System and method for limiting through-lamp ground fault currents in non-isolated electronic ballasts
US6291944A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 5, 2000 |
| Grant date | Sep 18, 2001 |
| Priority date | — |
| Expiry date | May 5, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/2985
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electronic ballast having a through-lamp ground fault sensor that may also function as an end-of-lamp-life sensor is disclosed. The electronic ballast has an inverter that receives power from a dc power supply, and delivers a high-frequency output voltage to a resonant tank circuit through a dc blocking capacitor. The ground fault sensor includes a filter circuit connected to a voltage sensor circuit. An input terminal of the filter circuit is connected to the resonant tank so as to be in communication with a voltage signal that exists between a ballast output terminal and a dc power supply output terminal. The filter provides a filtered voltage signal by attenuating high frequency ac voltage components of the voltage signal, and passing low frequency ac voltage components, such as a 60 Hz signal, and possibly also passing a dc voltage component. A through-lamp ground fault will generate a voltage signal at the power line frequency. A lamp that has reached the end of its useful life will generate a low frequency ac voltage component that is caused by flickering, as well as a dc voltage component caused by rectification. The voltage sensor provides a control signal in response to…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.