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AMOLED Pixel Circuit Using LTPO Technology Supporting Variable Frame Rate from 1 to 120 Hz for Portable Displays
Ching-Lin Fan1,2, Chun-Yuan Chen1, Shih-Yang Liu2
1Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
Micromachines
|September 23, 2022
Summary
A new 6T1C pixel circuit using low-temperature polycrystalline oxide (LTPO) technology enhances portable active-matrix organic light-emitting diode (AMOLED) displays. This circuit offers stable performance across variable refresh rates (1-120 Hz), compensating for transistor variations.
Area of Science:
- Electrical Engineering
- Materials Science
- Display Technology
Background:
- Active-matrix organic light-emitting diode (AMOLED) displays require efficient pixel circuits.
- Low-temperature polycrystalline oxide (LTPO) technology enables advanced display features like variable refresh rates.
- Pixel circuit degeneration and threshold voltage variations impact display performance.
Purpose of the Study:
- To propose and analyze a novel 6T1C pixel circuit for portable AMOLED displays.
- To achieve stable operation across a wide range of refresh rates (1-120 Hz).
- To ensure immunity to OLED degeneration and compensate for driving transistor variations.
Main Methods:
- Design of a 6T1C pixel circuit utilizing LTPO technology.
- Implementation of shared lines for switch-controlling signals.
- Analysis of programming time and selection of optimal storage capacitor.
- Simulations to evaluate performance under varying conditions.
Main Results:
- The proposed circuit demonstrates effective compensation for threshold voltage variations (±0.33 V) in driving transistors.
- Average shift in OLED currents is 1.8% at high frame rates (120 Hz).
- Maximum OLED current variation is minimal (3.56 nA) at low frame rates (1 Hz).
Conclusions:
- The novel 6T1C pixel circuit offers a simple structure with low-voltage driving capabilities.
- It provides robust performance and immunity to OLED degeneration.
- This circuit is a promising candidate for next-generation portable AMOLED displays.
