Winding structure for efficient switch-mode power converters

• US 20060038649A1
• Filed: 08/19/2004
• Published: 02/23/2006
• 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: Rockwell Scientific Licensing LLC (Teledyne Technologies Incorporated)
• Inventors: Sun, Jian, Mehrotra, Vivek
• Granted Patent: US 7,427,910 B2
• Time in Patent Office: Days
• US Class Current: 336/83
• 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. A power converter, comprising:

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

a winding around one of said legs, said winding having an interior cutout towards the center leg.

2. The power converter of claim 1, wherein said winding has an exterior keep away region that spaces the edge of the winding further away from the center leg.

3. The power converter of claim 2, wherein said cutout and said keep away region may increase the winding'"'"'s DC resistance but reduce the overall winding loss in the presence of a fringing field emanating from the air gap.

4. The power converter of claim 1, wherein said air gap creates a fringing field whose strength decreases moving down and away from the air gap, further comprising a plurality of said windings around said leg, any said windings that lie within a first multiple of a length of the air gap measured from the plate having both an interior cutout and an exterior keep away region, any said windings that lie between said first multiple and a second multiple having only an interior cutouts, and any remaining windings that lie outside said second multiple having neither interior cutouts or exterior keep away regions.

5. The power converter of claim 4, wherein said first multiple is five and said second multiple is ten.

6. The power converter of claim 4, wherein all said windings are spaced about 10 mils from the center leg, said exterior keep away region increasing said spacing to about 55 mils.

7. The power converter of claim 4, wherein said base, outer leg, center leg and plate define a vertical window area, said plurality of windings occupying at least eighty percent of said vertical window area.

8. The power converter of claim 4, wherein the winding structure improves the uniformity of currents flowing through the plurality of windings.

9. The power converter of claim 4, wherein the pattern of cutout and keep away regions keeps the total DC and AC resistance of the plurality of windings low to optimize the efficiency of the power converter.

10. The power converter of claim 1, wherein said winding is wound around one of said outer legs, said winding being asymmetric in that said interior cutout is only formed in the side of the winding towards the center leg.

11. The power converter of claim 10, further comprising another winding wound around the other outer leg, said another winding having an interior cutout towards the center leg.

12. The power converter of claim 1, wherein said winding is wound around the center leg, said winding comprising a pair of said interior cutouts on either side of the center leg.

13. The power converter of claim 1, wherein said base, center leg and one of the outer legs define a horizontal window area, said air gap creating a fringing field in said horizontal window area, said interior cutout spanning the horizontal window area to form an island in the winding with respect to the fringing field.

14. The power converter of claim 1, further comprising a printed circuit board on which said magnetic core is mounted, said winding lying in the plane of said printed circuit board around said leg.

15. The power converter of claim 14, wherein said winding is around one of said outer legs, said cut-out region being closer to said center leg than said outer leg on which the winding is wound.

16. A power converter, comprising:

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

a first plurality of alternating secondary and primary windings wound around said first outer leg; and

a second plurality of alternating secondary and primary windings wound around said second outer leg;

any said windings that lie within a first multiple of a length of the air gap measured from the plate having both an interior cutout and an exterior keep away region that spaces the edge of the winding further from the center leg, any said windings that lie between said first multiple and a second multiple having only an interior cutout, and any remaining windings that lie outside said second multiple having neither interior cutouts or exterior keep away regions.

17. The power converter of claim 16, wherein said base, center leg and the outer legs define horizontal window areas on either side of the center leg, said air gap creating a fringing field in said horizontal window areas, said interior cutouts spanning the horizontal window areas to form islands in the windings with respect to the fringing field.

18. The power converter of claim 16, wherein said windings that have interior cutouts and/or exterior keep away regions are asymmetric about the respective outer legs.

19. The power converter of claim 16, wherein said base, outer leg, center leg and plate define a vertical window area, said plurality of windings occupying at least eighty percent of said vertical window area.

20. The power converter of claim 16, further comprising an inductor winding wound around the center leg, said winding comprising a pair of interior cutouts on either side of the center leg.

21. The power converter of claim 20, wherein said inductor winding further comprises a pair of exterior keep away regions that space the respective interior cutouts away from the center leg.

22. The power converter of claim 16, wherein said cutout and said keep away region may increase the windings'"'"' DC resistance but reduce the windings'"'"' total losses consisting of ac and dc losses in the presence of a fringing field emanating from the air gap.

23. The power converter of claim 16, further comprising a printed circuit board on which said magnetic core is mounted, said first and second windings lying in the plane of said printed circuit board around said first and second legs.

24. The power converter of claim 23, wherein said cut-out regions are closer to said center leg than to the outer leg on which the windings are wound.

25. A power converter, comprising:

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

a first plurality of windings wound around said first outer leg; and

a second plurality of windings wound around said second outer leg;

any said windings that lie within a first multiple of a length of the air gap measured from the plate having both an interior cutout and an exterior keep away region that spaces the cutout further from the center leg, any said windings that lie between said first multiple and a second multiple having only an interior cutout, and any remaining windings that lie outside said second multiple having neither interior cutouts or exterior keep away regions, said cutouts and said keep away regions increasing the windings'"'"' DC resistance but reducing the windings'"'"' net losses in the presence of a fringing field emanating from the air gap to reduce the losses of any currents flowing in said windings and improve the uniformity of said currents.