Designs and Implementation of the Dimmable Electronic Ballast for Metal-Halide Lamps

This paper introduces technologies of the dimmable electronic ballast for metal-halide lamps (MHLs). The topology structure of the ballast includes AC/DC converter, DC/DC converter, DC/AC inverter, even dimming and protection functions that can be applied in many kinds of MHLs. The output power of the ballast is stably by means of feedback of the current from the lamp. Especially, the light intensity of MHLs can be varied linearly in the range from fifty to one hundred percent with control skills of the DC signal or DALI interface. Furthermore, due to the feedback control skill of lamp voltage, the lamp power can always be controlled under desired level. In addition, the powerful protection functions such as false ignition, open and short circuits are able to build up much more fixable system. Finally, the work performances such as the low current harmonic distortion (<9%), high system efficiency (>89%) and according with the international safety standard, are verified with experimental results of 150 watt MHL ballast.