Abstract:
There is provided an integrated type transformer that reduces the volume by integrating a plurality of transformers transmitting power for driving a plurality of lamps in an inverter circuit for an LCD into one transformer structure. An integrated type transformer according to an aspect of the invention includes a bobbin unit including a bobbin body having a predetermined length and a through hole therein in a longitudinal direction of the bobbin unit, and a core unit including an inner core inserted into the through hole of the bobbin unit, and an outer core formed along one surface in the longitudinal direction among outer circumferential surfaces of the bobbin unit and electromagnetically coupled to the inner core to form one magnetic path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 2007-27562 filed on Mar. 21, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an integrated type transformer, and more particularly, to an integrated type transformer that reduces the volume by integrating a plurality of transformers transmitting power for driving a plurality of lamps in an inverter circuit for an LCD into one transformer structure. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, liquid crystal display (LCD) products, such as LCD TVs or LCD monitors, have become larger. At the same time, however, there has been a need for a decrease in volume of the large LCD products. In order to satisfy the need, development has been carried out to realize small and compact built-in circuits and components that are used in the LCD products. This trend is also found in driving circuits, which are one of the main circuits in the LCD products. 
         [0006]    The above-described LCD driving circuit generally uses a power conversion transformer to supply a current to a plurality of lamps. According to a general method of making the LCD driving circuit smaller, the volume of the transformer that supplies the current to the lamps is decreased. 
         [0007]      FIG. 1A  is a plan view illustrating a transformer according to the related art. 
         [0008]    Referring to  FIG. 1A , the transformer according to the related art includes a bobbin B that has a plurality of winding sections, and a core Co that is electromagnetically coupled to the bobbin B. 
         [0009]    A primary coil C 1  is wound around the center winding section. Secondary coils C 2  are separately wound around both winding sections around the center winding section. The core Co that is coupled to the bobbin B surrounds the inside of the bobbin B and the bobbin B in a longitudinal direction thereof to form two magnetic paths, which will be described in detail with reference to  FIG. 1B . 
         [0010]      FIG. 1B  is a cross-sectional view illustrating the transformer taken along the line a-a′ according to the related art. 
         [0011]    Referring to  FIG. 1B , the core Co that is coupled to the bobbin B includes an inner core Coi that is inserted into the inside Bi of the bobbin, and outer cores Coo 1  and Coo 2  that are formed along two surfaces that face each other among outer circumferential surfaces of the bobbin B. The inner core Coi is electromagnetically coupled to the external cores Coo 1  and Coo 2  to form magnetic paths, that is, two magnetic paths. The current that flows into the primary coil C 1  is converted into AC power, which is set beforehand, and then transmitted to the lamps (not shown) by the secondary coils C 2 . 
         [0012]    In the transformer according to the related art, a plurality of transformers are integrated into one transformer structure. However, since the volume of the transformer is still large, it is difficult to manufacture a small, thin, lightweight driving circuit that uses the transformer. 
       SUMMARY OF THE INVENTION 
       [0013]    An aspect of the present invention provides an integrated type transformer that reduces the volume by integrating a plurality of transformers transmitting power for driving a plurality of lamps in an inverter circuit for an LCD into one transformer structure. 
         [0014]    According to an aspect of the present invention, there is provided an integrated type transformer including: bobbin unit including a bobbin body having a predetermined length and a through hole therein in a longitudinal direction of the bobbin unit; and a core unit including an inner core inserted into the through hole of the bobbin unit, and an outer core formed along one surface in the longitudinal direction among outer circumferential surfaces of the bobbin unit and electromagnetically coupled to the inner core to form one magnetic path. 
         [0015]    The integrated type transformer may further include a coil unit including a primary coil wound around the outer circumferential surfaces of the bobbin unit and a plurality of secondary coils electromagnetically coupled to the primary coil; and a terminal unit including an input terminal transmitting input power to the primary coil and an output terminal transmitting output power from the secondary coils. 
         [0016]    The output terminal of the terminal unit may be formed at the one surface of the bobbin unit at which the outer core is formed. 
         [0017]    The inner core may be an I-shaped core having one end and the other end, and the outer core may be a C-shaped core having a support part formed along one surface of the bobbin unit and protrusion parts formed at one end and the other end of the support part along the same direction and electromagnetically coupled to the one end and the other end of the I-shaped core. 
         [0018]    The core unit may include two open square-shaped cores each including: a support part having one end and the other end; an inner protrusion part formed at the one side of the support part and inserted into the through hole of the bobbin unit; and an outer protrusion part formed at the other side of the support part, formed along the same direction as a direction of the inner protrusion part, and formed along one surface of the bobbin unit, and the two open square-shaped cores may face each other and be electromagnetically coupled to each other, such that the inner protrusion parts of the two cores may form the inner core, and the outer protrusion parts and the support parts thereof may form the outer core. Further, the thickness of the inner protrusion part may be smaller than that of the outer protrusion part. 
         [0019]    The primary coil may be wound around the center of the outer circumferential surfaces of the bobbin unit, and the plurality of secondary coils may be wound around both sides of the circumferential surfaces around the primary coil along the longitudinal direction of the bobbin unit. 
         [0020]    A cross walk may be formed at the center of the outer circumferential surfaces of the bobbin unit to equally divide the winding number of the primary coil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0022]      FIG. 1A  is a plan view illustrating a transformer according to the related art. 
           [0023]      FIG. 1B  is a cross-sectional view taken along the line a-a′ of the transformer according to the related art. 
           [0024]      FIG. 2A  is a plan view illustrating a transformer according to an exemplary embodiment of the present invention. 
           [0025]      FIG. 2B  is a cross-sectional view taken along the line a-a′ of the transformer according to the exemplary embodiment of the present invention. 
           [0026]      FIG. 3A  is an exploded perspective view illustrating a transformer according to one exemplary embodiment of the present invention. 
           [0027]      FIG. 3B  is an exploded perspective view illustrating a transformer according to another exemplary embodiment of the present invention. 
           [0028]      FIG. 3C  is an exploded perspective view illustrating a transformer according to still another exemplary embodiment of the present invention. 
           [0029]      FIG. 3D  is an exploded perspective view illustrating a transformer according to yet another exemplary embodiment of the present invention. 
           [0030]      FIG. 4A  is a circuit diagram illustrating one example of a connection between the transformer according to the present invention and lamps. 
           [0031]      FIG. 4B  is a circuit diagram illustrating another example of a connection between the transformer according to the present invention and lamps. 
           [0032]      FIG. 5  is a graph illustrating a tube current of each of the lamps when the transformer according to the present invention and the lamps are connected to each other. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0034]      FIG. 2A  is a plan view illustrating a transformer according to an exemplary embodiment of the present invention.  FIG. 2B  is a cross-sectional view taken along the line a-a′ of the transformer shown in  FIG. 2A . 
         [0035]    Referring to  FIGS. 2A and 2B , the transformer according to the exemplary embodiment of the present invention includes a bobbin unit B, a core unit Co that is coupled to the bobbin unit B, coil units C 1  and C 2  that are wound around the bobbin unit B, and terminal units Ii and Io that are formed on the bobbin unit B. 
         [0036]    The bobbin unit B has a predetermined length and a through hole Bi formed therein. 
         [0037]    The core unit Co includes an inner core Coi and an outer core Coo. The inner core Coi is inserted into the through hole Bi of the bobbin unit B. The outer core Coo is formed along one surface of the bobbin unit B that is formed in a longitudinal direction of the bobbin unit B. The inner core Coi and the outer core Coo are electromagnetically coupled to each other to form a magnetic path that is a path of magnetic flux. Here, one inner core Coi and one outer core Coo are electromagnetically coupled to each other to form one magnetic path. 
         [0038]    The coil units C 1  and C 2  are wound around outer circumferential surfaces of the bobbin unit B. The coil units C 1  and C 2  include a primary coil C 1  and a plurality of secondary coils C 2 . The primary coil C 1  is wound around the center of the outer circumferential surfaces of the bobbin unit B. The plurality of secondary coils C 2  are wound around both sides of the outer circumferential surfaces, respectively, around the primary coil C 1  along the longitudinal direction of the bobbin unit B. The primary coil C 1  corresponds to the secondary coil C 2  to form one electric transformer. When the secondary coils C 2  are wound around both sides of the outer circumferential surfaces of the bobbin unit B, respectively, two transformers may be integrated into one transformer structure. When two of each of the secondary coils C 2  are wound, four electrical transformers may be integrated into one transformer structure. 
         [0039]    The terminal units Ii and Io include an input terminal Ii and an output terminal Io. The terminal units Ii and Io may further include a fixing or grounding terminal Ig. The input terminal Ii and the output terminal Io are formed at one surface and the other surface of the bobbin unit B, respectively, which are located opposite to each other. The input terminal Ii transmits input power to the primary coil C 1 , a first input terminal Ii 1  is connected to one end of the primary coil C 1 , and a second input terminal Ii 2  is connected to the other end of the primary coil C 1 . The output terminal Io transmits to the outside, output power that is set according to a winding ratio between the primary coil C 1  and the secondary coils C 2 . Then, a first output terminal Io 1  of the output terminal Io is connected to one end of the one secondary coil C 2  that is wound around the outer circumferential surfaces of the one side of the bobbin unit B, and a second output terminal Io 2  is connected to the other end of the secondary coil C 2  that is wound around the outer circumferential surfaces of the one side of the bobbin unit B. In the same manner, a third output terminal Io 3  is connected to one end of the other secondary coil C 2  that is wound around the outer circumferential surfaces of the other side of the bobbin unit B, and a fourth output terminal Io 4  is connected to the other end of the secondary coil C 2  that is wound around the outer circumferential surfaces of the other side of the bobbin unit B. 
         [0040]    Preferably, the output terminal Io and the outer core Coo may be formed on the same outer circumferential surface of the bobbin unit B. As shown below in Table 1, experiments show that an output current deviation can be reduced by an electromagnetic action between the input and output terminals Ii and Io, the core unit Co, and the coil units C 1  and C 2  when the output terminal Io and the outer core Coo are formed at the same outer circumferential surface. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Same 
                 Different 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Lamp 1 tube current 
                 8.2 mA 
                 6.9 mA 
               
               
                   
                 Lamp 2 tube current 
                 7.9 mA 
                 8.5 mA 
               
               
                   
                 Lamp 3 tube current 
                 7.9 mA 
                 8.0 mA 
               
               
                   
                 Lamp 4 tube current 
                 8.0 mA 
                 6.7 mA 
               
               
                   
                   
               
             
          
         
       
     
         [0041]    Referring to Table 1, when the output terminal Io and the outer core Coo are formed at the same outer circumferential surface of the same bobbin unit B, a tube current deviation between the lamps is 0.3 mA. On the other hand, when the output terminal Io and the outer core Coo are formed at the different outer circumferential surfaces of the bobbin unit B that are opposite to each other, the tube current deviation between the lamps is 1.8 mA. 
         [0042]    In general, when a rated output current (lamp tube current) is 8 mA, an output current deviation that is required by a user is 0.5 mA. Therefore, preferably, the output terminal Io and the outer core Coo are formed at the same outer circumferential surface of the bobbin unit B. 
         [0043]    Further, a cross walk Cw that equally divides the winding number of the primary coil C 1  may be formed at the center of the outer circumferential surfaces around which the primary coil C 1  of the bobbin unit B is wound. Taking into account the fact that the output power is determined according to the winding ratio between the primary coil C 1  and the secondary coils C 2 , the output power of each of the secondary coils C 2  can be equally controlled. 
         [0044]      FIG. 3A  is an exploded perspective view illustrating a transformer according to one exemplary embodiment of the present invention. 
         [0045]    Referring to  FIG. 3A , the one exemplary embodiment of the transformer according to the present invention relates to an exemplary embodiment of a core unit Co that is used in the transformer according to the invention. 
         [0046]    The core unit Co includes two open square-shaped cores that are coupled to form one magnetic path. That is, a first open square-shaped core includes a first support part V 1 , a first inner protrusion part Coi 1 , and a first outer protrusion part Coo 1 . The first support part V 1  has one side and the other side. The first inner protrusion part Coi 1  is formed at the one side of the first support part V 1  and inserted into a through hole Bi of a bobbin unit B. The first outer protrusion part Coo 1  is formed at the other side of the first support part V 1  along the same direction as a direction of the first inner protrusion part Coi 1 , and formed along one surface formed in the longitudinal direction of the bobbin unit B. 
         [0047]    In the same manner, a second open-square shaped core includes a second support part V 2 , a second inner protrusion part Coi 2 , and a second outer protrusion part Coo 2 . The second support part V 2  has one side and the other side. The second inner protrusion part Coi 2  is formed at the one side of the second support part V 2  and inserted into the through hole Bi of the bobbin unit B. The second outer protrusion part Coo 2  is formed at the other side of the second support part V 2  along the same direction as a direction of the second inner protrusion part Coi 2 , and formed along one surface formed in the longitudinal direction of the bobbin unit B. 
         [0048]    The first and second open square-shaped cores face each other and are coupled to each other. The first and second inner protrusion parts Coi 1  and Coi 2  form one inner core Coi. The first and second outer protrusion parts Coo 1  and Coo 2  and the first and second support parts V 1  and V 2  form one outer core Coo. 
         [0049]    Since a description of the bobbin unit B, coil units, and terminal units is the same as that with reference to  FIGS. 2A and 2B , the description thereof will be omitted. 
         [0050]      FIG. 3B  is an exploded perspective view illustrating a transformer according to another exemplary embodiment of the present invention. 
         [0051]    Referring to  FIG. 3B , the inner protrusion parts Coi 1  and Coi 2  of the first and second open square-shaped cores as described above in  FIG. 3A  may be thinner than the outer protrusion parts Coo 1  and Coo 2 . As the thickness of the inner protrusion parts Coi 1  and Coi 2  increases, the length of the bobbin unit B increases, which results in an increase in volume of the transformer. Therefore, when the thickness of the inner protrusion parts Coi 1  and Coi 2  is reduced within an allowable range in terms of electromagnetism, the volume of the transformer can be further reduced. 
         [0052]      FIG. 3C  is an exploded perspective view illustrating a transformer according to still another exemplary embodiment of the present invention. 
         [0053]    The still another exemplary embodiment of a core unit Co that is used in the transformer according to the invention will be described in detail. 
         [0054]    The core unit Co includes an inner core Coi and an outer core Coo. The inner core Coi is an I-shaped core that has a predetermined length, and the outer core Coo is a C-shaped core that has a plurality of protrusion parts V 1  and V 2 . 
         [0055]    The inner core Coi includes one end and the other end, and is inserted into a through hole Bi of a bobbin unit B. The outer core Coo is formed along one surface in a longitudinal direction of the bobbin unit B among outer circumferential surfaces of the bobbin unit B. Further, the outer core Coo includes protrusion parts V 1  and V 2  that are formed at one side and the other side thereof along the same direction. The first protrusion part V 1  of the outer core Coo is electrically connected to the one side of the inner core Coi, and the second protrusion part V 2  is electrically connected to the other end of the inner core Coi, thereby forming one magnetic path. In the above-described core unit according to the still another embodiment of the invention, the inner core Coi is shorter than the outer core Coo. For this reason, one end surface and the other end surface of the inner core Coi are electrically connected to surfaces that face the through hole Bi of the bobbin unit B among surfaces of the first and second protrusion parts V 1  and V 2  of the outer core Coo. 
         [0056]      FIG. 3D  is an exploded perspective view illustrating a transformer according to yet another exemplary embodiment of the present invention. 
         [0057]      FIG. 3D  illustrates the yet another exemplary embodiment of a core unit Co that is used in the transformer according to the invention when the inner core Coi and the outer core Coo of the core unit Co shown in  FIG. 3C  have the same length. 
         [0058]    Referring to  FIG. 3D , the inner core Coi has the same length as the outer core Coo. One side and the other side of a surface that faces the outer core Coo among surfaces of the inner core Coi are electromagnetically coupled to end surfaces of the first and second protrusion parts V 1  and V 2  of the outer core Coo, respectively, to thereby form one magnetic path. 
         [0059]      FIG. 4A  is a circuit diagram illustrating one example of a connection between the transformer according to the present invention and lamps. 
         [0060]    Referring to  FIG. 4A , the transformer according to the exemplary embodiments of the present invention may be connected to a plurality of lamps. First, input power that is transmitted to the primary coil C 1  through the input terminals Io 1  and Io 2  is converted into output power that is set beforehand according to a winding ratio between the primary coil C 1  and the plurality of secondary coils C 2 . Then, the output power is transmitted to the plurality of lamps through the output terminals Io 1 , Io 2 , Io 3 , and Io 4 . 
         [0061]    When each of the plurality of lamps is a long bar-shaped lamp, the four lamps receive the output power through the first to fourth output terminals Io 1 , Io 2 , Io 3 , and Io 4 . Here, the output terminals Io 1  and Io 2  are electrically connected to one end and the other end of one secondary coil C 2 , respectively, and the output terminals Io 3  and Io 4  are electrically connected to one end and the other end of the other secondary coil C 2 , respectively. Then, the four lamps emit light. 
         [0062]      FIG. 4B  is a circuit diagram illustrating another example of a connection between the transformer according to the present invention and lamps. 
         [0063]    Referring to  FIG. 4B , when each of the plurality of lamps is a U-shaped lamp, two lamps receive the output power through the first to fourth output terminals Io 1 , Io 2 , Io 3 , and Io 4 . Here, the output terminals Io 1  and Io 2  are electrically connected to one end and the other end of one secondary coil C 2 , respectively, and the output terminals Io 3  and Io 4  are electrically connected to one end and the other end of the other secondary coil C 2 , respectively. Then, the two lamps emit light. At this time, one end and the other end of one U-shaped lamp may be electrically connected to the first and second output terminals Io 1  and Io 2 , respectively, and one end and the other end of the other U-shaped lamp may be electrically connected to the third and fourth output terminals Io 3  and Io 4 , respectively. 
         [0064]      FIG. 5  is a graph illustrating a tube current of lamps when the transformer according to the present invention and the lamps are connected to each other. 
         [0065]    Referring to  FIG. 5 , four or eight transformers according to the exemplary embodiments of the present invention are used, and lamps are connected to output terminals of the transformers. The tube current of the sixteen lamps is measured. 
         [0066]    As shown in graph of  FIG. 5 , when taking into account the fact that an output current deviation that is required by a user is 0.5 mA when a rated output current (lamp tube current) is 8 mA, a deviation of the tube current that flows into the sixteen lamps is within the deviation of 0.5 mA. This means that even when the transformer according to the exemplary embodiments of the present invention has a structure in which a plurality of electric transformers are integrated into one transformer structure to form one magnetic path and reduce the volume of the transformer, the transformer accurately performs the proper function. 
         [0067]    As described above, characteristics of the transformer according to the exemplary embodiments of the present invention are compared with those of the transformer according to the related art shown in  FIGS. 1A and 1B . 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Related 
                 Present 
               
               
                   
                 Classification 
                 art 
                 Invention 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Core section width Ac(mm 2 ) 
                 43.5 
                 27.0 
               
               
                   
                 Duty ratio 
                 35.4 
                 37.9 
               
               
                   
                 Output current deviation(mA) 
                 ±0.5 
                 ±0.5 
               
               
                   
                 Volume(mm 3 ) 
                 5873 
                 4289 
               
               
                   
                 Volume reduction effect(%) 
                   
                 27.0 
               
               
                   
                   
               
             
          
         
       
     
         [0068]    Referring to Table 2, the transformer according to the related art forms two magnetic paths and a core section has a width of 43.5 mm 2 , while the transformer according to the exemplary embodiments of the present invention forms one magnetic path and a core section has a width of 27 mm 2 . As a result, the volume of the transformer according to the related art is 5873 mm 3 , while the transformer according to the exemplary embodiments of the present invention is 4289 mm 3 . 
         [0069]    Therefore, the transformer according to the exemplary embodiments of the present invention has almost the same electrical characteristic as the transformer according to the related art. However, the volume of the transformer according to the exemplary embodiments of the present invention is reduced by approximately 27%. 
         [0070]    As set forth above, according to exemplary embodiments of the invention, a plurality of electrical transformers are integrated into one transformer structure to form one magnetic path, thereby reducing the volume of the transformer. 
         [0071]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.