Dynamic Voltage Scaling Driving Method For Low Power AMOLED Display

Active-matrix organic light emitting diode?AMOLED?has been widely used in large-size TV,mobile phone display and virtual reality display.In the future,AMOLED display will achieve major technological breakthroughs and industrial applications in the fields of low power consumption,flexibility and intelligence.With the improvement in OLED luminous efficiency,the pixel area is reduced,and the required maximum pixel current has been reduced to a level of 10^-8A.At such low currents,most of the low grayscale will cause the drive transistor to operate in the sub-threshold region,and the conventional pixel internal compensation methods will not work properly.On the other hand,for mobile devices powered by batteries,the power consumption of the display nearly half of the energy consumption of the mobile phone.Low power consumption is very important to extend the working hours of the mobile phone.Traditionally designed displays use a constant maximum supply voltage to satisfy the maximum luminance of display requirements.The entire display always provides maximum supply voltage,resulting in power consumption waste.Therefore,the AMOLED display is required to reduce the display power consumption on the basis of ensuring image quality.However,for the existing display power management methods,the image actually displayed after voltage scaling differs from the original image.The threshold voltage variation of the drive transistor and the drive data voltage disturbance have a great adverse effect on display uniformity,and the existing dynamic voltage scaling method cannot improve the quality of the display image.There is a need to find a new dynamic voltage scaling method to satisfy the demands.This paper proposes a new dynamic voltage scaling driving method based on the two goals of improving display uniformity and reducing display power consumption.According to the drain bias characteristic of the LTPS TFT,the operating region of the transistor under low current is shifted from the subthreshold region to the region above the threshold voltage by reducing the voltage between the source and the drain of the transistor.By adjusting the pixel OLED cathode voltage,the rate of change of the drive transistor drain current with threshold voltage variation and drive data voltage disturbance is reduced.Apply dynamic voltage scaling method to the display,and independently adjustable supply voltage is set to several certain levels for display blocks.Determine the block supply voltage according to the maximum grayscale value of the block.According to the block supply voltage and the grayscale value of all the pixels of the block,look-up the mapping table to obtain the drive data voltage required for all pixels.The dynamic voltage scaling driving method is implemented by FPGA,and realized the physical layout of the block supply voltage line,which prove the hardware feasibility of this method.Assuming the values of threshold voltage variation and the driving data voltage disturbance,the Matlab simulation is used to compare the real display image affected by the pixels voltage with the original image to be displayed,the performance of this method to improve display quality was verified.Meantime,the method effectively reduces the static power consumption of the display under the premise of ensuring the quality of the displayed images.