A quick and simplified approach for understanding the dynamics of the SEPIC converter for low voltage applications: Simulation study

Designing the feedback compensator for the SEPIC (single ended primary inductance converter) converter is quite difficult due to the extreme amount of phase shift in the power stage and occurrence of double resonance. Hence the current mode control, which increases the complexity of the system, is the most commonly adapted for stabilizing the converter. However, the careful observation of the frequency response of power stage, which depends on the filter components and equivalent series resistance of the capacitor, of the power stage makes the process of controlling the dynamics of the converter easy. Sometimes the frequency response of the power stage of the converter is free of double resonance with minimum phase shift and resembles the second order converter. So, one can develop the compensator network similar to the second order converter. In this paper, the design of controller for the SEPIC converter based on single loop feedback control is presented without the need of current mode control and its associated complexity. The presented analysis does not require the complicated methods such as the principal component analysis and the model order reduction but it is as simple as observing the bode plot of the power stage of the converter. The entire simulation is carried out in Pspice.