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:
Jun. 17, 2003
Filed:
Feb. 14, 2002
Yoshinobu Murakami, Hirakata, JP;
Joji Oyama, Takaishi, JP;
Toshiya Kanja, Uji, JP;
Shigeru Ido, Shijonawate, JP;
Naokage Kishimoto, Hirakata, JP;
Matsushita Electric Works, Ltd., Kadoma, JP;
Abstract
A discharge lamp driving device capable of detecting a lamp life end reliably in a high or low temperature environment for circuit protection, yet preventing the occurrence of the cataphoresis phenomenon. Impedance elements Z and Z are inserted respectively between one filament ends of individual discharge lamps La and La and a node (the ground) having no high frequency amplitude in order to detect a difference between AC components of individual lamp voltages VLa and VLa in closed loops of the discharge lamps La and La and the impedance elements Z and Z in order to judge whether or not the depletion of the emitter occurs. Thus, it is possible to reliably judge the presence of abnormality even when the amplitudes of the lamp voltages VLa and VLa varies in a range of low to high temperature. Also, since there is no need to provide a DC blocking capacitor to a secondary winding N of a leakage transformer LT the discharge lamps La and La can be free from the DC component so as to be prevented from causing the cataphoresis phenomenon.