Time-shift Control of LLC Resonant Converters

This paper describes a new control technique for resonant converters that outperforms the direct frequency control (DFC) method implemented in all today’s commercially available control ICs. When applied to LLC resonant converters, the resulting dynamic behavior is that of a low-Q second-order system or that of a first-order system, depending on the operating conditions. Thus closing the control loop to meet stability and dynamic performance specifications becomes considerably easier. Due to its complexity, the mathematical description is limited; the approach is essentially empirical with an extensive use of simulations.