Pixel Circuit Gate Voltage Stabilization
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Solution Overview
Problem
Light emitting display devices experience a decrease in image quality due to uneven threshold voltages of drive transistors, which leads to fluctuations in the voltage of the gate electrode, resulting in an inconsistent current flowing through the light emitting diodes.
Innovation Solution
A pixel circuit and driving method that includes a first transistor, a second transistor, a light emitting diode, a first capacitor, and a second capacitor, where the second capacitor is connected to a constant voltage source to stabilize the voltage of the gate electrode, preventing fluctuations caused by the kickback phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If threshold voltage compensation is implemented, then image quality is improved, but gate electrode voltage fluctuation occurs due to kickback phenomenon
Solution Approach 1:
A second capacitor is introduced as an intermediary element connected between the gate electrode and a constant voltage source. This capacitor acts as a buffer that mediates between the kickback phenomenon and the gate electrode, absorbing voltage fluctuations and preventing them from affecting the drive transistor's operation, thereby maintaining both image quality and voltage stability
Solution Approach 2:
The second capacitor is configured to preemptively counteract the kickback phenomenon by providing a opposing reactive effect. When kickback causes voltage fluctuation, the capacitor's charge-discharge characteristics generate an opposing voltage change that cancels out the fluctuation, preventing gate electrode voltage instability before it can degrade image quality
2Illumination intensity
If drive current is increased to improve brightness, then illumination intensity is improved, but voltage fluctuation in light emitting diodes increases
Solution Approach 1:
The second capacitor serves as a voltage stabilizing intermediary between the drive transistor and the light emitting diode. By filtering out voltage fluctuations in the drive signal, it ensures that the light emitting diode receives a stable voltage even at higher current levels, maintaining both brightness and voltage consistency
Solution Approach 2:
The capacitor provides beforehand cushioning by storing energy during voltage peaks and releasing it during voltage dips. This pre-prepared energy buffer cushions the light emitting diode against voltage fluctuations, allowing high brightness operation without compromising voltage stability
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 stabilizes the voltage of the gate electrode, ensuring a consistent drive current to the light emitting diodes, thereby improving the image quality of the light emitting display device by reducing voltage fluctuations.
Implementation Method 1
a second capacitor having a first electrode connected to the third node and a second electrode connected to a constant voltage source which supplies a DC voltage
Data Source
AI summary
A light emitting display device includes a pixel circuit including: a first transistor having a first electrode connected to a first node coupled to a first power supply line, a second electrode connected to a second node, and a gate electrode connected to a third node; a second transistor having a first electrode connected to the first node, a second electrode connected to the third node, and a gate electrode connected to a first gate line; a light emitting diode connected to the first transistor; a first capacitor having a first electrode connected to the third node and a second electrode connected to a conductive line and an anode electrode of the light emitting diode; and a second capacitor having a first electrode connected to the third node and a second electrode connected to a constant voltage source which supplies a DC voltage.