Electrical – Choosing an SMD Resettable fuse for a 2.5 Ampere USB charger port

5vfusessurface-mountusb hub

So I have googled for more than an hour, trying to find the specific answer for this, and maybe Im searching all wrong, but here comes my question.

I have a USB-hub combined with one fast charging port, with ONLY power, and no data. The other day the fuse from the DC transformer (transfomer is at 5 volt, 3.5Amps) and the port failed after I connected an apperently faulty powerbank. The fuse is located right next to the USB port in the hub.

All the other, data-USB ports work just fine, even with only power from the DC transformer, but the 2.5 Amp charging port is dead.

The fuse on the board is marked with "J". But this gives me results of a 32 volt 1.25 Amp fuse… Is this the one I should go with?

I dont really get how the voltage and amperage of the SMD fuses coincides…

I would be so happy if I could get some help in findig a suitable small fuse for the job.

Best regards, Fredrik

EDIT

I have a resettable PTC, 6 volts with a tripping current of 3.5A and a holding current of 2A (it seems on the documentation Ive found) on another board that I dont use, marked with K. Is this a good alternative?

Best Answer

I would suggest a thermal fuse. Powerbanks need to have a power source capable of handling its inrush starting current.

To avoid thermal problems with the supply you can choose a tiny SMT thermal fuse.

I might choose a 2A thermal resettable fuse. This means the MUST hold current = 2A MIN. and the MUST trip = 3.5A MAX. but it may trip at any current between 2A & 3.5A or lower if enclosed and higher if soldered to a heatsink. The polyfuse runs from 85'C to 120'C during protection mode.

https://www.digikey.com/product-detail/en/bel-fuse-inc/0ZCG0200FF2C/507-1777-1-ND/4156280

They are cheap, (compared to shipping cost) so get a bunch in different ranges.

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