Inverter ballast circuit featuring current regulation over wide lamp load range

A ballast circuit for driving fluorescent lamps characterized by a minimum of components has a power transformer constructed to present a source impedance integrated with the transformer and in series with the lamp load sufficient to regulate the load current to within 10% for a selected maximum wattage fluorescent lamp load, such as 18 or 36 watt, and any lesser fluorescent lamp loads. The transformer has a high voltage secondary winding with a reflected impedance at least 6.0 times greater than the reflected impedance of the selected worst case fluorescent lamp wattage load. The integrated magnetics design of this ballast also provides passive short circuit protection, filament current reduction after lamp strike, and cold temperature start-up with a minimum of circuit components.