Arrangement for generating a beam current indicative signal
AssigneeThomson Consumer Electronics, Inc.
InventorJames A. Wilber
Life of this patent
Estimating the term…
Abstract
In a vertical deflection circuit, a vertical deflection current is controlled by a vertical sawtooth signal. A transistor generates a first control signal that is derived by sensing the beam current. The control signal is used for modulating the vertical sawtooth signal to compensate for a tendency of the raster height on a screen of a cathode ray tube to increase when the ultor voltage decreases. The transistor also clamps a second control signal that is indicative of the beam current to a predetermined level when the beam current is smaller than a predetermined value. The second control signal is coupled to an automatic beam current limiter.
Claims13
A video display deflection apparatus for controlling a raster on a screen of a cathode ray tube, comprising:
- a flyback transformer having a high voltage winding that is coupled to an ultor electrode of said cathode ray tube;
- means coupled to said transformer for generating high voltage pulses in said high voltage winding to produce an ultor voltage and a beam current;
- an impedance coupled in a current path that includes said high voltage winding for generating a first beam current indicative signal in accordance with a current in said high voltage winding, said beam current indicative signal being coupled to a beam current limiter for limiting excessive beam current;
- means responsive to said beam current for generating a clamping signal that varies in accordance with said beam current and that is coupled to said impedance in a manner to clamp said beam current indicative signal when said beam current is within a first range of values;
- and
- a deflection circuit responsive to said clamping signal for generating a deflection current that is modulated in accordance therewith in a manner to control said raster.
A video display deflection apparatus for controlling a raster on a screen of a cathode ray tube, comprising:
- a flyback transformer having a high voltage winding that is coupled to an ultor electrode of said cathode ray tube;
- means coupled to said transformer for generating high voltage pulses in said high voltage winding to produce an ultor voltage and a beam current;
- an impedance coupled in a current path that includes said high voltage winding for generating a first beam current indicative signal in accordance with a current in said high voltage winding, said beam current indicative signal being coupled to a beam current limiter for limiting excessive beam current;
- a transistor having a first terminal that is coupled to said impedance for clamping said beam current indicative signal when said beam current is smaller than a first threshold current level, said transistor having a second terminal for producing at said second terminal a second beam current indicative signal that varies in accordance with said beam current;
- and
- a deflection circuit responsive to said second beam current indicative signal for generating a deflection current that is modulated in accordance therewith in a manner to control said raster when said beam current varies.
Dependencies are inferred from the claim text.