What is USB Power Delivery?

September 2019

In the age of USB-C, the universal charger is king. Laptops, phones, tablets, so many devices are adopting the USB-C port for its versatile functionality and ability to carry high levels of power.

 

Developed by the USB Implementation Forum (USB-IF: the bigwigs behind all USB device standards), USB Power Delivery (USB-PD) is capable of delivering both high power to laptops and low power to your mobile phone.

 

But what is USB-PD? How does it work? What does it do?

Requirements

  • Device that supports USB-PD
  • Charger that supports USB-PD

How does USB-PD work?

When you connect a USB-PD charger to a device that supports the USB-PD charging standard, the charger initially supplies the device with the standard 5 Volts, traditionally found in USB devices.

It speaks with the device

After being plugged in, the charger communicates with the USB-PD device, asking for the device’s maximum supported charging voltage. The USB-PD device responds by communicating this information to the USB-PD charger.

It gives the device the power it needs

Having received the charging specifications from the device, the charger starts to output the required power to the device. USB-PD can output the standard 5 Volts you expect from your average USB supply, all the way up to 20 Volts (common laptop voltage), with a maximum current of 5 Amps (100 Watts).

 

The table below shows the current power profiles that USB-PD chargers support.

Voltage Maximum Current (Amps) Maximum Power (Watts)
5V 3A 15W
9V 3A 27W
15V 3A 45W
20V 5A 100W

E-Marker IC Chip

For a USB-C cable to carry at least 5A of power, a chip known as the E-Marker chip must be installed inside one of the USB connectors. The charging device communicates with the chip, to ensure the cable is USB-PD compliant.

Key advantages of USB-PD

Although Qualcomm’s Quick Charge (QC) standard is a fantastic charging solution, USB-PD has several advantages over QC.

It’s versatile

Thanks to USB-PD’s ability to supply up to a whopping 100W and ability to communicate with compatible devices, even USB-PD laptop chargers can fulfil the power requirements of less-demanding devices (e.g. phones).

 

Some manufacturers are modifying their charging circuitry to prevent the use of 3rd party chargers. Although this could be interpreted as forcing consumers to pay a premium for manufacturer approved products, this also enables the manufacturer to provide a level of quality control and prevent consumers from voiding their warranties.

It’s both practical and environmentally friendly

Adopting USB-PD simplifies the process of purchasing a laptop charger and helps to reduce electrical waste. It’s also nice to carry fewer cables in your backpack!

It multitasks & goes both ways

Data and power transfer can occur simultaneously over the same cable. USB-PD even allows power to flow in both directions, making it possible to share power between devices from the same port!