The　intelligent　AC　contactor　with　the　function　of　anti-voltage　sag　is　used　always　in　enterprises　where　the　continuous　power　supply　is　needed.　According　to　this,　a　new　intelligent　Anti-voltage　sag　control　module　for　AC　contactors　has　been　designed,　and　it　has　two　work-modes:　AC　mode　and　the　adjustable　DC　mode.　The　coil　of　the　AC　contactor　gets　adjustable　DC　voltage　through　a　module　with　the　function　of　anti-voltage　sag,　and　it　is　running　noiselessly　when　module　is　normal.　Once　the　module　itself　breaks　down,　a　conversion　circuit　starts　immediately　to　cut　off　the　module　and　AC　power　stimulus　the　coil　directly　through　the　contact　switch　circuit,　then　an　alarm　signal　is　given.　With　this　function,　the　module　keeps　the　power　supply　normally.　This　paper　analyses　the　principles　of　the　module,　especially　the　switched-mode　power　supply　and　the　conversion　circuit　used　for　contact　switching　and　non-contact　switching.　The　simulations　and　experimental　results　verify　the　validity　of　the　presented　module.　©　2012　Chin.　Soc.　for　Elec.　Eng.