Abstract: We designed an intrinsically safe power supply. Modular isolation voltage stabilizing method is adopted and overvoltage and over-current protection is realized by analog circuit, the AC / DC voltage input range can be achieved at 9 V to 36 V, with constant output voltage of 12 V; the working current is less than or equal to 500 mA. The test results show that the load effect is only 1%, and the source effect is less than 0.4%. The overall efficiency of the power supply can reach 83%, and it can run stably and reliably.