[54] LAMP PROTECTION CIRCUIT FOR ELECTRONIC BALLASTS
[75] Inventor: Bryce L. Hesterman, Fort Wayne, Ind.
[73] Assignee: Magnetek, Nashville, Tenn.
[21] Appl. No.: 644,209
[22] Filed: May 10,1996
[51] Int CI.6 H05B 37/02
[52] U.S. CI 315/127; 315/225
[58] Field of Search 315/225, 127,
315/DIG. 7,307
[56] References Cited
U.S. PATENT DOCUMENTS
Re. 32,901 4/1989 Nilssen 315/244
Re. 32,953 6/1989 Nilssen 315/224
4,398,126 8/1983 Zuchtriegel 315/127
4303,363 3/1985 Nilssen 315/225
4,562,383 12/1985 Kerscher 315/225
4,667,131 5/1987 Nilssen 315/275
5,004,955 4/1991 Nilssen 315/119
5,436,529 7/1995 Bobel 315/127
5,475,284 12/1995 Lester etal 315/225
5,493,180 2/1996 Bezdon 315/91
Primary Examiner—Robert Pascal
Assistant Examiner—Michael Shingleton
Attorney, Agent, or Firm—Mark P. Bourgeois
[57] ABSTRACT
An electronic ballast has a protection circuit particularly useful for smaller diameter gas discharge lamps including compact fluorescent lamps. The protection circuit prevents lamps from overheating by preventing the ballast from providing sustained output power when the magnitude of the ballast output voltage indicates abnormal lamp operation. The protection circuit has a voltage sensor which develops a voltage that is more negative than the negative DC supply terminal of the inverter so that an inexpensive low-voltage SCR can be used to turn off the inverter. The circuit provides automatic restarting of the ballast after a new lamp has been installed to eliminate the need for toggling the input power to the ballast.
20 Claims, 4 Drawing Sheets
