Modeling and Digital Implementing for Charge Control of LLC Resonant Converter with Duty Cycle Balance

This paper presents a digital implementation of charge control for LLC resonant converter with duty cycle balance. The control mode is analyzed, and the small-signal model is established and compared with SIMPLIS simulation results. The comparison indicates that within 1/10 of the switching frequency, the two results are closely aligned. Using the comparator and timer in the digital controller, charge control for the LLC converter is implemented with balanced duty cycle. The prototype of a 240W half-bridge LLC resonant converter is constructed, and the compensator is designed to realize a stable close-loop charge control. The experimental results show that the digital control method has good dynamic response while ensuring the duty cycle balance.