Shift Register Unit Discharge Circuit for TFT Display Residual Charge
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Solution Overview
Problem
Thin film transistor (TFT) liquid crystal displays experience charge residual during shutdown, leading to issues like image sticking and startup flickering, and are unable to support low-frequency driving due to incomplete discharge of pixels.
Innovation Solution
A shift register unit with an input circuit, pull-up circuit, control circuit, and discharge circuit is designed to control node potentials and discharge pixels using voltage terminals, ensuring complete discharge during shutdown and enabling low-frequency driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shift register is constituted by a plurality of stages of shift register units connected in series in the related art, then the basic shift register function is achieved, but charge residual occurs during shutdown process causing image sticking and startup flickering
Solution Approach 1:
The discharge circuit is activated before the shutdown process to preemptively discharge the pixel units and shift register units. This preliminary discharge action removes residual charges that would otherwise cause image sticking and startup flickering during subsequent shutdown and startup operations.
Solution Approach 2:
The invention converts the harmful residual charges into a beneficial discharge process. By intentionally introducing a discharge circuit that actively removes residual charges from pixel units and shift register units, the harmful charge accumulation is transformed into a controlled discharge mechanism that improves display reliability.
2Reliability
If the shift register units are connected in series without discharge circuit, then the device complexity is low, but charge residual causes poor screen display and startup flickering
Solution Approach 1:
The shift register system is segmented into multiple independent shift register units, each equipped with its own discharge circuit. This segmentation allows each unit to be discharged independently, ensuring complete charge removal while maintaining manageable circuit complexity through modular design.
Solution Approach 2:
The discharge circuit is designed with multi-functionality to serve multiple purposes: discharging pixel units, discharging shift register units, and preparing for both shutdown and startup operations. This universal discharge mechanism reduces overall system complexity by using a single circuit design for multiple functions.
3Adaptability or versatility
If pixel discharge is not implemented during shutdown, then the device operation is simple, but low-frequency driving is not supported due to charge residual
Solution Approach 1:
The discharge circuit operates periodically during shutdown processes, activating at regular intervals to discharge accumulated charges. This periodic discharge action enables the display to adapt to low-frequency driving by ensuring charges are removed at appropriate intervals, preventing image sticking and flickering.
Solution Approach 2:
The discharge circuit incorporates feedback mechanisms that monitor the shutdown state and activate discharge operations accordingly. This feedback control ensures discharge occurs at the appropriate times during shutdown and low-frequency driving operations, improving adaptability while maintaining ease of operation through automatic control.
Data Source
AI summary
A shift register unit provided according to embodiments of the present disclosure includes an input circuit, a pull-up circuit, a control circuit, and a first discharge circuit. The pull-up circuit is configured to control an output of the signal output terminal. The control circuit is configured to control a potential of the second node based on a second voltage signal of the second voltage terminal and a potential of the first node. The first discharge circuit is configured to control, after being turned on under the control of the potential of the second node, the first node and the signal output terminal by using the third voltage terminal, and discharging a pixel unit, the first node and the signal output terminal, the pixel unit being connected to the signal output terminal.