Rca Inc.

Thomson Consumer Electronics Inc.

Rca Licensing Corporation

Nancy D Graves

Ronald E Fernsler

Enrique Rodriguez-Cavazos

James E Hicks

Chin Piao Huang

Terry W Bunton

John Chen

A parabola generator for geometric correction of a television raster, comprises: a resettable circuit for generating a repetitive ramp signal and a resettable integrator for generating a repetitive parabola signal from said repetitive ramp signal. A first resetting circuit initializes the ramp circuit at a frequency related to a scanning frequency. An auxiliary resetting circuit initializes the integrator prior to integrating each repetitive ramp. The auxiliary resetting circuit minimizes timing errors from variations of the ramp signal due to transient conditions. In one embodiment, the scanning period is a horizontal scanning period and the ramp and parabola circuits are reset at the end of each horizontal scanning interval. In this case, the first and auxiliary resetting circuits are responsive to horizontal retrace pulses, for example the leading edges of the horizontal retrace pulses. A further circuit modulates the periodically reset parabolic signal at a vertical scanning rate. In another embodiment, the scanning period is a vertical scanning period and the ramp and parabola circuits are reset at the end of each vertical scanning interval. In this case, the first and auxiliary resetting circuits are responsive to vertical retrace pulses, for example the leading edges of the vertical retrace pulses. A further circuit modulates the periodically reset parabolic signal at a horizontal scanning rate. The parabolic waveform is also reset responsive to a timing signal, rather than by allowing the mimimum level of the waveform to be defined only by uncontrolled operation of an integrator.

Parabola generators with auxiliary reset function

A circuit provides North-South pincushion correction and gullwing compensation in a raster display of a television apparatus. A correction circuit generates a generally parabolic, horizontal rate correction signal to correct for North-South pincushion distortion. A gullwing compensation circuit is coupled to the correction circuit and forms a feedback path therein for amplitude modifying the correction signal to further correct for gullwing distortion. The gullwing compensation circuit amplitude modifies the generally parabolic signal as a function of itself, achieving an equilibrium condition. A vertical deflection circuit drives a vertical deflection coil with the gullwing compensated correction signal. The correction circuit comprises a ramp waveform generator having a controllable current source generating a constant component of current for pincushion correction and a variable component of current responsive to the feedback signal for gullwing compensation. The variable component of current varies inversely to the feedback signal, which is coupled in the feedback path to the controllable current source through an inverting amplifier. The output of the inverting amplifier modulates the current supply to modify the resulting shape for the parabolic signal to compensate for gullwing distortion by increasing the slope of the parabola on both lateral sides.

Pincushion correction circuit with gullwing compensation

A switched mode power supply for a video apparatus having an electrically isolated chassis incorporates a switching FET that has its conduction interval controlled by pulses of varying frequency. An inductor is connected between the FET and hot ground to provide a low impedance path for line conducted interference signals generated by the switching of the FET and to provide a sufficient impedance path to prevent damage to the FET due to current flow caused by a high voltage discharge, such as a lighting strike to the cold ground referenced antenna.

Suppression circuit for video

A protection circuit for a video display apparatus causes shutdown to occur at substantially the same high voltage level for all fault conditions. The video display apparatus incorporates an SCR regulator and a high voltage transformer tuned to the third harmonic. To counter the effect of shutdown to occur at a higher voltage level for a shorted SCR fault than for other faults, the SCR anode control pulse is processed to provide a signal having different voltage levels for normal SCR operation and shorted SCR operation. The voltage level which occurs during a shorted SCR condition is selected to cause shutdown of the video display apparatus at substantially the same high voltage level as that for other fault conditions.

Growing community of inventors

Indianapolis, IN, United States of America

Nancy D Graves