GOA Circuit All Gate ON Control for LCD Ghost Image Elimination
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Solution Overview
Problem
Liquid crystal display panels experience ghost images due to insufficient gate driving signals during abnormal power-off, leading to incomplete charge release from pixel electrodes, which affects display quality and user experience.
Innovation Solution
A GOA circuit with cascaded units, including output control, scanning control, node signal control, pull-down, and pull-up circuits, is designed to manage gate driving signals effectively during power-off scenarios, ensuring complete charge release by controlling the ON-OFF states of thin film transistors and preventing ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the GOA circuit uses NMOS type thin film transistors to simplify the process and reduce cost, then manufacturing cost and complexity are reduced, but the circuit cannot effectively achieve All Gate ON function during abnormal power-off, causing ghost images
Solution Approach 1:
The GOA circuit is divided into multiple cascaded GOA units, each independently controlling a segment of gate lines. Each unit contains separate control paths for forward and backward scanning, allowing independent control of different gate line segments during abnormal power-off conditions
Solution Approach 2:
A global control signal is introduced as an intermediary to coordinate the operation of multiple GOA units. This signal acts as a mediator to ensure all units switch to All Gate ON state simultaneously during abnormal power-off, eliminating ghost images while maintaining the simple NMOS structure
2Stability of the object's composition
If the gate driving signal potential is pulled down during abnormal power-off, then the circuit follows normal signal levels, but the pixel electrode charge cannot be released in time, resulting in ghost images
Solution Approach 1:
The circuit proactively prevents the harmful effect of charge retention by automatically switching to All Gate ON state when abnormal power-off is detected. The global control signal triggers preemptive action to pull up all gate driving signals before ghost images can form, counteracting the natural tendency of signals to be pulled down
Solution Approach 2:
The GOA circuit dynamically adjusts its operating state based on power-off conditions. During normal operation, it maintains standard signal levels for stable imaging. During abnormal power-off, it transitions to All Gate ON state to enable complete charge release, then returns to normal operation when power is restored
Data Source
AI summary
This invention provides a GOA circuit comprising m cascaded GOA units. An n-th GOA unit includes an output control module, a forward/backward scanning control module, a node signal control module, a second pull-down circuit, a first pull-down circuit and a pull-up circuit. The forward/backward scanning control module control the GOA circuit to perform a forward or a backward scanning. The output control module controls an output of an n-th gate driving signal. The first pull-down circuit comprises a seventh thin film transistor. The second pull-down circuit comprises a fifth thin film transistor. The node signal control module control the fifth thin film transistor. The pull-up circuit includes an eighth thin film transistor. After the LCD panel is powered off, the second global control signal becomes a low level. This invention can eliminate a ghost image in the LCD panel when electricity is powered off, and improve user experience.