Что мне нужно для питания устройства через USB?

If your USB device came with a Y cable, it probably means it is a USB 2.0 device that requires more current than the 500 mA limit of a single USB 2.0 connection. The Y cable allows it to use additional current from a second USB 2.0 connection. The voltage is always 5V for each connection (that remains constant, only the current is additive).

With a non-powered hub, all of the hub's power is limited to the 500 mA of the USB 2.0 connection between the hub and your computer. All devices on the hub share that power, which is fine if they are all low-powered devices like a keyboard, mouse, or data card reader.

A powered hub uses an external power adapter to provide the power, so each USB connection on the hub can receive up to the 500 mA limit. This puts you back in the same situation as attaching the Y connectors to your computer, only you aren't giving up a second USB connection on your computer.

If you don't need a bunch of extra USB connections and would be buying the hub only to not lose a USB connection on your computer, there is another route. My own experience with USB hubs is that they have a ridiculously high failure rate, so I would consider this alternative just for that reason. You can buy a USB Y cable where the extra, power-only, connector is double-sided. It is a pass-through that includes a female connector that you can use for a low-powered device. This lets you use the second USB port for another device in addition to tapping off extra power.

Another possibility is that the device, itself, may have a power socket, which would allow you to power it from an external power adapter. In that case, you can use a normal USB cable to make the connection (the Y cable would not be needed).

A powered hub would up the AMPs.. I think it's the current(ampage) the amps, that can potentially get consumed/lost, rather than the voltage. Hence the powered hub. A USB3 port can output much more amps than a USB2 port.

USB 2.0 allows only 0.5A

USB 3.0 standard allows up to 5 Amps.

A USB powered hub would be as good as a Y cable, because both get their power from USB anyway.

A Mains powered hub (>0.5A !) would be of use if you're using a USB 2.0 port. And if you're using a USB3 port and you need more than 5A shared across the dedvices e.g. maybe you have loads of devices then you could use use a powered hub that gives more than 5A shared across the devices.

Voltage drops can perhaps occur if a cable is a very long distance. But a normal size cable, just the amps needs a boost.

Here are causes of voltage drop

http://epb.apogee.net/foe/frvc.asp

Note that it's not device consumption - devices consume(use up/deplete) current not voltage.

1. Material - Copper is a better conductor than aluminum and will have less voltage drop than aluminum for a given length and wire size.

2. Wire Size - Larger wire sizes (diameter) will have less voltage drop than smaller wire sizes (diameters) of the same length.

3. Wire Length - Shorter wires will have less voltage drop than longer wires for the same wire size (diameter).

4. Current Being Carried - Voltage drop increases on a wire with an increase in the current flowing through the wire.