EP1523748B1 - Inductive component and use of said component - Google Patents

Description

The invention relates to an inductive component for forming a magnetic circuit, comprising at least one wire winding and at least one core with a ferromagnetic core material, wherein the core for interrupting the magnetic circuit has a gap and at least one further gap and the gaps each have a gap width, the is at least 1.0 mm. In addition, a use of the device is specified.

Out DE 198 84 902 A1 is an initially described inductive component known. The inductive component is a transformer.

US 4,885,445 A describes a transformer suitable for high frequency applications. In the transformer air gaps are provided for the core, which are filled with electrically insulating material.

Out EP 0 193 057 A2 For example, an inductive component in the form of a transformer for a television receiver is known. The core has air gaps with a gap width of about 1 mm.

An electronic ballast (ECG) is used as an electronic voltage and / or current transformer in the lighting area. ECGs have at least one inductive component. The inductive component is, for example, a choke coil or a transformer. The inductive component has a wire winding. The wire winding has a number of turns of electrical conductor for generating a magnetic flux through the current flowing in the conductor. The wire winding also serves to generate a voltage by changing the magnetic induction in the wire winding. to Increasing the magnetic induction and reducing stray magnetic leakage, the wire winding is mostly on a core of ferromagnetic material. The ferromagnetic core material is, for example, a ferrite. The core ensures a closed magnetic circuit.

These TOs are increasingly being miniaturized. The miniaturization relates in particular to an inductive component of the electronic ballasts. A small size of an inductive component can be achieved with a constant power throughput by a higher switching frequency. However, a higher switching frequency leads to an increase in the electrical losses and thus to a reduction in the quality of the inductive component. The quality is a measure of an electrical quality of the inductive component. As a result of the decreasing quality, with an increasing miniaturization of the inductive component, in particular with a high alternating voltage, with which the inductive component is operated, an inadmissibly high operating temperature may occur.

The object of the present invention is to provide an inductive component which has a high quality even with a high applied alternating voltage.

The object is achieved by an inductive component for forming a magnetic circuit, comprising at least one wire winding and at least one core with a ferromagnetic core material, wherein the core for interrupting the magnetic circuit has a gap and at least one further gap and the gaps each have a gap width , which is at least 1.0 mm. The inductive component is characterized in that the gap width (9) is selected from the range of 2.0 mm to 10 mm inclusive. The result is a relatively wide total gap, which is divided into at least two columns.

A gap is a desired interruption of the magnetic circuit. Preferably, over a total extent of the gap, the gap width is approximately equal. The extent is, for example, a width, a length or a radius of the gap. The gap has at least partially a non-ferromagnetic material to interrupt the magnetic circuit. The non-ferromagnetic material is, for example, a diamagnetic or paramagnetic material. According to the invention, the magnetic circuit is interrupted at least two places. The interruption takes place through the column. The gap widths cause the magnetic circuit to be interrupted in a length of at least 2 x 2.0 mm. Surprisingly, it has been found that, despite a control of the inductive component with an alternating voltage of several hundred volts, a relatively high quality Q can be achieved on account of this gap. Therefore, a smaller size of the inductive component is possible in comparison to an inductive component with differently designed columns.

In a particular embodiment, the core consists of at least two parts, which are arranged opposite one another on the columns and are spaced apart from one another by the gap widths.

Preferably, at least one of the gaps is an air gap. This means that the gap of the core defined by the gap contains air. The non-ferromagnetic material of the gap is air. However, it is also possible for another non-ferromagnetic, gaseous material to be arranged in the air gap. In contrast, a non-ferromagnetic solid or liquid material is conceivable. This material is for example a polymer material. For example, the use of an adhesive with which the parts of the core are glued together is advantageous. The glue does not just lead to one Interruption of the magnetic circuit. It also leads to a cohesive contact between the parts of the core.

In a further embodiment, the wire winding has an inner region and an outer region and the gaps of the core are arranged in the inner region and / or in the outer region of the wire winding. For example, a gap is arranged in the interior and two columns in the outer area. Preferably, the gaps in the outer area are characterized by the substantially same gap width. It may also be that the gap in the interior of the wire winding has a significantly higher gap width, as the two columns in the outer area. Preferably, however, the gap widths of all gaps are substantially the same.

The core can be unbalanced. This means that it can not be transformed into itself by applying a symmetry operation. In a further embodiment, the core is substantially symmetrical. Essentially, it means that there may be deviations in terms of exact symmetry. In addition, essentially, the symmetry means those components of the nucleus that are mainly responsible for the function and properties of the nucleus. The symmetrical core is transformed into a point (symmetry center), a straight line (symmetry axis) or a plane (symmetry plane) by reflection. For example, said symmetry elements are arranged in the interior of the wire winding. The symmetry element is, for example, a plane of symmetry which is arranged perpendicular to a winding axis of the wire winding. The winding axis of the wire winding is given by a direction in which the wire is wound. The core consists for example of two parts, which are each converted by the reflection at the plane of symmetry into each other. The plane of symmetry preferably also contains the gaps and the core consists of mutually mirror-inverted shaped parts. For example, the core has an RM6 or equivalent core shape. These core shapes are a combination of an E-core shape with a pot-core shape.

In particular, the entire wire winding and core component has a substantially symmetrical construction. This means that not only the core, but also the wire winding are constructed substantially symmetrical. For example, wire winding and core can be converted into themselves by mirroring at a common mirror plane. Essentially symmetrical means that deviations from the symmetry are conceivable. These deviations refer, for example, to a number or a shape of the turns of the wire winding, a shape of the core, and an arrangement of wire winding and core to each other.

In particular, the core material of the core is suitable for high frequency. Preferably, the core material is a ferrite in the form of an M33 core material having a cutoff frequency of about 10 MHz. This core material has manganese and zinc. Likewise, a K1, K6 or K12 core material is conceivable. These core materials include nickel and zinc. For example, the K6 core material has a cutoff frequency of 7 MHz.

In a particular embodiment, the wire winding on a high-frequency strand with a plurality of mutually electrically insulated individual wires. A strand is a wire wound or braided from many metal threads (individual wires). In a high-frequency strand, the individual wires are isolated from each other to reduce losses due to skin effect and eddy currents. As a result, a lower high-frequency loss resistance is achieved in comparison to a strand with individual wires not insulated from one another with the same cross-section. In particular, the individual wires have at least one selected from the range of 10 microns up to and including 50 microns single wire diameter. In particular, the plurality is in the range of 5 to 100 inclusive selected. Preferably, the plurality is selected from the range of 10 to 30 inclusive. For example, 10 or more individual wires are arranged to a high-frequency strand. This makes it possible to provide wire windings with a relatively large surface and thus with a relatively low high-frequency loss resistance.

In particular, the inductive component is a choke coil or a transformer. An inductor is permeable to direct current. In contrast, alternating current is limited by the choke coil. The choke coil has a high electrical reactance for a high frequency current. The transformer consists of at least two wire windings. But it can also be arranged more than two wire windings to the transformer. Alternatively, the transformer consists of a wire winding, which is divided by an electrical tap into two parts.

In order to further increase the already achievable by the described structural measure high quality, the inductive component is also cooled. For this purpose, according to a particular embodiment, at least one cooling device for cooling the wire winding is present, which has at least one composite material with at least one polymer material and at least one thermally conductive filler.

With the help of the cooling device, the heat generated in the wire winding during operation of the inductive component can be efficiently dissipated. The efficient dissipation of the heat leads to a relatively small increase in the temperature of the wire winding. The small increase in temperature leads to a relatively small increase in the electrical resistance in the wire winding. This results in an increased compared to an uncooled wire winding good of the inductive component.

The composite material preferably consists of an electrically insulating or electrically poorly conductive polymer material with a thermally conductive and electrically poorly conductive filler. The polymer material may comprise a natural and / or artificial polymer. The natural polymer is, for example, rubber. The artificial polymer is a plastic.

The polymer material forms as the base material of the composite material a matrix in which the filler is embedded. In this case, several fillers may be present. The filler or the fillers may be powdery or fibrous. A diameter of a filler particle is selected from the μm range, which ranges from 100 nm to 100 μm. A degree of filling of the filler in the polymer material is preferably chosen so that a coagulation limit is exceeded. Below the coagulation limit there is a very low probability that individual filler particles will touch each other. This leads to a relatively low specific thermal conductivity coefficient. If the coagulation limit is exceeded, the filler particles touch with relatively high probability. This results in a relatively high specific thermal conductivity coefficient of the composite material.

The filler is thermally conductive and preferably also electrically insulating or electrically poorly conductive. As a result, the inductive component can also be operated with a relatively high operating voltage. For example, the operating voltage is up to 2000 V. The composite material is resistant to breakdown even at an operating voltage of this magnitude. As a thermally conductive and at the same time electrically insulating or electrically poorly conductive filler is particularly suitable a ceramic material. A ceramic one Material with the properties mentioned is, for example, aluminum oxide (Al ₂ O ₃ ).

For efficient removal of heat, which arises during operation of the inductive component in the wire winding, the composite material of the cooling device is preferably connected directly to the wire winding. A heat transfer away from the wire winding occurs by heat conduction.

In a particular embodiment, the cooling device has at least one film with the composite material, which is in direct, thermally conductive contact with the wire winding. The film and the wire winding are connected in such a way that heat conduction from the wire winding to the film can take place. The foil and the wire wrap touch each other. A film thickness (film thickness) of the film is for example 0.22 mm. Depending on the composite material (type of polymer material, type and degree of filling of the filler, etc.), a specific thermal conductivity coefficient λ of 0.15 K / Wm up to 6.5 K / Wm can be achieved. The dielectric strength can be 1 kV to 6 kV despite the relatively low film thickness.

In order to ensure efficient heat dissipation by the cooling device, in particular a soft film is used with the composite material. The film is plastically and / or elastically deformable. The wire winding may be approximately positively embedded in the film. A thermal contact surface between the film and the wire winding over which the heat conduction takes place is particularly large.

In a particular embodiment, the cooling device has at least one potting compound which has at least one further composite material with at least one further polymer material and at least one further thermally conductive filler and which is in direct, thermally conductive contact with the wire winding and / or the film stands. The composite material and the further composite material may be the same or different. The same applies to individual components of the composite material and of the further composite material. The wire winding and / or the film are partly or completely embedded in the potting compound with the further composite material. Since the other composite material is thermally conductive and by embedding an almost complete positive connection between casting material and wire winding or film is present, the heat from the wire winding and the film on the casting material can be derived very efficiently. In addition, the use of the potting compound leads to a homogeneous temperature distribution within the inductive component. The wire winding of the device is cooled homogeneously. This also contributes to an increased quality of the inductive component.

Both in the case of the film and in the potting compound, it is possible for intermediate spaces (cavities) to be present between potting compound, film and wire winding which are filled with air and therefore contribute to thermal insulation of the potting compound, film and wire winding from one another. An efficient dissipation of heat is not possible due to the gaps. In a particular embodiment, therefore, a space present between the film and the wire winding and / or between the potting and the wire winding has a thermally conductive material for thermal bridging of the interspace. The gap is preferably completely filled with the thermally conductive material. This leads to improved heat dissipation away from the wire winding. Preferably, a thermally conductive material is used, which is additionally electrically insulating. The thermally conductive material is therefore selected in particular from the group Ö1, paste, wax and / or adhesive. With these thermally conductive and at the same time electrically insulating materials it is ensured that even when using high operating voltages is given a necessary voltage resistance.

The cooling device of the inductive component is designed such that the heat generated in the wire winding during operation of the inductive component can be efficiently dissipated to the outside. For this purpose, a further transport of heat away from the composite material of the cooling device is taken care of. The further transport of the heat takes place for example by convection. For this purpose, a fluid is passed past the cooling device with the composite material, which can absorb the heat. The fluid is for example a liquid or a gas or gas mixture.

Preferably, the further transport of the heat takes place by heat conduction. In a particular embodiment, the film with the composite material and / or the potting compound with the composite material with a heat sink by a_Wärmeleitung is therefore thermally conductively connected in the inductive component. With the help of the heat sink it is ensured that the smallest possible temperature difference between the wire winding, the cooling device and the heat sink is present during operation of the inductive component. For this purpose, the heat sink is preferably designed such that it can absorb a large amount of heat. The heat capacity of the heat sink is large. It is also conceivable that the heat sink ensures efficient removal of the heat. The heat sink is for example a heat sink made of a material that is characterized by a high thermal conductivity. To maintain the thermal gradient, the heat sink may be cooled by convection.

The inductive component is used according to a second aspect of the invention in an electronic ballast, in which an electrical input power is converted into an electrical output. Input power and Output power is usually different. In particular, the device is operated with an alternating voltage having a frequency in the range of 100 kHz inclusive up to and including 200 MHz. This frequency range is referred to as high frequency range.

In a particular embodiment, an AC voltage of up to 2000 volts is used. It has been shown that with the help of the column, a high quality can be achieved even with a few hundred volts with a frequency of a few MHz. This results in that the inductive component can be miniaturized and still a high power throughput can be achieved with high quality and low internal losses. The inductive component can thus be referred to as a miniaturized HF-HV (high-frequency high-voltage) component.

The inductive component can also be used in an ignition transformer for igniting a discharge lamp. To ignite the discharge lamp, the discharge lamp is driven via an electrical circuit with a high alternating voltage (initial voltage). In a further embodiment, therefore, a voltage pulse with an AC voltage of up to 40 kV is used. The component is driven with this high AC voltage for a short time within a few microns (ignition duration).

Figur 1

zeigt ein induktives Bauelement von der Seite.

Figur 2

zeigt ein Gütespannungsdiagramm des induktiven Bauelements.

Figuren 3a und 3b

zeigen eine RM-Bauform des Kerns des induktiven Bauelements von oben und im Querschnitt entlang der Verbindungslinie I-I.

Figuren 4 bis 6

zeigen das induktive Bauelement aus Figur 1 mit jeweils einer Kühlvorrichtung in einem seitlichen Querschnitt.

Figur 7

zeigt einen Ausschnitt des induktiven Bauelements mit der Kühlvorrichtung in einem seitlichen Querschnitt.

On the basis of several embodiments and the associated figures, the invention is presented in more detail. The figures are schematic and do not represent true to scale figures.

FIG. 1

shows an inductive component from the side.

FIG. 2

shows a Gutspannungsdiagramm of the inductive component.

FIGS. 3a and 3b

show an RM design of the core of the inductive component from above and in cross section along the connecting line II.

FIGS. 4 to 6

show the inductive component FIG. 1 each with a cooling device in a lateral cross-section.

FIG. 7

shows a section of the inductive component with the cooling device in a lateral cross-section.

The inductive component 1 is an HF-HV (high-frequency high-voltage) transformer ( FIG. 1 ). The component 1 has a wire winding 3 and a core 4. The wire winding is characterized by a winding axis 12, along which the wire of the wire winding 3 is wound. The wire winding 3 is a high-frequency strand 14 with 30 individual wires. The wire diameter of a single wire is about 30 microns. The core 4 is a ferrite core and consists of a M33 core material. The core has an RM6 core form ( FIGS. 3a and 3b ). The core is a combination of an E-core shape and a pot core shape with a central bore 15. The core 4 has a core-centered gap 7, which is arranged around the central bore 15 in the inner region 10 of the wire winding 3. Two further gaps 8 are arranged in the outer region 11 of the wire winding 3 in each case one of the core legs 6 of the core 4. All three columns 7 and 8 are air gaps. The gap widths of gaps 7 and 8 are substantially equal, each about 3 mm.

The core is essentially symmetrical. It consists of two to the mirror plane 13 mirror-symmetrically arranged parts 5, which are arranged opposite one another at the columns 7 and 8 and spaced from each other by the gap widths 9. The mirror plane 13 is located in the three columns 7 and 8. The arrangement is not only the core 4, but also the wire winding 3 arranged substantially symmetrically. The result is an inductive component, which is symmetrical to the mirror plane 13 substantially.

This in FIG. 2 shown voltage diagram is measured at a primary inductance of the RF-HV transformer 1 of 24 uH and a frequency of 2.7 MHz by means of the circular resonance method. It can clearly be seen that even with an effective alternating voltage (U _L [V _eff ]) of several hundred volts, a relatively high quality of the component can be achieved. Despite the high frequency, the high quality can be achieved with a small size, as is the case with an RM6 core mold.

The wire winding 3 of the miniaturized RF-HV transformer is cooled in accordance with further embodiments. For this purpose, a cooling device 20 for cooling the wire winding 3 is present.

According to a first embodiment, the cooling device 20 comprises a foil 21 with a thermally conductive composite material. The base material of the composite is a thermally and electrically poorly conductive polymer material. In the polymer material, a filler with high thermal and low electrical conductivity is embedded. The film 21 has a film thickness of about 0.22 mm. The specific thermal conductivity coefficient λ is about 4 K / Wm. The electrical dielectric strength reaches up to about 6 kV.

The high-frequency strand 14 of the wire winding 3 and the film 21 are wound around a wound body 30 adapted to the RM6 core shape. In this case, the film 21 and the wire winding 3 are arranged around the winding body 30 such that the high-frequency strand 14 of the wire winding 3 and the films 21 alternate from the winding body 30 in the radial direction ( FIGS. 4 and 5 ). The used film 21 serves as Intermediate insulating layer of the high-frequency strand 14 of the wire winding 3. An efficient heat conducting path 24 results from the wire winding 3 away in the radial direction. Along the heat conduction path 24, heat which arises during operation of the inductive component 1 in the high-frequency strand 14 is efficiently dissipated.

According to an alternative embodiment, the high-frequency strand 14 of the wire winding 3 and a plurality of films 21 are each radially aligned with the winding body 30. It is a multi-chamber solution realized, which is also referred to as disk winding. Here, too, an efficient dissipation of heat via the heat conduction path 24 is provided.

For further dissipation of the heat, the inductive component 1 or the cooling device 20 of the inductive component 1 is embedded in a potting compound 22 with a further thermally conductive composite material ( FIGS. 4 and 6 ). The potting compound 22 is contacted with a portion of the wire winding 3 thermally conductive directly. This means that the heat can be dissipated via heat conduction via a thermal contact surface between the high-frequency winding 14 of the wire winding 3 and the film 21 or the films 21. For efficient dissipation of heat, the potting compound 22 is thermally conductively connected to the heat sink 25 via heat conduction. The heat sink 25 is a board with a thermally highly conductive material. During operation of the inductive component, a relatively small temperature difference results between the wire winding 3 and the heat sink 25.

As an alternative to potting compound 22, the heat is further dissipated by a discharge fin 26 having a relatively high coefficient of thermal conductivity ( FIG. 5 ). About the Ableitfinne 26, which is connected via a spacer ceramic 28 having a relatively high coefficient of thermal conductivity with the films 21, the heat is transmitted from the films 21 and the wire winding 3 in the direction of the heat sink 25.

Both in the case of the potting compound 22 and in the case of the film 21, gaps 27 may be present which reduce the efficiency with which the wire winding 3 is cooled ( FIG. 7 ). These intermediate spaces 27 are filled according to a further embodiment with a thermally conductive and electrically insulating or poorly conductive paste.

Claims (21)

1. An inductive component (1) for the formation of a magnetic circuit, comprising at least one wire winding (3) and at least one core (4) with a ferromagnetic core material, the core (4) comprising a gap (7, 8) and at least one further gap (8, 7) to interrupt the magnetic circuit, and the gaps (7, 8) each have a gap width (9) of at least 1.0 mm, characterized in that the gap width (9) is selected from the range from 2.0 mm to 10 mm, inclusive.
2. Component according to Claim 1, the core (4) comprising at least two parts (5) which are arranged opposed to each other across the gaps (7, 8) and separated from each other by the gap widths (9).
3. Component according to Claim 1 or 2, at least one of the gaps (7, 8) being an air gap.
4. Component according to one of Claims 1 to 3, the gaps (7, 8) having an essentially equal gap width (9).
5. Component according to one of Claims 1 to 4, the wire winding (3) comprising an inner region (10) and an outer region (11) and the gaps (7, 8) of the core (4) being arranged in the inner region (10) and/or in the outer region (11) of the wire winding (3).
6. Component according to one of Claims 1 to 5, the core (4) being essentially symmetrical.
7. Component according to one of Claims 1 to 6, the core material of the core (4) being capable of accepting high frequencies.
8. Component according to one of Claims 1 to 7, the wire winding (3) comprising a high-frequency braided wire (14) with a multiplicity of individual wires that are electrically insulated from one another.
9. Component according to Claim 8, the individual wires having at least an individual wire diameter that is selected from the range from 10 µm to 50 µm, inclusive.
10. Component according to Claim 8 or 9, the multiplicity being selected from the range from 5 to 100, inclusive.
11. Component according to one of Claims 1 to 10, the component being a choke coil or a transformer.
12. Component according to one of Claims 1 to 11, there being at least one cooling device (20) for cooling the wire winding (3), which device comprises at least one composite material with at least one polymer material and at least one thermally conductive filler.
13. Component according to Claim 12, the cooling device (20) comprising at least one film (21) with the composite material which is in direct, thermally conductive contact with the wire winding.
14. Component according to Claim 12 or 13, the cooling device (20) having at least one casting compound (22), which comprises at least one further composite material with at least one further polymer material and at least one further thermally conductive filler and which is in direct, thermally conductive contact with the wire winding (3) and/or the film (21).
15. Component according to one of Claims 12 to 14, an intermediate space (27) that is present between the film (21) and the wire winding (3) and/or between the casting compound (22) and the wire winding (3) comprising a thermally conductive material for thermally bridging the intermediate space (27).
16. Component according to Claim 15, the thermally conductive material being selected from the group comprising oil, paste, wax and/or adhesive.
17. Component according to one of Claims 12 to 16, the film (21) with the composite material and/or the casting compound (22) with the further composite material being connected in a thermally conducting manner by heat conduction to a heat sink (25).
18. Use of a component according to one of Claims 1 to 17 in an electronic ballast, in the case of which an electrical input power is converted into an electrical output power.
19. Use according to Claim 18, the component being operated with an AC voltage at a frequency from the range from 100 kHz to 200 MHz, inclusive.
20. Use according to Claim 18 or 19, an AC voltage of up to 2000 V being used.
21. Use according to Claim 18 or 19, a voltage pulse with an AC voltage of up to 40 kV being used.

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