Apple Qi wireless charger USB C to A power issue - Page 1
Forum section: electronics / projects

author: gkmaia
author_rank: Frequent Contributor
timestamp: December 17, 2020, 05:31:50 am
content: I got an original brand new apple wireless power adapter that has a usb c connector.I connected it to my usb hub by using an A to C adapter and the power adapter does not work.The A to C adapter works on other devices.Then thought it could be an issue with the apple wireless charger, but no. If i connect it to my mac book usb c it charges ok. If I connect it to an apple usb C power adapter it works fine as well.Any idea why is that? is it another of those proprietary rubbish things from apple where you can only use apple stuff with apple stuff?Or there is a technical reason why the adapter does not enable power?

author: Someone
author_rank: Super Contributor
timestamp: December 17, 2020, 06:10:06 am
content: Hubs are hit and miss when it comes to power support, the charger wants to negotiate quite a bit of power:https://support.apple.com/en-au/HT211829That heavily massaged "support" document avoids explicitly mentioning it requires a USB PD source, but it may well refuse to negotiate with anything else.

author: ConKbot
author_rank: Super Contributor
timestamp: December 17, 2020, 06:23:03 am
content: Apple's website says it can delivery up to 15W, so USB-c is being used at a higher voltage than the normal 5V, or at least requires PD negotiation for 3A. A passive adapter cable may be limited to 1-2A,i forget what the standard is.Apple didn't care to include a lower power mode of operation to let you charge from a different power source. I'd expect something something yadda yadda consistent user experience as their justification.If it doesn't work with a 3rd party 15+w charger with the right voltage capacities, then that's blatant anti-consumer shenanigans. If it does work, then its just lazy anti consumer design, neglecting backwards compatibility. (make sure it can supply the right voltage, ive seen some 45W chargers that support 5,12,15, and 20V, so if the puck wants 9V@2A then one of those may not work. Thanks for the extra confusion, USB-IF)

author: gkmaia
author_rank: Frequent Contributor
timestamp: December 17, 2020, 07:13:27 am
content: Thanks, it makes sense now. The 9v pretty much killed it.

author: ConKbot
author_rank: Super Contributor
timestamp: December 17, 2020, 12:21:15 pm
content: Quote from: gkmaia on December 17, 2020, 07:13:27 amIm not sure what voltage it actually needs, the 9v was a hypothetical caveat ive noticed on some USB-C power supplies. Apples website gives no other information other than "gives 15w of power" and a list of compatible hardware. Same with the 20W USB-C power adapter they suggest to use with it.

author: Someone
author_rank: Super Contributor
timestamp: December 17, 2020, 08:51:13 pm
content: Quote from: ConKbot on December 17, 2020, 06:23:03 amExcept that support document does say it can work at 12W, so no, it doesn't require 9V. At a guess it will negotiate on 5V fine, but only using the recent PD standard which isn't on anything other than USB-C?

author: Someone
author_rank: Super Contributor
timestamp: December 17, 2020, 08:53:59 pm
content: Quote from: ConKbot on December 17, 2020, 12:21:15 pmSo even with the provided link to the manufacturers (admittedly wordy and not entirely obvious) information you dont bother to check.Quote from: Apple

author: ejeffrey
author_rank: Super Contributor
timestamp: December 17, 2020, 09:17:28 pm
content: USB type-CC can deliver up to 3A /15 W without PD, but only when both ends are USB C. A sense resistor in the upstream port indicates the current limit to the device which allows current negotiation independently of data negotiation. This mechanism doesn't work when the upstream port is type A as there are no pins for the sense resistor connection. A USB A-C cable is required to have internal resistors on the CC pin that indicate that the only power available is "legacy USB standard". This means that when attached to a standard data port such as a hub it can only draw 100 mA before enumeration and 500 mA (USB 2) or 900 mA (USB 3). When connected to a standard charger with shorted D+/D- pins it will usually draw no more than 1.5 A, although USB chargers vary widely. Technically I thinks USB BC standard allows combined data/charge ports that support data transfer and more power delivery but I don't think that was every widely used, and USB-PD for type-C connectors is kind of taking over from that. As such you will rarely be able to charge a device with a type-C connector by plugging it into a type-A hub, since the current will be limited to <1A.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 18, 2020, 02:12:01 am
content: Some A to C converters don't have the pullup resistor at all, which means they won't work on devices that expect such signaling. (Most "basic" USB-C peripherals like headsets don't care, hence why such adapters exist.)