US 5,313,294 AGranted

Beam current limiting arrangement having a peak amplitude, responsive threshold

AssigneeRCA Thomson Licensing Corporation

InventorPeter E. Haferl

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Abstract

An automatic beam current limiting arrangement of a television receiver or display monitor comprises an average beam current limiter coupled to the low side of the high voltage transformer for reducing the contrast of a reproduced image when the average beam current exceeds a threshold and a peak current limiter coupled to the cathodes of the picture tube for controlling a current source which determines the threshold of the average beam current limiter in response to the sum of the cathode currents of the picture tube. In one embodiment, the cathode current sensing circuits comprise the same cathode current sensing circuits utilized in an automatic black level setting arrangement. This beam limiting arrangement allows operation at high contrast levels while inhibiting excessive peak white areas.

Claims12

Dependent claims

In a display system, apparatus comprising:

a video signal processing channel for processing an video input signal to produce an video output signal suitable for display;
a power supply;
an image display device coupled to said video signal processing channel and to said power supply and drawing current from said power supply in response to said video output signal;
means coupled to said power supply for sensing the average current drawn by said display device from said power supply;
means coupled between said video signal processing channel and said average current sensing means for reducing an image property determining characteristic of said video output signal when said average current drawn by said display device from said power supply exceeds a controllable threshold;
means coupled to said video signal processing channel for sensing the amplitude of said video output signal;
and
means coupled to said reducing means for setting said threshold of said reducing means in response to the amplitude of video output signal.

5 more elements

In a display system, apparatus comprising:

a picture tube having at least one cathode;
a video signal processing channel for processing an video input signal to produce a video output signal;
said video signal processing channel including a picture tube drive amplifier for producing said output video signal so that it is capable of directly driving said cathode of said picture tube;
a power supply;
said picture tube being coupled to said video signal processing channel and to said power supply and drawing current from said power supply in response to said video output signal;
means coupled to said power supply for sensing the average current drawn by said picture tube from said power supply;
means coupled to said cathode of said picture tube amplifier for sensing the current flowing to said cathode;
and
means coupled between said video signal processing channel and said average current sensing means for reducing the peak to peak amplitude of said video output signal in response to said average current drawn by said picture from said power supply when said average current exceeds a controllable threshold;
means coupled to said video signal processing channel for sensing the amplitude of said video output signal;
and
means coupled to said reducing means for setting said threshold of said reducing means in response to the amplitude of said video output signal.

9 more elements

Dependencies are inferred from the claim text.