Resolving practical control issues in an industrial scale 1.2 kW LLC converter in closed loop operation

Some sensitive industrial loads enforce strict criterion on output voltage regulation with no voltage overshoots under any load and limited start-up time. LLC converters, which sometimes are used for a wide range of input voltages under closed loop operation, have difficulty in meeting these targets with low-cost processors. However, such resonant converters remain a popular choice in industry due to its superior power density and low system cost. Hence, this paper delineates some modifications to general state trajectory control for LLC converters that can help meet the industrial load requirements without control complexity. Also, some modifications are proposed to generalized-burst-mode-control that positively affects the efficiency and regulation of the converter under industrial hold up time requirements. These control changes are validated in a wideband gap based high frequency high step-down LLC converter set-up operating at 1.2 kW.