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Comment by smallmancontrov | Hacker News Reader

Speaking of which, does anyone know a line of PD Decoy modules to convert barrel jacks to USB-C without the atrocious behavior of "oh, the charger doesn't have 12V, here's 9V have fun!" that the early ones all did? Ideally I'd like a little red light to come on or something, but I'd settle for not silently browning out the device.

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The vflex has a status LED that shows negotiation status. When it fails it will still output 5V, though, they don't seem to have any mosfet to switch the output off entirely.

https://werewolf.us/

I don't think I've ever seen one of those type of converters output anything but 5V upon negotiation failure. Which one did you use that did that? Their logic being "pick the closest available voltage" I presume?

iirc theres ones that do. However I dont recall there being any clean fix to the amperage constraint issues. Especially when a lot of usb-c chargers will vary output as they heat up with usage.

Which is kinda part the issue, usb-c charging bricks, they aren't usb-c power supplies, there is no expectation of sustained output capacity. Thankfully at least some the multiport ones have renegotiation more or less solved cleanly rather than what is essentially rebooting the PD controller.

sounds like someone needs to create a DC-DC charger

I mean, so long as it cuts off and throws a red light I'll figure it out, especially if the brick got toasty, and then I can find a new brick. My problem is that "best effort" seems to be almost universal behavior among PD triggers and it multiplies the failure modes.

You ideally want to get a USB-C brick that's over specced and from a reputable brand. Like if you get a macbook 140w usb-c brick it will work fine with everything.

Even for actual PSUs it's always been the advice that you want a decent amount of headroom to avoid issues.

There are things like this: https://www.adafruit.com/product/5501 haven't used it, trying to find one for my mini pc, mostly so I can use a usb c power bank as a tiny DC ups.

The description explains (in bold, multiple times) that it has the awful behavior I am looking to avoid.

Those are called trigger boards. I haven't found one with buck converter to make 12V. 12V is in earlier PD standard so lots of chargers support it but you have to check each charger and lots don't say. The guaranteed solution is PPS chargers that have variable voltage.

Don’t think you’ll find it cause it’s not an issue with the decoy - that’s the expected behaviour. 12v isn’t mandatory. Which is insane but here we are.

On the plus side some of the bottom tier anker chargers will do 12v.

Plus I think the very new PPS ones should too

Transistors exist. Load switches exist. Looking at Digikey, the expensive ones cost $1 in quantity. I'd pay considerably more than $1 per unit to have this feature that I consider necessary for a minimum viable adapter. Based on these comments, though, TAM is probably tiny.

Think with these low end decoy triggers you’re lucky if it implements standard never mind the optional parts.

You could always request a non optional feature and convert it up/down yourself

Yes, this is one of those "I can't believe I'm considering making it" things. I might actually go forward if I had the slightest confidence I could sell it and amortize my time, but looking at the comments here, who not only didn't understand the problem but didn't understand the problem after having it explained to them -- TAM is tiny, it'll never amortize. Sometimes you just have to scratch an itch, though.

Actually, that was 5v, not 9!

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