JP2003319665A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter that enables a high-frequency capacitor used as a snubber circuit to be miniaturized or abolished. <P>SOLUTION: This power converter is provided with a switching module 2 that includes a switching element 6 to convert DC power into AC power, a smoothing capacitor 3 that smoothes the DC power supplied to the switching module 2, and a pair of bus bars 4, 5 that electrically connect the positive and negative poles of the switching module 2 to each of the smoothing capacitors 3 respectively and that are arranged to have each opposite regions in such a way that at least a part of the main surfaces faces roughly parallel to each other. By inserting a high-dielectric member 9 between the pair of bus bars 4, 5 in the opposite regions, a capacitor for a snubber circuit is constituted of the pair of bus bars 4, 5 and the high-dielectric member 9. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter represented by an inverter that reversely converts DC power into AC power.

[0002]

2. Description of the Related Art In recent years, electric vehicles and hybrid electric vehicles have been attracting attention as environmentally friendly vehicles.
Partial commercialization has begun. For example, a hybrid electric vehicle is equipped with an electric drive system in addition to a conventional engine. This electric drive system includes a battery that is a DC power source, an inverter device that is a power conversion device, an AC motor that is an electric motor, and the like. In a vehicle equipped with this electric drive system, the DC power supplied from the battery is converted into AC power by an inverter device, and the AC motor is driven using this AC power to obtain propulsive force of the vehicle.

FIG. 4 is a circuit diagram of a general electric drive system mounted on a vehicle. As described above, the electric drive system includes the battery 1, the inverter device that converts the DC power obtained from the battery 1 into the AC power, and the AC motor 8 that is driven by the AC power output from the inverter device. The inverter device includes a switching module 2 including a switching element 6, a switching control circuit (not shown) that controls the switching element 6, a smoothing capacitor 3 that smoothes DC power supplied to the switching element 6, and a switching device. The busbars 4 and 5 electrically connecting the module 2 and the smoothing capacitor 3 are provided.

An IGBT is used as the switching element 6.
(Insulated Gate Bipolar Transistor) and power MO
S-FET (Metal Oxide Semiconductor-Field Effect)
Transistor) is used. Further, the switching control circuit is an ECU (Electrical Control U
nit) to turn on switching element 6
By controlling the ON / OFF operation by PWM (Pulse Width Modulation), the inverter device is operated under optimum conditions according to the running state of the vehicle.

As the switching module 2, there are one in which the above-described switching control circuit is arranged outside the package of the switching module 2 and one in which the above-mentioned switching control circuit is incorporated in the package, called an IPM (Integrated Power Module). In recent years, IPMs have become the mainstream due to demands for improved assemblability and miniaturization of inverter devices.

As shown in FIG. 4, the P and N terminals, which are the positive and negative electrodes of the switching module 2, are connected to the battery 1
Are electrically connected to the positive electrode and the negative electrode of. Further, a smoothing capacitor 3 for smoothing the DC power supplied from the battery 1 is connected in parallel between the switching module 2 and the battery 1. The P and N terminals of the switching module 2 and the smoothing capacitor 3
Bus bars 4 and 5 which are plate-shaped bodies made of a conductive material are used for the connection wiring connecting the positive electrode and the negative electrode. On the other hand, the output side terminals of the switching module 2, U, V, and W terminals are electrically connected to the respective input terminals of the three-phase AC motor 8.

[0007] Normally, an electric drive system mounted on a vehicle is required to generate a very large driving force, and therefore a component corresponding to a large electric power having a large rated voltage and a large rated current is used. Therefore, the smoothing capacitor 3 also needs to have a very large capacity. As a smoothing capacitor 3 used in a practically used hybrid electric vehicle, several hundred μF to several thousand μF
A capacitor having a capacitance of is used. For this reason, the smoothing capacitor 3 becomes a very large capacitor, and is usually installed outside the package of the switching module 2.

In the above-described inverter device, switching element 6 is switched at a high speed operation of, for example, 10 kHz. Therefore, the internal wiring of the switching module 2 and the wiring inductance of the bus bars 4 and 5 cannot be ignored. The stray inductance due to these connection wirings causes a large surge voltage to be applied to the switching element 6 during switching. If the breakdown voltage of the switching element 6 is set sufficiently higher than the power supply voltage, no problem will occur, but if there is no margin, the surge element may destroy the switching element 6.

Therefore, it is necessary to dispose the smoothing capacitor 3 and the switching element 2 close to each other in order to reduce the wiring inductance. As a result, the connection wiring can be shortened, so that the wiring inductance is reduced. Also, the wiring inductance can be reduced by arranging the reciprocating lines of the connection wiring close to each other. This is because the wiring inductance is reduced due to mutual inductance by arranging the round-trip lines close to each other.

However, this alone cannot completely suppress the generation of the surge voltage. Therefore, by separately providing a circuit for protecting the switching element 6 called a snubber circuit, an inverter device configured to absorb the surge voltage generated in the circuit and prevent the surge voltage from being applied to the switching element 6 is provided. It is often seen.

FIG. 5 is a diagram showing a circuit configuration example of the snubber circuit. The snubber circuit 10 has a high frequency capacitor 11 connected between the collector and the emitter of the switching element 6 as shown in FIG. 5A (C snubber), and FIG.
A high-frequency capacitor 11 as shown in FIG. 5B in which a resistor 12 is connected in series (CR snubber), or a diode 13 in parallel with the resistor 12 as shown in FIG. 5C.
There are known ones that are connected (DRC snubber).
These snubber circuits 10 are appropriately selected depending on the operating conditions of the inverter device.

FIG. 6 is a schematic perspective view showing the structure of the above-mentioned inverter device. As shown in the figure, the smoothing capacitor 3 and the switching module 2 are connected by a pair of bus bars 4 and 5. Although not shown in the figure, the pair of bus bars 4 and 5 are further connected to the battery 1. Since the smoothing capacitor 3 has a very large capacity, it is divided into three parts and arranged, and connected to the switching module 2 in parallel.

The pair of bus bars 4 and 5 have facing areas in which the main surfaces thereof face each other and are close to each other in the area where the switching module 2 and the smoothing capacitor 3 are connected. This facing area is provided to reduce the above-mentioned wiring inductance. In this facing area, a pair of bus bars 4, 5
The insulating member 14 is interposed between them. This insulating member 14
Uses an insulating paper such as Nomex (R) to prevent a short circuit caused by disposing the bus bars 4 and 5 in close proximity. By interposing the insulating member 14 between the pair of bus bars 4 and 5, the wiring inductance is reduced and at the same time a short circuit is prevented.

Further, P of the switching module 2
A snubber circuit 10 including a high frequency capacitor 11 is connected between the N terminals so as to be located outside the package of the switching module 2. This snubber circuit 10 constitutes, for example, the above-mentioned C snubber, and its capacitance is about several μF, which is significantly smaller than that of the smoothing capacitor 3. By providing the snubber circuit 10, the surge voltage applied to the switching element 6 during the switching operation is absorbed, and the switching element 6 is prevented from being destroyed.

[0015]

However, when mounting the inverter device on an automobile, there is a strong demand for miniaturization of parts, and there is a strong demand for eliminating or miniaturizing the snubber circuit. In the inverter device having the above-described configuration, it is necessary to separately arrange a snubber circuit including a high-frequency capacitor outside the package, and the device is increased in size, and the number of parts is increased to increase the manufacturing cost.

Therefore, it is an object of the present invention to provide a power converter capable of miniaturizing or eliminating a high frequency capacitor used as a snubber circuit.

[0017]

A power conversion device according to the present invention includes a power conversion circuit, a smoothing capacitor, and a pair of conductive plates. The power conversion circuit includes a switching element and converts DC power to AC power. The smoothing capacitor smoothes the DC power supplied to the power conversion circuit, and the pair of conductive plates electrically connect the positive and negative electrodes of the power conversion circuit and the smoothing capacitor to each other, and at least mutually. Are arranged such that a part of the main surface of the has a facing area facing each other substantially in parallel. In the facing area, the high dielectric member is located between the pair of conductive plates so as to contact both of the pair of conductive plates, so that the pair of conductive plates and the high dielectric member form a capacitor.

As described above, a high dielectric member having a high dielectric constant is arranged between the facing regions of a pair of conductive plates that are closely arranged to reduce the wiring inductance, and the high dielectric member is used as a pair of conductive plates. By sandwiching by, the capacitor is formed in this facing area. As a result, it is possible to downsize or eliminate the high-frequency capacitor of the snubber circuit, which was required separately in the past, and to downsize the power converter and reduce the manufacturing cost by reducing the number of parts. To be

In the power converter according to the present invention, the high dielectric member is preferably a plate-shaped ceramic dielectric.

As described above, it is possible to use a plate-shaped ceramic dielectric as the high dielectric member. Since the ceramic dielectric has a high dielectric constant and is easily processed, it is suitable as a high dielectric member in the present power conversion device.

In the power conversion device according to the present invention, the high dielectric member is preferably a film-shaped high dielectric substance containing polypropylene or polyethylene terephthalate as a main raw material.

As described above, by using the film-form high dielectric material containing polypropylene or polyethylene terephthalate, the assembling property is improved and the manufacturing cost can be reduced. When a sufficient capacitance cannot be obtained, the capacitance can be increased by increasing the facing area of the pair of conductive plates or by reducing the thickness of the film-shaped high dielectric material.

In the power converter according to the present invention, preferably, in the cross section including the pair of conductive plates and the high dielectric member, the high dielectric member extends to the outside of the end faces of the pair of conductive plates. ing.

As described above, by disposing the high dielectric member so as to extend outside the facing area of the pair of conductive plates, it is possible to obtain a sufficient creeping distance between the pair of conductive plates.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing a structure of a power conversion device according to an embodiment of the present invention. The circuit configuration of the power conversion device according to the present embodiment is the same as that of the power conversion device described as the conventional example above, and thus description thereof will not be repeated.

As shown in FIG. 1, the inverter device according to the present embodiment includes a switching module 2 including a switching element 6 therein, a smoothing capacitor 3 for smoothing DC power supplied to the switching element 6, It is provided with a pair of bus bars 4 and 5 that electrically connect the switching module 2 and the smoothing capacitor 3. As shown in the figure, the P and N terminals, which are the positive and negative electrodes of the switching module 2, are connected to the positive and negative terminals of the smoothing capacitor 3 via a pair of bus bars 4 and 5 which are plate-shaped bodies made of a conductive material. It is connected. Although not shown in the figure, the pair of bus bars 4 and 5 are connected to a positive electrode and a negative electrode of the battery 1 (not shown).

The pair of bus bars 4 and 5 have facing areas in which the main surfaces thereof face each other and are arranged close to each other in the area where the switching module 2 and the smoothing capacitor 3 are connected. This facing area is provided to reduce the above-mentioned wiring inductance. In the facing area, a high dielectric member 9 is interposed between the pair of bus bars 4 and 5. As the high dielectric member 9, it is desirable to use, for example, a plate-shaped body made of a ceramic dielectric or a film-shaped high dielectric made mainly of polypropylene or polyethylene terephthalate. As a result, a capacitor is formed by the pair of bus bars 4, 5 and the high-dielectric member 9 sandwiched therebetween, and the wiring inductance can be reduced while preventing a short circuit between the pair of bus bars 4, 5 arranged close to each other. Planned.

The pair of bus bars 4, 5 and the high dielectric member 9
The capacitor constituted by and performs the same function as the high frequency capacitor of the snubber circuit arranged outside the package of the switching module 2 in the conventional inverter device. That is, the surge voltage applied to the switching element 6 can be absorbed by this capacitor.

FIG. 2 is a sectional view taken along line II-II in FIG. As a shape of the high-dielectric member 9 sandwiched between the pair of bus bars 4 and 5, as shown in FIG. 2A, a case where the end surface thereof coincides with the end surface of the bus bars 4 and 5, and a case where FIG. As shown in (b), it is considered that the bus bars 4 and 5 extend outward from the end surfaces.

FIG. 2A is applicable when the insulating distance between the pair of bus bars 4 and 5 is equal to or less than the thickness d of the high-dielectric member 9, and the high-dielectric member 9 is an expensive member such as a ceramic dielectric. It is effective in terms of cost reduction when using such as.

On the other hand, FIG. 2B shows a pair of bus bars 4,
This is applicable when the insulation distance of 5 is larger than the thickness d of the high dielectric member 9, and in particular, a film-shaped high dielectric member whose main raw material is polypropylene or polyethylene terephthalate having a lower dielectric constant than the ceramic dielectric. Is effective when is used. As is well known, in a capacitor, the capacity increases as the bipolar plates are brought closer to each other. For this reason, when a dielectric member having a relatively low dielectric constant is used, it is possible to increase the capacitance by bringing the main surfaces of the bus bars 4 and 5 serving as the bipolar plates of the capacitor close to each other. However, when the bus bars 4 and 5 are brought close to each other, the creepage distance thereof is shortened, so that it becomes difficult to secure the insulation property on the creepage. Therefore, by projecting the end surface of the dielectric member,
The creepage distance is increased from d to (d + 2e), and it is possible to increase the capacitance of the capacitor and ensure the insulation on the creepage surface.

As described above, in the facing area in which the pair of bus bars are closely arranged, by arranging the high-dielectric member instead of the insulating member conventionally arranged so as to be interposed therebetween, switching is performed in this facing area. A snubber circuit that suppresses the application of surge voltage to the element is configured. Therefore, it is not necessary to provide a separate snubber circuit, or even if a separate snubber circuit is provided, a low-capacity high frequency capacitor is sufficient. As a result, the power converter can be downsized, and the number of parts is reduced, so that the manufacturing cost can be reduced.

FIG. 3 is a schematic perspective view of an inverter device showing another modification of the embodiment of the present invention. As is well known, by increasing the area of both electrodes of the capacitor,
It is possible to increase the capacity of the capacitor. Therefore, in this modification, the capacitance of the capacitor is increased by increasing the facing area of the pair of conductive plates that are the bipolar plates of the capacitor.

That is, in this modification, bus plates 15 and 16 having a significantly larger facing area than the above-mentioned bus bar are used as a pair of conductive plates for connecting the switching module 2 and the smoothing capacitor 3. There is.
Along with this, the high dielectric member 9 sandwiched between the bus plates 15 and 16 is also larger than that described above.
As a result, the capacity of the capacitor can be increased. Further, when a bus plate having a large facing area is used as in this modification, the heat dissipation performance of the bus plate is also improved, which is also preferable in terms of cooling the inverter device. In this modification, the switching module 2 and the battery 1 are connected by the cables 17, 18 instead of the bus plates 15, 16. In this way, it is also possible to connect the switching module and the battery using the cable.

In the above-described embodiment, the case where the connection wiring for connecting the switching module and the smoothing capacitor is constructed as a pair of separately independent conductive plates has been described, but the conductive plates are integrally configured. It is also possible to make a laminated substrate with a thin ceramic conductor interposed therebetween.

Further, in the above-mentioned embodiment, the wiring structure inside the switching module is not mentioned, but the internal wiring inside the switching module is constructed so as to have a pair of conductive plates and have a facing area. There are many cases. Therefore, the snubber circuit can be downsized or eliminated by applying the present invention to the internal wiring of the switching module.

Further, in the above-described embodiment, the explanation has been given by exemplifying the inverter device for inversely converting the DC power into the AC power as the power conversion device. However, in the converter device for converting the AC power into the DC power in the forward direction. The present invention can also be applied. In this case as well, the capacitor may be formed by interposing a high-dielectric member between the conductive plates in the facing area of the pair of conductive plates that connect the converter device and the smoothing capacitor.

As described above, the above-described embodiments disclosed this time are exemplifications in all respects, and are not restrictive.
The technical scope of the present invention is defined by the claims, and includes the meaning equivalent to the description of the claims and all modifications within the scope.

[0039]

As in the present invention, a snubber circuit, which is conventionally provided separately, is configured by interposing a high-dielectric material in the facing area of a pair of conductive plates that connect the power conversion circuit and the smoothing capacitor. It becomes possible to abolish or downsize the high frequency capacitor. As a result, it is possible to provide a power converter that is small and can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a structure of an inverter device according to an embodiment of the present invention.

2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a schematic perspective view of an inverter device showing a modified example of the embodiment of the invention.

FIG. 4 is a diagram showing a circuit configuration of a general electric drive system.

FIG. 5 is a diagram showing a circuit configuration of a general snubber circuit.

FIG. 6 is a schematic perspective view for explaining the structure of a conventional inverter device.

[Explanation of symbols]

1 Battery, 2 Switching Module, 3 Smoothing Capacitor, 3a Positive Terminal of Smoothing Capacitor, 3b
Negative electrode terminal of smoothing capacitor, 4, 5 bus bar, 6
Switching element, 7 freewheeling diode, 8 AC motor, 9 high dielectric material, 10 snubber circuit, 11 high frequency capacitor, 12 resistor, 13 diode, 15,
16 bus plates, 17 and 18 cables.

Claims (4)

[Claims] 1. A power conversion circuit, which includes a switching element, converts DC power into AC power, a smoothing capacitor that smoothes DC power supplied to the power conversion circuit, the power conversion circuit, and the smoothing circuit. Each of the positive electrodes and the negative electrodes of the capacitors are electrically connected to each other, and a pair of conductive plates arranged so that at least a part of the main surfaces thereof face each other in substantially parallel, and a pair of conductive plates, A high dielectric member is positioned between the pair of conductive plates so as to contact both of the pair of conductive plates, thereby forming a capacitor with the pair of conductive plates and the high dielectric member. Power converter. 2. The power conversion device according to claim 1, wherein the high dielectric member is a plate-shaped ceramic dielectric. 3. The power conversion device according to claim 1, wherein the high dielectric member is a film-shaped high dielectric material containing polypropylene or polyethylene terephthalate as a main raw material. 4. The cross section including the pair of conductive plates and the high dielectric member, wherein the high dielectric member extends to the outside of the end faces of the pair of conductive plates. The power converter according to claim 1.