US2637011A - schwarz - Google Patents

Description

y April 28, 1953 I H'. G. SCHWARZ; l

' v PULSE TYPE Poma SUPPLY.

' File@ Dec. 1s.. 1949 l H. G. SCHWARZ EULSE TYPE Pom SUPPLY pn'i 28, A1953 Filed Dec. 1s.I 1949 f myn/TOR.

HANS G. scmaakz @K4/WQ A ORNE s .2,265,620 to Bahring, No. 2,074,495 to Vance, and

I .Application Bceeinber i6, 194,9. Serial No. 133,354

i 2 claims. (ci. 3er- 2) Y i The present invention relates to improvements in high voltage power supply systems for television receivers. I'here are fou'x` types of supply systems in general use:

' First, that which is based on step-up transformation andrectication of the 60 cycle alterhating current. supply, and modied forms involving the use of voltage multipliers, as described at pages 158.164, Grob, Basic Television, Principlesand Servicing, McGraw-Hill Book Company.

' Inc., New York, 1949;

Second, the R. F. type, wherein a rectier is l energized by a. high-frequency oscillator, as described in the article entitled Television High Voltage R. F. Supplies vby M -autner and Schade. RCA Review, March i947, vol. VIII, No. pp. 43-8l, R. C. 'A. Laboratories Division, Princeton. New Jersey, and also at pp. 164-168 of the aboiecited book by Grob;

Third, the ily-back type, `wherein energy is obtained by rectification from the inductive circuit provided for horizontal scanning, as de scribed at pages 168-170 of Grobs book and in U. S. Patent- No. 2,051,372 to Farnsworth, No.

No. 2,218,764 to Moller and Behring;

Fourth, the pulse-type, as described in the ar- ,Patented `Apr. 2.8,.1-953A f Nuntreu dstares; Pareri s631011 rfULsE-Trrnrowen SUPPLY l i .l ,i

G'. Schwarz, Cincinnati, Ohio, assigner to y 'Aveo Manufacturing Corporation, tncinnafi, v Oho,a corporation of Delaware ticle entitled Pulse-Type High-Voltage Supply,"

Siezen and Kerkhof, Proceedings of the Institute oi Radio Engineers, March 1948, pp. li0l407.

The advantages, disadvantages, and limitations of the various types of television receiver power supply systems are known to the art and are discussed in the literature, particularly in the pat-V ents and publicationscited above. Among the. primary desirable attributes of a power supply l system are: (1) A high voltage D. C. output,

which ranges from as low as two kilovolts for some types of directly viewed tubes to kilovolts or higher for projection tubes; (2) low average current output, ranging from 100 to 200 microamperes; (3) light weight; (4) small size; (5) minimum' shock hazard; (6) good power efciency; (7) minimum nonsynchronous R. F. interierence; (8) inexpensive ltering circuits.

These requirements often dictate the use of a 'pulse-type' power supply in specific designs, most frequently in projection type receivers. Constant pressure has been on those working in the art to obtain a higher voltage output per unit based on the periodic interruption o! acurrent the high voltage of the't-ransient oscillation induced by this reaction is rectied and filtered. Each interruption of current nowis followed by' 'a train of damped oscillations which occur during dissipation of energy and substantially corn'V plete collapse ,of the stored power, Then the magnetic iield is completely built up again and the cycle is repeated. Further, only the peaks of the rst cycle of the damped transient oscillation areA rectified and the available high voltage current is low since the total time during which peaks occur is small by comparison to the time of each series oi damped oscillations. The primary object of the present invention is to effect a. radical increase :in efiiciency by .maintaining most of the magnetic energy within'the system eindje-- creasing the number of useless cycles of the periodically recurring oscillations.

accordance with' the invention the natural frequency of `the transformer circuit is so related to the repetition rate of the interruptions of current in the transformez-,circuit and to the time during which the power tube is conducting that the time for one or only a few complete cycles of the fundamental frequency of the transformerl output voltage plus the time of each' increment of cnn-ent required -to reach peak current in the plate inductanceis equal to the reciprocal of the driving pulso frequency.

A pulse-type power supply in accordance with i the invention comprises 4an energy source. an irlductance which is periodically charged by that source, means including a switching tube for peicdically interrupting the new of current in said induetance, thereby causingr the magnetic field to collapse, whereby there appears across said inductance an oscillatory voltage, means for peakcally recurring applied increments of current in said inductance are initiated at times when the oscillatory current in the last-mentioned circuit is near or at its peak value and of 'the same polarity as those increments.

I prefer that the distributed capacitance of an inductor be utilized as the above-mentioned parallel capacitance. The frequencies involved are such that economies may oe effected in this manner. dispensing with the 'provision of a separate capacitor. The explanation of the basic concept of the invention may be simplified by drawing.an

'analogy between the conventional pulse-type power-.supply and the pendulum. The pendulous weight has `its maximum kinetic energy at the mld-point'of its swing. The inductance has its maximum energy at the end of' its charge."

The flow of' current into the inductance is terminatori at. that instant. It may be assumed, to

continue the analogy, that the manual operator .of the pendulum stops his "push at the mid-4 .of the pendulous system' must be entirely built up again in order to attain the maximum swing again. In the conventional type of pulse-type power' supply, the natural periodicity of the induotor circuit (correspondingto the pendulum) and the repetition rate of the driving impulses (each correspondingY to a push ceasing at the lmid-point of swing after a previous cycle of natural oscillations has ceasedl.- are such that the part of the originally stored magnetic energy which is left after the rst cycle, i. e., which is not used for the high-voltage rectification, is

2,637,011 a j I known prior art type of power supply as well as to the present invention. This known typeot power supply comprises a sawtooth signal generator, a power amplier l for converting the sawtooth voltage signals into periodically recur- 'ring sawtooth currents, an inductance i2 through stored in its magnetic ileld is at' a maximum.

completely dissipated between driving-impulses.l s

Only' the peak voltage portions of the irst oscillation are rectined and the vfollowing amplitudes,

decreasing in accordance with a logarithmic i decrement, of the many succeeding oscillations in each train, are such that these succeeding oscil-,

lations do not attain the threshold of rectificaf tion. The useless oscillations comprise by far the Y' greater portion of the total numberof oscillations in each train. Magnetic energy is dissipated to the point of lexhaustion during the time of these useless oscillations. The ratio 'of available high-voltage power to stored magnetic energy'isaccordingly low- I have found that the above-mentioned ratio' and the power em'ciency of a pulse-type power4 supply may be radically increased by applying power to the inductance at a'. repetition rate which is comparable to the natural frequency of the inductive circuit, or by so predetermining the natural frequency that it is comparable to the.

impulse'rate.

In my novel powecsupply. the number of oscillations between successive impulses is not a. substantial multiple of the number of applied impulses. In the prior art power supply, the number of useless power-dissipating oscillations is many times greater than the num-- ber of applied pulses. 4

Continuing the analogy, .my improved power supply may be likened to a pendulum in which an.

impulse is supplied in the correct phase at the mid-point of each swing, or perhaps every second 01' third swing. The prior art system may be likened to a. pendulum which uselessly swings many times and comes to rest before a new impulse is applied. The analogy 'was drawn a.

posteriori for the purpose ofcxplaining the operation of the invention and not a priori.

For a better understandingoi' the present in-l vention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following description of the accompanying drawil'igl1 Fig. 1 of which illustrates in schematic form apulse-type power supply system in accordance with the invention; and

Fig. 2 comprising a set of curves employed as an aid in describing the invention.

The symbols employed in the schematic diagram o! Fig. 1 are those which `are applicable to a appropriate `'control which these currents flow, and an energy source H, included in series with the inductance I2 in the plate circuit of the power tube i 4 for furnishing the' energy represented by these currents. In the priorl art circuit the tube I4 functions as a jswitc'hing tube and periodically closes or becomes non-conductii'e in order-to interrupt the ilow ofcurrent in inductor i2. Each interruption occurs at' the peak of a. sawtooth wave of current in 1n-l ductor I2 an at a time when. the ma gnetlc energy tinues after rectification has occured. During the continued oscillation following peak rectiiicatiom: the residual energy'of the system is dissipated.

until it attains a. value close to zero. The in' 4vention, although it may be represented by thesame symbols as the prior art power supply, operates on a.. distinct principle in that a. very sub- -stantial amount of stored energy is retained in the system between control signals. In the priorl a' art system'substantially all of the energy is dissipated following the termination of each controlling-sawtooth signal and before the beginning of the next controlling sawtooth signal. In a.

power supply in accordance with the presentin-v vention, on the other hand. a substantial amount of energy remains in the system after 'the first control pulse has performed its function and at the instant when the second control pulse becomes effective. In the prior art system the power amplier tube remains conductive, in re' sponse to each sawtooth control signal, sutil--4 ciently long to cause the current in the inductance i2 to build up from zero to its peak value. In the system providedby the invention, on the 'other hand, the intervals of conductivity of the power am-piiiier tube are relatively very short be cause it remains open during each interval only suihciently long to furnish an increment of curf rent from, a'substantial value (representative of the energy retained in the system) to a peak value.

In the new system provided by the invention, pulses as 'represented 'by curve Y, Fig. 2, are employed to govern the op' eration of amplier tube i4. These control pulses are produced by a pulse generator i6 (shown only in block form) such as a plate-coupled mul-4, tivibrator. The control pulses could also be produced by a pulse shaping network coupled to a' line or horizontal synchronizing system oi' the television receiver. LSince such expcdients as signal generators, pulse shaping networks and honplate current cut-ofi potential, rendering tube il non-conductive, and that the portion of each pulse during the interval tr-tv, for example. is

above cut-offend renders tube Il conductive. It will be seen from. the iollowlng'description and l. from. what has already' been mentioned that the intervals of conductivity of tube I4 in my System are relatively very short.

The control pulses are applied to the control 'electrode of tube I4 through a suitable coupling network comprising capacitor Il and grid resistor I8. The cathode of tube I4 is grounded as shown. 1c win be understood that inductan'ce I2 is'shunted by a number of capacitance parameters including its own distributed capacitance and the capacitance of the auto-transformer sec ondary circuit as reflected b ack to the primary. These parameters are collectively indicated by the reference numeral I9. In accordance with the invention the parameters of nductance I2 and capacitance IS are so determined that the magnetic energy in the system is not completely dissipated between successive increments of current in inductance I 2.

Each interruption of current in inductance I2 causes a transient oscillatory voltage to appear across the inductance (curve Z, Fig. 2). The peak of this voltage is stepped up by an autotransformer, the primary of which comprisesin-v .ductance [Zand thel secondaryof which comprises series winding portions I2 and 20, wound:

on the same core. Across the secondary isconne'cted the series combination of a. diode 'rectiiler tube 2l and load 22 (generally the acceleratarea ABC being'enti'rely dispensed with in the Acircuit comprising inductance I2` and capacitor I9. this -decrease being the first stage ofl a traning anode circuit of a cathode-ray picture tube.

not shown).` Across the load is a shunt nit-er capacitor 2.3. The filament 24 of diode 2I is provided with its own secondary windingV 25 4inductively coupled to the auto-transformer. The positive peak of the transient oscillatory voltage isrectined bytubeZI. The rectifier circuit per se. that is, the elements 20, 2i, 25, 23, and 22,A are individually and collectively a part of the prior art.

Coming now to describe the operation of my improved pulse type power supply, it will be assumed that tube I4 becomes conductive at ti'rne ti. As shown in curve X of Fig. 2, the plate current in tube Ii instantly assumes a substantial value Ii. tube i4. the current supplied to the inductor by the tube increases alongr a sawtooth characteristic (curve X, Fig. 2), finally attaining a maximum value I2, and additional energy is stored Y in the magnetic neld of inductance I2 over and The above that which it possesses at instant t1. maximum current value is attained at instant t2.

At thatinstant the control pulse applied to the During the interval of conductivity of ti with a sawtooth characteristic, but on the contrary 'is rapidly initiated at a value I1 (curve X, Fig. 2). This means that the time oi conductivity of tube I4 is4 short relative to the time which would be required to attain value I2, with a sawto'oth characteristic initiated -at zero value. Since the time of conductivity of tube I 4 is a measure of the power eiliciency of the system, it will be seen that thev invention radically improves lpower eiilciency, the area BCDE in curve W, Fig. 2, representing-the power applied during each period of conductivity of tube I4, being much smaller than the area ADE, `which is representative of applied power in prior art circuits, the

second cycle of` free oscillation.

a substantial current is nowing inthe inductance sient oscillation.v At time t: .the current through the inductance an'd the magnetic iield reach instantaneous values of zero (curve W) but attain their maximum rates of change. At time t:

the energy in circuit I2, i9 iS-stored in the el.ec.

trostatic neld and the voltage across tube I6 (curve Z) reaches itsA maximum in a positive direction. The peak of this voltage is rectified by tube 2|.

Inthe priorfart type of power supply, the tram sient oscillations of the type shown in curves W and Z (following t2 or 'power tube cut-oil are allowed to continue until all energy is dissipated from the system. T t is within the -teachings of the present invention to render tube I4 conductive again at or about timetr-when the energy from the electrostatic system has again been nverted into magnetic energy-'-i..e., at or near the 'end of the first cycle oi free oscillation in the pulses, and the output voltage for a given pulse repetition rate is smaller than is the case when the natural frequency is larger. output voltage requires a higher step-up ratio in the auto-transformer. I prefer to reducethis stepup ratio by rcnderinnr tube I4 conductive again at time t-i. e., at or near the end of the At instant te I2. This current is representative of magnetic energy retained within the system and not lost. As soon as tube I4 becomes conductive, at instant ts, this current ilows through the anode-cathode circuit' of the tube. The current through the inductance is again increased between instants ta and t1. and input energy is supplied by the tube during this interval. The cycle is then repeated. preferably, as indicated above, at horizontal line frequency.

.Thus it will be seen that the invention pro vides a pulse-type power supply comprising an energy source II (which may be the usual 10'.:7 voltage plate supply source of a television receiver), an nductance I2 which is periodically charged by that source (the expression "charged" being employed to designate the development o! sawtooth currents), means including a switchirig tube I4 for periodically interrupting the now oi current in the inductance. thereby causing the magnetic eld to begin to collapse (between times t2 and t3, whereby there appears across said nductance an oscillatory voltage (first peak in curve Z). means 2I for peak-rectifying said volt age (at instant ta) to derive a unidirectional voltage, and a capacitance (which may be the distributed capacitance Iil) effectively in parallel with said inductance I2 to form a circuit hav-- The lsmaller that this oscillatory current is of positive polarity at instants tz and4 te. 'and' that. the applied increases of current represented by the curve X.

Fig. 2, are of positive polarity.. The invention.

' provides a system in which thev natural frequency.

of theoseillatory circuit I2.. I9 is such that. the timeior two complete cyclesI (t1-ts) lot the. funisat. or near itspeal:I value. It will. alsobe seen.'

'agefwhich-isbulttunacrossinrluctur l2 during tire time. that; power tube .t4 is. conductive- As this voltage is very snail -compued tothe. transient oscillatory voltage (curve. Z, Fig. 2), it. is neg damental frequency of. the transformer output voltage plus the time required to build' up maxim'unr current in. the' plate. inductance (te-t7). is

equal to the reciprocal of the driving pulse fiequencytte., tv minustz. curvelhox: 1

' the pulse generator, in order to correlatethc pulse repetition rate and natural frequency of the oscillatory circuitV l2, i9. In the specic example shown, the time for two complete cycles of the resonant frequency plus the time necessaryto drive the plate inductance to maximum current value is equal to the reciprocal oi the' driving pulse frequency. V It is within thespirit oi the invcntion to make one. or. two or three -or a few complete cycles of the resonant frequency plus the time necessary to drive the plate inductanceV t'o maximum current value equal to lthe recipro.

cal of the line frequency, because the invention achieves useful results in minimizing the dissipation of magnetic energy from the system between control impulses. The invention becomes particularly useful from Vthe standpoint of iucreasing power. eiiiciency most economically when free oscillation of the resonant system for two os-I cillations is permitted, as in the specic illustrativeembodiment herein described in detail.

It is particularly important. to note that at in,- stant t4, the end of. the iirst cycle of the transient oscillation, a substantial amount of current of' positive polarity is flowing in inductor |22 (curve W, Fig. 2)'. It is within the teachings of the present invention to utilize. this current by opening tube i4 at an. instant corresponding to t4. and to supply an increment of current from Vtube i4 in order to build up the current in inductor l2 to its peak value. Such a result could be accomplishedL by making the natural frequency ot the circuit i2, i9 apaproximately one-half ot the. natural frequency on which Fig. 2 is based, relative. to, the. repetition. rate of the control pulses. In such case the natural frequency of the oscillatory circuit would be. such that the. time; required for one cycle of the oscillatory voltage plus the time required to build up maximum current in the plate inductance i2 would be equal to. the reciprocal of the driving pulse frequency.

It will be understood that the curves of Fig, 2

i represent simplified conditions, and while they take into consideration those factors bearing on the merits of the present invention, certain negllgible factors are not reflected therein. For example, curve W is premised on the assumption that at instant tz. the moment of interruption` of the current in inductorl l2, the current immediately decreases along a sinusoidal characteristic.

. This assumption neglects thev effect of the voltlected herein for purposes of clarification.

While there has been shown and; described what. is at 4presi-ent considered. to be the preferred; embodiment oi`. the present invention, it will be:

obvious to those: skilled in the art thatvariatie:L modifications and substitutions' ot 'equivalents may be made therein. without departing from the 1 true scope ci. the inventionas defined. by the appended claims.

I clarin:

1. A, pulse-type'- povver supply.'- comprjsing an energy source, an inducta'nceivhich is periodically' linearly given an increment of. chargebythat source, a source ot substantially rectangular posi-.- tive pulses anda switching tube4 controlled by said.- A

begin to collapse, whereby there appears. across:

said inductance an oscillatory voltage, rneansin-h cluding an auto-transforrner connected to Said. anode. and utilizing'said inductance as its primary for peakrectifying said voltage to derivea unidirectional voltage, and capacitance effectively in parallel with said inductance to form a circuit resonatlng at a frequency Fzvequal to l-FiT' inwhich n is an integer less than 4, FL is the repetition rate of the rectangular pulses, and T isthetime during which the tube is conductive.

2. vA. pulse-type power supply comprising an energy source. an inductance which is periodically given an increment of charge by that source. a source of substantially rectangular pulses and au switching tube controlled by said pulses, sald. tuba periodically interrupting the Iiow of. current in.

1 said-inducta'nce as the tube. is rendered non-con.-

ductive at the termination of each pulse, thereby whereby there appears across said inductance. an. oscillatoryvoltage, means for peak-rectifying said. voltage to derivev a unidirectional voltage, and capacitance. effectively in parallel with said inl` ductance to form a 4circuit resonating at a Irequency Frequal to A FL l 1-F1Z' in which` n isV an. integer not more thanflrll'r it the. repetition rate ofthe rectangular pulses, and; T is the time during which theptube is cmldwztive..

HANS C1. VSCHWARZ .References Cited in the lc of this patenia- UNITED- STATES PATENTS Date Number NameA 2,104,463 Johnson Jan. 4, 1938' 2,157,534 George et a1'. May 9, 193g 2,352,299 lValker .Y,.... June 27, 1944 2,424,972 ,Dubin n........ ..-e Aug.. 5, 1947. 2,435,414. Sziklai etal. Feb. 3, 1948 2,443,619 Hopper June 22, 1948 OTHER. REFERENCES Pulse-Type High-Voltage Supply, by sieren and Kerkhof, Proceedings of the L R. E., March 194B; e

VOL 36. DD. lOl-A07.

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