This is a placeholder topic for “USB-C 112W PD Device Power Supply” comments.
This slim & lightweight 112W USB-C power delivery (PD) charger offers fast recharging for MacBooks, Nintendo Switch and other type “C” devices. It’s also fitted with a 2.4A USB charging output for powering or charging other peripheral devices.Read more
It would be helpful to have more detailed specifications. What is the maximum current at each supported PD Voltage.
You should read the description thoroughly.
- Output: USB C cable (5-20V 5A max), USB A port (5V 2.4A Max)
- 90W power delivery 2.0 output for modern USB C type devices.
- Auxiliary USB type A charging output (2.4A max).
1, USB type C, 5 to 20V 90W. Work it out Current (A)= 90 (W) / volts. With a maximum of 5A or 90W (whichever is the lower) at any voltage
2, USB type A, 5V @ 2.4A = 12W
So all the information is there, you just have to extract it.
Now 90 + 12 = 102 so I don’t know where the 112W comes from. Maybe that is the absolute maximum from the device at any one time.
Thanks for the somewhat condescending reply. Nonetheless your effort at explaining P=IV is one of the better that I can recall.
I was seeking confirmation that the full 5A max is available at every PD voltage, and 5A negotiated power is available at every voltage over PD.
My apologies for not being clear on why I was requesting the full specification.
In theory if that is the case, this supply can power the new Raspberry Pi5 at its full requirement of 5V /5A.
I will buy one and test this.
The reply was not meant to be condescending by any means.
The implication does however suggest that at 20V you are not advised to assume 5A. It reads like 5A is available up to 90W and 5A @ 20V is 100W so reading the specs, at 20V the max advisable current would be 4.5A.
Yes that would be correct.
Keep in mind though that if requiring the full 5A or 90W you are asking the device to supply maximum. Now I don’t know how much “fudge factor” or headroom is built into these specs but I suspect none. So if you are asking and using the max you are pushing your supply to limits. It’s just something that I personally don’t like to do. I feel that by doing this you are making reliability a bit marginal. It’s just a habit that I have got into over the years but by following this line I tend not to have too many power supply problems.
Could be a throwback to my working days and involvement with high reliability requirements for projects (like military, Air traffic control etc). One later project everything had to be de rated to 50ºC. The rated 100W of a power supply disappears at an alarming rate when the temperature goes up a bit. I forget the percentage headroom used but could have been in excess of 50%.
Completely agree on the de-rating. Hopefully partly covered by the mysterious missing 10W…
Unfortunately very few PD supplies that can do 5V/5A for the Pi5 exist.
You can’t assume that the full rated power will be available at any particular voltage. It all depends on the version of USB_C that is implemented. It appears it might be 2.0 in this case, which would be 3A at 5V. See:
Welcome to the forum!!
I checked with our supplier and the box in stock, unfortunately each of the power ratings arent explicitly rated. I’m not sure where that 5A max came from, but can help with compatability Re: Pi 5.
When trying to boot with this power supply:
With one of our test supplies:
All is not lost though, we have an ETA for the official supplies, sometime in the next fortnight they ought to be available!
The web page says:
- Output: USB C cable (5-20V 5A max), USB A port (5V 2.4A Max)
So short story this will NOT be what the Pi 5 wants according to the pics.
Again I point to the information from the Raspberry Pi Corporation.
While USB-PD capable phone chargers advertise greater than 15W of power, virtually all of them achieve this by increasing the voltage instead of providing more current at +5V. If you are using a power supply that cannot provide 5A at +5V on first boot you will be warned by the operating system that the current draw to peripherals will be restricted to 600mA.
Just throwing in the 2c here. As far as I can tell, this supply can fluctuate from 5-20V depending on the negotiation with the connected USB-PD compatible device.
The quote Jim linked covers this perfectly, even though the wattage on this PD supply is sufficient, the voltage-to-current at 5V won’t be enough for the Pi 5. As with the Pi 4 the general recommendation is to always use the official Pi supply where possible, once it’s got Australian certs (assuming it hasn’t already, I haven’t checked recently) and available here it’d be best to just run with that.
The more I look into USB-C PD, the more concerned I get.
My biggest concern is, a poorly designed power supply will provide the wrong voltage leading to destruction of the device it is powering. ie 5V device gets hit with 20V.
Everything I read says 5V 3A, without going into the intricacies of the Standard.
This from the Wiki page, unsure if the Standard says this but makes sense to me.
All USB-C cables must be able to carry a minimum of 3 A current (at 5 V, for 15 W) but some can carry 5 A current (at 20 V, for 100 W). USB-C to USB-C cables supporting 5 A current must contain e-marker chips (also marketed as E-Mark chips) programmed to identify the cable and its current capabilities. USB charging ports should be clearly marked with power capability.
I wonder if the Raspberry Pi Corporation may have boxed themselves into a corner, wanting 5V 5A or is it clever marketing ploy to only use the official power supply. I would really like to hear their reasoning.
A youtube video by Jeff Geerling interviewing Eben Upton (CEO) cleared a few points for me. They consider all users and what users want; if something may only be used by 10% it does not get into the design. Makes sense on one level but can be very frustrating if you really need that feature and have to find another way to do it. The absence of ADC is used as an example.
This USB-C PD is something I will be watching closely as to how it develops.
There have been some excellent debates on the Raspberry Pi pages about PD, Standards, profiles etc. I won’t do it justice to provide a detailed summary here. In short the view held seems to be trending towards the consensus that the spec allows for more current than required to be advertised and delivered if a supply is able to do it.
Two supplies exist - the Pi official supply, and the Radxa supply for the Rock SBCs. Both advertise and deliver 5A at 5V.
The excellent debate and insights here are why I asked for the detailed specs, as several folks pointed out, assumptions don’t work for PD negotiations.
Jim, to your last point there are some useful but dirty hacks available on aliexpress and eBay - USB-C to 5x2.1 barrel plugs that contain e-marker chips asking for 5V, 9V, 12V etc. these are “hard” programmed, and basically dumb cables. The wrong one will absolutely be capable of sending 20V into a 5V socket etc.
Well said. You have put up a couple more reasons I don’t have a RPi. It seems that a lot of effort goes into shuffling around operating systems and software etc until a combination happens to work. Then, eureka, problem solved. Until the next release. I haven’t enough time to go into all that, If I purchase a processor to do a job I expect it to do that job with my power supply.
Anyway to date I have not had a use for a processor, a controller has done all I need so all good.
I have suspected that for some time.
I might be missing something here but how would say a RPi5 want 20V. Surely if any add ons like motor speed devices would be powered separately if such voltage needed. Or I shudder, don’t tell me this voltage is shunted through and provided via one of the USB ports. I don’t see RPi magically able to provide 20V at some amps via a GPIO pin. I might read about it somewhere if I feel inclined…
To the all important cable.
The voltage rating of the wire itself would be determined by the insulation, the cable as a whole would include any connectors.
The current rating of the wire is determined by the amount of copper or other material, the cable as a whole would once again include the rating of any connectors.
The reference to the cable standing 20V @ 5A being 100W is not relevant as far as the cable goes. It is not dissipating the 100W, the load is. The only time the cable would dissipate this sort of power as if it had a short circuit at the end. In which case it would probably melt unless the power supply gave up.
how would say a RPi5 want 20V. Surely if any add ons like motor speed devices would be powered separately if such voltage needed.
You’re spot on here. There wouldn’t be much of a Pi left if it were given 20V. I’m not sure of the current limit on the Pi 5’s GPIO pins but the Pi 4’s was 16mA per pin. Total not exceeding 50mA.
For the same reason that an Arduino would need 9V. Regulate it to 5V and 3.3V on-board for the processor and support chips, supply regulated 5V at 3A for multiple USB_C ports, perhaps even a regulated 12V supply. The reason that in this case it doesn’t want 20V is that it wasn’t designed for it. A different design could definitely take advantage of a 20V supply.