Thomson Consumer Electronics Inc.

Thomson Licensing

Joseph C Stephens

James A Wilber

Kenneth J Helfrich

David Ross Jackson

Enrique Rodriguez-Cavazos

Lawrence E Smith

Kenneth Jay Helfrich

Michael E Boyer

Brian Lee

Kevin E McClain

A magnetic field compensation winding arrangement for a cathode ray tube includes a magnetic field compensation winding positioned on the cathode ray tube to compensate for an ambient magnetic field. An operational amplifier is used for generating a magnetic field compensation current in the winding. A pair of digital-to-analog converters are used for generating a pair of signals, respectively, that are coupled to the amplifier to control the magnetic field compensation current.

Auxiliary coil driver circuit for a cathode ray tube

A switching circuit for a television set is coupled to the television microprocessor and associated power supply on one end, and to the standby power supply portion of a T-chip on the other end. The T-chip is not powered during the 'off' times of the television thus reducing the power consumption of the circuit. The switching circuit operates to enable the standby power supply of the T-chip upon receipt by the microprocessor of an 'on' command after which the T-chip will enable the horizontal drive circuits upon the receipt of a further 'on' command.

Standby circuit for a television

A bus controlled pulse modulator receives a digitally coded signal and generates a pulse-width modulated signal. The pulse-width modulated signal is coupled to a base electrode of a non-committed or open collector transistor. The transistor switches with a controlled duty cycle. The collector of the transistor is coupled to an inverting input terminal of an amplifier via a resistor. The amplifier produces a compensation current in a tilt compensation coil. The voltage at the inverting input terminal is maintained constant in closed loop operation. The constant voltage produces a magnitude of a collector current in the transistor that is unaffected by the duty cycle of the pulse-width modulated signal. The compensation current thereby varies linearly with the duty cycle.

Bus controlled arrangement using a duty cycle modulated control signal

A free running frequency alignment method in a video display having a sync generator comprising a first oscillator having a first frequency and a second oscillator having a second frequency. The first oscillator is phase modulated by the second oscillator which has a free running frequency different from a standard frequency. The free running frequency of the first oscillator is to be controllably aligned to the standard frequency by a method comprising the steps of applying a frequency determining initial control value to the first oscillator and measuring an average free running frequency responsive to the initial control value. An absolute difference frequency is calculated between the average frequency and the standard frequency. The absolute difference frequency is tested for a frequency value less than a predetermined value which signifies an aligned condition. If the difference frequency is less than the predetermined value the alignment is complete. If the difference frequency is greater than the predetermined value the alignment is continued and a new control value is generated responsive to the difference. The new control value is applied to the first oscillator and the steps of average frequency measurement, absolute difference frequency calculation and difference frequency value testing are repeated until alignment is achieved. Upon failure of the difference frequency test, a counter is incremented and the count examined to determine if a predetermined number of alignment attempts have been exceeded. Upon exceeding the predetermined number the alignment is determined to have failed and the alignment is ended.

Oscillator free run frequency setting by data bus control

A video display has microcomputer control via a data bus and comprises a first sync generator coupled to the data bus for control by data thereon. A second sync generator is without controllable coupling to the data bus. A deflection amplifier is coupled to a deflection coil for generating a deflection current therein. A circuit for controlling the second sync generator is coupled to the first sync generator and is responsive to a digitally controlled signal therefrom. The second generator output signal is coupled to the deflection amplifier for deflection generation responsive to the digitally controlled signal.

video display device employing two SYNC generators

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.

Deflection waveform correction circuit

An input signal at a horizontal frequency is coupled to a deflection circuit through an isolation transformer during a power-on operation but not during a power-off operation. A voltage at a horizontal deflection frequency is developed in a linearity inductor of the deflection circuit. The voltage in the linearity inductor is rectified to produce a rectified signal that is coupled to an input terminal of a regulator oscillator of a power supply. The rectified signal is coupled to the regulator oscillator in an electrically nonisolated manner with respect to electrical shock hazard isolation and is electrically isolated by the transformer from the input signal. The regulator oscillator generates trigger pulses for controlling the switching operation of an SCR switch of the power supply to produce an output supply voltage that energizes the deflection circuit. The regulator oscillator is energized during both power-up and power-off operation and is responsive to the rectified signal to cause the duty cycle of an output signal of the oscillator to increase during power-off operation. The increased duty cycle causes the anode-to-cathode voltage of the SCR switch to be small enough to prevent latching of the SCR switch during the power-off operation. By preventing SCR switch latching, audible parasitic vibrations in the power supply are avoided.

Voltage regulator in a television apparatus

A horizontal deflection circuit includes a flyback transformer. A secondary winding of the flyback transformer is coupled in series with a diode switch to produce a trace rectified supply voltage that energizes a vertical deflection amplifier. The diode switch also provides switching operation in an East-West diode modulator. During, for example, service mode operation, when the vertical raster is collapsed, the trace current in the secondary winding is substantially reduced. The reduced trace current is sensed for producing a control signal that causes the peak current supplied by the diode switch to the diode modulator to be smaller than the trace current in the secondary winding. This ensures that the diode switch remains conductive throughout horizontal trace, thereby, preventing an undesirable increase in the supply voltage from occuring.

Power supply protection circuit

A switch regulator includes a controllable SCR switch that is coupled in series with a filter inductor and a horizontal deflection generator, and the series combination is coupled across a source of unregulated direct voltage for providing a path for an increasing current flow in the inductor during a portion of a trace interval in which the switch is closed. Horizontal rate signals are coupled from the deflection generator to the switch via a first winding for controlling the opening of the switch. A catch diode is coupled to the filter inductor to form a path for a decreasing current flow in the first inductor during at least a portion of a retrace interval. The first winding is coupled in series with a second inductor to form an arrangement that is coupled between the unregulated voltage and the SCR switch. A current in the second inductor maintains the switch conductive during a portion of retrace that varies in accordance with a beam current for improving regulation of an ultor voltage.

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Fishers, IN, United States of America

Joseph C Stephens