Analysis and design of LLC resonant converter including parasitic components

Abstract

Nowadays, the trend of power supply market is more inclined to high switching frequency, high efficiency and high power density. To meet this trend, Resonant Power Supply holds more attraction, because it can be operated in high switching frequency with high efficiency. There are many Resonant Power Supplies such as Series-Resonant Converter, Parallel-Resonant Converter and Series-Parallel Resonant Converter. Among them, LLC Resonant Converter has a lot of advantages over the conventional Series-Resonant Converter and Parallel-Resonant Converter considering relatively narrow switching frequency variation over wide input and load variation, Zero-Voltage-Switching (ZVS) for entire load range. Therefore, the LLC Resonant Converter has been widely used and discussed. However, the conventional analysis of LLC Resonant Converter with Fundamental Harmonic Approximation can not explain the practical operation of LLC Resonant Converter. To overcome this limitation, in this thesis, analysis and design of the LLC Resonant Converter including parasitic components which are affecting converter operation, such as the leakage inductance at the transformer secondary side, the parasitic capacitance of transformer, and junction capacitance of rectifier diode, are proposed using a traditional analysis based on Fundamental Harmonic Approximation. The effect of each parasitic component is analyzed with simulation results and the design guideline standing on this analysis will be described. Moreover, the experimental results of prototype designing on the basis of the analysis are shown to demonstrate the proposed analysis and design guideline.