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:
Oct. 16, 2012
Filed:
Apr. 02, 2010
Wei Xiong, Madison, AL (US);
Thomas Lunn, Hazel Green, AL (US);
Christopher Radzinski, Huntsville, AL (US);
Wei Xiong, Madison, AL (US);
Thomas Lunn, Hazel Green, AL (US);
Christopher Radzinski, Huntsville, AL (US);
Universal Lighting Technologies, Inc., Madison, AL (US);
Abstract
A circuit for preheating filaments in lamps powered by an electronic ballast includes an inverter tank circuit and a preheat tank circuit. The preheat tank circuit has a preheat capacitor connected in parallel with a primary winding of a filament preheat transformer. A cut-back capacitor is connected between the preheat tank circuit and circuit ground. The filament preheat transformer has secondary windings coupled to the first and second lamp terminals to provide a filament preheat voltage. The inverter operates at a preheat frequency during a lamp preheat mode and at a steady-state frequency during a lamp steady-state mode, the steady-state frequency being lower than the preheat frequency. The preheat tank circuit has a natural resonant frequency that is approximately the same as the preheat frequency so that when the ballast is operating in the steady state mode, the filament voltage is substantially lower than when the ballast is operating in the preheat mode.