Dimming control by variation of the switching frequency for high-intensity discharge lamps

In this paper, a high-frequency dimmable electronic power supply for the high-pressure sodium lamp is presented. The method includes a full bridge rectifier generating a dc-link voltage and a half bridge inverter to generate a frequency swept lamp power signal to drive the lamp while avoiding acoustic resonance. A dimming technique for a resonant circuit electronic ballast based on a variable frequency is introduced. In addition, the ability in the dimming range is demonstrated by experiments and simulation in order to verify the performance of the proposed circuit. A dimming range from 100% to 50% has been achieved. The efficiency is always higher than 89% and the ballast can accurately follow a fixed dimming plan.