I do know it has been some time since this query has been requested initially however I am nonetheless seeing this query come up, and it has been my trying to find a solution to a query like this which introduced me right here.
USB Y-cables violate the USB specs and so solely work to supply extra energy to units that additionally violated the USB specs. It ought to solely be a shock to people who know little about how USB works when or if these USB Y-cables fail to supply extra energy to an connected machine than when related to a number with out the Y-cable. There are methods to make a form of USB Y-cable to supply extra energy to a tool when connected to a USB host that doesn’t present enough energy, and achieve this with out violating the USB specs. Answering that although is out of scope for this query since that applies to telephones and tablets that shouldn’t have Lightning ports.
I am going to see many complaints on how Apple does issues which can be “non-standard” however from studying the USB specs Apple really complies with the USB specs very effectively. Their concept on how their USB-An influence bricks handshakes with their iDevices may not be the identical manner different producers do their handshaking however it doesn’t seem to violate the USB specs. The unique submit mentions getting 900 mA from a USB 3.x port and 500 mA from a USB 2.0 port however these will not be maximums, these are minimums. A number laptop should provide not less than 900 mA from a USB 3.x port and 500 mA from a USB 2.0 port to be thought of in compliance with the USB specs. USB ports on Apple computer systems will provide greater than this, and it seems varied computer systems from different producers will as effectively.
USB 2.0 and USB 3.x enable for units to barter for as much as 1.5 amps earlier than having to resort to USB-PD or USB-BC to barter for extra. As finest I can inform Apple computer systems and iDevices use USB-PD to barter for as much as 12 watts, or 2.4 amps, of energy to the iDevice. With out help for USB-PD, or no matter it’s that Apple is utilizing, the speed of cost will likely be restricted to 2.5 watts (500 mA), 4.5 watts (900 mA), or 7.5 watts (1.5 A). The USB spec permits as much as 2.4 amps to peripherals related to hosts by USB-A and Apple computer systems will fortunately provide this. Or not less than these constructed after the USB-BC and USB 2.0 specs have been printed.
Should you want energy to your iDevice whereas related to some peripheral machine then the usage of a variety of Lightning dongles will enable this. Apple builds quite a lot of such dongles, as do producers that Apple partnered with. These dongles may have a Lightning port for as much as 12 watts of energy and a port for the peripheral. Examples for such ports embody HDMI, USB 3.x, Ethernet, and 1/8″ audio for headphones and headsets.
Connecting an Apple iDevice with a Lightning port to a pc that doesn’t present 12 watts does current an issue if the customers desires each knowledge switch and 12 watts to the iDevice. So far as I can inform there isn’t a Lightning dongle that may cut up out the facility and knowledge so that somebody can plug in a 12 watt energy brick to energy an iDevice whereas additionally it is nonetheless in a position to keep a USB connection to a pc.
Generally the issue is not that the pc is incapable of offering the facility Apple iDevices and their customers need, it is that the pc and iDevice will not be talking the identical language on negotiating the facility switch.
From what I’ve seen from my analysis thus far a USB dock or hub isn’t prone to allow a pc to supply extra energy to an Apple iDevice. The dock or hub is likely to be getting energy from someplace aside from the host laptop however it’s nonetheless the host laptop that’s managing the facility switch. The pc should nonetheless communicate the identical language because the iDevice to barter greater than 7.5 watts of energy. A USB hub or dock may be capable of present 2.4 amps to related units however an iDevice is not going to draw extra energy than it has been granted permission to attract.
What may enable a connection to a number laptop and supply 12 watts to an iDevice is a Thunderbolt dock. A USB-C to Lightning cable plugged right into a USB-C port on a Thunderbolt dock could enable knowledge switch to a Thunderbolt host whereas offering 12 watts of energy. Thunderbolt docks have an unbiased USB-PD controller, like that in a USB-PD energy brick, that doesn’t depend on the host to handle energy supply. The USB-C Thunderbolt ports on such docks will nonetheless help the USB 2.0 protocol that will likely be required to create the connection between the host and the iDevice.
I’ll emphasize that use of a Thunderbolt dock for getting 12 watts of energy whereas sustaining a knowledge connection to an Apple iPhone or iPad is concept. It is an informed guess however nonetheless a guess. I have never examined this concept and I do not (but) have the {hardware} to check this concept. I wrote this prolonged reply principally to make clear what I am seeing as misinterpretations of the USB specs. Whereas that is an older query it’s nonetheless related at this time and variations on this nonetheless come up.
