OLED Pixel Circuit Using N-Channel Transistors to Reduce Flicker
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Solution Overview
Problem
Existing organic EL display devices face issues with high driving power consumption and flickering due to large amplitude driving lines and source-drain leakage of p-channel transistors, leading to changes in gate potential.
Innovation Solution
The display device incorporates a pixel circuit with n-channel transistors, including a correction transistor, a switching transistor, and an initialization transistor, coupled with a capacitive element to reduce leakage current and stabilize gate potential, using oxide semiconductors for further reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If p-channel transistors are used in the pixel circuit, then the circuit can be configured with all p-channel transistors, but the amplitude of driving lines becomes large and driving power increases
Solution Approach 1:
The patent applies local quality by using different transistor types in different positions within the pixel circuit. Specifically, n-channel transistors are used for the correction transistor, switching transistor, and initialization transistor, while other transistors may be p-channel. This localized differentiation allows the circuit to benefit from the low leakage characteristics of n-channel transistors in critical positions without requiring all transistors to be n-channel, thus reducing driving power while maintaining configuration flexibility.
2Device complexity
If p-channel transistors are used, then the transistor configuration is simplified, but source-drain leakage during OFF state is large causing gate potential changes and flicker
Solution Approach 1:
The patent applies local quality by strategically placing n-channel transistors in specific positions (correction transistor, switching transistor, and initialization transistor) where low leakage is critical for maintaining gate potential stability. This localized approach ensures that the most leakage-sensitive parts of the circuit use n-channel transistors, thereby preventing flicker and maintaining image stability without requiring a complete redesign of the entire transistor configuration.
Solution Approach 2:
The patent converts the inherent advantage of p-channel transistors (simplicity in configuration) by selectively replacing only the critical transistors with n-channel types. This allows the circuit to retain the overall simplicity of p-channel configuration while eliminating the harmful leakage effect in specific positions, thus converting the potential harm of high leakage into a benefit of localized optimization.
3Ease of operation
If all transistors are configured as p-channel transistors, then the circuit design is uniform, but the amplitude of driving lines becomes large increasing power consumption
Solution Approach 1:
The patent applies local quality by introducing n-channel transistors in specific positions within the pixel circuit rather than maintaining uniform p-channel configuration throughout. This localized differentiation allows the circuit to reduce power consumption in critical areas where leakage control is most important, while maintaining ease of design in other areas that can remain p-channel.
Data Source
AI summary
A display device includes a current-driven electro-optical element, a first supply, a second supply, a driving transistor, a correction transistor, an anode switching transistor, an initialization transistor, and a capacitive element. A current is supplied from the first supply. The second supply is lower in potential than the first supply. The driving transistor is configured to drive the electro-optical element in accordance with a written image signal. The correction transistor is coupled between a gate of the driving transistor and a second terminal of the driving transistor. The anode switching transistor is coupled between the second terminal of the driving transistor and an anode of the electro-optical element. The initialization transistor is coupled between the anode of the electro-optical element and the second supply. The capacitive element is coupled to the gate of the driving transistor. The correction, anode switching, and initialization transistors are n-channel transistors.