Micro-LED Pixel Circuit Reset Scheme for Uniform Driving Current
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Solution Overview
Problem
Micro-LED display devices face issues with luminance unevenness and flicker due to leakage currents, which are exacerbated by process distribution variations and overlapping scan signal periods, leading to non-uniform driving currents.
Innovation Solution
A pixel circuit with an internal compensation circuit that directly resets both electrodes of the storage capacitor before sampling the data voltage, using non-overlapping scan signals to stabilize the reference voltage and reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuits are used with overlapping scan signals, then device complexity is reduced, but luminance unevenness and flicker occur due to leakage currents
Solution Approach 1:
The internal compensation circuit performs preliminary reset action on the storage capacitor before the data sampling phase. By resetting the capacitor in advance during the reset period (when ELT is active), the circuit prevents accumulation of leakage currents that would otherwise cause luminance unevenness and flicker during subsequent display periods.
Solution Approach 2:
The compensation circuit uses feedback mechanisms where the reset transistor (RT) is controlled by the scan signal (ELT) to continuously monitor and correct voltage levels on the storage capacitor. This feedback loop ensures that any leakage-induced voltage drift is compensated in real-time, maintaining uniform luminance across pixels.
2Manufacturing precision
If internal compensation circuit is added to reset storage capacitor, then luminance unevenness and flicker are reduced, but device complexity increases
Solution Approach 1:
The compensation functionality is merged with the existing pixel circuit structure by integrating the reset transistor (RT) and compensation capacitor (Cst) into the standard pixel layout. The reset transistor shares control with the scan signal line (ELT), and the compensation capacitor is positioned adjacent to the storage capacitor, combining multiple functions within a compact unified structure.
Solution Approach 2:
The pixel circuit performs self-compensation for leakage currents through its internal compensation circuit. The reset transistor automatically activates during the reset period to correct voltage deviations on the storage capacitor without requiring external intervention or additional complex control logic, enabling the circuit to self-correct manufacturing variations and leakage effects.
3Productivity
If reset period and data period overlap, then productivity is improved, but reference voltage becomes non-uniform due to leakage current
Solution Approach 1:
The circuit employs periodic reset action synchronized with the scan signal (ELT) to systematically clear leakage currents at regular intervals. The reset transistor activates during designated reset periods (when ELT is high), creating a periodic compensation rhythm that maintains voltage uniformity on the storage capacitor throughout the display refresh cycle, preventing reference voltage drift despite overlapping operational periods.
Data Source
AI summary
The present disclosure provides a pixel circuit that may output uniform driving current regardless of the process distribution of the micro-LED element and a micro-LED display device including the same. The pixel circuit includes a micro-LED; a driving transistor that controls the driving current of the micro-LED; a storage capacitor that samples a data voltage that determines the magnitude of the driving current; and an internal compensation circuit that directly resets a first node and a second node respectively corresponding to both opposing electrodes of the storage capacitor before the storage capacitor samples the data voltage.