Display Device Pixel Circuit Intermediate Node Potential Stabilization
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Solution Overview
Problem
Organic EL display devices experience display screen flickering during low-frequency drive due to variations in the potential of the intermediate node caused by parasitic capacitance between TFTs, leading to inconsistent luminance of the organic EL elements.
Innovation Solution
Incorporating a capacitor connected to the intermediate node and a control line, with the driver circuit changing the potential of the scanning line and control line in opposite directions to counteract the potential changes, thereby stabilizing the intermediate node's potential and preventing flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-frequency drive is performed to reduce power consumption, then power consumption is reduced, but display screen flickering occurs due to potential variations at the intermediate node
Solution Approach 1:
The patent applies preliminary anti-action by introducing a control line that actively counteracts the potential increase at the intermediate node caused by parasitic capacitance. The control line potential is changed in the opposite direction to the scanning line potential change, preemptively compensating for the harmful effect before it causes display flickering.
Solution Approach 2:
The patent implements feedback by using the control line to monitor and respond to potential changes at the intermediate node. The driver circuit adjusts the control line potential based on the scanning line potential changes, creating a feedback loop that stabilizes the intermediate node potential and prevents display instability.
2Reliability
If two TFTs connected in series are used as compensation transistor to prevent leakage current, then leakage current is prevented, but parasitic capacitance between the TFTs causes potential variation at the intermediate node
Solution Approach 1:
The patent uses the control line as an intermediary element that mediates the harmful effect of parasitic capacitance. The control line connects to the intermediate node and acts as a mediator to counteract potential changes, allowing the two-series-TFT configuration to maintain its leakage prevention function while eliminating the parasitic capacitance problem.
3Ease of operation
If the scanning line potential is changed to low level to turn on the TFTs, then the pixel circuit operates, but the potential at the intermediate node increases due to parasitic capacitance causing gate potential drift
Solution Approach 1:
The patent applies the anti-weight principle by introducing the control line potential change as a counteracting force against the parasitic capacitance effect. When the scanning line potential changes to low level, the control line potential changes in the opposite direction, creating a counterbalancing effect that stabilizes the intermediate node potential and prevents gate potential drift.
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
This solution effectively prevents display screen flickering by canceling out potential variations at the intermediate node, ensuring consistent luminance during low-frequency drive operations.
Implementation Method 1
Incorporating a capacitor connected to the intermediate node and a control line, with the driver circuit changing the potential of the scanning line and control line in opposite directions to counteract the potential changes
Data Source
AI summary
Provided is a display device with pixel circuits, each including first compensation transistor connected to a control terminal of a drive transistor at one conductive terminal, an intermediate node at another conductive terminal, and a scanning line at a control terminal, a second compensation transistor connected to the intermediate node at one conductive terminal, a conductive terminal of the drive transistor at another conductive terminal, and the scanning line at a control terminal, and a capacitor connected to the intermediate node at one electrode and a control line at another electrode. The driver circuit changes a potential of the scanning line from on to off level and also changes a potential of the control line from a second level to a first level, in an opposite direction to the change in the potential thereof.