A novel complex modulation method for the metal halide lamp ballast

This paper presents a novel complex modulation method for the metal halide lamp ballast. The proposed modulation method, which has a modulating signal of swept complex frequency, can eliminate the acoustic resonance more effectively than the conventional modulation method, which has a modulating signal of constant frequency. For the purpose of future application specific integrated circuits (ASIC), the proposed ballast controller has been designed only with erasable programmable logic devices (EPLDs), but without a microprocessor. In this paper, detailed modulation schemes are described and experimental results on the prototype 150 W metal halide lamp ballast with the proposed modulation method are discussed.