Device for reducing electromagnetic interference of a fiuorescent illumination device, arrangement, fiuorescent illumination element, fiuorescent tube element and method of reducing electromagnetic interference of a fiuorescent illumination device

Field of the invention

The present invention relates to fiuorescent illumination technology in general. In particular it relates to a device for reducing electromagnetic interference of a fluorescent illumination device, an arrangement comprising a device for reducing electromagnetic interference, a fiuorescent illumination element, a fiuorescent tube element and a method of reducing electromagnetic interference of a fluorescence illumination device. Background of the invention

A fiuorescent fixture employing a fiuorescent tube is a gas discharge lamp employing electrical power to excite mercury vapour. The excited mercury atoms generate shortwave ultraviolet light causing a phosphorous substance arranged at the inside of the fiuorescent tube to produce visible light.

A fiuorescent tube regularly is provided as an elongated tubular element, e.g. made of glass, having filaments at each of the two sides or ends of the tube. Each filament regularly is connected employing two pin-shaped elements, each pair constituting a dedicated connector element to allow a current flow through the filaments for preheating. A fluorescent fixture normally comprises a housing accommodating an inductive ballast as well as a starter unit, e.g. an automatic glow starter, for providing a starting means for applying high voltage to the fluorescent tube, in particular for starting the fluorescent tube, also known as striking the arc within the tube. The inductive ballast is employed for regulating the current flow through the tube, i.e. limiting the current flow.

The housing of a fluorescent fixture comprises socket elements for attaching and holding the fluorescent tube. According socket elements e.g. are referred to as G13 or G5 socket elements.

An electronic ballast unit may be employed instead of an inductive ballast resulting in a reduced power loss of the fluorescent fixture as compared to an inductive ballast. The electronic ballast unit may also comprise the functionality of the starter unit, so that a dedicated, separate starter unit may not be required any more when employing an electronic ballast unit. Since a fluorescent fixture normally comprises a dedicated socket for a starter unit, a short-circuited element being mechanically compatible to the starter unit socket may be employed for closing the circuit of the fluorescent fixture.

Fluorescent fixtures are differentiated regarding the fluorescent tube employed.

Fluorescent tubes are referred to as T12, T10, T8, T5 and T4 type tubes. Each tube standard or fixture standard comprises defined mechanical properties of the tube, e.g. a specific length, diameter and connecting means, as well as defined electrical properties, e.g. power consumption associated with an achievable illumination brightness.

Since one aspect of employing a tube of a newer type may also include employing an electronic ballast unit for a fluorescent fixture, which is inherently more power- efficient than e.g. an inductive ballast, the use of an electronic ballast unit may result in an increased voltage frequency possibly increasing electromagnetic radiation and thus electromagnetic interference. Accordingly, there may be a need for reducing electromagnetic interference of a fluorescent illumination device when employing an electronic ballast unit. Also, since tubes of a newer type or standard are preferable to tubes of an older type or standard, in particular regarding their power efficiency and illumination brightness there may be a need for retrofitting fiuorescent fixtures designed for an older standard with fiuorescent tubes of a newer standard as well. Document DE 198 53 138 describes an arrangement for an energy efficient fluorescent fixture.

Summary of the invention Accordingly, a device for reducing electromagnetic interference of a fiuorescent illumination device, an arrangement, a fiuorescent illumination element, a fluorescent tube element and a method of reducing electromagnetic interference of a fluorescent illumination device according to the independent claims is provided. Preferred embodiments of the present invention may be derived from the dependent claims.

One aspect of the present invention may be seen in employing a fiuorescent tube element of one type in a fiuorescent fixture designed for a different, possibly older type. E.g. a T5 type fiuorescent tube may be employed in a T8 type fluorescent fixture. Also an electronic ballast unit may be employed in addition to an inductive ballast.

However, employing an electronic ballast unit may result in an increase in electromagnetic interference, since also the cabling of the fiuorescent fixture is subjected to the high frequency generated by the electronic ballast unit. Accordingly, a filter unit may be employed for reducing electromagnetic interference. With dedicated electromagnetic interference measurements, e.g. according to EN55015, which measures electromagnetic interference in relation to ground potential, employing a filter unit may not be sufficient for passing EN55015. Accordingly, a further reduction of high frequency energy from the cabling of the fiuorescent fixture towards ground potential may be required.

One aspect of the present invention may be seen in employing an element for conducting high frequency energy from the cabling of the fiuorescent fixture towards the ground connector of the fiuorescent fixture. In particular, a capacitor element may be employed, acting as a high pass element for high frequency energy. An according capacitor element may e.g. be an Y-capacitance element, in particular a Y2-capacitance element, e.g. having 4,7 nF/250 V AC. A capacitance element of up to maximally 4,7 nF/250 V AC may be employed to satisfy safety regulations. An according capacitance element may be connected to the cabling of the fiuorescent fixture at one side with the other side of the capacitance or capacitor element being connected to the ground connector of the fiuorescent fixture.

Since it may be preferred to not be required to alter installed parts, e.g. mounted to a ceiling in a building installation, of a fiuorescent fixture in any way, an according element for conducting high frequency energy to ground potential may preferably be installed by/with an additional element introduced or employed when substituting a fluorescent tube element of one type with an fiuorescent fixture of another type.

E.g. in the case of a T5 type tube and a T8 type fixture, a filter unit and an electronic ballast unit may be attached each to one of the sides of the fiuorescent tube, thus accommodating the tube between the electronic ballast unit and the filter unit. The resulting arrangement of at least the fiuorescent tube of one type and the filter element but also an arrangement comprising an electronic ballast unit, a filter unit and a fiuorescent tube of one type, may be in accordance with a defined size of a fluorescent tube of a further type. E.g. when employing a T5 type tube, after the attachment of the filter unit and the electronic ballast unit, the resulting arrangement may be mechanically and electrically compatible to an T8 type tube. Subsequently, an according arrangement may be installed in a fluorescent fixture according to the T8 type standard.

In the case of employing an electronic ballast unit, a dedicated starter unit may not be required any more. Since a starter socket without a starter unit installed would result in the circuit of the fluorescent fixture being open, a short-circuited element, mechanically and electrically compatible with a starter unit may be employed, substantially bridging or short-circuiting the connectors of a starter unit socket.

In the context of the present patent application, an element that is mechanically and/or electrically compatible to a starter unit is to be understood as an element which is mechanically and/or electrically adapted for installation in a starter unit socket as known in the art.

Such a short-circuited element may provide a means for attaching one side of the capacitor element for conducting HF frequency to ground potential with the second side of the capacitor element being attached to an element of the fluorescent fixture substantially connected to or located on ground potential, e.g. the grounding conductor or protective conductor of the housing of the fluorescent fixture or for example the metallic housing of the fluorescent fixture itself, which regularly is connected to protective earth. Also, the filter unit attached to one side of the fluorescent tube may comprise the capacitor element arranged between the filter element and protective earth.

Furthermore, it may be conceivable that the electronic ballast unit employed provides a suitable means for connecting a capacitor element to ground potential or protective earth. E.g. within the electronic ballast unit, the capacitor element may be connected to one of the AC inputs, the high frequency ground/earth or a part voltage of the mains voltage/line voltage and the DC voltage. Since a position of the electronic ballast unit within the circuit of the fluorescent fixture may not be unambiguously determined but may rather be dependent on a specific implementation of setup, the main principle may be seen as providing a „virtual ground" or„virtual earth", e.g. comprising of 4 capacitance elements between„plus" and„minus" as well as„phase" and„neutral" or between DC and AC. The central connector of virtual ground may then be connected via the capacitor element according to the present invention to ground potential of the power feed. An according element, e.g. a short-circuited element, a filter unit or an electronic ballast unit may comprise the connecting means for connecting the capacitor element to ground potential. For example, an according connecting means may be a flexible connecting means, e.g. a cable conductor or spiral cable conductor, penetrating to the outside from the respective element. An according connecting means may subsequently be attached to a suitable part of the fluorescent fixture arranged connected ground potential. The connecting means may be attached to a metallic housing of the fluorescent fixture, e.g. by a magnetic element, possibly having a further element penetrating an insulation layer, e.g. a paint layer arranged on the outside of the housing of the fluorescent fixture.

A conductive connection may also be provided by employing an adhesive element, e.g. an adhesive metallic element or adhesive metallic disk-shaped element, to which the connecting means may be attached to by adhesion or by the magnetic element. When employing an adhesive metallic element, a further capacitor element may be generated on the surface of the metallic housing of the fluorescent fixture, suitable for conducting high frequency energy to ground potential.

The working principle of the electromagnetic interference reduction may be seen as follows.

The fluorescent tube itself or the fluorescent fixture, i.e. the cabling of the fluorescent fixture, may be considered an antenna emitting interference frequencies to the surroundings. Since grounded earth regularly is arranged in the vicinity of the fluorescent fixture, the earth conductor may be receiving a substantial part of the interference energy. In measurements relating to electromagnetic interference, an according behavior may result in an increase in electromagnetic interference, since e.g. according to EN55015, an interference measurement is conducted relative to protective earth.

Here, the capacitor element according to the present invention is employed to connect, at least for high frequency energy, the neutral conductor to protective earth. In other words, the HF interference voltage may be conducted to protective earth by employing the capacitor element. In particular, by employing the capacitor element a conducting high frequency connection between high frequency ground and fluorescent fixture ground is provided. In other words, for high frequency energy, neutral and earth are conductively connected by the capacitor element. In particular, interference energy shall be short-circuited within the fluorescent fixture by the capacitor element rather than being conducted by protective earth.

It may also be conceivable to employ instead of a capacitive connection to ground potential, a shielding element connected to neutral, e.g. a conductive or metallic reflector, for example the light reflector of a fluorescent fixture or an interceptor electrode, for a high frequency coupling of the shielding element to neutral.

However, also between the shielding element and neutral a capacitor element may be employed. A fluorescent tube comprises a first side and a second side with according connector elements. However, it is to be understood that the principle characteristic of a fluorescent tube is that both sides are substantially interchangeable, e.g. a tube may be considered to be symmetrical with regard to the first and the second side.

Accordingly, when in the context of the present patent application one element is attached to a first side, it flows from here that the side or reference to the side itself is non-limiting, e.g. the respective element may also be connected to the second side and vice versa. An electronic ballast unit according to the present invention may be one that is attached to a side of the fiuorescent tube or that may also be arranged to be situated, both mechanically and electronically compatible, in a starter unit socket.

Also, e.g. in the case of the United States and Japan, a fiuorescent fixture may not be comprising a starter unit socket at all, due to different standardized constructions of fluorescent fixtures in the respective countries. In case no dedicated starter unit socket is provided, the respective capacitor element may only be included in one of the electronic ballast unit or the filter unit for a fiuorescent tube element. In case no starter unit is employed for a respective fiuorescent fixture, a fiuorescent tube having a conductive element running inside or alongside, e.g. arranged on the outside of the fluorescent tube, for conductively connecting an electronic ballast unit and a filter unit to provide the necessary closed circuit for starting fiuorescent tube without a dedicated starter unit. An according conductive element alongside a fiuorescent tube may substantially be seen as a short-circuited starter unit socket. In this particular case, both the filter unit and the electronic ballast unit may comprise a further connection element adapted to contact with the conductive element of the fiuorescent tube for generating a closed electrical circuit.

It may be in particular beneficial to provide at least one of the filter unit and the electronic ballast unit or both in a specific dimension that results, when attached to a fluorescent tube of a specific type having a specific size or length, in an overall dimension of the composed arrangement, which dimension corresponds to a further defined length/dimension of a fiuorescent tube, e.g a fiuorescent tube of a different type.

E.g. by employing an electronic ballast unit and/or a filter unit and a T5 fiuorescent tube, the resulting arrangement may be having a length of a fiuorescent tube as standardized in the T8 standard. However, then applying a filter unit and/or an electronic ballast unit to a fiuorescent tube of a defined type, the resulting arrangement may also have a specific length of a further fluorescent tube of the same type.

In the context of the present patent application, an electronic ballast unit and/or filter unit that is "type adapted" is to be understood as being suitably dimensioned to result, when attached to a fluorescent tube, in an overall dimension or length of the arrangement equaling the dimension or length of a certain type of fluorescent tube. Also, a "type adapted" electronic ballast unit/filter unit is also electrically and mechanically compatible to both a fluorescent tube employed and to the tube sockets employed in the fluorescent fixture.

E.g. in the case of a T8 type fluorescent fixture and a T5 type fluorescent tube, both a "type adapted" electronic ballast unit and a filter unit comprise connecting means compatible to the G13 tube connectors of the fluorescent fixture and the G5 tube connectors of the T5 type tube.

An arrangement comprising a filter unit, a fluorescent tube and possibly an electronic ballast unit may be incorporated in a housing, which is at least partly translucent, e.g. translucent in an area where the fluorescent tube is arranged within the housing, with further a filter unit and/or an electronic ballast unit arranged within the partly translucent housing in a substantially rigid manner, thus resulting in an arrangement, which, to a user asked with the substitution of a fluorescent tube, substantially constitutes a single unit as compared to a fluorescent tube, a filter unit and/or an electronic ballast unit as separate elements. Such an arrangement may appear, e.g. as a T8 type fluorescent tube from the outside, both electrically and mechanically, while in the inside a filter unit, an electronic ballast unit and a T5, T8 or T10 type fluorescent tube may be arranged. An according arrangement may be considered a retrofit arrangement, thus allowing a newer technology fluorescent tube to be employed in an older technology fluorescent fixture without the need for changing any component of the fixture itself. Possibly, only the installation or exchange of a regular starter unit with a short-circuited element may be required. Any or all of the arrangement, the short-circuited element, the filter unit and/or the electronic ballast unit may comprise the capacitor element adapted for conducting high frequency energy to ground potential in accordance with the present invention.

Said elements may comprise a plug element for connecting e.g. a flexible connecting means to the element for further connecting the capacitor element to ground potential, e.g. by conductively connecting to the fluorescent fixture housing. Thus, to a user, it is substantially irrelevant what exact parts or what type of fluorescent tube are/is arranged inside of the at least partly translucent housing.

Rather, the user may only be required to pay particular attention to what type of fluorescent fixture is currently employed and whether an according retrofit adapter may be suitable for said fixture.

Employing a newer technology fluorescent tube in an older or different technology fluorescent fixture may in particular provide the benefits of increasing light quality, reducing energy consumption, C0 ₂ output and electromagnetic interference and may also provide means for employing different fluorescent tube arrangements, possibly specifically adapted to an application scenario in one and the same fluorescent fixture. Also, in case a fluorescent tube for an older technology fixture may not be available any more, the fixture or fixture itself may still be continued to be used with a retrofit arrangement rather than being replaced, resulting in reduced installation costs without the need to install new fluorescent fixtures.

The described technology may not only be employed for fluorescent tubes but may also be employed for LED arrangements, incandescent fixtures, halogen bulb fixtures, OLED arrangements, HQI fixtures, xenon fixtures or sulphur-argon fixtures. In case a fluorescent tube malfunctions, the electronic ballast unit may deactivate itself automatically to avoid overheating or destruction of the electronic components. After deactivation, after a defined interval the electronic ballast unit may be adapted to try a restart of the tube. E.g. after deactivation, every half hour or every 15 minutes an according restart may be performed or tried.

It is to be noted, that while multiple possibilities for a suitable connection position of the capacitor element according to the present invention are disclosed and described, each respective element, electronic ballast unit, filter unit and short-circuited element compatible to a starter unit is also performing their respective basic functionality without of said capacitor element. Thus, the electronic ballast unit, the filter unit and the short-circuited element compatible to a starter unit are also explicitly disclosed without and independent from said capacitor element, possibly comprising further features as described below and above.

The electronic ballast unit may also be adapted to perform a softstart of the fluorescent tube. A softstart may be characterized by a starting sequence first employing a high frequency for stating and a low voltage. During the starting sequence, the frequency of the starting pulse is reduced while at the same time, the starting voltage is increased. At first, a minor current is flowing through the fluorescent tube until in the end of the starting sequence, full operating current is flowing through the fluorescent tube. An according softstart is a gentle and material conserving starting process, which may be comparable to a warmstart of a common fluorescent tube.

These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereinafter.

Exemplary embodiments of the present invention will be described below with reference to the following drawings.

The illustration in the drawings is schematic. In different drawings, similar or identical elements are provided with similar or identical reference numerals.

The figures are not drawn to scale, however may depict qualitative proportions. Brief description of the drawings

Fig. 1 shows an exemplary embodiment of an arrangement according to the present invention;

Fig. 2 shows a further exemplary embodiment of an arrangement according to the present invention;

Fig. 3 shows a further exemplary embodiment of an arrangement according to the present invention;

Fig. 4 shows exemplary embodiments of the device of the present invention in the arrangement according to Fig. 1;

Fig. 5 shows an exemplary embodiment of a fiuorescent tube element according to the present invention;

Fig. 6 shows an exemplary embodiment of an installation of an arrangement

according to the present invention; and

Fig. 7 shows an exemplary embodiment of a filter unit according to the present invention.

Detailed description of embodiments

Now referring to Fig. 1, an exemplary embodiment of an arrangement according the present invention is depicted.

Fig. 1 displays a fiuorescent fixture 2 schematically. Fluorescent fixture 2 is employing a common power feed employing phase conductor 6, neutral conductor 8 as well as a ground conductor or earth conductor 10.

The fiuorescent fixture 2 comprises two tube sockets 12, e.g. G13 type sockets or any other applicable standardized tube socket. Tube sockets 12 are spaced apart a length Li, which may be seen as a specific tube length of a given fiuorescent tube type or standard. E.g. in the case of a T8 fiuorescent tube, Li may e.g. be 1500 mm and accordingly, sockets 12 are spaced apart such a length to allow mounting of a fluorescent tube 4 with a length of 1,5 m.

An inductive ballast may possibly still be arranged connected to fluorescent fixture 2, however it is not depicted in Fig. 1.

Fluorescent fixture 2 comprises a starter socket 18 for mounting of a regular starter unit. In case of Fig. 1 however, the starter unit is substituted by a short-circuited element 18a, depicted as connecting or bridging the two socket connectors of starter socket 18.

The succession of elements in fluorescent fixture 2 may be seen as follows. Starting from phase connector 6, a conductor enters socket 12, subsequently enters electronic ballast unit 14, which is only depicted schematically. From electronic ballast unit 14 the fluorescent tube is continues with filaments 28 being connected to the electronic ballast unit 14. The circuit enters at one filament 28 from electronic ballast unit 14 through one pin and leaves on the same side of tube 4 again to the electronic ballast unit 14, subsequently leaving electronic ballast unit 14 through the second

conductive element of tube socket 12. Following, starter socket 18 with short- circuited element 18a is arranged and subsequently the second tube socket 12 enters filter unit 16, leaves filter unit 16 for the second filament 28 on the second side of tube 4, crosses the filament 28, reenters filter unit 16 to subsequently leave filter unit 16 through the second pin of tube socket 12 towards neutral conductor 8. In case tube 4 is operating, i.e. illuminating, substantially no current is travelling through short-circuited element 18a and the respective conductors but rather the current is travelling through fluorescent tube 4 emanating from filaments 28.

The power feed provides exemplarily 240 V AC to fluorescent fixture 2.

Fluorescent tube 4, in case it is assumed that fluorescent fixture 2 is specified for a T8 type fluorescent tube, may however not be a T8 type fluorescent tube but may e.g. be a T5 type fiuorescent tube. A T5 type fiuorescent tube may e.g. have a length L ₃ of 1449 mm and may employ a G5 socket rather than a G13 socket of a T8 type fiuorescent tube. Accordingly, L ₂ of the filter unit 16 as well as L ₄ of the electronic ballast unit 14 may be arranged to provide an additional length to the arrangement of filter unit 16, fluorescent tube 4 and electronic ballast unit 14 so that Li = L ₂ + L3 + L ₄ . In other words, the arrangement of filter unit 16, tube 4 and electronic ballast unit 14 may equal in length and connection capability a T8 type tube having exemplarily a length Li = 1500 mm, while employing a T5 type tube having e.g. a length L3 = 1449 mm. Both the filter unit 16 and the electronic ballast unit 14 may thus be required to provide a G13 compatible connecting means on one side, the side connected to the fluorescent fixture 2, and a G5 compatible connecting means on the second side, the side connected to the fluorescent tube 4.

While in the description of Fig. 1 , T8 type fluorescent fixtures and T5 type fluorescent tubes are exemplarily given, it is to be understood that any desired fixture/tube combination, as long as mechanically and electrically feasible, may be provided by an according arrangement.

Now referring to Fig. 2, a further exemplary embodiment of an arrangement according to the present invention is depicted.

Fig. 2 substantially corresponds to Fig. 1 with the exception that fluorescent fixture 2 does not comprise a dedicated starter circuit and thus lacks starter socket 18 and the associated cabling between the two tube sockets 12. An according fixture may e.g. be employed in the United States and Japan.

In parallel to fluorescent tube 4, a conductor element 20 is arranged, which is providing a conductive connection between filter unit 16 and electronic ballast unit 14, comparable to the starter circuit conductor of Fig. 1. The conductor element may either be incorporated into fluorescent tube 4 or may be attached to the outside of fluorescent tube 4, possibly being insulated. The connection of conductor element 20 to filter unit 16 and electronic ballast unit 14 is only depicted schematically. Again, for a preferred substitution of one type of fluorescent tube 4 with another type of fluorescent tube 4 Li shall equal Li = L ₂ + L ₃ + L ₄ .

Now referring to Fig. 3, a further exemplary embodiment of an arrangement according to the present invention is depicted.

Fig. 3 substantially corresponds to Fig. 1 , with the exception that electronic ballast unit 14 is arranged suitably for being connected to the starter conductor circuit via starter socket 18. In particular, electronic ballast unit 14 is required to be both mechanically and electrically compatible to a common starter unit. Since in the case of Fig. 3, the extension of the electronic ballast unit 14, previously referred to as L ₄ is not present any more, arranged adjacent to fluorescent tube 4, either filter unit 16 may be required to be of a different dimension such that Li = L5 + L ₆ . Assuming that the length of fluorescent tube 4 of Fig. 3, L ₆ , equals the length of fluorescent tube 4 of Figs. 1 and 2, L ₃ , the length of filter unit 16 L ₅ may be required to correspond to L ₅ = L ₂ = L ₄ . However, it also is conceivable to employ a fluorescent tube 4 having a length L ₆ different from L ₃ , thus resulting in the only requirement of the length Li = L ₅ + L ₆ .

Since in the case of Fig. 3, one side of fluorescent tube 4 still has to be connected to the original tube socket of fluorescent fixture 2, this has to be taken into account when substituting different types of fluorescent tubes 4. Possibly, only a conversion element for tube socket 12, e.g. a conversion element from a G13 to a G5 tube socket may be employed, for providing mechanical compatibility without the necessity to include electronic components. Such a conversion element may also comprise a defined length for adapting the overall length of the resulting arrangement of filter unit 16, tube 4 and conversion element to correspond to a defined tube type length, e.g. to Li . Now referring to Fig. 4, exemplary embodiments of the device of the present invention in the arrangement according to Fig. 1 are depicted.

Fig. 4 substantially corresponds to Fig. 1 , further comprising capacitor elements 22a,b,c for reducing electromagnetic interference of the fluorescent fixture 2 depicted in detail. Each of the elements electronic ballast unit 14, filter unit 16 and short-circuited element 18a may comprise a capacitor element Ci, C ₂ , C ₃ 22a,b,c for connecting a part of the conductor circuit (phase/neutral) to ground potential 10. Capacitor elements 22a,b,c may thus be seen as providing a high frequency conductive path from fluorescent fixture 2 to ground potential. Capacitor elements 22a,b,c may e.g. be a Y-capacitor, in particular a Y2-capacitor.

Now referring to Fig. 5, an exemplary embodiment of a fluorescent tube element according to the present invention is depicted.

Fig. 5 shows a fluorescent illumination element 25, comprising a housing 26, which is exemplarily featuring a length Li in accordance with Figs. 1-4. Connection elements 24 are arranged on each of the two sides of the fluorescent illumination element 25 for connecting to tube sockets 12.

In the inside of housing 26, a filter unit 16, a fluorescent tube 4 as well as an electronic ballast unit 14 are arranged and conductive ly connected to provide a so- called retrofit or substitution fluorescent tube element. E.g. again in the case of the example of T8 and T5, the dimension Li and the connector elements 24 may correspond to an according length and connection tube socket 12 according to a T8 type fluorescent fixture 2 while fluorescent tube 4 inside the housing 26 actually constitutes a T5 type tube with appropriate electronic ballast unit 14 and filter unit 16 attached to its sides to provide compatibility to a T8 type. Housing 26 may comprise a translucent part 26a, in particular in the region of fluorescent tube 4 and possibly non-translucent parts 26b in the region of electronic ballast unit 14 and filter unit 16. Now referring to Fig. 6, an exemplary embodiment of an installation of an arrangement according to the present invention is depicted.

In Fig. 6, a fluorescent fixture 2 is depicted, e.g. for a T8 type fluorescent tube 4. Fluorescent fixture 2 is exemplarily ceiling-mountable and may be connected to a power source via power feed 34. The fluorescent fixture comprises a starter socket 18.

In the example of Fig. 6, fluorescent tube 4 is of a T5 type, employing G5 connectors, while fluorescent fixture 5, being of T8 type, comprises sockets 12 of G13 type.

Attached in between sockets 12, an arrangement comprising electronic ballast unit 14, fluorescent tube 4 and filter unit 16 is located. Both the filter unit 16 and the electronic ballast unit 14 comprise accommodations for receiving fluorescent tube 4 with its G5 type connectors. Both units are substantially cup-shaped having a circular opening for fluorescent tube 4.

In starter socket 18, a short-circuited element 18a is arranged, comprising a plug connection to conducting means 30, exemplarily a flexible spiral cable comprising a magnet element 32 for attaching to and conductively connecting with housing 26 of fluorescent fixture 2.

Now referring to Fig. 7, an exemplary embodiment of a filter unit according to the present invention is depicted. Filter unit 16 comprises an inductance element Li 36 arranged in parallel to the connectors of tube socket 12, thus substantially bridging the starter conductor to neutral 8. An according inductance element may be seen as a low pass filter element, filtering or blocking high frequency energy from neutral 8 while allowing the line voltage to pass substantially uninfluenced.

One side of the inductive element 36 is connected to the filaments 28, which are short-circuited by filament bridging element 38. The electronic ballast unit 14 is thus responsible for "cold-starting" fluorescent tube 4, i.e. without preheating the filaments 28, possibly only preheating the filaments at the side the electronic ballast unit 14 is attached to fluorescent tube 4. In case no preheating of the filaments is required, an according filament bridging element 38 may also be provided within the electronic ballast unit 14 or as a separate element to be attached to a side of fluorescent tube 4, e.g. in case electronic ballast unit 14 is arranged within starter socket 18. Bridging the filament pins may substantially result in a conversion to and may be comparable to an X-type fluorescent tube with only one instead of two connector pins penetrating the housing of the fluorescent tube. An X-type fluorescent tube may e.g. be preferably employed in explosive surroundings since no preheating of the filaments occurs.

Filament bridging element 38, i.e. conductively connection both sides of filament 28, results in a reduced power loss, while at the same time achievable illumination brightness may be increased by about 10%.

Particular attention shall be paid to the installation of filter unit 14 since tube sockets 12 are commonly provided as "insert-and-turn" elements, i.e. fluorescent tube 4 is inserted having a specific alignment and is subsequently turned, e.g. 90° in either direction. In case the fluorescent tube is turned in the wrong direction, instead of shielding HF energy from neutral 8, the inductive element 36 would rather be arranged "shielding" the starter conductor, thus resulting in an even possibly increased electromagnetic interference. An installation with increased EMI may be seen as an installation in which filter unit 16 is arranged mirrored with regard to the longitudinal axis of the fluorescent tube 4, i.e. with the filaments 28 being connected to the neutral 8 side of inductive element 36. The electronic ballast unit 14 may be adapted to determine whether the filter unit 16 has been installed correctly, i.e. with the correct alignment of the filaments 28 with regard to the connection to inductive element 36 and neutral 8 and the starter circuit, as depicted in Fig. 7. Determining an installation position is explicitly referred to as determining a connection position, in particular determining a preferred or correct connection position. In case the electronic ballast unit 14 determines an incorrect positioning of filter unit 14, it may refrain from starting the fluorescent tube 4 to avoid generating unnecessary, increased EMI. An operator may thus turn the filter unit 16 to a correct position, which the electronic ballast unit 14 then detects, subsequently starting the fluorescent tube 4 for illumination. Alternatively, the electronic ballast unit 14 may perform a starting procedure after a defined time interval of e.g. 5, 15 or 30 minutes.

Regularly, an inductance element 36 having an inductance value of about 2mH may be sufficient for shielding purposes as elaborated on before. However, also inductance elements 36 having inductance values of 4mH, 5mH, 6mH, 8mH, 10 mH or even more than lOmH may be employed. In particular, when employing an inductance element 36 with an according inductance value, e.g. lOmH, the increased inductance value may allow the electronic ballast unit to detect a correct or incorrect positioning of filter unit 16.

In case filter unit 16 comprises capacitive element 22b, said element may be attached to that side of the inductive element 36 that is subjected to the interference energy. In other words and as explained before, the installed filter unit 16 shields neutral 8 from the interference energy, thus the capacitve element 22b is attached to that side of inductive element 36 that is also arranged connected to the starter circuit or starter conductor or the conductor element 20. In Fig. 7, capacitive element 36 is attached to the side of inductive element 36 that is also connected to filaments 36. It should be noted that the term "comprising" does not exclude other elements or steps and that "a" or "an" does not exclude a plurality. Also, elements described in association with different embodiments may be combined. It should also be noted, that reference numerals in the claims shall not be construed as limiting the scope of the claims.

5

List of reference numerals

2 Fluorescent fixture

4 Fluorescent tube

6 Phase conductor

8 Neutral conductor

10 Ground conductor

12 Tube socket

14 Electronic ballast unit

16 Filter unit

18 Starter socket

18a Short-circuited element

20 Conductor element

22a,b,c Capacitor element

24 Connector element

25 Fluorescent illumination element

26 Housing

26a translucent

26b possibly non-translucent

28 Filaments

30 Conducting means/flexible conductor

32 Magnet element

34 Power feed

36 Inductance element

38 Filament bridging element