Adjustable pincushion correction circuit
AssigneeWarwick Electronics Inc.
InventorRichard L. Wilocki
Life of this patent
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Abstract
In a television receiver, a saturable transformer has three windings, one being in series with a horizontal deflection coil to introduce a parabolic reactance variation to correct for side pincushion distortion. An adjustable correction circuit includes a transistor integrator for producing in another winding of the saturable transformer a vertical parabolic current. The last winding of the saturable transformer is coupled through a pair of switching diodes to a pair of variable inductors. The diodes conduct alternately at the beginning and end of the vertical scanning period. The variable inductors may be mounted coaxially with a common movable core to allow inverse side correction, or may be mounted separately with separate movable cores to allow independent side correction.
Claims12
In a television receiver having first and second deflection coils for generating a raster, a first sweep circuit for supplying a first sweep signal for the first deflection coil, and a second sweep circuit for supplying a second sweep signal for the second deflection coil, a pincushion correction circuit, comprising:
- a saturable transformer having a saturable magnetic core, a first winding means wound on the saturable core, and a second winding means wound on the saturable core;
- a deflection circuit coupling the first sweep circuit to the first deflection coil through the first winding of the saturable transformer to pass a corrected first sweep signal to the first deflection coil;
- an adjustable correction means for modulating the first sweep signal with a pincushion correction signal derived from the second sweep signal to develop the corrected first sweep signal, including
- drive means coupled to the second sweep circuit for causing correction current to flow in the second winding means of the saturable transformer,
- first and second diodes,
- first and second variable inductors,
- third winding means wound on the saturable core,
- a first circuit connecting the first diode and the first variable inductor to the third winding means for passing current during a start portion of the second sweep signal and with a variable magnitude controllable by the first variable inductor, and
- a second circuit connecting the second diode and the second variable inductor to the third winding means for passing current during an end portion of the second sweep signal and with a variable magnitude controllable by the second variable inductor, whereby the current in said second and third windings means provides separately controllable pincushion correction at the sides of the raster.
In a television receiver having first and second deflection coils for generating a raster, a first sweep circuit for supplying a first sawtooth signal for the first deflection coil, and a second sweep circuit for supplying a second sawtooth signal for the second deflection coil, a pincushion correction circuit, comprising:
- a saturable transformer having a saturable core and a first winding, a control winding and an equalizing winding each wound on the saturable core;
- deflection means coupling the first sweep circuit to the first deflection coil through the first winding to pass a first sawtooth signal modulated with a generally parabolic correction signal having a rate corresponding to the second sawtooth signal;
- adjustable correction means for modulating the first sawtooth signal with the generally parabolic correction signal derived from the second sawtooth signal, including
- an integrator coupled between the second sweep circuit and the control winding for causing a parabolic current to flow at a rate corresponding to the second sawtooth signal,
- a diode,
- a variable inductor, and
- circuit means connecting the diode and the variable inductor across the equalizing winding with the diode being poled to pass a portion of the parabolic correction current with an amplitude controlled by the variable inductor.
Dependencies are inferred from the claim text.