Pixel Circuit Gate-Drain Feedback for Low-Gradation Stain Reduction
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Solution Overview
Problem
Display devices experience stains at low gradations due to large changes in current with grayscale changes, leading to rapid gradation changes in emitted light.
Innovation Solution
A pixel circuit with a gate-drain capacitor that adjusts voltage changes at different gradations, using transistors and capacitors to stabilize the gate node voltage, particularly at low gradations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used, then the display device can operate with standard circuit configuration, but stains occur at low gradations due to large current changes with grayscale changes
Solution Approach 1:
The gate-drain capacitor is pre-configured in the pixel circuit to counteract the harmful effect of large current changes at low gradations before they occur. By establishing a feedback mechanism through the capacitor connected between gate and drain, the circuit proactively compensates for voltage fluctuations, preventing stain formation rather than correcting it after occurrence
Solution Approach 2:
The gate-drain capacitor creates a feedback loop where the voltage at the drain is fed back to the gate through capacitive coupling. This feedback mechanism automatically adjusts the gate voltage in response to current changes, stabilizing the driving current and eliminating stains at low gradations without requiring external intervention
2Reliability
If the gate node voltage is stabilized using a gate-drain capacitor, then stains at low gradations are reduced, but the circuit complexity increases
Solution Approach 1:
The gate-drain capacitor serves multiple functions simultaneously: it provides feedback for voltage stabilization, compensates for threshold voltage variations, and regulates current at different gradations. By making this single component multi-functional, the patent achieves gradation stability without proportionally increasing circuit complexity
Solution Approach 2:
The feedback mechanism is merged into the existing transistor structure by utilizing the inherent gate-drain capacitance and adding a capacitor in parallel, rather than creating a separate feedback circuit. This integration approach minimizes additional components while achieving the desired stabilization effect
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
Stabilizes the voltage of the gate node, reducing rapid gradation changes in emitted light, thereby minimizing stains at low gradations.
Implementation Method 1
a gate-drain capacitor connected in parallel with the compensation transistor, where the gate-drain capacitor includes a first electrode connected to the gate node and a second electrode connected to the second node
Data Source
AI summary
A pixel circuit includes a driving transistor which generates a driving current and including a first electrode connected to a first node, a gate electrode connected to a gate node, and a second electrode connected to a second node, a writing transistor connected to the driving transistor through the first node and including a first electrode which receives a data voltage, a gate electrode which receives a write gate signal, and a second electrode connected to the first node, a compensation transistor including a gate electrode, a first electrode connected to the gate node, and a second electrode connected to the second node, a gate-drain capacitor connected in parallel with the compensation transistor and including a first electrode connected to the gate node and a second electrode connected to the second node, and a light emitting element that emits light based on the driving current.