Pixel Circuit Reference Voltage Initialization Short-Circuit Prevention
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Solution Overview
Problem
The existing pixel circuit structures for light-emitting elements in display devices are prone to reference voltage-related short-circuits during the initialization period, leading to display defects such as horizontal stripe stains, which affect the reliability and quality of the image displayed.
Innovation Solution
The proposed pixel circuit structure includes a capacitor connected between two nodes, with transistors that supply reference voltage to these nodes based on specific control signals, ensuring that both nodes are initialized with the same reference voltage during the initialization period, thereby preventing short-circuits and improving image reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sampling pixel structure is used to compensate for threshold voltage, then threshold voltage compensation is achieved, but reference voltage-related short-circuits occur during initialization causing display defects
Solution Approach 1:
The pixel circuit is divided into multiple transistor components (first transistor, second transistor, third transistor, fourth transistor) with distinct functions. The first transistor controls reference voltage application to the first node, the second transistor controls reference voltage application to the second node, the third transistor controls data voltage application, and the fourth transistor controls light emission. This segmentation allows independent control of each function, preventing the short-circuit issue while maintaining threshold voltage compensation capability.
Solution Approach 2:
The first transistor and second transistor are activated during the initialization period to pre-charge the first node and second node with reference voltage before the data voltage is applied. This preliminary action ensures that both nodes start at the same reference voltage level, preventing short-circuits during subsequent operations while enabling proper threshold voltage sampling and compensation.
2Manufacturing precision
If threshold voltage compensation is implemented, then brightness uniformity is improved, but initialization short-circuits cause horizontal stripe stains
Solution Approach 1:
The circuit is segmented into specialized transistor components where the first transistor specifically manages reference voltage application to the capacitor's first node, and the second transistor manages reference voltage application to the second node. This segmentation isolates the reference voltage application function from other circuit operations, eliminating the source of horizontal stripe stains while preserving brightness uniformity through proper threshold voltage compensation.
Solution Approach 2:
The first transistor and second transistor act as intermediary elements that control the application of reference voltage to the capacitor nodes. These intermediary transistors ensure that reference voltage is applied in a controlled manner during initialization, preventing direct short-circuits between high-potential driving voltage and reference voltage, thereby eliminating horizontal stripe stains while maintaining proper threshold voltage compensation for brightness uniformity.
Data Source
AI summary
A display device includes a light-emitting element; a capacitor connected to and disposed between a first node and a second node; a first transistor including a first electrode connected to a reference voltage supply line and a second electrode connected to the first node, and supplying a reference voltage to the first node in response to a light-emission control signal of an n-th pixel row; a second transistor including a first electrode connected to the reference voltage supply line and a second electrode connected to the second node, and supplying the reference voltage to the second node in response to a first scan signal of an (n−1)-th pixel row; and a driving transistor including a gate electrode connected to the second node, a first electrode receiving a high-potential driving voltage, and a second electrode connected to a third node. Thus, for example, occurrence of a reference voltage related short-circuit in the light-emitting element of the display device is suppressed to prevent occurrence of defective image display in each pixel and to improve reliability thereof.