Using pulse density modulation for controlling dimmable electronic lighting ballasts
US7642735B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 5, 2006 |
| Grant date | Jan 5, 2010 |
| Priority date | — |
| Expiry date | Sep 15, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/3921
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Pulse Density Modulation (PDM) is used to control the amount of light from a fluorescent lamp by applying a voltage to the lamp filaments at a low frequency that is approximately at a series resonant frequency of the lamp ballast inductor and the lamp filament capacitor, no voltage and a voltage at a high frequency. The lamp gas ionizes to produce light only when the low frequency voltage is applied. The fluorescent lamp gas does not ionize when the voltage at the high frequency is applied, but the high frequency voltage keeps the lamp filaments warm during low light output conditions. The low frequency, no and high frequency voltages have time periods that occur within a modulation frame time period that repeats continuously. The ratio of the low frequency voltage time period, and the no voltage and/or high frequency voltage time periods determine the light output of the fluorescent lamp.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.