An AMOLED Pixel Circuit With a Compensating Scheme for Variations in Subthreshold Slope and Threshold Voltage of Driving TFTs

Park

IEEE J. Electron Devices Soc.

et al. 2023

In this paper, we propose a novel amorphous In-Ga-Zn-oxide (a-IGZO) thin film transistor (TFT) pixel circuit for pulse width modulation (PWM) driving active matrix micro light-emitting diode (LED) displays. The proposed pixel circuit compensates for wavelength shifts according to gray level and threshold voltage (VTH) variation of TFTs with only two capacitors. This compact operation can be achieved by simultaneous compensation for VTH along with data input in the constant current generation (CCG) circuit and the PWM circuit, which consist the pixel. Since the VTH variation in TFTs is compensated, the proposed pixel circuit can supply a uniform and stable current to the LED throughout all gray levels. The compensation accuracy was verified by HSPICE with an oxide TFT model based on the measurement data.In addition, we analyzed the optimization method to improve the PWM driving by controlling the electrical properties of TFT, and verified this approach by simulation.

Section: Simulation and Discussionmentioning

confidence: 78%

A Compact Amorphous In-Ga-Zn-Oxide Thin Film Transistor Pixel Circuit With Two Capacitors for Active Matrix Micro Light-Emitting Diode Displays

Park

IEEE J. Electron Devices Soc.

et al. 2023

IEEE J. Electron Devices Soc.

“…The power consumption of the AMOLED panel can be categorized into the following parts: dynamic power consumption of data lines and scan lines, and the static power consumption during the light-emitting phase [23], [24]. The dynamic power consumption 𝑃 𝑑𝑦𝑛𝑎𝑚𝑖𝑐, 𝑝𝑎𝑛𝑒𝑙 for charging and discharging of loading capacitance of data lines can be expressed as…”

Section: A Power Consumptionmentioning

confidence: 99%

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

Qiu

Wang

et al. 2022

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.

Symp Digest of Tech Papers

“…To solve the aforementioned problems, the diode connection and the source follower schemes have been used to compensate for variations in VTH of driving TFT [9][10][11][12]. In the case of a-IGZO TFT-based pixel circuits, source follower method is adopted more commonly, but it requires additional signal lines than diode connection method, which takes extra layout area of the pixel circuit.…”

Section: Introductionmentioning

confidence: 99%

“…To compensate for SS variations, the currentprogramming methods, the external compensation methods, and extending compensation time method for diode connection scheme based on p-type low temperature polycrystalline silicon (LTPS) TFTs have been researched. Since humans further detect deviations at a low current level, it is necessary to compensate for deviations in the subthreshold region [12][13][14]. However, the pixel circuit based on a-IGZO TFT that compensates for SS variation has not been studied much so far.…”

Section: Introductionmentioning

confidence: 99%

P‐25: An AMOLED Pixel Circuit Compensating for Variation of Sub‐threshold Swing and Threshold Voltage Based on Double Gate a‐IGZO TFTs ^†

Kim,

Lee

2023

In this paper, an AMOLED pixel circuit based on amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) thin‐film transistors (TFTs) compensating for variations in sub‐threshold swing (SS) and threshold voltage (VTH) of driving TFT is proposed. The proposed pixel circuit is composed of five TFTs and one capacitor. From the simulation results, when the SS and VTH shifts of the driving up to ±10% and ±1 V, the maximum OLED current error can be suppressed to 3.6% and 7.2%, respectively.