US 4,677,350 AGranted

Raster width correction apparatus for multi scan frequency monitors

AssigneeRCA Corporation

InventorsJames H. Wharton, Lawrence E. Smith

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Abstract

In a deflection circuit that operates in any scan frequency selected from a plurality of frequencies, the supply voltage that is DC-coupled to a first terminal of a trace capacitor is increased when the scan frequency increases. The deflection circuit includes a diode modulator that is controlled by a modulation voltage having an AC component voltage that varies at a vertical rate. The increase in the supply voltage causes an increase in a DC component voltage of the modulation voltage that is coupled to a second terminal of the trace capacitor such that the voltage in the trace capacitor increases in the same proportion as the supply voltage. The proportional increase in the trace capacitor voltage maintains the raster width unchanged when the scan frequency increases.

Claims21

Dependent claims

A deflection apparatus for generating a deflection current in a deflection winding, said apparatus being capable of generating said deflection current at any frequency selected from a plurality of frequencies such that the width of a raster formed by said deflection current is maintained unchanged at the selected frequency, comprising:

a source of an input signal at a frequency that is related to the selected frequency;
a source of a supply voltage;
means coupled to said source for varying said supply voltage to have a level that is different at correspondingly different selected scan frequencies;
a deflection winding;
swithching means coupled to said supply voltage and responsive to said input signal for generating said deflection current in said deflection winding;
first and second retrace capacitance coupled in series across a pair of main current conducting terminals of said switching means for developing corresponding first and second retrace voltages;
a modulation inductance having a terminal that is coupled at a junction between said first and second retrace capacitance;
a source of modulating voltage coupled via said modulation inductance to said terminal of said inductance to provide East-West pincushion correction;
and
means responsive to said supply voltage for coupling to said terminal of said inductance, via said modulation inductance, a correction voltage representative of said level of said supply voltage such that varying said supply voltage causes said correction voltage also to vary in a manner that maintains the raster width the same at the different selected frequencies.

7 more elements

A deflection apparatus for generating a deflection current in a deflection winding at any frequency selected from a plurality of frequencies such that at a given selected scan frequency said deflection current is capable of forming a raster having a predetermined characteristic that tends to change with scan frequency, comprising:

a source of an input signal at a frequency that is related to the selected scan frequency;
a deflection winding;
a deflection circuit responsive to said input signal and coupled to said deflection winding for producing in said deflection winding said deflection current at the selected scan frequency;
a source of a supply voltage coupled to said deflection circuit and having a level that, in accordance with said frequency of said input signal, is different at correspondingly different selected scan frequencies, such that a change in said supply voltage caused by a change in the selected scan frequency tends to reduce a variation in said predetermined characteristic of said raster that is caused by said change in the selected scan frequency;
and
means responsive to said supply voltage for generating in accordance with said level of said supply voltage a raster control voltage having a level that is different at said correspondingly different scan frequencies, such that a change in said raster control voltage is caused by said change in the selected scan frequency, said raster control voltage being coupled to said deflection circuit to develop in said deflection circuit a deflection current control voltage that is related to the difference between said supply and raster control voltages, such that a change in said level of said supply voltage, that defines a first proportional change relative to said supply voltage, and that is caused by said change in the selected scan frequency, causes a concurrent change in said deflection current control voltage that defines a second proportional change relative to said deflection control voltage, wherein said change in said raster control voltage causes said second proportional change to be closer to said first proportional change absent said change in said raster control voltage for further reducing said variation in said predetermined characteristic of said raster.

3 more elements

Dependencies are inferred from the claim text.