Shift Register Precharge Circuit for GOA Transistor Drift
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Solution Overview
Problem
In display technology, particularly for high refresh frequency applications like 3D displays, the high power voltage used to charge Gate Driver On Array (GOA) accelerates transistor characteristic drift, leading to insufficient charging of pull-up nodes and reduced display device lifespan.
Innovation Solution
A shift register unit design incorporating double bootstrap capacitors to improve the charging capability of pull-up nodes, ensuring stable operation and extended lifespan by precharging nodes before output signals are generated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high power voltage is used to charge GOA to meet high refresh frequency requirements, then the charging speed is improved, but transistor characteristic drift accelerates and device lifespan is reduced
Solution Approach 1:
The patent introduces a precharge node and precharge transistor that charge the pull-up node in advance during the non-output phase. This preliminary charging action ensures that the pull-up node is fully charged before the output phase begins, eliminating the need for high power voltage during normal operation and thereby reducing transistor stress while maintaining charging speed requirements.
Solution Approach 2:
The charging process is divided into two distinct phases: a precharge phase using a dedicated precharge transistor during the non-output phase, and an output phase using the main output transistor. This segmentation allows each transistor to operate under optimized conditions, with the precharge transistor handling the high-current charging task separately from the output transistor, thereby reducing overall transistor stress and drift.
2Productivity
If high power voltage is used to charge GOA, then the refresh frequency is improved, but transistor characteristic drift accelerates
Solution Approach 1:
The precharge node and precharge transistor perform the high-current charging operation in advance during the non-output phase. This preliminary action ensures that the pull-up node reaches full charge voltage before the output phase, enabling high refresh frequency operation without requiring high power voltage during the critical output phase, thereby maintaining transistor characteristic stability.
Solution Approach 2:
The circuit operates in periodic cycles alternating between non-output phase (precharge phase) and output phase. During the non-output phase, the precharge transistor charges the pull-up node; during the output phase, the output transistor drives the signal. This periodic alternation allows the system to achieve high refresh frequency while keeping each transistor's stress within safe operating limits, preventing characteristic drift.
3Power
If conventional single bootstrap capacitor design is used, then the circuit complexity is low, but the charging capability of pull-up nodes is insufficient
Solution Approach 1:
The charging function is segmented into two independent charging paths: one through the precharge transistor during the non-output phase, and another through the output transistor during the output phase. This segmentation provides sufficient charging capability for each phase without requiring a single high-capacity bootstrap capacitor, thereby achieving high charging capability while keeping individual capacitor sizes moderate and circuit complexity manageable.
Solution Approach 2:
The precharge transistor and associated capacitor perform the primary charging function in advance during the non-output phase. This preliminary charging action ensures that the pull-up node is fully charged before the output phase begins, eliminating the need for oversized capacitors or complex charging circuits while providing sufficient charging capability for high refresh frequency operation.
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 design enhances the charging capability of pull-up nodes, stabilizing the circuit structure and extending the service life of display panels by addressing the issue of transistor characteristic drift at high refresh frequencies.
Implementation Method 1
the first node control circuit is configured to receive a precharge control signal from a precharge control terminal and charge the first node in response to the precharge control signal
Data Source
AI summary
A shift register unit, a gate driving circuit, a display device, and a driving method are provided. The shift register unit includes an input circuit, an output circuit, and a first node control circuit. The input circuit is configured to charge a first node in response to an input signal; the output circuit is configured to output an output signal at an output terminal under control of a level signal of the first node; and the first node control circuit is configured to receive a precharge control signal from a precharge control terminal and charge the first node in response to the precharge control signal before the output terminal outputs the output signal.