A hybrid strategy with Simplified Optimal Trajectory Control for LLC resonant converters

In this paper, a Simplified Optimal Trajectory Control (SOTC) for the LLC resonant converters is proposed. During the steady state, linear compensator like PI or PID is used, controlling the switching frequency (f_s) to eliminate the steady error. However, during load transients, the Simplified Optimal Trajectory Control (SOTC) method takes over, controlling the pulse widths of the driving signals. Using the state-plane analysis, the pulse widths are estimated, letting the state variables track the optimum trajectory locus in the minimum period of time. Experimental results show that digital logic requirement is very small, but the performance improvement is significant.