DE102014202179A1 - High voltage transformer arrangement with high, adjustable stray inductance, inverter circuit with a high voltage transformer arrangement and use of a high voltage transformer arrangement - Google Patents

Abstract

The invention provides a high-voltage transformer arrangement (11) with a transformer core (1), a secondary winding (6) and a first primary winding (4) arranged below the secondary winding (6). The arrangement further comprises a second primary winding (5) spatially separated from the first primary winding (4), wherein the first and the second primary windings (4, 5) are electrically connected in series and wherein the winding sense of the first and the second primary winding (4 , 5) is designed such that a magnetic partial flux (Φ23) of the second primary winding (5) flowing through the first primary winding (4) is structurally superposed with a first magnetic flux (Φ1) of the first primary winding (4). The invention also provides an inverter circuit (13) having such a high voltage transformer arrangement (11) and a use of such a high voltage transformer arrangement (11). The spatial division of the primary winding according to the invention selectively increases the magnetic dispersion of the transformer arrangement. In particular, very high levels of magnetic scattering can be achieved that can not be achieved with a conventional transformer design.

Description

Field of the invention

The invention relates to a high-voltage transformer arrangement with a high, adjustable stray inductance, an inverter circuit comprising such a high-voltage transformer arrangement for generating a high voltage, for example for X-ray tubes. The invention also relates to a use of such a high-voltage transformer arrangement for forming an inductance of a resonant circuit of an inverter circuit.

Background of the invention

High-voltage transformers for operation with inverters, in which the scatter of the transformer is used as an inductance or as a resonant circuit component, u.a. used to generate the high voltage required to operate an X-ray tube. For example, such inverter arrangements are important for imaging in medical diagnostics.

High-voltage transformers used in inverters are often designed so that the spread of the transformer is as small as possible. This applies, for example, to flyback converters. In this case too large a spread at the time of switching off the semiconductor switches would lead to undesired overvoltages.

In contrast, in other circuit concepts, for example, in a series resonant converter with transformer, in which a series resonant circuit is formed in series with the transformer, the leakage inductance can be used selectively as a series reactor of the resonant circuit. By a corresponding design of the transformer, the leakage inductance is usually adjustable so that it is equal to the inductance required for the series resonant circuit.

One way to set the leakage inductance is to change the numbers of turns of the windings of the transformer. The leakage inductance is proportional to the square of the number of turns.

Another possibility is to adapt the geometric conditions in the transformer. For example, the leakage inductance of a transformer in which primary and secondary windings are realized in two stacked winding packages can be increased by choosing a greater distance between the winding packages. This reduces the magnetic coupling between the primary and secondary windings. The flux in the primary winding is no longer completely magnetically coupled to the secondary winding. Part of the river closes as stray flux in the space between the winding packages. The leakage inductance is proportional to the leakage flux.

If high values of the leakage inductance are to be achieved, it is no longer possible or advisable to adjust the leakage inductance to the aforementioned types. Because the winding losses increase as the number of turns increase, or increasing the distance between the primary and secondary windings would lead to an undesirable increase in the transformer. For high inductances, therefore, an additional series reactor is usually connected in series with the transformer.

Such an inverter circuit with a high-voltage transformer with a leakage inductance is for example in the published patent application DE 10 2011 005 446 A1 described.

Summary of the invention

It is an object of the invention to provide a high voltage transformer arrangement having a high, adjustable stray inductance, an inverter circuit having such a high voltage transformer arrangement, and a use of such a high voltage transformer arrangement for forming a resonant circuit inductor in an inverter circuit.

According to the invention, the stated object is achieved with the arrangement, the inverter circuit and the use of the arrangement of the independent claims. Advantageous developments are specified in the dependent claims.

The basic idea of the invention is to apply to a transformer core two spatially separate primary windings, the primary windings being electrically connected in series with each other and their sense of winding being chosen so that the magnetic fluxes are in the same direction, ie. superimpose constructively in the transformer core. The secondary winding is applied above or below one of the two primary windings. Preferably, the transformer core is closed and has two legs, on which sit the windings.

The invention claims a high voltage transformer arrangement comprising a transformer core, a secondary winding and a first primary winding arranged below and / or above the secondary winding. The arrangement comprises the Furthermore, one of the first primary winding spatially separated second primary winding, wherein the first and the second primary winding are electrically connected in series and wherein the winding sense of the first and the second primary winding is formed such that a first primary winding flowing through the magnetic partial flux of the second primary winding a first magnetic flux of the first primary winding constructively superimposed.

The spatial division of the primary winding according to the invention selectively increases the magnetic dispersion of the transformer arrangement. In particular, very high levels of magnetic scattering can be achieved that can not be achieved with a conventional transformer design.

In a further development, the high-voltage transformer arrangement may comprise a jacket-shaped transformer core, a first leg of the transformer core, on which the first primary winding sits, and a second leg of the transformer core, on which the second primary winding is seated.

As a result, a simple spatial separation of the first primary winding of the second primary winding is possible.

In a further embodiment, the transformer core may be in two parts and without gaps, and the two parts may each be C-shaped.

Furthermore, the first and second primary windings can be wound in opposite directions.

Preferably, the transformer core may be formed of a ferrite. As a result, the core losses remain low.

In one development of the invention, the first and the second primary winding may be formed as multi-layer film windings.

In a further embodiment, the high-voltage transformer arrangement may comprise a first primary coil body sitting on the transformer core, in which the first primary winding is arranged, and a second primary coil body sitting on the transformer core, in which the second primary winding is arranged.

In a further development, the secondary winding can be formed from enameled copper wire.

Furthermore, the high-voltage transformer arrangement may comprise a multi-chamber secondary coil body arranged on the first primary winding and in which the secondary winding is arranged.

By distributing the secondary winding over a plurality of chambers, both the parasitic winding capacitance and the position-to-position voltage of the layers of the windings in the individual chambers can be kept small.

In addition, the high voltage transformer assembly may include an insulating cover disposed above the secondary winding and configured to electrically isolate the secondary winding from the transformer core and the second primary winding.

The invention also claims an inverter circuit having a high-voltage transformer arrangement according to the invention, wherein the circuit has a resonant circuit with an inductance, which is formed in part by the leakage flux of the second primary coil.

The advantage compared to a realization by a circuit with a transformer of known type and an upstream series reactor is that the series reactor can be magnetically integrated into the transformer.

The primary windings of the transformer simultaneously fulfill the function of winding the series choke. The transformer core also contributes both to the function of the series choke and to the function of the transformer.

Due to the fact that the assemblies of the transformer arrangement fulfill several tasks and the number of required components of two (series reactor and transformer) can be reduced to one component (transformer with magnetically integrated series choke), both a cost saving and a reduction of the total installation space is possible.

The invention also claims a use of a high-voltage transformer arrangement according to the invention for forming an inductance (series reactor) of a resonant circuit of an inverter circuit, wherein the inductance of the resonant circuit can be changed by changing the number of turns of the second primary winding.

By distributing the total number of primary windings to two spatially separated windings, the magnetic dispersion of the transformer arrangement responsible for the formation of the inductance can be set very easily. The scattering and thus the inductance of the Oscillating circuit, the higher, the more turns the second primary winding has.

Other features and advantages of the invention will become apparent from the following explanations of an embodiment with reference to schematic drawings.

Show it:

1 FIG. 3: a longitudinal section through a high-voltage transformer arrangement, FIG.

2 FIG. 2: a cross section through a high-voltage transformer arrangement, FIG.

3 FIG. 1 is a block diagram of a high voltage transformer arrangement; FIG.

4 : A view of a high voltage transformer arrangement with representation of the magnetic fluxes and

5 : A block diagram of an inverter circuit with a high voltage transformer arrangement.

Detailed description of an embodiment

The 1 and 2 show a high frequency high voltage transformer arrangement 11 with high, adjustable magnetic scattering, where 1 the transformer 11 in a longitudinal section across the arrangement and 2 a cross section along the cutting axis AB of 1 represents. The transformer arrangement 11 includes a jacket-shaped, two-legged transformer core 1 formed by two C-shaped parts, resulting in two legs and two yokes.

On the first thigh 2 of the split transformer core 1 are a first primary winding 4 and a secondary winding arranged above it 6 applied. On the second leg 3 there is a second primary winding 5 , The transformer core 1 is preferably made of ferrite to keep the core losses low.

The first and the second primary winding 4 . 5 are preferably designed as multi-layer foil windings and for mechanical fixation on a first primary coil body 7 or a second primary coil body 8th applied.

The secondary winding 6 is made of enamelled copper wire and is spread over several chambers, for example four 1 shown, a secondary bobbin 9 wrapped wrapped. For isolation between the secondary winding 9 and the transformer core 1 and the second primary winding 5 is an insulation cover 10 over the secondary winding 6 appropriate.

Alternatively, other transformer core forms, such as toroidal cores, are used. The cores may be formed with or without a gap.

By the inventive nesting of the first primary winding 4 , the secondary winding 6 and the second primary winding 5 The amplitude of the magnetic field strength permeating the three windings can be reduced. Thus, at the same time the high frequency losses in the windings 4 . 5 . 6 , which arise due to this field, reduced. It is particularly advantageous to choose the same number of turns for the first and the second primary winding. In this case, the amplitude of the field strength halves in comparison to a conventional transformer with a single primary winding.

3 shows the wiring of the first with the second primary coil 4 . 5 using a block diagram. The first and the second primary winding 4 . 5 are electrically connected in series. The second terminal P2 of the first primary winding 4 is connected to the first terminal P3 of the second primary winding 5 connected so that the first and second primary winding 4 . 5 are electrically connected in series and the first terminal P1 of the first primary winding 4 and the second terminal P4 of the second primary winding 5 the primary-side terminals of the transformer assembly 11 form.

Through the first and second primary winding 4 . 5 the primary current I _{1 flows} . Through the secondary winding 6 flows the current induced by the primary current I ₁ secondary current I. ₂

4 shows the magnetic fluxes of the high voltage transformer 11 and the winding sense of the first and second primary windings 4 . 5 , For the sake of simplicity, consideration is given to the representation and representation of the magnetic fluxes of the secondary winding 6 waived. The winding sense of the two primary windings 4 . 5 is chosen so that the one with the first primary winding 4 chained first magnetic flux Φ ₁ and the second primary winding 5 chained the second magnetic flux Φ ₂ in the transformer core 1 superimpose constructively, ie have the same direction and thereby add. The windings 4 . 5 are therefore opposite to each other.

Between the first magnetic flux Φ _{1 of} the first primary winding 4 and the magnetic flux of the secondary winding 6 There is a good magnetic coupling, since these windings 4 . 6 are arranged one above the other. In contrast, the coupling between the second primary winding 5 and the secondary winding 6 worse, so that the second magenta river Φ ₂ , as in the 4 simplified, divided into the magnetic partial flux Φ ₂₃ and the magnetic leakage flux Φ _2σ . The magnetic leakage flux Φ _2σ closes in the space between the second primary winding 5 and the secondary winding 6 ,

The first terminal P1 of the first primary winding 4 and the second terminal P4 of the second primary winding 5 form the input of the transformer 11 , The first terminal S1 and the second terminal S2 of the secondary winding 6 form the output of the transformer 11 ,

If at the same total number of turns of the series connected first and second primary winding 4 . 5 the ratio of the number of turns of the second primary winding 5 to the first primary winding 4 is increased, also increases the magnetic leakage flux Φ _2σ and thus the leakage inductance of the transformer _assembly 11 at.

5 shows a simplified block diagram of a resonant circuit inverter circuit with a high voltage transformer arrangement 11 after the 1 to 4 , An inverter 13 Downstream is one with the high voltage transformer 11 series resonant circuit capacitor 12 , which together with the stray inductance of the high voltage transformer 11 a series resonant circuit 14 forms. The primary side of the primary current I ₁ and secondary side of the secondary current I _{2 flows} .

LIST OF REFERENCE NUMBERS

1

transformer core

2

first leg

3

second leg

4

first primary winding

5

second primary winding

6

secondary winding

7

first primary coil body

8th

second primary coil body

9

Secondary bobbin

10

insulating cover

11

High voltage transformer assembly

12

Resonant circuit capacitor

13

inverter

14

resonant circuit

A, B

section axis

I ₁

primary current

I ₂

secondary current

P1

first connection of the first primary winding 4

P2

second terminal of the first primary winding 4

P3

first connection of the second primary winding 5

P4

second terminal of the second primary winding 5

S1

first connection of the secondary winding 6

S2

second connection of the secondary winding 6

Φ ₁

first magnetic flux

₂

second magnetic flux

Φ ₂₃

partial magnetic flux

Φ _2σ

magnetic leakage flux

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

• DE 102011005446 A1 [0008]

Claims (12)

High voltage transformer arrangement ( 11 ) with - a transformer core ( 1 ), - a secondary winding ( 6 ) and - one below or above the secondary winding ( 6 ) arranged first primary winding ( 4 ), characterized by: - one of the first primary winding ( 4 ) spatially separated second primary winding ( 5 ), - wherein the first and the second primary winding ( 4 . 5 ) are electrically connected in series and - wherein the winding sense of the first and the second primary winding ( 4 . 5 ) is formed such that a first primary winding ( 4 ) flows through the magnetic partial flux (Φ ₂₃ ) of the second primary winding ( 5 ) with a first magnetic flux (Φ ₁ ) of the first primary winding ( 4 ) superimposed constructively. High voltage transformer arrangement ( 11 ) according to claim 1, characterized by: - a jacket-shaped transformer core ( 1 ), - a first leg ( 2 ) of the transformer core ( 1 ) on which the first primary winding ( 4 ), and - a second leg ( 3 ) of the transformer core ( 1 ), on which the second primary winding ( 5 ) sits. High voltage transformer arrangement ( 11 ) according to claim 2, characterized in that the transformer core ( 1 ) is two-piece and gapless and the two parts are each C-shaped. High voltage transformer arrangement ( 11 ) according to claim 2 or 3, characterized in that the first and the second primary winding ( 4 . 5 ) are wound in opposite directions. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized in that the transformer core ( 1 ) is formed of a ferrite. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized in that the first and the second primary winding ( 4 . 5 ) are formed as multi-layer foil windings. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized by: - one on the transformer core ( 1 ) sitting first primary coil body ( 7 ), in which the first primary winding ( 4 ), and - one on the transformer core ( 1 ) sitting second primary bobbin ( 8th ), in which the second primary winding ( 5 ) is arranged. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized in that the secondary winding ( 6 ) is formed of copper enamel wire. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized by: - one on the first primary winding ( 4 ) arranged multi-chamber secondary coil body ( 9 ), in which the secondary winding ( 6 ) is arranged. High voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized by: - an insulation cover ( 10 ) above the secondary winding ( 6 ) is arranged and formed, the secondary winding ( 6 ) from the transformer core ( 1 ) and the second primary winding ( 5 ) electrically isolate. Inverter circuit ( 13 ) with a high-voltage transformer arrangement ( 11 ) according to one of the preceding claims, characterized by: - a resonant circuit ( 14 ) with an inductance which is partly due to the magentic leakage flux (Φ _2σ ) of the second primary winding ( 5 ) is formed. Use of a high-voltage transformer arrangement ( 11 ) according to one of claims 1 to 10 for forming an inductance of a resonant circuit ( 14 ) an inverter circuit ( 13 ), characterized in that by changing the number of turns of the second primary winding ( 5 ) the inductance of the resonant circuit ( 14 ) is changeable.

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