Abstract:
Disclosed is a lamp transformer and method of assembling a lamp transformer within an igniter module or housing. The lamp transformer comprising a potted bar core transformer; and a carrier attached to the potted bar core transformer, the carrier adapted to position the potted bar core transformer on a pc board at a predetermined location.

Description:
BACKGROUND OF THE INVENTION 
   This disclosure relates to a high voltage igniter module used to ignite a lamp, for example a HID (High Intensity Discharge) lamp. Specifically, the disclosure relates to the mechanical design of a high voltage transformer and the associated igniter module. 
   Conventionally, high voltage igniter circuits are used to start HID lamps. One example of a HID lamp requiring a high voltage ignition is an automotive lamp commonly referred to as a head light. To produce the high voltage ignition signal, an igniter circuit is operatively connected to the HID lamp. Conventional configurations of an automotive headlamp assembly include an igniter circuit housed within the HID lamp assembly, the igniter circuit including a pc board and a transformer. The igniter printed circuit board carries electrical components to produce a high voltage ignition signal. In addition, the pc board provides electrical connection points to power the ignition circuit and deliver the high voltage ignition signal to a HID lamp. 
   One example of a conventional embodiment of a high voltage igniter circuit includes a lamp receptacle mounted to the igniter circuit pc board. In addition, it is common to mount the igniter circuit transformer either directly to the pc board or separate from the pc board. In the later case, the transformer may be mounted to the lamp housing where the pc board provides the necessary winding connection points. 
   As previously indicated, this disclosure relates to the mechanical design of the igniter module transformer. Conventionally, high voltage igniter transformers have been used to produce the high voltage signals necessary to provide an ignition signal. In general, the igniter transformer includes a magnetic core, a secondary winding surrounding the magnetic core and a primary winding surrounding the secondary core. The output voltage associated with the secondary winding is related to the ratio of the number of secondary windings to the number of primary windings. 
   During the assembly of a HID lamp, it is common practice to pot the transformer with an insulating material to provide electrical insulation of the windings from other electrical components contained within the lamp housing. In addition, potting of the transformer increases the overall stability of the transformer&#39;s performance. One drawback associated with potting of the transformer is the necessary step of characterization of the transformer subsequent to potting. 
   Conventionally, the characterization of an igniter transformer occurs after the igniter module has been fully assembled or the transformer has been mounted within a lamp housing chamber separate from the pc board. In the first case, the igniter pc board carries all electrical components associated with the igniter circuit, including the transformer. Subsequent to the assembly of the pc board, the pc board is potted. Characterization of the transformer is performed with the transformer mounted and potted on the completed pc board assembly. In the event the characterization of the potted igniter transformer is not within the required specifications, the entire pc board is discarded or extensive rework is required to remove the potting material to replace the transformer. 
   In the second case, the igniter transformer is mounted and potted within a separate chamber of the lamp housing. The transformer is characterized subsequent to mounting and potting within the lamp housing. In the event the characterization of the igniter transformer is not within the required specification, the housing and transformer assembly are discarded or extensive rework is required to remove the potted transformer from the housing to replace the transformer. 
   This disclosure provides an igniter module and associated transformer to enable characterization of the transformer prior to the assembly of the transformer within the lamp housing or mounting of the transformer to an igniter pc board. The disclosed igniter module eliminates the need to discard/rework a pc board or housing as previously discussed if the characterization of an igniter transformer is determined to be out of specification subsequent to potting. 
   BRIEF DESCRIPTION OF THE INVENTION 
   According to one aspect of this disclosure, an exemplary embodiment of a lamp transformer is disclosed. The lamp transformer comprises a potted bar core transformer; and a carrier attached to the potted bar core transformer, the carrier adapted to position the potted bar core transformer on a pc board at a predetermined location. 
   According to another aspect of this disclosure, a lamp igniter module is disclosed. The lamp igniter module comprises a housing, a pc board and a potted igniter transformer attached to the pc board. The potted igniter transformer is characterized before being attached to the pc board; wherein the pc board and attached potted igniter transformer are attached to the housing. 
   According to another aspect of this disclosure, a method of assembling a lamp is disclosed. The method of assembling a lamp comprises of potting one or more igniter transformers mounted to one or more respective carriers; characterizing the one or more potted igniter transformers to determine if the potted igniter transformers are within acceptable tolerances and proceeding with the assembly of the lamp using a potted igniter transformer within acceptable tolerances; and positioning the carrier on an igniter circuit pc board using locator pins attached to the carrier and/or the pc board. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a lamp igniter transformer according to an exemplary embodiment of this disclosure; 
       FIG. 2A  and  FIG. 2B  illustrate a front and side view, respectively, of a lamp igniter transformer according to an exemplary embodiment of this disclosure; 
       FIG. 3  illustrates the placement of an igniter transformer and carrier within a housing, according to an exemplary embodiment of this disclosure; and 
       FIGS. 4A through 4I  illustrate the assembly steps associated with a lamp assembly according to an exemplary embodiment of this disclosure. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   This disclosure provides a mechanical design of a high voltage transformer and an associated igniter module for a gas discharge lamp, especially for automotive lamp products. Substantively, the module design comprises a printed circuit board (PCB) with low voltage electronic components inserted into the PCB and a pre-assembled high voltage core transformer encased in a high voltage potting material. The high voltage core transformer is mounted on the PCB by means of a carrier. 
   The pre-potting of the high voltage core transformer before attachment to the PCB provides an opportunity to discard a potted high voltage core transformer without discarding the PCB or associated housing in the event the characterization of the potted core transformer is not within acceptable tolerances. In other words, the required characterization of the potted high voltage transformer is performed before the transformer is attached to the PCB or mounted within the igniter module housing. This design and embodiments thereof is distinguishable from the prior art which requires potting of an igniter module high voltage transform after the transformer is attached to an igniter PCB or mounted within an igniter module chamber. As discussed in the background section of this disclosure, characterization of the high voltage transformer occurs subsequent to potting of the transformer. Accordingly, the prior art ignition module requires a potted PCB with attached transformer, or lamp housing with potted transformer to be discarded in the event the transformer&#39;s characterization is not within acceptable tolerances. 
   With reference to  FIG. 1 , illustrated is a perspective view of a potted bar core transformer assembly  10  according to an exemplary embodiment of this disclosure. The transformer assembly  10  comprises a potted core transformer  12 , a first carrier end part  14 , and a second carrier end part  16 . The carrier end parts include slots  17  and  18  which provide positioning of the potted bar core transformer assembly within a housing (not shown). 
   In one exemplary embodiment, the bar core transformer includes a rod shaped core. However, other core shapes are within the scope of this disclosure. The carrier end parts  14  and  16  are made of a high temperature plastic, for example, PPS or ULTEM. The carrier end parts  14  and  16  perform three functions when attached to the longitudinal ends of the core material. They function as bobbin walls to efficiently wind the transformer core using a maximum length of the core. In addition, the carrier end parts  14  and  16  function as support for an insulating material positioned between a mold and the carrier end part, the mold holding the transformer potting material while it is curing. Finally, the carrier end parts  14  and  16  function as positioners of the potted bar core transformer within a housing (not shown). 
   The transformer illustrated in  FIG. 1  is potted after the transformer winding process by casting the wound transformer in a lined mold. Subsequent to the curing of the potting material, a full characterization and testing of the potted bar core transformer  10  is completed. Notably, this characterization and testing of the potted bar core transformer  10  occurs prior to any further assembly of the igniter module, thereby avoiding discardmerit and/or rework of a more completed igniter module assembly in the event the potted bar core transformer does not meet tolerances related to the said characterization and testing. 
   With reference to  FIG. 2A  and  FIG. 2B , illustrated are a front and end view, respectively, of a potted bar core transformer assembly  20  according to an exemplary embodiment of this disclosure. The potted bar core transformer assembly  20  comprises a potted bar core transformer  22 , a first carrier end part  24 , and a second carrier end part  26 . The potted bar core transformer  22  comprises a bar core  28 . The first carrier end part  24  comprises a carrier end part slot  30 , a carrier end part tab  32 , an inner recess  34  and an outer recess  36 . Similarly, the second carrier end part  26  comprises a carrier end part slot  38 , a carrier end part tab  40 , an inner recess  42  and an outer recess  44 . The carrier inner recesses  34  and  42  attach to the longitudinal ends of the transformer core  28 , for example by means of a pressed fit or adhesive. Notably, the carrier outer recesses  36  and  44  enable the same carrier end part to be used at either end of the transformer core  28 . 
   With reference to  FIG. 3 , illustrated is an end view  50  of a potted bar core transformer assembly mounted within a housing  54 . The housing  54  comprises a housing locator tab  56  which mates with the carrier end part  52  slot  38  as previously discussed with reference to  FIGS. 2A and 2B . 
   With reference to  FIGS. 4A-4I , illustrated is a series of process steps to assemble an igniter module and associated lamp according to an exemplary embodiment of this disclosure. 
   With reference to  FIG. 4A , illustrated is a bar core transformer assembly representing the initial stage  60  of assembly of an igniter module according to an exemplary embodiment of this disclosure. The bar core transformer assembly comprises a bar core transformer  62 , a first carrier end part  64 , a second carrier end part  66  and a carrier transformer lead guide  70 . The first carrier end part  64  comprises a carrier locator pin tab  76  and the attached carrier locator pins  77  and  78 . Similarly, the second carrier end part  66  comprises a carrier locator pin tab  79  and an attached carrier locator pin  81 . In addition to providing a means for attachment of the carrier end parts to the PCB in a subsequent assembly step, the carrier locator pins can provide electrical connection points for the primary winding wires and/or secondary winding wires associated with the transformer. For example, a bar core transformer assembly without a carrier transformer lead guide can be configured to electrically connect the primary winding lead wires to two separate metal locator pins, such as locator pins  77  and  81 . The secondary winding lead wires can be connected to a third and fourth locator pin or alternatively a combination of a locator pins  81  for a first secondary winding lead connection and simply routing the second secondary winding lead through a hole provided on the second carrier end port  66 . Notably, this disclosure is not limited to a particular configuration of the carrier locator pins or carrier feed through holes associated with electrically connecting the transformer windings to a PCB or other connection point. 
   With reference to  FIG. 4B , illustrated is step two  80  of assembling the igniter module according to an exemplary embodiment of this disclosure. The second step  80  comprising potting the transformer bar core and windings with an insulating material, for example a silicone or epoxy material. 
   With reference to  FIG. 4C , illustrated is step three  90  of assembling the igniter module. The third step comprising the electrical connection of the potted transformer leads  72  and  74  to the PCB  92  at transformer lead connection points  98  and  100 , for example by means of soldering. In addition, the potted bar core transformer  82  and carrier are attached to the PCB at the PCB carrier locator pin receivers  94  and  96 , for example by means of soldering. 
   With reference to  FIG. 4D , illustrated is step four  110  of assembling the igniter module according to an exemplary embodiment of this disclosure. The fourth step comprising inserting a lamp  116  into the lamp receptacle  114  attached to a housing  112  and threading the lamp leads (not shown) into the housing. 
   With reference to  FIG. 4E , illustrated is step five  120  of assembling the igniter module according to an exemplary embodiment of this disclosure. The fifth step comprising the electrical connection of a first lamp lead to the metal strip  122  located on the inside of the housing. Notably, a metal strip continuity point  124  is provided as illustrated. Connection of the lamp lead may include laser welding, soldering or other means for electrically connecting an electrical lead and metal strip. 
   With reference to  FIG. 4F , illustrated is step six  130  of assembling the igniter module according to an exemplary embodiment of this disclosure. The sixth step comprising inserting the completed PCB  92  into the housing  112  and electrically connecting a second lamp lead (not shown) to the PCB. 
   With reference to  FIG. 4G , illustrated is step seven  140  of assembling the igniter module according to an exemplary embodiment of this disclosure. The seventh step comprising the electrical connection of a potted bar core transformer primary winding lead to a metal strip  142  molded in the housing  112 , where the PCB  92  provides the necessary access hole to reach the metal strip  142 . 
   With reference to  FIG. 4H , illustrated is step eight  150  of assembling the igniter module according to an exemplary embodiment of this disclosure. The eighth step comprising locating a bottom cover  152  over the PCB  132  connector  154  and attaching the said bottom cover  152  with glue or other means for mechanical attachment. 
   With reference to  FIG. 4I , illustrated is a perspective view of an assembled igniter module including a lamp according to an exemplary embodiment of this disclosure. 
   The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations.