US2829312A

US2829312A - Arrangement for controlling a gas- or vapour-filled discharge tube

Info

Publication number: US2829312A
Application number: US479580A
Authority: US
Inventors: Jacob Buys
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1954-02-13
Filing date: 1955-01-03
Publication date: 1958-04-01
Anticipated expiration: 1975-04-01
Also published as: DK85567C; BE535680A; GB779024A; DE958141C; CH327901A; FR1122283A

Description

Apnl l, 1958 J. BUYS 2,829,312

ARRANGEMENT FOR CONTROLLING A-GASOR VAPOUR-FILLED DISCHARGE TUBE 5 Sheets-Sheet 1 Filed Jan. 3, 1955,

if a e (i ,a d *a7 l i c I A \d E +I X .in CZ 'j INVENTOR JAcoB Buysy AGENT April 1, 1958 J. BUYS ARRANGEMENT FOR CONTROLLING A GAS-0R VAPOUR-FILLED DISCHARGE TUBE 5 Sheets-Sheet 2 Filed Jan. 3. 1955 .lNvENToR JACO B B UY5 yAGENT v 20gb a .v7/

Apnl 1, 1958 .1. BUYS 2,829,312

ARRANGEMENT FOR CONTROLLING A GAS'OR VAPOUR-FILLED DISCHARGE TUBE Filed Jan. 3, 1955 5 Sheets-Sheet 3 f lNvENToR i9 2' JAcn Buys- AGENT Unite ARRANGEMENT FOR CONTROLLING A GAS- VAPOUR-FILLED DISCHARGE TUBE Application January 3, 1955, Serial No. 479,580

Claims priority, application Netherlands f February 13, 1954 Claims. (Cl. 315-165) The present invention relates to arrangements for controlling gas or vapor-filled discharge tubes. More particularly, the invention relates to an arrangement for controlling a gas or vapor-lled discharge tube which is supplied with alternating current and preferably has a positive ignition characteristic, with the aid of a controllable high-vacuum tube. In accordance with the present invention, a direct voltage is provided in series with an alternating voltage in the control circuit of the high vacuum tube. The direct voltage is controllable preferably from a positive to a negative value. A resistor is connected in the anode circuit of the high Vacuum tube, which resistor is connected in series with a control alternating voltage in the control circuit of the discharge tube.

Such an arrangement provides a very satisfactory control of the discharge tube permitting the output current strength to be controlled within a wide range. In a discharge tube which has a positive ignition characteristic, so that a positive ignition voltage pulse must be used, it is particularly desirable for the grid voltage to become negative after the anode voltage has been made negative in order to prevent the tiow of anion current to the negative anode, which might produce back-ignition. This is made possible by the arrangement of the invention, since the resultant control voltage at the control electrode of the discharge tube is approximately shaped in the form of a peaked'voltage despite the fact that the resultant voltage is obtained from sinusoidal voltages. Although it would actually be more simple to use peaked voltages adapted to be displaced in phase for the control of the discharge tube, this frequently cannot be realized in practice in a simple manner when using certain circuit arrangements comprising unconventional apparatus (for example a quick-switch protection against back ignition of the discharge tubes and the like which is also manually controllable and adjustable). In such cases the arrangement in accordance with the invention can provide a solution of these diliiculties.

In order that the invention may be readily carried into effect, it will now be explained more fully with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of an embodiment of the circuit arrangement of the present invention;

Fig. 2 is a graphical presentation of the anode current and grid voltage curves of the tube 1 of the circuit arrangement of Fig. 1;

Fig. 3 is a graphical presentation of the grid controlvoltage curves of the tube v8 of the circuit arrangement of Fig. 1;

Figs. 4, 5 and 6 are graphical presentations of the grid control voltage curves of Fig. 3 combined with the lalternating voltage curve of the source 7 of Fig. 1;

Fig. 7 is a graphical presentation of the ignition cycle of the tube 8 under selected conditions;

Fig. 8 is a schematic diagram of a modication of the embodiment of Fig. 1; and

.Fig 9 is a graphical presentation of the iguitionzcycle States Patent@ 2,829,312 Patented Apr. l, 1958 FVice of the tube 8 under a modification of the conditions of Fig. 7.

In Fig. 1 the control circuit of a high-vacuum tube 1 includes a direct voltage source 2 in series with an alternating voltage source 3 and a variable direct voltage source 4. The direct voltage source 2 provides a positive grid voltage and the direct voltage source 4, for example from a quick-switch protection, provides an oppositely connected variable direct voltage. The resultant voltage of the two

direct voltage sources

2 and 4 supplies a grid direct voltage which varies between a positive value (if the voltage of the source 3 is zero) and a negative value (if the source 4 has a higher negative value than the value of the voltage from the source 2). sequently, the resultant control voltage produced in the grid circuit of the high-vacuum tube 1 is a sinusoidal alternating voltage superposed on a direct voltage varying between a positive and a negative polarity.

The anode circuit of the high-vacuum tube 1 includes a resistor S in series with an anode voltage source 6. T he resistor S is connected in series with an alternating voltage source 7 in the control circuit of a gas or vapor-filled discharge tube 8. The anode circuit of the discharge tube 8 includes a load 9 and an alternating voltage supply source 10.

Neglecting the control voltage source 7, the arrangement operates as follows. from the device 4 is zero. In this case the grid voltage of the high vacuum tube is positive to' such an extent that despite the alternating voltage from the transformer' 3 superposed on it the tube 1 remains within the saturation range with respect to the anode current. The saturation current I, (Figure 2) passing through the resistor" 5 in said case produces a voltage drop across this resistor such that the discharge tube 8 is invariably kept cutoft` (the transformer 7 being still neglected). vice 4 supplies a small direct voltage, the positive grid voltage of the tube 1 decreases, for example, to a value shown in Fig. 2by grid voltage magnitude 11. In Fig. 2 the anode-current versus grid-voltage characteristic of the tube 1 is designated 12. On the positive grid voltage 11 the alternating voltage 13 from the transformer 3 is superposed. Consequently vthe anode current will vary according to the curve a--b-c-d, that is, the voltage drop across the resistor 5 in Fig. 1 will be much less at the minimum value c of the anode current (Figure 2) with the vresult that at this instant the negative grid voltage of theV discharge tube 8 is greatly decreased. The grid voltage of the discharge tube 8 with the current variation a-b-c-d is shown in Fig. 3 by the 'same reference symbols. tube 8 has a negative variation, as is shown for example in Fig. 3 by magnitude 14, the tube 8 will ignite at the instant 15; that is, during the second half of the positive halt-cycle 16 of the anode voltage of said tube (the anode` voltage 16 is raised in Fig. 3 for the sake of clarity).

If (by manual adjustment or automatically) the device 4 supplies a negative voltage exceeding the positive voltage from the source 2, in the grid circuit of the tube l.,

the point 18, at an earlier instant in the half-cycle 16.

If the voltage from the source 4 is driven even more negative so that, for example, the negative grid voltage r 19 of Fig. 2 is obtained, the ignition instant of the discharge tube 8 will accordingly take placeat a still earlier instant in the half-cycle 16,'and so on (see the curves.:

j-j and k-k in Figs. 2 and 3). n f

Con-

It is assumed that the voltage If the ignition characteristic of the discharge are' asada 12 However, if the discharge tube 8 'has a positive ignition characteristic such as indicated by magnitude 20 in Fig. 3, the tube 8 cannot ignite. it will only ignite if an additional positive direct voltage is supplied in series with the control voltages. that the control voltage curves a-b-c-d, e--f-gh, j-j and k-k have a positive value with respect to the zero line, after the anode voltage has become zero at 21. However, it is frequently desirable that the grid voltage be negative when the anode voltage becomes negative in order to prevent the flow ot residual ions to the negative anode, which might cause back-ignition in the discharge tube. Consequently the above-mentioned control voltage curves do not satisfy this requirement.

However, the desired grid voltage curve of the discharge tube 3 is obtainable by combining the abovementioned control voltage curves with the alternating voltage from the transformer7 (Fig. l) which has been neglected thus far, as is shown in Figs. 4, 5 and 6.

ln Figs. 4, and 6, the alternating voltage from the source 7, which .is Slightly out of phase, is designated 22 and is combined with the control voltage curves rr--b-c-d, e-f-g-h and j-j of Fig. 3.

A resultant control voltage, curve 23 in Fig. 4, is obtained which does not intersect with thc ignition charp acteristic so that the discharge tube S does not yct ignite.

In Fig. 5 `the resultant control voltage curve 2d is obtained havinga point of intersection 25 with the ignition characteristic 20. Consequently ignition is effected at the instant 26 during the positive halfwave 16 of the anode voltage.

1n this case, however, it is obvious The instant at which the positive half-wave of the control alternating voltage 13 from the source 3 (Fig. 2) is set up at the grid circuit of the high vacuum tube 1 is shown by 27 in Figures 2 to 6. ln a practical embodiment of `an arrangement in accordance with the invention the control voltage 13 leads the control alternating voltage 22 from the source 7 by approximately 45 electrical degrees, while the .latter leads the anode voltage 16 of the discharge tube 8 by approximately 30 electrical degrees. ln Figures 3 to 6 these phase displacements are not shown exactly, since different phase angles are Aalso possible. Obviously, the choice of these phase angles depends ou the position of the ignition characteristic of the discharge tube 8, the amplitudes of the alternating voltages 13 and 22, the controlling direct voltages from the sources 2 and 4 (Figure l), an additional positive or negative direct `r voltage which may be set up in the grid circuit of the tube 8 and the desired ignition range of the discharge tube 8.

Finally, in Figure 6 the combination of the control alternating voltage22 with the control voltage curve j-j provides a resultant control voltage 28 which at 29 has a point of intersection with the ignition characteristic 20, so that the ignition instant 30 in the positive halhwave 16 is obtained and a larger current is supplied from the discharge tube 8 than in the case shown `in Figure 5.

At an even smaller amplitude of the control voltage curve j-j in Figure 6, the positive left-hand edge of the curve 28 is displaced more to the left until the control voltage 22 is reached so that an even earlier ignition in the anode voltage wave 16 is obtained. However, the positive right-hand edge of the curve `28 invariably remains in the same place similarly to the curve 24 in Fig-- ure 5. From Figures 5 and 6 it may be seen that the control voltage curves 24 and 28 `invariably have a negative value at the'instant at which the positive anode voltage 16 changes'to a negative voltage when passing through zero at 31, so that back ignition is not likely.

With respect to the choice of the phase `of the control alternating voltage 22 with .respect to the anode voltage 16 the following may be taken into account:

In the entirely conductive condition of the discharge tube 8, in which the tube 1 has a negative voltage at its grid such that the anode current is zero for the entire duration of the cycle of the voltage 13, the grid of the discharge tube 8 only has the control alternating voltage 22 applied to it. -lf the discharge tube 8 is used in a threephase arrangement or a three-phase Greetz arrangement, current flows through this tube during approximately electrical degrees. (Figure 7.) ir, now, the control alter nating voltage 22 leads the `anode voltage 16 by 30 electrical degrees, the trst passage through zero, at point 32, of the control voltage 22, will coincidewith the first passage through zero of the reverse voltage 33 so that, if the voltage 33 increases in a negative sense, the control alternating voltage 22 is driven negative and the grid-cathode space of the tube 8 is not ignited. Consequently, backignition in the tube 3 is not likely. Beyond the second passage through zero, at point 34, of the voltage 22 thc control electrode of the tube S is driven positive to such an extent that the tube is enabled to ignite.

The ionization period of the gas in the tube delays this ignition process when the reverse voltage is decreasing.

The likelihood of back-ignition is very slight, since the anode-cathode space will only be enabled to ionize after the grid-cathode space is ignited, and at this point thc reverse voltage is small. The period of time during the tube 8 is ignited may, "if required, be reduced even further by causing the tube 8 itself to produce a negative voltage 35 (Figure 9) in its grid circuit due to the grid current and a suitable RC element of the kind shown in Figure 8 by 36 and 37.

In addition, this causes the voltage 22 `from the transformer 7 (the voltage of the resistor 5 is zero) to reach the grid of the tube 8 With a lag of a determined number' of electrical degrees due to the phase displacement of this RC element. f

'Consequcntly, it is possible that the voltage at the grid of -tube S be in phase with the anode voltage of said tube,

and said tube be ignited for approximately '140 (more than 120 due to the commutation).

Consequently, the initial voltage 22 must lead the anode voltage 16.

A 3'0" phase displacement between the voltages 16 and `22 may be produced in a simple manner by including a A-Y or a Y-A transformer between the low voltage and the high voltage.

It will be obvious that in a half-wave or full-wave system which may be connected in a Graetz arrangement the control alternating voltage 22 may be in phase with the anode voltage 16 since at full load the tube `8 must be ignited during the entire positive cycle of the anode voltage 16.

If required, a positive or a negative direct voltage may be connected in series with the voltage 22 depending upon the positive or the negative ignition characteristic and the commutation time.

*While the inventiony lhas been described by means of specific embodiments, l do not wish to belimited thereto, for obvious modifications will occur toV those `skilled in the art without departing from the spirit and scope of lthe invention.

kWhat is claimed is:`

1. A circuit arrangement for controlling a gas discharge tube having an anode, a cathode and a control grid, said tube having `a positive ignition characteristic, said circuit arrangement comprising means for applying an alternating voltage to the anode of said gas tube, an electron discharge tube of high vacuum type having an anode and a control grid, a first source of alternating voltage,means for supplying a direct voltage of variable polarity connected 1in series combination with :said first` source `of alternating voltage, said series combination -be-` ing connected to the control grid of said vacuum tube, coupling-means connecting the anode of said vacuum tube to the control grid of said gas tube, a resistor connected to said coupling means, and a second source of alternating voltage connected in series with said resistor whereby a resultant control voltage determined by the anode voltage of said vacuum tube and the second alternating voltage is applied to the control grid of said gas tube, said resultant control voltage having a phase displacement with respect to the alternating voltage applied to the anode of said gas tube whereby said resultant control voltage has a negative polarity relative to the voltage on the cathode of said gas tube at the instant when the alternating voltage applied to the anode of said gas tube changes from a positive polarity to a negative polarity.

2. A circuit arrangement as claimed in claim l, further comprising a source of direct Voltage coupled to the control grid of said gas tube by said resistor.

3. A circuit arrangement for controlling a gas discharge tube having an anode, a cathode and a control grid, said tube having a positive ignition characteristic, said circuit arrangement comprising meansy for Vapplying an alternating voltage to the anode of said gas tube, an electron discharge tube of high vacuum type having an anode and a control grid, a first source of alternating voltage, means for supplying a direct voltage of variable polarity connected in series combination with said rst source of alternating voltage, said series combination being connected to the control grid of said vacuum tube, phase shifting means coupled to the grid of said gas tube, means coupling the anode of said vacuum tube with said phase shifting means, a resistor connected to said coupling means, and a second source yof alternating voltage connected in series with said resistor whereby a resultant control voltage determined by the anode voltage of said vacuum tube and the second alternating voltage is applied to the control grid of saidgas tube, said resultant control voltage having a phase displacement with respect to the alternating voltage applied to the anode of said gas tube whereby said resultant control voltage has a negative polarity relative to the voltage on the cathode of :said gas tube at the instant when the alternating voltage applied to the anode of said gas tube changes from a positive polarity to a negative polarity.

4. A circuit arrangement for controlling a gas discharge tube having an anode, a cathode and a control grid, said tube having a positive ignition characteristic, said circuit arrangement comprising means for applying an alternating voltage to the anode of said gas tube, an electron discharge tube of high vacuum type having an anode and a control grid, a lirst source of alternating voltage, means forsupplying a direct voltage of variable polarity connected in series combination with said tirst source of alternating voltage, said series combination being connected to the control grid of said vacuum tube, coupling means connecting the anode of said vacuum tube to the control grid of said gas tube, a resistor connected to said coupling means, and a second source of Igas tube changes from a positive polarity to a negative polarity, said direct voltage having a maximum magnitude of positive polarity which renders said vacuumtube conductive substantially in the saturation range of the grid voltage versus anode current characteristic of said vacuum tube and a maximum magnitude of negative polarity which renders said vacuum tube nonconductive.

v5. A circuit arrangement for controlling a gas discharge tubehaving an anode, a cathode and a control grid, said tube having a positive ignition characteristic, said circuit arrangement comprising means for applying an alternating voltage to the anode of said gas tube, an electron discharge tube of high vacuum type having an anode and a control grid, a rst source of alternating voltage, meansl for supplying a direct voltage of variable polarity connected in series combination with said rst source of alternating voltage, said series combination being connected to the control grid of said vacuum tube, coupling means connecting the anode of said vacuum tube to the control grid of said gas tube, a resistor connected to said coupling means, and a second source of alternating voltage connected in series with said resistor, the rst alternating voltage leading the second alternating voltage in phase by substantially 45 electrical degrecs and said second alternating voltage leading the alternating voltage applied to the anode of said gas tube in phase by substantially 30 electrical degrees whereby ya resultant control voltage determined by the anode voltage of said vacuum tube and said second alternating voltage is applied to the control grid of said gas tube, said resultant control voltage having a negative polarity relative to the Voltage on the cathode of said gas tube at the instant when the' alternating voltage applied to the anode of said gas tube changes from a positive polarity to a negative polarity.

References Cited in the le of this patent UNITED STATES PATENTS 1,927,676 Bedford Sept. 19,' 1933 1,985,069 Anschutz Dec. 18, 1934 2,306,784 Lord Dec. 29, 1942 `2,503,735 Hess Apr. 11, 1950 2,511,981 Hanchen June 20, 1950