Evaluation of close loop digital control based in a microcontroller and used to eliminate acoustic resonances in HID lamps

A closed loop digital control to eliminate acoustic resonances (AR) in electronic ballast for high intensity discharge lamps is proposed in this paper. The system senses the AR intensity and a microcontroller compares this signal with a reference level in order to apply different frequency modulation patterns to reduce the AR intensity until a smaller level to the reference value. The use of different frequency modulation patterns allows avoiding the AR intensity due to changes in the lamp eigenfrequencies, ambient temperature and the lamp aging.