Reliability Analysis of the Circuit and FM Modulation Parameters for the First Harmonic Level Reduction of the Forward Switching Power Supplies

摘要

In this paper, the sensitivity of first harmonic of switching power supplies with the FM modulation of switching signal is investigated. Inspections are done with respect to the circuit and FM modulation parameters. In this regard, sets of orthogonal experiments are designed based on the Latin Cubes concept. Then the results of the experiments (I.e., the level of the 1st harmonic) are interpolated on a response surface. The response surface shows the self and the mutual effects of the factors on the level of the 1st harmonic. It is seen that the minor changes of the circuit and modulation parameters has a major effect in the level of the 1st harmonic. Consequently, after circuit design process, sensitivity analysis must be done with respect to the circuit parameters and the level of 1st harmonic can be reduced by small changes in the circuit parameters. It is seen that the response surface can be readily used for analysis of the effects of parameters and with the small amounts of experiments, suitable results are achievable on the level of the 1st harmonic. The harmonic level is more sensitive to the reactive elements and the load than the parameters of modulation. Therefore in the design for low EMI, reactive elements must be seffected with care. Dominant interference depends on the load. The effect of load has positive sign in response surface. Therefore increasing the load intensifies the harmonic level.