Pixel Circuit Current Flow Management for Display Defect Reduction
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Solution Overview
Problem
In organic light emitting display apparatuses, pixel circuits can generate short circuits during the initialization period, leading to display defects like horizontal stripe spots, which affect the display quality.
Innovation Solution
A pixel circuit comprising a capacitor connected between two nodes, with specific transistors and connections to manage current flow during the initialization period, thereby minimizing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used during the initialization period, then the circuit structure is simple, but short circuits occur between high-potential voltage line and reference voltage line causing display defects
Solution Approach 1:
The pixel circuit is divided into multiple transistor components (first transistor, second transistor, third transistor, fourth transistor, fifth transistor, sixth transistor) that independently control different current paths. This segmentation allows separate management of initialization current flow and display current flow, preventing short circuits while maintaining circuit functionality.
Solution Approach 2:
The second transistor acts as an intermediary component between the high-potential voltage supply line and the reference voltage supply line during initialization. By controlling this intermediate path, the circuit prevents direct short circuits while enabling proper voltage initialization of the emission element.
2Reliability
If the current flow path is changed during initialization period, then display defects are minimized, but the control complexity increases
Solution Approach 1:
The pixel circuit operates in distinct periodic phases: initialization period where the second transistor controls current flow between high-potential and reference voltage lines, and display period where normal operation occurs. This periodic control simplifies the operation by providing clear temporal separation of different functional requirements.
Solution Approach 2:
During the initialization period before normal display operation, the circuit performs preliminary voltage setting by controlling current flow through the second transistor. This preliminary action ensures proper voltage levels are established in advance, preventing display defects during subsequent normal operation.
Data Source
AI summary
A pixel circuit can include a capacitor connected between a first node and a second node, a first transistor connected between a data line and the first node, a driving transistor including a gate electrode connected to the second node, a first electrode connected to a first voltage supply line, and a second electrode connected to a third node, a second transistor connected between the second node and a fourth node, the fourth node being connected to a reference voltage supply line, a third transistor connected between the fourth node and a fifth node, and an emission element connected to the driving transistor and connected to the third transistor through the fifth node.