US 5,856,730 AGranted

Scan loss detector

AssigneeThomson Consumer Electronics, Inc.

InventorJohn Barrett George

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Abstract

A display system includes a kinescope. A horizontal scan detector is coupled to a source of a horizontal scan current signal and detects a loss of horizontal scanning. In addition, a vertical scan detector is coupled to a source of a vertical scan current signal including a feedback path and detects a loss of vertical scanning. A vertical feedback detector is also coupled to the vertical scan current signal source, and detects a failure of the feedback path in the vertical scan current signal source. A controllable kinescope driver circuit, coupled to the kinescope, the horizontal scan detector, the vertical scan detector and the vertical feedback detector, blanks the kinescope if the horizontal scan detector detects a loss of horizontal scanning, the vertical scan detector detects a loss of vertical scanning or the vertical feedback detector detects a failure of the feedback path.

Claims8

Dependent claims

A video display apparatus, comprising:

a deflection amplifier responsive to an input signal at a frequency related to a deflection frequency for generating an output voltage coupled to a deflection winding to produce a deflection current that is capable of producing an electron beam in a cathode ray tube;
a protection circuit responsive to a first scan loss indicative signal for disabling a corresponding stage when said first scan loss indicative signal is generated;
and
a first scan loss detector comprising a differential amplifier having a pair of input terminals coupled to a pair of terminals of a current sensing resistance that is coupled in a current path of said deflection current for generating said first scan loss indicative signal when a difference between signals developed in said pair of terminals is indicative that a magnitude of said deflection current is outside a normal operation range, said differential amplifier providing common mode rejection with respect to the signals that are developed in said pair of terminals of said current sensing resistance.

1 more element

Dependencies are inferred from the claim text.