V_t Compensated voltage‐data a‐Si TFT AMOLED pixel circuits

Abstract

Abstract— Active‐matrix organic light‐emitting‐diode (AMOLED) displays are now entering the marketplace. The use of a thin‐film‐transistor (TFT) active matrix allows OLED displays to be larger in size, higher in resolutions and lower in power dissipation than is possible using a conventional passive matrix. A number of TFT active‐matrix pixel circuits have been developed for luminance control, while correcting for initial and electrically stressed TFT parameter variations. Previous circuits and driving methods are reviewed. A new driving method is presented in which the threshold‐voltage (Vt) compensation performance, along with various circuit improvements for amorphous‐silicon (a‐Si) TFT pixel circuits using voltage data, are discussed. This new driving method along with various circuit improvements is demonstrated in a state‐of‐the‐art 20‐in. a‐Si TFT AMOLED HDTV.

Reducing image sticking in AMOLED displays with time‐ratio gray scale by analog calibration

“…Various driving methods and pixel circuits have been developed to overcome the sensitivity of the OLED current to the I-V characteristic of the driving TFT. [2][3][4][5][6][7][8][9][10][11][12][13] Among them, a time-ratio gray-scale method with a simple pixel circuit comprised of two transistors and a storage capacitor, is known to give excellent image uniformity. 14,15 In this method, a gray level is produced by turning the OLED in each pixel on or off during each of multiple subframe periods.…”

52.2: A Low‐Cost Stable Amorphous Silicon AMOLED Display with Full VT‐ and VOLED Shift Compensation

“…Interest in amorphous silicon (a-Si) as the backplane of choice for active matrix organic light emitting (AMOLED) displays has been accentuated due to its low-cost fabrication and availability of industrial infrastructure [1]. However, the instability of the thin film transistors (TFT) fabricated in this technology mandates driving schemes that provide compensation [1][2][3][4][5]. The current programming technique can solve the instability issue with intrinsic immunity to the temperature variation and spatial mismatches.…”

“…On the other hand, voltage programming provides fast programming, but the compensation scheme is complex with relatively high cost of assembly, integration, and external drivers [3][4][5]. Also, voltage drive schemes are not immune to the spatial mismatches and temperature variation.…”

V th compensated AMOLED pixel employing dual-gate TFT driver

“…If not compensated for, this shift will yield to a substantial OLED current degradation and the pixel brightness decay. So far, several V th compensation methods in 2TC1 pixels [3-5] have been described, but they require either non-conventional complex voltage driving schemes [3,5] or an excessively long programming period [4]. In this Letter, a novel V th shift compensated 2T1C pixel is proposed, which maintains a conventional voltage driving scheme for compatibility with well developed LCD display driver ICs.…”