Investigation on the start-up of low wattage metal halide lamp controlled by low-frequency square-wave ballast

Using conventional three-stage low-frequency square-wave electronic ballast, low-wattage MH lamps may have trouble in starting-up instantly and smoothly. This paper investigates the special starting-up characteristics of low-wattage MH lamps and presents some novel control strategy according to the lamps' special characteristics. A prototype of 70 W electronic ballast with the new control circuit designs was constructed and experimental results verified the novel control strategy can greatly increase the probability for lamps to successfully start up instantly and smoothly.