Circuit for producing a dynamic focusing voltage in a television set
AssigneeDeutsche Thomson-Brandt GmbH
InventorAchim Elgert
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Abstract
A circuit for generating a dynamic focusing voltage in a television receiver utilizing overscan periods includes a focusing voltage generator. The focusing voltage is compared to a reference voltage and a switching signal is provided when the focusing voltage goes below the reference voltage. A switch is responsive to the switching signal and provides a direct focusing voltage during the overscan periods. The direct focusing voltage has a level which maintains the arithmetic mean of the focusing voltage the same during the normal scan period and the overscan periods.
Claims5
A circuit for generating a dynamic focusing voltage in a television receiver having a tube utilizing overscan periods comprising:
- means for generating a focusing voltage;
- means for applying said focusing voltage to said tube during a normal scan period and during overscan periods;
- means for comparing said focusing voltage and a reference voltage and providing a switching signal when said focusing voltage goes below said reference voltage;
- switch means responsive to said switching signal for applying a direct focusing voltage to said tube during said overscan periods, said direct focusing voltage having a level which maintains the arithmetic mean of said focusing voltage the same during said normal scan period and said overscan periods.
A method of generating a dynamic focusing voltage for a television receiver including a tube which overscans an electron beam, comprising the steps of:
- deflecting said electron beam to trace a line of a visible display across the screen of the tube during a normal scan period between overscan periods;
- and
- applying a direct focusing voltage during said overscan periods, said direct focusing voltage having a level which maintains the arithmetic mean of the focusing voltage constant for said normal scan period and said overscan periods.
Dependencies are inferred from the claim text.