USB Power Delivery
lastmod 2020-09-22created 2020-09-223 edits
Buying guide
This refers to models that support USB-PD (Power Delivery) through the USB Type-C port on a laptop. A USB-PD charger usually allows stable, fast charging of the laptop, and since laptops are carried around often, the advantage is that a low battery can be charged away from home with a power bank or portable charger that meets the standard. For laptop charging, the USB-PD spec is usually at least 5V 2A or more, but it may differ by model, so check the model's specifications with the seller or manufacturer.
What is USB PD?
"USB PD" is short for "USB Power Delivery", a power supply standard for charging devices such as PCs and smartphones through a USB port. Its biggest feature, above all, is that by adopting the "Type-C" connector for the USB port it can deliver "up to 100 W". Compared to the conventional Type-A (the so-called "standard-size USB port") and micro USB ports, which could only handle about 5–10W, that is roughly 10–20 times the power.
This is only a simple calculation, but it means that with USB charging devices, depending on the device, charging can in theory be up to 20 times faster than conventional USB charging. That said, at present only a few devices such as the MacBook Pro (15-inch) support 100 W charging, so there are not many, but if USB PD adoption gains momentum in the future, such fast charging is likely to become possible in no time.
You might think, "I already have a USB cable with a Type-C connector, so I should be able to PD charge with it." But that is a bit hasty. Surely that cable has a Type-C connector, but isn't the other end a "USB Type A (standard size)" connector?
Up to 100W (watts) power delivery
With the arrival of the iPhone 8 and iPhone X, the term 'PD' started getting attention. It is short for "Power Delivery", one of the USB power standards, and currently the latest technology. To describe PD in a word, it is fast charging that can deliver up to 100W of power. In terms of smartphone charging speed, it feels like charging faster than "normal charging" is "quick charging", and charging even faster than "quick charging" is "fast charging".
I wrote up to 100W of power delivery, but that is only the maximum, and small devices such as smartphones do not draw that much. Measuring an iPhone X with the genuine 61 W adapter and cable, a quick check found that about 18W was the maximum.
- It might be one level higher (36W), but searching online I could not find any 36W.
PD revisions
During its development, PD evolved from "USB Power Delivery 1.0" → "USB Power Delivery 2.0" → "USB Power Delivery 3.0". These are called revisions, written as Revision 1.0, Revision 2.0, and Revision 3.0. Revision1.0 defined three levels of 5V / 12V / 20V, while Revision2.0 and Revision3.0 defined four levels of 5V / 9V / 15V / 20V. In other words, there are two voltage patterns even within PD.
You may wonder, so what? But remember it, because it matters when choosing a mobile battery. This applies when the smartphone and the mobile battery use different PD revisions: there may be a mismatch between 12V support and 9V or 15V support. I think protection features will bring it to an appropriate voltage, but it is best to avoid risky use where possible, so be careful. Almost nobody states the PD revision in their descriptions, so it is important to check the output and input voltages carefully.
Type-C is not PD
A long explanation is easy to get confused by, so just remember that 'Type-C' and 'PD' are not the same. It is fine to think of it as Type-C being the connector and PD being fast charging. Strictly speaking this is not accurate either, but I think it is better to remember it this way than to mix up various things.
How is it different from 'Quick Charge'?
Besides USB PD, another well-known fast charging standard is 'Quick Charge', and in short it is something completely different from 'USB PD'. Quick Charge is Qualcomm (US) extending the existing USB standard on its own to achieve fast charging, and the latest version reportedly delivers up to 20V output. However, to use it, the cable, the charger, and even the device must all support Quick Charge.
Here is another tricky point, though: the latest "Quick Charge 4 /4+" is actually compatible with USB PD. Simply put, a "Quick Charge 4/4+" charger can also use USB PD fast charging. Of course, this compatibility applies only to Quick Charge 4/4+, and earlier versions have no compatibility with USB PD at all. When Quick Charge and USB PD are mixed, normal USB charging still works but fast charging is not supported, so be careful.