USB Power Delivery (USB PD) Explained

USB PD is why one USB-C charger can run a phone, a tablet and a laptop. The rest of this page covers how the agreement works, what the voltage and wattage tiers are, and what it means for the charger you buy.

How does USB PD work?

The charger and the device talk to each other before power flows. Wikipedia says PD-aware devices use a bidirectional data channel to request a certain level of electrical power from the source. The USB-IF describes the result in simple terms: USB PD provides more flexible power along with data over one cable, and devices can take only the power they need and get more when required.

Power direction is not fixed either. The USB-IF says the product that has power can supply it, which is why a phone can sometimes power an accessory and a laptop can charge a phone.

What power levels does USB PD offer?

Wikipedia describes two ranges. The Standard Power Range uses four fixed voltage levels, 5, 9, 15 and 20V. Revision 3.1 added an Extended Power Range with higher fixed voltages of 28, 36 and 48V, giving up to 240W at 48V and 5A. The wattage is the voltage multiplied by the current.

Range	Fixed voltages	Top figure	Cable requirement
Standard Power Range	5, 9, 15, 20V	100W before revision 3.1 (20V at 5A)	USB-IF: earlier 100W limit used cables rated at 5A
Extended Power Range	28V, 36V, 48V	140W, 180W and 240W	Wikipedia: electronically marked cables that support 5A

The USB-IF also describes an adjustable voltage mode in which the device can request voltages between 15V and the charger’s highest fixed voltage. The 100W row comes from the USB-IF’s statement that revision 3.1 raised the limit from 100W to 240W.

What are the USB PD revisions?

Revision	What Wikipedia says
1.0	Finalization announced by the USB Promoters Group in July 2012
2.0	Released as part of the USB 3.1 suite; defined four voltage levels (5, 9, 15, 20V)
3.0	Defines the optional Programmable Power Supply feature; see PPS
3.1	Launched May 2021; adds Extended Power Range, up to 240W
3.2	Launched October 2023

How is USB PD different from older charging?

Before USB PD, charging speed was limited and often proprietary. Wikipedia lists the Battery Charging 1.2 specification, released in 2010, at 1.5A at 5V, which is 7.5W, and says default USB high-power devices draw 500mA. It says phone makers used custom protocols before USB PD, with Qualcomm’s Quick Charge 2.0 delivering 18W at a higher voltage, and that some of those technologies later became compatible with USB PD.

What does USB PD mean for my phone?

Phones use a small share of the range. The wattage guide collects the published figures by charging type. Samsung’s fast charging builds on USB PD 3.0 with PPS. The cable matters too, so read cable buying safety and USB-C explained.

Chargers hub, GaN chargers, which charger is safe for my phone.

Frequently asked questions

Q01

What is the maximum wattage of USB PD?

The USB-IF says revision 3.1 enables up to 240W over a full-featured USB-C cable and connector. Before that update the limit was 100W. Phones use only a small share of that range, so the ceiling matters more for laptops than for a phone charger.

Q02

Do I need a special cable for USB PD?

Only for the highest power levels. The USB-IF says the earlier 100W limit used cables rated at 5A, and the USB Type-C specification was updated to define 240W cable requirements. Wikipedia says the 28V to 48V range needs electronically marked 5A cables.

Q03

Is a USB PD charger backwards compatible?

Yes. The USB-IF says certified USB Fast Chargers are backwards compatible with devices that support USB Type-C and USB Power Delivery. An older device simply negotiates a level it supports instead of the charger's highest one.

Q04

How does a phone and charger agree on power?

Wikipedia says PD-aware devices talk to the power source over a bidirectional data channel and request a certain level of electrical power. The USB-IF adds that a device can take only the power it needs and get more when required.

Q05

Is USB PD the same as Quick Charge?

No. Wikipedia says that before USB PD, phone makers used custom protocols, and gives Qualcomm's Quick Charge 2.0 as an example that delivers 18W at a higher voltage. It adds that some of those technologies, such as Quick Charge 4, later became compatible with USB PD again.

Q06

When did USB PD 3.1 arrive?

Wikipedia says the USB PD promoter group launched revision 3.1 in May 2021, adding Extended Power Range mode with 28V, 36V and 48V and up to 240W. A later revision, 3.2, followed in October 2023.