Abstract:
An integrated inductor comprises a first winding (C 1 ) and a second winding (C 2 ); a first internal magnetic core in the first winding (C 1 ) and a second internal magnetic core in the second winding (C 2 ); and at least one external magnetic core (M) outside the first winding (C 1 ) and the second winding (C 2 ), used for being connected to end portions of the first and second internal magnetic cores to form a magnetic path, the external magnetic core (M) being formed by multiple sub-magnetic cores joint with each other; the magnetic conductivity of at least one sub-magnetic core of the multiple sub-magnetic cores is greater than the magnetic conductivity of other sub-magnetic cores, and the at least one sub-magnetic core at least covers a part of end faces of the first internal magnetic core and the second internal magnetic core. The integrated inductor can alleviate the phenomenon of flux leakage, and can reduce costs of the magnetic cores.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to an inductor and, more particularly, to an integrated inductor having cores comprising of a plurality of blocks. 
       BACKGROUND OF THE INVENTION 
       [0002]    At present, the requirements for the design and cost of inductors are becoming increasingly high with the continuous development of high-efficiency and high-power UPS and inverter devices for meeting the market requirements and enhancing the competitiveness. The size of a core increases accordingly with the increase of the size of the inductor. However, the cost is very high to manufacture a one-piece and large-volume core. Therefore, it is usually adopted in the prior art to splice a plurality of smaller blocks into a larger core in a splicing way, and the resulted core is generally referred to as an integrated inductor. 
         [0003]      FIG. 1  shows such an integrated inductor. As shown in  FIG. 1 , this integrated inductor comprises a first winding C 1  and a second winding C 2  connected to each other. Each of the first winding C 1  and the second winding C 2  wraps around a respective internal core (not shown in  FIG. 1 ), and the two internal cores corresponding to the first winding C 1  and the second winding C 2  are connected by means of two external cores M located outside the windings in order to achieve a communicating magnetic circuit, wherein the distribution of the magnetic induction lines is shown substantially as the dashed arrow of  FIG. 1 . The external cores M need a relatively large volume. However, the manufacturing cost is very high if each of the external cores M is made of a one-piece and large-volume material. Consequently, in order to reduce the cost, each external core M is usually formed by splicing six small-volume cuboid-shaped sub-cores a, b, c, d, e and f. 
         [0004]    However, there will be gaps between the sub-cores inevitably even if the sub-cores are spliced very closely, such as a gap G 1  substantially perpendicular to the magnetic induction lines, and gaps G 2  and G 3  substantially parallel to the magnetic induction lines. Such gaps will result in flux leakage, which may cause a certain degree of eddy-current loss to the metal near the inductor and ultimately result in the increase of power consumption of devices comprising such inductors. 
       SUMMARY OF INVENTION 
       [0005]    In view of the foregoing, an object of the present invention is to provide an integrated inductor which can weaken the flux leakage and reduce the cost of cores. 
         [0006]    An integrated inductor is provided, comprising: 
         [0007]    a first winding and a second winding; 
         [0008]    a first internal core located inside the first winding and a second internal core located inside the second winding; and 
         [0009]    at least one external core formed by splicing a plurality of sub-cores and located outside the first winding and the second winding for connecting to the ends of the first internal core and the second internal core to form a magnetic circuit, 
         [0010]    wherein at least one sub-core of the plurality of sub-cores has a higher magnetic permeability than other sub-cores, and the at least one sub-core at least covers a portion of end faces of the first internal core and the second internal core. 
         [0011]    Preferably, the at least one sub-core which has a higher magnetic permeability than other sub-cores at least covers the midpoints of the end faces of the first internal core and the second internal core. 
         [0012]    Preferably, the at least one sub-core which has a higher magnetic permeability than other sub-cores at least covers the total areas of the end faces of the first internal core and the second internal core. 
         [0013]    Preferably, the external core is flat-shaped. 
         [0014]    Preferably, the at least one sub-core which has a higher magnetic permeability than other sub-cores is prismatic shaped. 
         [0015]    Preferably, there are respectively at least one sub-core at both sides of the at least one sub-core which has a higher magnetic permeability than other sub-cores. 
         [0016]    Preferably, there are respectively at least one sub-core at both ends of the at least one sub-core which has a higher magnetic permeability than other sub-cores. 
         [0017]    Preferably, the ends of the external core are arc shaped. 
         [0018]    Preferably, some of the plurality of sub-cores have arc shaped edges, and the sub-cores with arc shaped edges are located at the ends of the external core after the external core is formed. 
         [0019]    In the integrated inductor provided by the present invention, by optimizing the position relationships between the magnetic induction lines and the gaps among the sub-cores and making the central sub-core have a higher permeability than its ambient sub-cores, the intersection of the magnetic induction lines and the gaps is avoided, in other words, less magnetic induction lines intersect with the gaps, thereby the flux leakage and the cost of the external cores are reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]    The present invention will be further explained in combination with the embodiments with reference to the accompanying figures, wherein: 
           [0021]      FIG. 1  is the structure diagram of a prior integrated inductor; 
           [0022]      FIG. 2  is the structure diagram of an integrated inductor according to an embodiment of the present invention; 
           [0023]      FIG. 3  shows the position relationship between the integrated inductor according the embodiments of the present invention and the test aluminum sheets A 1  and A 2 ; 
           [0024]      FIG. 4  shows the position relationship between the prior integrated inductor and the test aluminum sheets A 3  and A 4 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    In the following parts, the present invention will be described in greater details with reference to the embodiments and the accompanying drawings so as to make its objects, solutions and advantages clearer. It should be understood that the specific embodiments described herein only intend to interpret the present invention, without making any limitation thereto. 
         [0026]    In an embodiment, an integrated inductor, the structure of which is shown in  FIG. 2 , is provided and the integrated inductor comprises: 
         [0027]    a first winding C 1  and a second winding C 2  connected to each other, wherein, each of the first winding C 1  and the second winding C 2  wraps around a respective internal core (not shown in  FIG. 2 ); 
         [0028]    two external cores M located outside the first winding C 1  and the second winding C 2 , wherein the two external cores M are located at both sides of the first winding C 1  and the second winding C 2  for connecting the internal cores located inside the first winding C 1  and the second winding C 2 , so that the two internal cores and the two external cores M can constitute a communicating magnetic circuit (the distribution of the magnetic induction lines thereof is shown substantially as the dashed arrow of  FIG. 2 ) together. Each external core M is formed by closely splicing a plurality of sub-cores m 1 , m 2 , m 3 , m 4 , m 5 , m 6  and m 7 . The sub-cores m 1 , m 2  and m 3  are cuboids, and sub-core m 1  is located between sub-cores m 2  and m 3 . There are a gap G 4  between the sub-cores m 1  and m 2  and a gap G 5  between the sub-cores m 1  and m 3 . The sub-cores m 4 , m 5 , m 6  and m 7  are fan-shaped, wherein the sub-cores m 4  and m 5  are spliced into a semicircular shape at a side of a unit composed of the sub-cores m 1 , m 2  and m 3 , and the sub-cores m 6  and m 7  are spliced into another semicircular shape at the other side of the unit composed of the sub-cores m 1 , m 2  and m 3 . There are a gap G 7  between the sub-cores m 4  and m 5  and a gap G 6  between the unit composed of the sub-cores m 4  and m 5  and the unit composed of the sub-cores m 1 , m 2  and m 3 . There are a gap G 9  between the sub-cores m 6  and m 7  and a gap G 8  between the unit composed of the sub-cores m 6  and m 7  and the unit composed of the sub-cores m 1 , m 2  and m 3 . 
         [0029]    As shown in  FIG. 2 , the plurality of sub-cores m 1 , m 2 , m 3 , m 4 , m 5 , m 6  and m 7  are finally spliced into a flat external core M, which is connected to the ends of the internal cores located inside the first winding C 1  and the second winding C 2  at the ends thereof. The length and width of the unit composed of sub-cores m 1 , m 2  and m 3  are designed to at least cover a portion of end faces of the internal cores located inside the first winding C 1  and the second winding C 2 , preferably at least cover the midpoints of the end faces of the internal cores, more preferably cover the total areas of the end faces of the internal cores. 
         [0030]    The general distribution of the magnetic induction lines of the integrated inductor provided by the embodiment is shown as the dotted arrow of  FIG. 2 . The closer the position is from the dotted arrow, the denser the magnetic induction lines are. The magnetic induction lines traverse the internal cores inside the first winding C 1  and the second windings C 2  and the two external cores M, and form a complete magnetic circuit. 
         [0031]    Research carried out by the applicant shows that in comparison with gaps parallel to the magnetic induction lines, gaps intersecting with the magnetic induction lines, in particular perpendicular to the magnetic induction lines, are more likely to induce flux leakage. Therefore it is desirable to avoid the formation of the gaps intersecting with the magnetic induction lines, in particular the gaps perpendicular to the magnetic induction lines. 
         [0032]    In the integrated inductor of this embodiment, as shown in  FIG. 2 , because the unit composed of sub-cores m 1 , m 2  and m 3  at least covers a portion of the end faces of the internal cores inside the first winding C 1  and the second windings C 2 , part of the magnetic induction lines do not traverse the gaps G 6  and G 8  perpendicular to the direction of the magnetic induction lines. Especially when the unit composed of sub-cores m 1 , m 2  and m 3  at least covers the midpoints of the end faces of the internal cores, a majority of magnetic induction lines do not traverse the gaps G 6  and G 8  perpendicular to the direction of the magnetic induction lines. More preferably, when the unit composed of sub-cores m 1 , m 2  and m 3  covers the total areas of the end faces of the internal cores, none of the magnetic induction lines traverses the gaps G 6  and G 8  perpendicular to the direction of the magnetic induction lines in the external cores M. This can significantly reduce the flux leakage in comparison with the case shown in  FIG. 1  (all the magnetic induction lines traverse the gap G 1  perpendicular to the magnetic induction lines). 
         [0033]    According to another embodiment of the present invention, the sub-core m 1  has a higher permeability than other sub-cores m 2 , m 3 , m 4 , m 5 , m 6  and m 7 . The length and width of the sub-core m 1  are designed to make the sub-core m 1  at least cover a portion of the end faces of the internal cores inside the first winding C 1  and the second windings C 2 , preferably at least cover the midpoints of the end faces of the internal cores, more preferably cover the total areas of the end faces of the internal cores. 
         [0034]    Because the permeability of the sub-core m 1  is higher than those of the sub-cores m 2  and m 3 , more magnetic induction lines are concentrated into the sub-core m 1 , such that the magnetic induction lines near the gaps G 4  and G 5  in parallel with the magnetic induction lines are relatively sparse, thereby the influence of the gaps G 4  and G 5  in parallel with the magnetic induction lines is further lessened, and then the flux leakage is further reduced. Moreover, because the permeability of the sub-core m 1  is higher than those of the sub-cores m 4 , m 5 , m 6  and m 7 , and the sub-core m 1  at least covers a portion of end faces of the internal cores (preferably covers the midpoints of end faces of the internal cores, and more preferably covers the total areas of end faces of the internal cores), more magnetic induction lines induced from the internal cores are concentrated into the sub-core m 1 , and only a small part of magnetic induction lines traverse sub-cores m 4 , m 5 , m 6  and m 7 , thereby the magnetic induction lines traversing the gaps G 6  and G 8  are further reduced, and then the flux leakage is further reduced. 
         [0035]    In addition, the integrated inductor according to the embodiment can also reduce the cost of the external cores M. Generally speaking, materials with higher permeability will be more expensive, and the permeability must reach a threshold value in order to meet the requirements of the inductors Therefore, it is difficult to reduce the prices thereof In the integrated inductor provided by the embodiment, the sub-core m 1  has a higher permeability than other sub-cores m 2 , m 3 , m 4 , m 5 , m 6  and m 7 . The volume of the sub-core m 1  with higher price and higher permeability only occupies a small part of that of the external cores M, and other sub-cores may be formed by using materials with lower price and lower permeability. The total cost of the whole external cores can be reduced by means of designing the plurality of sub-cores to have different permeabilities. As for the specific permeability values and the volume fraction of the sub-core m 1 , a person skilled in the art may easily obtain preferable solutions according to the permeability values and the market price of various materials without creative labor. 
         [0036]    Moreover, since the sub-cores m 4 , m 5 , m 6  and m 7  are designed to be fan-shaped, the volume and weight of the external cores can be reduced in comparison with the rectangular external cores shown in  FIG. 1 . In addition, the fan-shaped sub-cores m 4 , m 5 , m 6  and m 7  have arc-shaped edges, in comparison with the rectangular external cores shown in  FIG. 1 , under the same external conditions, the former makes the corners of the external cores M farther away from the ambient metal parts and thus the eddy-current interference to the metal parts are lessened. 
         [0037]    In order to demonstrate the advantages of the integrated inductor provided by this embodiment, the integrated inductor is simulated and the eddy-current loss created in metal sheets A 1  and A 2  near the integrated inductor is calculated. In this embodiment, the sub-core m 1  covers the midpoints of the end faces of the internal cores.  FIG. 3  shows the position relationship between aluminum sheets A 1  and A 2  near the integrated inductor. Wherein, the aluminum sheet A 1  is located near one end of the two external cores M, near sub-cores m 6  and m 7 , and is perpendicular to a plane defined by the first winding C 1  and the second winding C 2 . The aluminum sheet A 2  is parallel to one of the external cores M. 
         [0038]    In contrast, the prior integrated inductor shown in  FIG. 1  is also simulated, and the eddy-current loss created in aluminum sheets A 3  and A 4  near the integrated inductor is also calculated. The positions of aluminum sheets A 3  and A 4  are shown in  FIG. 4 , which are corresponding to the positions of A 1  and A 2  with respect to the present integrated inductor. 
         [0039]    The simulation results show that the eddy-current loss of the metal sheet A 1  near the integrated inductor provided by this embodiment decreases by 22.2% with respect to the eddy-current loss of the metal sheet A 3  near the prior integrated inductor. And the eddy-current loss of the metal sheet A 2  near the integrated inductor provided by this embodiment decreases by 29% with respect to the eddy-current loss of the metal sheet A 4  near the prior integrated inductor. 
         [0040]    In view of above, by optimizing the position relationships between the magnetic induction lines and the gaps among the sub-cores and making the sub-core m 1  have a higher permeability than other sub-cores m 2 , m 3 , m 4 , m 5 , m 6  and m 7 , the integrated inductor of the present invention tries to avoid the intersection of the magnetic induction lines and the gaps, in other words, make less magnetic induction lines intersect with the gaps, thereby the flux leakage and the cost of the external cores are reduced. 
         [0041]    The shapes of various sub-cores described in the above embodiment are not limitations to the present invention, and a person skilled in the art is able to make various modifications to the solutions of the present invention. For example, according to another embodiment of the present invention, the sub-cores m 1 , m 2  and m 3  may be prismatic shaped with rhombic cross-sections, and may also be other shapes being able to be matched with each other and spliced into a whole body. The sub-cores m 4 , m 5 , m 6  and m 7  may also be other shapes with arc-shaped edges other than fan-shape, which can also realize the object of the present invention. 
         [0042]    According to another embodiment of the present invention, the external cores may be formed by splicing more sub-cores. For example, there may be more sub-cores outside the sub-cores m 2  and m 3 . 
         [0043]    According to another embodiment of the present invention, the windings C 1  and C 2  can be electrically connected or un-electrically connected. 
         [0044]    According to another embodiment of the present invention, the ends of the external cores are preferably arc, more preferably semicircle, and most preferably semicircle coinciding with the circular section of the internal cores. Thereby, the requirement of permeability is satisfied and the cost is minimized. 
         [0045]    It should be noted that the “gap(s)” of the present invention are gaps introduced unavoidably by splicing, rather than gaps created deliberately. It is well known by a person skilled in the art that it is expected to make the gaps between various sub-cores smaller, in order to avoid flux leakage as far as possible. 
         [0046]    It should be also noted that the embodiments described above are only used to explain the solutions of the present invention, rather than limitations to the present invention. Although the present invention has been described in terms of the preferred embodiment, it is recognized by a person skilled in the art that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.