Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-02-05
2003-04-01
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S092000, C345S089000, C345S205000, C348S674000, C348S792000
Reexamination Certificate
active
06542143
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display driving device for driving a display element such as a liquid crystal, a display device including the display element driving device, an information processing apparatus including the display device, and a display element driving method.
DESCRIPTION OF THE RELATED ART
FIG. 21
shows a circuit of a conventional data driver disclosed in Japanese Unexamined Patent Publication No. 6-222741. In this data driver, by using voltages V
1
to V
9
having nine levels and externally driven, a 64-level applied voltages are applied to signal lines. The three upper bits of digital data of an image signal are converted into 8-value data by a decoder
923
. Voltage selection circuits
927
and
925
select corresponding ones of the voltages V
1
to V
9
on the basis of the 8-value data, and output the selected voltages as VH and VL, respectively. The three lower bits of the digital data of the image signal are converted into 8-value data by a decoder
924
. A resistor division scheme D/A converter
926
selects one of voltages obtained by equally dividing the voltages VH and VL by eight and outputs the selected voltage to a signal line as Vout. Even if the conventional arrangement is used, when the externally input voltages V
1
to V
9
are optimized in accordance with the &ggr; characteristics of a liquid-crystal element, &ggr;-correction can be performed to some extent.
However, since an output voltage is generated by interpolating the voltages V
1
to V
9
in the above method, the resultant output voltage is different from a voltage to be displayed in an original state, and display characteristics are degraded disadvantageously.
On the other hand,
FIG. 22
shows a case wherein &ggr;-correction is performed by using a data driver using an analog scheme. In this method, an image signal is converted into analog data by a D/A converter
930
. A &ggr;-correction circuit
934
performs a &ggr;-correction process on the basis of the analog data and correction data from a &ggr;-correction table ROM
932
. Therefore, analog data subjected to &ggr;-correction is input to an analog-type data driver
942
in a liquid-crystal display device
940
.
However, the analog-type data driver
942
has high power consumption because an analog circuit must be incorporated in the data driver
942
, and the data driver
942
is generally improper for a display of a portable computer.
In recent years, it is tried to integrally form the data driver
942
or the like on a substrate having a TFT (thin-film transistor)
944
. When the TFT
944
is integrally formed, a considerable reduction in size of the liquid-crystal display device and a reduction in cost can be realized. When such integral formation is to be performed, an incorporated analog circuit must be also constituted by a TFT in the analog-type data driver.
942
. However, when the analog circuit is constituted by a TFT, the following various problems are posed. That is, the transistor characteristics of the TFT change with time, or it is difficult to obtain desired performance. In addition, when it is tried to incorporate the &ggr;-correction circuit
934
in the data driver
942
, a large amount of current flows in the &ggr;-correction circuit
934
serving as an analog circuit. For this reason, a problem of a change in transistor characteristics of a TFT with time is posed.
As described above, the conventional data driver has various problems.
Some information processing apparatus such as a multi-media terminal or a graphic accelerator do not process an RGB signal used in a liquid-crystal display device, but process an image signal called a YUV or processes both RGB and YUV. When the liquid-crystal display device is used as a display of the information processing apparatus, it is desired that both the image signals, i.e., RGB and YUV, can be displayed. For this purpose, in a conventional arrangement, a conversion circuit
950
as shown in
FIG. 23
is arranged to convert a YUV signal into an RGB signal, D/A conversion is performed by the D/A converter
952
, and analog data obtained by the D/A conversion is applied to a data driver
962
.
However, in this arrangement, since an analog-type data driver must be used as the data driver
962
, a problem about an increase in power consumption is also posed as described above. In addition, there is a problem of difficulty of the data driver
962
integrally formed on a substrate on which a TFT
964
is formed.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and has as its object to provide a display element driving device, a display device, an information processing apparatus, and a display element driving method each of which can obtain a low power consumption, can be increased in scale, and exhibit high performance.
It is another object of the present invention to provide a display element driving device or the like which can compensate for the display characteristics of a display element with an arrangement having low power consumption and a small scale.
It is still another object of the present invention to provide a display element driving device or the like which can display image signals having different formats with an arrangement having a low power consumption and a small scale.
It is still another object of the present invention to provide a display element driving device or the like which is optimally integrated with a substrate on which a TFT and the like are formed.
In order to solve the above problems, according to the present invention, there is provided a display element driving device comprising a D/A converter for giving an applied voltage based on a given image signal to an electrode line electrically connected to the other side of a capacitive display element having one side to which a given voltage is applied.
The D/A converter includes first to Nth charge storage means for respectively receiving first to Nth digital data corresponding to the image signal and storing charges corresponding to the values of the first to Nth digital data first to Nth connection means for electrically connecting the first to Nth charge storage means and the electrode line to each other and discharging the charges stored in the first to Nth charge storage means to the electrode line at a given timing.
According to the present invention, for example, in case of N=2, a charge corresponding to the value of the first digital data and a charge corresponding to the value of the second digital data are stored in the first charge storage means and the second charge storage means. When the first and second connection means electrically connects the first and second charge storage means and the electrode line to each other, the charges stored in the first and second charge storage means are discharged to the electrode line. At this time, on the basis of the discharged charges, capacitances of, e.g., the display element, the electrode line, and the first and second charge storage means, and the like, an applied voltage to the electrode line is determined. According to the present invention, the moment D/A conversion is performed, processes such as addition and subtraction processes between the digital data are performed or the process multiplying the digital data by given coefficients can be performed.
The present invention is characterized in that the first to Nth charge storage means store the charges on the basis of the first to Nth digital data can be performed and at least one given voltage. In this manner, when various-given voltages are prepared, or a given voltage is changed, not only a simple addition process of digital data but also various processes such as a subtraction process, a multiplication process of a coefficient can be easily performed.
The present invention is characterized in that the first to Nth charge storage means include capacitor elements having one sides to which a given voltage is applied and capacitances which are binarily weighted, and the first to Nth connection means include s
Lao Lun-Yi
Oliff & Berridg,e PLC
Seiko Epson Corporation
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