DE29723301U1 - Electronic transformer - Google Patents

Description

TER MEER STEINMEISTER & PARTNER GBR

PATENT ATTORNEYS - EUROPEAN PATENT ATTORNEYS

Dr. Nicolaus ter Meer, Dipl.-Chem. Helmut Steinmeister, Dipl.-Ing.

Peter Urner, Dipl.-Phys. Manfred Wiebusch

Gebhard Merkle, Dipl.-Ing. (FH)

Mauerkircherstrasse 45 Artur-Ladebeck-Strasse

D-81679 MUNICH D-33617 BIELEFELD

HLM P01/97/G 8.5.1998

Eckhard Haiemeier

Bakusbrink 5 32120 Hiddenhausen

ELECTRONIC TRANSFORMER

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DESCRIPTION

The invention relates to an electronic transformer with an electronic circuit, a transmitter and a housing.

Such electronic transformers are used, for example, in lighting systems with halogen recessed lights to transform the mains voltage down to the 12V voltage that is usual for halogen lamps. The mains alternating voltage of 50 Hz is converted by the electronic circuit into an alternating voltage with a higher frequency, which can then be transformed into the secondary voltage of 12V with the help of a relatively small transformer.

Since the recessed lights are usually designed for installation in holes with a diameter of 58 mm in wooden ceilings, furniture parts or the like, it is desirable to reduce the dimensions of the electronic transformer so much that the transformer housing can also be inserted into such a hole or at least pushed through such a hole into the ceiling cavity. However, since the transformer of an electronic transformer must also have certain minimum dimensions for a given output so that the waste heat can be dissipated and the necessary air and creepage distances between the primary winding and the secondary winding of the transformer can be maintained, there are limits to the reduction in size of the transformer housing, especially for transformers with higher output.

In some known electronic transformers, the necessary clearance and creepage distances between the primary winding and the secondary winding of the transformer are achieved by providing the wire of the secondary winding wound directly onto the primary winding with an insulating sheath. In other embodiments, the primary winding is encapsulated in an insulating housing, and this housing is wound with the secondary winding, the wire of which only has an insulating varnish. In both cases, the transformer has relatively large external dimensions, so that a correspondingly large housing is required to accommodate the transformer and the electronic circuit.

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From DE 42 08 660 C2 an electronic transformer is known in which the transmitter and the electronic circuit are housed in separate housings that are only connected to each other by cables so that they can be pushed one after the other through the standardized holes in the ceiling cavity.

The object of the invention is to create an electronic transformer with only a single housing, in which the housing has smaller external dimensions than a conventional electronic transformer with the same power.

This object is achieved according to the invention in that the electronic circuit and the primary winding of the transformer are accommodated in the housing and the secondary winding of the transformer is wound onto the outside of the housing.

This solution has the advantage that the material thickness of the wall of the transformer housing is used to form the necessary air and creepage distances between the primary winding and the secondary winding, so that a corresponding material thickness can be saved when encapsulating the primary winding or insulating the secondary winding. Overall, the dimensions of the transformer can thus be reduced. Another significant advantage is that the heat loss can be dissipated more effectively, since the secondary winding, which is formed by a relatively thick wire with high thermal conductivity, is no longer surrounded by a housing and can therefore serve as a heat sink. Since the secondary voltage of the transformer is not dangerous for people, there are no safety problems arising from the fact that the secondary winding is no longer surrounded by a housing.

The measure according to the invention makes it possible, for example, to design a transformer with a primary voltage of 230V and a secondary voltage of 12V and a nominal power of 70W or more so compact that it fits into a hole with a diameter of 58 mm and has a height of no more than 18 mm.

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Advantageous embodiments of the invention are specified in the subclaims.

In the following, a preferred embodiment is explained in more detail using the drawing.

Show it:

Fig. 1 the electronic transformer in plan view; and
10

Fig. 2 is an enlarged, partially cutaway view of the transformer.

The electronic transformer shown in Figure 1 has a housing 10 made of plastic, which has the shape of a flat circular disk with a diameter of 58 mm and a thickness of 18 mm. A removable cover 12 arranged on the edge of the housing allows access to connection terminals (not shown) for a power cable 14.

On the side opposite the cover 12, the housing 10 has an eccentric hole 16. The secondary winding 18 of a transformer 20 is formed by an insulated conductor that is wound around the part of the housing 10 that lies between the hole 16 and the edge of the housing adjacent to it. In the example shown, the extended ends 22, 24 of the conductor forming the secondary winding 18 are held together by an annular holder 26 and are connected directly to a plug 28, from which the secondary voltage of the transformer can be tapped.

Alternatively, it is also possible to combine the ends 22, 24 of the conductor into a secondary cable. Instead of the ring-shaped holder 26, a differently designed holder can also be provided, which prevents undesirable loosening of the secondary winding. This holder can also be formed in one piece with the housing 10.

In the example shown, the secondary winding 18 is located in flat recesses 30 in the end walls of the housing 10, so that it does not protrude beyond the end walls.

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surfaces of the housing. The peripheral wall of the housing 10 can also be provided with a corresponding recess in the area of the secondary winding 18, so that the external diameter of 58 mm is not exceeded in the area of the secondary winding 18. It is also possible to have the primary cable 14 and the ends 22, 24 of the secondary conductor extend axially from the housing 10 rather than radially, so that the transformer can be completely accommodated in a hole in a wooden ceiling or the like with an internal diameter of 58 mm.

Figure 2 shows an electronic circuit 32 with electronic components 34, which are housed on a circuit board 36 inside the housing 10.

The circuit board 36 largely fills the inner cross section of the housing 10 and has a hole that corresponds to the hole 16 of the housing. The transformer 20 has a ring-shaped or toroidal primary winding 38, which is arranged on the circuit board 36 and surrounds the hole 16 of the housing. The secondary winding 18, which only needs to have a few turns, surrounds the primary winding 38 in the area that is closer to the edge of the housing 10. In this way, the necessary magnetic coupling between the primary winding and the secondary winding is achieved. The primary and secondary windings are separated from each other everywhere by the wall of the housing 10, which thus forms an air and creepage distance between the primary winding and the secondary winding. The primary winding 38 therefore does not need to be encapsulated again in a special housing, so that a very compact design is possible. The heat loss of the transformer 20 can be dissipated unhindered to the outside via the good heat-conducting secondary winding 18. The heat generated in the primary winding 38 can also be dissipated more effectively through the hole 16 in the housing surrounded by air.

In a modified embodiment, the circuit board 36 lies completely outside the contour of the hole 16. The primary winding 18 then protrudes beyond the edge of the circuit board or is completely separated from the circuit board and is only connected to the electronic circuit 32 by electrical conductors.

Claims (7)

TERMEER STEINMEIS-CEPC&· 15AT^TNgR ©BR "I I I HLM P01/97/G PROTECTION CLAIMS 1. Electronic transformer with an electronic circuit (32), a transformer (20) and a housing (10), characterized in that the electronic circuit and the primary winding (38) of the transformer are accommodated in the housing (10) and the secondary winding (18) of the transformer is wound externally onto the housing. 2. Transformer according to claim 1, characterized in that the housing (10) has a hole (16) which is surrounded by the primary winding (38) of the transformer, and that the turns of the secondary winding (18) run through the hole (16). 3. Transformer according to claim 2, characterized in that the housing (10) has a circular outer contour. 4. Transformer according to claim 2 or 3, characterized in that the hole (16) is arranged eccentrically in the housing (10). 5. Transformer according to claim 3 or 4, characterized in that the housing (10) has an outer diameter of at most 58 mm and a height of at most 18 mm. 6. Transformer according to one of the preceding claims, characterized in that the secondary winding (18) lies in a recess (30) formed in the outer surface of the housing (10). 7. Transformer according to one of the preceding claims, characterized in that the ends (22, 24) of the conductor forming the secondary winding (18) are fixed by a holder (26) and/or directly connected to a plug (28).