Abstract:
A filter package includes a pair of spaced circuit boards; a magnetic core between the circuit boards; a plurality of windings on the core extending to at least one of the boards; and a plurality of conductor bars mechanically fastening and electrically interconnecting the circuit boards.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to an improved filter package and more particularly to such a filter package for EMI/RFI and inverter frequencies. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional EMI/RFI filter and inverter frequency filters typically include a filter stage having a common mode core with two or more windings: e.g. two for d.c., three for a.c., four for “Y” connected a.c. with a neutral. There is also a common mode filter capacitor circuit including one or more capacitors and a differential filter capacitor circuit also including one or more capacitors. The core may be ferrite, iron powder, Mn—Zn or other material depending upon the desired permeability and current requirements. The capacitors are typically disc ceramic. The cores tend to be large and heavy and there may be more than one stage required to meet the filtering demands thereby increasing the number of cores and the size and weight of the filter package. And higher current demands require even larger components. The size and weight are particularly critical in mobile applications such as electric and hybrid vehicles. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    It is therefore an object of this invention to provide an improved filter package. 
         [0004]    It is a further object of this invention to provide such an improved filter package which is applicable to EMI/RFI filters and inverter frequency filters. 
         [0005]    It is a further object of this invention to provide such an improved filter package which is lighter and smaller and compact even with high current capabilities. 
         [0006]    It is a further object of this invention to provide such an improved filter package which is easier to fabricate. 
         [0007]    The invention results from the realization that a smaller, lighter, compact filter package can be achieved by packaging the core between a pair of circuit boards with the core windings interconnected to/through the circuit board(s) and a plurality of connector bars mechanically fastened and electrically interconnecting together the circuit boards. 
         [0008]    The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives. 
         [0009]    This invention features a filter package including a pair of spaced circuit boards, a magnetic core between the circuit boards, and a plurality of windings on the core extending to at least one of the boards. There are a plurality of conductor bars mechanically fastening and electrically interconnecting the circuit boards. 
         [0010]    In a preferred embodiment there may a differential capacitor filter circuit carried by at least one of the circuit boards and electrically interconnected with the windings. There may be a common mode filter capacitor circuit carried by at least one of the circuit boards and electrically interconnected with the windings. There may be at least two differential inductors disposed on the windings with the core between the circuit boards. The circuit boards may each include a ground plane conductor. There may be least one filter capacitor circuit on at least one of the circuit boards on the outside of the circuit board from the ground plane and core. The circuit boards may be generally rectangular and there may be a conductor bar proximate each corner or they may be generally circular with three spaced conductor bars. There may be at least two windings on the core for d.c. filtering and at least three for a.c. three phase filtering. The core may be a nanocrystalline amorphous core. The windings may electrically connect to at least one board. The windings may extend through at least one board. 
         [0011]    This invention also features an EMI/RFI filter package including a pair of spaced circuit boards, a nanocrystalline amorphous magnetic core between the circuit boards and a plurality of windings on the core extending to at least one of the boards. There may be a plurality of conductor bars mechanically fastening and electrically interconnecting the circuit boards. 
         [0012]    In a preferred embodiment the circuit boards may each include a ground plane conductor. There may be a common mode capacitor filter circuit and/or a differential capacitor filter circuit disposed on at least one of the boards on the outside of the ground plane conductor and core. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which: 
           [0014]      FIG. 1  is an exploded three dimensional diagrammatic view of a filter package according to this invention implementing a d.c. filter; 
           [0015]      FIG. 1A  is a side sectional diagrammatic view of the package of  FIG. 1  according to this invention collapsed to a normal unexploded view; 
           [0016]      FIG. 2  is an exploded three dimensional diagrammatic view of a filter package according to this invention implementing an a.c. filter; 
           [0017]      FIG. 3  is a schematic elevational view of a circuit board showing enlarged conductor bars for attachment to the housing; 
           [0018]      FIG. 4  is a schematic side elevational view of a circuit board showing winding leads to and through the board; and 
           [0019]      FIG. 4A  is a view similar to  FIGS. 1 and 2  with parts removed showing round circuit boards; 
           [0020]      FIGS. 5 ,  6 , and  7  are schematic diagrams of the d.c. a.c. Δ, connected and a.c. Y connected filter networks, respectively, that may be contained in the filter package of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer. 
         [0022]    There is shown in  FIG. 1  a d.c. EMI/RFI filter  10  package including inductor  11  having a core  12  which may be a nanocrystalline amorphous material such as Metglas FT-3M available from Metglas, Inc. and may include two d.c. windings  14  and  16 . Winding  14  has one lead  18  soldered at  20  to circuit board  22  and its other lead  24  soldered at  26  to circuit board  28 . Winding  16  has one lead  30  soldered at  32  to circuit board  22  and lead  34  soldered at  36  to circuit board  28 . Either one or both of circuit boards  22  and  28  may include one or more capacitors  40 ,  42 ,  44 ,  46 ,  48 , and  50  which may make up a common mode capacitor circuit or differential filter capacitor circuit. The capacitors, for example, may be lower frequency filter film capacitors of for example 0.022 μf for approximately a 200 to 300 KHz range. Or they may be multi-layer ceramic capacitors for example of 470 pf for filtering in the range of 200 MHz. 
         [0023]    Also included in the package there may be differential inductors  52 ,  54  which may be for example ferrite beads which are mounted on the leads, for example leads  18  and  30 , with core  12  between circuit boards  22  and  28 . Circuit boards  22  and  28  are both shown as generally rectangular in shape. The package may be mechanically fixed together by bars  60 ,  62 ,  64 ,  66  which may be copper bars or other conductor bars that are mechanically fastened proximate the corners of circuit boards  22  and  28  for mechanical rigidity and which also electrically interconnect those boards. The entire package  10  may be installed in five sided housing  70  made of metal such as steel for example and drawn to be seamless. Housing  70  may be closed by metal cover  72  being welded, brazed or soldered to it. Metal cover  72  may contain a connector  74  which connects to the various leads and conductors in package  10 . Leads  76 ,  78  from connector  74  may be connected at solder contacts  20 ,  32  to leads  18 ,  30 , respectively. Each printed circuit board may have a ground plane conductor  84 ,  86  on it or embedded in it to reduce emissions of electromagnetic interference. Preferably capacitors such as  40 ,  42 ,  44 , and  46 ,  48 ,  50 ,  FIG. 1  are on the outside of the ground plane conductors and inductor  11 . When completed package  10 ,  FIG. 1A , constitutes a small, compact, lightweight package which can have a volume as little as a two inch cube at lower currents in the milliamp range and as small as a three inch cube at higher currents in 10 or 100 amp range. 
         [0024]    In accordance with this invention the filter package may be used with single phase a.c filters in which case the construction would be the same as in  FIG. 1  or it may be used for multi-phase Δ or Y connected a.c. as shown in  FIG. 2 . In  FIG. 2  and the following figures similar parts have been given like numbers accompanied by a lower case letter. In  FIG. 2  a third winding  17  has been added to core  11   a,  wound around core  12   a  which again may be nanocrystalline amorphous material. Now, in addition to windings  14   a  and  16   a,  there is a third winding  17  which has lead  31  soldered to circuit board  22   a  at  35  and lead  37  soldered at  39  to circuit board  28   a.  A third differential inductor  55  is disposed on lead  31 . Third winding  17  has lead  31  connected at solder contact  35  to circuit board  22   a,  where it may be connected to lead  78   a  from connector  74   a.  The other lead  37  of winding  17  is connected at solder connect  39  to circuit board  28   a.  Connector  74   a  may also provide ground lead  80  and frame lead  82 . 
         [0025]    Although the conductor bars  60 ,  62 ,  64 ,  66  are shown connected to circuit boards  22   a  and  28   a  proximate their corners but within their periphery this is not a necessary limitation of the invention. For example, it is often advantageous to have bars  60   b,    62   b,    64   b,    66   b,    FIG. 3 , extend slightly beyond the periphery of boards  22   b  and  28   b  so that they can be mechanically fastened to and electrically connected to housing  70   b  for increased rigidity and electrical security. In some cases, leads  18 ,  30 ,  31 ,  24 ,  34 , and  37  may be connected as exemplified by leads  18  and  30  in  FIG. 4 . They may extend to circuit board  26  or  28  and end there at solder connections  20  and  32 , respectively, or they may continue through the circuit boards as shown at  18 ′ and  30 ′,  FIG. 4 , and may or may not have a solder connection at  20  and  32 . Although circuit boards  22  and  28  are shown, supra, as generally rectangular in shape, this in not a necessary limitation of the invention they could be any suitable shape. For example, they could be round  22   a,    28   a,    FIG. 4A , in which case perhaps only three bars  60   b,    62   b,    64   b  spaced at 120° could be used to fix them together and the could be mounted in a pipe-like or deep drawn cylindrical container. 
         [0026]    A typical d.c. EMI/RFI filter or single phase a.c. EMI/RFI filter that may be packaged in accordance with this invention is shown at  100 ,  FIG. 5 , as including a common mode inductor  102 , including two coils  104 ,  106  and a core  108  typically made with amorphous nanocrystalline material in accordance with this invention. Inductor  102  including core  108  and windings  104 ,  106  are inside of ground plane conductors  110  and  112 . Also inside of ground plane conductors  110  and  112  are differential inductors  114  and  116 . External of ground plane conductors  110  is differential capacitor filter circuit  118  including single capacitor  120  and common mode filter capacitor circuit  122  composed of two capacitors  124  and  126 . For this filter the electrical inputs may be d.c.+ and d.c.− on lines  128  and  130  or they may be for a single phase a.c. circuit. A second differential capacitor filter circuit  132  including capacitor  134  and a second common mode capacitor filter circuit  136  including capacitors  138  and  140  may be disposed outside ground plane  112 . 
         [0027]    The filter package according to this invention also applies to three wire filter circuits,  100   a,    FIG. 6 , where the inputs are the three a.c. A connected phases  128   a,    130   a  and  131 . Inside ground planes  110   a  and  112   a,  core  108   a  now has three windings on it  104   a,    106   a  and  107 . And there are three differential inductors  114   a,    116   a,  and  117 . External to ground plane  110   a  differential filter  118   a  has, in addition to capacitor  128   a,  two more capacitors  121  and  123 . Common mode filter capacitor circuit  122   a  has a third capacitor  127  in addition to capacitors  124   a  and  126   a.  Likewise, external to ground plane conductor  112   a,  differential capacitor filter circuit  132   a  includes capacitor  134   a  and additional capacitors  135  and  137  while common mode capacitor filter circuit  136   a  includes additional capacitor  141  along with capacitors  138   a  and  140   a.    
         [0028]    The filter package of this invention may also be used to package four wire systems. For example, four wire a.c. Y connected filter  100   b,    FIG. 7 , includes three phase inputs  128   b,    130   b,    131   b,  and neutral  133 . There may also be a differential capacitor filter circuit  132   b  including capacitors  134   b,    137   b  and  135   b  and a common mode capacitor filter circuit  136   b  including capacitor  143  in addition to capacitors  138   b,    140   b,    141   b.    
         [0029]    Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. 
         [0030]    In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended. 
         [0031]    Other embodiments will occur to those skilled in the art and are within the following claims.