Jae-Hyuck Woo

A line inversion-based stepwise data driving for low-power mobile TFT-LCDs

This paper proposes a line inversion-based stepwise data driving scheme for use in low-power mobile TFT-LCDs. The proposed stepwise data driving scheme adopts a stepwise pull-up and pull-down transition operations of source and common lines in an LCD penal, resulting in greatly reduced power consumption as compared to the conventional line inversion-based data driving schemes. Moreover, the proposed scheme shows relatively uniform power consumption for different image patterns, making background image design easy for use in commercial portable display devices. Three test chips for mobile devices having QCIF+, QVGA, and HVGA resolutions were fabricated in a 6-V/0.7-μm quadruple-metal CMOS process. The experimental results showed that overall power reductions of 25%-37% for QCIF+, 31%-47% for QVGA, and 42%-53% for HVGA TFT-LCDs were achieved, depending on image pattern, with a die size overhead of less than 1%. They also indicated that the proposed driving scheme allowed around 55% to 32% reduction on image pattern-dependent power variation as compared to conventional driving schemes.

Line inversion-based mobile TFT-LCD driver IC with accurate quadruple-gamma-curve correction

Line inversion-based mobile TFT-LCD driver IC with novel quadruple-gamma-curve correction is presented. The driver IC allows for a cost-effective accurate curve correction for multiple gamma values of γ^1.0, γ^1.8, γ^2.2, and γ^2.5 by adopting novel voltage-symmetric gray curve synthesis and variable reference resistor-tap biasing schemes. A test chip in a 6 V/0.7-μm triple-well CMOS process indicated a gray voltage error of ±8 mV with gray-to-gray error difference under ±3 mV.

Accurate quadruple-gamma-curve correction for line inversion-based mobile TFT-LCD driver ICS

A line inversion-based gamma-curve correction scheme is presented for use in mobile TFT-LCD driver ICs. Novel voltage-symmetric gray curve synthesis (VSGS) method using a polarity-inverting gray voltage generator and variable resistor-tap biasing (VRTB) scheme using multioutput drivers have been adopted for accurately correcting gray curves for quadruple gamma values of y1.0, y1.8, y2.2, and y2.5. A test chip fabricated in a 6 V/0.7-μm triple-well CMOS process indicated that a gray voltage error was less than +8 mV, a gray-to-gray error-voltage difference was under +3 mV, and a pin-to-pin variation of each source driver output was +5 mV1.

Analysis on panel power consumption of mobile TFT-LCDs based on line inversion driving

This paper analyzes and compares the penal power consumption for mobile TFT-LCDs. Three representative penal driving schemes (the basic data driving, the charge-recycling data driving, and the stepwise data driving) based on the line inversion driving method are considered in this analysis, and equations for representing the penal power consumption of respective driving schemes are derived. This is the first to analyze the panel power consumption of line inversion-based mobile TFT-LCDs including parasitic capacitance effect. The analysis procedure presented here is helpful for power study, and gives benefits of providing accurate estimation of the total power consumption of mobile TFT-LCDs driven a line inversion driving.

An Opportunistic Source Line Driving Scheme for Low Power Mobile TFT-LCD Driver IC

An opportunistic source line driving (OSLD) scheme is proposed for use in mobile TFT_LCD driver ICs (T-LDIs). In OSLD scheme, the operation of the source drivers of a T-LDI is controlled by the equivalence of RGB color data for adjacent pixels. That is, one source driver drives the neighboring source lines as well as the corresponding one when the color data of adjacent pixcels are identical to each other. With this scheme, all the source drivers associated with the neighboring source lines can be completely turned off, allowing the reduction of static and dynamic current of these drivers. Test chip was fabricated in a 5-V/0.8-um 2.5V/0.25-um triple-metal CMOS process, and the experimental result shows that the power reduction of 12% ~ 21% was obtained with die size overhead less than 0.5%.