Electronics > Projects, Designs, and Technical Stuff
Overvoltage protection circuit w/ TVS diode and resettable fuse?
(1/3) > >>
thinkfat:
Hi,

I'm making a small adapter board for my Efratom LPRO-101 and I want to add some kind of over-voltage protection. The idea I came up with is to use a TVS diode in combination with a resettable fuse, like shown in the below schematic.

Does this make sense?
thm_w:
Yes, makes sense.
Can change to a unidirectional TVS (what is shown in the schematic is bidirectional), to protect against reverse voltages as well.
Also the diode is only capable of dissipating about 0.3W or so, so it might blow up before the SRF (fuse) does. What is the fuse spec?
thinkfat:
The fuse is an ECE SD200-8, it's rated at 2A hold and 3.5A trip current. But I realize that for reverse polarity protection the voltage rating isn't high enough. In that case, the fuse will have to withstand whatever voltage is applied in reverse - that's kind of impractical. But now looking at it, the TVS diode is also not suitably rated. I'll have to use something that can take more then 3.5A, I guess I'll use a LDP24A.

For reverse polarity protection I'll probably go with a suitably rated p-channel mosfet.
thinkfat:
Updated schematic. It doesn't feel quite right, though, combining the LDP with the Mosfet like that. When the LDP trips, the FET would still have to bear the load until the polyfuse trips as well. But if I exchange the ordering, the FET would be essentially useless.
nuclearcat:
Please take my opinion with truck size grain of salt, as i'm not experienced at all in this question :)

I think you might like to check this discussion, about protecting circuit with P-channel FET and zener:
https://electronics.stackexchange.com/questions/121670/zener-mosfet-overvoltage-protection

But it looks like polarity protection, and it should be connected different way.
I am not sure FET is anyhow useful in current way of connection, especially with transients, as mentioned in that link(if it is correct) - broken FET most likely will short out and silently become useless. Also internal diode might be be burned on overvoltage, even if you manage to switch it off and keep same way of connection.

I did simulation, and it seems this part of circuit does exactly nothing: https://easyeda.com/editor#mode=sim,id=522581dc59d447bba902f6b4457daf8b
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod