Electromagnetically shielded electrical converter and an improved electromagnetic shield therefor
First Claim
1. An electromagnetic interference shield for electrically enclosing a source of electromagnetic interference signals and thus substantially reducing the emanation of such signals beyond the enclosure boundary, said electromagnetic interference shield comprising:
- an electrically conductive surface defining the boundary of a substantially enclosed volume for containing said source therewithin; and
an electrical center tap connection electrically connected to a first predetermined electrical reference point,said electrical center tap connection being located at a predetermined null point on said surface where voltages induced in said surface by said electromagnetic interference signals are substantially balanced out whereby injection of such induced interference voltages to said first reference point are substantially reduced.
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Accused Products
Abstract
Electromagnetic interference shields are connected to electrical reference points from specially selected null or "center tap" connection points where noise voltages induced in the surface of the electromagnetic shield are substantially balanced out such that injection of such induced interference noise voltages to the connected reference points are substantially reduced. Special selection of isolated reference points for the input and output circuits as well as a special combination of electromagnetic interference shields substantially reduces the electromagnetic interference emanations from an electrical power supply circuit incorporating an inverter and transformer windings therewithin which normally constitute sources of unwanted electromagnetic interference signals unless suppressed.
30 Citations
49 Claims
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1. An electromagnetic interference shield for electrically enclosing a source of electromagnetic interference signals and thus substantially reducing the emanation of such signals beyond the enclosure boundary, said electromagnetic interference shield comprising:
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an electrically conductive surface defining the boundary of a substantially enclosed volume for containing said source therewithin; and an electrical center tap connection electrically connected to a first predetermined electrical reference point, said electrical center tap connection being located at a predetermined null point on said surface where voltages induced in said surface by said electromagnetic interference signals are substantially balanced out whereby injection of such induced interference voltages to said first reference point are substantially reduced. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An electromagnetically shielded electrical converter having an electrically isolated input and output for converting input electrical energy to output electrical energy having desired voltage and current characteristics, said converter comprising:
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inverter circuit means having an input connected for converting said input electrical energy to a predetermined form of alternating electrical energy; transformer means; said transformer means comprising a primary winding electrically connected to receive said predetermined form of alternating electrical energy and to produce a corresponding magnetic flux; said transformer means further comprising a secondary winding magnetically coupled to said primary winding for responding to said magnetic flux and for producing induced electrical energy in said secondary winding having predetermined electrical voltage and current characteristics; a first electrical reference point electrically associated with only said input electrical energy; a primary winding shield means substantially enclosing said primary winding and being electrically connected to said first electrical reference point, a second electrical reference point electrically associated with only said output electrical energy, said first and second electrical reference points being electrically isolated with respect to each other, and a secondary winding shield means substantially enclosing said secondary winding and bearing electrically connected to said second electrical reference point whereby the converter input and output are maintained in safe electrical isolation while yet providing substantial electromagnetic shielding for both the primary and secondary winding. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. An electromagnetically shielded electrical power supply for converting an a.c. input voltage into a d.c. output voltage, said power supply comprising:
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input means having input leads connected for reserving said a.c. input voltage; input rectifier means connected to receive said a.c. input voltage and to produce a d.c. voltage therefrom at an output which includes a common return connection for such d.c. supply voltage; inverter means connected to the output of said input rectifier means for producing a substantially square shaped alternating voltage output of predetermined electrical characteristics; primary winding means connected to said alternating voltage output for producing a corresponding alternating magnetic flux; secondary winding means magnetically coupled to said primary winding means for producing another alternating voltage output corresponding to said alternating magnetic flux; output rectifier means connected to said secondary winding means for producing said d.c. output voltage at output leads from said another alternating voltage output; a primary winding shield means comprising a first electrically conductive surface defining the boundary of a substantially enclosed volume containing said primary winding means therewithin; and a first electrial center tap connection electrically connecting said common return to a predetermined null point on said first surface where voltages induced by electromagnetic interference emanating from therewithin are substantially balanced out whereby injection of such induced interference voltages to said common return are substantially reduced. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. An improved electromagnetically shielded electrical converter having at least one electrical reference point, and inverter and transformer windings therewithin constituting at least one source of electromagnetic interference signals, said improvement comprising:
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an electrically conductive surface defining the boundary of a substantially enclosed volume for containing said source therewithin; and an electrical center tap connection for electrically connecting said surface to a first predetermined electrical reference point, said electrical center tap connection being located at a predetermined null point on said surface where voltages induced in said surface by said electromagnetic interference signals are substantially balanced out whereby injection of such induced interference voltages to said first reference point are substantially reduced. - View Dependent Claims (44, 45, 46, 47, 48, 49)
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Specification