Ballast circuit and system for dimming gaseous discharge lamps

Claim 1

A BALLAST CIRCUIT FOR STARTING AND OPERATING AT LEAST ONE FLUORESCENT LAMP AT VARIOUS LEVELS OF LUMINOUS INTENSITY FROM AN ALTERNATING CURRENT SUPPLY IN CONJUNCTION WITH A PHASE CONTROL AND SWITCHING CIRCUIT ADAPTED TO CONNECT ONE SIDE OF THE ALTERNATING CURRENT SUPPLY IN CIRCUIT WITH A SWITCHING NETWORK LINE AT A PREDETERMINED POINT IN EACH HALF CYCLE, SAID BALLAST CIRCUIT COMPRISING A FIRST AND SECOND INPUT TERMINAL LEAD FOR CONNECTION ACROSS THE ALTERNATING CURRENT SUPPLY, A HIGH REACTANCE TRANSFORMER HAVING A PRIMARY WINDING CONNECTED ACROSS SAID INPUT TERMINAL LEADS, A HIGH LEAKAGE REACTANCE SECONDARY WINDING, AT LEAST ONE SWITCHING TERMINAL LEAD FOR CONNECTION TO THE SWITCHING NETWORK LINE, A TAP PROVIDED ON SAID SECONDARY WINDING AND DIVIDING SAID SECONDARY WINDING INTO A FIRST WINDING PORTION AND A SECOND WINDING PORTION, SAID SWITCHING TERMINAL LEAD BEING CONNECTED TO ONE END OF SAID FIRST WINDING PORTION, CIRCUIT MEANS INCLUDING AT LEAST A PAIR OF OUTPUT LEADS FOR CONNECTION TO THE FLUORESCENT LAMP TO SUPPLY THE OUTPUT OF THE HIGH REACTANCE TRANSFORMER THERETO, A CAPACITOR CONNECTED IN CIRCUIT WITH THE OTHER END OF SAID FIRST WINDING PORTION AND ONE OF SAID OUTPUT LEADS, AT LEAST SAID FIRST WINDING PORTION AND SAID CAPACITOR FORMING AN OSCILLATORY CIRCUIT UNDER OPEN CIRCUIT CONDITIONS TO PROVIDE A TRANSIENT VOLTAGE TO AID THE IGNITION OF SAID LAMP AND SAID SECOND WINDING PORTION OF SAID SECONDARY WINDING AUGMENTING SAID TRANSIENT VOLTAGE BY AUTOTRANSFORMER ACTION.