Video circuit with screen-burn-in protection
AssigneeU.S. Philips Corporation
InventorsJean-Pierre Asmus, Joseph Soto, Sebastianus J. Op Het Veld, Henri W. Schneider
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Abstract
To prevent display screen burn-in of a picture having, for example, bright lines or other picture components remaining stationary for a long period of time, a video circuit is examined to detect how long the information has not been changed. If a predetermined time limit is exceeded, the picture brightness is limited to a sufficiently low average value or, if so desired, to zero brightness, by means of one or more protection switches.
Claims13
A video circuit for generating video signals for displaying pictures on a picture screen, the video circuit comprising a picture signal source for providing picture signals containing visual picture information, means for controlling said picture signal source coupled thereto, at least one luminance circuit coupled to said picture signal source for generating a luminance signal, and a protection circuit coupled to said luminance circuit for protecting the picture screen from burning-in due to a prolonged nonchanging picture, wherein the protection circuit comprises an electric protection switch, having a control input, for suppressing in a switched-off state the luminance signal generated in the video circuit, a detection circuit, having a output, for detecting changes in an electric control signal from said controlling means to the picture signal source, which changes in the control signal would be indicative of active use of said video circuit, and a timer circuit having a start input and an output, the output of the detection circuit being coupled to the start input of the timer circuit, the output of the timer circuit being coupled to the control input of the protection switch, whereby absent an output from said detection circuit, which output would be indicative of active use of said video circuit and which would reset said timer circuit, after a predetermined period of time, said timer circuit causes said protection switch to suppress the luminance signal.
A video circuit as claimed in any of the preceding claims, comprising a carrier oscillator, a modulation circuit, an auxiliary aerial input and an aerial change-over switch, for applying a video signal, modulated on a carrier to an aerial input of a television receiver, the aerial change-over switch coupling in a first switching state the aerial input to an output of the modulation circuit and in a second switching state to the auxiliary aerial input, characterized in that the aerial change-over switch is coupled to the protection switch which in a switched-on state adjusts the aerial change-over switch to the first switching state and in a switched-off state adjusts the aerial change-over switch to the second switching state.
Dependencies are inferred from the claim text.