Shift Register Reset Control Circuit for Narrow-Frame Displays

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Solution Overview

Problem

In narrow-frame display modules, the reset transistor in the shift register unit generates carriers due to illumination, leading to a large leakage current, which causes the potential of the pull-up node to be pulled down during the output stage, resulting in unstable gate driving signals and abnormal displays.

Innovation Solution

A shift register unit is designed with a reset circuit connected to the pull-up node to reset its potential during the reset stage, and a reset control circuit is added to maintain the potential at a first voltage during the output stage by controlling the reset transistor to be in a reverse locked state, reducing leakage current and ensuring stable output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the reset transistor is used to reset the pull-up node potential during reset stage, then the reset function is achieved, but leakage current increases due to illumination-generated carriers

Engineering Contradiction:

Improvereset functionVSAvoidleakage current

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The control of the reset transistor is segmented into different stages: during the reset stage, the reset transistor is activated to reset the pull-up node potential; during the output stage, the reset transistor is placed in reverse locked state to minimize leakage current. This temporal segmentation allows the reset transistor to serve dual purposes at different times.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

During the output stage, the reset transistor is operated in reverse locked state by applying reverse voltage between drain and source, which is the opposite of its normal operating mode. This inversion of the transistor's operating state effectively suppresses leakage current caused by illumination-generated carriers while maintaining the reset functionality during the reset stage.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the reset transistor operates during output stage, then reset control is maintained, but pull-up node potential drops due to leakage current

Engineering Contradiction:

Improvereset controlVSAvoidpull-up node potential

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The reset transistor is placed in reverse locked state before the output stage begins, as a preliminary action to prevent leakage current from affecting the pull-up node potential during signal output. This preventive measure ensures stable potential maintenance throughout the output stage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The illumination-generated carriers that cause harmful leakage current are converted into a beneficial effect by applying reverse voltage to the reset transistor during the output stage. This reverse bias condition causes the leakage current to flow in a controlled manner that actually helps maintain the pull-up node potential stability rather than destabilizing it.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Length of moving object

If no light-shielding tape is used, then narrow-frame design is achieved, but reset transistor leakage current increases due to direct illumination

Engineering Contradiction:

Improveframe widthVSAvoidleakage current

Core Design Contradiction:

Length of moving objectVSObject-generated harmful factors

Solution Approach 1:

The operating parameters of the reset transistor are dynamically changed based on the display stage: during the reset stage, the transistor is activated with forward bias; during the output stage, the transistor is switched to reverse locked state with reverse bias. This parameter change allows the system to achieve narrow-frame design without light-shielding tape while controlling leakage current through electrical parameter adjustment rather than physical shielding.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively maintains the pull-up node potential, allowing the shift register unit to output gate driving signals normally, ensuring proper display by minimizing leakage current and preventing abnormal displays.

Implementation Method 1

the reset transistor is put in a reverse locked state by controlling a potential of the reset control terminal and/or a potential of the reset voltage terminal during the output stage

Methodology Applied

Scientific EffectReverse locked state:

Implementation Method 2

the reset transistor of a shift register unit included in the GOA generates carriers due to illumination

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11302242B2Shift register unit including reset control, method of driving the same, gate driving circuit and display device

Publication Date: 2022.04.12 BEIJING BOE OPTOELECTRONCIS TECH CO LTD

AI summary

A shift register unit, a driving method thereof, a gate driving circuit and a display device are provided. The shift register unit includes a reset circuit and a reset control circuit, the reset circuit is connected to a pull-up node, and configured to reset a potential of the pull-up node during a reset stage; and the reset control circuit is connected to the reset circuit and configured to maintain the potential of the pull-up node at a first voltage during an output stage of each display period.