US3051871A - Gas discharge tube supply system - Google Patents

Description

23, 1952 e. H. M. DANIEL 3,051,871

GAS DISCHARGE TUBE SUPPLY SYSTEM Filed March 14, 1960 I/VVE/VTDR GEORGES m OAAl/EL United States Patent ()fiiice 3,5l,'ll Patented Aug. 28, 1962 3,051,871 GAS DESCHARGE TUBE SUPPLY FaYS'lEM Georges Henry Marie Daniel, Mazargues (Marseille), Bouches-du-Rhone, France, assignor to ociete Triliux, Marseille, France Filed Mar. 14, 1969, Ser. No. 14,677 Claims priority, application France May 6, 1955 7 Claims. (Cl. 315-268) This application is a continuation-in-part of my application Serial No. 581,587, filed April 30, 1956, entitled, Gas Discharge Tube Supply System, now abandoned.

The present invention relates to supplying current to luminescent lamps.

At the present time the usual practice is to supply luminescent lamps with current at a low voltage. For starting they require a voltage which is substantially double the operating voltage. When operating, the terminal voltage remains substantially constant and on the contrary the current passing through them is not limited by their internal resistance. Under such conditions unless precaution is taken for limiting the current by some means the lamp will quickly deteriorate.

For example, a tubular luminescent lamp having a length of four feet requires a starting voltage of about 320 volts while its operating voltage is only about 135 volts. It is therefore necessary to introduce an impedance in series with the lamp to limit the current to the desired value. At the present time inductance coils or leakage transformers are used for this purpose.

Because of the characteristics of these lamps they cannot operate in parallel without the use of supplemental means. When the first lamp is lighted it will be noted that the voltage at its terminals falls to a value corresponding to its operation. This voltage which is not sufficient to light the other tubes therefore requires the placing of an impedance in series with each of the tubes.

When the current used is a current of low frequency, for example 60 cycles per second, the impedance placed in series with each lamp cannot be a condenser because there would be an extinction and a relighting of the lamp 120 times per second and the condenser charge would deform the current and diminish the life of the lamps because of the instantaneous super-intensity at the moment of their relighting.

An object of the invention is therefore a system for supplying a high frequency current to luminescent lamps wherein the current has such a frequency that the period thereof would be substantially shorter than the time for deionizing the gas or vapor in the lamps. Therefore in a lamp containing only mercury vapor the frequency used should be from to kilocycles per second. Practically in order to take into account the existence in the usual lamps of rare gases such as argon, neon, krypton and the time of deionization of these gases, frequencies of the order of 100 kilocycles per second are used.

The upper limit of the frequency that can be used is limited so as not to cause trouble in radio telegraphic transmissions and broadcastings. On the other hand too great difficulties are encountered in the transmission to a distance of a very high frequency due to resonance phenomena in the lines, skin effects in the conductors, etc.

A further object of the invention is to provide a system whereby a current may be supplied to any number whatsoever of luminescent lamps from a single supply source without the necessity of any other operation than the switch operation for placing the lamps in the circuit or circuits that comprise the system.

Another object of the invention consists in feeding the lamps with a high frequency current from a high frequency self-oscillating current generator with multigrid tubes, to obtain a self-regulation of the generator corresponding to the load, that is, the generator remains constantly tuned Whatever may be the value of the load, which is the number of lamps placed in service. Furthermore, means are provided for regulating automatically the voltage of the screen grid of the tube of the generator to maintain the current of the control grid of the tube at a suitable value, that is, not exceeding the limit value compatible with the limit characteristics of the operation of the tube.

A still further object of the invention is to provide a system wherein important advantages are secured. On one hand due to using a high frequency current the yield of the luminescent lamp is increased and by using a current of suflicient high frequency such lamps are not permitted to be deionized. Also by using a current of high frequency it becomes possible to use condensers in series with each lamp in order to secure a limitation of the voltage. The use of condensers is economical and it is possible to locate them easily in the socket of the lamps. Moreover, the brilliance of the lamps may be regulated with great facility.

With the above and other objects in view which will become apparent from the detailed description below, some preferred methods for carrying out the invention are described below and shown in the drawings in which:

FIGURE 1 is a schematic showing of a circuit for supplying luminescent lamps with current by means of a self-oscillating generator using a tetrode, and

FIGURE 2 is a schematic showing of a modification of such a construction wherein the self-oscillating generator is formed by two tetrode tubes.

In the drawings, similar reference characters are applied to like parts.

Referring to FIGURE 1, a tetrode tube 10 of usual construction comprises a cathode 11, an anode 12, and the control grid 13 and screen grid 14. Connected to the anode 12 is the output circuit which comprises the inductance coil 15 which is connected to a high voltage at 16 and a condenser Zll. To the inductance coil 15 is coupled an inductance coil 17. The coil 17 is wound in a direction opposite the winding of coil 15 which gives to the control grid 13, in series with a condenser 18, an induced voltage of opposite phase to that of the anode 12 and allows consequently the oscillations of the tube as is well known in the operation of oscillators. The current of the grid 13 flows to the cathode 111 through a resistance 19.

The inductance coil 15 is coupled to an inductance coil 21 which is connected by a line 22 to the luminescent lamps 23, 23a, and 2312 which are to be supplied with current and which are connected in parallel. A switch 24 and a condenser 25 are connected in series with each lamp.

It is known that a self-oscillating tube having its anode connected to the load, would have a grid reaction which is adapted in each case to the normal current of the tube if it is desired that such tube would operate under normal conditions. in particular, if the tube is drawing the maximum power that it can give, the reaction grid having been regulated to its normal value, then the cutting out of the load brings about an increase of the grid current which can deteriorate the tube.

The system as shown provides automatic regulation of the grid current within very large limits and provides self regulation during operation regardless of the load upon the tube.

It is known that in a tetrode tube, mounted as usual,

the current feeding the screen grid varies in the opposite direction to the anodic current which increases as the power demanded by the tube increases. It results therefore that the current of the screen grid diminishes when the power demanded by the tube increases. On the other hand it is known that the slope of a tetrode tube and consequently its amplifying power Varies proportionally to the screen voltage.

In accordance with the invention the variation of the current of the screen grid is used in order to produce a variation of the screen voltage which in each case adapts the amplification of the tube to the anodic load, while maintaining substantially constant the grid reaction and therefore the current of the grid.

Under these conditions the more the anodic current increases the more the current of the screen grid diminishes and consequently the more the screen voltage increases which brings about an increase of the slope of the tube and of the amplification.

As shown in FIGURE 1, current for this purpose is supplied to the screen grid 14 across a resistance 26 of suitable value which is connected at 27 to a voltage which is very much greater than the normal operating voltage of the screen grids.

Therefore, if a single lamp is fed by closing one of the switches 24 the current of the anode is slight and consequently the current of the screen grid is high with a small screen voltage. The slope of the tube is slight which corresponds to a small grid current.

As the number of lamps in service are increased the anode current increases, the screen grid current diminishes and the screen voltage increases from which there is an increase of amplification.

In this way there is therefore obtained a correct operation of the oscillator regardless of the load, that is the number of lamps placed in service, the system according to the invention allowing securing an automatic regulation of the screen voltage in order to maintain the grid current within normal limits.

As an example, when a commercial tetrode tube of the type 4-250 A/5D 22 mentioned in RCA Tube Handbook HB3 vol. 9-10 is used, the values of the difierent elements in the system are the following:

The inductance 15 :800,u.h with the condenser 20 of 3000/J4Lf, which tunes the output circuit of the tube to about 100 kilocycles per second.

The voltage at the terminals of coil 21 is about 340 volts. If the tube 10 is not loaded, that is, if no lamp is lighted the anodic current is about 80 ma, the screen current is 62 ma. and the screen voltage is about 250 volts. Under these conditions, the current of the grid 13 in the resistance 19 is about 20 ma. If all the tubes are lighted,that is if a power of the order of 1 kw. is charged, the anodic current will be 500 ma. and the screen current goes down to 50' ma. The screen voltage will therefore be 500 volts and the grid current in the resistance 19 will be about ma. Between Zero load and full load the currents and voltages will be between the extreme values indicated above.

It is also possible to use some other types of oscillators than that described above. For instance, an oscillator 4 such as that shown in FIGURE 2 may be used which comprises two tetrodes 30 and 30a with the anodes 50 and 50a, the cathodes S1 and 51a, the screen grids 44 and 44a and control grids 43 and 43a respectively. The circuits of the anodes 50 and 50a of these tubes are connected to the output circuit 31 which comprises an inductance coil 32 and the capacities 4S and 45a. The middle point of the inductance 32 is connected to a high tension at 33 through a choke coil 34 designed to stop parasitic oscillations. The middle point between the condensers 45 and 45a is connected at 51. to the ground.

The inductance 32 is coupled to an inductance 35 connected by a line 36 with the fluorescent lamps 37, 37a to be fed with current which are connected in parallel. In series with each lamp is an interruptor 33 and a condenser 39.

To the screen grid 44 of the tube 30 is connected a resistance 40 and to the screen grid of the tube 30a is connected a resistance 40a. The middle point between the two resistances 40 and 40a is connected by a resistance 42 to a source 41, whose voltage is higher than the normal voltage for the operation of the screens. Between the grid 44 and the resistance 40 and between the grid 44a and the resistance 40a are connected respectively the condensers 48 and 43a connected to the ground.

The anode 50 of the tube 30 is connected through a condenser 46a to the control grid 43a of the tube 30a, a resistance 47a being coupled to the cathode 51a and being connected between the said grid and the condenser 46a. Likewise the anode 50a of the tube 30:! is connected through a condenser 46 to the control grid 43 of the tube 30, said grid being coupled to the cathode 51 through a resistance 47.

The operation of this arrangement is the same as that of FIGURE 1.

The high frequency generator formed by the tubes 30 and 30a is self oscillating. In fact, the grid 43 of the tube 30 has the same phase as the anode 50a of the tube 30a and the current 43:: of the tube 30a has the same phase as the anode 50 of the tube 30. In this Way there is realized an equilibrium mounting in which the grids 43 and 43a have phases of opposite signs to the anodes of their respective tubes, that is, respective to the anodes 50 and 500. It is therefore a self-oscillating generator as in the case of FIGURE 1.

The arrangement of FIGURE 2 also allows in the same way as that of FIGURE 1, obtaining a regulation of the current of the grids 43 and 43a of the tubes 30 and 30a. The more the anodic current increases in the tubes, the more the current of the screen grids 44 and 44a diminishes by reason of the voltage fall in the resistances 40, 40a and 41 which play the same role as the resistance 26 of FIGURE 1. Whatever may be the load within the limit compatible with the maximum output power that can be given to the generator, that is, whatever may be the number of lamps 37 placed in service the amplification of the generator adapts itself to the anodic load by maintaining the currents of the grids within normal limits.

- Condensers 46 and 46a automatically regulate the voltage applied to and discharging from grids 43 and 43a, which, on one hand, prevents the high voltage from being applied upon the grid while allowing the application of the induced voltage and, on the other hand, blocks the grid current towards the anode while allowing the passage of the current through the resistances 47 and 47a, to the cathodes 51 and 51a which are automatically polarized.

The condensers 48 and 48a have for a function to decouple the screen grids of the tubes, that is, to prevent the appearance of the high frequency tensions upon the grids.

For constructing different modifications it is possible to use tubes similar to the tube of the preceding modification, the values of the different elements being the following:

Inductance 32: 8000 ,uh.

Condensers td-45a: 6000 ,u Lf. each. Winding 34: 8,000 f.

Condensers 4646a: 1,000 ,u/Af. each. Condensers 48-48a: 0.1 ,tf. each. Resistances 474ia: 15,000 ohms each. Resistances 40-40a: 10,000 ohms each. Resistance 42: 5,000 ohms.

The load circuit is the same as in the preceding modification.

It is understood that the invention may be applied to the lighting of all types of luminescent lamps. Fluorescent lamps which do not comprise electrodes or filaments may be used and in particular lamps having at each end a simple plate provided with points.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the process, form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the forms hereinbefore described and illustrated in the drawings being merely preferred embodiments thereof.

I claim:

1. A gas discharge lamp system comprising a tube type self oscillating high frequency generator having a cathode, anode, control grid and screen grid, means automatically regulating the voltage of said screen grid maintaining the grid current Within a suitable range, an output Winding for said generator, a plurality of gas discharge lamps connected in parallel circuits, a separate capacitance in series with the lamp in each parallel circuit, a coupling Winding connected across all of said parallel circuits and inductively coupled With said output Winding, switch means for selectively connecting and disconnecting any number of said gas discharge lamps, said gas discharge lamps being supplied with supply voltages of the order of 100 kiloc cles so that the cycle duration thereof will be substantially shorter than the deionization time of the gas in said lamps.

2. A gas discharge lamp system as set forth in claim 1 6 wherein a high voltage source is connected to said screen grid including a resistance.

3. A gas discharge lamp system, which comprises a self-oscillating high-frequency generator having an output Winding, a number of gas discharge lamps connected in parallel circuits, a capacitance and a cut-01f switch in series with the lamp in each parallel circuit, and a coupling Winding connected across all of said circuits and inductively coupled with said output Winding.

4. A gas discharge lamp system, comprising a number of discharge lamps, an oscillation generator adapted for generating a frequency such that each cycle thereof is substantially shorter than the time required to de-ionize any of said lamps, an output Winding in said generator, means connecting said lamps in a number of parallel circuits each containing in series a particular one of said lamps, a cut-off switch and an impedance, and a load winding connected in parallel with all of said circuits and inductively coupled with said output winding.

5 A gas discharge lamp system comprising a self oscillating high-frequency generator having an output Winding, a plurality of gas discharge lamps connected in parallel circuits, a capacitance in series with the lamp in each parallel circuit, a coupling Winding connected across all of said parallel circuits and inductively coupled With said output Winding, and switch means for selectively connecting and disconnecting any number of said lamps.

6. A system as claimed in claim 5, wherein said capacitance has a capacity value of the same order of magnitude as the impedance of said lamp in operation.

7. A system as claimed in claim 5 wherein said generator comprises electron tubes including screen grids therein, and means for automatically regulating the screen grid voltage for maintaining the grid current Within predetermined limits.

References Cited in the file of this patent UNITED STATES PATENTS 1,843,288 Leonard Feb. 2, 1932 2,001,836 Craig May 211, 1935 2,050,135 Tour Aug. 4, 1936 2,086,668 Fodor July 13, 1937 2,488,169 Browner Nov. 15, 1949

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