AMOLED Pixel Circuit Reducing LTPS Leakage
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Solution Overview
Problem
The leakage current of low temperature poly-silicon thin film transistor (LTPS TFT) in AMOLED panel driving circuits is high, leading to unstable gate potential and flickering brightness due to varying output current within one frame.
Innovation Solution
A pixel circuit design that includes a driving circuit connected to multiple thin film transistors, reducing the number of direct connections to the driving circuit and thereby minimizing current leakage paths, comprising a driving circuit, light-emitting control circuits, data writing circuit, reset circuit, storage circuit, and thin film transistors, with specific terminal connections to stabilize current output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LTPS TFT is used to drive AMOLED panels, then the panel can be driven with thin film transistor technology, but the leakage current is large causing gate potential instability and brightness flicker
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: driving circuit, light-emitting control circuits, data writing circuit, reset circuit, and storage circuit. Each module performs a specific function, and the segmentation allows for optimized signal routing and reduced interference paths, thereby stabilizing gate potential while maintaining manufacturability
Solution Approach 2:
A storage circuit is introduced as an intermediary between the driving circuit and the light-emitting device. The storage circuit holds the drive signal and isolates it from direct leakage paths, acting as a buffer that maintains gate potential stability even when LTPS TFT leakage current is present
2Device complexity
If multiple thin film transistors are directly connected to the driving circuit, then the circuit can be simplified, but the current leakage path increases causing output current variation
Solution Approach 1:
The patent extracts and isolates the leakage current paths by introducing separate control circuits and storage circuits that are not directly connected to the driving circuit. The light-emitting control circuits and reset circuit are separated from the main driving path, allowing the driving circuit to operate independently from leakage paths while maintaining overall circuit functionality
Solution Approach 2:
The reset circuit performs preliminary action by resetting the potential of the light-emitting device before the driving circuit operates. This preliminary reset ensures that any leakage current is cleared before the main driving signal is applied, preventing leakage-induced potential variations during the driving period
Data Source
AI summary
A pixel circuit and a display panel are provided. In the pixel circuit, a first terminal of the driving circuit is connected to a first terminal of the first light-emitting control circuit and a first terminal of the data writing circuit, a second terminal is connected to a source of the first thin film transistor, and a third terminal is connected to a drain of the first thin film transistor and a first terminal of the storage circuit, respectively. The number of thin film transistors directly connected to the driving circuit is reduced so that the current leakage path of the driving circuit is reduced.