Timed ballast circuit for sodium vapor lamp

摘要

A ballast circuit for driving a sodium vapor lamp includes a ballast transformer having a primary winding connected to a constant current power source. A secondary winding of the transformer is connected across the lamp. A high voltage oscillator responsive to the voltage across the lamp superimposes high voltage pulses across the lamp when the voltage across the lamp is above a predetermined level. A time delay circuit, triggered by the initial voltage across the primary winding when the power from the power source is turned on, opens a normally closed switch connected across the primary winding a predetermined time interval after the time delay circuit is triggered.