Efficient, low leakage inductance, multi-tap, RF transformer and method of making same

• US 6,664,881 B1
• Filed: 06/08/2000
• Issued: 12/16/2003
• Est. Priority Date: 11/30/1999
• Status: Expired due to Fees

• Current Assignee: Ambrell Corporation (inTEST Corporation)
• Original Assignee: Ameritherm, Inc. (inTEST Corporation)
• Inventors: Thompson, Leslie L., Chiarilli, Francisco
• Primary Examiner(s): Nguyen, Tuyen T.
• Application Number:
  US09/589,656
• Time in Patent Office: 1,286 Days
• Field of Search: 336/200, 336/223, 336/232, 336/199, 336/185, 336/147, 336/146, 336/145, 336/148, 336/83, 336/183
• US Class Current: 336/200
• CPC Class Codes: H01F 17/02 without magnetic core
• CPC Class Codes: H01F 21/12 discontinuously variable, e.g. tapped
• CPC Class Codes: H01F 27/2823 Wires H01F27/2866 takes precedence
• CPC Class Codes: H01F 27/292 Surface mounted devices
• CPC Class Codes: H01F 29/025 Constructional details of transformers or reactors with tapping on coil or windings
• CPC Class Codes: H01F 5/003 Printed circuit coils

Abstract

A low leakage inductance, versatile RF transformer with multiple input/output voltage ratios. The transformer has many applications. For example, and not by way of limitation, the transformer can be used with switching power supplies, RF induction power supplies, and RF plasma power supplies. The efficiency of the transformer is on the order of 99% to 99.7%. These efficiencies have been measured at power levels of 3 kilowatts (KW) to 10 KW.

Claims

1. A transformer, comprising:

a plurality of conductors stacked on top of each other, thereby forming a conductor stack, the conductor stack being wound, at least once, around an axis, thereby forming a coil, wherein each of said plurality conductors has a first end and a second end; and

a printed circuit board (PCB) comprising a plurality of traces, wherein

said first end and said second end of each of said plurality of conductors is connected to said PCB and electrically coupled to at least one of said traces.

2. The transformer of claim 1, wherein a first subset of said plurality of conductors and a first subset of said plurality of traces form a primary winding of the transformer, and a second subset of said plurality of conductors and a second subset of said traces form a secondary winding of the transformer.

3. The transformer of claim 2, wherein the PCB comprises means for enabling the transformer to have more than one input to output voltage ratio.

4. The transformer of claim 1, wherein each of said conductors is made substantially from litz wire.

5. The transformer of claim 1, wherein the conductor stack is wound, at least twice, around the axis.

6. The transformer of claim 2, wherein the conductors that make up said first subset of conductors are interleaved in said conductor stack with the conductors that make up said second subset of conductors.

7. The transformer of claim 2, wherein said first subset of traces are used to connect said first subset of conductors in series, and said second subset of traces are used to connect said second subset of conductors in series.

8. The transformer of claim 1, wherein said PCB comprises a plurality of plated slots, each of said plurality of plated slots receiving one end of one of said plurality of conductors.

9. The transformer of claim 8, wherein each of said plurality of slots is connected to at least one of said plurality of traces.

10. The transformer of claim 1, wherein each of said plurality of conductors is a thin strip of an electrically conductive material.

11. The transformer of claim 10, wherein said material is copper.

12. The transformer of claim 1, wherein the transformer is an auto-transformer having a single winding and said plurality of conductors and said plurality of traces form said single winding, and wherein said plurality of traces are used to connect said conductors in series.

13. A transformer, comprising:

a printed circuit board (PCB) comprising a first trace and a second trace;

a primary winding; and

a secondary winding, wherein

said primary winding comprises said first trace, a first electrically conducting element, and a second electrically conducting element, wherein said first trace electrically connects one end of said first electrically conducting element to one end of said second electrically conducting element,

said primary winding comprises said second trace, a third electrically conducting element, and a fourth electrically conducting element, wherein said second trace electrically connects one end of said third electrically conducting element to one end of said fourth electrically conducting element,

said electrically conducting elements are stacked on top of each other, thereby forming a stack of electrically conducting elements, such that said third electrically conducting element is disposed between said first and said second electrically conducting elements and said second electrically conducting element is disposed between said third and said fourth electrically conducting elements, and

said stack of electrically conducting elements is wound, at least once, around an axis.

14. The transformer of claim 13, wherein each of said electrically conducting elements is coated with or encased within an electrically insulating material.

15. The transformer of claim 13, wherein each of said electrically conducting elements comprises a thin, elongated strip of copper.

16. The transformer of claim 15, wherein said copper strip has a width of greater than about 1 inch and less than about 2 inches.

17. The transformer of claim 13, wherein said PCB comprises at least eight slots, wherein each of said slots receives, at least, one end of one of the electrically conducting strips.

18. The transformer of claim 13, wherein the PCB comprises means for enabling the transformer to have more than one input to output voltage ratio.

19. The transformer of claim 13, wherein said stack of electrically conducting elements is wound, at least twice, around said axis.

20. The transformer of claim 13, wherein each of said electrically conducting elements comprises litz wire.