DD206617A5 - HIGH FREQUENCY FERRO RESONANCE POWER CIRCUIT - Google Patents

Abstract

The invention relates to ferro-resonance power supply circuitry using temperature-stable core materials to supply regulated steady-state output voltage. The object of the invention is to reduce the frequency of the hydrogen saturation and spin current losses in the Ferro-Resonance Transformer Core. According to a preferred embodiment of the invention, a controlled power supply circuit operating with a sealing core has an energizing power circuit coupled to an input power source and a magnetizable core having a sealable core cut. ON THE CORE, A WINDING ARRANGES, AND A DEVICE CONTROLLED BY THE ACTIVITY GENERATES A MAGNETIC FLOW IN THE MAGNETIC CORE, A MAGNETIC FLOW CHAINED WITH THE WINDING FOR PRODUCING AN OUTPUT VOLTAGE CHANGING POLARITY. THE SAFETY NOMINAL CUTTING IS MADE FROM A LITHIUM REFERENCE OR FROM A SUBSTITUTED LITHIUM REFERENCE.

Description

-I 231850

RCA 75551 / Sch / Ro.

Hochfreguenz-ferroresonant power supply circuit. Field of application of the invention:

The invention relates to ferroresonant power supply circuits using temperature stable core materials to provide regulated stable output voltages.

Characteristic of the known technical solutions;

A power supply circuit having a ferroresonant transformer or a saturable ferroresonance reactor as a control element utilizes the principle of magnetic saturation to keep an output voltage relatively constant. The control element, together with a resonant circuit whose resonant frequency is typically chosen below the frequency of the input voltage, provides for relatively effective regulation of the output voltage with changes in the load and 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.

t \ i.dkQ C!

i 2 318 5 0 4

] Operating at a relatively high input frequency, such as the TV horizontal deflection frequency of about 16 kHz, a ferroresonant transformer is relatively compact and lightweight and inherently provides output voltage regulation without the need for a relatively complicated and expensive electronic control circuit.

In terms of a reasonably good efficiency at a high operating frequency of 16 kHz, the magnetizable core of a ferroresonant transformer made of magnetizable material of relatively high resistivity can be made, such as a ferrite. However, even using a ferrite core material, eddy current losses and core hysteresis losses and resistance losses due to resonant current flowing in the capacitor coupled to the ferroresonant transformer winding can result in significant saturation core heating.

The saturation flux density B .... of many magnetizable materials

sa u.

decreases with increasing temperature. Since the output voltage of a ferroresonant transformer depends in part on the value B... Of the saturable core material, an increase in the temperature of the saturation core can lead to an undesirable reduction in the output voltage.

Hysteresis and eddy current losses in the saturable core of the ferroresonant transformer or saturable reactance contribute to heating of the core and insulated coil wire wound around the core. Relatively large losses are however undesirable because they reduce the efficiency of the power supply circuit and because high operating temperatures lead to excessive restrictions.

visibly meet the insulation requirements.

Object of the invention:

It is an object of the present invention to provide a ferro-resonance phenomena for control utilizing power supply circuit in which the magnetizable material is selected for a saturable core having a relatively stable saturation flux density B... And relatively high coercive force H. A material that is just one of those

. {. 231 8 50 4 has two desirable properties is not suitable for use in a ferroresonant power supply circuit.

Explanation of the invention of the invention:

According to a preferred embodiment of the invention, a saturable core regulated power supply circuit has an exciting current circuit coupled to an input voltage source and a magnetizable core having a saturable core portion. A winding is disposed on the core, and means controlled by the exciting current generates in the magnetizable core a magnetic flux which is chained to produce an output voltage of alternating polarity with the winding.

The winding is associated with a capacitance for generating a magnetic force field of alternating polarity in the saturable core section together with the energizing current circuit. The magnetizing force field generates a magnetic flux which substantially magnetically saturates the saturable core portion during each cycle of the alternating polarity output voltage to produce a resonant current in the capacitor for regulating the output voltage of varying polarity.

The saturable core portion is made of a lithium ferrite or a substituted lithium ferrite. Exemplary embodiments: In the accompanying drawings:

1 shows a high frequency ferroresonant power supply device with 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;

Fig. 2 shows a high frequency ferroresonant end anode power supply circuit having a saturable reactance using the same or a similar saturable core material as in the case of Fig. 1;

-'- 2318 5 0 k 3 shows diagrams of the saturation flux density versus temperature for various magnetized ferrites.

Fig. 4 is a comparison with FIG. 1 modified configuration of core and winding and

Fig. 5-8 Nomarski micrograms of polished surfaces of various examples.

In Fig. 1, a high-frequency ferroresonant power supply circuit 10 is illustrated with a saturable reactor, which generates at the terminals 18 and 19, a regulated voltage of alternating polarity for feeding a in Fig. 1 schematically denoted by R, load. For example, the power supply circuit 10 may be sized to provide a relatively low regulated output voltage V. of for example 24 V _f ^ generated.

The power supply circuit 10 comprises a high frequency power oscillator 23 which generates an unregulated AC input voltage at the terminals 16 and 17 and an input choke 25 via which the input AC voltage is coupled to a high frequency ferroresonance arrangement 24 of saturable reactance. The assembly 24 includes a resonant capacitor 26 connected across the output terminals 18 and 19 and across a reactance winding 22 of a saturable magnetic element or saturable reactor SR. The reactor SR has a winding 22 wound over a hollow plastic bobbin 21 and a magnetizable core 20 located inside the winding 22 and the bobbin 21

is

 30

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

Winding current in the saturable reactor is partly due to the

2318 50th

] AC input voltage source 23 and is transmitted via the input inductor 25 to winding 22, and in part on the delivered by the resonance capacitor 26 current.

The output voltage V _t is controlled against amplitude variations of the input voltage and load variations due to the ferroresonant effect of the device 24 which causes the inductance of the saturable magnetic element SR to alternate between a state of relative high inductive impedance and each half cycle of the output voltage V _t State relatively low inductive impedance is switched. When the element SR is in the high impedance state in which its impedance is 10 times or more the load impedance R, for example, a relatively small magnetizing current flows in the reactor winding 22. When the small magnetizing current flows in the winding 22, they generate from the output voltage V. in the core 20 impressed volt-seconds, a flux reversal in the magnetizable core 20 and a subsequent flux build-up in the opposite direction. If the element SR has a high impedance, then the magnetic operating point of the magnetizable core 20 is in the linear region of the BH curve of the magnetizable core material below the bend of this curve.

When the volt-seconds impressed across the winding 22 of the saturable core displace the magnetic operating point of the core material beyond the bend of the BH curve into the magnetic saturation region, the inductance of the element SR, that is the saturable reactor, changes to a relatively low value , Then, a circulating or resonant current flows between the resonant capacitor 26 and the choke winding, causing a current pulse in the winding and leading to a polarity reversal of the output voltage V _Qut .

In terms of relatively good output voltage regulation, ^{OJ may} be desirable to design the saturable inductor such that the inductor inductance during magnetic saturation of the core

-I 2 31850

] is as small as practicable. The magnitude of the inductance of the winding 22 in the saturation case or in the interval where the core 20 is magnetically saturated, for example, to one-tenth of the impedance value of the load circuit R ₁ can be selected.

The input AC voltage source 23 may comprise a high frequency sine or octane power oscillator operating at a relatively high input frequency of, for example, 16 to 20 kHz. Then, the ferroresonant power supply device 10 may be embodied as a relatively low weight, compact unit having inherent output voltage control characteristics without requiring relatively expensive and expensive electronic control circuits.

High frequency operation allows the use of low value inductors for the input inductor 25 and low capacitance values for the resonant capacitor 26. If the power supply 10 is provided for a DC regulated supply then the load circuit R ₁ will include a rectifier assembly connected across a filter capacitor is switched, on which the DC voltage occurs. Operation of the power supply 10 at a high frequency then permits the use of a relatively small value capacitor to filter the rectified output voltage of the ferroresonant array 24 having the saturable reactor.

An operation of the power supply device 10 at high frequency also allows a realization of the saturable reactor SR as a small compact unit, as shown in FIG. 1, the core 20 only a single strip of magnetizable !! Material has. Other configurations for the saturable reactor SR may be used. As shown in FIG. 4, the saturable reactor may have a toroidal core 120, around which a choke winding 122 is wound, whose winding ends, not shown, to the capacitor 26

^OD in Fig. 1 would be connected.

2318 50th

If the ferroresonant power supply device 10 is operated at relatively high input frequencies of 16 to 20 kHz, then the eddy current losses in the magnetizable core 20 of FIG. 1 or in the core 120 of FIG. 4 may become excessively large when measured in terms of saturable Throttle SR not considered. As a magnetizable material for the core of the saturable reactor, a magnetizable ferrite can be selected, which is prepared so that it provides a relatively high resistance to eddy current formation, ie with specific

2 resistors in the volume of more than 10 ohm-cm.

Furthermore, many magnetizable ferrites exhibit satisfactorily large unsaturated permeabilities and suitably high saturation flux densities, as is required with ferro-magnetic ferroresonant chokes and transformers, in order for the saturable reactor to have relatively large unsaturated inductances without requiring excessively large cross-sectional areas or an excessively large number of coil turns a given output voltage would be needed.

Using a magnetizable ferrite as the core material in a saturable choke high frequency ferroresonant array, the magnetic flux traverses substantially all of the larger B-H hysteresis loop of the core material during each cycle of alternating polarity output voltage. During each cycle, energy is consumed as heat in the bulk of the core material, which is proportional to the area of the larger B-H hysteresis loop. The magnetizable core of the saturable reactor therefore heats up to an operating temperature that is above ambient temperature and depends on 1) the hysteresis and vortex current losses within the material, 2) the core geometry and the surface to volume ratio, and 3) the thermal conductivity of the ferrite material. The geometry of the core 20 of FIG. 1 as a thin strip and the narrow thin-walled shape of the

Kernes of Fig. 4 give a relatively large surface / volume ratio and thus a relatively good cooling of the core.

I 2 31850 A

] The regulated output voltage of a ferroresonant arrangement with saturable inductor depends on the saturation flux density B ... _{t of} the magnetizable material of the saturation core. The output voltage decreases, for example, with decreasing flux density. The magnitude of the 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 saturable reactor ferroresonant power supply device in which a relatively stable output voltage is required.

As a magnetizable material of the saturation core of a Ferroresonanzeinrichtung with saturable throttle a magnetizable ferrite with temperature-stable saturation flux density B- .. is selected. The magnetizable material comprises a ferromagnetic or magnetizable ferrite selected from a lithium ferrite or a substituted lithium ferrite. A suitable substituted lithium ferrite may include a lithium manganese ferrite or lithium zinc ferrite. When properly prepared, such a lithium cation containing ferritic has the advantageous properties of both a temperature stable saturation flux density and a relatively low coercive force H. When used as a saturant core material in a saturable reactor ferroresonant system, lithium ferrite or a substituted lithium ferrite undergoes a relatively small change in the regulated output voltage with changes in core temperature, and at the same time, the increase in core operating temperature due to hysteresis and eddy current losses remains relatively small.

Lithium ferrites have the nominal formula Li _nc Fe _{0 c} 0 *. The lithium

U, D £, 0 <t

and iron metal ions can be known to 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 _c of about 1.5 oersted or less at room temperature. You also have one

* "large grain size of about 50 to 200μ or above.

231850 k The ferrites used as part of the invention are prepared by admixing the ferrite constituents, for example Fe 1 Cl and 1 COg, to 2O as sintering agent, preferably in an amount of at least 1 to about 3% by weight of the lithium ferrite constituents. 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 1500 ⁰ C and preferably at about 1250-1450 ⁰ C again. If the sintering temperature is too low, the coercive force becomes too high. On the other hand, if the sintering temperature is too high, the material will blister and form voids that affect the optical appearance and the mechanical strength.

While the exact reason why the present lithium ferrite differs from the known material is not known, it is believed that the presence of bismuth oxide acts as a liquid phase for the formation of a lithium ferrite having a large crystalline grain size which is found throughout of high temperature burning trains.

The bismuth oxide is preferably added to the lower temperature before firing, but it may be added afterwards. The bismuth oxide may be added to the calcined ferrite during the milling process, where a well uniform mixture of ferrite and bismuth oxide before firing results.

The material manufacturing method will be further explained by the following examples.

example 1

A lithium ferrite was prepared by mixing together 18.08 g of lithium carbonate with 194.04 g of iron-containing oxide. The ingredients were mixed for two hours in isopropanol, the

23185

Solvent was filtered off, the material dried and two

Burned for hours in oxygen at 875 ° C. The ferrite material

was then ground in a ball mill for 24 hours, and it became

a paraffin binder of 3 wt.% Added to the ferrite.

The mixture was pressed and oxygenated at various

Heated temperatures for two hours and then cooled to room temperature.

The value H and the core temperature were measured and determined when used in a high-frequency ferroresonant transformer. The specimens or samples discussed above were compared to a commercial sample of lithium ferrite, Trans-Tech Inc. 71-3750, designated Control.

The results are summarized in Table I below.

sintering temperature Table I 2 1 1 ^H c Transformer core temperature sample 1300 1350 ⁰ C , 45, 75, 5 > 180 ⁰ C 148 ° C 143 ° C 20 ' Control 1A 1B

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

Example 2

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

summarized

 35

J ₁ 2 31850

Table II

IA weight O, .% H_ Transformer core sample 2A Bi ₂ 1, ° 3 C temperature example 2 B 3, 1.75 148 ° example 2C 1 1.6 - example 0 1.15 138 ° example 0 0.8 116 °

The above information shows 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 lithiurocarbonate, 64.679 g of iron oxide and 2.121 g of bismuth oxide were mixed in isopropanol for two hours, filtered to remove the solvent, dried and then fired in oxygen at 875 ° C for two hours. The resulting substance was ball milled for 24 hours, filtered in vacuo, and then 3 wt% of a paraffin binder was added. The mixture was then pressed into a desired shape in a steel mold and fired in oxygen to a temperature of 1430 ^° C. which was maintained for two hours, then cooled to 870 ^° C. and maintained at that temperature for 12 hours and then at room temperature cooled.

Samples pressed from this material had more favorable hysteresis rates

Lost properties and an H value of 0.6 Oersted.

Example 4

From 888.1 parts of iron oxide, 82.8 parts of lithium carbonate and 27.1 parts of bismuth oxide, a dry mixture was prepared, pelletized and then fired at 900 ^° C for one hour.

- "Wr

231850

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

The cores were fired at 1300 ^° C. for eight hours in oxygen, cooled to 900 ^° C. and held at this temperature for six hours, and then cooled down to room temperature. The lithium ferrite thus obtained has a coercive force of H _c equal to 1.0 Oersted at 25 ^° C.

Example 5

The surfaces of several lithium ferrite samples prepared according to Examples 1 and 2 were polished and the grain size was measured from Nomarski micrographs as shown in Figs. 5-8. The results are in the

Table III below. 30

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sample 1 control -H- Grain size, mm figure 1 example 1A Table III 20 - 5 example 2 B % Bismuth oxide 20 - 6 5 example 2C 0 30 - 7 example 0 50 - 8th 1 3 O   50 Example 6   60 -120 -> 200

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

In general, the value of H decreased when manganese alone or manganese 2Q and zinc were added, but the temperature stability of the saturation flux density also decreased. This is determined by measuring B at room temperature and 150 ^° C. and calculating the stability according to the following equation

B ^RT - B ¹⁵⁰ ° ^C

max. max

ΔΒ =

B ^RT max

in which RT is the room temperature. The flux density B was

Loaded A at a magnetic field strength of 25 oersteds.

A first series with zinc content is summarized in Table IV below. These samples had been fired at 1435 ° C.

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1 ^Li o, Tabel composition le IV H _c , 0e. composition H _c , 0e. ΔΒ TT ^Li o, 5 ^Mn O, O6 ^Fe 2.52 0.7 5 ^Mn 0.06 ^Fe 2.52 0.8 LJ 7.9% 5 ^Li o, 475 ^Mn 0.06 ^Zn 0.05 ^Fe 2.495 0.7 475 ^Mn 0.06 ^Zn 0.05 ^Fe 2.495 0.7 9% ^Li o, 45 ^Mn 0.06 ^Zn 0.10 ^Fe 2.470 0.55 45 ^Mn 0.06 ^Zn 0.10 ^Fe 2.470 0.7 8.1% 425 ^Mn 0.06 ^Zn 0.15 ^Fe 2.445 0.55 0.65 10.8% A 10 second row with the same compositions but one Burning temperature of 138O ⁰ C was ι produced, the in the aftermath Table I listed below. i St. Table V 15 ΔΒ "B" 4.7% ^L1 o, 7.4% 20 ^L1 o, 9.5% Li _n 10.4%

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

In a third series, the manganese content and the firing temperature were changed and the results are summarized in Table VI.

3 1 8 5 O A

1 composition Table VI H _c , 0e. ΔΒ ^Li 0.5 ^Mn 0.02 ^Fe 2.48 Burning temperature ⁰ C 0.85 3.8% 5 ^Li 0.5 ^Mn 0.06 ^Fe 2.48 1400 0.6 3.2% ^Li 0.5 ^Mn 0.1 ^Fe 2.4 1420 0.6 8.9% ^Li 0.5 ^Mn 0.15 ^Fe 2.46 1400 0.7 8.1% ^Li 0.5 ^Mn 0.06 ^Fe 2 _s 52 1420 0.65 5.3% O 1275 Example 7 , 25 ^Fe 2,395 ^ Two samples of lithium manganese _{zinc ferrite} (Li _n , _7ς Μ

were prepared and fired at 1300 ^° C., but the bismuth oxide content was changed. The results are shown in Table VII.

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

In Fig. 3, the saturation flux density curves Bv _t + are plotted against temperature for various magnetizable ferrite compositions denoted by their mole fraction formula. The flux density obtained at an excitation field strength of 50 oersteds has been referred to as saturation flux density B _sa - + t for the sake of simplicity. The slope of each curve is a measure of the temperature stability of the value B _s v4-4. the relevant ferrite compound. The slope of the curve determines the temperature coefficient a "of the material, where a _D = (ΔΒ ^ ··. ₊ / Β _W4 ..) (1 / ΔΤ) or a _o , ie the same

ο SatL satL β

the change of fraction of B _c . _{a> +} per ⁰ C is. 35

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In general, the flatter the slope of the curve in Figure 3, the more temperature stable the ferrite compound is and the more suitable it is for use as a magnetizable core material in a high frequency ferroresonant power supply, provided that the coercivity H of the material is not too high is great. In general, according to the invention, ferro-spinels containing lithium ions can be used as a magnetizable material for saturation cores in a suitably sized high-frequency ferroresonant power supply unit, a formulation giving curves corresponding to curves B, C and E. Each of the three lithium compounds B, C and E in Fig. 3 was prepared by 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 ferrofinsel compound of lithium ferrite prepared according to the above recipe. The lithium ferrite according to curve E has a relatively small temperature coefficient of ctg equal to -0.63 units per thousand, in part because of its relatively high Curie temperature of T _c around 67O ⁰ C. The coercive force H _c is 0.85 oersted and is sufficiently small to prevent excessive core temperature rise in the operation of a suitable high frequency ferroresonant power supply circuit.

If it becomes desirable to further limit the core temperature increase in the operation of a ferroresonant power supply circuit, then lithium ferrite compounds of a mixed or substituted ferrospinellic structure, as represented by curves B and C in FIG. 3, may be used. Curve B represents a mixed ferrospinell with a zinc cation used for the substitution, while the curve C represents a mixed ferrospinell with a manganese cation used for the substitution. When using a lithium zinc ferrite or lithium manganese ferrite of suitable composition and preparation, the coercive force H _c for a lithium zinc ferrite according to curve B can be reduced to ^;

2 318 5 0 A

a value of H _c of 0.72 oersted and for a lithium manganese ferrite according to curve C to H equals 0.78 oersted. The use of zinc and manganese as substitutes in a mixed ferro-spinel containing lithium as one of the cations lowers the coercive force H _{c of} the material as compared to the coercive-force recipes of a single ferro-spinel lithium ferrite. The reduced coercive force is obtained at the expense of a decreasing Curie temperature T of the mixed ferrospinell composition, lithium zinc ferrite having a Curie temperature of 570 ^° C. and lithium manganese of 500 ^° C. Because of the reduced Curie temperatures of Lithiumzink- and lithium manganese ferro spinels the temperature coefficient cu rises slightly to a value of -0.72 parts per thousand per ⁰ C for Lithiumzinkferrit and -0.96 parts per thousand per ⁰ C for Lithiummanganferrit. Although the temperature coefficient of this mixed ferro-spinel is higher than the temperature coefficient of a single-ferrite lithium ferrite, it is still suitable for use in a properly sized high frequency ferroresonant power supply.

Lithium ferro-spinel and suitable mixed ferrous spinels containing lithium cations as described above are well suited as magnetizable ferrite material for high frequency ferroresonic power supplies because the lithium-containing ferromagnets have a relatively small temperature coefficient of saturation flux density and relatively low coercive force H respectively. These two properties are desired for a magnetizable ferrite material for use in a ferroresonant saturable reactor means with, because a small temperature coefficient of a _SS is a sign that a relatively large amendments

tion of the core temperature brings only a small change in the output voltage, and that only a relatively small drop in the regulated output voltage occurs when the magnetizable core has warmed to its operating temperature. A relatively small coercive force H means that the increase in the operating temperature reached by the core material is not very large.

* 231850

-n-

] Other magnetizable ferrites used in high frequency power transformers are not suitable for use in high frequency ferroresonant power supply circuits where the output voltage is to be stable against temperature changes and where excessive core temperature rise is to 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 may be, for example, RCA 540 ferrite from RCA Corporation, Indianapolis, Indiana, and as a core for a flyback transformer in a RCA series color television receiver CTC-85 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 of a _SS 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 2O ⁰ C to 100 ⁰ C, the saturation flux density of the manganese zinc ferrite of the curve takes Aetwa 25% from a value of 4400 Gauss to 3300 Gauss. Such a percentage change in saturation flux density would result in a correspondingly large undesirable percentage change in the regulated output voltage of a high frequency ferroresonant transformer. Although the coercive force H _{c of} the manganeseinkferrites after curve A much smaller

When the coercivities of the lithium-containing ferrites are as shown by curves B, C, and E, with which the manganese saturated core has a significantly smaller core temperature rise, the extremely large temperature coefficient of saturation flux density of manganese zinc ferrite makes this material unsuitable for use in a high frequency ferroresonant power supply circuit, if not expensive Cooling measures are provided to significantly limit the core temperature increase. Even then, an ambient temperature change will be independent of the intended ones

thermal measures to a significant flux density change. 35

-2fr-

231850 A

Ferro spinels, such as nickel-Ferrospinell the curve D may also be unsuitable as a saturable core material, although nickel ferrite having a relatively high Curie temperature T _c of 58o ⁰ C and a relatively small temperature coefficient ou -0.9 parts per thousand per ^0C. However, the coercive force H _c of nickel ferrite is around 5.0 oersted or 7 times the coercive force of the lithium ferrite and substituted lithium ferrites according to curves B, C and E. The relatively high coercive force of nickel ferrite leads to an extremely high core temperature increase when this ferrite Saturation core material used in a high-frequency ferroresonant power supply circuit. Although the relatively small temperature coefficient of nickel ferrite results in a relatively small temperature-induced drop in the regulated output voltage, the excessively high temperature rise of the saturable core above ambient temperature makes the core material relatively unsuitable for such use unless special cooling constructions or particularly temperature resistant winding wire insulations and core materials are used. The relatively high coercive force of nickel ferrite, which is indicative of relatively large hysteresis losses occurring in the saturable core during each cycle of AC output voltage, also results in poor efficiency in operation as a power current source.

Figure 2 illustrates a high frequency ferroresonant power current 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 low-frequency AC line voltage via input terminals 32 and 33 of a full-wave bridge rectifier ^ O 28 is connected, which provides an unregulated DC voltage V at an output terminal 30. Between the output terminal 30 and a current return terminal 31 of the bridge rectifier 28, a filter capacitor 29 is connected. The input voltage V _in our input choke 34 is fed to supply a horizontal deflection generator.

supplied in a horizontal deflection winding 36 a

Deflection generated.

_ »2 318 5 0

The Horizontalablenkgenerator 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, with the horizontal deflection frequency 1 / T. , is periodic, formed at the collector of the horizontal output transistor 40 at terminal 43 and is coupled via a DC block capacitor 44 and an input inductor 45 for exciting a high frequency ferroresonance means 46 with saturable inductor.

The device 46 includes a resonant capacitor 47 connected across a winding 48 which is wound around a magnetizable saturable core consisting of the above-mentioned lithium ferrite or substituted lithium ferrite. The unsaturated inductance of the choke winding 48 is for example 2 mH, while the saturated inductance is, for example, 100 μΗ. The regulated output voltage V generated by the saturable reactor ferroresonance means 46. is applied to the primary winding of a high-voltage transform high-voltage autotransformer 50 whose secondary winding is connected to a high-voltage circuit 51 which may, for example, contain a high-voltage multiplier circuit to produce an anode DC high voltage for supply to an anode terminal of a television picture tube, not shown.

In the high-frequency ferroresonant power supply circuit 60 shown in Fig. 2 for generating the anode high voltage of a television receiver, the flyback pulse voltage 42 which the deflection generator 35 generates comprises the AC input voltage to the saturable reactor ferroresonance device 46.

In a preferred arrangement, the source of unregulated high frequency AC input voltage includes a high frequency inverter which generates a high frequency square wave voltage from the unregulated DC input voltage. The ferroresonant arrangement with saturable reactor contains a ferroresonant transformer whose

£ 2318504

Primary winding is supplied from the inverter derived rectangular input voltage, and a resonant capacitor, which is connected via a magnetically loosely coupled to the primary winding secondary winding of the ferroresonant transformer. The regulated alternating voltage occurring at the secondary winding is then used to derive a regulated supply voltage B + for the supply of a Horizontalablenkgenerators. A high voltage winding is magnetically coupled tightly to the secondary winding of the ferro-resonance transformer and creates a regulated AC voltage across it, from which a regulated anode high voltage is generated. Such a high frequency ferroresonant power supply circuit for television receivers is disclosed in U.S. Patent Application No. 144,150 by inventor F.S. Wendt, filed under the designation "HIGH FREQUENCY FERRORESONANT POWER SUPPLY FOR A DEFLECTION AND HIGH VOLTAGE CIRCUIT" on April 28, 1980, and corresponding to the British Patent Application 2,041,668A, published on September 10, 1980, for further description in U.S. Patent No. 4,262,245 also to FS Wendt, issued on April 14, 1981, entitled "HIGH FREQUENCY FERRORESONANT TRANSFORMER".

According to the teachings of the invention described above with respect to the use of lithium ferrite or substituted lithium ferrite in a high frequency ferroresonant power supply scheme, the magnetizable core of the television receiver ferroresonant transformer as described in the aforementioned U.S. application and Wendt advantageously, lithium ferrite or substituted lithium ferrite as transformer

Have saturable core material

 30

According to the disclosure of the co-pending U.S. patent application by W.E. Babcock et al, Ser. No. 250,130 of 2 April 1981 entitled "TELEVISION RECEIVER FERRORESONANT POWER SUPPLY USING A TWO-MATERIAL MAGNETIZABLE CORE ARRANGEMENT" is still in demand

only the secondary winding saturable core portion of the magnetizable core of the Ferroresonant transformer made of lithium ferrite or

-e 2 318 5 0 4

] substituted lithium ferrite to give the advantageous results explained herein of using lithium-containing ferrospinell as the saturable core material. The primary winding core portion of the ferroresonant transformer described in the aforementioned Babcock application can be chosen as described therein to have magnetic properties which are advantageous when the magnetizable core is operated in the substantially linear region of its BH characteristic as is the case with the primary core portion of the ferroresonant transformer described in the Babcock application.

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

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 in terms of using lithium ferrite or substituted lithium ferrite at a high frequency -Ferroresonanz power supply circuit. As a contrast, the results when using a Manganzinkferrits (Example 3) or a nickel ferrite (Example 4) as

^OJ secondary saturating core section material indicated.

231850 4 The values given in Table I in the column "ΔΤ" represent the temperature rise above ambient temperature of 25 ⁰ C is occurring in the saturable core portion of the ferroresonant transformer in the secondary winding by switching on the television receiver, when the core operating temperature has reached. The values in the column "AU" represent the drop of the anode high voltage below the nominal value of 32 kV in the ferroresonance transformer after the television receiver is switched on for the first time. The nominal voltage of 32 kV was obtained using the materials of Examples 1 to 4, although they differ in their saturation flux density B... By keeping the total saturation flux constant by adjusting the core cross-sectional area of the saturation core. The values for the flux density obtained at a magnetization field strength of 25 Oersteds were commonly referred to as B- ₁ . The values for H and B - _tt given in Table II result at 15.75 kHz and at a room temperature of 25 ° C.

From the tables, it can be seen that the magnitudes of the temperature coefficient otn 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: Thus, 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 core temperature increase ΔΤ arises in part due to the relatively low coercive force H of manganese zinc ferrite. Nevertheless, a Manganzinkferrit may be an unusable for use saturable core material because of excessive high anode voltage drop of 3.5 kV, partly due to the relatively _ß ^ου high temperature coefficient a of the material. The manganeseinkferrit leads to a relatively large change of the anode high voltage of 110 parts per thousand, and thus may be useless as a saturable core section material for the secondary winding.

The nickel ferrite given in Example 4 in the Tables has a relatively good temperature coefficient of saturation flux density

- »- 2 3 1 8 5 O 4

-4

of -9.0x10 / ⁰ C. Nevertheless, the nickel ferrite may also be a unusable saturable core material because of its relatively large coercive force of 5.0 oersted. The large coercive force gives rise to an extraordinarily high temperature rise ΔΤ and a very large anode high voltage drop of 3.4 kV.

For example, a reasonably acceptable change in the 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 a power supply assembly. An acceptable value of the size of a _{D of} the material above the normal

The operating range of the core temperature may be equal to or less than 1.5 parts per thousand per ⁰ C. A useful coercive value may be at or below 1.5 oersted. Acceptable values of otn, H, and AU / U depend on parameters such as the amount of output voltage regulation desired, the temperature range including ambient temperature changes within which the power supply assembly is to operate satisfactorily, the size of the display and power consumption, the maximum allowable temperature of the components, and the amount of oversampling allowed during TV operation (beyond the edges of the picture).

Thus, according to the invention, the use of lithium ferrite and substituted lithium ferrite having the characteristics of a small temperature coefficient of saturation flux density and a small coercive force is extremely favorable for the construction of a ferroresonant power supply device which provides an output voltage which is relatively insensitive to temperature change, and which leads to a very limited increase in temperature

^{ου of} the saturation ^{core exceeds} the ambient temperature.

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

are defined as BJB _m ^ ", where B," is the remanent induction of the

r max r

Material and ß _mu at a magnetization field strength of max

-S- 2 318 5 0

50 Oersted obtained flux density is. A squareness ratio equal to or greater than 0.6 may be desirable for improving the output voltage control.

Table I

Beisp.Nr. Saturated core section (secondary winding) -Äll (kV) -UU / U) (x100) ΔΤ (° II 1 4.6 92 C) , 94 1 Li ferrite 1.5 -α _Β (χ10 7.2 89 70 2 LiMnZnFerrit 2.3 y, 1.0 51 24 3 MnZnFerrit 3.5 10 _{4 /} 0.5 > 165 , 0 4 Ni ferrite > 3.4 32 4 table 9 7 ⁰ C) ^B sat (Gauss) Beisp.Nr. Saturated core section (secondary winding) ^T c ( ⁰ C) 0 2900 1 Li ferrite 670 0 3400 2 LiMnZnFerrit 500 4300 3 MnZnFerrit 200 3200 4 Ni ferrite 585 ^H c (Oersted) O O O , 5

Claims (10)

* 2 318 5 0 4 RCA 75551 / Sch / Ro. High frequency ferroresonant power supply circuit. 20 claims 1.)
A saturated saturable core power supply circuit having an input voltage source, excitation current generating means coupled thereto, a magnetizable core containing a saturable core portion, a winding disposed on the core, a polarity alternating to produce an output voltage due to the energizing current in the magnetizable core the winding chained magnetic flux generating means, one of the winding associated capacity for generating a magnetizing force field of alternating polarity in the saturable core portion in cooperation with the exciting current generating means, wherein the magnetizing force field causes a magnetic flux, the saturable The core portion is substantially magnetically saturated during each cycle of the alternating polarity output voltage to produce a resonance current in the alternating polarity output voltage regulating capacitor, characterized in that the saturable core is formed of a lithium ferrite or a substituted lithium ferrite. 2.) Power supply circuit according to item 1, characterized in that the substituted lithium ferrite lithium zinc ferrite comprises. 3.) power supply circuit according to item 1, characterized gekennzei chnet that the substituted lithium ferrite lithium manganese ferrite comprises.
15 4.) Power supply circuit according to item 1, characterized in that the substituted lithium ferrite lithium manganese zinc ferrite comprises. 5.) circuit according to one of the preceding points. ¹ , characterized gekennzei CHnet that the ferrite has a low temperature coefficient of saturation flux density and a low coercive force. 6.) Power supply circuit according to item 1 to 5, characterized in that the coercive force of the saturable core portion is equal to or less than 1.5 Oersted. 7.) Power supply circuit according to one of the preceding points, ^ow characterized in that the magnitude of the fractional change in the saturation flux density per ⁰ C of the material of the saturable core portion over the normal operating temperature range of the power supply circuit is equal to or smaller than 1.5 parts per thousand per ⁰ C.
35 -t 2 3 1 8 5 O 8) power supply circuit according to any one of the above items :, characterized in that the material of the saturable core section has a squareness ratio of equal to or greater than 0.6. 9.) A saturated saturable core power supply circuit according to any one of the preceding claims for providing a stable anode high voltage for a television display system, characterized in that the regulated power supply circuit comprises a high voltage generator having a polarity responsive to the regulated voltage of alternating polarity to produce a regulated high voltage of alternating polarity and a high voltage alternating polarity includes an anode DC voltage generating rectifier. 10.) Regulated saturable core power supply circuit according to item 5, characterized in that the television display system includes a deflection winding and a deflection generator, which is fed by a supply voltage and is coupled to the deflection winding for generating a deflection current therein, and in that the regulated power supply circuit from the regulated high voltage of alternating polarity containing the anode high voltage generating means. 11.) power supply circuit according to item 9, characterized in that the size of the fractional change of the anode high voltage between the end points of the normal operating temperature range of the power supply circuit is equal to or is less than 75 parts per thousand.
30 For this 5 sheets of drawings