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:
Jul. 11, 1989
Filed:
Dec. 30, 1983
Robert W Wisbey, Arlington Heights, IL (US);
Joseph S Droho, Chicago, IL (US);
Advance Transformer Co., Chicago, IL (US);
Abstract
A hybrid ballast apparatus for starting and operating a plurality of series-connected discharge lamps and which provides protection against electric shock. The ballast apparatus includes first and second bidirectional thyristors connected in parallel with first and second ones of said lamps, respectively, and a trigger control circuit for simultaneously triggering the thyristors into conduction. Each lamp has two filaments and means are provided for connecting an L-C ballast device, the lamp filaments and the first and second thyristors in a series circuit across the AC supply voltage terminals. If one end of a lamp is removed from its socket, the series circuit is opened so that the maximum voltage at any lamp electrodes is limited to the AC supply voltage.