ABSTRACT
INTRODUCTION Up to now, the lighting industry is using shaped high voltage low pressure mercury discharge tubes behind a coloured plastic plate for advertising. However, plastic plates reduce the system efficiency due to light absorption and scattering losses. Illuminated signage needs flat, large and freely shaped illuminated surfaces showing low degradation. With a fluorescent dielectric barrier discharge (DBD), it is possible to fulfil all these requirements without the use of Hg. In addition, the absence of mercury leads to nearly temperature independent operation of the lamp. In our experiment, we use a highly efficient pulsed Xe excimer discharge to excite an especially designed phosphor inside the DBD-lamp. With a DBD, it is possible to get large areas of high luminance, uniformity and stability [1]. Due to the absence of metal electrodes in the discharge, the lifetime of the lamp is significantly increased and under certain conditions it is mainly limited by the degeneration of the phosphor. The most important demand on illuminated signage is the flexibility of lamp shape. Our lamp design can easily be adapted to illuminate every desired shape. The novel lamp is made of two shaped plates of floated borosilicate glass which are connected using a novel solder technique. In terms of electrical circuit, a DBD represents a capacity which depends on the area of the lamp. To guarantee a stable discharge, independent of the area of the lamp, and to reduce power losses the electronic gear has to be adapted to the capacity of the lamp. Our novel pulse gear is self-adapting to the lamp by adjusting the voltage rise time. This has been realised only by means of switching pattern variation of the full bridge converter.
