Power Supply On 19V adapters and peak surge currents

[Shahmatt]

I'm trying to decide on a 19V external adapter to pair with a 160W 19V internal DC-DC unit.

In many reviews it's been suggested that any laptop 19V adapter will work fine.

But I remember reading in another thread (I think here on SFF) that laptop adapters do not handle peak surge current requirements very well as they are usually designed to charge laptop batteries where the demand is more stable.

If this is the case does it make sense to purchase a laptop 19V adapter? Or is it better to go with the kits that comes with the DC-DC unit?

I have no electronics experience whatsoever so any input is appreciated. Apologies if this is a dumb question.

 

[Josh | NFC]

This isn't a dumb question at all. Really good question to ask. The BEST way to answer your question is to ask what your hardware is, that way we can look up actual power requirments for the components. We have done ALOT of experimenting here to find the best quality bricks for powering these systems--the information that any laptop brick will work sadly is not good info.

For the most part, Nvidia and Intel's published TDP is a great way of ballparking if your brick will work, but there are certain GPUs that can peak surge as you put it and make that number useless.

Generally, I keep it simple and recommend the DA330PM111 as a 19v solution. The genuine Dell 330 I find is a pretty tough brick that can handle some minor peaking, but be aware it varies from brick to brick, and silicon to silicon in your PC.

If you go with a 12v solution, there are several really good bricks I recommend that can handle really crazy peaks, but the HDPLEX 160 is so good that its hard to justify the extra work needed for 12v.

 

[Kmpkt]

The safe rule of thumb with laptop adapters is add 10% for peak. The HDPlex units (300W in particular) are built with a much higher peak. I know the 300W will hit auto protection shutoff at 400W.

 

[Shahmatt]

Thanks for the replies. My concern was actually more about the slew (I think that's what it's called?). In the other thread it was pointed out that the components power requirements can ramp up quite suddenly with Turboboost for example. But with laptops the brunt of this is taken up by the battery. The adapters are spared of this surging and they are in fact designed to cut off if the slew is too high.

I guess the Dell might be handling slew quite well, but how about other units? Is it possible to tell from the specs?

Edit: Based on my planned future build I'm looking at about 130W. No GPU, assuming 65W TDP AMD Ryzen APU.

 

[Kmpkt]

The reason people use the 330W Dell is that for the bulk of the hardware we're using, 330W is overkill so the overcurrent issue becomes somewhat moot. I had a ~120W system on a 150W Razer Laptop brick last year and fried it on what I can only suspect was a coordinated CPU/GPU spike. Given what you're planning on, I would suggest nothing less than a 180-200W brick. The HDPlex 160W AC-DC would also be a solid choice.

 

[Shahmatt]

The reason people use the 330W Dell is that for the bulk of the hardware we're using, 330W is overkill so the overcurrent issue becomes somewhat moot. I had a ~120W system on a 150W Razer Laptop brick last year and fried it on what I can only suspect was a coordinated CPU/GPU spike. Given what you're planning on, I would suggest nothing less than a 180-200W brick. The HDPlex 160W AC-DC would also be a solid choice.

I've just been talking to a friend of mine who is an Electrical/Computer engineer and does this sort of thing for a living. I asked him about adapters.

He basically said something like this about laptop adapters:
1. It's true that laptop adapters are not designed to react to and be stable with rapidly changing power draw.
2. No adapter of this sort is easily available commercially.
3. Increased power draw may cause the voltage to dip but it would not cause a cut-out - according to him no one designs under-voltage trips. Under-voltage conditions is usually treated through a feedback loop to boost voltage.
4. But the CPU may not like the voltage changes and may restart - cause glitches - be unstable.

Coming to the ATX psu:
1. ATX PSUs handle changing voltages through having lots and lots of capacitors which store charge and discharge when necessary to smooth out the power draw. So get a PSU with lots of capacitors.

I didn't ask him but I guess he'll like the HDPlex 400W which seems to have plenty of capacitors on it.

 

[Julio Espinosa]

You can use the PSU calculators, like:
https://outervision.com/power-supply-calculator
Those use an average power draw per item and give you an estimated wattage use and a recommended psu.
If you won't use a dedicated Graphics Card, I would suggest the HD Plex 300W AC-DC.

Just remember that Ryzen 3, 5 and 7 don't have Integrated Graphics (they are not APUs), so you will need a Graphics Card.