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AMOLED 패널 측정 시스템을 위한 소면적 고해상도 범용 데이터 드라이버 IC

Title
AMOLED 패널 측정 시스템을 위한 소면적 고해상도 범용 데이터 드라이버 IC
Other Titles
A Small-Area and High-Resolution Universal Data Driver IC for AMOLED Panel Test Systems
Author
설현천
Alternative Author(s)
Seol, Hyeon-Cheon
Advisor(s)
권오경
Issue Date
2017-08
Publisher
한양대학교
Degree
Doctor
Abstract
Active-matrix organic light emitting diode (AMOLED) displays have been highlighted as alternatives to liquid crystal displays (LCDs) due to their outstanding performance including high contrast ratio, fast response time, wide viewing angle, and high color reproducibility. Moreover, since AMOLED displays do not require a backlight unit, they can be manufactured in a light and thin form factor, thereby being widely employed in multimedia products. However, the non-uniform electrical characteristics of thin-film transistors (TFTs) and OLED degradation, which deteriorate image quality, prevent AMOLED displays from dominating the display market. To solve these issues, various external compensation systems have been studied. To implement an accurate external compensation system, its driving and sensing ranges should be properly determined according to the initial variations in the electrical characteristics of the TFTs and OLEDs of the target panel. Therefore, a panel test system that can accurately measure the initial variations in electrical characteristics is necessary for testing prior to assembling the external compensation system with the panel. However, since conventional panel test systems have been developed only for panels with specific backplane structures, they cannot be used for panels with various backplane structures and should be redeveloped whenever a new AMOLED panel with a different backplane structure is made. This leads to an increase in the research-and-development cost and the turn-around time for developing AMOLED displays. Therefore, this dissertation proposes a panel test system including small-area and high-resolution data driver ICs, a general purpose architecture for various backplane structures, and a fast and accurate measurement method to achieve high-image quality and low-development cost of AMOLED displays. First, an area-efficient and high-resolution resistor-string digital-to-analog converter (R-DAC) with a reverse ordering scheme is proposed. The proposed R-DAC is designed in a two-stage DAC along with a DAC-embedded amplifier. The proposed reverse ordering scheme decreases the area of the proposed R-DAC, which occupies most of the area of the data driver IC. To verify the proposed reverse ordering scheme, a 640-channel data driver IC with a 12-bit two-stage DAC was fabricated using a 0.18-μm CMOS process with 1.8 V and 18 V devices. The fabricated 12-bit two-stage DAC consists of a 10-bit R-DAC with the reverse ordering scheme and a 2-bit DAC-embedded amplifier. The proposed 10-bit R-DAC occupies only 50.1% of the area of the conventional 10-bit R-DAC. Measurement results show that the differential nonlinearity and integral nonlinearity are +0.25/-0.26 LSB and +0.54/-0.42 LSB, respectively. The measured inter-channel and inter-chip deviation of voltage outputs are 2.40 mV and 7.42 mV, respectively. Second, a small-area and low-power data driver IC using a two-stage DAC with a capacitor array is proposed. The proposed data driver IC employs a capacitor array in the two-stage DAC so as to both decrease the DAC area and eliminate the need for the resistor-string, which has high power consumption. To verify the proposed two-stage DAC, a 20-channel data driver IC with the proposed 10-bit two-stage DAC was fabricated using a 0.18-μm CMOS process with 1.8 V and 6 V CMOS devices. The proposed 10-bit two-stage DAC occupies only 43.8% of the area of a conventional 10-bit two-stage DAC. Measurement results show that the differential nonlinearity and integral nonlinearity are +0.58/-0.52 LSB and +0.62/-0.59 LSB, respectively. The measured inter-channel deviation of the voltage outputs is 8.8 mV, and the measured power consumption of the 20-channel data driver IC decreases to 7.1 mW, which is less than half of the power consumed by the conventional one. Finally, a test system for AMOLED panels with various backplane structures with external compensation method is proposed. The proposed AMOLED panel test system employs universal data drive ICs to measure the current of a driving TFT and the anode voltage of the OLED in various backplanes by only programming the field-programmable gate array in the proposed test system. The universal data driver IC is fabricated and implemented in the proposed AMOLED panel test system whose test board is assembled with a 55-inch full high-definition AMOLED panel. A fabricated universal data driver IC includes 640 data channels with a 12-bit linear gamma DAC and 12-bit variable current sources. To evaluate the repeatability error of the proposed panel test system, the driving TFT current is repeatedly measured and the measured maximum repeatability error is 9.8 nA. Moreover, to evaluate the measurement accuracy of the proposed panel test system, the variation in the currents of the driving TFTs are measured and compensated for, and its maximum value after compensation is measured to be 26 nA.
URI
http://hdl.handle.net/20.500.11754/33596http://hanyang.dcollection.net/common/orgView/200000430852
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > ELECTRONICS AND COMPUTER ENGINEERING(전자컴퓨터통신공학과) > Theses (Master)
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