A swift PSA about the problem you’ll find with GaN chargers and single board computers and other USB-C powered devices…
GaN is cool
What? What’s with the picture? That’s Gan, from Blake’s Seven (a fine SF show of the seventies and one that screams for a modern reboot) who happens to share a name with GaN chargers. GaN in this case stands for Gallium Nitride, a substance which allows designers to build transistors that run at higher voltages and temperatures. That makes them great for building small but powerful chargers.
As single board computers become more power hungry, they are also great, for powering that Pi 5 with an AI board on top and an SSD underneath, or that small WiFi router you use at events to get everyone bridged and online.
Single port GaN chargers are not a problem in this scenario, but a time will come when you see multiple USB-C ported GaN chargers and think, because they put out lots of power, they’ll be great for powering your board, your wifi and whatever other gadget you are working on your worktop.
How it goes wrong
And thats where things will currently come unstuck. You’ll have your WiFi and then plug in the SBC and, wait did the WiFi reset? It did! Lets unplug and plug in the Wifi router and, WOAH, the SBC just reset!
As I understand it, GaN chargers have chipsets which take the charger part of the name very seriously. Chargers are there to charge battery devices, they aren’t power supply units. The chipsets expect the devices they are powering to be battery powered and it won’t be affected by a short disconnection.
But why a disconnection? Well, when another device is plugged in, the chipset in the charger needs to renegotiate all the power its supplying to all the devices its connected to so it can work out how to balance the power across all the devices. And that means disconnecting all the currently plugged in devices and restarting the power. And thats why the multiple port GaN chargers will disconnect when you plug another device in and stop your WiFi or reboot your SBC.
Fixing it
The solution? Only use the multiport GaN chargers for things you plug in and leave on. Don’t be tempted to pop in anything to that spare port. Use single port chargers or single cable power supplies for anything you need to be consistently powered or mingling with devices being plugged in and out. Save yourself the embarassment of when you figure out why everyone keeps saying the WiFi keeps disappearing.
That said, there’s are chargers coming on the market which don’t suffer the disconnect and renegotiate problem. But I’ve yet to get and test one of them in the field. So for now, I suggest taking care.