| Intrinsic safe behavior of two basic switching converters, i.e., buck DC-DC converter and boost DC-DC converter are investigated to guild the design of Intrinsic safe switching power supplies. The short-circuit protection and isolating measures of buck converter and boost converter are put forward, respectively. The steady state behavior of buck converter and boost converter are analyzed, respectively. As for above two kinds of converters, the inner-intrinsic safety is determined by comparing the maximum current through the inductor with the minimum ignition current. The maximum discharged energy in case of output short-circuit of buck converter and boost converter in CCM and DCM are deduced, respectively. The rules to check the output intrinsic safe property of the two kinds of converters are proposed. The design regions of inductor and capacitor are obtained according to the requirements of inner-intrinsic safety, output intrinsic safety and the desired output voltage ripple level within the input voltage and load ranges. The converter is also guaranteed to be in CCM in case of larger output power. The capacitance is expressed by the inductance according to the desired output voltage ripple level. Taking the derivatives with respect to inductance on the output short circuit discharged energy and letting the results to be zero, the optimal values of inductance and capacitance are obtained which enable the output short circuit discharged energy of a buck converter to be minimum. Spice simulation and experiments were made. Prototypes of a buck converter and a boost converter are implanted. Experiment and simulation results are in positive to the analysis showing the feasibility of the proposed methods.
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