Thomson Consumer Electronics Inc.

Thomson Licensing S.a.

Thomson Licensing

David Ross Jackson

Joseph C Stephens

Kenneth J Helfrich

Kevin Michael Williams

Dal Frank Griepentrog

Robert Joseph Gries

Leroy W Nero

Angela Renee Burnett

Charles Hardinge

Robert Goah Watson, Iii

Michael Maiorano

Snehali Choksi

Method for preventing a high voltage circuit form generating excessive high voltage, wherein the method comprises the following steps:

Method for preventing the generation of excessive high voltage

A video display includes a scanner operable at a first frequency and a higher second frequency. A switch mode power supply drives a transformer with three secondaries. First and second rectifiers & filters are associated with the first and second secondaries. A rectifier is coupled to the third secondary and by way of a switch to the first filter. Feedback from the first filter controls the SMPS. In a first operating mode, the scanner is operated at the first frequency, the switch is open, the scanner supply is a first voltage from the first filter, and ancillary equipment is supplied with a third voltage by the second filter. In a second operating mode, the scanner is operated at the second frequency, the switch is closed, the scanner supply is a second voltage, higher than the first, from the first filter, and ancillary equipment is supplied with the same third voltage.

Deflection supply voltage feedback control in conjunction with frequency change

An apparatus and a method for protecting a video display device, having an anode and a cathode, against excessive beam current conditions. In particular, the present invention protects the video display device against zero-biasing of the device, wherein the cathode driver circuit is supplied by a plurality of power supplies and the loss of anyone of the power supplies causes zero-biasing of the cathode. The invention provides, in a video display device () having an anode () and a cathode () for generating and controlling beam currents in the display device, a protection circuit comprising: a source of video signals (); a driver circuit () coupled to the source of video signals and the cathode (), the driver circuit coupled to a driver circuit power supply (+12V,+215V), the driver circuit causing a cathode voltage to be generated on the cathode in response to the video signals and the driver circuit power supply; a high voltage power supply (X) coupled to the anode () for providing high voltage accelerating potential in the display device; and a shutdown circuit () coupled to the driver circuit power supply and the high voltage power supply, the shutdown circuit disabling the high voltage power supply if the driver circuit power supply voltage decreases below a threshold level.

Video display protection circuit

A power supply for a video display tube includes a deflection transformer with a primary winding powered with a scan voltage which has a first value when displaying signal according to a first video standard and a second voltage when displaying video according to a second standard. A secondary winding of the transformer produces filament voltage for the display tube. A variable coupler couples the filament voltage to the filament of the picture tube in an amount established by a control signal. A memory produces a first control signal in response to the first scan voltage and a second control signal in response to the second scan voltage. The first and second control signals are selected so that the voltage coupled from the transformer to the filament is the same at both scan voltages.

Cathode ray tube filament voltage control with a multifrequency deflection scanner

A frequency compensation circuit influences an X-radiation protection (XRP) circuit in a high voltage regulator circuit for a cathode ray tube (CRT) to operate properly under varying frequencies of voltage energizing a high voltage transformer. The frequency compensation circuit includes an input to a source of first voltage related to a high voltage output of the high voltage regulator circuit, a voltage source generator responsive to a high voltage generator frequency of the CRT. A voltage controlled circuit is responsive to the voltage source generator for controlling conveyance of the first voltage to the XRP circuit so that a relatively constant proportion of the high voltage output is reported to the XRP circuit under varying high voltage generator frequencies.

Frequency dependent X-ray protection for a multimedia monitor

A high-voltage power supply of a video display apparatus provides an ultor voltage and a focus voltage to a cathode ray tube. A low-voltage power supply provides a variable voltage to a primary winding of a flyback transformer of the high-voltage power supply. The magnitude of the variable voltage is responsive to first and second feedback signals provided by first and second negative feedback paths. The first feedback signal is derived from the ultor voltage and is used to regulate the ultor voltage. The second feedback signal is provided by the low-voltage power supply via a path that bypasses the high-voltage power supply, and is summed with the first feedback signal to ensure that the focus voltage remains at or above a predetermined minimum voltage.

High-voltage power supply for video display apparatus

A deflection apparatus comprises a deflection amplifier coupled to a deflection waveform modulation circuit such as a diode modulator. A source for generating a modulation signal. The modulation signal comprises a symmetrical periodic AC component having equal first and second portions of a trace period. A feedback amplifier alters the amplitude of a first portion of the trace period relative to a second portion of the trace period to render the AC component asymmetrical. The asymmetrical AC component is coupled to the deflection waveform modulation circuit for deflection waveform modulation.

Deflection waveform correction circuit

A deflection apparatus comprises a deflection amplifier coupled to a deflection waveform modulation circuit such as a diode modulator. An East-West modulation signal is generated by a digital to analog convertor in accordance with a reference potential coupled thereto. The modulation signal has a DC component for width control, and is coupled to an input of a comparator. The reference potential is also coupled to an input of the comparator to establish a reference bias therefor. The comparator has an output coupled to the deflection waveform modulation circuit to provide the East-West modulation.

Horizontal deflection waveform correction circuit

A deflection apparatus comprises a deflection amplifier coupled to a deflection waveform modulation circuit such as a diode modulator. A source for generating a modulation signal. The modulation signal comprises an AC component and a DC component, each having levels which define an amplitude ratio. An amplifier alters the amplitude ratio, and the altered amplitude ratio signal is coupled to the deflection waveform modulation circuit for deflection waveform modulation.

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. A horizontal deflection driving circuit is coupled to a horizontal deflection coil and provides deflection current to the horizontal deflection coil for scanning the beam repetitively on the screen. The focusing coil is driven from a current step-down transformer having a primary winding coupled in series with the horizontal deflection coil. A secondary winding of the transformer is coupled to the focusing coil for driving the focusing coil with a horizontal rate parabolic current. A capacitor-resistor circuit is coupled in parallel with the focusing coil and with the secondary winding of the transformer for adjusting a phase relationship of the parabolic current relative to the horizontal deflection current and for adjusting the amplitude of the parabolic current.

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Indianapolis, IN, United States of America

David Ross Jackson