彩色有源OLED显示屏上像素仿真及外围驱动电路设计

有机发光二极管(Organic Light Emitting Diode,OLED)由于高对比度、高亮度、超薄、低功耗、宽视野、快响应速度等特性,日益引起人们的兴趣。通过对部分周边驱动电路集成于衬底的2英寸(5.08cm,64×3×80)有源矩阵显示屏(Active Matrix OLED,AMOLED)上像素驱动电路的仿真,确定彩色OLED显示屏维持白平衡时R、G、B三种OLED所需的驱动电压、电流等工作参数。OLED的发光亮度和电压并不是线性关系,为了维持显示屏的色彩均衡性,对图像数据编码进行校正,保证了灰阶电压与发光亮度呈线性变化。从BMP格式的文件中提取出图像数据部分,进行数据变换,生成符合INTELHEX文件格式并且满足D/A输出要求的数据文件,刻录到E²PROM中,完成外围驱动电路所需要的图像数据准备。AMOLED显示屏采用逐行扫描的显示方式,因此外围驱动电路的目的是要在行、列扫描有效的同时,为每个像素送入相应的灰阶数据。现在,OLED专用驱动芯片比较少见,而液晶驱动芯片具有集成度高,电压输出范围大等优点,尤其是其内部集成了数据移位寄存器、数据锁存器、D/A转换器等电路,所以设计了基于FPGA和TFT-LCD液晶驱动芯片的外围驱动电路,实现了AMOLED显示屏的彩色图像显示。

Pixel Simulation and Peripheral Driving Circuit Design on the Color AMOLED

Organic light-emitting diode has been emphasized and regarded as one of the best technologies of flat panel displays for its many advantages,such as low-voltage driving,low power dissipation,wide visual angle,thin and light-weight and so on.We want to introduce the full process of designing the AMOLED,which includes three sides content.Firstly,simulations using poly-TFT SPICE models are performed on the pixel driving circuit of a 2 inch(5.08cm,64×3×80) AMOLED panel,and on its substrate some peripheral driving circuits are integrated.The results are evaluated and analyzed,and confirmed the driving voltage and current of RGB OLED pixels while the color AMOLED is in white balance.At the same time,through the simulation we can find that the circuit can keep the current very well in the voltage range we confirmed,this means that if we provide the proper voltage the OLED panel can display high quality images.Secondly,we mention a means to make the image data for OLED panel displaying.This means encodes the BMP data to fit our design,and then puts the encoding file into E²PROM,to prepare the picture data for peripheral driving circuitry.At last the peripheral driving circuitry is designed based on FPGA and TFT-LCD chip.Through the simulation we can confirm that the peripheral driving circuitry can complete the driving OLED tasks.Now the OLED driving ASIC is few and expensive,however the TFT-LCD driving circuit is very mature and cheap.So if we can utilize the TFT-LCD driving circuit to design the OLED driving circuit,that is a very meaning thing.In the TFT-LCD driving chips, it integrates the shift register,the buffer,the latch,and inner D/A,at the same time it can output 256 gray level driving voltage.So using it not only reduces the complexity and periods of developing peripheral driving circuitry but also enhances the stabilization of peripheral driving circuitry and more existed TFT-LCD driving chips can exert more use in OLED driving circuit design.From the result we can prove that the model of using TFT-LCD driving chips to drive OLED is possible and can get better effect.