A novel dimming control electronic ballast for 250W high voltage sodium lamp

This paper presents a new kind of dimming control electronic ballast for 250W high voltage sodium lamp. A simple new kind of pulse igniting circuit is presented here, with this circuit; the lamp ignites easily with little current and voltage stress for the switches. A new kind of dimming control circuit is also presented here for fixed dimming plan, with this circuit and proper control method, soft dimming control can be achieved easily. A simple method to realize closed-loop control of lamp power is adopted, and frequency varying is adopted here to realize dimming control. Experimental results show that when the ballast dims from 30% to 100% rated power, its efficiency is always higher than 90%, and the ballast can follow exactly with the fixed dimming plan.