Abstract:
A transformer for an inverter circuit, comprising: a core module having a first core portion and a second core portion; a first bobbin having a first coiled portion and a first hollow portion for receiving the first core portion; a second bobbin substantially disposed parallel to the first bobbin, the second bobbin having a second coiled portion and a second hollow portion for receiving the second core portion; primary coils wound around the first coiled portion; and secondary coils wound around the second coiled portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a transformer, and particularly to a thin-type high power transformer for use in an inverter circuit. 
     2. Description of the Related Art 
     With improvement of display technologies, liquid crystal display (LCD) monitors have gradually become common in the field of computer or other displays. Compared to CRT monitors, LCD monitors have the advantages of slimmer profiles and better display quality with less flicker. In an LCD monitor, a backlight module has high power-driven fluorescent tubes for the required backlight system. Generally, an inverter with a driving circuit is used to drive the fluorescent tubes, and the inverter has a high-voltage transformer. Thus, in order to minimize the volume of the LCD monitor, it is necessary for the transformer used in the inverter circuit to have a thin-type structure. 
     A conventional transformer for the inverter circuit is generally constructed such that primary coils and secondary coils are wound around a hollow bobbin, with a core inserted into the hollow portion of the bobbin. FIG. 1 a  shows an embodiment of the conventional transformer for the inverter circuit, and FIG. 1 b  shows the cross-section of the bobbin of the transformer, with the coils wound around the bobbin. 
     As shown in FIG. 1 a , the conventional transformer  10  for the inverter circuit has a first E-shaped core  30   a  and a second E-shaped core  30   b . The first E-shaped core  30   a  and the second E-shaped core  30   b  can be combined to form a closed magnetic loop. Further, the conventional transformer  10  has a bobbin  50 , with a primary winding window  510  and a secondary winding window  520 , and pins  530  for connecting the wire of the coils to the circuit board are provided on the two ends of the bobbin  50 . A flange  515  is provided between the primary winding window  510  and the secondary winding window  520 , and flanges  525  are provided to separate the secondary winding window  520  into several wound areas. 
     In the aforementioned structure of the bobbin  50 , as shown in FIG. 1 b , the primary winding window  510  is used wound the primary coils  610 , and the secondary winding window  520  is used wound the secondary coils  620 . The wire of the secondary coils  620  has a smaller diameter and winds in multi-layers; therefore, it is necessary to separate the secondary winding window  520  into several wound areas with flanges  525  in order to prevent arcing fault resulting from the high voltage difference between two adjacent layers of coils. 
     In the aforementioned conventional transformer for the inverter circuit, however, the primary and secondary coils are wound on the same bobbin. This structure may result in problems. 
     First, in the conventional transformer, the primary winding window  510  has a limited winding range, and the wire of the primary coils has a relatively larger diameter. Therefore, if the transformer is required to have primary coils  610  with more winding turns, or an additional set of primary coils  610 , the coil wound thickness will be significantly increased, compromising the transformer&#39;s thin profile. 
     Further, if the power supplied by the transformer increases as is the case when at least two fluorescent tubes are driven by a single transformer, a noticeable raise in temperature occurs in the primary coils portion, possibly overheating the transformer. Increasing the wire diameter of the primary coils alleviates the temperature problem. By using a thick wire, however, the coil thickness will be increased. As a result, this method is not preferred. 
     Further, in conventional transformers, it is necessary to perform the mains isolation of the primary and secondary coils on the same bobbin. This may cause difficulty in voltage-resist treatment of the high-voltage coils, which increases the difficulty and cost of the transformer manufacture. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to disclose a transformer used in the inverter circuit that solves the thickness problem. 
     Another object of the present invention is to disclose a transformer used in the inverter circuit that solves the temperature problem in the primary coils. Thus, overheating is prevented, and high power demands are met. 
     A further object of the present invention is to disclose a transformer used in the inverter circuit that corresponds to the requirement of mains isolation. With the present invention, the pressure-resistant treatment of the high-voltage coils is simplified, and a selected variety of coil wires may be applied, so that the difficulty and cost of transformer manufacture are alleviated. 
     The present invention discloses a transformer for an inverter circuit, comprising: a core module having a first core portion and a second core portion; a first bobbin having a first coiled portion and a first hollow portion for receiving the first core portion; a second bobbin substantially disposed parallel to the first bobbin, the second bobbin having a second coiled portion and a second hollow portion for receiving the second core portion; primary coils wound around the first coiled portion; and secondary coils wound around the second coiled portion. 
     In the above-mentioned transformer of the present invention, the core module may be a U-U structure constituted by two U-shaped cores, a U-I structure constituted by a U-shaped core and an I-shaped core, an L-L structure constituted by two L-shaped cores, an E-E structure constituted by two E-shaped cores, an E-I structure constituted by an E-shaped core and an I-shaped core, or a U-T structure constituted by a U-shaped core and a T-shaped core. 
     Further, the present invention discloses a thin-type high power transformer comprising: a first U-shaped core; a second U-shaped core; a first bobbin having a first hollow portion for inserting a part of the first U-shaped core and a part of the second U-shaped core; a second bobbin substantially disposed parallel to the first bobbin, the second bobbin having a second hollow portion for inserting a part of the first U-shaped core and a part of the second U-shaped core; primary coils wound around the first bobbin; and secondary coils wound around the second bobbin. 
     In the transformer of the present invention, the primary coils are wound around an independent first bobbin so that the winding area is not limited. Therefore, the winding layers of the primary coils are reduced, and the thin-type transformer may be achieved. 
     Further, in the transformer of the present invention, the wire diameter of the primary coils can be increased without significantly increasing the thickness of the transformer. Therefore, a selective variety of coil wires of the primary coils may be applied in the transformer of the present invention. 
     Further, in the transformer of the present invention, the primary coils does not stack windings, so the transformer maintains a relatively low temperature, and can be used in high power situations. 
     Further, in the transformer of the present invention, the primary and secondary coils are disposed parallel to each other, and no contact occurs between the coils, achieving the mains isolation requirement. 
     Further, in the transformer of the present invention, the primary and secondary coils are respectively wound around the first and second bobbins, so that the wound areas increase, and the transformer length is reduced. 
     Further, the transformer of the present invention is manufactured in a simpler process, and the costs are reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein: 
     FIG. 1 a  is a perspective exploded view of a conventional transformer for an inverter circuit; 
     FIG. 1 b  is a cross-section showing the primary and secondary coils wound around the bobbin of the conventional transformer; 
     FIG. 2 a  is a perspective exploded view showing an embodiment of the transformer for an inverter circuit of the present invention; 
     FIG. 2 b  is a cross-section showing the primary coils of the transformer of the present invention; 
     FIG. 2 c  is a cross-section showing the secondary coils of the transformer of the present invention; 
     FIG. 3 is a plan view showing the embodiments of the combination structure of the core module; and 
     FIG. 4 is a plan view showing other embodiments of the combination structure of the core module. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the transformer for the inverter circuit of the present invention is shown in FIG. 2 a  to FIG. 2 c . As shown in FIG. 2 a , the transformer  100  for the inverter circuit of the present invention has a first bobbin  110  for the winding of the primary coils, a second bobbin  120  for the winding of the secondary coils, and a core module  130 . The first bobbin  110  and the second bobbin  120  are substantially arranged in parallel, and each has a first hollow portion  112  and a second hollow  122  respectively, and each has a winding window respectively for winding of the primary and secondary coils. In order to prevent arcing fault of the secondary coils, the winding window of the second bobbin  120  is separated into several wound areas by a plurality of flanges. Further, the core module  130  has a first U-shaped core  130   a  and a second U-shaped core  130   b , which can be inserted to the first hollow portion  112  and the second hollow portion  122  from the opposite ends of the first bobbin  110  and the second bobbin  120  to form a O-shaped closed magnetic loop. In this case, the part of the first U-shaped core  130   a  and the part of the second U-shaped core  130   b  received in the first hollow portion  112  are hereinafter referred to a first core portion C 1 , and the part of the first U-shaped core  130   a  and the part of the second U-shaped core  130   b  received in the second hollow portion  122  are hereinafter referred to a second core portion C 2 . 
     Description of the primary and secondary coils will be hereinafter disclosed in reference to FIG. 2 b  and FIG. 2 c . 
     As shown in FIG. 2 b , the primary coils  150  of the present invention are wound around the first bobbin  110 . First pins  115  are provided at opposite sides of the first bobbin  110 , and the first core portion C 1  is inserted in the first bobbin  110 . Compared to the conventional transformer, the primary coils  150  are wound around the independent first bobbin  110 , so that the wound area is not limited as in the prior art. Therefore, the thickness of the primary coils is reduced, and the wire diameter of the primary coils can be increased without significantly increasing the thickness of the transformer, which induces a selective variety of coil wires of the primary coils. In the transformer of the present invention, the primary coils are preferably wound in two layers and most preferably wound in a single layer. The primary coils do not stack windings, so the transformer maintains a relatively low temperature, and can be used in high power situations. 
     Further, as shown in FIG. 2 c , the secondary coils  160  of the present invention are wound around the second bobbin  120 . Second pins  125  are provided at opposite sides of the second bobbin  120 , and the second core portion C 2  is inserted in the second bobbin  120 . The first bobbin  110  and the second bobbin  120  are substantially in a parallel arrangement; that is, the first core portion C 1  and the second core portion C 2  are substantially in a parallel arrangement, and the primary coils  150  and the secondary coils  160  wound around the bobbins  110 ,  120  are thus arranged in parallel. Due to the parallel arrangement of the primary and secondary coils  150 ,  160 , no contact occurs between the wires of the coils, so that it is simple to achieve the mains isolation requirement and perform the voltage-resist treatment. 
     In the above-mentioned arrangement, the primary and secondary coils  150  and  160  are respectively wound around the first bobbin  110  and the second bobbin  120 , so that both of the bobbins have a wider wound area; that is, the total length of the transformer can be relatively reduced. As shown in FIG. 2 a , the first bobbin  110  does not have a flange, and the second bobbin  120  has flanges at an equal distance; as a result, the unequal areas of the first winding window and the second winding window as shown in the conventional bobbin are not required. Therefore, the transformer of the present invention can be manufactured with a simplified process, effectively reducing the cost. 
     It should be noted that, as shown in FIG. 3, the core module  130  of the present invention shown in FIG. 2 a  to FIG. 2 c  is a U-U structure  210  constituted by two U-shaped cores. In the U-U structure  210 , the joint positions (the dotted line in the core module  130  of FIG. 2 b  and FIG. 2 c ) can be for example connected with glue or other adhesive methods. However, various shapes or structures of the core module  130  with a first core portion and a second core portion arranged in parallel can be applied to the present invention. For example, an L-L structure  220  constituted by two L-shaped cores and a U-I structure  230  constituted by a U-shaped core and an I-shaped core as shown in FIG. 3, or an E-E structure  310  constituted by two E-shaped cores, an E-I structure  320  constituted by an E-shaped core and an I-shaped core, and a U-T structure  330  constituted by a U-shaped core and a T-shaped core as shown in FIG. 4 are respectively applicable in the present invention. Any other core module structures with two core portions arranged in parallel are also acceptable. 
     While the present invention has been described with reference to the preferred embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. On the contrary, the invention is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.