高效高功率闪光灯设计技巧

　　Although the xenon lamps dominate the standard camera market， they are not applicable in the portable phone. As a matter of fact， the large reservoir capacitor and high voltage associated with the xenon flash make such a concept not suitable for the cellular phone equipments. The semiconductor based White LED devices provide the right choice when limited flash light becomes necessary to illuminate a photographic scene. This paper depicts the basics of the xenon concept and details a typical White LED flash application. XENON LAMP CONCEPT A low pressure of a rare gas mixture fills a glass envelope with two ends electrodes on both sides. In steady state， the voltage across the electrodes is set to a value well below the trigger voltage as depicted Figure 1. At this point， no current flows and the system is stable until a trigger voltage is applied to the third electrode. This high voltage pulse， in the 1 kV range， comes from a transformer built with a small magnetic tore triggered by an abrupt discharge of the capacitor C2 （see Figure 2）.