What is USB PD (Power Delivery)?

It provides a detailed explanation of what USB PD (Power Delivery) is. It includes a functional explanation and basic information about the PD standards such as USB PD 3.0 and the latest USB PD 3.1, along with recent developments in USB technology.

Since the announcement of USB PD products at Techno Frontier 2018, we have received numerous inquiries asking “What is USB PD (Power Delivery)?” This page explains it in detail. This multifunctional charging device automatically adjusts its power output according to the connected device, making it highly convenient.

At the previous Techno Frontier event, we showcased two types of our new USB PD (Power Delivery) products. We received excellent feedback from attendees, for which we are deeply grateful. In response to customer demand, Unifive developed two USB PD products, one rated at 40W and another at 60W. Since then, we have expanded our lineup to include a 65W model as well.

What is USB PD (Power Delivery)?

USB PD – The Future USB Enabling Data Transfer and High Power Delivery

USB PD (USB Power Delivery) is a new USB technology that enables both data transfer and high-power delivery through a single cable. Evolved from earlier USB standards, USB PD-compatible AC adapters can deliver both power and data via a USB Type-C cable, maximizing USB’s performance. With this technology, significantly more power can be supplied compared to traditional USB charging, allowing not only smartphones and tablets but also higher-power devices such as laptops to be charged.

Here is a summary of the functions of USB PD:

• Compared to older USB versions such as USB1.1 (2.5W), USB3.0 (4.5W), and USB-BC1.2 (7.5W), USB PD can deliver power up to 100W.

• Eliminates the fixed roles of power provider and receiver, allowing roles to be swapped (role swap). For example, an external battery that was charging from a PC can instead charge the PC via role swapping. (Applicable when using a Type-C cable)
• Enables power optimization across multiple external devices.

• Automatically adjusts power according to the connected device.

Current USB Trends

Nowadays USB ports are found everywhere, from vehicles to public transportation like buses and airplanes. It has also become normal to draw power from a PC’s USB port. Indeed, USB has become a ubiquitous charging solution for small devices like smartphones.

Previously, USB ports were mainly used for data transfer through USB drivers. Gradually, users began shifting to also using them as power sources for charging and other purposes.

Reliable USB PD with USB PD 3.0

USB PD 3.0, the latest specification defined by the USB Implementers Forum (USB-IF), aims to eliminate poor-quality cables and products that do not meet standards, ensuring safe use of USB PD.

Compared to version 2.0, USB PD 3.0 offers faster role swapping, reducing the risk of data loss even if power supply is unexpectedly interrupted.

A mutual authentication feature called C-AUTH (USB Type-C Authentication) has also been added. Devices and cables are mutually authenticated to verify reliability, and if any issues are detected, functionality will be blocked for safety.

*Click here for more information on USB Type-C

USB PD 3.1: Evolution to 240W Power Supply

While USB PD 3.0 is currently the mainstream in the market, USB-IF announced the new specification for USB Power Delivery Revision 3.1 on May 26, 2021.

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

Correspondingly, USB Type-C standard was updated in Revision 2.1 to define specifications for 240W cables. Updated power protocol definitions now allow USB PD support for many high-power devices previously limited by the 100W cap.

The new USB PD architecture includes more rigorous power negotiation protocols to ensure safe access and usage of this high power. Products consuming 100–240W power have stricter safety requirements than lower-powered ones and must adhere to regional safety standards where they are sold.

With the new features of USB Power Delivery 3.1, high-power devices such as large laptops may transition from traditional power connectors to a USB Type-C connection.

Three New Fixed Voltage Options with EPR (Extended Power Range)

One of the major features of USB PD 3.1 is the ability to select from three new fixed voltages. In addition to the existing SPR PDO and SPR APDO specifications (5V, 9V, 15V, 20V), USB PD 3.1 now offers 28V (above 100W), 36V (above 140W), and 48V (above 240W).

The key new feature, EPR (Extended Power Range), enables power delivery above 20V. EPR introduces fixed voltages of 28V, 36V, and 48V, allowing support for power levels exceeding 100W, 140W, and 180W respectively.

EPR Mode: Protocol for Safe High Power Delivery

EPR mode is a communication protocol to ensure safe delivery of high power. Before entering EPR mode, the source (power provider) and sink (device) verify each other’s capabilities and agree on safe power delivery settings.

The table below summarizes the evolution and specifications of USB PD up to USB 3.1.

An Optimal and Fast Charging Experience with USB PD

In addition to delivering high-power output, USB Type-C includes a dedicated signal line called a CC (Configuration Channel). Upon connecting a USB Power Delivery-compatible device, the optimal power is automatically detected, enabling rapid charging.

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

With the expansion of USB PD 3.1, USB Type-C cable specifications have been updated to version 2.1. EPR-compliant cables include a chip called an E-Marker, indicating compatibility with 50V and 5A. This improves safety and reliability during high-output charging.

High Efficiency and Miniaturization with GaN Technology

GaN (gallium nitride) is gaining attention as a next-generation semiconductor material. Compared to conventional silicon power devices, GaN-based power devices offer lower power loss and faster switching speeds. Incorporating GaN into USB PD 3.1 power systems achieves both higher efficiency and smaller device size.

The History of USB PD in Chronological Order

The previous sections explained what USB PD is and the features of the latest USB PD 3.1. Here, we look back on the history of USB PD to better understand its technological evolution.

Before USB PD: Low Power Charging and Proliferation of Standards (1996–2012)

• 1996: USB 1.0 was introduced. Initially used for data transfer, it could also supply power to peripherals. However, with only 5V and 100mA output, it was inadequate for charging purposes.
• 2000: USB 2.0 was released. Along with faster data transfer, power output improved to 5V and 500mA, making it usable for charging cell phones and similar devices.
• 2007: USB BC (Battery Charging) 1.1 was introduced, allowing a fixed 5V voltage with up to 1.5A current, enabling 7.5W power delivery.
• 2010: USB BC 1.2 was released, further strengthening charging specifications.
• During this era, USB charging began to spread but was still limited by low power and disparate standards. Devices like laptops, requiring higher power, were beyond USB charging capabilities.

Birth and Development of USB PD: Era of High Power and Bidirectional Supply (2012–2021)

• 2012: USB PD 1.0 launched, enabling up to 100W (20V, 5A) power delivery, making it suitable for charging high-power devices like laptops.
• PD 1.0 used five standard “profiles” to define power capabilities. Safe power delivery was achieved through voltage and current negotiation between host and device. However, dual-direction power delivery was not possible due to constant 5V on legacy USB connectors.
• 2014: USB PD 2.0 introduced. Transition from profile-based to PDO (Power Data Object) approach enabled more flexible power control. The release of the USB Type-C connector enhanced USB PD’s evolution. Type-C is compact and reversible, allowing insertion without alignment.
• 2015: USB PD 3.0 introduced PPS (Programmable Power Supply), allowing voltage adjustments in 20mV increments for greatly improved efficiency. PPS optimized lithium-ion battery charging, and authentication features enhanced safety.

USB PD 3.1 and GaN Technology: Toward Higher Output and Efficiency (2021–)

• 2021: USB PD 3.1 introduced EPR (Extended Power Range), enabling up to 240W (48V, 5A) power delivery. Advances in GaN technology further improved the efficiency and miniaturization of USB PD power supplies. GaN-based reference designs like EPC9195 leverage the full potential of USB PD 3.1.

The Future of USB PD: Powering All Devices

USB PD is expected to be used across various fields, not just for mobile devices like laptops, smartphones, and tablets, but also for home appliances and industrial equipment. With advances in USB PD 3.1 and GaN technology, we may see an era where all devices are charged via USB Type-C cables.

Unifive offers a wide variety of next-generation compact AC adapters incorporating GaN for the latest PD solutions.

We also support small-lot custom orders and provide flexible proposals. For samples or other inquiries, please feel free to contact our sales department.

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