Discharge lamps always require ballasts. They have a negative current-voltage characteristic: ignition is followed by massive ionisation of the inert gas or metal vapour in the lamp, which causes a surge in lamp current that would destroy the lamp within a very short time. Ballasts limit that current and, in conjunction with starters, play a role in lamp ignition.

EBs achieve the highest efficiency

A distinction is made between magnetic ballasts and electronic ballasts (EBs). The greatest energy efficiency, as well as maximum lighting comfort, is achieved where lamps are operated by EBs. They offer the latest technology, superseding the inductive low-loss ballasts that followed the high-loss conventional ballast. Ballasts may be integrated in lamps – as in the case of energy-saving lamps with a screw base – or may form part of luminaires.