Abstract: Emergency lighting for an aircraft has a primary power source for light units provided by the normal aircraft power supply and a secondary power source provided by power supply units operable to back-up the primary power source. Each light unit may have its own power supply unit operable to power the light unit in an emergency if the normal aircraft power supply fails or is otherwise unable to power the emergency lighting. Each power supply unit includes one or more electric double layer capacitors that are charged whenever the normal aircraft power supply is operational to provide the primary power source. The useful life of the electric double layer capacitors may be prolonged by reducing the capacitor voltage when the emergency lighting is switched off.

Abstract: An LED light unit is provided with terminal pins at each end for fitting the light unit in place of a fluorescent tube of a fluorescent lighting fixture connected to a power source. The light unit has a circuit board with a plurality of diodes configured to provide at least one string of visible light producing LEDs and at least one string of zener diodes. The strings are driven by drive means whereby a constant input operating voltage to the light unit is provided when the light unit is used with a ballast and the power derived is dissipated in any one or more of the strings.

Abstract: Emergency lighting for an aircraft has a primary power source for light units provided by the normal aircraft power supply and a secondary power source provided by power supply units operable to back-up the primary power source. Each light unit may have its own power supply unit operable to power the light unit in an emergency if the normal aircraft power supply fails or is otherwise unable to power the emergency lighting. Each power supply unit includes one or more electric double layer capacitors that are charged whenever the normal aircraft power supply is operational to provide the primary power source. The useful life of the electric double layer capacitors may be prolonged by reducing the capacitor voltage when the emergency lighting is switched off.