Hardware Insights Forum

Vishay VF30100S
http://www.vishay.com/docs/88941/v30100s.pdf
I've been wondering why most half bridge units won't accept this rectifier as a replacement for ultra fast recovery diodes, but I've never tried replacing schottky rectifiers with these in a half bridge unit. Is it because they're Power MOSFET's that they won't work? Would these be okay to use? I like the low forward voltage drop

EDIT: Also, what is the purpose of having a ferrite bead on the outer legs of schottky rectifiers?

Simple: It's not a double diode (with common cathode) as you need. It's a single diode that just happens to be wired similarly. Result is that the whole transformer secondary is shorted out, and the unit will never, ever power on with that rectifier in place.

Thank you sir, for pointing that out. Noted. I guess I'll just replace the two MBR20100CT's with two STPS4045CW's. Should still see a good efficiency increase.

I assume two TO-247 15A bipolar transistors on the primary are capable of 400W? With an 8A bridge, 820µF bulk caps, 39 transformer, good heatsink?

Pentium wrote:I guess I'll just replace the two MBR20100CT's with two STPS4045CW's.

Well, you can try that, but you do realise what the 45 in STPS4045CW means, right? Yeah, it's the reverse voltage limit. Survival not guaranteed.

LongRunner wrote:

Pentium wrote:I guess I'll just replace the two MBR20100CT's with two STPS4045CW's.

Well, you can try that, but you do realise what the 45 in STPS4045CW means, right? Yeah, it's the reverse voltage limit. Survival not guaranteed.

Yeah, I realize that. I figured it was okay since the other schottky's on the secondary use 45 reverse voltage rectifiers, and I've seen 45's work before. I'll look in my scrap pile and see if I have any with 60 max reverse voltage

45V VRRM Rectifiers will work OK on the lower voltage rails, but 60 or higher is sometimes required for the 12V rail. It will usually work OK at first with a 45V part, but it will often kill it after 5-10 minutes of use.

Okay, good point. I found two STPS30H100CT's

Well, the piece of shit didn't accept the STPS30H100CT's so I just threw the MBR20100CT's back in. It actually has two rails. Thought it'd be nice to up the amperage but it should be okay as it is...