External power supplies and DC to DC converters for powered parts

Hello,

Part one :

I have this Question ,

as we know , Most notebooks power adapters are 19.5V output.

While the CPU and GPU works on 12V and the SSD works on 5V . , so the motherboard should have two DC to DC power converters ,

one from 19.5V to 12V for CPU and GPU

and another From 19.5v to 5V for SSD nd harddrives.

mainly the notebook will never need 19.5 V .. so why dont they choose 12V Power supplies for notebooks in General and use 19.5 V power supplies ?

Why bother making two DC to DC inverters instead of just one ?

in case of 12V power supply , they already have 12V ready and just need a DC to DC converter to get the 5V for SSD.

keep in mind that internal desktop power supplies never outputs 19.5 V , it just outputs 12V and 5 V and 3.3 V ... now imagine this power supply external (lol) the place is not a big deal isnt it ?

so back to the main Q , Why all External power supplies used for PC outputs 19.5V and not 12V like in the internal ones ? it makes no sense.

Part Two :

Graphic Cards power ..

As we all know , most mid range to high end Graphics cards needs more power , and they come either with a 6 pins 12 v plug or 8pins 12V plugs for more power it needs (150 watts to 250 watts)

My question is : If I use an external power supply of 12v outputs and plugged it into the Graphic cards direclty , would it work ? or is it better to use the 19.5V notebook external power supply and add a DC to DC converter from 19.5 to 12V and then plug it into the card?

and in case the 12V works , does it need some kind of Board to make that 12V inline with the card voltage specs ? for more stable 12V ? or is it Standardized and it will be within specs ?

some cards like the GTX 1070 needs 150 watts 12V input , and some like the 1080 , 180 Watts , and the 1080 Ti 250 watts.

I can find 150 watts external power with 12V output , but sadly anything more than this outputs 19.5 and needs DC to DC board ... example the DELL Notebooks power supply of 330 watts outputs 19.5 volts ...

Part Three :

some ATX power supplies come modular , and my question is : lets say I use just one 12V plug and ignore the other plugs , can I use the whole wattage from that single plug ? or is there a limitation of each plug watt?

They say it is single Rail (meaning watt is not divided between Vi) but I am concerned about the plug wattage and the wires if they can stand it or not.

Example : I need to power a graphics card of 300 watts .. and I use an ATX power supply with single rail of 350 watts ... the power supply has the motherboard connectors that I will not use , and has only one PCIe 6 pin plug for card .. but since I am not using it for mother board , can I use one port for the whole 300 watts or do I need to take 12 V from the Motherboard plug ?

I can use thicker wires for 300 watts , if the plug on the power supply can stand 300 watts ..

more over , on the PCB of the power supply itself , does it stand 300 watts since it is a single rail or must also be divided between plugs ?

Thanks for your replies .

Why are you mixing notebook and desktop power supply problems which are almost unrelated?

I'm not aware of any notebook PC using a 12V supply rail. They are running optionally from a Li-Ion battery with design specific cell count, all regulated internal supply rails are 5V and below.

Different ATX connectors have different current rating which must not be exceeded. PC motherboards and cards with auxiliary power connectors have clear specifications regarding required power supply.

FvM said:

Why are you mixing notebook and desktop power supply problems which are almost unrelated?

I'm not aware of any notebook PC using a 12V supply rail. They are running optionally from a Li-Ion battery with design specific cell count, all regulated internal supply rails are 5V and below.

Different ATX connectors have different current rating which must not be exceeded. PC motherboards and cards with auxiliary power connectors have clear specifications regarding required power supply.

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I am mixing them because I want to use notebook External power supply on a desktop machine.

I never said there are notebooks with 12V rails , I said why do they use 19.5v rails and not 12V rails. and the notebook CPU works on 12V and not 5V .

as for the ATX connectors , They do have Current specs and thats what I am asking. what is their maximum current. I cant find such detailed specs . and I am talking about Modding and changing things .. so I need to know the detailed specs , because for example , Companies who make GPU Give you and split adapter to take 150 watts from two cables of Molex connectors which gives the idea that it can stand more , but they dont include more plugs thats all to reduce the cost not because it cant take more. less cables and less plugs = lower price. does not mean you cant plug a Y cable to plug two plugs and get the current you want.

Thanks for your reply I am into some good project and I need info.

Think of the power rating of a desktop PC power supply, they typically range from 450W to about 1000W. Now look at the power rating of a typical notebook PSU, typically 45W to about 90W, in other words about 10% of the rating.

Look at the individual output current ratings of a desktop PC to see what you would have to replicate.

A notebook PSU is completely unsuitable for a desktop system. It's like running a car from an AAA battery!

Brian.

betwixt said:

Think of the power rating of a desktop PC power supply, they typically range from 450W to about 1000W. Now look at the power rating of a typical notebook PSU, typically 45W to about 90W, in other words about 10% of the rating.

Look at the individual output current ratings of a desktop PC to see what you would have to replicate.

A notebook PSU is completely unsuitable for a desktop system. It's like running a car from an AAA battery!

Brian.

Click to expand...

Actually a Desktop using quad cores i7-7700K and a GTX 1080ti at full load consumes only 400 Watts.

with a GTX 1070 , it will consume 300 watts at full load.

as a matter of fact , companies like Zotac and Asus are using notebook adapters to power their Desktop machines as we speak , but they design their own motherboard and add the DC to DC converter onboard.

the problem ? they ask for like 70% more price for this .. and I intend to make my own at much much lower price ..

here is a hint , Zotak 1080K magnus , comes with i7-7700k , GTX 1080 and without Memory or SSD or HD and they ask for 1800 euros for it.

a similar desktop with water cooling would cost around 1200 euros if not less ...

here is an example of very powerful desktops running on notebooks power supplies :

1- Zotak Magnus 1080K

https://www.zotac.com/product/mini_pcs/magnus-en1080k



2- Asus Rog G20-CB

https://www.asus.com/us/ROG-Republic-Of-Gamers/ROG-G20CB/



I want to make my own project using external power supply at half the cost and the FREEDOM of choosing my parts as well . because the parts Asus and Zotac are using are not the best in the market (motherbard/SSD/RAM/GPU ) .

as for the compact size case for this project ? its the DANCASE from Germany

https://www.dan-cases.com/dana4.php

The External power supply will save a place inside the case for watercooling.

Still not sure if I understand the question completely. Standard ATX power supplies are multi voltage supplies, to supply a desktop PC from a notebook power adapter (or e.g. a similar 12 V adapter), it needs an internal power converter generating multiple voltages.

So first question is which input voltages are needed by your system?

FvM said:

Still not sure if I understand the question completely. Standard ATX power supplies are multi voltage supplies, to supply a desktop PC from a notebook power adapter (or e.g. a similar 12 V adapter), it needs an internal power converter generating multiple voltages.

So first question is which input voltages are needed by your system?

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yes if you use external power you will need DC to DC converter to convert from 19.5V to 12V, 5V and 3.3 V ..

and I need to know from technical point of view , why do they make the External power adapter 19.5V and not 12V ? since the maximum Voltage needed is 12 and down. Just to learn more.

Why External power adapter are mostly 19.5 V there has to be a reason and I need to know to complete my knowledge about the Project I am intending to make.

I failed to find an 250+ watt external adapter with 12V output , all come 19.5V ...

19.5V is a compromise between needing high current and having enough voltage to charge the laptop battery. There has to be some overhead above battery voltage for the charge control circuit to operate. Bear in mind that the cells in a battery pack are usually 3.7V each so the next voltage down would be (19.5 - 3.7) 15.8V which might be too low to regulate down to 12V as the battery starts to discharge.

I disagree with your assumptions of power requirements, I'm using an i7 at 3.4GHz right now, it is fitted with 8GB of RAM and has a GT1050Ti graphics card. It 'ticks over' at around 360W but if I run highly intensive calculations, especially ones producing graphic output, it goes up to around 600W, about 40W of that in the cooling fans alone. I have a mains power meter in line with it to take the readings. Another i7 with similar configuration is used here exclusively for high-end video graphics production and editing, it regularly goes over 800W consumption (and keeps the room nice and warm too!).

Brian.

betwixt said:

19.5V is a compromise between needing high current and having enough voltage to charge the laptop battery. There has to be some overhead above battery voltage for the charge control circuit to operate. Bear in mind that the cells in a battery pack are usually 3.7V each so the next voltage down would be (19.5 - 3.7) 15.8V which might be too low to regulate down to 12V as the battery starts to discharge.

I disagree with your assumptions of power requirements, I'm using an i7 at 3.4GHz right now, it is fitted with 8GB of RAM and has a GT1050Ti graphics card. It 'ticks over' at around 360W but if I run highly intensive calculations, especially ones producing graphic output, it goes up to around 600W, about 40W of that in the cooling fans alone. I have a mains power meter in line with it to take the readings. Another i7 with similar configuration is used here exclusively for high-end video graphics production and editing, it regularly goes over 800W consumption (and keeps the room nice and warm too!).

Brian.

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I think you have power leak in your home check your home wires.

Where do you those watt numbers from ? i7 @ 3.4 ghz consumes 100 watts max at load , and the motherboard chipset around 25 watts , each drive 10 watts and each Fan 5-10 watts , give extra 25 watts for lan , usb and onboard sound chip, Plus the GTX 1050ti max watt usage is 75 watts max ...

This will be around 260 watts max ... and this is exaggerated as well.

here is total system power with GTX 1050 ti and Intel i7 5960X @ 4.3GHz running max load

**broken link removed**

System test :

**broken link removed**

another source :

https://www.bit-tech.net/reviews/tech/graphics/msi-geforce-gtx-1050-ti-gaming-x-4g-review/11/

Its a new house and I wired it myself.
The figures are accurate. You didn't factor in the hard drives, Blu-Ray burners and several other interface cards.

Even so, it doesn't help your task of inventing electricity from thin air.

Brian.

betwixt said:

Its a new house and I wired it myself.
The figures are accurate. You didn't factor in the hard drives, Blu-Ray burners and several other interface cards.

Even so, it doesn't help your task of inventing electricity from thin air.

Brian.

Click to expand...

Each hard drive consumes 10 watts max , and Blu-Ray 20watts max . I dont know where you get your 600 watt numbers from. more over the links I posted proves what I said ... there is no way a normal 3.4 Ghz not overclocked i7 with GTX 1050 ti reaches 600 watts .. not even 300 watts with full load.

you need at least 30 harddisk drives working TOGETHER at the same time in Raid to reach 600 watts with your system.

and interface cards ? like what ? which cards?

and dont worry about my inventions , I will do them with or without your help.

Your "estimates" seem to be off...

https://www.buildcomputers.net/power-consumption-of-pc-components.html

If you add up the high end stuff in that list you end up right around 600 W, now if your finances restrict you to the technological backwater of PC components then if you add up the low/mid range of the scale then you end up with less than 300 W.

Now given that a PC can have any number of items switched out to high end components (specifically the video card) one might end up with a system that used to require 200 W (minus the video card power) that suddenly needs >400 W just for the video card alone ().

So unless you build your system as a walled garden (i.e like Apple) and offer no upgrade possibilities then you have to have a 600 W minimum ATA power supply to allow for the flexibility of changing out components (to something better than the run of the mill graphics card that came with the system), without having to also change the supply.

Laptops are for the most part already self contained walled gardens, which is why they can use a supply that has much less wattage. They also tend to use much less capable hardware overall to reduce power consumption.

Engineering workstations like the HP Z840 workstations draw a lot more than 600 W when loaded. They work very well as space heaters in a cold office

ads-ee said:

Your "estimates" seem to be off...

http://www.buildcomputers.net/power-consumption-of-pc-components.html

If you add up the high end stuff in that list you end up right around 600 W, now if your finances restrict you to the technological backwater of PC components then if you add up the low/mid range of the scale then you end up with less than 300 W.

Now given that a PC can have any number of items switched out to high end components (specifically the video card) one might end up with a system that used to require 200 W (minus the video card power) that suddenly needs >400 W just for the video card alone ().

So unless you build your system as a walled garden (i.e like Apple) and offer no upgrade possibilities then you have to have a 600 W minimum ATA power supply to allow for the flexibility of changing out components (to something better than the run of the mill graphics card that came with the system), without having to also change the supply.

Laptops are for the most part already self contained walled gardens, which is why they can use a supply that has much less wattage. They also tend to use much less capable hardware overall to reduce power consumption.

Engineering workstations like the HP Z840 workstations draw a lot more than 600 W when loaded. They work very well as space heaters in a cold office

Click to expand...

HP Z840 workstation are dual CPU capable thats totally another Dimensions . and with a single CPU and GTX 1050 ti , they will never draw 600 watts .

yes you can hit 600 watts using Titan X or GTX 1080 Ti Cards or Quadro P5000 , P6000 cards with Very high end Xeon 150 watts CPU. and some 10 hard disks in the system working All the time 24/7.

but any ways , My project is about external power supply in the 450 watt range . and this is more than enough for i7 CPU and GTX 1080 ti running at maximum load with 2 hard disks in the system. and I can verify my estimates using Measured testing.

here is an example

This test has the following hardware :

Test System & Setup


Processor: Intel i7 5960X @ 4.7GHz <---- this is overclocked 8 cores i7 and NOT 4 cores one !!! rated at 140 watts Vs 91 watts
Memory: G.Skill Trident X 32GB @ 3000MHz 15-16-16-35-1T
Motherboard: ASUS X99 Deluxe
Cooling: NH-U14S
SSD: 2x Kingston HyperX 3K 480GB
Power Supply: Corsair AX1200
Monitor: Dell U2713HM (1440P) / Acer XB280HK (4K)
OS: Windows 10 Pro

link : **broken link removed**

and he tested the GTX 1080 Ti on it

and here is the total System power at load :

385 Watts using 8 cores CPU and the highest end Nvidia Card GTX 1080 ti !! and this has the same power draw of Quadro P6000 as well.

Link : **broken link removed**

System Power Consumption

For this test we hooked up our power supply to a UPM power meter that will log the power consumption of the whole system twice every second. In order to stress the GPU as much as possible we used 15 minutes of Unigine Valley running on a loop while letting the card sit at a stable Windows desktop for 15 minutes to determine the peak idle power consumption.

Click to expand...

**broken link removed**

and keep in mind , the System I am making is compact as well .. Thats the reason I want to use External power supply to begin with.

it will have the following :

i7 CPU , 2 harddisks , GTX 1080 Ti ...

Hello Horizons,
In answer to Part 1 of your questions:

so back to the main Q , Why all External power supplies used for PC outputs 19.5V and not 12V like in the internal ones ? it makes no sense.

Click to expand...

The reasons for notebook/laptop power supplies being at 19.5V is mainly due to the
unit requiring it to be used as a portable device, and as FvM quoted:

They are running optionally from a Li-Ion battery with design specific cell count, all regulated internal supply rails are 5V and below.

Click to expand...

So, the 19.5 volts is to account for the amount of cells that need to be charged, the voltage regulators needed for each voltage rail:
i.e. 12V, 5V and 3.3V and the current draw of each that can cause a voltage reduction. As no power supply is 100% efficient.
Also, due to space and size constraints, stepdown or switching transformers cannot be used. So direct mains use won't work without making the unit
more bulky and unsafe, due to mains live circuitry.

In answer to Part 2 of your questions:

My question is : If I use an external power supply of 12v outputs and plugged it into the Graphic cards direclty , would it work ?

Click to expand...

Yes, it would work, but you MUST tie the external PSU's ground to the internal one. i.e. Black wires of the power connectors.
You also need to ground (earth) the external with the internal one, by their cases, via a wire connecting the two.
You would need to be able to switch the two units on at the same time.

or is it better to use the 19.5V notebook external power supply and add a DC to DC converter from 19.5 to 12V and then plug it into the card?[/qoute]
A definite NO. Simply because you need to reduce the 19.5V down to 12V, which in turn would require an extensive circuitry
i.e. Pass transistors, high value capacitors etc. and a fairly hefty heatsink. Also, you'll end up losing its current capability due to all the losses in the separate circuit.
It just wouldn't be practical.

In answer to Part 3 of your questions:

some ATX power supplies come modular , and my question is : lets say I use just one 12V plug and ignore the other plugs , can I use the whole wattage from that single plug ? or is there a limitation of each plug watt?

Click to expand...

Yes, there are limitations of each plug, as PC PSU's are designed to output a certain amount of current for each voltage rail. This is mainly due to what wattage
rating of the output transistor/diodes within the supply that it can tolerate, as well as the wire thickness in any output inductors, also the circuit track thicknesses.
The 5V and 3.3V rails are more current hungry than the 12V rail, due to having to run the CPU, RAM, drives etc.
A 12V rail on average can deliver up to 12 Amps. Therefore you're looking at around 144W max output on a 450W PSU. Though the overall higher rating of the
PSU, the higher 12V wattage output you will be able to obtain.

They say it is single Rail (meaning watt is not divided between Vi)

Click to expand...

I'm not 100% on what you mean by this question but if I'm reading it right, then even though the 12V volts is a rail in of itself, it still needs to share the overall wattage of the PSU
with all the other rails. Here it still boils down to what I've already said: wattage rating the output transistor/diodes etc.

Example : I need to power a graphics card of 300 watts .. and I use an ATX power supply with single rail of 350 watts ... the power supply has the motherboard connectors that I will not use , and has only one PCIe 6 pin plug for card .. but since I am not using it for mother board , can I use one port for the whole 300 watts or do I need to take 12 V from the Motherboard plug ?

Click to expand...

No, see above...

I can use thicker wires for 300 watts , if the plug on the power supply can stand 300 watts ..
more over , on the PCB of the power supply itself , does it stand 300 watts since it is a single rail or must also be divided between plugs ?

Click to expand...

No need to use thicker wires, provided you use ALL the 12V wires together and their associated ground wires.
The 12V rail will not be delivering the 300 watts you desire. You'll only get what ever wattage the 12V rail is designed to deliver.

If you desire as much wattage for the 12V rail as possible from an external PSU, then consider purchasing a 1000 to 1200 watt unit and make the
modifications that will allow you to plug it into the rear of your new case and have it switch on at the same time.

I hope the above clarifies some of your questions. :smile:
Regards,
Relayer

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