Electrodeless Lamp Elektrodenlose Lampe Lampe Sans Électrode

Europäisches Patentamt *EP000678899B1* (19) European Patent Office

Office européen des brevets (11) EP 0 678 899 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.7: H01J 65/04, H01J 61/04, of the grant of the patent: H01J 61/35 24.07.2002 Bulletin 2002/30

(21) Application number: 95302442.9

(22) Date of filing: 12.04.1995

(54) Electrodeless lamp Elektrodenlose Lampe Lampe sans électrode

(84) Designated Contracting States: • Mieskowski, James Dominic DE FR GB IT NL Seven Hills, Ohio 44131 (US)

(30) Priority: 18.04.1994 US 228979 (74) Representative: Goode, Ian Roy et al London Patent Operation (43) Date of publication of application: General Electric International, Inc. 25.10.1995 Bulletin 1995/43 Essex House 12-13 Essex Street (73) Proprietor: GENERAL ELECTRIC COMPANY London WC2R 3AA (GB) Schenectady, NY 12345 (US) (56) References cited: (72) Inventors: EP-A- 0 585 108 DE-A- 4 433 040 • Nerone, Louis Robert US-A- 4 727 294 Brecksville, Ohio 44141 (US)

Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 0 678 899 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 0 678 899 B1 2

Description which can have both conducted and radiated components, is kept below a level which is in compliance with [0001] The present invention relates to an electrode- Government regulatory standards. For instance, Sec- less lamp. tion 18.307(c) of Chapter 47 of the US Code of Federal 5 Regulations requires that for RF lighting products oper- FIELD OF THE INVENTION ating between 1.6 and 30 MHz and being sold into com- mercial and industrial channels of trade, the conducted [0002] An illustrative embodiment of this invention re- emissions level not exceed 3000 microvolts which can lates to an external metallization configuration for an also be expressed as 70 dB(microvolts). For such prod- electrodeless discharge lamp. More particularly, this in- 10 ucts sold into consumer channels of trade, the emis- vention relates to such a metallization arrangement as sions level is even lower. Additionally, the International can be used on an electrodeless fluorescent lamp for ElectroTechnical Commission Standard dealing with the purpose of reducing electromagnetic interference Electromagnetic compatibility of lamps (CISPR 15) re- (EMI) yet at the same time, reduce the effects of eddy quires that the conducted component of EMI in the fre- currents on the performance of the components neces- 15 quency range of between 0.5 and 5.0 megahertz, be sary for driving the discharge within the lamp. less than 56 dB(microvolts). [0005] A number of proposals for the suppression of BACKGROUND OF THE INVENTION electromagnetic interference (EMI) have been made to alleviate this problem. One such proposal is to provide [0003] Compact fluorescent lamps and particularly, 20 a capacitive arrangement by means of a conductive lay- electrodeless discharge fluorescent lamps are consid- er disposed on the inside of the lamp envelope and a ered to be key elements in efforts to reduce energy de- conductive layer disposed on the outside of the lamp, mand stemming from the use of lighting products. Spe- such capacitive arrangement being coupled during lamp cifically, electrodeless discharge lamps offer significant operation to the supply mains. Such a proposal is set energy efficiency advantages over a conventional in- 25 forth in US Patent No. 4,727,294. US Patent Nos. candescent lamp and further offer life expectance ad- 4,568,859 and 4,940,923 also disclose emission sup- vantages even over the popular compact fluorescent pression techniques. While such proposals are some- lamps. Moreover, such an electrodeless fluorescent what effective, there is an inherent disadvantage to the lamp is expected to provide additional energy efficiency use of the metallized conductor placed on the outside gains in that the profile of the electrodeless fluorescent 30 of the lamp envelope to form one of the capacitive lamp as compared to a conventional compact fluores- plates, that is, there are significant eddy currents asso- cent lamp is significantly more consistent with that of ciated with such a conductive layer and such eddy cur- conventional incandescent lamps and as such, will fit rents are detrimental to the starting properties of the into more sockets than will a compact fluorescent lamp. lamp operating circuit. Specifically, the high eddy cur- [0004] An example of an electrodeless fluorescent 35 rents cause a lowering of the output voltage of the ex- lamp can be found in US Patent No. 4,010,400 in which citation coil which in some cases, results in an insuffi- the basic principles of such lamp are described. This cient starting voltage so that the fill does not initially patent discusses that an ionizable medium can be con- break down. tained in a lamp envelope and excited to a discharge [0006] Another proposal for the suppression of EMI state by the introduction of an RF signal in close prox- 40 emissions has been to connect one end of a parasitic imity to the lamp envelope, which lamp envelope con- coil to the exciter coil, that is, the coil member which tains the appropriate phosphor coatings to allow the dis- outputs the RF signal. The other end of the parasitic coil charge energy to be converted to visible light. This pat- would be allowed to float to a voltage equal and opposite ent further discusses that an electric field generated by to that developed across the exciter coil. This results in the RF signal initiates the discharge whereas a magnet- 45 electric field cancellation which can significantly reduce ic field then sustains continuous operation of such dis- the conducted component of RFI. Such an arrangement charge thereafter. In order to generate this RF signal the can be found in US Patent No. 4,710,678. Though ef- electrodeless discharge lamp contains a ballast circuit fective in reducing EMI, this approach also suffers in arrangement disposed in the base of the lamp and which that, by adding an additional relatively expensive com- circuit includes a coil member extending into a cavity 50 ponent, the parasitic coil, the overall cost of the dis- formed in the lamp envelope, the coil member being ef- charge lamp has again been increased by a measurable fective for outputting the RF signal. In order for the elec- amount. trodeless discharge lamp to reach widespread commer- [0007] Accordingly, it would be advantageous to pro- cial acceptance, it will be necessary to achieve this bal- vide a ballast circuit arrangement for an electrodeless last circuit arrangement in a reliable and cost effective 55 discharge lamp which has minimal numbers and cost of manner using as few a number of components as pos- components and satisfies the regulatory requirements sible. Additionally, it will be necessary in the generation relating to EMI suppression, yet does not result in high of the RF signal, electromagnetic interference (EMI), eddy currents which can adversely affect the starting

2 3 EP 0 678 899 B1 4 characteristics of the lamp operating circuit. fluorescent lamp 10 includes a lamp envelope 12 having a lower portion which fits within a housing base assem- SUMMARY OF THE INVENTION bly 17. A conventional threaded screw base 19 is mounted on the housing base assembly 17 for connecting line [0008] Accordingly, it is an object of this invention to 5 power to a ballast circuit arrangement 24 disposed with- provide an electrodeless low pressure discharge lamp in housing base arrangement 17. The ballast circuit ar- which includes an EMI suppression arrangement that is rangement 24 includes an RF coil 16 which extends implemented in a cost effective manner and which does within a re-entrant cavity 15 of the lamp envelope 12. not result in the generation of eddy current losses that The RF coil includes a core and a winding which are could otherwise adversely affect the starting character- 10 disposed around the exhaust tube 14 extending down istics of the lamp operating circuit. from the top of the re-entrant cavity 15 and into the re- [0009] In accordance with the present invention, there gion of the base housing assembly 17 in which the bal- is provided an electrodeless discharge lamp comprising last circuit arrangement 24 is disposed. When ener- a lamp envelope having a fill contained therein, said fill gized, the ballast circuit arrangement 24 is effective for being operable so as to produce a discharge upon cou- 15 generating an RF signal which is inductively coupled to pling of an RF signal thereto, a member on which said a fill contained within lamp envelope 12 so as to produce lamp envelope is mounted, a ballast circuit arrangement discharge 23. Discharge 23 is effective in a conventional receptive of line power and effective so as to produce manner for converting energy into visible light in coop- said RF signal therefrom and a capacitive filter member eration with the phosphor coating 20 disposed on the disposed on a portion of said lamp envelope and being 20 interior wall surface of lamp envelope 12. electrically coupled to said ballast circuit arrangement [0013] In addition to the phosphor coating 20, also dis- to suppress the electromagnetic interference generated posed on the lower portion of the interior surface of lamp upon coupling said RF signal to said discharge, wherein envelope 12 is a layer of a conductive material 26 which said capacitive filter member includes a first plate por- is applied to the lamp envelope before application of the tion formed by a layer of conductive material disposed 25 phosphor material. As will be described hereinafter in on a portion of the interior surface of said lamp envelope, further detail, this conductive material forms one plate a second plate portion disposed on the outside surface portion of a capacitive filter member effective for the of said lamp envelope opposite to said first plate portion suppression of EMI which occurs during the operation and said lamp envelope disposed between said first and of the coupling of the RF signal to the discharge. In one second plate portions, characterised in that said second 30 embodiment of the invention, the interior conductive lay- plate portion has a plurality of slots (32) formed therein er is provided by means of application of a fluorinated which are effective to reduce eddy current losses occur- tin oxide coating (FTO); such coating being fired onto ring at said second plate portion, and at least one of said the glass surface to insure durability of such coating plurality of slots extends across said second plate por- over the expected life of the lamp 10. tion to prevent a closed loop conduction path for eddy 35 [0014] Additionally, as shown in Fig. 1, the electrode- currents to occur in said second plate portion. less low pressure discharge lamp 10 can be provided in [0010] In the preferred embodiment of the invention, the form of a reflector type of lamp which would add the the plurality of slots formed in the second plate portion further requirement of providing a reflective coating are very thin slices cut into the metallized material of the such as a finely divided titania onto the lower portion of second plate portion and which are disposed in a man- 40 the lamp envelope 12 as well as the surface area of the ner substantially parallel to one another and which col- re-entrant cavity 15 in order to insure the appropriate lectively, do not substantially change the capacitive val- direction of light output through a face region located at ue of the capacitive filter member. the top portion of the lamp envelope 12. Of course, it can be appreciated that the emission suppression ar- BRIEF DESCRIPTION OF THE DRAWINGS 45 rangement of the present invention would work equally as well with other shapes of lamp envelopes for instance [0011] In the following detailed description, reference a conventional A-line configuration found on a typical will be made to the attached drawings in which: incandescent lamp, and is also suitable for use with high pressure discharge lamps. Fig. 1 is an elevational view in section of an elec- 50 [0015] Disposed on a portion of the external surface trodeless low pressure discharge lamp constructed of lamp envelope 12 opposite to the interior layer of con- in accordance with the present invention. ductive material 26 is a second metallized conductive Fig. 2 is an elevational view of the second plate por- layer 28. The second layer of conductive material, in co- tion of a capacitive filter member. operation with the interior layer of conductive material 55 26 and the glass material of the lamp envelope 12 dis- DETAILED DESCRIPTION OF THE INVENTION posed therebetween form a capacitor wherein the interior layer of conductive material and the second conduc- [0012] As seen in Fig. 1, a low pressure electrodeless tive layer form the plates of the capacitor and the glass

3 5 EP 0 678 899 B1 6 material of the lamp envelope 12 forms the dielectric be seen that the slots extend for a length substantially material. The second conductive layer can be provided equal to the width of the metallization that makes up the by use of a frit arrangement. Specifically, in the preferred second conductive layer 28, such width as is indicated embodiment, a silver layer is painted onto the lamp en- by reference "a" of Fig. 2. In fact, the plurality of slots velope 12 and then fired so that the second conductive 5 extend to the bottom edge of the second conductive lay- layer 28 formed thereby is essentially fused into the er 28 so as to result in an open section at the bottom of glass so as to result in a long-lasting, durable configu- each of the slots 32. Although this is not disclosed in the ration. This capacitive element can be electrically cou- figure, at least one of the slots extends from the bottom pled to the screw base 19 or can be coupled to other edge to the top edge so as to prevent a closed loop con- shielding elements (not shown) disposed within housing 10 duction path from occurring through the second conduc- base 17. Such connection is effective so as to prevent tive layer 28. against a charge building up on the exterior surface of [0019] The second conductive layer 28 is annularly the lamp and to further insure that conducted emission shaped and tapered at one end to conform to the shape limits are minimized by use of the filtering characteristics of lamp envelope 12. It can be seen that the plurality of of such capacitive element. Of course, other conductive 15 slots are disposed at approximately right angles to the materials could be utilized for the second conductive cross-sectional area of second conductive layer 28, al- layer 28 as well and could also be applied in a more though the slots could be at other angles. As shown, the conventional manner as, for instance, by means of an slots are extremely thin in width and are substantially adhesive cement. As further seen in Fig. 1, an outer pro- smaller in size than the width of the metallization mate- tective cover 30 is disposed over the second conductive 20 rial that spans between any two consecutive slots 32. layer 28. The protective cover most preferably would be The use of the plurality of slots 32 in the second con- formed of the same material as the housing 17 and in ductive layer 28 can reduce the circular flow of eddy cur- fact could be formed either by a separate piece or by rents, thus reducing the loss attributable to the second extending the upper lip portion of the housing 17. conductive layer 28 and thereby reducing the detrimen- [0016] As seen in Fig. 2, the second conductive layer 25 tal effect on the circuit Q. Moreover, by constructing the 28 is formed in a manner to substantially conform to the second conductive layer 28 such that the plurality of contour of the bottom portion of the lamp envelope 12. slots 32 are extremely thin in relation to the span of con- Of course, it would be possible to modify the shape of ductive material between successive slots, the surface the second conductive layer 28 in the event that a dif- area of the second conductive layer 28 is not significant- ferent shape lamp envelope were utilized, such modifi- 30 ly reduced so as to reduce the capacitive value of the cation being contemplated as within the scope of the capacitor arrangement formed by the interior conductive present invention. layer, the second conductive layer and the glass mate- [0017] Previous efforts to provide an emission sup- rial disposed therebetween. As such, the benefits of EMI pression arrangement using a conductive outer layer as suppression are not sacrificed by the reduction of the shown in previously referenced US Patent No. 35 eddy current losses associated with the use of the plu- 4,727,294, have suggested the use of a solid conductive rality of slots 32 formed in the second conductive layer. layer on the exterior surface of the lamp envelope. It has [0020] Although the above-described embodiment been found that such an arrangement results in the gen- constitutes the preferred embodiment of the invention, eration of eddy current losses which in turn results in the it should be understood that modifications can be made reduction of the Q-factor associated with the resonant 40 thereto without departing from the scope of the invention circuit used to provide the RF signal coupled to the dis- as set forth in the appended claims. For instance, it charge. It is known that the Q-factor is measured as the would be possible to vary the shape and placement of ratio of the inductance of the resonant circuit to the re- the plurality of slots 32 and yet achieve the reduction in sistance of such resonant circuit. The effect of this re- the eddy current losses that are achieved by such ar- duction in the Q-factor is that a lower output voltage is 45 rangement. Also, while the ballast is shown as being at present at the excitation coil of the RF circuit. This lower least partially contained in the housing, the capacitive output voltage reduces the starting capability of the bal- arrangement of this invention is equally applicable to last circuit arrangement 24 and in some cases, is such lamps in which the ballast is located elsewhere. that the RF coil voltage cannot reach sufficient ampli- tude to break down the mixture of mercury and krypton 50 which comprise the fill contained within lamp envelope Claims 12. [0018] As shown in Fig. 2, there are a plurality of slots 1. An electrodeless discharge lamp (10) comprising: 32 formed on the second conductive layer 28, such slots 32 extending completely through the thickness of the 55 a lamp envelope (12) having a fill contained second conductive layer 28. These slots are disposed therein, said fill being operable so as to produce in an equidistant manner relative to each other along the a discharge(23) upon coupling of an RF signal periphery of the second conductive layer 28. It can also thereto:

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a member (17) on which said lamp enve- Patentansprüche lope is mounted; a ballast circuit arrangement (24) receptive 1. Elektrodenlose Entladungslampe (10) enthaltend: of line power and effective so as to produce said RF signal therefrom; and 5 einen Lampenkolben (12) mit einer darin ent- a capacitive filter member disposed on a haltenen Füllung, wobei die Füllung betrieben portion of said lamp envelope (12) and be- werden kann, um bei Kopplung eines HF-Si- ing electrically coupled to said ballast cir- gnals damit eine Entladung (23) zu erzeugen, cuit arrangement (24) to suppress the elec- ein Teil (17), auf dem der Lampenkolben ange- tromagnetic interference generated upon 10 bracht ist, coupling said RF signal to said discharge eine Vorschaltanordnung (24), die Netzspan- (23); nung empfängt und daraus das HF-Signal erzeugt, und wherein said capacitive filter member in- ein kapazitives Filterteil, das auf einem Ab- cludes a first plate portion (26) formed by a layer of 15 schnitt von dem Lampenkolben (12) angeord- conductive material disposed on a portion of the in- net ist und elektrisch mit der Vorschaltanord- terior surface of said lamp envelope (12), a second nung (24) gekoppelt ist, um die elektromagne- plate portion (28) disposed on the outside surface tische Interferenz zu unterdrücken, die beim of said lamp envelope opposite to said first plate Koppeln des HF-Signals bei der Entladung (23) portion and said lamp envelope disposed between 20 erzeugt wird, said first and second plate portions; characterised in that wobei das kapazitive Filterteil einen ersten said second plate portion (28) has a plurality Plattenabschnitt (26), der durch eine Schicht von of slots (32) formed therein which are effective to leitfähigem Material gebildet ist, das auf einem Ab- reduce eddy current losses occurring at said sec- 25 schnitt von der Innenfläche des Lampenkolbens ond plate portion (28); and (12) angeordnet ist, einen zweiten Plattenabschnitt at least one of said plurality of slots (32) ex- (28) aufweist, der auf der Aussenseite des Lampen- tends across said second plate portion (28) to pre- kolbens gegenüber dem ersten Plattenabschnitt vent a closed loop conduction path for eddy cur- angeordnet ist, und der Lampenkolben zwischen rents to occur in said second plate portion (28). 30 den ersten und zweiten Plattenabschnitten angeordnet ist, dadurch gekennzeichnet, daß 2. An electrodeless discharge lamp (10) as set forth in der zweite Plattenabschnitt (28) mehrere dar- claim 1 wherein said first plate portion (26) is a fluor- in ausgebildete Schlitze (32) hat, die wirksam sind, inated tin oxide layer fired so that it is essentially um Wirbelstromverluste zu senken, die an dem fused into the glass of said portion of the interior 35 zweiten Plattenabschnitt (28) auftreten, und surface of said lamp envelope (12). wenigstens einer der mehreren Schlitze (32) sich über den zweiten Plattenabschnitt (28) er- 3. An electrodeless discharge lamp (10) as set forth in streckt, um zu verhindern, daß eine geschlossene claim 1, wherein said second plate portion (28) is Leiterschleife für Wirbelströme in dem zweiten Plat- annularly formed having at least one circumferential 40 tenabschnitt (28) auftritt. dimension associated therewith, and further wherein said plurality of slots (32) are formed in said sec- 2. Elektrodenlose Entladungslampe (10) nach An- ond plate portion (28) at approximately right angles spruch 1, wobei der erste Plattenabschnitt (26) eine relative to such at least one circumferential dimen- fluorierte Zinnoxidschicht ist, die so gebrannt ist, sion. 45 daß sie in das Glas von dem Abschnitt der Innen- fläche des Lampenkolbens (12) im wesentlichen 4. An electrodeless discharge lamp (10) as set forth in eingeschmolzen ist. claim 1, wherein spaces disposed between each of said plurality of slots (32) in said second plate por- 3. Elektrodenlose Entladungslampe (10) nach An- tion (28) are at least ten times larger in dimension 50 spruch 1, wobei der zweite Plattenabschnitt (28) than the width of a slot (32). kreisringförmig geformt ist und wenigstens eine zu- gehörige Umfangsabmessung aufweist, und wobei 5. An electrodeless discharge lamp (10) as set forth in ferner die mehreren Schlitze (32) in dem zweiten claim 3, wherein said plurality of slots (32) extend Plattenabschnitt (28) etwa in rechten Winkeln rela- to the end of one open end associated with said sec- 55 tiv zu dieser wenigstens einen Umfangsabmessung ond plate portion (28). gebildet sind.

4. Elektrodenlose Entladungslampe (10) nach An-

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spruch 1, wobei Räume, die zwischen jedem der 2. Lampe à décharge sans électrode (10) selon la re- mehreren Schlitze (32) in dem zweiten Plattenab- vendication 1, dans laquelle ladite première partie schnitt (28) angeordnet sind, eine wenigstens zehn de tôle (26) est une couche d'oxyde d'étain fluoré mal grössere Abmessung haben als die Breite von projetée de manière à être essentiellement fondue einem Schlitz (32). 5 dans le verre de ladite partie de la surface intérieure de la dite ampoule de lampe (12). 5. Elektrodenlose Entladungslampe (10) nach An- spruch 3, wobei die mehreren Schlitze (32) sich zu 3. Lampe à décharge sans électrode (10) selon la re- dem Ende von dem einen offenen Ende erstrecken, vendication 1, dans laquelle la deuxième partie de das dem zweiten Plattenabschnitt (28) zugeordnet 10 tôle (28) présente une forme annulaire dont au ist. moins une dimension circonférentielle lui est asso- ciée, et en outre dans laquelle ladite pluralité de fentes (32) sont formées dans ladite deuxième partie Revendications de tôle (28) approximativement à angle droit par 15 rapport à cette dimension circonférentielle au nom- 1. Lampe à décharge sans électrode (10) bre d'au moins une. comprenant : 4. Lampe à décharge sans électrode (10) selon la re- une ampoule (12) de lampe contenant un gaz vendication 1, dans laquelle des espaces disposés de remplissage, ledit gaz de remplissage pou- 20 entre chacune desdites pluralité de fentes (32) dans vant être utilisé de manière à produire une dé- ladite deuxième partie de tôle (28) ont une dimen- charge (23) lors du couplage à celui-ci d'un si- sion au moins dix fois plus grande que la largeur gnal RF : d'une fente (32).

un élément (17) sur lequel est montée la- 25 5. Lampe à décharge sans électrode (10) selon la re- dite ampoule de lampe; vendication 3, dans laquelle ladite pluralité de fen- un dispositif de circuit ballast (24) pouvant tes (32) s'étend à l'extrémité d'une extrémité ouver- recevoir une alimentation électrique du te associée à ladite deuxième partie de tôle (28). secteur et pouvant produire ledit signal RF à partir de celui-ci; et 30 un élément de filtre capacitif placé sur une partie de ladite ampoule de lampe (12) et couplé électriquement audit dispositif de circuit ballast (23) pour supprimer les inter- férences électromagnétiques générées 35 lors du couplage dudit signal RF à ladite décharge (23);

dans laquelle ledit élément de filtre capacitif comprend une première partie de tôle (26) formée 40 par une couche de matériau conducteur placée sur une partie de la surface intérieure de ladite ampoule de lampe (12), une deuxième partie de tôle (28) pla- cée sur la surface extérieure de ladite ampoule de lampe à l'opposé de ladite première partie de tôle 45 et ladite ampoule de lampe placée entre lesdites première et deuxième parties de tôle; caractérisée en ce que ladite deuxième partie de tôle (28) comporte une pluralité de fentes (32) formées dans celle-ci 50 qui servent à réduire les pertes par courants de Foucault se produisant dans ladite deuxième partie de tôle (28); et au moins une de ladite pluralité de fentes (32) s'étend sur ladite deuxième partie de tôle (28) pour 55 empêcher l'apparition d'un chemin de conduction en boucle fermée pour les courants de Foucault dans ladite deuxième partie de tôle (28).

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