HackSpace magazine

Direct from Shenzhen – USB-C power supply

By Ben Everard. Posted

Getting electricity into your projects can be surprisingly challenging. For low voltages and small currents, USB has become a very common standard. It gives you 5 V and, if you’re careful with your power supply, you can probably get about 2 A. Most people have a few of these power supplies hanging around and, if you need to take your project on the road, then there are lots of rechargeable power banks available at different capacities.
USB-C has the potential to provide much more power through something called Power Delivery (PD). When you first plug a USB-C device into a power supply, the power supply will send over 5 V. This should be enough to run the power supply circuity and get everything started. Your device can then request more power. Not all USB-C power supplies can supply more than 5 V, but your device can negotiate to receive up to 5 A at 20 V, if the supply can handle it. This is potentially a lot more flexible, but also requires some more sophisticated electronics than just a power socket.

Fortunately, there are off-the-shelf modules that help do the hard work for you. We tested out a PD 3.0 protocol current voltage trigger that came from Banggood (hsmag.cc/cr0UR2). For £9.36, we got the board and a USB-to-barrel-jack cable, including delivery to the UK.

The first thing to say about this board is that the output is via a regular USB port, but it outputs the full voltage from USB-C PD (up to 20 V). In other words, DO NOT PLUG ANYTHING INTO THIS USB PORT THAT IS EXPECTING A STANDARD USB VOLTAGE. You will damage it, and you might set it on fire. Why the designers chose this as an output connector, rather than having a barrel jack, is a mystery to us.

That warning in place, let’s take a look at what the module actually does. There are both male and female USB-C ports, but they both work in the same way, and you can supply power via either one. Having both is handy, as it means you can connect it directly to either a computer or a power supply. Once the board is powered up, the three seven-segment displays light up, displaying the voltage. There are two buttons on the board: one requests a higher voltage, the other a lower voltage. These allow you to scroll through the available power profiles.

Our laptop charger supplying a full 20 volts via the USB-C PD module

In this usage, you can select the power you need for your project and get it to come through a compatible USB-C device. In theory, it can supply up to 100 watts (20 V, 5 A); however, we would have some concerns about running this much power through the device. If you want to push the limits of USB-C, then we’d strongly recommend a module from a reputable manufacturer (there’s not even manufacturer’s information with this board).

This module works well for prototyping, but it would be nice if there was a way to set the voltage a little more permanently. It does remember the power profiles between power-offs, but if anything taps the button, it’ll shift the power. In principle, you could remove the buttons once you had the power profile you want selected. It would also be nice if there were a digital interface to this so you could interact with it from a microcontroller, but we’ve only seen this capability in more expensive boards.

We can’t explain the decision to have a USB port that outputs more than 5 V – it’s damaging, and potentially dangerous

If you have a spare USB-C power supply, or USB-C portable power bank, this is a cheap way of accessing its power modes for prototypes, but you’ll probably want a more robust solution if you’re planning on using the power for any length of time.


From HackSpace magazine store