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EP0131700B1 - Switch mode transformer having a ferrite core - Google Patents

Switch mode transformer having a ferrite core Download PDF

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Publication number
EP0131700B1
EP0131700B1 EP84104976A EP84104976A EP0131700B1 EP 0131700 B1 EP0131700 B1 EP 0131700B1 EP 84104976 A EP84104976 A EP 84104976A EP 84104976 A EP84104976 A EP 84104976A EP 0131700 B1 EP0131700 B1 EP 0131700B1
Authority
EP
European Patent Office
Prior art keywords
core
portions
legs
transformer
top surface
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84104976A
Other languages
German (de)
French (fr)
Other versions
EP0131700A3 (en
EP0131700A2 (en
Inventor
Giovanni Maddalon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Procond Elettronica SpA
Original Assignee
Zanussi Elettromeccanica SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zanussi Elettromeccanica SpA filed Critical Zanussi Elettromeccanica SpA
Priority to AT84104976T priority Critical patent/ATE31840T1/en
Publication of EP0131700A2 publication Critical patent/EP0131700A2/en
Publication of EP0131700A3 publication Critical patent/EP0131700A3/en
Application granted granted Critical
Publication of EP0131700B1 publication Critical patent/EP0131700B1/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H01F27/366—Electric or magnetic shields or screens made of ferromagnetic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F19/00—Fixed transformers or mutual inductances of the signal type
    • H01F19/04—Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range
    • H01F19/08—Transformers having magnetic bias, e.g. for handling pulses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/02—Casings
    • H01F27/027—Casings specially adapted for combination of signal type inductors or transformers with electronic circuits, e.g. mounting on printed circuit boards
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens

Definitions

  • the present invention relates to a switch mode transformer having a ferrite core, according to the pre-characterizing part of the patent claim.
  • the primary and secondary windings of a transformer of this type, disclosed in US-A-3 668 586, are wound in a concentric arrangement around one leg of a so-called "open" ferrite core substantially consisting of two E- or C-shaped portions joined to one another in a mirror-symmetrical arrangement.
  • the two core portions are secured to one another by means of a metal frame including integral bendable tabs capable of holding the two core portions together.
  • the assembly of the ferrite core and of the short-circuit winding obviously has to be carried out in two separate phases, whereby the assembly of the transformer as a whole is rendered undesirably complex.
  • An SMT-type transformer shown in the figure comprises a body 1 formed of a primary and a secondary winding, the terminals 2 of which are clamped in a per se known manner in a support body 3.
  • Body 1 is wound on a central leg (not shown) of a ferrite core 4 formed of at least two complementary portions 5 and 6 mirror-symmetrically joined to one another.
  • the two portions 5 and 6 are substantially E-shaped, although they may also be of other configurations as required.
  • the two portions 5 and 6 are joined to one another in abutting relationship as generally known, so that body 1 of the transformer and support body 3 are imprisoned on the central leg of the core.
  • the two portions of the core are secured in position by means of a retaining cage 7 which may be formed of a pre-shaped components as for instance by punching.
  • Cage 7 is preferably of a ferromagnetic material and includes a top surface 8 adapted to cooperate with the upper end of core portion 5.
  • legs 9 are formed with suitable tabs 10 (shown before bending) and 11 (shown after having been bent).
  • cage 7 is integrally formed with annular portions 12 extending between legs 9 so as to surround the windings 1 of the transformer.
  • the short-circuit winding is also effective to limit the dispersion of the magnetic field of the transformer.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Multimedia (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Soft Magnetic Materials (AREA)

Abstract

An SMT-type transformer comrprises a ferrite core formed of two complementary portions mirror-symmetrically joined to one another, and a body including a primary and a secondary winding supported on one of the legs of the core. The two core portions are retained in the assembled condition by a retaining cage (7) preferably formed of a ferromagnetic material and having a top surface (8) engaging one core portion (5), and a plurality of legs (9) extending from the top surface and having end portions (10, 11) adapted to be bent into angagement with the other core portion (6). Integrally foremd with the legs are annular portions (12) surrounding the winding body (1) so as to constitute a short-circuit winding therearound.

Description

  • The present invention relates to a switch mode transformer having a ferrite core, according to the pre-characterizing part of the patent claim. The primary and secondary windings of a transformer of this type, disclosed in US-A-3 668 586, are wound in a concentric arrangement around one leg of a so-called "open" ferrite core substantially consisting of two E- or C-shaped portions joined to one another in a mirror-symmetrical arrangement. The two core portions are secured to one another by means of a metal frame including integral bendable tabs capable of holding the two core portions together.
  • In the case of SMT-type transformers the need is generally recognized to reduce the extension of the electric field (with the resulting dispersions) in the surrounding environment, to eliminate RF interferences. This effect is obtained by disposing a short-circuit winding (normally made of copper) coaxially with the windings around the magnetic circuit of the transformer.
  • The assembly of the ferrite core and of the short-circuit winding obviously has to be carried out in two separate phases, whereby the assembly of the transformer as a whole is rendered undesirably complex.
  • It is therefore an object of the present invention to provide an SMT-type transformer having a ferrite core and short-circuit means which is of sturdy and functional construction, and the assembly of which is simple and rational, lending itself to automatization.
  • This object is attained by the characterizing features of claim 1. A preferred embodiment of the invention is subject matter of the dependent claim.
  • The characteristics and advantages of the invention will become more clearly evident from the following description of an exemplary embodiment with reference to the accompanying drawing which shows a perspective view of a transformer according to the invention, partially in cross-section.
  • An SMT-type transformer shown in the figure comprises a body 1 formed of a primary and a secondary winding, the terminals 2 of which are clamped in a per se known manner in a support body 3. Body 1 is wound on a central leg (not shown) of a ferrite core 4 formed of at least two complementary portions 5 and 6 mirror-symmetrically joined to one another. In the example shown, the two portions 5 and 6 are substantially E-shaped, although they may also be of other configurations as required.
  • The two portions 5 and 6 are joined to one another in abutting relationship as generally known, so that body 1 of the transformer and support body 3 are imprisoned on the central leg of the core. The two portions of the core are secured in position by means of a retaining cage 7 which may be formed of a pre-shaped components as for instance by punching.
  • Cage 7 is preferably of a ferromagnetic material and includes a top surface 8 adapted to cooperate with the upper end of core portion 5.
  • Downwards extending from the sides of top surface 8 are a plurality (four in the embodiment described) of legs 9 the free end portions of which are adapted to be bent into engagement with the lower end of core portion 6.
  • To this end the free end portions of legs 9 are formed with suitable tabs 10 (shown before bending) and 11 (shown after having been bent).
  • The facility of assembly of the entire transformer is clearly evident, particularly as far as it concerns the manufacture of cage 7 which may readily formed and mounted in position in an automatized process, as stated as the object of the invention.
  • According to the invention, cage 7 is integrally formed with annular portions 12 extending between legs 9 so as to surround the windings 1 of the transformer.
  • Annular portions 12, two of which are preferably provided diametrally opposite one another, effectively constitute a short-circuit winding limiting the dispersion of the electric field in the environment of the transformer in the known manner. As cage 7 is made of a ferromagnetic material, the short-circuit winding is also effective to limit the dispersion of the magnetic field of the transformer.
  • With the sole operation of mounting retainer cage 7 it is thus possible to achieve the assembly of the ferrite core as well as the limitation of the dispersions of the electric and magnetic fields.

Claims (2)

1. A switch mode transformer having a ferrite core (4) one leg of which carries a primary and a secondary winding, said ferrite core (4) comprising at least two complementary portions (5, 6) mirror-symmetrically joined to one another by a retaining cage (7) formed with a top surface (8) adapted to cooperate with one portion (5) of said core (4), a plurality of legs (9) extending from the sides of said top surface and having free end portions (10, 11) adapted to cooperate with the other portion (6) of said core (4), so that the two complementary core portions (5, 6) are clamped within said cage (7) between said top surface (8) and the end portions of said legs (9), characterized in that said retaining cage (7) is made of ferromagnetic material and includes integrally formed annular portions (12) extending between said legs (9) and forming a short-circuit winding around said windings (1) of the transformer.
2. An SMI-type transformer as claimed in claim 1, characterized in that the free end portions of said legs (9) are formed with tabs (10, 11) adapted to be bent into engagement with said core (4).
EP84104976A 1983-05-09 1984-05-03 Switch mode transformer having a ferrite core Expired EP0131700B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84104976T ATE31840T1 (en) 1983-05-09 1984-05-03 PULSE TRANSFORMER WITH FERRITE CORE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT3402383U 1983-05-09
IT8334023U IT8334023V0 (en) 1983-05-09 1983-05-09 SMT TRANSFORMER WITH FERRITE CORE.

Publications (3)

Publication Number Publication Date
EP0131700A2 EP0131700A2 (en) 1985-01-23
EP0131700A3 EP0131700A3 (en) 1985-05-15
EP0131700B1 true EP0131700B1 (en) 1988-01-07

Family

ID=11238756

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84104976A Expired EP0131700B1 (en) 1983-05-09 1984-05-03 Switch mode transformer having a ferrite core

Country Status (5)

Country Link
EP (1) EP0131700B1 (en)
AT (1) ATE31840T1 (en)
DE (1) DE3468578D1 (en)
ES (1) ES278941Y (en)
IT (1) IT8334023V0 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4937546A (en) * 1989-03-28 1990-06-26 Salom Electric Co., Ltd. Ring-core transformer
FR2655475B1 (en) * 1989-12-01 1992-02-21 Orega Electro Mecanique SHIELDING DEVICE FOR A CUT-OUT POWER TRANSFORMER.
US6950291B1 (en) 1999-11-29 2005-09-27 Lucent Technologies Inc. Electromagnetic interference shielding for small magnetic devices
CN111735994B (en) * 2020-08-25 2020-11-13 广东电网有限责任公司东莞供电局 Clamp for transformer detection

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3617854A (en) * 1970-04-20 1971-11-02 Raytheon Co Pulse transformer
US3668586A (en) * 1971-03-08 1972-06-06 Electronic Associates Transformer-inductor frame and kit
DE2209071A1 (en) * 1972-02-25 1973-08-30 Siemens Ag ADJUSTABLE ELECTRIC COIL, IN PARTICULAR FOR HYBRID AND PRINTED CIRCUITS
GB2035706B (en) * 1978-11-09 1983-05-05 Tdk Electronics Co Ltd Inductance element

Also Published As

Publication number Publication date
EP0131700A3 (en) 1985-05-15
DE3468578D1 (en) 1988-02-11
ES278941U (en) 1984-09-16
EP0131700A2 (en) 1985-01-23
ATE31840T1 (en) 1988-01-15
ES278941Y (en) 1985-04-01
IT8334023V0 (en) 1983-05-09

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