Research On Improving The Performance Of Output Intrinsically Safe Power Supply Based On Switching Converter

Currently inspection and monitoring equipment，alarm and communicationequipment are used widely in coal mine, coal mine’s production safety aresupplied by power source’s reliability and safety. Thus researching intrinsicallysafe power supply with good intrinsically safe, wide application, convenientusing has an important engineering significance for coal safety production. Curr-ently output intrinsically safe switching power supply with small size, lightweight, wide input voltage range is widely used in hazardous environments ofcoal and petrochemical, but there are some problems of large output ripple andprotection action for a long time.To solve these problems, firstly several common forms of discharge law arestudied in this paper, the safety circuit mainly research spark discharge form.Owing to output of switching power containing capacitance and capacitordischarge circuit having characteristics of relatively concentrated of dischargeenergy, large current changes, short discharge time, capacitor’ dischargecharacteristics are mainly researched and CL circuit’s discharge characteristicsare also studies, through a mathematical model and using Matlab completesimulation analysis, the influence of the inductance of the capacitor circuitdischarges is obtained.Secondly, the current designs of output intrinsically safe power supply incoal mine are designed. Based on analysis advantages and disadvantages and thefield of application of isolation topologies, flyback topology is selected as maincircuit structure of output intrinsically safe switching power supply. Throughindepth analysis the relationships between energy transfer process of different operating modes, witching frequency and voltage, which provides a method toimprove power supply’s performance of intrinsically safe and electricalspecifications. Some measures of decrease discharge spark energy of inductance,capacitance are researched,the method of increasing small inductance can beused in capacitance circuit, the method of paralleling resistors, capacitors,diodes can be taken in inductance circuit.Thirdly, according to the performance requirements of output intrinsicallysafe switching power supply, its design program is determined. According to thecore of KA5L0380R, a reasonable control strategy is developed, the parametersof flyback circuit’s high-frequency transformer are designed by using the APmethod, while the other major components in the power supply circuit are alsocalculated and selected. Output limit voltage circuit which consists regulatorcircuit LM2576and LM339four voltage comparator are designed to achieve thestable voltage, and improve the response speed of the power protection.Then, common topology, control and operating mode of PFC circuit areintroduced, peak current control Boost circuit of CRM mode is selected. As thecore of control chip FAN7527B, The overall of PFC circuit is designed, theparameters of main circuit and control circuit are designed. The design circuitwas validated by analyzing spectrum of input current waveform and other keywaveforms.Finally, based on Labview, output intrinsically safe power supply platform isset up. A virtual oscilloscope with multiple functions is designed. The hardwareconsists of a signal conditioning circuit, data acquisition card and computerconfiguration, which is to complete acquisition of switching power supply’svoltage, current and etc. Software design is carried out in Labview graphicaldevelopment environment, which is to complete displaying, measuring andstorage of signal. The performances of output intrinsically safe switching powersupply are verified by virtual oscilloscope.