EP0422397B1 - Transformateur d'impulsions - Google Patents

Transformateur d'impulsions Download PDF

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Publication number
EP0422397B1
EP0422397B1 EP90117496A EP90117496A EP0422397B1 EP 0422397 B1 EP0422397 B1 EP 0422397B1 EP 90117496 A EP90117496 A EP 90117496A EP 90117496 A EP90117496 A EP 90117496A EP 0422397 B1 EP0422397 B1 EP 0422397B1
Authority
EP
European Patent Office
Prior art keywords
core
coil
leg
transformer
windings
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 - Lifetime
Application number
EP90117496A
Other languages
German (de)
English (en)
Other versions
EP0422397A1 (fr
Inventor
Sergio Zanvettor
Vittorio Savi
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
Procond Elettronica 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 Procond Elettronica SpA filed Critical Procond Elettronica SpA
Publication of EP0422397A1 publication Critical patent/EP0422397A1/fr
Application granted granted Critical
Publication of EP0422397B1 publication Critical patent/EP0422397B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • 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

Definitions

  • the present invention relates to a so-called SMT transformer (Switch Mode Transformer), to be used in electronic switch-mode power supply circuits for picture tubes, for instance, or the like.
  • SMT transformer Switch Mode Transformer
  • SMT transformers are arranged substantially as disclosed in EP-A-0 126 365, i.e. with at least a primary winding and at least a secondary winding consisting of a coil of relevant metal bands which are wound with the interposition of an insulating film.
  • the coil including the windings is then fitted about a leg of a ferrite core.
  • the core of a SMT transformer is a substantially closed core.
  • a core is sometimes incorrectly referred to as an "open" core in order to distinguish it over the complex cores including an inner core portion and an outer core cap surrounding the transformer, it actually consists of two identical E-shaped or U-shaped portions which are specularly fitted together to form a substantially closed magnetic circuit.
  • the coil including the windings is arranged about one of the legs of the core which are defined by aligned pairs of legs of the E-shaped or U-shaped portions.
  • the leg of the core which is surrounded by the windings is provided with a central air gap, which however must have a short length.
  • the core consists of two specular portions which require particular working steps to be at first manufactured as separate parts and then assembled together with the windings, with the result of a relatively complicated and expensive manufacture of the whole transformer.
  • Another object of this invention is to provide a SMT transformer of the kind mentioned above in which undesired heating phenomena caused by magnetic losses are kept at a minimum.
  • the SMT transformer according to the invention comprises at least a primary winding 3 and at least a secondary winding 4 formed by relevant metal bands 5 (made of aluminium, for instance) superimposed on insulating film 6.
  • relevant metal bands 5 made of aluminium, for instance
  • metal bands 5 and insulating film 6 are arranged (preferably concentrically) about a portion of a magnetic core 7, for example made of ferrite, so that the primary and secondary windings form a coil 8 in which the core is inserted.
  • the core 7 only consists of one open, single-piece magnetic element provided with a first leg 9 about which is arranged the coil 8, as well as with at least a second leg 10 which is connected to the first leg through a crosspiece 11 of the core itself, so that the core has a substantially U-shaped configuration.
  • the magnetic core 7 preferably includes two of the said second legs, both illustrated at 10 and provided at opposite sides of the first leg 9, so that the core 7 has a substantially E-shaped configuration.
  • the free ends of each leg 10 are separated from the free end of the leg 9 by relevant air gaps 12.
  • an end face of the coil 8 is preferably disposed adjacent to the crosspiece 11 of the core 7, while the gap, or gaps 12 extend substantially at the side of the coil which is opposite to said end face.
  • the transformer also comprises a plurality of electric contact pins 13 and a shaped support frame 14 which is preferably located at the the side of the coil 8 opposite to the crosspiece 11 of the magnetic core 7.
  • the various elements may be mounted in place in the most convenient way, as the case may be.
  • the transformer comprises only one single-piece magnetic core 7 which may have an elementary configuration and thus may be readily and quickly assembled together with the windings 3 and 4, and further requires less material to be used and also does not involve any critical step for assembling the various elements, as it would be the case of specular magnetic elements to be coupled by glueing them together with special materials.
  • the switch mode transformer according to the present invention is arranged in contrast with the technical prejudice that the length of the gap provided in the magnetic core must be as short as possible. It is known, in fact, that in the conventional SMT transformers the inductance values of the windings depend not only on the characteristics of the material of which the magnetic core is made, but also on the dimensions of the gap provided in the leg of the core which bears the coil formed by the windings. In particular, such inductance values are inversely proportional to the length of the gap.
  • the magnetic core 7 actually is an open core, the gaps 12 having a remarkable length and the leakage flux being particularly high in correspondence of the free ends of the legs 9 and 10.
  • the SMT transformer according to this invention can provide, under the same general dimensional conditions, performances which are at least as good as those provided by a conventional SMT transformer.
  • the density of the flux lines 15 has a maximum value at the base of the leg 9 (connected with the crosspiece 11) and decreases along the leg 9 to reach a minimum value in correspondence of the gaps 12.
  • the magnetic flux leakages occurring in correspondence of the gaps 12 have an effect which is limited thanks to the low density of the magnetic flux itself; as a consequence, as it was experimentally found, in the SMT transformer according to the invention the core heating phenomenon caused by induced currents is advantageously reduced; in practice, it is perceptible only in correspondence of the base of the leg 9 of the core 7.
  • the inductance of the windings is in practice independent of the dimensions of the gap, or gaps 12, which are preferably spaced apart from the coil 8, anyway; on the contrary, the inductance depends on the height H of the wound metal bands and on the axial position of the coil 8 with respect to the leg 9 of the magnetic core. More particularly, the shorter the height H of the relevant metal bands and the closer the coil 8 to the base of the leg 9, the higher is the value of the inductance L of the windings 3 and 4. Indeed, it is a particularly surprising effect, which however was found experimentally, as already stated.
  • the SMT transformer according to the invention can be made with a remarkably compact construction, using a reduced amount of material for manufacturing the magnetic core 7 and the windings 3 and 4.
  • the SMT transformer described above may undergo many modifications without departing from the scope of the invention.
  • the axial position of the coil 8 with respect to the support leg 9 of the magnetic core may be changed, or the leg 9 and/or 10 of the magnetic core may be differently shaped, for instance with a different cross-section and/or inclination.
  • the various primary and secondary windings may be mutually offset axially, in a way known per se, as the case may be.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Multimedia (AREA)
  • Coils Of Transformers For General Uses (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Details Of Television Scanning (AREA)

Claims (2)

  1. Transformateur d'impulsions comprenant un enroulement primaire et un enroulement secondaire consistant en au moins une bobine (8) formée par des rubans métalliques qui sont enroulés, superposés sur un film isolant, autour d'un noyau magnétique (7), caractérisé en ce que ledit noyau magnétique (7) est formé par un élément magnétique ouvert en pièce unique comprenant une première branche (9), autour de laquelle est disposée ladite bobine (8), ainsi qu'au moins une seconde branche (10) reliée à ladite première branche par l'intermédiaire d'une pièce transversale (11) de ce noyau qui se trouve essentiellement à proximité d'une face d'extrémité de la bobine (8), les extrémités libres de cettes branches (9, 10) étant séparées l'une de l'autre par un entrefer (12) s'étendant essentiellement de ce côté-là de la bobine qui est opposé à ladite face d'extrémité.
  2. Transformateur d'impulsions selon la revendication 1, caractérisé en ce que cet entrefer (12) est essentiellement distancé de cette bobine (8).
EP90117496A 1989-10-11 1990-09-11 Transformateur d'impulsions Expired - Lifetime EP0422397B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT4578189 1989-10-11
IT04578189A IT1236433B (it) 1989-10-11 1989-10-11 Trasformatore smt

Publications (2)

Publication Number Publication Date
EP0422397A1 EP0422397A1 (fr) 1991-04-17
EP0422397B1 true EP0422397B1 (fr) 1994-06-01

Family

ID=11258160

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90117496A Expired - Lifetime EP0422397B1 (fr) 1989-10-11 1990-09-11 Transformateur d'impulsions

Country Status (5)

Country Link
EP (1) EP0422397B1 (fr)
DE (1) DE69009382T2 (fr)
DK (1) DK0422397T3 (fr)
ES (1) ES2057302T3 (fr)
IT (1) IT1236433B (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1634923A (en) * 1924-07-15 1927-07-05 J C Thullen Transformer
US3617854A (en) * 1970-04-20 1971-11-02 Raytheon Co Pulse transformer
IT1195595B (it) * 1983-05-09 1988-10-19 Ducati Elettrotechnica Spa Trasformatore smt per il pilotaggio proporzionale di alimentatori a commutazione statica

Also Published As

Publication number Publication date
IT1236433B (it) 1993-03-01
DE69009382D1 (de) 1994-07-07
EP0422397A1 (fr) 1991-04-17
DK0422397T3 (da) 1994-07-04
IT8945781A1 (it) 1991-04-11
IT8945781A0 (it) 1989-10-11
DE69009382T2 (de) 1995-01-19
ES2057302T3 (es) 1994-10-16

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