Rca Inc.

Thomson Consumer Electronics Inc.

Thomson Licensing S.a.

Peter Ronald Knight

Lawrence E Smith

Walter Truskalo

James A Wilber

Ronald E Fernsler

Marvin N Norman

Synchronization of a horizontal deflection circuit with horizontal synchronizing signal pulses is obtained by the use of a voltage controlled oscillator (VCO) that is included in a phase-lock loop circuit (PLL). A phase-control loop circuit (PCL) includes a phase detector having a first input terminal that is responsive to an output signal of the VCO and a second input terminal that is responsive to retrace pulses of a horizontal deflection circuit output stage. A sum signal of the phase detector output signal of the PLL and a vertical rate parabola signal is formed upstream of the loop filter of the PLL. Correction of a differential pin distortion is accomplished by dynamically phase shifting the phase of an output signal of the VCO in a vertical rate parabola manner.

Raster distortion correction arrangement

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

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 projection television receiver has a cathode ray tube with an electron gun for emitting an electron beam incident on a screen, an electromagnetic deflection yoke and an electromagnetic focusing coil. The focusing coil is included in a resonant circuit. The resonant circuit is energized by switching operation of a switching transistor in the vicinity of a retrace interval. Variations of the focusing coil current in the vicinity of the retrace interval provide dynamic focus.

Focus coil current generator for a cathode ray tube

A voltage at a control grid of a cathode ray tube is generated at a blanking level to provide beam current blanking when horizontal deflection loss occurs. The control grid voltage at the blanking level is developed in a capacitor prior to an instant in which the horizontal deflection loss occurs. When the capacitor voltage is applied to the control grid to provide the blanking level, the capacitor is discharged slowly. To maintain the capacitor charged, prior to such instant when horizontal deflection is lost, the capacitor voltage is not applied to the control grid as long as the horizontal deflection is normal, regardless of whether vertical deflection loss occurs. Either horizontal deflection loss or vertical deflection loss will disable a video driver stage that controls the cathode of the cathode ray tube for providing additional beam current blanking capability.

Projection TV deflection loss protection circuit

A side pincushion corrected deflection circuit for a television receiver includes a deflection winding, a trace capacitor and a first switch for generating scanning current in the deflection winding. A modulator circuit includes a modulator inductor and capacitor and a second switch for generating a sawtooth modulator current in the inductor. The trace and modulator capacitors are charged from a B+ operating voltage source through the primary winding of a flyback transformer. A transistor stage in the modulator circuit shunts current away from the modulator capacitor to control the modulator and trace capacitor voltages. A vertical rate bias voltage is applied to the transistor stage and varies the shunt current at a vertical rate in a parabolic manner to provide side pincushion correction. Under fault conditions, such as an open-circuited deflection winding or trace capacitor, the modulator capacitor voltage tends to undesirably increase above the peak voltage developed under normal operating conditions. To prevent overstressing the modulator transistor stage, a diode clamp is coupled between the modulator capacitor and a source of reference voltage, thereby preventing the modulator capacitor voltage from substantially exceeding the reference voltage level.

Side pincushion modulator circuit with overstress protection

The retrace pulse voltage developed across a television receiver flyback transformer winding is rectified and filtered to develop a voltage representative of picture tube ultor voltage. This representative voltage is applied to an input terminal of a comparator. A beam current representative voltage, obtainable, for example, at the input of a beam limiter circuit, is applied to a filter. The filter output voltage, which is the time integration voltage of the beam current representative voltage, is applied to another input terminal of the comparator. The comparator develops a disabling signal that is utilized to disable normal television operation when the ultor voltage exceeds a magnitude which differs with different values of the filter output voltage. The beam current information from the filter output increases the comparator sensitivity to ultor voltage increases at the higher beam current levels where greater amounts of X-radiation may be produced while avoiding unnecessary disabling of television operation at the lower beam current levels where greater increases in ultor voltage may be tolerated. The time constant associated with the filter is relatively short for relatively light beam current loading conditions and is changed to a relatively long time constant value under severe beam current loading conditions in order to ascertain whether a permanent current overload condition exists that requires disabling of the television receiver.

Television receiver high voltage protection circuit

A horizontal deflection generator includes the series arrangement of a horizontal deflection winding and a trace capacitor, a retrace capacitor, and a horizontal trace switch. The trace switch comprises a damper diode and a horizontal output transistor. Base drive for the horizonal output transistor is provided by a horizontal driver stage through a driver transformer. A secondary winding of a flyback transformer is coupled to a high impedance cascade rectifier arrangement to form a DC supply which provides collector supply voltage for the driver stage. The DC supply has a relatively large source impedance to changes in the load current being drawn from the supply by the driver stage. Such a large impedance is desirable in order to limit the base driver to the horizontal output transistor during picture tube arc-over and to allow for duty cycle tolerances in the horizontal oscillator output.

Horizontal deflection generator and driver circuit

A side pincushion corrected deflection circuit for a television receiver includes a deflection winding, a trace capacitor and a first switch for generating scanning current in the deflection winding. A modulator circuit includes a modulator inductor, a modulator capacitance and a second switch for generating a sawtooth modulator current in the inductor. The trace and modulator capacitors are charged from a voltage source through a flyback transformer winding. Reflected load currents from other television receiver circuits also flow in the flyback transformer winding. A transistor stage in the modulator circuit shunts current away from the modulator capacitor to control the modulator and trace capacitor voltages. A vertical rate bias voltage is applied to the transistor stage and varies the shunt current at the vertical rate to provide side pincushion correction. The transistor stage is operated in an open loop manner with no voltage feedback of the modulator capacitor voltage. An additional bias voltage, representative of the load current flowing in the flyback transformer, is applied to the transistor stage in order to reduce undesirable load current modulation of the side pincushion correction.

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Indianapolis, IN, United States of America

Peter Ronald Knight