Abstract: In view of mine inflammable and special explosive environment and sensor equipment static and group pulse EMC interference problem, a constant/closure output protection circuit has soft start, constant / closure output and self-recovery function. We detail the protection circuit design, soft start, constant current output, and the output of closure and self-recovery circuit design, compared by experiments and existing sensor equipment, power supply module; we design protection circuit with existing intrinsically safe power supply protective circuit. The protection circuit has soft start protection, anti-jamming and anti-load ability of the impact; overcurrent fault is lifted to automatic recovery, without the need to add additional recovery circuit. The circuit adopts the basic device with fast response time and good stability.