Method for dimming a fluorescent lamp
US5955847A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 2, 1998 |
| Grant date | Sep 21, 1999 |
| Priority date | — |
| Expiry date | Mar 2, 2018 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S315/05
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The illumination intensity of a fluorescent lamp which has cathodes and an ionizable medium separating the cathodes is controlled by a method in which the lamp is ignited once during each half-cycle of applied AC current and is thereafter extinguished during that same half-cycle. The lamp is ignited by creating and applying an ignition voltage pulse of a magnitude greater than a characteristic operating voltage of the ionizable medium between the lamp cathodes. The lamp is extinguished by reducing the voltage between the cathodes to a value less than the operating voltage, at a point prior to a zero crossing of the applied AC current half-cycle in which the lamp was illuminated. Because the extinguishing point occurs prior to the end of the applied AC current half-cycle, the illumination intensity is reduced during each half cycle. The characteristics of the ignition pulse reliably ignite the lamp, thereby allowing extinguishing control on a half-cycle by half-cycle basis. The current which flows through the cathodes between the occurrence of the extinguishing point and the ignition point in each applied AC current half-cycle keeps the cathodes warm. The extinguishing point within …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.