Harmonics Injection in Hps Electronic Ballast With Modulation Index Control

Abstract

The modulation index control is used in this work to control the lamp power supply permitting the removal of the output transformer out of the inverterresonant filter setup. The Acoustic resonance in HPS lamps can be avoided by using a controlled PWM inverter and third harmonic injection.Experimental and simulation results are shown for the control of the inverter power subject to variation in the input voltage. Results for different DC bus voltages are also provided which attest the transformer removal and avoid the acoustic resonance with different modulation indexes. An ignitor for high-intensity discharge lamps, based on forced oscillation via an external periodic voltage square wave, supplied by a digitally controlled inverter, is also presented. The crest factor of the current can also be reduced by this approach.1