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  • Author Author: dychen
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USB-PD - Explaining the Power Standard in the Raspberry Pi 5

dychen

In our ever-connected world, a universal charging solution has become a necessity. Imagine being able to charge your smartphone, laptop, tablet, and even some appliances with a single cable and charger. That's where USB Power Delivery (USB-PD) steps in – a game-changing technology that's reshaping the way we power and charge our devices.

Before we jump into the details of USB-PD, let's look at the state of charging technology a few years ago. You probably have a drawer filled with various chargers, each with a different connector and power rating. Charging your smartphone with your laptop charger? Forget about it. Charging your tablet with your camera charger? Not a chance. It was a world of tangled cables and compatibility issues.

What is USB-PD?

USB-PD, short for USB Power Delivery, is a standardized protocol and specification designed to deliver higher levels of power and greater flexibility in charging and powering electronic devices. In simpler terms, it's a universal power solution that eliminates the need for multiple chargers and cables.

USB-PD Power Range

Figure 1: USB-PD Power Range (Source: CUI, Inc.)

Remember the frustration of hunting for the right charger or cable when you needed to charge your various gadgets? With USB-PD, you can charge a wide range of devices, from smartphones and laptops to monitors and small appliances, all using a single cable and charger. No more clutter of tangled cables or confusion over which charger goes with what device.

Key Features of USB Power Delivery:

Increased Power Levels: USB-PD supports power levels from 5W to 100W or more. This means it can handle the charging needs of not just your smartphone, but also power-hungry devices like laptops and smaller household appliances.

Bi-Directional Power Flow: USB-PD allows power to flow in both directions. This means your laptop can charge your smartphone, or two laptops can share power between each other.

Negotiation of Power Levels: USB-PD devices communicate with each other to determine the right power level and voltage needed for charging or powering. This ensures safe and efficient power delivery based on the connected devices' capabilities.

Variable Voltage and Current: USB-PD can deliver power at various voltage and current levels, adapting to the specific requirements of the device. This helps prevent overcharging and ensures that your devices get the right amount of power.

USB Type-C Connector: USB-PD is often associated with the USB Type-C connector. This reversible and versatile connector can handle higher power levels and data transfer, making it a perfect match for USB-PD technology.

Fast Charging: USB-PD supports fast-charging capabilities, ensuring your devices charge quickly and efficiently.

Universal Compatibility: One of USB-PD's primary goals is universal compatibility. It's supported by numerous device manufacturers, making it easier for you to use a single charger or power bank for all your devices.

Does the Raspberry Pi 5 Support USB-PD?

Raspberry Pi 5 USB-PD Official ChargerYes! A new feature on the Pi 5 is support for USB-PD. There's a new official power supply for the Pi5: the 27W USB-C PD Power Supply . Normally, the total power available at the Pi 5's four USB ports is limited to a nominal 600mA. When the new power supply is detected, that increases to 1.6A, letting the Raspberry Pi 5 power a much wider range of peripherals.

Embracing the Future of Charging

USB-PD has quickly become a standard in the tech industry, simplifying power management and improving the user experience when it comes to charging and powering electronic devices. With its ability to deliver higher power, fast-charging capabilities, and universal compatibility, it's a technology that's transforming the way we stay connected.

For more information on USB-C and USB-PD, check out Tech Spotlight: What's Coming Up in the Changing World of USB?

Parents Comment
  • in reply to cstanton

    PDO is Power Data Object, which are used to negotiate a valid contract between the PD source and sink. I should have said fixed PDO, which are 5V/max3A; 9V/max3A; 15V/max3A and 20V/max5A. A lot of the PD supplies only have those fixed objects implemented. 5V/5A would require a variable PDO and likely a PPS (programmable power supply).

    It is not incorrect, just very bad design decisions, when a device requires a very special mode that not a lot of sources are able to supply. It is the device manufacturer's responsibility to educate the customer, imho. Not just tell them but our supply.

    It's complicated.

Children
  • in reply to wolfgangfriedrich

    It's definitely going to be an irritation just like Pi 4 supply. I think there's a market for an after-market product, which would basically be a USB-C PD sink which would negotiate 15V/3A, and then buck-convert it to 5V at up to 5A max. It would be far preferable to the Pi's official adapter, simply because they have a short cable on them usually. Whereas users could simply buy their favourite USB-C power adapter. I deliberately bought USB-C adapters for phone etc with a figure-8 cable connection, so I can stick a 2 meter or longer mains cable to it, and can stick any desired length USB-C cable to it too, e.g. even 2 meters if needed. That plus the figure-8 cable results in a total length which is perfect for use without a trailing mains lead.

    I'd rather an adapter than a 27W official power supply, which is under-powered for non-Pi uses - phones now charge at up to 45W, at least Android ones do, I don't know about Apple. Plus large laptops might well require the full 100W. 

  • in reply to wolfgangfriedrich

    "when a device requires a very special mode that not a lot of sources are able to supply"

    Frankly. I want a lot of the USB-C PD supplies to be encouraged to get in line to be reliable and be explicit in what they support. There is a huge mixed bag on USB-C cabling, power supplies and implementations of standards. WiFi has the same issue with ratified, uncertified, etc. and variable standards.

    I believe this partly goes back onto the "whose responsibility is that?" it's that clash between what's correct, what's morally correct and what's accurate - what it probably needs is regulation and accountability, like most standards.

    "It is the device manufacturer's responsibility to educate the customer, IMHO."

    I agree, with anything technical, there's always a gotcha of the assumed level of knowledge and it can be difficult to balance that for the audience. Especially when people digest information in different ways.

  • in reply to cstanton

    What if e14 turned this into a design challenge:

    design a USB-C PD that can take 110 - 240, 50-60 Hz, and

    • deliver the mandatory USB-C outputs
    • deliver the one requested by Raspberry Pi 5
    • comply with negotiation standards

    ?

  • in reply to Jan Cumps

    I'd personally love to see more electronics design - design challenges, often they're very focused on using already created mostly existing-solution products rather than building circuits and components to a reference design or similar for implementation.

  • in reply to shabaz

    I like this idea a lot, as a variant of Jan's design challenge idea only as DC/DC. 

    I checked TI's Power Designer. They claim switching efficiency of 98.3% for a 9V ->5V/5A switcher. I really want to try this now, might even work with a 9V/3A supply.

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