Patent ID: 8629574

Claim:
An emergency ballast for a light source, comprising: a rechargeable battery; a first circuit, wherein the first circuit receives an electrical voltage and provides a first charge to the battery, wherein the electrical voltage comprises one of a first amplitude and a second amplitude, and the first circuit provides the first charge to the battery without regard to whether the electrical voltage comprises the first amplitude and the second amplitude; a standard mode, wherein a fluorescent lamp is powered using mains power; an emergency mode, wherein the fluorescent lamp is powered using the battery, wherein the emergency ballast switches from standard mode to emergency mode in response to an interruption in mains power, and switches from emergency mode to standard mode in response to the resumption of mains power; and a transition circuit configured to delay the transition between the standard mode and the emergency mode, wherein the transition circuit comprises: a relay, wherein the relay switches the emergency ballast from emergency mode to standard mode; a transistor, electrically coupled to the relay, wherein the transistor prevents the relay from switching when the transistor is not conductive; and a capacitor, electrically coupled to mains power and the transistor, the capacitor configured to charge from mains power, wherein after charging the capacitor, current is delivered to the transistor rendering the transistor conductive and causing the relay to switch the emergency ballast into standard mode.