Ballast for one or more fluorescent lamps including threshold sensitive filament voltage preheating circuitry
US5583399A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 27, 1995 |
| Grant date | Dec 10, 1996 |
| Priority date | — |
| Expiry date | Jul 27, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/295
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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 …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.