Small signal modeling of a series resonant LLC converter under PWM condition

This paper presents small signal modeling of a series resonant LLC converter operating under PWM conditions. Unlike the traditional LLC converters where pulse-frequency-modulation (PFM) is adopted, the LLC converter dealt in this paper aims to work both in PFM and pulse-width-modulation (PWM) modes to cover wide voltage range. The modeling equations of the LLC converter are derived, and the small signal models are obtained by adopting extended describing functions (EDFs). The modeling procedure is explained in detail. The derived model is compared with the ac sweep simulation results using the simulation software MATLAB. The simulation results confirm that the derived small signal model is accurate and effective to describe the small signal behavior of the LLC converter operating under the PWM condition. The experimental results will be added in the final paper.