A Generalized Low-cost Solution for Resonant Frequency Tracking in LLC Converters

This paper presents a generalized low-cost analog controller for performing automatic resonant frequency tracking (ARFT) both in parallel and series LLC resonant converters (RCs). The key features of both these RC topologies are highlighted. Operating principle of the phase-relationship-based ARFT scheme is explained. For realizing ARFT in both the RCs, the proposed control circuit is designed with appropriate measures to enable easy reconfiguration. Selection criteria for the critical analog electronic components and associated passive elements are detailed. Experimental evaluation of steady-state and transient performance of the ARFT controller is performed.