Shift Register Unit Alternating Pull-Down Circuits
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Solution Overview
Problem
In display technology, long-term biased transistors in pull-down circuits of shift register units can cause threshold shifts, leading to abnormal display issues such as picture flutter when the display panel is turned off.
Innovation Solution
A shift register unit design that alternately outputs high and low levels from two signal terminals with opposite logic, using pull-down control circuits to manage the signals and prevent threshold shifts by alternating the threshold-shifting directions of transistors in the pull-down circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor in the pull-down circuit is in a long-term biased state, then the pull-down circuit can maintain the invalid signal, but the threshold of the transistor shifts causing display abnormality
Solution Approach 1:
The patent applies periodic action by alternately switching between first and second pull-down circuits in each frame period. The first pull-down circuit operates in one frame period and is switched to the second pull-down circuit in the next frame period, preventing any single transistor from remaining in a biased state continuously. This periodic switching resolves the contradiction by maintaining signal functionality while preventing threshold drift through regular circuit alternation.
Solution Approach 2:
The patent implements dynamics by making the pull-down circuit configuration changeable over time through the switching between first and second pull-down circuits. The circuit transitions from a static configuration to a dynamic one where the active pull-down circuit changes periodically, allowing the system to adapt and prevent threshold accumulation while maintaining the pull-down function.
2Reliability
If the shift register unit outputs invalid driving signal when pixel row is in non-scanning state, then the pixel row is protected, but the transistor threshold shifts causing picture flutter
Solution Approach 1:
The patent uses periodic action by alternating the operation of first and second pull-down circuits in successive frame periods. During each frame period, one pull-down circuit is activated while the other is deactivated, and they switch roles in the next frame period. This periodic switching maintains the protective invalid signal output while preventing continuous biasing of transistors, thereby eliminating picture flutter.
Solution Approach 2:
The patent converts the harmful effect of threshold shift into a beneficial outcome by using the alternation between two pull-down circuits. The threshold shift that would normally cause picture flutter is transformed into a controlled, periodic phenomenon that averages out over time. The alternating circuits ensure that no single transistor accumulates excessive bias, converting the potential harm into a stable operating condition.
Data Source
AI summary
The present disclosure provides to a shift register unit, a driving method, a gate driving circuit, and a display panel. The shift register unit includes: first and second signal terminals respectively outputting high and low levels alternately, a level logic of a signal output from the second signal terminal being opposite to that from the first signal terminal; first and second pull-down control circuits; a first pull-down circuit coupled to the first pull-down node, the first signal terminal, and a pull-down target node, and transmitting, in response to a signal of the first pull-down node, the signal of the first signal terminal to the pull-down target node; a second pull-down circuit coupled to the second pull-down node, the second signal terminal, and the pull-down target node, and transmitting, in response to a signal of the second pull-down node, the signal of the second signal terminal to the pull-down target node.