Sequential cycle stealing — A novel control method dedicated for resonant converters

The most popular control method for resonant converters, the frequency modulation control, has low efficiency at loads lower than 40%. The proposed new method called Sequential Cycle Stealing (SCS), based on patented solution (PCT/EP2012/064379), improves efficiency by introducing selective stealing of converter switching cycles, while ensuring ZVS switching. The paper presents a preliminary implementation of the SCS controller with a brief description of its operation. The SCS controller operation is then verified in a LCLC resonant converter. Performance measurements, such as switching conditions, load step response, efficiency and conducted EMI are included in the paper. Finally, some improvements for the SCS controller are suggested in order to remedy some disadvantages of current implementation.