Shift Register Unit With Segmented Pull-Down Nodes
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Solution Overview
Problem
Existing gate driver circuits in TFT-LCDs face issues with output errors due to threshold voltage drifts and interval operations in pull-down nodes, affecting noise reduction and stability.
Innovation Solution
A shift register unit design incorporating specific TFT configurations and modules, including input, output, pull-down driving, and discharging modules, utilizes AC signals at pull-down nodes to suppress output errors and ensure continuous discharging during non-output phases, enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-down node is arranged to pull down the potential at an output terminal of a shift register unit not corresponding to a row to which a gate driving signal is output, then the threshold voltage drifts of relevant thin film transistors would cause noise reduction issues, but using AC signal would reduce threshold voltage drift effects while causing output errors due to interval in the operation of pulling down
Solution Approach 1:
The pull-down function is divided into two separate pull-down nodes (first pull-down node and second pull-down node) that operate alternately. This segmentation allows one node to be pulled down while the other maintains the output, eliminating the interval problem where no pull-down operation occurs. The alternating operation of segmented pull-down nodes ensures continuous noise suppression without output errors.
Solution Approach 2:
The patent implements periodic alternating operation between the first and second pull-down nodes. During different time periods, different nodes perform the pull-down function, creating a continuous periodic action that eliminates gaps in noise suppression. This periodic alternation ensures that at least one node is always in the pull-down state, preventing output errors while maintaining noise reduction effectiveness.
2Object-affected harmful factors
If the pull-down node is in a direct current (DC) high level operation state for a long time, then it would cause drifts in threshold voltages of relevant thin film transistors affecting noise reduction, but switching to AC signal would reduce threshold voltage drift effects while causing output errors due to interval in operation
Solution Approach 1:
The pull-down function is segmented into two nodes operating alternately, allowing continuous AC-like operation without intervals. This segmentation enables the system to maintain AC signal characteristics that reduce threshold voltage drift effects while avoiding the interval problem that would cause output errors, thus simultaneously addressing noise reduction and output accuracy requirements.
Solution Approach 2:
The alternating operation of two pull-down nodes ensures continuity of the useful pull-down action. By switching between nodes without interruption, the system maintains continuous noise suppression functionality while avoiding gaps that would lead to output errors, achieving both noise reduction and output accuracy through uninterrupted operation.
Data Source
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AI summary
Provided are a shift register unit and a gate driver circuit, which are configured to suppress output errors caused by the drifts in the threshold voltages and the interval existed in the operation of pulling the output terminal, and thus to enhance stability of the shift register unit. The shift register unit comprises: an input module, a first output module, a pull-down driving module, a pull-down module and a first output discharging unit. The pull-down driving module is connected to the first clock signal input terminal and the second clock signal input terminal, and configured to provide the first clock signal to a first pull-down node in response to the first clock signal, provide the second clock signal to a second pull-down node in response to the second clock signal, provide a first low voltage signal to the first pull-down node and the second pull-down node in response to the voltage signal at the pull-up node, provide the first low voltage signal to the second pull-down node in response to a voltage signal at the first pull-down node, and provide the first low voltage signal to the first pull-down node in response to a voltage signal at the second pull-down node.