Electric lamp and discharge devices: systems – With radiant energy sensitive control means – Radiant energy controlled regulation of the current supply...
Patent
1987-08-06
1989-09-19
Groody, James J.
Electric lamp and discharge devices: systems
With radiant energy sensitive control means
Radiant energy controlled regulation of the current supply...
315308, 315309, 315 77, 350345, H05B 3904, H05B 3909, G09G 300
Patent
active
048684597
ABSTRACT:
In order to provide brightness-dependent control of a lamp which is used for illuminating a LCD display, it is known to switch the lamp on and off in dependence on the measured brightness of the incident ambient light. To prevent overheating of the liquid crystal display when it is, for example, exposed to direct sunlight, the operating voltage for the lamp is changed in dependence on the measured brightness of the incident ambient light. A further improvement is accomplished when, additionally, in dependence on the ambient temperature measured, the operating voltage for the lamp changes, more specifically the operating voltage is switched off when a presettable threshold value is exceeded. The circuit arrangement for performing the method requires very little design effort and cost and is integrable to a very large degree.
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Dennerlein Ludwig
Walters Eckhard
Franzblau Bernard
Groody James J.
Powell Mark R.
U.S. Philips Corporation
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