Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1992-10-29
1994-01-11
Issing, Gregory C.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
315387, G09G 104, H01J 2970
Patent
active
052784762
ABSTRACT:
One of the problems in display devices is that the black level is different for each type of display tube and is also dependent on temperature and ageing. The display devices hitherto known with black level setting circuits apply one control voltage to the relevant cathode during the field blanking interval, whereafter the cathode current is measured and subsequently compared with a reference current. Subsequently, the black level is adapted until the measured current approximately corresponds to the reference current.
The display device now includes a black level setting circuit with a control circuit adapted to successively apply at least two control voltages in a predetermined ratio to the cathode. Moreover, the black level setting circuit includes a correction circuit for supplying a correction value dependent on the ratio between the currents generated in the relevant cathode in response to the at least two control voltages.
REFERENCES:
patent: 4370674 (1983-01-01), Johnson et al.
patent: 4698557 (1987-10-01), Harlos
patent: 4705992 (1987-11-01), Ciocan
patent: 5107189 (1992-04-01), Page
De Bruijn Frederik J.
De Haan Willem J.
ten Pierick Hendrik
Teuling Dirk J. A.
Goodman Edward W.
Issing Gregory C.
U.S. Philips Corporation
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