A Novel Time Domain Analysis of the LLC-L Resonant Converter for the Use of the CLL and LLC Resonant Converter

The present work makes an effort to provide an accurate, approximation free time domain analysis of four elements LLC-L resonant converter for the precise modeling of the CLL and LLC resonant converters in high frequency applications. By this, the major contribution of this paper is to introduce the time domain modelling of the CLL resonant converter in the literature. The derived analytical expressions by modeling of LLC-L resonant tank is also useful for modeling of the series LC, parallel CL, series LCL topologies. Closed form solutions are being derived for converter's voltage gain, peak stress, tank RMS current, tank capacitor voltage, zero voltage switching (ZVS) angle etc. as a function of the load, frequency and other circuit parameters. The main feature of this novel time domain analysis has been accurately identifying the zero crossing points of various current flowing through the resonant tank. Analytically generated steady-state waveforms and design curves are verified and are an exact match with PSIM simulation studies. The other contribution of this paper by this way is to generate the accurate steady state waveforms for both LLC and CLL based on developed time domain mathematics. Performance curves are given, design issues are discussed and the resonant tank characteristics are demonstrated on an experimental setup of 320W power, 420V output voltage.