Shift Register Unit With Dual Pull-Up Nodes
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Solution Overview
Problem
In in-cell touch display devices, current leakage during touch periods can lead to a decrease in voltage at pull-up nodes, affecting the charging of pixels and causing issues with gate line enablement, especially due to the mutual restriction between pull-up and pull-down nodes, making it difficult to maintain the necessary width-to-length ratio of transistors.
Innovation Solution
A shift register unit is designed with two pull-up nodes and separate control circuits for each, allowing independent control of the gate driving signal output and potential at the pull-down node, reducing leakage current by increasing the voltage output during touch periods and preventing false outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pull-up node is used in the GOA unit, then the circuit structure is simple, but the voltage at the pull-up node decreases during touch periods due to current leakage, causing gate driving signal failure
Solution Approach 1:
The single pull-up node is segmented into two separate pull-up nodes (first pull-up node and second pull-up node), each controlled by independent control circuits. This segmentation allows independent optimization of each node's voltage maintenance capability, preventing the voltage degradation that occurs in single-node designs during touch periods.
Solution Approach 2:
A voltage signal line is introduced as an intermediary between the two pull-up nodes to transmit voltage signals. This intermediary mechanism enables coordinated voltage control across both nodes, ensuring that when one node experiences voltage drop due to leakage, the other node can compensate to maintain overall circuit reliability.
2Loss of energy
If the width-to-length ratio of transistors is increased to reduce leakage current, then leakage current is reduced, but the transistor dimensions become unrealistic and the circuit area increases
Solution Approach 1:
The leakage current reduction task is segmented between two pull-up nodes with separate control circuits. Each node's control circuit can be optimized with moderate transistor dimensions, and the combined effect of both nodes achieves the overall leakage reduction goal without requiring excessively large individual transistors.
Solution Approach 2:
The control voltages applied to the two pull-up nodes are dynamically adjusted based on operating conditions. During touch periods, the voltage signals are optimized to minimize leakage current effects without requiring permanent increases in transistor dimensions, thus maintaining compact circuit area while reducing effective leakage.
3Productivity
If the touch time period is extended to improve touch responsiveness, then touch detection capability is enhanced, but voltage degradation at pull-up nodes worsens due to prolonged current leakage
Solution Approach 1:
The extended touch period is managed by segmenting the voltage maintenance function across two independent pull-up nodes. Each node can be independently refreshed or boosted, allowing the system to maintain adequate voltage levels throughout extended touch periods without the cumulative voltage degradation that plagues single-node designs.
Solution Approach 2:
The two pull-up nodes operate in a coordinated continuous manner to maintain voltage levels throughout the extended touch period. By continuously monitoring and adjusting the voltage signals at both nodes, the system ensures uninterrupted gate driving signal generation even during prolonged touch operations, eliminating the voltage degradation issue.
Data Source
AI summary
A shift register unit includes a first pull-up node control circuit, a second pull-up node control circuit, a pull-down node control circuit, an output pull-up circuit and an output pull-down circuit. The first pull-up node control circuit is configured to control a first pull-up node to be electrically connected to a second voltage end under the control of an input signal, and control the first pull-up node to be electrically connected to a first voltage end under the control of a resetting signal. The second pull-up node control circuit is configured to control the second pull-up node to be electrically connected to the second voltage end under the control of the input signal applied to the input end, and control the second pull-up node to be electrically connected to the first voltage end under the control of the resetting signal from the resetting end.