US2504699A

US2504699A - Tube protective circuit

Info

Publication number: US2504699A
Application number: US665365A
Authority: US
Inventors: Edward C Kluender
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-04-27
Filing date: 1946-04-27
Publication date: 1950-04-18
Anticipated expiration: 1967-04-18
Also published as: GB635875A

Description

A ril 18, 1950 E. c. KLUENDER TUBE PROTECTIVE CIRCUIT Filed April 2'7, 1946 Fig. I.

Inventor. Edward C. Kluender,

DRIVER His Attorney.

Patented Apr. 18, 1950 UNITED STATES PATENT OFFICE TUBE PROTECTIVE CIRCUIT Edward C. Kluender, Schenectady, N. Y., assignor to General Electric Co New York mpany, a corporation of Application April '27, 1946, Serial No. 665,365

might resuit'i'rom a short or open circuit in the antenna or other load connected thereto causes. the radio frequency component of space path,

voltage greatly to decrease, thereby causing a greater average space path voltage during the conduction time of the device. The energy dis sipated therein is accordingly increased and, un-

less steps are taken immediately to disconnect the Space path potential source, destruction of the device will result.

It is an obJect of this invention to prevent accidental overload of electron discharge devices in energy converting equipment.

5 Claims. (Cl. l79171) 5 1. In the figure, curve electrode voltage applied to an electron discharge It is a further object of this invention to provide improved means to prevent overload of electron discharge devices in energy converting equipment, which means does not interfere with the normal functioning of the equipment for its intended purpose. while at the same time is capable of immediately interrupting overloadgerous operating temperatures are approached.

Yet another object of this invention is to 'provide overload protection for an electron discharge device used in power conversion equipment in a manner simple of construction and reliable in operation and readily applicable to various types of power conversion equipment.

j The novel features characteristicof my inven-' tion are set forth with particularity in the appended claims. My invention itself, however,

both as to its organization and method of opera--,v

tion may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 shows thereof or producing a suitable signal when danone method whereby electron discharge devices maybe overloaded and Fig. 2 shows an embodi ment of my invention capable of preventing this overload.

" By way of illustration, the method by which" class Cradio frequency oscillators and amplifiers mayjbe accidentally overloaded will first be described with reference to Fig. 1. It will be understood, of course, that this invention is applicable to protection of electron discharge devices used in power converting equipment generally and is not limited to this particular application;

' device.

average value of space path voltage is no indica- 2 L A represents the controldevice operating in the class C condition. In this case the negative unidirectional bias voltage 0Y maintains the control electrode voltage E; below the cut-ofi bias OX except during ,a small portion of the positive portion of each cycle. The

corresponding cathode-anode space path voltage is shown in curve B. This voltage consists of a sine wave voltage of radio frequency Ep super imposed on the unidirectional space path voltage OZ. The radio frequency component of this voltage is 180 out of phase with the control electrode voltage so that minimum cathode-anode voltage exists at the instant of maximum control electrode voltage.

control electrode voltage is less than the cut-off bias value and hasa sharp peaked wave shape Ip when the bias is above cut-oil.

The energy dissipated within the electron dis-,- charge device is determined by the integrated product of instantaneous space current ilow and space path voltage. These two values under nor mal conditions of operation are shown in the cross It should be noted that neitherspace path current flow nor space sectioned areas of' Fig. 1.

path voltage. drop of itself is a measure of this energy as a high value of one of these factors;

accompanied by a lowyalue of the other, maynot involve any increase in energy to be dissi-- pated. Hence neitherspace current flow nor space path voltage may be used to indicate the energy dissipated. within the electron discharge It'should further be noted that the tion of the energy dissipated within the electron discharge-device inasmuch as the space currentflows only during a portion of the cycle, this por--- tion corresponding to a period of minimum space path voltage. Hence, average space current flow cannot be combined with average space path voltage to measure the energy dissipated Within the electron discharge device. I

If maladjustment of the tuned circuits, a change in load impedance (such as an antenna short circuit or open circuit), or other event reduces the. alternating component of the space path voltage. across the electron discharge device, the space. path voltage during the instant current fiow occurs is increased as shown in the dashed curve labeled Ep', Fig. 1. This increased space path voltage causes a corresponding increase in space path current during the period of current flow as shown in curve 113'. These two efiects combine to cause an exaggerated increase in the energy, dissipated within the electron discharge device and, if the change is great, will quickly cause the r 9 e h a ca b eca e Often s Curve C shows the cathode-; anode space path current of the electron discharge'device'. This current is zero so longas thean anode, a control electrode, and a, screen grid 7 the. value of'ithis voitagfheingidterrninedibythe,

'tected in accordance with the princiiflesof this invention. In the figure, anelectaton device is indicated at I having-aheaterhcarthpd ag electrode. Radio frequency control electrode voltage is applied to this device 'fion'r drivers through coupling condenser 3. Unidirectional, control electrode bias is derived from voltage source 21 through radidfrequency choke coil 25. The voltage of source 2"! is-' cho sentojpil'odiice sufiicientnegative' potential atfthe control elec ti -ode" of devicei tocause" that'devi'oe" to" be biased: tocutoff except eurm me aesnee nor: tioncf ther-adio *frequenc'y' controlelectfod 7 volt?- age: curve; condensersbypasses radio? as; quency currents abon't source 21? Ca thode screen electrode spacepath voltage for device I is supplied from unidirectional voltage source through-relay-contactsTf Condenser ajbypassesf to-g round' anyradio freuuency voltage: appearing at the screen- Cathode-anode space, path voltage for device'1' isisuppliedirbhr unidirectien'a1- voltage'-sourcethroughf relay contacts; and radio frequency choke-won If)"; Itisf "the. purpeseof the latterdviceto prevent. source" F from bypassing radio frequency voltages from; the anode to reunde 1 I The anode of dvice i is: coupledhy'tondenser II- toa utilization' circuitishown gerreralhiiat I 2?, This circuit consists ofaresoriantfcircuithavifig a' load-such as'a'radiatingjantenna cqupledjtditl For purposes of explanation; it I isfshowr'r. as an.

' a'pproxi-rnateequivalent "circnificomprising corr l" denser'I3'; inductance Iitj andjresistane :11 Undernormal=operatingconditions;the resonant frequency ofcondenser" 'I 3and inductahcefllfcor responds to "the frequency-of-*the"applied:cbntiolf. electrode-voltage and the -value "of resistance 15} issufiicie'ntly larg" to roduce-0mg aifinited errect on thisfrequencyz" As 'expiainedapovefany maladjustment; short'circuitj or open circuitwilli cause device'- I 2"-to' heniistunedj thereby;- causing? a; decrease in the-impedance thereof: anfr'edil e ingthe radio frequency 'vol'tagefatithe'anodeof 5:0

device I: This correspondingly?" increases the losses within that devicei I The protective circuit-flier device 1 "includes 7 re? lay I6 and electrorr discharge dvice It is" the ur ose of the iattefdvicetc'fproducea 111112; direetio'nar voltage varying "i accordahcwith" the alternating componenttofsp'ace patl'r"'voltage: of device I. This' is' accomplishedfby" coupling? part of'the voitageacross'utilitatiorfdeviceil23:6 device I'I. This couplihg'fis' provided" bY'thf' capacitive voltage "divid'r comprisih'g capacitors,

parallelcombinationpfresistancei2i'fandjcapaci the periodof theradio rrqueneywaves-across utilizationdeviceI 2': 'rhis, causes"a-"supstantiailyf constant voltagato appear aeross resistancefi I radio frequencyyvoltagefacross: device I2; Th

r or device I from source 6.

. trodespace-current flowiirdevice I diic'edTby amplifying "the r A v p before applicationtode polarity of this "'voltage is such cause the 7 5 cathode of device I! to become positive with respecttoground' potentfaka Z k r relay; shown generall""at24';"is' provided to disconnect the anode and screen grid electrodes Current flow in coil L6 opens contacts 1 and 8. Operating coil I6 is con'riectedbetween the cathode of device I and the: cathode of device} I! so that the current flow therethroug-h; depends on the difierence between the relative voltage; at these points. 'When this I difierence exceeds a predetermined value in either direction; therelay operates, thereby opening contacts I and 8 to disconnect source 6 from the various electrodes of device I and preventing further spacepath energy flow to device I. 7

when an -inerease--iriaverage foathdde afilide space current" flow-in device I takes" place, the voltage d1"op-aci'ossresist 'nc'e" Wis accordingly increasedi This vifltage'dfp is" substantially constant by reason-off the smoothing? actio'r'i' of capacitor -5 However, ir-pa correspending; crease in radio frequency output'voltagtakesl placey-the'voltageat the'cathodeofdevic ITwiil be raised; thereby p ev-landmine increa's" rent "flow in operatingf coil" IS that would ther wise be associated" the in cre edspace cur: ism-flow; l-lcwevenif'irodh'cr in graditifrefquency output voltage" takesier 1; e potential. of the catho d-e ofd'evice ITwillreinainfcohstantf a'ndthe'-greater-catho dejvolfiagei device I- Willi r V overload is imnrirrentwlfile permitting lloadYin;

creases that do not involve such overload? It will be noted thati'twcathdd sereen e e resistance 4 and influencesperformaneeofrehy zfl accordinglyr Actuallyi 'thi's eurren't'is' sb small compared to the cathocfe-arro pace'path cuff rentthat thee'ffec'ts "so 'produfceti areliot 'signifi cant'inscfar as-rel ayfi is concernedi If; throu'gir-sorne changes-Entrie-amplifiererr: cii'itiardbadFth'e radicrfiequency outputvoitage' of device'l' is decreasedithe potent i of devic'e I Ms-cqrre nd V, p w p v chane'is' accompani V I y i ction in space current flow ofsufficient "magnitude? to "prevent V overheatingoffdvice I3 a; c m'sponamg redue tion inthe-cathodepotential fofthe latter? device-f will time place and n iner'easedf current new On the other hand; i thej spa c'e'current fiow ifi device il is-not reduced? the vortageiatth'e 'cath- I ode or device FWiH" remaifithe" 'sarne' j and" relay 2E will" operate, thereby preventing? the'ftube? damage that-would"0therwisbe 'associatedwith; this condition: j V e V f p 7 In" general; 1 prefer to: chooseresistance" 4 to:

I have the smallest:resiStancepbssibIe tirerebyre ducingfj 'the power; los'sassocia rdfw'ith thefpresjence ofthisf resistanf'ceiin the 'space "path u'rr'ent-fj path ofdevic'e I. Thispowerlossms Wel impedance efiects, associated with, condenstje 8;' I9; 256; and "22", reslsta, cesiiif an df'23jj and "device l'liimay be even furtherrreddeediby' actuatingyr' lay 24f'from a separateErriplififpioiiidd.for [thej purpose; Furthermore, the. effects. offthe coiitrbll circuit; acrossiutilizatiofi device; ITniayfbf rd': requencyybltageg If desired, tiine'fidelity apparatus iri'aybe'prm' vided in connection with relay 24 even further to improve the performance of the circuit. In this case, the time delay is made to correspond with the thermal time constants of the elements of device I so that the relay operates only after a time delay determined by the ability of device I to stand short time overloads.

If desired, relay 24 may be a single pole relay connected only to interrupt the supply of screen electrode potential to device I, choke coil Ill being directly connected to the positive terminal of source 6. In this case, device I will be protected from overload by loss of screen electrode voltage, an event sufficient to avoid overheating in most cases. Alternatively, relay 24 may be connected to actuate an alarm device, such as a bell or light, thereby to warn the operator of the equipment and enable him to take appropriate steps to prevent damage. It will, of course, be apparent to those skilled in the art that operation of relay 24 may be made to cause these events as well as many others without departing from the true spirit and scope of this invention.

The term energy converting equipment or energy conversion system as used herein refers to equipment wherein an electron discharge device is used as a means of converting energy of one type, as for example, unidirectional voltage, to another type, as for example alternating voltage, and characterized by the fact that the power dissipated in the electron discharge device is determined by the difference between the applied energy of one type and the output energy of another type.

While I have shown and described my invention as applied to a particu ar system of connections and embodying various devices diagrammatically shown. it will be obvious to those ski led in the art that changes and modifications may be made without departing therefrom. In particular, the methods described herein may be used to protect electron discharge devices in circuits other than the class C radio frequency amplifier shown, such other circuits including, for example. class C oscillators, class A oscillators and amplifiers, and class B oscillators and amplifiers. I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a high frequency electron discharge amp ifier having an output circuit coupled for energy transfer at said high frequency to a load impedance, means to derive a first unidirectional potential proportional to the peak voltage at said frequency developed across said impedance. means to derive a second unidirectional potential proportional to the average space current in said amplifier, relay means actuated by said potentials when the difference between them exceeds a predetermined value, and means controlled by actuation of said relay to limit said space current to a safe value.

2. In combination, an electron discharge amplifier having input and output circuits, means for supplying oscillations to said input circuit, a resonant load device coupled to said output circuit and tuned to the frequency of said oscillations, peak voltage rectifying means supplied with oscillations from said load device for developing a first unidirectional voltage, resistance means common to said input and output circuits and shunted by a low capacity at said frequency for developing a second unidirectional voltage, and

relay means responsive to said voltages for removing operating potential from said amplifier when the difference between said voltages exceeds a predetermined value.

3. In an energy conversion system, an electron discharge device having an anode-cathode space path, means to impress anode operating potential on said device, a utilization device, means to supply power from said space path to said utilization device, means to produce a first unidirectional voltage which is a function of the current in said space path, means to produce a second unidirectional voltage which is a function of the voltage appearing across said utilization device, a relay having an operating coil, means for impressing said voltages on said coil in opposing polarity, said relay being arranged to be actuated only when the difference between said voltages exceeds a predetermined value, and means controlled by actuation of said relay to limit said current to a safe value.

4.. In an energy conversion system, an electron discharge device having a cathode, a control electrode and an anode, means to apply oscillations to said control electrode, means to impress anode-cathode operating potential on said device, a utilization device, said last device including a resonant circuit normally tuned to the frequency of oscillations from said first means, means connecting said utilization device to said discharge device, means to produce a first unidirectional voltage proportional to the average value of space current fiow in said discharge device, rectifying means energized from said resonant circuit to produce a second unidirectional voltage proportional to the voltage across said circuit, a relay, means for impressing said voltages on said relay in opposite polarity, said relay being arranged to be actuated by said voltages only when the difference between them exceeds a predetermined value, and means controlled by actuation of said relay to limit said space current to a safe value.

5. In combination, an electron discharge device having a cathode, an auxiliary electrode, and an anode, means to impress anode-cathode operating potential on said device, means to impress operating potential on said auxiliary electrode, a utilization device, means to cause said discharge device to supply converted energy to said utilization device, means to produce a first unidirectional voltage proportional to the converted energy supplied to said utilization device, means to produce a second unidirectional voltage proportional to the average value of anode-cathode space current flow in said discharge device, and means responsive to the difference between said voltages to disconnect said second means from said auxiliary electrode when said difference exceeds a predetermined value, thereby to limit said space current.

EDWARD C. KLUENDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS