Patent Grant
8164408
This application claims the priority of Korean Patent Application No. 10-2009-0082423 filed on Sep. 2, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a planar transformer, and more particularly, to a planar transformer having a dual-bobbin structure.
2. Description of the Related Art
Recently, power supply units have been required to be slimmer due to the trend towards slimmer electronic devices.
Even if power supply units can have slim profiles by driving power terminals at high frequencies, the slimming of power supply units is limited by magnetic devices and capacitors contained therein.
Slimmer capacitors with heights and diameters small enough for slim power supply units have been recently developed, whereas there has been not much progress in the slimming of magnetic devices.
As for inductors and transformers, which are representative components of magnetic devices, a multilayer board having a printed circuit is stacked to thereby implement a winding of a magnetic device. In this way, magnetic devices can be slimmed; however, this process increases the manufacturing cost of the multilayer board.
Furthermore, the greater the number of turns (winding), the thicker the multilayer board becomes, adversely affecting the slimming of devices.
An aspect of the present invention provides a planar transformer having a dual bobbin structure.
According to an aspect of the present invention, there is provided a planar transformer including: a core unit including a pair of cores that are electromagnetically coupled to each other; and a bobbin unit including: an inner bobbin part including a bobbin body having a predetermined volume and having a through hole into which the core is inserted, and a first winding wound around an outer circumferential surface of the bobbin body; and a board part including at least one board including a board body having a predetermined surface area and having a through hole into which the inner bobbin part and the core are inserted, and a second winding formed on at least one surface of the board body and causing electromagnetic action with the first winding.
The board part may include a plurality of boards that are stacked.
The first winding may have a greater number of turns than the second winding.
The pair of cores may have first to third legs that are electromagnetically coupled.
The board may further include two side through holes, the first leg may be inserted into the through hole of the inner bobbin part and the through hole of the board, and the second and third legs may be inserted into the side through holes, respectively.
According to another aspect of the present invention, there is provided a planar transformer including: a core unit including a pair of cores that are electromagnetically coupled to each other; and a bobbin unit including: an inner bobbin part including a bobbin body having a predetermined volume and having a through hole into which the core is inserted, and a first winding wound around an outer circumferential surface of the bobbin body; and a board part including at least one board including a board body having a predetermined surface area and having a through hole into which the core is inserted, and a second winding formed on at least one surface of the board body and causing electromagnetic action with the first winding, wherein the board part and the inner bobbin part are stacked.
The plurality of boards may be stacked on the inner bobbin part. Alternatively, the inner bobbin part may be stacked between the plurality of boards.
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:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Referring to
The core unit 110 may include a pair of cores 111 and 112, and the pair of cores 111 and 112 have first to third legs 111a, 111b and 111c and are electromagnetically coupled together through the first to third legs 111a, 111b and 111c. The pair of cores 111 and 112 may realize an EI core or an EE core having first to third legs 111a, 111b and 111c. Even if only an EI core is illustrated in
The bobbin unit 120 may include an inner bobbin part 121 and a board part including at least one board 122.
The inner bobbin part 121 includes a bobbin body having a predetermined volume, and the bobbin body may have a through hole 121b in which the first leg 111a of the core inner bobbin part 121 of the core unit 110 is inserted. A first winding 121a is wound around the outer circumferential surface of the bobbin body. Thus, the first winding 121a may be wound perpendicularly to the longitudinal direction of the first leg 111a.
The board part may include at least one board 122, and the board 122 may be a monolayer or multilayer printed circuit board (PCB). The board 122 has a through hole 122b in which the inner bobbin part 121 may be inserted along with the first leg 111a of the core unit 110. In addition, the board 122 may further include side through holes 122c in which the second and third legs 111b and 111c may be inserted, respectively.
A second winding 122a may be printed on one surface of the board 122 along the circumference of the board 122. The second winding 122a may be printed around the through hole 122b in the form of a conductive pattern. The second winding 122a performs a voltage conversion function of the transformer through electromagnetic action with the first winding 121a. The first winding 121a and the second winding 122a may each have a preset number of turns. Considering the height of the transformer, the number of turns of the first winding 121a may be greater than the number of turns of the second winding 122a.
For example, the first winding 121a may serve as a primary winding of power conversion and the second winding 122a may serve as a secondary winding. Considering that the number of turns of a primary winding is generally greater than the number of turns of a secondary winding, the first winding 121a may be formed around the outer circumferential surface of the inner bobbin part 121 having a relatively large winding area. Also, considering that the level of current flowing in a secondary winding is higher than that of current flowing in a primary winding, the secondary winding needs to have a relatively small number of turns while having a thickness or width large enough to allow current to flow with a high level. Therefore, the second winding 122a may be printed on the board 122 having a wide surface area.
The inner bobbin part 121 is inserted into the through hole 122b of the board 122, thereby achieving a reduction in the volume of a transformer.
Referring to
Accordingly, the inner bobbin part 121, around which the first winding 121a with a greater number of turns than the second winding 122a is wound, is inserted into the through hole 122b of the board 122, thereby achieving a reduction in the height and volume of the transformer.
Referring to
Similarly to the planar transformer 100 of
Referring to
Accordingly, when the second winding 222a needs to have a wide winding area, the number of turns of the second winding 222a is increased by reducing the size of the through hole 222b of the board 222, and the board 222 may be then stacked on the inner bobbin part 221. The planar transformer 200 of this embodiment may have a greater volume than the planar transformer 100 depicted in
According to the third exemplary embodiment, the planar transformer 100 depicted in
Similarly to the planar transformer 100 depicted in
The board part may include a plurality of boards 322 to 32N when the second winding 322a needs to have a large number of turns exceeding the winding formation capacity of a single board, or when a plurality of second windings need to output power having respective different voltage levels through electromagnetic action with the first winding 321a. In this case, the plurality of boards 322 to 32N may be stacked. Second windings 322a to 32Na may be printed on the plurality of boards 322 to 32N, respectively. The inner bobbin part 321 is inserted into the through holes 322b to 32Nb of the plurality of boards 322 to 32N, so that the pair of cores 311 and 312 can be electromagnetically coupled together through the first leg 311a. Likewise, the second and third legs 311b and 311b are inserted into the side through holes 322c to 32Nc of the plurality of boards 322 to 32N, so that the pair of cores 311 and 312 can be electromagnetically coupled to each other. Here, the plurality of second windings 322a to 32Na respectively provided on the plurality of boards 322 to 32N may output power having respective preset voltage levels, or may be electrically connected to output power of a single voltage level.
As described above, according to this embodiment, even if a plurality of boards are stacked to cope with the case that the second winding needs to have a large number of turns or to output multiple outputs, the height of the transformer is reduced by inserting the inner bobbin part provided with the first winding into the through hole. Accordingly, the transformer may achieve a reduction in volume (slimming).
According to the fourth exemplary embodiment, a plurality of boards are provided in the planar transformer 200 depicted in
Similarly to the planar transformer 200 of
The board part may include a plurality of boards 422 to 42N when the second winding 422a needs to have a large number of turns exceeding the winding formation capacity of a single board, or when a plurality of second windings need to output power having respective different voltage levels through electromagnetic action with the first winding 421a. In this case, the plurality of boards 422 to 42N may be stacked. Second windings 422a to 42Na may be printed on the plurality of boards 422 to 42N, respectively. The first leg 411a is inserted into the respective through holes 422b to 42Nb of the plurality of boards 422 to 42N, so that the pair of cores 411 and 412 can be electromagnetically coupled. Likewise, the second and third legs 411b and 411b are inserted into the side through holes 422c to 42Nc of the plurality of boards 422 to 42N, so that the pair of cores 411 and 412 can be electromagnetically coupled. Here, the plurality of second windings 422a to 42Na, provided on the plurality of boards 422 to 42N respectively, may output power having respective preset voltage levels, or may be electrically connected to output power of a single voltage level. The plurality of boards 422 to 42N may be stacked on the inner bobbin part 421.
According to the fifth exemplary embodiment, the stacked order of the plurality of boards and the inner bobbin part in the planar transformer 400 of
As shown in
In addition, the board part may include a plurality of boards 522 to 52N, and the inner bobbin part 521 may be stacked between the plurality of boards 522 to 52N. In
As described above, a plurality of boards are stacked when the second winding needs to have a large number of turns or when multiple outputs are required. In this case, the boards may be stacked on the inner bobbin part 521 or the inner bobbin part 521 may be stacked between the plurality of stacked boards. This may increase a planar transformer's volume to some degree as compared to the planar transformer depicted in
As set forth above, according to exemplary embodiments of the invention, the planar transformer has a dual-bobbin structure in which a primary side with a greater number of turns is wound around the outer circumferential surface of an inner core and a secondary side with a smaller number of turns is printed on a board. Accordingly, the planar transformer can achieve slimness with low manufacturing costs, facilitate the manufacturing process thereof, easily ensure an insulating distance between the primary side and the secondary side of the transformer, and easily attain uniform leakage inductance.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2009-0082423 | Sep 2009 | KR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5175525 | Smith | Dec 1992 | A |
| 5781093 | Grandmont et al. | Jul 1998 | A |
| 6636140 | Fujiyoshi et al. | Oct 2003 | B2 |
| 6831544 | Patel et al. | Dec 2004 | B2 |
| 6876555 | Matsumoto et al. | Apr 2005 | B2 |
| 20020159214 | Perlick et al. | Oct 2002 | A1 |
| 20040032313 | Ferencz et al. | Feb 2004 | A1 |
| 20040113739 | Du et al. | Jun 2004 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20110050379 A1 | Mar 2011 | US |
