JP2006032861A - Ferrite core and inverter transformer using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferrite core and inverter transformer which can be made more efficient by a one-input and multiple-output structure and can be further reduced in the number of components and cost and has a high installation area reduction effect. <P>SOLUTION: The ferrite core comprises a leg portion 2 for a primary coil around which a primary coil 7 is to be wound, and leg portions 3, 4 and 5 for a secondary coil around which secondary coils 8, 9 and 10 are to be wound. These leg portions 3, 4 and 5 are magnetically coupled by a coupling portion 6. There are three or more leg portions 3, 4 and 5 for a secondary coil as opposed to just one leg portion 2 for a primary coil, and the leg portions 3, 4 and 5 for a secondary coil are formed at such positions that they may have nearly the same magnetic resistance with respect to the leg portion 2 for a primary coil. To be more specific, the distance between each of the leg portions 3, 4 and 5 for a secondary coil and the leg portion 2 for a primary coil is set nearly the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a so-called multi-leg ferrite core having a plurality of secondary coil legs for one primary coil leg, and further to an inverter transformer using the same.

  For example, an inverter transformer that performs voltage conversion in a lighting circuit that illuminates a backlight of a liquid crystal display device, for example, normally forms a closed magnetic circuit by abutting a pair of ferrite cores formed in the same shape, and a ferrite that has been abutted It is configured by winding a primary coil and a secondary coil having different numbers of turns around a core. As a basic shape of the ferrite core, for example, a U-shaped ferrite core having a pair of leg portions at both ends of a connecting portion, or an E-shape in which a center core and side cores symmetrically arranged on both sides thereof are connected by a connecting portion. A typical example is a ferrite core.

  FIG. 8 shows an example of an inverter transformer using a general U-shaped ferrite core 101. In the U-shaped ferrite core 101, a pair of parallel leg portions 102 are magnetically coupled by a connecting portion 103, and the pair of U-shaped ferrite cores 101 are abutted so that the tips of the leg portions 102 are in contact with each other. Thus, a closed loop magnetic circuit is formed. Then, the primary coil 104 is wound around one leg portion 102 and the secondary coil 105 having a different number of turns from the primary coil 104 is wound around the other leg portion 102 to constitute an inverter transformer. In the inverter transformer configured as described above, a necessary voltage can be obtained by setting the number of turns of the primary coil 104 and the secondary coil 105.

  FIG. 9 shows an example of an inverter transformer using an E-shaped ferrite core 111. The E-shaped ferrite core 111 is formed by magnetically coupling a center core 112 that is a leg portion and a pair of side cores 113 by a connecting portion 114. The E-shaped ferrite core 111 also forms a closed magnetic circuit by abutting the pair of E-shaped ferrite cores 111 so that the tips of the center core 112 and the side core 113 are in contact with each other.

  By the way, for example, in a liquid crystal display device, the screen is becoming larger, the number of backlights provided on the back of the liquid crystal panel tends to increase, and the number of inverter transformers that convert to a high voltage necessary for lighting increases. There is a need. In each of the inverter transformers described above, the primary coil and the secondary coil correspond one-to-one, and one inverter transformer needs to be used for one backlight.

  However, in the configuration where one inverter transformer is used for one backlight, it is necessary to increase the number of inverter transformers as the number of backlights increases, resulting in a decrease in work efficiency and an increase in parts cost due to an increase in the number of parts. In addition, the area required for mounting the inverter transformer increases, which may hinder the miniaturization of the liquid crystal display device. Under such circumstances, an inverter transformer that can turn on two backlights by one is proposed (see, for example, Patent Document 1 and Patent Document 2).

Specifically, in Patent Document 1, two outer leg portions around which the secondary winding is wound are provided, and one outer leg portion around which the primary winding is wound is provided so that the outer leg portions face each other. An inverter transformer having a configuration in which a middle leg portion is disposed so as to face each other between outer leg portions is disclosed. In Patent Document 2, two secondary windings are arranged opposite to the primary winding so as to have the same magnetic coupling as the primary winding, and the closed magnetic path magnetic core is inserted through the through hole of the first bobbin. An inverter transformer is disclosed in which a first magnetic core in which a leg and a second leg inserted through a through hole of a second bobbin are connected by a connecting leg and a flat second magnetic core are abutted.
Japanese Patent Laid-Open No. 2003-22917 JP 2003-309026 A

  However, in the inventions described in these patent documents, although a plurality of outer leg portions around which the secondary winding is wound are provided, in practice, only two examples of the number of outer leg portions are disclosed. The above configuration is not described at all. Liquid crystal display devices tend to have larger screens, and the number of backlights tends to increase further. In such a situation, if the number of outer legs is limited to two, the number of parts will be reduced. However, it is difficult to sufficiently reduce the mounting area. Further, when the number of outer leg portions is increased, there is a concern about variations in output current due to variations in magnetic resistance, and a technique for solving this is also necessary.

  The present invention has been proposed in view of such a conventional situation. That is, the present invention can achieve high efficiency by increasing the number of inputs and outputs, further reducing the number of parts and cost, and further reducing the installation area. It aims at providing, and also aims at providing an inverter transformer. Further, in addition to the above, the present invention can eliminate variations in output current due to variations in magnetic resistance, and evenly from secondary coils wound around each outer leg (secondary coil leg). An object of the present invention is to provide a ferrite core and an inverter transformer capable of taking out an output.

  The inventor has conducted various studies over a long period of time in order to achieve the above-described object. As a result, by arranging three or more secondary coil legs for one primary coil leg, the number of parts can be greatly reduced, for example, further increasing the number of backlights. In addition to being able to cope with it, it came to the conclusion that the effect of reducing the mounting area was much greater than when the number of outer legs was two.

  The present invention has been completed based on such knowledge, and the ferrite core of the present invention includes a primary coil leg portion around which a primary coil is wound and a secondary coil around which a secondary coil is wound. A ferrite core that is magnetically connected by a connecting portion, and has three or more secondary coil legs for one primary coil leg, Each of the secondary coil legs is formed at a position where the magnetic resistance is approximately equal to the primary coil leg.

  The inverter transformer of the present invention has a primary coil leg portion around which the primary coil is wound and a secondary coil leg portion around which the secondary coil is wound, and these are magnetically connected by the connecting portion. A first ferrite core connected to each other, a primary coil and a secondary coil wound around each leg portion of the first ferrite core, and each leg portion of the first ferrite core; And a second ferrite core that forms a closed magnetic circuit together with one ferrite core, and the first ferrite core has three or more secondary coil legs with respect to one primary coil leg. Each of the secondary coil legs is formed at a position where the magnetic resistance is substantially equal to the primary coil leg.

  In the ferrite core and the inverter transformer of the present invention, three or more secondary coil legs are provided for one primary coil leg, and therefore three or more outputs are extracted for one input. Here, since each secondary coil leg is formed at a position where the magnetic resistance is substantially equal to the primary coil leg, the output is evenly extracted without any difference in output current. It is.

  In addition, since three or more secondary coil legs are provided for one primary coil leg, three or more ferrite cores (inverter transformers) corresponding to the primary coil and the secondary coil are provided. In other words, the number of parts is reduced to 1/3 or less, and the cost of parts is greatly reduced.

  Furthermore, the reduction effect is remarkably large in terms of installation area. For example, in a ferrite core (inverter transformer) having two secondary coil legs with respect to one primary coil leg, a ferrite core (inverter transformer) in which the primary coil and the secondary coil correspond one-to-one. The installation area is almost the same as when two are installed. On the other hand, in a ferrite core (inverter transformer) having three secondary coil legs for one primary coil leg, the primary coil and secondary coil correspond one-to-one. The installation area is smaller than when three transformers are installed. As the number of secondary coil legs increases, the merit of reducing the installation area becomes more prominent.

  According to the ferrite core and the inverter transformer of the present invention, high efficiency can be achieved by increasing the number of inputs and outputs, and the number of parts and the cost can be further reduced. In addition, according to the present invention, for example, it is possible to greatly reduce the installation area compared to a ferrite core (inverter transformer) having two secondary coil legs for one primary coil leg. It is.

  Hereinafter, a ferrite core and an inverter transformer to which the present invention is applied will be described with reference to the drawings.

  FIGS. 1A and 1B show an example of a ferrite core to which the present invention is applied. The ferrite core 1 of the present embodiment has a primary coil leg 2 at the center and three or more, here three secondary coil legs 3, 4 and 5 around it. These are magnetically coupled by the plate-like connecting portion 6. Here, three secondary coil legs 3, 4, 5 are arranged around the primary coil legs 2 at substantially equal angular intervals.

  These primary coil leg 2, secondary coil legs 3, 4, 5 and connecting part 6 are all formed of a ferrite material, and these are integrally formed by a technique such as sintering. . As the ferrite material, any ferrite material such as Mn-Zn ferrite can be used, but in order to improve the performance, a ferrite material having a high magnetic permeability and magnetic flux density and excellent soft magnetic properties should be used. preferable.

  The primary coil leg 2 and the secondary coil legs 3, 4 and 5 are all cylindrical in this embodiment. However, the present invention is not limited to this. It is possible to have a shape of The same applies to the connecting portion 6. Here, the connecting portion 6 is a rectangular plate having a size including the primary coil leg 2 and all the secondary coil legs 3, 4, 5. If the magnetic path which connects the leg part 2 and each leg part 3, 4, and 5 for secondary coils is formed, it can be set as arbitrary shapes. For example, as shown in FIG. 2, it is possible to delete an unnecessary portion of the connecting portion 6 so as to have a substantially Y shape including only a magnetic path portion.

  In the ferrite core 1, as shown in FIG. 3, a primary coil 7 is wound around the primary coil leg 2, and the secondary coils 8, 9 are respectively wound around the secondary coil legs 3, 4, 5. , 10, and as shown in FIG. 4, the plate core 11, which is the second ferrite core, is in contact with the front end surfaces of the primary coil leg 2 and the secondary coil legs 3, 4, 5. The inverter transformer 20 is configured by matching.

  In this inverter transformer 20, a primary transformer is constituted by the primary coil leg 2 and the secondary coil leg 3, and the primary coil 7 and the secondary coil 8, and is converted from the secondary coil 8 into a predetermined voltage. Output is retrieved. Similarly, the primary coil leg 2 and the secondary coil leg 4 and the primary coil 7 and the secondary coil 9 constitute a second transformer, and the primary coil leg 2 and the secondary coil leg 5. , And the primary coil 7 and the secondary coil 10 constitute a third transformer. That is, the inverter transformer 20 functions as a 1-input 3-output inverter transformer.

  In the inverter transformer 20 having the above-described configuration, the ratio of the number of turns of the primary coil 7 and the number of turns of the secondary coils 8, 9, 10 is appropriately set according to the required voltage. On the other hand, the number of turns of each secondary coil 8, 9, 10 is the same number when the output from each secondary coil 8, 9, 10 is constant.

  Here, in order to obtain a constant output from each of the secondary coils 8, 9, 10, the distance from the primary coil leg 2 of the secondary coil legs 3, 4, 5 is important. The secondary coil legs 3, 4, 5 need to be formed at positions where the magnetic resistances are substantially equal to the primary coil legs 2. For this purpose, in the case of the ferrite core 1 of the present embodiment, it is preferable to design the distances between the secondary coil legs 3, 4, 5 and the primary coil legs 2 to be equal.

As shown in FIG. 1, the distances between the secondary coil legs 3, 4 and 5 and the primary coil legs 2 are L ₁ , L ₂ and L ₃ , respectively. Considering the magnetic resistance between each of the secondary coil legs 3, 4, 5 and the primary coil leg 2, the magnetic path between them is constituted by the connecting plate 6. Since the connecting plate 6 has a sufficient cross-sectional area between the leg portions 3, 4, 5 and the primary coil leg portion 2, it can be assumed here that the cross-sectional area A of the magnetic path is constant.

When the magnetic permeability of the connecting plate 6 constituting the magnetic path is μ, the magnetic resistance R ₁ between the secondary coil leg 3 and the primary coil leg 2 can be expressed as R ₁ = L ₁ / μA. it can. Similarly, the magnetic resistance R ₂ between the secondary coil leg 4 and the primary coil leg 2 can be expressed as R ₂ = L ₂ / μA, and the secondary coil leg 5 and the primary coil leg The magnetic resistance R ₃ between the legs 2 can be expressed as R ₃ = L ₃ / μA. As described above, the cross-sectional area A of the magnetic path is constant, and the magnetic path is constituted by the same connecting plate 6, so the permeability μ is also constant. In order to make the magnetic resistance between each of the secondary coil legs 3, 4, 5 and the primary coil leg 2 constant, that is, R ₁ = R ₂ = R ₃ , L ₁ = L ₂ = L ₃ would be good.

  As described above, an inverter transformer is constructed that can take out equivalent outputs from each of the secondary coils 8, 9, and 10 with one input and three outputs. From the same idea, one input and three outputs or more, for example, one input A 4-output inverter transformer or the like can be easily constructed.

  FIG. 5 shows an example of a 1-input 4-output inverter transformer. In this example, the secondary coil legs 33 to 36 are arranged around the central primary coil leg 31, that is, at the four corners of the rectangular coupling plate 32, and the primary coil leg 31 is primary. The secondary coil 38-41 is wound around the coil 37 and the leg part 33-36 for secondary coils, respectively. Moreover, the distance between the leg part 31 for primary coils and each leg part 33-36 for secondary coils is equal. As a result, an inverter transformer with one input and four outputs is configured, and the outputs taken out from the secondary coils 38 to 41 are substantially constant.

  As described above, the inverter transformer of the present invention can be a single-input multiple-output inverter transformer such as one-input three-output, one-input four-output, etc., leading to a reduction in the number of components and a reduction in component costs. In particular, when the installation area of the inverter transformer is considered, it is particularly effective to provide three or more secondary coil legs for one primary coil leg. explain.

  FIG. 6 is a diagram in the case of one input and two outputs. (A) is a case where two inverter transformers 51 corresponding to a primary coil and a secondary coil are installed on a one-to-one basis, and (b) is one primary coil. The case where the two leg portions 62 and 63 for secondary coils are provided with respect to the leg portion 61 for use is shown. In FIG. 6A, each inverter transformer 51 includes one primary coil leg 52 and one secondary coil leg 53. Correspondingly, the primary coil 54 and the secondary coil are formed. 55 is also provided one by one. In FIG. 6B, the primary coil 64 is wound around the primary coil leg portion 61, and the secondary coils 65 and 66 are wound around the secondary coil leg portions 62 and 63, respectively.

Here, in consideration of interference between the transformers and the like, assuming that the distance between the primary coil and the secondary coil and the distance between the secondary coils are constant, the inverter transformers in FIG. 51, a distance a ₁ between the primary coil leg 52 and the secondary coil leg 53, and a distance a between the primary coil leg 61 and the secondary coil legs 62, 63 in the inverter transformer of FIG. 6B. ₂ should be approximately equal. Further, the distance b ₁ between the secondary coil legs 53 in the adjacent inverter transformer 51 in FIG. 6A and the distance b between the secondary coil legs 62 and 63 in the inverter transformer in FIG. 6B. ₂ also needs to be equal.

In FIG. 6A, the installation area of the two inverter transformers can be expressed as a ₁ × b ₁ , while in FIG. 6B, the installation area of the inverter transformer can be expressed as a ₂ × b _2. it can. As described above, since a ₁ = a ₂ and b ₁ = b ₂ , a ₁ × b ₁ = a ₂ × b ₂ , and these installation areas are almost the same.

  Next, consider a case of 1 input and 3 outputs. FIG. 7 is a diagram in the case of one input and three outputs. FIG. 7A shows a case where three inverter transformers 51 corresponding to a primary coil and a secondary coil are installed one to one, and FIG. 7B shows one primary coil. The case where three leg portions 72, 73, 74 for secondary coils are provided for the leg portion 71 for use is shown. In FIG. 7B, the primary coil 75 is wound around the primary coil leg 71, and the secondary coils 76, 77, and 78 are wound around the secondary coil legs 72, 73, and 74, respectively. Has been.

In FIG. 7A, the installation area of the _three inverter transformers can be represented by a ₃ × b _3. However, since the three inverter transformers are arranged, the dimension b ₃ in the arrangement direction becomes large, and the installation area Will also be big. On the other hand, in FIG. 7B, the installation area of the 1-input 3-output inverter transformer can be expressed as a ₄ × b ₄ . At this time, in particular, the dimension b ₄ in the arrangement direction of the leg portions 72, 73, 74 for the secondary coil is greatly reduced compared to the dimension b ₃ , so that the installation area is smaller than that in the case of FIG. Greatly reduced. In the case of one input and four outputs, the installation area can be substantially the same as that in the case of one input and three outputs shown in FIG. 7B, and the area reduction effect becomes more remarkable.

An example of the ferrite core to which this invention is applied is shown, (a) is a top view of the ferrite core corresponding to 1 input 3 output, (b) is a side view. It is a top view which shows the other example of the ferrite core corresponding to 1 input 3 output. It is a top view which shows the winding state of the primary coil and secondary coil to the ferrite core shown in FIG. It is a side view which shows an example of the inverter transformer comprised using the ferrite core shown in FIG. It is a top view which shows the winding state of the primary coil and secondary coil to the ferrite core corresponding to 1 input 4 output. (A) is a plan view when two inverter transformers corresponding to one-to-one correspondence between the primary coil and the secondary coil are installed, and (b) is two secondary coil legs for one primary coil leg. It is a top view at the time of providing. (A) is a plan view when three inverter transformers corresponding to one-to-one correspondence between the primary coil and the secondary coil are installed, and (b) is three leg portions for the secondary coil with respect to one leg portion for the primary coil. It is a top view at the time of providing. It is a side view which shows an example of the trans | transformer using the conventional U-shaped ferrite core. It is a side view which shows an example of the trans | transformer using the conventional E-shaped ferrite core.

Explanation of symbols

1 Ferrite core, 2, 31, 52, 61, 71 Primary coil leg, 3, 4, 5, 33, 34, 35, 36, 53, 62, 63, 72, 73, 74 Secondary coil leg , 6 connecting plate, 7, 37, 54, 64, 75 primary coil, 8, 9, 10, 38, 39, 40, 41, 55, 65, 66, 76, 77, 78 secondary coil, 11 plate core, 20, 51 Inverter transformer

Claims (6)

A ferrite core having a primary coil leg portion around which a primary coil is wound and a secondary coil leg portion around which a secondary coil is wound, which are magnetically coupled by a coupling portion. ,
A position where three or more secondary coil legs are provided for one primary coil leg, and each of the secondary coil legs is substantially equal in magnetic resistance to the primary coil leg. A ferrite core characterized in that it is formed.   The ferrite core according to claim 1, wherein the distances between the respective secondary coil legs and the primary coil legs are set to be substantially equal.   3. The ferrite core according to claim 2, wherein the cross-sectional areas of the respective secondary coil legs are substantially equal. A first ferrite core having a primary coil leg portion around which a primary coil is wound and a secondary coil leg portion around which a secondary coil is wound, which are magnetically coupled by a coupling portion When,
A primary coil and a secondary coil wound around each leg of the first ferrite core;
A second ferrite core that is abutted against each leg portion of the first ferrite core and forms a closed magnetic circuit together with the first ferrite core;
The first ferrite core has three or more secondary coil legs with respect to one primary coil leg, and each of these secondary coil legs is connected to the primary coil leg. An inverter transformer characterized in that the magnetic resistances are formed at positions where the magnetic resistances are substantially equal.   5. The inverter transformer according to claim 4, wherein, in the first ferrite core, distances between the respective secondary coil legs and the primary coil legs are set to be substantially equal.   6. The inverter transformer according to claim 5, wherein the cross-sectional areas of the respective secondary coil legs are substantially equal.

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