System and Method for Reducing Power Losses for Magnetics Integrated in a Printed Circuit Board

Abstract

A system and method for integrating a magnetic component within a power converter includes a coil integrated on a PCB. The PCB includes multiple layers and traces on each layer to form a single coil or to form multiple coils on the magnetic component. The PCB further includes at least one opening in the PCB through which a core component may pass, such that the magnetic component is defined by the coils and the core material. To reduce eddy currents built up within the traces, the dimensions of traces on a layer are varied and the position of traces between layers of the PCB are varied. The widths and locations of individual traces are selected to reduce coupling of the trace to leakage fluxes within the magnetic component. A floating conductive layer may also be provided to still further reduce the magnitude of eddy currents induced within the coil.

We claim: 
     
         1 . A magnetic component, comprising:
 a circuit board having a plurality of layers and an opening extending through the circuit board; and   a coil defined by a plurality of traces, wherein:
 the plurality of traces includes at least one trace on each of the plurality of layers of the circuit board, 
 the at least one trace on each layer extends around the opening extending through the circuit board to define a plurality of loops on the respective layer, 
 the plurality of loops on one layer define an inner trace proximate the opening through the circuit board, an outer trace distal from the opening through the circuit board, and at least one intermediate trace located between the inner trace and the outer trace, 
 a first width of the inner trace is less than a second width of the at least one intermediate trace, and 
 a second width of the at least one intermediate trace is less than a third width of the outer trace. 
   
     
     
         2 . The magnetic component of  claim 1  wherein:
 the circuit board includes a top layer and a bottom layer, 
 the top layer is selected from the plurality of layers and is the layer closest to a first surface of the circuit board, 
 the bottom layer is selected from the plurality of layers and is the layer closest to a second surface of the circuit board, 
 the second surface of the circuit board is opposite the first surface of the circuit board, and 
 the magnetic component further comprises a first shield located on one of the plurality of layers between the top layer and the coil to induce eddy currents in the first shield and, thereby, reduce eddy currents induced in the coil. 
 
     
     
         3 . The magnetic component of  claim 2  further comprising a second shield located on one of the plurality of layers between the bottom layer and the coil to induce eddy currents in the second shield and, thereby, reduce eddy currents induced in the coil. 
     
     
         4 . The magnetic component of  claim 1  wherein:
 the inner trace on each layer has a first axis, 
 the at least one intermediate trace on each layer has a second axis, 
 the outer trace on each layer has a third axis, 
 at least one of the first axis, the second axis, and the third axis on one layer is offset from the corresponding axis on another layer. 
 
     
     
         5 . The magnetic component of  claim 4  wherein:
 the plurality of layers includes a top layer, a bottom layer, and at least one intermediate layer, 
 the first axis, the second axis, and the third axis on the at least one intermediate layer are each offset from the respective axis on the bottom layer, and 
 the first axis, the second axis, and the third axis on the top layer are each offset from the respective axis on the at least one intermediate layer. 
 
     
     
         6 . The magnetic component of  claim 1  wherein:
 a plane of symmetry extends through the circuit board parallel with the plurality of layers, 
 the first axis, the second axis, and the third axis on a first side of the plane of symmetry are offset from the corresponding axis on adjacent layers in a first pattern, and 
 the first axis, the second axis, and the third axis on a second side second side of the plane of symmetry are offset from the corresponding axis on adjacent layers in a second pattern symmetrical to the first pattern. 
 
     
     
         7 . The magnetic component of  claim 1  further comprising:
 a core material, wherein:
 the core material extends over the opening through the circuit board and laterally over at least a portion of the circuit board, 
 a portion of the core material extends through the opening in the circuit board, 
 a first portion of the coil located on the circuit board between the opening and a first side of the circuit board is under the core material, 
 a second portion of the coil located on the circuit board between the opening and a second side of the circuit board is under the core material, 
 a third portion of the coil located on the circuit board proximate a first end of the circuit board defines a first end turn of the coil and is beyond a first end of the core material, and 
 a fourth portion of the coil located on the circuit board proximate a second end of the circuit board defines a second end turn of the coil and is beyond a second end of the core material. 
 
 
     
     
         8 . The magnetic component of  claim 7  wherein each trace on one layer of the circuit board has a first sectional profile in the first portion of the coil and a second sectional profile in the second portion of the coil. 
     
     
         9 . A magnetic component, comprising:
 a circuit board having a plurality of layers and an opening extending through the circuit board; and   a coil defined by a plurality of traces, wherein:
 the plurality of traces includes at least one trace on each of the plurality of layers of the circuit board, 
 the at least one trace on each layer extends around the opening through the circuit board to define a plurality of loops on the respective layer, 
 the plurality of loops on one layer define an inner trace proximate the opening through the circuit board, an outer trace distal from the opening through the circuit board, and at least one intermediate trace located between the inner trace and the outer trace, 
 the inner trace on each layer has a first axis, 
 the at least one intermediate trace on each layer has a second axis, 
 the outer trace on each layer has a third axis, 
 at least one of the first axis, second axis, and third axis on one layer is offset from the corresponding axis on another layer. 
   
     
     
         10 . The magnetic component of  claim 9  wherein:
 the plurality of layers includes a top layer, a bottom layer, and at least one intermediate layer, 
 the first axis, the second axis, and the third axis on the at least one intermediate layer are each offset from the respective axis on the bottom layer, and 
 the first axis, the second axis, and the third axis on the top layer are each offset from the respective axis on the at least one intermediate layer. 
 
     
     
         11 . The magnetic component of  claim 9  wherein:
 the circuit board includes a top layer and a bottom layer, 
 the top layer is selected from the plurality of layers and is the layer closest to a first surface of the circuit board, 
 the bottom layer is selected from the plurality of layers and is the layer closest to a second surface of the circuit board, 
 the second surface of the circuit board is opposite the first surface of the circuit board, and 
 the magnetic component further comprises a first shield located on one of the plurality of layers between the top layer and the coil to induce eddy currents in the first shield and, thereby, 
 reduce eddy currents induced in the coil. 
 
     
     
         12 . The magnetic component of  claim 11  further comprising a second shield located on one of the plurality of layers between the bottom layer and the coil to induce eddy currents in the second shield and, thereby, reduce eddy currents induced in the coil. 
     
     
         13 . The magnetic component of  claim 9  wherein:
 a first width of the inner trace is less than a second width of the at least one intermediate trace, and 
 a second width of the at least one intermediate trace is less than a third width of the outer trace. 
 
     
     
         14 . The magnetic component of  claim 9  wherein:
 a plane of symmetry extends through the circuit board parallel with the plurality of layers, 
 the first axis, the second axis, and the third axis on a first side of the plane of symmetry are offset from the corresponding axis on adjacent layers in a first pattern, and 
 the first axis, the second axis, and the third axis on a second side second side of the plane of symmetry are offset from the corresponding axis on adjacent layers in a second pattern symmetrical to the first pattern. 
 
     
     
         15 . The magnetic component of  claim 9  further comprising:
 a core material, wherein:
 the core material extends over the opening through the circuit board and laterally over at least a portion of the circuit board, 
 a portion of the core material extends through the opening in the circuit board, 
 a first portion of the coil located on the circuit board between the opening and a first side of the circuit board is under the core material, 
 a second portion of the coil located on the circuit board between the opening and a second side of the circuit board is under the core material, 
 a third portion of the coil located on the circuit board proximate a first end of the circuit board defines a first end turn of the coil and is located beyond a first end of the core material, and 
 a fourth portion of the coil located on the circuit board proximate a second end of the circuit board defines a second end turn of the coil and is located beyond a second end of the core material. 
 
 
     
     
         16 . The magnetic component of  claim 15  wherein each trace on one layer of the circuit board has a first sectional profile in the first portion of the coil and a second sectional profile in the second portion of the coil. 
     
     
         17 . A method of integrating a magnetic component in a circuit board, the method comprising the steps of:
 defining a plurality of traces for a circuit board, the circuit board including a plurality of layers and an opening extending therethrough, wherein:
 the plurality of traces includes at least one trace on each of the plurality of layers of the circuit board, 
 the at least one trace on each layer extends around the opening through the circuit board to define a plurality of loops on the respective layer, 
 the plurality of loops on one layer define an inner trace proximate the opening through the circuit board, an outer trace distal from the opening extending the circuit board, and at least one intermediate trace located between the inner trace and the outer trace, 
 a first width of the inner trace is less than a second width of the at least one intermediate trace, and 
 a second width of the at least one intermediate trace is less than a third width of the outer trace, and 
   mounting a core to the circuit board, wherein a portion of the core is inserted through the opening and the core extends laterally over at least a portion of the plurality of traces.   
     
     
         18 . The method of  claim 17 , wherein:
 the inner trace on each layer has a first axis,   the at least one intermediate trace on each layer has a second axis,   the outer trace on each layer has a third axis,   at least one of the first axis, the second axis, and the third axis on one layer is offset from the corresponding axis on another layer.   
     
     
         19 . The method of  claim 18 , wherein:
 the plurality of layers includes a top layer, a bottom layer, and at least one intermediate layer,   the first axis, the second axis, and the third axis on the at least one intermediate layer are each offset from the respective axis on the bottom layer, and   the first axis, the second axis, and the third axis on the top layer are each offset from the respective axis on the at least one intermediate layer.   
     
     
         20 . The method of  claim 17  wherein:
 the circuit board includes a top layer and a bottom layer, 
 the top layer is selected from the plurality of layers and is the layer closest to a first surface of the circuit board, 
 the bottom layer is selected from the plurality of layers and is the layer closest to a second surface of the circuit board, and 
 the second surface of the circuit board is opposite the first surface of the circuit board, the method further comprising the step of defining a shield on one of the plurality of layers between the top layer and the coil to induce eddy currents in the shield and, thereby, reduce eddy currents induced in the coil.