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:
Feb. 24, 2004
Filed:
Mar. 05, 2003
Kazuhiro Nishimoto, Kashihara, JP;
Katsunobu Hamamoto, Neyagawa, JP;
Hiromitsu Mizukawa, Katono, JP;
Matsushita Electric Works, Ltd., Kadoma, JP;
Abstract
A ballast circuit for a discharge lamp capable of protecting the circuit when the lamp reaches its end of life with a cost effective circuit arrangement. The circuit includes a DC voltage sensing network for sensing a DC voltage which appears as a consequence of the lamp reaching its end of life. Upon the sensed DC voltage exceeding a threshold, a control is made to limit or stop supplying an output power to the lamp for protecting the ballast circuit from an otherwise generating excessive current. The sensing network is composed of a DC sensing capacitor and a resistor which are connected in circuit outside of a resonant circuit responsible for generating a high frequency voltage to operate the lamp. Thus, the DC sensing capacitor can be kept free from the high voltage generated by the resonant circuit and be of less cost for reducing a manufacturing cost.