HPS lamp control with adjacent frequency signal injection for acoustic resonance avoidance

Acoustic resonance has been an important problem in high pressure discharge lamp supplies at high frequency due to its undesirable effects such as arc distortion, fluctuation, lamp life reduction, discharge extinction and lamp destruction in the most severe cases. Our method for the injection of adjacent signals allows the restriction of certain selected power harmonics in the lamp in order to avoid the AR. As a result, the control of lamp current is important to assure lamp power harmonics and also discharge stability. In this paper, lamp current control by PI and resonant controller are studied in order to evaluate lamp operation with the injection of adjacent signals. Simulation and experimental results will be presented.