Patent Application
20050128706
1. Field of the Invention
This disclosure generally relates to electrical power converters, and more particularly to an architecture suitable for use in electrical power modules.
2. Description of the Related Art
Power modules are typically self-contained units that include a converter to transform and/or condition power from one or more power sources for supplying power to one or more loads. Converters commonly referred to as “inverters” transform direct current (DC) to alternating current (AC), for use in supplying power to an AC load. Converters commonly referred to as a “rectifiers” transform AC to DC. Converters commonly referred to as “DC/DC converters” step up or step down a DC voltage. An appropriately configured and operated converter may perform any one or more of these functions. The term “converter” is commonly applies to all converters whether inverters, rectifiers and/or DC/DC converters.
A large variety of applications require power transformation and/or conditioning. For example, a DC power source such as a fuel cell system, battery and/or ultracapacitor may supply DC power, which must be inverted to provide power to an AC load such as a three-phase AC motor in an electric or hybrid vehicle. A photo-voltaic array may produce DC power which must be inverted to provide or export AC power to a power grid of a utility. An AC power source such as a power grid or micro-turbine may need to be rectified to provide power to a DC load such as a tool, machine or appliance. A high voltage DC source may need to be stepped down to supply a low voltage load, or a low voltage DC source may need to be stepped up to supply a high voltage load. Other applications will become apparent to those of skill in the art based on the teachings herein.
Power modules typically employ transistors, diodes and other components that generate substantial heat during operation, particularly when operating at high loads. Excessive heat can cause the components to under perform or even fail if not adequately addressed. Conventional power module structures employ various electrically insulating layers for electrically insulating the various components from one another and from the exterior of the power module. For example, components are typically mounted on direct bond copper (DBC) or direct bond aluminum (DBA) substrates, which comprise a ceramic substrate with metal foil fused on both sides. Unadvantageously, these electrically insulating layers also tend to be thermally insulating, significantly decreasing the ability to transfer heat away from the electronics.
A power module with enhanced heat transfer characteristics is thus desirable.
In one aspect, a power module comprises a housing of electrically insulative material, the housing comprising an interior and an exterior; a first plurality of heat exchange members coupled to the housing; a second plurality of heat exchange members coupled to the housing and electrically isolated from the first plurality of heat exchange members; a first substrate of electrically and thermally conductive material received in the interior of the housing and thermally coupled to the first plurality of heat exchange members without any intervening thermally insulative structures; a second substrate of electrically and thermally conductive material received in the interior of the housing and thermally coupled to the second plurality of heat exchange members without any intervening thermally insulative structures, the second substrate electrically isolated from the first substrate; a first set of semiconductor devices each comprising at least a first terminal and a second terminal, each of the semiconductor devices of the first set surface mounted to the first substrate to electrically couple the first terminal of the semiconductor device to the first substrate and to thermally couple the semiconductor devices to the first plurality of heat exchange members via the first substrate; and a second set of semiconductor devices each comprising at least a first terminal and a second terminal, each of the semiconductor devices of the second set surface mounted to the second substrate to electrically couple the first terminal of the semiconductor device to the second substrate and to thermally couple the semiconductor devices to the second plurality of heat exchange members via the second substrate.
In another aspect, a power module comprises a housing of electrically insulative material, the housing comprising an interior and an exterior; a first plurality of heat exchange members coupled to the housing; a second plurality of heat exchange members coupled to the housing and electrically isolated from the first plurality of heat exchange members; a first substrate of electrically and thermally conductive material received in the interior of the housing and thermally coupled to the first plurality of heat exchange members without any intervening thermally insulative structures; a second substrate of electrically and thermally conductive material received in the interior of the housing and thermally coupled to the second plurality of heat exchange members without any intervening thermally insulative structures, the second substrate electrically isolated from the first substrate; a third substrate received in the housing and electrically isolated from the first substrate, the third substrate electrically coupled to the second substrate via at least one wire bond; a first set of semiconductor devices comprising at least one transistor and at least one diode, each of the semiconductor devices of the first set surface mounted to the first substrate to electrically couple a first terminal of the semiconductor device to the first substrate and to thermally couple the semiconductor devices to the first plurality of heat exchange members via the first substrate, wherein a second terminal of the semiconductor devices of the first set of semiconductor devices is electrically coupled to the second substrate; and a second set of semiconductor devices comprising at least one transistor and at least one diode, each of the semiconductor devices of the second set surface mounted to the second substrate to electrically couple a first terminal of the semiconductor device to the second substrate and to thermally couple the semiconductor devices to the second plurality of heat exchange members via the second substrate, wherein a second terminal of the semiconductor devices of the second set of semiconductor devices is electrically coupled to the third substrate, the first and the second set of semiconductor devices forming a half bridge inverter.
In a further aspect, a power module comprises a housing; a first heat exchange loop; a first set of semiconductor devices comprising at least a first transistor and at least a first diode; a second set of semiconductor devices comprising at least a first transistor and a first diode, the first and the second sets of semiconductor devices electrically coupled as a half bridge inverter; first means for thermally coupling the first set of semiconductor devices to the first heat exchange loop without any intervening thermally insulative structures; second means for thermally coupling the second set of semiconductor devices to the first heat exchange loop without any intervening thermally insulative structures, the second means electrically isolated from the first means.
In yet a further aspect, a power module comprises a housing of electrically insulative material, the housing comprising an interior and an exterior; a first substrate of electrically and thermally conductive material received in the interior of the housing, the first substrate comprising a coupling structure to selectively electrically couple to a first pole of an external DC device located in the exterior; a second substrate of electrically and thermally conductive material received in the interior of the housing and electrically isolated from the first substrate; a third substrate received in the housing and electrically isolated from the first substrate, the third substrate electrically coupled to the second substrate via at least one wire bond, the third substrate comprising a coupling structure to selectively electrically couple to a second pole of the external DC device; a first set of semiconductor devices comprising at least one transistor and at least one diode, each of the semiconductor devices of the first set surface mounted to the first substrate to electrically couple a first terminal of the semiconductor device to the first substrate and to thermally couple the semiconductor devices to the first substrate, wherein a second terminal of the semiconductor devices of the first set of semiconductor devices is electrically coupled to the second substrate; and a second set of semiconductor devices comprising at least one transistor and at least one diode, each of the semiconductor devices of the second set surface mounted to the second substrate to electrically couple a first terminal of the semiconductor device to the second substrate and to thermally couple the semiconductor devices to the second substrate, wherein a second terminal of the semiconductor devices of the second set of semiconductor devices is electrically coupled to the third substrate, the first and the second set of semiconductor devices forming a half bridge inverter.
In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures such as control systems including microprocessors and drive circuitry have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments of the invention.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
The headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.
The power converter 18 comprises a first substrate 20, second substrate 22, and third substrate 24. The substrates 20, 22, 24 are formed from one or more electrically and thermally conductive materials. For example, the material(s) may comprise copper or extruded aluminum, both of which are relatively inexpensive good electrical and thermal conductors. Each of the substrates 20, 22, 24 are electrically isolated from one another. For example, the first and second substrates 20, 22 are laterally spaced apart from one another, while the third substrate 24 is spaced relatively above the first substrate 20 and may be electrically isolated therefrom via one or more insulating materials 26, for example, a thin layer of Nomex® or Mylar® (e.g., 0.025-0.2 mm) available from E. I. Du Pont de Nemours and Company, with or without a silicon gel to prevent arcing.
The power converter 18 also comprises a first set of semiconductor devices 28 electrically and thermally coupled to the first substrate 20, and a second set of semiconductor devices 30 electrically and thermally coupled to the second substrate 22. For example, the first set of semiconductor devices 28 and the second set of semiconductor devices 30 each comprise a number of transistors and a number of diodes electrically coupled in anti-parallel or shunted across the transistors. As illustrated, the first set of semiconductor devices 28 comprises a “high” side (i.e., coupled to positive pole of DC power source) transistor Q1 and diode D1, while the second set of semiconductor devices 30 comprises a “low” side (i.e., coupled to negative pole of DC power source) transistor Q2 and diode D2. Each set of semiconductor devices 28, 30 may include additional transistor and diode pairs electrically coupled in parallel with the high side transistor Q1 and diode D1 and/or the low side transistor Q2 and diode D2, as may be suitable for the particular application (e.g., to accommodate the power ratings of the individual semiconductor devices).
The transistors Q1,Q2 may take a variety of forms, for example, insulated gate bipolar junction transistors (IGBTS) or metal oxide semiconductor transistors (MOSFETs). Such transistors Q1,Q2 are commercially available, individually, or in sets of two or six transistor switches. The transistors Q1,Q2 typically include the anti-parallel diodes D1, D2, which may or may not be an inherent portion of the fabricated semiconductor transistor Q1, Q2 structure. The transistors Q1, Q2 are essentially three element devices, comprising a pair of active elements (e.g., source/emitter, drain/collector) and a control element, (e.g., gate, base). While the terms emitters, collectors and base are occasionally used henceforth, those of skill in the art will recognize that such is for convenience only, and such use does not restrict the teachings or claims to IGBTs, but are also applicable to other types of transistors, for example, MOSFETs.
The transistors Q1, Q2 and associated diodes D1, D2 may be provided as unpackaged or bare dice. Each transistor Q1, Q2 bearing die is surface mounted to the corresponding one of the first and second substrates 20, 22, respectively, to electrically couple the collector of the transistor Q1, Q2 to the substrate 20, 22. The surface mounting may be via a solder 32, although other ways of mounting the transistors Q1, Q2 to the first and second substrates 20, 22 may be employed, for example, pressure assembly packaging, bolting or clamping. Surface mounting thermally couples substantially all of one surface of the transistor Q1, Q2 bearing die to the substrate 20, 22, respectively. This provides a maximum area for heat transfer from the transistors Q1, Q2 to the substrates 20, 22, respectively.
Alternatively, each of the transistors Q1, Q2 may be provided in a packaged form, typically comprising an electrically insulative body or case, and a heat sink extending from the case. For typical packaged transistors Q1, Q2, it is desirable to maximize the area of contact between the heat sink and the substrate. While the case provides the packaged transistors Q1, Q2 with enhanced environmental protection and consequently ease of handling, such transistors Q1, Q2 typically will not receive the full benefit of the heat transfer approach taught herein.
The diodes D1, D2 are two element devices, comprising a cathode and an anode. Like the transistors Q1, Q2, each of the diodes D1, D2 may be provided on the dice, and surface mounted to the corresponding one of the first and second substrates 20, 22, respectively, to electrically couple the cathode of the diode D1, D2 to the substrate 20, 22. The surface mounting may be via a solder 32, although other ways of mounting the transistors Q1, Q2 to the first and second substrates 20, 22 may be employed, for example, pressure assembly packaging, bolting or clamping. The surface mounting thermally couples the case of the diode D1, D2 to the substrate 20, 22, respectively.
Alternatively, each of the diodes D1, D2 may be formed as part of the packaged transistors Q1, Q2, as discussed above.
The emitter of the transistor Q1, and the anode of the diode D1 are electrically coupled to the second substrate 22 and the emitter of the transistor Q2, and the anode of the diode D2 are electrically coupled to the third substrate 24 to form a half bridge inverter circuit 34a (shown in
Returning to
Each of the first, second and third substrates 20, 22, 24, respectively, may include a coupling structure 42a, 42b, 42c to electrically couple the first and third substrates 20, 24 to the external DC power source 40 (
Optionally, the power module 10 may further comprise, or be coupled to a gate drive board 44. The gate drive board 44 is electrically coupled to the base or gates of the transistors Q1, Q2 to supply control signals thereto for operating the transistors Q1, Q2. The gate drive board 44 may be electrically coupled to the base or gates of the transistors Q1, Q2 via wire bonds (not shown) or other electrical connections. Gate drive circuits are known in the art and so will not be discussed in further detail.
While two openings are shown for making the connections to the DC power source 40 for each half bridge, the power module 10 may comprise additional bus bar structures, such as conductive members (not shown) that extend from the first and third substrates 20, 24, out of the openings. Such conductive members may be integral or discrete with the substrates 20, 24; Some exemplary additional bus bar structures which may be suitable are taught in commonly assigned U.S. application Ser. Nos. 09/882,708 and 09/957,047 both filed Jun. 15, 2001. Such auxiliary bus bar structures may facilitate external electrical connections and may further facilitate the sealing of the housing 12 by filling the openings in the housing with or without a sealant, thereby enhancing environmental protection. However auxiliary bus bar structures will likely require additional materials and introduce complexity in the manufacturing process, and thus disadvantageously increase costs.
The power module 10 may include heat transfer structure, discussed immediately below with reference to
The first and second substrates 20, 22 are thermally coupled to first and second pluralities of heat exchange members 46, 48, respectively. The heat exchange members 46, 48 may take the form of fins, pins, channels or other structures that increase the amount of surface area over that of bottom surfaces 50, 52 of the first and second substrates 20, 22. The heat exchange members 46, 48 may be integrally formed with the respective first and second substrates 20, 22, for example, by extruding, machining or casting, or may be attached thereto. For example, the heat exchange members 46, 48 may be welded directly to the bottom surface 50, 52 of the first and second substrates 20, 22, or may be mounted into complimentary retaining structures formed on the bottom surfaces 50, 52 of the first and second substrates 20, 22, for example, by press fitting, shrink fitting and/or soldering.
Alternatively, as illustrated in
With continuing reference to
While the first heat exchange loop 62 is illustrated as comprising a single first chamber 64 and first reservoir 66, other embodiments may employ separate and distinct sub-heat exchange loops, where one sub-loop circulates heat exchange medium past the first plurality of heat exchange members 46 and a another distinct sub-loop circulates heat exchange medium past the second plurality of heat exchange members 48. This may provide more efficient heat transfer, and/or may reduce any possibility of shorting where the heat exchange medium may act as a conductor (e.g., metal shavings or filings become suspended or dissolved in the heat exchange medium).
The power module 10 may further comprise, or may be coupled to a second heat exchange loop 78. The second heat exchange loop 78 comprises a second chamber 80, a second reservoir 82, an inlet 84 and an outlet 86 for circulating a second heat transfer medium 88, as illustrated by arrows 90a, 90b. The second heat transfer medium 88 may take a variety of forms, for example, a fluid such as a liquid, gas, or a fluid that changes phase as the fluid circulates through different portions of the second heat exchange loop 78. The circulation may be passive or active, for example relying on a pump, compressor or fan 92 to actively circulate the second heat transfer medium 88.
The first and/or second chambers 64, 80 and/or the first and/or second reservoirs 66, 82 may be formed from a single piece of material in a conventional manner, such as extruded or machined aluminum, or may be comprised of separate components assembled together in a conventional manner. The second heat exchange loop 78 may include a ring or seal 91 to seal the second chamber 80 with respect to the first reservoir 66.
While
Further, while
The above described structures eliminate an insulator and two interfaces from the thermal path of conventional designs, thereby increasing the efficiency of heat transfer from the semiconductor devices, thereby enhancing the efficiency, reliability and cost competitiveness of the power module. The above described structures integrate the bus bar and/or phase terminal function and the semiconductor mounting functions into single structures (e.g., first substrate 20 serves as the positive DC bus bar and as the physical, electrical, and thermal coupling structure for the high-side semiconductor devices 28; second substrate 22 serves as the AC phase terminal and as the physical, electrical, and thermal coupling structure for the low-side semiconductor devices 30), simplifying design, reducing parts count, and consequently lowering costs, volume and/or weight.
Although specific embodiments of and examples of the present power modules and methods are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the invention, as will be recognized by those skilled in the relevant art. The teachings provided herein can be applied to power module and power converters, rectifiers and/or inverters not necessarily the exemplary three phase half bridge power module generally described above. For example, it will be apparent to those of skill in the art from the above teachings that the semiconductor devices may be configured as full bridges, half bridges, and/or H-bridges, as suits the particular application. It will also be apparent that the first and third substrates 20, 24, respectively, may be electrically coupled to a DC load or a DC device that constitutes a DC source at some times and a DC load at other times (e.g., regeneration). Similarly, the second substrate 22 may be electrically coupled to an AC source, or an AC device that constitutes an AC load at some times and an AC source at other times (e.g., regeneration).
While elements may be described herein and in the claims as “positive” or “negative” such denomination is relative and not absolute. Thus, an element described as “positive” is shaped, positioned and/or electrically coupled to be at a higher relative potential than elements described as “negative” when the power module 10 is coupled to a power source. “Positive” elements are typically intended to be coupled to a positive terminal of a power source, while “negative” elements are intended to be coupled to a negative terminal or ground of the power source. Generally, “positive” elements are located or coupled to the high side of the power module 10 and “negative” elements are located or coupled to the low side of the power module 10.
The power modules described above may employ various methods and regimes for operating the power module 10 and for operating the semiconductor devices (e.g., transistors Q1, Q2). The particular method or regime may be based on the particular application and/or configuration, and basic methods and regimes will be apparent to one skilled in the art.
The various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents, patent applications and publications referred to in this specification, including but not limited to: Ser. Nos. 60/233,992; 60/233,993; 60/233,994; 60/233,995 and 60/233,996, each filed Sep. 20, 2000; Ser. No. 09/710,145, filed Nov. 10, 2000; Ser. Nos. 09/882,708 and 09/957,047, both filed Jun. 15, 2001; Ser. Nos. 09/957,568 and 09/957,001, both filed Sep. 20, 2001; Ser. No. 10/109,555, filed Mar. 27, 2002; Ser. No. 60/471,387, filed May 16, 2003, are incorporated herein by reference, in their entirety. Aspects of the invention can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments of the invention.
These and other changes can be made to the invention in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to comprise all power modules, rectifiers, inverters and/or converters that operate or embody the limitations of the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to be determined entirely by the following claims.
