Thomson Consumer Electronics Inc.

Thomson Licensing S.a.

Walter Truskalo

Ronald E Fernsler

Lawrence E Smith

Peter Ronald Knight

John Barrett George

Marvin N Norman

John Felix Shouse, Jr

A secondary winding of a horizontal flyback transformer of a horizontal deflection circuit develops a horizontal retrace pulse voltage. A secondary winding of a second transformer is coupled in series with a vertical deflection coil of a vertical deflection circuit. An R-C filter is coupled between the secondary winding of the flyback transformer and a primary winding of the second transformer. Horizontal parallelogram errors are corrected by a horizontal rate current injected in a current path of the vertical deflection coils. The R-C filter prevents the vertical deflection current from being parasiticaly coupled to the horizontal deflection circuit.

Deflection circuits coupled via a filter

An electron beam tends to slope downwardly as it is deflected horizontally to form a raster in a video display apparatus. The sloping of the beam can cause geometric errors in the raster, for example orthogonality and parallelogram errors. A raster correction circuit substantially offsets the downward slope of the electron beam by modulating a vertical deflection current with an induced horizontal-rate raster correction current, thereby substantially eliminating orthogonality and parallelogram errors in the raster. A raster correction transformer utilizes a raster centering inductor for a primary winding, and a horizontal-rate centering current is magnetically coupled into the vertical deflection coils to modulate the vertical deflection current.

Horizontal parallelogram correction combined with horizontal centering

In a horizontal deflection circuit output stage of a video display monitor capable of operating at multi-scan rates, a given S-capacitor, selected from a bank of S-capacitors, provide S-correction at a corresponding range of frequencies. A resistor-capacitor-diode clamp selected from a bank of clamps is coupled to the selected S-capacitor for reducing ringing by causing critical damping. The in-circuit selected resistor-capacitor-diode clamp is selectable, in accordance with the selected horizontal deflection frequency.

Selectable clampers for an S-shaping voltage of a video display

An electron beam tends to slope downwardly as it is deflected horizontally to form a raster in a video display apparatus. The sloping of the beam can cause geometric errors in the raster, for example orthogonality and parallelogram errors. A raster correction circuit substantially offsets the downward slope of the electron beam by modulating a vertical deflection current with an induced horizontal-rate raster correction current, thereby substantially eliminating orthogonality and parallelogram errors in the raster. In respective embodiments of an inventive arrangement taught herein, the horizontal-rate raster correction current is induced in the vertical deflection coils by magnetically coupling a filament pulse waveform, a horizontal deflection voltage waveform, or a horizontal deflection current into the vertical deflection coils.

Vertical deflection circuit with raster correction

Correction of linearity errors

An electron beam tends to slope downwardly as it is deflected horizontally to form a raster in a video display apparatus. The sloping of the beam can cause geometric errors in the raster, for example, orthogonality and parallelogram errors. A raster correction circuit offsets orthogonality and parallelogram errors in a raster by modulating a horizontal deflection current at a vertical scanning rate. The raster correction current is phased in relation to a horizontal-rate deflection current such that scan lines in an upper-half portion of the raster are shifted to the right, and scan lines in a lower-half portion of the raster are shifted to the left.

Horizontal deflection circuit with raster correction

A video display apparatus has a controllable, synchronized switch to control current conduction in an inductance. Responsive to a switching signal, a modulator switches the conductive states of the controllable switch. A signal generator is coupled to a source of retrace pulses, for generating at an output a horizontal rate sawtooth signal. The sawtooth signal comprising a first ramp of duration within the first half of the retrace pulse and a second ramp of duration equal to the trace interval. A source of a modulation signal is coupled to a means for generating the switching signal. Responsive to the modulation and sawtooth signals the means generates the switching signal having a first polarity which inhibits conduction in the switch and a second polarity which enables conduction in the switch. The first polarity of switching signal commences within the first half of the retrace interval and the second polarity commences within the remaining time of the horizontal interval.

Timing of deflection waveform correction circuit

A deflection waveform correction signal generator comprises a multiplying circuit for generating a pincushion correction signal. A horizontal frequency ramp is generated by a clipped retrace pulse. The ramp generator has an output coupled to an integrating circuit for generating a parabolic shaped signal. The ramp generator and ramp integrator are reset at a horizontal rate by reset pulses of differing duration. The different duration of reset pulses results in the parabolic signal having regions of non-parabolic shape. The parabolic shaped signal is coupled to an input of the multiplying circuit. A control circuit is coupled to the parabolic shaped signal for maintaining a peak amplitude thereof by controllable coupling to the ramp generator. A control loop is coupled to the integrator for controlling an integrator input bias current to generate the parabolic shaped signal at a predetermined time interval.

Deflection correction signal generator

In a horizontal deflection system, an nf.sub.H timing signal is generated synchronously with an f.sub.H horizontal synchronizing component in a video signal, where nf.sub.H is a higher frequency than f.sub.H. A first circuit is responsive to the nf.sub.H timing signal for generating an nf.sub.H scan synchronizing signal synchronously with the nfH timing signal. A horizontal deflection stage is operable at nf.sub.H and responsive to the nf.sub.H scan synchronizing signal. A second circuit is responsive to the same nf.sub.H timing signal for generating horizontal blanking pulses. The nf.sub.H timing signal can be generated by a first phase locked loop and a frequency divider. The first circuit responsive to the nf.sub.H timing signal can comprise a second phase locked loop. The second circuit responsive to the nfH timing signal can comprise a driver/inverter. The horizontal blanking pulses are combined with vertical blanking pulses to form a composite blanking signal.

Horizontal blanking

A horizontal rate parabolic voltage generator is responsive to a reset pulse at the horizontal rate for generating a horizontal rate parabolic voltage that includes a pulse in the vicinity of horizontal retrace. The parabolic voltage is coupled to an auxiliary coil mounted on a cathode ray tube to produce a vertical convergence error correction current. The pulse compensates for a slow response time in an amplifier that drives the auxiliary coil. A horizontal rate sawtooth voltage generator may also be responsive to the reset pulse for including a pulse component in its waveform.

Beam landing location error correction arrangement

A winding of a transformer is wound around a core bead that surrounds a wire conducting a horizontal deflection current. Close to a time when zero crossing occurs in the horizontal deflection current, at the center of horizontal trace, the core of the transformer changes from being saturated to being nonsaturated and a pulse is produced in the transformer. The pulse triggers a one-shot multivibrator arrangement that produces a reset pulse. A horizontal rate parabolic voltage generator is responsive to the reset pulse for generating a horizontal rate parabolic voltage that is coupled to an auxiliary coil mounted on a cathode ray tube to produce, for example, a vertical convergence error correction current.

Arrangement for correcting beam landing location error in a video display

An active amplifier is responsive to a vertical parabola voltage developed across a trace or S-shaping capacitor for developing a DC voltage at an increased voltage level than can be obtained by rectifying the parabola voltage. The increased voltage level is developed in a capacitor, during part of the period of each scan. The capacitor is discharged through a parallel resistor. During normal scanning, the capacitor voltage, alternately, increases and decreases, but remains above a threshold level as detected by a comparator. Upon scan loss, the capacitor discharges below the threshold and the comparator triggers blanking of the kinescope driver. In this way, the phosphors of a cathode ray tube of a television, especially a projection television, are protected from burning due to a loss of electron beam deflection.

Growing community of inventors

Indianapolis, IN, United States of America

Walter Truskalo