Apparatus for starting high pressure gaseous discharge lamps

Claim 1

In a ballast system for a high pressure metal vapor arc discharge lamp including an ionizable gas in which the gas discharge has been extinguished, an improved means for restarting said lamp while the pressure of said lamp is on the order of 1000 Torr and the temperature is approximately 4000° K, said means comprising: an inductor adapted to be connected to a low voltage, low frequency power source; a ferro-resonant autotransformer connected to said inductor; a capacitor connected in parallel with said autotransformer to provide parallel resonance at said low frequency; a transformer having primary and secondary windings, said secondary winding connected in series with said autotransformer and said lamp; means connected to said primary winding for applying a substantially undamped high audio frequency voltage of between 17,000 and 60,000 Hertz and of a magnitude sufficient to provide a voltage between 2500 and 4000 volts at said secondary winding for a sufficient time after extinction of said lamp and within 1 minute thereof to cause reionization of said gas and increase the level thereof until said lower frequency power source can maintain said ionization.