Electronic ballast and startup method

An electronic ballast receiving AC power and being operably connected to a lamp having a lamp filament, the electronic ballast comprising:

• a timer generating an inverter control signal and a preheat control signal;
• a converter receiving the AC power and generating DC power;
• a self-oscillating inverter receiving the DC power and being operable to provide lamp power to the lamp, the self-oscillating inverter being responsive to the inverter control signal;
• and
• a filament preheater receiving the DC power and being operable to provide filament power to the lamp filament, the filament preheater being responsive to the preheat control signal;
• wherein, when the AC power is initially applied, the preheat control signal directs the filament preheater to provide the filament power to the lamp filament, and the inverter control signal directs the self-oscillating inverter not to provide the lamp power to the lamp;
• and
• wherein the timer includes a filament heat/sense circuit to signal the filament preheater to provide the filament power to the lamp filament when the filament heat/sense circuit detects that the lamp has been reconnected, based on a predetermined change in time-averaged lamp filament voltage.