ZHCSQ75C June 2022 – March 2023 UCC28C50-Q1 , UCC28C51-Q1 , UCC28C52-Q1 , UCC28C53-Q1 , UCC28C54-Q1 , UCC28C55-Q1 , UCC28C56H-Q1 , UCC28C56L-Q1 , UCC28C57H-Q1 , UCC28C57L-Q1 , UCC28C58-Q1 , UCC28C59-Q1
PRODUCTION DATA
To start, we need to estimate the forward voltage (VF) of the output Schottky diode and the on-time of the MOSFET (tON_EST)
Next, estimate the transformer primary-to-secondary turns ratio
Calculate the reverse withstand voltage of output rectifier diode during tON_EST
Calculate the (expected) drain-to-source voltage of the MOSFET during the off time
The switching MOSFET and output rectifier generally experience voltage ringing due to transformer leakage and parasitic capacitance. Based on VSEC_REV, a 200V-rated Schottky diode is chosen, so the secondary RC snubber can damp the voltage spike and ringing with reduced snubber power loss. Based on VDS_OFF, a 1.7kV-rated SiC MOSFET is chosen, so a higher breakdown voltage of the primary TVS diode clamping circuit can clamp the switching voltage stress caused by the transformer leakage with reduced clamping power loss. If VDS_OFF is too high, the turns ratio can be reduced by decreasing DVIN_MIN, but VSEC_REV will increase. Deciding which component voltage is more critical and iterate again if necessary.