Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Utility Patent
1998-02-02
2001-01-02
Cuchlinski, Jr., William A. (Department: 2774)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S097000, C345S099000, C345S212000
Utility Patent
active
06169532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display apparatus and method for driving the display apparatus, and more particularly to a display apparatus and method for driving the display apparatus for displaying a still image.
2. Description of the Prior Art
Recently, a liquid crystal display apparatus has come into use in various products, such as personal computers, VCRs and digital still cameras. Most liquid crystal display apparatus adopt an active matrix driving system.
The active matrix liquid crystal display apparatus includes switching elements, such as thin film transistors (TFTs), which connect to picture element electrodes. The TFTs also connect to a gate driver by way of scanning (gate) lines and a drain driver by way of drain lines. The gate driver sequentially selects scanning lines in the manner of the line-sequential scanning in order to make on-state of the TFTs which are connected to the selected scanning line. The drain driver includes a shift register and a latch circuit. The shift register has the same number of stages as the number of the picture element electrodes coupled to one scanning line by way of the TFTs. Each stage of the shift register has a plurality of complimentary metal oxide semiconductor (CMOS) transistors and outputs a shift clock to the latch circuit. During a period in which the gate driver selects one scanning line, the display signals corresponding to one scanning line sequentially shift in the latch circuit based on the shift clock output from the shift register and are output from the latch circuit to the picture element electrodes coupled to the scanning line selected by the gate driver through the TFTs.
In the meantime, a CMOS transistor, comprising an n-type metal oxide semiconductor (NMOS) and a p-type metal oxide semiconductor (PMOS), consumes electric power at the moment of its switching operation since the current flows through both the NMOS and PMOS at the moment of being inverted the gate signal. Therefore, in high frequency operation, the CMOS consumes a large amount of the electric power.
In the display apparatus set forth above, a drain drivers utilizing many CMOS's consume a relatively large amount of electric power since these drain drivers operate with high frequency. Particularly, in a display apparatus with high resolution, as the frequency to operate the drain driver increases, the electric power consumed by the drain driver increases. The drain driver actually consumes most of the electric power consumed by a circuit for driving the liquid crystal display panel. For example, in certain models of commercial liquid crystal televisions, the gate driver operates with a frequency of 16 kHz and a current of 900 &mgr;A, while the drain drive operates with a frequency of 4 MHz and a current of 10 mA.
The active matrix liquid crystal display apparatus set forth above always performs the same operation whether it displays motion image data or still image data. That is, when the display apparatus displays the still image, a plurality of the same image data is repeatedly supplied to the picture element electrodes every frame by using the drain driver which consumes a large amount of the electric power.
An organic electroluminescent (EL) display apparatus and a light emitted diode (LED) display apparatus also have a drain driver which is similar to that of the liquid crystal display apparatus and perform the same operation whether they display a motion image data or a still image data. Thus, there is a need for improvements in energy usage of such devices.
SUMMARY OF THE INVENTION
The present invention provides a display apparatus and method for driving the display apparatus which conserve electric power when the display apparatus displays still image data. This is achieved by a display apparatus which comprises a display panel for displaying image data, which panel has a plurality of picture element electrodes arranged in matrix having rows and columns; image data processing means for producing a display signal of one line from the image data; scanning means for selecting the picture element electrodes on one of the rows of the display panel in sequence; display signal supplying means for supplying display signals produced by the image data processing means to the picture element electrodes selected by the scanning means; determining means for determining whether the image data represents a still image; and control means for stoping the operation of the display signal supplying means when the determining means determines that the image data represents a still image.
The present invention also provides a method for driving a display apparatus of the type described above. The method comprises an image data processing step of producing a display signal of one line from the image data; a scanning step of selecting the picture element electrodes on one of the rows of the display panel in sequence; a display signal supplying step of supplying display signal produced by the image data processing step to the picture element electrodes selected by the scanning step; a determining step of determining whether the image data represents a still image; and control step of stoping the operation of the display signal supplying step when the image data represents the still image.
REFERENCES:
patent: 4430648 (1984-02-01), Togashi et al.
patent: 4571584 (1986-02-01), Suzuki
patent: 4660030 (1987-04-01), Maezawa
patent: 4803480 (1989-02-01), Soneda et al.
patent: 5724061 (1998-03-01), Kanbara
patent: 5828367 (1998-10-01), Kuga
Kanbara Minoru
Sumi Shinobu
Casio Computer Co. Ltd.
Cuchlinski Jr. William A.
Marc-Coleman Marthe Y.
Pennie & Edmonds LLP
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