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:
Mar. 17, 1998
Filed:
Jul. 24, 1996
Guang Liu, Lake Zurich, IL (US);
Anand K Upadhyay, Libertyville, IL (US);
Motorola Inc., Schaumburg, IL (US);
Abstract
A protection method (10) and protection circuit (500) for protecting an inverter (300) in an electronic preheat ballast (100) for powering at least one fluorescent lamp (902). The inverter (300) includes a first inverter switch (306), a second inverter switch (310), an output circuit (800), and an inverter driver circuit (400) having a drive frequency. The protection circuit (500) comprises a frequency shift circuit (600), a latch circuit (700), a current source network (520), a current sensing circuit (510), and a DC supply capacitance (502). The protection method (10) includes the steps of (a) providing a filament preheat period by initially setting the drive frequency at a first frequency, (b) shifting the drive frequency to a second frequency for igniting and operating the lamps, (c) changing the drive frequency back to the first frequency in response to a lamp fault, and (d) providing, upon correction of the lamp fault, a filament preheat period prior to attempting to ignite and operate the lamps.