation Solution
A pixel structure incorporating eight transistors and two capacitors, where the eighth transistor stabilizes the voltage of a node, maintaining a constant gate voltage for the driving transistor, thereby minimizing luminance changes and reducing leakage current effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pixel structures with fewer transistors are used, then device complexity is reduced, but leakage current occurs through transistor paths, causing luminance changes and display defects
Solution Approach 1:
The pixel circuit is segmented into multiple functional blocks, each handled by a dedicated transistor. The eighth transistor specifically segments the voltage stabilization function for the fourth node, separating it from other circuit functions. This segmentation allows precise control of leakage current paths and voltage stabilization without requiring excessive transistors, resolving the contradiction between complexity and reliability.
Solution Approach 2:
The eighth transistor acts as an intermediary element between the fourth node and other circuit components. It mediates the voltage stabilization function by controlling the connection between nodes, preventing direct leakage current paths while maintaining proper voltage levels. This intermediary role allows the circuit to achieve better display quality without proportionally increasing overall complexity.
2Reliability
If more transistors are added to stabilize node voltage and reduce leakage, then display quality improves, but device complexity increases
Solution Approach 1:
The eighth transistor is designed with multi-functionality, serving both as a voltage stabilization element for the fourth node and as part of the overall transistor array structure. It performs multiple functions including voltage reference, leakage current blocking, and signal routing, thereby improving display quality without requiring a proportional increase in total transistor count. This multi-functionality reduces the complexity-quality trade-off.
Solution Approach 2:
The invention changes the operational parameters of the transistor network by introducing the eighth transistor with specific gate control signals. This transistor modifies the voltage parameters at the fourth node, stabilizing them during emission periods. By changing the parameter control strategy rather than simply adding more components, the circuit achieves improved reliability with minimal complexity increase.
3Stability of the object's composition
If the fourth node voltage is stabilized during emission periods, then driving current consistency improves, but additional transistor control circuitry is required
Solution Approach 1:
The eighth transistor is configured to perform preliminary voltage stabilization at the fourth node before the emission period begins. By pre-stabilizing the voltage through proactive control rather than reactive correction, the circuit maintains consistent driving current during emission without requiring complex real-time control circuitry. This preliminary action reduces the complexity-stability trade-off.
Solution Approach 2:
The voltage stabilization function is implemented using the existing transistor structure and control signals within the pixel circuit itself, rather than requiring external control circuitry. The eighth transistor utilizes gate signals that are already present in the driving scheme, allowing the circuit to self-stabilize voltages using its own components. This self-service approach minimizes additional complexity while achieving voltage stability.
Data Source
AI summary
A display device includes a display panel including a plurality of pixels and a panel driver that drives the display panel. Each of the pixels includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a first capacitor, and an emission element.