POWER CONVERSION DEVICE

A power conversion device includes a first solid pattern provided on a multi-layer wiring substrate and connected to a positive side of a first power supply, a second solid pattern provided on the multi-layer wiring substrate and connected to a negative side of the first power supply, and a third solid pattern provided on the multi-layer wiring substrate and connected to a negative side of a second power supply that is insulated from the first power supply. The first solid pattern and the third solid pattern are arranged so as to at least partially overlap in a first direction of the multi-layer wiring substrate, and the second solid pattern and the third solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a power conversion device.

2. Description of the Background Art

To reduce noise generated by a power conversion device, generally, an across-the-line capacitor (hereinafter, referred to as X capacitor) is mounted as a measure against15normal mode (differential mode) noise, and further, a line capacitor (referred to as Y capacitor) is mounted as a measure against common mode noise.

As conventional art, it is disclosed that a Y20capacitor formed by interposing an insulator between a P conductor and an extended portion of a ground conductor equipped with a module, and another Y capacitor arranged opposite to the P conductor with respect to the extended portion of the ground conductor and formed by interposing an insulator between an N conductor and the extended portion of the ground conductor are configured as filter circuit elements.Patent Document 1: Japanese Laid-Open Patent Publication No. 2013-219919

In a power conversion device according to Patent Document 1, in order to form a Y capacitor, bus bars on both of positive electrode and negative electrode are extended, and furthermore, an insulator is needed. Thus a problem of increasing the size and cost of the power conversion device occurs.

As the Y capacitor, it is also conceivable that a laminated ceramic capacitor is mounted on a multi-layer wiring substrate. However, in that case, the number of components is increased. Thus a problem of increasing the size and cost of the power conversion device occurs.

SUMMARY OF THE INVENTION

The present disclosure has been made to solve the above problem, and an object of the present disclosure is to reduce the size of a power conversion device and reduce cost, while effectively suppressing noise.

A power conversion device according to the present disclosure converts power of a first power supply by a plurality of switching elements and includes a multi-layer wiring substrate. The power conversion device includes a first solid pattern provided on the multi-layer wiring substrate and connected to a positive side of the first power supply, a second solid pattern provided on the multi-layer wiring substrate and connected to a negative side of the first power supply, and a third solid pattern provided on the multi-layer wiring substrate and connected to a negative side of a second power supply that is insulated from the first power supply. The first solid pattern and the third solid pattern are arranged so as to at least partially overlap in a first direction of the multi-layer wiring substrate, and the second solid pattern and the third solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate.

In the power conversion device according to the present disclosure, the device size is reduced and, further, cost is reduced, while effectively suppressing noise.

First Embodiment

The present embodiment relates to a power conversion device and, for example, relates to a filter for reducing noise in the power conversion device mounted on an electrified vehicle.

FIG.1is a circuit diagram showing a configuration of the power conversion device according to the first embodiment. As shown inFIG.1, a power conversion device1000is formed by components from a DC power supply101to a three-phase AC motor500, and a multi-layer wiring substrate1001including some of the components. The DC power supply (first power supply)101is connected to a smoothing capacitor300via a positive side wiring201and a negative side wiring202. At a stage subsequent to the smoothing capacitor300, a three-phase inverter circuit composed of a U-phase arm401in which switching elements401a,401bare connected in series, a V-phase arm402in which switching elements402a,402bare connected in series, and a W-phase arm403in which switching elements403a,403bare connected in series, is connected. At a stage subsequent to the three-phase inverter circuit, the three-phase AC motor500is connected. The switching elements401ato403bof the U-phase arm401to W-phase arm403are ON/OFF controlled in a predetermined order to generate three-phase AC current and to drive the three-phase AC motor500.

The multi-layer wiring substrate1001is one of the components that form the power conversion device1000, and is a necessary substrate in order to operate or support the power conversion device1000. A DC power supply (second power supply)102insulated from the DC power supply101is connected to the multi-layer wiring substrate1001. In addition, a plurality of power supplies produced by the power supply102, for example, a power supply for a microcomputer which controls power conversion of the power conversion device, a power supply for a current sensor, and further a power supply for driving a driver circuit410, are mounted on the multi-layer wiring substrate1001. The driver circuit410which is necessary in order to drive the switching elements401ato403b, and the other circuits such as a voltage sensor and a current sensor are also mounted on the multi-layer wiring substrate1001. A negative side of the DC power supply102is grounded to form a GND (ground) potential of the power conversion device1000.

As the switching elements401ato403b, an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or the like is used.FIG.1shows an example in which the MOSFET is used.

Electric charge is accumulated in the smoothing capacitor300while the power conversion device1000is in operation, and thus the smoothing capacitor300has electric charge accumulated therein even when the power conversion device1000is not in operation. A discharge resistor600discharges electric charge accumulated in the smoothing capacitor300so as not to cause malfunction due to the accumulated electric charge when the power conversion device1000is not in operation. The discharge resistor600is connected in parallel to the smoothing capacitor300.

A Y capacitor701on a positive side is arranged between the positive side wiring201connected to a positive side of the DC power supply101and a GND wiring800connected to the negative side of the DC power supply102. In addition, a Y capacitor702on the negative side is arranged between the negative side wiring202connected to the negative side of the DC power supply101and the GND wiring800. As a measure against common mode noise among noise generated by switching of the switching elements401ato403b, the Y capacitors701,702is effective and has an effect as a noise filter in order to reduce noise.

In addition, an X capacitor703is arranged between the positive side wiring201and the negative side wiring202. As a measure against normal mode noise among noise generated by switching of the switching elements401ato403b, the X capacitor703is effective and has an effect as a noise filter in order to reduce noise.

Normal mode noise is transmitted in a mode in which noise returns from a plus side of the power supply through a minus side to a noise source and such a mode is referred to as differential mode. On the other hand, common mode noise is transmitted in a mode in which noises having the same phase advance in the same direction on both of the plus side and the minus side of the power supply and return through the GND to the noise source.

FIG.2is a side sectional view showing a multi-layer wiring substrate portion according to the first embodiment,FIGS.3A to3Care plane views showing the multi-layer wiring substrate portion according to the first embodiment,FIG.3Ais the plane view showing a first wiring layer (surface layer),FIG.3Bis the plane view showing a second wiring layer, andFIG.3Cis the plane view showing a third wiring layer. InFIG.2, it is defined that Z direction is a substrate thickness direction (referred to as first direction), the upper side in the substrate thickness direction is the upper side in the first direction, and the lower side in the substrate thickness direction is the lower side in the first direction. InFIG.2andFIGS.3A to3C, X, Y directions each indicate a substrate horizontal plane direction (referred to as second direction).

A plurality of components are mounted on the multi-layer wiring substrate1001, and some of them are components that generate heat by operation or the like of the power conversion device1000.FIG.2andFIGS.3A to3Cillustrate the discharge resistors as heat generating components600, but a surface-mounted type semiconductor switching element, an integrated circuit (IC), and a reactor of a transformer or the like are conceivable as the heat generating component600other than the discharge resistor.

In wiring layers positioned directly below at least some of the heat generating components600, that is, on the lower side in the first direction, a positive side solid pattern (positive side wiring, first solid pattern)201and a GND solid pattern (GND wiring, third solid pattern)800are arranged so as to at least partially overlap each other, as seen from the substrate thickness direction (first direction) of the multi-layer wiring substrate1001. In addition, a negative side solid pattern (negative side wiring, second solid pattern)202and the GND solid pattern (GND wiring, third solid pattern)800are arranged so as to at least partially overlap each other, as seen from the substrate thickness direction (first direction) of the multi-layer wiring substrate1001. InFIG.3BandFIG.3C, parts indicated by dotted lines respectively show parts positioned directly below the heat generating components600, on the lower side in the first direction.

When layers having different patterns overlap each other as seen from the substrate thickness direction (first direction) of the multi-layer wiring substrate1001, a capacitance component (parasitic capacitance) is produced and its capacitance value can be calculated by the following formula (1), where C: parasitic capacitance [F], εr: relative permittivity, ε0: vacuum permittivity [F/m], S: pattern overlapping area [m2], and d: distance between patterns [m].

As indicated by the formula (1), the positive side solid pattern201and the GND solid pattern800or the negative side solid pattern202and the GND solid pattern800are wired so as to at least partially overlap each other, as seen from the substrate thickness direction (first direction) of the multi-layer wiring substrate1001. Thereby the capacitances of the Y capacitor701and the Y capacitor702are respectively produced.

According to the configuration of the power conversion device1000of the present embodiment, in the multi-layer wiring substrate1001indispensable to the power conversion device1000, a noise filter effective against common mode noise can be provided without adding any element such as a laminated ceramic capacitor, while effectively utilizing a space on the lower side in the first direction of the heat generating components600mounted on the multi-layer wiring substrate1001. Therefore, a small-sized, inexpensive power conversion device1000can be provided.

Next, it will be described that a permittivity ε (εr×ε0) of a material forming the multi-layer wiring substrate1001has a positive gradient. An example of the material whose permittivity has a positive gradient with respect to temperature rise is, for example, a glass epoxy substrate (FR-4). The heat generating components600mounted on the multi-layer wiring substrate1001raise the temperature of the wiring layer positioned directly below the heat generating components600, and the permittivity is also increased. According to the formula (1), when the permittivity ε is increased, the parasitic capacitance C produced by the pattern is also increased. Thereby the Y capacitors701,702can be formed more effectively.

As described above, the Y capacitor is formed as the parasitic capacitance to be produced by the solid pattern while effectively utilizing the wiring layer positioned directly below the heat generating components of the multi-layer wiring substrate. Thus a small-sized, inexpensive power conversion device can be provided while suppressing common mode noise.

Second Embodiment

FIG.4is a side sectional view showing a multi-layer wiring substrate portion according to the second embodiment,FIGS.5A to5Dare plane views showing the multi-layer wiring substrate portion according to the second embodiment,FIG.5Ais the plane view showing a first wiring layer (surface layer),FIG.5Bis the plane view showing a second wiring layer,FIG.5Cis the plane view showing a third wiring layer, andFIG.5Dis the plane view showing a fourth wiring layer.

InFIG.4andFIGS.5A to5D, the positive side solid pattern201and the negative side solid pattern202are wired on separate wiring layers.

InFIG.2andFIGS.3A to3C, the positive side solid pattern201and the negative side solid pattern202are wired on the same wiring layer. In this case, it is required to provide an insulation distance between the patterns in the substrate horizontal plane direction (second direction). When the insulation distance is provided, pattern areas of the positive side solid pattern201and the negative side solid pattern202are reduced. On the other hand, in the second embodiment, the positive side solid pattern201and the negative side solid pattern202are wired on separate wiring layers, and thus it is required to provide the insulation distance between the patterns in the substrate horizontal plane direction (second direction). Accordingly, the positive side solid pattern201and the negative side solid pattern202can be more widely installed. According to the formula (1), when the pattern area S is increased, the parasitic capacitance C to be obtained is also increased. Thereby the Y capacitors701,702can be more effectively formed. InFIG.4, the positions of the positive side solid pattern201and the negative side solid pattern202appear to completely match each other as seen from the upper side in the first direction. But it is not required to completely match each other.

Next, as shown inFIG.4, an effect of wiring the GND solid pattern800between the positive side solid pattern201and the negative side solid pattern202will be described.

For example, it is assumed that the positive side solid pattern201, the negative side solid pattern202, and the GND solid pattern800are arranged in this order from the upper side in the first direction, and wired on separate wiring layers. In order to form the Y capacitor701on the positive side, while the positive side solid pattern201and the GND solid pattern800are wired so as to overlap each other, it is required to wire the positive side solid pattern201and the negative side solid pattern202so as not to overlap as seen from the first direction of the multi-layer wiring substrate1001. Accordingly, an area in which the negative side solid pattern202can be wired is decreased. Thus, the capacitance value of the Y capacitor702on the negative side is decreased.

According to the formula (1), it is also found that the value of the parasitic capacitance C is inversely proportional to a distance d between the patterns. It is found that while a distance between the negative side solid pattern202and the GND solid pattern800is decreased, a distance between the positive side solid pattern201and the GND solid pattern800is increased, and thus the capacitance value of the Y capacitor701on the positive side is decreased.

On the other hand, when the GND solid pattern800is wired between the positive side solid pattern201and the negative side solid pattern202as shown inFIG.4, it is not required that the positive side solid pattern201and the negative side solid pattern202are wired so as not to overlap as seen from the first direction of the multi-layer wiring substrate1001. And the distance between the positive side solid pattern201and the GND solid pattern800is decreased, and the distance between the negative side solid pattern202and the GND solid pattern800is decreased. Thereby the parasitic capacitance C can be obtained most efficiently.

Third Embodiment

FIG.6is a side sectional view showing a multi-layer wiring substrate portion according to the third embodiment. As shown inFIG.6, a GND solid pattern800A, the positive side solid pattern201, the negative side solid pattern202, and a GND solid pattern800B are arranged in this order from the upper side in the first direction, and are respectively wired on separate wiring layers. The Y capacitor701is formed by the positive side solid pattern201and the GND solid pattern800A, the Y capacitor702is formed by the negative side solid pattern202and the GND solid pattern800B, and further, the X capacitor703is formed by the positive side solid pattern201and the negative side solid pattern202. Accordingly, measures against both common mode noise and normal mode noise can be taken without adding any element. And size reduction and cost reduction of the power conversion device can be achieved.

The GND solid pattern800A, the negative side solid pattern202, the positive side solid pattern201, and the GND solid pattern800B may be arranged in this order, which is different from that shown inFIG.6, from the upper side in the first direction and they are respectively wired on separate wiring layers. As described above, in the multi-layer wiring substrate1001, the GND solid patterns800A,800B may be respectively arranged at the topmost layer portion and the lowermost layer portion, and the positive side solid pattern201and the negative side solid pattern202may be arranged between the two GND solid patterns800A,800B. Furthermore, inFIG.6, the positions of the positive side solid pattern201and the negative side solid pattern202appear to completely match each other as seen from the upper side in the first direction. But it is not required to completely match each other. That is, the positive side solid pattern201and the negative side solid pattern202are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate1001in order to form the X capacitor703.

Next, as shown inFIG.2,FIG.4, andFIG.6, the GND solid pattern800grounded to a housing900of the power conversion device1000will be described.

The GND solid pattern800is connected to a through hole801to be wired up to a substrate surface. The substrate surface portion of the through hole801is grounded to the housing900. Since the GND solid pattern800is grounded to the housing900, the impedance between the Y capacitors701,702formed by the solid pattern and the housing900is small. Thereby noise attenuation characteristics can be improved.

The GND pattern of a substrate is generally connected to the negative side of the power supply102via a harness. However, when the GND pattern is connected via the harness, a path to the power supply102become longer, thereby impedance is increased. In that case, the housing900and the GND solid pattern800are grounded at a substrate screw fixing portion. The substrate includes a large number of substrate screw fixing portions. When the GND solid pattern800is grounded at the screw fixing portion close to the GND solid pattern800to be grounded, the path is shorter than that via the harness, thus the impedance between the Y capacitors701,702and the housing900is small.

When the path to the GND is long, a value of self-inductance is unnecessarily added to the Y capacitors701,702, their characteristics are deteriorated. Thus desired attenuation characteristics cannot be obtained. On the other hand, when the path to the GND is shortened in order to suppress the value of self-inductance, desired attenuation characteristics of the Y capacitor can be obtained. Thereby attenuation characteristics of the noise filter can be improved.

The above configuration can save the areas necessary for the positive side solid pattern201, the negative side solid pattern202, and the GND solid pattern800. As a result, size reduction and cost reduction of the power conversion device1000are achieved.

Next, an effect obtained when the heat generating component is the discharge resistor600will be described.

As shown in the formula (2), loss is generated in the discharge resistor600.

In a conventional electrified vehicle, the battery voltage for driving a motor is, for example, 400 V to 800 V, and the same voltage is also applied to the smoothing capacitor300. According to the formula (2), the higher the voltage is, the larger the loss to be generated in the discharge resistor600is. To smoothly perform discharge via the discharge resistors600without failure, a large number of chip resistors are, for example, connected in series or in parallel with each other in order to form a discharge circuit. Thereby it is able to reduce loss per resistor and to smoothly discharge without failure.

Since a plurality of the chip resistors are arranged, the mounting area is larger than that of a surface-mounted type semiconductor switching element, an integrated circuit (IC), or a reactor of a transformer or the like. The larger the mounting area of the heat generating components (discharge resistors600) is, the larger the area of the wiring layer directly below the heat generating components is. Accordingly, the areas of the positive side solid pattern201, the negative side solid pattern202, and the GND solid pattern800can be enlarged. According to the formula (1), the larger the pattern area S is, the larger the parasitic capacitance C to be obtained is. Thereby it is able that Y capacitors701,702are more effectively formed.

In addition, the higher the voltage of the DC power supply101is, the higher the noise level to be generated from the power conversion device1000is. In this case, since the voltage to be applied across the discharge resistor600is also increased, the loss in the discharge resistor600is increased, and the heat generation amount is also increased. therefore the parasitic capacitance C of the Y capacitors701,702is increased. That is, the higher the voltage of the DC power supply101is, the higher the noise level is. However, the parasitic capacitance C of the Y capacitors701,702is also increased. Thus it is effective that the heat generating component is the discharge resistor600.

Here, an example in which the discharge resistor600is used in order to discharge electric charge of the smoothing capacitor300is described. But a discharge resistor for discharging electric charge of the X capacitor703can be used to obtain the same effect.

In addition, the power conversion device1000is described as an inverter circuit in the above embodiment. But the same effect is also obtained when the power conversion device1000is a converter circuit.

Hereinafter, modes of the present disclosure are summarized as additional notes.

A power conversion device which converts power of a first power supply by a plurality of switching elements and includes a multi-layer wiring substrate, the power conversion device including:a first solid pattern provided on the multi-layer wiring substrate and connected to a positive side of the first power supply;a second solid pattern provided on the multi-layer wiring substrate and connected to a negative side of the first power supply; anda third solid pattern provided on the multi-layer wiring substrate and connected to a negative side of a second power supply that is insulated from the first power supply, whereinthe first solid pattern and the third solid pattern are arranged so as to at least partially overlap in a first direction of the multi-layer wiring substrate, and the second solid pattern and the third solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate.

The power conversion device according to additional note 1, whereinheat generating components are mounted on the multi-layer wiring substrate, andin a wiring layer positioned on the lower side in the first direction of at least some of the heat generating components,the first solid pattern and the third solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate, and the second solid pattern and the third solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate.

The power conversion device according to additional note 1 or 2, wherein a permittivity of a material forming the multi-layer wiring substrate has a positive gradient with respect to temperature rise.

The power conversion device according to any one of additional notes 1 to 3, whereinthe first solid pattern and the second solid pattern are respectively arranged on separate layers in the multi-layer wiring substrate, andthe third solid pattern is arranged between the first solid pattern and the second solid pattern.

The power conversion device according to any one of additional notes 1 to 4, whereina Y capacitor is formed by the first solid pattern and the third solid pattern arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate, andanother Y capacitor is formed by the second solid pattern and the third solid pattern arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate.

The power conversion device according to any one of additional notes 1 to 3, whereinthe third solid patterns are respectively arranged at a topmost layer portion and a lowest layer portion in the first direction of the multi-layer wiring substrate, andthe first solid pattern and the second solid pattern are respectively arranged on separate layers, between the third solid pattern arranged at the topmost layer portion and the third solid pattern arranged at the lowest layer portion.

The power conversion device according to additional note 6, wherein the first solid pattern and the second solid pattern are arranged so as to at least partially overlap in the first direction of the multi-layer wiring substrate in order to form an X capacitor.

The power conversion device according to any one of additional notes 1 to 7, wherein the third solid pattern is grounded to a housing of the power conversion device.

The power conversion device according to additional note 2, whereina smoothing capacitor is provided between positive side and negative side of the first power supply, andthe heat generating components are discharge resistors connected in parallel with the smoothing capacitor.