Ballast for one or more fluorescent lamps including threshold se

Details Ballast for one or more fluorescent lamps including threshold se Ballast for one or more fluorescent lamps including threshold se

1995-07-27

1996-12-10

Pascal, Robert

Electric lamp and discharge devices: systems

Current and/or voltage regulation

315225, 315107, 315106, H05B 3702

Patent

active

055833993

ABSTRACT:
To control preheating current flow through a fluorescent lamp supplied from high-frequency inverter (T1, T2, A) and a series resonance circuit, an electronic switching control circuit (SC) is connected to the preheating circuit of at least one electrode filament (E1, E2, E10, E20, E11, E21, E12, E22) of one or more of the fluorescent lamps. The switching control circuit senses the voltage across the pair of terminals (T1, T1', T2, T2') of the electrode filaments, or across all the electrode filaments. Since fluorescent lamp filaments have a positive temperature coefficient of resistance, the voltage across the filaments will rise as the filament or filaments of the lamp reach electron emission temperature. This rise in voltage is sensed, for example, by a threshold circuit which may include a Zener diode, and is used to break the preheating circuit. The preheating circuit is connected in-parallel to a series resistance circuit which, during the preheating phase, is highly damped; upon interruption of the preheating circuit, the quality of the series resistance circuit becomes high, providing ignition voltage to the fluorescent lamp or lamps. As an alternative, a timing circuit may be connected across the filament to open the preheating circuit after a predetermined time interval and/or severed voltage level, the timing circuit being reset immediately upon de-energization of the lamp.

REFERENCES:
patent: 4165475 (1979-08-01), Pegg et al.
patent: 4253043 (1981-02-01), Chermin et al.
patent: 4588924 (1986-05-01), Luursema et al.
patent: 4766390 (1988-08-01), Wharton et al.
patent: 4949013 (1990-08-01), Zuchtriegel
patent: 4949015 (1990-08-01), Nilssen
patent: 5122712 (1992-06-01), Hirschmann
patent: 5179326 (1993-01-01), Nilssen

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