USB Type C to USB 3 adapters

Type-C is a connector and USB3.1 is a signaling standard. Type-C

*usually* uses USB3.1 signaling but it's perfectly valid to use other USB signaling and a type-C connector.

As far as charging goes, the resistor just fakes the host's charger into a higher current limit than the device will claim for itself. It won't charge it any faster. It may allow an old device that doesn't know the secret handshake to charge faster (or at all) but it's not magic. Of course telling a slow charger that it has a "fast charge" device on it will do exactly nothing.

Thanks.

Apropos, what's the difference between USB 3.0 and USB 3.1 standards?

10Gbps vs. 5Gbps, mostly. IIRC, USB 3.0 was a fill-in, until 3.1 (the original goal) worked.

OK, the speed difference I understand. What I was wondering is how they accomplishing it. Different signaling method alone, and whether it also takes different pin-outs and cabling to achive the higher speed?

Just hardware (silicon), AIUI. The original goal was unattainable, so got pushed off to 3.1. Same wires, same connectors, different chips (though backward compatible) at each end.

I see. Thanks.

with the cable you can get a fast charge from a usb port not designed for a fast charge, this will probably be convenient, but has the potential to do danage to the USB port and the supporting wiring etc.

small chargers are usually based around a flyback switcher and thus have an inherent power limit. try to take 3A from a 0.5A charger and the output voltage will drop until your device thinks better and comes to some sort of compromise.

try to take 3A from a typical desktop PC USB 2 port, the 100W (or larger) power-supply in there won't even break a sweat. but the wiring between the power-supply and the socket will be under higher stress than it was designed for, it'll prpbably work, it might make "hot plastic smell" or even smoke.

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I thought USB was limited to 500 mA? No desktop PC I've seen will output much over 500 mA.

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Rick C

it depends on the version, I think usb3 is 900mA, if it support dedicated charging port something like 2A

Yes, Jasen specifically mentioned USB 2. This cable melting issue is exactly why they included current limiting in the spec.

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Rick C

I was not thinking charging from PC but from wall or car cigarette chargers. Who charges a phone from PC anyway?

No, USB can deliver 2A and there are many devices that charge at 2A. They may or may not charge from a PC port (or .5A charger) at all. Tablets, for example, really do need 2A and if they can't negotiate up to it, they'll not charge at all.

There is better information here in the "Power related specifications" section here:

I've done it (forgotten chargers when on a business trip). I doubt it'll work with my current phone.

I was responding to Jasen's comment, "try to take 3A from a typical desktop PC USB 2 port, the 100W (or larger) power-supply in there won't even break a sweat. but the wiring between..."

The purpose of the various resistors is to indicate the charging capability. No device is going to draw more current than it needs and a supply should always be built to only provide a safe current for its design. That said... I bought a dollar store cigarette lighter charger one day when I was without mine. I ended up connecting an inline meter which showed the voltage was good until the current draw got to about 75 mA at which point is dropped. Clearly worth the price paid, just!

I had a cell phone charger that I used to power a Raspberry Pi. It worked ok for some time until one day it gave up the ghost. It would seem to charge a cell phone however, but the phone wouldn't actually be charging. When I connected a voltmeter to it (this predated my possession of the inline I/V meter) it was only putting out about 3.5 volts, enough to make the phone think it was being charged, but not actually enough to charge it. lol I think that was the one I took apart and the only active device was a transistor.

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Rick C

I know it can be done, but then one has to put up with its limitation.

As I mentioned in another post, some devices will refuse to charge on a "slow" charger. This is common with smart phones and tablets.

I do it when I don't feel like dragging out a proper charger. My laptop bag has a small pocket I keep USB cables in so there is always one in easy reach. I just have to remember a phone is tethered when I move the laptop.

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Rick C