采用像素复用技术的IGZO-TFT AMOLED像素驱动电路设计

发布时间：2018-03-01 23:00

本文关键词： 有机发光器件像素驱动电路薄膜晶体管像素复用开口率　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：有机发光器件(Organic Light-emitting Device,OLED)是一种集众多优势于一身的新型显示器件,器件具有厚度薄、质量轻、视角宽、工作温度范围广等优点。OLED显示屏主要有无源驱动和有源驱动两种方式。无源驱动方式中采用较大的脉冲电压和脉冲电流驱动,导致OLED器件工作效率较低,采用该驱动方式的显示屏多用于小尺寸、低信息含量的显示领域;有源驱动中每个像素在一帧时间内持续发光,能够满足大面积高信息含量的显示需求。最初的有源驱动像素电路采用两个薄膜晶体管(Thin Film Transistor,TFT)和一个存储电容组成的传统2T-1C电路,其结构简单并且便于控制。但是,TFT长时间工作后阈值电压会发生偏移,导致流过OLED的电流发生变化。因此,具有阈值电压补偿功能的像素电路随之产生。但是,该类驱动电路与2T-1C电路相比结构更加复杂,使AMOLED显示屏的开口率降低,影响显示效果。尤其在实现高分辨率的显示时,开口率下降的影响更为严重。因此,本文采取了像素电路复用的方法,设计了具有阈值电压补偿功能的像素复用电路,提高了显示屏的开口率。首先,由于HSPICE仿真软件的元件库中不包含OLED仿真模型,选取了一种适用于像素驱动电路的OLED等效仿真模型。使用origin软件对实验室测得的OLED的I-V特性曲线进行拟合,获得了OLED等效模型中各元件的参数。经HSPICE软件仿真验证,该等效模型的误差较小,模型参数设定合理,适用于电路仿真。本文选取了一种经典的电流写入和电压写入型阈值电压补偿电路,驱动管采用新型的铟镓锌氧化物(Indium Gallium Zinc Oxide,IGZO)薄膜晶体管,对像素驱动电路进行了仿真分析。结果表明,当阈值电压发生漂移时,流过OLED的电流偏差较小,验证了电路的阈值电压补偿效果较好。但是,版图设计表明元件数目的增加使得像素开口率较低,影响显示效果和显示器件的使用寿命。因此,本文设计了一种具有阈值电压补偿功能的电流写入型像素复用电路,采取多个像素共用一套驱动电路的方式,实现了亮度范围为0.988~201.224cd/m~2的16级灰度显示。所设计的显示屏像素阵列为320×240,单个像素面积为159×53μm~2,显示屏的分辨率为160ppi。版图设计表明复用后的电流写入型像素电路的开口率由原来的20%增加到69%,证明了像素开口率有很大提高。由于电压写入与电流写入型像素驱动电路各有优势,因此本文又设计了一种采用像素复用技术的电压写入型IGZO-TFT像素驱动电路的复用电路。完成了电路的仿真分析,版图设计表明显示屏的开口率也有很大的提高。
[Abstract]:Organic Light-emitting device (Ole) is a new display device with many advantages. It has thin thickness, light weight and wide angle of view. There are two main ways of passive driving and active driving in OLED display screen, such as wide range of operating temperature, in which large pulse voltage and pulse current are used in the passive drive mode, which results in low efficiency of OLED devices. The display screen with this driving mode is mostly used in the small size, low information content display field, and each pixel in the active drive continuously emits light in a frame time. The original active driving pixel circuit consists of two thin film transistors, thin Film transistor-TFT) and a storage capacitor, a traditional 2T-1C circuit. Its structure is simple and easy to control. However, the threshold voltage will shift after long hours of operation, resulting in the change of the current flowing through the OLED. Therefore, the pixel circuit with threshold voltage compensation function will be generated. Compared with 2T-1C circuit, the structure of this kind of drive circuit is more complex, which reduces the opening rate of AMOLED display screen and affects the display effect. Especially in the realization of high resolution display, the decrease of opening rate is more serious. In this paper, a pixel multiplexing circuit with threshold voltage compensation is designed, which improves the opening rate of display screen. Firstly, the component library of HSPICE simulation software does not include OLED simulation model. A OLED equivalent simulation model suitable for pixel drive circuit is selected. The I-V characteristic curve of OLED measured in the laboratory is fitted with origin software, and the parameters of each component in the OLED equivalent model are obtained. The error of the equivalent model is small and the parameters of the model are set reasonably, which is suitable for circuit simulation. In this paper, a classical current write and voltage write threshold voltage compensation circuit is selected. A novel indium Gallium Zinc oxide thin film transistor is used to simulate the pixel drive circuit. The results show that when the threshold voltage drifts, the deviation of current passing through OLED is small. It is verified that the threshold voltage compensation effect of the circuit is better. However, the layout design shows that the increase in the number of elements makes the pixel opening rate lower, which affects the display effect and the service life of the display device. In this paper, a current-write pixel multiplexing circuit with threshold voltage compensation function is designed, in which several pixels share a set of driving circuits. The 16 grayscale display with luminance range of 0.988 / 201.224cd / mm2 is realized. The pixel array of the display screen is 320 脳 240, the area of a single pixel is 159 脳 53 渭 mm2, and the resolution of the display screen is 160 ppi.The layout design shows the opening rate of the multiplexed current written pixel circuit. The increase from the original 20% to 69 proves that the pixel opening rate is greatly improved. Because of the advantages of the voltage write and current write pixel drive circuits, Therefore, this paper designs a voltage write IGZO-TFT pixel driving circuit using pixel multiplexing technology, and completes the simulation analysis of the circuit. The layout design shows that the opening rate of the display screen is also greatly improved.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN873

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