JP2018098393A - Transformer, llc resonant converter, and design method of llc resonant converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer capable of easily achieving a desired performance without changing any design of a principal part of the transformer, and an LLC resonant converter and a design method of transformer.SOLUTION: The transformer has a primary wiring and a secondary wiring. In the primary wiring and the secondary wiring, the wiring which is pulled out from the side with fewer turns has a wiring length and a wiring shape which is designed so that to satisfy a predetermined inductance value the entire leakage inductance considering the wiring inductance.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a transformer, an LLC resonant converter, and an LLC resonant converter design method.

  Conventionally, as a charger mounted on an electric vehicle (EV), a plug-in hybrid vehicle (PHV), or the like, a configuration including an LLC resonant converter that converts power is known. A general LLC resonant converter includes a transformer having a primary winding and a secondary winding, a resonant capacitor connected to the primary side of the transformer, a switching circuit that controls the energization of the transformer and the resonant capacitor, and a secondary side of the transformer. A rectifier circuit to be connected and a smoothing capacitor for smoothing the rectified voltage are provided.

The LLC resonant converter uses this as a resonance inductance by actively generating a leakage inductance by reducing the coupling coefficient of the transformer. That, LLC resonant converter has transformer leakage inductance _{L e,} a resonance circuit consisting of the excitation inductance _{L m} and a resonant capacitor _{C r.}

  In a transformer of an LLC resonant converter, the bobbin shape and the turns ratio are usually designed so that a leakage inductance determined to obtain a desired performance is generated. Conventionally, when the transformer leakage inductance does not reach the target value, the bobbin shape is redesigned to change the gap between the primary and secondary windings or to change the turns ratio. It corresponds by that. In Patent Document 1, the ratio of the primary winding to the secondary winding is changed without changing the gap between the primary winding and the secondary winding, that is, without changing the design of the bobbin. A transformer capable of adjusting the leakage inductance to an optimum value is disclosed.

JP 2006-286880 A

  However, when the leakage inductance of the transformer is adjusted by widening the gap between the primary winding and the secondary winding, the size of the transformer main body is increased. Further, when desired performance cannot be obtained in the prototype transformer, and it is necessary to change the value of the leakage inductance, the transformer design must be reviewed and prototyped again.

  The transformer disclosed in Patent Document 1 can adjust the leakage inductance without changing the bobbin by changing the turns ratio of the primary winding and the secondary winding, but it is necessary to give the bobbin an extra size Therefore, it is not preferable from the viewpoint of miniaturization. Further, since the turn ratio cannot be changed after potting and fixing the winding, if the desired performance cannot be obtained in the prototype transformer, the transformer must be prototyped again.

  An object of the present invention is to provide a transformer, an LLC resonant converter, and an LLC resonant converter design method that can easily achieve desired performance without changing the design of the main part of the transformer.

The transformer according to the present invention is
A transformer comprising a primary winding and a secondary winding,
The wiring drawn from the smaller number of windings of the primary winding and the secondary winding has a wiring length and a wiring shape set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. It is characterized by having.

The LLC resonant converter according to the present invention is
A transformer having a primary winding and a secondary winding;
A resonant capacitor connected to the primary side of the transformer;
A switching circuit for controlling energization to the transformer and the resonant capacitor;
A rectifier circuit connected to the secondary side of the transformer;
A smoothing capacitor that smoothes the voltage after rectification by the rectifier circuit,
The wiring drawn from the smaller number of windings of the primary winding and the secondary winding has a wiring length and a wiring shape set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. It is characterized by having.

The design method of the LLC resonant converter according to the present invention is as follows:
A transformer having a primary winding and a secondary winding;
A resonant capacitor connected to the primary side of the transformer;
A switching circuit for controlling energization to the transformer and the resonant capacitor;
A rectifier circuit connected to the secondary side of the transformer;
A method of designing an LLC resonant converter comprising: a smoothing capacitor that smoothes a voltage after rectification by the rectifier circuit,
The wiring length and wiring shape of the wiring drawn from the smaller number of windings of the primary winding and the secondary winding are set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. It is characterized by.

  According to the present invention, desired performance can be easily realized without changing the design of the main part of the transformer.

It is a circuit diagram of the LLC resonant converter which concerns on one embodiment of this invention. 1 is an external perspective view of a transformer according to an embodiment. It is a disassembled perspective view of the transformer concerning an embodiment. It is a side view which shows the coil | winding part of the transformer which concerns on embodiment. It is a top view which shows the wiring part pulled out from the trans | transformer which concerns on embodiment. It is an external appearance perspective view which shows another example of a transformer. It is an external appearance perspective view which shows another example of a transformer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a circuit diagram of an LLC resonant converter 1 according to an embodiment of the present invention. The LLC resonant converter 1 is mounted on, for example, an in-vehicle charger.

As shown in FIG. 1, LLC resonant converter 1 converts the first DC voltage _{V in} input to output the second DC voltage _{V out.} The circuit configuration of the LLC resonant converter 1 is known, but has a feature in the configuration of the transformer T.

Specifically, the LLC resonant converter 1 includes a transformer T having a primary winding (number of turns N _p ) and a secondary winding (number of turns N _s ), a resonant capacitor C _r connected to the primary side of the transformer T, and a transformer T and the switching elements Q _1, Q 2 _(switching circuit) for controlling the energization of the resonant capacitor C _r, the rectifying element D ₁ connected to the secondary side of the transformer _T, D 2 _(rectifying circuit), and the rectified voltage A smoothing capacitor or the like for smoothing is provided. LLC resonant converter 1 comprises a leakage inductance _{L e,} the resonant circuit consisting of the excitation inductance _{L m} and a resonant capacitor _{C r} of the transformer T.

In LLC resonant converter 1 steps down the first DC voltage V _in that is input, when outputting the second DC voltage V _out, the number of turns N _s of the secondary winding than the number of turns N _p of the primary winding Is set smaller. Conversely, boosts the first DC voltage V _in that is input, when outputting the second DC voltage V _out, the direction of turns N _p of the primary winding than the turns N _s of the secondary winding Set small. In this embodiment, when stepping down in LLC resonant converter 1, that is described the case than the number of turns N _p of the primary winding smaller in the number of turns N _s of the secondary winding N _s.

  FIG. 2 is an external perspective view of the transformer T1 according to the embodiment. FIG. 3 is an exploded perspective view of the transformer T1. FIG. 4 is a side view showing a winding portion of the transformer T1. FIG. 5 is a top view showing a wiring portion drawn from the transformer T1.

  2-5, the transformer T1 includes a primary winding 11, a secondary winding 12, a bobbin 13, an upper core 14, a lower core 15, a case 16, a lead wire 21, a printed circuit board 22, and a guide member 23. Etc. 2 to 5 show only the secondary-side wiring L2, the transformer T1 also has a wiring (not shown) on the primary side. The wiring on the primary side is referred to as “wiring L1” for convenience.

  In the transformer T1, the primary winding 11 and the secondary winding 12 are, for example, enamel wires obtained by baking an insulating film on a conductor (for example, a copper wire). As the primary winding 11 and the secondary winding 12, a litz wire obtained by twisting a plurality of enamel wires may be applied.

  The bobbin 13 is formed of, for example, an insulating synthetic resin material. The bobbin 13 has a winding part (reference numeral omitted) for winding the primary winding 11 and the secondary winding 12. The bobbin 13 has, for example, a first winding portion (reference numeral omitted) around which the primary winding 11 is wound in the center in the axial direction, and a secondary winding on both sides in the axial direction of the first winding portion. 12 has the 2nd coil | winding part (code | symbol abbreviation) by which it is wound. The first winding portion and the second winding portion are separated by a partition plate 131. The primary winding 11 and the secondary winding 12 are wound around the winding portion of the bobbin 13 while being insulated by the partition plate 131.

  The upper core 14 and the lower core 15 are EE cores formed of a magnetic material such as ferrite, for example. The upper core 14 and the lower core 15 are assembled to the bobbin 13 around which the primary winding 11 and the secondary winding 12 are wound, and form a magnetic path when the primary winding 11 and the secondary winding 12 are energized. . In a state where the primary winding 11 and the secondary winding 12 are wound around the bobbin 13, the primary winding and the secondary winding 12 are fixed to the bobbin 13 by pouring and curing the potting resin. The upper core 14 and the lower core 15 are assembled to the bobbin 13 to which the primary winding 11 and the secondary winding 12 are fixed, and the main part of the transformer T1 is formed. The case 16 accommodates the main part of the transformer T1.

  The lead wire 21 constitutes a part of the secondary wiring L2 drawn from the secondary winding 12 having a small number of turns. One end of the lead wire 21 is electrically connected to the secondary winding 12. The other end of the lead wire 21 is electrically connected to the wiring pattern (copper foil) 221 of the printed circuit board 22. The lead wire 21 has a configuration in which, for example, an end portion of the secondary winding 12 is inserted through an insulating tube (reference numeral omitted), and can be easily deformed.

The printed circuit board 22 has a wiring pattern 221. One end of the wiring pattern 221 is electrically connected to the lead wire 21. The other end of the wiring pattern 221 is electrically connected to the rectifying elements D ₁ and D ₂ . The wiring pattern 221 constitutes the wiring L <b> 2 drawn from the secondary winding 12 together with the lead wire 21.

  The guide member 23 is made of, for example, a synthetic resin material. The guide member 23 holds the lead wire 21 in a predetermined shape. That is, the guide member 23 functions as a fixing structure that holds the wiring length and the wiring shape of the wiring L2. The guide member 23 can be easily changed according to the design of the transformer T1. The guide member 23 may be configured separately from the case 16 or may be formed integrally with the case 16.

  Specifically, the guide member 23 has a groove (reference numeral omitted) for disposing the lead wire 21. The lead wire 21 is drawn along the groove of the guide member 23. Thereby, the state of the lead line 21 is maintained, and as a result, the wiring L2 has a predetermined wiring length and wiring shape.

The specifications of the transformer T1 (including capacity, frequency, primary side voltage, secondary side voltage, secondary side current, exciting inductance L _m , leakage inductance _Le, etc.) are based on the performance required for the LLC resonant converter 1. It is determined. And the design of the transformer T1 (including the selection of the primary winding number N _p , the secondary winding number N _s , the primary winding diameter, the secondary winding diameter, the bobbin, etc.) so as to satisfy the determined specifications of the transformer T1 Done.

In other words, the total leakage inductance L _e of the transformer T1 is set in advance based on the required performance of the LLC resonant converter 1. Leakage inductance _{L e} is expressed by the sum of the wiring inductance _{L E_line2} leakage inductance _{L E_tf} of the transformer body, wiring inductance _{L E_line1} the primary side of the wiring L1, and the secondary side wiring L2.

Here, the wiring inductance L _{e_line2} on the secondary side is proportional to the square of the turns ratio N _p / N _s of the transformer T1, and the wiring inductance L _{e_line1} on the primary side is the reciprocal N _s / N of the turns ratio of the transformer T1. _It is proportional to the square of _p . The leakage inductance L _{e_tf} of the transformer main body is determined by the design of the main part of the transformer T1 (gap between the primary winding 11 and the secondary winding 12 and the turn ratio N _p / N _s ).

Against leakage inductance _{L E_tf} of the transformer body, wiring inductance _{L E_line1,} when the value of _{L E_line2} is small, the leakage inductance _{L e} is the leakage inductance _{L E_tf} of the transformer body is dominant. In this case, leakage inductance L _e is to satisfy a predetermined inductance value (design value), the leakage inductance L _{E_tf} of the transformer main body is adjusted. Specifically, as the leakage inductance L _e satisfies a predetermined inductance value (design value), the gap and the turns ratio N _{p /} N _s between the primary winding 11 and secondary winding 12 are adjusted .

On the other hand, depending on the turns ratio N _p / N _{s of the} primary winding 11 and the secondary winding 12, the primary wiring inductance L _{e_line1} or the secondary wiring inductance L _{e_line2} is approximately the same as the leakage inductance L _{e_tf of the} transformer body. It becomes an order. In this case, the wiring inductance _{L e_line1} on the leakage inductance _{L e,} can not ignore the influence of _{L e_line2.} That is, such a case, the wiring inductance _{L E_line1,} by adjusting the _{L E_line2,} it is possible to adjust the leakage inductance _{L e.} Note that the wiring inductance _{L E_line1,} when the influence against leakage inductance _{L e} by one of _{L E_line2} increases, the effect on the leakage inductance _{L e} by the other can be ignored.

In the present embodiment, in the transformer T1, the turn ratio N _p / N _s is set so that the wiring inductance L _{e_line2} on the secondary side is on the same order as the leakage inductance L _{e_tf of the} transformer body. For example, the number of turns _{N s} of the secondary winding 12 is one turn, the number of turns _{N p} of the primary winding 11 is 12 turns. In this case, it is possible by adjusting the wiring inductance _{L E_line2} the secondary side, to adjust the leakage inductance _{L e.}

That is, in the transformer T1, the wiring inductance _{L e_line1, L e_line2} total leakage inductance _{L e} in consideration of the, so as to satisfy predetermined inductance value (design value), drawn from the number of turns less secondary winding 12 lines The wiring inductance L _{e_line2 of} L2 is adjusted. The secondary-side wiring inductance L _{e_line2} can be adjusted by the wiring length and the wiring shape of the secondary-side wiring L2. Here, the secondary-side wiring inductance _{Le_line2} is adjusted according to the wiring length and wiring shape of the lead wire 21.

Since the secondary-side wiring inductance L _{e_line2} depends on the inter-line area A of the wiring L2 (the area of the hatched portion in FIG. 5), the wiring length and the wiring shape of the wiring L2 are determined based on the inter-line area A. It can be set easily. For example, if you want to increase the leakage inductance L _e of the transformer T1, it may be adjusted so as to enlarge the line between the area A.

At this time, even if the wiring length of the secondary side wiring L2 is the same, if the wiring shape changes, the wiring inductance L _{e_line2} changes according to the square of the turns ratio N _p / N _s , and thus the leakage inductance L _e May deviate from a predetermined inductance value. Therefore, the transformer T1 preferably has a fixed structure that holds the wiring shape of the wiring L2.

In the present embodiment, the wiring length and the wiring shape of the secondary wiring L2 are fixed by fixing the wiring length and the wiring shape of the lead wire 21 by the guide member 23. As a result, the value of the wiring inductance L _{e_line2} is stabilized and the value of the leakage inductance L _e is also stabilized, so that a desired performance is realized in the LLC resonant converter 1. In addition, since the resistance to vibration is increased, the reliability of the LLC resonant converter 1 is significantly improved.

When the leakage inductance L _e of the transformer T1 is adjusted by the wiring inductances L _{e_line1} and L _{e_line2} as in the present embodiment, the wiring shape of the secondary side wiring L2 is a bent shape, and the wiring length is the wiring destination ( Here, it becomes longer than the shortest distance to the rectifying elements D ₁ and D ₂ ).

As described above, the transformer T1 according to the present embodiment is a transformer including the primary winding 11 and the secondary winding 12, and includes the secondary winding 12 (the number of turns of the primary winding 11 and the secondary winding 12). line L2 drawn from lesser) of the wiring inductance _{L E_line1,} the set wiring length and the wiring shape as the leakage inductance of the entire considering _{L e_line2 L e} satisfies a predetermined inductance value (design value) Have.

Further, LLC resonant converter 1 according to this embodiment includes a transformer T1 having a primary winding 11 and secondary winding 12, the resonant capacitor C _r which are connected to the primary side of the transformer T1, transformer T1 and resonant capacitor the switching element _Q 1, _{Q 2} for controlling the energization of the C _r and (switching circuit), the rectifying element _D 1 connected to the secondary side of the transformer T1, _{D 2} and (rectifying circuit), the rectifying element _D 1, D _And a smoothing capacitor C ₀ for smoothing the voltage after rectification by ₂ , and the wiring L 2 drawn from the secondary winding 12 (the one with the smaller number of turns of the primary winding 11 and the secondary winding 12) is a wiring inductance _{L e_line1,} wire length leakage inductance _{L e} of the total in consideration of the _{L E_line2} is set so as to satisfy a predetermined inductance value (design value) And a wiring shape.

According to the transformer T1 and the LLC resonant converter 1, it is easy without changing the design of the main part of the transformer T1 (for example, the gap between the primary winding 11 and the secondary winding 12 or the turn ratio N _p / N _s ). Desired performance can be realized. Also, since not change the main part of the design of the transformer T1, without size of the transformer T1 becomes large, it is possible to increase the leakage inductance L _e of the transformer T1.

Further, not the desired performance is obtained in transformer T1 for the prototype, if it is necessary to change the value of the leakage inductance L _e, it is not necessary to review the main part of the design of the transformer T1, the secondary side of the interconnection of the interconnection L2 By changing the length and wiring shape, it can be easily handled. Specifically, it is possible to easily cope with this by simply reviewing the design of the guide member 23 and changing the wiring length and wiring shape of the lead wire 21.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and can be changed without departing from the gist thereof.

For example, in the embodiment, the leakage inductance L2 of the transformer T1 is adjusted by changing the wiring length and shape of the lead wire 21 and adjusting the wiring inductance L _{e_line2} on the secondary side. The wiring length and wiring shape of the wiring pattern 221 may be changed. Further, the wiring length and wiring shape of the lead line 21 may be fixed, and the wiring length and wiring length of the wiring pattern 221 may be changed.

Further, for example, the secondary side wiring L2 may be configured by the bus bar 24 and the wiring pattern 221 as in the transformer T2 shown in FIG. In this case, the leakage inductance L2 of the transformer T1 can be adjusted by changing the wiring length and the wiring shape of the bus bar 24 and / or the wiring pattern 221 to adjust the secondary-side wiring inductance _{Le_line2} .

Further, for example, the secondary-side wiring L2 may be configured by only the wiring pattern 221 as in the transformer T3 illustrated in FIG. In this case, the leakage inductance L2 of the transformer T1 can be adjusted by changing the wiring length and the wiring shape of the wiring pattern 221 and adjusting the wiring inductance _{Le_line2} on the secondary side.

In the embodiment, the step-down transformer T and the LLC resonant converter 1 have been described. However, the present invention can also be applied to a step-up transformer and an LLC resonant converter. In this case, since the direction of turns N _p of the primary winding is less than the number of turns N _s of the secondary winding, the wiring inductance of the primary side the primary side to change the wiring length and the wiring shape of the wiring L1 of L _{E_line1} by adjusting the can adjust the transformer leakage inductance L _e.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  INDUSTRIAL APPLICABILITY The present invention is suitable for general transformers, LLC resonant converters, and LLC resonant converter design methods including the use of in-vehicle chargers.

1 LLC Resonant Converter 11 Primary Winding 12 Secondary Winding 13 Bobbin 14, 15 Core 16 Case 21 Leader Line 22 Printed Circuit Board 221 Wiring Pattern 23 Guide Member 24 Bus Bar T, T1, T2, T3 Transformer Q ₁ , Q ₂ Switching Element (Switching circuit)
C _r resonant capacitor D ₁ , D ₂ rectifier (rectifier circuit)
C ₀ smoothing capacitor L _e Leakage inductance L _m Excitation inductance

Claims (11)

A transformer comprising a primary winding and a secondary winding,
The wiring drawn from the smaller number of windings of the primary winding and the secondary winding has a wiring length and a wiring shape set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. A transformer characterized by having.   The turn ratio of the primary winding and the secondary winding is set so that the wiring inductance of the wiring is on the same order as the leakage inductance of the transformer body. Trance.   The transformer according to claim 1, wherein the wiring length and the wiring shape are set based on an area between the wiring lines. The wiring shape is a bent shape,
The transformer according to any one of claims 1 to 3, wherein the wiring length is longer than a shortest distance to a wiring destination.   The transformer according to any one of claims 1 to 4, further comprising a fixing structure that holds the wiring length and the wiring shape.   The transformer according to claim 5, further comprising a guide portion that holds the wiring in a predetermined shape.   The transformer according to claim 5, wherein the wiring has a bus bar.   The transformer according to claim 5, wherein the wiring has a wiring pattern formed on a printed circuit board.   The transformer according to any one of claims 1 to 8, wherein the number of turns with the smaller number of turns is one turn. A transformer having a primary winding and a secondary winding;
A resonant capacitor connected to the primary side of the transformer;
A switching circuit for controlling energization to the transformer and the resonant capacitor;
A rectifier circuit connected to the secondary side of the transformer;
A smoothing capacitor that smoothes the voltage after rectification by the rectifier circuit,
The wiring drawn from the smaller number of windings of the primary winding and the secondary winding has a wiring length and a wiring shape set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. An LLC resonant converter, comprising: A transformer having a primary winding and a secondary winding;
A resonant capacitor connected to the primary side of the transformer;
A switching circuit for controlling energization to the transformer and the resonant capacitor;
A rectifier circuit connected to the secondary side of the transformer;
A method of designing an LLC resonant converter comprising: a smoothing capacitor that smoothes a voltage after rectification by the rectifier circuit,
The wiring length and wiring shape of the wiring drawn from the smaller number of windings of the primary winding and the secondary winding are set so that the entire leakage inductance considering the wiring inductance satisfies a predetermined inductance value. A method for designing an LLC resonant converter.

Images