Power Supply Looking for suggestions for the smallest possible ~240W 12V PSU

[Marmotta]

I've started toying with the idea of a compact PC build, just to push my skills as far as possible and hopefully learn some new ones along the way.

I've been thinking of a build using an ASRock X300 motherboard and Alphacool ST25 120mm radiator, which should just about fit side-by-side in an Xbox One S case. I'm also looking at installing an RTX 4070 FE or something of a similar footprint (laying on top of the motherboard, but with custom waterblocks), but my current idea of having dual Xbox One S 120W power supplies leaves little to no room for a GPU since even the smallest one would be a couple of centimetres longer than the X300 motherboard. I can remove the left (in the photo) PSU from the plastic enclosure to gain a little bit of room, but probably not much due to the I/O on the rear of the case.

Therefore I'm also looking for other PSU options which might just about squeeze in the case and create a little more room where needed. Combined TDP for the CPU and GPU would be 235W (which for now I'm definitely looking at undervolting), so would need something with a minimum of 240W (same as the combined Xbox One PSUs). I've had a little look around and haven't seen any standout options that would definitely fit, so just wondering if anyone knew of any options off the top of their head?

 

[Gingerbeer]

It's pricey, but I can recommend one of these. Currently running a 9700T and RTX A2000 in a 4 litre chassis - they don't come close to your projected power use, but I have no complaints. Though, I'd probably recommend pointing a small fan at it or, at the very least, making sure it gets some air from the rad fans if you're using 200W+.

Really not sure how realistic it is to try and power a 4070 from that, regardless of undervolting. I can't say I've spent much time researching though.

Depending on your space - you might be better with a beefy DC-ATX converter and an external brick.

[edit] Just realised HDplex do a 500W GAN PSU now, which is much better value than the 250W model, but a bit girthy in comparison.

 

[scatterforce]

External bricks with 240 watts:
Dell
SlimQ
Walmart

External 330 watt brick:
Dell (Dell's website sells the OG fat model)

All of these will need a DC-DC converter to get to 12/5/3 volts the PC needs, but it will free up a bunch of space. Otherwise, @Gingerbeer already recommended the best internal PSU's.

 

[princess_daphie]

There's also this guy:

https://www.mouser.ca/ProductDetail/MEAN-WELL/GST360A12-C8P?qs=rSMjJ%252B1ewcQsFVFxjhSAPg%3D%3D

Which you can combine with cheaper 12V pico units, like this one could be beefy enough to support your setup: https://www.aliexpress.com/item/1005005377974011.html

Or this one maybe even, but would require a tiny bit of soldering to add the 12V PCIe connector: https://www.aliexpress.com/item/1005004125633668.html

And as far as internal 12V AC/DC power supplies, I've bought this one and it seems pretty reliable and compact: https://www.aliexpress.com/item/1005004992822044.html

Good luck, that looks to be a fun project!

 

[princess_daphie]

It's pricey, but I can recommend one of these. Currently running a 9700T and RTX A2000 in a 4 litre chassis - they don't come close to your projected power use, but I have no complaints.

I'd be very interested in seeing that build!!!

 

[Marmotta]

The RTX 4070 FE has a TDP of 200W, I plan on using a Ryzen 7 5700GE with a default TDP of 35W, so it'd be tight which is why I was planning on undervolting.

I had a look at the HDPlex range, but I think most of them are a bit too big, plus the GAN PSU ATX connections would be pretty redundant. I'd also really like to keep everything internal if possible, in order to maintain a 100% stock look.

Had a bit of a search this morning and was looking at this one that might fit:

VCCS300S-12 | Digi-Key Electronics

Order today, ships today. VCCS300S-12 – Open Frame AC DC Converters 1 Output 12V 85 ~ 264 VAC, 120 ~ 370 VDC Input from Vox Power Ltd.. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.co.uk

It's obviously a lot more expensive than using two Xbox power supplies, but might be small enough to fit - printing 3D models of them to visualise how to place it in the console - and 300W gives me a bit of headroom.

 

[princess_daphie]

Oh geez, I realized the STX board only takes 12V as input, right? Then ignore my picopsu recs, lol! But my 12V AC/DC suggestions are still valid, I think. The 330w external brick, or the 250w (with a fan) internal one.

 

[Marmotta]

Oh geez, I realized the STX board only takes 12V as input, right? Then ignore my picopsu recs, lol! But my 12V AC/DC suggestions are still valid, I think. The 330w external brick, or the 250w (with a fan) internal one.

It's advertised as 19V, but the AM4 X300 can run on 12V as well, which should be less of a headache.

 

[princess_daphie]

It's advertised as 19V, but the AM4 X300 can run on 12V as well, which should be less of a headache.

Ohhh! I see, well, I don't know but many devices can't deliver as much power when you run them on lower than their rated input voltage? Hopefully this board has very good step-down conversion. If not, the 250w AC/DC unit I recommended has 12V/19V/24V options, cost the same thing!

 

[msystems]

For this plan its easier (smaller overall?) to use a 19v gan brick and a 19->12v step down (not atx just a step down) just for the gpu which is about the size of a matchbox, or double them up for a bit more wattage (one for the riser and one for the 8-pins). For this method you only have to worry about the power the GPU will use since the x300 can just use 19v. There are also pico dc-atx in the 200-320w range which can do this in a little bigger size. The annoying things about this way are making a lot of custom cables and making a relay to turn the GPU on if you want it to intelligently turn on with the stx board.

Since the 500w gan came out, the total size is probably similar to the slimQ 330w 19v gan brick + matchbox picos. So that might be a good option also.

 

[REVOCCASES]

If you're OK buying via Superbuy from China...

1) 330W 19.5V GaN from SAVAGO (it's small enough to put it inside your build, if needed): https://item.jd.com/10073230587838.html

2) for 12V conversion:

either this: https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-4240825827.35.509546ba7xlKq5&id=677451355552

or this: https://item.taobao.com/item.htm?spm=2013.1.0.0.12f32b2cr6jiTQ&id=623738560461

however, like @msystems mentioned, there is still the problem about switching the GPU on/off together with the STX board... unfortunately I've run out of Load Switches for this kind of application, so I'm now using an "eGPU Riser" from JHH Link in my current build and that works like a charm...

 

[Marmotta]

Thanks everyone for the suggestions, as much as it's sort of cheating in my own head, I'm now leaning more towards using the SAVAGO GaN as an external power supply (I have a friend in Beijing who can probably forward it to me). The internal 12V options I've been looking at drop off in performance drastically around the 50C mark whether using forced air or not and I'm not sure how effectively I'd be able to cool them. Using 19V would also allow me to potentially use the Deskmini B660 instead of the X300 - I'm not sure there's any performance advantage despite it being a lot newer, but the 35W Intel -T processors are easier/cheaper to get hold of than the -GE Ryzen ones.

It would still be a bit tight to drop in one of the ready made Taobao 12V stepdown converters into the build, so thinking of designing my own integrated into the system PCB (which will be there anyway for I/O) using a buck converter with an enable pin that I can either connect directly to the motherboard or via a MOSFET as a switch (as EN pins tend to be active low), so that the 12V will only go to the GPU when say 5V is detected on one of the USB headers on the motherboard or something similar. This should give me enough room to move the radiator away from the very edge of the housing so that I can use the original mounting screws in each corner of the case to hold it together (as below), as well as some space behind the motherboard for a small pump/reservoir.