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USB Power Delivery explained: What you need to know about ubiquitous charging
Fast charging is a godsend when our gadgets run low on juice. However, the vast array of charging standards and plugs, both proprietary and licensed, makes it difficult to know exactly what charging speed you’ll receive when using a third-party charger. This means that gadgets all tend to ship with their own adapters to ensure they charge quickly. USB Power Delivery (USB PD), the latest official charging specification from the USB Promoters Group, aims to fix all that.
USB Power Delivery is a universal specification designed as a common fast-charging standard that can be implemented in all USB gadgets. USB PD has actually been around since 2012, around the same time that the USB-C port was unveiled. Yes, it really has been that long. Power Delivery is a replacement for the older USB Battery Charging (USB BC) specification, designed to augment the basic power specifications of a USB port. USB Power Delivery is now in its third revision, sporting even more configurable power configurations for optimal fast-charging.
Read more: USB-C in 2021: Why it’s still a mess
Here’s everything that you need to know about USB Power Delivery and what it means for your gadgets.
USB Power Delivery – what you need to know
Modern USB-C ports are complicated beasts and actually support several levels of charging. And that’s before manufacturers add proprietary capabilities on top of that.
To start with, all USB ports support a very basic level of charging at just 5V and up to 500mA, with more modern ports supporting 5V and 900mA of current. This is based on legacy support and is very slow to charge all but the most low-power gadgets. USB-C ports can be configured with 5V 1.5A and 3A for up to 15W of power, which is a bit quicker but still rather slow compared to other fast-charging standards.
USB Power Delivery is much more powerful, supporting up to 100W of power to charge up even the most demanding gadgets such as laptops. It’s also safer, as gadgets and chargers communicate with each other over the USB cable to confirm the optimal charging power level. This handshaking approach supports voltage steps at 5V, 9V, 15V, and 20V for power outputs ranging from 0.5W to 100W. The new USB Power Delivery Programmable Power Supply (USB PD PPS) standard supports configurable voltages too, enabling more optimal charging. If two devices fail to communicate a suitable power rule, USB Power Delivery will default to the next power option supported by the relevant USB protocol, such as USB-C 1.5A.
USB Power Delivery is now commonly used to fast-charge smartphones, laptops, and other gadgets. Examples include the entire line-up of Google Pixel handsets, Samsung’s Galaxy S smartphone range, and Apple’s iPhone and MacBooks. A huge range of other smartphones support the standard too, often in addition to their faster proprietary standards.
USB Power Delivery versions compared
With USB Power Delivery now into its third revision, the standard is broken down into devices with slightly different capabilities. Although modern versions of the standard are backward compatible with older gadgets and chargers.
USB PD 1.0 was a little more basic than the modern version. It simply offered six fixed power profiles for different device categories. This version supports 10W (5V, 2A), 18W (12V, 1.5A), 36W (12V, 3A), 60W (12V, 5A), 60W (20V, 3A), and 100W (20V, 5A) of power exclusively. That’s OK, but not exactly flexible for a wide range of gadgets, including small smartphone batteries that prefer lower voltage charging.
The more modern USB Power Delivery 2.0 and 3.0 variations drop fixed profiles in favor of more flexible power rules. These rules keep fixed voltage brackets but allow for a wider range of negotiated current levels. The end result is a much more flexible standard that is better suited to a wide range of devices. USB Power Delivery 3.0 also extends the communication protocol to support features like battery condition, enhanced security, and fast role swapping.
USB PD Power Range:0.5 - 15W
Current Range:0.1 - 3.0A
Example devices:Headphones, small USB accessories
USB PD Power Range:15 - 27W
Current Range:1.67 - 3.0A
Example devices:Smartphones, cameras, drones
USB PD Power Range:27 - 45W
Current Range:1.8 - 3.0A
Example devices:Tablets, small laptops
USB PD Power Range:45 - 100W
Current Range:2.25 - 3.0A
3.0 - 5.0A only with rated cable
Example devices:Large laptops, displays
The majority of modern smartphones make use of the USB Power Delivery 2.0 and 3.0 specification. At least in some form. 18W of power is quite typical for smartphones and around 60W for laptops. Although some smartphones that use USB PD as their primary fast charging technology are a bit faster.
USB Power Delivery Programmable Power Supply explained
Despite improvements with USB Power Delivery 2.0 and 3.0, they’re still not entirely suited to the flexible requirements of very fast charging. Battery charging speed is sensitive to specific voltages and this changes depending on the battery’s current charge. The 5V, 9V, 15V, and 20V set voltages in the standard specification aren’t ideal for optimal fast charging.
The USB Power Delivery 3.0 revision released in 2018 also introduced the Programmable Power Supply protocol into the standard. USB PD PSS is much more flexible, allowing for configurable voltage levels at very small 20mV granular increments. Combined with device-to-charger communication and voltage-control charging algorithms, the ideal voltage can be negotiated and even changed during charging. This makes USB PD PPS far better suited to fast-charging than the standard USB PD protocol.
As the newer part of the standard, support for USB PD PPS is limited to just a handful of gadgets and charging accessories in 2021. Support is starting to grow, particularly in the charger market, but the latest specification is leading to a few headaches for consumers. For example, Samsung’s Galaxy S21 series can only be fast-charged at their full 25W of power using USB PD PPS chargers. Otherwise, consumers are stuck with a slower 18W when using standard USB PD.
How fast is USB Power Delivery?
Given the variable nature of USB PD charging and the wide range of battery capacities, it’s impossible to give a precise speed for the standard. Very broadly speaking though, large battery capacity phones charge to full using 18W USB Power Delivery in a little over an hour. Large capacity laptops using 60W charging can take between an hour or two.
Unlike laptops, smartphones generally don’t like to use high voltages to charge their batteries. Typically, smartphone fast charging uses 5V or 9V and high currents to charge up the battery. For example, OnePlus’ 65W charging tech uses 10V and 6.5A charging and Huawei’s 40W option uses a similar 10V and 4A. Although both of these are proprietary technologies.
9V is the closest USB PD voltage setting, which is capped at a much slower 27W of maximum power. Most USB Power Delivery smartphones we’ve seen don’t actually use the full 3A either, capping their power at 18-20W. Hence why the fastest charging phones are still based on proprietary charging technologies.
USB PD PPS is more promising for universal fast charging. The Samsung Galaxy S21 series fast charges at 25W with a 9.5V PPS voltage setting. Samsung actually deployed 45W USB PD PPS charging in its Galaxy Note 10 Plus too, so it’s technically possible to utilize fast charging with this standard. However, Samsung hasn’t seen fit to continue with such high power charging, likely because faster charging is harder on the handset’s battery.
Proprietary technologies are pushing the boundaries even further, with Oppo teasing 100W capabilities and Xiaomi 120W charging already deployed in a smartphone. USB PD and PPS are unlikely to ever rival these speeds without further revisions, but there are diminishing returns in terms of power consumption versus charge time anyway. Around 40W is plenty to charge a smartphone super fast.
Consumer convenience and the ecological argument
While charging speed is an important factor in the design of USB Power Delivery, and PPS in particular, it’s not the primary design goal. USB PD was created as a single standard to power a wide range of USB gadgets. Thereby reducing the need for proprietary ports, connectors, and plugs.
First and foremost, this should make it much easier for consumers to just plug and charge. A happy side-effect is that manufacturers won’t need to bundle a new charger with every new device. E-waste from old chargers and cable is a growing problem, not just for landfills but as a drain on precious metals and other finite resources. There are strong environmental reasons for consumers and manufacturers to embrace a unified charging technology like USB Power Delivery.
Smartphone brands removing charging bricks from the box may be a controversial decision today. Particularly as consumers don’t necessarily own a compatible USB PD PPS charger. But in the long term, we might not pay a second thought to the lack of bundled chargers as all our gadgets charge quickly from plugs we already own. That’s the theory anyway.
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