Patent Publication Number: US-8120455-B2

Title: Transformer structure

Description:
FIELD OF THE INVENTION 
     The present invention relates to a transformer, and more particularly to a transformer having enhanced heat-dissipating efficiency and reduced electromagnetic interference. 
     BACKGROUND OF THE INVENTION 
     A transformer has become an essential electronic component for voltage regulation into required voltages for various kinds of electric appliances. Referring to  FIG. 1 , a schematic exploded view of a conventional transformer is illustrated. The transformer  1  principally comprises a magnetic core assembly  11 , a bobbin  12 , a primary winding coil  13  and a secondary winding coil  14 . The primary winding coil  13  and the secondary winding coil  14  are overlapped with each other and wounded around a winding section  121  of the bobbin  12 . An insulating tape  15  is provided for isolation and insulation. The magnetic core assembly  11  includes a first magnetic part  111  and a second magnetic part  112 . The middle portion  111   a  of the first magnetic part  111  and the middle portion  112   a  of the second magnetic part  112  are embedded into the channel  122  of the bobbin  12 . The primary winding coil  13  and the secondary winding coil  14  interact with the magnetic core assembly  11  for voltage regulation. 
     Although the transformer  1  is effective for power conversion, there are still some drawbacks. For example, since the heat generated by the transformer  1  is dissipated away via a natural convection mechanism, the magnetic core assembly  11  and the winding section  121  of the bobbin  12  are exposed in order to increase the heat-dissipating efficiency. Under this circumstance, the transformer  1  readily generates electromagnetic interference (EMI), which adversely affects the neighboring circuits. Generally, additional high-level filters are used for suppressing EMI. The uses of the filters increase complexity of the circuitry layout and the fabricating cost. 
     In a case that the transformer  1  is used in a poorly ventilated environment, the heat generated by the transformer  1  is accumulated and the temperature of the transformer  1  is gradually increased because the heat is difficult to be transferred to the ambient air. The elevated temperature of the transformer  1  may result in damage of the transformer  1  and/or the electronic components neighboring the transformer  1 . Under this circumstance, the performance and the use life of the transformer  1  and/or the whole electronic appliance will be deteriorated. Therefore, in designing a transformer, it is important to enhance the heat-dissipating efficiency of the transformer. 
     For increasing the heat-dissipating efficiency of the transformer  1 , some measures are taken. For example, the material of the magnetic core assembly  11  is improved, the diameters and/or the coil turns of the primary winding coil  13  and the secondary winding coil  14  are modified, or the primary winding coil  13  and the secondary winding coil  14  are replaced by copper foils to increase the heat transfer area. Since the transformer structure is altered, a new mold of the transformer should be designed and made. The process of designing and making the new mold of the transformer increases extra cost. 
     Therefore, there is a need of providing a transformer having enhanced heat-dissipating efficiency and reduced electromagnetic interference so as to obviate the drawbacks encountered from the prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a transformer having enhancing heat-dissipating efficiency, so that the possibility of casing heat accumulation is reduced and the use life of the transformer is extended. 
     Another object of the present invention provides a transformer with low electromagnetic interference. 
     In accordance with an aspect of the present invention, there is provided a transformer. The transformer includes a case, a magnetic device and a thermally conductive layer. The case has a receptacle. The magnetic device is disposed within the receptacle, and includes a winding member and a magnetic core assembly. The thermally conductive layer is arranged between the magnetic device and the case for electrically isolating the magnetic device from the case. The heat generated by the magnetic device is transferred to the case through the thermally conductive layer and dissipated away to ambient air. 
     In accordance with another aspect of the present invention, there is provided a transformer. The transformer includes a case, a magnetic device and a thermally conductive layer. The case has a receptacle. The magnetic device is disposed within the receptacle, and includes a primary winding assembly, a secondary winding assembly and a magnetic core assembly. The thermally conductive layer is arranged between the magnetic device and the case for electrically isolating the magnetic device from the case. The heat generated by the magnetic device is transferred to the case through the thermally conductive layer and dissipated away to ambient air. 
     The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic exploded view of a conventional transformer; 
         FIG. 2A  is a schematic exploded view of a transformer according to an embodiment of the present invention; 
         FIG. 2B  is a schematic assembled view illustrating the combination of the magnetic device and the case of the transformer as shown in  FIG. 2A ; 
         FIG. 2C  is a schematic assembled view illustrating the transformer as shown in  FIG. 2A ; and 
         FIG. 3  is a schematic exploded view of a transformer according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
       FIG. 2A  is a schematic exploded view of a transformer according to an embodiment of the present invention.  FIG. 2B  is a schematic assembled view illustrating the combination of the magnetic device and the case of the transformer as shown in  FIG. 2A .  FIG. 2C  is a schematic assembled view illustrating the transformer as shown in  FIG. 2A . 
     In  FIG. 2A , the transformer  2  principally comprises a magnetic device  21  and a case  22 . The magnetic device  21  includes a winding member  211  and a magnetic core assembly  212 . The winding member  211  includes a primary winding assembly  211   a  and a secondary winding assembly  211   b.  In this embodiment, the primary winding assembly  211   a  and the secondary winding assembly  211   b  are formed of copper foils. For isolation and insulation, an insulating tape  211   d  is wound around the outer periphery of the transformer  2 . The primary winding assembly  211   a  is produced by circularly winding a copper foil and thus a channel  211   c  is defined in the center of the primary winding assembly  211   a.  The secondary winding assembly  211   b  is wound around the primary winding assembly  211   a.  The magnetic core assembly  212  includes a first magnetic part  212   a  and a second magnetic part  212   b.  The upper portion and the lower portion of the winding member  211  are partially sheltered by the first magnetic part  212   a  and the second magnetic part  212   b , respectively. In addition, the middle portions of the first magnetic part  212   a  and the second magnetic part  212   b  are partially embedded into the channel  211   c  of the winding member  211 . It is noted that, however, those skilled in the art will readily observe that numerous modifications and alterations of the magnetic core assembly  212  may be made while retaining the teachings of the invention. 
     Please refer to  FIG. 2A  again. The magnetic device  21  includes at least one pin  213 . An end of the pin  213  is connected to the winding member  211 . The other end of the pin  213  is mounted on and electrically connected to a circuit board  25 . For example, the primary winding assembly  211   a  and the secondary winding assembly  211   b  are electrically connected to the circuit board  25  through a first pin  213   a  and a second pin  213   b , respectively. As such, the primary winding assembly  211   a  and the secondary winding assembly  211   b  interact with the magnetic core assembly  212  to achieve the purpose of voltage regulation. 
     In this embodiment, the winding member  211  includes the primary winding assembly  211   a  and the secondary winding assembly  211   b.  In some embodiments, the winding member  211  may include a single winding assembly, which is produced by circularly winding an enameled wire or a copper foil according to the practical requirements. 
     Please refer to  FIGS. 2A and 2B  again. The case  22  is made of a thermally conductive metallic material such as copper or aluminum. The case  22  of the transformer  2  is substantially a rectangular hollow box, and includes an entrance  221  and a receptacle  222 . The entrance  221  is communicated with the receptacle  222 . The magnetic device  21  is introduced into the receptacle  222  through the entrance  221  such that the magnetic device  21  is accommodated within the receptacle  222 . After the magnetic device  21  is accommodated within the receptacle  222 , a thermally conductive layer is interposed between the magnetic device  21  and the case  22 . In some embodiments, the thermally conductive layer is a thermally conductive adhesive  24 . The thermally conductive adhesive  24  is filled between the gap between the inner walls of the case  22  and the magnetic device  21  to encapsulate the magnetic device  21  within the receptacle  222 . The use of the thermally conductive adhesive  24  can increase the heat transfer area of the magnetic device  21 . As a consequence, the heat generated by the magnetic device  21  will be transferred to the case  22  through the thermally conductive adhesive  24 . For increasing the heat-dissipating efficiency, the thermally conductive adhesive  24  is made of a material having a thermal conductivity. As such, the possibility of casing heat accumulation is largely reduced and thus the use life of the transformer is extended. 
     Please refer to  FIG. 2B  again. The pins  213   a  and  213   b  are bent by about 90 degrees and then extended in the downward direction. When the magnetic device  21  is disposed within the receptacle  222  of the case  22 , the pins  213   a  and  213   b  are exposed outside the case  22 . Since the pins  213   a  and  213   b  are flexible metallic sheets, the bending degrees of the pins  213   a  and  213   b  are readily shifted if the pins  213   a  and  213   b  are subject to an impact. Under this circumstance, the pins  213   a  and  213   b  are no longer aligned with corresponding insertion holes  251  of the circuit board  25  and thus fail to be successfully mounted on the circuit board  25 . For facilitating positioning the pins  213   a  and  213   b , the transformer  2  further includes a positioning plate  23 . The area of the positioning plate  23  is greater than the bottom area of the case  22 . Corresponding to the pins  213 , perforations  231  that have the same number as the pins  213  are formed in the positioning plate  23 . After the magnetic device  21  is disposed within the receptacle  222  of the case  22 , the pins  213   a  and  213   b  are penetrated through corresponding perforations  231  of the positioning plate  23 , so that the pins  213   a  and  213   b  are initially positioned by the positioning plate  23 . The resulting structure is shown in  FIG. 2C . The use the positioning plate  23  can facilitate positioning the pins  213   a  and  213   b.  In addition, the positioning plate  23  can be used to support the case  22 . 
     Please refer to  FIGS. 2A ,  2 B and  2 C again. The case  22  has a first side plate  223 . Several bolt holes  223   a  are formed in the first side plate  223  of the case  22 . By penetrating fastening elements  27  (e.g. screws) through corresponding bolt holes  223   a , another heat-dissipating device  26  (e.g. a water cooling device or a heat sink) may be attached onto the first side plate  223  of the case  22 . The heat generated by the magnetic device  21  is transferred to the case  22  through the thermally conductive adhesive  24  and then quickly dissipated away by the heat-dissipating device  26 , so that the heat-dissipating efficiency is enhanced. Moreover, since the case  22  is made of a metallic material and the magnetic device  21  is shielded by the case  22 , the electromagnetic interference generated by the transformer  2  is effectively suppressed. Under this circumstance, less number of filters (not shown) needs to be mounted on the circuit board  25  and thus the circuitry layout of the circuit board  25  is simplified. 
       FIG. 3  is a schematic exploded view illustrating a transformer according to anther embodiment of the present invention. As shown in  FIG. 3 , the transformer  3  principally comprises a magnetic device  31 , a case  32  and a thermally conductive layer  33 . The magnetic device  31  includes a winding member  311  and a magnetic core assembly  312 . The winding member  311  is electrically connected to a circuit board  34  through at least two pins  313 . The magnetic core assembly  312  includes a first magnetic part  312   a  and a second magnetic part  312   b . The upper portion and the lower portion of the winding member  311  are partially sheltered by the first magnetic part  312   a  and the second magnetic part  312   b , respectively. In addition, the middle portions of the first magnetic part  312   a  and the second magnetic part  312   b  are partially embedded into a channel (not shown) of the winding member  311 . As such, the primary winding assembly  311   a  and the secondary winding assembly  311   b  interact with the magnetic core assembly  312  to achieve the purpose of voltage regulation. In this embodiment, the winding member  311  includes a winding frame  311   a . A winding assembly  311   b  is wound around the winding frame  311   a . According to the practical requirements, the winding assembly  311   b  is produced by circularly winding an enameled wire or a copper foil. 
     The case  32  is made of a thermally conductive metallic material such as copper or aluminum. Similarly, the case  32  of the transformer  3  is substantially a rectangular hollow box. In some embodiments, the thermally conductive layer is a thermal pad  33 . The thermal pad  33  is attached on an inner wall  321  of the case  32 . The length d 1  of the thermal pad  33  is substantially equal to the length d 2  of the magnetic device  31 . Consequently, after the magnetic device  31  is accommodated within the receptacle of the case  32 , the thermal pad  33  is also in direct contact with the magnetic device  31 . The use of the thermal pad  33  can increase the heat transfer area of the magnetic device  31 . As a consequence, the heat generated by the magnetic device  31  will be transferred to the case  32  through the thermal pad  33 . For increasing the heat-dissipating efficiency, the thermal pad  33  is made of a material having a thermal conductivity. As such, the possibility of casing heat accumulation is largely reduced and thus the use life of the transformer is extended. 
     Moreover, the thermal pad  33  can also provide an insulating efficacy in order to avoid short circuit between the magnetic device and the case and meet the safety demand. 
     The concepts of the present invention can be expanded to many applications. For example, if the temperature of a magnetic device mounted on a circuit board is very high, the user may enclose a case around the magnetic device and interpose a thermal pad between the magnetic device and the case. Under this circumstance, the purpose of increasing the heat-dissipating efficiency of the magnetic device is achievable and thus the temperature of a magnetic device is decreased. In other words, the magnetic device can continuously work without the need of designing a new magnetic device or replacing the original magnetic device with a new one. As a consequence, the use of the transformer of the present invention is very cost-effective. On the other hands, if the transformer is used in different environments, the user only needs to select a proper case complying with the environment. That is, the cost and the time of reproducing different transformers are saved. 
     In the above embodiments, the magnetic device of the transformer includes a primary winding assembly and a secondary winding assembly, or includes a single winding assembly. It is noted that, however, those skilled in the art will readily observe that numerous modifications and alterations of the winding member and the magnetic core assembly may be made while retaining the teachings of the invention. In other words, the structure of the transformer of the present invention is not restricted as long as a magnetic device is sheltered by a case and a thermally conductive layer is interposed between the magnetic device and the case. Since the heat-dissipating efficiency of the magnetic device is enhanced and the thermally conductive layer offers an insulating efficacy, the transformer of present invention can be used in a stringent or poorly ventilated environment (e.g. a motor room, an automobile and the like) for an extended period. 
     From the above description, the transformer of the present invention includes a case, a magnetic device and a thermally conductive layer. The use of the thermally conductive layer can increase the heat transfer area of the magnetic device. As a consequence, the heat generated by the magnetic device will be transferred to the case through the thermally conductive layer. Since the possibility of casing heat accumulation is largely reduced, thus the use life of the transformer is extended. Moreover, since the case is made of a metallic material and the magnetic device is shielded by the case, the electromagnetic interference generated by the transformer is effectively suppressed. Under this circumstance, less number of filters needs to be mounted on the circuit board and thus the circuitry layout of the circuit board is simplified. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.