Patent ID: 7061189

Claim:
An electronic ballast for driving at least one gas discharge lamp from a source of AC power which has a substantially sinusoidal line voltage at a given line frequency, comprising: a rectifying circuit having AC input terminals and DC output terminals; said AC input terminals connectable to the source of AC power; said rectifying circuit producing a rectified output voltage at its said DC output terminals when said AC input terminals are energized by said source of AC power; an inverter circuit having input terminals connected to said output terminals of said rectifying circuit and producing a high frequency drive voltage for driving a lamp current through said at least one gas discharge lamp when said AC input terminals are energized by said source of AC power; and a cat ear circuit connected to said source of AC power, said cat ear circuit being adapted to conduct current for a first relatively short time following a first zero crossing of said line voltage and for a second relatively short time prior to the next zero crossing of said line voltage thereby to reduce the total harmonic distortion of the current drawn from said source of AC power below that which would occur in the absence of said cat ear circuit.