JP7403220B2 - power converter - Google Patents

Description

The present invention relates to a power conversion device.

For example, Patent Document 1 discloses a configuration in which a filter capacitor for noise removal is connected to a three-phase inverter circuit. In this patent document 1, two filter capacitors are connected in series. Among these, the terminal of one filter capacitor is connected to the positive electrode side, the terminal of the other filter capacitor is connected to the negative electrode side, and the midpoint potential of the two filter capacitors is connected to the ground.

Japanese Patent Application Publication No. 2008-4953

However, in the configuration of Patent Document 1, it is necessary to provide filter capacitors on each of the positive electrode side and the negative electrode side. Therefore, the problem is that the power conversion device has many members and is large in size.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to downsize a power conversion device.

In order to achieve the above object, in the present invention, as a first means related to a power conversion device, a power conversion device includes a negative electrode side capacitor connected to the negative electrode side of a power supply, and an insulating substrate on which a power semiconductor element is mounted. The insulating substrate has a positive electrode side metal layer formed on one surface and electrically connected to the power semiconductor element, and a positive electrode side metal layer formed on the other surface at a position corresponding to the positive electrode side metal layer. and a ground side metal layer electrically connected to a grounding member, and the capacitance of the capacitor formed between the positive electrode side metal layer and the ground side metal layer is equal to that of the negative electrode side capacitor. A configuration is adopted in which the capacitance is set equal to the capacitance.

As a second means related to the power conversion device, a configuration is adopted in which the grounding member is a cooler joined to the insulating substrate.

A third means related to the power conversion device includes a conversion circuit that converts DC power into multiphase AC power, and the positive electrode side metal layer and the ground side metal layer have a plurality of layers corresponding to each phase of the AC power. A configuration is adopted in which a switch is provided for each switching element.

According to the present invention, the capacitor capacitance between the positive electrode side metal layer and the negative electrode side metal layer is used in the insulating substrate, and the total capacitance of the positive electrode side capacitor is made equal to the capacitance of the negative electrode side capacitor. ing. This makes it possible to reduce the number of capacitors that are separately connected on the positive electrode side. Therefore, it is possible to downsize the power conversion device.

1 is a schematic partial cross-sectional view showing a part of a power conversion device according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing a conversion circuit in an embodiment of the present invention. It is a typical partial sectional view showing a modification of the power converter device concerning one embodiment of the present invention. It is a schematic diagram of the conversion circuit which shows the modification of the power conversion device based on one Embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power conversion device according to the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the power conversion device 1 includes a casing 2, a cooler 3 (grounding member), an insulating substrate 4, a plurality of power semiconductor chips 5, connection conductors 6a and 6b, and a smooth a negative electrode side filter capacitor 8, a solder layer 9, and power lines 10n, 10p, 10w, 10v, and 10w.

The casing 2 is a resin member that accommodates a plurality of power semiconductor chips 5. The casing 2 is a container that holds the insulating substrate 4 with the insulating substrate 4 provided on the cooler 3 and the power semiconductor chip 5 placed on the insulating substrate 4.

The cooler 3 is provided with one surface in contact with the insulating substrate 4. The cooler 3 is, for example, of a water-cooled type, and cools the insulating substrate 4 and the power semiconductor chip 5 by circulating cooling water therein. Furthermore, the cooler 3 functions as a ground by being electrically connected to an external member (for example, an aluminum casing, not shown). That is, the cooler 3 is at the same potential as the ground.

The insulating substrate 4 has the conversion circuit A shown in FIG. 2 formed thereon, a power semiconductor chip 5 bonded to one surface, and a cooler 3 bonded to the other surface. The insulating substrate 4 includes a substrate main body 4a made of an insulating material such as ceramic, a plurality of positive electrode side copper layers 4b (positive electrode side metal layer) provided on the surface to which the power semiconductor chips 5 are bonded, and a cooler 3. On the surface to be joined to the positive electrode side copper layer 4b, a plurality of ground side copper layers 4c (ground side metal layer) provided at positions corresponding to the positive electrode side copper layer 4b are provided. Thereby, the insulating substrate 4 functions as a capacitor C between the positive electrode side copper layer 4b and the ground side copper layer 4c. Therefore, the positive electrode side copper layer 4b and the ground side copper layer 4c have the same shape and the same surface area, and the capacitance of the capacitor C is the capacitance required for removing common node noise, that is, the negative electrode side filter The surface area S is set to be equal to the capacitance of the capacitor 8. The surface area S is calculated as the thickness L of the substrate main body 4a based on the following formula. Note that ε indicates a dielectric constant.

The power semiconductor chip 5 is, for example, an RC-IGBT (Reverse-Conducting Insulated Gate Bipolar Transistor) having a built-in FWD (Free Wheeling Diode) in an IGBT (Insulated Gate Bipolar Transistor), and is connected to the insulating substrate 4 by a solder layer 9. It is joined. Such power semiconductor chips 5 are mounted for the purpose of converting direct current into alternating current by combining a plurality of them.

The connection conductor 6a is a conductive member whose one end is joined to the positive electrode side copper layer 4b by the solder layer 9, and whose other end is connected to the power line 10p buried in the casing 2.
The connecting conductor 6b is a conductive member whose one end is joined to the power semiconductor chip 5 by the solder layer 9, and whose other end is connected to the power line 10u buried in the casing 2. By connecting an external terminal to the connection conductor 6b, the power semiconductor chip 5 is electrically connected to the outside (motor, battery, etc.).

The smoothing capacitor 7 is connected in parallel to the conversion circuit A formed on the insulating substrate 4, as shown in FIG. The smoothing capacitor 7 has one end connected to the positive side of the conversion circuit A, and the other end connected to the negative side of the conversion circuit A.

The negative side filter capacitor 8 has one end connected to the negative side and the other end connected to the ground. The capacitance of this negative filter capacitor 8 is equivalent to that of the capacitor C formed on the insulating substrate 4.

The power line 10p is a wiring that electrically connects the positive electrode side P of the battery and the plurality of power semiconductor chips 5, as shown in FIGS. 1 and 2. The power line 10n is a wiring that electrically connects the negative electrode side N of the battery and the plurality of power semiconductor chips 5. The power lines 10u, 10v, and 10w are wirings that electrically connect each phase (U phase, V phase, W phase) of the motor M, which will be described later, to the conversion circuit A in the insulating substrate 4, respectively.

In such a power conversion device 1, as shown in FIG. 2, in the conversion circuit A, each of an AC U phase, an AC V phase, and an AC W phase is electrically connected to each phase of the motor M. Further, the conversion circuit A includes a plurality of switching elements for each phase. The conversion circuit A has one end connected to the positive electrode side P of the battery (power source), and the other end connected to the negative electrode side N of the battery. That is, the power conversion device 1 converts DC power supplied from a battery into three-phase AC power and supplies it to the motor M.

Further, in the conversion circuit A, one capacitor C is provided for each phase, and a negative electrode side filter capacitor 8 connected to the negative electrode side is provided. Common mode noise in the conversion circuit A is removed by using the capacitor C and the negative filter capacitor 8 having the same capacitance.

The power converter 1 according to the present embodiment has a positive electrode by making the capacitance of the capacitor C formed by the positive electrode side copper layer 4b and the ground side copper layer 4c equal to that of the negative electrode side filter capacitor 8 on the insulating substrate 4. It is possible to remove noise without providing a filter capacitor on the side. Therefore, it is possible to reduce the capacitance of the filter capacitor, and the power converter 1 can be downsized.

Further, according to the power conversion device 1 according to the present embodiment, the ground side copper layer 4c is electrically connected to the cooler 3, thereby being connected to the ground. Therefore, it is possible to remove common mode noise without providing a filter capacitor on the positive electrode side.

Further, in the power conversion device 1 according to the present embodiment, one capacitor C is provided for each of the plurality of switching elements of each phase. Therefore, the size of the insulating substrate 4 can be made uniform, and the mounting of the insulating substrate 4 becomes easy.

Although preferred embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the above embodiments. The various shapes and combinations of the constituent members shown in the embodiments described above are merely examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

For example, as shown in FIGS. 3 and 4, in the power conversion device 1, the capacitor C is connected to the power semiconductor chip 5 disposed on the negative side, thereby electrically connecting to the power line 10n on the negative side. It can also be used as a thing. Note that the capacitance of the capacitor C formed between the copper layers in the power semiconductor chip 5 on the positive electrode side is equal to the capacitance of the capacitor C formed between the copper layers in the power semiconductor chip 5 on the negative electrode side. It is set. At this time, the power converter 1 does not include the negative filter capacitor 8. In this case, as shown in FIG. 4, since a capacitor C is formed for each phase on the negative side, it is possible to reduce the capacitance of the negative side filter capacitor 8 and to reduce the size of the insulating substrate 4. can be made uniform, and mounting of the insulating substrate 4 becomes easy.

In the above embodiment, the ground side copper layer 4c is grounded by bonding the insulating substrate 4 to the cooler 3, but the present invention is not limited to this. The ground side copper layer 4c may be electrically connected to a separate external ground member.

In the above embodiment, one capacitor C is formed for each of the U phase, V phase, and W phase, but the present invention is not limited to this. The number of capacitors C provided may vary depending on the arrangement on the insulating substrate 4.

1 Power converter 3 Cooler 4 Insulating substrate 4b Positive side copper layer 4c Ground side copper layer 5 Power semiconductor chip 8 Negative side filter capacitor

Claims (3)

A power conversion device comprising a negative side capacitor having one end connected to the negative side of a power source and the other end connected to ground, and an insulating substrate on which a power semiconductor element is mounted,
The insulating substrate has a positive electrode side metal layer formed on one surface and to which the power semiconductor element is bonded, and a positive electrode side metal layer formed on the other surface at a position corresponding to the positive electrode side metal layer and electrically connected to a grounding member. and a ground side metal layer connected to the
The positive electrode side metal layer and the ground side metal layer each have the same shape and have the same surface area,
The power conversion device characterized in that the surface area is set so that the capacitance of the capacitor formed by the positive electrode side metal layer and the ground side metal layer is equal to the capacitance of the negative electrode side capacitor. . The power conversion device according to claim 1, wherein the grounding member is a cooler joined to the insulating substrate. A conversion circuit comprising a plurality of the power semiconductor elements and converting DC power supplied from the power source into multiphase AC power,
3. The power conversion device according to claim 1, wherein the positive electrode side metal layer and the ground side metal layer are provided for each of the plurality of power semiconductor elements corresponding to each phase of AC power.

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