600 V, 8 A HEXFRED — hard-switching PFC and inverter diode
The VS-HFA08SD60STR-M3 is a Vishay HEXFRED ultrafast recovery diode rated for 600 V DC reverse and 8 A average rectified current in a D-PAK (TO-252AA) surface-mount package. Its 55 ns reverse recovery time (trr) places it in the fast-recovery class for hard-switching power stages — PFC boost, output rectification in flyback converters, and motor-drive snubber circuits where recovery charge directly impacts switching loss and EMI.
55 ns trr — what it buys in a switching stage
The 55 ns trr is the time from zero current to full reverse blocking after forward conduction. In a continuous-conduction-mode PFC stage switching at 100 kHz, a 55 ns recovery cuts the diode turn-off loss by roughly 60 % compared to a 200 ns standard-recovery part at the same junction temperature. The HEXFRED structure achieves this without the snap-off characteristic of some ultrafast diodes — the soft-recovery profile reduces ringing and keeps the EMI filter from growing. Forward voltage is 1.7 V maximum at 8 A and 25 °C junction. That 1.7 V at 8 A gives a 13.6 W conduction loss at rated current — the designer sizes the copper pad on the D-PAK tab to keep junction temperature below the 150 °C absolute maximum. The 5 µA reverse leakage at 600 V is a room-temperature figure; leakage doubles roughly every 10 °C above 25 °C, so at 125 °C junction the leakage contribution to standby loss needs to be included in the thermal model.