Abstract: We proposed a new intrinsically safe DC regulated power supply design that based on switching buck regulator LM2576-ADJ and the four differential comparator-LM339. Firstly, we design a voltage regulator circuit with adjustable output and take a selection and optimization of key components, which realizes a high stability of the output voltage; and then on the basis of combining over-voltage protection circuit and over-current protection circuit, we design a double over-voltage and over-current protection circuit which has automatic recovery feature and reduces the internal energy consumption by cutting down the use of switching devices. The experimental results show that this intrinsic safe power source has wide voltage input from 18.5 V to 26.0 V. Its output voltage is 12 V and operating current is no more than 500 mA. What's more, its load effect is only 1% and the overall efficiency of the power supply can reach 85.7% with a stable and reliable operation.