This　paper　designed　a　tristate　driver　topology　for　the　ac　contactor.　Based　on　the　topology,　a　slope　closed-loop　control　scheme　was　put　forward.　During　the　closing　process,　the　slope　of　the　coil　current　is　used　as　the　outer　loop　to　control　the　inner　loop　of　the　coil　current　so　as　to　reduce　the　contacts　bounces;　during　the　holding　process,　only　the　inner　closed-loop　of　the　coil　current　works　which　makes　the　ac　contactor　energy-saving　and　noise-free;　in　the　breaking　process,　the　negative　voltage　is　forced　on　the　coil　that,　in　turn,　causes　the　armature　of　the　contactor　to　be　rapidly　demagnetized　to　improve　the　opening　velocity　of　the　contacts　and　to　reduce　the　arc　erosion.　With　these　measures,　a　whole　process　dynamic　control　which　includes　the　closing,　holding　and　breaking　is　formed.　Through　the　co-simulation,　the　slope　control　principle　and　the　control　laws　are　verified.　Introducing　the　digital　control　technology,　an　intelligent　control　module　is　designed,　and　the　related　experiments　verify　the　validity　of　the　slope　control　and　the　tristate　driver.　©　2017　Chin.　Soc.　for　Elec.　Eng.