Abstract:
Disclosed herein is an inductor core usable with an interleaved Power Factor Correction (PFC) circuit. The inductor core for a power factor correction circuit, the inductor core may include: a first leg on which a first inductor is wound; a second leg on which a second inductor is wound, wherein the first and second inductors are alternately operable in an interleaved manner; and a third leg provided between the first leg and the second leg, wherein the third leg has a different shape from that of the first leg and the second leg.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Korean Patent Application No. 10-2010-0083884, filed on Aug. 30, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Exemplary embodiments of the present invention relate to an inductor core usable with an interleaved power factor correction circuit. 
         [0004]    2. Description of the Related Art 
         [0005]    A Power Factor Correction (PFC) circuit serves as a radio-frequency device of a variety of electronic and electric appliances (for example, a display device). Such a PFC circuit has been generally employed in a power source device and serves to match a phase of input voltage with a phase of input current, so as to minimize reactive power, thus enabling efficient use of active power. 
         [0006]    A PFC circuit has been recommended to follow European Standard IEC555-2 and IEC555-4 and American National Standard IEEE519. There are various types of PFC circuits and one example thereof is an interleaved PFC circuit. In the interleaved PFC circuit, switching elements of a control integrated circuit are controlled in a dual phase manner such that two boost inductors are alternately operated with a phase angle of 180 degrees. The dual-phase interleaved PFC circuit may more efficiently minimize reactive power than a single-phase PFC circuit and also, may reduce ripple current and Electro Magnetic Interference (EMI). 
         [0007]    In the interleaved PFC circuit, however, each of the two boost inductors has a dual core winding configuration. Thus, each boost inductor is wound on a pair of cores and therefore, winding of the two boost inductors may require four cores. This may increase element costs and the area of a Printed Circuit Board (PCB) for arrangement of the elements. As such, there is a need for an improved core/core configuration. 
       SUMMARY 
       [0008]    An aspect of the present invention provides an inductor core for a power factor correction circuit, wherein the inductor core may include: a first leg on which a first inductor is wound; a second leg on which a second inductor is wound, wherein the first and second inductors are alternately operable in an interleaved manner; and a third leg provided between the first leg and the second leg, wherein the third leg has a different shape from that of the first leg and the second leg. 
         [0009]    A first bobbin for winding the first inductor may be disposed on the first leg and a second bobbin for winding the second inductor may be disposed on the second leg. 
         [0010]    The first inductor wound on the first leg and the second inductor wound on the second leg may have opposite winding directions. 
         [0011]    A number of turns of the first inductor may be equal to a number of turns of the second inductor. 
         [0012]    The first leg and the second leg may have a same shape. 
         [0013]    The third leg may have a greater surface area than that of the first leg and the second leg. 
         [0014]    The inductor core may include a first core which may be “E”-shaped and a second core, wherein the first core may include the first leg, the second leg and the third leg, and wherein the first core may be coupled to the second core. 
         [0015]    Gaps may be between the first leg of the first core and a corresponding first leg of the second core, and the second leg of the first core and a corresponding second leg of the second core. 
         [0016]    The second core may be “E”-shaped. 
         [0017]    The second core may be “I”-shaped. 
         [0018]    The inductor core may include a first core which is “E”-shaped, and a second core, wherein the first core may include the first leg, the second leg and the third leg, and wherein the first core and the second core may be coupled. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
           [0020]      FIG. 1  is a diagram of an interleaved Power Factor Correction (PFC) circuit according to an exemplary embodiment of the present invention; 
           [0021]      FIG. 2  is a perspective view illustrating a configuration of an inductor core according to an exemplary embodiment of the present invention; 
           [0022]      FIG. 3  is a plan view according to an exemplary embodiment of the present invention; 
           [0023]      FIG. 4  is a perspective view illustrating a coupling configuration of inductor cores according to an exemplary embodiment of the present invention; 
           [0024]      FIG. 5  is a view illustrating a magnetic flux path according to an exemplary embodiment of the present invention; 
           [0025]      FIG. 6  is an operating wave diagram of the interleaved PFC circuit according to the exemplary embodiment of the present invention; 
           [0026]      FIG. 7  is a perspective view illustrating a coupling configuration of inductor cores according to another exemplary embodiment of the present invention; 
           [0027]      FIG. 8  is a view illustrating a magnetic flux path according to an exemplary embodiment of the present invention; 
           [0028]      FIG. 9  is a perspective view illustrating a configuration of an inductor core according to another exemplary embodiment of the present invention; 
           [0029]      FIG. 10  is a plan view according to an exemplary embodiment of the present invention; 
           [0030]      FIG. 11  is a perspective view illustrating a coupling configuration of inductor cores according to an exemplary embodiment of the present invention; 
           [0031]      FIG. 12  is a view illustrating a magnetic flux path according to an exemplary embodiment of the present invention; 
           [0032]      FIG. 13  is a perspective view illustrating a configuration of an inductor core according to a further exemplary embodiment of the present invention; 
           [0033]      FIG. 14  is a plan view of an exemplary embodiment of the present invention; 
           [0034]      FIG. 15  is a perspective view illustrating a coupling configuration of inductor cores according to an exemplary embodiment of the present invention; and 
           [0035]      FIG. 16  is a view illustrating a magnetic flux path according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0037]      FIG. 1  is a diagram of an interleaved Power Factor Correction (PFC) circuit according to an exemplary embodiment of the present invention. The PFC circuit includes a rectifier unit  10 , an inductor unit  20 , a switching unit  30 , and a control unit  40 . 
         [0038]    The rectifier unit  10  includes a bridge diode, and rectifies the wavelength of commercial Alternating Current (AC). 
         [0039]    The inductor unit  20  includes a first boost inductor  21  (hereinafter, referred to as a first inductor) and a second boost inductor  22  (hereinafter, referred to as a second inductor). The first inductor  21  and the second inductor  22  are electrically connected in parallel to the rectifier unit  10 . The first inductor  21  and the second inductor  22  are wound on a pair of cores. The configuration of the cores, on which the first inductor  21  and the second inductor  22  are wound, will be described later with reference to  FIG. 2 . 
         [0040]    The switching unit  30  includes a first power switching element  31  and a second power switching element  32 . The first power switching element  31  switches on or off power from the first inductor  21  and the second power switching element  32  switches on or off power from the second inductor  22 , thus allowing the first inductor  21  and the second inductor  22  to be alternately operated with different periods, more particularly, with a phase angle of 180 degrees. 
         [0041]    The switching unit  30  further includes a first diode  33  and a second diode  34  to rectify power upon switching of the first power switching element  31  and the second power switching element  32 , and a condenser  35  to stabilize output power. The first diode  33  and the second diode  34  are connected respectively to the first power switching element  31  and the second power switching element  32  and serve to prevent reverse current from occurring when the first power switching element  31  and the second power switching element  32  are alternately switched. 
         [0042]    The control unit  40  is an interleaved control Integrated Circuit (IC), and serves to control the operational state of the first inductor  21  and the second inductor  22  by applying induced current to allow the first inductor  21  and the second inductor  22  to be alternately operated with different periods and also, by controlling On/Off of the first power switching element  31  and the second power switching element  32  to transform input currents having different phases to be in phase. 
         [0043]    Now, a configuration of the cores, on which the first inductor  21  and the second inductor  22  of the interleaved PFC circuit are wound, will be described with reference to  FIG. 2 . 
         [0044]      FIG. 2  is a perspective view illustrating a configuration of an inductor core according to an exemplary embodiment of the present invention, and  FIG. 3  is an example of a plan view of the exemplary embodiment of  FIG. 2 . 
         [0045]    In  FIGS. 2 and 3 , the core  100  according to the exemplary embodiment of the present invention is an “E”-shaped core having first to third legs  110 ,  120  and  130 . The first leg  110  and the second leg  120  are provided at opposite sides of the core  100  and have the same shape and the same surface area. 
         [0046]    The third leg  130  is located midway between the first leg  110  and the second leg  120  and has a greater surface area than that of the first leg  110  and the second leg  120  by about 2 times. The third leg  130  has a greater surface area than that of the first leg  110  and the second leg  120  so as to prevent a magnetic flux path Φ created by the first inductor  21  from overlapping with a magnetic flux path Φ created by the second inductor  22 . 
         [0047]    Opposite surfaces of the third leg  130  facing the first leg  110  and the second leg  120  are curved to enable insertion of winding bobbins  21   a  and  22   a  of the first inductor  21  and the second inductor  22 . When providing the third leg  130  with the curved opposite surfaces facing the first leg  110  and the second leg  120 , it may be possible to maximize the number of turns of the first inductor  21  and the second inductor  22  wound on the first leg  110  and the second leg  120 , thereby realizing optimization of the core  100  based on power capacity. 
         [0048]    A core configuration in which the first inductor  21  and the second inductor  22  are wound on the “E”-shaped core  100  having the first to third legs  110 ,  120  and  130  will be described hereinafter with reference to the examples shown in  FIGS. 4 and 5 . 
         [0049]      FIG. 4  is a perspective view illustrating a coupling configuration of the inductor cores according to the exemplary embodiment of the present invention, and  FIG. 5  is a view illustrating an example of a magnetic flux path of the exemplary embodiment shown in  FIG. 4 . 
         [0050]    In  FIGS. 4 and 5 , two “E”-shaped cores  100  each having the first to third legs  110 ,  120  and  130  are coupled to face each other to have an “EE”-shaped coupling configuration while being magnetically connected to each other. The first inductor  21  is wound on the two first legs  110  via the bobbin  21   a , and the second inductor  22  is wound on the two second legs  120  via the bobbin  22   a . If the first power switching element  31  and the second power switching element  32  are alternately switched according to an interleaved switching operation with a phase angle of 180 degrees, the first inductor  21  and the second inductor  22  alternately create magnetic flux paths Φ between the two third legs  130  located at the center of the cores  100  and the first legs  110  provided at one side of the cores  100  and between the two third legs  130  and the second legs  120  provided at the other side of the cores  100 . 
         [0051]    Gaps  140  to adjust inductance are defined respectively between the two first legs  110  on which the first inductor  21  is wound and between the two second legs  120  on which the second inductor  22  is wound. The gaps  140  allow the first inductor  21  and the second inductor  22  wound on the pair of “EE”-shaped cores  100  to define the two magnetic flux paths Φ. 
         [0052]    In the PFC circuit of  FIG. 1 , the first power switching element  31  and the second power switching element  32  are alternately switched. Therefore, to prevent overlap of excited current upon switching of the first power switching element  31  and the second power switching element  32 , the first inductor  21  wound on the two first legs  110  and the second inductor  22  wound on the two second legs  120  may have opposite winding directions. In addition, the number of turns of the first inductor  21  may be equal to the number of turns of the second inductor  22 , to ensure equilibrium of excited current. 
         [0053]    The inductor core configuration in which the two “E”-shaped cores  100  are coupled to face each other to have the “EE”-shaped coupling configuration may cut the number of cores used in the conventional configuration in half (four→two). Reducing the number of cores  100  may optimize the arrangement of elements and the size of the core  100 , resulting in a reduction in overall element costs. 
         [0054]    Operating waves of the interleaved PFC circuit using a single core configuration, such as the examples proposed in  FIGS. 2 to 5 , are illustrated in the example shown in  FIG. 6 . 
         [0055]      FIG. 6  is an operating wave diagram of the interleaved PFC circuit according to the exemplary embodiment of the present invention. 
         [0056]    As illustrated in  FIG. 6 , if the first power switching element  31  and the second power switching element  32  are alternately switched according to an interleaved switching operation with a phase angle of 180 degrees, the first inductor  21  wound on the two first legs  110  and the second inductor  22  wound on the two second legs  120  serve as boosters, and show the same operating waves as those measured using the conventional PFC circuit using four cores without deterioration in electric characteristics. 
         [0057]    Next, in addition to the “EE”-shaped coupling configuration of the two “E”-shaped inductor cores  100  coupled to face each other which may cut the number of the cores  100  in half and optimize the size of the core  100  as compared to the conventional interleaved PFC circuit, another exemplary embodiment of the inductor core coupling configuration, which is applicable to a PFC circuit usable with a slim power source device, will be described with reference to  FIGS. 7 and 8 . 
         [0058]      FIG. 7  is a perspective view illustrating a coupling configuration of inductor cores according to another exemplary embodiment of the present invention, and  FIG. 8  is a view illustrating an example of a magnetic flux path of the inductor core shown in  FIG. 7 . 
         [0059]    As illustrated in  FIGS. 7 and 8 , the “E”-shaped core  100  having the first to third legs  110 ,  120  and  130  illustrated in  FIGS. 2 and 3  is coupled to a bar-type “I”-shaped core  200  having no legs to have an “EI”-shaped coupling configuration while being magnetically connected to each other. In the “EI”-shaped coupling configuration of the cores  100  and  200 , the first inductor  21  is wound on the first leg  110  of the core  100  via the bobbin  21   a , and the second inductor  22  is wound on the second leg  120  of the core  100  via the bobbin  22   a . The first inductor  21  and the second inductor  22  respectively create magnetic flux paths Φ between the third leg  130  and the first leg  110  and between the third leg  130  and the second leg  120 . 
         [0060]    Gaps  240  to adjust inductance are defined respectively between the first leg  110  of the core  100  on which the first inductor  21  is wound and one end portion of the core  200  and between the second leg  120  on which the second inductor  22  is wound and the other end portion of the core  200 . The gaps  240  allow the first inductor  21  and the second inductor  22  wound on the pair of “EI”-shaped cores  100  to define the two magnetic flux paths Φ. 
         [0061]    In the “EI”-shaped coupling configuration, similar to the “EE”-shaped coupling configuration, to prevent overlap of excited current upon switching of the first power switching element  31  and the second power switching element  32 , the first inductor  21  wound on the first leg  110  and the second inductor  22  wound on the second leg  120  may have opposite winding directions. In addition, the number of turns of the first inductor  21  may be equal to the number of turns of the second inductor  22 , to ensure equilibrium of excited current. 
         [0062]    As will be appreciated from  FIG. 8 , in the inductor cores  100  and  200  having the “EI-”shaped coupling configuration, the number of turns of the first inductor  21  and the second inductor  22  wound on the first leg  110  and the second leg  120  of the core  100  is less than those of the inductor cores  100  having the “EE”-shaped configuration. Thus, the inductor cores having the “EI”-shaped coupling configuration has a smaller overall size than the inductor cores having the “EE”-shaped coupling configuration illustrated in  FIG. 5  and thus, may realize a PFC circuit usable with a slim power source device. 
         [0063]    Next, various inductor configurations applicable to the interleaved PFC circuit will be described with reference to the exemplary embodiments shown in  FIGS. 9 to 16 . 
         [0064]      FIG. 9  is a perspective view illustrating a configuration of an inductor core according to another exemplary embodiment of the present invention, and  FIG. 10  is an example plan view of the exemplary embodiment of  FIG. 9 . 
         [0065]    Although the core  300  illustrated in  FIGS. 9 and 10  is an “E”-shaped core having first to third legs  310 ,  320  and  330  similar to the core  100  illustrated in  FIGS. 2 and 3 , the core  300  has a modified configuration of the basic configuration of the core  100  illustrated in  FIGS. 2 and 3  such that the first leg  310  and the second leg  320  of the core  300  have an elliptical cross section rather than a circular cross section. Of course, the “E”-shaped modified core  300  illustrated in  FIGS. 9 and 10  may also be modified to have other various shapes in consideration of the arrangement of elements, the overall size, or the power capacity of the PFC circuit. 
         [0066]    The first leg  310  and the second leg  320  of the “E”-shaped modified core  300  are provided at opposite sides of the “E”-shaped modified core  300  and have the same shape and the same surface area. 
         [0067]    The third leg  330  of the “E”-shaped modified core  300  is located midway between the first leg  310  and the second leg  320  and has a modified shape different from the first leg  310  and the second leg  320  to have a greater surface area and height than those of the first leg  310  and the second leg  320  by about 2 times. 
         [0068]      FIG. 11  is a perspective view illustrating a coupling configuration of the inductor cores of  FIG. 9 , and  FIG. 12  is a view illustrating an example of a magnetic flux path of the exemplary embodiment of  FIG. 11 . 
         [0069]    In  FIGS. 11 and 12 , two “E”-shaped modified cores  300  each having the first to third legs  310 ,  320  and  330  are coupled to face each other to have an “EE”-shaped coupling configuration while being magnetically connected to each other. The first inductor  21  is wound on the two first legs  310  via the bobbin  21   a , and the second inductor  22  is wound on the two second legs  320  via the bobbin  22   a . The first inductor  21  and the second inductor  22  create magnetic flux paths Φ between the two third legs  330  and the first legs  310  and between the two third legs  330  and the second legs  320 . 
         [0070]    Gaps  340  to adjust inductance are defined respectively between the two first legs  310  on which the first inductor  21  is wound and between the two second legs  320  on which the second inductor  22  is wound. The gaps  340  allow the first inductor  21  and the second inductor  22  wound on the pair of “EE”-shaped cores  300  to define the two magnetic flux paths Φ. 
         [0071]    As described above, in the PFC circuit of  FIG. 1 , the first power switching element  31  and the second power switching element  32  are alternately switched. Therefore, to prevent overlap of excited current upon switching of the first power switching element  31  and the second power switching element  32 , the first inductor  21  wound on the two first legs  310  and the second inductor  22  wound on the two second legs  320  of the “E”-shaped modified core  300  may have opposite winding directions. In addition, the number of turns of the first inductor  21  may be equal to the number of turns of the second inductor  22 , to ensure equilibrium of excited current. 
         [0072]    The inductor core configuration in which the two “E”-shaped cores  300  are coupled to face each other to have the “EE”-shaped coupling configuration may cut the number of cores used in the conventional configuration in half (four→two), and also, may realize various sizes of the core  300 , expanding the utilization range of the core  300 . 
         [0073]      FIG. 13  is a perspective view illustrating a configuration of an inductor core according to a further exemplary embodiment of the present invention, and  FIG. 14  is an example of a plan view of the exemplary embodiment of  FIG. 13 . 
         [0074]    Although the core  400  illustrated in  FIGS. 13 and 14  is an “E”-shaped core having first to third legs  410 ,  420  and  430  similar to the core  100  illustrated in  FIGS. 2 and 3 , the core  400  has a modified configuration of the basic core  100  illustrated in  FIGS. 2 and 3  such that the third leg  430  has a modified height. Of course, the “E”-shaped modified core  400  illustrated in  FIGS. 13 and 14  may also be modified to have other various shapes in consideration of the arrangement of elements, the overall size, or the power capacity of the PFC circuit using the inductor core  400 . 
         [0075]    The first leg  410  and the second leg  420  of the “E”-shaped modified core  400  are provided at opposite sides of the “E”-shaped modified core  400  and have the same shape and the same surface area. 
         [0076]    The third leg  430  of the “E”-shaped modified core  400  is located midway between the first leg  410  and the second leg  420  and has a modified shape different from the first leg  410  and the second leg  420  to have a greater height than those of the first leg  410  and the second leg  420  by about 2 times. 
         [0077]      FIG. 15  is a perspective view illustrating an example of a coupling configuration of the exemplary embodiment of  FIG. 13 , and  FIG. 16  is a view illustrating an example of a magnetic flux path of the exemplary embodiment of  FIG. 15 . 
         [0078]    In  FIGS. 15 and 16 , two “E”-shaped modified cores  400  each having the first to third legs  410 ,  420  and  430  are coupled to face each other to have an “EE”-shaped coupling configuration while being magnetically connected to each other. The first inductor  21  is wound on the two first legs  410  via the bobbin  21   a , and the second inductor  22  is wound on the two second legs  420  via the bobbin  22   a . The first inductor  21  and the second inductor  22  create magnetic flux paths Φ between the two third legs  430  and the first legs  410  and between the two third legs  430  and the second legs  420 . 
         [0079]    Gaps  440  to adjust inductance are defined respectively between the two first legs  410  on which the first inductor  21  is wound and between the two second legs  420  on which the second inductor  22  is wound. The gaps  440  allow the first inductor  21  and the second inductor  22  wound on the pair of “EE”-shaped cores  400  to define the two magnetic flux paths Φ. 
         [0080]    As described above, in the PFC circuit of  FIG. 1 , the first power switching element  31  and the second power switching element  32  are alternately switched. Therefore, to prevent overlap of excited current upon switching of the first power switching element  31  and the second power switching element  32 , the first inductor  21  wound on the two first legs  410  and the second inductor  22  wound on the two second legs  420  of the “E”-shaped modified core  400  may have opposite winding directions. In addition, the number of turns of the first inductor  21  may be equal to the number of turns of the second inductor  22 , to ensure equilibrium of excited current. 
         [0081]    The inductor core configuration in which the two “E”-shaped cores  400  are coupled to face each other to have the “EE”-shaped coupling configuration may cut the number of cores used in the conventional configuration in half (four→two), and also, may realize various sizes of the core  400 , expanding the utilization range of the core  400 . 
         [0082]    In the case of the inductor cores having the coupling configurations illustrated in  FIGS. 4 ,  7 ,  11  and  15 , all the inductor cores may be mounted on a Printed Circuit Board (PCB) in a standing manner or in a laying manner. 
         [0083]    As is apparent from the above description, an interleaved PFC circuit according to the exemplary embodiments of the present invention has an improved core configuration in which two boost inverters are wound on a pair of cores, thereby cutting the number of cores used in the conventional core configuration in half, resulting in optimized element arrangement and core size and consequently, reduced costs. In the case of a small-capacity PFC circuit, a bar-type core may be used to realize a boost inductor configuration using a single-core. 
         [0084]    Although a few exemplary embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.