4 ms·

The relevant number here is 15W. In principle USB C goes up to 240W now, but that isn't relevant here. USB-C power is negotiated, with a full blown two way ne

The relevant number here is 15W. In principle USB C goes up to 240W now, but that isn't relevant here. USB-C power is negotiated, with a full blown two way negotiation if you want more than 5 volts (or to draw more than 3 amps). Framework laptop ports don't support outputting more than 5V or 3A and so will max out at 15W. That is, this isn't a "struggle" -- because USB-C has negotiated power in general, just because it is possible to build USB-C ports that support 240W doesn't mean that a random port on a battery powered laptop has to support anything close to that.

koromak 3y ago
Can you explain what "negotiated power" means? Never heard of it, maybe the hardware on the receiving end needs to have built-in circuits which signal to the generating device that it can handle a certain voltage?
- zmgsabst 3y ago
  That’s correct. The port powers up in the default low power mode, but the attached device can signal that it supports more if the device can provide it. You want to start off with low power — since starting off with high power could damage devices that don’t support it.
- deleted 3y ago
  [deleted]
- zamnos 3y ago
  Yes exactly. You plug in the cables and then there's the following conversation: Laptop: *Om nom nom, 5 volts, yum!* Power supply: Hey, I can do 5 V, 9 V, 15 V and 20 V Laptop: I hear ya. Laptop: Can I get 20 Volts? Power supply: I hear ya. Power supply: Here's 20 volts! You get the idea. All the way up to whatever the device will accept. Past that, the device rejects the offer from the power supply. The original spec lists 5 V, 9 V, 15 V and 20 V, with support of for volts being kinda common because that's what cars use so the circuitry support already exists. According to spec, the charger is supposed to support all the voltages lower than it's max, but ofc not everything is spec compliant. 20 Volt @ 5 Amp is 100 watts which was the old maximum power usb-c PD could do. But it turns out that wasn't enough, so they renamed that to be Standard Power Range (SPR) and released when Extended Power Range (EPR). EPR adds adds 28 V, 36 V and 48 V @ 5 Amps, to the spec, for a new maximum of 240 Watts of power. (Longer desc of the conversation in table 5 in https://www.ti.com/lit/an/slva842/slva842.pdf https://www.ti.com/lit/an/slva842/slva842.pdf )
eru 3y ago
Oh, when I wrote 'struggle' I wasn't referring to the negotiation or USB-C. I was referring to the ability of the rest of the laptop to keep that power flowing, even if they wanted to.

koromak 3y ago

Can you explain what "negotiated power" means? Never heard of it, maybe the hardware on the receiving end needs to have built-in circuits which signal to the generating device that it can handle a certain voltage?

zmgsabst 3y ago
That’s correct. The port powers up in the default low power mode, but the attached device can signal that it supports more if the device can provide it. You want to start off with low power — since starting off with high power could damage devices that don’t support it.
deleted 3y ago
[deleted]
zamnos 3y ago
Yes exactly. You plug in the cables and then there's the following conversation: Laptop: *Om nom nom, 5 volts, yum!* Power supply: Hey, I can do 5 V, 9 V, 15 V and 20 V Laptop: I hear ya. Laptop: Can I get 20 Volts? Power supply: I hear ya. Power supply: Here's 20 volts! You get the idea. All the way up to whatever the device will accept. Past that, the device rejects the offer from the power supply. The original spec lists 5 V, 9 V, 15 V and 20 V, with support of for volts being kinda common because that's what cars use so the circuitry support already exists. According to spec, the charger is supposed to support all the voltages lower than it's max, but ofc not everything is spec compliant. 20 Volt @ 5 Amp is 100 watts which was the old maximum power usb-c PD could do. But it turns out that wasn't enough, so they renamed that to be Standard Power Range (SPR) and released when Extended Power Range (EPR). EPR adds adds 28 V, 36 V and 48 V @ 5 Amps, to the spec, for a new maximum of 240 Watts of power. (Longer desc of the conversation in table 5 in https://www.ti.com/lit/an/slva842/slva842.pdf https://www.ti.com/lit/an/slva842/slva842.pdf )

eru 3y ago

Oh, when I wrote 'struggle' I wasn't referring to the negotiation or USB-C. I was referring to the ability of the rest of the laptop to keep that power flowing, even if they wanted to.