Fast transient response of series resonant converter using an average large signal model

Resonant converters have gained popularity for a variety of applications due to their ability to provide soft switching conditions and high power density. Controlling these converters is complex because of their non-linear behavior and high frequency resonant tank. Controllers are often designed by using small-signal models, which are limited to operating around a quiescent point. However, the small-signal model cannot predict the large-signal behavior during start up and load transients, resulting in undesirable transient behavior. This paper presents an average large-signal model of a Series Resonant Converter (SCR) to provide predictable large transient response. This novel model can be used to control the converter during transient mode using trajectory or geometrical control strategies, leading to outstanding and predictable responses. The theoretical model and transient behavior are validated with simulation and experimental results.