What is USB PD (Power Delivery)?

What is USB PD (Power Delivery)? This article provides a detailed explanation. It covers the PD standards such as USB PD 3.0 and the latest USB PD 3.1, along with current USB developments, offering functional explanations and basic information.

Since announcing our USB PD products at Techno Frontier 2018, we have received many inquiries such as "What is USB PD (Power Delivery)?" Therefore, we will provide an explanation on this page. This device, which enables multi-device charging, is very convenient as it automatically adjusts the power supply according to the connected device.

At the previous Techno Frontier, our company exhibited two new USB PD (Power Delivery) products. We received very positive feedback from visitors, for which we are sincerely grateful. In response to growing customer demand, Unifive has developed two USB PD models with 40W and 60W outputs. Since then, we have expanded our lineup and released a 65W model as well.

What is USB PD (Power Delivery)?

USB PD: The next-generation USB that enables data transfer and high-power delivery

USB PD (USB Power Delivery) is a new USB technology that allows for data transfer and high-power delivery through a single cable. Evolved from conventional USB, USB PD-compatible AC/DC power adapters — desktop & wall-mount — enable simultaneous power and data transmission via USB Type-C cables, maximizing USB’s potential. With this technology, much higher power delivery is possible compared to traditional USB charging methods, making it suitable for charging not only smartphones and tablets but also power-demanding larger devices such as laptops.

Below is a summary of USB PD's features:

• Compared to traditional USB versions like USB 1.1 (2.5W), USB 3.0 (4.5W), and USB BC 1.2 (7.5W), USB PD can deliver up to 100W of power.

• Eliminates the fixed roles of power source and sink, allowing for power direction reversal (role swap). For example, a PC charging an external battery can switch to being charged by the battery itself with the role swap function (for Type-C cables).
• Enables power optimization for multiple external devices.

• Automatically adjusts power according to the connected device.

Current USB Trends

Nowadays, USB ports are found everywhere — in cars, public buses, and even airplanes. It's now common to power devices via a computer’s USB port. USB has indeed become a ubiquitous charging solution for small gadgets like smartphones.

These conventional USB ports were primarily designed for data transfer using USB drivers, but over time, users started to also use them as power sources for charging.

Reliable Charging with USB PD 3.0

The latest USB PD 3.0 standard, defined by the USB-IF (Implementers Forum), aims to eliminate substandard cables and products that fail to meet established specifications, ensuring safe use of USB PD.

Compared to version 2.0, USB PD 3.0 offers faster role swapping, reducing the risk of data corruption in the event of unexpected power cutoffs.

It also introduces C-AUTH (USB Type-C Authentication), a mutual authentication feature between connected devices. It checks whether the connected device or cable is trustworthy. If a problem is detected, functionality may be blocked for safety.

* Click here for an explanation of USB Type-C

USB PD 3.1: Evolving to deliver up to 240W of power

While USB PD 3.0 currently dominates the market, the USB-IF announced a new USB Power Delivery (USB PD) specification revision 3.1 on May 26, 2021.

This major update enables power delivery of up to 240W via USB Type-C® cables and connectors. Previously, USB PD solutions were limited to 100W using 20V and 5A Type-C cables.

The USB Type-C specification was also updated in version 2.1 to define cable requirements for 240W support. Updates were also made to USB PD protocols and power profiles, enabling support for more devices previously underserved by the 100W limit.

The new USB PD architecture defines a strict power negotiation protocol to ensure safe access and usage of this higher power supply. Products using power between 100W–240W are subject to stricter safety standards based on regulations in their respective countries.

USB Power Delivery 3.1 allows high-power products such as large laptops to move from traditional power connectors to USB Type-C.

Three New Fixed Voltage Options: Enhanced Output via EPR

One of the main updates in USB PD 3.1 is the addition of three new fixed voltage levels. Beyond the traditional SPR PDO and SPR APDO specifications of 5V, 9V, 15V, and 20V, 28V (100W+), 36V (140W+), and 48V (240W+) have been added.

The core new feature of USB PD 3.1 is EPR (Extended Power Range), which enables power supply at voltages exceeding 20V. EPR adds 28V, 36V, and 48V fixed voltage levels, each capable of delivering power beyond 100W, 140W, and 180W respectively.

EPR Mode: A Safety Protocol for Delivering High Power

EPR mode is a communication protocol designed to ensure the safe delivery of high power. Before entering EPR mode, the source and sink devices verify each other's capabilities to reach a mutual agreement for secure power transfer.

Below is a table summarizing the evolution and key specifications of USB up to the introduction of USB 3.1.

Fast and optimized charging experience enabled by USB PD

USB PD is not just about higher power output. USB Type-C includes a dedicated signal line called CC (Configuration Channel) that allows USB PD-compatible devices to detect optimal power automatically and begin charging quickly upon connection.

Evolution of Type-C Cables: Enhanced Safety with EPR Support

With the expansion of USB PD 3.1, USB Type-C cable specifications were updated to version 2.1. EPR-compatible cables feature a chip called an E-Marker, indicating compliance with 50V and 5A. This improves safety and reliability in high-power applications.

High Efficiency and Miniaturization with GaN Technology

GaN (Gallium Nitride) is a next-generation semiconductor material. Compared to traditional silicon-based power devices, GaN offers lower power loss and faster switching speeds. Integrating GaN with USB PD 3.1 power supplies enables both higher efficiency and smaller size.

History of USB PD in Chronological Order

Until now, we have focused on what USB PD is and what the latest USB PD 3.1 entails. Here, we will review the chronological history of USB PD to better understand its technological evolution.

Before USB PD: Low-Power Charging and Standard Fragmentation (1996–2012)

• 1996: USB 1.0 launched. While primarily aimed at data transfer, it could also supply power to peripherals. However, with only 5V and 100mA, it was unsuitable for charging.
• 2000: USB 2.0 introduced, offering improved data transfer speeds and 5V/500mA power supply, enabling usage for charging mobile phones.
• 2007: USB Battery Charging specification BC 1.1 launched, allowing fixed 5V voltage and up to 1.5A current, enabling up to 7.5W of power.
• 2010: USB BC 1.2 released, providing more robust specifications for charging behavior.
• During this period, USB charging became widespread, but power limitations and standard fragmentation were still major issues, especially for high-power devices like laptops.

USB PD Emerges and Evolves: Era of High-Power, Bidirectional Charging (2012–2021)

• 2012: USB PD 1.0 released, enabling up to 100W (20V/5A) of power — suitable for laptops and other large devices.
• USB PD 1.0 defined power capabilities via five standard "profiles," and used voltage/current negotiation between host and device for safe power delivery. However, existing connectors were always 5V, making bidirectional charging impossible.
• 2014: USB PD 2.0 introduced, moving from the profile-based system to Power Data Object (PDO), improving flexibility. It also marked the arrival of USB Type-C, which accelerated USB PD’s growth with its compact, reversible design.
• 2015: USB PD 3.0 launched with PPS (Programmable Power Supply), allowing voltage adjustments in 20mV increments, drastically improving charging efficiency. PPS also enabled optimized charging of lithium-ion batteries. USB PD 3.0 implemented device authentication for improved safety.

USB PD 3.1 & GaN Technology: Toward More Power & Efficiency (2021–)

• 2021: USB PD 3.1 released with EPR (Extended Power Range), enabling up to 240W (48V/5A). Progress in GaN (Gallium Nitride) technology has furthered efficiency and miniaturization of USB PD power sources. Reference designs like the EPC9195 maximize USB PD 3.1’s capabilities.

The Future of USB PD: Powering All Devices

USB PD is expected to expand into mobile devices (laptops, smartphones, tablets), home electronics, and industrial equipment. With the advancement of USB PD 3.1 and GaN technology, a future where all devices can be charged via USB Type-C cables may become a reality.

Unifive offers a wide lineup of next-generation compact AC/DC power adapters — desktop & wall-mount — utilizing GaN for advanced PD solutions.

We also offer custom solutions in small lots, providing flexible proposals. Please feel free to contact our sales team for samples or inquiries.

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