| At present the most of explosive-proof DC power supplies are linear power supplies, which is low in efficiency, narrow in operating range and ponderous. However, switching power supply stands on the contrary, which will replace linear ones and become competitive in the future. With the increase of switching frequency, the inductors in switching power supplies become smaller and smaller, while the output capacitor is still great which affect the behavior of intrinsically safe output of the switching power supply badly. In this thesis, the influence of the capacitor on the switching power supply is studied for the design of the intrinsically safe switching power supplies, main work of the dissertation can be summarized as follows: 1. Considering the intrinsic safety, the discharge process of capacitive circuit is observed with IEC spark test apparatus, voltage, current and energy of spark discharge are analyzed with numerical method. The mathematical models of spark discharge for the capacitive circuits are established, and it is discovered that the energy of capacitor which ignites explosive mixture is released at the moment of electrodes just closing. The influence of the inductor on the discharge of capacitor is also studied. 2. The characteristics of intrinsically safe DC power supply and how to design it are researched and analyzed in detail, and the intrinsically safe protection methods for reserve energy elements are presented. 3. The schemes to connect reserve power supply with chief circuit are discussed. A novel flame-proof&intrinsically safe DC switching power supply with its reserve power supply is developed, by integrating uninterrupted power supply, stabilizing output voltage and regulating function in one convertor. The fundamental principle of the power supply is particularized and the principal steps and calculation methods of design are given in detail. Through the result of the circuit experiment, the feasibility of design and the correction of the conclusions are proved.
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