Traditionally, lighting comprised some form of incandescent, fluorescent or halogen lamps. That has changed with the ever increasing popularity of light emitting diodes (LEDs) which are finding applications in both indoor and outdoor luminaires. The main drivers of this trend are energy savings, long service life, the robustness of solid state devices and the incredible flexibility that an LED luminaire can bring to a lighting application. However, to maximise these the power source needs to be carefully chosen.