My 5v circuit board draws more Amps than my 5v 2A USB charger can provide. I also I have a 12v 4.5A charger. Now I'm thinking of getting a USB hub with 12v barrel Jack port.

My question is this: will the 12v 4.5A charger connected to the USB hub provide all the power required to run the board at optimal levels?

  • \$\begingroup\$ You're asking whether enough power will be supplied, but nowhere do you say how much power is needed... \$\endgroup\$ – replete Jun 25 '18 at 6:39
  • \$\begingroup\$ @replete 4amps Max. \$\endgroup\$ – Allen Jakpa Jun 25 '18 at 6:46
  • \$\begingroup\$ Are you proposing using a USB cable to connect to your board? If so, that's way beyond specification. It's also impossible to say anything about the USB hub in question because you haven't given enough information about it. \$\endgroup\$ – replete Jun 25 '18 at 6:50
  • \$\begingroup\$ Yes. I'm proposing powering my board (still In prototype stage) from USB. The hub is more like a USB extension with an external power source since computers do not supply more than 1amp to USB ports. What I plan to do it power the USB hub from my 12v power adapter and then plug in my board to the hub. \$\endgroup\$ – Allen Jakpa Jun 25 '18 at 7:31
  • \$\begingroup\$ As the old joke goes, USB cables can carry 4A just fine, so long as you only need the current, and the cable, for a few seconds. 4A is grossly out of spec for a USB cable. You need another solution. \$\endgroup\$ – replete Jun 25 '18 at 7:34

If you plan to develop a BUS-POWERED device with 5V 4 A power requirement, and expect it to run from legacy USB ports (which are still something like 95% of all USB hosts) and using standard legacy cables, this would be a bad business proposition. First, most legacy (Type-A and uAB) ports have connectors with rating under 1.8 - 1.5 A. Then, most legacy cables are designed for 0.5 A ampacity. So your device won't fly.

If you are thinking if a regular hub can solve this problem, even if it is self powered with 12V-4.5A supply, it could accidentally have ganged power and supply more current, but the limitations are the same - connectors and old cables were not designed to carry 4 A load. So your device might work with this particular hub, but not with 90% of other hubs.

The 5V@4A power is, however, within basic specifications for the newer Type-C connector. Full-featured Type-C - Type-C cables must be able to carry up to 5A at 5V without delving into Power Delivery Protocol (elevated voltage allows to deliver more power). However, all 5-A cables must have an "electronic marker" (a special IC embedded into cable's overmold), and Type-C port controllers at both ends of Type-C link should refuse to supply any power if the marker is not found.

As one can imagine, all these special PD and marker protocols increase the cost of power links and ports, and substantially, and technically are quite beyond capabilities of a typical DIY person. So in this particular case you should abandon the idea to have your device to be bus powered, and resort to a wall AC-DC adapter with proper power rating (there are plenty of 5V4A wallwarts used for hubs). Or you need to re-design or re-think power specifications for your device using less power-hungry processors.


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