JP2006108391A - Transformer core and leakage transformer employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize low profile, decrease the number of components, simplify the structure, and reduce the cost while enhancing the efficiency by one input multiple output system. <P>SOLUTION: The transformer core has an outer circumference core 1 of rectangular frame shape, and a coil winding core 2 being secured to the bottom face of the outer circumference core 1 to link two opposing sides of the outer circumference core 1. The coil winding core 2 is a large diameter portion 3 having a larger diameter at least partially as compared with other parts, wherein a part of the large diameter portion 3 faces the outside between a primary coil and a secondary coil and constitutes a leakage gap to the leakage gap forming portion 1a of the outer circumference core 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transformer core in which a leakage gap forming a leakage magnetic path is formed between a primary coil and a secondary coil, and further relates to a leakage transformer using the transformer core.

  As a liquid crystal TV inverter circuit system, a collector resonance type circuit system is generally used, but this collector resonance type circuit also has a resonance circuit on the primary side and causes interference with the resonance circuit on the secondary side. Has the disadvantage of being bad. In addition, when the waveform is asymmetrical, it is necessary to use a ballast capacitor in order to cut off a direct current component (cause of abnormal discharge) caused by the rectifying action of the cold cathode discharge lamp (CFL), which causes an increase in cost. .

  In recent years, with the increase in size of liquid crystal TVs and the like, a secondary side resonance type circuit system that stably turns on a cold cathode discharge lamp without using a ballast capacitor which causes a decrease in efficiency and an increase in cost has come to be adopted. ing. The secondary-side resonance type circuit (externally-excited resonance type circuit) uses a so-called leakage transformer, in which secondary side leakage inductance and parasitic capacitance, or an auxiliary resonance capacitor resonates. This is based on the fact that the power factor seen from the transformer primary side near the point is dramatically improved. The secondary side resonance type circuit does not require the ballast capacitor, and has an advantage of improving the power factor (efficiency improvement) of the transformer.

  By the way, with the increase in size of the liquid crystal TV, it is necessary to turn on a large number of cold cathode discharge lamps. Accordingly, the number of transformers used increases and the space occupancy of the transformer tends to increase. The case where the leakage transformer is used is not an exception. For this reason, various one-input / multi-output type leakage transformers having two or more secondary coils for one primary coil have been proposed (for example, (See Patent Document 1 and Patent Document 2).

  For example, in Patent Document 1, an inner core is wound with one primary coil connected to an inverter circuit and at least two secondary coils connected independently to a fluorescent lamp, and between the coils. A leakage transformer is disclosed in which an outer core having a magnetic leg constituting a leakage magnetic path is arranged so as to surround each coil. Patent Document 2 discloses an inverter transformer in which one primary winding and a plurality of secondary windings are provided and each secondary winding is electromagnetically coupled to the primary winding with the same degree of coupling. It is disclosed that each secondary winding of an inverter transformer is connected to a different discharge lamp. In the inverter transformer described in Patent Document 2, the projection serves as a leakage magnetic leg. Therefore, when this projection is provided, the inverter transformer operates as a leakage transformer.

In this way, if a single-input multiple-output type leakage transformer is used, it is not necessary to correspond the number of cold cathode discharge lamps to the number of transformers on a one-to-one basis, and the space occupancy can be reduced by reducing the number of transformers. it is conceivable that.
JP 59-40513 A JP 2001-126937 A

  However, when considering further reduction in the height of the leakage transformer and simplification of the structure, there are still many points to be improved in the inventions described in the patent documents. For example, the invention described in Patent Document 1 has a structure in which the outer core is abutted against the inner core from both sides, and the number of cores is three. If the number of cores is large, the structure becomes complicated and the assembly work is required.

  On the other hand, in the invention described in Patent Document 2, since the coil is sandwiched in the height direction from the board surface to be mounted, it is difficult to reduce the height of the transformer. Further, as the number of secondary coils increases, it is necessary to increase the number of second legs, which causes problems such as an increase in the area required for mounting and a complicated core shape.

  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, and can further reduce the number of parts and simplify the structure, and is advantageous in reducing the height of the transformer core. The purpose is to provide a leakage transformer.

  In order to achieve the above-mentioned object, the transformer core of the present invention is for winding a coil that is fixed to the bottom surface of the outer peripheral core so as to connect the outer peripheral core of the rectangular frame shape and the two opposite sides of the outer peripheral core. The coil winding core has a large diameter portion at least partially larger in diameter than other portions, and a portion of the large diameter portion is externally provided between the primary coil and the secondary coil. A leakage gap is formed between the outer peripheral core and the outer peripheral core. The leakage transformer of the present invention includes the transformer core, and either the primary coil or the secondary coil is wound around the large-diameter portion of the coil winding core, and the other part is wound at the other portion. The coil is wound, a part of the large-diameter portion faces outside between the primary coil and the secondary coil, and a leakage gap is formed between the outer peripheral core.

  In the transformer core of the present invention, the large-diameter portion of the coil winding core is provided for the purpose of forming a leakage magnetic flux path, and has a structure in which a leakage gap is formed between the outer core and the outer core. It has become. This structure makes it possible to control the leakage magnetic flux.

  In the leakage transformer of the present invention, for example, the primary coil is arranged in the center of the coil winding core, there is a leakage gap near both sides thereof, and the secondary coil is arranged on the outside thereof. . Therefore, the secondary coil is arranged symmetrically with respect to the primary coil, and the voltage fluctuation between the secondary coils can be suppressed to be small. In addition, the primary coil and the secondary coil are separated by the leakage gap formed between the large diameter portion and the outer core, and a sufficiently large leakage inductance is ensured.

  In the present invention, the transformer core is composed of two core parts, that is, an outer peripheral core and a coil winding core. Therefore, for example, as compared with the invention described in Patent Document 1, the number of necessary cores is reduced and the structure is simplified.

  In addition, the transformer core or leakage transformer of the present invention is basically arranged horizontally rather than having a structure in which the coil is sandwiched in the height direction as in the invention described in Patent Document 2, so that the height is reduced. Is advantageous.

  Furthermore, in the present invention, for example, it is not necessary to correspond the number of core portions around which the secondary coil is wound with the number of secondary coils, and only one coil winding core is disposed. Therefore, an increase in mounting area and an increase in structure due to an increase in the number of outer legs as in the invention described in Patent Document 2 are avoided.

  In the leakage transformer of the present invention, it is also possible to arrange the soft magnetic thin plate so as to cover the upper surface when it is placed horizontally by utilizing its structural characteristics. In this case, in addition to the above-described configuration, a soft magnetic thin plate is disposed on the upper surface side of the outer peripheral core when it is horizontally disposed. By placing a soft magnetic thin plate on the upper surface side, the primary and secondary coils are shielded, reducing magnetic flux leakage. For example, when mounted on a board, the influence of leakage magnetic flux to the surroundings is suppressed. Will be.

  According to the transformer core and the leakage transformer of the present invention, it is possible to achieve high efficiency by increasing the number of inputs and outputs, realizing a reduction in height, reducing the number of parts, simplifying the structure, and reducing costs. Is possible. Further, according to the present invention, it is possible to design so that the output is taken out from each secondary coil almost evenly.

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

(First embodiment)
The transformer core 1 of the present embodiment is composed of two core portions. First, the first core portion is composed of a rectangular frame-shaped outer peripheral core 1 as shown in FIGS. 1a and 1b. Is done. The outer peripheral core 1 has a height that can accommodate a primary coil and a secondary coil, which will be described later, and has a hollow casing-like appearance that is open at the top and bottom.

  In addition, a leakage gap forming portion 1a is formed at the center position of the long side portion of the outer core 1 so as to project the height of the frame. This leakage gap formation 1a forms a leakage gap with a large-diameter portion of a coil winding core, which is a second core portion described later, and therefore, the formation position and formation of the leakage gap formation portion 1a. The length is set corresponding to the large diameter portion of the coil winding core.

  A concave portion 1b for positioning and fixing the coil winding core as the second core portion is formed on the bottom surface of the outer peripheral core 1 on the short side, and the coil winding core is fitted and disposed therein. Thus, the first core part (outer peripheral core 1) and the second core part (coil winding core) are integrated in a positioned state and are also magnetically coupled.

  In the present embodiment, the leakage gap forming portion 1a constituting the leakage gap is formed so as to protrude from the bottom side of the outer core 1, but the entire height of the outer core 1 is defined as the coil winding core. It is also possible to form a leakage gap between the inner surface of the outer peripheral core 1 and the large diameter portion of the coil winding core by fitting the coil winding core into the concave portion 1b, for example, with a height sufficient to face each other. is there. In this case, it is not necessary to form the leakage gap forming portion 1a, and the outer peripheral core 1 may have a simple outer frame shape.

  The coil winding core 2 that is the second core portion is a single rod-shaped core, and both the primary coil and the secondary coil are wound around the core. As shown in FIG. 2, the coil winding core 2 has a large-diameter portion 3 having a diameter larger than that of both sides of the central portion, and small-diameter portions 4 and 5 having relatively small diameters on both side portions. It is said that.

  As shown in FIGS. 3a and 3b, the coil winding core 2 is disposed on the bottom surface side of the outer core 1, and the outer core 1 is further leaked by fitting both ends thereof into the recess 1b. It is positioned and fixed with respect to the gap forming portion 1a. Here, the positional relationship between the large diameter portion 3 of the coil winding core 2 and the leakage gap forming portion 1a will be described. The large diameter portion 3 of the coil winding core 2 and the leakage gap forming portion 1a are as follows. , And are arranged to face each other by the positioning and fixing. A leakage gap g is formed at a predetermined interval between the large diameter portion 3 of the coil winding core 2 and each leakage gap forming portion 1a. The gap length (the interval) of the leakage gap g can be adjusted by, for example, the diameter of the large-diameter portion 3 of the coil winding core 2, and the leakage flux (leakage inductance) can be controlled by this structure. .

  On the other hand, the small diameter portions 4 and 5 of the coil winding core 2 are not opposed to the leakage gap forming portion 1a of the outer peripheral core 1, and a sufficient distance from the outer core 1 is secured. A leak gap is not formed in this portion.

  The cross-sectional shapes of the large diameter portion 3 and the small diameter portions 4 and 5 of the coil winding core 2 may be, for example, rectangular. In this case, a rectangular shape having corners may be used. However, for example, when it is considered to directly wind a primary coil or a secondary coil, winding of the winding is facilitated and winding is performed at the corner. In order to prevent the insulating coating from being inadvertently peeled off, it is preferable to form a rectangular shape with chamfered corners or in an arc shape.

  In each core portion of the transformer core of the present embodiment, the outer peripheral core 1 and the coil winding core 2 are both formed of a ferrite material or the like, and are formed, for example, by molding into a predetermined shape and sintering. Yes. As the ferrite material, any ferrite material such as Mn-Zn ferrite can be used, but in order to improve performance, a ferrite material having a low iron loss and a high saturation magnetic flux density is used. It is preferable.

  Next, a leakage transformer configured using the above-described transformer core will be described. In the leakage transformer of this embodiment, as shown in FIG. 4, a coil bobbin 7 in which a primary coil 6 is wound is inserted into the central portion (large diameter portion 3) of the coil winding core 2, and the outside (small diameter portion 4) is inserted. 5), the coil bobbin 10 wound with the secondary coils 8 and 9 and the coil bobbin 13 wound with the secondary coils 11 and 12 are inserted, and the coil winding core 2 is inserted into the first core portion. The outer peripheral core 1 is configured by being attached to the concave portion 1b on the bottom surface. 5 and 6 show the assembled state.

  In the present embodiment, the primary coil is arranged in the central part (large diameter part 3), and the secondary coils are arranged on both sides (small diameter parts 4 and 5), but conversely the central part (large diameter part 3). It is also possible to arrange a secondary coil and primary coils on both sides (small diameter portions 4 and 5). However, since the secondary coil generally requires more turns, the former arrangement is more advantageous in securing the winding space for the secondary coil.

  As described above, the primary coil 6 and the secondary coils 8, 9, 11, and 12 are used for winding a coil while being wound around bobbins 7, 10, and 13 formed of an insulating material (for example, plastic). The winding length of each coil (primary coil 6 and secondary coils 8, 9, 11, 12) is regulated by bobbin flange portions 7a, 9a, 12a. Here, in particular, the primary coil 6 needs to be set to have a dimension slightly smaller than the length of the large-diameter portion 3, so that both end portions 3 a and 3 b of the large-diameter portion 3 are primary as shown in FIG. 5. It is exposed on both sides of the bobbin 7 around which the coil 6 is wound, and faces the outside. As a result, both end portions 3 a, 3 b of the large diameter portion 3 face the leakage gap forming portion 1 a of the outer core 1, and the leakage gap between the secondary coils 8, 9, 11, 12 on both sides of the primary coil 6. g will be formed.

  A terminal plate 14 to which the coil ends are connected is attached to the bottom of the primary coil 6 and the secondary coils 8, 9, 11, 12. Moreover, the terminal pin 15 is attached to this terminal board 14, For example, when it mounts in a board | substrate, the input to the primary coil 6 and the output from the secondary coils 8, 9, 11, and 12 are as follows. This is done via the terminal plate 14 and the terminal pin 15.

  In the leakage transformer of the present embodiment, four transformers are configured by the primary coil 6 and two secondary coils (secondary coils 8, 9, 11, 12), two on each side. Therefore, the leakage transformer of this embodiment functions as a 1-input 4-output inverter transformer.

  In the leakage transformer configured as described above, the ratio between the number of turns of the primary coil 6 and the number of turns of each of the secondary coils 8, 9, 11, and 12 is appropriately set according to the required voltage. On the other hand, the number of turns of each secondary coil 8, 9, 11, 12 is set to the same number when the output output from each secondary coil 8, 9, 11, 12 is constant.

  The leakage transformer having the above configuration is arranged and mounted so that the magnetic path directions of the outer peripheral core 1 and the coil winding core 2 are substantially parallel to the board surface of the mounting board. That is, the mounting form of the leakage transformer of this embodiment is a so-called horizontal arrangement. Therefore, for example, the height can be reduced as compared with the structure in which the coil is sandwiched in the height direction.

  Further, in the leakage transformer of the present embodiment, the transformer core is constituted only by the outer peripheral core 1 and the coil winding core 2, and the number of core portions is two. Therefore, the number of cores can be reduced and the structure can be simplified as compared with the leakage transformer described in Patent Document 1, for example. Furthermore, as a coil winding core, one coil winding core 2 may be prepared. For example, unlike the invention described in Patent Document 2, it is not necessary to form legs corresponding to the number of secondary coils. Therefore, the structure can be simplified also in this respect.

  In the leakage transformer of the present embodiment, the leakage gap formed by the both end portions 3a and 3b of the large diameter portion 3 and the leakage gap forming portion 1a is between the primary coil 6 and the secondary coil 9, and between the primary coil 6 and the secondary coil. It arrange | positions between the coils 11, and the primary winding (primary coil 6) and the secondary winding (secondary coils 8, 9, 11, and 12) are isolate | separated. Further, the secondary coils 8 and 9 and the secondary coils 11 and 12 are arranged symmetrically with respect to the primary coil 6. Therefore, the voltage fluctuation on the secondary side can be reduced.

  Further, in the leakage transformer of the present embodiment, a sufficiently large leakage inductance can be ensured between the both end portions 3a, 3b of the large diameter portion 3 and the leakage gap forming portion 1a. For example, when used in a liquid crystal TV inverter circuit In addition, it is possible to suppress variations in the discharge operation of the plurality of cold cathode discharge lamps.

(Second Embodiment)
The leakage transformer of this embodiment is an example in which the number of secondary coils is further increased. The number of secondary coils is preferably an even number. In the first embodiment, four secondary coils are arranged. In this embodiment, four coils are provided on one side of the primary coil, for a total of eight. The secondary coil is arranged. The configuration of the leakage transformer of this embodiment is shown in FIGS. Since the structure of the transformer core is the same as that of the first embodiment, the description thereof is omitted here.

  In the leakage transformer of the present embodiment, eight secondary coils 21, 22, 23, 24, 25, 26, 27, and 28 are attached to one primary coil 6. Therefore, an inverter having one input and eight outputs is provided. Functions as a transformer. Four secondary coils are arranged on one side of the primary coil 6, and leakage is formed by both end portions 3a, 3b of the large diameter portion 3 and the leakage gap forming portion 1a, as in the first embodiment. The primary winding (primary coil 6) and the secondary winding (secondary coils 21, 22, 23, 24, 25, 26, 27, 28) are separated by the gap, and the secondary coils 21, 22, 23, 24 and the secondary coils 25, 26, 27, and 28 are arranged symmetrically with the primary coil 6 interposed therebetween. Therefore, as in the first embodiment, it is possible to extract outputs from the eight secondary coils 21, 22, 23, 24, 25, 26, 27, and 28 substantially evenly.

(Third embodiment)
The present embodiment is an example in which a shielding soft magnetic thin plate is attached to the upper surface of the outer peripheral core 1. As shown in FIGS. 9 and 10, a soft magnetic thin plate 30 for shielding is attached to the upper surface of the outer core 1. Therefore, the shield plate (soft magnetic thin plate 30) is arranged so as to cover the space in which the primary coil 6 and the secondary coils 21, 22, 23, 24, 25, 26, 27, and 28 are accommodated. Since other configurations are the same as those of the transformer core and the leakage transformer of the second embodiment, the same members are denoted by the same reference numerals, and the description thereof is omitted.

  As the soft magnetic thin plate 30, for example, a thin plate or the like in which 10 microcrystalline ribbons having a thickness of 25 μm are stacked and integrated can be used, but not limited thereto, any material may be used as long as it is a soft magnetic thin plate having a shielding effect. It may be a configuration.

  By providing the soft magnetic thin plate 30, leakage magnetic flux from the primary coil 6 and the secondary coils 21, 22, 23, 24, 25, 26, 27, and 28 is shielded and put into a shield case or mounted. Even if a separate shield plate is not provided around the transformer, the influence of leakage magnetic flux on surrounding components and the like can be effectively suppressed.

It is a top view which shows the shape of the outer periphery core in the trans | transformer core of 1st Embodiment. It is a side view which shows the shape of the outer periphery core in the transformer core of 1st Embodiment. It is a top view which shows the shape of the core for coil winding in the trans | transformer core of 1st Embodiment. It is a top view which shows the attachment state to the outer periphery core of the coil winding core. It is a side view which shows the attachment state to the outer periphery core of the coil winding core. It is a disassembled perspective view which shows the mounting state of the primary coil and the secondary coil to the transformer core of 1st Embodiment. It is a top view of the leakage transformer of a 1st embodiment. It is a side view of the leakage transformer of a 1st embodiment. It is a top view of the leakage transformer of a 2nd embodiment. It is a side view of the leakage transformer of 2nd Embodiment. It is a top view of the leakage transformer of a 3rd embodiment. It is a side view of the leakage transformer of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer core, 1a Leakage gap formation part, 1b Recessed part, 2 Coil winding core, 3 Large diameter part, 4,5 Small diameter part, 6 Primary coil, 7, 10, 13 Bobbin, 8, 9, 11, 12, 21, 22, 23, 24, 25, 26, 27, 28 Secondary coil, 14 terminal plate, 15 terminal pin, 30 soft magnetic thin plate

Claims (11)

A rectangular frame-shaped outer peripheral core, and a coil winding core fixed to the bottom surface of the outer peripheral core so as to connect two opposing sides of the outer peripheral core;
The coil winding core is at least partly a large diameter part having a larger diameter than the other part, and a part of the large diameter part faces outside between the primary coil and the secondary coil, Transformer core, characterized in that a leakage gap is formed between them.   2. The transformer core according to claim 1, wherein a part of the outer peripheral core on the bottom side is enlarged, and this part is opposed to a large diameter part of the coil winding core to constitute a leakage gap.   The transformer core according to claim 1, wherein a center portion of the coil winding core is the large diameter portion.   The transformer core according to any one of claims 1 to 3, wherein a concave portion into which the coil winding core is fitted is formed on a bottom surface of the outer peripheral core.   The transformer core according to claim 4, wherein the coil winding core has a corner chamfered in an arc shape.   The transformer core according to any one of claims 1 to 5, wherein the outer core and the coil winding core are disposed horizontally so as to be substantially parallel to a substrate surface of a substrate on which the outer core and the coil winding core are mounted. . The transformer core according to any one of claims 1 to 6, comprising:
While either the primary coil or the secondary coil is wound around the large diameter part of the coil winding core, the other coil is wound around the other part,
A leakage transformer, wherein a part of the large-diameter portion faces the outside between a primary coil and a secondary coil, and a leakage gap is formed between the outer peripheral core.   The coil winding core has a central portion as the large diameter portion, and a primary coil is wound around the large diameter portion, and secondary coils are wound on both sides thereof. The leakage transformer according to claim 7.   The leakage transformer according to claim 8, wherein a plurality of secondary coils are wound around both sides of the primary coil. It is placed horizontally so as to be substantially parallel to the substrate surface of the substrate on which the outer peripheral core of the transformer core and the coil winding core are mounted,
The leakage transformer according to any one of claims 7 to 9, wherein when mounted on a substrate, the height of the upper surface of the outer peripheral core is higher than the height of the upper surfaces of the primary coil and the secondary coil.   The leakage transformer according to claim 10, wherein a soft magnetic thin plate is disposed on an upper surface side of the outer peripheral core.

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