Method and apparatus for reducing EMI emissions from a power inverter
View Patent ↗A power inverter for a hybrid automotive vehicle having a case with an interior and at least one electrical port mounted on the case to electrically connect electrical signals from the interior of the case to an exterior device. A cable connector is associated with each electrical port while a non-electrical sensing conductor extends serially through each electrical port and its associated cable connector. A circuit is provided which detects a break in the continuity of the sensing conductor and generates a signal representative of that break in continuity. The non-electrical sensing conductor thus minimizes the emission of EMI from the inverter. Additionally, a circuit board is mounted within the interior of the case by fasteners which minimize the spacing between the circuit board and the case to further reduce EMI emissions.
1. In a power inverter having a metal case and a control circuit board having a ground plane mounted in said case, a method for reducing electromagnetic interference generated from the power inverter contained in said case comprising the steps of:
positioning a metal base plate between said circuit board and said case,
spacing first metal fasteners around an outer perimeter of said circuit board so that said first fasteners extend through and are electrically connected to said circuit board ground plane,
securing said circuit board to said base plate by said first fasteners so that said first fasteners electrically connect said circuit board ground plane with said base plate,
spacing second metal fasteners around an outer perimeter of said base plate so that said second fasteners are spaced outwardly from said first fasteners,
securing said base plate to said case by second fasteners so that said second fasteners electrically connect said base plate with said case, and
wherein said spacing said second fasteners step further comprises the step of minimizing the spacing between adjacent first and second fasteners.
2. The power inverter as defined in claim 1 comprising metal base plate between said circuit board and said case, and wherein said securing step comprises the step of securing said circuit board to said case by said plurality of first fasteners, each first fastener extending through said circuit board and base plate and into said case.
3. The power inverter as defined in claim 1 and further comprising the step of providing an elongated edge abutment between each side of said base plate and said case.
4. A power inverter construction for an electric automotive vehicle comprising:
a metal case,
a power inverter positioned in said case,
a control circuit board having a ground plane,
a metal base plate positioned between said control circuit board and said case,
a plurality of first metal fasteners extending through said control circuit board and into said base plate, said first fasteners electrically connecting said circuit board ground plane to said case base plate, and
a plurality of second metal fasteners extending through said base plate and into said case, said second fasteners electrically connecting said base plate to said case, said second fasteners being positioned closely adjacent said first fasteners so that said base plate shields said circuit board from electromagnetic radiation.
5. The invention as defined in claim 4 wherein said case includes at least one elongated ledge, said base plate flatly abutting against said elongated edge of said case to thereby increase an area of contact between said case and the control circuit board ground plane.
6. The invention as defined in claim 4 wherein said case includes a plurality of elongated ledges extending around an interior of said case, said base plate flatly abutting against said elongated edges of said case.