A Digital Real-Time Computation Algorithm Utilizing Time-Domain Analytic Model for Bidirectional CLLC Synchronous Rectifier in 6.6-kW 300-kHz SiC Portable EV Chargers

It is extremely important to use synchronous rectifier (SR) as the diode forward voltage of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small>s may be up to six times higher than Si <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small>s, which causes much higher conduction loss. Conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> SR typically uses detection circuits or builds complex models, but they are susceptible to high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> generated from SiC devices, or have difficulty in implementing SR online due to the complex numerical calculation. A digital real-time computation SR algorithm is proposed for bidirectional SiC <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> converter. Analytic models in the time domain are constructed to calculate the SR conduction time online. It not only achieves low conduction loss by optimizing the on-time of SR MOSFETs, but also provides high immunity to the high switching frequency noise. A prototype of 300-kHz 6.6-kW SiC bidirectional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> charger was built to verify the proposed control. With the proposed SR, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> efficiencies are up to 97.56% and 97.75% at full load in the forward and reverse modes, respectively. Moreover, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> full load efficiencies improves 0.42% and 0.35% over the conventional SR control in the forward and reverse modes. The power density of proposed charger increment is also up to 20% over Wolfspeed charger.