Tim　paper　presents　a　digital　close　loop　control　technology　for　AC　contactors　that　include　making　close　loop　and　keeping　close　loop　using　the　digital　power　supply　chip.　As　the　current　inner　loop,　the　high-speed　ADC　samples　the　coil　current　actual　value　and　compares　with　the　coil　current　given　value;　therefore　an　error　can　be　given　to　update　the　digital　duty　cycle.　During　the　making　process　of　the　contactor,　the　motion　electromotive　force　of　the　movable　core　compels　the　coil　current　falling.　The　falling　slope　directly　relates　to　the　velocity　of　the　movable　core,　the　sharper　the　slope,　the　higher　the　velocity.　So　the　coil　current　falling　slope　can　reflect　the　velocity　of　the　movable　core　indirectly　As　a　velocity　outer-loop,　the　measured　value　of　the　falling　slope　is　compared　with　the　given　value　of　the　slope　and　the　error　sets　the　coil　current　given　value.　Contact　bounces　and　electrical　wear　can　be　reduced　greatly　by　setting　the　proper　given　value　of　the　slope.　It　improved　the　reliability　and　the　electrical　life　of　the　AC　contactors.　The　control　scheme　has　good　application　prospect,　particularly　in　the　control　of　the　large-capaciry　contactors.　©　2014　VDE　VERLAG　GMBH.　All　rights　reserved.