Coupled inductor with improved leakage inductance control

1. An M-winding coupled inductor having a length and a depth, M being an integer greater than one, the coupled inductor comprising:

a first end magnetic element;

a second end magnetic element;

M connecting magnetic elements disposed along the length of the coupled inductor, each connecting magnetic element disposed between and connecting the first and second end magnetic elements;

M windings, each winding wound at least partially around a respective one of the M connecting magnetic elements; and

at least one top magnetic element adjacent to and extending at least partially over, when seen looking perpendicular to a plane including the length and the depth, at least two of the M connecting magnetic elements to provide a path for magnetic flux between the first and second end magnetic elements.

2. The coupled inductor of claim 1 , the at least one top magnetic element separated from the first end magnetic element by a first gap, the at least one top magnetic element separated from the second end magnetic element by a second gap, each of the first and second gaps including a respective gap material having a lower magnetic permeability than a one or more magnetic materials forming the magnetic elements.

3. The coupled inductor of claim 2 , each winding having a respective leakage inductance value that is a function of a thickness of the first gap and a function of a thickness of the second gap.

4. The coupled inductor of claim 3 , further comprising a non-magnetic material selected from the group consisting of glue and a non-magnetic spacer, the non-magnetic material separating the at least one top magnetic element from the first and second end magnetic elements.

5. The coupled inductor of claim 1 , each connecting magnetic element having a respective width, adjacent connecting magnetic elements being separated by a separation distance that is less than 10% of the respective width of either adjacent connecting magnetic element.

6. The coupled inductor of claim 1 , the at least one top magnetic element forming a gap including a gap material, the gap material having a lower magnetic permeability than a one or more magnetic materials forming the magnetic elements.

7. The coupled inductor of claim 6 , each winding having a respective leakage inductance value that is a function of a thickness of the gap.

8. The coupled inductor of claim 7 , M being an integer greater than two.

9. The coupled inductor of claim 8 , at least one of the first and second end magnetic elements forming an opening adjacent to the at least one top magnetic element.

10. The coupled inductor of claim 1 , the at least one top magnetic element comprising a first and a second top magnetic element forming a gap therebetween.

11. The coupled inductor of claim 1 , the at least one top magnetic element comprising a single top magnetic element.

12. The coupled inductor of claim 1 , each winding being a single layer and single turn winding having rectangular cross section.

13. The coupled inductor of claim 1 , the at least one top magnetic element forming an outer surface, at least a portion of the outer surface being planar.

14. The coupled inductor of claim 1 , each connecting magnetic element having a respective width, adjacent connecting magnetic elements being separated by a separation distance that is less than 25% of the respective width of either adjacent connecting magnetic element.

15. The coupled inductor of claim 1 , the at least one top magnetic element adjacent to and extending over all of the M connecting magnetic elements.

16. The coupled inductor of claim 1 , the at least one top magnetic element adjacent to and extending over fewer than all of the M connecting magnetic elements.

17. The coupled inductor of claim 16 , at least one of the first and second end magnetic elements forming an opening adjacent to the at least one top magnetic element.

18. An M-winding coupled inductor, M being an integer greater than one, the coupled inductor comprising:

a first end magnetic element;

a second end magnetic element;

M connecting magnetic elements, each connecting magnetic element disposed between and connecting the first and second end magnetic elements;

M windings, each winding wound at least partially around a respective one of the M connecting magnetic elements; and

at least one top magnetic element adjacent to and extending at least partially over at least two of the M connecting magnetic elements to provide a path for magnetic flux between the first and second end magnetic elements;

the at least one top magnetic element separated from the first end magnetic element by a first gap,

the at least one top magnetic element separated from the second end magnetic element by a second gap,

each of the first and second gaps including a respective gap material having a lower magnetic permeability than a one or more magnetic materials forming the magnetic elements,

each winding having a respective leakage inductance value that is a function of a thickness of the first gap and a function of a thickness of the second gap, and

at least one of the M windings serving as a spacer between the at least one top magnetic element and the first and second end magnetic elements.

19. An M-phase power supply, M being an integer greater than one, the power supply comprising:

a coupled inductor having a width and a depth, the coupled inductor including:

a first end magnetic element,

a second end magnetic element,

M connecting magnetic elements disposed along the length of the coupled inductor, each connecting magnetic element disposed between and connecting the first and second end magnetic elements,

M windings, each winding wound at least partially around a respective one of the M connecting magnetic elements, each winding having a respective first end, a respective second end, each first end electrically coupled to a common first node, and

at least one top magnetic element adjacent to and extending at least partially over, when seen looking perpendicular to a plane including the length and the depth, at least two of the M connecting magnetic elements to provide a path for magnetic flux between the first and second end magnetic elements; and

M switching circuits, each switching circuit electrically coupled to the second end of a respective winding and configured to switch the second end between at least two different voltages.

20. The power supply of claim 19 , M being an integer greater than two.

21. The power supply of claim 19 , the at least one top magnetic element separated from the first end magnetic element by a first gap, the at least one top magnetic element separated from the second magnetic element by a second gap, each of the first and second gaps including a respective gap material having a lower magnetic permeability than a one or more magnetic materials forming the magnetic elements, each winding having a respective leakage inductance value that is a function of a thickness of the first gap and a function of a thickness of a second gap.

22. The power supply of claim 19 , the at least one top magnetic element forming a gap including a gap material having a lower magnetic permeability than a one or more magnetic materials forming the magnetic elements, and each winding having a respective leakage inductance value that is a function of a thickness of the gap.

23. The power supply of claim 19 , each connecting magnetic element having a respective width, adjacent connecting magnetic elements being separated by a separation distance that is less than 25% of the respective width of either adjacent connecting magnetic element.

24. The power supply of claim 19 , each switching circuit configured to switch its respective second end between at least two different voltages at a frequency of at least 20 kilohertz.

25. The power supply of claim 19 , the power supply configured to operate as a DC-to-DC converter selected from the group consisting of a buck converter, a boost converter, and a buck-boost converter.