CA2098100A1

CA2098100A1 - High-voltage transformer

Info

Publication number: CA2098100A1
Application number: CA002098100A
Authority: CA
Inventors: Walter Goseberg; Wolfgang Reichow; Hans-Werner Sander
Original assignee: Individual
Current assignee: Deutsche Thomson Brandt GmbH
Priority date: 1990-12-10
Filing date: 1991-12-03
Publication date: 1992-06-10
Also published as: EP0561839B1; DE4039373A1; HUT64660A; PT99742A; KR930703789A; FI932627A; ZA919724B; HK1000744A1; JP3280965B2; MY107209A; MX9102455A; TR25836A; ES2097823T3; PT99742B; WO1992010906A1; FI932627A0; SG46549A1; JPH06503448A; DE59108593D1; HU9301604D0

Abstract

H90/08/A?WP 281191 - 10 -ABSTRACT

1. High voltage transformer 2.1. With a high voltage transformer, in particular a diode-split transformer, there generally exists the requirement that the entire arrangement is, for reasons of cost and weight, to be proportioned as small as possible and likewise, the heat losses during operation of such a high voltage transformer must be sufficiently reduced so that the warming-up of the transformer does not reach temperatures at which other circuit components of a television receiver are damaged or interfered with in a disturbing way. It is the task of the invention to minimize the losses from a high voltage transformer, in particular however, the electrical losses.

2.2. According to the invention, for a high voltage transformer of the aforementioned type the task is solved in that a space is formed between the primary winding and the high voltage winding which is almost free of fields.

2.3. Television receivers, in particular television receivers with a large number of lines for the HDTV
standard.

3. Fig. 1

Description

~IC~0~08~W~ 2~ 2 ~ ~ 8 1 ~ O

High voltage trans~ormer for a television receiver The invention i5 hased on a high voltage transtormer according to the preamble o~ claim 1. Such a transformer is known from DE-OS 35 14 308. Such transEormers genarate a high voltage for television receivers in the order of magnitude of 25 kV .

For television receivers with larger picture tubes (kinescopest, for example, with an aspect ratio of 16:9 or a screen diagonal ot 85 cm, greater high voltages in ~he order o~ magnitude of 35 kV are required. qransformers for such a great high voltage exhibit, unavoidably. an increased power loss, thereby causing the build-up of heat to be greater and increasing the geometrical dimensions reqlJired tor the dissipation of the heat.

It is the object of the invention ~o reduce the power dissipation at the transformer with such high voltage transformers. This ~ask is solved by the invention specified in clai~ 1. Further advantageous developments of the invention are given in the subclaims.

The invention is firstly based upon an analysis of all the types of losses which appear altogether with such a transformer. A first type of 108R consists of ferrite losses through magnetic reversal of the core corresponding to the area formed by the hysteresis curve. Such losses can only be reduced by the use of better quality ferrite materials. A second type of 1088 consists of copper losses through the oh~ic resistance oE the wire and the s~in (Kelvin) effect. A third type of 1088 consists of losses in the high voltage rectifier diodes, i.e~ through the rorward (flow) voltage ànd the on-state current, the off-state voltage and the off-state current, and ~he swirch:in(~ lossex - ' ' ~190/08/A~WP 2~11'31 - 2 - ~ 9 ~ -upon switching over ~rom the blocked to ~he conduct;ing states and vice versa. A four~h type o~ loss consists of dielectric losses thro11gh displace1nent c1lrrents in ~he insula~or ger1erally made from a sealing resin. As far as the first three types of los~ are concerned, there are lower limits caused by, in particular, techno~Logical reason6 and the available componen~s. The invention now concentrates on the fourth type of loss. In doing this the invention is based on the following consideration. The dielectric losses appear especially in the region between the primary winding and the secondary or high voltage winding because it iB here that the greatest voltages differences exist. Therefore, if it were possible to successfully construct this region as free from electrical fields as possible, then the dielectric losses could be considerably reduced. With the invention this is achieved merely by a particularly advantageous division of the impulse voltages at the pri~ary winding and the secondary winding in such a way that in this named region the impulses have roughly the same amplitude and polarity at the primary winding and at the secondar~
winding. 1'he difLerence between the impulse volta~3e:; in ~he two windings is then practically lost so that, :in a desired an1ler, a space is obtained which is f:ree fro1a electric fields and losses through dielectric ctisplacement currents are avoided a~ far as possible. A signl~icant advar1tage is that the field-free space is achieved not ~hrough the use o~
additional means but rather only through a skil~ul arrangement of the parts that are required anyway.
Furthermore, by reducing the dielectric displacement currents in the insulator surrounding the windings, the harmonic content of the voltages generated is reduced. This leads to less natural re30nances which otherwise are caused by displacmen~ currents. The reduction in the harmonic waves causes an i~provement to the internal resistance and, in addition, a~reduction of the acoust:ic noise appearing at the transformer. Further, the material surrounding the ll~)0/08/A~WP 28l191 - 3 - 20~

windings, preferably a cac;t resin, is also placed urlder less s t: res~ .

The invention is explained in the following by means of the drawing. Therein i8 showrl:
ig. 1 the configuration of a high volta~e ~rans~ormer according to the invention, ancl ~ig. 2 a replacement circuit diagram for the tran~former according to Fig. 1.

In the Eollowing description only the impulses voltages effective at the transformer are talterl into consideration.
The direct voltages which appear are not considered b~allse these cause no dielectric displacement currents and, consequently, no power losses.

In Fig. 1 the coil former 7, carrying the primary winding 3, is supported on the core 1. The primary winding 3 consists of six layers. The lead-out wire from the lower layer is connectsd to the terminal 'b' wil:h the operatirlg voltage +UB. The lead-ou~ wire from the upper layer is `:
connected to the terminal 'd' and to the switching transistor 13 which is controlled by a line-frequency switchi.ng voltage Z at terminal 'c'. The impulse vol~age at ~erminal 'b' is zero. The impulse voltage at termirlal 'd' has the full value of ~he flyback voltage, i.e. ~1~00 V.
Therefore, the impulse voltage continually increases, from winding to winding, from the value zero at terminal 'b' up to the maximum value at terminal 'd'. q'his means that the impulse voltage decreases by about l~ per cent over ~he axial length of the upper layer of the winding ~ and tt~e impulse voltage at the right-hand end of the upper layer has a value of ~1000 V. The impulse voltage is, therefore, essentially constant over the axial leng~h of the coil i ~l~0/~8/A~WP 2~119L - ~ - 2 ~ 9 81 ~ O

forlller 7 in the upper layer o~ wind:ing ~ and ha-s a mean ~alue of 1100 V.

Arranged above the coil former 7 with the primary windinc~t 3 is the compartment coil former 2 whic}l has a total o~ 16 cells Ka through Kp ~separated by walls 8 which are filled with partial windings 4a through 4p of the secondary or high voltage winding 4. The lead-out wire ~rom the upper layer of the first partial winding 9a i~ conrlected to ground. Each of the lead-out wires at the base o~ a cell i3 coupled to the anode of a high voltage rectifier diode 6 the cathodes of which are alway4 coupled to the lead-ou~
wire from the upper end of the following partial winding 9.
~rhe lead-out wire ~rom the bas~ o~ the linal partial winding ~`~
4p in cell ~p forms the high voltage terminal a . I`he winding process for the entire secondary win~ing ~ scarts at the base of cell Kp. As always one diode 6 is positioned between each pair of cells 15 diodes 6 are provided ~or a ~ -total of 16 cells K. A high voltage UH of 32 kV ensues at terminal a . These values assumecl an impulse of +ll0~ V
results always at the base of each cell ~ which i'3 iderltiCal ~`
for all cells. An impulse of -130~ V re-;ults at the upper end of winding 9.

Consequently impulses with an esselltially constant amplitude of +1100 V are present along the upper layer of winding 3. On the other hand as described above impulses with the constan~ amplitude of ~1~00 V also ensue throug}l the high voltage ~inding 9 in the region associated wilh the winding 3 i.e. in the region of the lower ends of the cells. Apart from that the impulse~ ~-tt windincg 3 and at;
winding 4 are isochronous. Therefore a voltage differerlce practically no longer e4Yists be~ween the impulse.~3 a~ win(iing 3 and the impulses at winding 4 so that a space free from electric fields results as indicated by the dotted line ~.

~90/08/A~P 2811~ 5 - 2 ~ 3 ~

The .impulses a~ the upper enli of the wind-i.ngs 9 i.n ~act have the wrong neyat:ive polarity ~or ~uild.irlg the fi.eld-f.ree space. However, ~he impul3e~ present at this point are sufficiently d:is~ant from the primary windirl~ 3 tha~ t~ley no longer cause any signi~icant displacement currerlts through the insulator.

The upper end of the first winding 4a is connected to ground and therefore conducts no impu1.se vol.~age while, on the other hand, the lower end of the final winding 9p, which is connected to ground via the capacitance of ~he picture tube, also conducts no impulse voltage. The voltage ratios of these two windings are, therefore, different with respect to those of the other windinys 4b through 9o. fn order to also produce the desired amplitude ratios betweer~ ~he impulse voltages in this ragion, it is advantageous to, in contrast to the remaining cells, only half spool the cells Ka and Kp. The primary winding 3 is preferably wound ~rom stranded conductor in order to keep the losses due to the skin effect low.

Fig. 2 shows the replacemerlt ci.rcuit dia~ram associated with Fig. 1. The capacitor 1.9, essen~i.ally formed by tt~e anode terminal tanode layer) of picture tube L5, :
connected to the t:erminal 'a' conclllctirlg ~lle Illgtl voltage UH. The diode 6b therelore corresponds to the f:irst diode in Fig. 1 between the base o~ cell Ka and the lead-out wire at the upper end of cell Kb. The :inal diode 6p corresponds to the diode between the lower und of the winding of cell Ko and the upper lead-out wire of the final cell Kp.

It is also possible to sub-divide the primary winding 3 into several partial windings which lie adiacen~ each o~her in the axial direction on the core 1 and are wired in parallel be~ween the terminals 'b' and 'd'. C;erlerall.y, the - : ~

, H90/~8/A~WP 281:L~Y:I - 6 - 2 0 ~ g ~ O

amplitude at the upper layer of primary winding 3 varies over the axial length. This can be taken into account in that the cells Ka through Kp are filled accordingly differently so that the impul~es of each o~ the partial winding~ 4a through 9p also have correspondirlg:Ly differing amplitudes at the bases of the cells. The filling Lactor for the cells K with the partial windings ~ wou~.d then decrease from the le~t- to the right-hand end of the coil formers 7, 2, in the same way as the amplitude of the impulses at the upper layer o~ win~lir~g ~ (iecrea~e~, ~rom, in Fig. l, +1200 V to ~1000 V.

. ' .
`: ' ' . ' ' .. . .

Claims

H90/08/A*WP 281191 - 7 -P a t e n t C l a i m s

1. High voltage transformer for a television receiver with a primary winding (3) and a secondary winding (4) arranged above this, the partial windings (4a through 4p) of which are located in cells (K) of a compartment coil former (2) and are connected to each other via diodes (6), c h a r a c t e r i z e d i n t h a t the primary winding (3) and the secondary winding (9) are sub-divided and polarized in such a way that they produce impulses of roughly equal amplitude and polarity in the regions of the windings (3, 4) adjacent each other, and that a space almost free of electric fields is formed between the windings (3, 4).

2. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the primary winding (3) is wound in layers with several layers lying above each other and the lead-out wire (b) from the lower layer is provided for connecting to the operating voltage (UB) and the lead-out wire (d) from the upper layer for connecting to a periodic switch (13).

3. Transformer according to claim 2, c h a r -a c t e r i z e d i n t h a t the partial windings (4a through 4p) are so polarized that there is a positive-directed impulse always at the lead-out wire from the base of each of the cells (K).

4. Transformer according to claim 3, c h a r -a c t e r i z e d i n t h a t the number of cells (K) and partial windings (4a through 4p) is proportioned sufficiently large so that the positive-directed impulse at the base of a cell (K) has approximately the same amplitude as the positive-H90/08/A*WP 281191 - 8 -directed impulse at the upper layer of the primary winding (3).

5. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t always one diode (6) is connected via its anode to the lead-out wire from the base of a cell (K) and the cathode of each said diode is connected to the lead-out wire from the upper layer of the partial winding (4) of the next cell (K).

6. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the start of the winding for the secondary winding (4) forms the terminal (a) supplying the high voltage (UH).

7. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the primary winding (3) consists of several partial windings (3a through 3c) wired in parallel which are arranged adjacent each other in the axial direction of the coil former (2).

8. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the transformer is constructed as a diode-split transformer.

9. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the cells (K) are filled differently by the partial windings in such a way that the impulses at the base of each cell have roughly the same amplitude as the impulses at the neighboring winding of the primary winding (3).

10. Transformer according to claim 1, c h a r -a c t e r i z e d i n t h a t the first (Ka) and the last (Kp) cells are, relative to the other H90/08/A*WP 2831191 - 9 -cells (Kb through Ko), only half filled with the partial windings (4).