Title of Invention

"MAINS FILTER"

Abstract The present invention relates to a mains filter comprising a first coil (C1), a second coil (C2), and a common core (K1, K2), the coils (C1, C2) being arranged as conductor trades on substrates (P1, P2); the core (K1, K2) being a E/I or E/E ferrite core with a central core leg, each coil being arranged as windings, with conductor tracks on both sides of said substrates (P1, P2). Each of the windings is routed spirally inwards on one side around an opening and being coupled via a plated-through hole to the other side of the respective substrate, and being routed spirally outwards again. The opening constitutes a central opening through which the central leg of the core is passed. The substrates have H-shaped extensions for arranging the inputs and the outputs for the windings of each coil on opposite sides in the corners of the extensions of the mains filter, a dielectric interlayer being arranged between the two coils. And the substrates for the two coils comprise printed circuit boards of same shape and arranged symmetrically with respect to one another and to the opening, and without play on the core.
Full Text PD980085*Ar
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The invention is based on a mains filter having two coils arranged on a common core.
Filters of this kind are used, in particular, at the input in switched-mode power supplies for connection to the mains supply. They not only prevent high-frequency interference produced in the switched-mode power supply from reaching the mains supply via the mains connection but also prevent high-frequency interference from reaching the appliance via the mains supply, whilst allowing the 50-Hz mains frequency through essentially unattenuated.
In this arrangement, the coils are usually produced on a cylindrical coil former which is divided into chambers and has windings made from a copper wire, a core being passed through the coil former. The operating principle of such a filter is explained with reference to Figure 1. In this case., each wire in the mains line is passed through a respective coil, Cl or C2, the two windings Cl, C2 having opposite polarities, with reference to the two inputs El and .E2.| This means that high-frequency interference propagating on one input line, for example over input line El, is subjected to the full inductance of the coil Cl. On the other hand, .however, at the mains supply's 50-Hz frequency, which is applied to the two inputs El, E2 simultaneously, the different polarities of the two windings cause the magnetic fields in the core to be cancelled out. The filter should therefore be of__ symmetrical deign, so thaj> no input impedance is formed for the 50-Hz_frecruency. The two coils Cl, C2 are coupled to one another magnetically by means of a common core (not shown).
The object of the present invention is to specify a filter of the type mentioned above which has good electrical properties together with compact dimensions.

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This object is achieved by the inventive features indicated in Claim 1. Advantageous developments of the invention are indicated in the subclaims.
The filter of the invention contains coils with windings which are arranged on (s^ibstratesj for example conventional thin printed circuit boards,, ^s conductor tracks. In this arrangement, a coil can contain one or more substrates, which are in contact with one another in the case of a plurality of substrates. In the centre, the substrates have an opening through which a core is passed.
A substrate contains, in particular, a plurality of windings which are routed spirally inwards and through a plated-through hole to the other side of the substrate. On the reverse, the winding is routed spirally outwards again, so that the two connections for the winding can be made at the edge of the circuit board. In particular, this means that the input and the output for a coil can also be arranged on opposite sides of the circuit board. With an appropriate number of windings, one substrate is sufficient for one winding, so that only one substrate per coil is required for the filter. The two substrates for the two coils can, in particular, be of identical design, the input and the output for a coil being arranged on a substrate in the region of opposite corners. Symmetrical considerations mean that an E/E core or an E/I core is advantageous.
I With/plated-through hoTe^) insulation betweenthe ,
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two coils is necessary. For this, a Mi electric)
interlayer, for example a plastic film,' can be used. However, it is also possible to coat the opposite sides of the substrates accordingly with jCTdielectric material. The insulation requirements for a mains filter are significantly lower than for a transformer'. This means that virtually the full width of the substrates can be used in the region inside the openings in the core.
Both the core and the substrates with the conductor tracks arranged on them can be manufactured

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with very high precision. In this respect, the substrates can be dimensioned such that they are held without play by the core alone, particularly its openings. A coil former is therefore not required. Known etching methods are used to arrange the conductor tracks, on the substrates, in particular extremely symmetrically, so that a mains filter with substrates has significantly better electrical properties than one with a coil former having a copper wire winding with a great deal of asymmetry.
The core used can be a narrow E/E core or E/I core, in particular, so that the filter is very compact and can be arranged perpendicularly on a circuit board in a power supply unit using appropriate retaining means, the space requirement on the circuit board being very low. In many appliances, the switched-mode power supply is arranged in a screened metal cage as an external unit with a circuit board. Since a switched-mode power supply frequently uses two mains filters, this means that the size of the power supply unit is significantly reduced.
The filter is used, in particular, for current-compensated mains filters in switched-mode power supplies, for example in electronic entertainment appliances.
The invention is explained below by way of example with reference to schematic drawings, in which: Figure 1 shows the electrical design of a symmetrical
filter {prior art), Figure 2 shows a section through a filter with an E/I
core,
Figure 3a shows a core half with the first coil, and Figure 3b shows a core half with the second coil.
Figure 1 shows a current-compensated mains filter having two coils Cl and C2 and the corresponding inputs El, E2 and outputs Al, A2, as already explained above. The two coils are'arranged symmetrically in this case and are connected to one another magnetically by means of a common core. The winding direction of the windings of the

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two coils Cl and C2 is such that the two windings are counter-coupled.
Figure 2 shows a section through the core and the two coils Cl and C2 of the filter according to the invention. In this exemplary embodiment, the core comprises an E/I core having two core halves Kl and K2. In place of an E/I core, an E/E core can also be used and gives the filter comparable electrical properties. The two coils Cl and C2 are merely indicated here as windings. A dielectric and thus nonconductive interlayer I is situated between the two.
The coil Cl is designed as shown in Figure 3a, which shows a plan view of a substrate PI and a section through the core half Kl. In this arrangement, the coil Cl is applied to both sides of the substrate PI as a conductor track, for example using a conventional etching method, the conductor track being routed from an input El spirally inwards on the top around the central core limb of the core half Kl. The centre of the substrate PI has an opening which matches the central core limb of the core part Kl as exactly as possible. At the end of the spiral, the conductor track is routed to the other side of the substrate PI, for example through a plated-through hole, and again spirally around the opening to an output Al. In this arrangement, the windings on the two sides of the substrate PI can be arranged symmetrically with great precision, the top and bottom conductor tracks advantageously being congruent. For the coil Cl, substrates using multilayer technology are also particularly suitable, and these can be used to produce a large number of windings.
The coil C2, which is of identical design to the coil Cl but is mounted in the core symmetrically with respect to said coil Cl, is shown in Figure 3b. It is likewise arranged on one or more substrates P2, but their input E2 and output A2 are arranged in opposite corners in relation to the input and the output for the coil Cl. The symmetry of the substrates implies that the substrate

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PI for the coil Cl can be converted to the substrate P2 for the coil C2 by turning it round.
The substrates PI, P2 can be manufactured to fit the core limbs of the two core parts Kl and K2 virtually exactly, so that the two coils Cl, C2 are very symmetrical with respect to the core, which produces improved electrical properties as compared with previously known filters, At the same time/ the coil former becomes superfluous. The flat substrates PI, P2 mean that a very flat E/E ferrite core or E/I ferrite core can be used, as shown in Figure 2. This ferrite core can be arranged perpendicularly on the circuit board of an appliance using appropriate retaining means, so that the space requirement on the circuit board is very low.


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We Claim
1. Mains filter having a first coit (Ci), a second coil (C2), and a common core (Ki/ K2), said coils (Ci, C2) being arranged as conductor tracks on substrates (Pi, P2);
said core (Ki, K2) being a E/I or E/E ferrite core with a central core leg,
each coil being arranged as windings, with conductor tracks on both sides of said substrates (Pi, P2), each winding being routed spirally inwards on one side around an opening and being coupled via a plated-through hole to the other side of the respective substrate, and being routed spirally outwards again,
said opening being a central opening through which said central leg of said core is passed,
said substrates having H-shaped extensions for arranging the inputs and the outputs for said windings of each coil on opposite sides in the corners of said extensions of the mains filter,
a dielectric interlayer being arranged between said two coils, and
said substrates for said two coils being printed circuit boards of same shape and being arranged symmetrically with respect to one another and to said opening, and without play on said core.

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2. Main filter as claimed in claim 1, wherein the mains filter is a current-
compensated mains fitter for a switched-mode power supply.
3. Mains filter as claimed in claim 1, wherein the mains filter has a
rectangular contour with a narrow side and a broad side, and wherein the
mains filter has retaining means for being coupled by its narrow side on a
circuit board.
The present invention relates to a mains filter comprising a first coil (C1), a second coil (C2), and a common core (K1, K2), the coils (C1, C2) being arranged as conductor trades on substrates (P1, P2); the core (K1, K2) being a E/I or E/E ferrite core with a central core leg, each coil being arranged as windings, with conductor tracks on both sides of said substrates (P1, P2). Each of the windings is routed spirally inwards on one side around an opening and being coupled via a plated-through hole to the other side of the respective substrate, and being routed spirally outwards again. The opening constitutes a central opening through which the central leg of the core is passed. The substrates have H-shaped extensions for arranging the inputs and the outputs for the windings of each coil on opposite sides in the corners of the extensions of the mains filter, a dielectric interlayer being arranged between the two coils. And the substrates for the two coils comprise printed circuit boards of same shape and arranged symmetrically with respect to one another and to the opening, and without play on the core.

Documents:

00895-cal-1999-abstract.pdf

00895-cal-1999-claims.pdf

00895-cal-1999-correspondence.pdf

00895-cal-1999-description(complete).pdf

00895-cal-1999-drawings.pdf

00895-cal-1999-form-1.pdf

00895-cal-1999-form-18.pdf

00895-cal-1999-form-2.pdf

00895-cal-1999-form-3.pdf

00895-cal-1999-form-5.pdf

00895-cal-1999-letters patent.pdf

00895-cal-1999-p.a.pdf

00895-cal-1999-priority document others.pdf

00895-cal-1999-priority document.pdf


Patent Number 203246
Indian Patent Application Number 895/CAL/1999
PG Journal Number 10/2007
Publication Date 09-Mar-2007
Grant Date 09-Mar-2007
Date of Filing 11-Nov-1999
Name of Patentee DEUTSCHE THOMSON-BRANDT GMBH
Applicant Address HERMANN-SCHWER-STR.3, D-78048 VILLINGEN-SCHWENNINGEN
Inventors:
# Inventor's Name Inventor's Address
1 HALLER HANS-OTTO UNTERM HERRSCHAFTSWALD 2, D-78078 NIEDERESCHACH
2 RIESLE THOMAS GEMEINDEWALDSTR.14, D-78052 VS-TANNHEIM
3 RODRIGUEZ-DURAN JOSE BRENDWING 16, D-78050 VILLINGEN-SCHWENNINGEN ,
PCT International Classification Number H 01 F 10/26
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 19853510.4 1998-11-20 Germany