Circuit for starting and operating fluorescent lamps

Claim 1

A circuit for starting and operating one or more fluorescent lamps from an a-c sine wave electrical power source of given frequency, comprising reactive ballast means connected in series with said power source and said lamps and having a non-linear characteristic for producing a plurality of harmonics of said given frequency, a cathode heating transformer comprising a primary wnding and secondary windings for connection to the cathodes of said lamps, a capacitor connected in series with said primary winding, means connecting one or both of said series-connected capacitor and primary winding across said lamps, the combined reactance of said capacitor and said primary winding being at least partially in resonance, in cooperation with inductance of said reactive ballast means, over a frequency range simultaneously encompassing a plurality of said harmonics of the given power source frequency, and a switch interposed in series with said series-connected capacitor and primary winding, said switch being closed during starting of said lamps to cause said resonance and to cause heating of said cathodes, and said switch being open after starting of and during operation of said lamps.