JP2019041067A - Transformer and power converter - Google Patents

Abstract

To provide a thin transformer which is excellent in shape retention and easy to be mounted on a printed circuit board, and yet has a desired leakage inductance value.SOLUTION: A transformer includes cores 41a and 41b mounted on a printed circuit board 30, a secondary winding 20 formed as a wiring pattern of the printed circuit board 30, and a primary winding 11 magnetically coupled to the secondary winding 20, and the primary winding 11 is formed as a solid component by winding and resin-molding an electric wire or winding a self-bonding winding. Furthermore, a spacer 50 is disposed between the primary winding 11 and the secondary winding 20, or a leakage inductance generating winding 12 connected in series to the primary winding 11 is disposed outside the core 41a to obtain a desired leakage inductance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transformer used for a DC / DC converter, for example, and a power conversion device including the transformer.

As a transformer used for a DC / DC converter, a laminate in which a plurality of printed boards on which primary windings and secondary windings are formed by a wiring pattern is laminated is known.
In this type of transformer, for example, when the primary side has high voltage and low current specifications, the primary winding needs to have a thin conductor width and a large number of turns. There are restrictions on the spacing between adjacent conductors, and the number of turns per layer in a desired substrate size is limited.
For this reason, in order to secure a predetermined number of turns, the number of stacked printed circuit boards must be increased, resulting in an increase in cost and an increase in size of the transformer.

  Therefore, for example, in Patent Document 1, the primary winding is formed by a method such as bonding a flat spiral coil punched by press working or a spiral coated wire coated with a conductor having a predetermined diameter to the surface of the insulating sheet. Is described.

Further, in Patent Document 2, a core is mounted from the front and back of a printed circuit board, a primary wire is formed by winding a round wire or a flat wire around the central leg of the core, and a secondary coil is formed according to the wiring pattern of the printed circuit board. The formed transformer is described.
FIG. 5 is a cross-sectional view schematically showing the transformer described in Patent Document 2, wherein 10 is a primary winding, 20 is a secondary winding formed as a wiring pattern of the printed circuit board 30, 40a, Reference numeral 40b denotes a core, and reference numeral 40c denotes a central leg portion of the core.

  According to the prior art described in Patent Literature 1 and Patent Literature 2, it is not necessary to form a primary winding by laminating a plurality of printed boards, so that an increase in the number of laminated printed boards can be avoided.

On the other hand, as shown in Patent Document 3, in a resonant converter, the leakage inductance of a transformer may be actively used as an element of a resonant circuit.
FIG. 6 is a circuit diagram of the half-bridge resonant converter described in Patent Document 3. 70 is a DC power supply, 71 and 72 are semiconductor switching elements, 73 is a transformer, 73a is a primary winding, and 73b is a secondary. Winding, 73c is a leakage inductance generating winding, 73d is an exciting inductance generated by the magnetic resistance of the primary winding 73a and the core, 74 is a capacitor that forms a series resonance circuit with the windings 73a, 73c, etc., and 75 is a load Is shown.

In this prior art, for example, a desired resonance characteristic is obtained by a method of intentionally increasing the inductance value of the leakage inductance generating winding 73c.
However, it is difficult to accurately set the leakage inductance value in advance, and in many cases, the structure is determined by trial and error by repeating trial manufacture and measurement, so that much time is required for development. In particular, the optimum value of the leakage inductance varies depending on the circuit conditions (voltage, current, operating frequency, etc.). Therefore, if the product is a low-volume production of various products, design and evaluation of the circuit is required each time. There is a problem that the cost increases as the period until the time increases.

JP-A-55-166913 (page 3, upper left column, line 1 to lower right column, line 17, FIG. 3 to FIG. 5) JP 2003-197439 A (paragraph [0015], FIG. 2, FIG. 3, etc.) Japanese Patent Laying-Open No. 2015-23760 (paragraphs [0002] to [0004], FIG. 2)

In the transformers described in Patent Documents 1 and 2 described above, there is a risk that the primary winding is displaced and loosened, and the workability when attached to the printed circuit board is poor.
Moreover, the transformer described in Patent Document 3 has a problem that it is difficult to obtain a desired leakage inductance value as described above.

  Accordingly, the problem to be solved by the present invention is to provide a transformer and a power converter having an optimum leakage inductance value according to specifications while improving shape retention by forming the primary winding as a solid part. is there.

  In order to solve the above-mentioned problem, the invention according to claim 1 is the one in which the secondary winding formed by the wiring pattern of the printed circuit board and the conductive wire are wound and further formed as a solid part using a fixing means, or self-melting. A primary winding wound around the incoming winding and formed as a solid part and magnetically coupled to the secondary winding; and a core on which the secondary winding and the primary winding are mounted. It is characterized by.

  The invention according to claim 2 is the transformer according to claim 1, wherein the transformer is arranged between the primary winding and the secondary winding, and an interval between the primary winding and the secondary winding is adjusted. A possible leakage inductance value adjusting spacer is provided.

  The invention according to claim 3 is the transformer according to claim 1 or 2, wherein the shape of the primary winding, the wire diameter, the number of turns, or the positional relationship between the primary winding and the secondary winding is changed. In this way, the leakage inductance value can be adjusted.

  The invention according to claim 4 is the transformer according to claim 1, further comprising a leakage inductance generating winding connected in series to the primary winding and disposed outside the core. The inductance generating winding is formed as a solid part by winding a conducting wire and further forming it as a solid part using a fixing means, or by winding a self-bonding winding as a solid part. To do.

The invention according to claim 5 is characterized in that, in the transformer according to claim 4, the leakage inductance value can be adjusted by changing the shape, wire diameter, or number of turns of the leakage inductance generating winding. .
The invention according to claim 6 is the transformer according to any one of claims 1 to 5, wherein the fixing means is molded using a resin.
The power converter device which concerns on Claim 7 has a transformer as described in any one of Claims 1-6, It is characterized by the above-mentioned.

According to the present invention, by forming the primary winding as a solid part, it is possible to improve the workability when assembling the transformer and the handleability during storage.
In addition, by changing the thickness of the spacer interposed between the primary winding and the secondary winding, or by connecting a leakage inductance generating winding arranged outside the core in series with the primary winding. A transformer having a desired leakage inductance value can be manufactured.

It is sectional drawing of the transformer which concerns on 1st Embodiment of this invention. It is a perspective view of the primary winding and spacer in FIG. It is a perspective view which shows arrangement | positioning of the primary winding and secondary winding in 1st Embodiment of this invention. It is sectional drawing of the transformer which concerns on 2nd Embodiment of this invention, an exploded perspective view, and an equivalent circuit schematic. It is sectional drawing which showed roughly the transformer described in patent document 2. FIG. FIG. 10 is a circuit diagram of a half-bridge resonant converter described in Patent Document 3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a transformer according to a first embodiment of the present invention. The first embodiment corresponds to the invention according to claims 1 to 3 and 6.

In FIG. 1, cores 41a and 41b are attached to the printed circuit board 30 from the front and back sides, and an insulating spacer 50 and a primary winding 11 are formed on the upper surface of the printed circuit board 30 around the central leg 41c of the core 41b. It is laminated on the same axis. Further, the secondary winding 20 having a predetermined number of turns is formed on the printed circuit board 30 by a wiring pattern. Although not shown, both ends of the primary winding 11 and the secondary winding 20 are connected to an external circuit via a wiring pattern formed on the printed circuit board 30.
Here, the specific shapes and structures of the cores 41a and 41b are not limited to the example of FIG.

2A and 2B are perspective views showing the primary winding 11 and the spacer 50. FIG.
The primary winding 11 is formed as a cylindrical or annular solid part as a whole by winding an electric wire and molding the whole with resin, or winding and heating a self-bonding winding. The The central through hole of the primary winding 11 has a diameter that allows the central leg 41c of the core 41b shown in FIG. 1 to be inserted.
The spacer 50 is also formed in an annular shape having a through hole through which the central leg portion 41c can be inserted, and a plurality of spacers having different axial thicknesses may be prepared.

  In order to assemble the transformer, as shown in FIG. 1, the core 41b is mounted in the mounting hole 30a of the printed circuit board 30 in which the secondary winding 20 is previously formed, and the spacer 50 and the primary coil 11 are mounted on the central leg 41c. Insert sequentially. Then, the core 41a is joined and the whole is formed integrally.

Here, the thickness of the spacer 50 corresponds to the distance between the primary winding 11 and the secondary winding 20 (the distance along the axial direction of both the windings 11 and 20). Is changed, the magnetic coupling state between the primary winding 11 and the secondary winding 20, in other words, the number of interlinkage magnetic fluxes changes, and the leakage inductance value as a transformer changes.
Therefore, by connecting the primary winding 11 and the secondary winding 20 to an appropriate measurement circuit and measuring the leakage inductance value while exchanging the plurality of spacers 50 having different thicknesses, the optimum leakage inductance corresponding to the specification is obtained. A transformer having a value can be constructed.

In addition to changing the thickness of the spacer 50, a plurality of primary windings 11 with different wire diameters and turns are prepared, and the primary winding 11 and the spacer 50 are connected to the same secondary winding 20. A desired leakage inductance value may be generated in combination.
Furthermore, as shown in FIG. 3A, the outer diameters of the primary winding 11 and the secondary winding 20 are made different, or as shown in FIG. The leakage inductance may be adjusted by changing the overlapping area of the two windings 11 and 20 by a method such as deforming the coil.

As described above, according to the first embodiment, a primary winding as a cylindrical or annular solid part is obtained by winding an electric wire and resin-molding the whole or by using a self-bonding winding. 11 can be obtained. Since the primary winding 11 is excellent in shape retention, the workability when connecting to the wiring pattern of the printed circuit board 30 is good, and it is convenient for storage.
In order to assemble the transformer, it is only necessary to place the primary winding 11 on the upper surface of the spacer 50 on the printed circuit board 30 and join the cores 41a and 41b to each other, so that the assembly work can be facilitated and the work time can be shortened. It is.
Further, as described above, a transformer having a desired leakage inductance can be manufactured by changing the thickness of the spacer 50, the wire diameter, the number of turns, and the shape of the primary winding 11.

Next, a second embodiment of the present invention will be described. This 2nd Embodiment is equivalent to the invention concerning Claims 4-6.
4A is a cross-sectional view of a transformer according to the second embodiment, FIG. 4B is an exploded perspective view, and FIG. 4C is an equivalent circuit diagram.

In these drawings, reference numeral 12 denotes a winding for generating a leakage inductance arranged outside the core 41a. One end of the leakage inductance generating winding 12 is connected to one end of the primary winding 11, and the other end is connected to the wiring pattern of the printed circuit board 30. As apparent from FIGS. 4B and 4C, the leakage inductance generating winding 12 is connected in series to the primary winding 11.
Note that the spacer 50 may or may not be provided as indicated by a broken line in FIG.

As with the primary winding 11, the leakage inductance generating winding 12 is entirely formed by winding an electric wire and molding the whole with resin, or by winding a self-bonding winding and heating it. It is formed as a cylindrical or annular solid part.
The leakage inductance generating winding 12 is fixed to the outer surface of the core 41a with an adhesive or attached with a double-sided tape or the like.

  In the above configuration, as shown in FIG. 4A, most of the magnetic flux (indicated by a broken line) generated by the current of the leakage inductance generating winding 12 passes through the outside of the core 41a and the inside of the cores 41a and 41b. Never go through. Further, most of the magnetic flux generated by the current of the primary winding 11 (shown by dotted lines) passes through the cores 41a and 41b, and the magnetic flux generated by the current of the secondary winding 20 (indicated by the solid line) so as to cancel the magnetic flux. Occurs).

  That is, in this embodiment, the leakage inductance is actively generated by arranging the leakage inductance generating winding 12 outside the core 41a. Therefore, by preparing a plurality of leakage inductance generating windings 12 having different shapes, wire diameters, and turns and replacing them in advance, an optimum leakage inductance value can be obtained according to the intended specification. .

  The transformer of the present invention described as the first and second embodiments can be used for various power converters including the DC-DC converter such as the resonant converter shown in FIG.

11: Primary winding 12: Leakage inductance generating winding 20: Secondary winding 30: Printed circuit board 30a: Mounting holes 41a, 41b: Core 41c: Central leg 50: Spacer

Claims (7)

A secondary winding formed by the wiring pattern of the printed circuit board;
A primary winding wound with a conducting wire and further formed as a solid part using a fixing means, or formed as a solid part by winding a self-bonding winding, and magnetically coupled to the secondary winding;
A core on which the secondary winding and the primary winding are mounted;
A transformer characterized by comprising:   2. A leakage inductance value adjusting spacer disposed between the primary winding and the secondary winding and capable of adjusting a distance between the primary winding and the secondary winding. The described transformer.   3. The leakage inductance value can be adjusted by changing a shape, a wire diameter, the number of turns of the primary winding, or a positional relationship between the primary winding and the secondary winding. Transformer described in. A leakage inductance generating winding connected in series to the primary winding and disposed outside the core;
The leakage inductance generating winding is formed as a solid part by winding a conducting wire and further forming it as a solid part using a fixing means, or winding a self-bonding winding as a solid part. The transformer according to claim 1.   The transformer according to claim 4, wherein the leakage inductance value can be adjusted by changing a shape, a wire diameter, or the number of turns of the leakage inductance generating winding.   The transformer according to any one of claims 1 to 5, wherein the fixing means is molded using a resin.   A power conversion apparatus comprising the transformer according to claim 1.

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