Display Gate Driver Stage for Q Node Voltage Hold Under HVDS
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Solution Overview
Problem
Transistors in gate driving circuits of display apparatuses experience high voltage drain stress (HVDS) due to repeatedly applied boosted high voltages, leading to deterioration and negative shifts in threshold voltage, which can result in insufficient Q node voltage maintenance and gate driving circuit defects.
Innovation Solution
Incorporating a first pull-up transistor and a first pull-down transistor connected to a Q node, along with a series connection of 3a and 3b transistors and a charging capacitor connected to a Qc node, to form a discharge path that alleviates HVDS and maintains Q node voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor discharges the voltage of the Q node, then the Q node voltage can be maintained, but the transistor experiences high voltage drain stress leading to deterioration and threshold voltage negative shift
Solution Approach 1:
The discharge path transistor is divided into two transistors connected in series (first discharge transistor and second discharge transistor), with the Qc node located between them. This segmentation reduces the source-drain voltage stress on each individual transistor while maintaining the overall discharge function of the Q node.
2Manufacturing precision
If manufacturing processes deviate or deteriorate, then transistor threshold voltage shifts negatively, but the Q node voltage cannot be sufficiently maintained and drops
Solution Approach 1:
A charging capacitor is connected to the Qc node to store charge in advance. When the threshold voltage of the discharge transistors shifts negatively due to manufacturing variations, the charging capacitor provides additional charge to maintain the Q node voltage, cushioning against the voltage drop.
3Device complexity
If a single transistor discharges the Q node, then the circuit structure is simple, but the transistor suffers from continuous high voltage drain stress causing deterioration
Solution Approach 1:
The discharge function is segmented across two transistors connected in series, reducing the voltage burden on each transistor. This segmentation improves transistor durability and reliability while maintaining a relatively simple circuit structure.
Solution Approach 2:
The Qc node acts as an intermediary between the two discharge transistors, allowing the voltage to be distributed across multiple components. This intermediary structure reduces the stress on individual transistors and improves overall system reliability.
Data Source
AI summary
A display apparatus includes a display panel including a pixel and a gate line connected to the pixel. The apparatus includes a gate driving circuit including a stage that outputs a gate signal to the gate line. The stage includes a first pull-up transistor and a first pull-down transistor that are connected to each other with a first output terminal, which outputs the gate signal, therebetween. The stage includes a Q node and a Qb node that are respectively connected to the first pull-up transistor and the first pull-down transistor. The stage includes a 3a transistor and a 3b transistor which are located in a discharge path of the Q node and are connected in series with each other with a Qc node therebetween, and whose gate electrodes are connected to the Qb node. The stage includes a charging capacitor connected to the Qc node.