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Dell PSU is “PD3” but cannot do PPS. Isn’t that non-conformant? OTOH, there is no USB-PD indicator to begin with. (thelemmy.club)
submitted 3 days ago* (last edited 3 days ago) by to c/askelectronics@discuss.tchncs.de
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I am trying to get a grasp of how to identify what power standards various PSUs claim to conform to. The label on this Dell PSU is ram-packed with info, but I see no direct claim that it supports USB-PD at all.

The range of voltages might imply that perhaps maybe it’s USB-PD, but I see no indication where they take credit for that; much less a particular PD revision. IIUC, that means if it’s USB-PD non-compliant and someone drags Dell into court, they can say to the judge “we never said it was USB PD-compliant”.

The review that probes this thing shows that the PSU is detected as PD3.0. Yet at the same time it does not support PPS according to the blogger. So wtf.. how can it be PD3 if it does not support PPS?

It seems Dell is banking on consumers not being keen to read the label. According to the blogger:

The odd thing is that it is advertising itself as a 96W adapter (20V/4.8A) which is different to the printed 20V/5A rating on the rear.

So it seems has Dell decided that if they do not benefit from advertising a capability, they might as well not mention it and downplay what it can do, for legal purposes.

The blogger goes on to test it with all kinds of fancy costly gear that no typical consumer would have. When I am at a street market rifling through a pile of dumped electronics, how do I know what I am looking at? Do any of the cryptic symbols on that Dell label suggest USB-PD?

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[–] [S] 3 points 3 days ago* (last edited 3 days ago)

Counter question: where does it say on there that it’s PD3.0?

Nowhere. I found no mention of PD anything which inspires some of my questions.

Perhaps it follows since stuff from the PD3 specs and that’s why that tester said it, but this is guesswork.

That’s indeed the sort of answer I was looking for. The testing device detects PD3. This somewhat suggests that electronically the PSU (falsely) identifies itself as PD 3.0-compliant.

Perhaps I’m misunderstanding you but the gist of your text is “why is this item not saying what a random guy said it should say??”

I want to understand the contradiction. The testing device declares that the PSU is PD3. But the test results led the blogger to claim it’s not PPS. So where is the lying occuring? I expect the PD protocols to establish a handshake whereby each side of the handshake discloses the PD revision it adheres to. Otherwise the protocol is quite shitty.

If we assume a non-shitty protocol, than the Dell PSU is falsely announcing itself as PD3 and the tester is just a messenger.

Edit: remember that companies need to pay fees when they advertise with the standard - they can just follow its spec without advertising it at all, I can see that happening for laptop producers specially as they don’t sell their power units as generic products (i.e. with a focus to market them).

That’s interesting. I suppose the fees finance a certification effort. And I suppose that’s fair enough. But if a device claims to be PD3 not on the label but makes this claim in the electronic protocol, the claim is still a claim nonetheless. People and machines rely on claims made by protocols. And I suppose it’s all legally dicey. Dell could not be easily prosecuted for false advertising if they wrote nothing on the box or label that a buyer would see. But the hardware is still lying about its capability and I would think that would (or should) have consequences.

legal liability?Dell’s ass might be covered as well if these PSUs are sold only with the appliance they drive, and the docs say to only ever use X with Y, do not sell separately, yada yada. Dell knows that most consumers just look for the USB-C connector and are happy enough if they see it.

But is Dell safe? What if someone attaches this Dell PSU to a 17.5v appliance. The appliance is told by Dell’s handshake that it’s PD3-compliant. So the appliance starts the negotiation at 20v and tries to use PPS to get the voltage down to 17.5. But because the Dell PSU lied, it sticks with 20v and fries the appliance. Is that possible?

what happens at the street marketThe reality is that the laptops get separated from the chargers. At my local street market, laptops almost never come with a charger. Then some other people are only selling chargers and no laptops. Chargers were fished out of dumpsters, often. Of course it’s an ecocidal defeat of the purpose of USB PD to a large extent if Dell’s business model flies.. if they can still say their Dell charger is only for Dell laptops, then it’s basically e-waste when separated from the laptop.

Dell buyers should pay attention to whether new laptops are advertised as using USB PD. Because if so, then it’s a deception that the laptop includes a charger that is not. Or is left for Dell owners to guess that their laptop depends on a USB PD PSU?

Can sophisticated consumers get stung by this?An advanced consumer would show up to the street market with a test rig that feeds PSUs from an inverter. They would quickly see “PD3” on their fancy test tool and conclude the PSU is worth buying. Only to later find after deeper tests that it’s not actually PD3. Because the PSU lies in the handshake.

Yet another element of the USB-PD shit showWhen OEM PSUs are sold on the 2nd-hand market with a list of output voltages and a USB-C connector, buyers are obviously going to expect the PSUs to drive their USB-PD appliance. It does not say on the label of that Dell PSU “only for Dell laptops, not USB PD compliant”. But by arbitrary chance, the PSU will happen to work for some non-Dell appliances. But we cannot count it. We can only guess. It’s indeed a fucking shit show.

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