DE19711815A1 - Transformer for switching network - Google Patents

Abstract

The transformer has a coil body configuration contg. Two coil bodies (1,2), each with a tube section (14) carrying the primary (3) or secondary (4) winding of the transformer and with lateral sections (15,16) and bores (17) and apertures (18,19) for transformer core sections. The coil body lateral sections butt together to produce a square, oval, rectangular or circular configuration. A transformer core configuration has two core sections (10,11) engaging the bores and apertures and butting together at the ends to form a square, oval, rectangular or circular core configuration. The coil bodies with coils and cores fitted are embedded in a housing (13) using a setting material (12).

Description

The invention relates to a transformer for a switching power supply, the this transformer has distributed windings (primary and secondary windings), that are on a bobbin configuration and face each other lie and wherein a transformer core configuration the magnetic flux leads. The switching power supply equipped with such a transformer can can be used for example with IGBT gate drives in which a potential isolation voltage of, for example, 10 to 20 kV is required.

Typically, transformers with tubular or disc windings are used when low leakage inductance is required becomes. Due to the high potential isolation and the associated isolati However, transformers of this type are disadvantageously re relatively voluminous. With resonance switching power supplies with soft switching operations transformers with higher leakage inductances can be used because the Stray inductors are used specifically as resonance elements for the resonance circuits will.

The invention has for its object to provide a transformer for a resonance Specify switching power supply that meets very high insulation requirements and there at is compact.  

This object is achieved by a transformer for a switching network partially released with a coil former configuration formed from two coil formers, where each coil former travels the primary winding or the secondary winding pipe section and adjoining side sections on both sides has and through holes and recesses for receiving transforma has core sections and the bobbin has its side sections abut each other so that there is a square, rectangular, circular or oval coil body configuration results. The transformer core configuration is formed from two core sections, with the core sections in the holes and engage recesses of the bobbin and each other via their ends butt so that there is a square, rectangular, circular or oval Transformer core configuration results. Those equipped with windings and cores Coil bodies are embedded in a housing by means of a casting compound.

The advantages that can be achieved with the invention are, in particular, that the proposed transformer with regard to the dielectric strength achieved is extremely compact. As a result of the proposed configuration with konse quente sheathing of the consisting of an electrically conductive material Transformer core by means of the coil former are the primary and secondary Därwick in mutually electrically insulated chambers to master the high potential differences serve additionally inserted creepage distances.

Here are the individual components of the transformer - as in particular the windings and their connection technology - or their arrangement to each other kon sequentially designed such that a uniform formation of the electric field is guaranteed. Since the two windings comply with the required Insulation distance directly opposite, this results in a homogeneous electrical field distribution.

The relatively high leakage inductance of the transformer is for use with egg nem resonant switching power supply desired, the leakage inductance is relatively accurate is calculable or adjustable, which when used as a resonance element of Advantage is. The transformer is using simple machine processing extremely inexpensive to manufacture.

The invention is described below with reference to the embodiment shown in the drawing Examples explained. Show it:

Fig. 1 shows the basic construction of the transformer,

Fig. 2 is a side view of a coil bobbin,

Fig. 3 is a view of the end face of a bobbin.

In Fig. 1, the basic construction of the transformer is shown. The transformer has two bobbins, namely a bobbin 1 for the primary winding 3 and a bobbin 2 for the secondary winding 4th In the plan view accelerator as Fig. 1 it can be seen that each of the coil body is formed like U-essentially, wherein the windings are located on the base legs and the side legs of the two bobbin abut each other so that a qua dratische or rectangular Spulenkörper- Configuration results. The primary winding connections 5 , 6 and the secondary winding connections 7 , 8 are located at the corners of the square or rectangle formed. These connections are preferably designed as solder pins. Ribs 9 on the side legs of the coil body 1 , 2 serve to extend the creepage distance.

The transformer core is composed of two U-shaped core sections 10 , 11 . These two core sections preferably have a circular cross-section and consist of an electrically conductive high-frequency ferrite. The core sections engage in corresponding bores and recesses (see paragraphs 17 , 18 , 19 in FIG. 2) of the bobbin, so that their sides abut each other and result in a square or rectangular transformer core configuration. The butt joints of the core sections cannot be seen in FIG. 1, since they lie in the area of the primary winding and secondary winding and are therefore covered.

The transformer with coil formers 1 , 2 , primary winding 3 , secondary winding 4 and the core sections 10 , 11 is inserted into a housing 13 made of an electrically insulating plastic and embedded in an electrically insulating casting compound 12 , preferably a soft casting compound. The primary winding connections 5 , 6 and the secondary winding connections 7 , 8 penetrate the sealing compound in the open bottom part of the housing.

In Fig. 2 is a side view of the bobbin 2 made of an electrically insulating plastic be shown. The bobbin has a Ba sis leg forming central tube section 14 , the sections on both sides of sides 15 , 16 (side leg) is limited, so that - as mentioned above vorste - results in a U-shaped arrangement. The secondary winding is wound in one layer on the tube section 14 . The ribs 9 already mentioned are arranged between the beginning or end of the winding and each side section. The tube section 14 has a central bore 17 for carrying out the core sections. In a similar manner, the two side sections 15 , 16 are provided with recesses 18 , 19 in the side, into which the core sections also engage.

On both side sections 15 , 16 , connection carriers 20 , 21 are formed, which are provided with bores 22 , 23 to form the winding connections. In these holes 22 , 23 are preferably inserted metal pins, which are suitable for the solder connection of the winding start and winding end within the transformer and on the other hand - as already mentioned - pierce the bottom of the housing and can be soldered to external circuit board connections. At the circuit carrier 20 , 21 protrude beyond the tube section 14 in the immediate vicinity of the ribs 9 , so that the beginning and end of the winding can be closed in a straight line. This is important for the uniform formation of the electric field and prevents local increases in field strength.

In Fig. 3 shows a view of the front side of the bobbin 2. There are the side portion 15 with recess 18 , the tube portion 14 with central Boh tion 17 and ribs 9 and the connector bracket 20 with bore 22 to form the secondary winding connection.

The above statements regarding the bobbin 2 and the secondary winding 4 naturally also apply in the same way to the further bobbin 1 and the primary winding 3 .

In general, it applies to the transformer with distributed windings described above that the high insulation requirements are met more easily than with transformers with tubes or disk windings. The distance a between primary winding 3 and secondary winding 4 (see FIG. 1) is essentially ge depending on the potential difference occurring between the two windings ge, accordingly there is a more square or more rectangular coil body configuration with correspondingly shorter or longer sides from cut 15 , 16 .

The choice of single-layer windings with a low conductor height means that losses caused by the skin effect even at high switching frequencies in tolerable limits.

It is important that the insulation and potting materials used - such as the material of the coil former 1 , 2 , potting compound 12 , material of the housing 13 - are precisely matched to one another in terms of their electrical properties, for example the electricity constants, in order to achieve the most homogeneous field distribution possible. The potting material must be able to penetrate completely, especially in the insulation area between the primary and secondary windings, and the inclusion of air bubbles must be excluded, which is ensured, for example, by potting under vacuum.

As already indicated above, the individual turns of the windings very close to each other and arranged in one layer with no significant gaps, to avoid locally increased values of the electric field strength. To one to ensure uniform distribution of the electric and magnetic fields to achieve a wrap width of at least six to eight mm.

In addition to the UU-shaped transformer core used in the exemplary embodiment, Configuration with two U-shaped core sections, which over their side legs  butting, other configurations can be used, for example a UI configuration with a U and an I-shaped core section.

To avoid locally increased field strengths are treated in addition to the above ten square arrangements in particular also round or oval configurations toroidal or oval bobbins and toroidal or oval Transformer cores are an advantage.

Claims (5)

1. transformer for a switching power supply,
with a coil former configuration formed from two coil formers ( 1 , 2 ), where each coil form has a tube section ( 14 ) carrying the primary winding ( 3 ) or the secondary winding ( 4 ) and adjoining Seitenab sections ( 15 , 16 ) on both sides and has bores ( 17 ) and recesses ( 18 , 19 ) for receiving transformer core sections and the bobbins abut one another via their side sections, so that a square, rectangular, circular or oval bobbin configuration results,
with a formed from two core sections ( 10 , 11 ) transformer core confi guration, the core sections engaging in the bores ( 17 ) and recesses ( 17 , 18 ) of the coil former and abutting each other via their ends, so that a square, rectangular, annular or oval transformer core configuration,
wherein the bobbins equipped with windings and cores are embedded by means of a casting compound ( 12 ) in a housing ( 13 ). 2. Transformer according to claim 1, characterized in that the tenabschnitte Be ( 15 , 16 ) of the bobbin ( 1 , 2 ) are each provided with ribs ( 9 ) for creepage extension. 3. Transformer according to claim 1 or 2, characterized in that on the edge regions of the tube sections ( 14 ) of the coil former ( 1 , 2 ) connection carriers ( 20 , 21 ) are formed, which have bores ( 22 , 23 ), can be inserted into the metal pins are which primary winding connections ( 5 , 6 ) and secondary winding connections ( 7 , 8 ) form. 4. Transformer according to one of the preceding claims 1 to 3, characterized in that the primary winding ( 3 ) and secondary winding ( 4 ) are wound very closely to one another, with a small conductor height and without any significant gaps. 5. Transformer according to one of the preceding claims 1 to 4, characterized in that the primary winding ( 3 ) and secondary winding ( 4 ) have a winding width te of at least six to eight mm.