Derivation of transfer function of LLC current resonant converter using numerical calculation

Among various converters, the LLC electric current resonant converter attracts attention because of high power density, low noise and high efficiency. However, this converter cannot apply the analysis of averaging method, and impossible to derivate the transfer function, so designing is difficult. In this study, we devised a method to derive a frequency response characteristic with a transfer function type using based on the way of thinking of averaging method, and succeeded expressing transfer function of the bode diagram which agreed with actual survey. Moreover, we derived poles from the transfer function, and showed the relation between the shape of the bode plots and poles.