Apparatus responsive to plural color video signals for amplitude limiting the video signals to assist beam current limiting
AssigneeRCA Corporation
InventorWayne E. Harlan
Life of this patent
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Abstract
Excessive peak beam currents conducted by a kinescope in a color television receiver are limited by apparatus which compares the combined instantaneous magnitudes of plural color signals with a fixed threshold and, if exceeding the threshold, the combined signal is detected. The detected signal is used to limit the magnitudes of the color signals, thereby limiting excessive kinescope beam currents otherwise developed in response to the color signals. The apparatus is used in the receiver together with a more conventional automatic kinescope beam current limiter of the type which operates in conjunction with a kinescope resupply current source.
Claims2
In a system for processing and displaying color video signal image information, apparatus comprising:
- a source of plural color video signals;
- a current-conducting color image display device;
- a supply network including a source of high voltage coupled to said image display device for providing a high operating voltage and resupply current to said image display device;
- a display device beam current limiter network coupled to said supply network and to said source of video signals, said beam current limiter network being responsive to the magnitude of resupply current representative of beam currents conducted by said image display device for providing a first control signal representative of the magnitude of said representative resupply current above a threshold level;
- means for coupling said first control signal to said signal source for limiting the magnitudes of said plural color signals from said source in accordance with the magnitude of said first control signal;
- plural color signal output paths associated with respective outputs of said source of plural color signals;
- a video output signal display driver stage for providing plural amplified color signals suitable for driving signal inputs of said display device in response to plural color signals received as inputs from said plural signal output paths;
- combining means for providing a combined signal representative of the sum of the instantaneous magnitudes of said plural color signals from said source;
- means for comparing said combined signal with a substantially fixed threshold reference level to provide an ouput signal representative of said combined signal when said combined signal exceeds said threshold level in a white image direction;
- means for detecting said representative output signal to provide a second control signal;
- and
- means for coupling said second control signal to said signal source for limiting the magnitudes of said plural color signals from said source in accordance with the magnitude of said second control signal.
Dependencies are inferred from the claim text.