Oxide TFT Voltage Control Circuit for Stable AMOLED Driving
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Solution Overview
Problem
Conventional active matrix driving organic light emitting diode (AMOLED) displays face challenges in maintaining stable light emission due to high off-state leakage current in transistors, which affects the driving current and stability of OLEDs, especially when using conventional thin film transistors with high electron mobility.
Innovation Solution
Incorporating oxide thin film transistors with lower electron mobility into the voltage control circuit directly coupled to the driving transistor, reducing off-state leakage current and minimizing voltage changes at the gate of the driving transistor, thereby ensuring stable and constant driving current output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional thin film transistors with high electron mobility are used in the voltage control circuit, then the response speed is improved, but the off-state leakage current increases causing unstable light emission
Solution Approach 1:
The patent applies different transistor types in different circuit locations: oxide thin film transistors are specifically used for transistors directly coupled to the gate of the driving transistor where low leakage is critical, while other transistors may use conventional thin film transistors. This local differentiation resolves the contradiction by optimizing each position's transistor type according to its specific functional requirements.
Solution Approach 2:
The patent changes the material parameter (electron mobility) of the transistor used in the voltage control circuit from high mobility conventional thin film to lower mobility oxide thin film. This parameter change reduces off-state leakage current while maintaining acceptable response speed, thereby stabilizing light emission.
2Reliability
If oxide thin film transistors with lower electron mobility are used in the voltage control circuit, then the off-state leakage current is reduced and light emission stability is improved, but the response speed decreases
Solution Approach 1:
The patent strategically places oxide thin film transistors only in positions where low leakage is most critical (directly coupled to the driving transistor gate), while allowing conventional transistors in other positions. This localized application maintains overall circuit response speed while achieving stability where it matters most.
Solution Approach 2:
The pixel circuit uses a composite transistor architecture combining oxide thin film transistors and conventional thin film transistors. Each transistor type contributes its strengths: oxide TFTs provide low leakage for stability, while conventional TFTs provide high speed where needed, achieving a balanced performance through material composition.
3Use of energy by stationary object
If the output stage duration is extended to enable low-frequency driving, then power consumption is reduced, but voltage changes at the gate of the driving transistor increase affecting current stability
Solution Approach 1:
The oxide thin film transistor in the voltage control circuit maintains stable gate voltage control over extended periods, enabling continuous stable operation during low-frequency driving. The low leakage characteristic ensures voltage stability throughout the extended output stage, allowing the display to operate at lower refresh rates without compromising current stability.
Data Source
AI summary
The present disclosure provides a pixel circuit including: a driving transistor and a voltage control circuit; wherein in the voltage control circuit, at least one transistor directly coupled to a gate of the driving transistor is an oxide thin film transistor. The disclosure also provides a display substrate and a display apparatus.