Design and implementation of half-bridge LLC resonant converter with integrated transformer for compact design

Higher power densities in SMPC circuits can be achieved by operating converter at high switching frequencies, which can reduce size of passive components. Operating at higher switching frequencies with hard switching leads to increase in switching losses. By using soft-switching methods, switching losses can be reduced. It is preferred to use Half-Bridge LLC resonant converter operating under Zero-Voltage switching (ZVS) for entire load range, ZVS is obtained by oscillations made by the LLC resonant tank. By designing resonant tank inductances using Integrated transformer makes converter more compact. Half-Bridge LLC resonant converter switches are driven by pulse frequency modulation (PFM) technique using external IC. This LLC resonant converter is designed to operate between 90kHzs to 55kHzs from no load to full load respectively. In this paper, equivalent circuit analysis of resonant tank with integrated transformer, design procedure, experimental results and waveforms are presented to validate design for 80W model.