Flat Panel Display Pixel Circuit Leakage Current Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high leakage current in thin film transistors of active matrix flat panel displays leads to image quality degradation due to variations in data voltage and differences in leakage currents between pixels, making it difficult to maintain image quality over time.
Innovation Solution
The design incorporates a pixel circuit with N-type or P-type switching elements and a drive transistor, along with a capacitive element and organic light emitting diode or liquid crystal cell, where the switching elements are configured to minimize voltage differences and increase OFF resistance, thereby reducing leakage current and maintaining stable drive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crystallization methods (solid phase, excimer laser, metal induced) are used to create poly-silicon thin film transistors, then electron mobility and optical stability are improved, but leakage current increases due to metal catalysts remaining in the crystallized layer
Solution Approach 1:
The patent extracts and removes metal catalysts from the crystallized silicon layer through selective etching processes. The metal-induced lateral crystallization method is used to form poly-silicon, and subsequent etching steps remove the remaining metal catalysts that cause high leakage current, thereby resolving the contradiction between achieving crystallization and eliminating harmful metal residues
Solution Approach 2:
The patent introduces an intermediary etching process between crystallization and device operation. This intermediary step uses selective etchants to remove metal catalysts without damaging the poly-silicon structure, serving as a mediator that eliminates harmful metals while preserving the beneficial crystallized structure
2Device complexity
If the pixel circuit uses a simple structure with fewer transistors, then device complexity is reduced, but leakage current effects become more significant and image quality degrades
Solution Approach 1:
The patent segments the pixel circuit into multiple functional blocks: a drive transistor for current control, a switching element for data input, and a capacitive element for voltage storage. This segmentation allows each component to perform its specific function optimally, with the capacitive element isolating the drive transistor from data voltage changes, thereby reducing leakage current effects while maintaining reasonable complexity
Solution Approach 2:
The capacitive element performs preliminary action by storing the data voltage before it is applied to the drive transistor. This pre-storage function isolates the drive transistor from subsequent data voltage changes, preventing leakage current variations from affecting the drive current, thereby maintaining image quality stability without requiring a overly complex circuit
Data Source
AI summary
Disclosed is a flat panel display that prevents image quality degradation by preventing the current leakage to the organic light emitting diode. The flat panel display comprises: a first switching element whose control electrode is electrically coupled to a scan line, being electrically coupled between a data line and a first voltage line; a second switching element whose control electrode is electrically coupled to the scan line, being electrically coupled between the first switching element and first voltage line; a capacitive element whose first electrode is electrically coupled between the first and second switching elements; a drive transistor whose control electrode is electrically coupled to the second switching element, being electrically coupled between the first voltage line and a second voltage line; and an organic light emitting diode electrically coupled between the drive transistor and second voltage line.