Power Delivery 3.1 Charger

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Oday Forster

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Aug 3, 2024, 5:41:11 PM8/3/24

to garekady

Fast charging is a godsend when our gadgets run low on juice. However, there are numerous fast charging standards in existence today, making it difficult to pick the right charger for your smartphone, laptop, or even external monitor. Furthermore, while most gadgets historically shipped with an adapter in the box, many brands are now asking you to bring your own. Luckily, USB Power Delivery (USB PD) is a universal charging specification that allows you to sidestep the fragmented phone charger market altogether.

USB Power Delivery is a common fast-charging standard that can be implemented in all USB-powered gadgets. USB PD has actually been around since 2012, around the same time that the USB-C port was unveiled. Prior to that, the only universal option was the (significantly slower) USB Battery Charging specification.

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 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.

The newer 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.

With USB Power Delivery now in 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.

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.

Proprietary technologies are pushing the boundaries even further, with OPPO teasing 240W and Xiaomi already offering 120W charging. That said, there are diminishing returns in terms of power consumption versus charge time anyway. Around 45W is plenty to charge a smartphone super fast.

First and foremost, this should make it much easier for consumers to just plug and charge. E-waste from old chargers and cables 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.

I recently bought a laptop that is able to be powered via USB-C Power Delivery 3.0 on 100W (20V). From what I understand, PD (3.0) can be used to charge the battery, but also 'run' a device, i.e. the laptop recognises the power of the PD charger, and performance is reduced in order to cope with the lower wattage via USB-C instead of the default AC adapter. As I perceived it, it thus should not drain the battery on the way, and it should be even possible to run it off an empty battery (battery passthrough), given that it acts as a lower-power AC adapter.

Before PD it was simply 5V with some current limit, which was usually slightly higher than the spec required and even higher with appropriate voltage divider between data lines (exact values expected varied between vendors).

1 With rare exceptions. For example OnePlus Warp Charge 30T wall wart contains actual charger. When a compatible mobile phone is connected, it can bypass phone's internal charger. This way some of the heat is generated away from the battery, allowing for faster charging.

The USB Power Delivery (USB PD) Specification enables the maximum functionality of USB by providing more flexible power delivery along with data over a single cable. Its aim is to operate with and build on the existing USB ecosystem.

Announced in 2021, the USB PD Revision 3.1 specification is a major update to enable delivering up to 240W of power over full featured USB Type-C cable and connector. Prior to this update, USB PD was limited to 100W using a solution based on 20V using USB Type-C cables rated at 5A. The USB Type-C specification has also been updated to Release 2.1 to define 240W cable requirements, and with the updated USB PD protocol and power supply definition, this extends the applicability of USB power delivery to a large number of applications where 100W wasn't adequate.

Power Delivery is designed to co-exist with standard USB Battery Charging implementations. Implementers should note that if they include battery charging capability in their devices or support for host adapters such as docks or ACAs they should also reference the Battery Charging Specification.

USB-C connectors have been designed hand-in-hand with USB-C Power Delivery, to handle these new high levels of power. USB-C circuit boards are specially designed to carry this increased wattage without being damaged or overheating, for enhanced safety to users and their devices.

A 45-watt wall charger will charge all your USB-C PD-enabled devices, but if you are looking to charge an iPhone X, which will only accept 18-watts of power, your 45-watt charger will only deliver 18-watts.

A 45-watt wall charger will charge all your USB-C PD-enabled devices, but if you are looking to charge a Google Pixel, which will only accept 18-watts of power, your 45-watt charger will only deliver 18-watts.

Engineered for safety, efficiency and durability, Belkin cables and chargers are accredited or approved for compatibility by companies such as Apple, Google and the USB-Implementers Forum (aka USB-IF).

I have a Qi wireless charging pad for my phone, powered via a micro-usb port. The markings on it indicate that it will accept the typical 5V that nearly every USB port provides, or it will accept 9V for "fast charge".

I was under the impression that USB standards allowed for no more than 5V.
My research shows that USB Power Delivery has several profiles (up to 20V), and Revision 2.0 Version 1.2 includes a 9V profile.

Now I'm wondering: How can voltages above the usual 5V be provided without worry of damaging an expensive phone when connecting them directly (no wireless pad)? If things are running at different voltages, wouldn't that cause an issue?

In this example, 9V is used for fast charging, but could that 9V be sent to my phone? Do phones have a safeguard for this? The USB standard allows for up to 20V. That's a lot when expecting only 5V. Some "dumb" devices are powered directly off of USB, like cheap LEDs and fans that have no IC. Surely they would blow upon 20V!

I'm guessing there is data exchanged between the power source and the peripheral, ultimately telling the power source whether or not it's okay to provide more than 5V. Some USB charging cables don't have data pins though, which can allow for faster charging. In this case, it seems that not having data pins would be a restriction. Maybe the power source would have to default to 5V?. Unfortunately I cannot find an explicit protocol/explanation of how the different potentials are managed.

For USB-PD through micro-usb, it needs to be done through a PD aware cable. USB-OTG added an additional pin to the micro connectors (the ID pin) which is left floating on the micro-b connector. A USB-PD device uses that pin to negotiate the power profile determine if the cable is PD aware.

It has also been updated to include type C connectors, which as you mentioned have the CC pin, and use BMC encoding to communicate on that pin. It is important to note however that this protocol is backward compatible with the USB 2.0 devices that implement 1.0 as well.

Adding new information based on Ali Chen's answer. Your device may make use of the Qualcomm Quick Charge protocol, which uses the data lines to negotiate. Specifically, the portable device puts a pair of voltages on the D+ and D- lines, and the Quick Charge IC applies a different voltage depending on whether or not the IC is configured to connect to class A or B devices. For Quick Charge 3.0, the negotiation table is as follows:

To determine if this applies to you, simply connect a USB cable that does not have data lines inside to your wireless charger or to your phone. If it reads 9V, then it's not using the Quick Charge protocol to negotiate voltage (or, at the very least, it's not negotiating over the data lines, since there could be other protocols in use). Also, and probably more effective, You could also put the D+ and D- lines on a scope, and observe the voltage changes. Here is also a state diagram for reference, taken from a Quick Charge 3.0 IC, the NCP4371:

The higher voltages and capabilities of power providers are only available upon mutual negotiations between a device (consumer) and a port (provider). If the device does not support this intelligence, no elevated power will be delivered, and no problem will occur. [ADDENDUM: details of identification of Power Delivery capabilities and mechanisms of negotiations are cumbersome and still evolving, and are beyond the scope of a single stackexchange article]

Now about the current state of PD: unfortunately, specifications appears to evolve slightly faster than wikipedia contributors bother to check. In the new Rev.3.0 of PD specifications (V1.0a, March 25, 2016, + ECNs of August 2, 2016) the BFSK negotiations over VBUS are depreciated.

In reality, the PD v1.0 with PD negotiation over VBUS with BFSK data coding did never take off, maybe one or two devices were ever made in the entire world. So, currently going forward, the only way to negotiate Power Delivery is through Type-C CC pin.