Pixel Circuit Switching Transistor Initialization Path
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Solution Overview
Problem
In some pixel circuits, the disconnection of high potential voltage and reference voltage lines during the initialization period can lead to display defects such as horizontal stripes, affecting the display quality of organic light emitting diode (OLED) display apparatus.
Innovation Solution
A pixel circuit design is implemented with a switching transistor between the gate node of the driving transistor and the reference voltage input node, altering the current flow path during the initialization period to prevent driving failure and improve display quality, while also dispersing the load of gate signals for enhanced operation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used without additional switching transistors, then the device complexity is low, but display defects such as horizontal stripes occur due to disconnection of voltage lines during initialization
Solution Approach 1:
A second switching transistor is introduced as an intermediary component between the reference voltage line and the gate node of the driving transistor. This mediator ensures continuous voltage supply during initialization by providing an alternative current path when the first switching transistor disconnects the high potential voltage line, thereby preventing display defects without significantly complicating the overall pixel circuit structure
Solution Approach 2:
The second switching transistor is activated in advance during the initialization period to pre-charge or maintain the gate node voltage before the main switching operation begins. This preliminary action ensures that the gate node is properly initialized and prevents display defects such as horizontal stripes from occurring during subsequent operation
2Reliability
If the current flow path is changed during initialization, then driving failures are reduced, but the control signal complexity increases
Solution Approach 1:
The second scan signal is designed to serve multiple functions: it controls the second switching transistor to establish the alternative current path during initialization, and can be coordinated with the first scan signal to manage the overall switching sequence. This multi-functional approach allows a single additional control line to achieve both initialization and operational control, minimizing the increase in control signal complexity while ensuring reliable pixel circuit operation
Data Source
AI summary
According to an aspect of the present disclosure, a pixel circuit includes a first capacitor connected between a first node and a second node, a first transistor connected to the first node and supplied with a first scan signal, 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 the third node and supplied with a second scan signal, a third transistor connected between the third node and a fourth node, a fourth transistor which is connected to the fourth node and is supplied with a second scan signal of a previous pixel row and a light emitting diode connected to the fourth transistor and the third transistor at the fourth node.