Intrinsical Safety Behavior & Design Considerations Of Buck-Boost Converter

Electronic equipments applied in flammable and explosive conditions must meet the requirements of anti-explosive. Intrinsical safety is the optimal means for anti-explosive. The direct-current power supply is one of the important elements of the electronic equipment, however, the published anti-explosive direct-current power supplies are usually linear ones with hulking anti-explosive shells and low efficiency. Therefore, intrinsically safe switching power supply will be competitive in the future. Buck-Boost converter is one of the important elements of switching power supply, which can realize step-up,step-down and negative output voltage easily. The intrinsical safety property and design of Buck-Boost converter is presented in this paper.Energy transmission modes (ETM) of Buck-Boost converter are analyzed deeply. Comparing the minimum current through the inductor with the output current, ETM can be divided into to two types, i.e., the Complete Inductor Supply Mode (CISM) and the Incomplete Inductor Supply Mode (IISM). The critical inductance and critical condition are deduced. The expression of output ripple voltage in various operating mode and the maximum output ripple voltage are obtained.The peak current through inductor in various operating mode within the whole operating range is deduced. The inner-intrinsic safety of the Buck-Boost converter is determined by comparing the maximum peak current through the inductor with the minimum ignition current. The maximum short-circuit discharged energy in various operating mode within the whole operating range is deduced. The critenion checking the output intrinsic safety property of the Buck-Boost converters is proposed.The minimum 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...