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:
Dec. 04, 2012
Filed:
Jan. 26, 2010
Katsuyoshi Nakada, Kyoto, JP;
Tomoyuki Nakano, Osaka, JP;
Koji Watanabe, Kyoto, JP;
Panasonic Corporation, Osaka, JP;
Abstract
A high pressure discharge lamp ballast is provided with a control operation for stable transition from a lamp ignition mode into a preheating mode. An inverter is coupled across a DC source and has a plurality of switching elements coupled to the high pressure discharge lamp. A series resonant LC circuit is coupled to the inverter outputs and to the high pressure discharge lamp. A control circuit is coupled to the switching elements and configured to control switching operation. An ignition mode has one or more time periods during each of which a driving frequency of the switching elements is swept through a predetermined range of frequencies and then controlled at a first driving frequency less than the predetermined range of frequencies. A preheating mode follows wherein the switching elements are controlled at a second driving frequency less than the predetermined range of frequencies.