Abstract: For problems of large output voltage ripple-wave and poor intrinsic safety performance existed in mine-used intrinsic safety type power supply caused by large filtering capacitor of switching converter, a filtering capacitor resolution scheme was proposed by use of active capacitor technology. Working principle, control strategy and mathematical model of the active capacitor were analyzed. The active capacitor technology transfers instantaneous power difference of DC bus to a non-DC bus capacitor for energy balance through controlling an internal full-bridge converter, so as to realize filtering capacitor resolution of DC bus. Application of the active capacitor technology in mine-used intrinsic safety type power supply was introduced by taking a power supply based on Buck converter as an example. The simulation and experiment results show that the active capacitance technology can meet intrinsic safety output requirement with small capacitor.