Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
2001-01-17
2003-05-06
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C345S087000, C345S204000, C345S211000, C345S213000, C345S215000
Reexamination Certificate
active
06559838
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a power management system for a monitor, a method of power management for a monitor, and a display apparatus with such a power management system.
2. Description of the Related Art
In principle, the determination of eventual variations in time of the video signal may be performed by comparing, in any frame, the value of every pixel with the value of the corresponding pixel in the preceding/following frames. Such an approach is known from Japanese Patent Application No. JP-A-5,344,371. This type of solution may be the most efficient one in terms of certainty of comparison, but, on the other hand, it is the most difficult one to realize in practice in that:
it requires very fast and large memories capable of storing at least one frame;
it requires a sampling signal at the pixel rate for the video input, which is not available in current analog monitors; and
it requires A/D converters operating at very high frequencies, leading to possible errors in the sampling in subsequent frames.
SUMMARY OF THE INVENTION
It is, inter alia, an object of the invention to provide power management in a monitor in which variations of a video signal are detected with a less complex circuit which operates at a lower frequency.
To this end, a first aspect of the invention provides a power management system for a monitor having a display screen, the power management system comprising a detector for determining, during successive periods in time, transition numbers indicating a number of transitions in a video signal for a predetermined area of the display screen, a comparator for comparing said transition numbers, and a controller for activating a power down mode of the monitor when at least two of said transition numbers are substantially equal. A second aspect of the invention provides a method of power management for a monitor having a display screen, the power management method comprising the steps of determining, during successive periods in time, transition numbers indicating a number of transitions in a video signal for a predetermined area of the display screen, comparing said transition numbers, and activating a power down mode of the monitor when at least a predetermined number of said transition numbers is substantially equal. A third aspect of the invention provides a display apparatus comprising a power management system as described above.
More particularly, the invention relates to power management in a monitor through the sensing of the steadiness/variation in time of the content of the video signal.
The power management system comprises a detector for determining, during successive periods in time, transition numbers representing a number of transitions in a video signal for a predetermined area of the display screen. Thus, during a period in time of the video information corresponding to part of the video signal which is displayed on the selected area on the display screen, the number of transitions in the video signal are indicated by the transition number. This is repeated in successive periods in time wherein video information is written to the same area of the display screen. In this way, a sequence of transition numbers occurs representing the number of transitions in the video signal for the same area of the display screen in successive periods of time. Two or more transition numbers which are substantially equal in the different time periods, indicate that the video signal in the selected area has the same number of transitions, and thus it is likely that the video signal did not change. Therefore, a comparator compares these transition numbers, and a controller activates a power down mode of the monitor if a sufficient number of transition numbers is equal.
In this way, it is not required to store the values of all the video samples (or pixels) in the selected area for several time periods, and to compare all the corresponding values to determine whether a value of a video sample changed from the one time period to another time period. It suffices to keep track of the number of transitions during each time period. Only a single value per time period needs to be compared. It is possible to compare two or more successive transition numbers to determine whether two or more transition numbers are equal, and if yes, to activate a power down mode of the monitor wherein parts of the monitor or the complete monitor are inactive. It is also possible to continuously compare two successive transition numbers and to keep track of the number of successive transition numbers that are equal. If this number of equal transition numbers surpasses a predetermined value, the power down mode is activated.
A counter counting the number of transitions during the selected time period may generate the transition number which equals the number of transitions occurring during the time period. Alternatively, a pseudo-random generator, also referred to as sequencer, may generate the transition number. Now, the transition number is a pseudo-random number of which the value does not directly provide the number of transitions which occurred during the time period, but which value is indicative for this number of transitions. Such a sequencer may have advantages over a counter.
In an embodiment of the invention characterized in that the predetermined area of the display screen is the whole area covered by a visible part of the video signal, and the successive periods in time are frames of the video signal, each transition number represents the number of transitions in the active part of a complete frame of the video signal. This active part of the frame is displayed as the visible part of the video signal on the screen.
In an embodiment of the invention characterized in that the detector comprises a slicer for supplying a slicer output signal indicating when the video signal crosses a threshold, the slicer compares the video signal with a reference value or level to indicate whether a transition in the video signal occurred. If the video signal is a digital signal, the slicer may compare the samples of the video signal with a reference value. If the video signal is an analog signal, the slicer may compare the video signal with a reference level.
In an embodiment of the invention characterized in that the video signal comprises a first color signal, a second color signal, and a third color signal, the detector comprising a first slicer for receiving the first color signal, and a first pseudo-random generator for receiving an output signal of the first slicer to supply a first sequence of numbers, a second slicer for receiving the second color signal, and a second pseudo-random generator for receiving an output signal of the second slicer to supply a second sequence of numbers, a third slicer for receiving the third color signal, and a third pseudo-random generator for receiving an output signal of the third slicer to supply a third sequence of numbers, the first pseudo-random generator further having an input for receiving an output signal of the third pseudo-random generator such that the first sequence of numbers also depends on the third sequence of numbers, three slicers, and three pseudo-random generators are used, each one to generate the transition number for one of the three color components (also referred to as color signals, usually: the Red, Green and Blue color signals) of the video signal. Each of the slicers compares the color signal sliced with a reference value or level to indicate whether a transition in this color signal occurred. In case of an analog video signal, the slicers may be threshold comparators for converting the analog video levels (for example, in the nominal range 0 . . . 0.7V) in a sequence of digital signals (for example, in the range 0 . . . 5V or 0 . . . 3.3V). Therefore, in any row of the active video, for each of the three colors, a certain number of 0-to-1 or 1-to-0 transitions occur, depending on the picture which is represented on the screen.
A simple counting of these transitions in any fra
Lonoce Giovanni
Palmero Augusto
Ramolfo Alberto
Goodman Edward W.
Koninklijke Philips Electronics , N.V.
Kovalick Vincent E.
Shalwala Bipin
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