Winding structure for efficient switch-mode power converters

• US 7,427,910 B2
• Filed: 08/19/2004
• Issued: 09/23/2008
• Est. Priority Date: 08/19/2004
• Status: Active Grant

• Current Assignee: Flextronics International USA Incorporated (Flex, Ltd.), MyPAQ Holdings Ltd. (Transpacific IP Group Limited)
• Original Assignee: ColdWatt, Inc. (Flex, Ltd.)
• Inventors: Mehrotra, Vivek, Sun, Jian
• Primary Examiner(s): Nguyen; Tuyen T.
• Application Number:
  US10/922,064
• Publication Number:
  US 20060038649A1
• Time in Patent Office: 1,496 Days
• Field of Search: 336/65, 336/83, 336/170, 336/178, 336/200, 336/225, 336/232, 323/355
• US Class Current: 336/200
• CPC Class Codes: H01F 2027/2819 Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/34 Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Abstract

Cutout and/or keep away regions are etched in the winding structure near the gapped center leg of a magnetic core. This reduces eddy current losses caused by the leakage field and improves current uniformity and current sharing between windings thereby increasing converter efficiency. Windings closest to the air gap are suitably formed with both keep away regions and cutouts. Windings a little further away are formed with only cutouts, and the windings furthest away are unchanged. This approach keeps the net winding losses low in the presence of a fringing field. The precise configuration is determined by the core structure, air gap and winding arrangements.

Claims

1. An integrated magnetic structure, comprising:

a magnetic core having a base, a center leg and outer legs on said base, and a plate on said outer legs opposite said base and forming an air gap with said center leg; and

a winding around one of said legs and having an interior cutout towards said center leg without employing an insulative gap in said winding.

2. The integrated magnetic structure as recited in claim 1 wherein said winding is about 10 mils from said center leg.

3. The integrated magnetic structure as recited in claim 1 wherein said winding has an exterior keep away region that spaces an exterior edge thereof away from said center leg.

4. The integrated magnetic structure as recited in claim 3 wherein said winding is about 55 mils from said center leg.

5. The integrated magnetic structure as recited in claim 1 further comprising another winding around one of said legs.

6. The integrated magnetic structure as recited in claim 1, further comprising:

horizontal window areas between said center leg and said outer legs, and

vertical window areas between said winding and said plate.

7. The integrated magnetic structure as recited in claim 1 wherein said interior cutout forms an island in said winding towards said center leg.

8. The integrated magnetic structure as recited in claim 1 wherein said winding is around said center leg and said interior cutout is formed in one side of said winding towards said center leg, thereby providing an asymmetric winding.

9. The integrated magnetic structure as recited in claim 1 wherein said winding is around said center leg and has a pair of interior cutouts formed on both sides of said winding towards said center leg, thereby providing a symmetric winding.

10. The integrated magnetic structure as recited in claim 1 wherein said magnetic core is mounted in a printed circuit board, said winding lying in a plane of said printed circuit board around one of said legs.

11. The integrated magnetic structure as recited in claim 1 wherein said interior cutout improves a uniformity of currents flowing through said winding.

12. An integrated magnetic structure, comprising:

a magnetic core having a base, a center leg and outer legs on said base, and a plate on said outer legs opposite said base and forming an air gap with said center leg; and

a winding arrangement, including;

a first winding, around one of said legs, having an interior cutout towards said center leg without employing an insulative gap in said first winding and an exterior keep away region that spaces an exterior edge thereof away from said center leg,

a second winding, around one of said legs, having an interior cutout towards said center leg without employing an insulative gap in said second winding, and

a third winding around one of said legs.

13. The integrated magnetic structure as recited in claim 12 wherein at least one of said first, second and third windings is about 10 mils from said center leg.

14. The integrated magnetic structure as recited in claim 12 wherein said first winding is about 55 mils from said center leg.

15. The integrated magnetic structure as recited in claim 12, further comprising:

horizontal window areas between said center leg and said outer legs, and

vertical window areas between said first winding and said plate.

16. The integrated magnetic structure as recited in claim 12 wherein said interior cutout forms an island in said first and second windings towards said center leg.

17. The integrated magnetic structure as recited in claim 12 wherein said first winding is around said center leg and said interior cutout is formed in one side of said first winding towards said center leg, thereby providing an asymmetric winding.

18. The integrated magnetic structure as recited in claim 12 wherein said first winding is around said center leg and has a pair of interior cutouts formed on both sides of said first winding towards said center leg, thereby providing a symmetric winding.

19. The integrated magnetic structure as recited in claim 12 wherein said magnetic core is mounted in a printed circuit board, said first, second and third windings lying in a plane of said printed circuit board around one of said legs.

20. The integrated magnetic structure as recited in claim 12 wherein said interior cutout improves a uniformity of currents flowing through said first winding.

21. The integrated magnetic structure as recited in claim 12 wherein said interior cutout and said external keep away region increases a DC resistance of said first winding and reduces a winding loss in a presence of a fringing field emanating from said air gap.

22. The integrated magnetic structure as recited in claim 12 wherein ones of said first, second and third windings form primary and secondary windings of a transformer.

23. The integrated magnetic structure as recited in claim 12 wherein one of said first, second and third windings forms a winding of an inductor.