A circuit is disclosed to implement an energy saving electronic ballast (1A) for driving a fluorescent lamp or tube (2). The circuit is characterized by a high power factor, low harmonic distortion and minimized radio frequency interference. The circuit includes a unique DC power supply (4) comprising a high pass filter (8), which receives an AC input signal, a diode bridge rectifier (6) and a high speed diode rectifier (D2) which cooperates with the bridge rectifier to provide the power supply with first and second rectification stages. A current regulating capacitor (C4) for driving the fluorescent lamp or tube is connected to the DC power supply between the first and second rectification stages. A trigger and high frequency oscillator are provided after the second rectification stage of the power supply to provide the DC current necessary to operate the ballast circuit. A protection circuit (30) is connected to the ballast and operable to disable the oscillator and thereby prevent damage to the ballast in the event that the tube or lamp is defective or disconnected from the ballast or subjected to abnormal operating conditions.