Preheating circuit for electronic ballast

A circuit for preheating a filament of a lamp, the circuit comprising:

• a filament preheating circuit electrically coupled to the filament;
• a resonant inverter comprising a resonant inductor or a transformer magnetically coupled to the filament preheating circuit to provide electrical power to the filament;
• and
• a switching device configured to enable power to flow from the filament preheating circuit to the filament in a preheating stage.

A ballast for driving a gas discharge lamp, the ballast comprising:

• an inverter configured to generate a lamp supply voltage signal;
• and
• a filament preheat circuit electrically coupled to the inverter and the gas discharge lamp, the filament preheat circuit configured to preheat a filament of the gas discharge lamp, the filament preheat circuit comprising:
• inductively coupled winding magnetically coupled to the inverter, the inductively coupled winding configured to provide electrical power to the filament during preheating;
• and
• a switching circuit configured to electrically connect the power from the inductively coupled conductor of the filament preheat module to the filament, wherein the switching module is configured to enable power to the filament during preheating and cutoff the power to the filament from the filament preheat module after a predetermined time period during preheating.