Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1997-09-08
2001-08-21
Cuchlinski, Jr., William A. (Department: 3661)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S077000, C345S182000, C315S169100, C315S169200, C315S169300, C315S169400
Reexamination Certificate
active
06278421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for controlling the power consumption of a display apparatus, especially a display apparatus having a plasma display panel, and more particularly a display apparatus having an AC-driven plasma display panel, a display system equipped with such a power consumption control apparatus, and a storage medium with a program stored therein for implementing such a power consumption control method.
2. Description of the Related Art
Usually, power consumption control for a display apparatus, especially a display apparatus having an AC-driven plasma display panel (PDP), is performed by continuously monitoring the power consumption that changes as the total value of display data changes, and by forcefully reducing the brightness of the entire screen when the power consumption has exceeded its upper limit value and increasing the brightness when the power consumption drops below its lower limit value. In performing the control, in order to minimize the unnaturalness perceived by the viewer viewing the display, brightness is reduced gradually when it is necessary to reduce the brightness because power consumption is too large, and is increased quickly when the brightness can be increased because the power consumption is low enough to permit it.
In the case of an AC-driven plasma display, the control of brightness is accomplished by varying the number of sustain pulses during one frame period and thereby varying the length of the sustained-discharge period. The brightness of each pixel, based on display data, is achieved by dividing one frame into a plurality of sub-fields with varying sustained-discharge periods and by selectively enabling or disabling the sub-fields in accordance with whether the bits forming the pixel data are on or off. For example, when data of each pixel consists of eight bits, one frame is divided into eight sub-fields the ratio of whose sustained-discharge periods is 2
0
:2
1
:2
2
: . . . 2
7
, and the corresponding sub-fields are enabled or disabled in accordance with the bit pattern of the pixel data. In the case of color display, the above control is performed independently for each of the three kinds of pixels corresponding to R, G, and B. The brightness of the entire screen is achieved by increasing or decreasing the sustained-discharge periods of all the sub-fields while maintaining the above ratio.
As described above, in a display apparatus such as a PDP having a power consumption control function, the speed with which the brightness of the entire screen is reduced to control power consumption is set slower than the speed with which the brightness is increased, in order to minimize the unnaturalness perceived by the viewer viewing the display. In other words, power consumption is quick to rise but slow to fall; therefore, when images with rapidly varying load, such as flashing images, are successively displayed, the power consumption rises quickly in the off period, but does not fall readily in the on period because the speed with which the power consumption is lowered is slow. If such patterns are repeated, the average power consumption does not settle down to the set value but exceeds the set value. If the set value is set lower than the actually permitted power consumption value to avoid the above situation, there arises a problem when displaying images with stable load, that is, the brightness and contrast are reduced more than necessary, resulting in degradation of picture quality.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a method of power consumption control that can hold average power consumption within a specified value whether images with rapidly varying load continue or whether image load is stable, and can yet maintain as good a picture quality as possible.
According to the present invention, there is provided a method of controlling power consumption of a display unit, comprising the steps of: measuring the power consumption of the display unit; increasing display brightness of the display unit, or decreasing the display brightness at a speed different from the speed of increasing, in accordance with the measured value of the power consumption; summing the power consumption; and controlling the display brightness in accordance with the sum value of the power consumption and thereby controlling the power consumption to within a target value.
According to the present invention, there is also provided an apparatus for controlling power consumption of a display unit, comprising: means for inputting a measured value of the power consumption of the display unit; means for increasing display brightness of the display unit, or decreasing the display brightness at a speed different from the speed of increasing, in accordance with the measured value of the power consumption; means for summing the power consumption; and means for controlling the display brightness in accordance with the sum value of the power consumption and thereby controlling the power consumption to within a target value.
Preferably, the display unit includes a plasma display panel and a plasma display panel control circuit capable of increasing or decreasing the brightness by increasing or decreasing the number of sustain pulses applied to the plasma display panel during one frame period.
Also preferably, the above control circuit includes an input for setting the number of sustain pulses for the entire display as a display brightness value, and an input for data of each pixel defining the number of sustain pulses for each pixel, the increasing or decreasing of the brightness is achieved by increasing or decreasing the display brightness value and thereby increasing or decreasing the display brightness, and the control of the brightness is achieved by correcting the increasing or decreasing of the display brightness value in accordance with the sum value of the power consumption and thereby controlling the display brightness.
Alternatively, the control of the brightness may be achieved by determining a subtrahend based on the sum value of the power consumption, and by subtracting the subtrahend from data of all the pixels and thereby controlling the display brightness.
According to the present invention, there is also provided a method of controlling power consumption of a display unit, comprising the steps of: measuring the power consumption of the display unit; summing differences between the power consumption and its target value; determining a display brightness value for the display unit from the sum value of the power consumption; and setting the determined display brightness value in the display unit.
According to the present invention, there is also provided an apparatus for controlling power consumption of a display unit, comprising: means for inputting a measured value of the power consumption of the display unit; means for summing differences between the power consumption and its target value; means for determining a display brightness value for the display unit from the sum value of the power consumption; and means for setting the determined display brightness value in the display unit.
According to the present invention, there is also provided a display system comprising: the above-described power consumption control apparatus; a plasma display panel; a drive circuit for driving the plasma display panel; and a control apparatus for controlling the drive circuit in accordance with a set value supplied from the power consumption control apparatus.
According to the present invention, there is also provided a storage medium readable by a computer, the storage medium storing therein a program for implementing the above-described power consumption control method when connected to the computer.
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patent: 3778673 (1973-12-01), Eisenberg et al.
patent: 5329288 (1994-07-01), Kim
patent: 5343215 (1994-08-01), Tanaka
patent: 5406305 (1995-04-01), Shimomura et al.
patent: 5532935 (1996-07-01), Ninomiya et al.
patent: 55
Ishida Katsuhiro
Kariya Kyoji
Kojima Ayahito
Kuriyama Hirohito
Tajima Masaya
Cuchlinski Jr. William A.
Fujitsu Limited
Marc-Coleman Marthe Y.
Staas & Halsey , LLP
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