Shift Register Unit Pull-Up Node Reset Circuit for Display Threshold Drift
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Solution Overview
Problem
The existing gate driving circuits in display technology suffer from threshold voltage drift issues due to the leakage current of thin film transistors, leading to dark lines on the display screen caused by prolonged transistor operation, which affects display brightness and overall performance.
Innovation Solution
A shift register unit is designed with a pull-up node reset circuit, signal output terminal reset circuit, pull-down control circuit, pull-down circuit, and noise reduction circuit, which control the voltage levels and reset signals to minimize transistor operation time and reduce noise, thereby mitigating threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin film transistors are used in the gate driving circuit, then the circuit can be integrated on the array substrate, but leakage current causes threshold voltage drift and dark lines
Solution Approach 1:
The patent applies preliminary action by resetting the pull-up node voltage to a predetermined level before the transistor operates. The reset circuit proactively prepares the circuit state in advance, ensuring that even if leakage current occurs during operation, the threshold voltage can be restored to its correct value, preventing dark line defects.
Solution Approach 2:
The patent changes the voltage parameter of the pull-up node by introducing a reset circuit that can actively adjust the node voltage back to a predetermined level. This parameter change compensates for the threshold voltage drift caused by leakage current, maintaining reliable transistor operation throughout the display refresh cycle.
2Duration of action of stationary object
If transistors operate for prolonged periods, then the gate driving circuit can maintain continuous operation, but threshold voltage drift increases causing dark lines
Solution Approach 1:
The patent implements periodic action by resetting the pull-up node voltage at specific intervals (e.g., at the beginning of each frame or scan period). This periodic reset prevents threshold voltage drift from accumulating over prolonged operation, ensuring display brightness uniformity is maintained throughout continuous operation.
Solution Approach 2:
The reset circuit performs preliminary action by restoring the pull-up node voltage to a predetermined level before the next operation cycle begins. This proactive reset prevents threshold voltage drift from affecting display quality during prolonged operation.
3Reliability
If reset circuits are added to control voltage levels, then threshold voltage drift is reduced, but circuit complexity increases
Solution Approach 1:
The reset circuit is designed with multi-functionality, serving both to reset the pull-up node voltage and to control the timing of operations. By combining multiple functions into a single circuit block, the patent reduces the need for additional separate components, thereby limiting the increase in circuit complexity while maintaining threshold voltage stability.
Data Source
AI summary
A shift register unit, a gate driving circuit and a driving method thereof, a display device. The shift register unit includes: a first input circuit configured for outputting a voltage of a first voltage terminal to a pull-up node under a control of a first signal terminal; a second input circuit configured for outputting a voltage of a second voltage terminal to the pull-up node under a control of a second signal terminal; an output circuit configured for outputting a clock signal of a clock signal terminal to the signal output terminal under a control of the pull-up node; a pull-up node reset circuit configured for outputting a voltage of the third voltage terminal to the pull-up node under a control of the third signal terminal.