A　two-stage　low-frequency　square-wave　electronic　ballast　with　good　performance　is　proposed　to　operate　MH　lamps　in　the　paper.　The　PFC　stage　is　used　to　obtain　high　power　factor,　The　DC/DC　stage　is　derived　from　combining　a　buck　dc/dc　converter　and　a　full-bridge　dc/ac　inverter,　it　supplies　the　lamp　with　low-frequency　square-wave　current.　Due　to　its　low-frequency　operation,　no　acoustic　resonance　occurs.　The　discrete　control　is　used　to　realize　the　matching　of　ballasts　and　lamps.　The　circuit　operation　and　control　method　are　detailed.　The　main　parameters　are　calculated.　The　proposed　ballast　can　save　a　controller,　two　active　switch,　reduce　size　and　possibly　increase　system　reliability　over　a　conventional　three-stage　low-frequency　square-wave　electronic　ballast.　Computer　simulation　results　and　experimental　measurements　are　used　to　verify　the　theoretical　prediction　and　analytical　discussion.