Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-04-18
2001-04-17
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S704000, C361S719000, C361S707000, C361S818000, C174S034000, C257S718000, C165S104330
Reexamination Certificate
active
06219245
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to heat sinking of power switching devices and, in particular, to liquid-cooled heat sink assemblies located within the power electronics module of an electric vehicle (i.e., electric and hybrid electric vehicles).
BACKGROUND OF THE INVENTION
Electric vehicles typically utilize an inverter in the form of a switch-mode power supply to provide three phase operating power to the vehicle's electric drive motor. The inverter includes a number of power switching devices that can supply the high currents needed. The inverter is usually located in an environmentally sealed module that is commonly referred to as the power electronics bay (PEB). This module typically includes other electronic circuits, such as those used to run the vehicle's electronic power steering, climate control compressor motor, and traction control system.
In an effort to minimize the amount of electromagnetic interference (EMI) radiated from the inverter and other circuitry within the power electronics bay, the circuits themselves are enclosed together within a grounded metal chassis. This chassis normally includes a housing having feedthrough electrical connectors (for power, control, and data signals) as well as an inlet and outlet coolant manifold that permit liquid coolant to be circulated through the power electronics bay for cooling of the inverter's power switching devices. In a typical liquid-cooled inverter application, the power switching devices are mounted by their baseplates to a conductive metallic liquid-interface heat exchanger. The coolant manifold of the heat exchanger that leads into and out of the chassis is metallic and is attached to the chassis. Thus, there is no electrical isolation between the power switching device baseplates, the heat exchanger and chassis. Where thermal grease or some other non-electrically insulating thermal interface is used between the switching device baseplates and heat exchanger, the baseplates themselves will be electrically connected to both the coolant and chassis. This produces capacitive coupling between the power switching devices and the chassis that is typically about 12-100 pF per die cm
2
, which can result in as much as 190 pF or more of capacitance. This allows undesirably high currents to be injected into the chassis, resulting in unwanted radiated emissions. Isolation of the baseplates and heat exchanger can be achieved using an insulating thermal interface such as a gasket; however, this seriously degrades the thermal coupling between the baseplates and heat exchanger.
Accordingly, there exists a need for a power electronics liquid-cooled heat sink mounting assembly that maintains good thermal conduction from the power switching devices while reducing the radiated EMI due to currents flowing from the switching devices and into the chassis.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a liquid cooled mounting assembly for heat sinking one or more power switching devices within an electrically conductive electronics housing. The mounting assembly includes a heat exchanger, one or more power switching devices, and an electrically non-conductive coolant manifold. The heat exchanger has a mounting surface and an internal space for containing a volume of liquid coolant within the heat exchanger. The internal space is defined at least in part by a wall having an inner surface that is thermally coupled to the mounting surface. The one or more power switching devices are supported by and thermally coupled to the mounting surface of the heat exchanger such that heat generated by the power switching devices is thermally coupled to the internal space within the heat exchanger. The coolant manifold has an inlet and outlet for passage of liquid coolant into and out of the electrically conductive electronics housing, with the inlet and outlet being in fluidic communication with the internal space of the heat exchanger. Thus, the coolant manifold permits circulation of liquid coolant into the chassis housing, through the heat exchanger, and back out of the chassis housing while maintaining electrical isolation between the liquid coolant and chassis housing.
This configuration not only provides electrical isolation of the coolant from the chassis housing, but does so in a manner that significantly reduces the parasitic capacitance between the switching devices and chassis housing. As a result, when used for an electric vehicle power electronics module containing an inverter for the vehicle's electric drive motor, the invention significantly reduces the radiated EMI outside of the chassis, as compared to conventional liquid-cooled heat sinking assemblies.
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Downer Scott D.
Nagashima James
Ward Terence G.
Datskovsky Michael
General Motors Corporation
Picard Leo P.
Simon Anthony Luke
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