constant 1A @ 5v to all ports

Thread Starter

falade47

Joined Jan 24, 2017
178
Building a buck converter of 3.7v to 5v for my usb hub. I have 5 ports in the hub. How can I be able to have a constant 5v @ 1A across each port?
 

Thread Starter

falade47

Joined Jan 24, 2017
178
Use a 5 ohm resistor as your load on each port. Or do you mean 5V, with a current limited at 1A?
yes, I meant 5v with a current limited @ 1A across each port. So if connect all devices to individual ports I should getting a constant charging current of 1A through each devices.

I thought of having a regulated 5v output and a constant current source of 5A then a 5ohms resistor before each port to get 1A at still 5v for every port. Will that work?
 

AlbertHall

Joined Jun 4, 2014
12,345
You need a 5V regulated supply capable of supplying 5A connected to each and every usb port.
That means that if only one port is used you could draw 5A from it

If you want to limit the current to a maximum of 1A from any single port then you could use five separate current limited regultaors, for instance 7805.
 

Dodgydave

Joined Jun 22, 2012
11,285
Building a buck converter of 3.7v to 5v for my usb hub. I have 5 ports in the hub. How can I be able to have a constant 5v @ 1A across each port?
Which circuit are you using,? there should be a Current limit pin on the chip, if so you need to set it to 1Amp.

Also your psu must be capable of giving out at least 5Amps.
 

Tonyr1084

Joined Sep 24, 2015
7,853
You'll need to build current mirrors for each port if you want all of them to deliver no more than 1 amp. And you (as already noted) need a supply capable of pushing 5 amps in the event you're using all five ports at once.

Thing with current is that it depends on what load it is dealing with. If you plug in something that draws half an amp, having 500 amps available doesn't change anything. The load is going to draw only what it will draw - as long as the supply is capable of sustaining that level of power. So if you want dedicated 1 amp and ONLY 1 amp available at each port then you need to build in current limiting circuitry.

But suppose you have only two devices plugged in at once. Suppose one draws 1 amp but the other device wants or needs 2 amps. Your limited design (limited to 1 amp at each outlet) can't handle that. Now, if you're thinking about plugging in 5 phones at the same time to this USB Hub then knowing how much current each phone will draw is crucial. Your supply needs to be able to carry the full load of all those phones. However, in the case of phone charging, if you use an under powered supply it will simply take longer for the phone to charge.
 
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