Patent ID: 7880391

Claim:
A backup ballast for use in combination with a primary ballast for providing power to one or more lamps, said backup ballast comprising: an output switch circuit having a first operating mode for electrically connecting a primary power source via the primary ballast to a first set of the one or more lamps, and said output switch circuit having a second operating mode for electrically connecting a backup power source with a second set of the one or more lamps, wherein said output switch circuit operates in the first operating mode when said output switch circuit is energized and said output switch circuit operates in the second operating mode when said output switch circuit is not energized; and a delay circuit adapted for electrically connecting to the primary power source for receiving power from the primary power source, said delay circuit being electrically connected to the output switch circuit for energizing said output switch circuit while said power is being received and for a delay period thereafter, wherein said delay circuit includes an energy-storage component for storing energy while said power is being received and for discharging the stored energy when said power is not being received in order to energize the output switch circuit for the delay period.