The STTH10R04D is a 10 A, 400 V fast-recovery epitaxial diode from STMicroelectronics, housed in a through-hole TO-220AC package. Its 40 ns reverse recovery time (trr) places it in the ultrafast class for a 400 V part, making it suited for continuous-conduction-mode PFC boost stages, output rectification in flyback converters, and snubber clamping where reverse-recovery charge drives switching loss and EMI. The 1.7 V forward drop at 10 A is the conduction-loss figure to budget for at full load.
STMicroelectronics lists the STTH10R04D as Obsolete. If the design is still in development, an alternative in the STTH10 family with the same TO-220AC footprint and similar 40 ns trr should be evaluated for new production.
10 A continuous, 400 V blocking — the application envelope
Rated for 10 A average rectified current and 400 V DC reverse voltage, this diode fits power stages up to roughly 1 kW in a single-switch PFC or a 300–400 W flyback. The TO-220AC tab is electrically connected to the cathode — account for that in the heatsink layout and isolation scheme.