Power Supply A Guide to 12V PSU

[Valantar]

I.e. HTTPS as opposed to HTTP?

Not quite sure what he meant, but sounds like that. Might be a security certificate error, though. https://meanwell.com works just fine in Chrome at least.

Alrighty, is there a PSU calculator for mini-ITX boxes? The usual ones are geared for loaded boxes ... multiple GPUs, storage, opticals, lots of fans, etc. None offers options for the "GPU" to be onboard video. My tries on them, using a 35 watt CPU, 2 x 4GB DRAM, an M.2 SSD and a CPU fan, result in what seems to me to be very high wattage.

What is the accepted way to determine the PSU size?

Thanks,
Jeff

@Thehack beat me to it, but I'll post this anyhow, as I was pretty far into it before their post

PSU calculators are (usually) garbage, and routinely recommend ridiculously overpowered PSUs, so I'd stay away from them. Part TDPs are a decent measure, at least when adjusted through real-world numbers from reviews (some parts use far less power than their TDPs, like low-end Intel Pentiums or Ryzen 3s, while other blow way past them, like the 9700K and 9900K that can easily double their TDP in short-term turbo power). If you're using onboard graphics, the TDP of the chip accounts for that unless you're using an unlocked/overclocked part. For example, the 65W TDP Ryzen 5 2400G can indeed run at or below 65W, but it's also capable of using more than twice that if overclocked. There's also stuff like MCE for Intel (and similar schemes/manufacturer-specific power limit adjustments for AMD - not all motherboards will enforce TDP as a strict power limit at stock settings) to take into account. Reading reviews of your specific parts is a must.

For minor components, I usually calculate around 5W per SSD (SATA drives consume less than this, NVMe drives can consume a bit more, but not much), 15W for any 3.5" HDDs (they consume less in use, but need power when they spin up), and 10-20W for the motherboard and RAM combined depending on how many sticks, how big/complicated the motherboard is (number of controllers etc) and if you plan to OC (OC'ing = increased power delivery losses = increased power draw on the motherboard).

On top of this, add 20-30% margin for safety, power spikes, acts of god, etc.

For non-ATX PSUs you also have to look at two numbers: sustained power and peak power. For example the HDPlex 160W DC-ATX board can sustain 160W, but has no problem with 200W peaks. Peak power is what you should account for if you have a GPU with automatic clock adjustment, for example, as variable loads can lead to short-term power spikes before the clock speeds adjust.

So, let's say you're running a stock-clocked/power limited Ryzen 5 2400G, 2x8GB of DDR4, a single NVMe drive, and no GPU.
CPU: 65W.
SSD: 5W
GPU: N/A
Motherboard, RAM, etc: 15W
= 85W
+ 30% for safety
= 110W

Which jives pretty well with, for example, the ASRock Deskmini A300, which supports that + 1-2 2.5" drives and comes with a 120W power brick.

On the other hand, if you have the same configuration but let the CPU and iGPU run free:
CPU: 160W +
SSD: 5W
GPU: N/A
Motherboard, RAM, etc.: 20W
= 185W
+ 30% for safety
= 240W

 

[pepar]

Thanks. My build will be with a mini-ITX motherboard, 35 watt CPU, 2 x 4GB (or 2 x 8GB) DDR4, an M.2 SSD (and maybe an SATA SSD), Intel's onboard video connected to a computer display and an A/V receiver HDMI and a CPU fan. What would your experience lead you to recommend?

Oh, and the case I want to use will force me to use a pico ATX PSU.

Jeff

 

[Thehack]

Thanks. My build will be with a mini-ITX motherboard, 35 watt CPU, 2 x 4GB (or 2 x 8GB) DDR4, an M.2 SSD (and maybe an SATA SSD), Intel's onboard video connected to a computer display and an A/V receiver HDMI and a CPU fan. What would your experience lead you to recommend?

Jeff

You can probably get away with a 65W brick if size is an issue, but I recommend 90-120W as they're readily available.

 

[pepar]

You can probably get away with a 65W brick if size is an issue, but I recommend 90-120W as they're readily available.

I edited and added the pico ATX requirement due to a small case .. so a 120W is still recommended?

Jeff

 

[Thehack]

I edited and added the pico ATX requirement due to a small case .. so a 120W is still recommended?

Jeff

Yes. 95W is also good. 12V units are cheaper, but wide input units, like Hdplex or minibox wide input version may be better if getting a good quality brick is difficult where you are. 19V bricks are more available.

 

[pepar]

Not quite sure what he meant, but sounds like that. Might be a security certificate error, though. https://meanwell.com works just fine in Chrome at least.

That link works perfectly on my Windows/Firefox box. When I can, I will investigate my iPad/Safari issue.

Thanks for all of the help!
Jeff

 

[pepar]

OK, back again. I read the first post and found that the Mouser links aren't current. Is the first post maintained/relevant? People aren't soldering their PSU rigs, are they?

Jeff

 

[NateDawg72]

OK, back again. I read the first post and found that the Mouser links aren't current. Is the first post maintained/relevant? People aren't soldering their PSU rigs, are they?

Jeff

Yeah looks like the mouser links are broken. I've actually just googled stuff like "EPP-400-12" and shopped around, so I bought mine from arrow.com. I bought the "RPS-400-12-C" which is basically the EPP-400 with a steel chassis. I found & ordered all the JST connectors I needed after a bit of searching so I haven't done any soldering (yet)

Here are current links to mouser, who knows when these will break too. EPP-100-12 & EPP-200-12
https://www.mouser.com/productdetail/mean-well/epp-100-12?qs=Uzd/wh%2bZzhCwRoLkE3s%2boA==
https://www.mouser.com/productdetail/mean-well/epp-200-12?qs=C9r8PV/%2boWPIHyreaGus8g==

 

[pepar]

OK, I am willing to be sold on this but I must ask what is the advantage of buying one of these and adapting it as opposed to a brick that is enclosed and has built in wiring with connectors?

Jeff

 

[NateDawg72]

The advantages are just in form factor and/or reducing the amount of wires in the setup. If you find there is a complete brick / power supply with the connectors you need in a form factor that fits your PC, that's a much easier way to go.

If you find yourself in a situation where there isn't a computer power supply that fits your size / power / cable requirements, then going DIY with a meanwell power supply might be one of your only options The other option might be something HDPlex offers.

 

[pepar]

I have been an ATX guy since I started and only recently used an SFX. Now, to fit a mini-ITX board into a 7-3/4" x 7-3/4" case, I need to use a pico ATX PSU. From what I see out there, the DC-to-DC part is built on a small board attached to the 24-pin main board connector with other output and input connectors originating there. One of those is the input connector which will mount in the case so that the 12VDC output of a "brick" will plug into it.

You have guided me on the wattage of the PSU, the parts list I need seems clear, so my remaining question is do 80+ Silver, Gold, etc ratings apply to either the DC-to-DC or AC-to-DC parts? As this build will have some (non-critical viewing) video streaming from an NAS, is the "cleanness" of the AC-to-DC part important?

Jeff

 

[Valantar]

I have been an ATX guy since I started and only recently used an SFX. Now, to fit a mini-ITX board into a 7-3/4" x 7-3/4" case, I need to use a pico ATX PSU. From what I see out there, the DC-to-DC part is built on a small board attached to the 24-pin main board connector with other output and input connectors originating there. One of those is the input connector which will mount in the case so that the 12VDC output of a "brick" will plug into it.

You have guided me on the wattage of the PSU, the parts list I need seems clear, so my remaining question is do 80+ Silver, Gold, etc ratings apply to either the DC-to-DC or AC-to-DC parts? As this build will have some (non-critical viewing) video streaming from an NAS, is the "cleanness" of the AC-to-DC part important?

Jeff

Ah, I think you've misunderstood a bit here - these MeanWell units are for internal mounting, not external - most of them have exposed or semi-exposed circuitry and should definitely not be left around willy-nilly. If you're not going to mount the AC-DC unit inside of your case, you want and need a brick - and you'd then likely be better off getting a HDPlex 160 or KMPKT DC-ATX unit, as those accept 19V input an thus work with any off-the-shelf laptop power brick given a matching barrel jack.

There are of course also 12V external PSUs available, but the are more rare (simply because laptops are very common). If you're set on a PicoPSU or similar 12V DC-ATX unit, MeanWell also has external bricks that will likely do a good job. This one, for example, ought to work, or this one if you want more reserve power (though I doubt you'll need it) (the last one also uses a 4-pin DIN power connector, which would be tricky to adapt - standard 2.5x5.5mm barrel jacks are usually not seen above 100W).

80+ ratings are only applicable for ATX-compliant retail PSUs, and are thus not relevant for setups like this. In theory I guess you could submit a MeanWell+PicoPSU combo for 80+ certification, but that would be odd, as the parts could be swapped for others. The most common MeanWell series have pretty good efficiency (>90% across a large portion of their output range), but you also have to add in some (minor) conversion losses for the 3.3V and 5V rails off the DC-ATX board. External power bricks are rated by a system labeling them Level I, II, III, IV, V, and VI, where VI is the most efficient. If you can, get a level VI-rated brick (or EU CoC tier 2, though that's not as common), as it will have the lowest standby power, highest efficiency across its output range, and likely generally be produced to a higher standard.

 

[pepar]

Thanks. I kept researching after post and had found that Mean Well indeed makes "bricks." I found the model you linked and the one you thought you were linking and was stopped by the DIN on the latter. The 90-watter is Level VI so it's evidently as good as it gets.

Edit: I searched on the HDPlex you mentioned ... apparently I have more research/decidin' to do ..
Edit 2: Good grief, mission creep already ...

 

[Valantar]

Thanks. I kept researching after post and had found that Mean Well indeed makes "bricks." I found the model you linked and the one you thought you were linking and was stopped by the DIN on the latter. The 90-watter is Level VI so it's evidently as good as it gets.

Edit: I searched on the HDPlex you mentioned ... apparently I have more research/decidin' to do ..
Edit 2: Good grief, mission creep already ...

There's no such thing as mission creep in SFF. Any project should be expected to require infinite time and resources, and anything less than that is a nice surprise

But joking aside, once you get into the world of DIY PSU setups, it's a rabbit hole. @Thehack summed it up nicely earlier: The HDPlex and KMPKT units (as well as Mini-Box's wide input models) are useful as they work with standard laptop power bricks, but they cost more and need more space and cooling as they convert the 12V stage on board from your 19V (well, 16-24V or some such) source. They also top out at relatively modest powers due to this - anything above 160W sustained requires a larger separate unit to allow space to convert the the 12V rails (HDPlex has a 400W (IIRC) model that's on a separate board). 12V input units obviously don't need to convert any voltage for their 12V rails, so they're cheaper, smaller and run cooler, but limit your choice of AC-DC units as 12V bricks are somewhat rare. Finding them is no problem if you look, but they're not as plentiful. I have two or three 95W 19V bricks lying around from old laptops, ready to use - the most powerful 12V "brick" that's come into my hands is a 3A plug-in PSU from an external HDD. Not quite the same utility in that.

Tl;dr: I'd go with a 12V system if you can find a reasonably priced brick for it. If not, or if you have a spare 95W-or-so 19V brick lying around already, go HDPlex/KMPKT.

 

[pepar]

Thanks. The Mean Well GST90A12-P1M will work nicely and I found it on e-by-the-bay for $35 delivered. Anybody have any pointers for the pico ATX part? Please don’t point me to any 10x overkill part!

Jeff

 

[smitty2k1]

Thanks. The Mean Well GST90A12-P1M will work nicely and I found it on e-by-the-bay for $35 delivered. Anybody have any pointers for the pico ATX part? Please don’t point me to any 10x overkill part!

Jeff

I'd suggest PicoPSU's 90w plugin board (http://www.mini-box.com/picoPSU-90) because the 80w board doesn't appear to have a 4 pin motherboard header)

 

[Thehack]

I'd suggest PicoPSU's 90w plugin board (http://www.mini-box.com/picoPSU-90) because the 80w board doesn't appear to have a 4 pin motherboard header)

That one is missing 4pin eps. Most motherboards need both 24pin and 4pin atx. That one is just 20+4.

 

[Choidebu]

Thanks. The Mean Well GST90A12-P1M will work nicely and I found it on e-by-the-bay for $35 delivered. Anybody have any pointers for the pico ATX part? Please don’t point me to any 10x overkill part!

Jeff

https://j-hackcompany.com/?product=one2-plugin-120

From the man himself

 

[pepar]

I have been all over the place with which mini-ITX board I will use. Thin models, simplify the power supply issue by have a 12v/19v DC INPUT, one of them accessible on the rear I/O panel. While regular mini-ITX boards have either the usual 24-pin or 24+4 pin connectors on the mobo and require the pico ATX/AC-to-DC brick combo. Of course, complicating things further, there are pluses and minuses with each format, e.g. PCIe versions/lanes, M.2 capabilities, video out connectors, etc.

So, other than the case, I am back to square one ... with a headache.

Jeff

 

[smitty2k1]

That one is missing 4pin eps. Most motherboards need both 24pin and 4pin atx. That one is just 20+4.

Ah didn't realize it was only a 20pin ATX connector. Guess he would need to step up to the 150XT or J-Hack as @Choidebu mentioned