Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-08-27
2004-02-17
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S211000, C345S690000
Reexamination Certificate
active
06693614
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a display apparatus and more particularly to the display apparatus having a liquid crystal display (LCD) panel.
PRIOR ART
In the display apparatus having a transmissive type of LCD panel, a backlight system is used to illuminate the display image from a rear side of a LCD panel. In the transmissive type of LCD panel for a note-book type of personal computer and PDA (Portable Digital Apparatus), if operating means such as a key board, a mouse or the like is not operated after a lapse of a certain time, the power consumption is reduced because of transition to a stand-by mode (a sleep mode) to shut off the backlight and to shut off a display signal to the LCD panel. Specifically, since power consumption of the backlight is large, an effect of power reduction of transiting to a stand-by mode is remarkable.
PROBLEMS TO BE SOLVED BY THE INVENTION
However, power reduction has not been realized in a reflecting-type LCD panel effectively, because the backlight system is not used. A reflecting-type LCD is used in a portable phone which requires low power consumption. However, in the stand-by mode for an incoming wait, an incoming notice can not be displayed by shutting off the display signal to the LCD panel. Display means to indicate the incoming notice is required. Moreover, there is a case that only a present time is desired to display. For this purpose, in the display apparatus having the reflecting-type LCD panel without a backlight, there has been a problem of a tradeoff between more power reduction and a display with the minimum required.
The object of the invention is to provide a display apparatus capable of realizing more power reduction and capable of displaying the display with the minimum request.
To this end, the display device according to the invention comprises a display unit and display control means for generating the display signal to be supplied to the display unit, having functions of the usual mode and the stand-by mode in a state where electric power is supplied from a power source, wherein in the usual mode, the display control means generates a multivalued display signal which can represent gradation levels, while in the stand-by mode, the display control means generates a binary display signal which does not represent gradation levels.
Since the binary display signal is generated instead of the multivalued display signal, of which power consumption is large in the stand-by mode, more power reduction can be realized, and the display with the minimum required incoming notice and time indication can be displayed.
In the display device according to the invention, the display control means has a first circuit that generates the multivalued display signal and a second circuit that generates the binary display signal. In the stand-by mode, the display control means stops supply of the electric power to the first circuit and supplies the binary display signal generated by the second circuit to the display unit. According to this constitution, applying the electric power to a circuit with large power consumption is stopped and the display signal is generated by a circuit with less power consumption, whereby power reduction can be realized effectively, and a minimum display can be realized.
In the display device according to the invention, the first circuit includes a circuit to convert a plural-bits digital signal into an analog signal. According to this constitution, in the stand-by mode, the circuit with large power consumption is inactivated, whereby a large amount of power reduction becomes possible.
Moreover, in the display device according to the invention, the first circuit includes a circuit to convert a plural-bits digital signal into an analog signal and an amplification circuit to amplify the analog signal. According to this, constitution, the amplification circuit can be also inactivated, whereby a large amount of power reduction becomes possible.
Moreover, in the display device according to the invention, the display control means includes an amplification circuit having serially-connected two active elements. In the normal mode, the display control means supplies a multivalued display signal to the display unit through the two active elements in accordance with input of analog signal, while in the stand-by mode, the display control means supplies the binary display signal to the display unit through one of the two active elements. According to this constitution, the binary display signal is generated in a state where the electric power for the circuit is reduced by using the amplification circuit to generate the multivalued display signal, so that the addition of the circuit may not be required in order to generate the binary display signal.
Moreover, in the display device according to the invention, the display control means has plural digital circuits that generate plural-bits digital signals to generate the multivalued display signal, and in the stand-by mode, the display control means activates only one digital circuit that generates a particular 1-bit digital signal among the plural bits, and inactivates the other digital circuits. According to this constitution, power consumption can be reduced not only in the circuit to generate the multivalued display signal, but also in the circuit to generate the digital signal.
Moreover, in the display device according to the invention, the display unit is constituted by a reflective-type liquid crystal display unit, and the display control means supplies the display signal to a driving circuit of this liquid crystal display unit. According to this constitution, power consumption of batteries for the note type personal computer and PDA can be reduced, and the successive use time of the device can be extended inevitably.
EMBODIMENT OF THE INVENTION
FIG. 1
shows block diagrams for a part of a display device with a reflecting-type LCD panel according to the invention.
Referring to
FIG. 1
, an operation detection circuit
1
, a digital circuit
2
as a first circuit, an analogous circuit
3
as a second circuit are connected with a power source
5
via a power source line
4
, and a constant voltage VC is supplied thereto. The LCD panel (the display unit)
6
is connected with the power source
5
via a power source line
7
and a constant voltage VD is supplied thereto. When the time for no operation of the display device exceeds a predetermined time, the operation detection circuit
1
supplies STBY as a stand-by signal of Low-active to the digital circuit
2
and the analogous circuit
3
through a signal line
8
for the transition to a stand-by mode.
The digital circuit
2
is constituted by C-MOS IC to generate the digital signal for generating the display signal, which signal is supplied to the analogous circuit
3
through a signal line
9
. The analogous circuit
3
generates the display signal in response to this digital signal, which display signal is supplied to a driving circuit of the LCD panel
6
through a signal line
10
. The LCD panel
6
drives pixel electrodes by TFTs (thin film transistors) to display images.
TFT is the thin film transistor which is constituted by a gate located at a crossing point of matrix comprising a gate bus in a horizontal display direction and a source bus in a perpendicular display direction, the source and the drain, and a channel between the gate and the source. The channel is turned on by supplying a pulse signal to the gate bus under the condition that the display signal is supplied to the source bus and the display signal supplied to the source is applied to the pixel electrode which is connected with the drain. That is, the above-mentioned analogous circuit
3
constitutes a source driver circuit and generates the display signal every perpendicular scanning time of a plurality of source lines, which display signal is supplied to the LCD panel.
The digital circuit
2
and the analogous circuit
3
shown in
FIG. 1
constitute the display control means which supplies the display signal to the sourc
Kamiya Takeo
Miyazaki Akihiko
Yasui Masaru
Fatahi-yar M.
Hjerpe Richard
Koninklijke Philips Electronics , N.V.
Miyazaki Akihiko
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