Modeling of DC-DC SEPIC Converter at CCM Considering Input Filter Effect

The single-ended primary inductance converter (SEPIC) is a popular DC-DC topology due to its ability to produce output voltages either higher or lower than the input while maintaining the same polarity. Although input current ripple of SEPIC converter is lower than its counterparts, to reduce the current ripple and electromagnetic interference (EMI) noise, an input filter is often used. In addition, using LCL filter as an input filter is very common. In this paper, modeling of the SEPIC converter at continuous conduction mode (CCM) mode by considering the effect of LCL filter is realized which is not presented in the literature. First of all, the state space average model of the CCM SEPIC converter is introduced, then small signal analysis is made, and transfer functions are obtained and analyzed by cascading the filter transfer function. Modeling of the converter by considering filter effect is verified by the simulations. With the 15W experimental set up of the converter, the filter effect on the EMI noise and current ripple is investigated and compared with its LTspice simulation.