DE3128178A1 - HIGH FREQUENCY FERRORESONANCE POWER SUPPLY CIRCUIT - Google Patents

Description

GB-Ser.No. 8023282
AT: July 16, 1980

yS Ser.Nos. 250128/250131 'A

AT: April 2, 1981 RGA 75551 / Sch / Ro.

RCA Corporation, New York, NY (V.St.A.)

High frequency ferroresonance power supply circuit. 20th

The invention relates to ferroresonance power supply circuits using temperature-stable core materials for delivery regulated stable output voltages.

A power supply circuit with a ferroresonance transformer or a saturable ferroresonance choke as a control element the principle of magnetic saturation in order to keep an output voltage relatively constant. The control element works together with a resonance circuit, the resonance frequency of which is typically below- The frequency of the input voltage is chosen for a relatively effective regulation of the output voltage with changes in the load and the input voltage. The use of passive reactance elements results in reliable operation. The applied ferroresonance principle also prevents excessively large output voltages from being generated in the event of operational errors.

Operating at a relatively high input frequency such as the Television horizontal deflection frequency of approximately 16 kHz is a ferroresonance transformer relatively compact and lightweight and inherently provides output voltage regulation without the need for one relatively complicated and expensive electronic control circuit.

In terms of a reasonably good degree of efficiency at a high operating frequency of 16 kHz can be the magnetizable core of a ferroresonance transformer made of magnetizable material relatively high Specific resistance can be produced, such as a ferrite. Even if you use a ferrite core material, but eddy current losses and hysteresis losses in the core and resistance losses as a result of the in the with the winding of the ferroresonance transformer coupled capacitor flowing resonance current to a considerable heating of the saturation core over the Ambient temperature.

The saturation flux density B, ... +. many magnetizable materials

SoLC

decreases with increasing temperature. Since the output voltage of a ferroresonance transformer _{depends in part on the value B gtt of} the saturation core material, an increase in temperature of the saturation core can lead to an undesirable reduction in the output voltage.

Hysteresis and eddy current losses in the saturation core of the ferroresonance transformer or saturable reactance add to the heating of the core and the insulated coil wire that surrounds the Core is wound. However, relatively large losses are undesirable because they reduce the efficiency of the power supply circuit and because high operating temperatures lead to severe restrictions

visible of the insulation requirements.

A feature of the invention is the creation of a power supply circuit which utilizes ferroresonance phenomena for regulation, in which the magnetizable material is selected for a saturation core with a relatively stable saturation flux density B _s - _tt and a relatively high coercive force H. A material that is just one of these

] has both desirable properties is not suitable for the Use in a ferroresonance power supply circuit.

According to a preferred embodiment of the invention, one has a saturation core working regulated power supply circuit an excitation current circuit coupled to an input voltage source and a magnetizable core with a saturable core section. A winding is arranged on the core, and a device controlled by the excitation current generates in the magnetizable core a magnetic flux that alternates to generate an output voltage Polarity is concatenated with the winding.

The winding is assigned a capacitance in order to coincide with the Excitation current circuit in the saturable core portion is a magnetic Generate force field of alternating polarity. The magnetizing one A force field creates a magnetic flux which swings the saturable core portion during each cycle of the output voltage of alternating polarity saturates substantially magnetically, so that a resonance current in the capacity to regulate the output voltage of changing polarity arises.

The saturable core portion is made of a lithium ferrite or a substituted lithium ferrite.

In the accompanying drawings show:

1 shows a high-frequency ferroresonance power supply device having a saturable reactance using a saturable core material, whose saturation flux density is relatively temperature stable and whose coercive force is relatively low, such as a Lithium ferrite or a substituted lithium ferrite, according to the Invention;

Figure 2 shows a high frequency ferroresonance ultor power supply circuit having a saturable reactance using the same or a similar saturation core material as in the case of Fig. 1;

-δ-Fig. 3 diagrams of the saturation flux density versus temperature for various magnetizable ^ ferrites;

4 shows a modified configuration of the core and compared to FIG Turn and. ■.

Figures 5-8 Nomarski micrograms of polished surfaces of various Examples.

1 shows a high-frequency ferroresonance power supply circuit 10 with a saturable choke which generates a regulated voltage of alternating polarity at the connections 18 and 19 for supplying a load schematically designated by R. in FIG. The power supply circuit 10 can, for example, be dimensioned so that it _{generates a relatively low regulated output voltage V. of, for example, 24 V 6} ^.

The power supply circuit 10 comprises a high frequency power oscillator 23, which generates an unregulated AC input voltage at terminals 16 and 17, and an input choke 25, via which the input AC voltage to a high-frequency ferroresonance arrangement 24 is coupled with saturable reactance. The arrangement 24 includes a resonance capacitor 26, the Output terminals 18 and 19 and via a reactance winding 22 one Saturation magnetic element or a saturable choke SR is connected. The choke SR has a winding 22 which has a hollow Plastic bobbin 21 is wound, and a magnetizable core 20, which is located within the winding 22 and the bobbin 21

is located. ■

A magnetizing current flows in the winding 22 for generation a magnetic alternating flux in the magnetizable core 20, which is linked to the winding, to an output voltage alternating Polarity V. to create. The magnetizing current, or the

oc OUX

Winding current in the saturable choke comes in part from the

Input AC voltage source 23 and is via the Eipgcingsdrossel 25 to winding 22, and in part from that through the resonance capacitor 26 delivered electricity.

The output voltage V _{Q t} is regulated against changes in the amplitude of the input voltage and against load fluctuations, namely as a result of the ferroresonance effect of the arrangement 24, which causes the inductance of the saturation magnetic element SR during each half cycle of the output voltage V. between a state more relative

] Q high inductive impedance and a relatively low inductive impedance state is switched. If the element SR is in the high impedance state, in which its impedance is, for example, 10 times or even more the load impedance · R ^, then a relatively small magnetizing current flows in the inductor winding 22.

When the small magnetizing current flows in the winding 22, the volt-seconds impressed by the output voltage V _t in the core 20 produce a flux reversal in the magnetizable core 20 and a subsequent build-up of flux in the opposite direction. If the element SR has a high impedance, then the mag-.

netic working point of the magnetizable core 20 in the linear region of the BH curve of the magnetizable core material below the kink of this curve.

If the volt-seconds impressed over the winding 22 of the saturable core shift the magnetic operating point of the core material over the bend of the BH curve into the magnetic saturation area, then the inductance of the element SR, i.e. the saturable choke, changes to a relatively low value . A circulating or resonance current then flows between the resonance capacitor 26 and the inductor winding, which causes a current pulse in the winding and leads to a polarity reversal of the output voltage V _Qut .

In terms of a relatively good output voltage regulation, it can It may be desirable to design the saturable reactor so that the reactor inductance during magnetic saturation of the core

as small as practicable. The size of the inductance of the winding 22 in the case of saturation or in the interval where the core 20 is magnetic is saturated, for example, to a tenth of the impedance value the load circuit R. can be selected.

The input AC voltage source 23 can be a high frequency sine or -Rectangular power oscillator that works with a relatively high input frequency of 16 to 20 kHz, for example. Then the ferroresonance power supply device 10 can be considered relative compact, low-weight unit, which has inherent output voltage regulation properties, without having to do so relatively complex and expensive electronic control circuits are required would.

Operation at high frequency allows the use of low-value inductances for the input choke 25 and low-value capacitances for the resonance capacitor 26. If the power supply device 10 is dimensioned for supplying a regulated DC voltage, the load _{circuit R 1 contains} a rectifier arrangement which is passed through a filter capacitor is connected, at which the DC voltage occurs. Operation of the power supply device 10 at a high frequency then allows the use of a capacitor of a relatively small value for filtering the rectified output voltage of the ferroresonance arrangement 24 having the saturable choke.

Operating the power supply device 10 at a high frequency also allows the saturable choke SR to be implemented as a small one compact unit, as FIG. 1 shows, the core 20 of which is only a single one Has strips of magnetizable ^ material. It can other configurations for the saturable reactor SR can also be used. As shown in Fig. 4, the saturable reactor may have a toroidal core 120 have around which a choke winding 122 is wound, whose winding ends (not shown) are connected to the capacitor 26

* "in Fig. 1 would have to be connected.

-δι If the ferroresonance power supply device 10 at relative high input frequencies of 16 to 20 kHz, then can the eddy current losses in the magnetizable core 20 according to 1 or in the core 120 according to FIG. 4 become excessively large if they are not taken into account when dimensioning the saturable choke SR. As a magnetizable material for the core of the saturable Choke, a magnetizable ferrite can be selected which is manufactured to create a current in a vortex opposed relatively high resistance, so with specific

Resistances in volume greater than 10 ohm-cm.

Furthermore, many magnetizable ferrites show satisfactorily large unsaturated permeabilities and suitably large saturation flux densities, as is the case with saturable ferroresonance chokes and -Transformers is needed to make the choke relatively saturable has large unsaturated inductances without being excessive large cross-sectional areas or an excessively large number of coil turns were required for a given output voltage.

Is used as the core material in a high-frequency ferroresonance arrangement with a saturable choke a magnetizable ferrite, then the magnetic flux passes through essentially the entire larger B-H hysteresis loop of the core material during each Output voltage cycle of alternating polarity. During each cycle, energy is dissipated as heat in the bulk of the core material, proportional to the area of the larger B-H hysteresis loop is. The magnetizable core of the saturable choke therefore heats up to an operating temperature that is above the Ambient temperature and depends on 1) the hysteresis and Eddy current losses within the material, 2) the core geometry and the ratio of surface area to volume and 3) the thermal Conductivity of the ferrite material. The geometry of the core 20 according to Fig. 1 as a thin strip and the narrow, thin-walled shape of the

° the core of FIG. 4 result in a relatively large surface / Vdlumen ratio and thus a relatively good cooling of the core.

The regulated output voltage of a ferroresonance arrangement with a saturable choke depends on the saturation _{flux density B »tt of} the magnetizable material of the saturation core. The output voltage decreases with decreasing flux density, for example. The amount of change in saturation flux density with temperature is relatively small for many magnetizable ferrites, so that these ferrites are relatively unsuitable for use in a ferroresonance power supply device with a saturable choke, in which a relatively stable output voltage is required.

_{A magnetizable ferrite with a temperature-stable saturation flux density B s tt is} selected as the magnetizable material of the saturation core of a ferroresonance device with a saturable choke. The magnetizable material has a ferrospinel or magnetizable ferrite selected from a lithium ferrite or a substituted lithium ferrite. Suitable substituted lithium ferrite can include lithium manganese ferrite or lithium zinc ferrite. When properly manufactured, a lithium cation containing such ferrites has the advantageous properties of both a temperature-stable saturation flux density and a relatively low coercive force H. When used as a saturation core material in a ferroresonance system with a saturable choke, with lithium ferrite or a substituted lithium ferrite there is a relatively small change in the regulated output voltage with changes in the core temperature, and at the same time the increase in the operating temperature of the core due to hysteresis and eddy current losses remains relatively small.

Lithium ferrites have the nominal formula Li _{Q 5} Fe ₂ gO ^. As is known, the lithium and iron metal ions can be partially replaced by smaller amounts of one or other metals, such as manganese, zinc, nickel or cobalt. However, the lithium ferrites used as part of the invention described herein have a coercive force H of around 1.5 oersted or less at room temperature. They also have a large grain size of around 50 to 200μ or larger.

] The ferrites used as part of the invention are made by admixing the ferrite components, for example FegOo and Li ^ COg, to BIgO ₃ as a sintering agent, preferably in an amount of at least 1 up to about 3% by weight of the lithium ferrite components. Other materials such as manganese, zinc and the like can also be added in desired amounts in the form of their carbonates. After firing, preferably at about 800 to 950 ⁰ C, grinding and shaping of the ferrite material in a conventional manner, the material is then fired at temperatures of at least about 1200 to 150Q ⁰ C and preferably at about 1250-1450 ⁰ C again. If the sintering temperature is too low, the coercive force becomes too high. If, on the other hand, the sintering temperature is too high, the material will bubble and form voids, which impair the optical appearance and mechanical strength.

True, the exact reason why the present lithium ferrite differs from the known material, not known, however, it is believed that the presence of bismuth oxide as a liquid Phase for the formation of a lithium ferrite acts, which is a large has crystalline grain size that forms during high temperature firing.

The bismuth oxide is preferably the lower before the firing process Temperature added, but you can also add it afterwards. The bismuth oxide can be added to the burned ferrite during the grinding process be added where there is a well even mixture of ferrite and bismuth oxide before firing.

The material manufacturing method will now be based on the following Examples further explained. ·

example 1

A lithium ferrite was prepared by mixing together 18.08 g lithium carbonate with 194.04 g ferrous oxide. The parts were mixed in isopropanol for two hours, the

Solvent was filtered off, the material dried and two Burned in oxygen at 875 ° C for hours. The ferrite material, was then ball milled for 24 hours and it became a paraffin binder of 3% by weight of the amount of ferrite was added. The mixture was pressed and in oxygen at various Heated temperatures for two hours and then to room temperature cooled down.

The value H. and the core temperature were determined for an application in measured and determined using a high-frequency ferroresonance transformer. The specimens or samples discussed above were made with a commercially available Sample from Lithium Ferrite, Trans-Tech Inc. 71-3750, which is labeled Control.

The results are summarized in Table I below.

Table I. 2
1
1 ^H c Transformer core
Temperature. sample Sintering temperature ° C , 45
, 75
, 5 > 180 ⁰ C
148 ⁰ C
143 ° C control
1A
1B 1300
1350

These data show that the value H and the operating temperature decrease when the sintering temperature of a lithium ferrite increases.

Example 2 .

A lithium ferrite was made as in Example 1, but the amount of sintering agent, bismuth oxide, added during the initial mixing process was changed. The sintering temperature was 1300 ^° C. in all cases. The results are summarized in Table II.

. '■' "■

1A Weight% -12- II H. Transformer core 2A Bi ₂ O ₃ Table C. temperature 2 B 1.75 148 ° sample 2C 0.1 1.6 example UO 1.15 138 ° example 3.0 0.8 116 ° example example

The above data show that H and the core temperature decrease as the amount of bismuth oxide added is increased.

Example 3

A lithium ferrite was prepared as follows: 6.027 g of lithium carbonate, 64.679 g of iron oxide and 2.121 g of bismuth oxide were obtained mixed together in isopropanol for two hours, for * Removed the solvent, filtered, dried and then calcined in oxygen at 875 ° C for two hours. The resulting Substance was ground in a ball mill for 24 hours, vacuum filtered, and then 3% by weight of a paraffin binder was added added. The mixture was then pressed into the desired shape in a steel mold and in oxygen to one Fired temperature of 1430 ° C, which was held for two hours, then cooled to 870 ° C and held at that temperature for 12 hours and then cooled to room temperature.

Samples pressed from this material had more favorable hysteresis loss properties and an H value of 0.6 oersted.

Example 4

A dry mixture was prepared from 888.1 parts of iron oxide, 82.8 parts of lithium carbonate and 27.5 parts of bismuth oxide, Shaped into spheres and then baked at 900 ° C for one hour.

The material was then pulverized (50% of the particles pass through a 40-mesh screen) and slurried with 2000 parts of deionized water, the 25 parts of glacerin, 25 parts of polyethylene glycol with a molecular weight of 200, 100 parts polyvinyl alcohol, Gelvatol 20-30 (available from duPont de Nemours and Co.) » 0.15 part octyl alcohol, 0.16 part silicon dioxide (available from the name Cabosil MS7 from Cabot Corporation), 0.16 parts Calcium carbonate (available as marble powder) and 10 parts of one Solvent Tamol 901 (available from Rohm and Haas Company), contained. The slurry was in a ball mill to one Particle size of 10μ ground, spray-dried to remove the water and cooled, and then were added 5 parts of a lithium stearate lubricant and the material was molded into the desired shape to a density of 2.91 g per cubic centimeter pressed.

The cores were ^{burned in oxygen at 1300 °} C. for eight hours, ^{cooled to 900 °} C. and kept at this temperature for six hours, and then cooled down to room temperature. The lithium ferrite obtained in this way has a coercive force of Η _ς equal to 1.0 oersted at 25 ° C.

Example 5

The surfaces of several lithium ferrite samples as they were after the Examples 1 and 2 were polished and the grain size was determined from Nomarski micrographs as shown in FIGS 5-8 are measured. The results are in the

shown below in Table III. 30th

31ÜÖTYÖ

-14-Table III

sample % Bismuth oxide grain size, mm figure

Example 1 control 0 20-50 5

Example 1A 0 20 - 60 6

Example 2B 1 30 - 120 7

Example 2C 3 50 -> 200 8

Example 6

A number of lithium ferrites were produced which, in addition to the lithium , contained manganese or manganese and zinc in accordance with the general procedure according to Example 1, but the firing temperature was changed. All samples contained 1% by weight bismuth oxide.

In general, when manganese alone or manganese and zinc were added, the value of H decreased, but the temperature stability of the saturation flux density also decreased. This is determined by measurement of B at room temperature and at 15O ⁰ C and calculating the stability according to the following equation

β ^RT - B ¹⁵⁰ ° ^C

. η _Ä max max

W- RT.

Max

in which RT the room temperature is: The flux density B ■ "" was

ma χ obtained at a magnetic field strength of 25 Oersteds.

A first row with zinc content is shown in Table IV below compiled. These samples were fired at 1,435 ° C.

-15-Table IV

Composition H ^ ₉ Oe, ΔΒ

^Li 0.5 ^Mn 0.06 ^Fe 2.52 ° ' ^{7 7} ' ^9%

^Li 0.475 ^Mn 0.06 ^Zn 0.05 ^Fe 2.495 ° ' ^{7 9%}

^Li 0.45 ^Mn 0.06 ^Zn 0.10 ^Fe 2.470 ° ^{'55 8} > ^1%

^Li 0.425 ^Mn 0.06 ^Zn 0.15 ^Fe 2.445 ° ^{'55 10} ' ^8%

A second series with the same compositions but a firing temperature of 1380 ° C was prepared, as shown in the following Table V is listed.

composition

Table V ^H c , Oe. ΔΒ
T 0 ,8th 4.7% 0 , 7 7.4% 0 , 7 9.5% 0 , 65 10.4%

^Li 0.5 ^Mn 0.06 ^Fe 2.52 Lio, 475 ^Mn O, O 06 ^Zn, 05 ^Fe 2.495 ^Mn 0.06 ^Zn 0.45 ^Li 0.10 ^Fe 2.470 ^Mn 0.06 ^Zn 0.15 0.425 ^{Ll Fe} 2,445

It can be seen that the temperature stability is at lower firing temperatures something is better.

A third row was the manganese content and the firing temperature and the results are shown in Table VI.

35

■ 3 T 28 T

-16-Table VI

..Composition-. - Firing temperature ^ ' ⁰ C. 0.85 . : δβ 5 ^Ll 0.5 ^Mn 0.02 ^Fe 2.48 1400 0.6 3.8% ^Li 0.5 ^Mn 0.06 ^Fe 2.48 1420 0.6 3.2% ^Li 0.5 ^Mn O _? 1 ^Fe 2.4 1400 0.7 8.9% ^Li 0.5 ^Mn 0.15 ^Fe 2.46 1420 0.65 8.1% ^{0 L1} 0.5 ^Mn 0.06 ^Fe 2.52 1275 5.3% Example 7

Two samples Lithiummangangzinkferrit (Li "375 ^^ QgZn ^ 25 ^Fe 2 were prepared and fired at 1300 ⁰ C, but the bismuth oxide content was varied. The results are shown in Table VII.

sample Bi ₂ O ₃ ^H c Tabel VII Core temperature 20th 7A
7B 1%
3% 0
0 , Oe. ΔΒ 97 ⁰ C
89 ⁰ C ,8th
, 75 -15.6%
-14.5%

FIG. 3 shows the saturation flux density curves B. For the sake of simplicity, the flux density obtained at an excitation field strength of 50 Oersted was referred to as the saturation flux density B _s v _tt . The slope of each curve is a measure of the temperature stability of the value B ... of the ferrite compound in question. The slope of the curve determines the temperature coefficient ctg of the material, where a _D = (ΔΒ --JJ / B · - ++) (1 / ΔΤ) or a _D , i.e. the same

D SuuL SauU D- ■

the fractional change of Β ^ ·. ₊ ^ per ^0C . ^{Fed up}

3128173

In general, the flatter the slope of the curve in Fig. 3, the more temperature stable the ferrite compound and the more suitable it is for use as a magnetizable core material in a high-frequency ferroresonance power supply device, provided that the coercive force H _{c of} the material is not is too big. In general, according to the invention, ferrospinels containing lithium ions, a formulation which gives curves corresponding to curves B, C and E, can be used as a magnetizable material for saturation nuclei in a suitably sized high-frequency ferroresonance power supply unit. Each of the three lithium compounds B ₃ C and E in Fig. 3 was prepared using a predetermined amount of a bismuth oxide additive as a sintering agent to promote the growth of large microscopic ferrite grains and thus to form a lithium ferrite having a relatively small coercive force H _c

Curve E is obtained for a single ferrospinel compound of lithium ferrite which was produced according to the above recipe. The lithium ferrite according to curve E has a relatively small temperature coefficient of a _SS equal to -0.63 units per thousand, in part because of its relatively high Curie temperature of T ⁰ to 670 G. The coercive force H _c is 0.85 oersteds and is sufficiently small in order to prevent an excessive core temperature rise in the operation of a suitable high-frequency ferroresonance power supply circuit.

If it becomes desirable to further limit the core temperature rise in the operation of a ferroresonance power supply circuit, then lithium ferrite compounds of a mixed or substituted ferrospinel structure, as shown by curves B and C shown in Fig. 3 can be used. Curve B is setting Mixed ferrospinel with a zinc cation used for substitution, while curve C shows a mixed ferrospinel with a represents the manganese cation used for the substitution. Using a lithium zinc ferrite or lithium manganese ferrite is more suitable Composition and preparation, the coercive force H for a lithium zinc ferrite according to curve B can be reduced to

] a value of H of 0.72 oersted and for a lithium manganese ferrite according to curve C on H equal to 0.78 oersted. The use of zinc and manganese as substitutes in a mixed ferrospinel containing lithium as one of the cations reduces the coercive force H of the material compared to the coercive force sensor formulations of a lithium ferrite with a single ferrospinel. The reduced coercive force is obtained at the expense of a falling Curie temperature T of the mixed ferrospinel composition, lithium zinc ferrite having a Curie temperature of 570 ^° C. and lithium manganese of 500 ^° C. Because of the reduced Curie temperatures of lithium zinc and lithium manganese ferrospinels, the temperature coefficient α _{β increases} somewhat to a value of -0.72 parts per thousand per ⁰ C for lithium zinc ferrite and -0.96 parts per thousand per ⁰ C for lithium manganese ferrite. Although the temperature coefficient of these mixed ferrospinels is higher than the temperature coefficient of a lithium ferrite with only one ferrospinel, it is still more suitable for use in an appropriately sized high frequency ferroresonance power supply.

Lithium ferrospinels and suitable mixed ferrospinels containing lithium cations, as described above, are well suited as magnetizable ferrite material for saturation cores in high-frequency ferroresonance power supply devices because the ferrospinels containing lithium have a relatively small temperature coefficient ctn of the saturation flux density and a relatively small coercive force Have H _c . Both of these properties are desirable for a magnetizable ferrite material for use in a ferroresonance device with a saturable choke because a small temperature coefficient a "indicates that a relatively large change in core temperature results in only a small change in output voltage, and that only a relatively small drop in the regulated output voltage occurs when the magnetizable core has heated up to its operating temperature. A relatively small coercive force H means that the rise in the operating temperature reached by the core material is not very great.

Other magnetizable ferrites used in high frequency power transformers are not suitable for use in high frequency ferroresonance power supply circuits where the output voltage should be stable against temperature changes and where excessive core temperature rise should be avoided. For example, curve A represents the saturation flux density versus temperature for a manganese zinc ferrite used as the core material of a conventional flyback transformer of a television receiver. Such a manganese zinc ferrite can be, for example, a ferrite RCA 540 from RCA Corporation, Indianapolis, Indiana and as the core for a flyback transformer in a color television receiver RCA CTO85 series can be used. Since manganese zinc ferrites generally have low Curie temperatures - the Manganzinkferrit according to curve A has a Curie temperature of T of 200 ⁰ C - is the temperature coefficient cu extremely large, namely about 3.3 parts per thousand per ⁰ C.

Over a typical operating temperature range of a core of 80 ⁰ C, namely for example from 20 ⁰ C to 10O ⁰ C, the saturation. Flux density of the manganese zinc ferrite of curve A about 25% from a value of 4400 Gauss to 3300 Gauss. Such a percentage change in the saturation flux density would result in a correspondingly large undesired percentage change in the regulated output voltage of a high-frequency ferroresonance transformer. Although the coercive force H of the manganese zinc ferrite according to curve A is significantly smaller than the coercive force of the lithium-containing ferrites according to curves B, C and E, with which the manganese zinc saturation core has a considerably smaller core temperature rise, the extraordinarily large temperature coefficient of the saturation flux density of manganese zinc ferrite makes this material unsuitable for Use in a high-frequency ferroresonance power supply circuit if no complex cooling measures are provided in order to considerably limit the rise in core temperature. Even then, an ambient temperature change leads independently of the intended

thermal measures lead to a significant change in flux density. 35

Ferrospinels such as the nickel ferrospinel of curve D can also be unsuitable as saturation core material, although nickel ferrite has a relatively high Curie temperature T of 580 ^° C. and a relatively small temperature coefficient a _ß of -0.9 parts per thousand per ^° C. However, the coercive force H of nickel ferrite is around 5.0 Oersted or 7 times the coercive force of lithium ferrite and substituted lithium ferrite according to curves B, C and E. The relatively high coercive force of nickel ferrite leads to an extremely high rise in core temperature if this ferrite is used as Saturated core material used in a high frequency ferroresonance power supply circuit. Although the relatively small temperature coefficient of nickel ferrite results in a relatively small temperature-related drop in the regulated output voltage, the extremely high temperature rise of the saturation core above ambient temperature makes the core material relatively unsuitable for such applications unless special cooling constructions or particularly temperature-resistant winding wire insulation and winding body materials are used. The relatively high coercive force of nickel ferrite, which is indicative of the relatively large hysteresis losses that occur in the saturation core during each cycle of the AC output voltage, also results in poor operating efficiency as a power source.

Fig. 2 illustrates a high frequency ferroresonance power supply source using a temperature stable lithium ferrite or substituted lithium ferrite which provides a regulated anode high voltage for a television receiver. In Fig. 2, a source 27 of low-frequency AC mains voltage is connected via Eirtgangverbindungen 32 and 33 of a Vonweg bridge rectifier 28, which at an output terminal 30 delivers an unregulated DC voltage V ·. A filter capacitor 29 is connected between the output connection 30 and a current return connection 31 of the bridge rectifier 28. The input voltage V- is fed to an input choke 34 for feeding a horizontal deflection generator 35, d <
Deflection current generated.

a filter capacitor 29 is connected. The input voltage V- becomes an input choke 34 for feeding a horizontal sensor gate 35 fed to the 36 one in a horizontal deflection

The horizontal deflection generator 35 includes a horizontal oscillator and driver 41, a horizontal output transistor 40, a damping diode 39, a flyback capacitor 38 and the series connection of a horizontal deflection winding 36 and an S-shaping or trace capacitor 37. The horizontal flyback pulse voltage 42, which is at the horizontal deflection frequency 1 / T ^ is periodically produced at the collector of Horizontalausgangstransis'tors 40 at terminal 43 and is supplied via a DC blocking capacitor 44 and an input inductor 45 for exciting a high frequency ferroresonant inputs] Q directionally coupled to saturable reactor 46th ·

The device 46 contains a resonance capacitor 47, which over a winding 48 is connected, which around a magnetizable Saturated core made of the above-mentioned lithium ferrite or substituted lithium ferrite. The unsaturated The inductance of the choke winding 48 is, for example, 2 mH, while the saturated inductance is, for example, 100 μΗ. The by the ferroresonance device 46 with saturable choke generated regulated output voltage V. is attached to the primary winding a high-voltage, high-transforming autotransformer 50 placed, the secondary winding of which is connected to a high-voltage circuit 51 is connected, for example, a high-voltage multiplier circuit may contain an anode DC high voltage for supply to an anode terminal of a not shown To produce television picture tube.

In the high frequency ferroresonance power supply circuit shown in FIG 60 for generating the anode high voltage of a television receiver comprises the flyback pulse voltage 42, which the Deflection generator 35 generates the input AC voltage for the Ferroresonance device 46 with a saturable choke.

In a preferred arrangement, the source includes unregulated high frequency AC input voltage a high-frequency inverter that converts the unregulated input DC voltage into a high-frequency Square wave voltage generated. The ferroresonance arrangement with saturable Choke contains a ferroresonance transformer, its

312b Ί 7

Primary winding the square-wave input voltage derived from the inverter is fed, and a resonance capacitor, .der via a secondary winding magnetically loosely coupled to the primary winding of the ferroresonance transformer is switched. The regulated alternating voltage occurring at the secondary winding is then used to derive a regulated supply voltage B + for feeding a horizontal deflection generator. A high voltage winding is magnetically close to the secondary winding of the Coupled ferroresonance transformer, and one is created above it regulated alternating voltage, from which a regulated anode high voltage is produced. Such a high frequency ferroresonance power supply circuit for television receivers, inventor F.S. Wendt described that under the Designation "HIGH FREQUENCY FERRORESONANT POWER SUPPLY FOR A DEFLECTION AND HIGH VOLTAGE CIRCUIT" filed on April 28, 1980 and corresponds to British Patent Application Laid-Open No. 2,041,668A, published September 10, 1980, for a further description located in U.S. Patent No. 4,262,245 also to F.S. Wendt, issued April 14, 1981 with the designation "HIGH FREQUENCY FERRORESONANT TRANSFORMER ".

In accordance with the teachings of the preceding with regard to the use of Lithium ferrite or substituted lithium ferrite in a high frequency ferroresonance power supply circuit invention described can be the magnetizable core of the television receiver ferroresonance transformer, as described in the aforementioned US application and the Wendt patent, advantageously Lithium ferrite or substituted lithium ferrite as a transformer saturation core material exhibit.

According to the disclosure of the co-pending US patent application by WE Babcock et al, Ser.No. 250,130 dated April 2, 1981 with the designation "TELEVISION RECEIVER FERRORESONANT POWER SUPPLY USING A TWO-MATERIAL MAGNETIZABLE CORE ARRANGEMENT", also needs

only the secondary winding saturation core part of the magnetizable Core of the ferroresonance transformer made of lithium ferrite or

Substituted lithium ferrite to be prepared to the advantageous results of the use of lithium discussed here Ferrospinell as a saturation core material. Of the Primary weight core part of that in the aforementioned Babcock application described ferroresonance transformer can, as described there, be chosen so that it has magnetic properties, which are advantageous when the magnet! si erable core in the practical linear range of its B-H characteristic is operated, as is the case with the primary core part of the described in the Babcock application Ferroresonance transformer is the case.

Tables I and II below illustrate the effects when using different saturation core materials for the secondary section in a ferrite core consisting of two materials when operating a ferroresonance transformer in a television receiver for the delivery of a regulated supply voltage B + for deflection and a regulated anode high voltage as described in the aforementioned U.S. Patent Application No. 250,130. The primary core material for each of the examples of secondary core section material is a manganese zinc ferrite. The ferroresonance transformer was used to power a modified CTC-99 color television receiver made by RCA Corporation, its The picture tube was a 19 inch tube with a 100 ° wide-angle deflection. the The power consumption of the entire television receiver was 98 watts with one milliampere beam current.

Examples 1 and 2 of the tables show the advantages of using either a lithium ferrite (example no. 1) or a substituted lithium ferrite such as a lithium manganese zinc ferrite (Example 2) according to the teachings of the invention regarding the use of lithium ferrite or substituted lithium ferrite in a high frequency ferroresonance power supply circuit. In contrast, there are also the results when using a manganese zinc ferrite (Example 3) or a nickel ferrite (Example .4) as

³ - Secondary saturation core section material indicated.

The values given in Table I in the column "ΔΤ" represent the Temperature rise above the ambient temperature of 25 ° C in the saturable core section of the ferroresonance transformer in the area of the secondary winding after switching on the television receiver occurs when the core has reached its operating temperature. The values in the "AU" column indicate the drop in the anode high voltage below the nominal value of 32 kV in the ferro resonance transformer the first time the television receiver is switched on again. The nominal voltage of 32 kV resulted when the materials were used Examples 1 to 4, although these differ in their saturation flux density B ..., in that the total saturation flux through Setting the core cross-sectional area of the saturation core constant was held. The values for the flux density obtained at a magnetizing field strength of 25 oersteds have usually been expressed as EL

L ..;, sa xx

result at 15.75 kHz and at a room temperature of 25 ° C.

designated. The values given in Table II for H _c and

From the tables it can be seen that the size of the temperature coefficient OU of lithium ferrite and lithium manganese zinc ferrite are below 1 to 1.5 parts per thousand and per ⁰ C and that the coercive force at 25 ° C is less than 1.0 oersted: This is the voltage drop the high voltage is less than 2.4 kV from the nominal value of 32 kV.

In the case of the manganese zinc ferrite (example 3 in the tables), a relatively small increase in core temperature ΔΤ occurs partly as a result of the relatively low coercive force H of manganese zinc ferrite. Nevertheless, a manganese zinc ferrite can be a saturation core material unusable for use because of the excessive anode high voltage drop of 3.5 kV, partly due to the relatively high temperature coefficient a _{ß of} the material. The manganese zinc ferrite results in a relatively large change in the anode high voltage of 110 parts per thousand and may therefore be unusable as the saturation core section material for the secondary winding;

The nickel ferrite listed in the tables in Example 4 has a relatively good temperature coefficient for the saturation flux density

-4

of -9.0x10 / ⁰ C. Nevertheless, the nickel ferrite can also be an unusable saturation core material because of its relatively large coercive force of 5.0 Oersted. The large coercive force results in an extremely high temperature rise ΔΤ and a very large anode high voltage drop of 3.4 kV.

For example, a reasonably acceptable change in anode high voltage AU / U may be a change of 75 parts per thousand or less between the endpoints of the normal operating temperature range of its power supply arrangement. An acceptable value for the size of a _{D of} the material over the normal operating range of core temperature may be equal to or less than 1.5 parts per thousand per ^0C . A useful value for the coercive force can be at or below 1.5 oersteds. Acceptable values of a «, H and AU / U depend on parameters such as the degree of output voltage regulation desired, the temperature range including ambient temperature changes within which the. Power supply arrangement should work satisfactorily, the size of the screen and the power consumption, the maximum permissible temperature of the components and the permissible degree of overscan during operation of the television (beyond the image edges).

Thus, according to the invention, the use of lithium ferrite and substituted lithium ferrite, which has the properties of a small temperature coefficient of saturation flux density and a small temperature coefficient Has coercive force, extremely beneficial for the construction of a ferroresonance power supply device which has a Provides output voltage that is relatively insensitive to temperature change, and which leads to a very limited temperature rise

^{ου of} the saturation core leads to the ambient temperature.

Other desirable properties that the lithium ferrite may have are relatively high resistivity and fairly rectangular B-H hysteresis curve. A rectangle ratio can

are defined as B _r / B _max »where B is the remanent induction of the material and B is the magnetization field strength of

J IZo I / ö

50 oersted obtained flux density. Equal to a rectangle ratio or greater than 0.6 may be desirable for improving output voltage regulation.

Table I saturable core material

At s p. No. (Secondary winding) ■ -AU (kV) - (Δϋ / ϋ) (λ100) . AT ( ⁰ C) 1 Li ferrite 1.5 4.6 92 2 LiMnZnFerrit 2.3 7.2 89 3 MnZnFerrit 3.5 11.0 51 4th Ni ferrite > 3.4 ? 10.5 - •> 165

Table-II

Example No. Saturable core
cutting material
(Secondary winding) ^T c
( ⁰ C) -a _B (x10 ⁴ / ° C) ^B sat
(Gauss) Λ
(Oersted) 1 Li Ferri t 670 5.4 2900 0.94 2 LiMnZnFerrit 500 10.7 3400 0.70 3 MnZnFerrit 200 32.0 4300 0.24 4th Ni Ferri t 585 9.0 3200 5.0 ■

Claims (1)

Claim Power supply arrangement with a saturable core, with a magnetizable core containing a saturable core section, a winding arranged on the core, a device for generating a magnetic flux in the core for generating an alternating voltage across the winding, a capacitance associated with the winding that generates a current due to the voltage which causes a magnetic flux which contributes to the saturation of the saturable core portion during each alternating current cycle for the regulation of the output voltage, characterized in that the saturable core portion is formed from a lithium ferrite or a substituted lithium ferrite.