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US 6,646,637 B1Granted
Liquid crystal display device
AssigneeHitachi, Ltd.
InventorsHiroshi Kageyama, Hideo Sato, Yoshiro Mikami
Life of this patent
Estimating the term…
Abstract
Each of a plurality of D/A conversion circuits DA1˜DA4 is constituted by a plurality of switching thin film transistors (TFTs), each having substantially the same ON resistance, and a control circuit performing ON and OFF control of the switching TFTs in such a manner that, during a D/A conversion operation a predetermined same plural number of switching TFTs are turned ON for any digital input signal representing gradations to be displayed, thereby, the output resistance of each of the D/A conversion circuits is kept substantially constant. Accordingly, multi-gradation and high resolution of a liquid display device are easily achieved and the image quality thereof is improved.
Claims26
A liquid crystal display device comprising a pair of substrates at least one of which is transparent;
- a liquid crystal layer sandwiched between the substrates;
- a display region;
- and a periphery circuit for driving the display region both of which are mounted on one of the pair of substrates, the display region being formed by a plurality of drain lines and a plurality of gate lines arranged in a matrix shape and a plurality of thin film transistors each being disposed near the respective related matrixes and the periphery circuit being provided with a driving circuit which is permitted to receive digital image signal inputs, wherein the driving circuit is provided with a plurality of D/A conversion circuits each being constituted by a plurality of switches each having substantially the same ON resistance and a control circuit which controls ON and OFF of the switches in such a manner that at a time of D/A conversion operation a plurality of switches in same number are turned ON for respective input signals representing respective gradations;
- wherein the D/A conversion circuit is constituted by a plurality of switch groups each being constituted by a plurality of switches connected in parallel, one terminals of the respective switch groups are respectively connected to different distribution lines being supplied of respectively different reference voltages, the other terminals of the switch groups are connected in common to constitute a voltage output portion, and the control circuit controls to turn ON a predetermined plurality number n of switches among one or two of the switch groups at the same time during D/A conversion operation.
1 more element
A liquid crystal display device comprising:
- a pair of substrates at least one of which is transparent;
- a liquid crystal layer sandwiched between the pair of substrates;
- a display region being formed on one of the pair of substrates and being constituted by a plurality of drain lines and a plurality of gate lines arranged in a matrix shape and a plurality of thin film transistors each being disposed in connection with respective relating matrixes defined by the plurality of drain lines and the plurality of gate lines and a plurality of display electrodes each being related to the respective thin film transistors;
- and
- a periphery driving circuit which drives the display region and includes a drain driver connected to the plurality of drain lines, a gate driver connected to the plurality of gate lines and a precharge circuit connected to the plurality of drain lines which applies a predetermined pre-charging voltage to the plurality of drain lines for every horizontal one line period,
- wherein, the drain driver comprises a plurality of pairs of first and second D/A conversion circuits and a plurality of distribution circuits each of which input terminals are connected to one of the pairs of first and second D/A conversion circuits and each of which output terminals are connected to a predetermined plurality number of the drain lines, the first D/A conversion circuit being connected to a plurality of reference voltages in a lower range of liquid crystal drive voltage and outputting gradation voltages in response to digital input signals representing gradations to be displayed and the second D/A conversion circuit being connected to a plurality of reference voltages in a higher range of liquid crystal drive voltage and outputting gradation voltages in response to digital input signals representing gradations to be displayed, the pair of first and second D/A conversion circuits in combination apply an AC voltage to the liquid crystal layer, each of the distribution circuit is constituted by a plurality of switching thin film transistors each having substantially the same ON resistance and any combination of the plurality of input terminals and the plurality of output terminals is established through turning on one of the plurality of the switching thin film transistors.
3 more elements
Dependencies are inferred from the claim text.