GOA Circuit Charge Release for Liquid Crystal Image Sticking
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Solution Overview
Problem
NMOS type GOA circuits in liquid crystal display devices face issues with image sticking due to abnormal power off, as they fail to effectively enable all gate driving signals simultaneously, leading to charges not being released in time.
Innovation Solution
A GOA circuit comprising cascaded units with specific TFT configurations, including output control, forward-reverse scan control, pull-down, and pull-up circuits, along with a voltage stabilizing circuit, to manage gate driving signals and prevent image sticking during abnormal power off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NMOS type GOA circuit is used to increase yield rate and decrease cost, then manufacturing cost is reduced, but image sticking occurs during abnormal power off
Solution Approach 1:
The patent applies preliminary action by enabling all gate driving signals in advance before abnormal power off occurs. The control module detects power off status and proactively activates all scanning lines simultaneously, ensuring that pixel electrodes can release accumulated charges even when power is suddenly lost, thereby preventing image sticking while maintaining the cost-effective NMOS circuit design
2Loss of energy
If forward scan control signal and clock signal are pulled down simultaneously during abnormal power off, then power consumption is reduced, but TFT NT5 remains turned on and charges cannot be released
Solution Approach 1:
The patent applies preliminary action by activating all gate driving signals before power off occurs, ensuring that the pulling down of control signals during power off does not prevent charge release. By preemptively enabling all scanning lines, the system ensures that pixel charges can be discharged even when subsequent control signals are pulled down to save power
Solution Approach 2:
The patent applies beforehand cushioning by preparing the circuit state in advance to compensate for the harmful effect of simultaneous signal pulling down. The control module pre-configures the circuit to maintain scanning capability during power off, cushioning against the potential image sticking caused by abrupt signal termination
3Loss of energy
If gate driving signal G(n) is pulled down during abnormal power off, then scanning stops to prevent further power loss, but pixel charges cannot be released causing image sticking
Solution Approach 1:
The patent applies preliminary action by enabling all gate driving signals before power off occurs. This preliminary activation ensures that when power is suddenly lost and control signals are pulled down, the pixel electrodes are already in a state that allows charge release, preventing image sticking while still stopping scanning to prevent further power loss
Data Source
AI summary
A GOA circuit comprises m cascaded GOA units, wherein a nth-stage GOA unit comprises: an output control module, a forward-reverse scan control module, a first pull-down circuit, a second pull-down circuit and a pull-up circuit, the forward-reverse scan control module is used for controlling the GOA circuit to perform a forward scanning or a reverse scanning; the output control module outputs a nth gate driving signal; the first pull-down circuit comprises a seventh TFT; the second pull-down circuit comprises a third TFT, a fourth TFT and a fifth TFT; and the pull-up circuit comprises an eighth TFT and a thirteenth TFT. After power of the liquid crystal display panel is turned off, the fifth TFT is turned off by overlapping of the forward scan control signal and the reverse scan control signal and a first global control signal is high potential.