JP6516910B1 - Step-down converter - Google Patents

Abstract

An object of the present invention is to downsize a step-down converter and to reduce the number of assembling steps into a case. In a step-down converter having a step-down transformer 2, a rectifying element 3 and a smoothing reactor 4, the primary winding 8 of the step-down transformer 2 has four layers, and the secondary winding 9 of the step-down transformer 2 has two layers, The primary winding 8 has two layers on the upper side and two layers on the lower side so as to sandwich the secondary winding 9, and between the upper primary winding 8 b and the secondary winding 9, a secondary The resin separators 10a, 10b and 10c of the insulating members are disposed between the layers of the side winding 9 and between the lower primary winding 8c and the secondary winding 9, respectively, and the primary winding of the step-down transformer The wire 8 and the secondary winding 9, the smoothing coil 42 of the smoothing reactor 4 and the resin separators 10a, 10b and 10c are integrally formed of the resin 1a except for the portion where the rectifying element 3 is mounted. [Selected figure] Figure 3

Description

  The present application relates to a step-down converter that has a transformer, a rectifying element, and a smoothing reactor, and steps down from a high voltage to a low voltage.

2. Description of the Related Art A DC / DC converter device that reduces the voltage of a high-voltage battery to a low voltage of 12 V is used in motorized vehicles such as plug-in hybrid vehicles and electric vehicles.
The DC / DC converter device includes a transformer having a primary coil and a secondary coil, a rectifying element for rectifying a voltage induced on the secondary coil of the transformer, and a choke connected to the secondary coil of the transformer It has a coil. And a secondary side coil has a plurality of coil conductor parts, and an end of each coil conductor part is soldered to a conductor pattern formed on a metal substrate via an insulating layer, and a primary side coil is a secondary side coil. As a configuration inserted between the plurality of coil conductor portions, a structure has been devised in consideration of downsizing of the transformer, reduction of the number of assembling steps to the housing, and heat radiation (see, for example, Patent Document 1).

  In addition, a secondary coil unit whose outer surface is covered with an insulating material is sandwiched between two primary coil units, and is sandwiched between a pair of cores, and the secondary coil unit is made of two secondary copper plates With a spacer made of an insulating material sandwiched between side coils, resin molding is performed by injection molding and integrated, and a transformer capable of flowing a large current by reducing the number of parts of the transformer and the number of assembling steps has been devised. (See, for example, Patent Document 2).

JP 2007-221919 A JP, 2000-173840, A

  Patent Document 1 and Patent Document 2 are both in consideration of the reduction of the number of assembling steps in a single transformer, and the number of assembling steps as a converter including a winding and a core of a smoothing reactor connected to a step-down transformer via a rectifying element However, there are still problems in reducing the size of the converter and reducing the number of assembly steps in the case.

  The present application has been made to solve the above-described problems, and it is an object of the present invention to provide a step-down converter capable of reducing the size of a transformer and the number of assembling steps in a housing.

  The step-down converter according to the present application is a step-down converter having a step-down transformer, a rectifying element, and a smoothing reactor, wherein the primary side winding of the step-down transformer is four layers, the secondary side winding of the step-down transformer is two layers, and the primary side winding In the upper side and the lower side, two layers are disposed on the upper side and the lower side so as to sandwich the secondary side winding, and between the upper side primary winding and the secondary side winding, the layer of the secondary side winding, and the lower side The resin separators of the insulating members are respectively disposed between the primary side winding and the secondary side winding, and the primary side winding and the secondary side winding of the step-down transformer, the smoothing coil smoothing coil and the resin separator Is integrally molded of resin except for the portion where the rectifying element is mounted.

  In the present application, the winding ratio can be increased by arranging two layers on the upper side and two layers on the lower side so that the primary side winding of the step-down transformer sandwiches the secondary side winding of the two layers. It is possible to cope with high voltage and miniaturization by the step-down transformer. Furthermore, since the smoothing coil of the smoothing reactor connected to the step-down transformer via the rectifying element is also integrally formed with the winding of the step-down transformer, it is possible to reduce the number of assembling steps to the housing.

FIG. 1 is a circuit diagram of a step-down converter according to a first embodiment. FIG. 1 is an entire perspective view of a step-down converter according to a first embodiment. FIG. 1 is a development view of a step-down converter according to a first embodiment. FIG. 2 is a cross-sectional view of a step-down transformer used in the step-down converter according to Embodiment 1. 5 is a development view showing a primary side winding of a step-down transformer used in the step-down converter according to Embodiment 1. FIG. FIG. 6 is a perspective view of the step-down transformer and the smoothing reactor before integral molding in the step-down converter according to Embodiment 1; FIG. 5 is a development view of a thermistor mounting unit applied to the step-down converter according to the first embodiment. FIG. 1 is a top view of a step-down converter according to a first embodiment. FIG. 3 is a cross-sectional view showing a heat radiation path of the step-down converter according to the first embodiment.

Embodiment 1
Hereinafter, the step-down converter according to the first embodiment of the present invention will be described based on FIGS. 1 to 9.
A step-down converter is, for example, a device that converts power from a high voltage battery mounted in a hybrid vehicle to a low voltage battery to supply power, and an example of its main circuit is shown in FIG.

  In FIG. 1, the step-down converter includes switching elements 11A to 11D, step-down transformer 2, rectifying element 3, smoothing reactor 4, and smoothing capacitor 5 serving as input drive circuit 1 between high voltage battery 100 and low voltage battery 200. Are connected and configured.

  The input side drive circuit 1 has four switching elements 11A, 11B, 11C, 11D (in the case of generically referred to as switching elements 11). The primary side winding 8 of the step-down transformer 2 is connected to the switching element 11, and the secondary side winding 9 is connected to the anodes of four rectifying elements 3A, 3B, 3C, 3D (collectively referred to as rectifying element 3). It is done. The smoothing reactor 4 is connected to the cathode of the rectifying element 3, and the smoothing capacitor 5 is connected between the smoothing reactor 4 and the low voltage battery 200.

  In the input side drive circuit 1, the switching elements 11A and 11B connected in series and the switching elements 11C and 11D connected in series are connected in parallel. A connection point 15 exists between the switching element 11A and the switching element 11B, and a connection point 16 exists between the switching element 11C and the switching element 11D. The primary winding 8 of the step-down transformer is connected between the connection point 15 and the connection point 16.

  Since the switching element 11 is connected to a control circuit (not shown), the control circuit controls the switching elements 11A to 11D to alternately turn on and off. Specifically, a first state in which the switching element 11A and the switching element 11D are turned on and a second state in which the switching element 11B and the switching element 11C are turned on appear alternately at constant time intervals. Thereby, in the input side drive circuit 1, between the first state and the second state, the input voltages from the voltage Vin of the high voltage battery 100 are opposite to each other (one positive voltage, the other Is applied to the primary winding 8 of the step-down transformer 2 (as a negative voltage). Therefore, the input side drive circuit 1 can form a circuit in which the direction of the current changes with time using the high voltage battery 100.

  As described above, the input side drive circuit 1 configures a so-called full bridge circuit by the four switching elements 11A to 11D. However, if voltages in opposite directions are alternately applied to the primary winding 8 of the step-down transformer 2 alternately between the first state and the second state, the aspect of the switching element 11 is the same as the aspect of FIG. For example, a so-called half bridge circuit configured by two switching elements may be employed.

  The step-down transformer 2 has two output side coils 9 a (first output side coil) and 9 b (second output side coil) as the secondary side winding 9. Of the ends of the output side coils 9a and 9b, one end is connected to the reference potential on the output side of the step-down converter, and the other end is connected to the anodes of the rectifying elements 3A, 3B, 3C, and 3D.

  The cathodes of the rectifying elements 3A, 3B, 3C, 3D are connected to one end of the coil (smoothing coil) of the smoothing reactor 4. Further, one end of the smoothing capacitor 5 is connected to an end of the pair of ends of the smoothing coil opposite to the side connected to the rectifying elements 3A to 3D. A low voltage battery 200 is connected between both ends of the smoothing capacitor 5, and an output voltage Vo is input to the low voltage battery 200 as an output of the step-down converter.

Next, the structure of each member constituting the step-down converter according to the first embodiment will be described with reference to FIGS.
FIG. 2 is a perspective view of an assembly component in which the step-down transformer 2, the rectifying element 3 and the smoothing reactor 4 are integrally configured, which constitute the step-down converter. FIG. 3 is a developed view thereof, and for convenience of explanation, the integrally molded resin covering the assembly parts is not shown.

In the step-down converter according to the first embodiment, the step-down transformer 2 has a core 7, a primary side winding 8 and a secondary side winding 9, and the rectifying element 3 is of a surface mounting type. The smoothing reactor 4 also has a smoothing core 41 and a smoothing coil 42.
As shown in FIGS. 3 and 4, the primary winding 8 of the step-down transformer 2 has two layers of primary windings 8a and 8b on the upper side and two primary layers of winding 8c and 8d on the lower side. In this case, it has a four-layer structure having a primary side winding 8). The secondary winding 9 of the step-down transformer 2 has a two-layer structure having secondary windings 9a and 9b (generally referred to as the secondary winding 9).

The primary side winding 8 of the step-down transformer 2 which is to be four layers is disposed in two layers on the upper side and two layers on the lower side of the figure so as to sandwich the secondary side winding 9 of two layers. Among the upper two layers, one primary winding 8a is integrally molded with the molding resin 8a ', and the other primary winding 8b is fitted in a recess provided in the molding resin 8a'. Similarly, of the lower two layers, one primary winding 8d is integrally molded with the molding resin 8d ', and the other primary winding 8c is fitted in the recess provided in the molding resin 8d' Be
The primary side windings 8b and 8c fitted in the recess are provided with projections (not shown) so that the width of the recess is narrowed so that the primary windings 8b and 8c are press-fitted at a plurality of places.

The layer structure of the primary winding 8 and the secondary winding 9 of the step-down transformer 2 will be described in detail with reference to FIGS.
Between upper primary winding 8b and secondary winding 9a, between two layers of secondary windings 9a and 9b, and lower primary winding 8c and secondary winding 9b and The resin separators 10a, 10b and 10c (generally referred to as the resin separator 10) of the insulating members are disposed between them. The resin separator 10b at the center has convex portions for positioning the two secondary side windings 9a and 9b in the vertical direction of the figure, and the secondary side windings 9a and 9b are engaged with it. There is a hole.

The resin separators 10a and 10c disposed outside the secondary side windings 9a and 9b also have holes for fitting with the convex portions of the central resin separator 10b. Further, on the outer periphery of the outer resin separators 10a and 10c, an L-shaped (see FIG. 4) convex portion is provided for securing the insulation creepage distance with the primary side winding 8.
Two layers of primary windings 8a and 8b are disposed above the outer resin separator 10a, and two layers of primary windings 8c and 8d are disposed below the outer resin separator 10c.
The winding end portions 9ao and 9bo of the secondary side windings 9a and 9b are L-shaped as shown in FIG. 6, and the lower side thereof is a flat portion and is a mounting portion of the rectifying element 3 .

  The primary winding 8 has one end 8 ai of the outermost primary winding 8 a integrally formed with the molding resin 8 a ′ and one end 8 bi of the primary winding 8 b of the second layer fitted in the molding resin 8 a ′. Are joined on the inner circumferential side of the winding as shown in FIG. The remaining primary windings 8d and 8c are similarly joined at their one ends 8di and 8ci. The other end 8bo of the primary side winding 8b and the other end 8co of the primary side winding 8c are joined after combining the members of the step-down transformer 2 in the state shown in FIG.

Junction of one end 8ai of primary winding 8a and one end 8bi of primary winding 8b, junction of one end 8di of primary winding 8d and one end 8ci of primary winding 8c, other end of primary winding 8b Ultrasonic welding, brazing or the like is used for joining 8 bo to the other end 8 co of the primary side winding 8 c. The other ends 8ao and 8do of the outermost primary side windings 8a and 8d are disposed side by side in the same direction as shown in FIG. 6, and are connected to the switching element 11 via a substrate (not shown).
Further, the outer diameter of the primary side winding 8 of the step-down transformer 2 is equal to the outer diameter of the secondary side winding 9 or smaller than the outer diameter of the secondary side winding 9.
Although it is assumed that the primary side winding 8 and the secondary side winding 9 in the present structure are manufactured by a sheet metal press, the manufacturing method may be any other method as long as the same configuration can be taken.

The smoothing coil 42 of the smoothing reactor 4 is configured by stacking two coils 42 a and 42 b as shown in FIG. 3, and is manufactured by a sheet metal press.
The four layers of the primary side windings 8a to 8d of the step-down transformer 2, the two layers of the secondary side windings 9a and 9b, the resin separators 10a to 10c of the insulating member and the smoothing coil 42 of the smoothing reactor 4 are shown in FIG. And the bottom of the winding ends 9ao and 9bo of the secondary side windings 9a and 9b except for the portion on which the rectifying element 3 is mounted and the integrally molded resin 1a (FIG. 2, FIG. It shape | molds according to FIG. 8), and comprises as a subassembly part.

The material of both the primary side winding 8 and the secondary side winding 9 is preferably copper in terms of the efficiency of the step-down converter. For the secondary side winding 9, when joining two windings 9a and 9b by welding such as TIG welding, oxygen free copper is suitable. In the case of using another bonding method, tough pitch copper or the like may be used. As shown in FIG. 6, a protrusion 9c may be provided on the mounting portion of the rectifying element 3 which is the winding end 9ao or 9bo of the secondary winding 9a or 9b so that the thickness of the solder can be controlled.
In the subassembly component consisting of the step-down transformer 2 and the smoothing reactor 4 which are integrally molded, the mounting portion of the rectifying element 3 which is the winding ends 9ao and 9bo of the secondary side windings 9a and 9b is surface mounted The rectifying element 3 of the type is mounted, and is soldered and connected between the winding ends 9ao and 9bo of the secondary side winding 9 of the step-down transformer 2 and the smoothing coil 42 end of the smoothing reactor 4.

Subsequently, configurations other than the winding layer structure of the step-down transformer 2 and the rectifying element 3 and the smoothing reactor 4 will be described.
A thermistor 6 for temperature detection is fixed to the secondary side winding 9 of the step-down transformer 2 to which the anode of the rectifying element 3 is connected, and the rectifying element 3 is within the rated temperature together with a control circuit (not shown). Make it work.

As shown in FIG. 7, in the mounting portion 6a of the thermistor 6 extended from the winding end 9bo of the secondary winding 9b, a cap nut 14 combined with the thermistor fixing screw 13 is integrally formed. If the cap nut 14 is press-fit into the hole provided in the resin separator 10b before integral molding, the insert supply time during integral molding can be shortened. The thermistor 6 may be fixed not by screws but by welding.
Further, the secondary winding 9 is configured such that the current is more likely to flow to the rectifying element 3 closer to the thermistor 6 so that the temperature of the rectifying element 3 closer to the thermistor 6 becomes higher.

  As shown in FIG. 6, the reference potential portion 9ag, which is the connection portion between the secondary side windings 9a and 9b of the step-down transformer 2, and the downstream side terminal portion 4bo of the smoothing coil 42 are arranged to be drawn out in the same direction. The bus bar length of the smoothing capacitor 5 can be shortened so as to further suppress the fluctuation of V.

In this embodiment, the anode side of the rectifying element 3 is the heat spreader side, and the positioning of the rectifying element 3 is also performed by positioning the heat spreader with the resin part of the integral molding.
The transformer cores 7a and 7b and the smooth cores 41a and 41b are assembled to a subassembly component in which the primary winding 8 and the secondary winding 9 of the step-down transformer 2 and the smoothing coil 42 of the smoothing reactor 4 are integrally formed of resin. Thus, an assembly component in which the step-down transformer 2 and the smoothing reactor 4 are integrated is configured.

As shown in FIG. 3, the transformer cores 7 a and 7 b are provided with projections fitted in the central holes of the primary side winding 8 and the secondary side winding 9 of the step-down transformer 2. Similarly, the smooth cores 41 a and 41 b are provided with projections fitted in the central holes of the smooth coils 42 a and 42 b of the smooth reactor 4.
The step-down transformer 2 configured by inserting the transformer cores 7a and 7b into the primary winding 8 and the secondary winding 9 has two adhesive tapes 15a and 15b attached thereto as shown in FIG. Fix the core to a single piece.
Similarly, as shown in FIG. 2, the smoothing reactor 4 configured by fitting the smoothing cores 41 a and 41 b into the smoothing coils 42 a and 42 b adheres the adhesive tapes 15 c and 15 d to integrally form two cores. Fix to the product.

  The adhesive tape 15a shown in FIG. 2 is a case in which the transformer cores 7a and 7b are housed in the housing 19 serving as a cooler, in which the assembly component in which the step-down transformer 2, the rectifying element 3 and the smoothing reactor 4 are integrally configured is integrated. A portion in contact with a spring (not shown) for pressing 19. The adhesive tape 15c is a portion in contact with a spring (not shown) for pressing the smooth cores 41a and 41b against the housing 19 when the assembly component is housed in the housing 19 which also serves as a cooler. , 7b, 41a, 41b and the metal spring are stuck to the core so as not to come in direct contact and the metal powder is released.

Further, as shown in FIG. 9, a heat dissipation member 18 is disposed between the winding end portions 9ao and 9bo bottom portions of the secondary side winding 9 of the step-down transformer 2 and the casing 19 serving as a cooler. The heat generation H1 of the two primary side windings 8 is dissipated from the casing 19 via the resin separator 10, the secondary side windings 9 and the heat dissipation member 18 as indicated by the arrows. Further, the rectifying element 3 having a large amount of heat generation is also dissipated from the housing 19 via the secondary side winding 9 and the heat dissipation member 18. As described above, in the rectifying element 3, the heat radiation path is shared with the secondary side winding 9 of the step-down transformer 2.
On the other hand, the lower surface of the transformer core 7b and the lower surface of the smooth core 41b are disposed in direct contact with the housing 19, and the heat from the transformer cores 7a and 7b and the smooth cores 41a and 41b is directly dissipated from the housing 19 .

In the assembly components of the step-down transformer 2 and the smoothing reactor 4, as shown in FIG. 8, the resin portions 1b are disposed outside the four corners of the transformer cores 7a and 7b and the smoothing cores 41a and 41b.
The assembly components of the step-down transformer 2 and the smoothing reactor 4 are screwed to a housing 19 (not shown) via six metal collars 17 integrally molded with the integrally molded resin 1a as shown in FIG. The transformer core 7 and the smooth core 41 are fixed to the housing 19 by pressing them with a spring, but in the direction perpendicular to the spring load, the product of the spring load and the coefficient of friction, so-called friction force is generated from the force generated by vibration. It must be big.

In vibration from a normal engine, there is no problem in fixing with a spring, but in order to prevent the transformer core 7 and the smooth core 41 from moving, it is assumed that strong acceleration such as a collision occurs. A coking agent may be filled between the cores 7a and 7b and the smooth cores 41a and 41b and the resin portion 1b. If chamfered shapes are provided at the four corners of the transformer core 7 and the smooth core 41, the caulking agent can be easily filled. A silicone adhesive or the like is used as the coking agent.
Furthermore, the heat dissipating effect of the step-down transformer 2 and the smoothing reactor 4 is enhanced by filling the heat sink material in the coking agent filling spaces at the four corners of the transformer cores 7 a and 7 b of the step-down transformer 2 and the smooth core 41 of the smoothing reactor 4.

As described above, the step-down converter according to the first embodiment is a step-down converter including the step-down transformer 2, the rectifying element 3, and the smoothing reactor 4, in which the primary winding 8 has four layers and the secondary winding. The line 9 has a two-layer six-layer structure. By making the primary side winding 8 into four layers, the turn ratio to the secondary side winding 9 can be increased to cope with higher voltage with one step-down transformer 2.
In addition, the smoothing coil 42 of the smoothing reactor 4 connected to the downstream side of the step-down transformer 2 via the rectifying element 3 is also integrally molded with the winding of the step-down transformer 2 so that mounting on the cooler serving as the housing 19 is easy. As a result, the number of assembling steps can be reduced, and the heat radiation path of the primary winding 8 and the secondary winding 9 of the step-down transformer 2 can be made common.

  The primary winding 8 of the step-down transformer 2 has a configuration in which two layers are disposed on the upper side and two layers on the lower side so as to sandwich the secondary winding 9 of two layers, thereby reducing high frequency resistance and loss The transformer can be miniaturized because it is reduced. The heat generation of the primary side winding 8 of the step-down transformer 2 can be dissipated to the casing 19 serving as a cooler through the resin separator 10 of the insulating member, the secondary side winding 9 and the heat radiating member 18. Further, as shown in FIG. 9, a concave portion on which the transformer core 7 b and the smooth core 41 b are placed is provided at the bottom of the housing 19 and the secondary winding 9 of the step-down transformer 2 is By lowering the lower surface of the transformer core and the lower surface of the smooth core, the overall height of the step-down converter can be reduced and the size can be reduced.

Although the present application describes exemplary embodiments, the various features, aspects, and features described in the embodiments are not limited to the application of the specific embodiments, either alone or The embodiments can be applied in various combinations.
Accordingly, numerous modifications not illustrated are contemplated within the scope of the technology disclosed herein. For example, when deforming at least one component, it is assumed that the case of adding or omitting is included.

1: Input side drive circuit, 1a: integrally molded resin, 1b: resin portion, 2: step-down transformer,
3: Rectifying element, 4: Smoothing reactor, 4bo: Winding end of smoothing reactor,
5: smoothing capacitor 6: 6: thermistor, 7, 7a, 7b: core of step-down transformer,
8, 8a, 8b, 8c, 8d: primary winding of step-down transformer,
9, 9a, 9b: secondary winding of step-down transformer,
9c: convex portion of secondary winding end of step-down transformer,
9ag: Secondary winding reference potential portion of step-down transformer,
10, 10a, 10b, 10c: resin separators,
15a, 15b, 15c, 15d: adhesive tape, 17: metal collar, 18: heat dissipation member,
19: Case, 41, 41a, 41b: Smooth core, 42, 42a, 42b: Smooth coil,
100: High voltage battery, 200: Low voltage battery.

Claims (10)

  A step-down converter having a step-down transformer, a rectifying element, and a smoothing reactor, wherein the primary side winding of the step-down transformer is four layers, the secondary side winding of the step-down transformer is two layers, and the primary side winding is the secondary side. Two layers are disposed on the upper side and two layers on the lower side so as to sandwich the side winding, and between the upper primary side winding and the secondary side winding, an interlayer of the secondary side winding, and the above A resin separator of an insulating member is disposed between the lower primary winding and the secondary winding, and the primary winding and the secondary winding of the step-down transformer, and the smoothing of the smoothing reactor. A step-down converter characterized in that the coil and the resin separator are integrally molded of resin except for the portion where the rectifying element is mounted. The step-down converter according to claim 1, wherein a heat dissipation member is disposed between an end portion of a secondary side winding of the step-down transformer and a housing accommodating the step-down converter.   The step-down voltage according to claim 2, wherein an outer diameter of a primary side winding of the step-down transformer is equal to or smaller than an outer diameter of the secondary side winding. converter.   3. The device according to claim 2, wherein the rectifying element is a surface mounting type, and is soldered between an end of the secondary winding of the step-down transformer and an end of a smoothing coil of the smoothing reactor. The step-down converter according to claim 3. The step-down converter according to claim 4, wherein a convex portion is provided on a flat portion of a secondary side winding end portion of the step-down transformer on which the rectifying element is mounted, so that the thickness of the solder can be controlled. .   The step-down converter according to any one of claims 2 to 5, wherein a thermistor is fixed to a secondary side winding of the step-down transformer. The lower surface of the core of the step-down transformer and the lower surface of the core of the smoothing reactor are lower than the contact surface of the heat dissipation member provided in contact with the end of the secondary winding of the step-down transformer. A step-down converter according to any one of the preceding claims.   The reference electric potential part of the secondary side winding of the step-down transformer and the drawing direction of the winding end of the smoothing reactor are made the same. The method according to any one of claims 1 to 7, Step-down converter.   A resin portion is formed at four corners of at least one of the core of the step-down transformer and the smooth core of the smoothing reactor, and a coking agent is filled between the resin portion and the core or the smooth core. A step-down converter according to any one of claims 8 to 12.   The step-down converter according to claim 9, wherein a heat-dissipating material is filled in caulking agent-filled spaces at four corners of the core of the step-down transformer and the smooth core of the smoothing reactor.

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