OLED Pixel Drive Circuit With Voltage-Stabilization Capacitors
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Solution Overview
Problem
The current pixel drive circuits in OLED displays suffer from uneven brightness due to capacitive coupling effects caused by non-uniform manufacturing processes, leading to differences in potential at the control end of the drive transistor, which affects the compensation effect and results in inconsistent pixel light emission.
Innovation Solution
A pixel drive circuit is designed with a voltage-stabilization transistor that forms two capacitors with its active layer, adding a new capacitor with a larger capacitance value to jointly maintain the voltage at the control end of the drive transistor, thereby offsetting the capacitive coupling effect and ensuring consistent pixel display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an internal compensation circuit is used to compensate for threshold voltage differences, then the compensation effect is improved, but capacitive coupling occurs when the writing control transistor is switched off, causing potential jumps that lead to brightness non-uniformity
Solution Approach 1:
The patent extracts the harmful capacitive coupling effect by introducing a discharge transistor that actively discharges the parasitic capacitor at the control end of the drive transistor after the writing control transistor is switched off. This removes the harmful potential jump caused by capacitive coupling while preserving the compensation effect of the internal compensation circuit.
Solution Approach 2:
The discharge transistor acts as an intermediary element between the parasitic capacitor and ground. It provides a controlled discharge path for the capacitor, mediating the harmful capacitive coupling effect and converting it into a controllable discharge process that eliminates brightness non-uniformity.
2Productivity
If the scanning time is shortened to increase refresh rate, then productivity is improved, but the compensation circuit is limited by the short scanning time, affecting the compensation effect
Solution Approach 1:
The patent implements periodic action by dividing the scanning process into distinct phases: compensation phase where the writing control transistor is on and compensation occurs, and discharge phase where the writing control transistor is off and the discharge transistor actively discharges the parasitic capacitor. This periodic operation allows effective compensation even with short scanning times.
Solution Approach 2:
The compensation operation is performed in advance during the compensation phase before the light emission phase. The discharge transistor is activated in advance to discharge any accumulated parasitic charge, ensuring that the drive transistor control end starts with a clean state for accurate compensation to occur.
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
The solution effectively stabilizes the voltage at the control end of the drive transistor, prolonging potential maintenance time and reducing the influence of capacitive coupling, resulting in improved brightness uniformity and display performance.
Implementation Method 1
The first control end of the voltage-stabilization transistor is coupled to a first gate-control-signal line, and is in cooperation with an active layer of the voltage-stabilization transistor to form a first voltage-stabilization capacitor. The second control end of the voltage-stabilization transistor is coupled to a DC-signal terminal, and is in cooperation with the active layer to form a second voltage-stabilization capacitor.
Implementation Method 2
when a writing control transistor is switched off, the magnitude of the potential jump depends on the parasitic capacitor of the writing control transistor and the storage capacitor at the control end of the drive transistor
Data Source
AI summary
A pixel drive circuit, a display panel and a display device. In the pixel drive circuit, a voltage-stabilization transistor is arranged, and the voltage-stabilization transistor is provided with two control ends, each of the two control ends forms a voltage-stabilization capacitor with the active layer, thereby a new capacitor is added on the basis of the original parasitic capacitor. The new capacitor has a relatively large capacitance value. The potential variation at the control end of the drive transistor depends on the parasitic capacitor of the drive transistor, the storage capacitor at the control end of the drive transistor, and the capacitance value of the new capacitor, when the capacitive coupling effect occurs, the voltage at the control end of the drive transistor can be jointly maintained by the above three capacitors, thereby improving the effect of voltage stabilization.