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. 27, 2012
Filed:
Oct. 27, 2009
Daisuke Yamahara, Shijonawate, JP;
Naoki Komatsu, Kobe, JP;
Daisuke Yamahara, Shijonawate, JP;
Naoki Komatsu, Kobe, JP;
Panasonic Electric Works Co., Ltd., Osaka, JP;
Abstract
An electronic ballast is provided for controlled preheating of filaments in a discharge lamp. A power converter has a plurality of switching elements and converts DC power from a DC power source into AC power for the lamp. A starting circuit generates a high voltage for starting the lamp. A half-wave discharge detecting circuit detects an absolute value for each polarity peak of a lamp current, calculates an asymmetrical current value from the detected peaks with respect to a predetermined current threshold, and detects a half-wave discharge of the lamp wherein an absolute value of the asymmetrical current value is equal to or more than the current threshold for a predetermined determination time. A control circuit regulates on-times for the switching elements in an filament heating operation wherein the power converting circuit provides a high output frequency for heating each filament of the discharge lamp, and further regulates the on-times to reduce half-wave discharge detected during the filament heating operation.