Yong-sung Park

35.1: 2.5‐in. AMOLED with Integrated 6‐Bit Gamma Compensated Digital Data Driver

6-bit gamma compensated digital data driver using LTPS TFTs was integrated in AMOLED panel. We have applied conventional register ladder D/A converter circuits with 9 points reference voltage for each color. We have obtained both good gray scale and good white balance by optimizing the reference voltage. DC/DC converter and serial to parallel converter have also been integrated by TFT. The number of pixels is 768 × 228 dots. The width of the data driver designed by 2micron rule is only 2.6mm.

4.2: Integrated Scan Driver with Oxide TFTs Using Floating Gate Method

An on-glass integrated scan driver is proposed for oxide thin film transistors TFTs with negative threshold voltage. A coupling capacitor and a TFT for setting the initial voltage to the gate of a TFT were added to minimize the off-state current. Simulated and measured results indicate that the proposed scan driver shows no ripple and fast rise time/fall time of scan outputs. Circuit operation was verified with a 14-inch AMOLED panel.

49.3: Oxide TFT Scan Driver with Dynamic Threshold Voltage Control

Oxide TFTs have a negative threshold voltage (Vth), which can become even more negative in response to DC or AC stress. Therefore, these voltage stresses can cause severe leakage current in a scan driver. In this paper, a scan driver with dynamic threshold voltage control (DTVC) is proposed to minimize the leakage current and enlarge operating margin. Effectiveness of DTVC was verified with a 14-inch AMOLED.

High-speed pixel circuits for large-sized 3-D AMOLED displays

— Large-sized active-matrix organic light-emitting diode (AMOLED) displays require high-frame-rate driving technology to achieve high-quality 3-D images. However, higher-frame-rate driving decreases the time available for compensating Vth in the pixel circuit. Therefore, a new method needs to be developed to compensate the pixel circuit in a shorter time interval. In this work, image quality of a 14-in. quarter full-high-definition (qFHD) AMOLED driven at a frame rate of over 240 Hz was investigated. It was found that image degradation is related to the time available for compensation of the driving TFT threshold voltage. To solve this problem, novel AMOLED pixel circuits for high-speed operation are proposed to compensate threshold-voltage variation at frame rates above 240 Hz. When Vth is varied over ±1.0 V, conventional pixel circuits showed current deviations of 22.8 and 39.8% at 240 and 480 Hz, respectively, while the new pixel circuits showed deviations of only 2.6 and 5.4%.

21.2: Driving Method for a 2D-3D Switchable AMOLED Display Using Progressive or Simultaneous Emission

A driving method has been developed for a 2D-3D switchable AMOLED using progressive emission PE or simultaneous emission SE. The proposed method is implemented by selecting PE mode for 2D to improve light emission ratio and SE mode for 3D to reduce left-right crosstalk without sacrificing luminance. This method also improves the contrast ratio by removing unnecessary light emission and can offer better uniformity by increasing the threshold voltage compensation time. A 240Hz-driven 30″ 3D AMOLED display was built and it was confirmed that there is no ELVDD surge current in the SE mode.

An 8b Source Driver for 2.0 inch Full-Color Active-Matrix OLEDs Made with LTPS TFTs

An 8b source driver for 2.0 inch QVGA active-matrix OLEDs is fabricated using LTPS TFTs. This driver uses an 8b DAC that is separated into two parts, a 1-to-3 DEMUX, and a pre-charge method. This scheme reduces the source driver size by 40%. The maximum DNL is under 1LSB. The output voltage variation of the source driver is less than 1 LSB even though the variation of the threshold voltage is plusmn0.5V

53.5: High-Speed AMOLED Pixel Circuit and Driving Scheme

An active matrix organic light emitting diode pixel circuit and its driving scheme for high frame frequency are proposed for implementation of a 3D display. The proposed pixel circuit can compensate the threshold voltage distribution of low temperature poly silicon-thin film transistors at high-speed operation of 240Hz or more. According to the simulation, current deviation of 1.73% and 3.94% are obtained at frame rates of 240Hz and 480Hz when Vth distribution is ±0.5 V.

38.4: 6-bit AMOLED with RGB Adjustable Gamma Compensation LTPS TFT Circuit

RGB adjustable gamma compensation circuit to choose one of the three different gamma characteristics for each color has been integrated by LTPS TFT for AMOLED. A timing controller to generate all timing signals for a 6-bit data driver and a scanning driver has also been integrated by the TFT on the AMOLED panel.

21.3: Low Frequency Driving Methods for 3D Displays

Stereoscopic 3D displays are generally operated at 240Hz in order to fully separate left eye and right eye images. New low frequency driving methods are proposed for 3D displays. In addition to reducing driving frequency, the new driving methods can increase luminance and reduce cross-talk and power consumption.

P‐12: Novel Positive‐Intrinsic‐Oxide Semiconductor (P‐I‐OS) Photo Sensor for Flat Panel Displays

For the first time, photo sensors employing p-type Si and IGZO semiconductor (P-I-OS) have been fabricated with a sensor dimension of W/L = 1600/5. The IGZO layer was deposited using DC sputtering and replaces the conventional n+-doped cathode electrode. The P-I-OS photo sensor is more sensitive to light with shorter wavelengths, and high to low photo-current dynamic range is almost constant from −15V to −2.5V of anode bias. The P-I-OS photo sensor exhibits dynamic range of 53.3 dB under −5V of anode bias and 10,000 lx of illuminated light intensity