The Research And Design On The Data Converters In The Peripheral Driving System Of The AMOLED

1,The significance of the subjectThe organic electroluminesence display is considered as a plate display technique with magical displaying characteristic,which is a important issue of the organic electroluminesence display.The research for the driving system of OLED is just placed into developing position, whose the part of the driving system in theories research is one of the focus research in the international OLED research field,and which is a main problem in the developing of OLED industry in our country. The research and design on the peripheral driving system and Driving IC is the necessary and important link of the development of OLED display tehconolage.Nowadays, the driving IC for PMOLED is familiar, but for AMOLED especially for the intergration AMOLED is still infrequent.In 2001, we began to develop the design and simulation for the driving circuitry of AMOLED, which is integrated on the substrate on the panel. We have designed the pixel driving circuit, and the parameters simulation has been done.Finally, the relevant results was announced at"Chinese Journal of Luminescence". We present an AC pixel driving circuit and improve traditional constant current driving method, and do a lot of research on the design of the drving structure which is integrated on the substrate of the panel and using polycrystalline silicon TFT, and base on which we have developed AMOLED drive circuit board by ourselves, whose resolution ratio is 64×3×80. This driving circuit uses the integrated digital to analog conversion chip AD558 and level conversion chip IH5142. Considering to make better the practicability of AMOLED drive system and to fit in with OLED display specially characterist, we hope we can increase the intergration level of system base on this, reducing the area of drive circuit to adapt more application.The subject is to use the CMOS digital to analog conversion circuit and the level conversion circuit in design peripheral driving system of AMOLED display. By this way, we can incresase the integration level, decrease the drive circuit board area, adapt OLED display specially characterist, and do a little contribution on our own to develop AMOLED display and its drive chip.2,Research contents and workIn this text, it tells the design of AMOLED display peripheral driving system date convertion circuit with 64×3×80 resolution ratio. The main job is as follows:(1) The research and design of D/A convertorIn the design of the DAC, we used the basic DAC topology with the R-2R ladder network and operational amplifier. Base on this, according to the specially characterist and requirement of the peripheral driving circuit of AMOLED, to improve the D/A convertor behavior, the following aspects[0] is researched:First, in order to improve the D/A convertor precision, and increase its temperature stability and the antinoise ability, the design used the bandgap voltage reference. The output voltage of this voltage reference changes very little with workmanship and temperature change, so it can offer comparatively stability reference voltage.Second, in order to improve the synchronism characteristics[0] of the inputs, reduce the burr of the output from D/A convertor, This paper uses the input data latch on the input ports of the D/A convertor to put all the signal on the input ports add to the D/A convertor synchronistically by control the pulse.Third, the control circuit is designed in this paper. By choosing the whole D/A convertor work status, make the circuit to two work status: first, data input status; second, data keeping status.Fourth, in order to enlarge the D/A convertor output range, base on classical operational amplifier structure, use the operational amplifier with the rail to rail input stage and the folded-cascode output buffer stage.(2) The design of the level convertor circuitIn the design of the level convertor, this paper draws lessons from traditional level convertor circuit structure, and uses a new improvement of structure. By improving structure, it raises the open speed of the device, so it makes the efficiency of the level convertor; reduce the area of the chip and save the cost.(3) The design of the parameter measurementAccording to integral nonlinearity deviation and differential nonlinearity deviation definition, we use HSpice as a simulation tool, and propose a method of illustrating two kinds of deviation in measurement, and get the DAC nonlinearity deviation curve.3,ConclusionsIn the process of the circuit design, we use HSpice as the simulation tool, and the simulation for D/A convertor and DC-DC convertor has been done. We get the best parameters of all parts of the circuit through the method of conjoining theory calculation and simulation viryfication.(1) The bandgap voltage reference is designed in the paper, the structure is simple and as good temperature characteristics , when it works in 20-70℃, reference changes in the output voltage is less than 0.1V.(2) When the input of D/A changes, the output signal will deviate ideal output signal, and get peaks. An input data latch is designed to solve this problem, and it is able to eliminate the peaks effectively.(3) Through the simulation, we can get the following message: The output range of the D/A convertor is 0.08V to 9.95V, the setup time is less than 160ns. Power is 57mw. We get the DAC nonlinearity deviation curve. By mesuremnet, its intergral nonlinearity deviation belongs to (-1.5LSB,1.5LSB),and differential non-linear deviation definitionn belongs to (-1/2LSB,1/2LSB), We also give out corresponding measurement waveform.(4) The amplitude of input is 0~3v, and the output of the DC-DC convertor is -10v~5v. Other corresponding simulation results can be gotten in the right position in this paper.In this paper, he deep research for AMOLED has been done. And we designed the D/A convertor for AMOLED whose resolution is 64×3×80. The D/A convertor is used in the peripheral driving circuit. The simulation using HSpice hasve been done, and we get the reasonable parameter, the design get the right output signal and achieve the expected goal. The design in this paper can meet the requirement of the driving system of AMOLED, whose resolution is 64×3×80.