Accurate Extraction of Body-Diode-Conduction for Synchronous Rectification of CLLC Resonant Converters in High Voltage Application

Mainstream adaptive drain-source voltage-sensingbased synchronous rectification (ADVS-SR) has rarely been used for CLLC convertersin higher output-voltage applications (HOVA) due to the issue of sensing accuracy and high dv/dt. This letter proposes a novel body-diode-conduction (BDC) extraction circuit consisting of an accurate DVS circuit and a customized valleyconduction-detection (VCD) circuit for ADVS-SR in HOVA. The compensation diodes packaged together with blocking diodes can eliminate the sensing error accurately with a single PNP transistor instead of complex current mirror. Absorption diodes and series combination of blocking diode effectively solve the high dv/dt issue. The traditional external negative threshold voltage for the voltage comparison in VCD circuit can be omitted. Thus, the proposed BDC extraction circuit is accurate, high-dv/dt-immune and easyto-implement, and the performance of which have been validated from the experimental results in a 1kW-500V CLLC prototype.