Shift Register Cut-Off Module Prevents Internal Discharge
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Solution Overview
Problem
Depletion-mode oxide thin film transistors (TFTs) cause voltage drop at the first node in shift registers, preventing normal operation when used in gate driving circuits for display devices, as they can discharge through precharge and reset transistors during the pull-up stage.
Innovation Solution
Incorporating a cut-off module between the precharge and reset modules and the pull-up module in the shift register, which disconnects their electric connection during the pull-up stage, preventing discharge and ensuring stable signal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If depletion-mode oxide TFTs are used in the shift register, then manufacturing simplicity and cost are improved, but voltage stability deteriorates due to discharge through precharge and reset transistors
Solution Approach 1:
The circuit is divided into distinct functional modules: precharge module, reset module, pull-up module, and cut-off module. Each module performs a specific function, and the cut-off module acts as an independent segment to isolate the precharge and reset modules from the pull-up module during the pull-up stage, preventing unwanted discharge paths while maintaining manufacturing simplicity of oxide TFTs
Solution Approach 2:
The cut-off module serves as an intermediary component between the precharge/reset modules and the pull-up module. It mediates the electrical connection by disconnecting during the pull-up stage, thereby preventing the discharge of the first node through the precharge and reset transistors. This intermediary mechanism resolves the voltage stability issue while allowing the use of simpler depletion-mode oxide TFTs
2Device complexity
If depletion-mode TFTs are used as precharge and reset transistors, then device complexity is reduced, but harmful discharge effects increase during the pull-up stage
Solution Approach 1:
The cut-off module is activated in advance during the pull-up stage to prevent the harmful discharge effect before it can occur. By disconnecting the precharge and reset modules from the pull-up module at the appropriate time, the invention applies a preliminary counter-action to block the discharge path through the depletion-mode TFTs, thereby eliminating the harmful effect while maintaining simple device structure
Solution Approach 2:
The invention converts the inherent discharge characteristic of depletion-mode TFTs from a harmful effect into a manageable behavior. By using the cut-off module to control when the discharge path is active, the discharge characteristic is effectively utilized during stages where it is acceptable (precharge and reset stages) while being blocked during the pull-up stage, thereby transforming a potential harm into a controlled feature that simplifies device design
Data Source
AI summary
The present invention provides a shift register, a gate driving circuit and a display device. The shift register comprises a precharge and reset module, a pull-up module, a pull-down module and a cut-off module, the cut-off module, the pull-up module and the pull-down module are connected at a first node, and the cut-off module is connected between the first node and the precharge and reset module. In the present invention, the cut-off module is provided to disconnect electric connection between the precharge and reset module and the pull-up module, such that the first node cannot discharge through the precharge and reset module, which effectively avoids internal discharge of the shift register, and further ensures normal output of the signal output from the output terminal of the shift register, and improves stability of the shift register.