Oct. 7, 1952 C. F. Otls ET Al

Oct. 7, 1952 c. F. oTls ET Al. 2,613,334 ELECTRICAL SYSTEM Filed Jan. 18, 1952

lNvENToRs CH/IRLâS E 07/5 BY ¿Ul/)5mn H. .STH/9K5 MMV.: ATTOR Patented Oct. 7, 19‘52

` Charles F._ t Philadelphia, Pa., assígnorsto,` Philco Corpora- - i »_i f tion, Philadelphia, Pa., a corporation o'i’ Remb“U ‘ A Sylvania. nppiieationianuaryis,1952,seria1n0.2s7,i4s‘ ' `s claims. (ci. 31a-27).» t This invention relatesïto electrical systems and yoke'duringA theVscan'ning cycle may 'bèfdissi more particularly, to< _improved èlectromagnetic pated to a greater or lesser extentby means of "a systems of the type `commonly’used4 for deilecting suitably poled damping tube. Preferably; this Y the beam of av catliode•rayïtubeadapted to prof energy is‘rec‘ove'red, foi-example, by >~means` of‘a duce a television image. "j ' j j ¿ì , ` l so-called “boost"‘circuit`~which converts-'the mag- ‘ In their‘usual form;A electromagnetic deflection netic field energy into additional Supply` energy systems for the beam of a cathode-ray tube com- for the source. -Sucha boost circuit may take the;l prise a scanning' yoke‘induçtor‘whichsurrounds a“ form of acapacitor coupled in series "with'a‘vrecti portion of the tube` infc'ooperative relationship ñer- whichusually isf the damper tubeabove re with >the cathddeH-‘ray beam,'a source ofa deflec 10 ferred to.` This series combination is "connected tion signal forenergizing?the yoke, and a cou in shunt with thel yoke insofar as'yoke currents pling systemby which’the source is coupled to are concerned,` and in series vWith‘the anode sup- " the yoke in proneA ¿impedance matching rela ply‘of the source tube insofar as direct-»voltages tionship. " ` ’ ` ‘ ' ` are concerned. The energy source for the electromagnetic de- ‘ Because of the leakage inductancereferred td' nection system`> generallyv comprises a _ìmultigrid above, the boost circuit -is ‘tunable to recoverall of'v electron discharge tube of thebeam tetrode or the energy stored in the' deflection system at the pentode type, such-"tubesibeing used because of end of the deflection cycle'.l y This unrecovered en their large power sensitivity; Tubes of these ergy hasbeen' found ‘to Produce spuriousoscil types are characterized by relatively `high plate lations or` ringing currents in ythe‘trans‘formerV resistance values. _Whereasin Iits usual form, the windingsfÜTh'ese' spurious‘oscillations are un scanning yoke `thas" an impedance which is’rela desirable from twostan’dp'oints.’ `First, they may , tively small., Iri vvorder to‘achieve a satisfactory` be radiatedfi‘om the "circuits in which they ap? impedance match, the _coupling ¿element between pean‘f causinglfi interference in Äthe' nearby radio , source and yokejis 'thusjnecessarily a step-down and television equipment. Secondly, 4tlieserlng i coupling element. Thefcoupling element generf ing currents: are` coupled toptheïlanode 'of the ally takesjthe form‘gof aÄítransformer the input tube constituting~~the source, and vvary tlie‘anode` and output windings of vvvhic‘zh are appropriately potential duringthe Vflybaclr period. In practice, related as to their numbers of `turns, to produce these spurious oscillations may have ysufll‘cie‘nt the desired impedance ratio. Ìn one form, the 30 4amplitude to cause theanode toîassume periodi transformer maybe an autotransformer having a ` callyl a. considerablyfnegative potential "with `:re- ' single winding `With appropriate taps, to which spect to,` theY screen grid of Vthe tube,` and mayk taps the source vandthe yoke are connected. even cause the anode; »to assume a negative `po-` Most‘efficient energy transfer occurs when the tential `with respect tothe cathode òf the tube» s coupling between‘the ‘sourcejandyoke is unity.` It hasloeen >found thatfwhen theïpotentîal of' Howeven‘in view ofv the different numbers of the anode of a beam tetrode or pentode undergoes i turnsof the input .and output windings, unity variations ofthe above type, -the negative 'voltage « coupling cannot be fully achieved. The departure gradient between thegscreen grid V,and the ànode from unity coupling >manifests itself as a leak.; may -bringgabout furtherspurious oscillations of . age inductance effect, vthe magnitude of which is primarily determined bythe geometry of `the 40 thetype known as transit-timeoscillations, and more especially, asÍBarkhausen-Kurz ¿or Gillê-v y windings.` Y ` ` ` “ , Morrell ,v oscillations. ~ l These oscîllational whoseÁ In the normal scanning cycle of the cathode frequencyisa function o_f thegeometry of.' the ray beam, the beam, starting from a given posi tube, the tube electrodepotentialsand the exter tion, is advanced in ‘one direction at a fairly uni 45 nal circuitry associated with the tube, may occur ` form predetermined velocity and, at the vend of over a wide range of frequencies-.fof theorder of4 ¿ the scanning cycle, is returned to its initial posi- ` fifty tothousands of ina/sec. „Such highire. tion. These movements of the beam maybe pro quency 'currents have associatedwith them elec duced by applying a signal of suitable Waveform 4tromagn'etic,Waves which àre ,readily radiated to the source, e. g., a sawtooth signal which, at 50 bythe tube4 and ìts associated .circuits to sur the end of the Scanning period. cuts off the source . rounding circuits of the-cathode-ray'tube, e. gl. , for atleast a part of the flyback period and causes , a collapse of the magneticfleld in the coupling te the videdcircuits‘of the receiver. Unless spe-, cial precautions are taken;y these'radiatio'ns may ` transformer and the. deflection yoke.- The energy overload the video-signal systemof `the receiver,` which has been stored in the transformer and Oi Ul and degrade the image seen upon the screen of ' > 2,613,334

the cathode-ray tube. I In some instances, thel ringing currents and lhas la high impedance at -presence of vthese oscillations are manifested by the scanning frequency. 1 irregular~ black lines onzthe screen of the cath- ,Y The invention will be described in greater de - 1ôde-rayftube, which lines are substantially per- ~ tail with reference to the appended ldrawing ,pendicular to the :direction of scanning, and forming part of the specification, the single' iigure „ points of which lines usually occur‘near the start of which is a schematic diagram of a magnetic denection system èmbodying ythe invention. of_1t the nasfbeenfproposodtoï'euminate scanninglines;l - tnësetìansitr ,Referring .tothe drawing,V the ldeflection sys „ `time oscillations by modifying the structure' of ‘ tern there shown comprises a source tube I0, an . the tube» serving asy the scanning signal source.` ioy autotransformer I2,'and ya yoke 32. -Tube I6 ~ i' Such a procedure, however, considerably increases comprise‘sl'fa cathode I4, a control grid I6, a screen v '_the cost of the tube and has been found to be not grid'IIB and an anode 20. (Although tube l0 is specîiicallyV shown as a beam tetrode, it is ap effective forall circuit arrangements: _ »v j . y' 1 ,',Another proposalV has 'beenâ to >shieldv `,c_iarefully L'parentithat'the source tube'rnay be a pentode or ' Athe ' circuits in lwhich the transit-time »oscillations Vother.,multi-’element tube.) The control grid I6 are likely to arise. While shielding may' reduce , is energized by .a vsuitableA sourceof scanning po l image degradation by attenuating the radiated. . tentiall (not shown), said source Vproviding a ' scanning signal of generally sawtooth waveform „ . Waves, itis an expensive expedient, particularly Ap ' »y in assembly -lineÃproçïluction~ Furthermore; since . in accordance with Well-known practice. ` shieldingI does nothing to eliminate the transit proximate operating potentials are .applied` to time. oscillations themselves,_ the loss. of , energy> the control grid _I6 and the screen grid I8 from a n repreysen'ßfëíl''therebyV reduces the efficiency ofthe Í sourcel_.(notshown).`V> f . ,. o . 'I‘heautotransformer I 2 comprises three> wind-` v scanningacircuit. o , . Ü ‘j p ` v , ~ -f w , v y l,It hasalso beenïvproposed ,to preventthese os ing sections, 22, 24 and 426, connected in series. V „ cillationsbyreducing the screen-'grid yoltag'e of The anode ¿Ill of vacuum tubevr I0 is connected the source Ytube during the ñybaclc Vperiod._ How-_ to the -junction 30 of _sections 22 and 24, whereby . ever,¿this' ymethod requires A'auxiliary equipment, the windingI sections 24 and 26 together serve .thefëoperationrof which.` must be carefully syn. as an output coupling impedance for the tube I0, ' . c_hroni'zed-çin order, that` the screen grid potential whereas theyoke 3_2 is connected to the junction is,reducedto-the‘çproper .value at‘tlie proper time. 30 64 of_..sections y24 and 26, whereby the 'yoke is .. It is'anobject of the inventionto provide an coupled to the winding 2,6.~> In accordance with well-known practice, the turns ratio of the wind’- . ing sections 24 and 26 is so selected that a desired ‘ ' nother object of the invention'_isîçtofprovide impedance match between the tube I0 and the yoke >32 is eil‘ected. ` _ an- improved magnetic deflectionA scanning‘cir Winding'section 22 ...is the usual high voltage rcuitq-ini-Iwhich spurioussignals >are reducedv to a winding lhaving a terminal 28 which may be con` tolerable value A«or‘ eliminated. ' ' nectedl't'o la suitablerectiñersystem (not shown) ' À> further i obj ect ofthe inventionïislto provide ~ anj improved„magnetic` deflection scanning cir for supplyingan accelerating potential for the 40 beam'of the cathode-ray tube. cuitf-injuwhich radiationoi .spurious signals is The ‘anode 20 of tube I0 is supplied from ka `reduced -».to.¿a; .tolerable f ,value or eliminated.V - suitab1e.D.`C. source. 4(not shown), introduced at . A f specific: -object of :the inventionY is -.„to pro-' Br'terminal V44, and connected through a voltage vide an; ~,.improved> magnetic fîdeflection »scanning boost circuit comprising a diode 36 and a boost circuit which is, substantially'éffreeï from transit capacitor 46. Diode 36 has .itscathode 38 con time"-cscillatio~ns».«jl . . - 1 nected vto' the junction 34 and its anode 42 con g A2 still further vobject oftheinventionis’to pro nected to'thef'Btjterminal 44. Capacitor 46 in-> _ videuangimproved magnetic deflection scanning te'rconnects lthe anode 42 of tube 36 and the ter circuit» characterized by.. siinplicityri'o'f? circuitry min'al '.46 of thewinding 26.. ' and 4lovmicost.VIK „ A 1 ‘ In the normal operation of the scanning circuit, ¿According-‘to the invention, the .foregoing ob- r energy, is stored§’during the scanning period of jects arefachieved, invanßelectromagnetic deflec thebeain in the transformer 'l2 and the yoke 32. tion systemvof `the above-describedA type; by pro At the endof the 'scanning period the amplitude viding‘a' low‘ impedance Apath. for the ringing cur- y of thefrsawtooth'voltage applied to grid I-6 under rents,'_lfrom the-anodeI o'f the 4tube serving as a 55, goesfa'sudden change, with the result that the deflection-'energy source tothe damping orv boost anode current of source-tube III isl suddenly cut componeiitföf’~ï‘the deilection circuit.` By'means on”. ' This current'` cut-off causes Vthe magnetic of"the‘ilow` impedance `pathso provided, varia field of 'transformer I2 to collapse. The collaps-~ „ tions-‘bf-“ïthe 'anode ¿potentialrwhich normally ing magnetic field induces a voltage across the occu?atfthefrequency or frequencies ofthe’rìng 60 winding sections/'of the transformer, of such po ingÁ currents generatedf‘be'cause of the 'shock larity as to place terminal 28 lof winding section . excitationlof‘fthefleakageinductance in _the cou-,p 22 at a high posi-tive potential with respect to pling transformer, arediminishedgf The anode ground. As already discussed, terminal 28 may is' thus prevented from assuming a potential suin be connected *to> a, suitable rectifier system (not ciently negative with respect to the screen grid, shown), so that part of the transformer energy particularly at or after the `time at which'the is> used to providean accelerating voltage for the sourceV tubeobyegins to conduct„to produce the _beamof the cathode-ray tube. ` , transitf-time «oscillationsabove referred to. >In rAfseco'nd r'voltage ípulse is further induced the preferredarrangement of the invention, this across "sectioni26, by the changing magnetic field, lov/*impedance path between the anode of the 70 of such ' polarity that the diode 36 conducts source and the damping or boost circuit is a pas through the series path constituted by the di sivey electrical network which comprises a series ode,I the capacitor 46 and the parallel combina capac'zit'or-'infçluc1~zorA circuit, the components of tion of the Winding section 26 and the yoke 32.` which haveivalues'so rselected _that the circuit Anj‘additio’nal partl of the energy existing in the lhas "a low“ impedance at theA frequencyof the .15 transformera and the yokeaz at the end of the ¿hasta e" scanning vperiod- is vaccordingly' fsupplliêCíÍlëf-i '61.151 Thel‘value‘of the d ` ping resistor fdeterè " capacitor 46. This energy charges rthecapacitor mined by the amount of energystored in theinf- ` 46 in a direction such that the yvoltage’ there-4 ductor ànd is fselectedV so/that the ìmpedance of across is in additive series relationship to the the network ‘56,’ remains suii‘iciently flow toV pre~ voltage at,B1+. so that the anode 20 of‘tubeißf; ventthe`> ringing currents ìnduced inthe trans is thereby energized at a totalvvoltagegequal to vformer:windings fromcontin'uing‘lfor a time be-V ' the sum of the B-l- voltageand the voltagejacross ‘ _ ` i ` I0 „begins >to; `conduct."` capacitor46. , » . , ` Typical‘va1ues` for resistor54in _a network 56 Because of the leakage inductance of the trans-__ which embogdiesan inductorjand capacitor ‘ofV the former winding sections, al1 of the stored ‘energy’ values given àbo fe, *_rangrejjfrom ten thousandxto is not'recovered by the‘high voltage system cou'-u ` thirty thousand Lohrfns; pled to winding section 22, and by"the.boosftlcirfl ‘I‘he `_above-noted values Vfor capacitor 5U, in` l cuit. The remaining part of theenergy causes diictin‘ji.’> ‘and’ resistor 54‘ are given .in comico-_` ringing currents to be set up in theresonant sys,- 1‘ tion‘with ‘a'"transformer system‘havingga `self tem constituted by the aforementioned leakage y resonant frequency of the order of’ï220-“kc~l/s. *as* inductance and the distributed capacitance'` as,` above specifically described. ' When ringing cur-f sociated’with the. transformer windings', which rents of frequency `_'other than `that specifically ringing currents »flow in winding`24.y It has been \ described "are induced, the values Vof Vthe kcapaci~ found that these ringing currents are normally` tor"5ll,_inductor-52> and resistor 54 are‘modiñed of suilicient magnitude to cause the anode> 20 of 20 tube l0 to be periodically‘driven .to a. potential , appropriate1y,"as` will be readilyl‘apparent to those ’ considerably negative with respect to screen grid ski1ledin`the1art.„ ` . . . , . I8. The ringing currents are of sufficiently long The `‘preceding‘discussion has assumedrthe ex duration so that the'periodic lowering of the` po- . istence ‘of spurious ringing', currents at only one frequency. " In some instances, the transformer tential of the anode of tube l0 continues until 25 ' conduction in the tube l0 is again initiated by I2 mayfexhîbit a plurality of such. ringing curn` the sawtooth wave applied- to the control lgrid I6. , rents, each occurring at a dìfîerentïfrequency, in . Under these conditions, wherein af conduction which „ Acase »additional-4 sériesereslonant »circuits path is provided through the tube i0, andthe (not shown) ì. conforming _; to'fthe characteristics of> anodethereof is at a large negative potential with .network 56, mayY be connected between junctions respect to the screen grid thereof, the criteria for 30 andf34, each suchseries-resonant circuitbeu generating transit-timeoscillations inthe tube“,` ing tuned to the‘frequency ofgone of» thesaid I0 vare fulfilled. ringing currents.4 , ‘A 1, l « ¿_ - l In accordance with the inventionithese transit- Í While the network ».56 ‘has ,been shownf to be time oscillations are substantially.,.suppressed by connected across the wholegof the-winding "24, ìn ' insuring that the anode 20 does not assume an some instances‘it has been :found that satisfactory" excessively negative Vpotential with respect to suppression of-_the ringingk currents in the wind' screen grid I 8 during the conduction period of ing section 24' maybe eifectedby connecting the tube lil. This result is accomplished in accord network 56 between thejunction 30, or- the junc ance with the invention by means of an aux 40» tion 34,»and a-tap-on winding section 24 interme iliary path coupled between the winding sections diate to» the_ junctions 30 andvv 34», orlbetween a of vthe transformer I2 and the dampingrdiode‘SB‘. tap on winding section 22 and; a tap on winding This auxiliary path is so constituted that it pro section 24. d . ` .. i » i i l vides a low impedance to the ringing currents, While Werhave~described ourunvention by shunting them to alternating current ground po‘ 45 means Vofspecific examples andin specific em tential through the diodev 36, while" nevertheless bodiments, we do not wishwto-‘be limited thereto, providing à high impedance `path for theîscan» for obvious modiiications•ïwill occur» to those ning currents in the transforrr'ierj,` _As show_i‘rgin skilled in the‘art without’ departingfrom the the drawing, this path` is‘an electrical network spirit’and‘scope‘of thei vention. Y "ï F ì 56 which comprises a capacitor 50 and an in ductor 52 connected in series, and which is con 1. A magnetic deñection system comprising a nected between the junction 30 of the trans pulse signal source operating at a given repeti former and diode cathode 38. Preferably this tion rate, a transformer comprising a plurality path is series resonant at the frequency of the of winding elements connected in series and ringing currents so as to provide a desirably low 55 ‘susceptible to‘ringing currents at a frequency impedance at the ringing frequency, and a de different from said repetition rate, means to sirably high impedance at the scanning fre couple said winding elements to said source as a quency. In a typical arrangement, in which the load therefor, a deñection element coupled to ringing currents in winding section 24 have a one of `said winding elements, means to damp frequency of the order of 220 kc./s., the capacitor 60 oscillations in said one winding element, vand 50 may have a value of 56 micromicrofarads and means to suppress ringing currents in another the inductor 52 may have a value of 9.5 milliA of said winding elements, said last-named. means henries. comprising a network shunting a portion of said In some instances, the inductor 52 may store other winding element, said network having a sufñcient energy to produce ringing currents of 65 low impedance at the said frequency of said ring-r its own and thereby partially nullify the sup ing currents and a high impedance at a frequency pressive action of the path shunting the winding corresponding to said repetition rate. lsection 24. In accordance with afurther feature 2. A magnetic deflection system as claimed in Iof the invention, these ringing currents in the claim 1, in’which said means to damp oscillations inductor 52 are attenuated by means of a damp 70 in said one winding section comprises a unidi ing resistor 54, which, as shown, is connected in l rectional electrical conductor. and in which said shunt with inductor 52, but which, as is well means to suppress ringing currents in another known to those skilled in the art, may be con of said winding sections comprisesan electrical nected in series with capacitor 50 and inductor _ network, one terminal of which is connected to 52. v75 the source and a second terminal of which is