MXPA00000328A - Diode-split high-voltage transformer - Google Patents

Abstract

The invention specifies a compact and cost-effective diode-split high-voltage transformer for high voltages of, in particular, above 20 kV, in which the high-voltage winding (W2 - W5) lies in chambers (8) of a coil former (9) underneath the primary winding (W1), and which contains means by which the electric field between the coil former (9) and the core is reduced in order to avoid corona effects. These means are, for example, a conductive coating of the surface (15) of the inner cavity (11) of the coil former (9), which coating preferably comprises colloidal graphite. The conductive coating may also be realized by a metallized plastic film which is wound between the core and the coil former (9). As an alternative, the cavity (11) between the core and the coil former (9) may be filled with a material whose relative permittivity&egr;r is distinctly greater than that of air. The use of a larger number of diodes is also possible as the means for reducing the electric field. The high-voltage winding (W2 - W5) is essentially covered completely by the primary winding (W1), with the result that the interference radiation produced in the high-voltage winding is virtually completely screened. Applications arise in particular for television sets and computer monitors.

Description

HIGH VOLTAGE TRANSFORMER DIVIDED BY DIODES The present invention relates to a high voltage transformer divided by diodes, having a core, a main winding and a high voltage winding, which is arranged in chambers of a coil former. For example, in EP 0 529 418 Bl, a high-voltage transformer divided by diodes of this type is described. This transformer contains a first coil former, which adjusts the first winding and additional auxiliary windings, and a second coil former, in which the high voltage winding is arranged in the form of a chamber winding. The two coil formers are usually produced and wound separately. During the final assembly, the coil former with the high voltage winding, having a correspondingly larger inner diameter, is pushed onto the coil former with the primary winding. The coil formers are subsequently surrounded with a plastic housing and are further encapsulated with a synthetic resin composition for the purpose of suppressing corona effects and high voltage spark discharges. The modalities of this type are used in television sets, for example, and provide high voltages in continuous operation of 24 kV up to over 30 kV. DE 38 22 284 A1 describes a high-voltage transformer having small dimensions for approximately 7 kV for copiers and the like. This transformer also has two coil formers, the coil former with the primary winding that is pushed over the coil former with the high voltage winding and snapped into place therein. It is not designed as a high-voltage transformer divided by diodes and can not achieve high voltages above 20 kV as required for television sets. It does not contain rectifier diodes, these are arranged separately in the associated circuit. The particular intention, when using a camera type coil former, was to solve the high voltage problems that appear there due to the small distance between the high voltage winding and the core. Despite the considerably lower voltage of 7 kV, however, this design has not demonstrated satisfactory high voltage power in sustained operation, even with complete encapsulation, and therefore has not been put into production. The object of the present invention is to specify a high-voltage transformer divided by diodes of the type mentioned in the introduction which is constructed in a very compact manner and which is effective in cost and in particular, has good high voltage power in the operation Continues at voltages above 20 kV. This object is achieved by means of the invention specified in claim 1. Advantageous developments of the invention are specified in the subclaims. In the case of the high-voltage transformer divided by diodes of the invention, the main winding is above the high-voltage winding and the high-voltage transformer contains a means by which the electric field between the winding former and the winding conductor is reduced. core, so as to avoid crown effects. For example, the surface of the inner cavity of the coil former is provided with a conductive coating, which, during operation, is grounded as a result of contact with the core, or at the same potential as the core. As a result, the electric field can be detected in the inherently unavoidable air separation between the core and the coil former, thereby effectively suppressing corona and voltage discharging effects. Corona effects are produced in particular by the ozone produced in the air by a high electric field. The conductive coating concentrates the electric field in the material between the high-voltage winding and the conductive coating of the coil former, which ensures a long-term high-voltage power with an appropriate material and sizing. The conductive coating used must be a high impedance layer, for example, colloidal graphite, which can be applied in a simple manner by means of a nozzle that sprays in the radial direction. A layer of low impedance, for example, metal, will constitute a short circuit turn and lead to losses. As an alternative, instead of a conductive coating, the remaining cavity between the core and the coil former can be filled with a material, so that corona effects are also avoided by this means. The material preferably has the highest possible relative permittivity e, for example 2 - 3 or 4, and can be, for example, a viscous paste, possibly also the encapsulation material of the high voltage transformer itself. The material can also have a low conductivity. No inclusions of air should occur during the filling process since, due to the relative permittivity low in e = 1, a high electrical voltage accumulates in these inclusions and the air can be easily ionized under the conditions of volt- age that prevail there. Since the primary winding is carried together with an insulating layer directly in the high-voltage winding, the complete arrangement becomes very compact. The chambers of the coil former also provide, with a multi-leaf winding, a sufficiently smooth surface on which the primary winding can be wound in a uniform and tight manner with a wire thickness of, for example, 0.3 to 0.8 mm. The thickness of the wall under the chambers of the high-voltage winding in the direction of the core are advantageously chosen such that they increase as the high voltage in the bottom of the chamber increases. The high voltage diodes can be arranged sideways with respect to the high voltage chambers in the coil former, or alternatively they can be integrated between the high voltage winding and the primary winding. In order to obtain a very cheap mode, the high-voltage winding is subdivided into four windings, a diode which is respectively connected between the first and the third and the fourth windings and a branch that is routed between the second and third windings for the Focus voltage of a kinescope. The compact structure of the coil former allows not only the housing of the high-voltage transformer, but also its core to be considerably reduced in size. As a result of this, the encapsulation compound can also be considerably reduced since there is no longer any high voltage potential outside the high voltage transformer. This not only leads to a considerable reduction in cost, but also gives space and weight advantages. In this way, it is possible to achieve a weight reduction of 25%, given the same electrical properties, with a high-voltage transformer divided by diodes (DST) that has two diodes compared to a high-voltage transformer. voltage divided by diodes that has three diodes. In addition, RLC circuits are avoided to attenuate interference radiation. In a further exemplary embodiment, the high-voltage transformer divided by diodes contains only one coil former, in which the high-voltage winding, the primary winding that is above the high-voltage winding, is arranged in chambers and it is wound on a sleeve interposed or rewind of sheet. As an alternative, it is also possible to use a coil former, simple - for the primary winding, a coil former that is pushed over the coil former with the high voltage winding. If a sleeve is used, it can also be made up of two or more parts. Advantageously, the primary winding is somewhat wider than the high voltage winding and covers the latter as much as possible in a complete manner. The high-frequency interference radiation produced in the high-voltage winding is virtually completely filtered by this means since the core (usually in ground potential) of the high-voltage transformer is located inside the high-voltage transformer and the hermetically wound primary winding, the cover is located on the outside, and the outer chambers of the high-voltage winding carry either only a very small or none of the impulse voltage, depending on the design, since they are connected either to the reference potential or to the high-voltage connection. voltage directly or via an additional camera. These interference voltages are produced as a result of the oscillations between the inductances and the parasitic capacitances of the high voltage transformer when the diodes change from the conductive phase to the blocking phase. These facts have already been indicated comprehensively to the literature, for example, in EP 0 735 552 Al, therefore they are not discussed in further detail herein. Since the main winding is advantageously situated such that it fits above the high-voltage winding, the diodes can be arranged directly between the corresponding partial windings, for example, in the frame of the chambers or above the chambers, rather It has to be outside. The connections of the diodes to the high-voltage cameras are in this case routed via high-voltage, interposed cameras. A very good coupling between the high voltage winding and the primary winding is achieved, moreover, by compact arrangement of the high voltage transformer. It is possible to fix up to two diodes in a chamber in the lower part of the coil former which is in the direction of the circuit board. On the upper side of the coil former, diodes can be arranged in a continuation of the coil former. In particular, the lower diodes are arranged parallel to the lower part of the lower extremity of the nucleus and the upper diodes are arranged perpendicular to the upper part of the upper extremity of the nucleus, with the result that it is possible to use a core whose clear width is only slightly greater than the length of those of the primary and high voltage windings, since in this case the core can be passed laterally out of the coil former through the cuts. The upper diodes are further arranged in such a way that after the winding of the high-voltage winding and the mounting and connection of the diodes, a sleeve of an individual part that fits exactly on the high-voltage winding can be pushed, on the diode and the high-voltage winding. However, diode arrays are equally possible between the high-voltage winding and the primary winding. These can be, for example, axially with respect to the coil former above the high-voltage chambers, parallel to the core, with the result that the connections between the partial windings of the high-voltage winding are simultaneously established in this way. The periphery of the primary winding therefore becomes slightly larger and can also acquire an oval shape. The use of a larger number of diodes is also possible as the means to reduce the electric field for the purpose of avoiding corona effects. In further developments, it has surprisingly been found that such a high voltage transformer operates reliably even without a conductive coating. In this way, for example, a high voltage of 32 kV can be generated in sustained operation with four diodes. It is still possible to obtain up to approximately 28 kV with three diodes, but this represents an uncertain upper limit. In a type with three diodes, therefore, a conductive coating is recommended since the latter can be applied in a working operation with virtually no additional costs. The explanation for sufficient high-voltage power for high-voltage transformers that have three or more diodes without a conductive coating is that the outer chambers do not carry virtually impulse voltages and in the inner chambers, by virtue of the larger number of diodes , impulse voltages do not reach a voltage value that can lead to corona effects between the high voltage chambers and the core.

The high-voltage transformer can be produced in an cost-effective manner, since it only has one complicated plastic component, the coil former with the high-voltage winding. Since the thin wire of the high voltage winding, typically about 0.05 mm, is wound first in this case, this winding operation can be controlled very well. The sleeve or a sheet winding is subsequently applied and the coarse wire of the primary winding and any of the additional auxiliary windings can be wound onto it without any problem. Since in this arrangement, there are virtually no high voltage carrying parts, in particular there are no parts having impulse voltages, the outside of the coil former being, thus on the outer edge of the high voltage transformer, the thickness of the the synthetic resin composition between the coil former with the windings and the outer plastic housing of the high voltage transformer can be reduced from 3 mm to less than 1 mm, as a result of which the plastic housing can be considerably reduced in size. Since the primary winding is now outside the high voltage winding instead of inside the latter, it is comparatively far away from the parasitic fields of the core, which are pronounced highly particularly around the air gap. Since the interference oscillations contain higher harmonics of up to more than 1 MHz, pronounced losses occur in the primary winding due to film effects and eddy currents, which can be maintained at a tolerable level only by means of thin wires of the primary winding, in particular when using expensive multi-strand wire. The new arrangement makes it possible to use thin wire, for example, copper having a thickness of 0.475 mm or more, without the appearance of sharp film losses, as a result of which it is also possible to reduce the resistive losses in the primary winding. However, the primary winding located on the outside must absorb the interference radiation emitted. In a preferred embodiment, the primary winding is at a distance of about 5 mm from the core, whereas in the previous designs the distance is typically 1.5 mm. The smaller periphery of the high voltage winding means that the capacitances of the windings are considerably smaller. This allows the number of turns to increase, as a result of which the diameter of the ferrite core can be reduced. This not only saves space and space and saves space, but also reduces the losses in the ferrite core. The additional advantages are safe operation since, in the case of a short circuit in the high voltage winding, and which can lead to overheating, the transformer can not explode any longer because the high voltage winding is encircled very solidly by the primary winding, which is typically wound with thick wire. Additionally, there is no need for an RLC circuit connected to the primary winding since the high voltage is sufficiently stable. A design that has four diodes allows, for example, a high voltage transformer with 60 watts output voltage on the high voltage side at 32 kV that has a cost reduction of more than 20%, and is approximately the same size as a pre-transformer of 30 or 40 watts, with a weight of 200 grams. The weight can be reduced completely by 30% compared to previous types that have the same power output. Additionally, the height of the high voltage transformer can be kept very low since the high voltage can be routed to the bottom of the chambers and pass via a plastic sleeve in the housing from the bottom of the top to the connection. The insulation needs a tube of approximately 4 cm, virtually all of which is in the housing of the high-voltage transformer. The present high voltage transformer in this way is excellently suited for the recent television set or monitor chassis since the chassis structure becomes even more compact as a result of the integrated circuits having higher levels of integration. There is no need any longer to fear that interfering radiation that interferes with the tuner circuit. The invention is explained later by way of example with reference to the schematic drawings, in which: Figures 1 and 2 show a block diagram with a high-voltage transformer divided by diodes having two diodes and three diodes, respectively, for generate a high voltage for a kinescope, Figure 3 shows a coil winding with two diodes for a high voltage transformer, Figures 4 and 5 show the set of circuits of the high voltage diodes and the partial windings of the high voltage windings; and Figure 6 shows a coil former with windings, four diodes and a core for a high voltage transformer. Figure 1 illustrates a high-voltage transformer Tr divided by diode having a primary winding Wl and a high-voltage winding that is subdivided into the partial windings W2-W5. One end of the primary winding Wl is connected to an operating voltage UB and the other end is connected to a switching transistor 2, which is turned on and off periodically by a drive signal 1. One end of the partial winding W2 is connected to a reference potential and the high voltage that is routed to a UH connection for the operation of a kinescope 7 is presented at a winding end W5. The high voltage UH is usually smooth by the capacitances of the connecting cable and capacitances of the kinescope 7, indicated here by the capacitance C. The high voltage winding is subdivided into four windings W2, W3, W4 and W5, a diode 3 and 5 high voltage, respectively, for the purpose of rectification that is interposed between the first and the second and the third and the fourth winding. A lead A to provide a high voltage for the kinescope focusing electrode 7 is routed between the second and third high voltage windings W3, W4. The switching transistor shuts off in the short time of the horizontal return of the point. This results in a high impulse load for the high voltage transformer Tr, and this load must be taken into account in the design of the transformer. Since the rectifying diodes are integrated between the windings of the high-voltage transformer in the arrangement of FIG. 1, it is evident that the outer ends of the high-voltage winding are free of the AC voltage. Therefore, the pulse loads are essentially applied only to diodes 3 and 5 and the ends of the windings adjacent to the diodes. As a difference of Figure 1, a transformer divided by diodes having three diodes is illustrated in the circuit of Figure 2. A respective diode 3, 4, 5 is arranged between the partial windings W2 -W5 and the branch A for the focusing electrode is in this case routed from the partial winding W3, as explained later with reference to Figure 4. In both Figures, and also in a later, identical concepts with the same reference numbers are provided.

Circuits of this type are usually used in television sets and computer monitors, reference to which is done in this way. The embodiments of the high voltage transformer divided by diodes that are illustrated in Figures 1 and 2 are only by way of example; in particular, the high-voltage winding can also be subdivided into more than four partial windings W2-W5. Figure 3 illustrates, in a sectional drawing, a coil former 9, which accommodates both the primary winding Wl and the high voltage winding subdivided into the individual windings W2-W5, the windings W2-W5 which are below the primary winding Wl. The coil former 9 contains an axial cavity 11, which accommodates the ferrite core (not shown). The coil former 9 contains a multiplicity of chambers 8, the bottom of which is approximately 1 mm thick in the direction of the cavity and in which the individual windings W2-W5 of the high voltage winding are wound. The coil former 9 advantageously contains twelve chambers 8, one of the windings W2-W5 which is arranged in three of these chambers 8 in this case. The thickness of the bottom of the chambers 8 in the direction of the cavity 11 can be varied according to the high voltage load in the DC and AC voltage form, as described for example by EP 0 028 383 Bl. An insulating layer 10, consisting of a number of layers of a sheet winding in this exemplary embodiment, is above the chambers 8. The primary winding Wl is wound into one or more hermetically wound layers directly on this insulating layer 10. In addition, the auxiliary windings WH are applied to the primary winding Wl, auxiliary windings which can be advantageously wound with the same wire thickness as that of the primary winding Wl in a working operation. Examples of practical wire thicknesses are 0.335 mm or more for the primary winding W1 and 0.05 mm enameled copper wire for the high voltage winding. Similarly, the diode 5 can also be placed in the lower chamber 14 opposite the diode 3. At the ends of the chamber, the coil former 9 has side edges 13 to accommodate the sheet winding 10 and the primary winding Wl. These lifted parts are followed, outwards, by two additional cameras 14, 16 which serve to adjust the two high-voltage diodes 3, 5. The high-voltage diodes 3, 5 are connected to the windings W2-W5 of the winding of high voltage.

As a result of this design, the chambers 8 with the high voltage winding are completely covered by the leaf winding 10 and the primary winding Wl, with the result that the low impedance primary winding Wl implements an effective filtering of the interference radiation , intense, high frequency that is increased by the ratio of transformation. Due to the short return lengths (periphery of the coil former at the bottom of the chamber) of the high-voltage windings W2-W5 and the smaller self-capacitance of the high-voltage windings that are caused as a result, it is possible to achieve a sufficiently stable high voltage with only two high voltage diodes 3, 5, the stability of the high voltage which is better in the case of the high voltage transformers, divided by diode, previously known, which have three diodes. It is also possible to use three or more diodes by means of which the stabilization of the high voltage also becomes even better, or that will allow a greater output power. In this exemplary embodiment, the inner cavity 11 of the coil former 9 is provided with a conductive coating on its entire surface 15, conductive coating that can be earthed, for example by contact with the ferrite core (not shown) . The conductive coating used can advantageously be a layer of colloidal graphite which can be applied in a spraying process and has a high impedance conductivity. Hereby, the air-filled interspace, inherently undable between the ferrite core and the coil former 9 is filtered against the high voltage, with the result being completely suppressed in the formation of the corona effect by this measurement. The conductivity of the coating is chosen such that all currents, capacitive currents and eddy currents in the coating are ded. The layer with the colloidal graphite can preferably be applied by means of a liquid spray containing colloidal graphite and adhesive in a solvent and which additionally lightly dissolves the plastic of the coil former 9 in order to increase the addition. This spraying can be applied in a simple manner, for example, using a nozzle that sprays in the radial direction and is directed through the cavity 11 of the coil former 9. On its underside, the coil former 9 contains electrical connections 12 through which the high-voltage transformer is directly fixed on a circuit board. Additionally it will be enclosed by a plastic housing (not shown) that opens to the bottom, and is completely encapsulated together with the latter by means of a synthetic resin composition. As an alternative to a multiple sheet winding, a plastic sleeve is also possible as the insulating layer between the primary winding and the high voltage winding, which can be pushed down on the coil former 9 with the high voltage winding W2 - W5. The primary winding can then be wound up together with the auxiliary windings directly into the plastic sleeve. If both diodes 3, 5 are arranged in the chamber 14 which is at the base of the high voltage transformer in the direction of the connections 12, then the entire coil former can be kept very compact even when a sleeve is used. The sleeve is then in a positively clamped manner on the chambers 8 of the high-voltage winding W2-W5 and covers the latter completely. Referring to Figure 4, the high-voltage winding W2-W5 of Figure 2 is explained in more detail. The high-voltage winding is designed as a camera-type winding having twelve cameras Kl-K12, the partial winding W2 which is it distributes between two chambers, the partial winding W3 between four chambers and the partial windings W4 and W5 in each case between three chambers. The partial windings W2-W5 alternate respectively in terms of their winding direction in order to obtain a fable tuning to higher harmonics, as a result of which the internal resistance of the high voltage transformer is reduced. Therefore, in order to take into account the direction of the winding, the reference potential is connected to the winding of the second chamber and the high voltage output UH is connected to the twelfth chamber K12. In this high-voltage transformer, the diodes 3 - 5 are not spatially between the partial windings W2-W5, but outside, for example the diode 3 in the background and the diodes 4 and 5 in the upper part, as explained in more detail with reference to figure 5. The chambers are wound up as follows: first the chamber Kl and then the second chamber K2 are wound and subsequently the wire for the connection for the reference potential is routed. The K3 - K6 cameras are subsequently wound. Then the winding is continued starting with the camera K12 to the tenth chamber that is connected to the diode 5. The ninth, eighth, and seventh cameras can be subsequently rolled up. The focusing connection A is advantageously routed to the winding of a camera, in this case the camera K5 of the partial winding W3, which is symmetrical with respect to the two diodes, with respect to the diodes 3 and 4 in this example embodiment, of so that the focusing voltage is virtually free of the AC voltage. Partial winding W3 and the other partial windings W2, W4, W5 are constructed in such a way that the desired voltage value for focusing is approximately available in the focus connection F. Figure 5 illustrates a high voltage winding having five partial W2 windings, W3a, W3b, W4 and W5 and having four diodes 3 - 6. The partial windings W2 - W5 are also alternating in this case, the reference potential that is connected to the camera Kl plus the bottom and the high voltage connection UH that connects to the uppermost chamber K12. This example mode allows a beam current of 2 mA at a high voltage of 32 kV, while the example mode of Figure 4 allows a maximum beam current of 1.5 mA at a high voltage of 28 kV. In terms of the spatial dimensions of the cameras, both types are identical; the essential difference is that the partial winding W3 of figure 4 is subdivided in figure 5 into two partial windings W3a and W3b between which the fourth diode 4 is connected. In principle, the cameras Kl-K12 can be wound in the same sense as the cameras of figure 4. In the example embodiment of figure 5, diodes 3 and 4 are below chamber Kl and diodes 5 and 6 are above chamber K12 and the connecting wires between the diodes and the cameras are in each case driven back on the corresponding cameras. Figure 6 is a sectional drawing illustrating a further example embodiment, a coil former 9 and a ferrite core comprising two core halves 17a and 17b. The partial windings W2-W5 are arranged in twelve chambers 8 of the coil former 9, as already explained with reference to figures 4 and 5. The thickness of the bottoms of the chambers towards the inner cavity 11 of the coil former 9 in which the two halves 13a and 13b of the core are introduced is approximately 1-2 mm, depending on the level of impulse voltage in the individual chambers. The chamber type coil 9 contains connection pins 12 by which the high voltage transformer is fixed to a circuit board. Located below the chambers 8 with the high-voltage winding, on the left in the figure, there is an additional chamber 14 in which two diodes 3 and 4 are arranged. The two additional diodes 5, 6 are arranged above the chambers 8 to an extension 16 of the coil former 9. The diodes 3 - 6 and the high voltage chambers 8 are wired according to the example embodiment of Figure 5. In this example embodiment, the primary winding Wl is wound on a sleeve 10, instead of a sheet winding, which completely covers the high-voltage windings W2-W5. The sleeve 10 is as airtight as possible, in a positively secured manner, on the chambers 8. The diodes 5 and 6 are arranged in the extension 16 in such a way that the sleeve 10 can be pushed on them without any obstruction. By this means, there is no need for a longitudinally divided sleeve, of two parts, or a sheet winding, to avoid these diodes. The additional auxiliary windings, WH, with the same wire thickness are applied to the primary winding Wl in an additional winding operation. The chambers 8 with the windings W2-W5 are surrounded by the primary winding Wl towards the outer side and by two halves 17a, 17b of the core towards the inner side, the halves of the core which are in potential to ground. The outer chambers 8 are at a DC voltage potential, as already explained with reference to FIGS. 4 and 5. Under this arrangement, the inner chambers carrying pulses of the high-voltage winding are virtually completely enclosed by the elements that have voltage of CD or drivers that have a low internal resistance, with the result that these cameras are filtered very effectively. Even if one of the external chambers does not connect directly to a DC voltage potential, as such, for example, because of the alternating direction of the winding, as explained in FIG. 4, the filtration still exceeds 90%. During final assembly, the coil former 9 is further enclosed by a plastic housing (not shown) which, on the upper side, has a square junction that receives the extension 16 of the coil former 9. The diodes 5 and 6 are in this case perpendicular to the upper part 13b of the core, with the result that the core can be driven away in a laterally direct manner over the windings Wl-W5 and the primary winding Wl. In the lower part of the coil former 9, the diodes 3, 4 are arranged parallel to the lower part 13a of the core, thus allowing a cut in the coil former 9 through which the lower half of the core is led out. . This compact arrangement makes it possible to reduce the core weight from 133 g to only 80 g, compared to a previous type with the same power output. It was possible to reduce the core diameter even further by using a core material having a greater permeability. It is evident from this arrangement that, except for the connecting wires of the diodes, there is no longer any part that carries high voltage on the outside of the coil former. Therefore, it was possible to reduce the synthetic resin layer between the coil former 9 and the outer housing from 3 mm to less than 1 mm, allowing considerable savings in weight and space. Likewise, additional modalities having more than four diodes are possible. In embodiments having at least four diodes, a conductive coating on the surface 15 of the inner cavity 11 of the coil former 9 is no longer required, on the contrary a type having two diodes in which this is absolutely necessary. Tests to date for types with four or more diodes show that even under high load and sustained operation, corona effects or disruptive discharges are not present between the high voltage windings arranged in the chambers 8 and the two halves 17a, 17b of the core. Since the conductive coating can be applied without great effort and without significant costs on the surface 15 of the inner cavity 11, it can also be applied, depending on the design, for example for a type having 3 diodes, since at 28 kV This design is approximately at the limit of the voltage carrying capacity, and must be undertaken for the long-term safety of the high-voltage transformer. For a type of three diodes with 29.5 kV, the coating is absolutely necessary. For the four-diode type, the high voltage pulses are in the 2 - 3 kV region or below in which the corona effects do not occur. But at 32 kV or above for that type a coating is also suggested. The crown effects have to be totally avoided because even very small crown effects can damage the high voltage transformer after a prolonged time of operation.

Claims (11)

1. REIVGNDICACTGNES: 1. High voltage transformer divided by diodes for voltages above 20 kV up to 35 kV, comprising a core, a primary winding and a high voltage winding, which is arranged in chambers of a coil former, the former of coil comprising an inner cavity to accommodate the core, and the primary winding and the high-voltage winding which are arranged concentrically around the core, characterized in that the primary winding is above the high-voltage winding and that the high-voltage transformer The voltage comprises a means by which the electrical effect between the coil former and the core is reduced, in order to avoid corona effects.
2. 2. The high-voltage transformer divided by diodes according to claim 1, characterized in that the surface of the inner cavity of the coil former is provided with a conductive coating.
3. 3. The high-voltage transformer divided by diodes according to claim 2, characterized in that the conductive coating contains colloidal graphite.
4. The high-voltage transformer divided by diodes according to claim 2, characterized in that the conductive coating is made by a metallized plastic film that is wound in an overlapped manner between the coil former and the core.
5. The high-voltage transformer divided by diodes according to one of claims 1-4, characterized in that an insulating layer is arranged between the primary winding and the high-voltage winding, insulating layer consisting of either a multiple winding sheets, a single coil former or a sleeve.
6. The high voltage transformer divided by diodes according to claim 5, characterized in that the primary winding is arranged in one or more layers tightly wound in the insulating layer and essentially covers the high voltage winding for the purpose of filtering the radiation of interference.
7. The high voltage transformer divided by diodes according to claim 5 or 6, characterized in that the high voltage diodes, for the purpose of rectification, are arranged laterally with respect to the high voltage chambers.
8. 8. The high-voltage transformer divided by diodes according to claim 7, characterized in that one or two diodes are arranged to the left of the chambers, in the direction of a connection board, and one or more diodes to the right of the high voltage winding chambers in the coil former.
9. 9. The high-voltage transformer divided by diodes according to claim 8, characterized in that the diodes placed on the left are arranged in a chamber parallel to the lower part of the core and in which the diodes placed on the right are arranged perpendicular to the upper part of the core in a continuation of the coil former.
10. The high-voltage transformer divided by diodes according to one of the claims 5-9, characterized in that the insulating layer consists of a sleeve with side walls.
11. 11. The high voltage transformer divided by diodes according to one of the preceding claims for use in television sets and monitors. SUMMARY OF THE INVENTION The invention specifies a high-voltage transformer, divided by diodes, compact and cost effective for high voltages, in particular, above 20 kV, in which the high-voltage winding (W2-W5) is in chambers (8). ) of a coil former (9) below the primary winding (Wl), and containing a means by which the electric field between the coil former (9) and the core is reduced in order to avoid corona effects. This means is, for example, a conductive coating of the surface (15) of the inner cavity (11) of the coil former (9), which coating preferably comprises colloidal graphite. The conductive coating can also be made by a metallized plastic film that is wound between the core and the coil former (9). As an alternative, the cavity (11) between the core and the coil former (9) can be filled with a material whose relative permittivity er is distinctly greater than that of the air. The use of a large number of diodes is also possible as the means to reduce the electric field. The high-voltage winding (W2-W5) is essentially completely covered by the primary winding (W1), with the result that the interference radiation produced in the high-voltage winding is virtually virtually completely filtered. Applications appear in particular for television sets and computer monitors.