Pixel Circuit Holding Capacitor Negative Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pixel circuits using organic EL elements face issues with non-uniform mobility and unstable threshold voltage in transistors, leading to irregular display images and increased complexity and cost due to the need for compensation circuits, especially when using inorganic oxide thin film transistors with negative OFF-operation threshold voltage, which result in power consumption increases or additional IC development.
Innovation Solution
A pixel circuit design incorporating inorganic oxide thin film transistors with negative OFF-operation threshold voltage, utilizing a holding circuit with first and second capacitor elements to divide voltage and supply a negative voltage, allowing for a conventional drive circuit to be used without increasing power consumption, and employing a scan drive circuit with positive voltage and a data drive circuit with positive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic oxide thin film transistors with negative OFF-operation threshold voltage are used, then mobility uniformity and threshold voltage stability are improved, but the transistor cannot perform OFF operation with conventional 0V minimum gate voltage
Solution Approach 1:
The patent changes the voltage parameter by introducing a negative voltage source connected to the holding circuit. This allows the gate voltage of the driving transistor to be maintained at a negative level during OFF operation, enabling inorganic oxide TFTs with negative threshold voltage to properly turn off while maintaining their mobility uniformity and threshold voltage stability advantages.
2Manufacturing precision
If a compensation circuit is added to correct threshold voltage, then display image uniformity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the complex compensation circuit with a simple negative voltage source and holding circuit configuration. This simpler approach achieves the same goal of ensuring proper OFF operation and uniform display images without requiring additional complex compensation components, thereby reducing device complexity and manufacturing cost.
3Ease of operation
If ground wire voltage is raised above 0V to enable OFF operation, then transistor OFF operation is achieved, but overall power consumption increases
Solution Approach 1:
The patent introduces a negative voltage potential level specifically for the holding circuit and gate terminal, creating a local equipotential reference that enables proper OFF operation. This approach avoids raising the overall ground wire voltage, thereby maintaining low power consumption while achieving the required OFF operation capability for inorganic oxide TFTs.
Data Source
AI summary
A pixel circuit including a light emitting element, a driving transistor, connected to the light emitting element, that applies a drive current to the light emitting element, a holding circuit connected to a gate terminal of the driving transistor, and a switching transistor connected between the holding circuit and a data line through which a data signal to be held by the holding circuit flows, in which the driving transistor and the switching transistor are inorganic oxide thin film transistors whose OFF-operation threshold voltage is a negative voltage, and the holding circuit includes a first capacitor element connected between the switching transistor and the gate terminal of the driving transistor, and a second capacitor element connected between a point located between the first capacitor element and the gate terminal of the driving transistor and a voltage source that supplies a negative voltage.