The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 18, 2001
Filed:
May. 05, 2000
Bryce L. Hesterman, Madison, AL (US);
Ali Fawaz, Madison, AL (US);
Universal Lighting Technologies, Inc., Nashville, TN (US);
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 the filtered voltage signal that may be used by an inverter control circuit to control the output of the inverter. In response to the control signal, the inverter control circuit either shuts down the inverter or increases the frequency of the inverter in order to reduce the output current of the inverter.