OLED Pixel Circuit PWM Emission for Mura Reduction
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Solution Overview
Problem
Organic light-emitting display apparatuses suffer from mura defects due to coupling between wires and driving signal issues, affecting image quality uniformity.
Innovation Solution
A pixel circuit design with a first and second switch element, driven by PWM, alternately repeating emission phases with different gate voltage pulses to stabilize pixel driving voltage and reduce gate-off voltage deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PWM driving is applied to switch elements in the emission phase, then mura defects are reduced and image quality uniformity is improved, but device complexity increases due to additional control phases and alternating emission sequences
Solution Approach 1:
The patent applies periodic action by implementing alternating first and second emission phases in the PWM driving sequence. During the emission phase, the pixel circuit alternates between applying gate-on voltage and gate-off voltage to the light-emitting element in periodic cycles, which stabilizes the pixel driving voltage and reduces mura defects by preventing voltage drift accumulation
Solution Approach 2:
The emission phase is segmented into distinct first emission phases and second emission phases that alternate in sequence. Each emission phase type applies different voltage patterns to the light-emitting element, allowing the system to break down the continuous emission into manageable periodic segments that maintain voltage stability
2Stability of the object's composition
If multiple switch elements are used with alternating emission phases, then pixel driving voltage stability is improved and gate-off voltage deviations are reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent implements dynamics by making the switch elements alternately conductive and non-conductive during different emission phases. The first and second switch elements dynamically change their states in response to alternating emission phase signals, enabling adaptive voltage control that maintains stability while managing manufacturing complexity through standardized switching mechanisms
3Reliability
If PWM driving with alternating emission phases is implemented, then mura defects are reduced, but the driving signal complexity and power consumption increase
Solution Approach 1:
The PWM driving employs periodic action by cycling through first and second emission phases with alternating gate-on and gate-off voltages. This periodic switching reduces mura defects by preventing voltage drift while managing power consumption through controlled duty cycles that balance emission quality with energy efficiency
Data Source
AI summary
Disclosed is a pixel circuit and a display apparatus having the same. The pixel circuit includes a first node connected to a VDD line to which a first constant voltage is applied; a third node connected to a fourth node connected to a light-emitting element; a fourth-first switch element arranged between the VDD line and the first node; and a fourth-second switch element arranged between the VDD line and the first node. An initialization phase, a sampling phase, an addressing phase, and an emission phase during a driving step are repeatedly performed. The fourth-first switch element and the fourth-second switch element are PWM-driven in the emission phase. With this configuration, a display apparatus with improved Mura may be provided.