Abstract:
A description is given of a gas-discharge lamp base ( 11 ) with a housing comprising an upper part ( 10 ) and a cover ( 40 ), a support ( 16 ) accommodated in the housing for receiving the components, with a transformer, with inductances connected in series with the lamp ( 1 ) and a capacitance connected in parallel with the lamp ( 1 ), the transformer comprising a bar transformer ( 23 ). This construction permits particularly efficient production, because the support can be constructed as a simple leadframe which permits automatic component fitting.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Phase of International Application Serial No. PCT/EP01/15036, filed Dec. 19, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a gas-discharge lamp base with igniting device of the type known from WO 00/59269 (D1). 
     2. Description of the Background Art 
     In the case of the known gas-discharge lamp base, the voltage supply and the igniting device for the lamp, and consequently a voltage of about 30 kV, have been successfully “accommodated” in a space of about 4×4×3 cm. However, the known lamp base is quite complicated in the way in which it is constructed and produced, since most of its components cannot be fitted automatically. Therefore, considerable manual work is necessary. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of providing a gas-discharge lamp base which is of a simpler construction and permits automatic component fitting. 
     U.S. Pat. No. 4,677,348 A1 (D2) already discloses a gas-discharge lamp base in which the transformer comprises a bar transformer. The publication does not disclose any details about how the gas-discharge lamp base is constructed. 
     In the case of the base according to the invention, the toroidal-core transformer  23  of D1 is replaced by a bar-core transformer. In the case of the latter, securely mounted connecting elements (winding ends) which allow automatic component fitting can be provided. The bar-core transformer is accommodated in an enclosed chamber formed in the housing. 
     The chamber is preferably formed on an outer wall of the upper part and a dividing wall provided in the upper part. The chamber is preferably provided with a recess for receiving the high voltage contact (“hot conductor”) ( 120 ) of the bar-core transformer. The bar-core transformer is preferably cast in the chamber with casting compound. 
     A ferrite plate is preferably attached to one or both ends of the bar-core transformer (mushroom-core or H-core transformer). As a result, a lower secondary resistance is achieved with the same ignition voltage. 
     The bar-core transformer is preferably designed in such a way that the inductors  24  and  25  of D1 can be omitted. It is also possible to omit the capacitor  26  of D1, connected in parallel with the lamp, if the base is enclosed by a metal housing according to  FIG. 16  of D1. Consequently, in the case of the base according to the invention, there is now only one element carrying high voltage, that is the bar-core transformer. Furthermore, in the case of the lamp base according to the invention, the support  16  of D1 is omitted. Its insulating function is taken over by a modified construction of the outer base part  10  and of the cover  40 . The labyrinth on the cover and on the outer base part in this case takes over the insulating function of the support  16  of D1. The metal bushings  71  ( FIG. 15  of D1) for the connection wires  72 , which serve as sealing elements and insertion aids, can be omitted entirely. 
     According to the invention, the function of the return conductor connection  63  ( FIG. 12  of D1) is integrated in the leadframe  60  ( FIG. 12  of D1), thereby resulting in a further reduction in the number of individual parts and making assembly easier. Furthermore, according to the invention, the capacitor  28  is designed as a foil capacitor suitable for automatic component fitting. In the case of the component  27  ( FIG. 12  of D1), the special bending of the connection wire is omitted, the new geometry of the support  16  making more space available, so that here, too, component fitting can be performed with standard automatic machines. 
     According to the invention, the collar  39  for the connection plug ( FIG. 13  of D1) is integrated into the outer base part  10  or the leadframe  60 , whereby a full-area connection is achieved between the cover  40  and the outer base part  10  of D1. In this case, splash water protection of up to IP 67 (DIN 40050 “protection against electric shock and water”) is possible. The function of the capacitor  29  can be moved out of the igniter into the electrical ballast. The arrangement of the components including the bar-core transformer on the support  16  of D1 allows automatic component fitting. In a further, particularly space-saving embodiment, the leadframe is formed in an angled manner (L- or U-shaped). 
     The aforementioned modifications now permit a three-part construction of the base. Fully automatic component fitting on the support for the electronics (alternatively leadframe or PCB (Printed Circuit Board)) can be carried out, as can the assembly of the three individual components. Further conceivable variants are 
     leadframe construction in MID technology, 
     outer base part in MID technology, whereby elimination of the leadframe is possible, 
     partial or full encapsulation of the leadframe to achieve the function of the outer or upper part of the base. 
     Components in MID technology (Molded Interconnect Devices) are molded parts with an integrated conductor structure (3D). Apart from the integration of electronics and mechanics, they make it possible to save individual parts. MIDs can be produced by means of various production processes, which differ according to their metallization and structuring. A distinction is drawn essentially between two different technologies: 3D-MID technology and shielding technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail on the basis of the accompanying drawings, in which: 
         FIG. 1  shows an exploded perspective representation of the main component parts of a gas-discharge lamp base according to the invention, 
         FIG. 2  shows the exploded perspective representation of a slightly modified embodiment of a lamp base, 
         FIG. 3  shows the upper housing part and the leadframe of  FIG. 2  from a changed viewing angle, 
         FIG. 4  shows the exploded perspective representation of a third embodiment of a lamp base, 
         FIG. 5  shows the perspective view of the leadframe of  FIG. 4 , 
         FIG. 6  shows the circuit diagram of a lamp base according to the invention, 
         FIG. 7  shows the perspective view of an at this stage only partly wound bar-core transformer with the receptacle for the cental contact of the lamp formed as a separate component, 
         FIG. 8  shows the upper housing part with the bar-core transformer inserted, 
         FIG. 9  shows a perspective plan view of the leadframe with the components fitted, 
         FIG. 10  shows an exploded perspective representation of the main component parts of one embodiment of the gas-discharge lamp base according to the invention with the bar-core transformer of  FIGS. 7 and 8 , and 
         FIG. 11  shows an angled leadframe fitted with the components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the three main component parts of the gas-discharge lamp base  11  according to the invention, with the upper housing part  10 , the leadframe  60  and the lower housing part or cover  40 . The upper housing parts  10  have a central stub  80  and a lateral stub  81  of a smaller diameter, through which the leads to the lamp (not shown here), to be placed on from below, are led. When this happens, the conductor in the central stub  80  is placed onto the upper face of the latter from the outside and subsequently cast. A dividing wall  82  in the upper housing part  10  forms a chamber  84 , having a stepped indent or recess  83 . In the case of the embodiment of  FIG. 2 , the collar  39  for receiving the plug is formed onto the housing of the upper part  10 ′. The leads are identifiable as upright red marks, in the same way as the foot contact on the stub  80 . 
     In the case of the embodiment according to  FIG. 1 , the collar  39  is formed onto the leadframe  60 . The leadframe  60  carries the bar-core transformer  23 , the sparking gap  27 , a foil capacitor  28  ( FIG. 4 ) and a return conductor  85 . 
     A lower housing part  40  substantially comprises a covering plate  86  and a cylindrical, hollow, downwardly open hollow cylinder or stub  87 , which is formed onto the plate  86 . 
     During assembly, the leadframe  60  is pushed together with its fitted components into the upper housing part  10 , the bar-core transformer  23  being received in the chamber  84 . In this case, the recess  83  serves for receiving the connections of the bar-core transformer  23 . The bar-core transformer  23  is subsequently cast, only little casting compound being required as a result of the dividing wall  82 , much less than in the case of the known lamp base according to D1. The conductor ends of the lamp led up through the stubs  80 ,  81  are welded or soldered to the printed circuit board. To be specific, the stub  80  (Hv contact of the lamp) is connected via the injection-molded-in central contact to the hot end of the transformer. The stub  81  (Lv contact of the lamp) is connected to the printed circuit board or the leadframe  60 . 
     The lower housing part  40  is subsequently inserted with its stub  87  into the upper housing part  10 , the stub  87  enclosing the stub  80  and so forming the labyrinth necessary for the avoidance of flashovers. The lower surface of the covering plate  86  lies on the upper surface of the leadframe  60 . 
       FIG. 4  shows the exploded perspective representation of a third embodiment of the lamp base. The leadframe  60  is provided on its upper side with a number of encircling lamellae  90 , with a bore for the leading through of the “hot conductor” of the lamp being located in the inner oval. The upper housing part  40  bears corresponding lamellae (which cannot be seen in the representation of  FIG. 4 ), which reach into the grooves formed between the lamellae  90  on the leadframe. 
     Arranged on the underside of the leadframe  60 , shown in  FIG. 5 , are the already mentioned components of the circuit. A lamella  2 , which follows the outer contour of the leadframe  60 , encloses the bar-core transformer  23  and is led to a central circular-cylindrical eye  94 , encloses the bar-core transformer  23  and in this way forms a chamber  84 , which is filled with casting compound. It is also the case in this embodiment that only little casting compound is required. 
     The upper housing part  10  is provided on its lower face in  FIG. 4  with a circular opening  96 . During assembly, the leadframe  60  is inserted into the upper housing part  10 . The lamp (not shown) is placed onto it through the opening  96  and the circular-cylindrical lamella  94 , in such a way that the “hot conductor” protrudes through the bore provided for it in the printed circuit board  60  into the central oval between the lamellae  90 . Here it is welded to a connection located there. Subsequently, the lower housing part  40  is placed onto the leadframe  60 , so that the lamellae  90  of the leadframe  60  and those of the lower housing part  40  engage in one another and form the labyrinth. 
     In contrast with the embodiments of  FIGS. 1 ,  2  and  3 , in which the welded collar  88  for the lamp is formed onto the upper housing part  10 , in the case of the embodiment of  FIGS. 4 and 5  the lamp must be provided with the welded collar. 
     The embodiment of  FIGS. 4 ,  5  has the advantage over those of  FIGS. 1 ,  2 ,  3  that, for the most part, the same, that is existing, tools can be used as in the case of D1. At the same time, no adaptations to the production line are required at the customer&#39;s premises, that is to say where the base and lamp are assembled. 
       FIG. 6  shows the circuit diagram of the igniting device and of the power supply of the ballast. As a comparison with  FIGS. 11 and 17  of D1 shows, the circuit has being considerably “slimmed down”. The igniting device is a so-called asymmetric pulse igniting device. Of three DC voltage connections  47 ,  48 ,  49 , two are used according to choice. The DC voltage connection  49  is connected to ground and is looped through to the lamp connection  51 . Between the connections  47  and  49  there lies one or two so-called TRANSIL® diodes  52 , which serve as threshold switches. The connection  47  is led to a respective terminal of the primary winding  30  and of the secondary winding  110  of the bar-core transformer  23 . Between these terminals and the connection  48  there lie a foil capacitor  28  and a discharging resistor  26 . The second connection of the primary winding N 1  is led via a sparking gap  27  to the connection  48 . The second terminal of the secondary winding  110  of the bar-core transformer  23  is led to the lamp connection  50 . The discharging resistor  26  may be welded before assembly to the capacitor  28  or to the sparking gap  27 , according to choice, in automatic production, so that the component fitting and laser welding of the resistor  26  to the lead frame or the printed circuit board can be omitted. 
       FIG. 7  shows a perspective representation of a bar-core transformer  23 , on the coil former of which a primary winding  30  is wound, to be precise respectively in portions between lamellae  111  formed on the coil former. The end face  112  of the bar core, which is enclosed by the coil former and the secondary winding  110 , can be seen. The lamellae  111  are provided on the upper side (and correspondingly on the underside) with grooves  114 , into which the primary winding  30  is laid. Arranged at the rear end of the bar-core transformer  23  are the contacts  116  for the primary winding  30 . One contact is connected to the beginning of the primary coil  30  and the beginning of the secondary coil  110 , the other is connected to the end of the primary winding  30 . The primary winding  30  is configured in a multiply bandaged construction or with a multiply extruded construction in order to achieve a high dielectric strength. 
     Connected to the coil former is a receptacle  115  for the “hot conductor” of the lamp. The molded part forming the receptacle  115  is provided with a wall  117 , on the outer edges of which grooves are provided. With the aid of these grooves  118 , the receptacle  115  is inserted into a corresponding relief of the dividing wall  82  ( FIG. 8 ). In this way, a labyrinth is formed to extend the length of the leakage path. 
     At the end of the bar-core transformer, a thickening can be seen. This is in this case a ferrite plate  130  attached to the end of the actual bar core. The ferrite plate allows a lower secondary resistance to be achieved with the same ignition voltage. 
       FIG. 8  shows the upper housing part  10  with the inserted bar-core transformer  23 , the base  119  of the lamp  1 . Above the base  119 , the “hot conductor”  120  of the lamp  1  can be seen, to the right of it the return conductor  121  of the return  2  of the lamp  1  can be seen. In practice, the leadframe  60  is firstly fitted with all the components and then inserted into the upper housing part  10 . The state shown in  FIG. 8  therefore never occurs in practice. 
       FIG. 9  shows the plan view of the leadframe  60  fitted with the components. To be specific, the following can be seen: the sparking gap  27 , the foil capacitor  28 , the optional input capacitor  29 , the bar-core transformer  23  with the primary winding  30  and the two ends  31  and  32 , which are connected to the beginning of the primary winding  30  and the beginning of the secondary winding  110  or the (hot) end of the secondary winding. Attention should also be drawn to the ends of the hot conductor  120  and of the return conductor  121 . 
       FIG. 10  shows an exploded representation of the component parts of the gas-discharge lamp base  1  with the upper housing part  10 , the leadframe  60  fitted with components and the cover  40 .  FIG. 10  also shows the lamp  1  to be inserted into the base after the assembly of the latter. 
       FIG. 11  finally shows a U-shaped printed circuit board  60  fitted with the components, which may be configured by the leadframe technique or as a printed board.