Pixel Transistor Layout for Low-Frequency Luminance Stability
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Solution Overview
Problem
Display devices driven at low frequencies experience increased leakage currents, leading to decreased luminance and potential flicker due to the difference between initial and ending luminance of image frames, as the compensation voltage cannot be maintained effectively.
Innovation Solution
The display device incorporates specific transistor configurations, including sub-transistors with varying channel widths and lengths, and convex or concave channel portions, to manage leakage currents by adjusting the capacitances of parasitic capacitors, thereby controlling the direction and magnitude of leakage currents to maintain luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the display device is driven at a low frequency (e.g., 15 Hz), then power consumption is reduced, but leakage current increases causing luminance degradation and flicker
Solution Approach 1:
The patent applies local quality by creating asymmetric channel widths in different sub-transistors within the pixel circuit. Specifically, the first sub-transistor has a first channel width while the second sub-transistor has a second channel width that is different from the first. This localized differentiation allows each sub-transistor to contribute differently to current control, enabling the circuit to compensate for leakage current effects at low driving frequencies while maintaining overall luminance stability.
2Reliability
If the channel width of sub-transistors is increased to compensate for leakage current, then luminance stability improves, but device area increases
Solution Approach 1:
The patent employs parameter changes by varying the channel width parameter of different sub-transistors rather than uniformly increasing all transistor dimensions. The first sub-transistor has a first channel width and the second sub-transistor has a second channel width, creating an optimized parameter distribution that provides sufficient leakage compensation while constraining the overall pixel area within acceptable limits.
Data Source
AI summary
A display device includes pixels. Each of the pixels includes: a first transistor including a gate electrode connected to a first node, a first electrode connected to a second node, and a second electrode connected to a third node; a second transistor including a gate electrode connected to a first scan line, a first electrode connected to a data line, and a second electrode connected to the second node; a first sub-transistor including a gate electrode connected to the first scan line, a first electrode connected to the first node, and a second electrode connected to a fourth node; and a second sub-transistor including a gate electrode connected to the first scan line, a first electrode connected to the fourth node, and a second electrode connected to the third node. A channel width of the second sub-transistor is wider than a channel width of the first sub-transistor.