Display Backplate Pixel Circuit to Prevent Driving Transistor Drift
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Solution Overview
Problem
Conventional display technologies experience electrical drift on driving transistors due to high capacitance values between the gate and source, leading to instability in pixel driving circuits.
Innovation Solution
A display backplate design with a luminescent unit comprising a switch transistor, driving transistor, luminescent component, and storage capacitor, where the storage capacitor's second electrode plate is connected to a constant-voltage signal line, reducing the relative area of the capacitor between the gate and source, thereby minimizing charge carrier entry and electrical drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitance value between gate and source of driving transistor is increased to improve charge storage, then the stability of pixel driving circuit deteriorates due to electrical drift
Solution Approach 1:
The patent extracts the storage capacitor function from the gate-source capacitance of the driving transistor. By introducing a separate storage capacitor Cst with its first electrode plate connected to the first node and second electrode plate connected to a constant voltage signal line, the storage function is separated from the driving transistor, preventing charge accumulation in the gate insulating layer while maintaining the required charge storage capability.
Solution Approach 2:
The patent introduces a constant voltage signal line as an intermediary element. The second electrode plate of the storage capacitor is connected to this constant voltage signal line, which acts as a mediator to provide a stable reference potential and prevent charge carriers from entering the gate insulating layer, thus eliminating electrical drift while maintaining capacitance function.
2Object-affected harmful factors
If the area of capacitor between gate and source is reduced to prevent charge carrier entry, then the charge storage capability deteriorates
Solution Approach 1:
The patent segments the pixel driving circuit into distinct functional components: the driving transistor T2 for current control, and a separate storage capacitor Cst for charge storage. The storage capacitor is formed with first and second electrode plates on different layers, separated by an insulating layer, allowing independent optimization of each component's area and function without compromising the other.
Solution Approach 2:
The patent transitions from a planar capacitor structure to a three-dimensional structure by placing the first electrode plate and second electrode plate on different layers. This vertical stacking approach increases the effective capacitance area without expanding the planar footprint, preventing charge carrier entry while maintaining charge storage capability within the same device area.
Data Source
AI summary
A display backplate and a mobile terminal are disclosed. A luminescent unit of the display backplate includes a switch transistor, a driving transistor, a luminescent component, and a storage capacitor. The driving transistor and the switch transistor are connected at a first node. The luminescent component and the driving transistor are connected at a second node. A first electrode plate of the storage capacitor, the switch transistor, and the driving transistor are connected at the first node. A second electrode plate of the storage capacitor is connected to a first constant-voltage signal line.