Advice 3L Project - Help w/ Dual-Voltage Solution

JLatte64

Cable Smoosher
Original poster
Oct 6, 2023
10
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I'm designing a custom chassis to house an STX motherboard, a low-profile Mean Well PSU, and an RTX 4060 Low-Profile, but I need advice from experienced folk on a power solution.

First off, here's the component layout I've come up with (click the left/right arrows to scroll through - there are 4 pictures, including CAD dimensions so you can get a sense of the space I'm working with).

The motherboard I'll be using is the one from ASRock's DeskMini B660 unit, which only runs off 19V.
The power supply will be a Mean Well LOP-300-12 unit.

I'll be using the PSU's 12V DC output for the GPU and M.2 riser power, but I need a way to step up the voltage from 12V to 19V to deliver power to the motherboard.
Ideally, I'd like it to fit somewhere within this component layout to be as small as possible, but I can go slightly bigger if necessary.

Though I'm not an electrician, I've researched it a bit - TDK-Lambda's i7C series DC-DC boards look interesting but from what I can tell, they need other hardware to function correctly. Their voltage ripple is also 60mV above the ATX spec, and they're not isolated, nor do they have filter circuits on them... so that may also cause safety concerns?

I want to avoid buying cheap converters like this one from Amazon - I've tried to stick to electronic sites like Mouser, TRC and DigiKey, but nothing I've found fits my space and power needs.

I'd like some advice from experienced crafters here on a 12V-to-19V DC-DC solution that would fit my project. Is there anything that you'd recommend?
Also, advice on the approach to wiring up the system is very welcome! As is just general feedback.

Thanks for helping!
 
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msystems

King of Cable Management
Apr 28, 2017
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It would be easier to use a 19v GAN brick (which there are many now) and 19v pico dc-dc as the stepdown for gpu, or keeping the Meanwell (or hdplex 250w gan) and using a stx board that will accept 12v, like the Deskmini x300, or possibly some other 4x4 boards... research required. The performance loss isn't going to be all that bad when using the x300 vs the b660 since the bottleneck will be the 4060. Third option is waiting for the deskmini x600 and Ryzen 8700g which may or may not support 12v.

Also you will find out the layout of the GPU isn't quite as simple as just putting it nice and neatly next to the board with parallel rear I/O. The location of the m.2 slot and the construction of the m.2 riser affects where the GPU can realistically be placed. The flexibility and orientation of the m.2 to x16 riser will ultimately determine where the GPU will be placed. It can take a few tries getting just the right length and orientation ADT riser. You want the riser as short as possible, unless it will need a "Z" shaped bend in the riser cable in order to get the card to align correctly laterally. In that case you are better off ordering it longer than needed to allow for the Z bend like this example on @REVOCCASES 4070 project.

Last issue is you do need some kind of circuitry solution to turn the GPU on intelligently (if desired) such as the load switch discussed here. Otherwise the GPU/PSU will always be powered up when the power supply is plugged in, because the STX board isn't using ATX power supply and doesn't communicate the On signal. Which isn't necessarily bad, but it would just result in higher standby power when plugged in.
 
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Tyrael

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Jun 5, 2022
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Last issue is you do need some kind of circuitry solution to turn the GPU on intelligently (if desired) such as the load switch discussed here. Otherwise the GPU/PSU will always be powered up when the power supply is plugged in, because the STX board isn't using ATX power supply and doesn't communicate the On signal. Which isn't necessarily bad, but it would just result in higher standby power when plugged in.

Thanks for the heads up. I'm starting a build very similar to OP, using the b760 in the mini. Found a fancy GaN brick and will pair it with one of the multiple hdplex 250w GaN's I have laying around to power the GPU. Thought I had it all figured out. Nope.

There. Is. Always. A. Bump. In. The. Road.

How would that work in theory? Does the PC instantly recognize the GPU once you "plug it in" like it would when you insert a Lan cable?
 

REVOCCASES

Shrink Ray Wielder
REVOCCASES
Apr 2, 2020
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www.revoccases.com
I'm designing a custom chassis to house an STX motherboard, a low-profile Mean Well PSU, and an RTX 4060 Low-Profile, but I need advice from experienced folk on a power solution.

First off, here's the component layout I've come up with (click the left/right arrows to scroll through - there are 4 pictures, including CAD dimensions so you can get a sense of the space I'm working with).

The motherboard I'll be using is the one from ASRock's DeskMini B660 unit, which only runs off 19V.
The power supply will be a Mean Well LOP-300-12 unit.

I'll be using the PSU's 12V DC output for the GPU and M.2 riser power, but I need a way to step up the voltage from 12V to 19V to deliver power to the motherboard.
Ideally, I'd like it to fit somewhere within this component layout to be as small as possible, but I can go slightly bigger if necessary.

Though I'm not an electrician, I've researched it a bit - TDK-Lambda's i7C series DC-DC boards look interesting but from what I can tell, they need other hardware to function correctly. Their voltage ripple is also 60mV above the ATX spec, and they're not isolated, nor do they have filter circuits on them... so that may also cause safety concerns?

I want to avoid buying cheap converters like this one from Amazon - I've tried to stick to electronic sites like Mouser, TRC and DigiKey, but nothing I've found fits my space and power needs.

I'd like some advice from experienced crafters here on a 12V-to-19V DC-DC solution that would fit my project. Is there anything that you'd recommend?
Also, advice on the approach to wiring up the system is very welcome! As is just general feedback.

Thanks for helping!

If you go for the AsRock A300/X300 STX you can run it on 12VDC directly, no need to step up to 19VDC.

Example:

Completed - DSX1 - DeskMini Series X Game Console Style Case - STX with internal PSU and GPU Support | SFF.Network (smallformfactor.net)

If your board really only accepts 19VDC, you can step down the voltage to 12VDC for the GPU with one of the PicoBox converters:

首页-PICOBOX 电源厂家-淘宝网 (taobao.com)

1704195262132.png

Example:

Log - RCC Pocket Rocket No.2 - Ryzen 9 & RTX 4070 <4L build | SFF.Network (smallformfactor.net)
 

msystems

King of Cable Management
Apr 28, 2017
791
1,388
Thanks for the heads up. I'm starting a build very similar to OP, using the b760 in the mini. Found a fancy GaN brick and will pair it with one of the multiple hdplex 250w GaN's I have laying around to power the GPU. Thought I had it all figured out. Nope.

There. Is. Always. A. Bump. In. The. Road.

How would that work in theory? Does the PC instantly recognize the GPU once you "plug it in" like it would when you insert a Lan cable?

Without the relay or load switch you have to manually power up the gpu prior to booting the board. This could be with a latching switch, or just plugging it in. As long as it's powered up it will get recognized at POST though.

If you are using an atx psu, the simplest way it to "short" the psu ON (hdplex can use a jumper on the control pins) and plug it into a power strip. Then the power strip is essentially then your switch.
 
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JLatte64

Cable Smoosher
Original poster
Oct 6, 2023
10
2
It would be easier to use a 19v GAN brick (which there are many now) and 19v pico dc-dc as the stepdown for gpu, or keeping the Meanwell (or hdplex 250w gan) and using a stx board that will accept 12v, like the Deskmini x300, or possibly some other 4x4 boards... research required. The performance loss isn't going to be all that bad when using the x300 vs the b660 since the bottleneck will be the 4060. Third option is waiting for the deskmini x600 and Ryzen 8700g which may or may not support 12v.

Also you will find out the layout of the GPU isn't quite as simple as just putting it nice and neatly next to the board with parallel rear I/O. The location of the m.2 slot and the construction of the m.2 riser affects where the GPU can realistically be placed. The flexibility and orientation of the m.2 to x16 riser will ultimately determine where the GPU will be placed. It can take a few tries getting just the right length and orientation ADT riser. You want the riser as short as possible, unless it will need a "Z" shaped bend in the riser cable in order to get the card to align correctly laterally. In that case you are better off ordering it longer than needed to allow for the Z bend like this example on @REVOCCASES 4070 project.

Last issue is you do need some kind of circuitry solution to turn the GPU on intelligently (if desired) such as the load switch discussed here. Otherwise the GPU/PSU will always be powered up when the power supply is plugged in, because the STX board isn't using ATX power supply and doesn't communicate the On signal. Which isn't necessarily bad, but it would just result in higher standby power when plugged in.
Hey, thanks for your thorough and detailed reply! Much appreciated.

Unfortunately, I'm wanting to make this build brickless, so I'd like to stay away from using a GaN brick. Even when going with one, they are large and flat, and don't fit well within the space I've allotted for the power supply.

For the GPU, here is where the M.2 slot is on the rear of the motherboard - I'll be using this riser to power it, so it should fit neatly, given that extra wiggle-room for bending the riser under it. It's just a straight cable run with a bend at the top of the motherboard.

And for the load switch, that's really interesting - another goal of this build is also low power consumption, so I definitely will look into that. Is it just a high-side load switch that can handle 300W that I'm looking for? Or are there other specs I should be concerned with as well, like minimum voltage and whatnot? I know that there are 5V pins on the motherboard that can tell when it needs power..
 

JLatte64

Cable Smoosher
Original poster
Oct 6, 2023
10
2
If you go for the AsRock A300/X300 STX you can run it on 12VDC directly, no need to step up to 19VDC.

Example:

Completed - DSX1 - DeskMini Series X Game Console Style Case - STX with internal PSU and GPU Support | SFF.Network (smallformfactor.net)

If your board really only accepts 19VDC, you can step down the voltage to 12VDC for the GPU with one of the PicoBox converters:

首页-PICOBOX 电源厂家-淘宝网 (taobao.com)

Example:

Log - RCC Pocket Rocket No.2 - Ryzen 9 & RTX 4070 <4L build | SFF.Network (smallformfactor.net)
Thanks for your reply and the examples - those are great references!

Unfortunately, I do want to go with this B660 board, as I'd like to keep an Intel CPU for the build. I also want this unit to be brickless, as contained as possible, so I'm going to need a DC-DC converter from 12V to 19V.

Though as @msystems mentioned, I'll also need a load switch, and with my current configuration, it will be a very tight fit along with the DC-DC.
 

msystems

King of Cable Management
Apr 28, 2017
791
1,388
You can try to find a compact 12v to 19v step-up I guess, I have never seen one. This site looks a little promising though https://www.cartft.com/catalog/il/2026

If you must have internal psu then recommend going with the x300 so can use the best in class hdplex GAN 250w. Saves time since it already has 8-pin connector for gpu
 

Tyrael

Cable Smoosher
Jun 5, 2022
12
9
Without the relay or load switch you have to manually power up the gpu prior to booting the board. This could be with a latching switch, or just plugging it in. As long as it's powered up it will get recognized at POST though.

If you are using an atx psu, the simplest way it to "short" the psu ON (hdplex can use a jumper on the control pins) and plug it into a power strip. Then the power strip is essentially then your switch.

Just to be clear, an eGPU riser or the ADT m.2 riser (connected to the mb) will not turn on the gpu?
 

JLatte64

Cable Smoosher
Original poster
Oct 6, 2023
10
2
You can try to find a compact 12v to 19v step-up I guess, I have never seen one. This site looks a little promising though https://www.cartft.com/catalog/il/2026

If you must have internal psu then recommend going with the x300 so can use the best in class hdplex GAN 250w. Saves time since it already has 8-pin connector for gpu
I might go with a DC-DC from the i7c series, as it's compact (and fits my solution save for the ripple), and connect it to a filter circuit to eliminate the ripple..
I think that can be done in the space I have?

Though, I have no idea how to wire all of those things together along with a load switch for the 12V rail.. 😅 I definitely need help on that.

And enclosing all of this compact power solution is another can of worms, too. I want to do so without interference between components... I am guessing I'll have to screw the boards to mounting plates cut from aluminum, and use thermal pads?
Again, I'm very new to this electrical stuff - I'm not sure if the way I enclose it all will have a bearing on the performance of the components.
 

REVOCCASES

Shrink Ray Wielder
REVOCCASES
Apr 2, 2020
2,068
3,346
www.revoccases.com
an eGPU riser or the ADT m.2 riser (connected to the mb) will not turn on the gpu?

It will turn the GPU on and off with your PC if you choose an eGPU dedicated riser like the JHH or ADT Link, they have a load switch (for the PCIe slot) on board.

PS: if you want to use a "normal" M.2 riser, I just saw one of my load switches is on sale in the trade section...

Selling - [Selling] GxR-DIY Edition - a tiny 12V 600W load switch module + 230W 12V Dell DA-2 power adpater | SFF.Network (smallformfactor.net)
 
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JLatte64

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Oct 6, 2023
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Is there anyone here that could help me on how to wire up the PSU, load filter, DC-DC, DC filter, and GPU/Riser?
 

JLatte64

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Original poster
Oct 6, 2023
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An update on this:
I found a 250W AC-DC Power Supply unit that outputs 19V here (its rated voltage ripple is 190mV, the website spec is wrong - though that should be fine for powering the STX motherboard, though I'm not 100% on that.. I think a 1% voltage ripple is pretty standard though): https://www.audiophonics.fr/en/smps...r-supply-module-250w-19v-13a-pfc-p-18109.html

I also found a wide-input 24V to 12V DC converter rated for 120W, which is just over the TDP for my GPU (RTX 4060 LP - 115W) - this, I can use to feed 12V @ 10A to my GPU and riser: https://daygreen.com/products/24v-to-12v-10a-120w-dc-dc-step-down-converter-voltage-regulator

Do these parts look okay? All I'd need after these is a load switch and I'd be good to go - I'd just have to figure out how to squeeze them into my chassis.
 

msystems

King of Cable Management
Apr 28, 2017
791
1,388
it would probably work. remember that the AC psu will be creating heat and might need cooling

for the step down id suggest literally anything other than the "Shenzen Special" if possible. like the pico box or the pololu

I do have a spare pico box x3-200 id be willing to sell for what I got it for. A few of us have used it and its good for 150w gpu
 
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REVOCCASES

Shrink Ray Wielder
REVOCCASES
Apr 2, 2020
2,068
3,346
www.revoccases.com
I found a 250W AC-DC Power Supply unit that outputs 19V here (its rated voltage ripple is 190mV, the website spec is wrong - though that should be fine for powering the STX motherboard, though I'm not 100% on that.. I think a 1% voltage ripple is pretty standard though): https://www.audiophonics.fr/en/smps...r-supply-module-250w-19v-13a-pfc-p-18109.html

this PSU is 0.3L @ 180W (passive cooled) - then you could as well go for the 0.25L 330W GaN which I suggested before (or the 240W Slimq) - I know it's a "brick" and not open frame, but you can as well mount a "brick" inside your case, if you do not like external PSUs.

I also found a wide-input 24V to 12V DC converter rated for 120W, which is just over the TDP for my GPU (RTX 4060 LP - 115W) - this, I can use to feed 12V @ 10A to my GPU and riser: https://daygreen.com/products/24v-to-12v-10a-120w-dc-dc-step-down-converter-voltage-regulator

Like @msystems and me already suggested, I'd go for the PicoBox DCDC converters. They have been developed to work with PC equipment, are quite compact and have already been used on several projects here on the forum.

For wiring things up, you can refer to my project I have linked before...

for your project, just replace the eGPU riser I used with a normal one and use the PicoBox DCDC 200W step down converter instead of the X9-ATX-320, then you also do not need additional filters and stuff...
 

JLatte64

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Original poster
Oct 6, 2023
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@msystems Thanks for the recommendation - I think that Pololu board would be perfect. I have seen some builds here use them to step-down 19V to 12Vdc for a GPU without a problem (afaik). So it should be good.

And @REVOCCASES thank you for all of your links as well - looking at how you wired your build really helped me to understand things better.
I think I'm still going to go with that 19Vdc 250W Power supply I found, as that shape fits in my case a bit better.

Right now, I'm trying to understand what I need for a load switch - do I just need a MOSFET, something like this, or would I need a whole controller board like this?
(Edit: I also found these MOSFET boards, though I'm not sure if they're what I want. Board 1, Board 2)

Then afterwards, I just have to diagram out a circuit to make sure the wiring's okay before I go ahead with anything.

Also, going to page @aquelito - I've seen their work in other threads w/ this kind of stuff, and I would love input as well.
 
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JLatte64

Cable Smoosher
Original poster
Oct 6, 2023
10
2
Bumping the thread - For the load switch, it seems I can just use a MOSFET and resistor soldered to a board.
I'm curious about the MOSFET choice here - would the right one be something like a P-Channel, switching on the high side, rated for (assuming we have +19V from the power supply and 12V from the ground pin of a fan header on the motherboard) -7V Vgs(th)?

I've seen the gate-to-source voltage spec vary a lot, and I just want to find something that works. I have also heard that I might need a backflow diode, as the PSU load is inductive and might have residual current that I want to be dissipated.

Any help is appreciated ^^