Fluoresent lamp current level controller
US5367223A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 14, 1993 |
| Grant date | Nov 22, 1994 |
| Priority date | — |
| Expiry date | Oct 14, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S315/07
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for automatically adjusting the light intensity output of a fluorescent lamp of a document scanner. The fluorescent lamp current level control apparatus comprises preheating circuitry for applying low voltage pulses of alternating polarity across filaments of the lamp, the low voltage pulses sufficient to preheat the filaments but insufficient to cause the lamp to fluoresce; high voltage circuitry for applying high voltage pulses of alternating polarity across the lamp, the high voltage pulses sufficient to cause the lamp to fluoresce; and control circuitry for receiving a first signal (PWM (D)) indicative of a desired level of current in the filaments, sensing a current indicative of the actual level of current in the filaments, and controlling the high voltage circuitry to cause the actual level of current to tend toward the desired level of current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.