Can I make a parallel USB circuit to power a device from my PC?

Question

Hey so I'm making a Virtual reality head mounted display and the LCD driver board says it needs 2A. I bought the right power source but the problem is it has to be plugged into a wall. For convenience I'd like to be able to plug the HMD into my PC when I use it because it will already be plugged in there for a video signal. While picking things up from radio shack today I saw they had both USB adapters and the plug I need to power the LCD driver board which made me wonder if I could make my own power cable that plugged into my PC but I need some help and have a few questions.

1. Is my PC capable of supplying 2A to my display? I just built my computer and it has a nice power supply but I've heard USB ports only deliver 1A or so. Is cheaping out on the amps a big problem? Would there be any way to create a parallel circuit that drew amps from 2 USB ports to power the display?

This is the display I bought - http://www.amazon.com/Tontec%C2%AE-Raspberry-Display-AT070TN90-Controller/dp/B00G60FJNG/ref=sr_1_5?ie=UTF8&qid=143328730… - Mine does have a higher resolution though.

2. If step one is possible what kind of wire would I need for this cable between the USB port(s)?

Thank you for any help!

dougw · Accepted Answer

Using multiple ports seems to be a valid way to increase current - as long as the current from each port is kept within its limit. This requires a method of ensuring the current is evenly shared between ports.

I have a commercial CD drive that uses 2 USB ports to get enough current - so the method is used.

dougw · Answer

USB 2 is only specified to supply 0.5 A at 5 Volts (2.5 Watts)

USB 3 can supply 0.9 A. (4.5 Watts)

Your device is demanding 2 A at 12 Volts (24 Watts) so USB is not close to meeting this requirement.

That being said your device may mot actually need 2A, that is just what they recommend as a power supply capability.

For example, the backlight on your display requires a maximum of 0.2 A and the rest of the display probably requires even less current.

The display will likely run from much less than 12 Volts, requiring even less power, (some of these displays will run fine down to around 9 Volts) but you would need to test it with a variable power supply to determine exactly what voltage and current are actually needed.

Even with all of these optimizations, it is unlikely the display will work well with just 2.5 Watts.

If you do want to try your own cable, try to keep the wire at least 22 gage or heavier to minimize power loss in the wire.

There are lots of lithium batteries available with 12 Volt output - maybe you could embed one of them behind the display panel...

Former Member · Answer

The display is supposed to run off of 5 to 12 volts so that shouldn't be an issue but I guess I'll have to try the display on different settings to see if 0.9A is enough (I do have USB 3.0).

What if I used two ports for more Amps though? It seems very unconventional but if it's safe I think I'll try it.

The left circuit is kind of what I'm talking about.

Can I make a parallel USB circuit to power a device from my PC?

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