[vcf-midatlantic] [off topic] - GaN USB chargers and temps

[David Riley]

On Feb 21, 2024, at 2:57 PM, John Heritage via vcf-midatlantic <vcf-midatlantic at lists.vcfed.org> wrote:
> 
> Hey folks -
> 
> Looking for some insight from the hardware inclined here.
> 
> GaN USB chargers are touted as being able to deliver higher power in
> smaller form factors (I.e. charging a 65W USB device while the size of a
> “standard silicon” ~ 10-20W USB charger).

Lower parasitics and higher electron mobility are a real game-changer, though the real winners are the people building radars with it. :-)

> I know on paper GaN can run a lot hotter successfully than silicon (>150C
> for example), but I’m wondering - when you have a GaN USB charger that runs
> pretty hot for long period of time, is it really safe?   Aren’t there
> likely other components in the charger that don’t have the increased heat
> tolerance of GaN semiconductors?

This is a valid concern, though in most consumer equipment, my concern would be the plastics surrounding everything; if it gets too hot, things can soften and do things like cause mains shorts, which are Big Problems.  If it's well designed, the majority of the heat should be localized (though any heating shortens the life of every component because it accelerates the effect of inevitable chemical effects, Bil Herd did a great VCF EDU talk on this wrt MTBF calculations), but cheaper devices may fail prematurely, sometimes catastrophically.  I've generally been happy with the build quality of Anker devices, if that helps.

> I’m asking as one of my GaN chargers gets hot enough to the point that I’d
> be really worried with a traditional PSU.  It only happens if I had two
> devices attached that need a full charge - once they’re topped off or
> higher up in charge temperature is no issue.

Hard to say.  If you smell the telltale smell of hot plastic, be worried.


- Dave