Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2000-05-01
2001-08-28
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S224000, C315S2090SC, C315S291000, C315S127000, C315SDIG007
Reexamination Certificate
active
06281641
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to electronic ballasts, and more particularly, this invention pertains to an electronic ballast that can be wired to operate multiple lamps.
Typical electronic ballasts have a source of DC power, an inverter, and a resonant circuit. A series resonant tank circuit is commonly used to operate two or more fluorescent lamps connected in series. Further prior art is found in U.S. Pat. No. 5,635,799 issued to Hesterman on Jun. 3, 1997 which discloses a “lamp Protection Circuit for Electronic Ballasts.” This patent is hereby incorporated by reference. The disclosure of the patent shows several series-connected two-lamp ballast circuits having a series resonant tank circuit and end-of-lamp-life sensor. The disclosure of this patent has a limitation because if one lamp were to be operated instead of two lamps, the lamp current would go up, and the end-of-lamp-life sensor would not operate properly.
What is needed is a ballast that can sense how many lamps are present, and adjust an inverter control circuit to maintain essentially equivalent operation regardless of how many lamps are connected.
SUMMARY OF THE INVENTION
The present invention is directed towards an electronic ballast apparatus for powering one or more gas discharge lamps. The electronic ballast includes an inverter that is controlled by an inverter control circuit. The inverter control circuit adjusts certain ballast operating characteristics in order to operate one or more lamps under nearly the same operating conditions irrespective of how many lamps are connected to the ballast. The inverter control circuit includes a lamp quantity sensor, a regulator circuit and an end-of-lamp-life sensor. The lamp quantity sensor provides a lamp quantity signal that indicates how many lamps are connected to the ballast. The regulator circuit includes a reference adjustment circuit that receives the lamp quantity signal and provides a scaled reference signal to a reference terminal of an error amplifier. The error amplifier also has a feedback terminal that receives a signal that is proportional to the power delivered by the inverter to the lamps. The regulator circuit provides a signal to an inverter power control circuit to ensure that the total power delivered by the inverter to the lamps is proportional to the number of lamps connected to the ballast. Regulating the lamp power has the effect of controlling the lamp current because the voltage across the lamps is relatively constant. Alternative embodiments may utilize other control methods including a feedback signal adjustment circuit connected to the lamp quantity sensor in combination with a fixed reference input to the error amplifier to achieve the same results.
The output of the lamp quantity sensor is also used to adjust an end-of-lamp-life sensor so that it will properly sense the end-of-lamp-life condition for one or two lamps. In alternative embodiments, additional lamp quantity sensors may be connected together to create an overall lamp quantity signal appropriate for use in ballasts that are capable of operating more than two lamps.
REFERENCES:
patent: 5563473 (1996-10-01), Mattas et al.
patent: 5635799 (1997-06-01), Hesterman
patent: 5751115 (1998-05-01), Jayaraman et al.
patent: 5877592 (1999-03-01), Hesterman et al.
patent: 5973455 (1999-10-01), Mirskiy et al.
European Patent Application No. 94104797.9 filed Mar. 25, 1994, by Applicant Toshiba Lighting & Technology Corporation.
European Patent Application No. 84105786.2 filed May 21, 1984 by Applicant Siemens Aktiengesellschaft.
Chen Daoshen
Hesterman Bryce L.
Patterson Mark J.
Philogene Haissa
Universal Lighting Technologies
Waddey & Patterson
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