Bi-directional Shift Register Unit for Gate Driver Noise Reduction
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Solution Overview
Problem
Existing shift register units in gate driver circuits for display devices suffer from issues such as short high-level periods for the fourth transistor, DC bias drift, susceptibility to parasitic capacitance, uneven brightness, and inability to implement bi-directional scanning, leading to faulty operations and coupling noise voltage.
Innovation Solution
A shift register unit design incorporating a pre-charging and scanning module, a reset module, and a switching module that uses two clock signals with opposite time sequences to enable bi-directional scanning, exchanging shift trigger and reset signals and power supply voltages to maintain pull-up node stability and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional shift register unit with four transistors and one capacitor is used, then the circuit structure is simple, but the high-level period for the fourth transistor is short causing DC bias drift and susceptibility to parasitic capacitance
Solution Approach 1:
The shift register unit is divided into multiple functional modules: a pre-charging module (first transistor M1 and capacitor C1), a scanning module (third transistor M3), and a reset module (second transistor M2 and fourth transistor M4). This segmentation allows each module to perform its function independently, improving reliability while maintaining structural clarity.
Solution Approach 2:
The pre-charging module charges the pull-up node PU to a high level before the scanning operation begins. This preliminary action ensures that the node is properly prepared and reduces susceptibility to parasitic capacitance effects during subsequent operations, addressing the reliability issue.
2Area of stationary object
If the conventional shift register unit is used, then the circuit is compact, but faulty operation occurs due to susceptibility to parasitic capacitance and DC bias drift
Solution Approach 1:
The output terminal 8 is connected back to the gate of the second transistor M2 and fourth transistor M4, forming a feedback loop. This feedback mechanism ensures that the reset transistors are properly controlled based on the current state, improving operation reliability while maintaining compact design.
Solution Approach 2:
The shift register unit automatically performs pre-charging, scanning, and reset operations through its internal transistor and capacitor configuration, without requiring external intervention. This self-service capability enhances reliability while keeping the circuit compact.
3Device complexity
If the conventional shift register unit is used, then the design is simple, but bi-directional scanning cannot be implemented and coupling noise voltage is generated
Solution Approach 1:
The shift register unit incorporates dynamic control through the switching module that can exchange the connections of the first and second clock signals based on the scanning direction requirement. This dynamic reconfiguration enables bi-directional scanning capability while maintaining relatively simple design.
Solution Approach 2:
The same shift register unit circuit can perform both forward and reverse scanning operations by switching the clock signal connections, making it a universal module that handles multiple scanning directions without requiring separate circuits for each direction.
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 enables bi-directional scanning, reduces the impact of coupling noise, improves reliability, and enhances the stability and cost-effectiveness of the gate driver circuit by simplifying its structure and managing power supply levels effectively.
Implementation Method 1
its gate is connected to the output terminal 8 via the capacitor C
Implementation Method 2
the potential at the pull-up node PU is pulled-up again because of a Bootstrapping Effect
Data Source
AI summary
The present disclosure provides a bi-directional scanning gate driver and its shift register unit. The shift register unit comprises a shift trigger signal/reset signal input terminal (1), a reset signal/shift trigger signal input terminal (2), the first clock terminal (6) and an output terminal (8). The shift trigger signal/reset signal input terminal (1) and the reset signal/shift trigger signal input terminal (2) are coupled to one of the shift trigger signal and the reset signal. When it is switched between the forward shift and the reverse shift, the signals coupled to the shift trigger signal/reset signal input terminal (1) and the reset signal/shift trigger signal input terminal (2) are exchanged. The first clock terminal (6) is coupled to a clock signal for providing a driving level to the output terminal (8). The circuit of such a shift register unit is constituted of at least four transistors and one capacitor. The structure of the circuit of the present disclosure is simple and may solve the technical problem of coupling noise voltage generated by the clock signal.