Ballast circuit for a 220-volt improved lighting unit

Claim 1

In a lighting unit having a gas discharge tube as the main light source, a filament as a supplementary light source and in serial arrangement with said discharge tube and a starting circuit for the gas discharge tube, a resistive ballast circuit for the gas discharge tube being adapted to accept across its first and second input terminals an applied alternating current (A.C.) voltage having a typical value of 220 volts at a frequency of 50 Hz, said ballast circuit having an output stage comprised of a parallel arrangement of a full-wave rectifier and a filter capacitor both for developing a D.C. operating voltage for the gas discharge tube, said full-wave rectifier having two input nodes one of which is connected to one of said input terminals and two output nodes connected across said output stage, said output stage being capable of accepting across its first and second output terminal said arrangement of said filament and said gas discharge tube, said ballast circuit further comprising a resistor-capacitor network at its input stage connected between one of the input terminals and the other input node of the full-wave rectifier; said resistor-capacitor network having values selected so as to reduce the A.C. voltage by a factor in the range of about 2 to about 1 in the development of said D.C. operating voltage of said gas discharge tube.