GB2138629A

GB2138629A - High-frequency gas-discharge lamp system

Info

Publication number: GB2138629A
Application number: GB08408948A
Authority: GB
Inventors: Jozsef Laz
Original assignee: Tungsram Rt
Current assignee: Tungsram Rt
Priority date: 1983-04-08
Filing date: 1984-04-06
Publication date: 1984-10-24
Also published as: JPS59205147A; GB2138629B; DE3412686A1; HU186682B; NL8401057A; GB8408948D0

Abstract

The gas-discharge lamp has an outer envelope (5), a gas-discharge tube (2) with electrodes displaced therein, high frequency ballast means (3) for energising the gas-discharge tube (2) by means of conductors (6,7), wherein the supply conductors (6,7) and the gas-discharge tube (2) are so arranged that at least two current- providing loops are formed whose resulting magnetic moment (represented by the curved arrows) oppose and tend to cancel each other out, thereby reducing radio-frequency noise. In other such arrangements the conductor to the electrode farthest from the lamp base is divided into two branches (Figs. 2 and 3); alternatively, (Fig. 4) a separate auxiliary conductor may provide one of the loops. <IMAGE>

Description

SPECIFICATION High-frequency gas-discharge lamp system The invention relates to a high-frequency gasdischarge lamp system, comprising according to the art an outer envelope, a gas-discharge tube with a first and a second electrode displaced in the outer envelope, high-frequency ballast means for energizing the gas-discharge tube connected by a first and a second conductor to the first and second electrode, respectively and contact means for energizing the high-frequency ballast means from an outer current source, wherein the highfrequency ballast means are advantageously arranged in an electromagnetic screen element.

The high-frequency ballast means can be displaced in the neck part of the lamp or in a greater distance from it. The high-frequency gasdischarge lamp system according to the invention is intended to be used in arrangements wherein the allowed level of the radio-frequency radiation is low, or practically equal zero.

By the use of high-frequency electronic ballast means it is possible to increase the light efficiency of the gas discharge tubes and to decrease the price and dimensions of the ballast means. The gas-discharge lamps can be used in a wide freuqency range, however, for diminishing the acoustic and radio-frequency noises polluting the environment the typical values of the operating frequency are from 10 to 100 kHz.

The electric circuit arrangement of a gasdischarge tube and connected high-frequency ballast means generates during use magnetic field with changing intensities which-can cause intensive radio-frequency noise in the work frequency and at the harmonics. The level of the radio-frequency radiation generated by the highfrequency ballast means can be minimalized by use of an electromagnetic screen, e.g. of an earthed metallic housing.The screening of the gas-discharge tube and the supply conductors connected with its electrodes is practically impossible because of the high light losses caused by such a screening if the gas-discharge tube is desired to be used to enterieurs, e.g. in flats it is very important to have a construction generating radio-frequency radiation polluting the environment with very low level, i.e. in distances over 1 to 2 meters the noise level should be practically zero.

In lamp systems with gas-discharge tube without electrodes, supplied with high-frequency current of several 100 kHz to several MHz range there are known solutions for diminishing the level of radio-frequency noises. For example, according to the US-PS 4 187 445 some toroidal coils have to be displaced in the field of the gas discharge in an arrangement ensuring practically zero magnetic dipole moment.

Another solution is described in the US-PS 4 187 447 according to which a conducting loop is displaced around the lamp envelope in order to generate a magnetic field working oppositely to that of the lamp.

In lamp systems with gas-discharge tubes comprising electrodes there is no solution known for diminishing the level of radio-frequency noises of the high-frequency gas-discharge lamp systems except of screening the high-frequency ballast means.

Summary of the Invention The object of this invention is to provide an arrangement for diminishing or in best case avoiding the radio-frequency noises caused by the high-frequency current flowing through a gasdischarge tube of a high-frequency gas-discharge lamp system and the connected conductors and by its harmonics.

The object set can be reached by elaborating a high-frequency gas-discharge lamp system comprising an outer envelope, a gas-disch-arge tube with a first and a second electrode, highfrequency ballast means advantageously arranged in an electromagnetic screen element, for generating high-frequency current energizing the gas-discharge tube connected by a first and a second conductor to the first and second electrode, respectively and contact means for energizing the high-frequency ballast means from an outer current source. The main distinguishing feature of the proposed lamp system is that it applies at least two loops including the conductors, the gas-discharge tube or, if advantageous, an auxiliary conductor, the geometrical arrangement of which is intended to generate magnetic fields with dipole moments acting oppositely to each other giving a zero or low resulting value.

Hence, the invented high-frequency gasdischarge lamp system comprises high-frequency ballast means, a gas-discharge tube with electrodes displaced in an outer envelope and conductors connecting the gas-discharge tube with the high-frequency ballast means, wherein it is advantageous to use an electromagnetic screening element around the high-frequency ballast means. The conductors and the gasdischarge tube are arranged in loops formed in the inner space of the envelope for generating magnetic forces acting against each other. One of the loops includes at least the two conductors. It is possible to use in it also a part of or the whole gas-discharge lamp. A second loop can be constructed also by means of an auxiliary conductor connected to the high-frequency ballast means. The loops are arranged so as to minimalize their resulting magnetic dipole moment.For this aim it is very advantageous to use two loops.

The loop is in the meaning of this description a circuit arrangement wherein the plane projection of the current way forms a loop.

An advantageous embodiment of the porposed high-frequency gas-discharge lamp system comprises the mentioned loops in a symmetrical arrangement It is especially suitable to have an arrangement with central symmetry the axle of which lies parallel or perpendicular with the gasdischarge tube.

In another proposed embodiment one of the conductors is divided into two branches with the gas-discharge tube in-between. The divided branches have a common terminal connected to the gas-discharge tube and it is advantageous to connect their other end to a common point and the common point to the high-frequency ballast means.

As it is conventionally accepted the frequency of the high-frequency current supplying the gasdischarge tube is in the range from 10 kHz to 100 kHz.

Brief Description of the Drawings Further objects, features and advantages of the invention will become better understood by the following detailed description when considered in conjunction with the accompanying drawings, wherein Fig. 1 is a cross-section of a proposed embodiment of the high-frequency gas-discharge lamp system according to the present invention -shown by way of example, wherein the gasdischarge tube and the conductors form gemetrical arrangements with central symmetry of projections, Fig. 2 is a cross-section of a further proposed embodiment of the high-frequency gas-discharge lamp system according to the present invention shown by way of example, wherein the gasdischarge tube and the conductors form geometrical arrangements lying symmetrical to an axle, Fig. 3 is a cross-section of another proposed embodiment of the high-frequency gas-discharge lamp system according to the present invention shown by way of example, wherein the gasdischarge tube and the conductors form geometrical arrangements Ining symmetrical to an axis and one of the conductors is divided into two parts surrounding the gas-discharge tube, and Fig. 4 is a cross-section of a further proposed embodiment of the high-freqeuncy gas-discharge lamp-system according to the present invention shown by way of example, wherein a further loop is formed from an auxiliary conductor.

The invention will be described on the example of lamp systems comprising two loop-shaped geometrical arrangements with current paths lying symmetrically to one another/fig. 1 to 3/and including a part of or the whole gas-discharge tube. It should be understood that lamp systems with higher number of loop-shaped geometrical arrangements are also possible and can be constructed on the basis of the principles shown herebelow. The only requirement is that the arrangement of these loops should ensure a minimal resulting magnetic dipole moment.

As it can be seen from Fig. 1 to 3 a basic embodiment of the proposed high-frequency gasdischarge lamp system 1 comprises highfrequency ballast means 3 surrounded by, if desired, for facilitating the noise protection of the environment an electromagnetic screen 4; an outer envelope 5 and a gas-discharge tube 2 displaced in the inner part of the outer envelope 5.

The gas-discharge tube 2 is a unit with electrodes connected by means of a first conductor 7 and a second conductor 6 to the high-frequency ballast means 3.

The high-frequency ballast means 3 can be an element with well known circuitry according to the art, as it commonly is used in the technics of light sources.

Fig. 1 shows an embodiment with central symmetrical arrangement of two loops, wherein both loops comprise a part of the first and second conductors 7, 6 and one of them includes also the gas-discharge tube 2. The symmetrical arrangement means that the crossing point of the conductors 6 and 7 is a point on the axis of symmetry. The surface of the loops given by the current paths and the direction of the current flow are chosen in a way as to minimalize the resulting magnetic dipole moment of the loops, i.e. the magnetic fields of the loops should ensure mutual weakening of the resulting magnetic forces.If the outputs of the high-frequency ballast means 34n direction of the gas-discharge tube 2 lie not too far from another and a cylindrically shaped gasdischarge tube 2 is used the condition of diminishing the resulting magnetic dipole moment to zero reads as follows: following continuously the contour of a plane projection of the conductor 6 and 7 and the central line of the gas-discharge tube 2 in a direction the surrounded surfaces have to be summed taking into account the sign of the direction of current and the summed surface should give a zero value.

In Fig. 2 an embodiment can be seen wherein two loops are arranged symmetrical to an axis lying in the middle line of the gas-discharge tube 2 and in the plane of the loops. The conductors 6 and 7 lie in the axis of symmetry and from a common terminal the first conductor 7 is divided into the parts forming branches 7a and 7b. In this way two loops come into being which are closed only by the high-frequency ballast means 3 and the directions of the current are opposite. The vectorial sum of the magnetic dipole moments of such loops gives zero or near to zero resulting value. This means that there is an interference between the two current loops in the lamp system according to the invention and this interference ensures a mutual wakening of the magnetic forces acting in the environment of the lamp.

The branches 7a and 7b can be connected to another common point also before connection with the high-frequency ballast means 3, as can be seen in Fig. 3. In this case a part of the conductor 7 remains without compensation and the resulting magnetic dipole moment can not reach the zero value. The resulting moment is, however, low and gives a reasonable, acceptable level of noise in the environment.

It is also possible, as shown in Fig. 4, to use an auxiliary conductor 8. This is a way, too, whereby the magnetic dipole moment of the loop consisting of the first and second conductors 6, 7 and of the gas-discharge tube 2 can be neutralised by means of a second loop consisting of the auxiliary conductor 8. While connected to the high-frequency ballast means 3 the auxiliary conductor 8 is supplied also by a high-frequency current and so it is capable of generating a magnetic field acting against the existing one generated by the loop mentioned above. As described above, the first current loop comprises in this case the first and second conductor 6, 7 and the gas-discharge tube as well and the second the auxiliary conductor 8. In this way a mutual weakening of the generated magnetic fields can also be reached.

It is obvious that the embodiments shown above by way of example are only some advantageous realisations. A man skilled in the art can construct further embodiments. Therefore our invention not to be limited by the examples given above; the scope of portection should be determined on the basis of the attached claims. It can be suitable also to prepare lamp systems with higher number of loops.

The main advantage of the porposed highfrequency gas-discharge lamp system is that by means of a relatively simple construction it is possible to eliminate or at least extensively diminish the level of the radio-frequency noises generated by the gas-discharge tubes supplied through electrodes during operation.

Claims

1. A high-frequency gas-discharge lamp system comprising an outer envelope, a gas-discharge tube, with a first electrode and a second electrode, high-frequency ballast means for generating a high-frequency current for energising the gasdischarge tube connected by a first and a second conductor to the first and second electrode, respectively, and contact means for energising the high-frequency ballast means from an external current source, wherein at least two currentproviding loops are formed from conductors connected to the high-frequency ballast means and from the gas-discharge tube, the loops being arranged so as to minimise their resulting magnetic moment.

2. A lamp system according to claim 1, wherein the high-frequency ballast means is arranged in an electro-magnetic screen.

3. A lamp system according to claim 1 or 2, wherein the loops are arranged so as their current paths are symmetrical.

4. A lamp system according to any preceding claim, wherein there are only two of said loops.

5. A lamp system according to any preceding claim, wherein one loop includes the gasdischarge tube and at least a part of said first and second conductor connected to the high frequency ballast means.

6. A lamp system according to claim 4 or 5, wherein one loop is formed by a part of the first conductor divided into two branches connected by their first terminals to the high-frequency ballast means and by their second common terminal to the gas-discharge tube.

7. A lamp system according to claim 6, wherein the first terminals are connected to one another, so that the second conductor surrounds the gasdischarge tube.

8. A lamp system according to any of claims 4 to 7, wherein in the gas-discharge tube is a part of both loops.

9. A lamp system according to claim 4 or 5, wherein one of the loops consists of the first and second conductor.

10. A lamp system according to any of claims 1 to 5, wherein one of the loops consists of an auxiliary conductor connected to the highfrequency ballast means in the outer envelope.

11. A lamp system according to any preceding claim, wherein the frequency of the current energising the gas-discharge tube is in the range between 10 and 100 kHz.

12. A lamp system substantially as herein described with reference to and as shown in any one of the Figures of the accompanying drawings.

13. A lighting unit comprising a lamp system according to any preceding claim.