Abstract: This article introduces a kind of intrinsic safety type slow start circuit and the design of each part. The circuit carries on voltage conversion by high performance LM22671 power chip, and it can improve power conversion efficiency and reduce the output ripple and noise by the LC collocation. The voltage stabilized after a delayed start circuit control, which could eliminate the high current impact of instruments on power supply equipments in power up moment, the power input had "anti reverse connection", " anti impact" and other functions after treatment. This design can be used in underground coal mine equipments with small volume, low cost, intrinsic safety output, and strong load capacity.