Design And Research Of OLED-on-silicon Microdisplay Driver Chip Based On Multi-Frame Digital-Analog-Hybrid Scan Strategy

With the development of computer technology and the continuous maturity of new display materials,microdisplay technology has also made great progress,which has led to the explosive growth of the market for near-eye display terminal equipment such as virtual reality and augmented reality.Organic Light-Emitting Diode(OLED)stands out among many microdisplay luminescent materials due to its low power consumption,wide operating temperature range,high contrast ratio,fast response,large viewing angle,and no backlight,has great competitiveness and a wide application market.This dissertation researches the OLED-on-silicon microdisplay in three aspects that scanning mode,driving chip architecture and pixel driving circuit.There are three main problems: Existing scanning methods include analog amplitude modulation and digital pulse width modulation,where analog amplitude modulation relies on the performance of a digital to analog converter(DAC).Digital pulse width modulation requires a huge amount of data transmission,and at the same time,the efficiency of data transmission is reduced due to the presence of the blanking subfield.And there is a problem of gray scale nonlinearity.Since the DAC needs to drive a large number of pixel units,and its driving ability is limited,the data written to the pixel unit is inaccurate.Since the switching control MOSFET of the pixel unit has leakage current,and the OLED luminous current is very small(nA level),so a very small leakage current causes a deviation of the pixel data.In view of the above problems,the research content of this paper mainly includes the following three aspects:1.This dissertation proposes a new type of scanning mapping strategy: multi-frame digital-analog-hybrid scan strategy.Firstly,the data bit width of the DAC is reduced by the digital-to-analog modulation method.This method can reduce the dependence of the microdisplay driver chip on the high conversion accuracy of the DAC.Then,by optimizing the mapping mode of the digital pulse width modulation part,the blanking subfield is merged,the data transmission efficiency is improved,the data transmission frequency is reduced.At the same time the gray scale data is corrected to improve the gray scale linearity.2.A scanning controller and a OLED-on-silicon microdisplay driver chip are designed to adapt to the multi-frame digital-analog-hybrid scan strategy.This dissertation improves the column driver circuit structure of the driver chip,and increases the charging time of the DAC to make up for the lack of driving capability.3.This dissertation proposes a pixel drive circuit structure of a three-switch control MOSFET,which increases the accuracy of pixel data by reducing the leakage current of switch control MOSFET.After testing,the driver chip function is correct,and the OLED-on-silicon microdisplay with resolution of 1280?1024 can be successfully illuminated.Compared with the conventional pixel driving circuit,the leakage current can be reduced by 71.13%,and the pixel data precision is improved.The transmission efficiency of multi-frame digital-analog-hybrid scan strategy is up to 100% under the condition of 256 gray scale,1280?1024 resolution and 120 Hz refresh frequency.The data transmission frequency is only 19.66 MHz,and the corrected linearity can reach 99.79%.