This paper proposes a new pixel circuit using lowerature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of VTH variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased TCOMP of 33.3 μs results in higher contrast ratio and lower required data voltages than those at TCOMP values of 4.3 and 2.2 μs. Red, green, and blue images displayed by the fabricated panel with a TCOMP of 33.3 μs with a 255 gray level are all much more uniform than with TCOMPS of 4.3 and 2.2 μs. White images with a TCOMP of 33.3 μs for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with TCOMP values of 4.3 and 2.2 μs are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering