Micro-LED Pixel Circuit Stabilizing Current Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micro-LED display devices face challenges in achieving high contrast and stable current density, leading to issues like color cast and efficiency reduction due to drifting electrical characteristics, which affect display performance and gray scale accuracy.
Innovation Solution
A pixel circuit with a current control circuit and time control circuit, including resetting, data writing, threshold compensation, and switch sub-circuits, that adjusts voltage and controls electrical coupling to manage current density and operation time, ensuring the Micro-LED operates within a stable range for improved contrast and gray scale control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuits are used in Micro-LED displays, then the basic driving function is achieved, but the electrical characteristics drift leading to color cast and reduced display quality
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: current control circuit (including driving transistor and compensation capacitors), time control circuit (including switching transistor and control capacitors), and resetting circuit. This segmentation allows each module to be optimized independently for its specific function, improving overall stability while managing complexity through modular design.
Solution Approach 2:
The circuit performs preliminary threshold voltage compensation for the driving transistor before the display phase, and pre-charges the capacitor with the desired voltage level. This preliminary action ensures that when the display phase begins, the electrical characteristics are already stabilized, preventing color cast and improving reliability.
2Measurement precision
If simple current control is used, then the circuit complexity is low, but the current density becomes unstable affecting gray scale accuracy
Solution Approach 1:
The current control circuit implements feedback mechanisms where compensation capacitors monitor and store voltage levels corresponding to current density, and switching transistors adjust the current based on stored reference values. This feedback ensures stable current density and accurate gray scale control despite variations in transistor characteristics.
Solution Approach 2:
The circuit dynamically adjusts multiple parameters including voltage levels across different capacitors, switching timing durations, and transistor gate voltages to maintain precise current density control. By changing these parameters in coordination, the circuit achieves high measurement precision for gray scale accuracy.
3Reliability
If extended operation time is used to improve display quality, then the gray scale control is enhanced, but the electrical characteristics drift more due to prolonged operation
Solution Approach 1:
The pixel circuit operates in periodic cycles with distinct phases: reset phase where capacitors are recharged to reference voltages, display phase where the image is maintained, and compensation phase where threshold drift is corrected. This periodic action refreshes the electrical characteristics regularly, preventing accumulation of drift effects during extended operation.
Solution Approach 2:
Before each display phase, the circuit performs preliminary resetting and compensation actions to recharge capacitors and correct any drift that occurred during the previous display period. This preliminary action ensures that each new display cycle begins with stabilized electrical characteristics, maintaining quality over extended operation times.
Data Source
AI summary
The present disclosure provides a pixel circuit including: a current control circuit and a time control circuit, the time control circuit includes: a first resetting sub-circuit configured to write a reference voltage and a first initialization voltage to a first node and a second node, respectively; a first data writing sub-circuit configured to write a first data voltage to the first node; a first threshold compensation sub-circuit configured to perform threshold compensation on a transistor within a switch sub-circuit; a ramp writing sub-circuit configured to write a preset ramp signal to the first node; and the switch sub-circuit configured to control electrical coupling and decoupling between a third node and a fourth node. The present disclosure further provides a driving method of the pixel circuit and a display device.