||During the early 1980s, Philips developed to the state of advanced prototype the XL induction lamp featured here. It was created in low wattages of 13-25W to match the lumen packages of 60-100W incandescent lamps, and features integrated electronic gear to function as a full retrofit. Despite the immense investments, the project was abandoned because just before launch it became clear that the parallel developments in CFL technology would be more cost effective. Electrodeless developments then shifted to higher powers where the increased cost could be justified in commercial lighting applications, resulting in the better known QL lamp.
To keep electromagnetic interference under control, the XL lamp employs conductive silver rings on the outside of the bulb to reduce magentic fields, thereby removing the problem of induced currents in the mains terminals. Additional shielding is effected with a fluorine doped tin oxide semi-conducting film on the inner bulb surface, which also serves as a starting aid. By connecting this and a copper heat-sinking rod inside the bulb stem to one terminal of the mains, the striking voltage is reduced by 15% to around 175V. The phosphor is a high efficiency blend believed to consist of green-luminescing cerium magnesium aluminate activated by terbium, and red-luminescing yttrium oxide activated by trivalent europium.
The construction of the glass discharge vessel is also worthy of mention. It consists of an inner re-entrant portion with a flared base, this area mating with the similarly flared out area of the bulb neck. The two are sealed together with a low melting temperature lead-based glass enamel, with the electrically conductive film sandwiched in between. By this method external connections to the film can easily be made.