Acoustic Resonance Avoidance in High Pressure Sodium Lamps Via Third Harmonic Injection in a PWM Inverter-Based Electronic Ballast

Third harmonic injection in the high pressure sodium lamp voltage by means of a controlled pulsewidth modulation inverter is studied in this paper. It can be shown that acoustic resonance can be avoided by using this technique with a judicious amount of third harmonic injection. Furthermore, the crest factor in the lamp current can also be reduced