JP5852933B2 - DC-DC converter - Google Patents

Description

  The present invention relates to a DC-DC converter having a transformer, a rectifier circuit unit, and a base plate on which these are mounted.

  In the DC-DC converter, a rectifier circuit unit that rectifies an output current is connected to a secondary coil of the transformer. In order to prevent electromagnetic noise radiated from the rectifier circuit unit from affecting other electronic components in the DC-DC converter and components around the DC-DC converter, the rectifier circuit unit (diode module) There has been proposed a DC-DC converter in which a conductor (a grounding bus bar) is disposed so as to cover (Patent Document 1). In the configuration described in Patent Document 1, the conductor is made of copper. In other words, the conductor is a bus bar, and its main role is to pass a large current, so copper having high conductivity is employed.

JP 2000-324839 A

  However, in the configuration described in Patent Document 1, since the copper covering the rectifier circuit portion is a non-magnetic material, it has an effect of shielding relatively low frequency electromagnetic noise even though it has an effect of shielding high frequency electromagnetic noise. There is a problem of being small. Therefore, in the configuration in which the bus bar is disposed so as to cover the rectifier circuit unit, it may be difficult to shield relatively low frequency electromagnetic noise among the electromagnetic noise radiated from the rectifier circuit unit.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a DC-DC converter that can suppress electromagnetic noise radiated from a rectifier circuit section over a wide frequency range.

One aspect of the present invention is a DC-DC converter including a transformer including a primary coil and a secondary coil, a rectifier circuit unit connected to the secondary coil, and a base plate on which the transformer and the rectifier circuit unit are mounted. Because
A magnetic body disposed so as to cover the rectifier circuit portion from the side opposite to the base plate;
A pedestal fixed to the base plate and supporting the magnetic body from the rectifier circuit side;
Pedestal, together with a conductor, when viewed from the laminate direction of the base plate and the rectifier circuit portion and the magnetic body have a shape which is circular,
The DC-DC converter is characterized in that the rectifier circuit portion is housed inside an annular inner peripheral contour of the pedestal when viewed from the stacking direction .

  In the DC-DC converter, the magnetic body is disposed so as to cover the rectifier circuit portion from the side opposite to the base plate. Thereby, the electromagnetic noise radiated | emitted from the said rectifier circuit part to the opposite side to a baseplate can be shielded with the said magnetic body. In particular, the magnetic material can shield relatively low frequency noise. Therefore, by arranging the magnetic body so as to cover the rectifier circuit portion, relatively low frequency electromagnetic noise may be generated with respect to other components in the DC-DC converter and components around the DC-DC converter. It is possible to suppress the influence.

  The DC-DC converter includes a pedestal that supports the magnetic body from the rectifier circuit side. Therefore, the pedestal is disposed on the side opposite to the base plate with respect to the rectifier circuit portion. The pedestal is made of a conductor. Thereby, the electromagnetic noise radiated | emitted from a rectifier circuit part can be shielded by a base. That is, when the magnetic flux (radiated magnetic flux) radiated from the rectifier circuit unit is linked to the pedestal made of a conductor, an eddy current flows in the pedestal in a direction to cancel the radiated magnetic flux. Thereby, the electromagnetic noise radiated | emitted from a rectifier circuit part can be suppressed.

And since the said magnetic body is mounted in the base, generation | occurrence | production of the magnetic flux by the eddy current which flows into a base is accelerated | stimulated. Therefore, the radiant magnetic flux can be canceled out more effectively.
The pedestal is formed in an annular shape when viewed from the stacking direction. Therefore, an eddy current generated when the radiant magnetic flux is linked flows in an annular shape along the annular pedestal. Therefore, the shielding effect of electromagnetic noise is not particularly reduced even if the area of the pedestal is reduced because the inner portion of the annular shape is hollowed out. On the other hand, by making it annular, the pedestal can be reduced in weight and cost can be reduced.

  Further, since the electromagnetic noise due to the eddy current as described above can be reduced, the shielding effect by the pedestal is particularly effective for relatively high frequency noise. That is, in the DC-DC converter, a relatively high frequency component of the electromagnetic noise radiated from the rectifier circuit unit is suppressed by the pedestal, and a relatively low frequency component is suppressed by the magnetic body. it can. Therefore, in the DC-DC converter, electromagnetic noise radiated from the rectifier circuit portion toward the side opposite to the base plate can be suppressed over a wide frequency range.

  As described above, according to the present invention, it is possible to provide a DC-DC converter that can suppress electromagnetic noise radiated from the rectifier circuit section over a wide frequency range.

FIG. 3 is a cross-sectional explanatory diagram of a part of the DC-DC converter in the first embodiment. Explanatory drawing of the rectifier circuit part and pedestal seen from the lamination direction in Example 1. FIG. 1 is a circuit diagram of a DC-DC converter in Embodiment 1. FIG. FIG. 3 is a cross-sectional explanatory diagram of a part of the DC-DC converter including the transformer in the first embodiment.

The magnetic body is preferably formed so as to cover the entire rectifier circuit unit, but may be formed so as to cover at least a part thereof. Moreover, the said magnetic body consists of ferrite, iron, etc., for example, The shape is not specifically limited.
The pedestal may be a conductor, and may be made of a nonmagnetic material such as copper or aluminum, or may be made of a magnetic material such as iron.

  However, it is preferable that the magnetic body is a core of a magnetic component that constitutes a part of the converter circuit. In this case, it is not necessary to add a new magnetic material to shield electromagnetic noise. Therefore, it is possible to obtain a low-cost DC-DC converter by reducing the number of parts. Examples of the magnetic component include the transformer, choke coil, filter reactor, and the like.

  The base plate is preferably made of a conductor. In this case, it is possible to suppress electromagnetic noise from the rectifier circuit section from being radiated from the base plate side. Thereby, it is possible to prevent electromagnetic noise from affecting the components adjacent to the base plate side with respect to the DC-DC converter.

  The pedestal is preferably connected to the base plate and grounded (claim 4). In this case, the potentials of the pedestal and the base plate are stabilized, and the electromagnetic noise shielding effect by these can be enhanced.

Further, when viewed from the laminating direction, the rectifier circuit portion, that have accommodated inside the inner circumferential contour of the annular shape in the pedestal. Thereby , weight reduction and cost reduction of a base are realizable, suppressing the reduction of the shielding effect of the electromagnetic noise by the said base. That is, in this case, most of the magnetic flux generated from the rectifier circuit portion can be passed inside the inner peripheral contour of the pedestal. Thereby, the eddy current by this magnetic flux can be efficiently produced in a base, and the shielding effect of electromagnetic noise can be obtained efficiently. On the other hand, the volume of the pedestal can be reduced to reduce its weight and cost.

Example 1
Examples of the DC-DC converter will be described with reference to FIGS.
As shown in FIGS. 1, 3, and 4, the DC-DC converter 1 of this example includes a transformer 2 including a primary coil 21 and a secondary coil 22, and a rectifier circuit unit 3 connected to the secondary coil 22. And a base plate 4 on which the transformer 2 and the rectifier circuit unit 3 are mounted.

As shown in FIG. 1, the DC-DC converter 1 includes a magnetic body 5 disposed so as to cover the rectifier circuit unit 3 from the side opposite to the base plate 4, and a magnetic body 5 fixed to the base plate 4 and the rectifier circuit. And a pedestal 6 supported from the part 3 side.
The pedestal 6 is made of a conductor and has an annular shape when viewed from the stacking direction of the base plate 4, the rectifier circuit unit 3, and the magnetic body 5 as shown in FIG. 2.

  The magnetic body 5 is a core of a magnetic component that constitutes a part of the converter circuit. In this example, the magnetic body 5 is a core of a choke coil 12 described later. The magnetic body 5 that is the core of the choke coil 12 is made of ferrite. The magnetic body 5 is disposed so as to cover the entire rectifier circuit unit 3 from the side opposite to the base plate 4.

  The base plate 4 is made of a conductor. In this example, the base plate 4 is made of a metal such as aluminum, for example, and constitutes a part of a case that houses the components of the DC-DC converter 1. That is, for example, the base plate 4 is configured as a bottom plate portion of an aluminum case. The pedestal 6 is fixed to a support part 41 provided on the base plate 4.

  The pedestal 6 is connected to the base plate 4 and grounded. When viewed from the main surface direction, the base plate 4 has an annular shape having a rectangular outer peripheral contour 62 and an inner peripheral contour 61 as shown in FIG. For example, the base 6 is formed by hollowing out the inside of a rectangular metal plate into a rectangle. Further, as shown in FIG. 1, a bent portion 63 is provided on the outer peripheral portion of the base 6. Thereby, the load bearing strength of the base 6 with respect to the magnetic body 5 (choke coil 12) supported by the base 6 is improved. In addition, it is preferable that the bending part 63 is formed over the perimeter of the outer periphery outline 62 of the base 6. FIG.

  The rectifier circuit unit 3 includes a plurality of diodes 31 as shown in FIG. The rectifier circuit unit 3 constitutes a diode module in which a plurality of diodes 31 are sealed with resin. The rectifier circuit section 3 which is this diode module has a substantially rectangular parallelepiped shape, and as shown in FIGS. 1 and 4, one of a pair of main surfaces 32 which is the widest surface is brought into contact with the base plate 4. In this state, it is mounted on the base plate 4. The rectifier circuit unit 3 may be mounted on the base plate 4 with an adhesive having thermal conductivity interposed therebetween.

  In the diode module (rectifier circuit unit 3), the plurality of diodes 31 are arranged side by side in a direction parallel to the main surface 32. The two input side terminals (anode side terminals) of the diode module are connected to the secondary coil 22 of the transformer 2, so that the diode module is substantially parallel to the main surface 32 of the rectifier circuit unit 3. One current loop is formed. From this current loop, electromagnetic noise is radiated in a direction orthogonal to the main surface 32, that is, in the stacking direction.

  Further, as shown in FIG. 4, the transformer 2 is also mounted on the base plate 4. A center tap 221 in the transformer 2 is in contact with and fastened to a boss 42 provided on the base plate 4. Thereby, the heat dissipation of the transformer 2 can also be improved.

As shown in FIG. 2, the rectifier circuit unit 3 is housed inside an annular inner peripheral contour 61 of the base 6 when viewed from the stacking direction. The inner peripheral contour 61 of the pedestal 6 is formed larger than the outer shape of the rectifier circuit unit 3 (diode module), and the rectifier circuit unit 3 is disposed inside the inner peripheral contour 61 when viewed from the stacking direction. It has become.
However, the magnitude relationship and the positional relationship between the inner peripheral contour 61 of the base 6 and the outer shape of the rectifier circuit unit 3 are not particularly limited to this. Further, the shape of the base 6 is not particularly limited as long as it is annular, and may be an annular shape, an elliptical shape, or other shapes.

  The DC-DC converter 1 is mounted on, for example, an electric vehicle or a hybrid vehicle, and is configured to step down the voltage of a driving battery as an input-side power source 7 and charge an auxiliary battery as an output-side power source. Can do. As shown in FIG. 3, the DC-DC converter 1 includes a switching circuit unit 11 that converts DC power input from the input-side power supply 7 into AC, and the switching circuit unit 11 serves as a primary coil 21 of the transformer 2. It is connected. The rectifier circuit unit 3 connected to the secondary coil 22 side of the transformer 2 includes a pair of diodes 31. The DC-DC converter 1 of this example is a half-bridge type, and the center tap 221 of the secondary coil 22 is electrically connected to the base plate 4 and grounded.

  A choke coil 12 is connected to the output side of the rectifier circuit unit 3. As a result, the output voltage is smoothed to prevent noise current from leaking through the output line. In this example, the core of the choke coil 12 is the magnetic body 5 disposed so as to cover the rectifier circuit unit 3.

  Note that the DC-DC converter 1 is not limited to the half-bridge type, and can be a full-bridge type, a forward type, and the like, and the wiring of the diode 31 in the rectifier circuit unit 3 has various shapes according to this. It can be taken. In this example, the diode rectification type DC-DC converter is shown. However, a synchronous rectification type DC-DC converter may be used. In this case, the rectification circuit unit 3 is, for example, a MOSFET instead of the diode 31. Can be configured.

Next, the function and effect of this example will be described.
In the DC-DC converter 1, the magnetic body 5 is disposed so as to cover the rectifier circuit unit 3 from the side opposite to the base plate 4. Thereby, the electromagnetic noise radiated from the rectifier circuit unit 3 to the side opposite to the base plate 4 can be shielded by the magnetic body 5. In particular, the magnetic body 5 can shield relatively low frequency noise. Therefore, since the magnetic body 5 is arranged so as to cover the rectifier circuit unit 3, relatively low frequency electromagnetic noise causes other parts in the DC-DC converter 1 and parts around the DC-DC converter 1. Can be suppressed.

  The DC-DC converter 1 includes a pedestal 6 that supports the magnetic body 5 from the rectifier circuit unit 3 side. Therefore, the pedestal 6 is disposed on the side opposite to the base plate 4 with respect to the rectifying circuit unit 3. The pedestal 6 is made of a conductor. Thereby, the electromagnetic noise radiated | emitted from the rectifier circuit part 3 can be shielded by the base 6. FIG. That is, when the magnetic flux (radiated magnetic flux) radiated from the rectifier circuit unit 3 is linked to the pedestal 6 made of a conductor, an eddy current flows through the pedestal 6 in a direction to cancel the radiated magnetic flux. Thereby, the electromagnetic noise radiated | emitted from the rectifier circuit part 3 can be suppressed.

Moreover, since the magnetic body 5 is mounted on the pedestal 6, the generation of magnetic flux due to the eddy current flowing through the pedestal 6 is promoted. Therefore, the radiant magnetic flux can be canceled out more effectively.
The pedestal 6 is formed in an annular shape when viewed from the stacking direction. Therefore, the eddy current generated when the radiant magnetic flux is linked flows in an annular shape along the annular pedestal 6. Therefore, even if the area of the pedestal 6 is reduced by the amount of the inner portion of the annular shape being hollowed out, the electromagnetic noise shielding effect is not particularly reduced. On the other hand, by making it annular, the base 6 can be reduced in weight and cost can be reduced.

  Further, since the electromagnetic noise due to the eddy current as described above can be reduced, the shielding effect by the pedestal 6 is particularly effective for relatively high frequency noise. That is, in the DC-DC converter 1, a relatively high frequency component of the electromagnetic noise radiated from the rectifier circuit unit 3 is suppressed by the pedestal 6, and a relatively low frequency component is suppressed by the magnetic body 5. it can. Therefore, in the DC-DC converter 1, electromagnetic noise radiated from the rectifier circuit unit 3 toward the side opposite to the base plate 4 can be suppressed over a wide frequency range.

  The magnetic body 5 is a core of the choke coil 12 that is a magnetic component that constitutes a part of the converter circuit. Therefore, it is not necessary to add a new magnetic body 5 to shield electromagnetic noise. Therefore, the number of parts can be reduced and the low-cost DC-DC converter 1 can be obtained.

  Further, since the base plate 4 is made of a conductor, it is possible to suppress electromagnetic noise from the rectifier circuit unit 3 from being radiated from the base plate 4 side. Thereby, it is possible to prevent electromagnetic noise from affecting the components adjacent to the base plate 4 side with respect to the DC-DC converter 1.

  The pedestal 6 is connected to the base plate 4 and grounded. Therefore, the electric potential of the base 6 and the base plate 4 is stabilized, and the electromagnetic noise shielding effect by these can be enhanced.

  Further, when viewed from the stacking direction, the rectifier circuit unit 3 is housed inside the annular inner peripheral contour 61 of the base 6. Therefore, weight reduction and cost reduction of the pedestal 6 can be realized while suppressing the reduction of the electromagnetic noise shielding effect by the pedestal 6. That is, in this case, most of the magnetic flux generated from the rectifier circuit unit 3 can be passed inside the inner peripheral contour 61 of the base 6. Thereby, the eddy current by this magnetic flux can be efficiently produced in the base 6, and the shielding effect of electromagnetic noise can be obtained efficiently. On the other hand, the volume of the pedestal 6 can be reduced to reduce its weight and cost.

  As described above, according to this example, it is possible to provide a DC-DC converter that can suppress electromagnetic noise radiated from the rectifier circuit section over a wide frequency range.

(Example 2)
In this example, the core of the transformer 2 is used as the magnetic body 5 arranged so as to cover the rectifier circuit unit 3 from the side opposite to the base plate 4.
The positional relationship between the base plate 4, the rectifying circuit unit 3, the pedestal 6, and the transformer 2 is substantially the same as the positional relationship between the base plate 4, the rectifying circuit unit 3, the pedestal 6, and the choke coil 12 shown in FIG. It is the same. That is, in FIG. 1, the configuration in which the choke coil 12 is replaced with the transformer 2 is the configuration of this example.
Others are the same as in the first embodiment.
Also in the case of this example, the same operational effects as those of the first embodiment can be obtained.
In addition to the choke coil core and the transformer core, for example, a core of another magnetic component such as a filter reactor core may be used as the magnetic body 5.

DESCRIPTION OF SYMBOLS 1 DC-DC converter 12 Choke coil 2 Transformer 3 Rectifier circuit part 4 Base plate 5 Magnetic body 6 Base

Claims (4)

A transformer (2) including a primary coil (21) and a secondary coil (22), a rectifier circuit unit (3) connected to the secondary coil (22), the transformer (2), and the rectifier circuit unit A DC-DC converter (1) having a base plate (4) on which (3) is mounted,
A magnetic body (5) disposed so as to cover the rectifier circuit portion (3) from the side opposite to the base plate (4);
A pedestal (6) fixed to the base plate (4) and supporting the magnetic body (5) from the rectifier circuit portion (3) side;
Pedestal (6), together with a conductor, when viewed from the laminate direction of the base plate (4) and the rectifier circuit portion (3) the magnetic body (5) have a shape which is circular,
The DC-DC converter (1) characterized in that the rectifier circuit portion (3) is housed inside the annular inner peripheral contour (61) of the pedestal (6) when viewed from the stacking direction. .   The DC-DC converter (1) according to claim 1, wherein the magnetic body (5) is a core of a magnetic component (2, 12) constituting a part of the converter circuit. Converter (1).   The DC-DC converter (1) according to claim 1 or 2, wherein the base plate (4) is made of a conductor.   The DC-DC converter (1) according to claim 3, wherein the pedestal (6) is connected to the base plate (4) and grounded.

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