Pixel Circuit Compensation for Low-Grayscale Luminance Uniformity
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Solution Overview
Problem
In organic light emitting display devices, deviations in panel fabrication processes can lead to differences in capacitance of parasitic capacitors, causing variations in charging times and luminance uniformity, particularly in low grayscale regions.
Innovation Solution
A pixel circuit design that includes a compensation circuit to initialize the anode electrode to a reference voltage and apply a compensation voltage before the emission period, compensating for luminance deviations in low grayscale regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional pixel circuit is used without compensation voltage, then the device complexity is low, but luminance uniformity deteriorates in low grayscale regions due to parasitic capacitor capacitance differences
Solution Approach 1:
The patent applies preliminary action by initializing the anode electrode to a reference voltage and applying compensation voltage before the emission period. This pre-charging of the anode electrode compensates for the luminance deviation that would occur during low grayscale operation, ensuring uniform luminance across different in-plane positions without requiring complex real-time adjustment mechanisms during emission.
Solution Approach 2:
The patent changes the voltage parameter of the anode electrode by applying a predetermined compensation voltage (higher than the reference voltage) before emission. This voltage parameter change compensates for the charging time differences caused by parasitic capacitor variations, thereby improving luminance uniformity in low grayscale regions while maintaining a relatively simple circuit structure.
2Manufacturing precision
If the anode electrode is initialized to reference voltage without compensation, then the circuit operation is simple, but charging time varies due to parasitic capacitor differences, affecting luminance consistency
Solution Approach 1:
The patent performs preliminary charging of the anode electrode to a compensation voltage higher than the reference voltage before the emission period. This preliminary action ensures that all light emitting elements start from a consistent elevated voltage level, reducing the variation in charging time caused by differences in parasitic capacitor capacitance and improving luminance consistency.
3Manufacturing precision
If compensation voltage is applied to all pixels, then luminance uniformity in low grayscale improves, but power consumption increases
Solution Approach 1:
The patent applies local quality by targeting the compensation voltage application specifically to pixels operating in low grayscale regions where luminance uniformity is most affected. The mode selection signal enables selective activation of the compensation mechanism, applying compensation voltage only when needed for low grayscale operation, thereby improving luminance uniformity while minimizing unnecessary power consumption in other operating conditions.
Data Source
AI summary
A pixel circuit and a display device including the same are discussed. The pixel circuit can include a first light emitting element, a second light emitting element, a driving element configured to drive the first and second light emitting elements, a compensation circuit connected to the driving element, a first switch element connected between the driving element and the first light emitting element and driven by a first mode selection signal, a second switch element connected between the driving element and the second light emitting element and driven by a second mode selection signal, and a third switch element configured to apply a predetermined compensation voltage to at least one of anode electrodes of the first light emitting element and the second light emitting element.