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What is USB power delivery? All you need to know

Tech giants like Apple and Samsung have stopped shipping chargers with their devices, and according to Apple, “There are over two billion Apple power adapters out in the world. So we are removing these items from the iPhone box to reduce carbon emissions and avoid the mining and use of precious metals.”

Looking at Apple’s statement, you would be under the impression that you could use the chargers you own to charge your device, but there is a catch.

You can’t fast charge your device using any power adapter; to do the same, you need a special power adapter, which supports a technology called USB power delivery.

So what is USB power delivery, and how does it fast charge your device?

In this article we will look at USB power delivery and help you understand why you need a different adapter to charge your devices faster.

Also read: Electric vehicle buying guide: All you need to know


Understanding USB and the need for fast charging

Before USB came out in 1996, users had to use different connectors to connect their monitors, keyboards or pointing devices, so if you wanted to connect a keyboard to your computer, you needed a PS/2 connector.

Not only this, when you connected a device, you had to install device-specific drivers, and that wasn’t it. Once you had done everything, you had to restart your device so that your computer could discover the peripheral.

With the invention of USB, all you had to do was connect the device, and it would work like magic.

Although USB solved many problems, it was developed keeping data transfer and compatibility in mind, and with the advent of mobile computing, we had another problem, charging.

USB categoryMaximum Voltage(V) Maximum current(A)Power(W)Estimated Time in hours to charge (4000 mAh battery)Year of launch
USB 2.050.52.56.52000
USB 3.050.94.53.62008
USB Battery charging 1.251.57.522010
USB Type C (Current @ 1.5A) 51.57.522014
USB Type C (Current @ 3A) 531512014
Amount of power delivered by different USB charging specifications and the estimated time they would take to juice up your device.

Back in the day, batteries in phones were smaller and the phone’s output from the USB port(2.5W) was enough to charge the phone’s battery.

As the size of the batteries increased, the power from the power adapter was not enough to charge the batteries in time.

To solve this problem, higher amounts of power had to be injected into the battery, but this solution had a problem.

Supplying higher amounts of power to a lithium-ion battery caused internal heating of the battery, degrading the battery life of the smartphone.

Therefore to solve this problem, intelligent communication methodologies we’re needed so that higher amounts of power could be supplied to the battery pack without degrading its battery life, and that is what fast charging is. It is a set of communication protocols between the battery pack power management system and the charging adapter.

By using these communication protocols, both the charger and the smartphone can communicate with each other. This communication helps in keeping the battery in better heath while charging it at higher speeds.

Also read: Is 64GB enough for iPhone?


Why are there so many types of fast charging protocols?

Now that we know what fast charging is, we need to understand why so many different types of fast charging protocols exist.

Well, as we explained earlier, the power provided by the USB port according to the USB standard was not enough for fast charging.

To solve this problem, different mobile manufacturers came up with newer technologies like Adaptive fast charging(Samsung), Quick charge(Qualcomm) and Warp charge(One plus). These technologies increased the maximum voltage/current compared to the USB specifications enabling devices to charge faster.

TechnologyMaximum power(W)
Samsung Super fast charging 2.045
Turbo power 3028.5
Oppo Super VOOC50
Xiaomi Hypercharge120
Huawei SuperCharge 44+
Qualcomm Quick charge 5100+
Power output of different proprietary charging technologies.

Although this method helped OEMs charge their device faster, it created several problems for the customer. The biggest one being the inability to fast charge a device if the appropriate fast charging adapter/cable was unavailable.

So if you were to buy a one-plus device, you would get an adapter supporting warp charging. This could fast charge your device in a matter of minutes, but if you forgot your adapter, your device would charge at a speed which would make you want to pull your hair out, to solve this problem, we have USB power delivery.

Also read: Chromebook not charging: 6 Fixes


What is USB Power Delivery?

USB power delivery is a protocol for fast charging developed by USB-IF. As this protocol is part of the USB standard, it is non-proprietary and can be used by any OEM manufacturer.

Both the power adapter and the smartphone need to comply with the specifications of USB power delivery to take advantage of the protocol.

Below is the amount of power that can be delivered using different variants of USB PD.

USB categoryMaximum Voltage(V) Maximum current(A)Power(W)Year of launch
USB PD 1.0 (Micro B connector)203602012
USB PD 1.0 (Standard A/B connector)2051002012
USB PD 2.0(Type C connector)2051002014
USB PD 3.0 Programmable Power Supply (PPS)2051002017
USB PD 3.1 4852402021

To deliver power above 60W electronically marked cable assemblies are required.

As you can see, the USB PD standard provides power of up to 240W. This power can be used to charge multiple devices from a single power adapter and can even charge laptops.

Due to the non-proprietary nature of USB PD, it can be used for charging different devices. This approach makes life easier for the consumer and helps reduce e-waste as people don’t have to buy new chargers when they buy new devices.

In addition to the points mentioned above, USB power delivery can be used in tandem with the data transfer mechanism offered by the USB port. Due to this, your device can get charged when connected to external monitor. Not only this, with USB PD, its possible to have a bi directional flow of power. What this means is that a USB PD compliant device can charge another device if needed.

Also read: Why is my laptop plugged in and not charging?


How does USB PD work?

As mentioned earlier USB power delivery is a communication mechanism and in this section we will try to understand how it works.

As mentioned earlier, USB power delivery can work with USB A/B type connectors, but we will look at how this protocol is implemented over USB type C connectors.

Before we get into understanding USB power delivery its important to look at a special pin on the C type connector called the Configuration Channel port also know as CC port.

This port is responsible for establishing communications between the charger and the charging device enabling fast charging

A brief overview of the power delivery protocol is given below:

Device identification: When a device is connected to a USB PD complaint adapter, the adapter sends a voltage of 5v over the Vbus line. As soon as the device is connected it states the power roles it will be working in. These roles can be the following

Start of communication: Communication between the power adapter and the connected device begins over the communication pin. The overview of the communication is as follows

Power transmission: The power adapter transmits a particular voltage on the power line based on the selected power mode.

Current regulation: The connected device controls the amount of current based on the charging state of the battery.

Now that we know how USB power delivery works, we can look at the different power levels which can be transmitted using USB power delivery.

Also read: What is Fast Charging? 5 common fast charging techs explained


Understanding the differnt power levels of power delivery

If you look at the data given in the previous sections you will come to the understanding that USB PD increases the amount of voltage which is sent to the device.

This provision of higher voltages was not available in the older USB standards as the port was designed for transmitting data. This increase in voltage levels enabled devices to charge faster.

That said, different devices require different levels of power and due to this reason, the power delivery protocol lets the device select the amount of power it needs.

Given below are power levels for USB PD 1.0

Power modeVoltage(V) Current(A)Power(W)
15210
2121.518
312336
420360
5205100

In the case of power delivery 1.0, we have differnt power modes but the current and voltage levels are constant for a particular selection. Due to this, there is a lot of energy loss in the battery management IC as it has to convert the voltages/current on the bases of how much the battery is charged.

Power modeVoltage(V) Current(A)Power(W)
150.1-3.010
291.67-3.015-27
3151.8-3.027-45
4202.25-3.0
or
3.0-5.0
45-100
Power levels for USB PD 2.0

USB PD 2.0 defines differnt power levels and lets the charging device manipulate the amount of current they need based on the state of the battery. This reduces the power dessipation during charging keeping the phone cooler.

Although USB PD 2.0 offers different current configurations, the voltage level in PD 2.0 is still constant. To improve upon this flaw USB-IF came up with a new USB PD 3.0 standard which supports a Programmable Power Supply(PPS).

This new standard enables the device to ask for voltage between 3.3v and 21v at increments of 20 millivolts. This enables the device to control both the voltage and current which is used to charge the battery. Due to this granular control over both voltage and current the device does not heat up during fast charging.

The USB PD 3.0 standard offers granular control on the voltage levels, but the 100w of maximum power can be less for demanding gaming laptops. To solve this issue the USB 3.1 was released and it supported power up to 240 W.

Power modeVoltage(V) Current(A)Power(W)
150.1-3.010
291.67-3.015-27
3151.8-3.027-45
4202.25-3.0
or
3.0-5.0
45-100
5285140
6365180
7485240
Power levels for USB PD 3.1

Also read: Is charging your phone overnight bad? 5 ways to improve battery life


Is USB PD making the world a better place?

The USB implementation forum wants to change the way we charge our electronics. Supporting power delivery of up to 240 watts, the USB PD standard can charge any device you own.

Once USB PD is implemented by several OEMs customers will no longer have to buy proprietary adapters to fast charge their devices.

To make the process faster Google states the following in its Android 7.0 CCD release, “Type-C devices are STRONGLY RECOMMENDED to not support proprietary charging methods that modify Vbus voltage beyond default levels, or alter sink/source roles as such may result in interoperability issues with the chargers or devices that support the standard USB Power Delivery methods. While this is called out as “STRONGLY RECOMMENDED”, in future Android versions we might REQUIRE all type-C devices to support full interoperability with standard type-C chargers.”

Looking at this statement various OEMs like One plus and Qualcomm have implemented USB PD along with their proprietary charging technologies.

One plus for example offers 65W fast charging with it Warp charger, but also lets users fast charge their devices at up to 45 W if they have a charger that supports USB power delivery.

So, if you look at it, with USB PD, the USB implementation forum wants to streamline the way we charge so that we don’t have to worry about carrying tons of chargers every time we move out of the house.

Also read: Wireless Charging: Yay or Nay? Is wireless charging better than wired?

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