Looking at the price for circuit breakers, I'd rather be sure it's necessary before getting one of these. Surely no one would make 20A (and higher) glass fuses if they couldn't be safely and efficiently used at around 20A?
Why do you bother finding a 20A fuse? Every switch mode power supply has a build in over current protection
(1) I didn't know that, but (2) is there a guarantee the over-current is close to 20A? How would the PSU know how much current is too much for my circuit?
PS. You have forgotten the series resistor to the gate of the MOSFET in your schematic.
Very good point, thank you. Will add that.
You cannot operate a 20 amp car fuse at 20 amps for very long before it blows, you will need at least a 30 amp fuse on a 20 amp circuit if not a 40 amp one. Take a look at car fused circuits they usually have a fuse that is twice the expected current in the circuit.
It's actually closer to 17A given the 400W output of my PSU. I can add a 30A fuse instead (max I have on hand), which is about twice the current. I was just thinking it should be close to the expected current for safety. For example, my control board which is supposed to supply a little under 11A to a heater has an 11A polyfuse. Perhaps those work differently though.
Stay away from the car type blade fuses, unless you get good quality ( Bosch, not OHL ones) fuses, and good quality fuse holders. The glass fuses are perfect, though you probably will find that you need a 25A fuse, if you are always sitting at 20A current. Your fuse should have a voltage drop of less than 1V across it at rated current.
Is there a good reason the glass ones are so much better? Some of those fuse clips for glass fuses don't look that much more reliable than the auto fuse holders. In fact, if you could suggest a good glass fuse holder I'd be really grateful, I spent something like an hour browsing ebay for different ones and have no clue which would be high quality.
Thanks for the link, I'll check it out.