US2609506A - Gaseous tube oscillator - Google Patents

Description

Sept. 2, 1952 G. J. SIEZEN 2,609,

GASEOUS TUBE OSCILLATOR Filed Aug. 3. 194a 3 Sheets-Sheet 1 G'ERRIT JAN SIEZEN INVENTOR AGENT 3 Sheets-Sheet 2 Filed Aug. 5, 1948 ll khllll llllllllll GERRIT JAN SIEZEN INVENTOR AGENT G. J. SIEZEN 2,609,506

Sept. "2, 1952 I GASEOUS TUBE OSCILLATOR 3 Sheets-Sheet 5 Filed Aug. 3, 1948 GERRIT JAN SI EZEN INVENTOR AGENT Patented Sept. 2, 1952 GASEOUS TUBE OSCILLATOR Gerrit Jan Siezen, Eindhoven, Netherlands, as-

.signor to Hartford National Bank and Trust Company, Hartford, Comp, as trustee Application August s, 1948, Serial No. 42,264

In the Netherlands August 14, 1947 7 Claims. (01.250-36) This invention relates to av circuit for generating alternating voltage with the aid of a source of direct voltage and the series-combination ofpa condenser andan inductance, the series-coma resistance 3 represents the resistance which is invariably provided in such a circuit) of which one extremity is connected to the negative terminal of a battery 4 having a terminal voltage E, is connected at its other extremity, by means of a mechanic switch 5, alternately to the positive and the negative terminal of the battery 4.

Assuming that the mechanic switch 5 is operated at a frequency which equals the natural frequency of the series combination, hence in which 0, L and R represent the capacity of the condenser I, the inductance of the coil 2, and the value of the resistance 3, respectively.

If in this case the switch alternately makes contact at either of the positions during exactly a half-wave an electromotive force produced at the input of the series-combination exhibits a variation which is shown as a function of time bythe ful lineia inFig.2. I

As is well-known, this F. comprises a firs-t harmonic having an amplitude which is indicated by the dotted line b in Fig. 2.

The frequency of this first harmonic equals thev natural frequency f of the series-combination, so that the amplitude of the condenser voltage V will attain a value the 'so-called quality factor of the circuit.

Consequently, if Q has a high value, which implies that the losses occurring in the seriescombination are small, a high ouput voltage V may be obtained.

As disadvantages of such a circuit we may mention the following.

The mechanic switch exhibits inertia, so that the switching frequency and hence also the resonant frequency of the circuit is limited, which may result in excessive values of the inductance and the capacity.

Furthermore, the tuning of the switching frequency to the resonant frequency of the circuit causes difliculty, more particularly if the quality factor Q of thi circuit is high and hence the width of the resonance curve is small.

Finally, a certain period of time is required for switching, over from one position of the switch to the other, so that the current pulses through the switch are of a duration shorter than a half wave, which results in sparking during the switching operation.

The circuit according to the invention mitigates the said disadvantages and exhibits the characteristic that .the direct voltage supply is connected to the series-combination of the condenser and the inductance by way of an element which is conductive in only one direction, whilst the circuit constituted by the series-combination of the condenser and at least a part of the inductance is likewise completed by way, of such an element.

Some forms of the circuit according to the invention will now be explained more fully by reference to the accompanying drawings.

Fig. 4a shows as a function of time the varia- I tion of the voltage V set up at the condenser, whereas Figs. 4b and 4c show the variations of currents i1 and i2 indicated by arrows inFig. 3, as a function of time in the stationary position.

If, at the moment t=t1, the voltage V has a value V2 and if the switch 5 at thismoment establishes the contact 8, the voltage V rises from V2 to V1 according to the first part of a damped harmonic oscillation which has the value +E as a zero line and of which the continuance is indicated by the dotted line 0 in the line V= as the zero line and of which the further variation is indicated by the dotted line 61. I

At the moment t=t5, the current-i2 tends to change its direction, but this is prevented by the rectifier 1, so that the voltage V remains V2 until the switch again changes its position.

For the values V1 and V2, between which the voltage V varies when the stationary position is attained, we may simply find:

For a high value of Q is then found approximately:

vi vz cs so that the amplitude of the alternating voltage set up across the condenser approximately equals that which occurs in a known circuit as shown in Figure 1. However, in practice it will appear that the voltage produced has a slightly lower value as a result of the internal resistance of the rectifiers which bring about higher damping.

Consequently, in this circuit the frequency of the mechanic switching operation may be chosen to be considerably lower than the resonance frequency of the series-combination, so that the lat ter may be given a high value, which permits of obtaining a higher value of the quality factor Q.

Figure 4 furthermore shows that half the periodic time of the series-combination extends, for example, from h to t2 or from 134 to is, whilst the time during which the switch occupies the position 8 or 9 extend from 131 to t; or from 154 to 156 respectively.

Th periods during which the switching arm moves from one position to the other correspond to the periods ta-ti and lie to tv.

In this circuit, however, during the periods in which the rectifiers 6 and 7 are conductive, the switching arm acquires a voltage equal to the instantaneous value of the condenser voltage, that is +V1 or V2, so that the rectifiers are required to resist a high blocking voltage and sparking still occurs in the contact-making of the switching arm.

A further advantageous form of the circuit according to the invention does not exhibit this disadvantage, whilst furthermore the mechanic switch is omitted.

In' such a circuit, which is shown in Fig. 5, use is 'madeof gas-filled discharge tubes Hi and H. In this case it is'possible to provide that the switching operation is performed wholly automatically under the action of the natural oscillation of the resonant circuit.

The igniting and operating voltages of the discharge tubes are required to be such that alternately one of the tubes is conductive whilst for the automatic starting of the circuit it is furthermore necessary that the igniting voltage of tube l0 should be lower than the battery voltage E, since otherwise ignition does not take place when condenser I is uncharged.

If: I

V010 is the igniting voltage of tube 10 V011 is the igniting voltage of tube I l Vbm is the operating voltage of tube I0 and Vbu is the operating voltage of tube II 1 the above-mentioned conditions are fulfilled if:

The operation of the circuit may appear from Fig.4, which, as before, shows the stationary waveform.

Starting from the voltage V2, the condenser voltage, if tube [0 is conductive, will again rise to the voltage V1, tube H then being inoperative on the ground of relation 1). As soon as the voltage V1 is attained, the current i1 will inverse its polarity, whereby tube 10- extinguishes. The

voltage at the point 12 in Fig. 5 will then rap-idly increase, since the condenser voltage has a high value, but as soon as the voltage at the said point has reached the value V011, tube II will ignite, so that the condenser voltage decreases to the value Vz. Tube I0 remains inoperative during this period on the ground of condition (3). When V attains the value V2, the current i2 will change its polarity, so that tube H extinguishes. The voltage at the point l2 then rapidly decreases since the condenser voltage is negative, but as soon as the voltage at this point reaches the value E-VOlo, tube l0 reign-ites and the cycle described is repeated.

The value of the voltage at point 12 evidently varies between the values EVb1o and Vbll. Consequently, only the part AE of the battery voltage E is effectively used forthe excitation of the circuit, given by:

From this it follows with (1) and (2) 1 AE V0l1-Vbl1 (5) AE V01oVblo (6) so that A-E is always smaller than the difference between the igniting and operating voltages of the discharge tubes used. The amplitude of the alternating voltage V set up at the condenser,

V= QAE 7| is thus always smaller than In order to ensure a maximum difference between the igniting and operating voltages, it is advantageous to utilise gas-filled discharge tubes each comprising a control-grid which is suitably biassed in such manner that the igniting voltage of the tubes has a high value. Such tubes fre- J quently. have a low operatingvoltage; .so :tha't a high potential. difference may be: obtained;

One form of such a circuit is shown in; Figure-6.. v

Inthiscase. eachtoffthe; gas-filled discharge 5 and? iii-tubal! conductive? tubes. [3, ll comprises. a: controlgrid I15, and: 1.8 respectively, to. which a. negative voltage is sup-- plied across resistances l1 and [8 respectively,

which permit of adjusting. the: igniting voltage of i the tubes. If. the.- operating voltages Vbrx and,

Vbit have. small, values. the. voltage.

AE= EVbi3 -.V b14,

is available-for the. excitation f the circuit,

which voltage-may be substantially equal to E. If,:-for example, the igniting voltage Von of tube [-4 is chosen to be-substanti-a-lly edual. to 12,,

then it follows from conditions analogous to (2) and (3) that -EVb 14 Vo13 E.

If Vbit has, a small value, the adjustmentof the igniting voltage V013. is comparatively critical, which may be avoided. however, byconnect ing the point [9 to a. negative potential ---Vo,-

which results in the condition I i i I VO13 E+VO Consequently, the igniting voltage of. tube l3 may be chosen between two further. different values, viz. EVb14 and E+Vo.

Furthermore, itmay be. observed. that it is advantageous, in order to avoid additional damping, to utilise tubes having a minimum internal resistance.

Very satisfactory results may be obtained if use is made of tubes exhibiting a declining currentvoltage characteristic curve over as large a current region as possible, such as shown, for example, in Figure 7. Here the voltage of the. tube. is. plotted against the current traversing the tube,

the characteristic. curve exhibiting. a-declining.

charge tube, upon the extinction of one of thetubes and the ignition of the other, the. firstmentioned tube reignites, so that short-circuit of the battery would occur. y Y

Some examples of circuits in .which this disadvantage is alsosuppressed will be described by reference to Figs. 8, 9 and 10.

The circuit shown in Fig. 8 only differs from that shown in Fig. 6 in that inductances and 2| are included between the cathode of tube I3 and the point [9 and between theanode of tube l4 and the point I9 respectively.

As soon as tube l3 extinguishes and tube I4 ignites the cathode of tube l3 acquires a positive increase in voltage since the voltage V at this moment has a high positive value. Consequently, more rapid deionisation occurs in tube l3.

Conversely, a decrease in anode voltage after the extinction takes place in tube I4, which also results in more rapid deionisation in this tube.

If the voltages set up across the tubes are called V13 and V14 with the polarities shown in the figure, and if the inductances of the coils 20 and 2| are Leo and L21 respectively and that of the coil 2 is L2, we have, if tube [3 is conductive:

The voltages V131 and V14 thus.- acquire acornpm nent which is proportional to V and ,whichjis,

always of a polarity such that a. decreaseioccurs immediatelyafter extinction. This component must not bringaboutignitionat the end of the period concerned, when, V? changes its polarity,

which. maybe ensured-by adjusting the igniting voltages to sufiiciently highvalues by, means-oi the control-grid voltages;v since the voltage V has a. valuevery. much higher than the. voltage- E, the values of the inductances Lzoand L2; maybe chosen to be small with respect to the value Li.

In .thecircuit shown in Figure9, rapid deionisationofgthe gas-filled discharge tubes is; also.

obtained subsequent to the extinction .of the; tubes. 7 H 7 In this-case however, it is not thewhole series.- combination of the condenser. and the. inductance, but: only a part, viz; the condenser and a partof the inductance, which is included in the discharging circuit of the condenser.

The part 25 of the'coil 23 .forms inthiscircuit only; part ofv the charging circuits whereas; the

remaining part; 24 i included-in both. the charging and discharging circuits of the condenser 2-2.-

The: series-combination further 7 comprises, as

before,- the usual damping resistance .25. discharge tubes 21, 28. are: of the gas-filled type,

as before, and, their control grids are suitably biassed by wayiof resistanccs29 and 30.,

It, the inductance of the coil 23. is L23 andthe: inductance ofrthe part 2:4 of, this coil is 11. 1123, and if t-he voltagesset up across the-discharge tubes are Var and. Vzsrespectively; We have. :1

1r tube ZTisconductil/e:; U

' avbei f-V. 2 H171 m which v satisfies the difierentiale uates With reference to the above equations an'dirf ierence in velocity occurs in the increase and decrease of thevoltage with the result that the voltage V acquires a sawtooth character.

Such a variation of the voltage V as a function of the time t is shown in Fig. 10. Here a rapid decrease in voltage occurs during the period of time t1-t2 in which tube Moi Fig. 8 is conducslowly increasing voltage duringthe period of time tz-ta, in which tube I3 is, conductive.

From the two differential equations deduced for the circuit shown in Fig, 9; it follows that a sawtooth voltage V automatically occurs, since the angular frequency for the rising branch is n-times that of the declining branch.

The so-called' feedback ratio of the sawtooth voltage thus equals the ratio 11 in which the coil 23 is divided.

'What I claim 1. An alternating voltage generatorcomprising said network being connected through said'iirst device to said source, and means connecting said second device between the end of saidcapacitance remote from said element and a point said element, said first device having a value "of ignition voltage which is less than said predetermined magnitude and having a prescribed value of operating voltage, said second device having a valued ignition voltage relative to that of said first device and a value of operating volt-' age relative to that of said first device at which said devices are automatically rendered alternately conductive.

2. An arrangement, as set forth in'claim 1, wherein said network further includes a resistance interposed between said capacitance and said element.

3. An arrangement, as set forth in claim 1, wherein said devices are each characterized'by a declining-current-voltage characteristic curve between the ignition and operating voltage.

4. An alternating voltage generator comprising a source of direct voltage of predetermined magnitude, first and second gaseous dischargeidevices, an oscillatory network constituted'by a capacitance connected in series with an inductance element formed by first and second serially-cone.

nected inductors, said network being connected through said first device to said source, a third inductor, and means connecting said second device between the end of said capacitance remote from said element and through said third inductor to the junction of said first and second inductors, said first device having a value of ignition voltage which is less than said predetermined magnitude and having a prescribed value of operating voltage, said second. device having a value of ignition voltage relative to that of said first device and a value of operating voltage relative to that of said first device at which said devices are automatically rendered alternately conductive. r

5'. An arrangement, as set forth in claim...4,-

whereinsaid :first and third inductors'arefof difie'rent value. a.

6. An alternating voltage generator comprising a sourceof direct'voltage of predetermined magnitude; first and second gaseous discharge-devices, an oscillatory network constituted by a capacitance connected in'series with an inductive element formedby a single inductor, said network beingconnected-through said first device to-s'aid source, and means connecting said second device between the end of said capacitance remote from said inductor and an intermediate tap in said inductor, said first device having a value of ignition voltage which is less than said predetermined magnitude and having a prescribed operating voltage; said second device having a value'of ignition voltage relative to that of said first device and a value of operating voltage relative to that of said first device at which said devices are automatically rendered alternately conductive.

'7. A11 alternating voltage generator comprising a source of direct voltage of predetermined mag-' nitude, first and second gaseous discharge deviceseach having a cathode, an anode and an ignition electrode, an oscillatory network constituted by a capacitance connected in series with an inductive element, means connecting the anode of the first deviceto the positive terminal of the source.

and the cathode thereof to the, free 'end of said element, the free end of said capacitance being connected to the negative terminalof said source, means connecting the cathode of said second device to the free end of said capacitance and the anode thereof to a point in said element, means to apply a bias to the ignition electrode of saidfirst device at which the resultant value of ignition voltage for said first device is less than said predetermined magnitude, and means to apply'a bias to the ignition electrode of said second. device at which the resultant value of igni: tion voltage for'lsaid second device relative to the value ignition voltage of said first device causes said devices to become alternately conductive.

GERRITv JAN SIEZEN.

- 5 FERENCES 01 1:1115 w The following references are of record in the f fi -zpatentz w

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