0
\$\begingroup\$

I'm thinking about replacing input fuses for switch-mode and linear power supplies by PPTCs.

PPTCs are more desirable because it's ability to recover itself after being tripped by overcurrent.

There are some high voltages (up to 250VAC) PPTCs out there: Mouser listing for high voltage PPTCs.

Can I do that? Are there any shortcomings in doing that?

\$\endgroup\$
  • \$\begingroup\$ Not always. Sometimes a positive disconnection until repair is a good way to prevent fires... \$\endgroup\$ – Brian Drummond Jan 8 '16 at 14:09
1
\$\begingroup\$

The fuse is an integral part of a switched mode power supply in an installation. It's there to protect the wiring in the building's walls from melting and causing a fire should the SMPS develop a short circuit fault.

Fuses have to meet a high degree of reliability when they go open circuit and they can deal with voltages present on the AC line that a polyfuse won't i.e. a fuse won't bat an eyelid should a spike of 600V come along. A polyfuse might melt shut and therefore offer no further protection.

I'm sure there's a possibility that someone has made a range of polyfuses that work as reliably as a standard fuse so keep looking - none of those listed by mouser appear to fit the criteria required of a conventional fuse.

| improve this answer | |
\$\endgroup\$
1
\$\begingroup\$

A good SMPS itslef has a current limiter when the output is overoalded. The main fuse is mounted to prevent fire when SMPS fails, so when SPMS goes bad the fuse will blow and you can throw everything into trash. In normal situation the fuse will never blow, so you don't need the recover feature.

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.