Power conversion device

A power conversion device possesses a capacitor module, a power module, a circuit board on which a control circuit is mounted and which has a ground layer formed in a control circuit mounting region, a noise shielding plate, and a metal housing. The circuit board is above the capacitor module, and the noise shielding plate faces the control circuit mounting region between the circuit board and the capacitor module, in which the noise shielding plate has a plurality of connection parts to be electrically connected to the metal housing. A first end part on the power module side of the noise shielding plate is on the power module side more than a second end part on the power module side of the ground layer, and the connection part which is the closest to the first end part is provided on the power module side more than the second end part.

TECHNICAL FIELD

The present invention relates to a power conversion device.

BACKGROUND ART

In the power conversion device, a DC current is converted into an AC current by performing switching by a power semiconductor. The power conversion device possesses a power module which possesses a plurality of power semiconductors, a capacitor module to be connected to a DC bus bar between a DC power source and the power module in parallel with the power module, a drive circuit part which drives the power semiconductors, and a control circuit part which outputs a switching control signal to the drive circuit part and so forth, and these are contained in a metal housing (for example, see Patent Literature 1). In the power conversion device, a heavy electricity system (the power module, the drive circuit part, the capacitor module and so forth) and a light electricity system (the control circuit part) are contained in the same housing in this way.

As described above, since the power semiconductor switches high voltage, electromagnetic noise generates with switching. Therefore, in a conventional power conversion device, a member (a metal plate) which shields the electromagnetic noise to the control circuit part is provided in order to reduce conduction noise to a power supply source of the light electricity system.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2012-152104

SUMMARY OF INVENTION

Technical Problem

Incidentally, in power conversion devices to be loaded on electrically driven vehicles such as a hybrid vehicle, an electric vehicle and so forth, miniaturization of the devices is requested. Also a distance between a noise source and the control circuit part is made small and also an arrangement space of the noise shielding member is restrained with miniaturization. Therefore, noise shielding becomes insufficient and the conduction noise becomes a problem.

Solution to Problem

According to an aspect of the present invention, the power conversion device possesses a capacitor module which smooths a DC current from a DC power source, a power module which converts the DC current into an AC current on the basis of a drive signal from a drive circuit, a circuit board on which a control circuit which outputs a control signal for generating the drive signal is mounted and which has a ground layer formed in a control circuit mounting region, a noise shielding plate which shields noise from the power module, and a metal housing in which the capacitor module and the power module are contained side by side, the circuit board is contained above the capacitor module, and the noise shielding plate is contained at a position which faces the control circuit mounting region between the circuit board and the capacitor module, in which the noise shielding plate has a plurality of connection parts to be electrically connected to the metal housing, and a first end part on the power module side of the noise shielding plate is provided on the power module side more than a second end part on the power module side of the ground layer, and the connection part which is the closest to the first end part among the plurality of connection parts is provided on the power module side more than the second end part, in planar view viewed from above a containing part of the metal housing.

Advantageous Effect of the Invention

According to the present invention, the conduction noise which flows out of the power conversion device can be reduced.

DESCRIPTION OF EMBODIMENTS

In the following, modes for carrying out the present invention will be described with reference to the drawings. Although in the following, a power conversion device to be loaded on the electrically drive vehicles such as the electric vehicle, the hybrid vehicle and so forth will be described by way of example, the power conversion device of the present invention can also be applied to a power conversion device used in an ordinary industrial power supply system, not limited to the on-vehicle one.

FIG. 1is a block diagram showing one embodiment of the power conversion device according to the present invention. The power conversion device1converts a DC current supplied from a battery80which is a DC power source into an AC current and supplies it to a rotating electric machine MG. In addition, the rotating electric machine MG operates as a generator upon regeneration, and the power conversion device1converts the AC current from the rotating electric machine MG into the DC current and charges the battery80.

The power conversion device1possesses a power module10, a capacitor module20, a driver circuit30, a control circuit40and so forth, and a housing100which contains them. DC bus bars2a,2bprovided in the power conversion device1are connected to a DC connector90at one ends and are connected to the power module10at the other ends. The battery80is connected to the DC connector90. The capacitor module20possesses a capacitor21which smooths the DC current, a capacitor22ato be connected to the DC bus bar2aand a housing ground terminal, and a capacitor22bto be connected to the DC bus bar2band the housing ground terminal. The capacitors22a,22bwork so as to release common mode noise to the ground.

The power module10possesses a plurality of switching power semiconductors11,13which configure an inverter circuit. In the present embodiment, an insulated gate type bipolar transistor is used as the switching power semiconductor and will be denoted as the IGBT for short hereinafter. Three sets of series circuits of the IGBT11and the IGBT13are provided on the power module10in correspondence with alternate currents of three phases of a U-phase, a V-phase and a W-phase. Diodes12,14are respectively parallel-connected to the IGBTs11,13. Incidentally, as the switching power semiconductor, a metal oxide semiconductor-type field effect transistor (denoted as the MOSFET for short hereinafter) may be used. In that case, the diodes12,14become unnecessary.

One ends of corresponding AC bus bars3a,3b,3care connected between the IGBT11and the IGBT13in each series circuit. The other ends of the respective bus bars3a,3b,3care connected to an AC connector70to which the rotating electric machine MG is to be connected. The currents flowing through the AC bus bars3a,3b,3care detected by a current sensor50.

The control circuit40possesses a microcomputer (hereinafter, described as a “Micon”) adapted to arithmetically process a switching timing of the IGBTs11,13. A target torque value which is requested to the rotating electric machine MG1is input into the control circuit40from a not shown host controller via a connector for signal60. The control circuit40generates control pulses which are control signals for controlling the IGBTs11,13on the basis of the target torque value which has been input from the host controller, current information from the current sensor50, and a magnetic pole position of a rotor of the rotating electric machine MG and inputs them into the driver circuit30. Incidentally, the magnetic pole position is the one which is detected on the basis of a detection signal which has been output from a rotating magnetic pole sensor (not shown) such as a resolver provided on the rotating electric machine MG.

Wiring for gate drive signal, wiring for emitter current detection and so forth are provided on signal wiring15which connects together the power module10and the driver circuit30. The driver circuit30supplies a drive pulse for controlling each of the IGBTs11,13to each of the IGBTs11,13via the wiring for gate drive signal on the basis of a control pulse from the control circuit40. Each of the IGBTs11,13performs a conducting or cut-off operation on the basis of the drive pulse from the driver circuit30and converts the DC current into a three-phase AC current.

FIGS. 2, 3are schematic diagrams describing arrangement of each constitutional component in the power conversion device1.FIG. 2is a sectional diagram having viewed the power conversion circuit1sideways. The housing100possesses a case body100awhich contains the constitutional components, and a cover100bwhich covers an upper opening of the case body100a. The housing100is formed by a conductive material such as a metal and so forth (for example, an aluminum material), and serves so as to reduce emission of radiation noise from the power conversion device1, or intrusion of the radiation noise into the power conversion device1.

A heavy electricity unit200to which a DC current of several hundred volts is supplied, a metal base plate300for noise shielding, and the abovementioned circuit board400are arranged in order from the bottom face side of the case body100a, in a containing space which is formed by the case body100aand the cover100bof the housing100. The power module10, the capacitor module20, the DC bus bars2a,2b, and the AC bus bars3ato3cwhich have been described above are included in the heavy electricity unit200. A gate terminal150is drawn out of the power module10so as to extend upward. A leading end of the gate terminal150is connected to gate wiring (not shown) of the circuit board400.

In the circuit board400(FIG. 2), the control circuit40is mounted in a board region400a above the metal base plate300, and the driver circuit30(FIG. 1) is mounted in a board region400babove the power module10. In addition, a ground pattern layer401relating to the control circuit40is formed in the board region400a.

Since a high voltage of several hundred volts is applied from the battery80to the power module10of the power conversion device1, and the DC current is converted into the AC current by switching that high voltage at a high speed, noise is generated from the power module10. Therefore, the abovementioned metal base plate300is provided in order to prevent the noise of the heavy electricity unit200from coupling with the ground pattern layer401of the board region400a. The noise is shielded by arranging the metal base plate300and conduction noise from the ground pattern layer401to a power supply source500of the light electricity system is reduced.

The metal base plate300is screw-fixed onto protruded parts102of a base plate fixing part101formed in the case body100aand is electrically connected to the case body100a. In addition, the circuit board400which has been arranged above the metal base plate300is fixed onto the metal base plate300via conductive supports410. The supports410electrically connect together the ground pattern layer401of the circuit board400and the metal base plate300. The case body100ais connected to a chassis ground of a vehicle, and a potential of the metal base plate300which has been fixed to the case body100aand a potential of the ground pattern layer401of the circuit board400which has been fixed to the metal base plate300become a potential of the chassis ground.

Incidentally, in the power conversion device1of the present embodiment, the control circuit40of the light electricity system and the driver circuit30of the heavy electricity system are mounted on the same circuit board400in order to promote miniaturization of the device. Therefore, distances between the heavy electricity unit200, and the control circuit40and the metal base plate300are made shorter in comparison with the case of the aforementioned conventional power conversion device. Therefore, noise coupling to the metal base plate300becomes more noticeable and it becomes a cause for an increase in conduction noise in the ground pattern layer401.

In addition, since connection parts of the gate terminal150and the power module10which have been described above with the DC bus bars2a,2bare present on an upper part of the power module10, the metal base plate300cannot be extended to a part under the board region400b. Therefore, the noise from the power module10is directly coupled with the ground pattern layer401of the circuit board400and causes the conduction noise to generate.

FIG. 3is a plan view viewing the inside of the power conversion device1from above the device, and in regard to the circuit board400, a board position has been shown only by a broken line for easy understanding of a positional relation among the power module10, the metal base plate300, and the ground pattern layer401. Though not shown in the drawing, the capacitor module20is arranged under the metal base plate300, and the capacitor module20and the power module10are connected together by the DC bus bars2a,2b. Each of the DC bus bars2a,2bis configured by a wide-width conductive plate and one pair of the conductive plates is made into a layered structure.

A plurality of connection parts301a,301b,301c,301dare formed on the metal base plate300, and these connection parts301ato301dare fixed to the protruded parts102of the base plate fixing part101. The noise of the power module10couples with the metal base plate300and the ground pattern layer401of the circuit board400. However, in the case of the ground pattern layer401, part of the noise is shielded by the metal base plate300, and therefore a degree of coupling is small in comparison with the metal base plate300.

In the present embodiment, the metal base plate300which is the noise shielding plate has the plurality of connection parts301ato301dto be electrically connected to the base plate fixing part101, and an end part300aon the power module side of the metal base plate300is provided on the power module10side more than an end part401aon the power module side of the ground pattern layer10. Further, in the plurality of connection parts301ato301d, the connection part301awhich is the closest to the end part300aof the metal base plate300is provided on the power module10side more than the end part401aof the ground pattern layer401.

That is, in regard to distances in a left-right direction (a direction from the power module10toward the noise shielding plate) shown inFIG. 3which has been viewed from above the containing space, when a distance between the power module10and the end part401aof the ground pattern layer401is denoted by A, a distance between the power module10and the connection part301a(a fixing position for screw fixing) is denoted by B, distances between the end part300aof the metal base plate300and the connection parts301a,301bare denoted by C, D, and a distance between the power module10and the end part300aof the metal base plate300is denoted by E, they are set such that all of A>B, C<D, A>E are satisfied. Incidentally, although inFIG. 3, power module side base points of the distances A, B, E are set at a right end (the ground pattern layer401side) of the power module10, the center of the power module10may be set as the power module side base points thereof.

As described above, the closer it comes to the power module10which is a noise generation source, the larger coupling of the metal base plate300with the noise is and the larger the current density of noise current is. The noise current generated in the end part300aof the metal base plate300flows to the connection part301awhich is the closest to the end part300aas schematically shown by a broken line R1and flows from the connection part301ato the chassis ground via the base plate fixing part101and the case body100a.

FIG. 4are the ones showing comparative examples relative to a configuration shown inFIG. 3. A configuration shown inFIG. 4(a)is an example of a case where they have been configured so as to be A<E. Since also in this case, they are set so as to be A>B, C<D, the noise current flows from the end part300aof the metal base plate300to the connection part301awhich has been arranged on the power module side more than it similarly to the case inFIG. 3. However, since the ground pattern layer401extends to the shown left side more than the end part300aof the metal base plate300, a current caused by this noise current is generated in the ground pattern layer401and a reduction in conduction noise cannot be promoted.

In addition, in a configuration shown inFIG. 4(b), although C<D and A>E are satisfied, they are set so as to be A<B. In this case, the noise current flows from the end part300aof the metal base plate300toward the connection part301awhich is the shortest in current path as shown by a broken line R2. The connection part301ais arranged on the opposite side of the power module10relative to the end part300aof the metal base plate300. Therefore, when the noise current flows from the end part300aof the metal base plate300to the connection part301alike the broken line R2, the noise current flows right under the ground pattern layer401and the conduction noise cannot be reduced as in the case inFIG. 4(a).

On the other hand, in the embodiment shown inFIG. 3, since the end part300aof the metal base plate300is located on the power module side more than the end part401aof the ground pattern layer401(A>E), and the connection part301awhich is the closest to the end part300aof the metal base plate300is located on the power module side more than the end part401aof the ground pattern layer401(A>B), the noise current shown by the broken line R1would flow through a place remote from the ground pattern layer401. As a result, the conduction noise generated in the ground pattern layer401can be reduced. In addition, the noise level of the entire of the board region400acan be reduced, and a degree of freedom in installation of the connector for signal60becomes high.

Incidentally, the end part401aof the ground pattern layer401moves backward from the end part300aof the metal base plate300to a noise shielding region (a region on the shown right side of the end part300a) of the metal base plate300by setting them so as to be A>E. As a result, coupling thereof with the noise in the grand pattern layer401can be reduced, and the noise current density in the vicinity of the end part401aof the ground pattern layer401can be reduced.

FIG. 5is a diagram showing another example in a case where they have been set so as to be A>B, C<D, A>E. In the example shown inFIG. 5, the connection part301awhich is the closest to the end part300aof the metal base plate300is arranged not on the power module side relative to the end part300abut on its opposite side (the side away from the power module10). In this case, a metal base plate region between the end part300aof the metal base plate300and the end part401aof the ground pattern layer401is widened, and the end part401aof the ground pattern layer401can be largely separated from the noise current path as shown by a broken line R3. In addition, direct coupling of the noise to the ground pattern layer401can be reduced. As a result, the reduction in conduction noise can be promoted.

FIGS. 6, 7are diagrams showing the second modification of the present embodiment. Also in this case, the abovementioned conditions A>B, C<D, A>E are satisfied. In the abovementioned example inFIGS. 2, 3, the arrangement region of the metal base plate300was limited to a region almost above the capacitor module20between the heavy electricity unit200and the circuit board400. On the other hand, in the second modification, as shown inFIGS. 6, 7, the metal base plate300was provided over the entire of a region above the heavy electricity unit200, and an opening302through which the gate terminal150passes was formed in a region above the power module10. On the metal base plate300, a connection part301eis provided also on the shown left side of the opening302, and the connection part301eis fixed to the base plate fixing part101of the case body100a.

An edge of the metal base plate300which is present between the board region400ain which the control circuit40is to be mounted and the power module10corresponds to the end part300aof the abovementioned metal base plate300. Therefore, in the case of the second modification, an edge portion on the ground pattern layer401side of the opening302is equivalent to the abovementioned end part300a. The noise current flows from the end part300aof the metal base plate300to the connection part301awhich is the closest to it as shown by a broken line R4. Since the end part401aof the ground pattern layer401is far from the path (the broken line R4) of the noise current, the reduction in conduction noise in the ground pattern layer401can be promoted.

In the case of the second modification, since a region between the end part300aof the metal base plate300and the end part401aof the ground pattern layer401is widened as shown inFIG. 7, a noise shielding effect is improved in comparison with the metal base plate300shown inFIGS. 2, 3, and the reduction in conduction noise in the circuit board400can be improved further.

Incidentally, since in the second modification, the end part300aof the metal base plate300is located at a position above the power module10, the power module side base points of the distances A, B, E are set on the center of the power module10.

FIG. 8is a diagram showing the third modification of the present embodiment. In the third modification, a metal spring member600was added to the configuration shown inFIG. 2. The spring member600is provided so as to interpose between the vicinity of the end part300aof the metal base plate300and the cover100b, a lower end part is pressed against the metal base plate300and an upper end part is pressed against the cover100b. That is, also the spring member600functions as a connection part which electrically connects together the metal base plate300and the housing100.

Since a contact position of the spring member600with the metal base plate300is closer to the end part300athan it is to the connection part301a, the noise current in the end part300aof the metal base plate300flows to the cover100bvia the spring member600as shown by the broken line R4. Also in this case, since the path (the broken line R4) of the noise current is remote to the end part401aof the ground pattern layer401, the conduction noise in the ground pattern layer401can be reduced.

For example, in the example shown inFIG. 4(a), the connection part301ais provided near the end part300aof the metal base plate300. However, even in a case where it cannot be made into such a configuration, this spring member600functions as the connection part which is the closest to the end part300aof the metal base plate300by providing the spring member600in the vicinity of the end part300aof the metal base plate300. As a result, the noise current flows through the spring member600, and the conduction noise in the ground pattern layer401can be reduced. Incidentally, although the configuration inFIG. 8is the one in which the spring member600has been added to the configuration shown inFIG. 2, it can also be applied to the configuration shown inFIG. 7similarly.

In the above-described embodiment, as shown inFIG. 3, the metal base plate300for noise shielding has the plurality of connection parts301ato301dto be electrically connected to the metal housing100, and the end part300aof the metal base plate300is provided on the power module10side more than the end part401aof the ground pattern layer401. Then, in the plurality of connection parts301ato301d, the connection part301awhich is the closest to the end part300aof the metal base plate300is provided on the power module10side more than the end part401aof the ground pattern layer401. The noise current generated in the end part300aof the metal base plate300flows to the connection part301athrough the place remote from the end part401aof the ground pattern layer401, and the conduction noise in the ground pattern layer401can be reduced by having made them into such a configuration.

In the configuration shown inFIG. 3, the driver circuit30is mounted in the region that the power module10faces of the circuit board400on which the control circuit40is mounted. In a case where the driver circuit30and the control circuit40are provided on the same circuit board400in this way, since the driver circuit30is provided so as to come close to the power module10, also the control circuit40would be arranged at a position near the power module10. Accordingly, the reduction in conduction noise can be promoted by configuring the metal base plate300and the ground pattern layer401aas shown inFIG. 3. Incidentally, also in the case of a configuration in which the driver circuit30is provided in the power module10, the configuration of the metal base plate300and the ground pattern layer401ashown inFIG. 3can be applied similarly.

Incidentally, the above description is absolutely one example, and when interpreting the invention, it is neither limited to nor bound by a corresponding relation between the matters described in the abovementioned embodiment and the matters described in the scope of the patent claims.

The disclosure of the following priority basic application is incorporated herein as the citation.

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