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US 4,047,078 AGranted
Pulse differentiating high voltage shutdown circuit
AssigneeZenith Radio Corporation
InventorDavid H. Meehan
Life of this patent
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AssigneeZenith Radio Corporation
InventorDavid H. Meehan
Estimating the term…
A television receiver includes a conventional tri-color cathode ray tube display system having horizontal and vertical scansion systems. Conventional signal receiving and processing circuitry recovers picture, sound and scansion synchronizing information. A high voltage detector includes a high pass filter, couples to the horizontal scansion amplifier, differentiating the horizontal retrace pulse to detect both amplitude and duration changes therein. A diode rectifies the derivative signal which is then filtered to produce a high voltage error signal. A PNP, NPN transistor pair configured to form a switch analogous to a silicon controlled rectifier responds to a detected excess of high voltage and loads down the operating supply to the horizontal scansion oscillator to terminate high voltage generation. The transistor pair accommodates a degenerating network to better reject false triggering.
In a television receiver having a cathode ray tube display device in which one or more electron beams are directed to a viewing screen, horizontal scansion means producing a scansion signal having a long duration trace portion and a short duration retrace portion causing said beams to scan said viewing screen from side-to-side, vertical scansion means causing a top-to-bottom progression of successive side-to-side scans and high voltage generating means producing an electron accelerating potential for said cathode ray tube from said short duration retrace portion of said horizontal scansion signal, the improvement comprising:
Dependencies are inferred from the claim text.