75 ns reverse recovery — what it buys the switching stage
The STTH112RL is a 1200 V, 1 A fast-recovery rectifier from STMicroelectronics, built with planar technology to deliver a 75 ns typical reverse recovery time. That trr figure puts it squarely in the continuous-current PFC boost diode class — fast enough to minimise turn-off losses in a 50–100 kHz hard-switched converter without the snap-off characteristic of an ultrafast diode.
1200 V blocking — derating headroom for 400 VDC rails
With a 1200 V DC reverse voltage rating and a 1.9 V forward drop at 1 A, this diode is sized for the boost stage of a single-phase PFC front end where the bulk rail sits at 400 VDC. The 1200 V rating gives a 3× derating margin against the nominal rail, which covers the ringing overshoot from the boost inductor and the MOSFET drain node during turn-off transients.
DO-41 axial — mounting and thermal note
The DO-204AL (DO-41) axial-lead package is a through-hole form factor that has been a workhorse for PFC boost diodes and output rectifiers in open-frame power supplies for decades. The junction temperature ceiling is 175 °C, so the thermal design is limited by the lead-to-ambient path — a 0.5-inch lead length to the PCB copper plane is the practical heatsink. The tape-and-reel variant (STTH112RL) is the production-friendly option for auto-insertion; the cut-tape option suits prototype or low-volume builds.