Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1994-09-08
1996-04-30
Rogers, Scott A.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
G09G 104
Patent
active
055128041
ABSTRACT:
A dynamic focus circuit of electromagnetic focusing type for a cathode ray tube of a video image displaying apparatus, is provided with a first oscillating circuit and a second oscillating circuit. The first oscillating circuit is provided with: an electric power source; a first switching device; and a capacitor, which are connected in series to form a loop, the first oscillating circuit being opened and closed by the first switching device. The second oscillating circuit is provided with: a second switching device; the capacitor, which is commonly used with the first oscillating circuit such that the first and second oscillating circuits are parallel with respect to the capacitor; and a focus coil for focusing an electron beam of the cathode ray tube, the second switching device, the capacitor and the focus coil being connected in series to form a loop, the second oscillating circuit being opened and closed by the second switching device. The first switching device opens and closes at a timing in correspondence with a blanking time period or a video image time period based on a horizontal scanning frequency of video image data of the video image displaying apparatus, to charge and discharge the capacitor. The second switching device opens and closes at a timing according to an inverse logic of the first switching device, to charge and discharge the capacitor.
REFERENCES:
patent: 3177396 (1962-04-01), Brooks
patent: 4460851 (1984-07-01), Bistline et al.
patent: 4644230 (1987-02-01), Federle
patent: 4795946 (1989-01-01), Nishiyama
patent: 5179322 (1993-01-01), Gibbs
patent: 5283505 (1994-02-01), Bando
patent: 5381079 (1995-01-01), Perreault
patent: 5455492 (1995-10-01), Turnbull
Grant II Jerome
Pioneer Electronic Corporation
Rogers Scott A.
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