JP2011238750A - Thin transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin, small and light transformer.SOLUTION: Multiple layers of thin plates of an Fe-based soft magnetic alloy, which is mainly composed of Fe and to which Si, B, Cu, and at least one kind of elements selected from a group of Nb, W, Ta, Zr, Hf, Ti and Mo is added, are wound, and a core case 13 made of an insulator is integrally molded on an entire outer periphery of the wound body. U-plane-shaped magnetic core half bodies 14a, 14b are jointed with each other, so as to constitute a magnetic core 2 having a closed-loop magnetic path. One layer of a square-sectioned primary coil 3 is wound around one joint 15a of the magnetic core half bodies 14a, 14b via the core case 13 in an aligned condition. One layer of a square-sectioned secondary coil 4 is wound around the other joint 15b of the magnetic core half bodies 14a, 14b via the core case 13 in an aligned condition, so that the primary coil 3 and the secondary coil 4 are separated from each other.

Description

  The present invention relates to a thin transformer such as a thin switching transformer for a TV AC-DC converter power source, and more particularly to a magnetic core and its peripheral components.

As background art, for example, there are proposals described in Patent Documents 1 and 2 below. In Patent Document 1, the magnitude of magnetostriction is in the range of −1.2 × 10 ⁻⁶ ≦ λs ≦ + 1.2 × 10 ⁻⁶ , and an amorphous magnetic material having a hardness of Hv320 or more is wound or laminated, A magnetic core is described in which a magnetic path is molded and then molded using an organic insulating resin having a shrinkage ratio upon curing of 0.05% or more.

  Further, Patent Document 2 describes an amorphous wound magnetic core that is impregnated with an epoxy resin and partially cut to provide a gap.

Japanese Examined Patent Publication No.59-172221 Japanese Patent Publication No.59-189610

  The magnetic core used in a conventional thin-type switching transformer for TV AC-DC converter power supply uses ferrite that is formed by pressing and firing a powder mainly composed of ferric oxide and can be processed relatively freely. . The relative permeability of this ferrite is in the range of about 2400-5300.

The inductance of the transformer is proportional to the square of the number of turns of the coil, and increases as the number of turns increases and decreases as the number of turns decreases.
Similarly, leakage inductance increases as the number of turns increases and decreases as the number of turns decreases, and also changes depending on the degree of coupling between the coils due to the arrangement of the primary and secondary windings.

In the current thin TV power supply using a ferrite magnetic core, the switching circuit uses a high-current, low-loss switching loss and high-efficiency current resonance circuit system, and a capacitor Cs arranged in series with the switching transformer, The switching transformer operates by resonating with a leakage inductance (reed gauge inductance) L ₂ , and ideally, a reage gauge inductance of 105 μH is required inside the transformer.

  However, since the reage gauge inductance of this type of conventional transformer is as small as 35 μH, three transformers are connected in series to ensure a reage inductance of (35 × 3 =) 105 μH as a whole.

The core loss of a conventional ferrite core is 0.75 W / cm ³ , and if this core loss is large, the temperature rise of the transformer during use is high, and if the core loss is small, the temperature rise of the transformer during use is low. .

  Because the ferrite core is easily cracked due to the temperature difference during the temperature shock test of the transformer or during board reflow, the total height of the transformer cannot be made too thin. At present, the total height of the transformer is limited to about 9.3 mm. Yes, it is more than that.

  In order to reduce the total height of the transformer to 6 mm, for example, while ensuring the characteristics of the current transformer, it is necessary to suppress the thickness of the magnetic core to 2 mm or less in consideration of the thickness of the coil (electric wire) part.

However, if the thickness of the ferrite magnetic core is 2 mm or less, there is a problem that the magnetic core breaks due to a temperature difference during a temperature shock test or substrate reflow.

  Further, when three transformers are used as described above in order to ensure the leakage inductance of 105 μH, there is a problem that the area occupied by the transformer with respect to the area of the power supply substrate becomes large.

Further, since three transformers are used, there is a disadvantage that the cost is increased.

  Furthermore, if the core loss is large, the iron loss of the transformer increases, so that the core temperature rises and the temperature rise of the entire transformer increases. In order to reduce this temperature rise, it is necessary to reduce the number of magnetic fluxes. For this purpose, it is necessary to increase the number of turns of the primary coil. However, when the number of turns of the primary coil is increased, the winding portion of the transformer becomes higher and larger, and therefore the entire transformer is higher and larger, which has the disadvantages that it becomes an obstacle to thinning and miniaturization of the transformer. Yes.

  An object of the present invention is to provide a transformer that can eliminate the drawbacks of the prior art and can be reduced in thickness, size, and weight.

To achieve the purpose,
The first means of the present invention comprises Fe as a main component and at least one element selected from the group consisting of Si, B, Cu, and Nb, W, Ta, Zr, Hf, Ti and Mo. A thin sheet of Fe-based soft magnetic alloy is cut into a strip, wound, and then heat-treated to insulate the entire outer periphery of the wound body of Fe-based soft magnetic alloy ribbon with the majority of the composition as fine crystal grains A magnetic core having a closed loop magnetic path is formed by joining together a U-shaped magnetic core half that is integrally molded with a core case made of a body,
A primary coil having a quadrangular cross section is wound around one joint between the magnetic core halves in a single-layer aligned state via the core case,
A secondary coil having a quadrangular cross-sectional shape is wound in a single layer alignment state on the other joint between the magnetic core halves through the core case, and the primary coil and the secondary coil are spaced apart from each other. It is characterized by that.

  According to a second means of the present invention, in the first means, an insulating binder layer is provided between the thin plates of the thin plate winding body so that the thin plates are bonded to each other. The end portion of this is integrated with the core case.

According to a third means of the present invention, in the first or second means, the primary coil and the lower coil of the secondary coil of the printed wiring board on which the assembly of the magnetic core, the primary coil, and the secondary coil is surface-mounted. Forming a notch for accommodating the coil at a position facing the part,
The primary coil and the secondary coil are mounted on the printed wiring board, and the lower coil portion of the primary coil and the secondary coil are respectively dropped into the notch portion for accommodating the coil.

  According to a fourth means of the present invention, in the third means, a bridging portion is formed on the outer periphery of the coil housing notch portion of the printed wiring board.

  According to a fifth means of the present invention, in the first or second means, a positioning hole and a positioning protrusion to be inserted into the positioning hole in a portion facing the lower surface of the core case and the core case of the printed wiring board Is provided.

  According to a sixth means of the present invention, in any one of the first to fifth means, the primary coil or the secondary coil is molded by resin impregnation such as self-bonding wire or varnish. It is a feature.

  The present invention is configured as described above, and can provide a transformer that can be thinned, reduced in size, and reduced in weight.

It is a top view of the transformer for thin TVs concerning the embodiment of the present invention. It is sectional drawing on the XX line of FIG. It is a top view of the printed wiring board used for the embodiment of the present invention. It is a top view of the magnetic core used for embodiment of this invention. 4 is a cross-sectional view taken along line YY. It is a partially expanded sectional view of the magnetic core. It is a bottom view of one core case. It is an expanded sectional view showing engagement relation of a printed wiring board and a core case. It is a top view which shows the modification of a printed wiring board.

  In the present invention, an Fe-based soft magnetic alloy containing Fe as a main component and containing at least one element selected from the group consisting of Si, B, Cu, and Nb, W, Ta, Zr, Hf, Ti, and Mo. Is used as a magnetic core material.

This Fe-based soft magnetic alloy is represented by the following general formula.
Formula _{(Fe 1-a M a)} 100-x-y-z-α Cu x Si y B z M'α
Where
M is Co and / or Ni,
M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti, and Mo;
a, x, y, z, and α are 0 atomic% ≦ a ≦ 0.5 atomic%, 0.1 atomic% ≦ x ≦ 3 atomic%, 0 atomic% ≦ y ≦ 30 atomic%, and 0 atomic% ≦, respectively. The numerical values satisfy z ≦ 25 atomic%, 5 atomic% ≦ y ₊ z ≦ 30 atomic%, 0.1 atomic% ≦ α ≦ 30 atomic%.

As described above, Fe may be substituted with Co and / or Ni in the range of 0 to 0.5 atomic%, and particularly preferably in the range of 0 to 0.1 atomic%.
The Cu content is 0.1 to 3 atomic%, and particularly preferably 0.5 to 2 atomic%.

The content of Si is 0 to 30 atomic%, and particularly preferably 6 to 25 atomic%.
The content of B is 0 to 25 atomic%, and particularly preferably in the range of 2 to 25 atomic%.

The content rate of Si + B is 5 to 30 atomic%, and the range of 14 to 30 atomic% is particularly preferable.
The content of M ′ (Nb, W, Ta, Zr, Hf, Ti, Mo) is 0.1 to 30 atomic%, and particularly preferably in the range of 1 to 10 atomic%.

 As the Fe-based soft magnetic alloy used in the present invention, at least one element selected from the group consisting of Fe, Si, B, Cu, and Nb, W, Ta, Zr, Hf, Ti, and Mo is used. An Fe-based soft magnetic alloy in which most of the composition is finely crystallized by adding and making it amorphous once and then heat-treating is particularly suitable. In this soft magnetic alloy, at least 50% of the structure is composed of fine crystal grains having an average grain size of 1000 mm or less, and the remainder is substantially amorphous.

  A ribbon-like amorphous alloy is obtained from a melt having a predetermined composition ratio by a liquid quenching method, and the plate thickness is 5 to 100 μm. A high-frequency transformer having a plate thickness of 25 μm or less is particularly suitable. In this embodiment, a plate having a plate thickness of 20 μm is used.

The amorphous alloy thin plate is processed into a predetermined shape by, for example, punching or etching before heat treatment.
The amorphous alloy thin plate after the processing is heat-treated in a vacuum or in an inert gas such as hydrogen or nitrogen. The heating temperature and heating time vary depending on the composition, shape, size, etc. of the amorphous alloy sheet, but are about 500 to 650 ° C. and about 5 minutes to 6 hours. The heat treatment is preferably performed in a magnetic field.

Examples of the composition of the Fe-based soft magnetic alloy include the following.
Fe _71.5 Cu ₁ Nb ₅ Si _13.5 B ₉
Fe _73.5 Cu ₁ Nb ₃ Si _13.5 B ₉
Fe ₇₁ Cu _1.5 Nb ₅ Si _13.5 B ₉
Fe _71.5 Cu ₁ Mo ₅ Si _13.5 B ₉
The core loss of these Fe-based soft magnetic alloys is 0.22 to 0.25 W / cm ³ .

  In the present embodiment, a 20 μm-thick ribbon having the Fe-based soft magnetic alloy composition is wound in a laminated manner to constitute the core. The width of the ribbon can be narrowed to 2 mm or less, and a core height of 2 mm can be realized by casting a synthetic resin such as an epoxy resin between the ribbons. In addition, with such a configuration, the core strength during the temperature cycle test can be sufficiently secured.

  The relative magnetic permeability of the Fe-based soft magnetic alloy is as high as about 16000, which is about 5 times that of conventionally used ferrite.

Further, by disposing the primary coil and the secondary coil apart from each other, in the case of the same number of turns, the reage gauge inductance is 175 μH with one transformer.

In addition, the core loss of the Fe-based soft magnetic alloy is 0.25 W / cm ³ , which is about 1/3 of the conventionally used ferrite and the core loss is also about 1/3, and the core temperature rises during use. Can be kept low.

  Since the above-described relative magnetic permeability is high and the core loss (iron loss) is low, the number of parts can be reduced because only one transformer is required in the past, but three transformers are necessary.

  Further, by reducing the number of transformers, the area occupied by the transformer with respect to the power supply board can be reduced. In addition, the reed gauge inductance is set to 105 μH of the specification, so that the number of turns can be reduced by about 20%. For this reason, the transformer can be reduced in thickness, size, and weight.

  Next, the structure of a thin TV transformer according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a thin-film TV transformer according to the embodiment, and FIG. 2 is a cross-sectional view taken along the line XX in FIG.

  As shown in FIG. 1, a thin-screen TV transformer according to an embodiment of the present invention includes a printed wiring board 1, a magnetic core 2 mounted on the printed wiring board 1, and a primary coil 3 mounted on the magnetic core 2. It is mainly composed of the secondary coil 4 and the monitor coil 5.

  FIG. 3 is a plan view of the printed wiring board 1 used in the present embodiment. As shown in the figure, a primary coil connection terminal 6, a secondary coil connection terminal 7, and a monitor coil connection terminal 8 are provided at both front and rear ends of the printed wiring board 1, and the connection terminals 6, 7 are provided. , 8 are connected to a conductive pattern 9 formed on the printed wiring board 1.

  In addition, coil portion housing notches 10a and 10b having a substantially square planar shape cut inward from the side end portions are formed at substantially intermediate positions of the printed wiring board 1.

4 is a plan view of the magnetic core 2 used in the present embodiment, FIG. 5 is a cross-sectional view taken along the line YY of FIG. 4, and FIG. 6 is a partially enlarged cross-sectional view of the magnetic core 2.
The magnetic core 2 is obtained by cutting a ribbon having the iron-based soft magnetic alloy composition into a strip having a width of 2 mm, winding the ribbon into an ellipse having an inner diameter of 10 mm, an outer diameter of 40 mm, and a length of 80 mm. For about 1 hour. By this heat treatment, most of the structure becomes fine crystal grains having an average grain size of about 100 mm.

  After the heat treatment, this winding is dipped in a synthetic resin solution such as an epoxy resin for a predetermined time, and the synthetic resin solution is permeated between the thin strips 11 and 11 wound in multiple layers as shown in FIG. Then, it is taken out after a lapse of a predetermined time, and a synthetic resin such as an epoxy resin is cured to form the binding layer 12 (see FIG. 6).

  Since the laminated thin strips 11 are bound by the binding layer 12, the wound body cannot be unwound by subsequent machining or the like, and is easy to handle.

  This wound body is again immersed in a synthetic resin solution such as an epoxy resin for a predetermined time, and then removed to form a relatively thick coating layer on the entire outer periphery of the wound body by curing the synthetic resin, This clothing layer is referred to as a core case 13. As shown in FIG. 6, the bonding portions of the binding layers 12 and the core case 13 are integrated.

  Thereafter, the intermediate portion in the longitudinal direction of the wound body is cut in a direction perpendicular to the longitudinal direction, and the magnetic core halves 14a and 14b having a U-shaped planar shape as shown in FIG. 4 are obtained. As described above, the ribbon 11 and the ribbon 11 are bound by the binding layer 12, and the entire outer periphery of the wound body is covered with the core case 13, so the stacked ribbon 11 is cut. Sometimes the ribbon 11 is not peeled off or cracked, and cutting is performed smoothly.

  In this embodiment, an epoxy resin is used as a constituent material of the binder layer 12 and the core case 13, but other types of curable synthetic resins can also be used.

  The cross-sectional shapes of at least the primary coil 3 and the secondary coil 4 are quadrangular as shown in FIG. 2, and are not wound around multiple layers but are single-layered. Compared with a coil having a circular cross-sectional shape, a coil having a square cross-sectional shape has a higher area efficiency within a predetermined space, so that even if the primary coil 3 and the secondary coil 4 are wound in one layer, the function is sufficient. Can be demonstrated.

  In addition, by using an air-core coil that is wound around a self-bonding wire or a thin film such as a polyester film as a winding core and impregnated with varnish, etc., it is easy to assemble, resulting in a thinner transformer. it can.

  In this embodiment, the monitor coil 5 also uses a coil having a square cross-sectional shape and is integrated with the secondary coil by heat fusion to form a bobbinless hollow coil.

  As shown in FIG. 4, a magnetic core 2 having a closed loop magnetic path is formed by joining a magnetic core half body 14a and a magnetic core half body 14b having a U-shaped planar shape. The primary coil 3 and the secondary coil 4 are fixed to each other by fitting the hollow primary coil 4 and the monitor coil 5 side by side on the other joint 15b side. The distance L can be separated and insulated (see FIG. 1).

  A plurality of (two in the present embodiment) positioning projections 17 are formed on the lower surfaces of the two core cases 13 at predetermined intervals (see FIG. 7), while the core case of the printed wiring board 1 is formed. A through hole 13 is formed at a position facing 13 (see FIG. 3). The two magnetic core halves 14a and 14b are placed on the printed wiring board 1, and the positioning protrusions 17 of the core case 13 are fitted into the positioning holes 18 of the printed wiring board 1 (see FIG. 8). The magnetic core 2 (magnetic core halves 14a and 14b) can be positioned on the wiring board 1.

  Further, by positioning the magnetic core 2 (magnetic core halves 14a and 14b), the lower coil portion 3a of the primary coil 3 enters the coil portion accommodation notch portion 10a formed on the printed wiring board 1 as shown in FIG. Although not shown, the secondary coil 4 and the lower coil part of the monitor coil 5 enter the coil part accommodating notch 10b formed on the printed circuit board 1 (not shown), contributing to the reduction in thickness of the transformer. Yes.

After the magnetic core 2 is positioned on the printed wiring board 1 in this way, both ends of the primary coil 3 are connected to the primary coil connection terminal 6 via the solder layer 16 and the conductive pattern 9, and the secondary coil. 4 is connected to the secondary coil connection terminal 7 via the solder layer 16 and the conductive pattern 9, and both ends of the monitor coil 5 are connected to the monitor coil connection terminal via the solder layer 16 and the conductive pattern 9. 8, the magnetic core 2 is surface-mounted on the printed wiring board 1.
The total height H (see FIG. 2) of the thin-screen TV transformer obtained by this embodiment is 6 mm.

FIG. 9 is a plan view of the printed wiring board 1 showing a modified example of the printed wiring board 1.
In the present embodiment, the difference from the printed wiring board 1 shown in FIG. 3 is that the bridge portion 19 is not provided on the outer periphery of the coil portion accommodation notches 10a and 10b, but on the outer periphery of the coil portion accommodation notches 10a and 10b. This is a point in which the peripheral portion of the printed wiring board 1 is reinforced by providing it integrally.

  In the above embodiment, the positioning protrusion 17 is provided on the core case 13 side and the positioning hole 18 is provided on the printed wiring board 1 side. Conversely, the concave positioning hole is provided on the core case 13 side, and the printed wiring board 1 is provided. It is also possible to provide a positioning projection on the side.

  In the above-described embodiment, the case of a thin switching transformer for a TV AC-DC converter power supply has been described. However, the present invention is not limited to this, and can be applied to a thin transformer used for other purposes.

  DESCRIPTION OF SYMBOLS 1 ... Printed wiring board, 2 ... Magnetic core, 3 ... Primary coil, 3a ... Lower coil part of primary coil, 4 ... Secondary coil, 5 ... Monitor coil, 6 ... Connection terminal for primary coil, 7 ... Connection terminal for secondary coil, 8 ... Connection terminal for monitor coil, 9 ... Conductive pattern, 10a, 10b ... Notch for accommodating coil part 11, thin ribbon, 12 tie layer, 13 core case, 14 a, 14 b magnetic half, 15 a, 15 b joint, 16 solder layer, 17 ... positioning protrusion, 18 ... positioning hole, 19 ... bridging part.

Claims (6)

A multilayered sheet of Fe-based soft magnetic alloy containing Fe as a main component and added with at least one element selected from the group consisting of Si, B, Cu, and Nb, W, Ta, Zr, Hf, Ti, and Mo The core having a closed loop magnetic path is formed by joining the U-shaped magnetic core halves with a planar shape integrally molded with a core case made of an insulator on the entire outer periphery of the wound body,
A primary coil having a quadrangular cross-sectional shape is wound around one joint of the magnetic core halves in a single layer alignment state via the core case,
A secondary coil having a quadrangular cross-sectional shape is wound in a single layer alignment state through the core case at the other joint between the magnetic core halves, and the primary coil and the secondary coil are spaced apart from each other. This is a thin transformer.   2. The thin transformer according to claim 1, wherein a binder layer of an insulator is provided between the thin plates of the thin plate winding body so that the thin plates are bonded to each other, and an end of each binding layer is A thin transformer characterized by being integrated with the core case. The thin transformer according to claim 1 or 2, wherein the magnetic core, the primary coil, and the assembly of the secondary coil are disposed at positions facing the primary coil and the lower coil portion of the secondary coil of the printed wiring board on which the assembly of the secondary coils is surface-mounted. Forming notches for coil storage,
A thin transformer, wherein the primary coil and the secondary coil are mounted on the printed wiring board, and the lower coil portion of the primary coil and the secondary coil is dropped into the notch portion for accommodating the coil.   4. The thin transformer according to claim 3, wherein a bridging portion is formed on the outer periphery of the coil housing notch portion of the printed wiring board.   The thin transformer according to any one of claims 1 to 4, wherein a positioning hole and a positioning protrusion to be inserted into the positioning hole are formed in a portion facing the lower surface of the core case and the core case of the printed wiring board. A thin transformer characterized by the provision.   The thin transformer according to any one of claims 1 to 5, wherein the primary coil or the secondary coil is molded by resin impregnation such as self-bonding wire or varnish.

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