Circuit for controlling an indicator light to turn off slowly
US5644194A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 17, 1995 |
| Grant date | Jul 1, 1997 |
| Priority date | — |
| Expiry date | Jul 17, 2015 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/30
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A circuit for turning off an indicator light operates in two phases that provide a first rapid discharge phase and a second slow discharge phase. This sequence dims the light in a visual approximation of the exponential dimming that occurs with lights that operate with power supplies that have capacitors that give a slow turn off. The preferred light is an electroluminescent element that will be called a glow-effect capacitor which stores sufficient charge for slow turn off. When a switch associated with the light is opened, an FET turns on to discharge the capacitor rapidly to a selected voltage. This FET is then turned off and other components discharge the capacitor slowly. The switching signal for this FET is formed as a logic function of the switch position (open or closed) and the occurrence of the selected voltage level on the glow-effect capacitor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.