USB-C Power Delivery (PD)

[B1ng]

Hello Fine Forum Folks.

I am looking for some information and experiences on using USB-C Power Delivery, or PD, in conjunction with newer mobile device and Laptops.

The standards and Internet Searches only bring more confusion.

The reason to ask is this; I have, as I suspect others do, a multitude of Laptops, Phones and Tablets with a variety of USB-C chargers and cables. I am finding that only certain combinations of cables and chargers will work between devices. This is especially true when a device requires more power, such as a Laptop. All pieces in the chain (Charger, Cable, Laptop) support the same 'standard' of power.

Is there somewhere that makes sense of all this, or is the multiple variants of PD standards really such a mess?

 

[Jupiter]

There are indeed multiple variations of the USB-C protocol, each with differences in throughput and power delivery capability. Instead of posting it all here, I'd recommend watching a video on the topic, or reading through an article.

 

[no_1_dave]

My understanding is that as long as it says PD (power delivery) it'll work with PD compatible devices.

You do get different watts though, but they're backwards compatible.
Most phones only need 20-35w, although some newer ones can use 100w. Laptops tend to use 65-120w

You can use a 35w charger to charge the 120w laptop but it will just charge slower
You can also use a 120w plug to charge a 35w phone, it will just max out at 35w because that's all the phone can use

To be future proof, just get the highest watt plug and cable and it will work with everything that supports power delivery. That's how I've been doing it the last few years and it's always been fine

 

[BUDFORCE]

There are many charging protocols.

But mainly QC or PD.

QC increases the voltage for more power (watts) by increasing the voltage not amps.

Advantage is you can still use thinner cables, as increasing voltage doesn't increase resistance (heat).

PD just puts more amps down and the same 5v, but thicker cables needed.

I think it has actually come on since then as well, but that used to be the basic difference.

Some are compatible with both, and that goes both ways some phones will charge with a PD charger and or QC and visa versa, some will not, this is fast charge I hasten to add.

If they are not compatible they'll revert to whatever it is, USB2 basic standard, so will still work but may charge very slowly.

 

[KompuKare]

@BUDFORCE not quite.
Like anything trying to put in more watts through cables, PD is also higher voltage.

No different to QC, POE etc. as all try to push more voltage.

The Wikipedia is a good start on this:
https://en.wikipedia.org/wiki/USB-C (tells you that not all USB-C implement PD or any alternative modes)

USB hardware - Wikipedia

en.wikipedia.org

So upto 48V (same as PoE I think) but also high enough amps.

Qualcomm's QC has even more variants:

Quick Charge - Wikipedia

en.wikipedia.org

Now whether all cable can actually handle 5A @ 48V? Probably not. And for somethings you may not want a 5A cable as they will be thick. Charging a phone with a 3.7V @ 5Ah ~ 18W or so battery at 100W always sounds like trouble. Yes, 12 mins for a full charge but won't the battery get hot, or at least wear out even faster. For ultra-fast charging, a removable and swappable battery is the way to go - pity that phone manufacturers in their quest for built-in obsolescences have almost totally stopped offering those!

 

[B1ng]

Thanks for the responses folks!

After a little more digging (and picking up a cheap 45w PD unit), things are still no clearer.

I'm not sure at this point if my current daily laptop is just picky, or if some of the newer chargers I have (65w and 100w PD) can't negotiate down for some reason. Different cables, all 'rated' up to 100w, behave subtly differently. Some refuse outright to charge, some will charge slowly, some only charge when the Laptop is in standby. The bargain bin 45w charger just works, with all cables I have.

Steam deck, PD in portable battery pack work fine in all cases. Going to write it off as another of the universe's great mysteries.