13-Tutorial 6a

LightingbyDesignSolid-state lighting requiresspecialized optical design for optimal performance.BY DAVID PELKA, TAILORED OPTICAL SYSTEMS INC.olid-state lighting is a technology of opportunity for a efficiencies. The best indium gallium nitride (InGaN)number of niche applications. Such systems do not LEDs (UV, blue, green, and white) achieve 30% to 35%S require imaging optics, which are actually counter- conversion efficiencies.productive. They do need careful light management, however. The drive voltages for AlInGaP LEDs typically range fromEnter non-imaging optics. 1.8 to 3.0 V dc, while drive voltages for InGaN range fromA light-emitting diode (LED) in its simplest form is a 3.4 to 4.0 V dc. In general, LED manufacturers recommendsemiconductor p-n junction device. When forward-biased that the junction temperature of all LEDs be kept at lesswith a direct current (DC), an LED emits photons as a than 125°C to avoid thermal degradation (yellowing) of theresult of the recombination of electrons and holes near the encapsulation epoxy. This yellowing greatly reduces lightjunction. The energy of the photons is determined primari- output and lifetime, particularly for blue and green LEDs.ly b The die for ory the energy bandgap of the semiconductor, where the dinary LED packages range from 0.25 to 0.35recombination occurs. III-V compound semiconductors are mm on a side, while those for the so-called power LEDthe materials of ...