EP0738419B1 - Fractionated-rectification high-voltage transformer with grouped diodes - Google Patents

Description

The present invention relates to a high transformer fractional rectification voltage, intended in particular to supply cathode ray tubes for televisions.

The fractional rectification of the high voltage of the transformer means that the secondary booster winding of transformer voltage has several high voltage outputs which are each rectified by means of diodes. In the case of the power of a cathode ray tube of television for example, the high voltage transformer must provide a very high voltage of output, of the order of 25 to 35 kVolts, to supply the anode of the tube cathodic ensuring the emission and acceleration of an electron beam for the operation of the tube, and a high output voltage called focusing, of the order of 10 to 12 kVolts, to adjust the concentration of the electron beam in the cathode ray tube.

Usually the secondary lifting winding of the transformer is in the form of a coil around a support substantially tubular. Secondary winding is axially divided at least in three stages by two diodes which are arranged so coplanar opposite the front face of the insulating housing transformer, face generally constituted by a block potentiometer connected to the focus voltage output. The fact that rectifier diodes are confined in a small space opposite of the potentiometric block, there is poor heat dissipation at level of diodes which can cause a rapid rise in temperature diodes during their operation, which is harmful for the duration of life of these diodes.

In addition, the high voltage outputs at the diodes of the transformer are located at different levels. Since the electrical safety of transformer use requires that the distance separating the cable connection points on the one hand voltage with the high voltage outputs of the step-up winding in the transformer housing and on the other hand the immediate environment of the transformer, or sufficiently large (of the order of 2 to 4 cm), the high voltage supply outlet generally located in the height of the lifting winding leads to oversizing in height of the corresponding chimney of the insulating box surrounding a part of the corresponding high voltage cable.

To reduce the additional insulation length of the cables, it is possible to bring the electrical connection point further to inside the transformer insulator, but this requires a additional connection means (using a terminal conductive for example) between the very high voltage output diode and the corresponding high voltage cable. This causes difficulties additional for manufacturing the transformer on the one hand and the made of high transformer operating voltage else go.

In addition, for reasons of withstand voltage during transformer operation, it is necessary to maintain a sufficient distance between the coplanar diodes and the block potentiometric, which constitutes a limitation in the search for the compactness of the transformer.

The object of the present invention is to propose a solution particularly simple and effective to remedy the drawbacks mentioned above by proposing a compact high voltage transformer with electrical connection and heat dissipation characteristics improved.

The invention also aims to improve the reliability of the transformer by reducing the operating temperature, particularly at the level of the diodes enclosed in the insulating housing.

Another object of the invention is to remove any element of additional connection to bring back the high voltage output power supply at the high voltage focusing output.

The high voltage transformer of the invention is defined in claim 1.

According to the invention, the high voltage transformer with fractional rectification includes an insulating housing enclosing a primary winding and a secondary voltage raising winding which coaxially surrounds the primary winding. The winding elevator has axially several stages or partial groupings which are each associated with a diode. According to the invention, at least two diodes associated with the high voltage outputs of two different stages are located at the same level (that is to say in the same radial plane), which allows the connection points to be brought down accordingly associated with these two output diodes at the same level without any means additional connection.

In the case where a potentiometer block constitutes the front face of the insulating housing, the two diodes are preferably arranged as well grouped at the same level, parallel to each other and so diametrically opposite and oriented perpendicular to the face inside of the potentiometric block. Preferably, the two diodes of output correspond to the diodes associated with the high voltage output on the one hand and at the high voltage focusing output secondly, respectively, when the high voltage transformer is intended for the supply of a cathode ray tube of television set.

Preferably, the two grouped diodes are arranged on as low as possible inside the case, this brings the points of electrical connection of high voltage cables more inward housing. Consequently, the height of the chimneys or the length of the resin coating of the cables projecting outside the transformer housing is reduced.

Advantageously, all the diodes of the winding are located away from the potentiometer block. This allows to remove the high voltage withstand constraint vis-à-vis the block potentiometric, so as to bring the block closer potentiometric with respect to the lifting winding. We can thus reduce the size of the transformer in a plane perpendicular to the axis of the primary and secondary winding.

The scattering of the diodes of the elevator winding in the insulating housing according to the invention allows a better distribution of the effect thermal generated by these diodes in the housing and therefore to obtain a better heat dissipation at the diodes.

• la figure 1 est une vue éclatée représentant schématiquement un transformateur haute tension selon l'état de la technique,
• la figure 2 est une vue en coupe axiale partielle selon Il-Il de la figure 3 représentant un transformateur haute tension selon une variante connue de la figure 1,
• la figure 3 est une vue en coupe radiale partielle du transformateur selon III-III de la figure 2,
• la figure 4 est une vue en coupe axiale partielle selon IV-IV de la figure 5 représentant un transformateur haute tension selon l'invention, et
• la figure 5 est une vue en coupe radiale partielle selon V-V du transformateur de la figure 4.

The invention will be better understood and other advantages of the invention will appear on studying the detailed description of an exemplary embodiment taken on a non-limiting basis and illustrated by appended drawings, in which:

• FIG. 1 is an exploded view schematically showing a high voltage transformer according to the state of the art,
• FIG. 2 is a view in partial axial section along II-II of FIG. 3 showing a high voltage transformer according to a known variant of FIG. 1,
• FIG. 3 is a view in partial radial section of the transformer according to III-III of FIG. 2,
• FIG. 4 is a view in partial axial section along IV-IV of FIG. 5 showing a high voltage transformer according to the invention, and
• FIG. 5 is a view in partial radial section along VV of the transformer of FIG. 4.

The high voltage transformer illustrated in Figure 1 is intended for the supply of a cathode ray tube of television (not represented). The transformer comprises a rigid housing 1 made of material electrically insulating plastic, a primary winding 2 wound around a tubular insulating support 3, a secondary winding 4 voltage booster wound around an insulating tubular support 5, a potentiometric block 6 which is removably mounted on the face open front 1a of the insulating housing 1.

The transformer is of the fractional rectification type, that is to say of the split secondary winding type 4 provided with several high voltage outputs rectified by means of diodes. The secondary winding 4 has an upper stage 4a, a stage intermediate 4b and a lower stage 4c (Figure 2). The upper diode 7 associated with the very high voltage output of the transformer is located above of the upper stage 4a of the secondary winding 4. The diode intermediate 8 and lower diode 9 respectively separate the stage upper 4a of the intermediate stage 4b, and the intermediate stage 4b of the lower stage 4c of the secondary winding 4. The lower diode 9 is associated with a high voltage output called focusing. The diodes 7, 8, 9 are arranged coplanar and supported by clip arms 10 of insulating plastic material forming part of the tubular support 5.

Electrical connectors 11 in the form of pins are connected to primary winding 2 and possibly to windings auxiliaries not shown which, arranged coaxially inside the tubular support 3, supply voltages of low values for the supply of other electrical circuits of the television not shown. The coaxial winding technique (primary, secondary and auxiliary) is known in particular from French Patent No. 2,632,798. The primary winding 2 is introduced coaxially inside the tube support 5 for the secondary winding 4 in order to obtain a good magnetic coupling between primary 2 and secondary 4 windings.

Two high voltage cables 12, 13 are electrically connected and respectively at the very high voltage output at the diode 7 at the potentiometer block 6 which is connected and at the high output voltage at lower diode 9. At connection electric with the upper diode 7 by welding, the high cable tension 12 is maintained by means of a clip 14 forming part of the support insulator 5. The cable 12 is intended to supply the anode of the cathode-ray tube of the television to emit an electron beam necessary for TV operation. The high voltage cable 13 connects the block potentiometer 6 from transformer to cathode ray tube for focus the electron beam emitted by the anode. The high voltage output at the lower diode 9 is connected to the block potentiometer 6 which can be adjusted by one or two buttons rotary 6a, 6b (Figure 2) the output voltage (s) actually carried by the high voltage cable 13.

The insulating housing 1 must be hermetically closed. The diodes coplanar 7, 8, 9 are facing the potentiometric block 6. The electrical safety to ensure the functioning of circuits surrounding (not shown) against parasitic signals generated by the high output voltage of the transformer, requires that the points of electrical connection between the high voltage cables 12, 13 to the inside of the insulating box 1 are separated from the outside by a certain safety distance. In practice, the high voltage cables 12 are coated, 13 of an insulating resin 15 up to a predetermined height at the outside of the transformer housing 1. The height of the coating in resin 15 depends on the value of the high output voltages.

Figures 2 and 3 show a known variant of high voltage transformer which differs from that illustrated in figure 1 mainly for electrical connections between high outputs voltage of the secondary winding 4 and the high voltage cables 12, 13. In order to facilitate understanding, the same elements of the transformer illustrated in different figures will bear the same references.

As shown in Figures 2 and 3, the high transformer voltage includes an insulating box 1 provided with two chimneys integrated 16,17 protruding outward from the housing 1 for receive respectively the high voltage cables 12, 13 of Figure 1 (not shown in Figures 2 and 3). The fireplaces 16.17 replace the insulating coating 15 of FIG. 1 in order to ensure the electrical safety required. The chimneys 16,17 also protrude inward of the housing 1 and have their lower ends each closed by a pellet 18, 19 made of powder-filled silicone conductive. The technique of electrical connection by means of conductive pads is described in detail in European Patent No. 0 236,642.

High voltage cables (not shown in Figures 2 and 3) have a rigid core which can sink into the faces upper conductive pads 18, 19 in the chimneys 16, 17. The electrical connection between the very high voltage outputs power supply and high focusing voltage on the one hand and the pellets conductive 18, 19 on the other hand are also provided by of a rigid conductor embedded in the undersides of the pads conductive 18, 19. Since the upper diodes 7 and lower 9 associated with these two high voltage outputs are located at different levels, conductive lugs 20, 21 are used respectively to extend the upper 7 and lower 9 diodes, the pods being driven into the undersides of the pellets conductive 18 and 19 associated with high voltage output cables.

The potentiometric block 6 is mounted on the front face of the insulating housing 1 and comprises two rotary knobs 6a, 6b in order to set two output voltages for focusing and accelerating in a manner known per se. The potentiometric block 6 has a small chimney 6c for the outlet of an auxiliary cable not shown. Over there construction of the transformer, chimneys 16, 17 are located vicinity of the front face of the insulating housing 1. The diodes 7, 8, 9 associated respectively with the upper 4a, intermediate 4b and lower 4c of the secondary winding 4 lie in a plane parallel to the front face of the insulating box 1. As on the front face of the insulating box is mounted the potentiometer block 6, it is necessary to take into account the voltage withstand of the transformer. Concretely, the distance 1 between diodes 7, 8, 9 and potentiometer block 6 must be large enough to avoid the phenomenon of arcing due to the high output voltage and which can cause destruction of the transformer.

In addition, the extension lugs 20, 21 are delicate when mounting and to arrange for the high voltage which must pass through them. These lugs also increase the size inside the housing insulator 1. The fact that the diodes 7, 8, 9 are in the same plane facing potentiometer block 6 and are in a confined space poses a problem of dissipation of heat generated at these diodes. The concentration of heat at the diodes risks deteriorate their functional characteristics quickly in case prolonged use of the transformer.

Figures 4 and 5 show an embodiment of the high voltage transformer according to the present invention. The example is supplied in comparison with the variant illustrated in FIGS. 2 and 3.

The secondary winding 4 always comprises three stages 4a, 4b and 4c with three associated 7 ', 8', 9 'diodes. Intermediate diodes 8 'and lower 9' are coplanar and form a right angle with the front face of the insulating block 1 constituted by the potentiometric block 6. The diode 7 ' associated with the upper stage 4a for the very high voltage output is arranged in the same radial plane as the lower diode 9 ', parallel to this and it is diametrically opposed.

The diodes 7 ', 8', 9 'are held by means of the clip arms 10 in a manner known per se. To ensure the electrical connection between the diode 7 'and the upper stage 4a, it suffices to extend the conductor the upper stage 4a downwards to be connected by one of the ends of the diode 7 'associated therewith. The 8 'intermediate diode is coplanar with the lower diode 9 '. Having the 7 'diodes, 8 ', 9' in this way shortens the height of the insulating support tubular 5 for secondary winding 4, to better distribute the heat inside the insulating housing 1, and therefore allow better heat dissipation at the diodes to ensure the reliability of their functioning, and to minimize their risk of breakdown in tension (electric arcs) since the diodes are no longer in a immediate vicinity of the potentiometric block 6. Thus, it is possible to bring the secondary winding 4 closer to the block potentiometer 6 constituting the front face of the insulating housing 1 and of content with a distance 1 ′ (FIG. 4) much less than the distance l (Figure 2) according to the state of the art. As a result, it is possible to reduce the dimensions of the insulating box 1 in the transverse direction and thus minimize the transverse space requirement L (FIG. 4) of the transformer.

The particular positioning of the diodes 7 ', 8', 9 ', according to the invention also makes it possible to eliminate the extension lugs 20, 21 additional for the electrical connection of the high outputs associated voltage. Indeed, the diode 7 'associated with the upper stage 4a and the diode 9 'associated with the lower stage 4c of the secondary winding 4 have ends oriented parallel so that can take advantage of this to ensure the electrical connection. It suffices to bend these sufficiently rigid conductive ends and push them in respectively in the underside of the conductive pads 18.19 fireplaces 16.17. Such a connection which is extremely simple improves the electrical behavior of the transformer by elimination of any parasitic phenomena linked to mounting and the location of the electrical extension lugs 20,21.

We can also bring back the lower end chimneys 16, 17 at the output diodes 7 'and 9', which allows more chimneys 16,17 to enter inside the insulating housing 1 so as to reduce the overall height of the transformer.

Of course, the invention is not limited to a winding secondary three-story. For a higher number of floors, we can group at least two output diodes on the same level, and possibly group other diodes on a different level depending on the stated principle of the invention.

Claims (5)

1. Fractionated-rectification high-voltage transformer comprising an insulating housing (1) which encloses a primary winding (2) and a voltage-booster secondary winding (4) coaxially surrounding the primary winding, the secondary winding comprising several stages (4a, 4b, 4c) which are each associated with a diode (7, 8, 9; 7', 8', 9'), at least two ducts (16, 17) built into the insulating housing (1) whose lower ends are each closed off by a conducting pellet (18, 19) so as to provide the electrical connection between high-voltage cables (12, 13) and the said outputs of the secondary winding, characterized in that at least two of the said diodes (7', 9') which are each also associated with a high-voltage output of the secondary winding are arranged at the same level in a radial plane, that the lower ends of the ducts (16, 17) are situated substantially at the same level as the said at least two high-voltage output diodes (7', 9'), and that the said high-voltage output diodes (7', 9') each have a conducting end sunk directly into the lower face of the corresponding conducting pellet (18, 19).
2. High-voltage transformer according to Claim 1 with a potentiometric unit (6) mounted on the front face of the insulating housing (1), characterized in that the said high-voltage output diodes (7', 9') are oriented parallel to one another, perpendicularly to the inside face of the pontentiometric unit, and diametrically opposite one another.
3. High-voltage transformer according to one of the preceding claims, intended for the power supply for a television set cathode-ray tube, characterized in that the said diodes (7', 9') are respectively associated with the very high voltage output for powering the anode of the cathode-ray tube, and with the high-voltage output for focusing the cathode-ray tube.
4. High-voltage transformer according to one of the preceding claims, characterized in this [sic] the said high-voltage output diodes (7', 9') are situated between the lower stage (4c) and an intermediate stage (4b) of the secondary winding (4).
5. High-voltage transformer according to one of the preceding claims, characterized in that none of the diodes (7', 8', 9') is arranged on the side neighbouring the potentiometric unit (6).

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