Selection of the current ripple ratio of converters and optimal design of output inductor

The general way to design the output inductor is taking the critical discontinue current as the basis, then selecting the inductor current ripple according to the experiential equations to calculate the inductor value. This method neglects the effects of the inductor current ripple on the overall stresses of the converter, and can´t provides ideal output inductor values, so it will affect the actual performance of the converter. In order to solve the shortcoming, the theoretical basis for selecting the current ripple ratio of Buck converter is analyzed deeply and an optimal design method of the output inductor is proposed in this paper. The overall stresses of the converter, the size of the filter inductor and dynamic performance of the converter are all considered in the proposed method. The optimum value of current ripple ratio is set at about 0.4 finally. The filter inductor value, which is calcultated in terms of the determined current ripple ratio, would not affect the dynamic performance of the converter, and the design of the converter is optimized. The correctness of theoretical analysis and the feasibility of the proposed method are verified by the simulation and experimental results.