A Simplified Time-domain Model Based Feedforward Control Strategy for LLC Resonant Converters with Wide Operation Range

This paper proposes an accurate simplified time-domain model based online feedforward control strategy covering all typical working conditions (i.e., PO, OPO, NP, NOP). By expanding inverse trigonometric functions from transcendental equations into polynomials and optimizing the order in which the variables are solved, the simplified equations can be solved quickly and iteratively while much more accurate than current advanced model. Meanwhile, a modified PI control strategy featuring desaturation capability is utilized, preventing integral saturation during transients while ensuring steady-state error compensation. Experiments are carried out to validate the proposed strategy. The results demonstrate that the settling time is 10x faster than the state-of-the-art methods and dramatically increases model accuracy, thus improving the dynamic performance of LLC converters.