Sequence start lamp ballast with current spike suppression means

Abstract

A ballast for a sequence start series operating circuit that includes two rapid start gaseous discharge lamps. The circuit includes a transformer with a primary winding and a loosely coupled secondary winding, a series first capacitor for providing a leading current when both lamps have been ignited and are operating and a second capacitor shunting the second-to-ignite lamp to by-pass that lamp during ignition of the first-to-ignite lamp and thereafter to develop a voltage across the second capacitor sufficient to ignite the second-to-ignite lamp when current flows in the by-pass branch. The lamps are of a variety which produces an undesirable current peak in the second-to-ignite lamp on each half cycle because the shunting second capacitor dumps its charge accumulated during each half cycle into the lamp. The secondary winding is made up of a main part and an auxiliary part, the auxiliary part being connected in series with the second capacitor in the by-pass branch so that an inductive reactance is added to the capacitance in that branch for suppressing the current peak in the second-to-ignite lamp on each half cycle. The auxiliary part of the secondary winding does not participate in the ignition of the first-to-ignite lamp but it does participate voltage-wise in the operation of both lamps in series.