A Low Power and IR Drop Compensable AMOLED Pixel Circuit Based on Low-Temperature Poly-Si and Oxide (LTPO) TFTs Hybrid Technology

Abstract

In this paper, an AMOLED pixel circuit based on low-temperature poly-crystalline silicon and oxide (LTPO) thin-film transistors (TFTs) hybrid technology is proposed, which features only two transistors in a serial connection with OLED. The power supply can thus be reduced by 25~30% in the "Always-on-Display" (AOD) mode compared with the earlier LTPO pixel circuits which usually have three transistors in the current path and need a higher supply voltage. Furthermore, in addition to a strong suppressing ability to Vth variations/shift, the proposed pixel circuit has an excellent compensation ability for current-resistance voltage drops (i.e. IR drop), which is also superior to the earlier LTPO ones where the IR drop has to be compensated externally. Therefore, the proposed LTPO pixel circuit is able to provide AMOLED displays with lower power consumption and higher display performance than the earlier ones.

P‐2: Narrow Bezel Gate Driver Generating Positive Pulse for AMOLED Display Using LTPO Technology with Depletion Mode Oxide TFTs

“…Nowadays, low-temperature polycrystalline silicon and oxide (LTPO) technology has received increasing attention in portable AMOLED displays, such as smartphone and smartwatch [1][2][3]. LTPO technology can get merits of low-temperature polycrystalline silicon (LTPS) and oxide thin-film transistors (TFTs), which are high on-state current of LTPS TFTs and low off-state current of oxide TFTs [2][3]. Especially, low off-state leakage current of oxide TFTs in pixel circuits make it possible to drive AMOLED display panel at low frame rates less than 10 Hz without image distortion [2][3].…”

“…LTPO technology can get merits of low-temperature polycrystalline silicon (LTPS) and oxide thin-film transistors (TFTs), which are high on-state current of LTPS TFTs and low off-state current of oxide TFTs [2][3]. Especially, low off-state leakage current of oxide TFTs in pixel circuits make it possible to drive AMOLED display panel at low frame rates less than 10 Hz without image distortion [2][3]. Low frame rate reduces power consumption, which is important in portable devices.…”

“…1 shows the block diagram of AMOLED display panel using LTPO technology. As LTPO technology has been used in AMOLED pixel circuits, additional integrated scan driver is necessary to control n-type oxide switching TFTs in the pixel circuits [2][3]. In Fig.…”

P‐22: Scan Driver Circuit with Multiple Outputs employing Low‐temperature Polysilicon and Oxide TFTs for Mobile Displays

“…Therefore, low-temperature polysilicon and oxide (LTPO) TFT technology has been proposed to solve the high-power consumption and flicker problems at low refresh rates [4]. By using the a-IGZO TFT, which has the advantage of a very low off-current, as the switching TFT, the gate node voltage of the driving TFT can be stably maintained even at a low refresh rate [5]. Therefore, to drive such a LTPO TFT-based pixel circuit, a scan driver circuits capable of turning on/off the n-type oxide TFT and the p-type LTPS TFT are required [6].…”

P‐9: LTPO TFTs Based PWM Pixel Circuit for AM‐Micro‐LED Display with Falling‐time <10μs

“…In addition, LTPS TFT based emissive display prone to have large dynamic power consumptions for high rate refreshing even displaying static images to mitigate off-current related distortions. Compared with LTPS TFT, the low-temperature poly-crystalline silicon and oxide hybrid TFTs shows higher potential for high-performance PWM driving, as the high driving ability of LTPS TFT, and ultra-low off-current of oxide TFT are smartly combined [11][12][13][14]. By adjusting the threshold voltage of the dual-gate oxide TFT to match the threshold voltage of the LTPS TFT [15][16][17], a high-gain LTPO TFTs inverter can be obtained, which lays the foundation for obtaining a PWM waveforms with a steep falling edge.…”