A　low-frequency　square-wave　electronic　ballast　with　a　good　performance　is　proposed　to　operate　automobile　MH　(metal　halide)　lamps　in　the　paper.　The　proposed　ballast　is　consisted　of　the　high　step-up　dc-dc　converter　with　coupled　inductors　and　the　low　frequency　dc-ac　inverter.　A　higher　efficiency　and　a　lower　devices　stress　are　achieved　due　to　that　the　leakage　energy　is　recycled.　Because　of　its　low-frequency　operation,　no　acoustic　resonance　occurs.　A　discrete　control　is　used　to　realize　the　dynamic　matching　of　electronic　ballast　and　MH　lamp,　and　its　control　method　is　also　detailed.　A　new　control　strategy　to　realize　constant　power　for　MH　lamp　under　different　battery　and　lamp　voltage　is　presented.　An　additional　high　voltage　pulse　generator　is　constructed　to　make　the　MH　lamp　be　fast　and　safely　turned　on.　The　design　considerations　are　analyzed　in　details.　Some　experimental　measurements　are　used　to　verify　the　theoretical　prediction　and　analytical　discussion.