Coil arrangement and wireless power transfer system comprising a coil arrangement

Abstract

A coil arrangement with reduced core losses is provided. The coil arrangement has a first coil and a second coil and a ferrite layer below the coils. A perpendicular recess in the ferrite layer is provided to reduce magnetic flux density in a center conduction path.

Claims

1. A coil arrangement, comprising a first coil arranged in a x-y plane; a second coil arranged in the x-y plane next to the first coil, the first coil and the second coil are electrically connected such that their directions of polarization are anti-parallel; a ferrite layer comprising a ferrite material below the first coil and the second coil, the ferrite layer having a perpendicular recess; a center conduction path arranged between a center of the first coil and a center of the second coil for magnetic flux; a first side conduction path for magnetic flux and a second side conduction path for magnetic flux, the center conduction path being arranged between the first and the second side conduction paths; and wherein the perpendicular recess in the ferrite layer is provided to reduce magnetic flux density in the center conduction path, the perpendicular recess in the ferrite layer has a longitudinal extension that extends in a y-direction of the x-y plane to define a length of the perpendicular recess; and wherein the ferrite layer includes a first parallel recess and a second parallel recess that are (i) generally parallel to each other and (ii) extend in an x-direction of the x-y plane so as to be generally perpendicular to the perpendicular recess, the first parallel recess being adjacent to the first side conduction path and the second parallel recess being adjacent to the second side conduction path, and wherein the perpendicular recess does not penetrate the first side conduction path and the second side conduction path.

2. The coil arrangement of claim 1, wherein at least one of the first and second parallel recesses has a differing width along a length in the x-direction.

3. The coil arrangement of claim 1, wherein the first and second parallel recesses are filled with a material having different magnetic properties than the ferrite material of the ferrite layer.

4. The coil arrangement of claim 1, wherein the lengths of the first and second parallel recesses in the x-direction are smaller than or equal to the extension of the ferrite material in the same direction.

5. The coil arrangement of claim 1, wherein a lateral width of the perpendicular recess is between 0.1 mm and 10 mm, and a lateral width of each of the first and second parallel recess is between 0.1 mm and 20 mm.

6. The coil arrangement of claim 1, further comprising at least one additional perpendicular recess arranged in the center conduction path and oriented parallel to the perpendicular recess.

7. The coil arrangement of claim 1, wherein the ferrite layer has a uniform thickness.

8. The coil arrangement of claim 1, wherein a lateral width of the perpendicular recess is between 0.1 mm and 10 mm.

9. The coil arrangement of claim 1, wherein the perpendicular recess is filled with a material having different magnetic properties than the ferrite material of the ferrite layer.

10. The coil arrangement of claim 1, wherein the length of the perpendicular recess in its longitudinal direction is smaller than or equal to the extension of the ferrite material in the same direction.

11. A wireless power transmission system comprising the coil arrangement of claim 1 as a power transmission coil arrangement.

12. A wireless power reception system comprising the coil arrangement of claim 1 as a power reception coil arrangement.

13. A wireless power transfer system comprising the coil arrangement of claim 1 as a power transmission and/or a power reception coil arrangement.

14. The coil arrangement of claim 1, wherein the ferrite layer has a variable thickness in the X-Y plane, the thickness being greater in a center region than in an edge region of the layer.

15. The coil arrangement of claim 10, wherein a lateral width of the perpendicular recess is between 0.1 mm and 10 mm, and a lateral width of each of the first and second parallel recess is between 0.1 mm and 20 mm.

16. The coil arrangement of claim 10, further comprising at least one additional perpendicular recess arranged in the center conduction path and oriented parallel to the perpendicular recess.

17. The coil arrangement of claim 10, wherein the first and second parallel recesses are filled with a material having different magnetic properties than the ferrite material of the ferrite layer.

18. The coil arrangement of claim 1, wherein the perpendicular recess is positioned between the first and second parallel recesses, but does not intersect the first and second parallel recesses.

19. The coil arrangement of claim 1, wherein the perpendicular recess is positioned between the first and second parallel recesses, and intersects the first and second parallel recesses.

20. The coil arrangement of claim 1, further including at least one additional parallel recess that is parallel to and positioned between the first and second parallel recesses.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a possible configuration and relative orientation of the paths and the coils.

(2) FIG. 2 shows a possible configuration of ferrite material below the coils.

(3) FIG. 3 shows a cross-section including a typical direction of magnetic field.

(4) FIG. 4 shows an alternative cross-section and the effect of the parallel recess.

(5) FIG. 5 illustrates a ferrite layer without parallel recesses.

(6) FIG. 6 shows parallel recesses having a different width than the perpendicular recess.

(7) FIG. 7 shows recesses arranged in the ferrite material such that the ferrite material remains a single piece.

(8) FIG. 8 shows the possibility of providing several recesses.

(9) FIG. 9 shows the possibility of providing a ferrite layer consisting of sublayers.

(10) FIG. 10 shows a layout with a divided center conduction path.

(11) FIG. 11 shows dependencies of core losses on recess widths of a perpendicular recess and of the parallel recesses.

(12) FIG. 12 shows dependencies of the coupling factor on recess widths of the perpendicular recess and the parallel recesses.

(13) FIG. 13 illustrates a wireless power reception system (WPRS) that includes a power reception coil arrangement (Power Reception CA).

(14) FIG. 14 illustrates a wireless power transmission system (WPTS) that includes a power transmission coil arrangement (Power Transmission CA).

(15) FIG. 15 illustrates a wireless power transfer system that comprises a coil arrangement from the previous embodiments in the form of a power transmission coil arrangement (Power Transmission CA) and/or a power reception coil arrangement (Power Reception CA).

DETAILED DESCRIPTION OF THE DRAWINGS

(16) FIG. 1 shows a first coil C1 and a second coil C2 arranged in the x-y plane to establish a coil arrangement (CA), in particular a polarized coil arrangement. Arranged at a position between the center of the coils, the area of a center conduction path CCP is located. The center conduction path CCP is arranged in a plane parallel to the x-y plane between a first side conduction path SCP and a second side conduction path. The direction from the center of the first coil towards the center of the second coil is perpendicular to the direction of the center of the first side conduction path to the second side conduction path.

(17) With reference to the vertical direction z orthogonal to the x-y plane, the center conduction path CCP and the side conduction paths SCP are mainly arranged below the two coils C1, C2. When conventional polarized coil arrangements are operated, then the flux density in the center conduction path is very high. By routing flux to the side conduction paths the homogeneity is improved.

(18) Similar to FIG. 1, FIG. 2 shows a top view onto the x-y plane indicating further possible details. A ferrite material F is arranged in the ferrite layer below the coils. At positions near the center of the respective coils the dotted circuits denote the tips of arrows indicating the direction of magnetic field MF. In areas between the centers of the coils, the magnetic field MF has components parallel to the x-y plane, i.e. horizontal components. In the upper part of the coil arrangement (CA), the horizontal component of the magnetic field may point towards the center of the upper coil. Correspondingly, in a polarized coil arrangement in the lower part shown in FIG. 2, the magnetic field has also a horizontal component pointing towards the center of the lower coil, i.e. antiparallel to the component shown in the upper part of FIG. 2. The magnetic fields of both coils meet at the center between the coils. This is why this region has relatively high magnetic flux densities.

(19) In this region the perpendicular recess RPE in the ferrite material F is arranged. On the left-hand side and, correspondingly, on the right-hand side the parallel recesses RPA are provided in the material F of the ferrite layer. The recesses have an elongated extension along their extension direction. The parallel recesses RPA extend parallel to the horizontal component of the magnetic field MF. The perpendicular recess has a longitudinal extension directing perpendicular to the horizontal component of the magnetic field MF. Lines AA and BB denote the positions of regarded planes in the cross-sectional views of FIGS. 3 and 4, respectively.

(20) Thus, FIG. 3 shows a cross-sectional view, i.e. a view of the z-x plane, at position AA denoted in FIG. 2. Usually, the coils are operated at a frequency around 85 kHz. For a regarded time the magnetic fields associated with the first coil C1 and the second coil C2 may be such that the direction of magnetic field in the center of the coils are parallel to the z-direction. Correspondingly, the vertical component of the magnetic fields outside the respective coil is anti-parallel to the z-direction. The magnetic fields accumulate at the position between the coils where the perpendicular gap RPE is provided. By providing the perpendicular gap RPE in this position, the reluctance with respect to the magnetic field in the magnetic core is increased and magnetic flux is transferred along the y-direction towards the side conduction paths to increase the overall homogeneity of magnetic flux.

(21) This can be seen in the cross-sectional view across plane BB in FIG. 4 showing a cross-sectional view of onto the z-y plane. In the center portion of FIG. 4—due to the presence of the recess—no ferrite material is present. However, ferrite material remains in the side conduction paths. Due to the presence of the perpendicular recess, the homogeneity of the magnetic field is improved although in the center conduction path the magnetic fields of both coils would accumulate.

(22) FIG. 5 illustrates a ferrite material F in a ferrite layer with a perpendicular recess but without parallel recesses. However, it is preferred that at least one or more parallel recesses are present.

(23) FIG. 6 shows the possibility of parallel recesses RPA and the perpendicular recess RPE having different widths and lengths.

(24) The recesses can be realized as gaps fully separating isolated segments of the ferrite material F.

(25) In contrast, FIG. 7 shows the possibility of maintaining a single segment of ferrite material F in which recesses are embedded. It is preferred that the extensions of the center conduction path and the perpendicular recess are mainly equal.

(26) FIG. 8 illustrates the possibility of having several perpendicular recesses in the center conduction path CCP and several additional recesses that extend in the y-direction but that are separated from the side conduction paths.

(27) Such additional recesses or further additional recesses can be provided to allow electric components such as coils or other circuitry to be contacted with circuitry on the respective other side of the ferrite material.

(28) It is possible and preferred that one or more or all parallel recesses reach from one side of the ferrite layer to the other side of the ferrite layer. However, the width of the parallel recesses can vary along their extension. It is possible that the width is smaller in the center of the ferrite layer, e.g. in the center conduction path.

(29) Distances between the center conduction path and a side conduction path can vary from distances between the center conduction path and other side conduction paths.

(30) It is also preferred that at least one or more recesses completely separates the center conduction path from the side conduction paths.

(31) FIG. 9 illustrates the possibility of the ferrite layer consisting of two or more sublayers. The lateral extension within the x-y plane of one sublayer can be different from the lateral extension of another sublayer. Thus, the lower sublayer with respect to the vertical direction z shown in FIG. 9, can have smaller lateral dimensions in the x-y plane than the upper sublayer. In particular, it can be preferred that in the center conduction path, despite the need for the perpendicular recess, additional material F can be useful while in the side conduction paths no additional ferrite material is needed. Thus, by making the thickness of the ferrite layer different for different locations in the x-y plane the overall need of ferrite material is further reduced without the risk of deteriorating the coil arrangements electrical and magnetic properties.

(32) FIG. 10 shows a layout of the ferrite layer with parallel recesses dividing the center conduction path into three segments. Between these three segments two additional segments of side conduction paths are arranged and formed by increasing the width of parallel recesses locally.

(33) FIG. 11 illustrates the effect of the width of the perpendicular recess and width of parallel recesses on the overall core losses. Thus, the overall core losses can have a minimum for a certain width of the perpendicular recess which may in the range between 0.1 and 10 mm. The shape of the minimum of the core losses, however, and the preferred width of the perpendicular recess can depend on the width of the parallel recesses. In particular for a width of the parallel recesses of 2 mm, a recess width of the perpendicular recess of approximately 1 mm is preferred. For a width of the parallel recesses of approximately 10 mm, a preferred with of the perpendicular recess is approximately 2 mm.

(34) In the coil arrangement to which FIG. 10 refers, the preferred recess width of the perpendicular recess increases with increasing width of the parallel recesses. However, for a width of parallel recesses being 20 mm or more, the core losses are nearly independent of the recess width of the perpendicular recess as long as this width is 6 mm or larger.

(35) FIG. 12 shows the dependence of the coupling factor on the width of the recesses. The top most curves correspond to parallel recesses of a width of 0.001 mm, 2 mm, 5 mm, 10 mm and 20 mm, respectively. The dashed lines show results of additional simulations.

(36) It can be deducted from FIG. 11 that the side conduction paths take a part of the magnetic flux from the center conduction path. This effect helps maintain the coupling factor.

(37) Thus, by finding suitable geometric parameters of the coil arrangement and recesses in ferrite material of the coil arrangement, core losses can be reduced and values of the coupling factor can be decoupled.

(38) The coil arrangement can further have additional circuit elements such as electrical connections to external circuit environments and between the coils and can have further coils and further structures in the ferrite material.

(39) In FIG. 13, a wireless power reception system (WPRS) comprises a coil arrangement as described above as a power reception coil arrangement (Power Reception CA).

(40) In FIG. 14, a wireless power transfer system (WPTS) comprises a coil arrangement as described above as a power transmission coil arrangement (Power Transmission CA).

(41) In FIG. 15, a wireless power transfer system may comprise a coil arrangement as described above in the form of a power transmission coil arrangement (Power Transmission CA) and/or a power reception coil arrangement (Power Reception CA).

LIST OF REFERENCE SIGNS

(42) C1: first coil C2: second coil CA: coil arrangement CCP: center conduction path F: ferrite material in a ferrite layer MF: direction of magnetic field RPA: parallel recess RPE: perpendicular recess SCP: side conduction path