JP7082267B2 - Transformers and DC-DC converters - Google Patents

Description

The present invention relates to transformers and DC-DC converters.

In an isolated DC / DC converter, the leakage inductance of the transformer may be used as an energy storage element of the converter. This can be expected to reduce the size of the entire circuit.

In order to adjust the leakage inductance of the transformer, there are various methods such as devising the structure of the core of the transformer (Patent Document 1) and devising the winding method of the winding (Patent Document 2).

Japanese Unexamined Patent Publication No. 2008-85004 Japanese Unexamined Patent Publication No. 2013-74144

When adjusting the leakage inductance by providing a magnetic gap in the core as shown in Patent Document 1, if the magnetic gap is made large in order to realize the desired leakage inductance, the core becomes large, which leads to an increase in size of the device. ..

Similarly, as shown in Patent Document 2, if the primary coil and the secondary coil are arranged side by side in the axial direction, the transformer becomes large in the axial direction, which leads to an increase in size of the device.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique capable of setting a leakage inductance to a predetermined value and reducing the size.

In order to solve the above problems, the transformer of the present invention is a transformer in which the primary coil and the secondary coil are coaxially provided, and the primary coil and the secondary coil are in a direction parallel to the axis or the said. In one of the directions perpendicular to the axis, the winding or block of the winding forming the primary coil is arranged so as to be adjacent to the winding forming the secondary coil or the block of the winding. The windings forming the primary coil and the windings forming the secondary coil are formed by an insulating barrier which is a non-magnetic insulator in the direction parallel to the axis or the direction perpendicular to the axis in the other direction. It is characterized by being isolated.

Here, the winding block is not a winding for one winding, but a unit of winding wound a predetermined number of times. In such a configuration, since leakage inductance is generated between the windings isolated by the insulating barrier, the leakage inductance can be set to a predetermined value by adjusting the distance between the windings, and the configuration functions as a choke. There is no need to install it separately. Therefore, the transformer can be miniaturized while setting the leakage inductance to a desired value.

In addition, since the windings forming the primary coil and the windings forming the secondary coil are separated from each other, it is possible to reduce the increase in resistance due to the proximity effect without reducing the degree of coupling between the primary coil and the secondary coil. can. As a result, loss and heat generation can be suppressed, and efficiency can be improved.

Further, in the primary coil and the secondary coil, a winding forming the primary coil or a block of the winding and a winding forming the secondary coil or a block of the winding are adjacent to each other in a direction parallel to the axis. The insulating barrier may be provided so as to separate the windings forming the primary coil and the windings forming the secondary coil in a direction perpendicular to the axis. Thereby, by adjusting the thickness of the barrier, the distance between the windings of the primary coil and the distance between the windings of the secondary coil can be set to any one according to the distance from the core.

In order to solve the above problems, the DC-DC converter of the present invention includes the transformer.

According to the present invention, it is possible to provide a technique capable of setting the leakage inductance to a predetermined value and reducing the size.

FIG. 1 is a circuit configuration diagram of a bidirectional DC-DC converter using a transformer according to the first embodiment. FIG. 2 is an external perspective view of the transformer according to the first embodiment. FIG. 3 is an exploded perspective view of the transformer according to the first embodiment. FIG. 4 is a cross-sectional view taken along the line AA shown in FIG. FIG. 5 is a diagram showing an example comparing a conventional configuration in which a choke coil is provided separately from the transformer and the transformer of the first embodiment. FIG. 6 is a cross-sectional view of a modified example of the transformer according to the first embodiment. FIG. 7 is an external perspective view of the transformer according to the second embodiment. FIG. 8 is an exploded perspective view of the transformer according to the second embodiment. FIG. 9 is a cross-sectional view taken along the line AA shown in FIG.

<Example 1>
Hereinafter, specific embodiments to which the present technique is applied will be described in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram of a bidirectional DC-DC converter 1 using a transformer according to an embodiment of the present invention. In FIG. 1, the bidirectional DC-DC converter 1 includes a primary conversion circuit unit 10 on the left side in the figure and a secondary conversion circuit unit 20 on the right side in the figure with the transformer 30 interposed therebetween. In this embodiment, the primary conversion circuit unit 10 is a high voltage side circuit, and the secondary conversion circuit unit 20 is a low voltage side circuit.

Between the positive electrode 11 and the negative electrode 12 which are the input / output ends of the primary conversion circuit unit 10, a smoothing capacitor C1 and a first switching arm formed by connecting the source of the switching element S1 and the drain of the switching element S3, switching. A second switching arm formed by connecting the source of the element S2 and the drain of the switching element S4 is connected in parallel.

Further, the primary coil 31 of the transformer 30 is connected between the connection point between the source of the switching element S1 and the drain of the switching element S3 and the connection point between the drain of the switching element S4 and the source of the switching element S2. ..

A smoothing capacitor C2 is connected between the positive electrode 21 and the negative electrode 22 which are the input / output ends of the secondary conversion circuit unit 20. Further, between the positive electrode 21 and the negative electrode 22, a first switching arm formed by connecting the source of the switching element S5 and the drain of the switching element S7, and the source of the switching element S6 and the drain of the switching element S8 are connected. A second switching arm is connected in parallel.

The secondary coil 32 of the transformer 30 is connected between the connection point between the source of the switching element S5 and the drain of the switching element S7 and the connection point between the drain of the switching element S8 and the source of the switching element S6.

In this embodiment, N-type MOSFETs are used as the switching elements S1 to S8, but the type of the switching element of the present invention is not limited to this. As the type of the switching element, for example, a P-type MOSFET, an IGBT, or another transistor may be adopted.

Reflux diodes D1 to D8 are connected between the drain and the source of the switching elements S1 to S8 so as to allow a current to flow from the source side to the drain side. Here, the parasitic diodes (body diodes) of the switching elements S1 to S8 can also be used as the freewheeling diodes D1 to D8. The switching elements S1 to S8 are switched and controlled by a control device (not shown).

The coils 310 and 320 shown in the transformer 30 in FIG. 1 are virtual ones showing the action of the leakage inductance of the primary coil 31 and the secondary coil 32 as equivalent circuits, respectively. By setting this leakage inductance to a predetermined value, the transformer 30 of this embodiment functions as an energy storage element like a choke coil.

2 is an external perspective view of the transformer 30 according to the present embodiment, FIG. 3 is an exploded perspective view of the transformer 30, and FIG. 4 is a cross-sectional view taken along the line AA shown in FIG. The transformer 30 includes a primary coil 31, a secondary coil 32, and a core 33. Note that FIGS. 2 to 4 schematically show the transformer 30, and the shapes of the primary coil 31, the secondary coil 32, and the core 33 in FIGS. 2 to 4 do not necessarily match the shapes of the respective parts in the actual transformer. It's not something to do.

The core 33 is an EI type having a first core portion 33A having an E-shaped cross section and a second core portion 33B having an I-shaped cross section. The first core portion 33A has a central leg 331, side legs 332 surrounding both sides thereof, and a plate-shaped portion 333 connecting the central leg 331 and the left and right side legs 332. In other words, the left and right side legs 332 and the plate-shaped portion 333 are connected in a U-shape, and the central leg 331 is joined to the center of the inner wall surface of the plate-shaped portion 333 which is the inside of the U-shape. The central leg 331 has a circular bottom surface joined to the plate-shaped portion 333, and has a cylindrical shape having a predetermined height from the inner wall surface of the plate-shaped portion 333. A primary coil and a secondary coil are coaxially wound around the central leg 331.

Then, the I-shaped second core portion 33B is assembled to the U-shaped opening portion formed by the left and right side legs 332 and the plate-shaped portion 333 to form a closed magnetic circuit. The material of the core 33 is not particularly limited, but in this embodiment, ferrite is used in order to suppress the core loss in the high frequency band.

The primary coil 31 and the secondary coil 32 are windings having a circular cross section around which a conducting wire is insulated and coated with copper or a copper alloy. The material and form of the primary coil 31 and the secondary coil 32 are not limited to this, and may be a flat wire or a stranded wire.

The transformer in the present embodiment has a width (hereinafter, also referred to as winding width) WA of the region between the inner wall of the plate-shaped portion 333 and the inner wall of the second core portion 33B in the direction parallel to the central axis of the central leg 331. The primary coil 31 and the secondary coil 32 are arranged adjacent to each other over the entire width. More specifically, the primary coil 31 is wound around half of the winding width WA on the outer circumference of the central leg 331, and the secondary coil 32 is wound around the other half.

Then, as shown in FIG. 4, the first layer 311A and the second layer 311B of the winding 311 forming the primary coil 31 are separated by the first insulating barrier 351 and further, the winding 311 forming the primary coil 31 is separated. The second layer 311B and the third layer 311C are separated by a second insulating barrier 352. Similarly, for the secondary coil 32, the first insulating barrier 351 is used between the first layer 321A and the second layer 321B of the winding 321 and the second insulating barrier 352 is used between the second layer 321B and the third layer 321C. It is configured to be isolated from each other. The first layer 311A, the second layer 311B, and the like of the winding 311 correspond to the "winding block".

Then, the end of the first layer 311A, which is one end of the winding 311 of the primary coil 31, is pulled out to the outside to form a leader wire 31A (FIG. 3), and the end of the third layer 311C, which is the other end of the winding 311, is outside. It is configured to be pulled out to form a leader line 31B. Similarly, for the secondary coil 32, the end portion of the first layer 321A, which is one end of the winding 321 is pulled out to the outside to form a leader wire 32A, and the end portion of the third layer 321C is pulled out to the outside to form a leader wire 32B. It has become.

In order to make such a configuration, for example, the first conductor is first wound around the outer periphery of the central leg 331 of the core 33 from the position where it is in contact with the inner wall of the plate-shaped portion 333 of the first core portion 33A, and the winding width WA is set. Wrap one layer until it reaches half. Next, the second conductor is wound from the position where it contacts the inner wall of the second core portion 33B, and is wound one layer until the winding width WA reaches half (that is, until the end of the first layer of the first conductor). .. Then, a first insulating barrier 351 is formed by a non-magnetic insulator (for example, insulating paper) on the outer periphery of the first and second layers of the wound first conducting wire. After that, the first conductor and the second conductor are wound around the outside of the first insulating barrier 351 in the same manner as the first to form the second layer, and the outer periphery thereof is formed in the same manner as the first insulating barrier 351. The second insulating barrier 352 is formed. Further, the first conductor and the second conductor are wound around the outside of the second insulating barrier 352 to form the third layer. In this way, the winding made of the first conductor becomes the winding 311 of the primary coil 31, and the winding made of the second conductor becomes the winding 321 of the secondary coil 32.

In this embodiment, the first conductor of each layer is wound up to half of the winding width WA (that is, the primary coil 31 and the secondary coil 32 occupy half of the winding width WA). It is not always necessary to do this, and it is sufficient that the position of the end of winding of the first conductor and the position of the end of winding of the second conductor are adjacent to each other. That is, the winding of the first conductor may be up to a position less than half of the winding width WA, or conversely, may be up to a position more than half.

As described above, the layers of the windings of the primary coil 31 and the secondary coil 32 are arranged adjacent to each other, thereby increasing the degree of coupling between the primary coil 31 and the secondary coil 32. Further, since the windings 311 of the primary coil 31 and the windings 321 of the secondary coil 32 are separated from each other by the insulating barriers 351 and 352, the proximity effect is reduced and the decrease in efficiency due to this can be suppressed. can.

Then, by separating the windings 311 of the primary coil 31 and the windings 321 of the secondary coil 32 at arbitrary distances by the insulating barriers 351 and 352, the leakage inductance can be set to a required value, as if it were a choke. It can function as if it had a coil. That is, the leakage inductance is not adjusted by changing the size of the transformer core, but by adjusting the distance between the windings of the primary coil and the windings of the secondary coil using an insulating barrier. I can do things. Further, in this way, since the leakage inductance is adjusted by the line-to-line distance of the winding, the coil turns ratio can be freely set.

As described above, according to the DC-DC converter 1 of the present embodiment, by setting the leakage inductance of the transformer 30 to a predetermined value, the same effect as that of the configuration including the choke coil can be obtained. Therefore, it is not necessary to separately provide a choke coil, and the size, weight, and loss can be suppressed as compared with the conventional configuration in which the choke coil is actually provided. Further, by improving the efficiency in this way, the heat generated from the transformer is suppressed, and thereby the configuration and processing for heat dissipation can be reduced.

FIG. 5 is a table showing an example comparing a conventional configuration in which a choke coil is provided separately from the transformer and the transformer of the present embodiment. In FIG. 5, an experimental example shows a transformer 30 having a capacity of 6 kW and a configuration of FIGS. 2 to 4, and a comparative example shows a conventional configuration in which a capacity is 6 kW and a choke coil is provided separately from the transformer. ing. The volume ratio, weight ratio, and loss ratio in FIG. 5 show the values of the experimental example when the comparative example is 100%.

As shown in FIG. 5, the experimental example has a volume ratio of 82.7%, a weight ratio of 88.3%, and a loss ratio of 35.8%, all of which are reduced as compared with the comparative example. It can be seen that the DC-DC converter 1 according to the embodiment is superior to the conventional configuration in all of size, weight, and efficiency.

<Modification example>
In the first embodiment, the primary coil 31 and the secondary coil 32 are arranged adjacent to each other, and the first layer 311A of the winding 311 of the primary coil 31 and the first layer 321A of the winding 311 of the secondary coil 32 are arranged. The structure was that they were adjacent to each other. That is, the block of the winding forming the primary coil 31 and the block of the winding forming the secondary coil 32 are adjacent to each other, but the configuration is not limited to this, and the configuration may be as shown below, for example. ..

FIG. 6 shows a cross-sectional view of another configuration example of the transformer 30. As shown in FIG. 6, in the transformer 30 according to this modification, the winding 311 forming the primary coil 31 and the winding 321 forming the secondary coil 32 are staggered in the direction parallel to the central axis of the central leg 331. It is configured to be placed in. That is, the winding 311 forming the primary coil 31 and the winding 321 forming the secondary coil 32 may be arranged so as to be adjacent to each other for each winding. With such a configuration, the degree of coupling between the primary coil 31 and the secondary coil 32 can be further increased.

<Example 2>
Subsequently, a second embodiment of the present invention will be described. In this embodiment, the coil winding and the insulation barrier arrangement in the transformer 30 are different from those in the first embodiment, and the circuit configuration of the bidirectional DC-DC converter 1, the shape of the core 33, and the like are described in the first embodiment. Since it is the same as that of the above, detailed description of such a portion will be omitted by using the same reference numerals as those in the first embodiment.

7 is an external perspective view of the transformer according to the present embodiment, FIG. 8 is an exploded perspective view of the transformer according to the present embodiment, and FIG. 9 is a cross-sectional view taken along the line AA shown in FIG. be. In the first embodiment, the transformer 30 has a configuration in which the primary coil 31 and the secondary coil 32 are arranged adjacent to each other in a direction parallel to the central leg 331 of the core, and an insulating barrier is arranged so as to separate each layer of the winding. However, in this embodiment, unlike this, the configuration is as follows.

As shown in FIGS. 8 and 9, the transformer 30 according to the present embodiment is wound so that the secondary coil 38 is arranged on the outer periphery of the primary coil 37, and each insulating barrier is placed on the central axis of the central leg 331. In the parallel direction, the windings 371 of the primary coil 37 and the windings 381 of the secondary coil 38 are separated from each other.

In order to make such a configuration, for example, first, three insulating barriers made of an insulating material (for example, epoxy resin) are arranged on the central leg 331 at equal intervals. Here, each insulating barrier is, for example, a donut-shaped plate member whose outer diameter is slightly smaller than the distance between the left and right side legs 332 of the core 33, and is equivalent to one conducting wire to be a coil winding. It has a slit.

Then, the first conductor is wound around the outer periphery of the central leg 331 of the core 33 from a position in contact with the inner wall of the plate-shaped portion 333 of the first core portion 33A to form a three-layer laminated winding. Subsequently, the conductor is passed between the first insulation barrier 355 and the second insulation barrier 356 from a slit provided in the insulation barrier, and the conductor is wound in three layers and wound in a laminated winding. Further, the conducting wire is subsequently passed between the second insulating barrier 356 and the third insulating barrier 357, and thereafter, the conducting wire is wound over the entire winding width WA in the same manner to form the primary coil 37. After that, the second conducting wire may be wound around the outer circumference of the primary coil 37 in the same procedure as that of the primary coil 37 to form the secondary coil 38.

<Others>
The transformer, DC-DC converter, etc. exemplified above are not limited to the description in each of the above examples, and their configurations, operations, operation methods, etc. may be appropriately changed within the scope of the technical idea of the present invention. Can be done.

For example, in each of the above examples, the insulating barrier in the transformer is configured to isolate the windings forming the primary coil and the windings forming the secondary coil one turn or one layer. Not limited to this, the windings may be separated by a unit of a plurality of windings. Further, the number of windings to be isolated may be different for each region separated by the insulating barrier. Further, the widths of the insulating barriers (that is, the isolation distances) do not have to be the same, and the respective insulating barriers may have different widths.

Further, the number of turns of the windings of the primary coil and the secondary coil does not have to be the same, and the thickness of the conducting wire constituting the winding does not have to be the same. These can be arbitrarily set according to the conditions.

Further, in each of the above examples, an example in which the primary conversion circuit section side is set to high voltage and the secondary conversion circuit section side is set to low voltage is shown, but the present invention is not limited to this, and the primary conversion circuit section side is low voltage and the secondary conversion circuit section side is low voltage. May be high pressure. That is, the DC power at the input / output end of the primary conversion circuit section is boosted and output from the input / output end of the secondary conversion circuit section, and the DC power at the input / output end of the secondary conversion circuit section is stepped down for primary conversion. It may be configured to output from the input / output end in the circuit unit.

Further, in each of the above examples, an example of a bidirectional DC-DC converter is shown, but the present invention is not limited to this, and the DC-DC converter of the present invention may be configured to convert a voltage in one direction. Further, the DC-DC converter of each of the above examples is a full bridge system, but the present invention is not limited to this, and a half bridge system, a push-pull system, or the like may be used.

Further, the transformer of the present invention can be used not only for a DC-DC converter but also for other devices such as a power supply circuit, an inverter, and a ballast of a welding machine.

1 ... DC-DC converter 30 ... Transformer 31, 37 ... Primary coil 32, 38 ... Secondary coil 33 ... Core 33A ... First core part 33B ... Second core Part 310 ... Coil 351, 352, 355, 356, 357 ... Insulation barrier

Claims (3)

The primary coil and the secondary coil are transformers provided coaxially, and the primary coil and the secondary coil are coaxially provided transformers.
In a direction parallel to the axis of the primary coil and the secondary coil, the winding or the block of the winding forming the primary coil and the winding forming the secondary coil or the block of the winding are adjacent to each other. Arranged so that
The windings forming the primary coil and the windings forming the secondary coil are separated from each other by an insulating barrier which is a non-magnetic insulator in a direction perpendicular to the axis. To do, transformer. The windings forming the primary coil and the windings forming the secondary coil are alternately arranged so as to be adjacent to each other in a direction parallel to the axis.
The transformer according to claim 1. A DC-DC converter comprising the transformer according to claim 1 or 2.

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