US2403716A - Combined amplifier and power supply circuit - Google Patents

Description

Y 94 HIGOLDBERGETAL N 2,403,716

COMBINE 2D AMPLIFIER AND POWER SUPPLY CIRCUIT Filed Feb. 7, 1944 2 Sheets-Sheet l 5 P l [M :m A a MAGNATRON DRIVER AMPLIFIER 1 -U UUI 6 8 N I COAXIAL.

I LINE o.c. men VOLTAGE I POWER SUPPLY 0.0. l Bmq/fl GENERQTES I q u| s s INDICATOR v W MODULATOR v 1 ANTENNA IN V EN TORS WFLTEE 6. THOMPSON H/ZQOLD 60405526 FTTOE/VEY July 9,1946. H. GOLDBERG ETAL 2,403,716 COMBINED AMPLIFIER AND POWER SUPPLY CIRCUIT Filed Fel a. 7, 1944 2 Sheets-Sheet 2 DRIVER DRIVER 2 LOAD INVENTORS Patented July 9, 1946 Es PAT-E-NT COMBINED AMPLIFIERA ND POWER 4 Y SUPPLY CIRCUIT 3 Harold Goldberg, Irondequoit, and Walter 0.1 l Thompson, Rochester, Stromberg-Carlson. Company, "Rochester, Yr,

Y., assignors to a corporation of New York- Application February '7, 1944, S eri al,No. 521,450 I TCIaimS. (Cl.'17197 This .inventionrelates to combined amplifier and power-supply circuits. i In a. radio locator and especially in a radio locator of the pulse .echo type, there is utilized a.

so-called driver which applies periodic pulses of relatively high voltage, such as nine hundred volts, to the grid of an electron tube included ina so-called amplifier-clipper. A highvoltage power supply unitsupplies to the amplifier-clipper, a high anode voltage. For example, in one particular locator this anode voltage is of the order of fifteen thousand volts and the amplifierclipper supplies to the load, a clipped and squared pulse at twelve thousand volts and twelve amperes.-

In the. past the power supply and amplifier units utilized what wasconsidered to be the irre ducibleminimum of components, However, in

accordance with the present invention,the numsuch equipment in aircraftfiyingat high altitudes under extreme conditions of, temperature and humidity. w vFor a clearer understanding of the invention, referenceis made to thefollowingdescription and claims when taken with the drawings in which:

Fig. 1 is adiagrammatic showing of a radio locator system having a modulatorincluding a combined amplifier-clipper and power supply of the present invention indicated at the left of the broken line and having-at the right ofthis broken. line a given load- ;such as:a transmitter with its related means @for; transmitting exploring pulses and a receiver with its indicator for the-returningor reflected exploringpulsesy l 1 Fig. 2 is ashowing of a conventional. amplifierclipper with its half wave power supply; Fig. 3 is a showing of afull wave doubler rectifierwhich canrbe substituted for the half. wave rectifier ofFig. 2; l i i H Figs. 4 and 5 aresuccessive steps in the improvement inq-the circuit arrangement of Fig. 2;

6 and 7 are successive steps {in the immovement in the circuit arrangement ofFig. 2 whenthe half wave rectifier thereof is replaced bythefullwaye-rectifier-of Fig. 3;yand

Figs. 8 and 9 arediagrams ,useful in setting forth the, electrical characteristics of a rectifier tube and a transformer, respectively. p i

i 2 In. Fig. .1, there is illustrated a diagrammatic showing ofaradio locat or system in which the present invention isincorporated. At'the left of the broken line inthis figure, there is, illustrated a modulator comprising a driverf5 (which genera ates control pulses?) with itsadirect current supplyjfi together with the combined amplifier-clipperwcircuit ljarid power supply circuit Bof the. present invention; The amplifier-clipper delivers,

pulses Pl; Theportionof thelocator systemat "the right of the. broken line,"butuforniing no part :of the presentinvention, comprisesa magnetron transmitter 91 todeliver radio frequency exploring pulses PZand also comprises a receiver 12 with itsiindicator I3 together withatransmitter and receiver switch unit II for alternately connecting the transmitterand the receiver to -.a coaxial line Ida and thence to an antenna assembly ltr J v. v The presentinvention is] particularly directed.

3 to the amplifiereclipper circuit], together with 13+ connection of wave rectifier (Fig. 2") comprises a diode D, a filter.

a highvoltage direct cur ent power supply .8. A conventional form ofthese circuits .usijngla half wave rectifier, is ,shownfin .FigLQZ; Likewise a conventionalrform of these circuits results when i the full wave doubler rectifier shown in @Fig. 3 is substituted for the ,half. wave rectifier whichis disconnected .atlterminal marked Bfl-land the nected to that terminal. 7 i i In accordance with knownpractice, thehalfcondenser C] and an iron; core transformer T connected to an alternating current source A. C.,

- as shown. Alsoin accordance with knownfpracrice, the full wave rectifierdoublerof Fig; 3; comprises the two diodes D and DI, filter condensers Cf, Cf and the iron core transformer .T con-.-

'nected to'a source -of alternating current A. C., as

shown. No explanation of. the operation of these rectifier circuits or their relative advantages is necessary since they are well known.

The amplifier-clipper (Fig. 2) includes a tetrode Iiihaving a control grid IT, a screen grid IS, a

cathode is and ananode 23, the screen grid being i normally supplied "with a voltage Vs." It will be understood-that a triode or pentode tube maybe used instead .of the tetrode It; -When in use, the

tetrode or amplifier tube 16 is ordinarily biased to cut-oil, so that during the time that no pulse P is supplied to the gridv llthereof by the driver 5, i the amplifier "tube does not aconduct,.-ia'ndthe coupling capacitor lCichargeswith the polarity shown, to approximately the voltage B supplied bythe power supply. When a pulse? from driver .5 causes the grid ll of the amplifiertube l6 to become positive to thepoint. of saturation, this tube is rendered conducting. Condenser C begilnstodischarge through anode Ziiand cathode isle-f the-tube l5 and through the parallel comthe "full waverectifier is COXll bination of Z2 and the load L, which includes the magnetron 9. This produces a voltage across the parallel combination of Z2 and the load L equal to the condenser voltage less the anode space drop between anode 20 and cathode I 9 in the amplifier tube. During this time, the power supply or rectifier tends to discharge through Zl and the amplifier tube it but the discharge current is kept small by reason of the impedance 2|; When the driver pulse P ends, the amplifier tube It is again rendered non-conducting so that the condenser C stops discharging. At the same time, the voltage across the load L drops to approximately zero, and condenser C, whose voltage dropped during the time it was discharging, is recharged by the power supply through impedance Zl and the parallel combination of the load L and impedance Z2.

Impedance Zl, may be a pure inductance, or pure resistance, or a combination of both, the latter being shown herein and respectively designated 2| and 22. Ordinarily, wire wound resistors of the inductive type may be used. The function of impedance ZI is to prevent the discharge of the power supply unit 8 durin the pulse. This impedance must not, however, be made of a size such that the charging current to condenser C gives rise to excessively large power losses. Impedance Z2 is also a combination of inductance 23 and resistance 24. It is needed only when the load is a unilateral or a very non-linear device such as a magnetron 9. Such a load acts in similar fashion to a diode, and if it were not for impedance Z2, condenser C could never be charged by the power supply 8.

Since it is usually desirable that the modulator deliver a flat-topped output pulse, it is necessary that the voltage across condenser C shall not fall more than some small percentage of the voltage to which it is initially charged. This means that the total charge "IAT delivered to the load L during the pulse (where I is the peak current and AT is' the duration of the pulse) must be a small percentage of the total charge in the condenser at the beginning of the pulse. If the drop is small, it is given, approximately, by

Thus if the requirements on the output pulse are known, the minimum value of condenser C can be determined.

' Since the charging of the power supply filter condenser Cf takes place at the power line frequency or a multiple of it, the voltage across condenser C) and across condenser Cwill have a power line ripple component. The amount of ripple will depend, to a large degree on the total capacitance of C plus Cf, and the average load current. For minimum ripple, the total capacitance must be made as large as possible. It should be noted that while the ripple is a function of the total capacitance; the drop in output voltage during each pulse is a function of the coupling capacitance, C, only.

In general, the obstacles to small size and weight in a modulator or pulser of this kind are the inevitable large sizes of high voltage components. Generally speaking, the smallest and light est design will also be the most efficient if the design is achieved by the elimination of elements which dissipate power or else by the use of elements in their most useful condition.

If only a certain volume of high voltage capacitors may be accommodated, the best design is one the half wave rectifier power supply but omitting the condenser C), which is employed in all conventional circuits. The operation is exactly as described before except that condenser C is recharged directly through the agency of the transformer and rectifier but without the cooperation of condenser Cjf The power line ripple is equivalent to that of a conventional circuit using a total capacitance equal to condenser C but the output pulse performance is equivalent to a conventional circuit with a coupling capacitor equal to C. Thus both the benefits of high coupling capacitance and adequatefiltering are obtained. A conventional circuit with the total capacitance of C divided between condensers C and Cf will have the same ripple but poorer pulse performance.

The combined amplifier and full-wave doubler rectifier of Figs. 2 and 3 cannot be modified in the manner shown in Fig. 4. Here the form of circuit improvement, that is, in the case of the full wave rectifier, is not merely effected by the elimination of the filter condenser Cf. Instead, the coupling capacitor C has been replaced by two . capacitors 2C, 20 in series, of half the voltage rating and double the capacitance. These capacitors serve both as coupling and filter capacitors. The combination in practice requires the same volume and weight as the single capacitor C since high voltage capacitors are usuallybuilt by connecting low voltage capacitors in series. The circuit performance is as previously described'except that the coupling capacitor network is charged directly through the full wave rectifier doubler circuit, Impedance Z3 serves a purpose similar to that served by impedance Zl The advantages of the circuit are those already given for the half wave circuit of similar design.

It has been discovered thatthe circuit arrangements of Fig. 4 and Fig. 6 can be further improved by the elimination of impedance Z! in the arrangement of Fig. 3 and bythe elimination of impedances Zl and Z3 from the arrangement of Fig. 6, provided that certain of the retained components haveappropriate characteristics. This is possible since a, rectifier tube has an inherent dynamic impedance and a power transformer has an i nt l a e inductance. In other Words, a rectifier tube may be represented as an ideal rectifierD in series with a resistance R (Fig. 8) and a power transformer may be represented as an ideal transformer T with the secondary winding thereof in series with the resistance RT and the leakage inductance LT of this winding (Fig. 9). It is possible, therefore, by proper choice of components to substitute these inherent circuit elements for Z! in Fig. 4 to give'the half wave rec'- tifier of Fig. 5 and for Zl and Z3 in Fig. '6 to provide the rectifier doubler circuit of Fig. 7. It should be noted, however, that this substitution cannot be done in the conventional circuits of Figs. 2 and 3 but is possible only after the filter condenser or condensers Cf, Cf have been removed. a

The capacitances and connections represented by dotted lines (Figs. 5 and 7) are the unavoidable stray capacitances inherent in the transformers. For short pulses, it is necessary to design the transformers so that these stray capacitances are kept small. It is also necessary that the transformers be designed to stand pulse voltages since the transformers are actually pulsed in these improved circuits but are not pulsed in the conventional circuits of Fig. 2 and 3. For use with certain magnetron loads, it is sometimes necessary to restore impedance Z3 into the doubler circuit Fig. '7 for the purpose of damping out certain undesirable transients. The circuits sh'own in Figs. 5 and '7, allow better performance than the conventional devices (Figs. 2 and 3) withfewer components, and with smaller size,

and with a weight reduction of as much as twenty pounds in certain models, as compared with prior devices.

What we claim is:

1. In an arrangement of the class described, an amplifier including an electron tube provided with a cathode, an anode and a control grid, said electron tube being normally biased to cut ofi, means including said grid for intermittently rendering said tube conducting, aload circuit, a capacitor coupling said anode to said load, a power supply unit including a diode rectifier, and a conductive connection substantially devoid of any physical impedance element linking said diode rectifier to said anode.

2. In an arrangement of the class described, an amplifier including an electron tube provided with a cathode, an anode and a control grid, means including said grid for rendering said tube conducting, a load circuit, a capacitor coupling said anode to said load, a power supply unit including a diode rectifier, and a conductive connection substantially devoid of any physical imsaid electron tube being normally biased to cut off, means for periodically applying positive voltage to said grid to render said electron tube conducting, a load circuit, a capacitor coupling said to said anode through a connection devoid of pedance element, linking said unit to said anode,

the inherent impedance of said diode rectifier alone serving to limit the current flow through said connection. I

3. In an arrangement of the class described,

an amplifier including an electron tube provided with a cathode, an anode and a control grid,

said electron tube being normally biased to cut off, means for periodically applying positive voltage to said grid to render said electron tube conducting, a/load circuit, a capacitor coupling said anode to said load, a power supply device including a diode conductively connected to said capacitor and servingto supply charging current a to said capaciton said capacitor being the sole physical capacitance element for coupling said amplifier to said load and for filtering out the ripple component from the power supplied by said rectifier,

4. In an arrangement of the class described, an amplifier including an electron tube provided with a cathode, an anode and a control grid, said electron tube being normally biased to cut off, means for periodically applying positive voltage to said grid to render said electron tube conducting, a load circuit, a capacitor coupling said anode to said load circuit, and a power supply unit including a rectifier and a transformer, said rectifier being provided with a cathode and with a plate, said transformer comprising a primary rent and a secondary winding included in the connection from said plate to a low reference potential, said rectifier cathode being conductivelyconnected to said capacitor whereby said 5. In an arrangement of the class described an amplifier including an electron tube provided with a cathode, an anode and a control grid,

' winding connected to a source of alternating curinductance or resistance elements, said trans former comprising a primary winding connected to a source of alternating current :and a secondary winding having one terminal thereof connected to said plate, the cathode return of said electron tube and the low potential side of said an amplifier including anelectron tube provided with a cathode, an anode and a control grid, said electron tube being normally biased to cut off, means for periodically applying positive voltage to said grid to render said electron tube conducting, a load circuit, two capacitors connected in series so that their voltages add, said capacitors serving to couple said anode to said load circuit, a rectifier including a transformer and two diodes, each having a cathode and a plate, said transformer havinga primary winding. and a secondary winding, said primary winding being connected to an alternating current source, one terminal of said secondary winding being conductively connected to the commonterminals of said capacitors, the other terminal of said secondary winding being joined bya conductive connection to the plate of the first diode and to the cathode of said second diode, the cathode of the first diode being joined by a conductive, connection to said anode, the plate of said second diode being joined by a conductive connection to the low potential side of, said load circuit, at least two of said conductive connections being devoid of inductor or resistor elements.

7. In an arrangement of the class described. an amplifier including an electron tube provided with a cathode, an anode and a control grid, said electron tube being normally biased to cut off, means for periodically applying positive voltage to said grid to render said electron tube conducting, a load circuit, two capacitors connected in series so that their voltages add, said capacitors serving to couple said anode to said load circuit, a rectifier unit including a transformer and two diodes, each having a cathode and a plate, said transformer having a primary winding and a secondary winding, said primary winding being connected to an alternating current source, one terminal of said secondary winding .being conductively connected to the common ter said second diode being. joined by a conductive connection to the low potential side of said load circuit, at least two of said conductive 00111183! tions being devoid of inductor or resistor elements, the stray capacitances of said unit being reduced to a low value.

HAROLD GOLDBERG. WALTER C. THOMPSON.

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