Display Gate Driver Q/QB Node Stabilization Against Threshold Shift
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Solution Overview
Problem
The threshold voltage shift of thin film transistors in gate drivers leads to the output of multiple scan signals for one frame, causing inefficiencies in display devices.
Innovation Solution
A display device with a gate driver that includes an output buffer responding to Q-node and QB-node signals, and transistors supplying low-level voltages to these nodes, coupled with capacitors to stabilize node voltages, preventing threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If thin film transistors are used in gate drivers, then device integration is improved, but threshold voltage shift occurs causing multiple scan signals per frame
Solution Approach 1:
The patent applies preliminary action by pre-charging the Q-node and QB-node to specific voltage levels before the switching operation. The first transistor supplies low-level voltage to the Q-node in advance, and the second transistor supplies low-level voltage to the QB-node in advance. This preliminary voltage setup ensures that when the clock signal transitions, the output buffer can reliably switch states without being affected by threshold voltage shifts in the thin film transistors, thus preventing multiple unintended scan signals.
Solution Approach 2:
The patent changes the voltage parameters at critical nodes (Q-node and QB-node) to compensate for threshold voltage shifts. By maintaining these nodes at predetermined voltage levels through the action of the first and second transistors, the circuit ensures stable operation of the output buffer even when the thin film transistors experience threshold voltage drift, thereby resolving the reliability issue while maintaining device integration.
2Device complexity
If threshold voltage shift is not compensated, then circuit simplicity is maintained, but multiple scan signals are output per frame reducing productivity
Solution Approach 1:
The patent introduces intermediary elements (the first transistor, second transistor, and associated capacitors) that mediate between the clock signal input and the output buffer. These intermediaries actively maintain the Q-node and QB-node at correct voltage levels, preventing threshold voltage shifts from propagating to the output. This mediation ensures that only one clean scan signal is output per frame, improving productivity while adding controlled complexity to the circuit.
Data Source
AI summary
A display device including a gate driver capable of preventing threshold voltage shift of thin film transistors constituting the gate driver from influencing an output of the gate driver is disclosed. The display device includes a display panel including a plurality of gate lines and a plurality of data lines, and a gate driver including at least one scan driver. The gate driver sequentially outputs a scan signal to the plurality of gate lines. The at least one scan driver includes an output buffer configured to output a first clock signal as a scan signal in response to signals of a Q-node and a QB-node, and a first transistor configured to supply a low-level voltage to the QB-node in response to a start signal or a scan signal of an upstream stage.