Method and apparatus for powering an electrodeless lamp with reduced radio ...

United States Patent [w]

Simpson

US005910710A [ii] Patent Number: [45] Date of Patent:

5,910,710 Jun. 8,1999

[54] METHOD AND APPARATUS FOR

POWERING AN ELECTRODELESS LAMP
WITH REDUCED RADIO FREQUENCY
INTERFERENCE

[75] Inventor: James E. Simpson, Gaithersburg, Md.

[73] Assignee: Fusion Lighting, Inc., Rockville, Md.

[21] Appl. No.: 08/754,858 [22] Filed: Nov. 22, 1996

[51] Int. CI. H05B 41/16

[52] U.S. CI 315/248; 315/39; 315/236;

315/344

[58] Field of Search 315/248, 39, 267,

315/344, 236; 333/81 A, 81 B, 81 R, 204, 205, 219, 246; 219/709

[56] References Cited

U.S. PATENT DOCUMENTS

3,662,140 5/1972 Jones et al 219/10.55

4,060.778 11/1977 Hefni et al 333/73 W

4,069,456 1/1978 Bensussan et al 328/165

4,359,668 11/1982 Ury 315/39

4,716,389 12/1987 Gawronski et al 333/81 A

4,859.906 8/1989 Ury et al 313/639

4,894,592 1/1990 Ervin et al 315/248

5,070,277 12/1991 Lapatovich 315/248

5,113.121 5/1992 Lapatovich et al 315/248

5,227,698 7/1993 Simpson et al 315/248

5,361,274 11/1994 Simpson et al 372/72

5,404,076 4/1995 Dolan et al 313/572

5,448,135 9/1995 Simpson 315/39

5,504,391 4/1996 Turner et al 313/570

Primary Examiner—Don Wong

Assistant Examiner—Haissa Philogene

Attorney, Agent, or Firm—Epstein, Edell & Retzer

[57] ABSTRACT

An electrodeless lamp waveguide structure includes tuned absorbers for spurious RF signals. A lamp waveguide with an integral frequency selective attenuation includes resonant absorbers positioned within the waveguide to absorb spurious out-of-band RF energy. The absorbers have a negligible effect on energy at the selected frequency used to excite plasma in the lamp. In a first embodiment, one or more thin slabs of lossy magnetic material are affixed to the sidewalls of the waveguide at approximately one quarter wavelength of the spurious signal from an end wall of the waveguide. The positioning of the lossy material optimizes absorption of power from the spurious signal. In a second embodiment, one or more thin slabs of lossy magnetic material are used in conjunction with band rejection waveguide filter elements. In a third embodiment, one or more microstrip filter elements are tuned to the frequency of the spurious signal and positioned within the waveguide to couple and absorb the spurious signal's energy. All three embodiments absorb negligible energy at the selected frequency and so do not significantly diminish the energy efficiency of the lamp.

35 Claims, 5 Drawing Sheets