Comparative transient response analysis of LLC resonant converter controlled by adaptive PID and fuzzy logic controllers

If properly controlled, LLC resonant converters can achieve zero voltage switching (ZVS) over the entire operating range, thus minimizing switching losses of the power MOSFETs and secondary diodes. For such a reason, this paper presents and compare a half bridge LLC resonant converter controlled by both an adaptive PID and a fuzzy logic controller (FLC). For obtaining the DC voltage transfer function, an analysis tool, the so called Fundamental Harmonic Approximation (FHA) method has been adopted. FHA is also used to determine circuit parameters and for predicting the transient response of the converter during sudden changes of input and load, which is then verified through simulations and laboratory measurements.