51–60 of 138 posts
Waste heat seems like it would be a thing? Even at 95% efficiency (which is unrealistic), we're looking at a 12W heater.
The size of these kinds of high wattage passively cooled power adapters is dictated less by component density and more by what you can spread and dissipate through the enclosure with safe touch temperatures.
Waste heat seems like it would be a thing? Even at 95% efficiency (which is unrealistic), we're looking at a 12W heater.
Is 12W meaningful heat? I mean, I have laptops that run 10-15W and it doesn't seem like much. I guess it feels hotter because it's a much smaller surface area, but not that much (laptop heat output is mostly over the CPU/mainboard anyways)
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Great ask. There's no reason devices couldn't negotiate lower power. With USB-PD, power sources offer Power Delivery Objects: different charge modes they can do. It's up to devices to pick. Right now most devices pick the highest power option (that they can handle). For a variety of reasons, it would be super sweet if we could pick lower power options! Maybe it's a multi-device charger & you want to leave more capaci…
PD interposer device that can mask PDOs?
why was 240W picked as the upper limit for PD? Why does there even need to be an upper limit?
Thus you get 5A @ 48V which is 240W.
On one side, I like the idea (and I use it a lot) with USB C to power a notebook. I have a small 65W travel adapter and I can charge my beefy HP Z-Book (it even works with a 45W adapter) or my smaller Fujitsu U939. But both notebooks still have real charging ports too and normaly I use those. A real charging port are much less fragile when moving the notebook while plugged in. USB C is very fragile and it is an very,…
Expensive in terms of cables or connectors?
In both cases, I've been paying considerably less for USB-C (cables and chargers combined) than for proprietary replacement chargers.
> it even works with a 45W adapter
My favorite thing about USB-C charging is that (at least Macbooks) it works even with lowly 5W chargers in a pinch! Sure, it takes more to fully charge a laptop that way – but I can sustain my Macbook Pro's charge with an 18W phone charger on an airplane no problem.
Earlier quoted context omitted.
Great ask. There's no reason devices couldn't negotiate lower power. With USB-PD, power sources offer Power Delivery Objects: different charge modes they can do. It's up to devices to pick. Right now most devices pick the highest power option (that they can handle). For a variety of reasons, it would be super sweet if we could pick lower power options! Maybe it's a multi-device charger & you want to leave more capaci…
> Very very achievable, with minimal effort. Not with how complicated the whole stack is... We still can't say "don't charge if other device has no AC power" even tho that info can be propagated via USB-PD...
There's a very old very extensive USB HID spec for a ton of battery & charger telemetry things, that for no good reason was never implemented. I'm not sure if USB-PD has overlapping way of sharing data like "is the other side also running on battery?" but we have had the technical possibility of answering that (and how much charge is left what the battery voltage is, but getting low power alarms, more) for literally decades & shame on us for never having implemented it.
why was 240W picked as the upper limit for PD? Why does there even need to be an upper limit?
Just watch: in the future we will have step up transformers instead of step down transformers so the charging cables can be thin again and charge fast
Obviously there's stepping up and down happening on both ends up this cable (since it's probably a 19V lithium ion battery in the computer), but at the end of the day you still need to decide on a safe and practical volts*amps number, and then spec the cables and connectors accordingly.
On one side, I like the idea (and I use it a lot) with USB C to power a notebook. I have a small 65W travel adapter and I can charge my beefy HP Z-Book (it even works with a 45W adapter) or my smaller Fujitsu U939. But both notebooks still have real charging ports too and normaly I use those. A real charging port are much less fragile when moving the notebook while plugged in. USB C is very fragile and it is an very,…
Is it? I’ve been using USB-C Macs since 2017 and I’ve never had any broken ports, despite some significant abuses (cable trips, grime in the port, etc). A few worn out cables, and failed chargers, maybe… but no problems on the laptop itself.
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That's not really how electricity works. Wall power is a stable supply. 120v going up & down in a sine wave. If someone is drawing 120w - 1 amp - your only control as a power source is to try to lower the voltage (voltage potential). Problem one: that will go out of spec with what devices expect, if you try to provide 80 vac instead. Problem two: switch mode power supplies that can handle sagged voltages will just tr…
There is, just not for "AC wall voltage". It could simply drop the voltage and expect the other device to say start limiting current when it goes 5% or more below nominal voltage. Akin to how MPPT works on solar chargers It "just" requires both sides to support that. Which won't happen as we already have USB-C if you want to negotiate the power usage.
Maybe the source sends S-O-S in Morse code. Maybe it sends a requested max power.
We can invent signalling strategies to communicate yes. EV chargers use HomePlug Green for example to commitcate. This could be consumerized & put into all devices, used to perform negotiations. https://en.m.wikipedia.org/wiki/HomePlug
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It’s designed around 48V and 5A. Higher voltages introduce additional risks around arcing and also get you into different safety regulations and requirements. Above 5A also starts to make cable and connector design difficult for a small connector like USB-C.
Last time I looked at the comms protocol, it seemed possible to request up to 10 amps. I'm not sure there's a physical spec for a matching cable, but there's also no way for a cable to communicate its current limitations.