CA3060965A1 - High density low inductance power inverter - Google Patents

Abstract

ABSTRACT
A power inverter including a busbar assembly with a first and an opposing second connection surface. A plurality of power modules are electrically coupled to the busbar assembly from the first connection surface and arranged in a coplanar fashion. A plurality of capacitors are electrically coupled to the busbar assembly from the second connection surface and arranged in a coplanar fashion. Each of the power modules is aligned with a corresponding capacitor such that the parasitic inductance introduced by electrical connections therebetween is minimized.

Description

HIGH-DENSITY LOW-INDUCTANCE POWER INVERTER
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None TECHNICAL FIELD

[0002] The present disclosure relates to electronic circuits, and in particular, to power inverters for electric automotive vehicles.
BACKGROUND

[0003] A power inverter for an electric automotive vehicle is typically a power conversion device that converts a DC voltage, such as from the vehicle's battery, to a suitable AC voltage to drive an electric motor, for example.

[0004] Generally, these power inverters include an inverter power circuit using semiconductor switches, such as insulated-gate bipolar transistors (IGBTs) that are finely controlled by a controller, to yield a suitable output voltage.

[0005] Specifically, the inverter input receives direct electrical current and supplies an alternating current as the output. Components of the inverter typically include power modules, DC capacitor, DC bus bars, and heatsink. The DC portion of the power conversion device generally comprises two electrical nodes: a positive and a negative. The AC portion of the power conversion device comprises N electrical nodes where N is the number of output phases.

[0006] The DC capacitor and DC bus bars are connected between the positive electrical nodes and negative electrical nodes, whereas the power modules are interconnected between the DC and AC electrical nodes. The power modules may be configured in a half-bridge configuration, wherein an upper switch which is connected between the positive electrical node and the phase N node, and the lower switch which is connected between the phase N node and the negative node. Other configurations, such as full-bridge configuration may also be possible.

[0007] Typically, the main power components such capacitor and power modules, are arranged side-by-side with electrical connections between them formed by bus bars on top. FIG. 1 illustrates a power inverter 10 with the commonly known side-by-side arrangement of the components. As shown, the power inverter 10 includes two DC input busbars 12 that may receive DC energy source from a battery (not shown) for example. Power modules 16 are positioned next to the DC link capacitor 14 in a coplanar fashion. The capacitor 14 is electrically coupled to the DC input of the power modules 16 via busbar 18 on top. The AC output of power modules 18 are electrically coupled to the output phase busbars 20. As may be appreciated by those skilled in the art, by being placed in a coplanar fashion as shown in FIG. 1, the main power components of the inverter 10 may require relatively long electrical connections that may introduce considerable parasitic inductance into the switching circuits.
The large parasitic inductances may in turn cause more stress on the semiconductor switches and thereby reduce the electrical current capacity of the inverter system.

[0008] Furthermore, as shown in FIG. 1, known inverters 10 typically employ one large DC link capacitor, such as capacitor 14, to be shared amongst all of the power modules 16, which may further contribute to the parasitic inductance of the inverter 10.
Additionally, the single large capacitor may require additional cooling elements to dissipate the heat generated therein, which may result in a bigger inverter package that is more costly to manufacture.

[0009] Further still, for certain high performance applications, it may be desirable to use the latest fast-switching power semiconductor technology, such as silicon carbide. However, the use of such fast switching semiconductor devices in a power conversion system generally requires the entire power electronic assembly to be optimized for low stray (parasitic) inductance.

[0010] Accordingly, there is a need for an improved power inverter that is more compact with minimized parasitic inductance.
SUMMARY OF THE INVENTION

[0011] In accordance with an example embodiment of the present disclosure, there is provided a power inverter, comprising: a busbar assembly configured to receive a DC energy source, the busbar assembly having a first connection surface and an opposing second connection surface; a power module configured to be electrically coupled to the busbar assembly from the first connection surface; and a capacitor configured to be electrically coupled to the busbar assembly from the second connection surface; wherein the power module is aligned with the capacitor.
BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Reference will now be made, by way of example, to the accompanying drawings which show example embodiments of the present application, and in which:

[0013] FIG. 1 shows an isometric view of a prior art power inverter in which the main power components are arranged in a side-by-side fashion that is commonly known in the art;

[0014] FIG. 2 shows an exploded isometric view of an inverter in accordance with one exemplary embodiment of the present disclosure;

[0015] FIG. 3 shows a partial isometric view taken along line A-A of the inverter in FIG. 2;

[0016] FIG. 4 shows an isometric view of an inverter in accordance with another exemplary embodiment of the present disclosure;

[0017] Similar reference numerals may have been used in different figures to denote similar components.
DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] With reference to FIGS. 2 and 3, there is provided an inverter 22 in accordance with one exemplary embodiment of the present disclosure in what is referred to as a "flat configuration". In the illustrated embodiment, inverter 22 includes a printed circuit board (PCB) control board 24, capacitors 26, a laminated busbar assembly 28, power modules 30, and a heat sink 32.

[0019] The PCB control board 24 is well known in the art. Typically, gate drivers located on the PCB control board 24 control the IGBTs in the power modules 30 by regulating their supply voltage. Additional circuitry may be located on the PCB control board 24 to issue command inputs and signals from various sensors to control the gate driver stage.

[0020] The inverter 22 may be electrically coupled to an external battery (not shown) through what is typically referred to as a DC link. DC link capacitors 26 may be used to stabilize the DC link and protect the battery and the power modules 30, by temporarily absorbing electrical energy, for example, to minimize ripple from the switching operation.

[0021] In the illustrated embodiment, the inverter 22 includes six capacitors 26 = arranged in two coplanar rows of three capacitors 26. However, it is to be appreciated that any number of capacitors 26 may be arranged in any suitable manner as discussed in further detail below.

[0022] Each capacitor 26 includes a first metal contact 34 running along a first longitudinal side of the capacitor thereby defining a positive capacitor node, and a second metal contact 36 running along a second opposing longitudinal side of the capacitor thereby defining a negative capacitor node. Each electrical contact 34 and 36 includes three flanges 38 configured to be electrically coupled onto the laminated busbar assembly 28. It is to be appreciated that the number or size of flanges 38 may vary.

[0023] As best shown in FIG. 3, each flange 38 is configured with a mounting opening 39 configured to receive a fastener 40. In some embodiments, fasteners may be of metallic construction and are electrically conductive. In some embodiments, fastener 40 maintains firm electrical contact between flanges 38 and layers of the laminated busbar 28 by exerting a downward pressure onto flange 38 up against portions of the laminated busbar assembly 28. Busbar spacers 42 may serve as a backstop. It is be appreciated that other means of establishing electrical connection between the flanges 38 and laminated busbar assembly 28 may be used. In some embodiments, the capacitor 26 may be customized with a desired form-factor as will be discussed in more detail below.

[0024] In some embodiments, such as the one shown in FIGS. 2 and 3, inverter 22 includes the same number of power modules 30 as the number of capacitors 26. As shown, the six power modules 30 are similarly arranged in two rows of three.
In some embodiments, the power modules 30 may be IGBT power modules that typically contain semiconductor devices (not shown) arranged in, for example, "half-bridge"
configurations with two IGBT's being connected in series extending from a positive DC
input node 44 to a negative DC input node 46. It is to be appreciated that other types of semiconductor-based power modules, such as full bridge configurations based modules, may be used.

[0025] As shown, each power module 30 includes a positive DC input node and a negative DC input node 46, as well as a phase output node 48. Each node and 46 include a corresponding number of fastener receiving openings 50 configured to secure, and form electrical contact with, fasteners 40. In the illustrated embodiment, the phase output node 48 is electrically coupled to an extension busbar 52, which may extend outside of the inverter package (not shown) for forming electrical connections with other components such as the motor (not shown).

[0026] In some embodiments, busbars spacers 42a and 42b, collectively referred to as busbar spacers 42, may be used to elevate the laminated busbar assembly above the phase output busbars 52 to, at least in part, electrically insulate the DC
laminated busbar assembly 28 from the busbar 52 which carries AC phase output signals. In some embodiments, the busbar spacers 42 are electrically conductive and may serve to form electrical contacts between the DC input nodes 44, 46 of the power module 30 and the laminated busbar assembly 28. As shown in the illustrated embodiment, both of the positive DC input node 44 and the negative DC input node 46 are in electrical contact with busbar spacers 42a and 42b respectively. The busbar spacers 42 extend up to, and forms electrical contact with, respectively layers within the laminated busbar assembly 28 as will be discussed in more detail below.

[0027] In the illustrated embodiment, the power modules 30 are in thermal contact with heat sink 32. Heat sink 32, as is commonly known in the art, may be liquid or air cooled. In some embodiments, all electrical contacts between the capacitors 26, the busbar assembly 28, and the power module 30 may also be thermally conductive such that heat generated within the power modules 30, as well as within the DC
link capacitors 26, and the busbar assembly 28 may be, at least partially, extracted through the heat sink 32.

[0028] The laminated busbar assembly 28 is a unified metallic structure for power distribution between power modules 30 and capacitors 26. The busbar assembly may be electrically coupled to a DC energy source, such as a battery (not shown) and serves as a power distribution component within the inverter 22. Specifically, the illustrated laminated busbar assembly 28 includes a first electrical layer 54 and a second electrical layer 56. As shown a positive DC contact tab 58a extends perpendicularly from an edge of the first electrical layer 54. Similarly, a negative DC
contact tab 58b extends perpendicularly from an edge of the second electrical layer 56.
The DC input contacts 58 may be configured to be in electrical contact with a DC
energy source, such as a battery (not shown). In some embodiments, DC input contact 58a may be in electrical contact with the positive electrical node of the DC
energy source, and input contact 58b may be in electrical contact with the negative electrical node of the DC energy source. Contact 58a may be integrally formed with the first electrical layer 54 to define a positive node, and similarly, contact 58b may be integrally formed with the second electrical layer 56 to define a negative node. As shown, three non-conductive insulation layers 58 may cover and separate the first and second electrical layers 54 and 56, thereby electrically insulating the positive node from the negative node. Those skilled in the art would appreciated that other means for establishing DC link with the DC energy source may be possible.

[0029] The first and second electrical layers 54, 56 may be of metallic construction and are electrically conductive. In the example embodiment shown in FIGS. 2 and 3, the laminated busbar assembly 28 is substantially flat as defined by the overall shape and size of the two electrical layers 54 and 56. The dimensions of the busbar 28 may be varied depending on, among other factors, the number and size of the main power components of the inverter and/or the arrangement of such components.

[0030] In the illustrated embodiment, the capacitors 26 are arranged in coplanar fashion on a first connection surface 60 of the laminated busbar 28. The flanges 38 extending from the first metal contact 34 of the capacitor 26 are in electrical contact with the first electrical layer 54 of the laminated busbar 28. The flanges 38 extending from the second metal contact 36 of the capacitor 26 are in electrical contact with the second electrical layer 56.

[0031] The power modules 30 are arranged in coplanar fashion just below the second connection surface 62. Busbar spacers 42a, extending from the positive DC
input node 44 of the power module 30 are in electrical contact with the first electrical layer 54. Busbar spacers 42b, extending from negative DC input node 46 of the power module 30, are in electrical contact with the second electrical layer 56.

[0032] In the illustrated embodiment, the number of DC link capacitors 26 is identical to that of power modules 30. Thus, each power module 30 may have a corresponding DC link capacitor 26 connected thereto, which may reduce the parasitic inductance compared to the known art.

[0033] Further, in embodiments such as the one shown in FIGS. 2 and 3, the capacitors 26 may be customized with a form factor that is similar to that of the power modules 30. This may permit each capacitor 26 to be in vertical alignment directly over one of the power modules 30s below as shown in the figures. Accordingly, each opening 39 on the flanges 38 from the capacitor 26 may be in vertical alignment with one of the openings 50 on the DC input nodes of the power module 30, which may advantageously minimize the electrical connection distance and hence minimize the parasitic inductance introduced therein. Advantageously, the low inductance connection between the power modules 30 and capacitors 26 may allow the capacitors 26 to act as snubbers that, for example, may limit the voltage overshoot across the upper or lower IGBT switches inside the power modules 30 when switching from "closed" to "opened"
state (turn-off of the switches).

[0034] Furthermore, by arranging the capacitors 26 and the power modules 30 on two separate and parallel planes directly over one another, the inverter 22 in accordance with the present disclosure may allow higher density inverters with a more compact inverter package.

[0035] FIG. 4 illustrates an inverter 72 in accordance with another exemplary embodiment of the present disclosure in what is referred to as the "U-shaped configuration". Generally stated, inverter 72 employs a U-shaped laminated busbar that may position capacitor and power module pairs around a centrally received heat sink.
Thereby further reducing the footprint of the inverter 72.

[0036] Capacitors 26 and power modules 30 shown in FIG. 4 are similar to those disclosed above with respect to FIGS. 2 and 3.

[0037] The power modules 30 are mounted onto a first surface 74 and a second surface 76 of the heat sink 32. Although it is shown that the same number of power modules 30 are mounted onto each of the first and second surfaces 74 and 76, it is to be appreciated that the distribution of the power modules 30 on the two surfaces may differ.

[0038] The U-shaped laminated busbar assembly 78 is configured to sleeve over the heat sink 32 and power modules 30 as shown. Specifically, the laminated busbar assembly 78 may be of similar construction as busbar assembly 28 but having a base portion 80 and two elongated portions 82a, 82b respectively extending perpendicularly from a first and a second longitudinal ends of the base portion 80.

[0039] As shown, the electrical contact tabs 58a and 58b may be positioned over the base portion 80 for forming electrical connections with an external DC
energy source, such as a battery (not shown). The elongated portions 82a and 82b may be configured to extend over all of the power modules 30 mounted onto each of surfaces 74 and 76 of the heat sink 32. The base portion 80 defines a gap between the elongated portion 82a and 82b so as to be able to receive the heat sink 32 mounted with power modules 30 therein.

[0040] Each of the elongated portions 82a and 82b defines an interior surface 84 and an opposing exterior surface 86. The DC input nodes of power modules 30 are electrically coupled to the first and second electric layers 54, 56 of the busbar assembly 74 from the interior surface 84. In some embodiments, such as the one shown in FIG. 4, busbar spacers 42a and 42b are used in the same way as disclosed above. The phase output 87 of the power modules may extend sideways as shown in the figure.

[0041] The first and second metal contacts 34, 36 of capacitors 26 may be electrically coupled to the corresponding electrical layers of the laminated busbar assembly 74 from the exterior surface 86.
,

[0042] In the illustrated embodiment, each of the power modules 30 is aligned with a corresponding capacitor 26 so as to minimize the distance therebetween, which may in turn minimize the parasitic inductance introduced by the electrical connection.

[0043] As shown, two PCB control boards 88a and 88b are respectively positioned above the capacitors 26 that are on the exterior surface 86 of the top elongated portion 82a, and below the capacitors 26 mounted on the exterior surface 86 of the bottom elongated portion 82b. In some embodiments, each of the control boards 88a and 88b is configured to control the power modules 30 respectively mounted on elongated portions 82a and 82b.

[0044] Certain adaptations and modifications of the described embodiments can be made. Therefore, the above discussed embodiments are considered to be illustrative and not restrictive. The present disclosure is not to be limited in scope by the specific embodiments described herein. Further example embodiments may also include all of the steps, features, compositions and compounds referred to or indicated in this description, individually or collectively and any and all combinations or any two or more of the steps or features.

[0045] Throughout this document, the use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one", but it is also consistent with the meaning of "one or more", "at least one", and "one or more than one". Similarly, the word "another" may mean at least a second or more. The words "comprising" (and any form of comprising, such as "comprise"
and "comprises"), "having" (and any form of having, such as "have" and "has"), "including"
(and any form of including, such as "include" and "includes") or "containing"
(and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0046] In the present specification and in the appended claims, various terminology which is directional, geometrical and/or spatial in nature such as "longitudinal", "horizontal", "front", "forward", "backward", "back", "rear", "upwardly", "downwardly", etc. is used. It is to be understood that such terminology is used for ease of description and in a relative sense only and is not to be taken in any way as specifying an absolute direction or orientation.

[0047] The embodiments described herein may include one or more range of values (for example, size, displacement and field strength etc.). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range that lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range. For example, a person skilled in the field will understand that a 10%
variation in upper or lower limits of a range can be totally appropriate and is encompassed by the disclosure. More particularly, the variation in upper or lower limits of a range will be 5% or as is commonly recognized in the art, whichever is greater.

[0048] Throughout this specification relative language such as the words 'about' and 'approximately' are used. This language seeks to incorporate at least 10%
variability to the specified number or range. That variability may be plus 10%
or negative 10% of the particular number specified.

Claims (10)

1. A power inverter, comprising:
a busbar assembly configured to receive a DC energy source, the busbar assembly having a first connection surface and an opposing second connection surface;
a power module configured to be electrically coupled to the busbar assembly from the first connection surface; and a capacitor configured to be electrically coupled to the busbar assembly from the second connection surface;
wherein the power module is aligned with the capacitor.

2. The power converter of claim 1, comprising a plurality of power modules configured to be electrically coupled to the busbar assembly from the first connection surface in a coplanar fashion;
a plurality of capacitors configured to be electrically coupled to the busbar assembly from the second connection surface in a coplanar fashion;
wherein each capacitor of the plurality of capacitors is aligned with a power modules of the plurality of power modules.

3. The power converter of claim 1, wherein the capacitor is configured with a form factor that is same as a dimension of the power module.

4. The power converter of claim 1, further comprising a heat sink configured to be in thermal contact with the power module.

5. The power converter of claim 1, further comprising a PCB control board configured to control the power module.

6. The power converter of claim 1, wherein the busbar assembly is substantially flat.

7. The power converter of claim 1, wherein the busbar assembly is U-shaped, and an interior surface of the U-shaped busbar assembly defines the first connection surface and an exterior surface of the U-shaped busbar assembly defines the second connection surface.

8. The power converter of claim 7, further comprising a heat sink configured to be in thermal contact with the power module, wherein the heat sink is configured to be received within a gap defined by the U-shaped busbar assembly.

9. The power converter of claim 7, further comprising a plurality of power modules, at least a portion of the plurality of power modules are configured to be electrically coupled to a first portion of the U-shaped busbar assembly from the first connection surface in a coplanar fashion, and at least a portion of the plurality of power modules are configured to be electrically coupled to a second portion of the U-shaped busbar assembly from the first connection surface in a coplanar fashion;
a plurality of capacitors, at least a portion of the plurality of capacitors are configured to be electrically coupled to the first portion of the U-shaped busbar assembly from the second connection surface in a coplanar fashion, and at least a portion of the plurality of power modules are configured to be electrically coupled to the second portion of the U-shaped busbar assembly from the second connection surface in a coplanar fashion;
wherein each capacitor of the plurality of capacitors is aligned with a power modules of the plurality of power modules.

10. The power converter of claim 9, further comprising two PCB control boards, wherein each of the two PCB control boards is configured to control at least a portion of a plurality of power modules.