DE102016201258A1 - Electric voltage converter with several storage chokes - Google Patents

Abstract

The present invention relates to an electrical voltage converter with a plurality of storage chokes, which are connected on parallel circuit branches between a first terminal and a second terminal of the voltage converter. At least two of the storage chokes have a common core set comprising, for each storage choke, core sheaths wrapped by coil windings of the storage choke, and returns for the magnetic fluxes in the core limbs having a lower magnetic resistance than the core limbs. The feedbacks are formed only by outer regions of the core set and the storage chokes are designed and interconnected so that in each case adjacent magnetic limbs, a magnetic flux is generated with opposite flow direction. In the proposed voltage converter, the storage chokes require less space than independently designed storage chokes and are still largely decoupled from each other.

Description

Technical application

The present invention relates to an electrical voltage converter with a plurality of storage chokes according to the preamble of claim 1.

Electrical voltage transformers are used for many technical applications, for example in electrical switching power supplies. Particularly in the case of DC converters (DC / DC converters) of high power, several parallel circuit or energy branches (so-called phases) are required in order to provide the required power. Each phase in this case has a storage inductor, which connects the pulsating half-bridge voltage with the DC voltage. The storage chokes must buffer energy and require corresponding space.

State of the art

To reduce the installation space, it is known to couple several of the storage chokes by using a common core set. Due to this coupling, however, the individual storage chokes often influence one another so that the individual phases of the voltage converter are no longer electrically independent of one another. The transforming effects must therefore always be taken into account and may lead to the loss of the effective inductance or the maximum saturation. Furthermore, higher demands are placed on the control of the voltage converter, since the neighboring phases influence each other.

From the US 2015/0287512 A1 a coil arrangement of two storage chokes is known, which are coupled via a common three-piece core set. The core set has, for each storage choke, a leg wrapped by coil windings of the storage choke with at least one air gap. The two wrapped legs thereby form the outer legs of the core set, between which a middle leg is arranged for the return of the magnetic fluxes generated in the outer legs. This middle leg has a smaller cross-section than the two outer legs. This leads to a more compact design and a weight saving compared to a training with two separate storage chokes. Also in this case unwanted magnetic coupling between the two storage chokes is greatly reduced by this design. However, this solution is only possible for arrangements with two storage chokes and also has no good shielding effect, so that external magnetic fields can occur.

The object of the present invention is to provide a voltage converter with a plurality of storage chokes, in which the storage chokes take up the smallest possible space, are well magnetically shielded and largely decoupled from each other.

Presentation of the invention

The object is achieved with the electrical voltage converter according to claim 1. Advantageous embodiments of the voltage converter are the subject of the dependent claims or can be found in the following description and the embodiments.

The proposed electric voltage converter has a plurality of storage chokes, which are connected on parallel circuit branches between a first terminal of the voltage converter and a second terminal of the voltage converter. The storage chokes have a common core set, which has for each storage choke a core legs wrapped by coil windings of the storage choke and feedback for the magnetic fluxes generated in the core limbs to form magnetic circuits. The core legs and the recirculations are designed such that the recirculations have a lower magnetic resistance than the core limbs, preferably a lower magnetic resistance by a factor of ≥ 10. This can be achieved for example by materials of different permeability for the core legs and the returns. Preferably, however, the core legs have one or more air gaps, through which their magnetic resistance is significantly increased.

The proposed voltage converter is characterized in that, on the one hand, the feedbacks are formed only by outer regions of the core set and, on the other hand, the coil windings of the storage inductors are designed and interconnected so that a magnetic flux with opposite flow direction is generated during operation of the voltage converter in adjacent core legs. This can be achieved by different winding sense of the coil windings of adjacent core legs or by reversed terminal polarity of the coils respectively adjacent core legs.

In the proposed design of the voltage converter is exploited that in many voltage converters, especially in DC-DC converters, the main current direction is identical by the individual circuit branches and the currents in the circuit branches are similar. This compensates for the proposed training of the core set with the storage chokes the magnetic currents largely. Residual differences caused, for example, by operational ripple (AC ripple) can flow across the external feedbacks. Due to these feedbacks, the windings of the storage chokes therefore remain decoupled. The proposed design and interconnection of the coil windings of the storage chokes adjacent core legs of the magnetic flux is significantly reduced in the feedback, so that their cross section can be reduced accordingly. The returns are formed only by outer areas of the core set and thus by outer core legs. There are therefore no repatriations between the individual wrapped core legs or the storage chokes longer required, so that the entire assembly takes up a smaller space. By eliminating internal recirculation and the smaller space and weight and cost savings. The external feedback also ensures that no external magnetic field occurs.

The core set may have different geometries in the proposed voltage converter. For example, the wrapped core legs may be arranged in a row between two or more than two outer return legs. A non-linear arrangement of the wrapped core legs is possible. The core legs are each connected on both sides via the magnetizable material of the core set with the returns and - where available - with the respective adjacent core legs. The core set is preferably formed in two parts. Particularly preferably, the two parts form two identical halves of the core set, which in particular represent the upper and the lower half of the core set when the core limbs are aligned vertically.

In a preferred embodiment, the sum of the cross-sectional areas of the recirculations formed perpendicular to the magnetic flux direction is smaller than the sum of the cross sections of the core legs wrapped by the coil windings that are perpendicular to the magnetic flux direction. This makes it possible to achieve almost any reduction in the return cross sections.

Particularly preferably, the sum of the cross sections of the recirculations formed perpendicular to the magnetic flow direction is as large as the cross section formed perpendicular to the magnetic flux direction of a single one of the core legs wrapped by the coil windings. Under the same size is to be understood a range between an exact match up to a maximum deviation of 10%. The cross sections of the individual core legs wrapped by the coil windings are at least approximately the same. Thus, magnetic saturation of the core material in the recirculations can be avoided.

An optimal compensation of the magnetic fluxes is achieved in the proposed voltage converter with an even number of storage chokes on a common core set.

The proposed voltage converter is preferably designed as a multi-phase DC-DC converter, wherein each of the circuit branches corresponds to a phase of the voltage converter. The proposed structure of the core set with the storage chokes, the volume and thus the weight and cost of the magnetic material (ferrite material or other magnetic materials) can be reduced. In the case of only two storage chokes or phases can thus be achieved, for example, a saving of the ferrite material of about 16%. With more than two phases, a saving of up to approx. 30% is achieved without systemic transformer coupling of the phases. This makes it possible to realize multiphase DC-DC converters (DC / DC converters) of all power classes. This also applies to all buck and boost converters as well as full bridges and resonant converters as long as the peak-to-peak AC content is less than twice the DC content. Examples of such converters are multiphase converters on PC and server mainboards, DC backbone supplies in telecommunications and data centers, fuel cell boosters in the stationary and mobile sector, traction network converters in the automotive sector or couplers of supercaps.

In principle, the proposed voltage converter can also be realized as an AC voltage converter (AC converter). In the case of AC voltage transformers, the characteristic of 3 phases is particularly favorable, since the three sinusoidal currents complement each other perfectly here. The outer feedback or outer leg decouple in exactly the same way the coils and allow the compensation of the switching ripple (Schaltripple).

Brief description of the drawings

The proposed voltage converter will be explained in more detail below with reference to embodiments in conjunction with the drawings. Hereby show:

1 a circuit diagram of a multi-phase DC-DC converter;

2 a cross-section through an exemplary structure of two adjacent storage chokes according to the prior art;

3 a cross-section through an exemplary construction of a core set with two storage chokes according to the present invention;

4 a cross-section through an exemplary structure of a core set with a larger number N of storage chokes according to the present invention; and

5 a schematic representation of a lower part of another exemplary construction of a core set with two storage chokes according to the present invention.

Ways to carry out the invention

The following is based on 1 an exemplary circuit for a DC-DC converter shown, as it can also be used in the proposed converter. The in 1 shown converter has a plurality of parallel energy or circuit branches, so-called. Phases, between a first terminal 1 and a second port 2 of the voltage converter. In the individual circuit branches each have a storage throttle 3 interconnected, which serves the intermediate storage of energy during operation of the voltage converter. In the present example, three parallel circuit branches are shown with corresponding switches, via the pulse width and thus the conversion factor of the voltage converter is set in a known manner.

In this example, the first port is located 1 the highside input voltage and the second connection 2 the low side output voltage. It is a down-converter. The converter may also have a larger number N of phases or storage chokes, as indicated by the dots in the figure. Due to the multi-phase structure, on the one hand, the ripple during the conversion can be reduced and, on the other hand, a greater electrical output power can be provided. The storage chokes require space for energy storage, which adds up to several storage chokes.

2 For this purpose, by way of example, shows in cross section two storage throttles arranged next to one another 3 , as they may be formed according to the prior art. Each storage choke here has a magnetically conductive core set 4 on, which in the present example in e-core design is made in two parts. The core set has a central core leg 5 on that of the coil windings 6 the storage throttle 3 is wrapped. On both sides of the central core leg are returns 7 for the core thigh 5 generated magnetic flux formed to form a magnetic circuit. The core thigh 5 each storage choke 3 each has an air gap 8th on that in the 2 is indicated. In an arrangement of the two storage chokes 3 next to each other, the magnetic fluxes φ1 and φ2 indicated in the figure occur and are distributed correspondingly to the returns 7 , The direction of flow of the magnetic fluxes is indicated in the figure by the arrows.

In order to reduce the installation space for the storage chokes in the voltage converter of the invention, a structure of the storage chokes with a common core, for each two or more phases selected. Although the use of a common core usually leads to a coupling of the storage chokes, which is largely compensated by the proposed structure again. The inventive design of the core set and the formation and interconnection of the coil windings of the storage chokes is achieved that the largest part of the magnetic flux is compensated in each case by the adjacent turns and remaining differential magnetic fields are short-circuited via external feedback. On internal feedback or legs between the individual storage chokes can be dispensed with. This leads to a reduction of the installation space for the storage throttles, to a weight and thus also to a cost savings.

3 shows a cross section through an exemplary structure according to the invention, the performance in its construction of the 2 is identical. In the figure, the two-part core set 4 with the two inner core legs 5 to recognize, each an air gap 8th and from the coil windings 6 the respective storage throttle 3 are wrapped. In the present example, the two inner core legs 5 each wrapped in opposite directions, so that in the left core leg of the river φ1 upwards and in the right core leg of the flow φ2 down, that is generated in the opposite direction of flow. Remaining differential flows are via the external returns 7 shorted. These returns 7 make sure that the two storage chokes 3 continue to be magnetically decoupled and no external magnetic field occurs. By the opposing magnetic fluxes in the adjacent inner core legs 5 can be dispensed with an intermediate recycling. From the 3 is clearly seen that so that the volume of the arrangement of storage chokes against a Embodiment according to the prior art, as in 2 is shown reduced.

Such a construction can be based on any number of storage chokes 3 expand. This is in 4 schematically illustrated in which a number of N storage chokes 3 with the corresponding core thighs 5 and coil windings 6 and the external returns 7 is indicated.

The structure of the arrangement of storage chokes according to the present invention can of course be done in other ways. So shows 5 schematically in a representation not proportional representation another possibility for the structure. In this example, the lower half of the core sentence 4 for two storage chokes and one coil winding 6 one of the storage chokes indicated. The core sentence 4 in turn has two inner core legs 5 on, each from a coil winding 6 the corresponding storage throttle are wrapped. Again, an air gap not apparent in this example is in the inner core legs 5 educated. The returns 7 are formed in this example by six outboard return legs. The recognizable in the figure cross-sectional areas of these returns 7 in sum, preferably correspond to the cross-sectional area of an inner core limb 5 , Of course, such a structure can be extended analogously to more than two storage chokes.

With the proposed structure and the corresponding interconnection of the storage chokes, space, weight and costs for the storage chokes can be reduced without negative influence of coupling. The coupling factor can be at least theoretically reduced to zero in such an embodiment. All interpretations, inductance and saturation can remain identical in comparison to a separate design of the storage chokes. Already performed simulations show the negligible mutual influence of the storage chokes. It has also been demonstrated by simulations that the storage chokes do not change their inductance compared to a separate version and remain electromagnetically independent.

LIST OF REFERENCE NUMBERS

1

 Input of the voltage converter

2

 Output of the voltage transformer

3

 Power inductor

4

 core

5

 core leg

6

 coil windings

7

 return

8th

 air gap

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2015/0287512 A1 [0004]

Claims (10)

Electric voltage converter with several storage chokes ( 3 ), which are connected on parallel circuit branches between a first connection ( 1 ) of the voltage converter and a second terminal ( 2 ) of the voltage converter, wherein at least two of the storage chokes ( 3 ) via a common core sentence ( 4 ), which - for each storage choke ( 3 ) one of coil windings ( 6 ) of the storage throttle ( 3 ) wrapped core legs ( 5 ) and - returns ( 7 ) for those in the core thighs ( 5 ) generated magnetic fluxes to form magnetic circuits, the feedback ( 7 ) has a lower magnetic resistance than the core legs ( 5 ), characterized in that the returns ( 7 ) only by outside areas of the core set ( 4 ) and the coil windings ( 6 ) of the storage throttles ( 3 ) are formed and connected in such a way that in each adjacent core legs ( 5 ) generates a magnetic flux with opposite flow direction. Electrical voltage transformer according to claim 1, characterized in that the of the coil windings ( 6 ) wrapped core legs ( 5 ) at least one air gap ( 8th ) exhibit. Electrical voltage converter according to claim 1 or 2, characterized in that the voltage converter an even number of storage chokes ( 3 ) having. Electrical voltage transformer according to one of Claims 1 to 3, characterized in that a sum of the cross sections of the return paths (90) formed perpendicular to the magnetic flux direction ( 7 ) as large as a perpendicular to the magnetic flux formed cross-section of one of the coil windings ( 6 ) wrapped core leg ( 5 ). Electrical voltage transformer according to one of claims 1 to 3, characterized in that a sum of the cross sections formed perpendicular to the magnetic flux direction of the coil windings ( 6 ) wrapped core legs ( 5 ) greater than a sum of the cross sections of the recirculations formed perpendicular to the magnetic flow direction ( 7 ). Electrical voltage transformer according to one of Claims 1 to 5, characterized in that the core set ( 4 ) two outer legs as returns ( 7 ), between which with the coil windings ( 6 ) wrapped core legs ( 5 ) are arranged in series. Electrical voltage transformer according to one of Claims 1 to 5, characterized in that the core set ( 4 ) more than two outer legs as returns ( 7 ), between which with the coil windings ( 6 ) wrapped core legs ( 5 ) are arranged in series. Electrical voltage converter according to one of claims 1 to 7, characterized in that the voltage converter is designed as a multi-phase DC-DC converter, wherein each of the circuit branches corresponds to a phase of the voltage converter. Electrical voltage converter according to one of claims 1 to 7, characterized in that the voltage converter is designed as a three-phase AC voltage converter, wherein each of the circuit branches corresponds to a phase of the voltage converter and all storage chokes ( 3 ) on the common core sentence ( 4 ) feature. Electrical voltage transformer according to one of Claims 1 to 9, characterized in that the core set ( 4 ) is designed as a two-part core sentence.

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