Design Of Capacitor Of Boost Converter Based On Monte Carlo Method

Capacitor is one of the main electronic elements of DC-DC converter, and has important influences on output ripple voltage. But, the effective capacity of capacitor decreases with the increasing of swithcing frequency in engineering application. Therefore, the frequency characteristic of capacitor is the key of designing DC-DC converter. By taking the Boost Circuit as the research object, the statistical results were given based on the mass data with the Monte-Carlo Method. And The relation curves between the capacity and the frequency of the Ceramic Capacitor,Aluminum Electrolytic Capacitor,Tantalum Electrolytic Capacitor, the design of parameter were also obtained.Firstly, the Monte-Carlo Method and the problems in the design of output filter capacitor of DC-DC converter were introduced.Secondly, the structural characteristics and the application range of common capacitors were summarized. The working mode of Boost Converter and it's output ripple voltage were analyzed. The randomness in generating pseudo random number with Matlab was proved. The theory of capacitor's frequency characteristic analysis and the flow diagram were given in paper.Thirdly, for the given capacitors, the random numbers that experiment required are generated by Matlab, and the output ripple voltages of each experiment are recorded. According to the ripple voltage formula, the ratio of the effective capacity and the nominal capacity are calculated. The average value of every frequency test points are calculated out based on the data that obtained before. The relation curves between the capacity and the frequency, and the mathematical model are both given. In addition, the detailed analysis of capacitance equivalent circuit are introduced. The important parasitic parameters such as the ESR(Equivalent Series Resistance), the ESL(Equivalent Series Inductance), the DF(Dissipation Factor) and the Resonant frequency etc, are also analyzed in detail. The frequency characteristic of capacitor is explained in principle.Finally, a design example of Boost Converter is given in the paper. The example is calculating the value of filter capacitor according to the frequency response curve and the mathematical model with the determined switching frequency and output ripple voltage. The experimental results indicate that this design method is correct, feasible and valid.