1
\$\begingroup\$

Today I saw a USB Wall charger for sale and it claimed it can output 3 amps at 5V and it only had one USB port. USB specs say a dedicated charging port is rated for 1.8A.

So how is this charger USB port able to handle 3A? I have looked online and I can't find a USB port that is rated to handle 3A. Best i could find is a USB port that has gold plated on the USB pins inside the port.

I have tried to draw 3A from a normal USB 2.0 and the USB connector got really hot. How can a USB charger with USB-A connector handle 3 Ampere?

\$\endgroup\$
  • \$\begingroup\$ Is it possibly Quick Charge-compatible? That would push out of the USB specs once both ends agree. \$\endgroup\$ – Aaron D. Marasco Mar 6 '17 at 22:24
1
\$\begingroup\$

Technically speaking, the USB PD (power delivery) specifications do define special "USB 3.1 PD Connectors", including Type-A style. This was before the Type-C connector was introduced. The connectors have additional contacts to detect cable insertions. The connectors are supposed to carry up to 5A with contact overheat of 30 deg.C over ambient (25 deg.C). Same goes for the 3A-rated connectors, see Section 3.6.5.1 of USB Power Delivery specifications. So the 55 deg.C on the connector seems to be within specifications, which should be painful to the touch.

However, I myself have never seen these connectors, and I have a suspicion that no one manufacturers them in reality. All regular USB Type-A connectors have typical contact rating of 1.5A, and only few (typically of odd up-right shape type mount) have rating of 2.5A. Of course, a wall charger can advertize whatever they wish, or you might be a lucky one to see the unique "PD connector".

\$\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.