High intensity electrodeless low pressure light source driven by a transformer core arrangement

• US 5,834,905 A
• Filed: 03/27/1996
• Issued: 11/10/1998
• Est. Priority Date: 09/15/1995
• Status: Expired due to Term

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Statnic, Eugene, Godyak, Valery A., Piejak, Robert B., Alexandrovich, Benjamin
• Primary Examiner(s): Lee, Benny T.
• Application Number:
  US08/624,043
• Time in Patent Office: 958 Days
• Field of Search: 315/248, 315/267, 315/344, 315/39, 315/57, 315/62
• US Class Current: 315/248
• CPC Class Codes: H01J 65/048 the field being produced by using an excitation coil

Abstract

An electric lamp assembly includes an electrodeless lamp having a closed-loop, tubular envelope enclosing mercury vapor and a buffer gas at a pressure less than about 0.5 torr, a transformer core disposed around the lamp envelope, an input winding disposed on the transformer core and a radio frequency power source coupled to the input winding. The radio frequency source supplies sufficient radio frequency energy to the mercury vapor and the buffer gas to produce in the lamp envelope a discharge having a discharge current equal to or greater than about 2 amperes. The electrodeless lamp preferably includes a phosphor on an inside surface of the lamp envelope for emitting radiation in a predetermined wavelength range in response to ultraviolet radiation emitted by the discharge.

Claims

1. An electric lamp assembly comprising:

an electrodeless lamp including a closed-loop, tubular lamp envelope enclosing mercury vapor and a buffer gas at a pressure less than 0.5 torr;

a transformer core disposed so as to surround a portion of said closed-loop lamp envelope;

an input winding disposed on said transformer core; and

a radio frequency power source coupled to said input winding for supplying sufficient radio frequency energy to said mercury vapor and said buffer gas to produce in said lamp envelope a discharge having a discharge current equal to or greater than about 2 amperes.

2. An electric lamp assembly as defined in claim 1 wherein said discharge emits ultraviolet radiation and wherein said electrodeless lamp includes a phosphor on an inside surface of said lamp envelope for emitting radiation in a predetermined wavelength range in response to the ultraviolet radiation emitted by said discharge.

3. An electric lamp assembly as defined in claim 1 wherein said radio frequency power source has a frequency in a range of 50 kHz to 3 MHz.

4. An electric lamp assembly as defined in claim 1 wherein said radio frequency power source has a frequency in a range of 100 kHz to 400 kHz.

5. An electric lamp as defined in claim 1 wherein said buffer gas comprises a noble gas.

6. An electric lamp assembly as defined in claim 1 wherein said buffer gas comprises krypton.

7. An electric lamp assembly defined in claim 1 wherein said tubular lamp envelope has a cross-sectional dimension in a range of about 1 to 4 inches.

8. An electric lamp assembly defined in claim 1 wherein said transformer core has a toroidal configuration.

9. An electric lamp assembly defined in claim 1 further including a second transformer core disposed so as to surround another portion of said closed-loop lamp envelope and a second input winding disposed on said second transformer core and coupled to said radio frequency power source.

10. An electric lamp assembly defined in claim 1 wherein said closed-loop lamp envelope has an oval shape.

11. An electric lamp assembly defined in claim 1 wherein said lamp envelope comprises first and second parallel tubes joined at respective ends thereof provide said closed-loop lamp envelope.

12. An electric lamp assembly defined in claim 1 wherein said transformer core comprises a ferrite material.

13. An electric lamp assembly defined in claim 12 wherein a core power loss is associated with said transformer core, wherein a total power is supplied by said radio frequency source and wherein said electric lamp assembly is configured shuch that said core power loss is less than or equal to 15% of the total power supplied by said radio frequency power source.

14. An electric lamp assembly as defined in claim 12 wherein said electrodeless lamp and said transformer core are configured such that a ratio of transformer core volume of said transformer core to discharge power associated with said electrodeless lamp is less than two cubic centimeters per watt.

15. An electric lamp assembly as defined in claim 1 configured such that the pressure in said lamp envelope is equal to or less than 0.2 torr and the discharge current is equal to or greater than 5 amperes.

16. An electric lamp assembly as defined in claim 1 wherein said lamp envelope comprises an ultraviolet-transmissive material and said electrodeless lamp emits ultraviolet radiation in response to said discharge.

17. An electric lamp assembly comprising:

an electrodeless lamp including a tubular lamp envelope enclosing mercury vapor and a buffer gas at a pressure less than 0.5 torr, said lamp envelope comprising first and second parallel tubes joined at a near one end thereof by a first lateral tube and joined at or near the other end thereof by a second lateral tube to provide a closed loop;

a first transformer core disposed so as to surround the first lateral tube of said lamp envelope;

a second transformer core disposed so as to surround the second lateral tube of said lamp envelope;

first and second input windings disposed on said first and second transformer cores, respectively; and

a radio frequency power source coupled to said first and second input windings for supplying sufficient radio frequency energy to said mercury vapor and said buffer gas to produce in said lamp envelope a discharge having a discharge current equal to or greater than 2 amperes.

18. An electric lamp assembly as defined in claim 17 wherein said discharge emits ultraviolet radiation and wherein said electrodeless lamp includes a phosphor on an inside surface of said lamp envelope for emitting visible radiation in response to the ultraviolet radiation emitted by said discharge.

19. An electric lamp assembly as defined in claim 17 wherein said lamp envelope comprises an ultraviolet-transmissive material and said electrodeless lamp emits ultraviolet radiation in response to said discharge.

20. An electric lamp assembly as defined in claim 17 wherein said radio frequency power source has a frequency in a range of 50 kHz to 3 MHz.

21. An electric lamp assembly as defined in claim 17 wherein said first and second parallel tubes of said lamp envelope each have a respective cross-sectional dimension in a range of 1 to 4 inches.

22. An electric lamp assembly as defined in claim 17 wherein said first transformer core and said second transformer core each has a respective toroidal configuration.

23. An electric lamp assembly as defined in claim 17 wherein said first transformer core and said second transformer core each comprise a respective ferrite material.

24. An electric lamp assembly as defined in claim 17 wherein the pressure in said lamp envelope is less than or equal to 0.2 torr and said discharge current is equal to or greater than 5 amperes.

25. A method for operating an electric lamp comprising an electrodeless lamp including a closed-loop, tubular lamp envelope enclosing a buffer gas and mercury vapor, comprising the steps of:

establishing a pressure, of said mercury vapor and said buffer gas, in said lamp envelope of less than 0.5 torr; and

inductively coupling sufficient radio frequency energy to said mercury vapor and said buffer gas to produce in said lamp envelope a discharge having a discharge current equal to or greater than 2 amperes.

26. A method for operating an electric lamp as defined in claim 25 wherein the step of establishing a pressure includes establishing a pressure of said mercury vapor and said buffer gas less than or equal to 0.2 torr and wherein the step of inductively coupling radio frequency energy comprises inductively coupling sufficient radio frequency energy to produce said discharge current at a level equal to or greater than 5 amperes.

27. An electric lamp assembly comprising:

an electrodeless lamp including a closed-loop, tubular lamp envelope enclosing mercury vapor and a buffer gas at a pressure of less than 0.5 torr; and

means for inductively coupling sufficient radio frequency energy to said mercury vapor and said buffer gas to produce in said lamp envelope a discharge having discharge current equal to or greater than 2 amperes.

28. An electric lamp assembly as defined in claim 27 wherein said discharge emits ultraviolet radiation and wherein said electrodeless lamp includes a phosphor on an inside surface of said lamp envelope for emitting radiation in a predetermined wavelength range in response to the ultraviolet radiation emitted by said discharge.

29. An electric lamp assembly as defined in claim 27 wherein said radio frequency energy has a frequency in a range of 50 kHz to 3 MHz.

30. An electric lamp assembly as defined in claim 27 wherein said buffer gas comprises krypton.

31. An electric lamp assembly as defined in claim 27 wherein said tubular lamp envelope has a cross sectional dimension in a range of 1 to 4 inches.

32. An electrodeless lamp assembly comprising:

an electrodeless lamp including a closed-loop, tubular lamp envelope enclosing krypton and mercury vapor at a pressure less 0.5 torr;

a ferrite transformer core disposed so as to surround a portion of said closed-loop lamp envelope; and

an input winding disposed on said transformer core for coupling to a radio frequency power source.