421,546

PATENT SPECIFICATION

Application Date: June 16, 1933. No. 17259/33.

" " " " Aug. 4, 1933. No. 220055/33.

One Complete Specification Left: June 15, 1934.

(under Section 16 of the Patents and Designs Acts, 1907 to 1932.)

Specification Accepted: Dec. 17, 1934.

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PROVISIONAL SPECIFICATION

No. 17259 A.D. 1933.

Improvements in and relating to the Supply of Electrical Energy to varying loads, for example to Thermionic Valve Apparatus

We, ELECTRIC & MUSICAL INDUSTRIES LIMITED, a British Company, of Blyth Road, Hayes, Middlesex, and ALAN DOWER BLUMLEIN, a British Subject, of 32, Woodville Road, Ealing, London, W.5, do hereby declare the nature of this invention to be as follows:-

The present invention relates to the supply of electrical energy to varying loads, for example to thermionic valve apparatus.

It is common practice to supply electrical energy to thermionic valve apparatus from a generator through a filter circuit. Such a filter circuit may comprise one or more inductances arranged in series and one or more condensers arranged in parallel. The electrical energy is usually taken from the terminals of a condenser of the filter and the size of this condenser is usually made such that it offers negligible impedance to the lowest frequency which the amplifier is to handle.

For some purposes, however, for example in television, apparatus is required to operate at frequencies extending effectively to zero an however large the condenser is made it has been found that the performance of the apparatus is adversely affected by the variation in regulation of the generator together with its filter at different load current frequencies. For example if an amplifier has been operating at a certain D.C. energy level and if this level is then increased, the current supply will momentarily change to its correct value, the condenser of the filter assisting in supplying the increased current, but in due course the current will fall to a lower value because of faulty regulation. If the condenser is made larger, the time taken by the current in falling will be increased but the fall will still take place. The result is that the response of the amplifier is not uniform over the working range of frequencies.

The same effect is noticeable with many other forms of apparatus, such as modulators and demodulators, where oscillations down to effectively zero frequency or where carriers modulated with such oscillations are being handled.

It is an object of the present invention to enable electrical energy to be delivered from a source associated with a reactive impedance to a load which varies at frequencies down to effectively zero without the supply voltage varying with the frequency.

It should be pointed out that the present invention is not concerned with arrangements in which there is provided an auxiliary source of energy, such as a floating battery, which acts as a reservoir of electrical energy and nullifies the effect of reactance associated with the main generator. In effect such arrangements can be regarded as being sources free from reactance since the auxiliary source is free from reactance. For many purposes it is inconvenient to use such auxiliary reactance-free sources and it is for these purposes that the present invention offers considerable advantages.

According to the present invention, in apparatus comprising a source of current associated with an impedance element either separate from or inherent in the source and having one or more reactive components, in which the source serves to supply a load which varies at frequencies down to effectively zero, there is provided a second impedance element also having one or more reactive elements of such nature and so arranged that this second impedance element functions as a mirror image impedance relatively to the first named impedance element.

In one arrangement according to this invention the second impedance element is associated electrically with the source in such a manner that the effective impedance of the source as seen from the load is purely resistive. In another arrangement according to the present invention the second impedance element is associated with the load r other part of the signal circuit and serves to compensate for the variation in regulation of the source at different frequencies.

The invention will be described by way of example as applied to a modulator comprising two thermionic valves arranged in push-pull relation. Carrier frequency oscillations are fed to the grids of the modulator valves through a transformer, the centre point of the secondary winding of this transformer being connected to the resistive anode load of the output valve of a low frequency amplifier, the filament of this valve being maintained at a suitable fixed voltage relative to earth. It will be assumed that the signals from this amplifier (which may for example be picture signals in television) contain components of frequencies extending to effectively zero. The anodes of the modulating valves are coupled by a transformer to an aerial system and the center point of the primary winding of the latter transformer is connected to the positive terminal of a source of current supply the negative terminal of the source being connected to the filaments of the modulator valves and to earth.

The source of current supply comprises an electric generator which may be a rectifier of alternating current of dynamo machine or other source of continuous current and, between the generator and the output terminals of the source, a filter. The filter comprises an inductance connected in series, say, in the positive lead, and two condensers connected between the ends of the inductance and the negative or earth lead.

Considering the voltage of the positive terminal of the source relative to earth, so long as the average value of the low frequency oscillations remains constant, this voltage remains constant because the filter condenser located between the output terminals of the source is capable of absorbing any fluctuations. If, however, (for example due to a change in general brightness of a picture in television) the signal changes in average value, a change takes place in the average current which the source is required to deliver. Supposing that the source is required to delivery a larger current, then the condenser of the filter will discharge to assist in supplying this increased current. however large the condenser may be it cannot maintain this discharge and consequently the voltage of the point under consideration falls.

One way of overcoming this difficulty according to the present invention consists in making the source, comprising the filter and generator, appear as a pure resistance when viewed from the load (that is to say when viewed from the filter terminals). This can be done as follows, and for convenience in description the various impedances will be given references:-

The generator can be regarded as a source of electromotive force in series with a resistance (R1) and an inductance (L1), the resistance R1 being the effective D.C. regulation resistance of the generator. It is known that the reactive properties of such a circuit can be completely annulled by connecting in parallel therewith a condenser (C1) and a resistance (R2) in series, so long as the value of this resistance equals R1 and the value (C1) of the condenser is such that EQUAT. HERE . The impedance element comprising C1 and R2 is known as the mirror image impedance of the element comprising L1 and R1. A suitable condenser C1 and resistance R2 are therefore connected in this way and the effective impedance seen from the terminals of the first condenser looking back into the generator is therefore a resistance of value equal to R1. The first condenser (C2) of the filter is thus effectively in parallel with a resistance R1 and, as is also known, the mirror image impedance thereof is an inductance (L2) in parallel with a resistance R3, such that R3 = R1 and EQUAT. HERE = R12, this circuit L2, R1, being arranged as a series element in the filter circuit. The whole circuit so far considered comprising elements L1, R1, R2, C1, C2, L2 and R3 behaves as a resistance of value R1. This resistance is effectively in series with the inductance L3 of the filter and to annul this reactance a mirror image circuit comprising a condenser C3 in series with a resistance D4 is shunted across the filter, as before the values being such that EQUAT. HERE = R12 and R4 = R1. Similarly the final condenser C4 of the filter which is in parallel with the effective resistance of the remainder of the circuit, namely R1, is compensated for by a series inductance L4 having a resistance R5 in parallel with EQUAT. HERE being made equal to R12 and R5 being made equal to R1.

Thus the whole source including the generator and the filter associated therewith can in the manner above described be made to simulate a pure resistance at all frequencies down to and including zero frequency and the regulation of the source will then be independent of the frequency of the load current. If desired a small condensers or acceptor circuit may be bridged across the end of such a filter circuit to by-pass the carrier frequency currents without upsetting the impedance of the smoothing system for modulation frequencies. It may be necessary in practice to represent the impedance of the source as a more complex network than R1 and L1 described above, in which case the first shunt circuit may be more complex than the C1 and R2 of this example. Similarly it may be necessary to increase the constant resistance to which the final filter is built out to allow for the D.C. resistance of smoothing inductances.

In an alternative method of achieving a similar result according to this invention, correction for the reactive impedance of the source is applied to the load itself, for example to the anode circuit of the output valve of the low frequency amplifier in the case above described. In order to permit of this correction taking place, it is necessary to arrange that the impedance of the source viewed from the load shall have a finite maximum value. In the case considered, using a generator followed by a filter comprising a series inductance and two parallel condensers, this is achieved by providing a resistance in parallel with the output terminals of the source. The maximum value of the effective impedance of the source is the value of the resistance, which may be large if desired.

There is then arranged in series between the anode of the amplifier valve and the terminal of its resistive anode load which is connected to the centre point of the secondary winding of the carrier frequency input transformer, a compensator resistance having a value equivalent to that of the resistance across the source, taking into consideration the voltage magnification occurring between the to points. That is to say that the insertion of compensator resistance will produce as greater a loss in modulated transmitter output as would be produced by changing the smoothing circuit impedance from zero to the value of the resistance across the source. Across the compensator resistance is then connected a circuit which is element by element the mirror image of the filter circuit and generator, the elements having values proportioned to the compensator resistance and the circuit in which they operate, so that the effect of the variable impedance supply circuit is neutralised for all modulation frequencies down to effectively zero frequency. This compensation may, if preferred, be made at any other point in the modulation frequency transmission circuit, and may also be performed by shunt circuits, or both shunt and series equaliser circuits.

In a combination of the two arrangements described, the source is corrected according to the first method and is thus made to simulate a pure resistance, a large condenser is shunted across the output of the source, and this effective combination of condenser in parallel with a resistance is compensated for by connecting an inductance in parallel with the resistance in the anode circuit of the amplifier valve. The inductance and shunt resistance are, as before, made to act as mirror image impedances relatively to the condenser and shunt resistance of the source.

In all cases the loss in transmission efficiency entailed by either neutralising or compensating the variable impedance of the filter circuit may be reduced by arranging the generator to have the minimum possible D.C. regulation as may be done by compounding a dynamo generator.

Although the invention has been described I some detail as applied to a modulator system it will be clear that it is applicable over a wide field in connection with the supply of electrical energy to apparatus operating at frequencies down to and including zero or operating with carrier oscillations modulated with a range of frequencies including zero frequency.

Further, the invention is not limited to cases where it is desired to compensate for the reactance of a smoothing filter associated with a source. It is also applicable, for example, to decoupling circuits where a desired drop of voltage is obtained by the provision of a series resistance in the lead to a point to be supplied and where undesired coupling between this point and other parts of the apparatus is prevented by a condenser located between the point and earth.

Dated this 16th day of June, 1933.

REDDIE & GROSE,

Agents for the Applicants,

6, Bream’s Buildings, London, E.C.4.

PROVISIONAL SPECIFICATION

No. 22005 A.D. 1933.

Improvements in and relating to the Supply of Electrical Energy to varying loads, for example to Thermionic Valve Apparatus

We, ELECTRIC & MUSICAL INDUSTRIES LIMITED, a British Company, of Blyth Road, Hayes, Middlesex, and ALAN DOWER BLULEIN, a British Subject, of 32, Woodville Road, Ealing, London, W.5, do hereby declare the nature of this invention to be as follows:-

The present invention relates to the supply of electrical energy to varying loads, for example to thermionic valve apparatus.

In co-pending Application No. 17259/33 there are described circuits whereby electrical energy can be delivered from a source associated with a reactive impedance to a load which varies at frequencies down to effectively zero without appreciable variation of the voltage across the load with change of frequency.

The present invention is concerned with similar circuits.

In the above mentioned co-pending Application it is shown that a voltage source, such as a rectifier fed from an alternating current source, associated with a smoothing circuit can be made to simulate a substantially pure resistance when viewed from the load by the provision of an impedance network which functions as a mirror image impedance relatively to the impedance associated with the source. Thus if the source including the smoothing circuit can be represented by a pure source of electromotive force connected through a resistance, representing regulation, and an inductance to the output terminals of the source which are connected to the load, together with a condenser connected between the output terminals, this source can be made to simulate a pure resistance by connecting a resistance in series with the condenser between the output terminals this resistance having a value R1, where R12 is made equal to EQUAT. HERE and R1 = R0 + RL, where L1 and C1 are the values of the inductance and capacity respectively and R0 and RL are the regulation resistance and the resistance of the inductance respectively. The inductance or capacity or both may be altered in value if necessary in order that the above equations can be satisfied. The circuit R1, C1 acts as a mirror image impedance with respect to the circuit L1, R0.

According to the present invention, in one aspect, when a source associated with one or more reactive elements has been built out, for example as above described, to simulate a substantially pure resistance when viewed from the load, additional means are provided to correct for stray reactances such as the self-capacity of inductances, the inductance of condensers and the capacity of the wiring at high frequencies so that the source when viewed from the load approximates still more closely to a purely resistive impedance over the working range of frequencies.

For example, taking the circuit described above, before resistance R1 is inserted in series with C1, the circuit viewed from the load will have an impedance R0, RL at very low frequencies and at high frequencies it will have a low impedance due to C1. At the resonant frequency of L1 and C1 it may have quite a high value. This change in impedance is greatly reduced by the insertion of the resistance R1 as already described.

If this arrangement involves an inconveniently high value of C1, the value of L1 my be reduced, or the D.C. regulation may be artificially increased by inserting resistances in series with the rectifier. The impedance seen from the load will at the very low frequencies be determined by the branch containing L1 and the rectifier, and at high frequencies by the branch containing R1 and C1. At a frequency (f1) given by f1 = EQUAT. HERE the impedance will be determined equally by both branches. Now it will be seen that at frequencies well above f1 the impedance of the arrangement will not be seriously altered if the impedance of the rectifier and L1 branch departs from that represented by a resistance R1 in series with an inductance L1, provided that impedance of this branch remains high. Suppose now that the inductance L1, which may consist of very many turns of wire, has a self capacity C2. At some frequency above the resonant frequency of L1 and C2, this capacity may cause the impedance of the rectifier branch to become quite comparable with R1, thus upsetting the constancy of impedance of the combination. The frequency at which this may occur will be called f2.

The bad effects of C2 may be avoided according to this invention by connecting between the junction point of the branch L1 and the branch R1 C1 and the output terminal to which this point is connected an inductance L3 of low self capacity compared with L1 and by connecting a further resistance R3 and condenser C3 across the output terminals, where EQUAT. HERE = R32 and R3 is made equal to R1 plus any additional regulation resistance introduced by L3. Further, the critical frequency f3 = EQUAT. HERE above which the branch R3, C3 substantially determines the impedance is made lower than f2 so that the harmful effects of the self capacity C2 are masked by the filtering action of L3 and C3.

Similarly, the arrangement thus obtained may not be perfect due to the self capacity of L3 or due to the inductance of capacity or both of the wiring from the output terminals to the load, that is to the point at which the D.C. power is required. A capacity, as might be produced by wiring will then be referred to as C4. Such a capacity would at very high frequencies alter the impedance seen from the right hand terminals of Fig. 3. The effect of this shunt capacity may be neutralised by inserting an inductance L4 shunted by a resistance R4 in series with the wiring to one of the load terminals and close to the load. The value of L4 would have to be fixed from the value of C4, which would depend on the constants of the wiring. Similarly, the wiring may be loaded by series inductances to the same resistive impedance as that to which the regulation of the smoothed source has been adjusted.

In an alternative arrangement for correcting for the capacity C4 there is provided in series in one lead of the wiring and close to the load an inductance L5. A circuit comprising a resistance R5 in series with a condenser C5 is shunted across the load terminals. The arrangement is made such that EQUAT. HERE = R52 and R5 equals the regulation resistance R4 to which the source has been built out plus any additional regulation resistance due to the wiring and the inductance L5. The critical frequency f5 = EQUAT. HERE is so chose that it is lower than the frequency at which C4 begins to affect materially the regulation resistance. As f5 will probably be a comparatively high frequency, the magnitude of L5 and C5 will probably be small so that they may easily be arranged as state at the point where the D.C. power is to be applied.

The circuit as a whole now comprises a succession of constant resistance circuits of decreasing inductance and capacity values employing inductive series elements and resistive capacitative shunt elements. The general principle is that a primary source such as a rectifier has over a frequency range O – f1 a regulation resistance which may be represented by a resistance, or by a resistance in series with simple impedance network. This rectifier is built out to a constant resistance by suitable resistance and reactance elements which mask the primary source impedance for frequencies above f1 and at the same time make the resultant built out source appear to be a constant resistance over a frequency range O – f2, where f2 > f1. Further, similar stages may be required in order to obtain sufficient smoothing. However, it may be impossible or inconvenient to construct the elements of lay-out of the first section of build out so that f2 is as high a frequency as is required, and in such a case a second stage of build out is arranged so that the impedance of the first stage is masked at frequencies above f2, and so that the resistance is maintained constant over a range O – f2. Similarly the combined arrangement may be built out again to reach a frequency f4 and so on.

In the case of a source having small regulation, it may be found that the regulating resistance of the source at low frequencies does not materially affect the operation of the load which it feeds. If, however, a smoothing circuit is used, the smoothing circuit may resonate at some frequency and so make the effective regulation very large at this frequency. For example, in the uncorrected circuit first described, if the regulation resistance of the rectifier is small compared with the reactance of L1 or C1 at the frequency where the resonate, the impedance seen from the output terminals will, at frequencies close to resonance, be very many times the D.C. regulation resistance of the source.

According to a further feature of the present invention, in apparatus comprising a source of current of which the regulation impedance is so small as to have no appreciable adverse effect upon the constancy of the voltage maintained across a load over the working range of frequency and in which a smoothing circuit is provided between the source and the load, there are provided damping means so arranged as to prevent the regulation impedance from rising to an unduly high value.

Thus in the uncorrected circuit first above described comprising a source of smoothing elements L1 and C1 arranged as described and assuming that the source is one having a very low regulation resistance, a resistance may be arranged in series with the condenser C1. The value of this resistance and the value of L1 and C1 need not in this case be proportioned so as to build the smoothing circuit to a constant resistance provided that sufficient damping is added to prevent the regulation of the smoothed source being sufficient at any frequency to affect adversely the operation of the device which it feeds. Alternatively to putting a resistance in series with C1, a resistance may be put in parallel with L1. The insertion of damping resistances into the filter will necessarily reduce its smoothing efficiency, especially for the higher ripple frequencies, or conversely it will be necessary to increase the sizes of the inductances of condensers or both to increase the number of filter sections in order to obtain the same degree of smoothing. Alternative methods of achieving the same results are so to proportion the condenser conductors or the laminations of the chokes as to introduce effective damping into these components.

Thus the damping, while reducing the smoothing efficiency of the filter, serves to limit the range of variation of regulation impedance. This arrangement is in effect a step towards building the filter to a pure resistance, but the resistances (or damping) introduced, and the values of the components used, are not necessarily adjusted to the exact values for a constant resistance system. Sufficient damping is introduced to prevent any resonances from causing the regulation impedance at any frequency to be much greater than the D.C. regulation resistance.

An alternative to the above arrangement is obtained by so proportioning the smoothing elements that, compared with the regulation resistance of the primary source, they present to the load at their resonant frequency or frequencies a low impedance.

When a source of direct current having very small regulation impedance is required, an accumulator battery is often used. The regulation of such a battery may sometimes be of importance and if it is desired to operate over a very wide range of frequencies, the variation with frequency of the regulation of the battery may also be of importance. Similarly the battery may have attached to or be connected through wiring, whose inductance and/or capacity is sufficient to cause the effective regulation alter with variation of frequency.

In order to correct the variations of regulation impedance, the battery may be built out to look like a pure resistance.

The impedance of the battery may be measured over the whole frequency range through which is must operate. The impedance may be found to approximate to the impedance of a certain electrical network. The battery is then built out by the inverse of this network, that is by a mirror image network, so as to present a constant resistive regulation at all frequencies. For example, the battery may be found to approximate to a resistance R1 in series with an inductance L1. The battery is then shunted by a resistance R1 and a condenser C1 arranged in series and having such values that EQUAT. HERE = R12. Similarly the battery may be found to approximate to a resistance R1 in series with an inductance L1, the whole being shunted by a condenser C2. The battery may then be shunted by R1 and C1 in series, where EQUAT. HERE = R12 and there is added a series element consisting of L2 in parallel with R1, where EQUAT. HERE = R12. Similar circuits can be devised for almost any possible configuration of elements found to approximate to the battery impedance, or to the impedance of the battery and the wiring from the battery to the point at which is required to operate.

As a second alternative, it may be found that up to and a little above a frequency f1, the regulation of the battery and its wiring approximates to a constant pure resistance equal to say R1. An inductance L1 is then connected in series with the battery and the resultant circuit is shunted by a resistance R2 and a capacity C1 in series, where EQUAT. HERE = R22, EQUAT. HERE = f1, and where R2 equals R1 plus the resistance of L1. Alternatively the battery may be shunted by a condenser C1 and built out by an inductance L1 in parallel with a resistance. The impedance of the battery and wiring is then masked for all frequencies well above f1. Any trouble due to self capacity of L1 can be dealt with by further stages in the manner described for the progressive smoothing circuit. By making L1 and C1 large (that is by making f1 low), the circuit becomes a smoothing circuit which can be used to smooth out any noise induced or arising in the battery.

Thus according to this aspect of the invention, with a source such as a battery having a regulation which is low and does not vary greatly with change of frequency, the regulation impedance can either be adjusted to a constant resistive value or can be masked and then adjusted.

It has been proposed to reduce the voltage regulation of generators or rectifiers by shunting across them an accumulator, glow discharge device, or other similar low resistance element. It may be found that even after this has been done the variation of resultant regulation impedance with frequency is more than can be tolerated. This frequency variation, or the effects of capacity and inductance in associated wiring, can be corrected in the manner described above for correcting the regulation of a battery.

In the foregoing, it has been assumed that the D.C. regulation of any device can be represented by a pure resistance. For many devices such as rectifiers and accumulators, this is not the case. The variation of voltage with load is not quite linear, especially for very small loads. Therefore when constructing a constant resistance building out circuit for such a device, a mean slope or value of regulation resistance should be taken. If it is required that the source and associated smoothing or masking circuits shall represent very closely fixed resistance at all working frequencies and loads, it is sometimes advantageous to put a dead load across the source in order to stabilise its regulation resistance. For example, the first part of the regulation curve of a valve rectifier usually shows a much steeper slope than the rest of the curve. If now either a dead load is bridged across the rectifier, or the range of load currents required is so chosen that the rectifier is never required to work over the first steep portion of its regulation characteristic, it will be found that the effective regulation characteristics approximates closely to a constant resistance.

Such a dead load may consist of a resistance or may be formed of thermionic triodes such triodes may for example be arranged to take certain steady current at no useful load from the rectifier or other source, a suitable negative bias being applied to their grids. A reduction of source voltage due to load current raises the impedance of the triodes, thus tending to equalise the variation of source regulation resistance.

The resultant mean regulation of source and dead load combined is of course, taken as the D.C. regulation to which the smoothing or masking circuit is built.

Dated this 4th day of August, 1933.

REDDIE & GROSE,

Agents for the Applicants,

6, Bream’s Buildings, London, E.C.4.

 

COMPLETE SPECIFICATION

Improvements in and relating to the Supply of Electrical Energy to varying loads, for example to Thermionic Valve Apparatus

We, ELECTRIC & MUSICAL INDUSTRIES LIMITED, a British Company, of Blyth Road, Hayes, Middlesex, and ALAN DOWER BLUMLEIN, a British subject, of 32, Woodville Road, Ealing, London, W.5, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:-

The present invention relates to the supply of electrical energy to loads which vary over a range of frequencies, for example to thermionic valve apparatus.

It is common practice to supply electrical energy to thermionic valve apparatus from a generator through a filter circuit. Such a filter circuit may comprise one or more inductances arranged in series and one or more condensers arranged in parallel. The electrical energy is usually taken from the terminals of a condenser of the filter and the size of this condenser is usually made such that it offers negligible impedance to the lowest frequency which the amplifier is to handle.

For some purposes, however, for example in television, apparatus is required to operate at frequencies extending effectively to zero and however large the condenser is made it has been found that the performance of the apparatus is adversely affected by the variation in regulation of the generator together with its filter at different load current frequencies. For example if an amplifier has been operating at a certain D.C. energy level and if this level is then increased, the current supply will momentarily change to its correct value, the condenser of the filter assisting in supplying the increased current, but in due course the current will fall to a lower value because of faulty regulation. If the condenser is made larger, the time taken by the current in falling will be increased but the fall will still take place. The result is that the response of the amplifier is not uniform over the working range of frequencies.

The same effect is noticeable with many other forms of apparatus, such as modulators and demodulators, where oscillations down to effectively zero frequency or where carriers modulated with such oscillations are being handled.

It is an object of the present invention to enable electrical energy to be delivered from a source associated with a reactive impedance to a load which varies over a range of frequencies down to effectively zero without the supply voltage varying with the frequency.

It should be pointed out that the present invention is not concerned with arrangements in which there is provided an auxiliary source of energy, such as a floating battery, which acts as a reservoir of electrical energy and nullifies the effect of reactance associated with the main generator. In effect such arrangements can be regarded as being sources free from reactance since the auxiliary source is free from reactance. For many purposes it is inconvenient to use such auxiliary reactance-free sources and it is for these purposes that the present invention offers considerable advantages.

According to the principal feature of the present invention apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies comprises a source of direct current and one or more reactive impedance elements either separate from or inherent in said source, means being provided whereby said apparatus, viewed from said load, has a substantially purely resistive impedance over the range of frequencies over which energy is to be supplied to said load.

According to a further feature of the present invention, apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies comprises a source of direct current associated with an impedance element either separate from or inherent in the source and having one or more reactive components, and the invention is characterised in that there is provided a second impedance element also having one or more reactive elements of such nature and so arranged that this second impedance element functions as a mirror image impedance relatively to the first named impedance element.

In one arrangement according to the last paragraph the second impedance element is associated electrically with the source in such a manner that the effective impedance of the source as seen from the load is purely resistive. In an alternative arrangement, the second impedance element is associated with the load or other part of the signal circuit and serves to compensate for the variation in regulation of the source at different frequencies.

The present invention further provides apparatus adapted from the supply of electrical energy to a load which varies over a range f frequencies, said apparatus comprising a source of direct current and a multi-section filter connected between said source and the load terminals of said apparatus, each section of said filter comprising a series branch containing an inductance element and a shunt branch containing a capacity element, wherein, in successive sections proceeding from said source, the products of the inductance and capacity decrease and the ratios of the inductance to the capacity remain substantially constant or increase.

In the case of a source having small regulation, it may be found that the regulation resistance of the source at low frequencies does not materially affect the operation of the load which it feeds. If, however, a smoothing circuit is used, the smoothing circuit may resonate at some frequency and so make the effective regulation very large at this frequency.

It is accordingly a further object of the present invention to prevent such large changes in effective regulation.

According to this aspect of the present invention there is provided apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current (such for example as a rectifier) having a D.C. regulation resistance which is so small as to have no appreciable adviser effect upon the constancy of the voltage maintained across said load at very low frequencies of load variation, and one or more reactive impedance elements associated with said source, wherein means are provided for preventing the reactive component of the regulation impedance, due to said reactive impedance element or elements, from rising at any frequency within said range to an unduly high value, that is to say a value which is more than about three times the resistive component of the regulation impedance.

According to a further feature of the present invention there is provided apparatus adapted from the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current of which the regulation impedance for low frequencies of lad variations is so small as to have no appreciable adverse effect upon the constancy of the voltage maintained across said load, a smoothing circuit between sad source and the load terminals of said apparatus and damping means of such value as to prevent the regulation impedance of said apparatus as a whole from rising, at any frequency within the working range, to an unduly high value, that is to say a value exceeding three times and preferably twice the direct current regulation resistance of the apparatus.

Other features of the present invention will be apparent from the following description and the appended claims.

The invention is illustrated by way of example in the accompanying drawings, in which

Fig. 1 is a diagram of known circuit to which the present invention is applicable,

Fig. 2 shows a portion of the circuit of Fig. 1 modified to include features of the present invention,

Fig. 3 is a circuit diagram similar to Fig. 1 but embodying the present invention,

Fig. 4 is a diagram of another known circuit arrangement,

Figs. 5 to 8 represent various modifications of the circuit of Fig. 4 embodying the present invention, and

Figs. 9 to 12 show further circuits according to the present invention.

Referring to Fig. 1, there is shown a modulator comprising two thermionic valves 1 and 2 arranged in push-pull relation. Carrier frequency oscillations are fed to the grids of the modulator valves through a transformer 3, the centre point of the secondary winding of this transformer being connected to the resistive anode load 4 of the output valve 5 of a low frequency amplifier, the filament of this valve being maintained at a suitable fixed voltage relative to earth. It will be assumed that the signals from this amplifier (which may for example be picture signals in television) contain components of frequencies extending to effectively zero. The anodes of the modulating valves 1 and 2 are coupled by a transformer 6 to an aerial system 7 and the centre point of the primary winding of the latter transformer is connected to the positive terminal 8 of a source of current supply, the negative terminal 9 of the source being connected to the filaments of the modulator valves and to earth.

The source of current supply comprises an electric generator 10 which may be a rectifier of alternating current or dynamo machine or other source of continuous current and, between the generator and the output terminals of the source, a filter. The filter comprises an inductance L2 connected in series, in the example shown in the positive lead, and two condensers C2 and C4 connected between the ends of the inductance L3 and the negative or earth lead.

Considering the voltage of the positive terminal 8 of the source relative to earth, so long as the average value of the low frequency oscillations remains constant, this voltage remains constant because the filter condenser C4 is capable of absorbing any fluctuations. If, however (for example due to a change in general brightness of a picture in television) the signal changes in average value, a change takes place in the average current which the source is required to deliver. Supposing that the source is required to deliver a larger current, then the condenser C4 of the filter will discharge to assist in supplying this increased current. however large the condenser may be it cannot maintain this discharge and consequently the voltage of the point under consideration falls.

One way of overcoming this difficulty according to the present invention consists in 1making the source, comprising the filter and generator, appear as a pure resistance when viewed from the load (that is to say when viewed from the load or filter terminals 8, 9). This can be done as shown in Fig. 2, which shows the circuit of Fig. 1 to the right of the load terminals 8, 9 modified according to the invention.

The generator 10 of Fig. 1 can be regarded as a source of electromotive force E in series with a resistance R1 and an inductance L1, the resistance R1 being the effective D.C. regulation resistance of the generator. It is known that the reactive properties of such a circuit can be completely annulled by connecting in parallel therewith a condenser C1 and a resistance R2 in series, so long as the value of this resistance equals R1 and the value C1 of the condenser is such that EQUAT. HERE = R12. The impedance element comprising C1 and R2 is known as the mirror image impedance of the element comprising L1 and R1. A suitable condenser C1 and resistance R2 are therefore connected in this way and the effective impedance seen from the terminals of the condenser C2 looking back into the generator is therefore a resistance of value equal to R1. The first condenser C2 of the filter is thus effectively in parallel with a resistance R1 and, as is also known, the mirror image impedance thereof is an inductance L2 in parallel with a resistance R3, such that R3 = R1 and EQUAT. HERE = R12, this circuit L2, R3 being arranged as a series element in the filter circuit. The whole circuit so far considered comprising elements L1, R1, R2, C1, C2, L2 and R5 behaves as a resistance of value R1. This resistance is effectively in series with the inductance L3 of the filter and to annul this reactance a mirror image circuit comprising a condenser C3 in series with a resistance R4 is shunted across the filter, as before the values being such that EQUAT. HERE = R12 and R4 = R1. Similarly the final condenser C4 of the filter which is in parallel with the effective resistance of the remainder of the circuit, namely R1, is compensated from by a series inductance L4 having a resistance R5 in parallel therewith, EQUAT. HERE being made equal to R12 and R5 being made equal to R1.

Thus the whole source including the generator and the filter associated therewith can in the manner above described be made to simulate a pure resistance at all frequencies down to and including zero frequency and the regulation of the source will then be independent of the frequency of the load current. if desired a small condenser shown in dotted lines at 11 of an acceptor circuit shown in dotted lines at 12 may be bridged across the end of such a filter circuit to by-pass the carrier frequency currents without upsetting the impedance of the smoothing system for modulation frequencies. It may be necessary in practice to represent the impedance of the source as a more complex network than R1 and L1 described above, in which case the first shunt circuit may be more complex than the C1 and R2 of this example. Similarly it may be necessary to increase the constant resistance to which the final filter is built out to allow for the D.C. resistance of smoothing inductances.

In an alternative method of achieving a similar result according to this invention illustrated in Fig. 3, correction for the reactive impedance of the source 10 is applied to the load circuit itself, for example to the anode circuit of the output valve 5 of the low frequency amplifier in the case above described. In Fig. 3 like elements are given the same references as in Fig. 1. In order to permit of this correction taking place, it is necessary to arrange that the impedance of the source viewed from the load (that is the impedance seen from load terminals 8 and 9 looking to the right) shall have a finite maximum value. In the case considered, using a generator 10 followed by a filter comprising series inductance L3 and two parallel condensers C2 and C4, this is achieved by providing a resistance 13 in parallel with the output terminals 8, 9 of the source. The maximum value of the effective impedance of the source is then the value of the resistance 13, which may be large if desired.

There is then arranged in series between the anode of the amplifier valve 5 and the terminal 14 of its resistive anode load 4, a compensator resistance 15 having a value equivalent to that of the resistance 13 across the source, taking into consideration the voltage magnification occurring between the two points. That is to say that the insertion of compensator resistance 15 will produce as great a loss in modulated transmitter output as would be produced by changing the smoothing circuit impedance from zero to the value of the resistance 13 across the source. Across the compensator resistance 15 is then connected a circuit represented diagrammatically at 16 which is element by element the mirror image of the filter circuit C4, L3, C2 and generator 10, the elements having values proportioned to the compensator resistance 15 and the circuit in which they operate, so that the effect of the variable impedance supply circuit is neutralised for all modulation frequencies down to effectively zero frequency. This compensation may, if preferred, be made at any other point in the modulation frequency transmission circuit, and may also be performed by shunt circuits, or both shunt and series equaliser circuits.

In a combination of the two arrangements described, the source is corrected according to the method shown in Fig. 2 and is thus made to simulate a pure resistance, a large condenser is shunted across the output of the source (for example condenser 11 may have a large value), and this effective combination of condenser in parallel with the resistance 15 in the anode circuit of the amplifier valve 5. The inductance and shunt resistance are, as before, made to act as mirror image impedances relatively to the condenser and shunt resistance of the source.

In all cases the loss in transmission efficiency entailed by either neutralising or compensating the variable impedance of the filter circuit may be reduced by arranging the generator to have the minimum possible D.C. regulation as may be done by compounding a dynamo generator.

It may be found in some cases where the source is required to simulate very closely a pure resistance or, if the correction for the variation in regulation of the source is applied to some part of the load circuit, where this correction is required to be very nearly complete, account has to be taken of stray reactances, such for example as the self-capacity of inductances, the inductance of condensers and the capacity of the wiring. For example in the known circuit shown in Fig. 4, a source 17, which may be a rectifier, is connected to load terminals 8 and 9 through a filter comprising a series inductance L3 and a shunt condenser C4. The resistance of the source 17 and the inductance L3 is represented by R6. At very low frequencies this source when viewed from terminals 8 and 9 will have an impedance R6 and at high frequencies it will have a low impedance due to C4. At the resonant frequency of L3 and C4 it may have quite a high value. By applying the present invention to this circuit as shown in Fig. 5 the impedance may be made much more nearly constant. In Fig. 5 the condenser C4 is replaced by a condenser C5 in series with a resistance R7 so proportioned that R7 = R6 and EQUAT. HERE = R62. If this arrangement involves an inconveniently high value of C5 the value of L3 may be reduced or the D.C. regulation may be artificially increased by inserting resistances in series with the rectifier.

It will be seen that with this circuit of Fig. 5 the impedance seen from the load terminals 8, 9 will at very low frequencies be determined by the rectifier branch R6, L3, 17 and at high frequencies by the shunt branch C5, R7. At a frequency f1 given by f1 = EQUAT. HERE the impedance will be determined equally by both branches. Now, at frequencies well above f1 the impedance of the arrangement will not be seriously altered if the impedance of the rectifier branch departs from that represented by an inductance L3 in series with a resistance R6 provided that the impedance of this branch remains high. Suppose now that the inductance L3, which may consist of very many turns of wire, has a self capacity C6 indicated by the condenser in dotted lines. At some frequency above the resonant frequency of L3 and C5, this capacity C6 may cause the impedance of the rectifier branch to become quite comparable with R7, thus upsetting the constancy of impedance of the combination. The frequency at which this may occur will be called f2.

The bad effects of C6 may be avoided according to a feature of this invention as shown in Fig. 6 by connecting between the junction point of the rectifier and shunt branches and the output terminal 8 an inductance L5 of low self capacity compared with L3 and by connecting a further resistance R8 and condenser C7 across the output terminals, where EQUAT. HERE = R82 and R8 is made equal to R6 plus any additional regulation resistance introduced by L5. Further, the critical frequency f3 = EQUAT. HERE above which the branch C7, R8 substantially determines the impedance is made lower than f2 so that the harmful effects of the self capacity C6 are masked by the filtering action of L5 and C7.

Similarly, the arrangement thus obtained may not be perfect due to the self capacity of L5 or due to the inductance or capacity or both of the wiring from the output terminals of the shunt branch C7, R8 to the load, that is to the point at which the D.C. power is required. A capacity, as might be produced by wiring is shown in dotted lines at C8. Such a capacity would at very high frequencies alter the impedance seen from the terminals 8, 9 of Fig. 6. The effect of this shunt capacity C8 may be neutralised by inserting an inductance L6 shunted by a resistance R9 in series with the wiring to the load terminal 8, the terminals 8 and 9 being disposed close to the load. The value of L6 is fixed from the value of C8, which depends on the constants of the wiring. Similarly, the wiring may be loaded by series inductances to the same resistive impedance as that to which the regulation of the smoothed source has been adjusted.

In an alternative arrangement for correcting for the capacity C8 shown in Fig. 7 there is provided in series in one lead of the wiring and close to the load an inductance L7. A circuit comprising a resistance R10 in series with a condenser C9 is shunted across the load terminals 8, 9. The arrangement is made such that EQUAT. HERE = R102 and R10 equals the regulation resistance to which the source has been built out plus any additional regulation resistance due to the wiring and the inductance L7. The critical frequency f5 = EQUAT. HERE is so chose that it is lower than the frequency at which C8 begins to affect materially the regulation resistance. As f5 will probably be a comparatively high frequency, the magnitude of L7 and C9 will probably be small so that they may easily be arranged as stated at the point where the D.C. power is to be applied.

The circuit as a whole now comprises a succession of constant resistance circuits of decreasing inductance and capacity values (proceeding from the rectifier 17) employing inductive series elements and resistive and capacitative shunt elements. The general principle is that a primary source such as a rectifier has over a frequency range O – f1 a regulation resistance which may be represented by a resistance, or by a resistance in series with a simple impedance network. This rectifier is built out to a constant resistance by suitable resistance and reactance elements which mask the primary source impedance for frequencies above f1 and at the same time make the resultant built out source appear to be a constant resistance over a frequency range O – f2, where f2 > f1. Further, similar stages may be required in order to obtain sufficient smoothing. However, it may be impossible or inconvenient to construct the elements or lay-out of the first section of build out so that f2 is as high a frequency as is required, and in such a case a second stage of build out is arranged so that the impedance of the first stage is masked at frequencies above f2, and so that the resistance is maintained constant over a range O – f3. Similarly the combined arrangement may be built out again to reach a frequency f4 and so on.

As already stated, in the case of a source having small regulation, it may be found that the regulation resistance of the source at low frequencies does not materially affect the operation of the load which it feeds. If however, a smoothing circuit is used, the smoothing circuit may resonant at some frequency and so make the effective regulation very large at this frequency. For example, in the circuit shown in Fig. 4, if the regulation resistance of the rectifier 17 is small compared with the reactance of L3 or C4 at the frequency where they resonate, the impedance seen from the output terminals 8, 9 will, at frequencies close to resonance, be very many times the D.C. regulation resistance of the source.

This difficulty can be overcome according to a feature of this invention by the provision of suitable damping means so arranged as to prevent the regulation impedance from rising to an unduly high value.

Thus in the circuit of Fig. 5, assuming that the source 17 is one having a very low regulation resistance, a resistance R7 may be arranged in series with the condenser C5. The value of this resistance R7 and the value of L3 and C5 need not in this case be proportioned, as already described in connection with this Figure so as to build the smoothing circuit to a constant resistance provided that enough damping is added to prevent the regulation of the smoothed source being sufficient at any frequency to affect adversely the operation of the device which it feeds. Alternatively to putting a resistance in series with C5, a resistance R11 may be put in parallel with L3 as shown in Fig. 8. The insertion of damping resistances into the filter will necessarily reduce its smoothing efficiency, especially for the higher ripple frequencies, or conversely it will be necessary to increase the sizes of the inductances or condensers or both or to increase the number of filter sections in order to obtain the same degree of smoothing. Alternative methods of achieving the same results are so to proportion the condenser conductors or the lamination of the chokes as to introduce effective damping into these components.

Thus the damping, while reducing the smoothing efficiency of the filter, serves to limit the range of variation of regulation impedance. This arrangement is in effect a step towards building the filter to a pure resistance, but the resistances (or damping) introduced, and the values of the components used, are not necessarily adjusted to the exact values for a constant resistance system. Sufficient damping is introduced to prevent any resonances from causing the regulation impedance at any frequency to be much greater than (that is to say more than two or three times) the D.C. regulation resistance.

An alternative to the above arrangement is obtained by so proportioning the smoothing elements that, compared with the regulation resistance of the primary source, they present to the load at their resonant frequency or frequencies a low impedance, that is to say an impedance which is not more than about twice the regulation resistance of the primary source.

When a source of direct current having very small regulation impedance is required, an accumulator battery is often used. The regulation of such a battery may sometimes be of importance and if it is desired to operate over a very wide range of frequencies, the variation with frequency of the regulation of the battery may also be of importance. Similarly the battery may have attached to it or be connected through wiring, whose inductance and/or capacity is sufficient to cause the effective regulation to alter with variation of frequency.

In order to correct the variations of regulation impedance, the battery may be built out to look like a pure resistance.

The impedance of the battery may be measured over the whole frequency range through which is must operate. The impedance may be found to approximate to the impedance of a certain electrical network. The battery is then built out by the inverse of the network, that is by a mirror image network, so as to present a constant resistive regulation at all frequencies. For example, as shown in Fig. 9, the battery 18 may be found to approximate to a resistance R12 in series with an inductance L8. The battery is then shunted by a resistance R13 and a condenser C10 arranged in series and having such values that EQUAT. HERE = R122 and R12 = R13. Similarly, as shown in Fig. 10, the battery 18 may be found to approximate to a resistance R12 in series with an inductance L8, the whole being shunted by a condenser C11. The battery may then be shunted by R13 and C10 in series, where EQUAT. HERE = R122 and R12 = R13 and there is added a series element consisting of L9 in parallel with R14, where EQUAT. HERE = R122. Similar circuits can be devised for almost any possible configuration of elements found to approximate to the battery impedance, or to the impedance of the battery and the wiring from the battery to the point at which it is required to operate.

As a second alternative, it may be found that up to and a little above a frequency f1, the regulation of the battery and its wiring approximates to a constant pure resistance equal to say R15. An inductance L10 Fig. 11 is then connected in series with the battery 18 and the resultant circuit is shunted by a resistance R16 and a capacity C12 in series, where EQUAT. HERE = R162, EQUAT. HERE = f1, and where R16 equals R15 plus the resistance of L10. Alternatively, as shown in Fig. 12 the battery 18 may be shunted by a condenser C13 and built out by an inductance L11 in parallel with a resistance R17. In either of these cases of Figs. 11 or 12 the impedance of the battery and wiring is masked for all frequencies well above f1. Any trouble due to self capacity of L11 can be dealt with by further stages in the manner described for the progressive smoothing circuit. By making L11 and C13 large (that is by making f1 low), the circuit becomes a smoothing circuit which can be used to smooth out any noise induced or arising in the battery 18.

Thus according to this aspect of the invention, with a source such as a battery having a regulation which is low and does not vary greatly with change of frequency, the regulation impedance can either be adjusted to a constant resistive value or can be masked and the adjusted.

It has been proposed to reduce the voltage regulation of generators or rectifiers by shunting across them an accumulator, glow discharge device, or other similar low resistance element. It may be found that even after this has been done the variation of resultant regulation impedance with frequency is more than can be tolerated. This frequency variation, or the effects of capacity and inductance in associated wiring, can be corrected in the manner described above for correcting the regulation of a battery.

In the forgoing, it has been assumed that the D.C. regulation of any device can be represented by a pure resistance. For many devices such as rectifiers and accumulators, this is not the case. The variation of voltage with load is not quite linear, especially for very small loads. Therefore when constructing a constant resistance building out circuit for such a device, a mean slope or value of regulation resistance should be taken. If it is required that the source and associated smoothing or masking circuits shall represent very closely a fixed resistance at all working frequencies and loads, it is sometime advantageous to put a dead load across the source in order to stabilise its regulation resistance. For example, the first part of the regulation curve of a vale rectifier usually shows a much steeper slope than the rest of the curve. If now either a dead load is bridged across the rectifier, or the range of load currents requires is so chosen that the rectifier is never required to work over the first steep portion of its regulation characteristic, it will be found that the effective regulation characteristic approximates more closely to a constant resistance.

Such a dead load may consist of a resistance or may be formed of thermionic triodes. Such triodes may for example be arranged to take a certain steady current at no useful load from the rectifier or other source, a suitable negative bias being applied to their grids. A reduction of source voltage due to load current raises the impedance of the triodes, thus tending to equalise the variation of source regulation resistance.

The resultant mean regulation of source and dead load combined is of course taken as the D.C. regulation to which the smoothing or masking circuit is built.

Although the invention has been described in some detail as applied to certain particular kinds of apparatus it will be clear that it is applicable over a wide field in connection with the supply of electrical energy to apparatus operating at frequencies down to and including zero or operating with carrier oscillations modulated with a range of frequencies including zero frequency.

Further, the invention is not limited to cases where it is desired to compensate for the reactance of a smoothing filter associated with a source. It is also applicable, for example, to decoupling circuits where a desired drop of voltage is obtained by the provision of a series resistance in the lead to a point to be supplied and where undesired coupling between this point and other parts of the apparatus is prevented by a condenser located between the point and earth.

Having now particularly described and ascertained that nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

  1. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current and one or more reactive impedance elements either separate from or inherent in said source, wherein means are provided whereby said apparatus, viewed from said load, has a substantially purely resistive impedance over the range of frequencies over which energy is to be supplied to said load.
  2. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising source of direct current associated with an impedance element either separate from or inherent in said source and having one or more reactive components, characterised in that there is provided a second impedance element also having one or more reactive components, the second impedance element also having one or more reactive components, the second impedance element being of such nature and so arranged as to function as a mirror image impedance relatively to the first named impedance element.
  3. Apparatus according to claim 2, wherein the second impedance element is of such nature and so associated electrically with said source that the effective impedance of said source, viewed from the load terminal, is substantially purely resistive.
  4. Apparatus according to claim 2, wherein the second impedance element is of such nature and so disposed that it serves substantially to compensate from the variation in regulation of the source together with the first named impedance element at different frequencies.
  5. Apparatus according to claim 4, wherein the second impedance element is associated with a load connected to the load terminals of said apparatus or with a signal circuit associated with said load.
  6. Apparatus according to claim 5, wherein said source, viewed from said load, is arranged to simulate a resistance in parallel with a condenser.
  7. Apparatus according to any of claims 2 to 6, wherein additional means are provided to correct for stray reactance.
  8. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current and a multi-section filter connected between said source and the load terminals of said apparatus, each section of said filter comprising a series branch containing an inductance element and a shunt branch containing a capacity element, wherein, in successive sections proceeding from said source, the products of the inductance and capacity decrease and the ratios of the inductance to the capacity remain substantially constant or increase.
  9. Apparatus according to claim 8, wherein the produce of the inductance and capacity in one of said sections is less than the produce of the inductance in a preceding section and the stray capacity effectively in parallel therewith.
  10. Apparatus according to claim 8 or 9, comprising means for compensating for capacity effectively in parallel with said load terminals.
  11. Apparatus according to claim 10, wherein said means comprise and inductance shunted by a resistance connected in series with the wiring to one of said load terminals and arranged close to this load terminal.
  12. Apparatus according to claim 8 or 9, comprising means for masking the effect, viewed from the load terminals, of capacity effectively in parallel with said load terminals.
  13. Apparatus according to claim 12, wherein said means comprise capacity and resistance elements connected in series with one another between said load terminals and close thereto.
  14. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current (such for example as a rectifier) having a D.C. regulation resistance which is so small as to have no appreciable adverse effect on the constancy of voltage maintained across said load at very low frequencies of load variation and one or more reactive impedance elements associated with said source, wherein means are provided for preventing the reactive component of the regulation impedance, due to said reactive impedance element or elements, from rising, at any frequency within said range, to an unduly high value, that is to say a value which is more than about three times said D.C. regulation resistance.
  15. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current (such for example as a rectifier) having a D.C. regulation resistance which is so small as to have no appreciable adverse effect on the constancy of voltage maintained across said load at very low frequencies, a smoothing circuit between said source and the load terminals of said apparatus and damping means of such value as to prevent the regulation impedance of said apparatus as a whole from rising, at any frequency within the working range, to an unduly high value, that is to say a value exceeding three times the direct current regulation resistance of the apparatus.
  16. Apparatus according to claim 15, wherein said damping means are arranged to be of such value as to prevent the regulation impedance of said apparatus as a whole from rising, at any frequency within the working range, to a value exceeding twice the direct current regulation resistance of the apparatus.
  17. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current of which the regulation impedance for low frequencies of load variation is so small as to have no appreciable adverse effect upon the constancy of the voltage maintained across said load and a smoothing circuit between said source and the load terminals of said apparatus, wherein the elements of said smoothing circuit are of such values that the impedance measured between the load terminals of the apparatus at the resonant frequency or frequencies of said elements is not unduly high, that is to say not more than twice the regulation resistance of said source.
  18. Apparatus adapted for the supply of electrical energy to a load which varies over a range of frequencies, said apparatus comprising a source of direct current which together with wiring and the like associated therewith has a regulation which approximates to a constant pure resistance up to a certain critical frequency but which changes above the said frequency, wherein there is provided between the load terminals of the apparatus and said source a circuit adapted when viewed from said load terminals to mask the impedance of said source and wiring at frequencies within the working range above the said critical frequency.
  19. Apparatus according to claim 18, wherein said source is a battery.
  20. Apparatus according to claim 18, wherein said source is constituted by a generator or rectifier shunted by a low resistance element.
  21. Apparatus comprising a source of direct current associated with an impedance element either separate from or inherent in said source and having one or more reactive components, in which the direct current regulation resistance of said source varies more at small values of load than at larger values thereof, wherein a dead load is shunted across said source and corrective means are provided whereby said source together with associated impedance element and corrective means present a substantially resistive impedance to the load terminals of the apparatus.
  22. Apparatus according to claim 21, wherein said dead load comprises one or ore thermionic valves connected in such a manner that the change of impedance thereof with change of voltage tends to compensate for variation in the regulation resistance of said source.
  23. Apparatus for the supply of electrical energy to varying loads substantially as hereinbefore described.

Dated this 15th day of June, 1934.

REDDIE & GROSE,

Agents for the Applicants,

6, Bream’s Buildings, London, E.C.4.

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Leamington Spa: Printed for His Majesty’s Stationery Office, by the Courier Press. - 1935.