DD201632A5 - POWER SUPPLY CIRCUIT WITH FERROR RESONANCE LOAD FOR A TELEVISION RECEIVER - Google Patents

Abstract

For controlling a supply voltage, such as for a load circuit of a Fernsehgehpfaengers, and / or the high voltage for a high voltage circuit, the primary winding (22a) of a transformer (22) to a source (21) of an input AC voltage is connected to generate a voltage of alternating polarity at a second winding (22d) of the transformer. A satellable coil includes a magnetizable core (137) around which a coil winding (37) is wound. The coil winding (37) and the secondary winding (22d) of the transformer are conductively coupled together to produce a voltage of alternating polarity on the coil winding (37). The secondary winding (22d) of the transformer is magnetically isolated from the satellable coil, so that the flowing in the coil core (137) Megnetfluss with the secondary winding (22d) of the transformer is not concatenated. Connected to the winding (37) of the salable core is a capacitor (38) for generating a circulating current, which contributes to magnetically saturating a part of the coil core (137) associated with the coil winding (37). The voltage across the conductively coupled secondary winding (22d) of the transformer is therefore regulated. The high voltage load circuit (24) is coupled to a third winding (22e) of the transformer (22) and is powered by the regulated supply voltage of alternating polarity appearing at the third winding (22e). Fig. 1

Description

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23 63 7 9

Power supply circuit with ferroresonant lasers for a television receiver

Field of application of the invention:.

The invention relates to ferroresonant power supply circuits for television receivers. Characteristic of the known technical solutions; : Ferroresonance transformers are known which provide controlled anode high voltages and regulated sampling voltages B + for television receivers. A ferroresonant power supply circuit for television receivers is described in US patent application no. 007815 of 30 January 19 79 (inventor: FS Wendt, title: "High frequency ferroresonant power supply for a deflection and high voltage circuit"), which is the 10 British Patent Application No. 2041668A. When operating at a relatively high input frequency, such as the horizontal deflection frequency of 15.75 KHz, a ferroresonant transformer is a relatively compact and lightweight structure which inherently has output voltage control characteristics without requiring relatively complicated and expensive electronic control circuitry become.

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To obtain a high efficiency at 16 KHz, the magnetizable core of a ferroresonant transformer can be made of a ferrite, such as a commercial manganese-zinc or nickel-zinc ferrite. Such ferrite materials have a high resistance to current flow, so that only relatively small eddy current losses occur, which would otherwise be very high at the relatively high operating frequency of 16 KHz. The hysteresis losses are also relatively low. However, even using a ferrite core, ohmic losses (I "R) in one or more windings, as well as eddy current losses and hysteresis losses, would cause a significant increase in core temperature.

The saturation flux density B of a magnetizable. material

sac.

decreases with increasing core temperature. For manganese-zinc ferrites, the 'saturation flux density of about 4.5 kG (kilogauss) at 20 ⁰ C can drop to 2.5 kG at 150 ⁰ C. Since the output voltage of a ferroresonant transformer from the value of the saturation gas flow density B, the core material within the

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Output windings depends, an increase in the core operating temperature leads to an undesirable decrease in the output voltage. For example, if the output voltage is an anode high voltage, then immediately after the television receiver is turned on, when the core of the ferro-resonance transformer is still at ambient temperature, the anode high voltage is higher than the anode high voltage which subsequently occurs in the acid temperature mode after the core is at its normal operating temperature has heated above the ambient temperature.

Heat removal from the core to reduce the temperature rise is relatively difficult in a high frequency ferroresonant transformer of a television receiver. The output windings of the ferroresonant transformer including the high voltage winding, which has a relatively large number of turns, are around the saturated one

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Core part of the transformer wound and magnetically closely coupled. The multiple output windings and the large number of turns of the high voltage winding limit access to the core for heat removal measures.

^Dar ^ ^e 9 ^and 9 of ^the essence of the invention:

According to a preferred embodiment of the invention, a self-regulating power source includes a transformer having first and second windings. The first winding has terminals for connection to an input AC voltage source; the second winding has connections for connection to a load.

A saturable coil includes a magnetizable core and at least one coil winding wound around the core.

This one coil winding is conductive with the second.

Connected winding of the transformer, so that when energized on the coil winding, a voltage of alternating polarity occurs. The second transformer winding is magnetically isolated from xäer saturable coil, so that the magnetic flux of the coil core is not concatenated with the second winding.

By magnetic saturation of the coil core, the voltages on the winding of the saturable coil and the secondary winding of the transformer, which are conductively connected together, regulated. A third winding of the transformer, such as the high voltage winding, generates a regulated output voltage of alternating polarity depending on the regulated voltage appearing on the secondary winding of the transformer. With this third winding of the transformer is a load circuit which is coupled about the anode circuit, which is fed by the regulated output voltage.

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An advantage of the arrangement described above is that the saturable core element which provides the voltage regulation is not part of the transformer core around which the output secondary windings are wound, which supply the regulated supply voltages to the television receiver. Thus, the high voltage winding is wrapped around the transformer core rather than around the core of the saturable coil, so that the saturable core portion is more readily accessible for heat dissipation.

Further, the transformer core around which the secondary output windings are wound may be operated substantially in the non-saturated region of the BH loop of the transformer core material. The output voltages at the transformer secondary windings are still controlled because the windings are magnetically tightly coupled to the "regulated" output winding, which is conductively connected to the coil winding.

Embodiments: In the accompanying drawings show

Fig. 1 shows a ferroresonant power supply circuit for television purposes according to the invention and

Fig, 2 and 3 waveforms as they occur during operation of the circuit of FIG.

Referring to Figure 1, a ferroresonant power supply circuit 10 for a television includes a transformer 22 and a ferroresonance load circuit 20 having a saturable coil. A primary winding 22a of the transformer is connected to a source 11 of unregulated AC input voltage V.sub.V having an inverter 21 and a DC input voltage terminal 23 coupled to a center tap of the primary winding 22a.

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The terminal 23 is an unregulated DC voltage V

fed. The inverter 21 is operated at a high frequency, for example, with the horizontal deflection frequency of 15.75 KHz. The inverter 21 generates the input AC voltage V as a horizontal frequency square wave voltage across the primary winding 22a.

When the voltage V.sub.1 is supplied to the primary winding 22a, horizontal frequency output AC voltages are generated

10. at the secondary output windings 22b to 22d and at a high voltage secondary winding 22e. The ends 49 and 50 of the output winding 22b are connected to diodes 29 and 30, respectively, which function as a full wave rectifier. The ends 48 and 51 of the output winding 22c are connected to diodes 27 and 23, respectively, which function as full-wave rectifiers. Also, the ends 47 and 52 of the output winding 22d are connected to diodes 25 and 26 operating as full wave rectifiers. A common center tap 53 is coupled to ground.

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The alternating polarity output voltage produced at winding 22b is full wave rectified by diodes 29 and 30 and filtered by a capacitor 34 to a DC operating voltage at a terminal 31 of, for example, +25 volts to power circuits of the television receiver such as the vertical deflection circuit and the audio frequency circuit. The alternating polarity output voltage produced at winding 22d is full wave rectified by diodes 25 and 26 and filtered by a capacitor 36 to a DC supply voltage at a terminal 33 of, for example, +210 to power circuits such as the kinescope driver.

-i- 23 6 37 9

The alternating polarity output voltage produced across the winding 22c is full wave rectified by the diodes 27 and 28 and filtered by a capacitor 35 for generating a deflection supply voltage B + at the terminal 32 for a horizontal deflection winding 41. To generate the horizontal deflection in the horizontal deflection winding 41, a Horizontalablenkgenerator 40 is connected via a Kingangsdrossel 39 to the terminal 32. The horizontal deflection generator 40 is fed by the deflection supply voltage B + and includes a horizontal oscillator and driver 43, a horizontal output transistor 44, a damping diode 45, a horizontal retrace capacitor 46, and an S-shaping or trace capacitor 42 connected in series with the horizontal deflection winding 41 above the horizontal output transistor 44 ,

The output voltage of alternating polarity occurring at the high voltage secondary winding 22e is applied to a high voltage circuit 2 4 for generating a high voltage. Anode DC voltage or acceleration voltage supplied to the terminal U for the picture tube, not shown, of the receiver. The high-voltage circuit 24 may be a conventional Cockroft-Walton voltage multiplier circuit or a multi-diode half-wave rectifier circuit, which together with a plurality of winding sections of the high-voltage secondary winding 22e not individually illustrated here, are molded into a single unit.

The secondary output windings 22b to 22d and the high voltage secondary winding 22e are magnetically coupled with each other closely. To achieve this tight coupling, the windings can be concentric about a common part of the magnetizable core 122 of the

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Transformers 22 wound around. Because of the close magnetic coupling of the windings, the alternating polarity output voltages appearing at the secondary output windings all have the same waveform, with little variation due to the relatively small stray inductances between the output windings.

To control the voltages at the secondary output windings against amplitude variations of the input voltage V. and against load variations of the load circuits connected to the terminals 31 to 33 and against beam current load changes at the anode terminal U, the ferroresonant load circuit 20 is coupled to one of the closely coupled coils. Secondary output windings of the transformer 22 connected. In · Fig. 1, the load circuit 20 is connected to the saturable coil, for example via the secondary output winding 22d.

The ferroresonant load circuit 20 includes a saturable coil or winding 37 wound around at least a portion of a saturable magnetizable core 137 and including a resonant capacitor 38 connected across the coil winding 37. The saturable coil core 13'7 may be a conventional toroidal core or a rectangular two-centered core.

In a ferroresonant circuit, such as the ferroresonant circuit 20 with saturable coil of FIG. 1, the output voltage V at the saturable coil 37 is controlled. By connecting the ferroresonant circuit 20 to the secondary output winding 22d of the transformer, the circuit 20 operates as a regulating load circuit coupled to the winding 22d to control the voltage at the

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To keep winding 22d on the regulated V. When the voltage on the secondary winding 22d is controlled by the ferroresonant load circuit 20, then the output voltages on all other secondary windings which are closely coupled to the winding 22d are also regulated. The output voltages at the windings 2 2e and 22c and at the high voltage output winding 22e are controlled by the regulation of the output voltage V. the ferroresonant circuit 20 thus regulated.

The transformer 22 exhibits significant stray inductance between the primary winding 22a and each of the closely coupled "regulated" secondary windings 22b-22e. The loose coupling of the primary winding to the secondary output windings allows the output voltage to be kept substantially constant by the ferroresonant circuit 20, even if the voltage supplied to the primary winding 22a should change with changes in the input AC voltage V. The leakage inductance between the primary winding 22a and each of the secondary windings 22b to 22e may be constructed into the transformer 22 in which the magnetizable core 122 of the transformer is formed as a closed loop of rectangular shape. The primary winding 22 may be wrapped around one leg of the core 122, and the secondary windings 22b through 22e may be concentrically wound around an opposite leg.

Considering the equivalent electrical circuit diagram of the transformer 22, the load circuits for the primary winding connected to the terminals 31 to 33 and the anode terminal appear as load impedances in parallel with the transformed ferroresonant load circuit 20. Because of the loose magnetic coupling between primary winding 22a and 5, the secondary windings 22b to 2 2e "see" the transformed

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Ferroresonanzlastschaltung and the other parallel loads an equivalent, impedance in series with the source 11 of the input AC voltage V. - This equivalent impedance, resulting from the loose magnetic coupling of the transformer, compensates for changes in the input voltage, while variations in the Ferroresonanzlastschaltung and the voltage amplitude significantly reduced at the output winding compared to voltage amplitude fluctuations of the primary winding,

FIG. 2 a shows a rectangular, alternating polarity input voltage V, which is applied from the source 11 to the primary winding 22 a of the transformer 22. FIG. 2 b illustrates the regulated output voltage V 1 appearing on the ferroresonant load circuit 20 with the saturated coil and the secondary output winding 22 b of the transformer 22. The regulated voltage. V is a voltage of alternating polarity and frequency as the input voltage V with generally flattened portions 14 of alternating polarity interconnected by generally sinusoidal portions 15.

In the intervals of the flattened parts of the regulated output voltage V, approximately between times t -t ,. in FIG. 2b, the magnetizable core part of the saturable coil belonging to the coil 37 is operated in the magnetically unsaturated region of the BH loop of the core material. The winding 37 of the saturable coil has relatively high inductance during the unsaturated intervals of the flattened parts. In the winding 37 flows between the times t -t. a relatively small current i drawn in solid lines in FIG. 2b.

Since the winding 37 of the saturable coil has a relatively high impedance during the flattened portions or magnetically unsaturated intervals of the output voltage V,

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The resonant capacitor 38 discharges only slightly into the winding of the saturable coil, and the capacitor retains a relatively constant output voltage V supplied to the coil terminals as indicated by the relatively small capacitor current i between times t_-t in FIG. 2b is.

If the output voltage V from the capacitor 38 is applied across the coil winding 37, it leads to a flux buildup in the core 137 until the core near the time t. is substantially magnetically saturated. If the core 137 magnetically saturates at time t ₁ , then the inductance of the coil winding 37 decreases significantly. The inductance of the coil 37 may, for example, be 20 to 60 times smaller than in the unsaturated case.

After the core 137 has been magnetically saturated, the capacitor 38 and the coil winding 37 undergo one half cycle of resonant current oscillation, as illustrated in FIG. 2b by the current pulse 12 of the coil current i and by the current pulse of the coil

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Capacitance current i between the times .t ₁ -t, is shown. The resonance current or oscillation current in the winding 3 of the saturable coil and in the capacitor 38 reaches a maximum magnitude at time t i. The output voltage V also reverses its polarity at this time.

Near the time t. has the resonant current pulse sufficiently reduced, so that the core 137 from the saturation herausgerät and the winding 37 of the coil can again have a high impedance. The voltage across the capacitor 38, that is, the regulated output voltage V, stops its rapid changes and transitions to the values of the flattened portion of the opposite polarity. During the interval t ₅ T. opposite polarity for the flattened portion of the core 137 is again in the magnetic un-

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saturated area of the BH loop operated. The flux in the core 137 reverses its direction during this interval and builds up substantially to the saturation flux value near time t ₅ , where the core again magnetically saturates. The current in the coil winding 37

, then goes through between the times t -t, - the other half-cycle of the oscillation.

The saturable coil ferroresonance load circuit 20 operates as a magnetic voltage regulator for maintaining an output voltage V of relatively constant amplitude with varying input voltage and varying load across the various secondary output windings, such as varying beam current. load at the anode connection. If the capacitor 38 has a sufficiently large value, then the AC component of the flattened parts of the output voltage

V relatively small. The area under the flattened out ^

Part of the voltage curve V, is also the temporal

^J out "integral of the output voltage V over the interval of the flattened part or, equivalently, represents the maximum change in the flux linkage of the coil winding 37.

The maximum flux linkage of the coil 37 is proportional

to the saturation flux density B. of the magnetizable Masai ^

coil core 137. Since the maximum flux linkage of the coil winding 37 is a substantially constant amount that is independent of input voltage variations, the area below the flattened portion of the output voltage is also V. independent of

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Input voltage changes constant. Thus, the amplitude of the output voltage V is regulated and has a virtually non-changing value, as long as the duration of the flattened portion of the output voltage V during

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which of the spool core 137 remains unsaturated, is relatively strong.

The period of the output voltage V changing in polarity is equal to that of the input voltage

V. and has a fixed duration. Also is within this in

Period the duration of the intervals t -t. and t ^ -t .. magnetic saturation determined by the value of the inductance of the winding 37 near or at saturation and by the value of the capacitor 38. The duration of the sections of the output voltage V without saturation is therefore also fixed, so that the output voltage can have relatively constant amplitude.

Since the secondary output winding 22d of the transformer is connected to the saturable coil via the ferroresonant load circuit 20, the voltage on the output winding 22 must take the value of the regulated output voltage V even if the amplitude of the output voltage V changes. All other secondary output windings 22b, 22c and high voltage winding 22e must also supply regulated voltages. Changes in the input voltage and the load of the output windings lead to phase shifts of the output AC voltage V with respect to the phase position of the input AC voltage V. However, the amplitude of the output voltage V remains relatively unchanged.

2a and 2b show that in an operating state with the target input voltage and an average load of the output windings 22b to 22e, so at a beam current load of about 1/2 milliamps, the output voltage V in their phase by an amount At with respect to the phase of Input voltage is delayed. The phase delay / \ t is due to the power losses in the load circuits associated with the secondary output windings

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22b to 22e are coupled. The phase delay between voltages V. and V permits power transfer from the source to the load at the secondary output winding during each cycle of input or output voltage oscillation.

FIGS. 2a and 3a show that when the input voltage V changes from the value of a high mains input voltage to a low mains voltage, the phase delay of the output voltage V. increases from a deceleration value ^ t- to A ^ ₂ . The phase delay increases with low input voltage because then a larger phase delay is needed to transfer the same average power to the secondary winding loads. Although the phase delay of the output voltage V, at a lower input voltage, increases, yet the amplitude of the output voltage V changes. and the average half-cycle voltage not appreciably, so as to obtain the desired control against input voltage changes.

Figures 3c and 3d show that as the beam current load on the anode terminal U increases from 0 to 1.7 milliamps, the phase delay of the output voltage V-from a delay value Et to At, for example

a * - · D

increases to the same nominal input voltage value. The phase delay increases because more phase delay 0 is required to transfer more average power at a higher secondary winding load. Although the phase delay of the output voltage V has also increased, the amplitude of the output voltage V _t in FIG. 3d and the mean half-cycle voltage has changed appreciably, so that the desired control against load fluctuations is achieved

receives. ,

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A feature of the invention is that it provides output voltages to the secondary windings of the transformer without the core part of the transformer associated with the secondary winding having to be saturated. Therefore, for the power transformer coupled to the AC power source, such as the transformer 22 in Fig. 1, there are not such design limitations as apply to a ferroresonant transformer. In contrast to using a ferroresonant transformer, the portion of the magnetizable core 122 of the transformer that lies within the secondary output windings 22b to 22d of the transformer may be in the linear region of the BH loop of the core material. The core therefore remains magnetically unsaturated during the entire AC output cycle. '

There are a number of advantages with the use of the arrangement according to the invention according to FIG. 1, in which a power transformer supplies regulated output voltages to secondary output windings, but nevertheless the core of the transformer is operated in the linear range of its BH loop and the regulation is effected by a separate Ferroresonant circuit saturable coil be-5 acts, which is connected as a regulating load via one of the output windings of the power transformer. For example, in a ferroresonant transformer arrangement different from the arrangement of FIG. 1, a relatively high circulating current or resonance current flows in one of the output windings of the ferroresonant transformer. To reduce the ohmic losses in this winding, a relatively thick conductor wire (ie one with a large cross section) is required. However, such a thick coil wire hinders a tight coupling, so that the leakage inductance is higher than desired.

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In contrast, no high resonant current flows in any of the output secondary windings of the power transformer 22 of Figure 1. For example, as shown in Figure 2c, the current i flowing out of the ferroresonant load circuit output winding 22d has a relatively small peak amplitude, for illustrative purposes ten times smaller or smaller than the peak value of the resonance current pulse 12 flowing in the coil winding 3 7. Only enough current i must flow out of the transformer 22d on average to compensate for the losses that occur during each cycle of the regulated output voltage V of alternating polarity. These are hysteresis losses, "eddy current heating of the magnetizable core 137 of the coil, and resistive losses in the coil winding 37, and also energy losses that occur in the capacitor 38 during each cycle of the output voltage V ^ due to the load current flowing out of the terminal 33 and because of the current flowing to the load circuits, which are connected to the terminals 31 and 32 and the pin-up terminal and appear transformed in the output winding 22d.

Another advantage of the arrangement according to FIG. 1 lies in the greater flexibility in the design, which is responsible for the choice of the parameters of the ferroresonance load circuit 20. of the power supply system 10 results without the power transformer 22 would have to be redesigned. Because the secondary output winding 22d of the transformer 22 is magnetically isolated from the winding 37 and the magnetizable core 137 of the saturable coil, that is, because the magnetic flux flowing in the spool core 137 is not interlinked with the transformer output winding 22d, design changes of the magnetizable core 137 and changes in the value of the magnetizable core 137 are required from the condenser

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provided resonant current no significant design changes of the transformer 22, provided that the changes in the Ferroresonanzlastschaltung 2 0, the regulation of the output voltage V does not deteriorate appreciably.

The amplitude of the output voltage V ^ generated by the ferroresonant load circuit 20 depends on the characteristics of the magnetic material of the spool core 137 with respect to the saturation flux density B. To reduce vortex

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Current loss in the core 137 when operating at a relatively high frequency of 16 KHz or higher, a core material having a relatively high resistance to eddy current flow is selected. Commercially available core materials suitable for the saturable core 137 are, for example, manganese-zinc ferrites, nickel-zinc ferrites or lithium ferrites. Manufacturing tolerances in the production of the ferrite core material can lead to relatively large tolerances of the value B of the material

sa -

0 lead.

To account for the tolerance of B between individual cores, the number of conductor turns of the coil winding 3 7 wound around the core 137 may be varied for each core so that the output voltage V does not vary from unit to unit. Because the regulated output voltages for most television receiver circuits are taken from the output windings of a separate transformer,

3.0 demand the tolerances of B, the core 137 and the

sat

Changes in the number of turns of the winding 37 to compensate for these tolerances do not cause corresponding changes in the numbers of turns or other parameters of the transformer 22

 35

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} The value B of the maanetisable material of the coil

kerns 137 'depends on the operating temperature of the core, namely, B decreases with increasing operating temperature.

sat

After the television receiver is initially switched on, the core 137 heats up due to the hysteresis and eddy current losses that occur during

heating by the ohmic losses (I R) of the conductor wire of the winding 37, which is wound around the bobbin 137. Before the power supply circuit TO is turned on, the saturable coil core 137 has the ambient temperature. After being turned on, the core 137 heats up to any continuous temperature above the ambient temperature. During the time interval where the core warms up, the value B of the core decreases.

sat

Therefore, the output voltage V ^ of the regulating ferroresonant load circuit 20 decreases from its on. when the television is turned on to a lower steady state value when the final operating temperature of the core 137 is reached.

:

In order to keep the temperature change between switch-on temperature and operating temperature small, one can in the usual way for a heat dissipation from the winding and the core. 137 of the saturable coil to a heat sink or metal chassis of the television. The heat dissipation from the saturable coil core 137 is achieved in the arrangement according to the invention, where only one or a small number of windings are wound around the coil core, with relatively less effort than from a saturable core part of a ferroresonant transformer, which provides many output voltages to many output windings wrapped around the saturable core portion of the resonant transformer. Furthermore, it is also more difficult to dissipate heat from a ferroresonant transformer having a high voltage winding because of the large number

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of turns wound around the saturable core portion of the transformer makes this core portion inaccessible.

In the arrangement acc. 1, no heat dissipation from the core 122 of the power transformer 22 is necessary because the core material of this transformer is operated in the linear region of its BH characteristic and therefore relatively low core losses and lower operating temperature rise occur. Furthermore, resonant currents do not flow in any of the output windings of the transformer 22. The ohmic (I R) losses in the output windings of the transformer and the heating of the transformer core 122 are therefore relatively insignificant. In one embodiment of the power transformer, the primary winding had - from the center tap to the end - an inductance L = 2.03 milliehenries, the secondary inductance of the secondary winding 22d was L "= 10.3 millieriesries and the mutual inductance between these two windings was M = 3, 35 millieries.

The core material may be a manganese-zinc ferrite, and the transformer core may have any suitable geometric shape which results in these inductance values and in which the core remains magnetically unsaturated.

In one embodiment of the ferroresonant load circuit 20 ^may:., The capacitor 38 has a value of 0.033 microfarads, the saturation flux density of the core material, the cross-sectional area and the number of turns may be selected so then, that the output voltage V j_ a waveform similar to Figure 2b during the " unsaturated "intervals t -t" and .t -that, wherein the value of the unsaturated inductance of the coil 37 is relatively large, namely of the order of 1 Henry. The number of turns, the core shape, like the

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Mean magnetic path length and the cross-sectional area, and the BH characteristic of the core material are so dimensioned that at the occurrence of a substantial magnetic saturation near the time t .. and t_ in Fig. 2a, the inductance of the coil 37 at peak currents drops significantly to about 500 Mikrohenry or even less. A suitable core material may be a ferrite, such as a lithium bismuth ferrite, which has the added advantage of a relatively small change in B with core operating temperature changes compared to many other ferrites. The core can be designed as a toroid or as a double E-core.

Claims (5)

ZO Ferroresonant power supply circuit for a television receiver He indian sans ρ ruch Claims 1. A self-regulating voltage supply circuit comprising a transformer having a first and a second second winding, the first winding having terminals for connection to an input voltage source for generating a voltage of alternating polarity at the second and third windings, characterized ge a saturable coil having a magnetizable core (137) and at least one coil winding (37) wound around the core, the coil winding (37) and the second winding (22d) of the transformer being conductively connected together to produce a voltage of alternating polarity the coil winding (37), that the second winding (22d) of the 23637 9 I Transformer magnetically isolated from the saturable coil is such that the magnetic flux flowing in the coil core (137) is not interlinked with the second winding (22d) of the transformer that the third winding (22e) of the transformer resulting from the second winding (22d) Voltage in a supply voltage changing. Polarity on the third winding (22e) transforms that a capacitance (38) is coupled to a winding (37) of the saturable coil for generating a circulating current, which contributes to that magnetic core part of the coil is substantially magnetically saturated, which is associated conductively connected to the second winding (22d) of the transformer coil winding (37), such that the circulating current changes of the voltage amplitude at the second winding (22d) of the transformer can be smaller than amplitude changes of the input voltage. 2. Power supply circuit after point - \, characterized in that the third winding is a .Hochspannungswicklung (22e) and that a high voltage circuit (24) is coupled to the high voltage winding (22e) for generating an anode high voltage. 3. A power supply circuit according to item 2, in particular for a television system, characterized in that the high-voltage winding (22e) is magnetically coupled closely to the second winding (22d) of the transformer and comprises a fourth transformer winding (22c) which magnetically coupled closely to the second winding (22d) of the transformer and that a deflection generator (40) is fed by the voltage supplied to the fourth winding (22c) of the transformer for generating deflection current. , 23 3637 9 4. Power supply circuit according to f ^{un! <T} 1 to 3, characterized in that the the second winding (22d) of the transformer remains magnetically unsaturated associated transformer core portion (122) during the entire cycle of the alternating voltage at the second transformer winding substantially. 5. power supply circuit according to point ι j-, j_ _s ^ _1, characterized in that the first and the second winding (22a and 22d) of the transformer magnetically are loosely coupled together such that the voltage at the second winding practically does not 'change its amplitude with voltage changes to the first winding. 15 Dazu._3 ^ Pages drawings