A Time-Domain-Model-Based Digital Synchronous Rectification Algorithm for CLLC Resonant Converters Utilizing a Hybrid Modulation

For bidirectional
CLLC
resonant converters, synchronous rectification (SR) is a key technique that can reduce the conduction losses in rectifying side by replacing the diodes with the switches’ channel. However, existing methods suffer from either complex hardware, or incomplete and imprecise control effect. Aiming at solving these problems, this article proposes a digital sensorless SR algorithm based on the time-domain model under a hybrid modulation for
CLLC
converters. The proposed approach can precisely enable the SR drive action within almost the whole load range and without any additional hardware, e.g., antiparallel diode, SR IC, and high bandwidth sensor. Its implementation only needs to measure dc signals (e.g., the output current), rather than any high-frequency resonant signals. Additionally, the presented algorithm can be easily implemented on a digital controller. Finally, experiments have been performed on a prototype to verify the validity and applicability of the presented SR algorithm.