I've got a laptop which charges through USB Power Delivery. The charger supports the following profiles:
- 5V x 3A
- 9V x 3A
- 12V x 3A
- 15V x 3A
- 20V x 3.25A
I know USB PD devices and chargers enumerate and negotiate the profile they will use together. I suspect my laptop to use the last, 65W profile, although I cannot guarantee it.
My question is: what happens when there's no exact match between the profile(s) the laptop expects and the ones the charger proposes? I am asking because I need to buy a second charger, but most of the ones I find only provide 60W (20V x 3A, not 3.25A). What would be the result of the PD negotiation if I plugged one of those chargers to my laptop? If it would work (which I suspect), why? Do the charger and device negotiate only based on voltage? If not, is there any limit of amp difference for a profile to be accepted?
In conclusion, would it work, and why? :-)