Aircraft emergency lights provide passengers and crew safety illumination and evacuation guidance in the event of an emergency evacuation from the aircraft. Internal emergency lights, which include lighted exit signs, ceiling flood lights and floor-level flood lights, are installed to illuminate the passenger cabin, emergency exits and interior exit paths. External emergency lights provide illumination along paths of egress and exterior areas around the passenger door and the service door. The emergency lights must activate and remain lighted upon failure of the normal electrical power of the airplane, an impact that leads to an excessive deceleration and velocity change, or occurrence of any other emergency condition that necessitates automatic activation of the emergency lighting. Aircraft emergency lights operate independent of the main cabin lighting system. Rechargeable batteries are typically used as the energy supply for the emergency lights and may be recharged from the main electrical power system of the airplane. High efficiency LEDs are the dominant choice for use in emergency lighting applications. They work with an LED driver which maintains power to the LED load in both normal and emergency operation.