wart overvoltage protection FAQ

søndag den 2. oktober 2022 kl. 20.05.14 UTC+2 skrev John Larkin:

it's LCSC not some dodgy ebay shop

Coincidentally, I recently ordered a couple of hundred of those on spec, for like $66.

They are a bit suspicious in that the 100-piece price is considerably lower than TI's, but we'll see.

Cheers

Phil Hobbs

Reverse protection is also important to protect against an input short, which can blow up stuff by forcing currents from output to input.

That's one of the three ways to blow up a 317, and one of the two to blow up an 78xx regulator. (Input overvoltage is the other main one, and for a 317, discharging a big ADJ pin bypass backwards.

Cheers

Phil Hobbs

Would that be a 'sidactor'? This variant works for AC limiting, should be OK with a polyfuse in series about not hurting a 24 supply

It has to be depowered completely to reset it, so the polyfuse will stay warm until unplugged. The breakover is built-in, rather coarse, so one hopes your nominal 12V box is OK with 15...

Get f***ed.

....... Phil

A soft gate drive, like just a zener, can make an SCR chip fire locally, near the gate wirebond, and fry that region before conduction spreads laterally. It's like 2nd breakdown failure in transistors.

There are specific crowbar controller chips to make a hard, fast gate drive.

Look it up.

I once mightily abused an LM317 adjust pin to see if I could break it. No feasible abuse did.

Cheers

Phil Hobbs