JP2003332146A - Transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an inconvenience caused by irregular magnetic flux distribution, magnetic flux leakage, or inductance leakage, related to a thin transformer used for a power convertor such as a small switching power source and an inverter. <P>SOLUTION: An insulating board 1 is provided with a plurality of slits 5 at a regular interval into which protruding parts 45 of a magnetic body 44 are inserted at a regular interval. On the upper surface of the insulating board 1, a primary-side conductor 21 constituting a primary-side conductor pattern 2 is so provided as to circulate zigzag the slits 5. The primary-side conductor 21 includes eight sections extending in the length direction of the slits 5, with the ends connected with a short primary connection conductor 22 (seven in total) to zigzag fold back, constituting the primary-side conductor pattern 2. On the lower surface of the insulating board 1, a secondary-side conductor 31 constituting a secondary-side conductor pattern 3 is provided in the slits 5. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer, and more particularly to a compact and thin transformer used in a power conversion device such as a small switching power supply or an inverter.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for miniaturization of various electronic devices. In particular, as electronic devices such as notebook computers are becoming more portable, thinness of the entire device is especially demanded, and thinning of the transformer used in the power supply unit is also required.

In many transformers used in electronic equipment, a bobbin is wound and a ferrite core is inserted, but it is difficult to reduce the thickness with this structure. Therefore, in recent years, a spiral conductor pattern formed on an insulating substrate without using a winding is used instead of the winding, and a thin ferrite core is inserted into a slit provided on the insulating substrate to achieve a thin shape. Can be seen (Japanese Patent Laid-Open No. 2000-
91138).

FIG. 11 shows an example of the structure of a conventional thin transformer.
Shown in. The primary-side conductor pattern 2 and the secondary-side conductor pattern (not shown) are obtained by processing conductor layers on both surfaces of the insulating substrate 1 into a spiral shape by etching or the like. A slit (through hole) 5 is provided at the outermost part. The ferrite core 4 serving as a magnetic body may have various shapes such as the EI type and the pot type other than the EI type shown in the drawing. In the EI core shown in FIG. 11, only the core on one side has the central leg 41 and the outer leg 42,
The leg portion is inserted into the slit 5 of the insulating substrate 1 and joined to the upper magnetic plate 43 which is a flat core to form a closed magnetic circuit.

[0005]

By the way, the conventional thin transformer shown in FIG. 11 has the following problems.

The first problem is the leakage magnetic flux. FIG. 12 illustrates a cross section including the central leg of the core of the conventional thin transformer shown in FIG. The loop with an arrow in the figure shows the path of the magnetic flux 7 during the transformer operation. When the core is a closed magnetic circuit, most magnetic flux passes only in the core like 7a. However, if the core has a flat structure in order to reduce the thickness of the transformer, the shape of the window portion 6 for accommodating the conductor in the core is inevitably flatter. When viewed as a magnetic circuit, this structure has a configuration in which the magnetic resistance in the longitudinal direction of the void in the window is reduced to the same level as the lateral magnetic resistance of the core. Therefore, a part of the magnetic flux has a distribution that penetrates the air gap of the window portion as shown by 7b. Therefore, an alternating magnetic field is directly applied to the primary side and secondary side conductor patterns 2 and 3 which are windings of the transformer, an eddy current flows, and a large loss occurs. This not only causes a decrease in efficiency as a transformer, but it is also necessary to pay attention to the occurrence of abnormal heating of the winding conductor and the occurrence of insulation failure.

Second, there is a problem of non-uniformity of magnetic flux distribution. Due to the spiral shape of the conductor, all the magnetic flux created by the winding current passes through the central leg 41 of the core at the center of the winding and towards the outer leg 42. As described above, due to the magnetic flux penetrating the window portion 6 shown by 7b, the strength of the magnetic field in the upper and lower plates of the core is strongest in the vicinity of the central leg 41 and weak in the vicinity of the outer leg 42.

By the way, when determining the size of the core, especially the thickness of the magnetic flux passage, magnetic saturation is a major determining factor. When the magnetic flux increases to the strength at which magnetic saturation occurs, the inductance decreases and the exciting current increases, causing problems such as unnecessary loss and abnormal heating of the winding conductor. To determine the core thickness so that magnetic saturation does not occur, it is necessary to determine the maximum magnetic flux density in the core. In this example, the central leg 41
Since the highest magnetic east density is in the vicinity, the core thickness is determined here. On the other hand, in the vicinity of the outer leg 42, the magnetic flux density is low, so that the core is wasted in its usage.

Thirdly, there is a problem of leakage inductance.
Leakage inductance is a magnetic flux that links only to one of the primary or secondary winding conductors, and is mostly determined by the arrangement of the winding conductors. In this case, the primary and secondary winding conductors are insulated substrate 1
Since it is attached on both sides of the structure, the leakage inductance value is almost uniquely determined by the structure. In general, the smaller the leakage inductance, the better in many cases. However, for example, in a resonance converter, the leakage inductance may be positively used. When it is desired to control the leakage inductance in this way, the conventional structure is uniquely determined from the structural point of view, and must be adjusted by another means.

Therefore, an object of the present invention is to provide a transformer which can solve the above problems.

[0011]

In order to achieve the above object, according to one aspect of the present invention, a first protrusion having a plurality of protrusions is formed.
Of the magnetic body, the second magnetic body joined to each surface of the protrusion, the gap between the first magnetic body and the second magnetic body, and the surface on the side of the second magnetic body. A transformer including an insulating substrate having a primary conductor formed thereon and a secondary conductor formed at a position where the primary conductor is electromagnetically coupled with the insulating substrate sandwiched between the first magnetic body. Is a plurality of the groove and the protrusion are formed in parallel, the insulating substrate has a plurality of slits formed at substantially the same interval as the interval of the protrusion, each slit is A transformer having a configuration in which the protrusions are inserted one by one and is interposed in the gap between the first magnetic body and the second magnetic body was implemented.

Here, the secondary-side conductor is formed on the back surface on the first magnetic body side, and a portion serving as a first path that circulates one of the plurality of formed protrusions, At least one portion that forms one second protrusion and that surrounds another adjacent protrusion, and the portion that forms the second path and the portion that forms the first path are connected in parallel. The primary-side conductor is formed by connecting, in series around the secondary-side conductor, a portion that substantially opposes the secondary-side conductor and that circulates the slits in a zigzag shape in series. It can be in the form.

In the above construction, each of the primary and secondary conductors is surrounded by a magnetic material, and the shape of the gap does not become flat unlike the conventional structure, so that the magnetic flux passing through the gap is small. It is possible to prevent an increase in eddy current loss in the conductor and abnormal overheating of the winding conductor. Further, since the magnetic fluxes generated by the adjacent conductors do not overlap with each other, the magnetic flux density in the core can be suppressed to a low level, so that it is difficult to saturate and the core thickness can be made small, which is particularly effective for thinning.

In another aspect, the secondary conductor may be wound around the groove of the first magnetic body.

In the above structure, the number of conductors inserted in the gap of the magnetic body can be made plural, and the conductors are constituted by windings of wires, so that the cost can be reduced.

In still another aspect, the insulating substrate has a multi-layer structure, and among the several layers forming the multi-layer structure, the primary conductor and the primary-side conductor are provided on the surfaces other than the respective surfaces of the uppermost layer and the lowermost layer. A conductor may be formed to face each other, and the conductor may be connected to at least the primary side conductor.

In the above-mentioned structure, the number of conductors inserted in the gap of the magnetic body can be made plural, and it is possible to cope with the case where the transformation ratio is large and the number of turns is large.

In still another aspect, a magnetic gap layer of a minute thickness made of a non-magnetic material interposed between each of the surfaces of the protrusion formed on the first magnetic body and the second magnetic body. And a structure in which the first magnetic body and the second magnetic body are joined via the magnetic gap layer.

By providing the magnetic gap layer having the above-described structure, the magnetic resistance of the entire circuit is increased so that the magnetic circuit is less likely to be magnetically saturated. As a result, the magnetic saturation is sufficiently taken into consideration even when a large current is used. It can be

In still another aspect, the primary side conductor and the secondary side conductor are among a plurality of voids formed by the groove of the first magnetic body joined to the second magnetic body. At least one of the primary-side conductors or the secondary-side conductors is connected so as not to be inserted, and the void portion that is not inserted may act as a reactor.

With the above-mentioned structure, it is possible to improve the disadvantage that the leakage reactance of the conventional thin transformer is structurally determined, and to provide a mechanism for adjusting the leakage reactance.

In another aspect, the gap length of the magnetic circuit forming the non-inserted void may be different from the gap length of the magnetic circuit forming the other void.

In another aspect, the second magnetic body may be formed in a flat plate shape, or a plurality of protrusions may be formed in the same manner as the first magnetic body.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a perspective view showing a first embodiment of the present invention. In FIG. 1, reference numeral 1 indicates an insulating substrate, and slits (through holes) for inserting the protrusions (convex portions, that is, tooth portions) 45 of the magnetic body 44 at a constant interval (constant pitch) in the insulating substrate 1. A plurality of holes 5 are formed at regular intervals. One side of insulating substrate 1 (upper surface in FIG. 1)
A primary-side conductor 21 forming the primary-side conductor pattern 2 is provided so as to circulate between the slits 5 in a zigzag shape. There are eight primary-side conductors 21 that extend in the longitudinal direction of each slit 5, and the primary-side conductor pattern 2 that is connected in a zigzag shape by being connected by short primary connection conductors 22 (total of seven) at each end is configured. Has been done.

In FIG. 1, the eight primary side conductors 21 and the seven primary connecting conductors 22 are all connected in series, and since they face a secondary winding, which will be described later, at four locations, the number of turns of the primary winding is Has been held four times. By combining parallel connections, it is possible to form various numbers of turns, not limited to four turns.

On the other hand, on the opposite surface of the insulating substrate 1 (the lower surface in FIG. 1), the secondary-side conductors 31 forming the secondary-side conductor pattern 3 are also provided between the slits 5. In FIG. 1, four secondary-side conductors 31 are illustrated in a state of being separated from the insulating substrate 1 to facilitate understanding, but actually, the secondary-side conductors 31 are wired on the insulating substrate 1 similarly to the primary-side conductor 21. And Each of the substantially U-shaped secondary conductors 31 is also connected at one end by a long secondary connection conductor 32 and at the other end to the adjacent secondary conductor 31.

In FIG. 1, the secondary side shows a state in which the number of turns is one in a combination of series connection and parallel connection. In terms of the circuit, four current paths are connected in parallel, and each current path is slit 5. It is a connection that goes around every other. In the case of such a connection, there is a portion where the secondary connection conductor 32 intersects, but the connection shown in FIG. 1 can be realized by connecting with a jumper wire on the insulating substrate 1. It is also possible to implement a connection method in which a pair of through holes is provided at each intersection, and the through holes lead to the upper surface of the insulating substrate 1 once and the through holes again return to the lower surface of the insulating substrate 1.

The operation of the thin transformer of the present invention will be described with reference to FIG. 2 which is a sectional view of the core and the conductor portion of FIG.

In FIG. 2, looking at one cross section of the conductor, the primary side conductor 21 is placed on the upper surface of the insulating substrate 1 and the secondary side conductor 31 is placed on the lower side, and the ferrite core 4 is surrounded by both conductors 21 and 31. A closed magnetic circuit is formed. Since the adjacent conductors are connected in opposite directions as shown in FIG. 1, the magnetic flux generated by the current flowing through both conductors passes through only one section of the closed magnetic circuit as indicated by reference numeral 7. Therefore, the voltage applied to the primary-side conductor 21 appears in the secondary-side conductor 31 as it is, and a transformer having a transformation ratio of 1: 1 is configured in this section. Therefore, when all the primary side conductors 21 and the primary connection conductors 22 are connected in series and all the secondary side conductors 31 are connected in parallel as shown in FIG. 1, a transformer having a transformation ratio of 5: 1 is constructed from FIG. Will be.

According to the transformer of the present embodiment, since the ferrite core 4 constitutes a closed magnetic circuit for one set of the primary and secondary conductors, the magnets in the horizontal direction in the drawings of the upper magnetic plate 43 and the lower magnetic plate 44 are shown. There is an advantage that the path length is short and there is little leakage magnetic flux that vertically penetrates the air gap of the window, which has been a problem in the conventional structure. Therefore, since there is almost no eddy current in the winding conductor of the transformer, the eddy current loss is also small. Further, since the magnetic fluxes generated by the adjacent conductors do not overlap with each other, the magnetic flux in the core is unlikely to be saturated, which is particularly effective in reducing the thickness.

(Second Embodiment) FIG. 3 is a sectional view showing an essential part of a second embodiment of the present invention, in which a small thickness is provided between the protrusions 46 of the upper magnetic plate 43 and the lower magnetic plate 44. The gap 8 is provided. The gap 8 can be implemented as a thin layer of an adhesive, which is a non-magnetic material, for example, and the gap 8 is formed entirely between the upper magnetic plate 43 and the lower magnetic plate 44.

In this structure, a pair of primary side conductors 2
The magnetic resistance Rm in the one-section magnetic circuit including the primary and secondary side conductors 31 is expressed by the following equation. In the following equation, Li
Is the magnetic path length of the magnetic material, Si is the cross-sectional area of the magnetic material, μi is the magnetic permeability of the magnetic material, Lg is the magnetic path length of the gap portion, Sg is the cross-sectional area of the gap portion, and μo is the magnetic permeability of the gap portion. Is. Rm = (Li / μiSi) + (2Lg / μoSg)

In general, the magnetic permeability μi of the magnetic material is several thousand times larger than the magnetic permeability μo of the gap portion, so the magnetic resistance Rm and the magnetic characteristics of this portion are almost determined by the size of the gap. FIG. 4 is a diagram showing an inductance coefficient (inductance value when the number of turns is 1) and a current limit (a limit ampere-turn value that can be used without saturating the magnetic material), which are typical magnetic characteristics. As the gap length Lg increases, the inductance coefficient AL decreases, but the current limit NIlimit can be increased, and a transformer that can handle a large current can be configured.

(Third Embodiment) FIG. 5 is a sectional view of an essential part showing a third embodiment of the present invention. In this embodiment, a multi-layer substrate is used as the insulating substrate, and the primary side conductor pattern has a three-layer structure. That is, the insulating substrate 11 of the intermediate layer is laminated on the lower surface of the insulating substrate 1 of the uppermost layer, and the insulating substrate 12 of the lowermost layer is laminated on the lower surface of the insulating substrate 11. The conductor 52 is formed on the upper surface of the insulating substrate 11, and the conductor 53 is formed on the upper surface of the insulating substrate 12.

The primary-side conductor 21 and the conductor 52 face each other, and their connections are in opposite directions, and the via hole 9 is formed at the winding end.
Are connected to each other using. If the conductors 53 and 52 are similarly connected on the opposite side using the via holes 9, all the conductors on the primary side can be connected in series. With this conductor connection, an appropriate transformation ratio can be obtained by arbitrarily combining series and parallel.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention. The thin transformer of the present embodiment has a secondary winding 60 on the side of the lower magnetic plate 44 having a groove (recess) 45.
There is a feature in the winding mode of. The secondary winding 60 is separately wound around the groove 45 at a plurality of locations, and is wound so as to circulate around the groove 45 and the back surface of the lower magnetic plate 44, respectively.

The effect of this embodiment is that the number of secondary windings 60 per one protrusion of the magnetic material can be made to be the same as in the third embodiment, but the cost is high. It is characterized in that it is composed of wire windings without using a substrate.

The secondary windings 60 at a plurality of locations may be connected in series or in parallel.

(Fifth Embodiment) FIG. 7 is a perspective view of a fifth embodiment of the present invention, and FIG. 8 is a sectional view of the same. In the thin transformer according to the present embodiment, only one of the primary or secondary winding conductors among the conductors inserted in the window portion (void portion) 6 (see FIG. 8) formed by joining the magnetic bodies 43 and 44 together. Is characterized in that it has a window portion 6 of a magnetic body through which is inserted. FIG. 8 shows a magnetic body having five window portions 6 as an example, but only the primary-side conductor 21 is inserted into the one window portion on the rightmost side in the figure.

In the transformer of the present invention, basically, both the primary and secondary conductors are inserted in one window portion, and one transformer is formed for each window portion. In the present embodiment, the window portion in which only the primary or secondary winding is inserted does not act as a transformer, and this portion acts as a reactor connected in series to the primary or secondary winding of the transformer. Become.

Therefore, for example, the effect can be exhibited in the case where the resonance reactor Lr of the resonance type converter shown in FIG. 9 is replaced by the leakage inductance of the transformer instead of a separate component, and the leakage reactance of the conventional thin transformer is exhibited. Has the drawback that it is structurally determined, and it is significant that an equivalent mechanism for adjusting the inductance that enters in series is incorporated here. For example, the structure in which the resonant reactor of the resonant converter and the transformer are integrated. Can be obtained.

(Sixth Embodiment) FIG. 10 shows the configuration of a sixth embodiment for adjusting the series inductance in a wider range. In the present embodiment, only the gap length of the magnetic circuit existing in the window portion 6 of the four magnetic bodies through which both the primary and secondary side conductors forming the transformer are inserted, and only the primary side conductor 21 which is the reactor is inserted. The gap lengths of the magnetic circuits existing in the window 6 of one magnetic material are different.

As described above with reference to FIG. 4, the inductance coefficient can be adjusted in a wide range by adjusting the gap length of the magnetic circuit. By setting the gap length of the magnetic circuit forming the transformer and the gap length of the magnetic circuit forming the reactor independently, it is possible to set the optimum operating point for each.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the first embodiment of the present invention.

FIG. 3 is a sectional view of a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship among a gap length, an inductance coefficient AL, and a current limit NIlimit.

FIG. 5 is a sectional view of a third embodiment of the present invention.

FIG. 6 is a perspective view showing a fourth embodiment of the present invention.

FIG. 7 is a perspective view showing a fifth embodiment of the present invention.

FIG. 8 is a sectional view of a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing an example of a main circuit of a resonant converter.

FIG. 10 is a sectional view of a sixth embodiment of the present invention.

FIG. 11 is a perspective view showing an example of a conventional thin transformer.

FIG. 12 is a cross-sectional view showing an example of a conventional thin transformer.

[Explanation of symbols]

1,11,12 Insulation substrate 2 Primary side conductor pattern 3 Secondary conductor pattern 4 Ferrite core 5 slits 6 windows 7 magnetic flux 7a Main magnetic flux 7b Leakage magnetic flux 8 gap 9 Via Hall 21 Primary conductor 22 Primary connection conductor 31 Secondary conductor 32 Secondary connection conductor 41 Central leg 42 Outer leg 43 Upper magnetic plate 44 Lower magnetic plate 45 groove 46 Projection 52,53 conductor 60 Secondary winding

Claims (8)

[Claims] 1. A first magnetic body having a plurality of projections formed thereon, a second magnetic body bonded to each surface of the projections, the first magnetic body and the second magnetic body. An insulating substrate having a primary conductor formed on the surface of the second magnetic body side, and a secondary side formed at a position electromagnetically coupled to the primary conductor with the insulating substrate interposed therebetween. In the transformer including a conductor, a plurality of the grooves and the protrusions are formed in parallel in the first magnetic body, and the insulating substrate is formed at substantially the same intervals as the intervals of the protrusions. A plurality of slits, each of which is interposed in the gap between the first magnetic body and the second magnetic body in such a state that one of the protrusions is inserted into each slit. . 2. The transformer according to claim 1, wherein the secondary side conductor is formed on a back surface of the first magnetic body side, and the secondary side conductor surrounds one of the plurality of formed protrusions. And at least a part that becomes a second path that goes around another adjacent projection part after the one projection part, and a part that becomes the second path and the first part. The parts that are paths are connected in parallel, and the primary-side conductor is a part in which the plurality of slits are arranged in a zigzag pattern so as to be substantially opposed to the secondary-side conductor in the winding part of the secondary-side conductor. A transformer characterized in that it is formed by being connected to. 3. The transformer according to claim 1, wherein the secondary-side conductor is wound around the groove of the first magnetic body. 4. The transformer according to claim 1, wherein the insulating substrate has a multi-layer structure, and each surface of an uppermost layer and a lowermost layer among several layers forming the multi-layer structure. On the other surface, a conductor is formed facing the primary side conductor, and the conductor is connected to at least the primary side conductor. 5. The transformer according to claim 1, wherein a non-magnetic element interposed between each surface of the protrusion formed on the first magnetic body and the second magnetic body. A transformer, comprising: a magnetic gap layer made of a material and having a minute thickness, wherein the first magnetic body and the second magnetic body are joined via the magnetic gap layer. 6. The transformer according to claim 1, wherein the primary-side conductor and the secondary-side conductor are the groove portions of the first magnetic body joined to the second magnetic body. A transformer in which the primary side conductor or the secondary side conductor is not inserted into at least one of a plurality of voids formed by the above, and the void which is not inserted acts as a reactor. 7. The transformer according to claim 6, wherein a gap length of a magnetic circuit that constitutes the void that is not inserted is different from a gap length of a magnetic circuit that constitutes another void. 8. The transformer according to claim 1, wherein the second magnetic body is formed in a flat plate shape, or a plurality of protrusions are formed similarly to the first magnetic body. A transformer that is characterized by.