Electronic ballast

Claim 1

An electronic ballasting system for illuminating electrical lamps comprising: a main power transformer having a primary winding and at least a first secondary winding, an electronic inverter coupled to drive current through said main power transformer primary winding sequentially in alternating directions characterized in that said electronic inverter has first and second transistors with the emitter of said first transistor coupled to the collector of said second transistor, and further comprising a pair of d.c. supply lines, one of which is coupled to the collector of said first transistor and the other of which is coupled to the emitter of said second transistor, a pair of charging capacitors series connected across said d.c. supply lines each coupled to at least partially turn on a single one of said transistors, a lead connecting said emitter of said first transistor to said main power transformer primary winding, and a lead connecting said main power transformer primary winding to a tap between said charging capacitors, means for driving said transistors in alternating sequence, a starting circuit for initially driving said electronic inverter and further characterized in that said starting circuit initially drives one of said transistors, an operating capacitor connected to said main power transformer first secondary winding, at least first and second lamp terminal means for receiving electrical discharge lamps having cathode elements therein, said lamp terminal means being series connected to said operating capacitor and to said main power transformer first secondary winding, and a high impedance capacitor connected in parallel across at least one and less than all of said terminal means.